Engineering Commons^™

Substrate Topography Design And Fabrication For Osteoblast And Dental Pulp Stem Cells Studies, Gloria Chen

All Theses

Research for cell guidance based tissue engineering has rapidly grown due to the increasing interest in tissue engineering and reconstructive medicine applications, such as cranial reconstruction. Many research teams have begun the process of identifying what factors influence cell behavior (including cell growth, proliferation, alignment and spreading). Published studies have pointed to the influence of the cell medial pH, substrate stiffness, chemistry and topography. Conclusive results are often hard to identify since researchers often vary many of these factors simultaneously and it is hard to decouple individual factor influence. These reports also points out that the cellular response can be …

Immersion Cooling Of Photovoltaic Cells In Highly Concentrated Solar Beams, Ahmed Darwish

UNLV Theses, Dissertations, Professional Papers, and Capstones

Concentrated solar radiation can be utilized to generate electrical power from photovoltaic cells, but concentrated solar radiation increases the photovoltaic cell’s temperature. This increase in temperature can lead to degradation of the cell efficiency, and too high of a temperature can damage the cell’s integrity. This is particularly important in dish and tower systems where a maximum uniform flux may be difficult to achieve. While a variety of approaches have been used to the keep the cells cool, most are based upon removal of heat from the back (opposite surface of the incident flux exposed surface) of the cell. This …

Raman Spectroscopic Study Of Solid Solution Spinel Oxides, Brian D. Hosterman

UNLV Theses, Dissertations, Professional Papers, and Capstones

Solid solution spinel oxides of composition MgxNi1−xCr2O4, NiFexCr2−xO4, and FexCr3−xO4 were synthesized and characterized using x-ray diffraction and Raman spectroscopy. Frequencies of the Raman-active modes are tracked as the metal cations within the spinel lattice are exchanged. This gives information about the dependence of the lattice vibrations on the tetrahedral and octahedral cations. The highest-frequency Raman-active mode, A1g, is unaffected by substitution of the divalent tetrahedral cation, whereas the lower frequency vibrations are more strongly affected by substitution of the tetrahedral cation. The change in wavenumber of many phonons is nonlinear upon cation exchange. All detected modes of MgxNi1−xCr2O4 and …

Structural, Electrical And Thermoelectric Properties Of Chromium Silicate Thin Films, Makram Abd El Qader

UNLV Theses, Dissertations, Professional Papers, and Capstones

Thermoelectric devices can generate electrical power as a result of their ability to produce electrical currents in the presence of thermal gradients. They can also produce refrigerative cooling when electrical power is supplied to them. Among the potential semiconducting silicides, CrSi ₂ is attractive because of its high thermal and chemical stability and its potential for thermoelectric application. CrSi₂ /SiO₂ thin-film structures were prepared using RF sputtering. As deposited and annealed (300°C to 600°C) thin films were characterized for their structural, electrical, and thermoelectric transport properties. As-sputtered CrSi ₂ film is amorphous at room temperature and crystallizes around …

Recycling Waste Latex Paint In Overlays, Rigid Pavements, And Pervious Concrete, Oscar Inez Quiroz

UNLV Theses, Dissertations, Professional Papers, and Capstones

With over 16 million gallons of latex paint (WLP) being disposed every year it is the largest by volume, liquid hazardous waste in the United States. WLP is difficult to recycle and hazardous to the environment due to the volatile organic compounds it contains. Several methods exist for disposing WLP including paint swaps, combustion, drying and discarding in a landfill, and by placing pigments in cement. Many communities are moving to dispose WLP by drying and placing in a landfill due to the reduced cost. However, this is the least preferred technique for the environment because it creates a need …

Domain Size And Structure In Exchange Coupled [Co/Pt]/Nio/[Co/Pt] Multilayers, Andrew G. Baruth, Shireen Adenwalla

