Engineering Commons^™

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 …

Fluctuation Of Mean Free Path And Transition Temperature Induced Vortex Pinning In (Ba,K)Fe2as2 Superconductors, S R. Ghorbani, Xiaolin Wang, Mahboobeh Shahbazi, S. X. Dou, C T. Lin

Faculty of Engineering - Papers (Archive)

The vortex pinning mechanisms of Ba0.72K0.28Fe2As2 single crystal have been studied systematically as a function of temperature and magnetic field. The temperature dependence of the critical current density, Jc(T), was analysed within the collective pinning model at different magnetic fields. It was found that both the dl pinning mechanism, i.e., pinning associated with charge-carrier mean free path fluctuation, and the dTc pinning mechanism, which is associated with spatial fluctuations of the transition temperature, coexist in the Ba0.72K0.28Fe2As2 single crystal in fields smaller than 4 T. Their contributions are strongly temperature and magnetic field dependent. At lower temperature and B

Modelling Of Temperature-Dependent Growth Kinetics Of Oxide Scale On Hot-Rolled Steel Strip, Xianglong Yu, Zhengyi Jiang, Dongbin Wei, Xiaodong Wang, Quan Yang

Faculty of Engineering - Papers (Archive)

A numerical simulation, developed to predict the temperature distribution and calculate the growth rale of the oxide scale formed on the microalloyed low carbon steel during the laminar cooling of hot strip rolling, was conducted by two-dimensional finite element method. The model takes into account the different thetmoPhYsical properties of the multilayered oxide scales and the film boundary conditions for the water jet impingement zone and the stable film boiling zone through the run-out table. Complied with the parabolic growth of the oxide layers and the distribution of the oxide phase, it is found that the present of wustite (FeO) …

Dependence Of Magnetoelectric Properties On Sintering Temperature For Nano-Sic-Doped Mgb2/Fe Wires Made By Combined In Situ/Ex Situ Process, Wenxian Li, Rong Zeng, Jiazhao Wang, Y Li, S. X. Dou

Faculty of Engineering - Papers (Archive)

Very fine nano-SiC particles (nm) were doped into a MgB2 superconductor. The influence of self-field supercurrent on the high-field performance of the nano-SiC-doped MgB2/Fe wires is discussed based on comparison of the critical current densities of the in situ processed nano-SiCdoped MgB2 wires and those of the nano-SiC-doped MgB2/Fe wires processed by the combination of in situ/ex situ methods.

Behaviour Of Frp Confined Concrete Cylinders Under Different Temperature Exposure, Muhammad N. S Hadi, B A. Louk Fanggi

Faculty of Engineering - Papers (Archive)

Bridge structures are exposed to the elements with a high variation in temperature. The purpose of this study is to investigate the effect of different high temperatures on the behaviour of concrete cylinders wrapped with Fibre Reinforced Polymer (FRP). Twelve concrete cylinders made of 60 MPa having 100 mm diameter and 200 mm height were cast and tested. The cylinders were divided into four groups: cylinders wrapped with a single CFRP layer, cylinders wrapped with two CFRP layers, cylinders wrapped with a single GFRP layer, and cylinders wrapped with two GFRP layers. Each group was exposed to temperatures of 20°C, …

Investigation On Temperature Change Of Cold Magnesium Alloy Strips Rolling Process With Heated Roll, Hailiang Yu, Qing-Bo Yu, Jin-Wu Kang, Xiang-Hua Liu

Faculty of Engineering - Papers (Archive)

Magnesium alloy strips are widely used in aerospace, automotive industry, etc., which are difficult to produce through cold forming process due to their poor deformation ability. In this article, we studied whether the rolling process with heated roll could be used to roll cold magnesium alloy strips. Thermal-mechanical finite element simulation of the rolling process, using heated roll and cold strips to produce the magnesium alloy strips, was carried out. Influences of roll temperature, rolling velocity, rolling reduction ratio, and initial strip thickness on the thermal field and the mean temperature of magnesium alloy strips were analyzed. Both the heated …

Influence Of Temperature On The Gas Content Of Coal And Sorption Modelling, Lei Zhang, Najdat I. Aziz, Ting Ren, Zhongwei Wang

Faculty of Engineering - Papers (Archive)

n experimental study was undertaken to examine the sorption and desorption characteristics of coal at temperatures of 35 °C, 45 °C and 55 °C. The study focused on the effect of changes in temperature and coal particle sizes on gas sorption and desorption characteristics. The coal size used ranged from fragmented coals, 16 mm, 8 mm, 2.4 mm, powdered coal of 150 μm and 54 mm core samples. The samples were tested in pressure vessels, known as bombs, and charged with CO2 gas at different pressure levels up to a maximum of 4000 kPa. It was found that temperature was …

