Engineering Science and Materials Commons^™

Numerical Simulation Of Waves And Fronts In Inhomogeneous Solids, A. Berezovski, M. Berezovski, J. Engelbrecht, G. A. Maugin

Publications

Dynamic response of inhomogeneous materials exhibits new effects, which often do not exist in homogeneous media. It is quite natural that most of studies of wave and front propagation in inhomogeneous materials are associated with numerical simulations. To develop a numerical algorithm and to perform the numerical simulations of moving fronts we need to formulate a kinetic law of progress relating the driving force and the velocity of the discontinuity. The velocity of discontinuity is determined by means of the non-equilibrium jump relations at the front. The obtained numerical method generalizes the wave-propagation algorithm to the case of moving discontinuities …

The Effects Of Environment On The Interlaminar Shear Performance Of An Oxide/Oxide Ceramic Matrix Composite At Elevated Temperature, Patrick D. Laffey

Theses and Dissertations

This research investigated the interlaminar shear performance of an oxide/oxide ceramic matrix composite consisting of Nextel™ 720 fibers in a high purity, porous alumina (Al₂O₃) matrix. The interlaminar shear performance was observed in both tension and compression of double notched specimens (DNS) at 1200 °C. Interlaminar shear creep behavior was examined in both laboratory air and in steam environment at 1200 °C. In air, the creep stress was -6.5 MPa. In steam creep stresses included -4.0, -5.0, and -6.5 MPa. Primary and secondary creep regimes were observed in all air creep tests and the creep test …

Effects Of Prior Aging At 191°C On Creep Response Of Im7/Bmi 5250-4, Robert A. Salvia

Theses and Dissertations

The creep behavior of IM7/BMI 5250-4 with fiber orientations of [± 45] and [0/90] that were aged in air at 191 °C for up to 1000 hours was evaluated. The total weight loss during the aging process was also evaluated. Weight loss due to aging was 0.64% for the [0/90] fiber orientation and 0.72% for the [± 45] fiber orientation. Tensile tests to failure were conducted to establish tensile properties. The [0/90] specimens have a much higher stiffness and Ultimate Tensile Strength (UTS) values than the [± 45] specimens. The tensile tests of the aged specimens revealed that the Ultimate …

Effects Of Prior Aging On The Creep Response Of Carbon Fiber Reinforced Pmr-15 Neat Resin At 288°C In An Air Environment, Christopher A. Back

Theses and Dissertations

The mechanical response of carbon fiber reinforced PMR-15 neat resin with a ± 45 fiber orientation was investigated at 288 °C. Mechanical testing was performed on unaged specimens and specimens that were aged up to 1000 hours in an air environment. Tensile tests were performed to determine Young's modulus of elasticity and Ultimate Tensile Strength. Creep tests were performed at creep stress levels of 30 and 60 MPa. Creep periods of at least 25 h in duration were followed by recovery at zero stress. Duration of the recovery period was at least twice the time of the creep period. Oxidation …

Compressive Creep Behavior Of Nextel™ 720/Alumina Ceramic Matrix Composite At 1200°C In Air And In Steam Environment, Neil R. Szymczak

Theses and Dissertations

The aerospace community continues to push the envelope in engineering aircraft that fly higher, faster, and safer while operating with a greater degree of efficiency. To meet these operational requirements innovative aerospace components must be designed to operate in aggressive environments. This research will investigate the ultimate compressive strength and the compressive creep behavior of Nextel^TM 720/Alumina ceramic matrix composite at 1200 °C in air and 100% steam environments. The effects of creep loading history on the tensile and compressive material behavior will also be examined. The primary strengths of the N720/A composite are its oxide/oxide composition which inherently …

Catalysis Of Nano Tio2 For Horseradish Peroxidase, Ya-Qi Zhu, Hai Wu, Hiu Liu, Jie Ma

Journal of Electrochemistry

Horseradish peroxidase immobilized on the surface of titanium dioxide nanoparticles and nanotube modified glassy carbon electrode.The HRP direct electron transfer reaction was compared between TiO₂ nanoparticles and nanotube GC electrode.The results demonstrated that the HRP on TiO₂ nanotube /GC electrode could catalyze electron exchange reaction between electroactivity center of HRP and electrode.And the research of antibody labeled HRP provides a selected signal for antibody-antigen immunoassay.

