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Articles 1 - 30 of 1669
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Effect Of Eccentric Load On Retrofitted Reinforced Concrete Columns Confined With Frp, Thong M. Pham, X Lei, Muhammad N. S Hadi
Effect Of Eccentric Load On Retrofitted Reinforced Concrete Columns Confined With Frp, Thong M. Pham, X Lei, Muhammad N. S Hadi
Faculty of Engineering - Papers (Archive)
Different behaviour of diverse sections of confined Reinforced Concrete (RC) columns under eccentric load is investigated in this study. Three types of sections are considered, which include square columns, square with rounded corners and modified circular columns. Twelve reinforced square concrete columns were made from normal strength concrete and subdivided into four groups. The first three columns were the Reference Group and had no modification.The next three columnswere modified with round corners and wrapped with three layers of Carbon Fibre Reinforced Polymer (CFRP), another three were bonded with four pieces of segmental circular concrete covers and wrapped with three layers …
Influence Of Ti/N Ratio On Simulated Cghaz Microstructure And Toughness In X70 Steels, Z X. Zhu, M Marimuthu, L Kuzmikova, H J. Li, F Barbaro, L Zheng, M Z. Bai, C Jones
Influence Of Ti/N Ratio On Simulated Cghaz Microstructure And Toughness In X70 Steels, Z X. Zhu, M Marimuthu, L Kuzmikova, H J. Li, F Barbaro, L Zheng, M Z. Bai, C Jones
Faculty of Engineering - Papers (Archive)
Three API 5L X70 steels with different Ti and N contents and otherwise identical chemistry were selected to investigate the effect of Ti/N ratio on the toughness in coarse grained heat affected zone (CGHAZ). A Gleeble 3500 thermomechanical simulator was used to simulate the thermal profile of CGHAZ of double submerged arc welding process. The microstructure was examined by optical microscopy. Statistics of CGHAZ grain coarsening were compiled by measuring the prior austenite grain size. Toughness of the simulated CGHAZ regions was evaluated by Charpy V-notch testing at -20 and -40°C. Morphology of the impact fracture surface was investigated using …
Effects Of Membrane Fouling On N-Nitrosamine Rejection By Nanofiltration And Reverse Osmosis Membranes, Takahiro Fujioka, Stuart J. Khan, James A. Mcdonald, Rita K. Henderson, Yvan Poussade, Jorg E. Drewes, Long Nghiem
Effects Of Membrane Fouling On N-Nitrosamine Rejection By Nanofiltration And Reverse Osmosis Membranes, Takahiro Fujioka, Stuart J. Khan, James A. Mcdonald, Rita K. Henderson, Yvan Poussade, Jorg E. Drewes, Long Nghiem
Faculty of Engineering - Papers (Archive)
The impact of fouling on N-nitrosamine rejection by nanofiltration (NF) and reverse osmosis (RO) membranes was investigated in this study. Membrane fouling was simulated using tertiary treated effluent and several model fouling solutions (that contained sodium alginate, bovine serum albumin, humic acid or colloidal silica) to elucidate the changes in rejection behaviour of N-nitrosamines. In general, the rejection of N-nitrosamines increased when the membranes were fouled by tertiary effluent. The rejection of small molecular weight N-nitrosamines was most affected by membrane fouling. In particular, the rejection of N-nitrosodimethylamine (NDMA) by the ESPA2 membrane increased from 34 to 73% after membrane …
Stabilization Of Nazn(Bh4)3 Via Nanoconfinement In Sba-15 Towards Enhanced Hydrogen Release, Guanglin Xia, Li Li, Zaiping Guo, Qinfen Gu, Yanhui Guo, Xuebin Yu, Hua-Kun Liu, Zongwen Liu
Stabilization Of Nazn(Bh4)3 Via Nanoconfinement In Sba-15 Towards Enhanced Hydrogen Release, Guanglin Xia, Li Li, Zaiping Guo, Qinfen Gu, Yanhui Guo, Xuebin Yu, Hua-Kun Liu, Zongwen Liu
Faculty of Engineering - Papers (Archive)
In the present work, the decomposition behaviour of NaZn(BH4)3 nanoconfined in mesoporous SBA-15 has been investigated in detail and compared to bulk NaZn(BH4)3 that was ball milled with SBA-15, but not nanoconfined. The successful incorporation of nanoconfined NaZn(BH4)3 into mesopores of SBA-15 was confirmed by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, 11B nuclear magnetic resonance, nitrogen absorption/desorption isotherms, and Fourier transform infrared spectroscopy measurements. It is demonstrated that the dehydrogenation of the space-confined NaZn(BH4)3 is free of emission of boric by-products, and significantly improved hydrogen release kinetics is also achieved, with pure hydrogen release at temperatures …
Effect Of Ply Configuration On Hollow Square Reinforced Concrete Columns Confined With Carbon Fibre-Reinforced Polymer (Cfrp), T D. Le, M T. Lester, Muhammad N. S Hadi
