Engineering Commons^™

Theoretical Modeling Of Protective Oxide Layer Growth In Non-Isothermal Lead-Alloys Coolant Systems, Yitung Chen

Transmutation Sciences Materials (TRP)

The goal of the proposed research project is to provide basic understanding of the protective oxide layer behaviors and to develop oxide layer growth models of steels in non-isothermal lead-alloys (lead or lead-bismuth eutectic) coolant systems. It is widely recognized that the corrosiveness of the lead-alloys is a critical obstacle and challenge for which it can be safely used or applied in the nuclear coolant systems. Active oxygen control technique can promote the formation of the “self-healing” oxide films on the structural material surface, drastically reducing steel corrosion and coolant contamination. Many experiments of steels exposed to flowing lead-alloys have …

High Temperature Heat Exchanger Project: Quarterly Progress Report October 1, 2004 Through December 31, 2004, Anthony Hechanova

Publications (NSTD)

UNLV hosted an NHI Systems Interface Meeting on Dec. 16 and a UNLVRF HTHX Kickoff Meeting on Dec. 17. The purpose of the meetings was to coordinate the FY05 research and development effort of the UNLV Research Foundation portion of the Nuclear Hydrogen Initiative among the DOE, national program technical directors and the UNLVRF collaborators. Collaborators also had the opportunity to discuss their research program plan and update their progress. It was decided that these type of collaboration meetings were very useful and they will be held quarterly at the various collaborator sites. The next meeting will be in March …

Dislocation Structures And The Deformation Of Materials, Marisol Koslowski, Richard Alan Lesar, Robb Thomson

Richard Alan Lesar

We present results from phase-field simulations of a two-dimensional model of dislocation microstructure development under increasing strain that incorporates the effects of the full, three-dimensional, microstructure in an approximate way. Despite its simplicity, the model yields quantitative predictions of both the deformation properties of face-centered cubic metals as well as key descriptors of the evolving microstructure over a wide range of stress and strain. The present results have important implications for how we interpret and describe the deformation properties of fcc materials.

Oscillatory Interlayer Exchange Coupling In [Pt/Co]N/Nio/[Co/Pt]N Multilayers With Perpendicular Anisotropy: Dependence On Nio And Pt Layer Thicknesses, Z. Y. Liu, Lanping Yue, D. J. Keavney, Shireen Adenwalla

Materials Research Science and Engineering Center: Faculty Publications

Interlayer exchange coupling has been studied in a series of [Pt( t_Pt Å)/Co(4 Å)]n/NiO( t_NiO)/[Co(4 Å)/Pt( t_Pt Å)]_n multilayers with perpendicular anisotropy. The coupling oscillates between antiferromagnetic and ferromagnetic as a function of t_NiO with a period of ~5 Å, and the oscillatory behavior is related to the antiferromagnetic ordering of the NiO layer. This interlayer coupling between two Co/Pt multilayers is shown to occur domain by domain by magnetic force microscopy imaging. For the strongest antiferromagnetic coupling at t_NiO = 11 Å, an oscillation with a period of ~6 Å is superposed …

Religious Sectarianism: Lessons To Be Learnt From Pakistan, Vikas Kumar

Vikas Kumar

No abstract provided.

Quantum Entanglement Of Anisotropic Magnetic Nanodots, Ralph Skomski, Andrei Y. Istomin, Anthony F. Starace, David J. Sellmyer

Materials Research Science and Engineering Center: Faculty Publications

Anisotropic magnetic nanodots are promising physical realizations of qubits for quantum computing at finite temperature owing to their well-separated low-lying energy levels and scalability. The entanglement of two interacting magnetic nanodots is investigated and shown both analytically and numerically to be resonantly dependent on their interaction strength and on differences in their properties. These results provide criteria for fabricating and coupling magnetic nanodots so that their low-lying eigenstates can be significantly entangled.

