2024-03-28T15:30:04Z
http://ro.uow.edu.au/do/oai/
oai:ro.uow.edu.au:engpapers-1000
2013-11-25T04:54:13Z
publication:xlwang
publication:journal_articles
publication:ssoltanian
publication:eis
publication:jhorvat
publication:engpapers
publication:sxdou
publication:engineering
publication:document_types
Magnetic shielding in MgB2/Fe superconducting wires
Horvat, J.
Soltanian, Saeid
Wang, Xiaolin
Dou, S. X.
Journal Article
10.1109/TASC.2003.812303
9634
2003-01-01T08:00:00Z
critical current density
superconductivity
critical currents
flux pinning
iron
magnesium compounds
magnetic shielding
silicon compounds
superconducting tapes
type II superconductors
<p>This paper was originally published as: Horvat, J, Soltanian, S, Wang, XL and Dou, SX, Magnetic shielding in MgB2/Fe superconducting wires, IEEE Transactions on Applied Superconductivity, June 2003, 13(2), 3324-3327. Copyright IEEE 2003.</p>
<p>Transport critical current (I/sub c/) was measured for MgB/sub 2//Fe round wires, with the magnetic field oriented perpendicular to the wire and parallel to it. Measurements were made on a wire with a pure MgB/sub 2/ core and another wire where the MgB/sub 2/ core was doped with nano-size SiC. This doping strongly improved the vortex pinning in MgB/sub 2/. The field dependence of I/sub c/ was strongly improved due to the presence of the iron sheath. At 30 K, I/sub c/ did not depend on the field for fields between 0.09 and 0.7 T. At lower temperatures, I/sub c/ increased with the field, after an initial decrease, resembling a "peak effect." This effect was extended to higher fields as the temperature was decreased: at 10 K the peak appeared at 3.5 T. This improvement was not due to mere magnetic shielding by iron, but more likely to an interaction between the iron sheath and the superconductor. Improvement of vortex pinning did not affect the range of fields within which this effect was observed. J/sub c/ of SiC doped MgB/sub 2//Fe wires at elevated fields already satisfies the requirements for their use in production of superconducting magnets for particle accelerators.</p>
Engineering
https://ro.uow.edu.au/engpapers/1
oai:ro.uow.edu.au:engpapers-1002
2013-05-21T04:22:41Z
publication:journal_articles
publication:ssoltanian
publication:eis
publication:engpapers
publication:sxdou
publication:document_types
Effect of nano-particle doping on the upper critical field and flux pinning in MgB2
Dou, S X
Soltanian, Saeid
Yeoh, W. K.
Zhang, Y.
Journal Article
10.1109/TASC.2005.848799
13705
2005-01-01T08:00:00Z
critical current
doping
magnesium diboride
silicon carbide
<p>This article was originally published as: Dou, SX, Soltanian, S, Yeoh, WK and Zhang, Z, Effect of Nano-Particle Doping on the Upper Critical Field and Flux Pinning in MgB2, IEEE Transactions on Applied Superconductivity, June 2005, 15(2), 3219-3222. Copyright IEEE 2005.</p>
<p><a href="http://ezproxy.uow.edu.au:2048/login?url=http://ereadings.uow.edu.au/dous1.pdf">eReading</a> test (University of Wollongong only).</p>
<p>The effect of nano particle doping on the critical current density of MgB<sub>2</sub> is reviewed. Most nano-particle doping leads to improvement of J<sub>c</sub>(H) performance while some shows a negative effect as with Cu and Ag. Nano-carbon containing dopants have two distinguishable contributions to the enhancement of J<sub>c</sub> field performance: increase of upper critical field and improvement of flux pinning. Among all the dopants studied so far, nano SiC doping showed the most significant and reproducible enhancement in J<sub>c</sub>(H). The nano SiC doping introduced many precipitates at a scale below 10 nm, which serve as strong pinning centers. J<sub>c</sub> for the nano SiC doped samples increased by more than an order of magnitude at high fields and all temperatures compared to the undoped samples. The significant enhancement in J<sub>c</sub>(H) of nano-SiC doping has been widely verified and confirmed, having a great potential for applications. An attempt is made to clarify the controversy on the effects of nano Fe and Ti doping on J<sub>c</sub>.</p>
Engineering
https://ro.uow.edu.au/engpapers/3
oai:ro.uow.edu.au:engpapers-1001
2014-05-12T04:39:10Z
publication:journal_articles
publication:eis
publication:jhorvat
publication:engpapers
publication:sxdou
publication:engineering
publication:document_types
Uranium Doping and Thermal Neutron Irradiation Flux Pinning Effects in MgB2
Silver, Tania M
Horvat, J.
Reinhard, M.
Yao, P.
Keshavarzi, S.
Munroe, P.
Dou, S. X.
Journal Article
10.1109/TASC.2004.825384
11365
2004-01-01T08:00:00Z
flux pinning
MgB2
U/n method
uranium doping
<p>This article was originally published as: Silver, TM, Horvat, J, Reinhard, M et al, Uranium Doping and Thermal Neutron Irradiation Flux Pinning Effects in MgB2, IEEE Transactions on Applied Superconductivity, March 2004, 14(1), 33-39. Copyright IEEE 2004.</p>
<p>The U/n method is a well-established means of improving flux pinning and critical current performance in cuprate superconductors. The method involves the doping of the superconductor with 235U followed by irradiation with thermal neutrons to promote fission. The resultant columnar damage tracks produced by the energetic fission products pin flux vortices and improve critical current performance in magnetic fields. No such improvement could be observed when the U/n method was applied to the MgB2 superconductor. No fission tracks could be observed in TEM, even for samples that were irradiated at the highest fluence. Gamma-ray spectroscopy indicated that fission had occurred in the expected way. The likely resistance of MgB2 to the formation of fission tracks is highly relevant to attempts to improve flux pinning and superconducting performance in this material through the introduction of columnar defects.</p>
Engineering
https://ro.uow.edu.au/engpapers/2
oai:ro.uow.edu.au:engpapers-1003
2014-05-06T01:13:02Z
publication:journal_articles
publication:eis
publication:jhorvat
publication:engpapers
publication:sxdou
publication:engineering
publication:document_types
Superconducting and Microstructural Properties of Two Types of MgB2 Films Prepared by Pulsed Laser Deposition
Zhao, Y.
Ionescu, M.
Roussel, M.
Pan, A. V.
Horvat, J.
Dou, S. X.
Journal Article
10.1109/TASC.2005.848847
13660
2005-01-01T08:00:00Z
Magneto-optic imaging
superconducting MgB2 films
transmission electron microscopy
<p>This article was originally published as: Zhao, Y, Ionescu, M, Roussel, M et al, Superconducting and Microstructural Properties of Two Types of MgB2 Films Prepared by Pulsed Laser Deposition, IEEE Transactions on Applied Superconductivity, June 2005, 15(2), 3261-3264. Copyright IEEE 2005.</p>
<p>Significant differences in superconducting and microstructural properties between two types of MgB<sub>2</sub> films prepared by pulsed laser deposition were determined. A very high H<sub>c2</sub>-T slope of 1.1 T/K was achieved in the in situ film. The J<sub>c</sub>-H curves of the in situ film also show a much weaker field dependence than that of the ex situ film. The magneto-optical (MO) images show that at 4 K the flux penetrates the in situ MgB<sub>2</sub> film through random paths, while for the ex situ film, the flux penetration pattern is mostly repeatable, indicating a defect-controlled flux penetration. Microstructural study (transmission electron microscopy and atomic force microscopy) revealed a relatively big grain size in the ex situ film. The correlation between the superconducting properties, microstructure and preparation conditions is discussed with regard to the two types of films.</p>
Engineering
https://ro.uow.edu.au/engpapers/4
oai:ro.uow.edu.au:engpapers-1005
2013-06-20T02:14:28Z
publication:arozenfeld
publication:journal_articles
publication:eis
publication:engpapers
publication:engineering
publication:document_types
Improvement of SOI microdosimeter performance using pulse-shape discrimination techniques
Cornelius, I.
Rosenfeld, Anatoly B.
Siegele, R.
Cohen, D. D.
Journal Article
10.1109/TNS.2002.805411
7620
2002-01-01T08:00:00Z
dosimeters
ion beam effects
silicon radiation detectors
silicon-on-insulator
<p>This article was originally published as: Cornelius, I, Rosenfeld, A, Siegele, R and Cohen, DD, Improvement of SOI microdosimeter performance using pulse-shape discrimination techniques, IEEE Transactions on Nuclear Science, December 2002, 49(6), 2805-2809. Copyright IEEE 2002.</p>
<p>The timing properties of a silicon-on-insulator microdosimeter for medical and space applications have been studied using an ion microprobe. These measurements were used with a pulse-shape discrimination technique to render the microdosimeter insensitive to ion strikes outside the ideal sensitive volume. These improvements have resulted in a microdosimeter with a cubic sensitive volume with dimensions 10/spl times/10/spl times/10 /spl mu/m/sup 3/, a charge collection spectrum close to Gaussian for a monoenergetic source, and a decreased sensitivity to radiation damage.</p>
Engineering
https://ro.uow.edu.au/engpapers/6
oai:ro.uow.edu.au:engpapers-1004
2013-05-21T04:21:40Z
publication:journal_articles
publication:eis
publication:engpapers
publication:sxdou
publication:document_types
Microstructural variations with uranium compound doping of Bi-Sr-Ca-Cu-O/Ag superconducting tapes
Milliken, D. A.
Ahn, J. H.
Dou, S X
Journal Article
10.1109/77.919949
6473
2001-01-01T08:00:00Z
X-ray chemical analysis
bismuth compounds
calcium compounds
critical current density
superconductivity
flux pinning
high temperature superconductors
strontium compounds
superconducting tapes
uranium compounds
<p>This article was originally published as: Milliken, DA, Ahn, JH and Dou, SX, Microstructural variations with uranium compound doping of Bi-Sr-Ca-Cu-O/Ag superconducting tapes, IEEE Transactions on Applied Superconductivity, March 2001, 11(1), 3964-3967. Copyright 2001 IEEE.</p>
<p>Doping of Bi-Sr-Ca-Cu-O based silver sheathed superconducting tapes (BSCCO/Ag) with various uranium compounds was carried out. This work was aimed at minimising the detrimental effects of doping to allow for later irradiation and fission to create columnar defects for strong flux pinning. The effects on the transport current density of BSCCO/Ag of doping with a variety of uranium compounds up to 2 at% was determined. Microstructural changes due to the doping were investigated. Removal of elements from the BSCCO matrix by uranium compound dopants was studied by energy dispersive spectroscopy. It was found that UCa1.5Sr1.5O6 least degraded electrical performance and microstructure, as it removed the least elements from the matrix. It would appear that UCa1.5Sr1.5O6 most closely approximates an ideal BSCCO compatible uranium compound, but it still removes some amount of copper.</p>
Engineering
https://ro.uow.edu.au/engpapers/5
oai:ro.uow.edu.au:engpapers-1006
2013-05-21T04:21:13Z
publication:journal_articles
publication:eis
publication:engpapers
publication:sxdou
publication:engineering
publication:document_types
Determination of the AC Losses of Bi-2223 HTS Coils at 77 K at Power Frequencies Using a Mass Boil-Off Calorimetric Technique
Darmann, F.
Dou, S X
Cook, C.
Journal Article
10.1109/TASC.2003.809828
7402
2003-01-01T08:00:00Z
AC loss
boil off
external field
HTS tape
hysteresis loss
transport loss
<p>This article was originally published as: Darmann, F, Dou, SX and Cook, C, Determination of the AC Losses of Bi-2223 HTS Coils at 77 K at Power Frequencies Using a Mass Boil-Off Calorimetric Technique, IEEE Transactions on Applied Superconductivity, March 2003, 13(1), 1-6. Copyright IEEE 2003.</p>
<p>A mass boil-off measurement system has been used to accurately measure and characterize the ac loss of high-temperature superconductor (HTS) coils at frequencies between 50 and 200 Hz, and in applied ac fields of up to 0.04 T. The mass boil-off calorimeter incorporated a glass cryostat, a copper field coil, and two mass flow meters. The response of the gas flow to a step change in the applied magnetic field was found to have a time constant of about 600 s. Under suitable experimental conditions, it was possible to measure the ac losses of coils with an accuracy of 0.3 W. The ac loss characteristics of an HTS pancake and two HTS solenoid coils are presented and the accuracy of mass flow calorimetry in liquid nitrogen is reported on.</p>
Engineering
https://ro.uow.edu.au/engpapers/7
oai:ro.uow.edu.au:engpapers-1007
2013-05-21T04:20:21Z
publication:journal_articles
publication:hkliu
publication:eis
publication:engpapers
publication:sxdou
publication:engineering
publication:document_types
Effect of the sinter-forging deformation rate on properties of Bi-2223 current leads
Fu, X. K.
Guo, Y. C.
Chen, W. M.
Liu, Hua-Kun
Dou, S. X.
Journal Article
10.1109/77.920388
6474
2001-01-01T08:00:00Z
bismuth compounds
calcium compounds
copper compounds
critical current density
superconductivity
forging
high-temperature superconductors
lead compounds
magnetic fields
sintering
strontium compounds
superconducting cables
<p>This article was originally published as: Fu, XK, Guo, YC, Chen, WM et al, Effect of the sinter-forging deformation rate on properties of Bi-2223 current leads, IEEE Transactions on Applied Superconductivity, March 2001, 11(1), 2551-2554. Copyright IEEE 2001.</p>
<p>The influence of the sinter-forging rate on the critical current density (Jc) behaviour in an external field and on the contact resistance Rc for Bi-2223 current leads has been investigated. The current leads were fabricated by a combination of cold isostatic pressing (CIP) and sinter-forging methods with the thickness reduction rate ranging from 0% to 90%. The two silver contact terminals of each sample were also prepared during the sinter-forging. The results revealed that Jc was strongly affected by the deformation rate of sinter-forging and reached a maximum of 725 A/cm2 at a deformation rate of 80%. From the measurements of the external magnetic field dependence on Jc. It was determined that sinter-forging could improve the Jc behaviour in external fields, particularly in the regime below 10×10-13 Tesla (i.e. 10 mT). The measurements of the contact resistance Rc were conducted for different transport currents at 77 K. The results showed that the contact resistance for the samples with higher deformation rates became less dependent on the transport current over a range of 0.5 A to 50 A.</p>
Engineering
https://ro.uow.edu.au/engpapers/8
oai:ro.uow.edu.au:engpapers-1008
2011-10-12T02:53:14Z
publication:eis
publication:conference_papers
publication:engpapers
publication:engineering
publication:document_types
Postgraduate and undergraduate mechatronics' courses at the University of Wollongong
Cook, C.
Naghdy, Fazel
de Boer, F.
Conference Paper
6401
2001-07-01T07:00:00Z
educational courses
engineering education
mechatronics
<p>This article was originally published as: Cook, C, Naghdy, F and de Boer, F, Postgraduate and undergraduate mechatronics' courses at the University of Wollongong, Proceedings of the IEEE/ASME International Conference on Advanced Intelligent Mechatronics, 8-12 July 2001, 2, 994-999. Copyright IEEE 2001.</p>
<p>This paper outlines the University's involvement with industry based manufacturing projects, and how this has lead to the recent establishment of postgraduate and undergraduate mechatronics degrees. The nature of the industrial projects is described with examples of specific problems, test equipment and experimental rigs given. This work can be used to explain the reasons for the design of the mechatronics courses at Wollongong. A new teaching methodology particularly suitable for mechatronic's education is also discussed.</p>
Engineering
https://ro.uow.edu.au/engpapers/9
oai:ro.uow.edu.au:engpapers-1012
2013-05-21T04:19:09Z
publication:xlwang
publication:journal_articles
publication:eis
publication:engpapers
publication:sxdou
publication:document_types
Co valence by K-edge X-ray absorption spectroscopy, magnetic properties, and structure of polycrystalline bulk Zn/sub 1-x/Co/sub x/O
Peleckis, Germanas
Wang, Xiaolin
Liu, R. S.
Dou, S. X.
Journal Article
10.1109/TMAG.2005.854689
13711
2005-01-01T08:00:00Z
Paramagnetic materials
spintronics
<p>This article was originally published as: Peleckis, G, Wang, XL, Liu, RS and Dou, Sx, Co valence by K-edge X-ray absorption spectroscopy, magnetic properties, and structure of polycrystalline bulk Zn/sub 1-x/Co/sub x/O, IEEE Transactions on Magnetics, October 2005, 41(10), 2727-2729. Copyright IEEE 2005.</p>
<p>We report on magnetic properties and a Co K-edge X-ray absorption spectroscopy (XAS) study of polycrystalline bulk Zn<sub>1-x</sub>Co<sub>x</sub>O (x=0.10,0.15,0.17) samples. All samples show paramagnetic behavior and no ferromagnetism was observed. XAS results showed that for all samples the valence of Co is 2+. Spin state assessment derived from Currie-Weiss fitting indicated a possible spin state transition from Co<sup>2+</sup> high spin to Co<sup>2+</sup> low spin. Calculated μ<sub>eff</sub> values for samples with x=0.10 and 0.15 indicated an orbital contribution to the effective magnetic moment of the Co ion.</p>
Engineering
https://ro.uow.edu.au/engpapers/13
oai:ro.uow.edu.au:engpapers-1013
2013-05-08T02:02:21Z
publication:xlwang
publication:journal_articles
publication:eis
publication:engpapers
publication:document_types
Structure, spin glass, and spin state in perovskite GdCo/sub 1-x/Mn/sub x/O/sub 3/ (x /spl les/ 0.5)
Farhoudi, M Mehdi
Wang, Xiaolin
Journal Article
10.1109/TMAG.2005.854767
2005-10-01T07:00:00Z
Ferromagnetism
magnetization
perovskite
spin glass
spin state
<p>This article was originally published as: Farhoudi, MM and Wang, XL, Structure, spin glass, and spin state in perovskite GdCo/sub 1-x/Mn/sub x/O/sub 3/ (x /spl les/ 0.5), IEEE Transactions on Magnetics, October 2005, 41(10), 3493-3495. Copyright IEEE 2005.</p>
<p>Perovskite GdCo/sub 1-x/Mn/sub x/O/sub 3/ (x=0.2,0.3,0.4,0.5) compounds have been prepared by solid-state reaction. Structures were characterized using X-ray diffraction and Rietveld Refinement method. The compounds crystallized in orthorhombic with Plmn space group. Crystal lattices decreased with the increase of Mn doping level. DC magnetization and ac susceptibility were studied over a wide temperature range and different frequencies. A typical spin glass state was observed in all samples around the same temperature of 122 K where the compounds turned from paramagnetic to ferromagnetic states. For x</p>
Engineering
https://ro.uow.edu.au/engpapers/14
oai:ro.uow.edu.au:engpapers-1010
2012-10-24T01:07:23Z
publication:xlwang
publication:journal_articles
publication:eis
publication:rlewis
publication:engpapers
publication:engineering
publication:document_types
Infrared-active phonons of perovskite HoMn/sub 1-x/Co/sub x/O/sub 3/ (x=0--0.8)
Gao, Feng
Wang, Xiaolin
Farhoudi, M Mehdi
Lewis, R. A.
Journal Article
10.1109/TMAG.2005.854829
13691
2005-10-01T07:00:00Z
Far-infrared spectroscopy
perovskites
phonon modes
<p>This article was originally published as: Gao, F, Wang, XL, Farhoudi, MM and Lewis, RA, Infrared-active phonons of perovskite HoMn/sub 1-x/Co/sub x/O/sub 3/ (x=0--0.8), IEEE Transactions on Magnetics, October 2005, 41(10), 2763-2765. Copyright IEEE 2005.</p>
<p>Polycrystalline perovskites compounds HoMn/sub 1-x/Co/sub x/O/sub 3/ (x=0--0.8) have been prepared by conventional solid-state reaction. Here, we used far-infrared (FIR) spectroscopy to study infrared active phonon modes and present a comparative analysis of infrared transmission spectra of polycrystalline HoMn/sub 1-x/Co/sub x/O/sub 3/ (x=0--0.8). The data indicated that phonon modes significantly changed with increase of cobalt doping level. Four main bands were assigned as external, torsional, bending and stretching bands. The external vibration energy remain same at /spl omega//sub 1//spl sim/190 cm/sup -1/ for Co doping x/spl les/0.5 and shift to higher energy for x>0.5. Torsional and bending bands exhibit splitting. The stretching band is at 600 cm/sup -1/ for all samples, but the bandwidth is reduced as Co doping increased. The transmission spectrum of HoMn/sub 4/5/Co/sub 1/5/O/sub 3/ was analyzed to obtain the spectrum of optical density. The minimum number of oscillators to obtain a reliable fit is 5 by using a sum of noninteracting harmonic oscillators.</p>
Engineering
https://ro.uow.edu.au/engpapers/11
oai:ro.uow.edu.au:engpapers-1009
2006-07-31T04:53:48Z
publication:eis
publication:rlewis
publication:conference_papers
publication:engpapers
publication:document_types
Terahertz Emission from (100) p-InA
Smith, M. L.