Effect Of Ply Configuration On Hollow Square Reinforced Concrete Columns Confined With Carbon Fibre-Reinforced Polymer (Cfrp), T D. Le, M T. Lester, Muhammad N. S Hadi
Faculty of Engineering - Papers (Archive)
This paper presents results of testing twelve hollow square reinforced concrete specimens wrapped with Carbon fibre reinforced polymer CFRP. The effect of ply configuration on the behaviour of the specimens is investigated. All specimens were 800mm high and had the dimensions of 200mm×200mm in cross-section and a hollow core of 80mm×80 mm. The specimens were divided into four groups with three specimens each. The specimens in the first group without bonding CFRP served as references. While the remaining three groups of specimens were externally wrapped with CFRP in three different ply configurations of hoop, vertical and 45◦ angle with reference …
An Elasto-Plastic Model For Liquefiable Sands Subjected To Torsional Shear Loadings, Gabriele Chiaro, Junichi Koseki, Nalin L. I De Silva
An Elasto-Plastic Model For Liquefiable Sands Subjected To Torsional Shear Loadings, Gabriele Chiaro, Junichi Koseki, Nalin L. I De Silva
Faculty of Engineering - Papers (Archive)
This paper presents a modeling procedure for simulating the monotonic undrained torsional shear behavior of sands, including stress-strain relationship, and excess pore water pressure generation, while considering the void ratio and stress level dependence of stress-strain-dilatancy behavior of sand. A unique set of soil parameters is required by the model to satisfactorily predict the undrained behavior of loose and dense Toyoura sand over a wide range of initial void ratios and confining pressures, as proven by simulating experimental data produced by the authors and found in the literature.
Microstructure Evolution And Alloying Elements Distribution Between The Phases In Powder Near-B Titanium Alloys During Thermo-Mechanical Processing, Mansur Ahmed, Azdiar A. Gazder, Dmytro G. Savvakin, Orest M. Ivasishin, E V. Pereloma
Microstructure Evolution And Alloying Elements Distribution Between The Phases In Powder Near-B Titanium Alloys During Thermo-Mechanical Processing, Mansur Ahmed, Azdiar A. Gazder, Dmytro G. Savvakin, Orest M. Ivasishin, E V. Pereloma
Faculty of Engineering - Papers (Archive)
In the present study, two powders near-β Ti alloys having a nominal composition of Ti-5Al-5Mo-5V-XCr-1Fe (X = 1–2, wt%) were studied. The alloys were produced via the blended elemental powder metallurgy technique using hydrogenated Ti powder. Microstructure evolution and the distribution of the alloying elements between the phases were investigated after each step of thermo-mechanical processing (TMP). Microstructures were refined through the TMP in both alloys. Porosity was reduced with deformation at 1173 K (900 °C) in the β phase field. The β → α phase transformation occurred during soaking at 1023 K (750 °C) in the α + β …
Development Of Reliability-Based Design For Railway Prestressed Concrete Sleepers, Sakdirat Kaewunruen, Alexander Remennikov, Martin H. Murray
Development Of Reliability-Based Design For Railway Prestressed Concrete Sleepers, Sakdirat Kaewunruen, Alexander Remennikov, Martin H. Murray
Faculty of Engineering - Papers (Archive)
Faster and heavier train services are a driven improvement aspect for leaner and more profitable transport logistics of either passengers or freights. Ballasted rail track has been adopted for modern railways because of its many superior advantages in design, construction, short- and long-term maintenance, sustainability, financial capital and life cycle cost. An important element of the railway track system, which distributes the wheel load to the formation and holds the rail gauge, is the railway sleeper. Field data has raised concerns about design techniques for prestressed concrete (PC) sleepers. Most current design codes for these rely on allowable stresses and …
Effect Of Grain Size On The Hydrogen Diffusion Process In Steel Using Cellular Automaton Approach, Druce P. Dunne, E V. Pereloma, Nima Yazdipour
Effect Of Grain Size On The Hydrogen Diffusion Process In Steel Using Cellular Automaton Approach, Druce P. Dunne, E V. Pereloma, Nima Yazdipour
Faculty of Engineering - Papers (Archive)
The role of microstructure in susceptibility to hydrogen uptake and property degradation is being evaluated using a number of high strength pipeline steels. To do so, a cellular automaton (CA) model has been used to examine the effect of grain size, as a first step in assessing the influence of microstructure. The simulation results of hydrogen diffusion into microstructures with different grain sizes are presented.
