Digital Commons Network^™

In Vivo Dosimetry And Seed Localization In Prostate Brachytherapy With Permanent Implants, Anatoly B. Rosenfeld, Dean Cutajar, M. L. Lerch, G. J. Takacs, T. Braddock, V. L. Perevertailo, J. Bucci, J. Kearsley, M. Zaider, M. Zelefsky

Faculty of Engineering - Papers (Archive)

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 …

Calculation Of The Nonlinear Free-Carrier Absorption Of Terahertz Radiation In Semiconductor Heterostructures, C. Zhang, J. C. Cao

Faculty of Engineering - Papers (Archive)

Nonlinear absorption of terahertz waves by electrons in a semiconductor heterostructure is calculated. We solve the quantum transport equation for electrons strongly coupled to terahertz photons. The electrical field of the laser radiation is included exactly, and the electron-impurity interaction is included up to the second order. It is found that Joule heating of the electronic system due to impurity scattering decreases rapidly due to the strong electron-photon interaction. Our result is the dynamic equivalence of electron localization in a strong field. In the limit of weak radiation field, the current is linear in the field strength.

Laboratory Determination Of Efficiency Of Prefabricated Vertical Drains Incorporating Vacuum Preloading, Buddhima Indraratna, Cholachat Rujikiatkamjorn

Faculty of Engineering - Papers (Archive)

This paper is mainly concerned with a laboratory study to investigate the effect of vacuum preloading. Two separate series of tests were conducted in a large-scale consolidation apparatus designed and installed at the University of Wollongong, with axial load increments of 30 and 50 kPa. The first series of tests were performed based on the conventional method (i.e. without vacuum preloading). For the second series, a vacuum pressure of 100 kPa was applied during the process of consolidation. The corresponding settlement behaviour was recorded and plotted. The extent of smear zone was examined by the variation of permeability of small …

Decoupling Transition Of Two Coherent Vortex Arrays Within The Surface Superconductivity State, Alexey Pan, P. Esquinazi

Faculty of Engineering - Papers (Archive)

In magnetic fields applied within the angular range of the surface superconductivity state a magnetically anisotropic layered medium is created in structurally isotropic, sufficiently thick niobium films. Surface (Kulik) vortices residing in the superconducting sheaths on both main film surfaces in tilted fields are shown to undergo a decoupling transition from a coherent to an independent behavior, similar to the behavior observed for Giaever transformer. At the transition a feature in pinning properties is measured, which implies different pinning for the lattice of surface vortices coherently coupled through the normal layer and for two decoupled vortex arrays in the superconducting …

Superconducting Screening On Different Length Scales In High-Quality Bulk Mgb2 Superconductor, J. Horvat, Saeid Soltanian, Alexey Pan, Xiaolin Wang

Faculty of Engineering - Papers (Archive)

High-quality bulk MgB₂ 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 μm, ∼10 μm, and whole of the sample (∼millimeter). Each of these screenings contributes to the measured irreversible magnetic moment (Δm). The analysis of the field dependence of Δm for samples of subsequently decreasing size showed that the critical current obtained using the simple critical state model …

A Chandra X-Ray Observation Of A1991: The Late Stages Of Infall?, M. Sharma, B. R. Mcnamara, P. Nulsen, M. Owers, M. W. Wise, E. L. Blanton, C. L. Sarazin, F. N. Owen, L. P. David

Faculty of Engineering - Papers (Archive)

We present results from a 38 ks Chandra X-ray observation of the z = 0.059 galaxy cluster A1991. The cluster has a bright X-ray core and a central temperature gradient that declines inward from 2.7 keV at 130 kpc to ≈1.6 keV at the cluster center. The radiative cooling time of the gas in the inner 10 kpc is about 0.5 Gyr, and it rises to 1 Gyr at a radius of 20 kpc. The cooling rate of the gas within the latter radius is ≲25 M⊙ yr-1. The Chandra ACIS-S3 image shows that the intracluster medium has an asymmetric …