Electrochemical Reduction Of Coals And The Oxygenic Functional Simulacrums Of Coals, Juan Lin, Zhao Wei

Journal of Electrochemistry

Electrochemical reduction of coals and the oxygenic functional simulacrums of coals has been studied.In this process,tetrabutylammonium was used as supporting electrolyte.The coal and the deoxidized coal were extracted by methanol.Qualitative analysis of the deoxidized products and the extractives was carried out on gas chromatograph-mass spectrometer.The deoxidized products of the oxygenic functional simulacrums of coals were analysed quantitatively with gas chromatograph spectrometer.The results show that the oxygenic functional groups on the coals surface decrease and the translation ratios of the oxygenic functional simulacrums of coals need further increase after electrochemical reduction,.The electrochemical tests show simultaneously the kinetics equations of every related …

Study On The Electricity Capability Of Ru((0.4-X))IrXTi(0.6)/Ti Electrode, Ling-Li Wang, Qiao Peng

Journal of Electrochemistry

The metal oxide anode of Ru_(0.4-x)Ir_xTi_0.6 has been prepared by thermal decomposition.The results indicate that,when the percent of IrO₂ is 10%,the electrode has low chlorine potential,high oxygen potential and excellent catalyze selectivity;strengthen life is long with IrO₂ content increased from 1.0h to 97h.It shows that the electrode anti-oxide corrosion perform is improved and intensifying life is long with addition of IrO₂.The film and reaction resistance are all fall with the addition of IrO₂.The addition of IrO₂ is in favor of thin crystal and makes the film more roughness.

Study On The Characteristics Of Vb(12) Modified Electrode By Electropolymerization, Hui-Ting Lian, Wen-Ji Wang

Journal of Electrochemistry

Preparation of the VB₁₂ modified electrode and its electrochemical characteristics were studied.The results showed that the VB₁₂ after electroactivated is able to electopolymerize on the GC by cyclic voltammetry(CV)in the DMSO solution.Differential pulse voltmmetry(DPV)showed that the VB₁₂ catalyzed the oxidation of NO₂^-,SO₃^2-and NH₂NH₂.The catalytic peak for NO₂^-on the modified electrode was observed at 0.76V(vs.SCE),but on the unmodified GC which at 1.0V.The catalytic currents increased linearly with the concentration of NO₂^-from 1.6×10^-6 to 4.3×10^-4 mol·L^-1 with a correlation coefficient …

Determination Of Ddopamine And Ascorbate On Gold Nanoparticle And 4,4-Bis (Methanethiol) Biphenyl (Mtp) Self-Assembled Monolayer Modified Gold Electrode, Hai-Yan Wang, Peng Liu, Ye Wang, Bao-Kang Jin

Journal of Electrochemistry

A new approach to construct an ampermetric biosensor was described.The 4,4-bis(methanethiol)biphenyl(MTP)is adsorbed on to a bare gold electrode to make self-assembled monolayers(MTP/Au SAMs).Then electrodeposited 2mg/mL HAuCl₄ at-200 mV,NG/MTP/Au electrode was prepared.When a differential pulse voltammetric(DPV)technique was used,the peak separation between DA and AA is 155 mV.Hence,the selective determination of dopamine(DA)and ascorbate(AA)in the binary mixture system can be performed.Under the chosen conditions,the peak currents are correspondent linearly to the concentrations of DA and AA in the range of 5.0×10^-7~1×10^-4 mol·L^-1 and 3.5×10^-6~1.0×10^-3mol·L^-1,respectively.The correlation coefficients were 0.998.The detection limit were 1.5×10 …

Corrosion Electrochemical Behavior Of Aluminum Flake Pigmented Water-Borne Epoxy Coating On Carbon Steel In Nacl Solution, Li-Li Xue, Li-Kun Xu, Qing-Fen Li, Hong-Qing Song, Wen-Juan Zhou, Guang-Zhang Chen

Journal of Electrochemistry

The corrosion electrochemical behavior of a water-borne epoxy coating pigmented with aluminum flake on carbon steel with artificial scratch defect was studied in 3.5% NaCl solution using electrochemical impedance spectroscopy(EIS)and scanning vibrating electrode technique(SVET).The results indicated that the defect presented anodic electroactivity at the initial stage of immersion,which extended gradually with time from the scratch into the neighboring coating,lowering the coating impedance.With further immersion,however,the electroactivity of the coating/steel interface decreased significantly due to the self-repairing of the corrosion products,causing an obvious increase of the coating impedance.In the later period of immersion,more scattered electroactive areas appeared under the coating because of …

Template Synthesis And Electrochemical Studies Of Ag(Core)Au(Shell) Nanowires, Li Ling, Ya-Xian Yuan, Min-Min Xu, Jian-Lin Yao, Ren-Ao Gu

Journal of Electrochemistry

Agcore Aushell nanowires with different thicknesses were prepared by combining template synthesis and chemical reduction method,and characterized by SEM and cyclic voltammetry(CV).The CV results revealed that the AgcoreAushell nanowires with pinhole were transferred to pinhole free structure after several potential scans.By using thiophenol(TP)and p-aminothiophenol(PATP)as probe,the surface enhanced Raman scattering(SERS)effect was investigated on the core-shell nanowires.The results indicated that AgcoreAushell nanowires could be served as a potential SERS substrate,and the difference in the spectral feature of PATP adsorbed onto Au and Ag nanowires enable us to diagnose the pinhole effect of core-shell nanowires by SERS.