Numerical Prediction Of Unsaturated Ground Behavior Influenced By Vegetation And Vacuum Consolidation, Cholachat Rujikiatkamjorn, Buddhima Indraratna, B Fatahi
Numerical Prediction Of Unsaturated Ground Behavior Influenced By Vegetation And Vacuum Consolidation, Cholachat Rujikiatkamjorn, Buddhima Indraratna, B Fatahi
Faculty of Engineering - Papers (Archive)
Bioengineering including native vegetation is an ancient method of improving the stability of slopes. In modern railway engineering, this technique is re-captured for increasing the soil stiffness and shear strength of subgrade beneath rail tracks. Currently this practice has become increasingly popular in Australia for stabilising railway corridors built over expansive clays and compressive soft soils. This paper looks at the stabilisation role by suction generated by both the natural vegetation and the artificial vacuum application using the numerical analysis. For demonstrating the role of native vegetation, a mathematical model for the rate of root water uptake was incorporated in …
Limit States Design Of Railway Concrete Sleepers, Sakdirat Kaewunruen, Alexander Remennikov, Martin H. Murray
Limit States Design Of Railway Concrete Sleepers, Sakdirat Kaewunruen, Alexander Remennikov, Martin H. Murray
Faculty of Engineering - Papers (Archive)
The recently updated information has raised a concern in not only the existing costineffective design method but also the unrealistic analysis mode of railroad prestressed concrete sleepers. Because of the deficient knowledge in the past, railway civil engineers have been mostly aware of the over conservative design methods for structural components in any railway track, which rely on allowable stresses and material strength reductions. Based on a number of proven experiments and field data, it is believed that the concrete sleepers complied with the allowable stress concept possess the unduly untapped fracture toughness. A collaborative research run by the Australian …
Effect Of Gas Atmosphere On Carbothermal Reduction And Nitridation Of Titanium Dioxide, Sheikh A. Rezan, Guangqing Zhang, Oleg Ostrovski
Effect Of Gas Atmosphere On Carbothermal Reduction And Nitridation Of Titanium Dioxide, Sheikh A. Rezan, Guangqing Zhang, Oleg Ostrovski
Faculty of Engineering - Papers (Archive)
This article examined the reduction/nitridation of rutile in the He-N2, Ar-N2, and He (Ar)-H2- N2 gas mixtures, as well as pure nitrogen, in the temperature-programmed and isothermal experiments in a fixed-bed reactor. The extents of reduction and nitridation were determined from the off gas composition and LECO analysis. The off-gas composition was monitored using the infrared sensor (CO, CO2, and CH4) and dew point analyzer (H2O). The phase composition of the reduced samples was analyzed using X-ray diffraction (XRD). The temperature and gas composition had a strong effect on the rutile reduction. The reduction was the fastest in the H2- …
Effect Of Compaction Energy On Shear Wave Velocity Of Dynamically Compacted Silty Sand Soil, Buddhima Indraratna, Ana Heitor, Cholachat Rujikiatkamjorn
Effect Of Compaction Energy On Shear Wave Velocity Of Dynamically Compacted Silty Sand Soil, Buddhima Indraratna, Ana Heitor, Cholachat Rujikiatkamjorn
Faculty of Engineering - Papers (Archive)
This study was focused on the effects of compaction energy on the dynamic properties of a silty sand in its as-compacted state in relation to the measured values of matric suction. The influence of the imparted energy on the shear wave velocity and the small-strain shear modulus of the compacted soil was studied for three different energy levels that correspond to the standard Proctor as well as reduced and enhanced. The specimens were prepared with moisture contents ranging from the dry to wet of optimum, and subsequently compacted to known dry unit weights for which the corresponding matric suction and …
Net Section Tension Capacity Of Bolted Connections In Cold-Reduced Steel Sheets, Lip H. Teh, Benoit P. Gilbert
Net Section Tension Capacity Of Bolted Connections In Cold-Reduced Steel Sheets, Lip H. Teh, Benoit P. Gilbert
Faculty of Engineering - Papers (Archive)