Characterization Of Nanocrystalline Si-Mcmb Composite Anode Materials, G. X. Wang, J. Yao, Hua-Kun Liu

Faculty of Engineering - Papers (Archive)

Nanocrystalline Si-mesocarbon microbeads ~MCMB! composite anode materials were prepared by ballmilling. Scanning electron microscopic observation showed that the spherical shape of MCMB particles can be retained via moderate ballmilling. Ballmilling conditions have an impact on the capacity and cyclability of nanocrystalline Si-MCMB composites. The optimized Si-MCMB composite anode demonstrated a reversible capacity of 1066 mAh/g with good cyclability. A reaction model has been proposed to explain the reaction mechanisms of lithium insertion and extraction in the Si-MCMB electrode.

Oxygen Vacancy Ordering And Magnetism In The Rare Earth Stabilised Perovskite Form Of “Srco3-D, M. James, D. Cassidy, K. F. Wilson, J. Horvat, R. L. Withers

Faculty of Engineering - Papers (Archive)

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 …

A Systematic Study Of Radio-Induced X-Ray Cavities In Clusters, Groups, And Galaxies, L. Birzan, D. A. Rafferty, B. R. Mcnamara, M. W. Wise, P. Nulsen

Faculty of Engineering - Papers (Archive)

We present an analysis of 16 galaxy clusters, one group, and one galaxy drawn from the Chandra Data Archive. These systems possess prominent X-ray surface brightness depressions associated with cavities or bubbles that were created by interactions between powerful radio sources and the surrounding hot gas. The central galaxies in these systems harbor radio sources with luminosities ranging between ∼2 × 1038 and 7 × 1044 ergs s-1. The cavities have an average radius of ∼10 kpc, and they lie at an average projected distance of ∼20 kpc from the central galaxy. The minimum energy associated with the cavities ranges …

Virgin Magnetization Of A Magnetically Shielded Superconductor Wire: Theory And Experiment, Y. A. Genenko, S. V. Yampolskii, Alexey Pan

Faculty of Engineering - Papers (Archive)

On the basis of exact solutions to the London equation, the magnetic moment of a type II superconductor filament surrounded by a soft-magnet environment is calculated and the procedure of extracting the superconductor contribution from magnetic measurements is suggested. A comparison of theoretical results with experiments on MgB2/Fe wires allows the estimation of the value of critical current for the first magnetic flux penetration.

Optimum Dynamic Balancing Of Planar Parallel Manipulators, G. Alici, B. Shirinzadeh

Faculty of Engineering - Papers (Archive)

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 …

Mathematical Modeling And Field Evaluation Of Embankment Stabilized With Vertical Drains Incorporating Vacuum Preloading, Buddhima Indraratna, Cholachat Rujikiatkamjorn

Faculty of Engineering - Papers (Archive)

This study presents the analytical modeling of vertical drains incorporating vacuum preloading in both axisymmetric and plane strain conditions. The effectiveness of vacuum pressure (i.e. both constant vacuum pressure and varied vacuum pressure) applied along the drain is considered. A multidrain plane strain model is employed to analyse an embankment at the site of Second Bangkok International Airport (SBIA) stabilised with prefabricated vertical drains. At this site, a significantly reduced height of sand surcharge was applied by reducing the pore pressures through vacuum preloading. The results of FEM analysis confirm the efficiency of vacuum preloading in comparison with the conventional …

Structural And Magnetic Properties Of Y0.33sr0.67coo2.79, D. J. Goossens, K. F. Wilson, M. James, A. J. Studer, Xiaolin Wang

Faculty of Engineering - Papers (Archive)