Analytic And Finite Element Solutions For Temperature Profiles In Welding Using Varied Heat Source Models, Djarot Darmadi, John Norrish, Anh Kiet Tieu

Faculty of Engineering - Papers (Archive)

Solutions for the temperature profile around a moving heat source are obtained using both analytic and finite element (FEM) methods. Analytic and FEM solutions are applied to study the temperature profile in welding. A moving heat source is represented using both point heat source and uniform distributed disc heat source models. Analytic solutions are obtained by solving the partial differential equation for energy conservation in a solid, and FEM results are provided by simulating welding using the ANSYS software. Comparison is made for quasi steady state conditions. The results provided by the analytic solutions are in good agreement with results …

Removal Of Micropollutants By Membrane Bioreactor Under Temperature Variation, Faisal I. Hai, Karin Tessmer, Luong N. Nguyen, Jinguo Kang, William E. Price, Long Nghiem

Faculty of Engineering - Papers (Archive)

The effects of controlled temperature variation in the range of 10–45 °C were assessed in a lab-scale MBR that treated synthetic municipal wastewater spiked with selected micropollutants. The effects were evaluated with respect to total organic carbon (TOC) and total nitrogen (TN) removal, micropollutant removal, sludge growth, level of soluble microbial products (SMPs) in the mixed liquor and membrane fouling. Overall, the temperature shifts caused high variation in the TOC and TN levels in the reactor supernatant, however that in membrane-permeate was relatively more stable, substantiating the robustness of the MBR process. Results regarding the removal of micropollutants at ambient …

Nanoconfinement Of Lithium Borohydride In Cu-Mofs Towards Low Temperature Dehydrogenation, W.W Sun, Shaofeng Li, Jianfeng Mao, Zaiping Guo, Hua-Kun Liu, S. X. Dou, Xuebin Yu

Faculty of Engineering - Papers (Archive)

Successful synthesis and investigation of a new material that uses copper-metal–organic frameworks (Cu-MOFs) as the template for loading LiBH4 are reported. The nanoconfinement of LiBH4 in the pores of Cu-MOFs results in an interaction between LiBH4 and Cu2+ ions, enabling the LiBH4@Cu- MOFs system to achieve a much lower dehydrogenation temperature than pristine LiBH4.

Robust High-Temperature Magnetic Pinning Induced By Proximity In Yba2cu3o7-8/La0.67sr0.33mno3 Hybrids, C.Z Chen, Z Y. Liu, Y M. Lu, L Zeng, C B. Cai, Rong Zeng, S. X. Dou

Faculty of Engineering - Papers (Archive)

An elaborately designed bilayer consisting of superconducting YBa₂Cu₃O_7-6 (YBCO) and ferromagnetic La_0.67Sr_0.33MnO_3-6 (LSMO) was prepared on a single crystal LaAlO₃ substrate by pulsed laser deposition (PLD), with a view to understanding the mechanism behind the influence of superconductor/ferromagnet proximity on the critical current density, J_c. The present bilayer system shows significant modifications in J_c, as evidenced by the suppressed decay of its temperature dependence, as well as the crossing behavior of the magnetic field dependence of J_c at high temperatures. This indicates that enhanced …

The Behaviour Of Carbon Fibre Reinforced Polymer Confined Concrete Cylinders Under High Temperature Exposure, Butje Alfonsius Louk Fanggi, Muhammad N. S Hadi

Faculty of Engineering - Papers (Archive)

This study investigates the effect of temperature on the behaviour of concrete cylinders wrapped with Carbon Fibre Reinforced Polymer (CFRP). The study used nine concrete cylinders in three groups; the first group was exposed to room temperature of approximately 20ºC, the second group was exposed to a cyclic temperature with a temperature range of 20ºC to 70ºC, and the third group was exposed to a prolonged temperature of 70ºC. All cylinders were then tested to failure. The study indicated that ultimate strength of cylinders wrapped with one and two layers of CFRP are significantly unchanged after being exposed to 20ºC …

Influence Of Temperature On Coal Sorption Characteristics And The Theory Of Coal Surface Free Energy, Lei Zhang, Najdat I. Aziz, Ting Ren, Zhongwei Wang

Faculty of Engineering - Papers (Archive)