This paper examines the accuracy of design equations specified in the North American, European and Australasian codes for coldformed steel structures in determining the net section tension capacity of bolted connections in flat steel sheets. It points out that the shear lag factors embedded in the code equations either yield “anomalous” results or become irrelevant when they exceed unity. The “anomaly” was demonstrated through laboratory tests and is explained by using simple calculus. The configurations of specimens tested in the laboratory include single shear- and double-shear connections, with single or double bolts in a line parallel or perpendicular to the …
Pesticide Removal By A Mixed Culture Of Bacteria And White-Rot Fungi, Faisal I. Hai, Oska Modin, Kazuo Yamamoto, Kensuke Fukushi, Fumiyuki Nakajiam, Long Nghiem
Pesticide Removal By A Mixed Culture Of Bacteria And White-Rot Fungi, Faisal I. Hai, Oska Modin, Kazuo Yamamoto, Kensuke Fukushi, Fumiyuki Nakajiam, Long Nghiem
Faculty of Engineering - Papers (Archive)
Combining activated sludge cultures with microbes harboring specific degradation pathways could constitute a relevant process for the removal of toxic and recalcitrant organic substances from wastewater. Enhanced removal of three widely used recalcitrant pesticides from their liquid mixture was demonstrated by implementing a non-acclimated mixed culture of bacteria and white-rot fungus. During an incubation period of 14 days, the mixed fungus–bacteria culture achieved 47, 98, and 62% removal of aldicarb, atrazine and alachlor from the liquid phase, respectively. This compared favorably to batches containing only non-acclimated fungus or previously published removal rates with nonacclimated bacterial cultures. Biosorption along with biodegradation …
Illustrative Sections Depicting Landslide Susceptibility Of The Illawarra Escarpment, Andrew Leventhal, Phillip Flentje
Illustrative Sections Depicting Landslide Susceptibility Of The Illawarra Escarpment, Andrew Leventhal, Phillip Flentje
Faculty of Engineering - Papers (Archive)
The challenge that land landslides pose to infrastructure and to domestic and commercial development in the Illawarra region haa been recognised in land-use planning for decades. The seminal regional mapping undertaken by Bowman (1974) and, before him the work reported by Shellshear (1890), set the technical benchmarks for others to follow. The challenges presenled to development and road and rail infrastructure were recognised by both Wollongong City Council and major infrastructure providers in the NSW Road and Maritime Services (previously NSW Roads and Traffic Authority) and NSW Rail orp (previouIy State Rail uthority). Continuing support from this group has permitted …
Performance And Prediction Of Surcharge And Vacuum Consolidation Via Prefabricated Vertical Drains With Special Reference To Highways, Railways And Ports, Buddhima Indraratna, Cholachat Rujikiatkamjorn, Xueyu Geng
Performance And Prediction Of Surcharge And Vacuum Consolidation Via Prefabricated Vertical Drains With Special Reference To Highways, Railways And Ports, Buddhima Indraratna, Cholachat Rujikiatkamjorn, Xueyu Geng
Faculty of Engineering - Papers (Archive)
Much of the world’s essential infrastructure is built along congested coastal belts that are composed of highly compressible and weak soils up to significant depths. Soft alluvial and marine clay deposits have very low bearing capacity and excessive settlement characteristics, with obvious design and maintenance implications on tall structures and large commercial buildings, as well as port and transport infrastructure. Stabilising these soft soils before commencing construction is essential for both long term and short term stability. A system of vertical drains combined with vacuum pressure and surcharge preloading has become an attractive ground improvement alternative in terms of both …
Inelastic Stability Analysis Of High Strength Rectangular Concrete-Filled Steel Tubular Slender Beam-Columns, Vipulkumar Ishvarbhai Patel, Qing Quan Liang, Muhammad N. S Hadi
Inelastic Stability Analysis Of High Strength Rectangular Concrete-Filled Steel Tubular Slender Beam-Columns, Vipulkumar Ishvarbhai Patel, Qing Quan Liang, Muhammad N. S Hadi
Faculty of Engineering - Papers (Archive)