The perovskite-based oxide Y0.33Sr0.67CoO2.79 has been magnetically and structurally characterized. The material shows a unit cell of 23234 simple perovskite cubes with space group I4/mmm. This is a different structure to that observed in the much-studied (La,Sr)CoO3 oxides. Oxygen stoichiometry is established through thermogravimetric analysis and correlated with ac and dc magnetic measurements and magnetic neutron diffraction. Hysteresis with field and temperature is observed in the dc magnetization measurements, yet the absence of an imaginary component in the ac susceptibility suggests a time-independent cause for these effects such as the presence of independently ordering ferromagnetic regions due to compositional inhomogeneities …

Active Control Of Cross Wind Response Of 76-Story Tall Building Using A Fuzzy Controller, B. Samali, M. Al-Dawod, K. C. Kwok, Fazel Naghdy

Faculty of Engineering - Papers (Archive)

This paper focuses on the benchmark problem application regarding the vibration control of tall buildings under cross wind excitation. The building under consideration is the 76-story, 306-m tall reinforced concrete office tower proposed for the city of Melbourne, Australia. The adopted control scheme consists of an active tuned mass damper (ATMD) where the control action is achieved by a fuzzy logic controller (FLC). The main advantage of the FLC is its inherent robustness and ability to handle any nonlinear behavior of the structure and the fact that its implementation does not require a mathematical model of the structure. This benchmark …

Asymmetric Kernel Regression, M. Mackenzie, K. Tieu

Faculty of Engineering - Papers (Archive)

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.

Local Buckling Of Steel Plates In Double Skin Composite Panels Under Biaxial Compression And Shear, Q. Q. Liang, B. Uy, H. D. Wright, M. A. Bradford

Faculty of Engineering - Papers (Archive)

Steel plates in double skin composite (DSC) panels are restrained by a concrete core and welded stud shear connectors at discrete positions. Local buckling of steel plates in DSC panels may occur in a unilateral mode between stud shear connectors when subjected to combined states of stresses. This paper studies the local and postlocal buckling strength of steel plates in DSC panels under biaxial compression and in-plane shear by using the finite element method. Critical local buckling interaction relationships are presented for steel plates with various boundary conditions that include the shear stiffness effects of stud shear connectors. A geometric …

A Two-Stage Decision Support Tool For Restoring Tidal Flows To Flood Mitigation Drains Affected By Acid Sulfate Soil: Case Study Of Broughton Creek Floodplain, New South Wales, Australia, W. Glamore, Buddhima Indraratna

Faculty of Engineering - Papers (Archive)

A 2-stage flood estimation and water quality decision support tool (DST) was developed, calibrated, and applied to a field site in south-eastern New South Wales (NSW) to simulate tidal restoration in a flood mitigation drain affected by acid sulfate soils leachate. The first stage of the DST employes a digital terrain map, geographic information tools, and measured water levels to calculate drain water overtopping due to tidal variations. Simulations using the GIS technique at the study site indicated that the primary drainage network can safely accommodate full tidal flushing (0.91 m AHD or a 58% increase), whereas at the same …

Optical Absorption In Terahertz-Driven Quantum Wells, X. W. Mi, J. C. Cao, C. Zhang

Faculty of Engineering - Papers (Archive)

The optical absorption spectra in a quantum well driven both by an intense terahertz (THz) and by an optical pulse are theoretically investigated within the theory of density matrix. We found that the optical absorption spectra and the splitting of the excitonic peaks splitting can be controlled by changing the THz field intensity and/or frequency. The Autler–Towns splitting is a result of the THz nonlinear dynamics of confined excitons, which is in agreement with the experiments. In addition, the dependence of the optical absorption on the quantum well width and the carrier density is also discussed.