Mendis, R.
Vickers, R. E. M.
Lewis, R. A.
Conference Paper
25198
2005-09-19T07:00:00Z
terahertz emission
photo-carrier transport
optical rectification mechanisms
This paper was originally published as: Smith, ML, Mendis, R, Vickers, REM and Lewis, RA, Terahertz Emission from (100) p-InA, Joint 30th International Conference on Infrared and Millimeter Waves and 13th International Conference on Terahertz Electronics, (IRMMW-THz 2005), 19-23 September 2005, 1, 253-254. Copyright IEEE 2005.
Terahertz emission from (100) p-type InAs illuminated by
ultrafast near-infrared pulses is investigated. A two-fold
rotational symmetry was observed when rotated about the
surface normal. A quadratic relationship was found for the
emission dependence on optical pump power. These suggest
the presence of photo-carrier transport and optical rectification
mechanisms. The InAs emission was found to exceed that of a
blackbody radiator for frequencies below 1 THz for nominal
input power levels. The generated power was found to be
roughly two orders of magnitude greater than a 1mm ZnTe
emitter.
Engineering
https://ro.uow.edu.au/engpapers/10
oai:ro.uow.edu.au:engpapers-1011
2013-05-21T04:19:55Z
publication:xlwang
publication:journal_articles
publication:eis
publication:engpapers
publication:sxdou
publication:document_types
Absence of ferromagnetism and strong spin-orbital coupling in polycrystalline in and Co codoped Zn/sub 1-x/Co/sub 0.075/In /sub x/O oxide
Peleckis, Germanas
Wang, Xiaolin
Dou, S X
Journal Article
10.1109/TMAG.2005.854731
13715
2005-01-01T08:00:00Z
Paramagnetic materials
spintronics
<p>This article was originally published as: Peleckis, G, Wang, XL and Dou, SX, Absence of ferromagnetism and strong spin-orbital coupling in polycrystalline in and Co codoped Zn/sub 1-x/Co/sub 0.075/In /sub x/O oxide, IEEE Transactions on Magnetics, October 2005, 41(10), 2739-2741. Copyright IEEE 2005.</p>
<p>Polycrystalline samples of In and Co codoped ZnO (Zn<sub>1-x</sub>In<sub>x</sub>Co<sub>0.075</sub>O; 0.010≤x≤0.020) oxide were prepared by solid-state synthesis technique. Phase purity and structure refinement done by means of the Rietveld analysis technique shows that both Co and In substitute properly into Zn positions. In doping, increased bulk conductivity of the samples at room temperature indicates an increase of charge carrier concentration. All samples showed paramagnetic behavior following Curie-Weiss law at close to room temperatures, with short range antiferromagnetic interaction with Θ≈-200 K. Effective magnetic moment (μ<sub>eff</sub>) calculations showed a strong orbital contribution to the value of μ<sub>eff</sub>, increasing with an increase of In content (x).</p>
Engineering
https://ro.uow.edu.au/engpapers/12
oai:ro.uow.edu.au:engpapers-1014
2013-06-20T02:14:01Z
publication:arozenfeld
publication:journal_articles
publication:eis
publication:engpapers
publication:document_types
A computational technique for simulating ionization energy deposition by energetic ions in complex targets
Cornelius, I.
Rosenfeld, Anatoly B.
Bradley, P. D.
Maughan, R. L.
Journal Article
10.1109/23.903787
5454
2000-01-01T08:00:00Z
dosimetry
energy loss of particles
ion beam effects
ionisation
silicon-on-insulator
<p>This article was originally published as: Cornelius, I, Rosenfeld, A, Bradley, PD and Maughan, RL, A computational technique for simulating ionization energy deposition by energetic ions in complex targets, IEEE Transactions on Nuclear Science, December 2000, 47(6)3, 2423-2427. Copyright IEEE 2000.</p>
<p>An ion transport code was developed for simulating ionization energy deposition by energetic ions in sensitive volumes of complex structures. The code was used to simulate recent microdosimetry measurements performed with silicon-on-insulator (SOI) microdosimeters in Fast Neutron Therapy (FNT).</p>
Engineering
https://ro.uow.edu.au/engpapers/15
oai:ro.uow.edu.au:engpapers-1015
2013-06-20T02:13:34Z
publication:arozenfeld
publication:journal_articles
publication:eis
publication:engpapers
publication:engineering
publication:document_types
A new silicon detector for microdosimetry applications in proton therapy
Rosenfeld, Anatoly B.
Bradley, P.
Cornelius, I.
Kaplan, G. I.
Allen, B. J.
Flanz, J. B.
Goitein, M.
Van Meerbeeck, A.
Schubert, J.
Bailey, J.
Takada, Y.
Maruhashi, A.
Hayakawa, Y.
Journal Article
10.1109/23.872983
5455
2000-01-01T08:00:00Z
dosimetry
radiation therapy
silicon radiation detectors
<p>This article was originally published as: Rosenfeld, AB, Bradley, P, Cornelius, I et al, A new silicon detector for microdosimetry applications in proton therapy, IEEE Transactions on Nuclear Science, August 2000, 47(4), 1386-1394. Copyright IEEE 2000.</p>
<p>A silicon-on-insulator diode array with a sensitive depth of 10 microns has been developed for microdosimetry in proton therapy. The detector was coupled to a radiation-hard charge sensitive amplifier with the probe assembly capable of measuring an LET down to 1.2 keV/μm. The device has been successfully tested at two proton therapy centers. The 230 MeV Northeastern Proton Therapy Center, Boston and the 250 MeV Proton Medical Research Center at Tsukuba, Japan. The device offers much improved spatial resolution compared with a proportional gas counter particularly in the critical high dose region around the proton Bragg peak. Due to its small cross-sectional area (0.04 cm2) measurements may also be made in facilities with short high intensity beams.</p>
Engineering
https://ro.uow.edu.au/engpapers/16
oai:ro.uow.edu.au:engpapers-1016
2013-06-20T02:13:07Z
publication:arozenfeld
publication:journal_articles
publication:eis
publication:engpapers
publication:document_types
Design and simulation of continuous scintillator with pixellated photodetector
Takacs, G. J.
Rosenfeld, Anatoly B.
Lerch, M. L.
Journal Article
10.1109/23.958369
5931
2001-01-01T08:00:00Z
biomedical electronics
gamma-ray detection
photodiodes
positron emission tomography
solid scintillation detectors
<p>This article was originally published as: Takacs, G, Rosenfeld, A & Lerch, MLF, Design and Simulation of Continuous Scintillator with Pixellated Photodetector, IEEE Transactions on Nuclear Science, August 2001, 48(4)2, 1412-1417. Copyright IEEE 2001.</p>
<p>Presents results of simulations performed as part of the development of a gamma-ray detector module comprising a nonpixellated scintillator and pixellated photodiode detector. The simulations have been carried out to determine the effect of surface treatment and dimensions of the scintillator on the ability to determine the two-dimensional position of interaction. A set of 32 different combinations of surface treatments have been considered for each crystal size. Scintillator dimensions considered have been 25×25×(3-6 mm3). For scintillator thicknesses at the low end of this range, an average accuracy of 0.5-0.6 mm is achievable for many different surface treatments. At the higher end of the thickness range, 6 mm, the average accuracy reduces to around 0.7 mm and is more dependent on the surface treatment.</p>
Engineering
https://ro.uow.edu.au/engpapers/17
oai:ro.uow.edu.au:engpapers-1018
2006-07-31T04:59:16Z
publication:journal_articles
publication:eis
publication:engpapers
publication:document_types
Results of AC loss tests on twisted and untwisted HTSC tape exposed to an external field
Hardono, T.
Cook, C.
Darmann, F.
Journal Article
10.1109/77.920355
6400
2001-03-01T08:00:00Z
magnetic losses
calorimetry
high temperature superconductors
power engineering
This article was originally published as: Hardono, T, Cook, C & Darmann, F, Results of AC Loss Tests on Twisted and Untwisted HTSC Tape Exposed to an External Field, IEEE Transactions on Applied Superconductivity, March 2001, 11(1), 2437-2440. Copyright IEEE 2001.
This paper presents the results of magnetic losstests on twisted and untwisted 37 multifilaments tapes exposed to an alternating field at power frequencies. The losses are measured using calorimetric methods, which are capable of measuring losses in short tapes with the accuracy of several microwatts per centimeter of tape. The losses of the tape due to the longitudinal field of the untwisted tape agree well with
theoretical calculations. The measurement results on the twisted
filament tape, with 50-mm twist pitch, show that the losses are
slightly lower than that in the untwisted tape. This is due to the reduction of the coupling losses between the filaments in the
tape. It is also shown that in the presence of normal fields, the
losses are about one order higher than for longitudinal fields
because of the anisotropic properties of the superconducting
parts and because of the existence of eddy current loss in the
silver sheath.
Engineering
https://ro.uow.edu.au/engpapers/19
oai:ro.uow.edu.au:engpapers-1019
2013-05-21T04:18:42Z
publication:journal_articles
publication:hkliu
publication:eis
publication:engpapers
publication:sxdou
publication:document_types
Magneto-optical images of Ag/Bi-2223 tapes processed by flat rolling, “sandwich” rolling and pressing
Liu, Hua-Kun
Polyanskii, A.
Chen, W. M.
Guo, Y. C.
Dou, S. X.
Apperley, M.
Journal Article
10.1109/77.919883
6476
2001-01-01T08:00:00Z
<p>This article was originally published as: Liu, HK, Polyanskii, A, Chen, WM et al, Magneto-optical images of Ag/Bi-2223 tapes processed by flat rolling, ‘sandwich’ rolling and pressing, IEEE Transactions on Applied Superconductivity, March 2001, 11(1), 3764-3767. Copyright IEEE 2001.</p>
<p>Magneto-optical imaging (MOI) has been used for study Ag/Bi-2223 tapes processed using flat rolling, “sandwich” rolling, and pressing methods for the intermediate mechanical deformation in powder-in-tube process. The results show that not only the density of the microcracks but also their distribution affect Jc. Rolled tapes have a higher density of microcracks than pressed tapes. Although the flat rolled tape and “sandwich” rolled tape have the same level density of microcracks at the same reduction, the cracks in the former are more in the transverse direction than in the latter. In all three cases, Jc reaches a maximum value at an optimal reduction rate.</p>
Engineering
https://ro.uow.edu.au/engpapers/20
oai:ro.uow.edu.au:engpapers-1020
2013-05-21T04:18:13Z
publication:journal_articles
publication:eis
publication:jhorvat
publication:engpapers
publication:sxdou
publication:engineering
publication:document_types
Effect of uranium doping and thermal neutron irradiation on the flux-pinning of silver-clad Bi-Sr-Ca-Cu-O tapes
Marinaro, D.
Dou, S X
Horvat, J.
Boldeman, J.
Weinstein, R.
Sawh, R.
Journal Article
10.1109/77.919920
6477
2001-01-01T08:00:00Z
<p>This article was originally published as: Marinaro, D, Dou, SX, Horvat, J et al, Effect of Uranium Doping and Thermal Neutron Irradiation on the flux-pinning of silver-clad Bi-Sr-Ca-Cy-O tapes, IEEE Transactions on Applied Superconductivity, March 2001, 11(1), 3896-3899. Copyright IEEE 2001.</p>
<p>Ag/Bi-2223 tapes doped with small quantities of 235UO 4 powder were prepared by the powder-in-tube process and irradiated in a thermal neutron environment. Substantial improvements in critical current density (Jc)-applied field (H) performance and anisotropy have been previously reported. However, the radioactivity of the silver sheath is a limiting factor for commercial and industrial applications of this technique. Here we report the performance of the technique using various doping levels (from 0.15 to 2 percent by weight (wt.%) UO4) and thermal neutron fluences (Φn), in order to further reduce the silver radioactivity. Optimum fluence levels are identified and an optimum combination in terms of Jc - H performance is discussed. At a doping level of 2% 235 UO4, a normalised Jc enhancement of 250 times is observed for an 0.8 T field aligned along the c-axis, and 25 times at 3 T along the ab-plane at 77 K, compared to pre-irradiation values. At 0.6%, these figures are 500 and 10 times, respectively. The effects of the uranium doping and thermal neutron irradiation on the flux pinning strengths are also directly probed using dynamic relaxation techniques. The results show an increase in the effective pinning potential after doping and irradiation.</p>
Engineering
https://ro.uow.edu.au/engpapers/21
oai:ro.uow.edu.au:engpapers-1021
2013-06-20T02:12:42Z
publication:arozenfeld
publication:journal_articles
publication:eis
publication:engpapers
publication:engineering
publication:document_types
Spectral characterization of a blue-enhanced silicon photodetector
Lerch, M. L.
Rosenfeld, Anatoly B.
Simmonds, Philip E
Taylor, G. N.
Meikle, S. R.
Perevertailo, V. L.
Journal Article
10.1109/23.958754
5930
2001-01-01T08:00:00Z
<p>This article was originally published as: Lerch, MLF, Rozenfeld, A, Simmonds, P et al, Spectral Characterisation of a Blue-Enhanced Silicon Photodetector, IEEE Transactions on Nuclear Science, August 2001, 48(4), 1220-1224. Copyright IEEE 2001.</p>
<p>In this paper, we report on spectral response data and gamma ray spectroscopy measurements using two newly developed silicon photodetectors that are designed to have enhanced sensitivity in the blue spectral region. The enhanced sensitivity is a result of our newly developed ion implantation profile used to create the active area of the photodetector. The quantum efficiency of the new photodetectors (without any optimized antireflective coating) has been measured to be ~40% at a wavelength of 420 nm. Gamma ray spectroscopy experiments have been performed using a thallium doped cesium iodide, [CsI(Tl)], and a cerium doped lutetium oxy-orthosilicate, (LSO) crystal excited by a 137 Cs or 22Na source and read out by the new photodetectors. We have measured an energy resolution of 7.7% and 22.7% full-width at half-maximum (FWHM) for the 662-keV gamma rays from a 137Cs for the CsI(Tl) and LSO scintillator crystal respectively. We intend to use the photodetectors, in the form of a detector array optically coupled to CsI(Tl) or LSO, in the development of a new scintillator detector module for use in positron emission tomography (PET).</p>
Engineering
https://ro.uow.edu.au/engpapers/22
oai:ro.uow.edu.au:engpapers-1022
2013-06-20T02:12:15Z
publication:arozenfeld
publication:journal_articles
publication:eis
publication:engpapers
publication:document_types
Feasibility study of online high-spatial-resolution MOSFET dosimetry in static and pulsed x-ray radiation fields
Rosenfeld, Anatoly B.
Lerch, M. L.
Kron, T.
Brauer-Krisch, E.
Bravin, A.
Holmes-Siedle, A.
Allen, B. J.
Journal Article
10.1109/23.983173
5929
2001-01-01T08:00:00Z
<p>This article was originally published as: Rosenfeld, A, Lerch, MLF, Kron, T et al, Feasibility Study of Online High-Sptatial-Resolution MOSFET Dosimetry in Static and Pulsed X-Ray Radiation Fields, IEEE Transactions on Nuclear Science, December 2001, 48(6)1, 2061-2068. Copyright IEEE 2001.</p>
<p>Improvements have been made in the measurement of dose profiles in several types of X-ray beams. These include 120-kVp X-ray beams from an orthovoltage X-ray machine, 6-MV Bremsstrahlung from a medical LINAC in conformal mode and the 50-200 keV energy spectrum of microbeams produced at the medical beamline station of the European Synchrotron Radiation Facility. Using a quadruple metal-oxide-semiconductor field-effect transistor (MOSFET) sensor chip in "edge on" mode together with a newly developed sensor readout system, the feasibility of online scanning of the profiles of quasi-static and pulsed radiation beams was demonstrated. Measurements of synchrotron pulsed microbeams showed that a micrometer-scale spatial resolution was achievable. The use of several MOSFETs on the same chip gave rise to the correction of misalignments of the oxide films of the sensor with respect to the microbeam, ensuring that the excellent spatial resolution of the MOSFET used in "edge-on" mode was fully utilized.</p>
Engineering
https://ro.uow.edu.au/engpapers/23
oai:ro.uow.edu.au:engpapers-1023
2006-07-31T05:06:50Z
publication:journal_articles
publication:eis
publication:engpapers
publication:document_types
Enhanced Stiffness Modeling, Identification and Characterization for Robot Manipulators
Alici, G.
Shirinzadeh, B.
Journal Article
10.1109/TRO.2004.842347
13850
2005-08-01T07:00:00Z
compliance/force control
manipulator kinematic
stiffness identification
stiffness modeling
This article was originally published as: Alici, G and Shirinzadeh, B, Enhanced Stiffness Modeling, Identification and Characterization for Robot Manipulators, IEEE Transactions on Robotics, August 2005, 21(4), 554 - 564. Copyright IEEE 2005.
This paper presents the enhanced stiffness modeling and analysis of robot manipulators, and a methodology for their stiffness identification and characterization. Assuming that the manipulator links are infinitely stiff, the enhanced stiffness model contains: 1) the passive and active stiffness of the joints and 2) the active stiffness created by the change in the manipulator configuration, and by external force vector acting upon the manipulator end point. The stiffness formulation not accounting for the latter is known as conventional stiffness formulation, which is obviously not complete and is valid only when: 1) the manipulator is in an unloaded quasistatic configuration and 2) the manipulator Jacobian matrix is constant throughout the workspace. The experimental system considered in this study is a Motoman SK 120 robot manipulator with a closed-chain mechanism. While the deflection of the manipulator end point under a range of external forces is provided by a high precision laser measurement system, a wrist force/torque sensor measures the external forces. Based on the experimental data and the enhanced stiffness model, the joint stiffness values are first identified. These stiffness values are then used to prove that conventional stiffness modeling is incomplete. Finally, they are employed to characterize stiffness properties of the robot manipulator. It has been found that although the component of the stiffness matrix differentiating the enhanced stiffness model from the conventional one is not always positive definite, the resulting stiffness matrix can still be positive definite. This follows that stability of the stiffness matrix is not influenced by this stiffness component. This study contributes to the previously reported work from the point of view of using the enhanced stiffness model for stiffness identification, verification and characterization, and of new experimental results proving that the conventional stiffness matrix is not complete and is valid under certain assumptions.
Engineering
https://ro.uow.edu.au/engpapers/24
oai:ro.uow.edu.au:engpapers-1024
2006-07-31T05:07:45Z
publication:eis
publication:conference_papers
publication:engpapers
publication:document_types
Optimum dynamic balancing of planar parallel manipulators
Alici, G.
Shirinzadeh, B.
Conference Paper
10764
2004-04-26T07:00:00Z
This article was originally published as: Alici, G and Shirinzadeh, B, Optimum Dynamic Balancing of Planar Parallel Manipulators, Proceedings IEEE International Conference on Robotics and Automation (ICRA-2004), 26 April-1 May 2004, vol 5, 4527-4532. Copyright IEEE 2004.
This paper presents a methodology for optimum dynamic balancing of planar parallel manipulators typified with a variable speed 2 DOF parallel manipulator articulated with revolute joints. The dynamic balancing is formulated as an optimisation problem such that a sum-squared values of bearing forces, driving torques, shaking moment, and the deviation of the angular momentum from its mean value are minimized throughout an operation range of the manipulator, provided that a set of balancing constraints consisting of the shaking force balancing conditions, the sizes of some inertial and geometric parameters are satisfied. Sets of optimisation results corresponding to various combinations of the elements of the objective function are evaluated in order to quantify their influence on the resulting bearing forces, the driving torques, shaking moment and force. The results prove that the proposed optimisation approach can be used to minimize any desired combination of the forces, moments, and torques involved in any parallel mechanism by choosing a suitable set of weighting factors. The method is systematic, versatile and easy to implement for the optimum balancing of the parallel manipulator and more general parallel manipulators.
Engineering
https://ro.uow.edu.au/engpapers/25
oai:ro.uow.edu.au:engpapers-1025
2013-06-20T02:11:50Z
publication:arozenfeld
publication:journal_articles
publication:eis
publication:engpapers
publication:engineering
publication:document_types
LET dependence of the charge collection efficiency of silicon microdosimeters
Cornelius, I.
Rosenfeld, Anatoly B.
Siegele, R.
Cohen, D. D.
Journal Article
10.1109/TNS.2003.820740
9043
2003-01-01T08:00:00Z
<p>This article was originally published as: Cornelius, IM, Rosenfeld, AB, Siegele, R and Cohen, DD, LET dependence of the charge collection efficiency of silicon microdosimeters, IEEE Transactions on Nuclear Science, December 2003, 50(6)1, 2373-2379. Copyright IEEE 2003.</p>
<p>A heavy ion microprobe was used to conduct ion beam induced charge (IBIC) collection imaging of silicon microdosimeters. The GEANT4 Monte Carlo toolkit was used to simulate these measurements to calculate ion energy loss in the device overlayer and energy deposition in the device sensitive volume. A comparison between experimental and theoretical results facilitated the calculation of charge collection efficiency profiles for several ions.</p>
Engineering
https://ro.uow.edu.au/engpapers/26
oai:ro.uow.edu.au:engpapers-1026
2013-06-20T02:11:24Z
publication:arozenfeld
publication:journal_articles
publication:eis
publication:engpapers
publication:document_types
Verification of Monte Carlo calculations in fast neutron therapy using silicon microdosimetry
Cornelius, I.