An experimental study was undertaken to examine the sorption and desorption characteristics of coal at temperatures of 35 °C, 45 °C and 55 °C. The study focused on the effect of changes in temperature and coal particle sizes on gas sorption and desorption characteristics. The coal size used ranged from fragmented coals, 16 mm, 8 mm, 2.4 mm, powdered coal of 150 μm and 54 mm core samples. The samples were tested in pressure vessels, known as “bombs”, charged with CO2 gas at different pressure levels up to a maximum of 4000 kPa. It was found that temperature has a …

Temperature Effect On Microstructure And Electromagnetic Performance Of Polycarbosilane And Sugar-Doped Mgb2 Wires, Andrey V. Shcherbakov, Josip Horvat, Olga V. Shcherbakova, Nikolina Novosel, Emil Babic, S. X. Dou

Faculty of Engineering - Papers (Archive)

The effect of processing temperature on structural and superconducting properties of 10 wt.% sugar- and 10 wt.% PCS-doped MgB₂ wires is systematically investigated. It is demonstrated that these dopants significantly enhance the electromagnetic performance of Fe-clad MgB₂ superconductor and increase its potential for practical application. The enhancement of in-field critical current density (J_c(B_a)) and upper critical field (B_c2) is due to formation of a large amount of lattice defects caused by impurities and C substitution into the MgB₂ crystal lattice. High temperature sintering of sugar-doped sample results …

Effect Of Bulk Temperature On The Tribological Performance Of Aqueous Symmetric Tri-Block Copolymers (Ppo-Peo-Ppo And Peo-Ppo-Peo) Based Lubricant, Oyong Novareza, P B. Kosasih, A K. Tieu, Hongtao Zhu

Faculty of Engineering - Papers (Archive)

This work investigates the effect of bulk temperature and the tribological performance of a number of symmetric triblock copolymers on MSI020 commonly in metal forming. It is to determine the best bulk temperature for the lubricants in order to apply in metal fOlming application. The triblock polymers are temperature dependant'. The polymers can be compeletly dissolved in solution since of hydrogen bonding in certain temperature. As temperature increases, the bond is weakend and the polymer break from the water and form dispersion in the water

Evaluation Of High Temperature Fatigue Behaviour Of P22 By Miniature Specimen Testing, M D. Callaghan, S. R Humphries, M Law, H Li, W.Y Yeung

Faculty of Engineering - Papers (Archive)

Miniature specimen testing to evaluate mechanical properties, presents a novel opportunity to undertake structural integrity assessments of in-service power generation components, by removing only a very small volume of material. In this study, high temperature fatigue testing of P22 steel was undertaken and a number of fatigue properties determined using a miniature specimen testing methodology. Good comparisons were observed between fatigue properties determined by miniature specimens and the more established standard-sized specimen testing reported in literature.

A Study Of The Continous Cooling Behaviour And Effect Of Preheat And Interpass Temperature On The Haz Of High Strength Quenched And Tempered Steel, Lenka Kuzmikova, Mark Callaghan, Nathan Larkin, Robert Scott, Robert De Jong, Huijun Li, John Norrish

Faculty of Engineering - Papers (Archive)

In this study, the continuous cooling phase transformation behaviour of a quenched and tempered armour steel was investigated. A continuous cooling transformation diagram was constructed providing valuable information for predicting microstructural evolution and mechanical properties at different cooling rates during actual welding fabrication. Welding trials were carried out utilising flux-cored arc welding technique in combination with an austenitic stainless steel consumable. The effect of various preheat and interpass temperatures on cooling rate and consequently on the heat affected zone microstructure and mechanical properties of multipass welds were investigated.

Vertical Absorption Edge And Temperature Dependent Resistivity In Semihydrogenated Graphene, Lei Chen, Zhongshui Ma, Chao Zhang

Faculty of Engineering - Papers (Archive)

We show that for graphene with any finite asymmetry in the on-site energy between the two sublattices (Δ), the optical absorption edge is determined by the Δ. The universal conductance will be broken and the conductance near the band edge varies with frequency as 1/ω². The onset conductance is σ_c = 2σ₀ = πe²/2h, independent of the size of the band gap. The total integrated optical response is nearly conserved despite of the opening of the band gap. Moreover, near the band edge, there is a change over of …

Improved Controller For High Temperature Super Conducting Magnetic Energy Storage (Hts-Smes), Danny Soetanto, M V. Aware

Faculty of Engineering - Papers (Archive)