Electricity Generation From A Microbial Fuel Cell Employing Desulfovibrio Salexigens, Ping Ding, Hai-Bo Shao, Guang-Zhou Liu, Dong-Xia Duan, Ting Ma, Si-Jun Chen, Jian-Ming Wang, Jian-Qing Zhang

Journal of Electrochemistry

A microbial fuel cell of laboratory scale employing Desulfovibrio salexigens in lactate based seawater substrate was proposed.Electricity was continuously harvested after inoculation.During 20 days of fermentation/discharge,COD values of the substrate decreased by 61.7%,in which 9.81% was converted to electricity.

The Research Of Several Electrodes For Spe Water Electrolysis, Jian-Bo Meng, Ge Sang, Yan Xue, Wei Cao, Xiao-Qiu Ye

Journal of Electrochemistry

Performances of the IrRu/Nafion 117/PbAg,IrRu/Nafion 117/Ni,IrRu/Nafion 117/TiNi,Ag/Nafion 117/Ni and C/Nafion 117/PtRu for the SPE water electrolysis have been investigated.The order of the electrocatalysis activity for the anodic electrodes as mentioned above is IrRu>Ag>C,and that of cathodic electrode is Ni>PbAg>TiNi.While the stability of TiNi was much better than Ni,and that of PbAg is best.Moreover,the current efficiency was raised with the increase of current density.

Study On The Contribution Of Cobalt Additives To Foam Nickel Electrodes, Xiao-Feng Li, Tong-Chi Xia, Shao-Peng Yi, Xiu-Juan Gu, Yu-Lin Song

Journal of Electrochemistry

Two incorporation ways of the cobalt additives into foam nickel electrodes,i.e.the co-precipitated and admixed method are used.The results of X-ray diffraction(XRD),cyclic voltammetry,electrochemical impedance spectrum(EIS)and galvanostatic charge-discharge curves show that(Ⅰ)there is a decrease in intensity and increase in half peak breadths of the diffraction peaks of Ni(OH)₂ with co-precipitated cobalt additive;(Ⅱ)the electrochemical activity of nickel hydroxide can be improved by both incorporation ways and the effect of admixed CoO is more notable;(Ⅲ)β-CoOOH derived from admixed CoO is not stable at lower potential,thus results in an irreversible capacity loss of nickel-metal-hydride(Ni-MH)battery after imposed overdischarged-state storage.

Determination Of Tetracyclines Based On The Flow-Through Electrochemical Detection Cell With Nickel Electrode, Dan-Mei Pan, Rong-Zong Hu, Dong-Ping Wei, Hao-Dong Ding

Journal of Electrochemistry

The electrochemical responses to tetracycline at the nickel electrode in alkaline solution were compared with that of gold and glassy carbon electrode by voltammetry.The electrocatalytic oxidation characteristics of tetracycline at nickel electrode were discussed.Subsequently a flow-through amperometric detection cell with nickel as the working electrode was designed to detect tetracycline,oxytetracycline,and doxycycline.Standard calibration graphs for the tetracyclines yielded linear ranges of 0.1~15 mg/L.Detection limits(S/N=3)of 35,45 and 43 μg/L were obtained for tetracycline,oxytetracycline and doxycycline,respectively.The system was applied for the determination of the three antibiotics in single-component drug formulations.

Study On The Electrogeneration And Properties Of Superoxide Ion In Aprotic Media By Using Carbon Nanotubes Powder Microelectrode, Ying-Liang Wei, Chen Shao, Hui Feng

Journal of Electrochemistry

Multi-wall carbon nanotubes are filled in the cavity at the tip of a microelectrode to form a carbon nanotubes powder microelectrode(CNTs-PME).The CNTs-PME is used to study the electrochemical reduction of oxygen in aprotic media.It is a nearly reversible redox process of the O₂/O₂^- couple at the CNTs-PME in the dimethyl sulfoxide(DMSO)solution.The heterogeneous electron transfer rate constant(ks)can be measured by steady-state voltammogram and the result is 9.8 10^-3cm /s.As a weak oxidant,the reaction of O₂^- with epinephrine was studied by cyclic voltammetry.Additionally,the reaction of O₂^- with benzoic acid was also discussed …