Influence Of Connection Placement To The Behavior Of Precast Concrete Exterior Beam-Column Joint, Elly Tjahjono, Heru Purnomo

Makara Journal of Technology

Influence of Connection Placement to the Behavior of Precast Concrete Exterior Beam-Column Joint. This paper presents an experimental study on the influence of connection placement to the behaviour of exterior beamcolumn joint of precast concrete structure under semi cyclic loading. Four half-scale beam-column specimens were investigated. Three beam-columns were jointed through connection that are placed in beam-column joint region and the forth is connected at the plastic hinge potensial region of the beam. Crack patterns, strength, stiffness and ductility of the test specimens have been evaluated. The test result indicated that all beam-column specimens show good ductility behavior.

The Effects Of Influent Debit On Hydrodynamic Characteristic Of Bojongsoang Facultative Pond: Without Wind Effects, Rositayanti Hadisoebroto, Suprihanto Notodarmojo

Makara Journal of Technology

The Effects of Influent Debit on Hydrodynamic Characteristic of Bojongsoang Facultative Pond: Without Wind Effects. The performance of facultative pond in Bojongsoang WWTP have reported to be unstable. One of the cause of the unstable performance is the hydrodynamic characteristics that not met the criterion. The improper hydrodynamic characteristics are included the existence of dead-zone, the short-circuiting, and the turbulence due to eddy current. The study was to analyze the effect of the influent debit variation on the hydrodynamic characteristics of the pond using mathematical model. The two-dimensional hydrodynamic model was built from two hydrodynamic equations which are continuity and …

Optic Properties On Aggase2 Polycristal Fabrication, A. Harsono Soepardjo, I Dewa Made Janusetiawan

Makara Journal of Technology

Optic Properties on AgGaSe2 Polycristal Fabrication. Polycristal AgGaSe2, is compound (I-III-VI2) a semiconductor as basic material for thin film for solar cell. Polycristal was succesfully grown using Bridgmann Method, heated on sequential temperature treatment until 850°C and cooled down slowly until room temperature. Results observed were in the form of ingot (bars) with more or less 3 cm length and 13 mm in diameter. By using X-Ray Fefraction, composition obtained of each element (weight %) was Ag = 29,3996 %, Ga = 36,8123 % and Se = 30,29 % while using X-Ray Difraction lattice parameter obtained/calculated a = 4,4112 Å, …

Modelling And Simulation Of Packed Bed Catalytic Converter For Oxidation Of Soot In Diesel Powered Vehicles Flue Gas, Mohammad Nasikin, Praswasti P.D.K. Wulan, Vita Andrianty

Makara Journal of Technology

Modelling and Simulation of Packed Bed Catalytic Converter for Oxidation of Soot in Diesel Powered Vehicles Flue Gas. Diesel vehicle is used in Indonesia in very big number. This vehicle exhausts pollutants especially diesel soot that can be reduces by using a catalytic converter to convert the soot to CO2. To obtain the optimal dimension of catalytic converter it is needed a model that can represent the profile of soot weight, temperature and pressure along the catalytic converter. In this study, a model is developed for packed bed catalytic converter in an adiabatic condition based on a kinetic study that …

Fuel Injection System For One Cylinder Motor Cycle Engine, Bambang Sugiarto

Makara Journal of Technology

Fuel Injection System for One Cylinder Motor Cycle Engine. Fuel injection has been developed for many years. But its common application is limited on car’s engine. With many reason fuel injection systems in motorcycle one cylinder engine has not been widely used yet. Fuel Injection System allows the amount of fuel, injected to be controlled appropriate to engine parameters such as engine speed, amount of air inducted to cylinder, temperature, for each cycle, over the entire engine operating conditions. This fuel injection research is done to find out the Volumetric Efficiency of the intake manifold system, the amount of fuel …

Synthesis And Ordering Of Nanostructures Using Laser Light, Yingfeng Guan

Doctoral Dissertations

This dissertation focuses on the formation of 1-D and 2-D nanoscale structures induced by the KrF excimer UV laser irradiation of silicon (λ=248 nm). Relatively low laser energy density (E_d<=1 J/cm²) is required to produce nanostructures. Alignment of 2-D nanoripple structures and nanoprotrusions has been realized by using Lloyd’s mirror configuration.