Shireen Adenwalla Papers

We investigate the competing effects of interlayer exchange coupling and magnetostatic coupling in the magnetic heterostructure ([Co/Pt]/NiO/[Co/Pt]) with perpendicular magnetic anisotropy (PMA). This particular heterostructure is unique among coupled materials with PMA in directly exhibiting both ferromagnetic and antiferromagnetic coupling, oscillating between the two as a function of spacer layer thickness. By systematically tuning the coupling interactions via a wedge-shaped NiO spacer layer, we explore the energetics that dictate magnetic domain formation using high resolution magnetic force microscopy coupled with the magneto-optical Kerr effect. This technique probes the microscopic and macroscopic magnetic behavior as a continuous function of thickness and …

Effect Of Accelerated Aging On Mechanical Properties And Structure Of Nano-Scale Composite Systems, David Economy

All Theses

Nano-scale composites are being investigated by academic, industrial, and national laboratories for potential applications such as wear resistant coatings and high strength foils. These structures are of interest due to their as-fabricated mechanical properties, such as high strength for nanolaminates. However, there have only been limited studies of the long-term mechanical stability. A greater understanding of how these systems might respond to sustained use is needed before these systems transition from research laboratories into widespread application. It is the objective of this thesis to clarify the link between accelerated aging using elevated temperatures over time and mechanical properties of two …

Time-Dependent Crack Growth Behavior Of Alloy 617 And Alloy 230 At Elevated Temperatures, Shawoon Kumar Roy

UNLV Theses, Dissertations, Professional Papers, and Capstones

Two Ni-base solid-solution-strengthened superalloys: INCONEL 617 and HAYNES 230 were studied to check sustained loading crack growth (SLCG) behavior at elevated temperatures appropriate for Next Generation Nuclear Plant (NGNP) applictaions with constant stress intensity factor (K _max = 27.75 MPa[checkmark]m) in air. The results indicate a time-dependent rate controlling process which can be characterized by a linear elastic fracture mechanics (LEFM) parameter - stress intensity factor (K). At elevated temperatures, the crack growth mechanism was best described using a damage zone concept. Based on results and study, SAGBOE (stress accelerated grain boundary oxidation embrittlement) is considered the primary reason for …

Thermoelectric Properties Of Nickel And Titanium Co-Intercalated Titanium Diselenide, Timothy Holgate

All Dissertations

Thermoelectric materials are involved in the direct conversion between thermal and electrical energy. They may be used to generate power from a thermal gradient or to pump heat in or out of a system when driven with DC power. Much of the recent advances in thermoelectric research have been in materials whose thermoelectric efficiency has been optimized at temperatures above room temperature where power generation is the main application.
The question that I seek to answer in this dissertation is to use our standard experimental techniques in order to assess the possibility of a class of transition metal dichalcogenides bases …

Quantitative Analysis Of The Reaction Between Gliadin And Citric Acid Under Weak Acidic And Weak Alkaline Conditions, Wei Li

Department of Agricultural and Biological Systems Engineering: Dissertations, Theses, and Student Research

Gliadin was reacted with citric acid under weak acidic and weak alkaline conditions in both wet and dry states and the reaction mechanism was studied. The low morphological stability in an aqueous environment and inferior mechanical properties have restricted the applications of plant proteins, although these materials possess a unique structure, biocompatibility and biodegradability. Carboxylic acids such as citric acid are inexpensive and nontoxic chemicals and are preferred for crosslinking proteins and cellulose to improve the desired properties of the materials.

In this study, gliadin was chosen as a model of plant proteins to react with citric acid. However, previous …

53rd Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Final program, abstracts, and information about the 53rd annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-endorsed by the Colorado Section of the American Chemical Society and the Society for Applied Spectroscopy. Held in Snowmass, Colorado, July 24-28, 2011.

Mapping Mos2-Co Catalytic Nanostructures Using Hrtem And Tem Simulations, Eduan Martínez-Soto ^, Brenda Torres, Domingo Ferrer, Gilles Berhault, Russell Chianelli, Manuel Ramos *

COURI Symposium Abstracts, Summer 2011

No abstract provided.