Square Wave Stripping Voltammetric Behaviors Of Actinomycin D On Glod Electrode And Its Application, Qing-Tao Zhu, Fang Liao, Xiao-Ying He

Journal of Electrochemistry

The electrochemical behaviors of Actinomycin D(ACTD)at glod electrode were investigated by square wave stripping voltammeter in the KH₂PO₄-Na₂HPO₄ buffer solution(pH=5.90).The sensitive oxidation peak of ACTD was observed and the potential peak for ACTD is-0.17 V(vs.SCE).The Experimental parameters,such as pH value,amplitude,accumulation potential and time were optimized,and a direct electroanalytical method for determining ACTD was developed.The peak currents were proportional to the concentration of ACTD in the range of 0.1μmol·L^-1～10.0μmol·L^-1,and the linear regression coefficient equaled 0.9991.The detection limit for ACTD was 1.0×10^-8mol·L^-1.

Voltammetric Behavior And Electrocatalytic Properties Of Hemoglobin At Glassy Carbon Electrode Modified With Lauric Acid, Xin-Rui Miao, Xu-Hong Zhang, Ying Xie

Journal of Electrochemistry

The electrochemical behavior of hemoglobin at glassy carbon(GC)electrode modified with Lauric Acid was studied.In the potential of +0.6～-0.7 V(vs.Ag/AgCl),an irreversible cathodic peak was observed at-0.3 V at the scan rate of 20 mV·s^-1.In the medium of 0.02 mol·L^-1 KH₂PO₄-Na₂HPO₄(pH 7.0),ip increased with the increasing concentration of Hb and the value of pH.The peak currents were proportional to the concentrations of hemoglobin in the range of 1.00×10^-8～5.00×10^-9 mol·L^-1 and 1.92×10^-6～2.06×10^-7 mol·L^-1.The data was analyzed in details by simulating in order to …

Modification Of Electrolytic Manganese Dioxide, Shu-Rong Ding, Xin-Hai Li, Zhi-Xing Wang, Hua-Jun Guo

Journal of Electrochemistry

The EMD samples coated with CMD-Bi compound were prepared by liquid-phase surface treatment method.XRD and SEM research indicated that the modified manganese dioxide, i.e, EMD/CMD-Bi, could keep γ-MnO₂ crystal structure of EMD and had more pores on its surface with an obvious floccule layer.Electrochemical test indicated that the second electron reduction peak current increased by 1.5 times and the discharge capacity increased by 40.8% and 78.3% respectively than that of pure EMD electrode under the condition of-0.8 V(vs.Hg/HgO) cut-off voltage at 30.8 mA/g and 102.7 mA/g current density.

Electrochemical Performance Of Li(1-X)MXFepo4 Cathode Materials Synthesized By Polymer Pyrolysis Route, Ting Li, Jiang-Feng Qian, Yu-Liang Cao, Han-Xi Yang, Xin-Ping Ai

Journal of Electrochemistry

Olivine Li_1-xM_xFePO₄(M=Cr³⁺, Mg²⁺, Mn²⁺, Ni²⁺) were synthesized by a polyacrylates-pyrolysis route. The structural and electrochemical properties of the as-synthesized cathode materials were investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical charge/discharge cycling. The results indicate that the metallic ions doped at low concentration do not affect the crystalline structure of the material, but considerably improve the rate capability and cycle performance of LiFePO₄ at high rate.

Design And Development Of An In-House Scanning Tunneling Microscope System, Esvar Subramanian

All Theses

ABSTRACT
The invention of Scanning Tunneling Microscope (STM) by Binnig and Rohrer in 1982 eliminated the use of optical lenses and replaced the conventional optical microscopes with a new class of microscopes called the Scanning Probe Microscopes (SPM). Because of their unique characteristics such as higher resolution and acquisition of nano level images without affecting the physical properties of the sample, they have found wide applications in a variety of scientific disciplines such as biology, material science and electrochemistry. After considerable advancements in instrumentation, the STM has evolved as a nanomanipulation and nanofabrication tool. It operates in two modes: constant …

Optimal Placement Of Metal Foils In Ultrasonic Consolidation Process, Raji Rexavier

All Theses

Ultrasonic Consolidation is a combination of additive and subtractive
manufacturing processes resulting in considerable material waste. This waste is a
function of the geometry of the part being manufactured and of the relative
placement of the layer with respect to the metal bands. Thus the waste may be
minimized by careful choice of the layer angle and offset from the original
position.
Previous work done in this field had developed an automated algorithm which
optimally places and orients the individual slices of the STL file of the artifact
being manufactured. However, the problem was solved on a 2-D scale and …