There is relatively little numerical study on the behavior of eccentrically loaded high strength rectangular concrete-filled steel tubular (CFST) slender beam-columns with large depth-to-thickness ratios, which may undergo local and global buckling. This paper presents a multi scale numerical model for simulating the interaction local and global buckling behavior of hlgh strength thin-walled rectangular CFST slender beam-columns under eccentric loading. The effects of progressive local buckling are taken into account in the mesoscale model based on fiber element formulations. Computational algorithms based on the Muller's method are developed to obtain complete load-deflection responses of CFST slender beam-columns at the macroscale …
Characterising Compacted Soil Using Shear Wave Velocity And Matric Suction, Ana Heitor, Buddhima Indraratna, Cholachat Rujikiatkamjorn
Characterising Compacted Soil Using Shear Wave Velocity And Matric Suction, Ana Heitor, Buddhima Indraratna, Cholachat Rujikiatkamjorn
Faculty of Engineering - Papers (Archive)
The manner in which soil compacts governs the practical and reliable criteria in controlling compaction in the field. A nuclear density meter, based on radioactive isotopes, is the method most commonly used for field compaction, and while it performs well for controlling placement, its localised natnre is not suitable for deeper fills or for assessing larger surface areas. In those types of conditions, alternative non-destrnctive methods should be considered. Numerous resea,:ch studies have focused on the characteristics of compacted soil at its optimum moisture content under saturated conditions, but only a few have evaluated compacted soil under unsaturated conditions using …
Performance Of Geosynthetically-Reinforced Rail Ballast In Direct Shear Conditions, Sd K Karimullah Hussaini, Buddhima Indraratna, J S. Vinod
Performance Of Geosynthetically-Reinforced Rail Ballast In Direct Shear Conditions, Sd K Karimullah Hussaini, Buddhima Indraratna, J S. Vinod
Faculty of Engineering - Papers (Archive)
In the recent past the use of geosynthetic-reinforcement to stabilise the rail tracks has been on the rise. The performance of such reinforced track is governed by the shear behavior of the ballastgeosynthetic interface. In view of this, large-scale direct shear tests were performed to explore the shear behaviour of rail ballast-geogrid interfaces. Fresh Latite ballast with an average particle size (D50) of 35 mm, and geogrids with different aperture sizes and shapes were used for this purpose. The laboratory experimental results indicate that the shear strength of ballast can be improved significantly when reinforced with geosynthetics, but the degree …
Field Monitoring Of Performance Of Ballasted Rail Track With Geosynthetic Reinforcement, P Anantanasakul, B Indraratna, S S. Nimbalkar, T Neville
Field Monitoring Of Performance Of Ballasted Rail Track With Geosynthetic Reinforcement, P Anantanasakul, B Indraratna, S S. Nimbalkar, T Neville
Faculty of Engineering - Papers (Archive)
Large cyclic stresses induced from heavy traffic can cause significant degradation of rail tracks, leading to poor track geometry and safety. Inclusion of resilient materials such as geosynthetics to reinforce the track substructure has been observed in the laboratory to be viable at reducing the impact of such adverse effects. Despite this, the ‘field’ performance of different geosynthetics to reinforce ballasted tracks has not been investigated in a systematic manner. An extensive field study was therefore undertaken on experimental track sections near Singleton, New South Wales. Four types of geosynthetics were installed at the ballast-subballast interface of track sections constructed …
Effect Of Coal Fines On The Shear Strength And Deformation Characteristics Of Ballast, S S. Nimbalkar, Buddhima Indraratna, Cholachat Rujikiatkamjorn, M Martin
Effect Of Coal Fines On The Shear Strength And Deformation Characteristics Of Ballast, S S. Nimbalkar, Buddhima Indraratna, Cholachat Rujikiatkamjorn, M Martin
Faculty of Engineering - Papers (Archive)
Ballast is the most common material supporting the rail track structure due to its large shear strength, high load bearing capacity and free-drainage. However, the fouling of ballast effects deterioration of track performance, and eventually demands track cleaning. Fouling refers to the progressive intrusion of fines into the ballast layer and subsequently filling the voids. Coal spilling from wagons during transport, sleeper and ballast degradation and soil pumping from soft subgrade are the major factors contributing to ballast fouling. Queensland rail network suffers mainly due to ballast breakdown and intrusion of coal fines. The maintenance costs of ballasted tracks can …