Synthesis And Characterization Of Cdse-Zns Core-Shell Quantum Dots For Increased Quantum Yield, Joshua James Angell

Master's Theses

Quantum dots are semiconductor nanocrystals that have tunable emission through changes in their size. Producing bright, efficient quantum dots with stable fluorescence is important for using them in applications in lighting, photovoltaics, and biological imaging. This study aimed to optimize the process for coating CdSe quantum dots (which are colloidally suspended in octadecene) with a ZnS shell through the pyrolysis of organometallic precursors to increase their fluorescence and stability. This process was optimized by determining the ZnS shell thickness between 0.53 and 5.47 monolayers and the Zn:S ratio in the precursor solution between 0.23:1 and 1.6:1 that maximized the relative …

Development Of Composition Modulated Multilayer Alloy Coatings And Their Corrosion Behavior, S Yogesha, A C. Hegde

Journal of Metals, Materials and Minerals

Multilayer Zn-Ni alloy coating was developed on mild steel from acid chloride bath containing thiamine hydrochloride, as additive. Composition modulated multilayer alloy (CMMA) coatings, or simply, multilayer coating with gradual change in composition were developed galvanostatically using triangular current pulses from single bath technique. CMMA coatings of Zn-Ni were developed under different conditions, such as cyclic cathode current densities (CCCDs) and a number of layers, and their corrosion behaviors were evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy method. Optimal configuration, (Zn-Ni)2.0/4.0/600 was found to exhibit ~50 times better corrosion resistance compared to monolayer (Zn-Ni)3.0 alloy, deposited from the same …

Chevron Crack Initiation In Mullti-Pass Drawing Of Inclusion Copper Shaped-Wire, S Norasethasopon

Journal of Metals, Materials and Minerals

In the copper superfine wire drawing, the internal cracks such as chevron cracks and breakage of the wire were fatal to the success of quantitative drawing operations. This paper shows how the main process parameters, the drawing pass numbers, influence the plastic deformation, hydrostatic stress, maximum principal tensile stress and chevron cracks initiation investigated by FEM simulation. The effect of the lateral and longitudinal sizes of a central cylindrical inclusion in the multi-pass copper shaped-wire drawing was studied. The plastic deformation, plastic strain, hydrostatic stress and maximum principal tensile stress of the copper shaped-wire containing an inclusion were obtained from …

Improving Quench Hardening Of Low Carbon Steel, T Korad, M Polboon, N Chumchery, J Pearce

Journal of Metals, Materials and Minerals

The carbon content in steel determines whether it can be directly hardened. If the carbon content is low (less than 0.25wt%) then an alternate means exists to increase the carbon content of the surface. In this study, the mixed quenchant consisting of brine and surfactants known as Superquench was applied in the quench-hardening process on AISI 1015 low carbon steel. The quench results were compared with quenching in heavy brine solution, water and oil which are recognized as the basic quenchants and cannot cause bulk-hardening low-carbon steels. The hardness tests on different points along the radius of cut round bar …

Immobilization Of Lipase Onto Cyperus Papyrus L. For Biodiesel Production By Transesterification And Hydrolysis-Esterification, S Charuchinda, P Suthianthong, W Chulalaksananukul

Journal of Metals, Materials and Minerals

Lipase of Candida rugosa was immobilized on biomass support, plant fiber from Cyperus papyrus L., for biodiesel synthesis. The two immobilization techniques investigated in this study were physical adsorption and covalent binding with 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC). Results showed that the prepared immobilized lipase by physical adsorption with adding heptane presented higher protein loading, lipase activity and degree of immobilization than that by physical adsorption in phosphate buffer solution and by covalent binding. This immobilized lipase was further applied as biocatalyst for biodiesel synthesis by transesterification and hydrolysis-esterification. The results showed that this immobilized lipase preferred to hydrolyze triglyceride in palm oil …

Self-Crack Closing Ability Of Mortar With Different Additives, D Jaroenratanapirom, R Sahamitmongkol

Journal of Metals, Materials and Minerals

Self-crack closing ability of cementitious materials has been studied in various aspects. However, most studies focus mainly on the cementitious material with only cement as a binder (without mineral additives), although many additives are commonly used at present. This research thus aims to investigate the effect of additives on this self-crack closing ability by observing and measuring crack width on the mortar specimens. Cracks were created on mortar specimens by splitting method at the age of 3 and 28 days. As most reports show that the best self-crack closing performance was achieved when a plenty of water was supplied, the …