Rosenfeld, Anatoly B.
Journal Article
10.1109/TNS.2004.829398
10672
2004-01-01T08:00:00Z
FNT
Fast neutron therapy
Monte Carlo
microdosimetry
<p>This article was originally published as: Cornelius, IM and Rosenfeld, AB, Verification of Monte Carlo calculations in fast neutron therapy using silicon microdosimetry, IEEE Transactions on Nuclear Science, June 2004, 51(3)3, 873-877. Copyright IEEE 2004.</p>
<p>Silicon microdosimetry measurements in Fast Neutron Therapy were simulated using the GEANT4 Monte Carlo toolkit. The possibility of using silicon microdosimeters for verification of Monte Carlo based treatment planning systems in hadron therapy is suggested.</p>
Engineering
https://ro.uow.edu.au/engpapers/27
oai:ro.uow.edu.au:engpapers-1028
2006-07-31T05:09:41Z
publication:journal_articles
publication:eis
publication:engpapers
publication:engineering
publication:document_types
Asymmetric kernel regression
Mackenzie, M.
Tieu, K.
Journal Article
10.1109/TNN.2004.824414
10675
2004-03-01T08:00:00Z
This article was originally published as: Mackenzie, M and Tieu, K, Asymmetric kernel regression, IEEE Transactions on Neural Networks, March 2004, 15(2), 276-282. Copyright IEEE 2004.
Kernel regression is one model that has been applied to explain or design radial-basis neural networks. Practical application of the kernel regression method has shown that bias errors caused by the boundaries of the data can seriously effect the accuracy of this type of regression. This paper investigates the correction of boundary error by substituting an asymmetric kernel function for the symmetric kernel function at data points close to the boundary. The asymmetric kernel function allows a much closer approach to the boundary to be achieved without adversely effecting the noise-filtering properties of the kernel regression.
Engineering
https://ro.uow.edu.au/engpapers/29
oai:ro.uow.edu.au:engpapers-1032
2013-05-21T04:17:46Z
publication:xlwang
publication:journal_articles
publication:hkliu
publication:eis
publication:jhorvat
publication:engpapers
publication:sxdou
publication:document_types
Magnetic hysteresis and relaxation in Bi2212 single crystals doped with Fe and Pb
Uprety, K. K.
Horvat, J.
Wang, Xiaolin
Gu, G. D.
Ionescu, M.
Liu, Hua-Kun
Dou, S. X.
Brandt, E. H.
Journal Article
10.1109/TASC.2003.812544
9635
2003-01-01T08:00:00Z
<p>This article was originally published as: Uprety, KK, Horvat, J, Wang, XL et al, Magnetic hysteresis and relaxation in Bi2212 single crystals doped with Fe and Pb, IEEE Transactions on Applied Superconductivity, June 2003, 13(2)3, 3770-3773. Copyright IEEE 2003.</p>
<p>Magnetic hysteresis and magnetic relaxation measurements have been performed to study vortex pinning behaviors for pure, Fe doped and heavily Pb doped Bi2212 single crystals. Unlike pure and Fe doped Bi2212 crystals, heavily Pb doped crystal showed strong vortex pinning behavior. We interpret the strong pinning in heavily Pb doped Bi2212 single crystals as arising from the improved Josephson coupling in Bi2212 single crystal after heavy Pb doping. In heavily Pb doped single Bi2212 crystals, H/sub dis/(T) was observed to decrease with increasing T. Here, H/sub dis/(T) is an order-disorder field that separates a weakly elastically disordered vortex lattice from a plastically disordered vortex solid. However, in pure and Fe doped Bi2212 single crystals, H/sub dis/(T) was observed to be temperature independent. We also report a significant shift of T/sub CR/, a crossover temperature separating two pinning regimes, toward higher temperatures with heavy Pb doping of Bi2212 single crystals. On the other hand T/sub CR/ did not shift with Fe doping of Bi2212 single crystals. It is argued that the temperature dependence of H/sub dis/(T) and the shift of T/sub CR/ in heavily Pb doped Bi2212 crystals was related to the enhanced c-axis conductivity caused by the Pb situated between the CuO/sub 2/ layers and imposing a 3D characteristic on the vortex lattice.</p>
Engineering
https://ro.uow.edu.au/engpapers/33
oai:ro.uow.edu.au:engpapers-1031
2013-09-24T04:56:07Z
publication:arozenfeld
publication:journal_articles
publication:eis
publication:engpapers
publication:engineering
publication:document_types
In vivo dosimetry and seed localization in prostate brachytherapy with permanent implants
Rosenfeld, Anatoly B.
Cutajar, Dean
Lerch, M. L.
Takacs, G. J.
Braddock, T.
Perevertailo, V. L.
Bucci, J.
Kearsley, J.
Zaider, M.
Zelefsky, M.
Journal Article
10.1109/TNS.2004.839089
10669
2004-12-01T08:00:00Z
<p>This article was originally published as: Rosenfeld, AB, Cutajar, DL, Lerch, MLF et al, In vivo dosimetry and seed localization in prostate brachytherapy with permanent implants, IEEE Transactions on Nuclear Science, December 2004, 51(6)1, 3013-3018. Copyright IEEE 2004.</p>
<p>This paper reports on the development of an interactive, intraoperative dose planning system for seed implant brachytherapy in cancer treatment. This system involves in vivo dosimetry and the ability to determine implanted seed positions. The first stage of this project is the development of a urethral alarm probe to measure the dose along the urethra during a prostate brachytherapy treatment procedure. Ultimately, the system will be used to advise the physicians upon reaching a preset dose rate or dose after total seed decay in the urethra during the seed placement. The second stage is the development of a method and instrumentation for in vivo measurements of the location of implanted seeds in the same frame as for dose planning and the use of these in intraoperative treatment planning. We have developed a silicon mini-detector, miniature front-end, and shaping amplifier with discriminator, connected to the mini-silicon detector at the end of a cable placed in a urological catheter, to satisfy the spectroscopic requirements of the urethral probe. This technique will avoid complications related to overdosing the urethra and the rectum.</p>
Engineering
https://ro.uow.edu.au/engpapers/32
oai:ro.uow.edu.au:engpapers-1027
2012-10-24T01:24:04Z
publication:journal_articles
publication:eis
publication:engpapers
publication:engineering
publication:document_types
Gaussian filters and filter synthesis using a Hermite/Laguerre neural network
Mackenzie, M.
Tieu, K.
Journal Article
10.1109/TNN.2003.820558
10657
2004-01-01T08:00:00Z
<p>This article was originally published as: Mackenzie, M and Tieu, K, Gaussian filters and filter synthesis using a Hermite/Laguerre neural network, IEEE Transactions on Neural Networks, January 2004, 15(1), 206-214. Copyright IEEE 2004.</p>
<p>A neural network for calculating the correlation of a signal with a Gaussian function is described. The network behaves as a Gaussian filter and has two outputs: the first approximates the noisy signal and the second represents the filtered signal. The filtered output provides improvement by a factor often in the signal-to-noise ratio. A higher order Gaussian filter was synthesized by combining several Hermite functions together.</p>
Engineering
https://ro.uow.edu.au/engpapers/28
oai:ro.uow.edu.au:engpapers-1029
2013-06-20T02:10:57Z
publication:arozenfeld
publication:journal_articles
publication:eis
publication:engpapers
publication:document_types
Neutron dosimetry with planar silicon p-i-n diodes
Rosenfeld, Anatoly B.
Yudelev, M.
Lerch, M. L.
Cornelius, I.
Griffin, P.
Perevertailo, V. L.
Anokhin, I. E.
Zinets, O. S.
Khivrich, V. I.
Pinkovskaya, M.
Alexiev, D.
Reinhard, M.
Journal Article
10.1109/TNS.2003.821390
9042
2003-01-01T08:00:00Z
<p>This article was originally published as: Rosenfeld, AB, Yudelev, M, Lerch, MLF et al, Neutron dosimetry with planar silicon p-i-n diodes, IEEE Transactions on Nuclear Science, December 2003, 50(6)1, 2367-2372. Copyright IEEE 2003.</p>
<p>New nonionizing energy losses (NIEL) sensors based on silicon planar p-i-n diodes of different geometry have been investigated and their response to fast neutron field compared with bulk diodes. The possibility of obtaining a wide range of sensitivities in these NIEL sensors simultaneously with measurements of IEL has been demonstrated.</p>
Engineering
https://ro.uow.edu.au/engpapers/30
oai:ro.uow.edu.au:engpapers-1030
2013-06-20T02:10:33Z
publication:arozenfeld
publication:journal_articles
publication:eis
publication:engpapers
publication:engineering
publication:document_types
Analysis of inelastic interactions for therapeutic proton beams using Monte Carlo simulation
Rosenfeld, Anatoly B.
Wroe, A. J.
Cornelius, I.
Reinhard, M.
Alexiev, D.
Journal Article
10.1109/TNS.2004.839072
10670
2004-01-01T08:00:00Z
<p>This article was originally published as: Rosenfeld, AB, Wroe, AJ, Cornelius, I et al, Analysis of inelastic interactions for therapeutic proton beams using Monte Carlo simulation, IEEE Transactions on Nuclear Science, December 2004, 51(6)1, 3019-3025. Copyright IEEE 2004.</p>
<p>The irradiation of various tissue-like materials by therapeutic proton beams was simulated using Monte Carlo. The contribution of inelastic reaction products to the depth-dose distribution was determined. The use of silicon microdosimeters for verifying Monte Carlo calculations was also investigated. The importance of these studies to Monte Carlo-based treatment planning systems is emphasized.</p>
Engineering
https://ro.uow.edu.au/engpapers/31
oai:ro.uow.edu.au:engpapers-1034
2013-05-21T04:16:51Z
publication:journal_articles
publication:hkliu
publication:eis
publication:engpapers
publication:sxdou
publication:engineering
publication:document_types
Calculation of the temperature dependent AC susceptibility of superconducting disks
Qin, M. J.
Li, G.
Liu, Hua-Kun
Dou, S. X.
Journal Article
10.1109/TASC.2003.812537
9646
2003-01-01T08:00:00Z
<p>This article was originally published as: Qin, MJ, Ki, G, Liu, HK & Dou, SX, Calculation of the temperature dependent AC susceptibility of superconducting disks, IEEE Transactions on Applied Superconductivity, June 2003, 13(2)3, 3742-3745. Copyright IEEE 2003.</p>
<p>The temperature dependent complex AC susceptibilities of high temperature superconducting disks in perpendicular AC magnetic fields (in absence of DC magnetic field) have been calculated from first principles. The temperature dependent AC susceptibilities for different AC field amplitudes, AC field frequencies, reduced pinning potential, and sample thickness have been derived, which demonstrate many features different from what has been observed in the configuration of infinite long slab or cylinder under a parallel-applied AC field. The results of such a realistic configuration of finite-thickness samples in perpendicular fields can be compared directly to the experimental results.</p>
Engineering
https://ro.uow.edu.au/engpapers/35
oai:ro.uow.edu.au:engpapers-1033
2013-05-21T04:17:19Z
publication:xlwang
publication:journal_articles
publication:hkliu
publication:ssoltanian
publication:eis
publication:jhorvat
publication:engpapers
publication:sxdou
publication:document_types
Transport critical current density in Fe-sheathed nano-SiC doped MgB/sub 2/ wires
Dou, S X
Horvat, J.
Soltanian, Saeid
Wang, Xiaolin
Qin, M. J.
Zhou, S. H.
Liu, Hua-Kun
Munroe, P. G.
Journal Article
10.1109/TASC.2003.812196
9636
2003-01-01T08:00:00Z
<p>This article was originally published as: Dou, SX, Horvat, J, Soltanian, S et al, Transport critical current density in Fe-sheathed nano-SiC doped MgB/sub 2/ wires, IEEE Transactions on Applied Superconductivity, June 2003, 13(2)3, 3199-3202. Copyright IEEE 2003.</p>
<p>The nano-SiC doped MgB/sub 2//Fe wires were fabricated using a powder-in-tube method and an in-situ reaction process. The depression of T/sub c/ with increasing SiC doping level remained rather small due to the counterbalanced effect of Si and C co-doping. The high level SiC co-doping allowed creation of the intra-grain defects and nano-inclusions, which act as effective pinning centers, resulting in a substantial enhancement in the J/sub c/(H) performance. The transport J/sub c/ for all the wires is comparable to the magnetic J/sub c/ at higher fields despite the low density of the samples and percolative nature of current. The transport I/sub c/ for the 10wt% SiC doped MgB/sub 2//Fe reached 660A at 5K and 4.5T (J/sub c/=133000A/cm/sup 2/) and 540A at 20K and 2T (J/sub c/=108000A/cm/sup 2/). The transport J/sub c/ for the 10wt% SiC doped MgB/sub 2/ wire is more than an order of magnitude higher than for the state-the-art Fe-sheathed MgB/sub 2/ wire reported to date at 5K and 10T and 20K and 5T respectively. There is a plenty of room for further improvement in J/sub c/ as the density of the current samples is only 50%.</p>
Engineering
https://ro.uow.edu.au/engpapers/34
oai:ro.uow.edu.au:engpapers-1038
2006-07-31T05:14:10Z
publication:journal_articles
publication:eis
publication:czhang
publication:engpapers
publication:engineering
publication:document_types
Terahertz-driven nonlinear electrical transport in semiconductor nanostructures
Zhang, C.
Journal Article
9660
2002-12-11T08:00:00Z
impurity scattering
laser beam effects
nanostructured materials
two-dimensional electron gas
This paper originally appeared in: Zhang, C, Terahertz-driven nonlinear electrical transport in semiconductor nanostructures, IEEE Conference on Optoelectronic and Microelectronic Materials and Devices, 11-13 December 2002, 405-408. Copyright IEEE 2002.
In this work, we used the quantum transport equation and density matrix formalism to calculate the frequency dependent electrical current of a two-dimensional electron gas directly driven by an intense terahertz laser. It is found that due to increased electron-photon coupling, the electron-impurity scattering decreases rapidly with the electric field.
Engineering
https://ro.uow.edu.au/engpapers/39
oai:ro.uow.edu.au:engpapers-1036
2006-07-31T05:13:07Z
publication:journal_articles
publication:hkliu
publication:eis
publication:jhorvat
publication:engpapers
publication:engineering
publication:document_types
A comparison of Ag and Ag-alloy sheathed Bi-2223 tapes
Liu, Hua-Kun
Zhang, Z. M.
Zeng, R.
Horvat, J.
Apperley, M.
Journal Article
10.1109/TASC.2003.812052
9644
2003-06-01T07:00:00Z
Ag and Ag-alloy sheath
Bi-2223 tape
mechanical properties
phase volume fraction
This article was originally published as: Liu, HK, Zhang, ZM, Zeng, R et al, A comparison of Ag and Ag-alloy sheathed Bi-2223 tapes, IEEE Transactions on Applied Superconductivity, June 2003, 13(2)3, 3004-3007. Copyright IEEE 2003.
Ag and Ag-alloy sheathed Bi-2223 tapes were fabricated by a powder-in-tube technique with different configurations of the precursor and restack sheath materials: Ag, AgAu7 wt%, AgSb0.6 wt%, AgMg0.2 wt%. Analysis of the I/sub c/ and volume fractions of the Bi-2223, Bi-2212, Bi-2201 and Bi-3221 phases indicated that volume fractions of Bi-2223>90%, Bi-2212/spl sim/5%, Bi-2201/spl sim/0% and Bi-3221<2%, normally result in tapes with the highest I/sub c/. The mechanical properties of the tapes revealed consistent results. Generally, the harder the sheath material, the higher tolerance to the bending strain and higher the tensile strength of the tape. The sequence of the alloys' hardness from highest to lowest was AgMg0.2 wt%, AgSb0.6 wt%, AgAu7 wt% or Ag.
Engineering
https://ro.uow.edu.au/engpapers/37
oai:ro.uow.edu.au:engpapers-1035
2013-05-21T04:16:19Z
publication:xlwang
publication:journal_articles
publication:hkliu
publication:ssoltanian
publication:eis
publication:jhorvat
publication:engpapers
publication:sxdou
publication:engineering
publication:document_types
Effect of grain size and doping level of SiC on the superconductivity and critical current density in MgB/sub 2/ superconductor
Soltanian, Saeid
Wang, Xiaolin
Horvat, J.
Qin, M. J.
Liu, Hua-Kun
Munroe, P. R.
Dou, S. X.
Journal Article
10.1109/TASC.2003.812223
9647
2003-01-01T08:00:00Z
critical current density
doping
magnesium
diboride
silicon carbide
<p>This article was originally published as: Soltanian, S, Wang, X, Horvat, J et al, Effect of grain size and doping level of SiC on the superconductivity and critical current density in MgB/sub 2/ superconductor, IEEE Transactions on Applied Superconductivity, June 2003, 13(2)3, 3273-3276. Copyright IEEE 2003.</p>
<p>SiC doped MgB/sub 2/ polycrystalline samples were fabricated by in-situ reaction using different grain sizes (20 nm, 100 nm, and 37 /spl mu/m) of SiC and different doping levels (0, 8, 10, 12, 15 wt%). Phases, microstructures, superconductivity, critical current density and flux pinning have been systematically investigated using XRD, SEM, TEM, and magnetic measurements. Results show that grain sizes of the starting precursors of SiC have a strong effect on the critical current density and its field dependence. The smaller the SiC grains are, the better the J/sub c/ field performance is. Significant enhancement of J/sub c/ and the irreversibility field H/sub irr/ were revealed for all the SiC doped MgB/sub 2/ with additions up to 15 wt%. A J/sub c/ as high as 20,000 A/cm/sup 2/ in 8 Tesla at 5 K was achieved for the sample doped with 10 wt% SiC with a grain size of 20 nm. Results indicate that the nano-inclusions and substitution inside MgB/sub 2/ are responsible for the enhancement of flux pinning.</p>
Engineering
https://ro.uow.edu.au/engpapers/36
oai:ro.uow.edu.au:engpapers-1037
2006-07-31T05:13:51Z
publication:journal_articles
publication:eis
publication:engpapers
publication:document_types
Hermite neural network correlation and application
Mackenzie, M. R.
Tieu, K.
Journal Article
10.1109/TSP.2003.819005
8998
2003-12-01T08:00:00Z
This article was originally published as: Mackenzie, M and Tieu, K, Hermite neural network correlation and application, IEEE Transactions on Signal Processing, December 2003, 51(12), 3210-3219. Copyright IEEE 2003.
A method for obtaining the correlation of two Hermite neural networks is developed. The method is based on the fact that a Hermite function is unchanged by the Fourier transform, which allows an expression for the correlation to be obtained directly from the network weights without the need for the Fourier transform. Comparative results with other neural network correlation methods are presented on simulated radar signals.
Engineering
https://ro.uow.edu.au/engpapers/38
oai:ro.uow.edu.au:engpapers-1039
2014-04-09T06:25:31Z
publication:arozenfeld
publication:journal_articles
publication:eis
publication:engpapers
publication:document_types
Nanodosimetric cluster size distributions of therapeutic proton beams
Wroe, Andrew J
Schulte, Reinhard
Bashkirov, Vladimir
Rosenfeld, Anatoly B.