Effects Of Normal Stress On Water Flow Through A Single Roughwalled Rock Joint, Z Zhang, B Indraratna, C Kumara, Jan Anton Nemcik, W Gale
Effects Of Normal Stress On Water Flow Through A Single Roughwalled Rock Joint, Z Zhang, B Indraratna, C Kumara, Jan Anton Nemcik, W Gale
Faculty of Engineering - Papers (Archive)
Water ingress to underground openings is one of the major concerns in mining and tunnelling, because, rock joints provide natural seepage paths for groundwater flow. To study the water flow through deformable rock joints, triaxial tests with water flow were conducted under various confining stress levels (0.7-5.0 MPa). Two tests were performed on fully mated fracture specimens, and three tests were performed on a non-mated specimen where the fractured surfaces were displaced by 2.0 mm at the start of the test. The results show that the volumetric flow rate decreases with the increase in the normal stress, but the decreasing …
Effects Of Initial Static Shear On Liquefaction And Large Deformation Properties Of Loose Saturated Toyoura Sand In Undrained Cyclic Torsional Shear Tests, Gabriele Chiaro, Junichi Koseki, Takeshi Sato
Effects Of Initial Static Shear On Liquefaction And Large Deformation Properties Of Loose Saturated Toyoura Sand In Undrained Cyclic Torsional Shear Tests, Gabriele Chiaro, Junichi Koseki, Takeshi Sato
Faculty of Engineering - Papers (Archive)
This study focused on the role which static shear plays on the large deformation behavior of loose saturated sand during undrained cyclic loading. A series of undrained cyclic torsional shear tests was performed on saturated Toyoura sand specimens up to single amplitude shear strain exceeding 50%. Three types of cyclic loading patterns, i.e., stress reversal, intermediate and non-reversal, were employed by varying the initial static shear level and the cyclic shear stress amplitude. The observed types of failure could be distinguished into liquefaction (cyclic and rapid flow) and residual deformation by comparing both monotonic and cyclic undrained behavior. It was …
Room-Temperature Strong Terahertz Photon Mixing In Graphene, Sultan Shareef, Yee Sin Ang, Chao Zhang
Room-Temperature Strong Terahertz Photon Mixing In Graphene, Sultan Shareef, Yee Sin Ang, Chao Zhang
Faculty of Engineering - Papers (Archive)
We demonstrate that single layer graphene exhibits a strong nonlinear photon-mixing effect in the terahertz frequency regime. Up to room temperature, the third-order nonlinear current in graphene grows rapidly with increasing temperature. The third-order nonlinear current can be as strong as the linear current under a moderate electric field strength of 104 V∕cm. Because of the unique Dirac behavior of the graphene quasi-particles, low Fermi level and electron fillings optimizes the optical nonlinearity. Under a strong-field condition, the strong-field-induced Dirac fermion population redistribution and nonequilibrium carrier heating effects further amplify the optical nonlinearity of graphene. Our results suggest that doped …
Track Stabilisation With Geosynthetics And Geodrains, And Performance Verification Through Field Monitoring And Numerical Modelling, Buddhima Indraratna, S Nimbalkar, Cholachat Rujikiatkamjorn
Track Stabilisation With Geosynthetics And Geodrains, And Performance Verification Through Field Monitoring And Numerical Modelling, Buddhima Indraratna, S Nimbalkar, Cholachat Rujikiatkamjorn
Faculty of Engineering - Papers (Archive)
All over the world, ballasted railway tracks form one of the major transportation networks designed to provide heavy haul freight and passenger traffic. However, large cyclic loading from heavy axle trains operating at high speeds often causes excessive deformation and degradation of ballast, as well as unacceptable differential settlement of compressible foundation and, or pumping of the soft subgrade soils. The problem becomes more severe under high impact loads due to rail or wheel imperfections, causing accelerated ballast breakage. A proper understanding of load transfer mechanisms and their effects on track deformations are essential prerequisites for minimising maintenance costs. The …