Laser-generated silicon microcone arrays were used as templates for the growth of nanocolumns. The formation mechanism of the microstructure is reviewed, and the origin and growth of nanocolumns are discussed. The formation mechanism of nanocolumns requires highly localized melting, which explains why they fail to form on …

A Study Of The Evolution Of Laser-Induced Periodic Surface Microstructures On Silicon And Electronic Transport In Composite Carbon Nanotube Networks, Stephen Jesse

Doctoral Dissertations

This dissertation addresses two main topics, the formation of micron-scale surface structures on single crystal silicon by irradiation with a KrF (248 nm) pulsed excimer laser source, and an investigation into electronic transport through composites of polymer (PMMA) and single-walled carbon nanotubes. It is shown that the spacing between laser-generated surface structures is determined primarily by the melt time and that the crystal orientation of the substrate can determine whether surface structures will form at all and also influence the shape of individual surface structures. During the melt/solidification cycle, the shape of liquid-vapor interface in modified by surface tension, and …

Fundamental Studies Of X-Ray And Secondary Electron Spectroscopy, Staya Prasad Mulapudi

Doctoral Dissertations

Microanalysis of submicron particles in the Scanning Electron Microscope (SEM) is only possible by using low incident electron beam energies due to smaller interaction volume and suppressed beam induced charging. Such low beam energies must use L- and M- lines rather than the familiar K-lines. The information about the fundamental parameters of X-ray emission and transport at low energies is limited, so the use of L- and M- lines is problematic. The rate of generation of X-rays from an element irradiated at some energy E depends on the product of the ionization cross-section (E) and the fluorescent yield . Unfortunately …

Fundamental And Applied Experimental Investigations Of Corrosion Of Steel By Lbe Under Controlled Conditions: Kinetics, Chemistry, Morphology, And Surface Preparation: Quarterly Report (October-December 2004), Allen L. Johnson, John Farley, Dale L. Perry

Transmutation Sciences Materials (TRP)

This project has four components:

(1) the fabrication of a materials test apparatus with unique capabilities,

(2) comparative studies of steel corrosion under gas phase conditions comparable to the Lead Bismuth Eutectic (LBE) oxygen control conditions,

(3) isotope labeling studies, and

(4) collaborative efforts with other workers in the field.

Microwave Pretreatment Of Corn Stover For Anaerobic Digestion, Abhishek D. Saxena

Masters Theses

Anaerobic digestion is one of the several technologies used for biomass conversion to electricity or heat. This thesis focused on microwave irradiation of corn stover as a pretreatment for anaerobic digestion, and studies its impact on methane production.

The first run comprised three sets of stover soaked overnight in water, dilute sulfuric acid and dilute acetic acid, and each treated to three different levels of microwave irradiation. The results indicated a high variability in the data of the water set, which showed that there was no clear impact of microwave pretreatment on methane production. The dilute sulfuric acid and dilute …

Ab Initio Calculation Of Electronic And Optical Properties Of Beryllium Chalcogenides (Bes, Bese, And Bete) Under The Effect Of Pressure, Aisha Ali Saif Bannan Al-Kaabi

Theses

There are several methods for materials simulation. Ab initio or first principles methods are used to solve the quantum mechanical equation which govern the behavior of a system. Ab initio calculation of the optical and electronic properties of solids is fundamental in solid state physics. APW+lo is used to examine different properties of BeS, BeSe and BeTe. Beryllium compounds show different features in structure under different pressures, and they also show a phase transition from Zinc blende to Hexagonal transitions in II-VI semiconductors. Little is known about the ground state properties of Beryllium Chalcogenides. The aim of this work is …

Effects Of Variable Contact Load On Fretting Fatigue Behavior Of Shot-Peened And Un-Peened Titanium Alloy, Chia-Hawa Lee

Theses and Dissertations

Fretting fatigue occurs between two components in contact under relative motion and reduces fatigue life when compared with plain fatigue. Shot-peening, on the other hand, is the most commonly used cold working process to improve material fatigue resistance in aeronautical industries. Nearly all work accomplished to date has assumed a constant contact load while investigating fretting fatigue. The primary goal of this study was to explore fretting fatigue behavior under constant and variable contact load configurations using both shot-peened and un-peened specimens made up of Ti-6Al-4V alloy. Contact loads were applied with four different frequencies. Applied axial loads were also …

Stabilization Of Desert Sand Using Water-Borne Polymers, Shihab Wagiealla Abdalla Mohamed

Theses

Soil stabilization is one of the various applications that have benefited from the advances in polymeric materials. In this research, three water-borne polymeric emulsions with different chemical and physical properties were tested as stabilizers for sandy soil.