Keeney, Brian
Spradlin, Patrick
Sadrozinski, Hartmut F. W
Grosswendt, Bernd
Journal Article
10.1109/TNS.2006.870445
17758
2004-01-01T08:00:00Z
Monte Carlo methods
biological effects of ionising particles
dosimetry
radiation therapy
<p>Rosenfeld, A., Wroe, A., Schulte, R., Bashkirov, V., Keeney, B., Spradlin, P., Sadrozinski, H. FW. & Grosswendt, B. (2006). Nanodosimetric cluster size distributions of therapeutic proton beams. IEEE Transaction on Nuclear Science, 53 (2), 532-538.</p>
<p>As we move into the new millennium, it is important that we improve our understanding of radiation effects on humans and nanoelectronic systems. This understanding is essential in a number of areas including radiation therapy for cancer treatment and extended human presence in outer space. Nanodosimetry in low-pressure gases enables measurement of the energy deposition of ionizing radiation on a scale equivalent to the dimensions of the DNA molecule. This is extremely important for not only biological applications but also electronic applications, as the effect of radiation on nanoelectronics needs to be determined before they are installed and deployed in complex radiation fields. However, before nanodosimetry can be widely applied, further investigation is required to link the output of gas-based nanodosimeters to the actual effect of the radiation on a biological or electronic system. The purpose of this research is to conduct nanodosimetric measurements of proton radiation fields at the proton accelerator of Loma Linda University Medical Center (LLUMC) and to develop a Monte Carlo simulation system to validate and support further developments of experimental nanodosimetry. To achieve this, measured ion cluster size distributions are compared to the output from the Monte Carlo simulation system that simulates the characteristics of the LLUMC beam line and the performance of the nanodosimeter installed on one of LLUMC's proton research beam lines.</p>
Engineering
https://ro.uow.edu.au/engpapers/40
oai:ro.uow.edu.au:engpapers-1040
2013-05-21T04:15:54Z
publication:xlwang
publication:eis
publication:conference_papers
publication:engpapers
publication:sxdou
publication:document_types
Absence of ferromagnetism and strong orbital coupling in carrier rich Zn/sub 1-x/In/sub x/Co/sub 0.075/O
Wang, Xiaolin
Peleckis, Germanas
Dou, S X
Conference Paper
2005-01-01T08:00:00Z
II-VI semiconductors
X-ray diffraction
carrier density
decomposition
electrical conductivity
indium compounds
magnetic moments
magnetisation
paramagnetic materials
semimagnetic semiconductors
wide band gap semiconductors
zinc compounds
<p>This paper originally appeared as: Wang, XL, Peleckis, G and Dou, SX, Absence of ferromagnetism and strong orbital coupling in carrier rich Zn/sub 1-x/In/sub x/Co/sub 0.075/O, Digests of the IEEE International Magnetics Conference, INTERMAG Asia 2005, 4-8 April 2005, 779-780. Copyright IEEE 2005.</p>
<p>Polycrystalline samples of Zn/sub 1-x/In/sub x/Co/sub 0.075/O (0.010/spl les/x/spl les/0.020) diluted magnetic semiconductors were prepared by the rapid oxalate decomposition technique. Phase purity is analyzed by means of X-ray diffraction technique and structures are refined by Rietveld refinement technique. Bulk conductivity of the polished pellets was measured by two-point probe technique at 295 K. Magnetic properties were analyzed with magnetic property measurement system. Samples show paramagnetic behavior and Curie-Weiss fitting at high temperature range gave effective magnetic moment of Co ions. Magnetization behavior caused by applied magnetic field was also investigated. High itinerant carrier concentration was achieved but no ferromagnetism was observed in the samples.</p>
Engineering
https://ro.uow.edu.au/engpapers/41
oai:ro.uow.edu.au:engpapers-1041
2006-07-31T05:15:55Z
publication:eis
publication:rlewis
publication:conference_papers
publication:engpapers
publication:document_types
Selective laser excitation spectroscopy of gallium and phosphorous in germanium
Freeth, C. A.
Lewis, R. A.
Conference Paper
9675
2002-12-11T08:00:00Z
Zeeman effect
elemental semiconductors
gallium
germanium
impurity absorption spectra
impurity states
infrared spectra
laser beam applications
phosphorus
photoexcitation
resonance
This paper originally appeared as: Freeth, CA and Lewis, RA, Selective laser excitation spectroscopy of gallium and phosphorous in germanium, Conference on Optoelectronic and Microelectronic Materials and Devices, 11-13 December 2002, 447-450. Copyright IEEE 2002.
Shallow impurity states of donors and acceptors in Ge have been investigated by far-infrared laser magnetospectroscopy. The Zeeman splitting of the impurity states produces resonant absorption of the laser radiation at certain magnetic fields. The data are compared to measurements made using a conventional spectrometer and good agreement is found.
Engineering
https://ro.uow.edu.au/engpapers/42
oai:ro.uow.edu.au:engpapers-1042
2013-05-21T04:15:17Z
publication:xlwang
publication:eis
publication:rlewis
publication:conference_papers
publication:engpapers
publication:sxdou
publication:engineering
publication:document_types
Infrared-active phonons of HoMn/sub 1-x/Co/sub x/O/sub 3/ (x = 0-0.8)
Gao, Feng
Wang, Xiaolin
Farhoudi, M Mehdi
Lewis, R. A.
Dou, S. X.
Conference Paper
10.1109/INTMAG.2005.1464165
2005-01-01T08:00:00Z
<p>This paper originally appeared as: Gao, F, Wang, XL, Farhoudi, M et al, Infrared-active phonons of HoMn/sub 1-x/Co/sub x/O/sub 3/ (x = 0-0.8), INTERMAG Asia 2005. Digests of the IEEE International Magnetics Conference, 4-8 April 2005, 1471-1472. Copyright IEEE 2005.</p>
<p>Polycrystalline HoMn/sub 1-x/Co/sub x/O/sub 3/ was synthesized by solid-state reaction. The infrared active phonons of the samples were investigated. The infrared transmission spectra of the sample at x = 0-0.8 doping level was also measured at room temperature. Also, X-ray diffraction (XRD) was used to analyze the crystal structure of the samples.</p>
Engineering
https://ro.uow.edu.au/engpapers/43
oai:ro.uow.edu.au:engpapers-1043
2014-01-24T00:58:48Z
publication:arozenfeld
publication:journal_articles
publication:eis
publication:engpapers
publication:engineering
publication:document_types
In vivo dosimetry and seed localization in prostate brachytherapy with permanent implants
Rosenfeld, Anatoly B.
Cutajar, Dean
Lerch, M. L.
Takacs, G. J.
Brady, J.
Braddock, T.
Perevertailo, V.
Bucci, J.
Kersley, J.
Zaider, M.
Zelefsky, M.
Journal Article
10.1109/TNS.2004.839089
10669
2004-01-01T08:00:00Z
amplifiers
brachytherapy
cancer
catheters
discriminators
dosimetry
nuclear electronics
prosthetics
silicon radiation detectors
<p>Rozenfeld, A., Cutajar, D., Lerch, M. L., Takacs, G. J., Brady, J., Braddock, T., Perevertaylo, V. L. & Bucci, J. (2004). In Vivo Dosimetry and Seed Localization in Prostate Brachytherapy with Permanent Implants. IEEE Transaction on Nuclear Science, 51 3013-3018.</p>
<p>This paper reports on the development of an interactive, intraoperative dose planning system for seed implant brachytherapy in cancer treatment. This system involves in vivo dosimetry and the ability to determine implanted seed positions. The first stage of this project is the development of a urethral alarm probe to measure the dose along the urethra during a prostate brachytherapy treatment procedure. Ultimately, the system will be used to advise the physicians upon reaching a preset dose rate or dose after total seed decay in the urethra during the seed placement. The second stage is the development of a method and instrumentation for in vivo measurements of the location of implanted seeds in the same frame as for dose planning and the use of these in intraoperative treatment planning. We have developed a silicon mini-detector, miniature front-end, and shaping amplifier with discriminator, connected to the mini-silicon detector at the end of a cable placed in a urological catheter, to satisfy the spectroscopic requirements of the urethral probe. This technique will avoid complications related to overdosing the urethra and the rectum.</p>
Engineering
https://ro.uow.edu.au/engpapers/44
oai:ro.uow.edu.au:engpapers-1044
2012-10-24T03:07:37Z
publication:xlwang
publication:eis
publication:conference_papers
publication:engpapers
publication:document_types
Structures, spin glass and spin states in perovskite GdMn/sub x/Co/sub 1-x/O/sub 3/ (x /spl les/ 0.5)
Farhoudi, M Mehdi
Wang, Xiaolin
Conference Paper
25199
2005-04-01T08:00:00Z
X-ray diffraction
ceramics
crystal structure
ferromagnetic materials
gadolinium compounds
lattice constants
magnetic susceptibility
magnetic transitions
spin glasse
valency
<p>This paper originally appeared as: Farhoudi, MM and Wang, XL, Structures, spin glass and spin states in perovskite GdMn/sub x/Co/sub 1-x/O/sub 3/ (x /spl les/ 0.5), INTERMAG Asia 2005. Digests of the IEEE International Magnetics Conference, 4-8 April 2005, 1679-1680. Copyright IEEE 2005.</p>
<p>The structures, ferromagnetism, spin glass and spin states of Co and Mn in a polycrystalline ceramic samples of GdCo/sub 1-x/Mn/sub x/O/sub 3/ (x = 0.2, 0.3, 0.4, 0.5) are presented. X-ray diffraction show that all the samples are single phase and crystallize as orthorhombic structures and that the lattice parameters gradually increase with x. Spin glass state and two peak features (corresponding to first order ferromagnetic and second order transition) in dc and ac susceptibility are observed. Curie-Wise fitting on the inverse susceptibility-temperature plots indicates that the valences of Co or Mn changed from 2+ or 4+ to 3+ when Co amount increases. Possible spin state transformation of Co and Mn is also suggested.</p>
Engineering
https://ro.uow.edu.au/engpapers/45
oai:ro.uow.edu.au:engpapers-1045
2013-02-01T02:42:08Z
publication:eis
publication:infopapers
publication:conference_papers
publication:engpapers
publication:engineering
publication:document_types
Accelerated iterative blind deconvolution of still images
Premaratne, Prashan
Premaratne, M.
Conference Paper
2003-10-15T07:00:00Z
convergence of numerical methods
deconvolution
image denoising
image restoration
iterative methods
optical transfer function
<p>This paper originally appeared as: Premaratne, P and Premaratne, M, Accelerated iterative blind deconvolution of still images, TENCON 2003. Conference on Convergent Technologies for the Asia-Pacific Region, 15-17 October 2003, vol 1, 6-10. Copyright IEEE 2003.</p>
<p>We propose an approach for blind deconvolution of still images with moderate noise contamination. The iterative technique is based on the general concepts of iterative techniques for blind deconvolution. The ill-convergence problem associated with most of the iterative techniques is circumvented in our approach using zero-sheet separation techniques. This technique can handle real images blurred by complex point spread functions (PSF), which is a common imaging problem, with blur signal-to-noise ratios (BSNR) of 70 dB and above for PSF of size 32/spl times/32 and larger. The technique performs much better for PSF of smaller sizes with low BSNR around 30 dB and provides convergence of the final solution with minimum iterations and is also capable of determining the size of the PSF.</p>
Engineering
https://ro.uow.edu.au/engpapers/46
oai:ro.uow.edu.au:engpapers-1047
2006-08-01T01:02:13Z
publication:journal_articles
publication:eis
publication:engpapers
publication:engineering
publication:document_types
Spectral characterization of broadband THz antennas by photoconductive mixing: toward optimal antenna design
Mendis, Rajind
Sydlo, C.
Sigmund, J.
Feiginov, M
Meissner, P.
Hartnagel, H. L.
Journal Article
10.1109/LAWP.2005.844650
14206
2005-01-01T08:00:00Z
broadband antennas
log periodic antennas
microwave photonics
multiwave mixing
optimisation
planar antenna arrays
resonance
submillimetre wave antennas
This paper originally appeared as: Mendis, R, Sydlo, C and Sigmund, J et al, Spectral characterization of broadband THz antennas by photoconductive mixing: toward optimal antenna design, Antennas and Wireless Propagation Letters, 2005, vol 4, 85-88. Copyright IEEE 2005.
The spectral characterization of a broadband antenna using a pump-probe photomixing continuous-wave (CW) terahertz (THz) system is presented. The high dynamic range of the system, comparable to or better than that of similar pump-probe systems reported in the literature, provides an accurate means of antenna characterization. The planar antenna exhibits a log-periodic behavior at low frequencies, a bow-tie behavior at high frequencies, and a resonance characteristic in between, well in agreement with the antenna geometry. It is predicted that an improved geometry that extends the log-periodic behavior to higher frequencies would contribute significantly in enhancing the broadband performance of antenna-coupled photomixers.
Engineering
https://ro.uow.edu.au/engpapers/48
oai:ro.uow.edu.au:engpapers-1049
2013-05-21T04:14:52Z
publication:eis
publication:rlewis
publication:conference_papers
publication:czhang
publication:engpapers
publication:engineering
publication:document_types
Thermal and electrical characteristics of a multilayer thermionic device
Lough, B. C.
Lee, S. P.
Dou, Z.
Lewis, R. A.
Zhang, C.
Conference Paper
9655
2002-01-01T08:00:00Z
<p>This paper originally appeared as: Lough, BCC, Lee, SP, Dou, Z et al., Thermal and electrical characteristics of a multilayer thermionic device, Conference on Optoelectronic and Microelectronic Materials and Devices, 11-13 December 2002, 511-514. Copyright IEEE 2002.</p>
<p>We report our recent experimental and numerical investigation into the thermal and electrical transport in GaAs-AlGaAs semiconductor multilayer structures. Electrical and thermal conduction measurements were performed on multilayer structures to determine the temperature gradient across the sample. AuGe was used for top contact metallisation, and an InGa eutectic for bottom substrate contact. Metallisation contacts were also grown directly onto the substrate in order to compare results with and without the device included. By using a variable load resistor connected in series with the device, we can accurately determine the current-voltage characteristics of the device. Thus the power input can be obtained. The temperature distribution on the top and bottom substrate was measured with micro thermocouples. Since the cooling device is grown on an n-type semiconductor substrate the effects of joule heating in the substrate had to be considered. Treating the substrate as bulk material and calculating joule heating showed that this effect is negligible. Comparing experimental measurements of the device and of the substrate alone support this. The experimental I-V characteristics of the device differ significantly in shape from theoretical I-V characteristics. This may be due to that fact that space-charge effects are not included in the currently accepted model (Richardson's equation). Due to the small size of the devices and therefore very large electric fields, this effect may be important. Work is currently being carried out to modify the model. The devices studied so far have been made from undoped GaAs-AI/sub 0.07/Ga/sub 0.03/As heterostructures. For large cooling power it is a requirement that the conduction band of the layers be close to the Fermi level.</p>
Engineering
https://ro.uow.edu.au/engpapers/50
oai:ro.uow.edu.au:engpapers-1048
2013-06-20T02:08:54Z
publication:arozenfeld
publication:eis
publication:conference_papers
publication:engpapers
publication:document_types
Readout of LYSO using a new silicon photodetector for positron emission tomography
Lerch, M. L.
Ward, R.
Simmonds, Philip E
Perevertailo, V. L.
Meikle, S. R.
Taylor, G. N.
Rosenfeld, Anatoly B.
Conference Paper
10683
2003-01-01T08:00:00Z
<p>This article was originally published as: Lerch, MLF, Ward, R, Simmonds, PE et al, Readout of LYSO using a new silicon photodetector for positron emission tomography, IEEE Nuclear Science Symposium, 19-25 October 2003, vol 2, 1408-1412. Copyright IEEE 2003.</p>
<p>This article focuses on the characterisation of three versions of a custom designed silicon photodetector using nuclear spectroscopy techniques. Room temperature gamma ray spectroscopy experiments have been performed using an LYSO excited by /sup 137/Cs and /sup 22/Na sources and read out by the new photodiodes. We have measured an energy resolution of 13.1% FWHM for the 511 keV gamma rays from a /sup 22/Na source and 11.2% FWHM for the 662 keV gamma rays from a /sup 137/Cs source. This is one of the best ever-reported energy resolutions for a lutetium based scintillator crystal read out by a silicon photodetector.</p>
Engineering
https://ro.uow.edu.au/engpapers/49
oai:ro.uow.edu.au:engpapers-1052
2013-05-21T04:13:25Z
publication:journal_articles
publication:eis
publication:engpapers
publication:sxdou
publication:engineering
publication:document_types
A non-destructive, non-contact, quality test of critical current for Ag-BiSCCO tape
Gandini, A.
Weinstein, R.
Parks, D.
Sawh, R.
Dou, S. X.
Journal Article
10.1109/TASC.2003.812305
9639
2003-01-01T08:00:00Z
<p>This paper originally appeared as: Gandini, A, Weinstein, R, Park, D et al, A non-destructive, non-contact, quality test of critical current for Ag-BiSCCO tape, IEEE Transactions on Applied Superconductivity, June 2003, 13(2)3, 3332-3334. Copyright IEEE 2003.</p>
<p>An accurate noncontact method of characterizing Ag-BiSCCO tape is reported, using the trapped field, B/sub t/, of a field-cooled tape. The dimensions of the tape make it possible to calculate in closed form a very simple expression, relating trapped field to transport current. Short lengths of tape, 4 cm, are used to experimentally confirm the model. The model applies to any length of tape for which length is greater than 5 times the tape width. A schematic of a proposed test apparatus is presented which should permit on-line testing for magnitude of the current, and for cracks, while the tape is in motion during production.</p>
Engineering
https://ro.uow.edu.au/engpapers/53
oai:ro.uow.edu.au:engpapers-1050
2013-05-21T04:14:25Z
publication:journal_articles
publication:hkliu
publication:eis
publication:engpapers
publication:sxdou
publication:document_types
Comparative studies on “sandwich” rolling and flat rolling in processing Ag/Bi-2223 tapes
Chen, W. M.
Guo, Y. C.
Fu, X. K.
Liu, Hua-Kun
Dou, S. X.
Apperley, M.
Journal Article
10.1109/77.919880
6475
2001-01-01T08:00:00Z
<p>This paper originally appeared as: Chen WM, Guo, YC, Fu, XK et al, Comparative studies on “sandwich” rolling and flat rolling in processing Ag/Bi-2223 tapes, IEEE Transactions on Applied Superconductivity, March 2001, 11(1)3, 3752-3755. Copyright IEEE 2001.</p>
<p>The normal rolling method is commonly used for intermediate mechanical deformation in the powder-in-tube process to make Ag-clad Bi-based superconducting tapes. To compare the effects of different reduction processing on the superconducting properties of Ag/Bi-2223 tapes, the reduction rate dependence of the critical current densities J c of tapes processed by three methods, including normal rolling, pressing and “sandwich” rolling, has been systematically studied. Experimental results show that Jc dependence on the reduction rate for the three processes follows the same law. There is an optimal reduction rate in each case, which gives the highest physical density and the highest Jc. When the reduction rate increases, Jc initially increases, reaches a maximum and then diminishes. The density-reduction rate follows a corresponding trend. However, the maximum Jc of the Ag/Bi-2223 tapes made using “sandwich” rolling is 35% higher than is the case for normal rolling even though the tapes in both cases have the same density of the oxide core. XRD analysis shows that the significant difference in Jc of tapes processed using the three different intermediate deformation procedures cannot be attributed to the phase composition. SEM images show that normally rolled tapes have much higher density of microcracks than “sandwich” rolled tapes. It is evident that the Jc of a tape is strongly dependent on oxide core density and deformation procedure.</p>
Engineering
https://ro.uow.edu.au/engpapers/51
oai:ro.uow.edu.au:engpapers-1051
2013-05-21T04:13:58Z
publication:journal_articles
publication:eis
publication:engpapers
publication:sxdou
publication:document_types
Improved in-field behaviour of uranium doped BiSCCO tapes by enhanced flux pinning
Tonies, S.
Weber, H. W.
Guo, Y. C.
Dou, S. X.
Sawh, R.
Weinstein, R.
Journal Article
10.1109/77.919923
6478
2001-01-01T08:00:00Z
<p>This paper originally appeared as: Tonies, S, Weber, HW, Guo, YC et al, Improved in-field behaviour of uranium doped BiSCCO tapes by enhanced flux pinning, IEEE Transactions on Applied Superconductivity, March 2001, 11(1)3, 3904-3907. Copyright IEEE 2001.</p>
<p>Uranium doped BiSCCO 2223 tapes were irradiated by thermal neutrons. The resulting fission-induced defects improve flux pinning and shift the irreversibility line to higher fields. Significant enhancements of the transport critical current density as well as a reduction of the Jc-anisotropy are found for the irradiated samples. Furthermore, inter- and intragranular critical current densities were determined from the remanent magnetic moments by SQUID magnetometry.</p>
Engineering
https://ro.uow.edu.au/engpapers/52
oai:ro.uow.edu.au:engpapers-1053
2013-05-21T04:12:41Z
publication:journal_articles
publication:eis
publication:engpapers
publication:sxdou
publication:document_types
On the limiting mechanism of irradiation enhancement of I/sub c/
Gandini, A.
Weinstein, R.
Parks, D.
Sawh, R.
Dou, S. X.
Journal Article
10.1109/TASC.2003.812058
9640
2003-01-01T08:00:00Z
<p>This paper originally appeared as: Gandini, A, Weinstein, R, Parks, D et al, On the limiting mechanism of irradiation enhancement of I/sub c/, IEEE Transactions on Applied Superconductivity, June 2003, 13(2)3, 2934-2936. Copyright IEEE 2003.</p>
<p>Irradiation may significantly increase I/sub c/ in HTS. A systematic pattern occurs: R=I/sub c/(afterirr.)/I/sub c/(beforeirr.) increases at low defect density, d. It reaches a peak, and then it falls below 1 at high d. The pinning center mechanism, which causes R to increase, has been extensively studied. The falloff in R has not. It has been considered a secondary effect. Here, we will show that the fall-off plays an important role in determining the maximum I/sub c/ enhancement achievable. A phenomenological model to describe the R-vs.-d curve, over the entire d range, is proposed. The idea is that R is the product of two competing effects. (i) Irradiation damage acts as pinning centers, hence increases critical current density, J/sub c/. (ii) Damage reduces the flow-area. Hence, it decreases the net critical current. Data on U/n processed Bi-2223 tapes are fitted to this model. The fitting indicates: (1) the reduction of the flow-area accounts for the majority of the R falloff; and (2) It is sufficient to describe J/sub c/ enhancement as linear with d, and it depending on field and temperature only through the ratio b=B/B/sub irr/, where B/sub irr/ is the irreversible field before irradiation.</p>
Engineering
https://ro.uow.edu.au/engpapers/54
oai:ro.uow.edu.au:engpapers-1055
2013-05-21T04:10:49Z
publication:journal_articles
publication:hkliu
publication:eis
publication:engpapers
publication:sxdou
publication:engineering
publication:document_types
Effects of the field dependent J/sub c/ on the vertical levitation force between a superconductor and a magnet
Li, G.