Nanodosimetric Cluster Size Distributions Of Therapeutic Proton Beams, Andrew J. Wroe, Reinhard Schulte, Vladimir Bashkirov, Anatoly B. Rosenfeld, Brian Keeney, Patrick Spradlin, Hartmut F. W Sadrozinski, Bernd Grosswendt

Faculty of Engineering - Papers (Archive)

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 …

Effect Of Sample Size On Magnetic Jc For Mgb2 Superconductor, J. Horvat, Saeid Soltanian, Xiaolin Wang, S. X. Dou

Faculty of Engineering - Papers (Archive)

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 …

Nanoscale-Sic Doping For Enhancing Jc And Hc2 In Superconducting Mgb2, S X. Dou, V. Braccini, Saeid Soltanian, R. Klie, Y. Zhu, S. Li, Xiaolin Wang, D. Larbalestier

Faculty of Engineering - Papers (Archive)

The effect of nanoscale-SiC doping of MgB2 was investigated in comparison with undoped, clean-limit, and Mg-vapor-exposed samples using transport and magnetic measurements. It was found that there are two distinguishable but related mechanisms that control the critical current-density-field JcsHd behavior: increase of upper critical field Hc2 and improvement of flux pinning. There is a clear correlation between the critical temperature Tc, the resistivity r, the residual resistivity ratio RRR=Rs300 Kd /Rs40 Kd, the irreversibility field H*, and the alloying state in the samples. The Hc2 is about the same within the measured field range for both the Mg-vapor-treated and the …

Cryogenic Magnetic Field Sensor Based On The Magnetoresistive Effect In Bulk Bi2212 + Usr2cao6, M. Ionescu, B. Winton, Tania M. Silver, S. X. Dou, R. Ramer

Faculty of Engineering - Papers (Archive)

A large magnetoresistive (MR) effect was observed in melt-textured (MT) Bi2212 in which USr2CaO6 was added in a proportion of 6 wt %. The resistivity measurements of MT Bi2212 + 6 wt % USr2CaO6 show high sensitivity to applied dc fields, as compared to pure Bi2212, in particular at low fields, below 3 T, and in a temperature range between 45 K and 85 K. In this temperature range, the MR effect of MT Bi2212 + 6 wt % USr2CaO6 is two orders of magnitude larger than the MR effect in pure Bi2212, and display a maximum that may be …

Improving The Ductility Of Knee Joints Between Rectangular Hollow Sections, Lip H. Teh, Gregory J. Hancock

Faculty of Engineering - Papers (Archive)

This paper proposes a new welding-based solution that significantly increases the rotation capacity of a stiffened welded knee joint between cold-formed rectangular hollow sections under opening moment. The proposed solution is more economical than the use of internal sleeves and can be applied to new as well as existing structures. The solution involves the use of extra layers of weld on the inner (tension) flange of a stiffened welded knee joint. Laboratory test results are presented to demonstrate that the solution enabled such a joint between DuraGal C450 150×50×4 or 150×50×5 rectangular hollow sections manufactured to AS 1163 to satisfy …

Beam Element Verification For 3d Elastic Steel Frame Analysis, Lip H. Teh

Faculty of Engineering - Papers (Archive)

The paper describes the attributes that should be possessed by a benchmark example for verifying the beam elements used to carry out 3D linear buckling analysis and 3D second-order elastic analysis of steel frames. Based on the attributes described, the paper proposes a suite of benchmark examples selected from the literature. The necessary features of a beam element required to pass the proposed benchmark problems are given, and beam elements that possess these features are cited. The paper also explains the merits of linear buckling analysis examples, and provides a commentary on two well-known examples.

Recycling Of Ladle Furnace Slags, Sima Aminorroaya-Yamini, Hossein Edris, Ali Tohidi, Jafar Parsi, Bahram Zamani

Australian Institute for Innovative Materials - Papers

Ferrous industry slag is waste product of all steelmaking manufactures. These materials should be reused or stocked. There is abundant literature on the subject of reuse and recycling of blast furnace(BF), basic oxygen furnace(BOF), electric arc furnace(EAF). However, due to the fact that ladle furnaces(LF) have only been constructed in significant numbers since the 1980's, the relatively low slag volume in comparison to the other slags and also the high variability in slag chemistry, very few papers have been published on the recycling of ladle slag as separate materials.