This paper describes a novel controller for a High Temperature Superconducting Magnetic Energy Storage (HTSSMES) that can ensure (a) fast return of energy to the superconducting coil under constant current mode and (b) a constant and sinusoidal input supply current irrespective of the varying load demand with and without harmonics. A special feature of this controller is its ability to smoothly charge the superconducting coil using constant current charging so that it can be ready for the next discharging operation as soon as possible. Analysis of the circuit operation under hysteresis control is presented in details. Simulation and experimental results …

Development And Performance Analysis Of A Saturated Core High Temperature Superconducting Fault Current Limiter, Jeffrey W. Moscrop, Scott Hopkins

Faculty of Engineering - Papers (Archive)

Recent international activity in the field of high voltage Fault Current Limiters (FCLs) has intensified since the North American blackout of 2003. A number of national and international peak body groups in the USA, Europe and Japan have been established to assess the need for FCLs and the issues associated with their design, specification, operation, protection and integration into the electricity grids. This paper details the development of a prototype 3-phase saturated core High Temperature Superconducting (HTS) FCL in Australia. Through experimental analysis, the performance of this device is characterised in terms of DC saturation, steady state performance, and fault …

Design And Development Of A 3-Phase Saturated Core High Temperature Superconducting Fault Current Limiter, Jeffrey W. Moscrop, Frank Darmann

Faculty of Engineering - Papers (Archive)

The occurrence of fault currents and system sensitivity to fault currents are both increasing in modern power systems. Along with extensive damage to network hardware, considerable consumer losses (due to network unavailability) can result from fault current events. One device that is designed to reduce the impact of fault currents and increase network availability is the fault current limiter (FCL). This paper describes the design and development of a 3-phase saturated core high temperature superconducting (HTS) FCL. This particular type of FCL exhibits negligible power losses during the un-faulted state and also provides instantaneous reaction and recovery during fault events. …

Thermodynamic Modelling Of High Temperature Systems, Winny Wulandari, Geoffrey A. Brooks, M Akbar Rhamdhani, Brian J. Monaghan

Faculty of Engineering - Papers (Archive)

• Thermodynamic modeling is valuable tool to predict phase equilibria in high temperature metals processing
• Thermo chemical packages makes modeling easier, but the fundamental knowledge such as how we determine the phase, species, and activity behaviour are the intellectual aspects
• An example in magnesium impurities illustrate both the predictive power of thermodynamic modelling but also the dilemmas associated with solution behaviour

Noise Temperature Spectrum Of Hot Electrons In Semiconductor Superlattices, Chang Wang, Chao Zhang, J C Cao

Faculty of Engineering - Papers (Archive)

The small signal response and thermal noise spectra in miniband superlattice are investigated. The properties of hot electron differential mobility, velocity fluctuation, and noise temperature are determined around a stationary condition. The field and frequency dependent drift velocity, electron energy, effective mass, and electron temperature are obtained. At low frequencies, noise temperature increases rapidly with the electric field. Our calculated noise temperatures for miniband superlattice are in good agreement with the experimental results, with the sample thickness estimated to be around 4 um.

A Comparative Study On Field, Temperature, And Strain Dependences Of The Critical Current For Doped And Undoped Mgb2 Wires Based On The Percolation Model, Sangjun Oh, Jung Ho Kim, Kyuhwan Cho, Chulhee Lee, Chan-Joong Kim, S. X. Dou, M Rindfleisch, Mike Tomsic, Jung-Ho Ahn

Faculty of Engineering - Papers (Archive)

Field, temperature, and strain dependences of the critical current for a SiC doped multifilamentary in situ MgB₂ wire have been studied. Measurement results were compared with that of the undoped wire, and the origin of the difference in the critical current is discussed. The critical current can be calculated with the percolation model considering the effect of anisotropy. The temperature dependence of the fitting parameters, the upper critical field along the ab-plane, and c-axis is compared with the dirty-limit two-gap theory. To assess the validity of the fitting parameters, resistive transition has been measured especially to …

Metal-Insulator Transition And Electroresistance In Ianthanum/Calcium Manganites La1-Xcaxmn03 (X=0-0.5) From Voltage-Current-Temperature Surfaces, Jonathan C. Knott, Daniel Pond, Roger A. Lewis

Faculty of Engineering - Papers (Archive)

Of the perovskites, ABX3, a subset of special interest is the family in which the A site is occupied by a lanthanide ion, the B site by a transition metal and X is oxygen, as such materials often exhibit a large change in electrical resistance in a magnetic field, a phenomenon known as "colossal" magnetoresistance (MR). Two additional phenomena in this family have also drawn attention: the metal-insulator transition (MIT) and electroresistance (ER). The MIT is revealed by measuring resistance as a function of temperature, and observing a change in the sign of the gradient. ER – the dependence of …