Qin, M. J.
Liu, Hua-Kun
Dou, S. X.
Journal Article
10.1109/TASC.2003.813019
9643
2003-01-01T08:00:00Z
<p>This paper originally appeared as: Li, G, Qin, MJ, Liu, HK et al, Effects of the field dependent J/sub c/ on the vertical levitation force between a superconductor and a magnet, IEEE Transactions on Applied Superconductivity, June 2003, 13(2)2, 2142-2145. Copyright IEEE 2003.</p>
<p>The vertical levitation force between a superconductor disk (SC) and a permanent magnet disk (PM) has been calculated from first principles using different J/sub c/(B) relationships of the magnetic field. Based upon the first principles, the current distribution inside the SC induced by the applied inhomogeneous magnetic field generated by the PM and the field profiles have been calculated with a power law E /spl sim/ J relationship: E(J) = E/sub c/(J/J/sub c/(B))/sup n/. The levitation force is highly hysteretic for the approaching and the retreating branches. The saturated current value, magnetization, and levitation force are found to depend strongly on the J/sub c/(B) relations. Features of the supercurrent distribution, the force loop, and the levitation force density are discussed.</p>
Engineering
https://ro.uow.edu.au/engpapers/56
oai:ro.uow.edu.au:engpapers-1054
2014-05-12T04:37:27Z
publication:journal_articles
publication:eis
publication:engpapers
publication:sxdou
publication:document_types
Developments in high temperature superconductivity
Silver, Tania M
Pan, A. V.
Ionescu, M.
Qin, M. J.
Dou, S. X.
Journal Article
10.1039/b111186h
2002-01-01T08:00:00Z
<p>This article was originally published as: Silver, T, Pan, AV, Ionescu, M et al, Developments in high temperature superconductivity, Annual Reports on the Progress of Chemistry, Section C Physical Chemistry, 2002, vol 98, 323-373. Reproduced by permission of the Royal Society of Chemistry. This pdf may not be further made available or distributed.</p>
<p>The past four years (1997–2001) have seen many exciting developments in high temperature superconductivity, most notably the discovery of the superconducting nature of magnesium boride in 2001 and the amazing critical temperatures of 52 K, then 117 K, achieved in 2000 by hole doping C60 fullerenes through incorporation into a field effect transistor (FET). Steady progress has also been made in understanding the recently discovered rutheno-cuprate superconducting ferromagnets. Theoretical work over this period has been focused on understanding the pseudogap in high temperature superconductors and on determining the mechanism behind superconductivity in MgB2.</p>
Engineering
https://ro.uow.edu.au/engpapers/55
oai:ro.uow.edu.au:engpapers-1056
2013-05-21T04:10:21Z
publication:journal_articles
publication:eis
publication:engpapers
publication:sxdou
publication:engineering
publication:document_types
Mechanisms of limitation and nature of field dependence of critical current in HTS epitaxial YBaCuO films
Pan, V. M.
Pashitskii, E. A.
Ryabchenko, S. M.
Komashko, V. A.
Pan, A. V.
Dou, S. X.
Semenov, A. V.
Tretiatchenko, C. G.
Fedotov, Y. V.
Journal Article
10.1109/TASC.2003.812523
11388
2003-01-01T08:00:00Z
<p>This paper originally appeared as: Pan, VM, Pashitskii, EA, Ryabchenko, SM et al, Mechanisms of limitation and nature of field dependence of critical current in HTS epitaxial YBaCuO films, IEEE Transactions on Applied Superconductivity, June 2003, 13(2)3, 3714-3717. Copyright IEEE 2003.</p>
<p>Magnetic field and temperature dependencies of the critical current density, J/sub c/(H/spl par/c, T) were measured by SQUID-magnetometry, ac magnetic susceptibility, and dc transport current techniques in the single-crystalline epitaxially-grown by off-axis dc magnetron sputtering YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) films with J/sub c/(H/spl par/c, 77 K) /spl ges/ 2 /spl middot/ 10/sup 6/ A/cm/sup 2/. The mechanism of vortex depinning from growth-induced linear defects, i.e., out-of-plane edge dislocations in low-angle tilt domain boundaries, is shown to describe quantitatively measured J/sub c/(H/spl par/c, T). The developed model takes into account a statistical distribution of the dislocation domain boundaries ordered in a network as well as the interdislocation spacing within boundaries. Actual structural features of YBCO film known from HREM data turn out to be extracted from J/sub c/(H/spl par/c, T)-curves by a fitting procedure within the proposed model.</p>
Engineering
https://ro.uow.edu.au/engpapers/57
oai:ro.uow.edu.au:engpapers-1057
2013-05-21T04:09:54Z
publication:journal_articles
publication:eis
publication:jhorvat
publication:engpapers
publication:sxdou
publication:engineering
publication:document_types
Effect of carbon nanotube size on superconductivity properties of MgB/sub 2/
Yeoh, W. K.
Horvat, J.
Dou, S X
Munroe, P.
Journal Article
10.1109/TASC.2005.848853
13708
2005-01-01T08:00:00Z
<p>This paper originally appeared as: Yeoh, WK, Horvat, J, Dou, SE et al, Effect of carbon nanotube size on superconductivity properties of MgB/sub 2/, IEEE Transactions on Applied Superconductivity, June 2005, 15(2), 3284-3287. Copyright IEEE 2005.</p>
<p>Experimental results are presented for the incorporation of carbon nanotube in polycrystalline MgB/sub 2/ superconductor based on X-ray diffraction and transmission electron microscopy measurements. Electron microscopy studies show that nanotubes are embedded into the MgB/sub 2/ matrix with a fraction of nanotubes found to be unreacted and entangled. In contrast, magnetization measurements indicate a change in the critical current density with the length of nanotubes and not with their outside diameter. This implies that longer nanotubes tend to entangle, preventing their homogenous mixing with MgB/sub 2/ and dispersion. Overall, carbon nanotube doping of MgB/sub 2/ enhanced the critical density and depressed the critical temperature.</p>
Engineering
https://ro.uow.edu.au/engpapers/58
oai:ro.uow.edu.au:engpapers-1058
2014-05-12T04:37:57Z
publication:xlwang
publication:journal_articles
publication:hkliu
publication:eis
publication:engpapers
publication:sxdou
publication:document_types
Microstructures and enhancement of critical current density in YBa/sub 2/Cu/sub 3/O/sub 7/ thin films grown by pulsed laser deposition on various single crystal substrates modified by Ag nano-dots
Li, Aihua
Ionescu, M.
Liu, Hua-Kun
Silver, Tania M
Wang, Xiaolin
Dou, S. X.
Journal Article
10.1109/TASC.2005.848731
13679
2005-01-01T08:00:00Z
<p>This paper originally appeared as: Li, AH, Ionescu, M, Liu, HK et al, Microstructures and enhancement of critical current density in YBa/sub 2/Cu/sub 3/O/sub 7/ thin films grown by pulsed laser deposition on various single crystal substrates modified by Ag nano-dots, IEEE Transactions on Applied Superconductivity, June 2005, 15(2), 3046-3049. Copyright IEEE 2005.</p>
<p>YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7</sub> (Y123) thin films were grown by pulsed laser deposition (PLD) on YSZ (100), SrTiO3 (100), and LaAlO3 (100) single crystal substrates. Prior to the film deposition, a discontinuous layer of Ag nano-dots was deposited on the substrates. The Y123 films grown on such surfaces modified with Ag nano-dots were characterized by Atomic Force Microscopy (AFM), X-ray diffraction (XRD), scanning electron microscopy (SEM), AC susceptibility and DC magnetization. The effects of the density of Ag nano-dots, which was controlled by the numbers of PLD shots, on the microstructures and resultant critical current density J<sub>c</sub> have been studied systematically. Results showed that at fixed physical deposition conditions J<sub>c</sub> increased monotonically with number of Ag shots, n, for films grown on both STO and LAO substrates. At 77 K, the J<sub>c</sub> increased from 10<sup>6</sup> to 3.2×10<sup>6</sup> A/cm<sup>2</sup> for LAO and from 8×10<sup>5</sup> to 3.5×106 A/cm<sup>2</sup> for STO as n increased from 0 to 150. At 5 K, the enhancement of J<sub>c</sub> was approximately four times at both low and high fields. However, for films grown on YSZ substrate, J<sub>c</sub> increased from 2×10<sup>5</sup> to 2×10<sup>6</sup> A/cm<sup>2</sup> as Ag shots increased from 0 to 30, and decreased to 9×10<sup>5</sup> for n≥60. Detailed microstructure investigations indicated that the crystallinity and ab alignment gradually improved as the number of Ag-nano-dots increased.</p>
Engineering
https://ro.uow.edu.au/engpapers/59
oai:ro.uow.edu.au:engpapers-1059
2013-05-21T04:09:02Z
publication:journal_articles
publication:eis
publication:engpapers
publication:sxdou
publication:document_types
Observation of vortex distribution in samples of Bi-2223 Ag-sheathed tapes with and without uranium doping by means of the high-resolution Bitter method
Ohshima, S.
Ujiie, K.
Kawai, T.
Moriai, K.
Yamada, H.
Marinaro, D. G.
Dou, S. X.
Journal Article
10.1109/TASC.2003.812073
9648
2003-01-01T08:00:00Z
<p>This article was originally published as: Ohshima, S, Ujiie, K, Kawai, T et al, Observation of vortex distribution in samples of Bi-2223 Ag-sheathed tapes with and without uranium doping by means of the high-resolution Bitter method, IEEE Transactions on Applied Superconductivity, June 2003, 13(2)3, 2953-2955. Copyright IEEE 2003.</p>
<p>We examined the distribution of vortices in both Bi-2223 Ag-sheathed tape and U-doped Bi-2223 Ag-sheathed tape applying the high-resolution Bitter method. In the low temperature region (T/spl Lt/T/sub c/), we found that the vortices in the undoped Bi-2223 Ag-sheathed tape developed into either a triangular arrangement or a heterogeneous arrangement along the grain boundaries of the Ag sheath, which form weak pinning centers. The vortex distribution for U-doped Bi-2223 samples was slightly different from the distribution for the undoped material. We observed some movement of the vortices in both the U-doped and the undoped Bi-2223 Ag-sheathed tapes at 50 K. At higher temperatures, T>75 K, the vortices in the Bi-2223 tapes moved even faster so that no deposition pattern, indicating the location for vortices, formed.</p>
Engineering
https://ro.uow.edu.au/engpapers/60
oai:ro.uow.edu.au:engpapers-1060
2006-08-01T01:07:04Z
publication:eis
publication:rlewis
publication:conference_papers
publication:engpapers
publication:document_types
Characterisation of indium phosphide using terahertz radiation
Causley, R. L.
Lewis, R. A.
Conference Paper
6525
2000-07-03T07:00:00Z
III-V semiconductors
carrier density
impurity absorption spectra
impurity states
indium compounds
infrared spectra
phonon spectra
reflectivity
This paper originally appeared as: Causley, RL & Lewis, RA, Characterisation of indium phosphide using terahertz radiation, International Semiconducting and Insulating Materials Conference, 3-7 July 2000, 101-104. Copyright IEEE 2000.
Specimens of undoped, n-type and p-type bulk InP have been investigated using THz radiation. Reflection spectroscopy permits the determination of the TO and LO phonon energies as well as the carrier concentration. Absorption spectroscopy reveals transitions between impurity states. We report the first absorption spectrum of an acceptor in InP. The transition energies agree well with electronic Raman scattering and photoluminescence data.
Engineering
https://ro.uow.edu.au/engpapers/61
oai:ro.uow.edu.au:engpapers-1061
2006-08-01T01:06:43Z
publication:eis
publication:conference_papers
publication:engpapers
publication:engineering
publication:document_types
Population inversion in an optically-pumped single quantum well
Green, T. J.
Xu, W.
Conference Paper
2000-07-03T07:00:00Z
III-V semiconductors
aluminium compounds
electron density
gallium arsenide
interface states
laser theory
optical pumping
population inversion
quantum well lasers
semiconductor device models
semiconductor quantum wells
This paper originally appeared as: Green, TJ & Xu, W, Population inversion in an optically-pumped single quantum well, International Semiconducting and Insulating Materials Conference, 3-7 July 2000, 224-227. Copyright IEEE 2000.
An optically-pumped intersubband laser generator is proposed in which the continuum states above an Al0.2Ga0.8As-GaAs-Al0.2Ga0.8 As single quantum well with a width of L=17 nm serve as the highest level in a four-level laser system. The design allows much greater flexibility in the choice of pumping source and simplifies considerably the device fabrication. We have obtained the electrode subband structure of the proposed device and utilized a simple rate equation approach to examine the electron density in different states under optical pumping.
Engineering
https://ro.uow.edu.au/engpapers/62
oai:ro.uow.edu.au:engpapers-1062
2006-08-01T01:06:18Z
publication:eis
publication:rlewis
publication:conference_papers
publication:czhang
publication:engpapers
publication:engineering
publication:document_types
Thermionic cooling of optoelectronic and microelectronic devices
Lee, S. P.
Lough, B. C.
Lewis, R. A.
Zhang, C.
Conference Paper
15083
2000-12-06T08:00:00Z
III-V semiconductors
aluminium compounds
cooling
digital simulation
gallium arsenide
optoelectronic devices
semiconductor device models
semiconductor heterojunctions
thermionic electron emission
This paper originally appeared as: Lee, SP, Lough, BC, Lewis, RA & Zhang, C, Thermionic cooling of optoelectronic and microelectronic devices, COMMAD 2000. Proceedings Conference on Optoelectronic and Microelectronic Materials and Devices, 6-8 December 2000, 415-418. Copyright IEEE 2000.
Solid-state thermionic cooling has gained attention recently because of its potential high cooling power. Thermionic devices based on semiconductor heterostructures utilize the band-edge offset at a heterojunction as the thermionic emission potential barrier and a thin layer to separate the cold and hot junction. In this paper, we present the behavior of thermionic coolers with periodic barriers using gallium arsenide/aluminium gallium arsenide (GaAs/Al/sub x/Ga/sub 1-x/As) semiconductor heterostructures. The exact numerical calculation to model the device performance has shown that the thermal efficiency in a multilayer structure is optimised when the effect of phonon scattering is introduced in the model. Besides, the thermal efficiency depends critically on applied bias.
Engineering
https://ro.uow.edu.au/engpapers/63
oai:ro.uow.edu.au:engpapers-1064
2013-06-20T02:07:56Z
publication:arozenfeld
publication:eis
publication:conference_papers
publication:engpapers
publication:engineering
publication:document_types
Design and simulation of continuous scintillator with pixellated photodetector
Takacs, G. J.
Rosenfeld, Anatoly B.
Lerch, M. L.
Lindsay, S. W.
Taylor, G. N.
Meikle, S. R.
Eberl, S.
Perevertailo, V. L.
Conference Paper
10.1109/NSSMIC.2000.949306
2000-01-01T08:00:00Z
<p>This paper originally appeared as: Takacs, GJ, Rosenfeld, AB, Lerch, MLF et al, Design and simulation of continuous scintillator with pixellated photodetector, IEEE Nuclear Science Symposium Conference Record, 15-20 October 2000, vol 3, 20/20-20/24. Copyright IEEE 2000.</p>
<p>Presents results of simulations performed as part of the development of a gamma-ray detector module comprising a non-pixellated scintillator and pixellated photodiode detector. The simulations have been carried out to determine the effect of surface treatment and dimensions of the scintillator on the ability to determine to 2-D position of interaction. A set of 32 different combinations of surface treatments have been considered for each crystal size. Scintillator dimensions considered have been 25 mm×25 mm×(3-6 mm). For scintillator thicknesses at the low end of this range, an average accuracy of 0.5 to 0.6 mm is achievable for many different surface treatments. At the higher end of the thickness range, 6 mm, the average accuracy reduces to around 0.8 mm, and is more dependent on the surface treatment.</p>
Engineering
https://ro.uow.edu.au/engpapers/65
oai:ro.uow.edu.au:engpapers-1063
2013-06-20T02:08:26Z
publication:arozenfeld
publication:eis
publication:conference_papers
publication:engpapers
publication:engineering
publication:document_types
Spectral characterisation of a blue-enhanced silicon photodetector
Lerch, M. L.
Rosenfeld, Anatoly B.
Simmonds, Philip E
Taylor, G. N.
Meikle, S. R.
Perevertailo, V. L.
Conference Paper
10.1109/NSSMIC.2000.949284
5460
2000-01-01T08:00:00Z
<p>This paper originally appeared as: Lerch, MLF, Rosenfeld, AB, Simmonds, PE et al, Spectral characterisation of a blue-enhanced silicon photodetector, IEEE Nuclear Science Symposium Conference Record, 15-20 October 2000, vol 1, 7/52-7/56. Copyright IEEE 2000.</p>
<p>In this work we report on spectral response data and gamma ray spectroscopy measurements using two newly developed silicon photodetectors that are designed to have enhanced sensitivity in the blue spectral region. The enhanced sensitivity is a result of our newly developed ion implantation profile used to create the active area of the photodetector. The quantum efficiency of the new photodetectors (without any optimised antireflective coating) has been measured to be ~40% at a wavelength of 420 nm. Gamma ray spectroscopy experiments have been performed using a CsI(Tl) and a LSO crystal excited by a 137Cs or 22Na source and read out by the new photodetectors. We have measured an energy resolution of 7.7% and 22.7% FWHM for the 662 keV gamma rays from a 137Cs for the CsI(Tl) and LSO scintillator crystal respectively. We intend to use the photodetectors, in the form of a detector array optically coupled to CsI(Tl) or LSO, in the development of a new scintillator detector module for use in positron emission tomography.</p>
Engineering
https://ro.uow.edu.au/engpapers/64
oai:ro.uow.edu.au:engpapers-1065
2013-07-02T03:43:51Z
publication:eis
publication:conference_papers
publication:engpapers
publication:engineering
publication:document_types
A mathematical model to describe bending mechanics of polypyrrole (PPy) actuators
Alici, Gursel
Metz, Philippe
Spinks, Geoffrey M
Conference Paper
10.1109/AIM.2005.1511145
13948
2005-01-01T08:00:00Z
<p>This article was originally published as: Alici, G, Metz, P & Spinks, GM, A mathematical model to describe bending mechanics of polypyrrole (PPy) actuators, Proceedings 2005 IEEE/ASME International Conference on Advanced Intelligent Mechatronics, 24-28 July, 2005, 1029-1034. USA: IEEE. Copyright IEEE 2005.</p>
<p>In order to make use of conducting polymer actuators such as PPy actuators suitable for many cutting edge applications, and more importantly to provide enhanced degrees of understanding and predictability in quantifying their performance, it is needed to establish a valid mathematical model of such actuators. With this in mind, the aim of this study is to establish and experimentally validate a lumped-parameter model of strip-type PPy actuators for use in improving their displacement and force outputs. With reference to their operation principle, we draw an analogy between the thermal strain and the real strain in the PPy actuators due to the volume change to set up the mathematical model, which is a coupled structural/thermal model. The Finite Element Method (FEM) is used to solve the model. The rate of propagation of the ion migration into the PPy layers is mimicked with a temperature distribution model. Theoretical and experimental results demonstrate that the model is practical and effective enough in predicting the bending angle and bending moment outputs of the PPy actuators quite well for a range of input voltages. We claim that it is a fruitless task to include the influence of their mechanical, electrical and chemical parameters in an analytical model describing their input/output behaviour.</p>
Engineering
https://ro.uow.edu.au/engpapers/66
oai:ro.uow.edu.au:engpapers-1067
2013-06-20T02:07:20Z
publication:arozenfeld
publication:eis
publication:conference_papers
publication:engpapers
publication:engineering
publication:document_types
Evaluation of Transmission Methodology for the microPET Focus 220 Animal Scanner
Lehnert, W.
Meikle, S. R.
Siegel, S.
Bailey, D.
Banati, R.
Rosenfeld, Anatoly B.