Studies reveal that there is significant percent calcium aluminate in ladle …

Mechanical Performance Of Ppy Helix Tube Microactuator, Mehrdad Bahrami Samani, Geoffrey M. Spinks, Christopher David Cook

Faculty of Engineering - Papers (Archive)

Conducting polymer actuators with favourable properties such as linearity, high power density and compliance are of increasing demand in micro applications. These materials generate forces over two times larger than produced by mammalian skeletal muscles. They operate to convert electro chemical energy to mechanical stress and strain. On the other hand, the application of conducting polymers is limited by the lack of a full description of the relation between four essential parameters: stress, strain, voltage and current. In this paper, polypyrrole helix tube micro actuator mechanical characteristics are investigated. The electrolyte is propylene carbonate and the dopant is TBA. PF6. …

Finite-Element Analysis To Determine Effect Of Monolimb Flexibility On Structural Strength And Interaction Between Residual Limb And Prosthetic Socket, Winson Lee, Ming Zhang, David A. Boone, Bill Contoyannis

Faculty of Engineering and Information Sciences - Papers: Part A

Monolimb refers to a kind of transtibial prostheses having the socket and shank molded into one piece of thermoplastic material. One of its characteristics is that the shank is made of a material that can deform during walking, which can simulate ankle joint motion to some extent. Changes in shank geometry can alter the stress distribution within the monolimb and at the residual limb-socket interface and, respectively, affect the deformability and structural integrity of the prosthesis and comfort perceived by amputees. This paper describes the development of a finite-element model for the study of the structural behavior of monolimbs with …

Finite Element Modeling Of Contact Interface Between Trans-Tibial Residual Limb And Prosthetic Socket, Winson Lee, Ming Zhang, Xiaohong Jia, Jason Cheung

Faculty of Engineering and Information Sciences - Papers: Part A

Finite element method has been identified as a useful tool to understand the load transfer mechanics between a residual limb and its prosthetic socket. This paper proposed a new practical approach in modeling the contact interface with consideration of the friction/slip conditions and pre-stresses applied on the limb within a rectified socket. The residual limb and socket were modeled as two separate structures and their interactions were simulated using automated contact methods. Some regions of the limb penetrated into the socket because of socket modification. In the first step of the simulation, the penetrated limb surface was moved onto the …

Load Transfer Mechanics Between Trans-Tibial Prosthetic Socket And Residual Limb-Dynamic Effects, Xiaohong Jia, Ming Zhang, Winson Lee

Faculty of Engineering and Information Sciences - Papers: Part A

The effects of inertial loads on the interface stresses between trans-tibial residual limb and prosthetic socket were investigated. The motion of the limb and prosthesis was monitored using a Vicon motion analysis system and the ground reaction force was measured by a force platform. Equivalent loads at the knee joint during walking were calculated in two cases with and without consideration of the material inertia. A 3D nonlinear finite element (FE) model based on the actual geometry of residual limb, internal bones and socket liner was developed to study the mechanical interaction between socket and residual limb during walking. To …

Study On The Mechanism Of The Squeeze-Strengthen Effect In Magnetorheological Fluids, Xianzhou Zhang, X L. Gong, P Q. Zhang, Q M. Wang

Faculty of Engineering and Information Sciences - Papers: Part A

Current magnetorheological (MR)fluids have the limitation that their yield stresses are not strong enough to meet some industrial requirements. X. Tang, X. Zhang, and R. Tao [J. App. Phys87, 2634 (2000)] proposed a method to achieve high-efficiency MR fluids by study of squeeze-strengthen effect. But there is little report on its mechanism. This paper aims to investigate this effect through experimental and theoretical approaches. For this purpose, an apparatus is designed to experimentally study the mechanism of this squeeze-strengthen effect. Taking account of a modified magnetic dipole model and the friction effect, a semiempirical model is proposed to explain this …