A Flexible Approach To On-Site Power Filtering And Supply Backup Using High Capacity High Temperature Smes For Maximum Equipment Utility, Dominic Cuiuri, Jeffrey W. Moscrop, Christopher David Cook

Faculty of Engineering - Papers (Archive)

With power systems subject to an ever-increasing variety of load types, power quality remains of concern to both utilities and consumers alike. Some of the most concerning issues to users of sensitive equipment include voltage sags, supply interruption and current harmonics. This paper describes a comprehensive power quality device that can be designed to compensate for harmonic load currents and mains voltage variations in a system, as well as providing mains failure backup for smaller critical system loads. The design process described integrates high capacity high temperature Superconducting Magnetic Energy Storage (SMES) technology with Active Power Filter (APF) switching technology …

Deformation-Induced Nanoscale High-Temperature Phase Separation In Co-Fe Alloys At Room Temperature, Laichang Zhang, M Calin, F Paturaud, C Mickel, J Eckert

Faculty of Engineering - Papers (Archive)

Instead of applying severe plastic deformation, high-temperature heat treatment or high pressure, grain refinement and high-temperature phase separation induced by deformation in single-phase body-centered-cubic (bcc) coarse-grained Co–Fe alloys have been achieved by simple room-temperature compression. The alloys exhibit large plasticity over 140% without fracture. Phase separation from the bcc phase to nanoscale face-centered-cubic Fe and Co phases, which generally occurs at high temperature above ∼ 1150 K, is formed in the deformed samples. The possible mechanisms are shear deformation and deformation-enhanced atomic diffusion rather than the temperature rise during deformation

Impact Of Sintering Temperature On The Physical Properties Of The Superconducting Ferromagnet: Rusr2eu1.5ce0.5cu2o10, Rashmi Nigam, Alexey V. Pan, S X. Dou

Faculty of Engineering - Papers (Archive)

We report the influence of the sintering temperature on the electromagnetic behavior for the RuSr₂Eu_1.5Ce_0.5Cu₂O₁₀ material, in which superconductivity and ferromagnetism coexist. The inadequate heat treatment results in the coexistence of the secondary Ru-1212 phase along with the dominant Ru-1222 phase. The presence of two phases leads to the magnetic superposition of the signals from both phases, which results in the observation of a small peak around 120–130 K. In the pure Ru-1222 no such magnetic anomaly is observed. In addition, the impure samples exhibit a double step superconductivity transition. In …

Amorphous Carbon-Coated Silicon Nanocomposites: A Low-Temperature Synthesis Via Spray Pyrolysis And Their Application As High-Capacity Anodes For Lithium-Ion Batteries, See How Ng, Jiazhao Wang, David Wexler, Sau Yen Chew, Hua-Kun Liu

Faculty of Engineering - Papers (Archive)

This article introduces an effective, inexpensive, and industrially oriented approach to produce carbon-coated Si nanocomposites as high-capacity anode materials for use in rechargeable lithium-ion batteries. Initially, nanosized Si particles (nm) were mixed in a citric acid/ethanol solution via ultrasonication. This mixture was further spray-pyrolyzed in air at low processing temperature (300-500 C), resulting in a homogeneous layer of carbon coating on the surface of the spheroidal Si nanoparticles. The effects of the processing temperature on the amorphous carbon content, the thickness of the carbon-coating layer, and the homogeneity of the carbon coating were studied in detail. These parameters strongly influenced …

Low-Temperature Synthesis Of Polypyrrole-Coated Liv3o8 Composite With Enhanced Electrochemical Properties, Sau Yen Chew, Chuanqi Feng, See How Ng, Jiazhao Wang, Zaiping Guo, Hua-Kun Liu

Faculty of Engineering - Papers (Archive)

A composite, LiV3O8 -polypyrrole (PPy), was synthesized by a low-temperature solution route followed by an in situ polymerization method. The as-prepared powders consisted of nanosized PPy distributed homogeneously within the layered lithium trivanadate. The electrochemical properties of LiV3O8–PPy composite were systematically investigated and compared with bare lithium trivanadate. It was found that the electrochemical performance of the LiV3O8–PPy composite was significantly enhanced, with a specific capacity of ∼183mAhg−1 retained after 100cycles . This suggests that nanostructured PPy could work well as a polymer-conducting matrix and also as a binding material to improve the overall electrochemical properties of the LiV3O8 when …