Conference Paper
25071
2005-01-01T08:00:00Z
<p>This paper originally appeared as: Lehnert, W, Meikle, SR, Siegel, S, Evaluation of Transmission Methodology for the microPET Focus 220 Animal Scanner, IEEE Nuclear Science Symposium Conference Record, 23-29 October 2005, vol 5, 2519-2523. Copyright IEEE 2005.</p>
<p>Attenuation Correction is important among other corrections for quantitative Positron Emission Tomography (PET). A common method is to acquire transmission data using an external source from which attenuation correction factors are derived. The aim of this work was to compare different transmission methodologies for the microPET Focus 220 animal scanner in terms of accuracy, signal-to-noise and scatter. This study included experiments in coincidence mode with and without rod windowing, singles mode with two different energy sources (68Ge and 57Co) and post-injection transmission scanning. In addition, the effectiveness of transmission segmentation was investigated. The propagation of transmission bias and noise into the emission images was also examined. Singles transmission scanning resulted in substantially improved signal-to-noise compared with coincidence measurements. The 57Co measurements provided attenuation coefficients close to the theoretical value for an energy window of 120-125 keV, while the 68Ge single measurements were degraded due to scattering from the object. Transmission scatter correction improved the accuracy for a 10 cm phantom but over-corrected for a mouse phantom. 57Co also resulted in low bias and noise in post-injection transmission scans for emission activities up to 20 MBq. Segmentation worked most reliably for transmission data acquired with 57Co but the minor improvement in accuracy of attenuation coefficients and signal-to-noise did not justify its use, particularly for small subjects. The accuracy and signal-to-noise of activity concentration measurements reflected the accuracy and signal-to-noise of transmission measurements. We conclude that 57Co singles transmission scanning is the most suitable method of attenuation correction on the microPET Focus 220 animal scanner.</p>
Engineering
https://ro.uow.edu.au/engpapers/68
oai:ro.uow.edu.au:engpapers-1066
2013-07-03T01:31:17Z
publication:eis
publication:conference_papers
publication:engpapers
publication:engineering
publication:document_types
Towards micro and nano manipulation systems: behaviour of a laminated polypyrrole (PPy) actuator driving a rigid link
John, Stephen W.
Alici, Gursel
Conference Paper
10.1109/AIM.2005.1500965
13932
2005-01-01T08:00:00Z
<p>This paper originally appeared as: John, SW & Alici, G, Towards micro and nano manipulation systems: behaviour of a laminated polypyrrole (PPy) actuator driving a rigid link, Proceedings, 2005 IEEE/ASME International Conference on Advanced Intelligent Mechatronics, 2005, 54-59. Copyright IEEE 2005.</p>
<p>Conducting polymer actuators, such as Polypyrrole (PPy), incorporated into the structure of a manipulation system may be able to achieve micro and nanoscale precision, by avoiding effects such as backlash or friction. As a step towards this goal, laminated PPy actuators were varied in size and their behaviour investigated while constantly loaded by a rigid link. This behaviour has been evaluated in terms of the bending angle and force outputs of the actuator. It was found that the bending angles varied with length, but displayed unexpected trends due to the loading effects on the PPy. Force output of the actuators was also measured, with unloaded PPy producing greater force across all lengths than the near constant output of loaded PPy, attributable to the polymer and load interface.</p>
Engineering
https://ro.uow.edu.au/engpapers/67
oai:ro.uow.edu.au:engpapers-1068
2013-06-20T02:06:55Z
publication:arozenfeld
publication:eis
publication:conference_papers
publication:engpapers
publication:engineering
publication:document_types
Verification of Monte Carlo calculations in fast neutron therapy using silicon microdosimetry
Cornelius, I.
Rosenfeld, Anatoly B.
Conference Paper
2003-01-01T08:00:00Z
Monte Carlo methods
dosimetry
neutron capture therapy
physiological models
radiation therapy
silicon radiation detectors
<p>This paper originally appeared as: Cornelius, IM & Rosenfeldf, AB, Verification of Monte Carlo calculations in fast neutron therapy using silicon microdosimetry, IEEE Nuclear Science Symposium Conference Record, 19-25 October 2003, vol 3, 1489-1493. Copyright IEEE 2003.</p>
<p>Silicon microdosimetry measurements in fast neutron therapy were simulated using the GEANT4 Monte Carlo toolkit. The possibility of using silicon microdosimeters for verification of Monte Carlo based treatment planning systems in hadron therapy is demonstrated.</p>
Engineering
https://ro.uow.edu.au/engpapers/69
oai:ro.uow.edu.au:engpapers-1070
2013-06-20T02:06:30Z
publication:arozenfeld
publication:eis
publication:conference_papers
publication:engpapers
publication:engineering
publication:document_types
Performance evaluation of a multipinhole small animal SPECT system
Meikle, S. R.
Kench, P.
Wojcik, R.
Smith, M. F.
Weisenberger, A. G.
Majewski, S.
Lerch, M. L.
Rosenfeld, Anatoly B.
Conference Paper
10690
2003-01-01T08:00:00Z
<p>This paper originally appeared as: Meikle, SR, Kench, P, Wojcik, R et al, Performance evaluation of a multipinhole small animal SPECT system, IEEE Nuclear Science Symposium Conference Record, 19-25 October 2003, vol 3, 1988-1992. Copyright IEEE 2003.</p>
<p>We have designed and constructed a small animal SPECT system based on compact, high resolution detectors and multipinhole apertures. The scanner is currently configured with two detectors mounted on a rotating gantry. Each detector comprises a NaI(Tl) crystal array (1/spl times/1/spl times/5 mm elements), a 12 cm diameter position-sensitive photomultiplier tube (Hamamatsu R3292) and a tungsten aperture with 1 or more pinholes. In this study, we performed phantom experiments to characterise the planar and tomographic performance of the scanner. Intrinsic resolution measured with a highly collimated /sup 99m/Tc point source stepped across the detector face was 1.0 /spl plusmn/ 0;.1 FWHM and 2.9 /spl plusmn/ 0.1 mm FWTM. Energy resolution at 140 keV varied from 14% FWIIM for central crystals to 19% for edge crystals and was 20% FWHM for the whole detector normalised spectrum. Intrinsic uniformity for the central field of view was 2.4% differential and 3.8% integral. Reconstructed spatial resolution was 1.2 mm FWHM at the centre of the field of view and 1.2, 1.7 mm FWHM (radial, tangential) at 10 mm off-axis, using typical geometric parameters for mouse and rat brain imaging. Reconstructed images of a micro deluxe hot rod phantom demonstrate the high resolution of the system and indicate similar resolution and improved signal-to-noise is obtained with a 2 pinhole aperture compared with a single pinhole. We conclude that the performance characteristics of this system make it suitable for high resolution imaging of small laboratory animals.</p>
Engineering
https://ro.uow.edu.au/engpapers/71
oai:ro.uow.edu.au:engpapers-1074
2013-06-20T02:04:51Z
publication:arozenfeld
publication:eis
publication:conference_papers
publication:engpapers
publication:document_types
Response of a SOI Microdosimeter to a /sup 238/PuBe Neutron Source
Reinhard, M. I.
Cornelius, I.
Prokopovich, Dale A
Wroe, A.
Rosenfeld, Anatoly B.
Pisacane, V.
Zeigler, J. F.
Nelson, M. E.
Cucinotta, F.
Zaider, M.
Dicello, J. F.
Conference Paper
13760
2005-01-01T08:00:00Z
<p>This paper originally appeared as: Reinhard, MI, Cornelius, I, Prokopovich, DA et al, Response of a SOI Microdosimeter to a /sup 238/PuBe Neutron Source, IEEE Nuclear Science Symposium Conference Record, 23-29 October 2005, vol 1, 68-72. Copyright IEEE 2005.</p>
<p>The response of a solid state microdosimeter based on semiconductor on insulator (SOI) technology to a 238PuBe neutron source was investigated. Simulations of the device response using the GEANT4 Monte Carlo Toolkit are also presented. The microdosimetric spectra was measured for lineal energies above 1 keV/&#;m. The possible application of the SOI microdosimeter for radiation protection applications in the form of a personnel microdosimeter is suggested.</p>
Engineering
https://ro.uow.edu.au/engpapers/75
oai:ro.uow.edu.au:engpapers-1076
2013-06-20T02:04:21Z
publication:arozenfeld
publication:journal_articles
publication:eis
publication:engpapers
publication:engineering
publication:document_types
Edge-on face-to-face MOSFET for synchrotron microbeam dosimetry: MC modeling
Rosenfeld, Anatoly B.
Siegbahn, E. A.
Brauer-Krisch, E.
Holmes-Siedle, A.
Lerch, M. L.
Bravin, A.
Cornelius, I.
Takacs, G. J.
Painuly, N.
Nettleback, H.
Kron, T.
Journal Article
10.1109/TNS.2005.860704
13762
2005-01-01T08:00:00Z
<p>This paper originally appeared as: Rosenfeld, AB, Siegbahn, EA, Bruaer-Krish, E et al, Edge-on face-to-face MOSFET for synchrotron microbeam dosimetry: MC modeling, IEEE Transactions on Nuclear Science, December 2005, 52(6)1, 2562-2569. Copyright IEEE 2005.</p>
<p>The dosimetry of X-ray microbeams using MOSFETs results in an asymmetrical beam profile due to a lack of lateral charged particle equilibrium. Monte Carlo simulations were carried out using PENELOPE and GEANT4 codes to study this effect and a MOSFET on a micropositioner was scanned in the microbeam. Based on the simulations a new method of microbeam dosimetry is proposed. The proposed edge-on face-to-face (EOFF) MOSFET detector, a die arrangement proposed here for the first time, should alleviate the asymmetry. Further improvement is possible by thinning the silicon body of the MOSFET.</p>
Engineering
https://ro.uow.edu.au/engpapers/77
oai:ro.uow.edu.au:engpapers-1072
2006-10-23T01:19:20Z
publication:eis
publication:rlewis
publication:conference_papers
publication:czhang
publication:engpapers
publication:document_types
The effect of the electron energy spectrum on electronic efficiency and power in thermionic and thermoelectric devices
O'Dwyer, Mark F.
Humphrey, T. E.
Lewis, R. A.
Zhang, C.
Conference Paper
25197
2005-06-19T07:00:00Z
This paper originally appeared as: O'Dwyer, MF, Humphrey, TE, Lewis, RA & Zhang, C, The effect of the electron energy spectrum on electronic efficiency and power in thermionic and thermoelectric devices, 24th International Conference on Thermoelectrics, 19-23 June 2005, 453-456. Copyright IEEE 2005.
We show that the details of the energy spectrum of transmitted electrons in thermionic and thermoelectric devices have a significant impact on their performance. We distinguish between traditional thermionic devices where electron momentum is filtered in the direction of transport only and a second type, in which the electron filtering occurs according to total electron momentum. Our main result is that the electronic efficiency of a device is not only improved by reducing the width of the transmission filter, but also strongly depends on whether the transmission probability rises sharply from zero to full transmission. Finally, we comment on the implications of the effect the shape of the electron energy spectrum has on the efficiency of thermoelectric devices and suggest an experimental measure for providing insight into the nature of the electron energy spectrum.
Engineering
https://ro.uow.edu.au/engpapers/73
oai:ro.uow.edu.au:engpapers-1073
2013-06-20T02:05:21Z
publication:arozenfeld
publication:journal_articles
publication:eis
publication:engpapers
publication:engineering
publication:document_types
A prototype coded aperture detector for small animal SPECT
Meikle, S. R.
Kench, P.
Weisenberger, A. G.
Wojcik, R.
Smith, M. F.
Majewski, S.
Eberl, S.
Fulton, R. R.
Rosenfeld, Anatoly B.
Fullham, M. J.
Journal Article
10.1109/TNS.2002.803802
8606
2002-01-01T08:00:00Z
<p>This article was originally published as: Meikle, SR, Kench, P, Weisenberger, AG, Wojcik, R, Smith, MF, Majewski, S, Eberl, S, Fulton, RR, Rosenfeld, AB & Fulham, MJ, A prototype coded aperture detector for small animal SPECT, IEEE Transactions on Nuclear Science, October 2002, 49(5)1, 2167-2171. Copyright IEEE 2002.</p>
<p>In a previous simulation study, we demonstrated the feasibility of using coded apertures together with pixelated detectors tors for small animal SPECT. In this paper; we further explore the potential of this approach with a prototype detector and simulated multipinhole apertures. We also investigated the effect of multiplexing due to overlapped projections on convergence properties, image signal-to-noise ratio (SNR) and spatial resolution. The detector comprises a 48/spl times/44 array of NaI(Tl) crystals, each 1 mm/spl times/1 mm/spl times/5 mm on a 1.25-mm pitch. The crystal array is directly coupled to a Hamamatsu R3941 8 cm position sensitive photomultiplier tube. Multipinhole apertures were simulated by performing repeated SPECT acquisitions of the same object with a single tungsten pinhole translated to different positions in the aperture plane. Image reconstruction is based on a three-dimensional ray driven projector which is an extension of a method described for single pinhole SPECT with a displaced center of rotation. Image estimates are updated using the maximum likelihood expectation maximization (ML-EM) algorithm. The effect of multiplexing was to slow convergence and reduce the achievable SNR by approximately 15% compared with nonmultiplexed data (but the result may be achieved in a fraction of the time). The reconstructed resolution obtained with a resolution phantom was 1.5-mm full width at half maximum and there was no appreciable difference between the resolution of multiplexed and nonmultiplexed data. These results encourage us to develop a prototype coded aperture system for high sensitivity, high resolution small animal SPECT.</p>
Engineering
https://ro.uow.edu.au/engpapers/74
oai:ro.uow.edu.au:engpapers-1075
2013-02-11T05:14:05Z
publication:eis
publication:conference_papers
publication:engpapers
publication:document_types
Sliding Mode Control of a Piezoelectric Actuator with Neural Network Compensating Rate-Dependent Hysteresis
Yu, S.
Alici, G.
Shirinzadeh, B.
Smith, J.
Conference Paper
2005-04-18T07:00:00Z
<p>This article was originally published as: Yu, S, Alici, G, Shirinzadeh, B & Smith, J, Sliding Mode Control of a Piezoelectric Actuator with Neural Network Compensating Rate-Dependent Hysteresis, Proceedings of the 2005 IEEE International Conference on Robotics and Automation, 18-22 April 2005, 3641-3645, Barcelona, Spain. Copyright IEEE 2005.</p>
<p>Piezoelectric actuators (PEA) are the fundamental elements for high-precision high-speed positioning/tracking task in many nanotechnology applications. However, the intrinsic hysteresis observed in PEAs has impaired their potential, specially, the motion accuracy. In this paper, the complicated nonlinear dynamics of PEA including hysteresis, creep, drift and time-delay etc. are treated as a black-box system exhibited as rate-dependent hysteresis. The multi-valued hysteresis is analyzed as a single-valued function so that a neural network (NN) can be built to model the hysteresis and its inversion. A sliding mode controller (SMC) augmented with inverse hysteresis model is then developed to compensate the hysteretic behavior, modeling error and disturbance to improve the positioning/tracking stability and accuracy. The effectiveness of this algorithm experimentally verified through the actual tracking control of a PEA.</p>
Engineering
https://ro.uow.edu.au/engpapers/76
oai:ro.uow.edu.au:engpapers-1071
2013-06-20T02:05:56Z
publication:arozenfeld
publication:eis
publication:conference_papers
publication:engpapers
publication:document_types
CoALA-SPECT: a coded aperture laboratory animal SPECT system for pre clinical imaging
Meikle, S. R.
Wojcik, R.
Weisenberger, A. G.
Smith, M. F.
Majewski, S.
Kench, P.
Eberl, S.
Fulton, R. R.
Lerch, M. L.
Rosenfeld, Anatoly B.
Conference Paper
2002-01-01T08:00:00Z
<p>This article was originally published as: Meikle, SR, Wojcik, R, Weisenberger, AG, Smith, MF, Majewski, S, Kench, P, Eberl, S, Fulton, RR, Lerch, M & Rosenfeld, AB, CoALA-SPECT: a coded aperture laboratory animal SPECT system for pre clinical imaging, 2002 IEEE Nuclear Science Symposium Conference Record, 10-16 November 2002, 2, 1061-1065. Copyright IEEE 2002.</p>
<p>We have previously demonstrated the potential of multi-pinhole coded apertures when used in conjunction with compact pixelated detectors for high resolution, high sensitivity small animal SPECT. We are now constructing a prototype SPECT system with three such detectors mounted on a rotating gantry. Each detector comprises a 12 cm diameter circular array of NaI(Tl) crystals, each 1/spl times/1/spl times/5 mm/sup 3/ on a 1.25 mm pitch. Each crystal array is coupled to a Hamamatsu R3292 12.7 cm diameter PS-PMT. Signals from the three detectors are read out by a custom subtractive resistive circuit and multiplexed. Data are acquired by a National Instruments PCI-6110E board running on a Macintosh dual processor G4 computer under Kmax software control. Images are reconstructed using a 3D iterative MAP-EM algorithm based on a multi-pinhole forward and back projector. The trade-off between contrast and variance was studied by simulation for a number of multi-pinhole configurations. We also performed initial planar imaging studies on one of the detectors. Our results indicate that spatial resolution approaching 1 mm full width at half maximum (FWHM) can be achieved with a single pinhole aperture, while improved contrast and variance may result from using optimized multi-pinhole apertures.</p>
Engineering
https://ro.uow.edu.au/engpapers/72
oai:ro.uow.edu.au:engpapers-1078
2013-06-20T02:03:44Z
publication:arozenfeld
publication:journal_articles
publication:eis
publication:engpapers
publication:document_types
Microdosimetry simulations of solar protons within a spacecraft
Wroe, A. J.
Cornelius, I.
Rosenfeld, Anatoly B.
Pisacane, V. L.
Zeigler, J. F.
Nelson, M. E.
Cucinotta, F.
Zaider, M.
Dicello, J. F.
Journal Article
10.1109/TNS.2005.860706
13761
2005-01-01T08:00:00Z
<p>This paper originally appeared as: Wroe, AJ, Cornelius, I, Rosenfeld, AB et al, Microdosimetry simulations of solar protons within a spacecraft, IEEE Transactions on Nuclear Science, December 2005, 52(6)1, 2591-2596. Copyright IEEE 2005.</p>
<p>The microdosimetric spectra derived by silicon microdosimeter in a proton radiation field traversing heterogeneous structures were simulated using the GEANT4 toolkit.</p>
Engineering
https://ro.uow.edu.au/engpapers/79
oai:ro.uow.edu.au:engpapers-1079
2013-07-02T03:04:38Z
publication:eis
publication:conference_papers
publication:engpapers
publication:document_types
A new methodology for deformable object simulation
Zhong, Yongmin
Shirinzadeh, Bijan
Alici, Gursel
Smith, Julian
Conference Paper
10.1109/ROBOT.2005.1570391
13947
2005-04-18T07:00:00Z
<p>This article was originally published as: Zhong, Y, Shirinzadeh, B, Alici, G & Smith, J, A new methodology for deformable object simulation, Proceedings of the 2005 IEEE International Conference on Robotics and Automation, 18-22 April 2005, 1902-1907. Copyright IEEE 2005.</p>
<p>This paper presents a new methodology for the deformation of soft objects by drawing an analogy between heat conduction and elastic deformation. The potential energy stored in an elastic body as a result of a deformation caused by an external force is propagated among mass points by the principle of heat conduction. An improved heat conduction model is developed for propagating the energy generated by the external force in a natural manner. A method is presented to derive the internal forces from the potential energy distribution. This methodology not only deals with large-range deformation, but also accommodates both isotropic and anisotropic materials by simply changing thermal conductivity constants. Examples are presented to demonstrate the efficiency of the proposed methodology.</p>
Engineering
https://ro.uow.edu.au/engpapers/80
oai:ro.uow.edu.au:asdpapers-1002
2013-02-03T23:09:26Z
publication:eis
publication:conference_papers
publication:asd
publication:engpapers
publication:asdpapers
publication:document_types
Realtime display of landslide monitoring data
Pennell, Russ
Ruberu, D.
Flentje, P.
Conference Paper
2005-07-05T07:00:00Z
<p>This paper was originally published as Pennell, R, Ruberu, D & Flentje, P, Realtime display of landslide monitoring data, <a href="http://ausweb.scu.edu.au/aw05/papers/refereed/pennell/paper.html">AusWeb05</a> - The 11th Australasian World Wide Web Conference, 5 July 2005. In A. Treloar & A. Ellis (Eds.), Australian World Wide Web Conference (pp. 1-9). Australia: AusWeb 05 Online.</p>
<p>In areas of high landslide risk, dangerous situations can develop rapidly. The system described here provides near real-time landslide information via the web to researchers, emergency personnel and others assisting them to assess developing risks. Remote field stations collect data continuously and download this to a central site at varying intervals via mobile phone. Processing and display software written using the ASP.NET framework stores the data in directly-graphable form and displays graphs in response to web requests. Design challenges included the changing nature of the instruments in the field, resolved by the use of user-editable configuration files that allowed for instrument changes at short notice.</p>
landslide
ASP.NET
remote
monitoring
configuration
REALbasic
Arts and Humanities
Social and Behavioral Sciences
https://ro.uow.edu.au/asdpapers/3
oai:ro.uow.edu.au:engpapers-1080
2014-04-09T06:34:25Z
publication:journal_articles
publication:hkliu
publication:eis
publication:engpapers
publication:engineering
publication:document_types
Characterization of thermal conductivity and mechanical properties of Ag-alloy sheathed Bi(Pb)-Sr-Ca-Cu-O superconductor tape
Jang, S. H.
Lim, J. H.
Kim, J. K.
Ji, B. K.
Jo, J.
Nah, W.
Volf, J. S.
Liu, Hua-Kun
Apperley, M.