This study is divided into three parts. In the first part, the performance of the three emulsions in reducing the hydraulic conductivity and improving the mechanical properties of the sand was investigated. Specimens with polymer contents of up to 2 wt. % were prepared using two preparation methods, mixing and spraying. Both types of specimens exhibited a significant improvement in the studied properties. …

Nanoscale Materials Processing: Electron Beam-Induced Etching Of Silicon And Silicon Dioxide, Steven Jeffrey Randolph

Masters Theses

Both silicon and silicon dioxide can be etched with an electron beam in the presence of a xenon difluoride atmosphere in a process known as electron beam-induced etching (EBIE). In order to study the EBIE process, a Hitachi S-3500N scanning electron microscope (SEM) was modified to accept a vapor delivery system. Evidence has been presented regarding the fundamental mechanisms by which EBIE occurs, as well as the microscope variables that effect the etch process.

The effects of beam current and beam energy on the EBIE process were examined for both materials. On silicon, it was observed that the increased current …

Combinatorial Design Of Nickel-Chromium Alloys By Physical Vapor Deposition And Electron Beam Welding, Jaret James Frafjord

Masters Theses

Combinatorial methods, which include high efficiency and high throughput methods to create a large compositional range of materials, have proven to be highly effective and efficient in research and development in the chemical and pharmaceutical industries. In this thesis, similar methods for the development and optimization of metals and alloy systems are explored. Combinatorial Ni-Cr alloy samples were developed by physical vapor deposition (PVD) of a wedged film on a bulk material, and then locally melting the two by electron beam welding (EBW). A combinatorial alloy gradient was thus created along the length of the weld. The samples were rapidly …

Failure In Internally Pressurized Bent Tubes, Robin Stevenson, Boon-Chai Ng, Peter Polidoro

Faculty Publications

The analysis and modeling of tube-hydroformed components is more complicated than that employed for sheet-metal panels, due to the lengthier process sequence and variable strain path - from flat-rolled sheet to tube; from straight tube to bent tube; and from bent tube to hydroformed component. These additional process steps make it difficult to determine whether post mortem analyses of tube failure during hydroforming can, and should, be conducted with the same tools and databases as used for simple stampings. To provide a partial answer, the properties of commercially fabricated welded straight tubes were evaluated using a free-expansion internal pressure test …

Stress Corrosion Cracking And Hydrogen Embrittlement Of Martensitic Alloy Ep-823, Mohammad K. Hossain

UNLV Theses, Dissertations, Professional Papers, and Capstones

This investigation is focused on the evaluation of stress corrosion cracking (SCC), localized corrosion, and hydrogen embrittlement (HE) susceptibility of martensitic Alloy EP-823 in neutral and acidic solutions at ambient and elevated temperatures. While no failures were observed in smooth specimens in the neutral solution, failures were noticed in the 90°C acidic solution at constant-load (CL) leading to a threshold stress (O'_th) of 102 ksi. The presence of a notch reduced the O'_th value to 91 ksi in a similar environment. The ductility (%El and %RA), time-to-failure (TTF), and true failure stress (O'_r) were gradually …

Environment Assisted Cracking Of Target Structural Materials Under Different Loading Conditions, Venkataramakrishnan Selvaraj

UNLV Theses, Dissertations, Professional Papers, and Capstones

Martensitic Alloy HT-9 has been tested for its evaluation of stress corrosion cracking resistance in neutral and acidic solutions at ambient and elevated temperatures incorporating smooth and notched cylindrical specimens under constant load and slow strain rate (SSR) conditions. C-ring and U-bend specimens have also been tested for stress corrosion cracking evaluation in the acidic solution. The role of hydrogen on the cracking tendency has been evaluated by cathodic applied potential.