Specular Andreev Reflection In The Interface Of A Two-Dimensional Semiconductor With Rashba Spin-Orbit Coupling And A D-Wave Superconductor, Bo Lv, C Zhang, Zhongshui Ma
Specular Andreev Reflection In The Interface Of A Two-Dimensional Semiconductor With Rashba Spin-Orbit Coupling And A D-Wave Superconductor, Bo Lv, C Zhang, Zhongshui Ma
Faculty of Engineering - Papers (Archive)
We reveal that the recently discovered specular Andreev reflection (SAR) [C. W. J. Beenakker, Phys. Rev. Lett. 97, 067007 (2006)] can occur in semiconductors where the spin-orbit coupling is finite. We demonstrate this finding in the hybrid of a two-dimensional electron gas with Rashba spin-orbit coupling and a superconductor. In the limit of low density or a strong spin-orbit coupling, specular Andreev reflection is finite. We also show that unit electron-hole conversion is possible in a specular Andreev reflection due to the different topological structures of the equal-energy surface between electrons and holes. The SAR in the semiconductor is determined …
The Importance Of Scattering, Surface Potential, And Vanguard Counter-Potential In Terahertz Emission From Gallium Arsenide, D L. Cortie, R A. Lewis
The Importance Of Scattering, Surface Potential, And Vanguard Counter-Potential In Terahertz Emission From Gallium Arsenide, D L. Cortie, R A. Lewis
Faculty of Engineering - Papers (Archive)
It is well established that under excitation by short (<1 ps), above-band-gap optical pulses, semiconductor surfaces may emit terahertz-frequency electromagnetic radiation via photocarrier diffusion (the dominant mechanism in InAs) or photocarrier drift (dominant in GaAs). Our three-dimensional ensemble Monte Carlo simulations allow multiple physical parameters to vary over wide ranges and provide unique direct insight into the factors controlling terahertz emission. We find for GaAs (in contrast to InAs), scattering and the surface potential are key factors. We further delineate in GaAs (as in InAs) the role of a vanguard counter-potential. The effects of varying dielectric constant, band-gap, and effective mass are similar in both emitter types
Stabilising Railway Embankments With Geosynthetic Grids And Drains And A Class A Prediction Of Track Behaviour, Buddhima Indraratna, Sanjay Nimbalkar, Cholachat Rujikiatkamjorn
Stabilising Railway Embankments With Geosynthetic Grids And Drains And A Class A Prediction Of Track Behaviour, Buddhima Indraratna, Sanjay Nimbalkar, Cholachat Rujikiatkamjorn
Faculty of Engineering - Papers (Archive)
The ballast layer is intended to provide a free draining base and sufficient bearing capacity to maintain a proper track alignment. Due to the growth in commuter and industrial traffic, the railway industry needs to fulfil the demands for faster, heavier, and longer trains. However, these high traffic loads often result in a large plastic deformations and degradation of ballast, which in turn, leads to a significant loss of track stability and high maintenance costs. The deformation and degradation of ballast are influenced by factors such as the amplitude and frequency of loading, the number of load cycles, track confining …
The Role Of Ballast Fouling Characteristics On The Drainage Capacity Of Rail Substructure, Nayoma Tennakoon, Buddhima Indraratna, Cholachat Rujikiatkamjorn, Sanjay Nimbalkar, Tim Neville
The Role Of Ballast Fouling Characteristics On The Drainage Capacity Of Rail Substructure, Nayoma Tennakoon, Buddhima Indraratna, Cholachat Rujikiatkamjorn, Sanjay Nimbalkar, Tim Neville
Faculty of Engineering - Papers (Archive)
The ballast layer is designed to be free draining, but when the voids of the granular medium are wholly or partially filled due to the intrusion of fine particles, the ballast is considered to be “fouled”. In order to ensure acceptable track performance, it is necessary to maintain good drainage within the ballast layer. This paper critically examines the current methods commonly used for evaluating the degree of ballast fouling and, due to their limitations, a new parameter, Void Contaminant Index is introduced. A series of large-scale constant head hydraulic conductivity tests were conducted with different levels of fouling to …