Journal Article
10.1109/TASC.2003.812074
9641
2003-06-01T07:00:00Z
<p>This paper originally appeared as: Jang, S, Lim, J, Kim, J et al, Characterization of thermal conductivity and mechanical properties of Ag-alloy sheathed Bi(Pb)-Sr-Ca-Cu-O superconductor tape, IEEE Transactions on Applied Superconductivity, June 2003, 13(2)3, 2956-2959. Copyright IEEE 2003.</p>
<p>We evaluated the effect of alloying additions to Ag on thermal conductivity and mechanical properties of Ag-alloy sheathed Bi-2223 (BSCCO) superconductor tape. The tapes were made with combinations of Ag alloys such as Ag-Mg, Ag-Sb, and Ag-Au for inner and outer sheath. Thermal conductivity of the tapes was evaluated by using thermal integral method at 10-120 K. It was observed that the addition of alloys reduced remarkably thermal conductivity and improved mechanical strength. The thermal conductivity for Ag-Mg, Ag-Sb, and Ag-Au at 40 K was measured to be 411.4, 142.3, and 109.7 W/(m/spl middot/K), respectively, which is approximately 2 to 9 times lower than that of Ag (1004.6 W/(m/spl middot/K)). In addition, the thermal conductivity of alloy-sheathed tape significantly depended on their thermal conductivity of sheath materials. For Ag-alloy sheathed tapes, the thermal conductivity was much lower (i.e., 5 -18 times lower) than that of the Ag sheathed tape The mechanical property of alloy-sheathed tape was also evaluated and correlated to the microstructural evolution.</p>
Engineering
https://ro.uow.edu.au/engpapers/81
oai:ro.uow.edu.au:engpapers-1083
2013-08-16T05:18:52Z
publication:xlwang
publication:journal_articles
publication:ssoltanian
publication:eis
publication:jhorvat
publication:engpapers
publication:document_types
Superconducting screening on different length scales in high-quality bulk MgB2 superconductor
Horvat, J.
Soltanian, Saeid
Pan, Alexey
Wang, Xiaolin
Journal Article
10.1063/1.1790069
11359
2004-10-01T07:00:00Z
MgB2 superconductor
superconducting screening
critical state model
critical current
size-effect
percolation
stretched exponential
<p>The article was originally published as Horvat, J, Soltanian, S, Pan, AV and Wang, XL, Superconducting screening on different length scales in high-quality bulk MgB2 superconductor, Journal of Applied Physics, 96(8), 2004, 4342-4351. Copyright American Institute of Physics. Original article available <a href="http://link.aip.org/link/JAPIAU/v96/p4342">here</a>.</p>
<p>High-quality bulk MgB<sub>2</sub> exhibits a structure of voids and agglomeration of crystals on different length scales. Because of this, the superconducting currents percolate between the voids in the ensuing structure. Magnetic measurements reveal that the superconducting currents circulate on at least three different length scales, of ∼1 <em>μ</em>m, ∼10 <em>μ</em>m, and whole of the sample (∼millimeter). Each of these screenings contributes to the measured irreversible magnetic moment (Δ<em>m</em>). The analysis of the field dependence of Δ<em>m</em> for samples of subsequently decreasing size showed that the critical current obtained using the simple critical state model is erroneous. This leads to the artifact of the sample size-dependent critical current density <em>J</em><sub><em>c</em></sub> and irreversibility field. Our data analysis enables the separation of the contribution of each of the screening currents to Δ<em>m</em>. The field dependence of each of the currents follows a <em>stretched exponential form</em>. The currents flowing around whole of the sample give a dominant contribution to Δ<em>m</em> in the intermediate fields (1 T<<em>H</em><4 T at 20 K) and they can be used to obtain the value of <em>J</em><sub><em>c</em></sub> from critical state model, which corresponds to the transport <em>J</em><sub><em>c</em></sub>. The stretched exponential field dependence of these currents is similar to the one obtained for high-temperature superconductors, and it seems to be connected with the percolation of the currents.</p>
Engineering
https://ro.uow.edu.au/engpapers/83
oai:ro.uow.edu.au:engpapers-1085
2013-05-21T04:08:08Z
publication:xlwang
publication:journal_articles
publication:ssoltanian
publication:eis
publication:jhorvat
publication:engpapers
publication:sxdou
publication:document_types
Improvement of critical current in MgB2 superconducting wires by a ferromagnetic sheath
Horvat, J.
Wang, X. L.
Soltanian, Saeid
Dou, S. X.
Journal Article
8673
2002-01-01T08:00:00Z
MgB2 wires
superconductor-magnet interaction
peak effect
magnetic shielding
critical current
<p>This article was originally published as Horvat, J, Wang, XL, Soltanian, S and Dou, SX, Improvement of critical current in MgB2 superconducting wires by a ferromagnetic sheath, Applied Physics Letters, 80, 2002, 829. Copyright American Institute of Physics. Original article available <a href="http://link.aip.org/link/APPLAB/v80/p829">here</a>.</p>
<p>Transport critical current (Ic) was measured for Fe-sheathed MgB2 round wires. A critical current density of 5.3 x 10^4 A/cm^2 was obtained at 32K. Strong magnetic shielding by the iron sheath was observed, resulting in a decrease in Ic by only 15% in a field of 0.6T at 32K. In addition to shielding, interaction between the iron sheath and the superconductor resulted in a constant Ic between 0.2 and 0.6T. This was well beyond the maximum field for effective shielding of 0.2T. This effect can be used to substantially improve the field performance of MgB2/Fe wires at fields at least 3 times higher than the range allowed by mere magnetic shielding by the iron sheath. The dependence of Ic on the angle between field and current showed that the transport current does not flow straight across the wire, but meanders between the grains.</p>
Engineering
https://ro.uow.edu.au/engpapers/87
oai:ro.uow.edu.au:engpapers-1084
2014-04-09T06:34:48Z
publication:xlwang
publication:journal_articles
publication:ssoltanian
publication:eis
publication:jhorvat
publication:engpapers
publication:sxdou
publication:document_types
Effect of sample size on magnetic Jc for MgB2 superconductor
Horvat, J.
Soltanian, Saeid
Wang, Xiaolin
Dou, S. X.
Journal Article
10.1063/1.1713031
11373
2004-01-01T08:00:00Z
MgB2 superconductor
superconducting screening
critical state model
critical current
size-effect
percolation
<p>This article was originally published as Horvat, J, Soltanian, S, Wang, XL and Dou, SX, Effect of sample size on magnetic Jc for MgB2 superconductor, Applied Physics Letters, 84, 2004, 3109-. Copyright American Institute of Physics. Original article available <a href="http://link.aip.org/link/APPLAB/v84/p3109">here</a>.</p>
<p>A strong effect of sample size on magnetic Jc(H) was observed for bulk MgB2 when Jc is obtained directly from the critical state model. Thus obtained zero-field Jc (Jc0) decreases strongly with the sample size, attaining a constant value for the samples larger than a few millimetres. On the other hand, the irreversibility field (Hirr) defined at Jc = 100 A/cm2 increases with the sample size. The decrease of Jc0 is described in terms of voids in the bulk MgB2 samples and superconducting screening around the cells of superconducting material between these voids (35 micro-m), because of concentration of the current in the narrow bridges connecting the cells. For samples larger than a few millimetres, the value of magnetic Jc is in agreement with the transport Jc and it is restricted by the voids. The critical state model is not suitable for obtaining Jc for small bulk MgB2. The increase of Hirr with the sample size is an artefact of defining Hirr by the value of Jc at which an additional superconducting screening on 1 micro-m scale dominates Delta(m).</p>
Engineering
https://ro.uow.edu.au/engpapers/85
oai:ro.uow.edu.au:engpapers-1081
2014-04-14T04:33:55Z
publication:journal_articles
publication:eis
publication:jhorvat
publication:engpapers
publication:engineering
publication:document_types
Interaction between superconductor and ferromagnetic domains in iron sheath: Peak effect in MgB2/Fe wires
Horvat, J.
Yeoh, W. K.
Miller, Leonie M
Journal Article
10.1063/1.2039993
13690
2005-08-01T07:00:00Z
MgB2 wires
superconductor-magnet interaction
peak effect
magnetic shielding
magnetic domains
critical current
<p>This article was originally published as Horvat, J, Yeoh, WK and Miller, LM, Interaction between superconductor and ferromagnetic domains in iron sheath: Peak effect in MgB2/Fe wires, Applied Physics Letters, 87, 102503-1-102503-3, 2005. Copyright American Institute of Physics. Original article available <a href="http://link.aip.org/link/APPLAB/v87/p102503">here</a>.</p>
<p>Interaction between the superconductor and ferromagnet in MgB2/Fe wires results in either a plateau or a peak effect in the field dependence of transport critical current, Ic(H). This is in addition to magnetic shielding of external field. Current theoretical models cannot account for the observed peak effect in Ic(H). This paper shows that the theoretical explanation of the peak effect should be sought in terms of interaction between superconductor and magnetic domain structure, obtained after re-magnetization of the iron sheath by the self-field of the current. There is a minimum value of critical current, below which the re-magnetization of the iron sheath and peak effect in Ic(H) are not observed.</p>
Engineering
https://ro.uow.edu.au/engpapers/82
oai:ro.uow.edu.au:engpapers-1082
2013-02-11T05:56:23Z
publication:journal_articles
publication:ssoltanian
publication:eis
publication:jhorvat
publication:engpapers
publication:engineering
publication:document_types
The relevance of the self-field for the 'peak effect' in the transport Jc(H) of iron-sheathed MgB2 wires
Horvat, J.
Soltanian, Saeid
Yeoh, W. K.
Journal Article
10.1088/0953-2048/18/5/017
13653
2005-04-01T08:00:00Z
MgB2 superconductor
critical current
self-field
overcritical state
magnetic sheath
peak effect
magnetic shielding
<p>This article was originally published as Harvat, J, Soltanian, S and Yeoh, WK, The relevance of the self-field for the 'peak effect' in the transport Jc(H) of iron-sheathed MgB2 wires, Superconductor Science and Technology, 18, 2005, 682-688. Copyright Institute of Physics. Journal available <a href="http://www.iop.org/EJ/journal/SUST">here</a>.</p>
<p>Ferromagnetic sheath around a superconducting wire results in an unusual transport Jc(H). For the field perpendicular to the current, there is a plateau in Jc(H) at high temperatures and intermediate fields. This plateau develops into a peak at lower temperatures, resembling a “peak effect”. A model based on cancellation of the self-field of the current and external field within the iron sheath was proposed for the explanation of the plateau in Jc(H). We test this model in three key experiments. Firstly, we show that the form of Jc(H) for round MgB2/Fe wires is strongly temperature dependent. This is in contradiction with the model, because the properties of the iron sheath do not change in the measured temperature range. However, the temperature dependence of Jc might still account for the change of Jc(H). Secondly, the model requires a substantial component of the self-field to be parallel to the external field. Our measurements of Jc(H) for field parallel to the current show a peak in Jc(H) at high temperatures and a pronounced plateau at low temperatures. The model cannot explain this because the self-field and external field are perpendicular in this experiment. Thirdly, the iron sheath was made thinner on one side of the wire, which should produce an asymmetry in Jc(H) in the model for two different orientations of external field. Such asymmetry was not observed. These experiments show that the effect of the self-field is of much lower importance than a yet unknown effect that results in the observed plateau and peak in Jc(H). Such effect is likely to be based on a specific interaction between the superconductor and ferromagnet, perhaps similar to the overcritical state effect.</p>
Engineering
https://ro.uow.edu.au/engpapers/84
oai:ro.uow.edu.au:engpapers-1086
2014-04-09T06:35:17Z
publication:journal_articles
publication:eis
publication:jhorvat
publication:engpapers
publication:engineering
publication:document_types
Oxygen Vacancy Ordering and Magnetism in the Rare Earth Stabilised Perovskite Form of “SrCO3-d
James, M.
Cassidy, D.
Wilson, K. F.
Horvat, J.
Withers, R. L.
Journal Article
10.1016/j.solidstatesciences.2003.03.001
11324
2004-06-01T07:00:00Z
strontium doped cobaltate
solid solution limits
perovskite superstructure
spin glass magnetism
<p>This article was originally published as James, M, Cassidy, D, Wilson, KF, Horvat, J and Withers, RL, Oxygen Vacancy Ordering and Magnetism in the Rare Earth Stabilised Perovskite Form of "SrCO3-d", Solid State Sciences, 6(7), 2004, 655-662.. Copyright Elsevier 2004. Journal available <a href="http://www.elsevier.com/wps/find/journaldescription.cws_home/620710/description#description">here</a>.</p>
<p>We have demonstrated that SrCoO3-d can be stabilised into phase pure perovskite forms by the introduction of small amounts ~5% of certain rare earth ions (Sm3+ - Yb3+). At the same doping levels, La3+ and Pr3+ crystallise with the same isostructural trigonal structure as SrCoO3-d; while the Nd3+ composition shows a mixture of both structure types. Powder X-ray diffraction showed only a simple cubic perovskite structure, however a combination of electron and neutron diffraction has revealed a tetragonal (P4/mmm) ap x ap x 2ap superstructure. Strontium and the rare earth ions are disordered over a single site, while the oxygen vacancies are localised on the apical O2 sites. Magnetisation measurements show that these materials undergo transitions to a spin-glass state at temperatures below 150 K, and that significant coupling occurs between the rare earth ions and the mixed Co3+/4+ ions. Magnetisation measurements as a function of applied field reveals that below the transition temperature ferromagnetic ordering takes place at relatively large fields.</p>
Engineering
https://ro.uow.edu.au/engpapers/88
oai:ro.uow.edu.au:engpapers-1088
2013-05-21T04:07:45Z
publication:journal_articles
publication:ssoltanian
publication:eis
publication:jhorvat
publication:engpapers
publication:sxdou
publication:engineering
publication:document_types
Effect of heating rates on superconducting properties of pure MgB2, carbon nanotube- and nano-SiC-doped in situ MgB2/Fe wires
Chen, S. K.
Tan, K. S.
Glowacki, B. A.
Yeoh, W. K.
Soltanian, Saeid
Horvat, J.
Dou, S. X.
Journal Article
10.1063/1.2126148
13706
2005-01-01T08:00:00Z
<p>This article was originally published as: Chen, SK, Tan, KS, Glowacki, BA, Yeoh, WK, Soltanian, S, Horvat, J & Dou, SX, Effect of heating rates on superconducting properties of pure MgB2, carbon nanotube- and nano-SiC-doped in situ MgB2/Fe wires, Applied Physics Letters, 2005, 87,182504-1-182504-3, and may be found <a href="http://scitation.aip.org/vsearch/servlet/VerityServlet?KEY=FREESR&smode=strresults&sort=chron&maxdisp=25&threshold=0&possible1zone=article&bool1=and&possible4=horvat&possible4zone=author&bool4=and&possible2=effect+of+heating+rates&possible2zone=multi&OUTLOG=NO&viewabs=APPLAB&key=DISPLAY&docID=1&page=1&chapter=0">here</a>. Copyright (2005) American Institute of Physics, This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.</p>
<p>The influence of heating rates and annealing temperatures on the transition temperatures (Tc) and critical current densities (Jc) of pure MgB2, carbon nanotube- and nano-SiC-doped in situ monofilamentary MgB2/Fe wires was investigated. It was found that higher Jc was obtained for pure MgB2 samples when heat treated with slower heating rates. SiC-doped samples also have higher Jc with slower heating rates, but the Jc is less sensitive to annealing temperatures. However, the Jc of the carbon nanotube-doped wire was found to be insensitive to heating rates. The variation in Tc and Jc with heating rate, and the different behaviors of differently doped MgB2/Fe wires, make it essential to carefully select the optimum heating rates for heat treatment.</p>
Engineering
https://ro.uow.edu.au/engpapers/89
oai:ro.uow.edu.au:engpapers-1090
2013-05-21T04:06:48Z
publication:journal_articles
publication:eis
publication:jhorvat
publication:engpapers
publication:sxdou
publication:engineering
publication:document_types
Effects of fission-fragment damage on vortex dimensionality in silver-sheathed Bi2Sr2Ca2Cu3Ox tapes
Marinaro, D. G.
Horvat, J.
Dou, S X
Journal Article
10.1103/PhysRevB.68.064518
9651
2003-01-01T08:00:00Z
<p>This article was originally published as: Marinaro, DG, Horvat, J & Dou, SX, Effects of fission-fragment damage on vortex dimensionality in silver-sheathed Bi2Sr2Ca2Cu3Ox tapes, Physical Review - Series B, 2003, 68, 064518(9 pages). This journal may be found <a href="http://scitation.aip.org/vsearch/servlet/VerityServlet?KEY=FREESR&smode=strresults&sort=chron&maxdisp=25&threshold=0&possible1zone=article&bool1=and&possible4=marinaro&possible4zone=author&bool4=and&possible2=effect+of+fission-fragment&possible2zone=multi&OUTLOG=NO&viewabs=PRBMDO&key=DISPLAY&docID=1&page=1&chapter=0">here</a>. Copyright 2003 American Physical Society.</p>
<p>We report on the vortex dimensionality of uranium-doped Ag/Bi2223 tapes, before and after irradiation to a thermal-neutron fluence. The effective activation energies, as a function of current density and applied field, were calculated from dynamic magnetization relaxation measurements. A dimensional crossover from a three-dimensional (3D) elastic creep regime to a 2D plastic creep was observed in the nonirradiated tape at an applied magnetic field µ0Hcr[approximate]0.37 T, with an associated change in the flux hop velocity and temperature dependence. After the introduction of the fission-fragment damage by irradiation, a shift in the crossover to µ0Hcr[approximate]0.65 T was observed. These results indicate an enhancement of the c-axis vortex coherence by the introduced splayed columnar defects, explaining the greater pinning efficiency of the uranium-fission method in Bi2223 rather than the less anisotropic Y123. Conflicting results obtained for the irradiated tape in the absence of any temperature scaling of the activation energies demonstrate the importance of the inclusion of scaling in the magnetization relaxation analysis.</p>
Engineering
https://ro.uow.edu.au/engpapers/91
oai:ro.uow.edu.au:engpapers-1089
2014-04-09T06:35:46Z
publication:xlwang
publication:journal_articles
publication:hkliu
publication:eis
publication:jhorvat
publication:engpapers
publication:sxdou
publication:document_types
Superconductivity, critical current density, and flux pinning in MgB2–x(SiC)x/2 superconductor after SiC nanoparticle doping
Dou, S X
Pan, A. V.
Zhou, S.
Ionescu, M.
Wang, Xiaolin
Horvat, J.
Liu, Hua-Kun
Munroe, P. R.
Journal Article
10.1063/1.1586467
9650
2003-01-01T08:00:00Z
<p>This article originally appeared as: Dou, SX, Pan, AV, Zhou, S, Ionescu, M, Wang, XL, Horvat, J, Liu, HK & Munroe, PR, Superconductivity, critical current density, and flux pinning in MgB2–x(SiC)x/2 superconductor after SiC nanoparticle doping, Journal of Applied Physics, 2003, 94(3), 1850-1856, and may be found <a href="http://scitation.aip.org/vsearch/servlet/VerityServlet?KEY=FREESR&smode=strresults&sort=chron&maxdisp=25∨igquery=%28%28superconductivity+%3CIN%3E+abstract+%3COR%3E+superconductivity+%3CIN%3E+title+%3COR%3E+superconductivity+%3CIN%3E+keywords%29+%3Cand%3E%28dou+%3Cin%3E+exactauthor%29%29&disporigquery=%28%28superconductivity+%3CIN%3E+abstract+%3COR%3E+superconductivity+%3CIN%3E+title+%3COR%3E+superconductivity+%3CIN%3E+keywords%29+%3Cand%3E%28dou+%3CIN%3E+author%29%29&threshold=0&pjournals=&pyears=&possible1zone=article&bool1=and&possible2=superconductivity&possible2zone=multi&possible3=horvat&possible3zone=author&bool3=and&OUTLOG=NO&viewabs=JAPIAU&key=DISPLAY&docID=4&page=1&chapter=0&aqs=">here</a>. Copyright (2003) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.</p>
<p>We investigated the effect of SiC nanoparticle doping on the crystal lattice structure, critical temperature Tc, critical current density Jc, and flux pinning in MgB2 superconductor. A series of MgB2–x(SiC)x/2 samples with x = 0–1.0 were fabricated using an in situ reaction process. The contraction of the lattice and depression of Tc with increasing SiC doping level remained rather small most likely due to the counterbalancing effect of Si and C co-doping. The high level Si and C co-doping allowed the creation of intragrain defects and highly dispersed nanoinclusions within the grains which can act as effective pinning centers for vortices, improving Jc behavior as a function of the applied magnetic field. The enhanced pinning is mainly attributable to the substitution-induced defects and local structure fluctuations within grains. A pinning mechanism is proposed to account for different contributions of different defects in MgB2–x(SiC)x/2 superconductors.</p>
Engineering
https://ro.uow.edu.au/engpapers/90
oai:ro.uow.edu.au:engpapers-1091
2013-05-21T04:06:21Z
publication:journal_articles
publication:eis
publication:jhorvat
publication:engpapers
publication:sxdou
publication:engineering
publication:document_types
Intense vortex pinning enhanced by semicrystalline defect traps in self-aligned nanostructured MgB2
Li, S.