College Of Engineering Senior Design Competition Spring 2007, University Of Nevada, Las Vegas

Fred and Harriet Cox Senior Design Competition Projects

Part of every UNLV engineering student’s academic experience, the senior design project stimulates engineering innovation and entrepreneurship. Each student in their senior year chooses, plans, designs, and prototypes a product in this required element of the curriculum. A capstone to the student’s educational career, the senior design project encourages the student to use everything learned in the engineering program to create a practical, real world solution to an engineering challenge.

The senior design competition helps to focus the senior students in increasing the quality and potential for commercial application for their design projects. Judges from local industry evaluate the projects …

Design Of A Controller For A Precision Positioning Machine, Joshua Tarbutton

All Theses

System identification was used to build an accurate model of a high-precision measurement system. The model built by system identification was compared to modeling by first laws and showed extremely similar results. Pole-placement control design based on the identified system was used to place the systems' dominant poles. The necessary gains to achieve the desired system response were determined by using the identified model and knowledge of the controller structure. The performance of the model-based controller was compared to actual data of the system and showed that control based on the identified model can be used to accurately control the …

Real Time Prognostic Strategies Application To Gas Turbines, Rajat Sekhon

All Theses

Gas turbines are increasingly deployed throughout the world to provide electrical and mechanical power in consumer and industrial sectors. The efficiency of these complex multi-domain systems is dependant on the turbine's design, established operating envelope, environmental conditions, and maintenance schedule. A real-time health management strategy can enhance overall plant reliability through the continual monitoring of transient and steady-state system operations. The availability of sensory information for control system needs often allow diagnostic/prognostic algorithms to be executed in a parallel fashion which warn of impending system degradations. Specifically, prognostic strategies estimate the future plant behavior which leads to minimized maintenance costs …

Machinability And Microstructure Stability During The Machining Of Pure Copper And Titanium Processed By Equal Channel Angular Pressing, Mason Morehead

All Theses

For ultrafine grained materials (containing microstructures of 100-300 nm) to be manufactured and used in industry, machining research is needed to form and shape these materials into their final dimensions. Because of their high internal energy, UFG materials are known to have microstructures which are susceptible to undesirable changes at low temperatures. In this study, pure ultrafine grained copper and titanium as well as their respective coarse grained (CG) counterparts were tested for their relative machinability and microstructure stability through lathe turning. To evaluate the machinability cutting forces, tool wear, chip morphology, and surface roughness were studied using different cutting …

A Study Of Induced Drag And Spanwise Lift Distribution For Three-Dimensional Inviscid Flow Over A Wing, Scott Monsch

All Theses

Numerical results for an untwisted, finite rectangular wing (NACA 0012, AR = 6.7) using no flap deflections are compared against theoretical lifting line predictions. The numerical approach used an Euler-based computational fluid dynamic (CFD) solver. A span-wise lift distribution was extracted from the CFD solution. The comparison between the predicted numerical and lifting-line span-wise lift distributions shows good agreement with a maximum deviation of only 2.4% over the wing span.
The induced drag was extracted from the downstream wake using a wake integral technique referred to as Trefftz plane analysis. The predictions for induced drag based on surface integration, wake …

Temperature Control Of An Air Shower, Vedik Bobba

All Theses

Accuracy and repeatability in measurement is a primary concern in improving and maintaining the quality of a product in an industry. In the case of coordinate measuring machines, these factors are affected due to the ambient conditions. Specifically, change in temperature affects machine geometry and causes positioning errors. As a result, temperature and humidity control inside the housing has become an important and integrated concern of measuring machine. This research concentrates on the modeling, design, control and validation of an air shower to meet a 20 ± 0.1 ¼C specification.
The optimum performance of the control of temperature of air …

Analysis Of Ride Quality Of Tractor Semi-Trailers, Christopher Spivey

All Theses

This thesis develops parameter variation techniques for calculating the set of vehicle parameters that result in the best ride comfort for the driver. The model is a fifteen degree-of-freedom (15 DOF) tractor semi-trailer vertical dynamic ride model. The modeling and simulation techniques used in this thesis are extensions of the research performed by Trangsrud and Vaduri. Features of the model include suspension characteristics for (a) each of the five axles (tractor steer axle, two tractor drive axles, and two trailer axles), (b) tires, (c) a flexible engine mount, (d) the tractor cab, (e) the driver's seat, and (f) a fifth …