The results of constant load testing enabled the determination of the threshold stress for stress corrosion cracking in susceptible environments. The magnitudes of ductility parameters were reduced with increasing …

Stress Corrosion Cracking Resistance Of Martensitic Stainless Steels For Transmutation Applications, Phani P. Gudipati

UNLV Theses, Dissertations, Professional Papers, and Capstones

The susceptibility of Alloy EP-823 to stress corrosion cracking has been evaluated using smooth and notched cylindrical specimens in neutral and acidic solutions at ambient and elevated temperatures using constant load and slow strain rate testing (SSR) techniques. C-ring and U-bend specimens have also been tested in the acidic solution. The effect of hydrogen on the cracking susceptibility has been evaluated under controlled cathodic potential. While no failures were observed with smooth specimens at constant load, the notched specimens showed failure. The SSR test results indicate that the true failure stress (o'_f), time to failure and ductility parameters …

Biomimetic Actuators: Where Technology And Cell Biology Merge [Review Article], Michael Knoblauch, Winfried Peters

Winfried S. Peters

Electrochemical Behaviours Of Hemoglobin-Ddab-Modified Powder Microelectrode And The Application Of The Powder Microelectrode In Determination Of Nitric Oxide, Zhi-Mou Guo, Huan Liu, Jian Chen, Wen-Ting Zhang

Journal of Electrochemistry

The electrochemical behaviours of DDAB-Hb-PME were studied in this paper. The (apparent) surface concentration of Hb was enhanced greatly by using the powder microelectrode (technique). NO reacts with Hb and absorbs on the surface of the modified carbon powder. Therefore, the output of the electrode was enhanced greatly by employing PME with higher reaction surface (area). The sensitivity of DDAB-Hb-PME is 3.1 mA/μmol·L~(-1)·cm~(2), which is much larger than the values obtained with the traditional electrodes. The detection limit is 9 nmol·L~(-1) and the linear response range is 9～100 nmol·L~(-1).

Electrocatalytic Performances Of Carbon Nanotube Air Electrode For Oxygen Reduction, Feng-Ming Zhao, Chun-An Ma

Journal of Electrochemistry

The air electrodes with different mass ratio of Pt/active carbon or carbon nanotube as catalyst layer material have been prepared. The electrocatalytic performances for oxygen reduction were evaluated by means of polarization curve and electrochemical impedance spectroscopy (EIS). The results disclosed that carbon nanotubes dealt with nitric acid in the catalyst layer had been improved obviously on the electrocatalytic activity. After the surface of carbon nanotube was oxygenated and aggraded with platinum, the catalyst had obviously effects on the electrocatalytic activity. The air electrode with the mass ratio of active carbon to Pt/carbon nanotube in 4∶1 showed better electrocatalytic activity, …

Electrochemical Investigations On Pitting Susceptibility Of Iron-Based Alloy, Wei-Shan Li, Hong-Yu Chen, Zhong-Zhi Yuan, Hong Li, Qi-Ming Huang, Dong-Sheng Lv

Journal of Electrochemistry

The formation process of passive film on iron and electronic properties and pitting susceptibility of an iron-based alloy are investigated by using linear potential sweep, alternative current impedance and electrochemical nose technologies. The relationship between reciprocal square capacitance and potential following the Mott-Schottky behavior is limited at a narrow rang of low potentials. At higher potentials, linear relationship between reciprocal capacitance and potential is obtained, which is ascribed to the increasing thickness of the passive film with potential. The donor density of the passive film is influenced by the formation potential of the film, passivator and microstructure. The decrease in …

Preparation And Electrochemical Magnesium Insertion Behaviors Of Mgv_2o_6, Hua-Tang Yuan, Li-Fang Jiao, Jian-Sheng Cao, Xiu-Sheng Liu, Ming Zhao, Yong-Mei Wang

Journal of Electrochemistry

MgV_2O_6was synthesized by conventional solid-state reaction from MgO and V_2O_(5)as starting materials. X-Ray diffraction analysis showed that the prepared sample belongs to the monoclinic structure. Electrochemical magnesium insertion from aprotic electrolytes such as organomagnesium halides into this host was found possible and exhibited charge/discharge circulation.