White, T.
Laursen, K.
Tan, T. T.
Sun, C. Q.
Dong, Z. L.
Li, Y.
Zho, S. H.
Horvat, J.
Dou, S. X.
Journal Article
10.1063/1.1591070
9632
2003-01-01T08:00:00Z
<p>This article originally appeared as: Li, S, White, T, Laursen, K, Tan TT, Sun, CQ, Dong, ZL, Li, Y, Zho, SH, Horvat, J & Dou, SX, Intense vortex pinning enhanced by semicrystalline defect traps in self-aligned nanostructured MgB2, Applied Physics Letters, 2003, 83(2), 314-316, and may be found <a href="http://scitation.aip.org/vsearch/servlet/VerityServlet?KEY=FREESR&smode=strresults&sort=chron&maxdisp=25&threshold=0&possible1zone=article&bool1=and&possible4=li&possible4zone=author&bool4=and&possible2=intense+vortex&possible2zone=multi&OUTLOG=NO&viewabs=APPLAB&key=DISPLAY&docID=2&page=1&chapter=0">here</a>. Copyright 2003 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.</p>
<p>In this work, we report the discovery of a vortex pinning source: semicrystalline defect wells in self-aligned nanostructured MgB2. It is demonstrated that these aperiodic regions trap numerous crystal defects migrating along nanodomain boundaries during self-alignment and act as intense vortex pinning centers that significantly enhance the high-field performance of MgB2. This suggests that the density of trapped defects in the wells is much greater than that found in other vortex pinning sources.</p>
Engineering
https://ro.uow.edu.au/engpapers/92
oai:ro.uow.edu.au:engpapers-1092
2013-08-05T01:43:30Z
publication:xlwang
publication:journal_articles
publication:hkliu
publication:ssoltanian
publication:eis
publication:jhorvat
publication:engpapers
publication:sxdou
publication:engineering
publication:document_types
Enhancement of the critical current density and flux pinning of MgB2 superconductor by nanoparticle SiC doping
Dou, S X
Soltanian, Saeid
Horvat, J.
Wang, Xiaolin
Zhou, S. H.
Ionescu, M.
Liu, Hua-Kun
Munroe, P.
Tomsic, M.
Journal Article
10.1063/1.1517398
8637
2002-01-01T08:00:00Z
<p>Dou, S. Xue., Soltanian, S., Horvat, J., Wang, X., Zhou, S., Ionescu, M., Liu, H. K., Munroe, P. G. & Tomsic, M. (2002). <a href="http://ro.uow.edu.au/engpapers/93">Enhancement of the critical current density and flux pinning of MgB2 superconductor by nanoparticle SiC doping</a>. Applied Physics Letters, 81 (18), 3419-3421.</p>
<p>Doping of MgB2 by nano-SiC and its potential for the improvement of flux pinning were studied for MgB2–x(SiC)x/2 with x = 0, 0.2, and 0.3 and for 10 wt % nano-SiC-doped MgB2 samples. Cosubstitution of B by Si and C counterbalanced the effects of single-element doping, decreasing Tc by only 1.5 K, introducing intragrain pinning centers effective at high fields and temperatures, and significantly enhancing Jc and Hirr. Compared to the undoped sample, Jc for the 10 wt % doped sample increased by a factor of 32 at 5 K and 8 T, 42 at 20 K and 5 T, and 14 at 30 K and 2 T. At 20 K and 2 T, the Jc for the doped sample was 2.4×105 A/cm2, which is comparable to Jc values for the best Ag/Bi-2223 tapes. At 20 K and 4 T, Jc was twice as high as for the best MgB2 thin films and an order of magnitude higher than for the best Fe/MgB2 tapes. The magnetic Jc is consistent with the transport Jc which remains at 20 000 A/cm2 even at 10 T and 5 K for the doped sample, an order of magnitude higher than the undoped one. Because of such high performance, it is anticipated that the future MgB2 conductors will be made using a formula of MgBxSiyCz instead of pure MgB2.</p>
Engineering
https://ro.uow.edu.au/engpapers/93
oai:ro.uow.edu.au:engpapers-1093
2013-05-21T04:04:44Z
publication:xlwang
publication:journal_articles
publication:ssoltanian
publication:eis
publication:jhorvat
publication:engpapers
publication:sxdou
publication:engineering
publication:document_types
Intrinsic nanostructural domains: Possible origin of weaklinkless superconductivity in the quenched reaction product of Mg and amorphous B
Li, S.
Prabhakar, O.
Tan, T. T.
Sun, C. Q.
Wang, Xiaolin
Soltanian, Saeid
Horvat, J.
Dou, S. X.
Journal Article
10.1063/1.1497712
7663
2002-01-01T08:00:00Z
<p>This article was originally published as: Li, S, Prabhakar, O, Tan, TT, Sun, CQ, Wang, XL, Soltanian, S, Horvat, J & Dou, SX, Intrinsic nanostructural domains: Possible origin of weaklinkless superconductivity in the quenched reaction product of Mg and amorphous B,Applied Physics Letters, 2002, 81(5), 874-876, and may be found <a href="http://scitation.aip.org/vsearch/servlet/VerityServlet?KEY=FREESR&smode=strresults&sort=chron&maxdisp=25&threshold=0&possible1zone=article&bool1=and&possible4=li&possible4zone=author&bool4=and&possible2=intrinsic+nanostructural&possible2zone=multi&OUTLOG=NO&viewabs=APPLAB&key=DISPLAY&docID=1&page=1&chapter=0">here</a>. Copyright 2002 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.</p>
<p>Smooth modulation structure of Mg–B alloy in the quenched reaction product of Mg and amorphous B was studied. It indicates that the MgB2 formed possibly in spinodal decomposition, thus resulting in MgB2 nanodomains. It was found that the nanodomains with small angle boundaries of atomic-scale width were distributed within the subgrains that constitute the clusters in MgB2 grains. This nanostructural characteristic may be intrinsic in the quenched reaction product of Mg and amorphous B. It makes the nanodomain boundaries not act as barriers to the current percolation path, thus exhibiting no weak-link problem in the MgB2.</p>
Engineering
https://ro.uow.edu.au/engpapers/94
oai:ro.uow.edu.au:engpapers-1094
2013-05-21T04:04:17Z
publication:xlwang
publication:journal_articles
publication:hkliu
publication:eis
publication:jhorvat
publication:engpapers
publication:sxdou
publication:document_types
Order-disorder transition in Bi2.1Sr1.9CaCu2O8 + delta single crystals doped with Fe and Pb
Uprety, K. K.
Horvat, J.
Wang, Xiaolin
Ionescu, M.
Liu, Hua-Kun
Dou, S. X.
Brandt, E. H.
Journal Article
10.1103/PhysRevB.65.224501
7591
2002-01-01T08:00:00Z
<p>This article was originally published as: Uprety, KK, Horvat, J, Wang, XL, Ionescu, M, Liu, HK, Dou, SX, & Brandt, EH, Order-disorder transition in Bi2.1Sr1.9CaCu2O8 + delta single crystals doped with Fe and Pb, Physical review - Series B, 2002, 65, 224501 (7 pages), and may be found <a href="http://scitation.aip.org/vsearch/servlet/VerityServlet?KEY=FREESR&smode=strresults&sort=chron&maxdisp=25&threshold=0&possible1zone=article&bool1=and&possible4=uprety&possible4zone=author&bool4=and&possible2=order-disorder&possible2zone=multi&OUTLOG=NO&viewabs=PRBMDO&key=DISPLAY&docID=1&page=1&chapter=0">here</a>. Copyright 2002 American Physical Society.</p>
<p>The magnetic field Hdis(T) where an order-disorder transition of the vortex lattice in high-Tc superconductors occurs, is investigated by measurements of the magnetization M(H) in Bi2.1Sr1.9CaCu2O8 + delta (Bi2212) single crystals doped with iron and lead. Comparative studies are made of the temperature dependences of the field Hpeak(T), where the second peak occurs in |M(H)|, and the fields Hmin(T), and Hinfl(T) where a minimum and an inflection point occur at the low-field side of this peak. It is proposed that Hdis(T) lies close to Hinfl. In Bi2.1Sr1.9Ca1.0(Cu1–yFey)2O8 + delta single crystals with Fe concentration y = 0, 0.005, 0.016, and 0.022, a pronounced peak in the derivative |dM/dH| is observed, whose position Hinfl(T) is independent of temperature T. We relate this peak to the field Hdis(T), which separates a weakly elastically disordered vortex lattice from a plastically disordered vortex solid. In heavily Pb-doped single Bi2212 crystals, Hinfl(T) decreases with increasing T. For the same crystals, a minimum in the normalized relaxation rate S(H) is observed at Hinfl, indicating two different flux-creep mechanisms above and below that field and two different solid vortex phases. It is argued that the negative slope of Hdis(T) in heavily-Pb-doped Bi2212 crystals is related to the enhanced c axis conductivity caused by the Pb sitting between the CuO2 layers and causing three-dimensional vortex lines, while in Fe-doped Bi2212 crystals the Fe ions sit on the CuO2 planes and thus do not enhance the coupling between pancake vortices.</p>
Engineering
https://ro.uow.edu.au/engpapers/95
oai:ro.uow.edu.au:engpapers-1097
2013-05-21T04:00:15Z
publication:journal_articles
publication:eis
publication:jhorvat
publication:engpapers
publication:sxdou
publication:engineering
publication:document_types
Effect of carbon nanotube doping on critical current density of MgB2 superconductor
Dou, S X
Yeoh, W. K.
Horvat, J.
Ionescu, M.
Journal Article
10.1063/1.1634378
9661
2003-01-01T08:00:00Z
<p>This article was originally published as: Dou, SX, Yeoh, WK, Horvat, J & Ionescu, M, Effect of carbon nanotube doping on critical current density of MgB2 superconductor, Applied Physics Letters, 2003, 83(24), 4996-4998, and may be found <a href="http://scitation.aip.org/vsearch/servlet/VerityServlet?KEY=FREESR&smode=strresults&sort=chron&maxdisp=25&threshold=0&possible1zone=article&bool1=and&possible4=dou&possible4zone=author&bool4=and&possible2=effect+of+carbon+nanotube&possible2zone=multi&OUTLOG=NO&viewabs=APPLAB&key=DISPLAY&docID=1&page=1&chapter=0">here</a>. Copyright 2003 American Institute of Physics, This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.</p>
<p>The effect of doping MgB2 with carbon nanotubes on transition temperature, lattice parameters, critical current density and flux pinning was studied for MgB2–xCx with x = 0, 0.05, 0.1, 0.2, and 0.3. The carbon substitution for B was found to enhance Jc in magnetic fields but depress Tc. The depression of Tc, which is caused by the carbon substitution for B, increases with an increasing doping level, sintering temperature, and duration. By controlling the extent of the substitution and addition of carbon nanotubes we can achieve the optimal improvement on critical current density and flux pinning in magnetic fields while maintaining the minimum reduction in Tc. Under these conditions, Jc was enhanced by two orders of magnitude at 8 T and 5 K and 7 T and 10 K. Jc was more than 10 000 A/cm2 at 20 K and 4 T and 5 K and 8.5 T, respectively.</p>
Engineering
https://ro.uow.edu.au/engpapers/98
oai:ro.uow.edu.au:engpapers-1095
2013-10-01T02:27:41Z
publication:xlwang
publication:journal_articles
publication:hkliu
publication:eis
publication:jhorvat
publication:engpapers
publication:sxdou
publication:engineering
publication:document_types
Superconductivity and flux pinning in Y and heavily Pb codoped Bi-2212 single crystals
Wang, Xiaolin
Liu, Hua-Kun
Dou, S X
Horvat, J.
Millikon, D.
Heine, G.
Lang, W.
Luo, H. M.
Ding, Shichao
Journal Article
10.1063/1.1356055
6528
2001-01-01T08:00:00Z
<p>This article was originally published as: Wang, XL, Liu, HK, Dou, SX, Horvat, J, Millikon, D, Heine, G, Lang, W, Luo, HM & Ding, SY, Superconductivity and flux pinning in Y and heavily Pb codoped Bi-2212 single crystals, Journal of Applied Physics, 2001, 89(11), 7669-7671, and may be found <a href="http://scitation.aip.org/vsearch/servlet/VerityServlet?KEY=FREESR&smode=strresults&sort=chron&maxdisp=25∨igquery=%28%28superconductivity+and+flux+pinning+%3CIN%3E+abstract+%3COR%3E+superconductivity+and+flux+pinning+%3CIN%3E+title+%3COR%3E+superconductivity+and+flux+pinning+%3CIN%3E+keywords%29+%3Cand%3E%28wang+%3Cin%3E+exactauthor%29%29&disporigquery=%28%28superconductivity+and+flux+pinning+%3CIN%3E+abstract+%3COR%3E+superconductivity+and+flux+pinning+%3CIN%3E+title+%3COR%3E+superconductivity+and+flux+pinning+%3CIN%3E+keywords%29+%3Cand%3E%28wang+%3CIN%3E+author%29%29&threshold=0&pjournals=&pyears=&possible1zone=article&bool1=and&possible2=superconductivity+and+flux+pinning&possible2zone=multi&possible3=liu&possible3zone=author&bool3=and&OUTLOG=NO&viewabs=JAPIAU&key=DISPLAY&docID=7&page=1&chapter=0&aqs=">here</a>. Copyright 2001 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.</p>
<p>Studies of superconductivity and flux pinning were carried out on (Bi1.64Pb0.36)Sr2Ca1–xYxCu2O8 + y (x = 0, 0.05, 0.11, 0.33) single crystals grown by the self-flux method. X-ray diffraction, transport, and magnetic measurements were performed for purposes of characterization. X-ray analysis revealed that the c lattice parameter systemically decreases as the Y doping level increases. The superconducting transition temperature Tc decreases from 80 to 30 K as x increases. A strong annealing effect on Tc and superconducting volume has been observed. Resistance measurements show that x = 0.33 samples are semiconductive over a wide temperature range between 4.2 and 300 K for the as-grown state, but become metallic with Tc of 65–70 K after air or oxygen annealing. Flux pinning was studied by measuring the hysteresis loop at different temperatures and different fields. A peak effect was observed in all the codoped samples. Results show that at low temperatures, the peak field is smaller than in solely Pb doped crystals and decreases as x increases (x>0.1). However, the peak field at high temperature for the x = 0.05 sample is higher than in heavily Pb doped Bi2212 crystals, indicative of a strong pinning due to the codoping.</p>
Engineering
https://ro.uow.edu.au/engpapers/96
oai:ro.uow.edu.au:engpapers-1096
2013-05-21T04:00:50Z
publication:journal_articles
publication:eis
publication:jhorvat
publication:engpapers
publication:sxdou
publication:engineering
publication:document_types
An alternative method for determination of the lock-in angle in twinned superconductors
Keshavarzi, S.
Horvat, J.
Pan, Alexey
Qin, M. J.
Dou, S. X.
Yao, X.
Munroe, P.
Journal Article
10.1063/1.2171772
13373
2006-01-01T08:00:00Z
<p>This article was originally published as: Keshavarzi, S, Horvat, J, Pan, AV, Qin, MJ, Dou, SX, Yao, X & Munroe, P, An alternative method for determination of the lock-in angle in twinned superconductors, Journal of Applied Physics, 2006, 99(4), pp. 043904-1-043904-5, and can be found <a href="http://scitation.aip.org/vsearch/servlet/VerityServlet?KEY=FREESR&smode=strresults&sort=chron&maxdisp=25&threshold=0&possible1zone=article&bool1=and&possible4=keshavarzi&possible4zone=author&bool4=and&possible2=an+alternative+method&possible2zone=multi&OUTLOG=NO&viewabs=JAPIAU&key=DISPLAY&docID=1&page=1&chapter=0">here</a>. Copyright 2006 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.</p>
<p>An alternative method for determining the lock-in angle phiL for pinning of the vortices on extended defects has been developed. This method does not require any preassumed criterion for defining phiL. Highly twinned Sm1+xBa2–xCu3O6+y single crystal was used for demonstrating the method. Appropriate scaling of the hysteresis loops measured for different angles between the field and twin planes in highly twinned SmBaCuO single crystal led to a clear discrimination between two vortex dynamics regimes. From this scaling, the lock-in angle was determined to be 6°±0.1° for the single crystal investigated. This method significantly reduces the uncertainty in determining the lock-in angle when compared to all the other currently employed methods.</p>
Engineering
https://ro.uow.edu.au/engpapers/97
oai:ro.uow.edu.au:engpapers-1099
2013-09-03T02:34:09Z
publication:arozenfeld
publication:journal_articles
publication:eis
publication:engpapers
publication:engineering
publication:document_types
Improved spatial resolution by MOSFET dosimetry of an x-ray microbeam
Kaplan, G. I.
Rosenfeld, Anatoly B.
Allen, B. J.
Booth, J. T.
Carolan, M. G.
Holmes-Siedle, A.
Journal Article
10.1118/1.598866
5457
2000-01-01T08:00:00Z
<p>This article was originally published as Kaplan, GI, Rosenfeld, AB, Allen, BJ et al, Improved spatial resolution by MOSFET dosimetry of an x-ray microbeam, Medical Physics, 27, 2000, 239. Original American Institute of Physics journal available <a href="http://scitation.aip.org/medphys/">here</a>.</p>
<p>Measurement of the lateral profile of the dose distribution across a narrow x-ray microbeam requires a dosimeter with a micron resolution. We investigated the use of a MOSFET dosimeter in an ‘‘edge-on’’ orientation with the gate insulating oxide layer parallel to the direction of the beam. We compared results using this technique to Gafchromic film measurements of a 200 micrometer wide planar x-ray microbeam. The microbeam was obtained by using a vernier micrometerdriven miniature collimator attached to a Therapax DXT300 x-ray machine operated at 100 kVp . The ‘‘edge-on’’ application allows utilization of the ultra thin sensitive volume of the MOSFET detector. Spatial resolution of both the MOSFET and Gafchromic film dosimeters appeared to be of about 1 micrometer. The MOSFET dosimeter appeared to provide more uniform dose profiles with the advantage of on-line measurements.</p>
Engineering
https://ro.uow.edu.au/engpapers/100
oai:ro.uow.edu.au:engpapers-1098
2013-08-27T05:44:40Z
publication:arozenfeld
publication:journal_articles
publication:eis
publication:engpapers
publication:engineering
publication:document_types
Measurement of radiotherapy x-ray skin dose on a chest wall phantom
Quach, K. Y.
Morales, J.
Butson, Martin
Rosenfeld, Anatoly B.
Metcalfe, Peter E
Journal Article
10.1118/1.599035
21597
2000-01-01T08:00:00Z
<p>This article was originally published as Quach, KY, Morales, J, Butson, MJ, Rosenfeld, AB and Metcalfe, PE, Measurement of radiotherapy x-ray skin dose on a chest wall phantom, Medical Physics, 27, 2000, 1676. Original American Institute of Physics journal available <a href="http://scitation.aip.org/medphys/">here</a>.</p>
<p>Sufficient skin dose needs to be delivered by a radiotherapy chest wall treatment regimen to ensure the probability of a near surface tumor recurrence is minimized. To simulate a chest wall treatment a hemicylindrical solid water phantom of 7.5 cm radius was irradiated with 6 MV x-rays using 20×20 cm<sup>2</sup> and 10×20 cm<sup>2</sup> fields at 100 cm source surface distance (SSD) to the base of the phantom. A surface dose profile was obtained from 0 to 180°, in 10° increments around the circumference of the phantom. Dosimetry results obtained from radiochromic film (effective depth of 0.17 mm) were used in the investigation, the superficial doses were found to be 28% (of <em>D</em><sub>max</sub>) at the 0° beam entry position and 58% at the 90° oblique beam position. Superficial dose results were also obtained using extra thin thermoluminescent dosimeters (TLD) (effective depth 0.14 mm) of 30% at 0°, 57% at 90°, and a metal oxide semiconductor field effect transistor (MOSFET) detector (effective depth 0.5 mm) of 43% at 0°, 62% at 90°. Because the differences in measured superficial doses were significant and beyond those related to experimental error, these differences are assumed to be mostly attributable to the effective depth of measurement of each detector. We numerically simulated a bolus on/bolus off technique and found we could increase the coverage to the skin. Using an alternate “bolus on,” “bolus off” regimen, the skin would receive 36.8 Gy at 0° incidence and 46.4 Gy at 90° incidence for a prescribed midpoint dose of 50 Gy. From this work it is evident that, as the circumference of the phantom is traversed the SSD increases and hence there is an inverse square fluence fall-off, this is more than offset by the increase in skin dose due to surface curvature to a plateau at about 90°. Beyond this angle it is assumed that beam attenuation through the phantom and inverse square fall-off is causing the surface dose to reduce.</p>
Engineering
https://ro.uow.edu.au/engpapers/99
135678/qualified-dublin-core/100//