Determination Of Forming Limit Stress Diagram For Formability Prediction Of Spce 270 Steel Sheet, S Panich, V Uthaisangsuk, J Juntaratin, S Suranuntchai

Journal of Metals, Materials and Minerals

The aim of this research is to apply numerical Finite Element Method (FEM) for determining Forming Limit Stress Diagram (FLSD) of sheet steel of grade SPCE 270. As a failure criterion for formability prediction in sheet metal forming process, the conventional Forming Limit Diagram (FLD) is often used. The FLD is a strain based criterion, by which the principal strains at failure are evaluated. Many investigations showed that the FLD is dependent on forming history and strain path. However, the stress based criterion does not confirm this dependency. This criterion is more robust against any changes in the strain path …

The Change Of Surface Alloy Compositions And Corrosion Behavior After Wedm Machining Of Commercially Pure Titanium (Grade 4) And Ti-6al-4v (Grade 5), K Sriprasertying, S Rhaiphu

Journal of Metals, Materials and Minerals

Nowadays, titanium and its alloys are widely used in medical applications because of excellent corrosion resistance and a high strength-to-weight ratio. Nevertheless, titanium and its alloys are classified as difficult-to-machine metals by conventional machining methods. Therefore, unconventional machining processes are recommended. Wire-electrical discharge machining (WEDM) has become an important non-traditional machining process, as it provides an effective solution for machining components made from difficult-to-machine metals. However, WEDM could damage the surface layer and have an effect on the biocompatibility properties. This research was focused on the effect of WEDM on grade 4 commercially pure titanium and Ti-6Al-4V (Grade 5) after …

Modification Of Montmorillonite With A Cationic Softener For Finishing Cotton Fabric With Hand Builder Performance, S Kittinaovarat, N Jiratumnukul, N Koolpreechanan

Journal of Metals, Materials and Minerals

Montmorillonite (Mont) was modified by cationic exchange with the cationic softener TEGO 28 (Di-Palm carboxyethyl hydroxyethyl methyl ammonium methosulfate). XRD analysis suggested that intercalation occurred in the modified Mont (mMont). Softening finishing solutions composed of pure TEGO 28 with and without mMont were treated on cotton fabrics by the pad-dry method and then evaluated for stiffness, whiteness, tear strength and thermal stability. TEGO 28 treatment alone increased the stiffness property of the finished fabrics, and this was increased further by the co-inclusion of mMont at 3 and 5% (w/v), but higher or lower mMont concentrations led to a marked and …

Chitosan And Trimethyl Chitosan Particles As Oral Vaccine Delivery Systems: Comparison Of The Potential To Initiate Immune Responses, S Boontha, H Ej Unginger, N Waranuch, A Polnok, T Pitaksuteepong

Journal of Metals, Materials and Minerals

In this study, particles having low MW (Chi-L), high MW (Chi-H) and their respective trimethyl chitosan (TMC) with a degree of quaternization (DQ) of about 40% (TMC-L-40 and TMC-H-40), and prepared by using chitosan, were used to compare their potentials for provoking immune responses to ovalbumin (OVA) following oral administration. The results showed that the Chi-L particles gave higher serum immunoglobulin G (IgG) responses to OVA than those induced with Chi-H, TMC-L-40 and TMC-H-40 particles. However, Chi-L and Chi-H particles gave similar secretory immunoglobulin A (sIgA) to OVA, and sIgA titers obtained from mice immunized with OVA-loaded TMC were negligible. …

Purification Of An Industrial Aluminum Alloy By Melt Stirring During Ohno Continuous Casting Process, S Fashu, L Jianguo, H Q. Dan

Journal of Metals, Materials and Minerals

With the purpose of upgrading the purity of a dilute industrial aluminum alloy during Ohno Continuous Casting (OCC) process through the use of forced melt stirring; the critical stirring intensity required under a casting speed of 2 mm/min was numerically determined. The determined critical stirring intensity induces convective velocity magnitudes into the melt which are effective in transporting solutes from the solute boundary layer into the bulk melt. It was found that, with adequate melt stirring, production of substantially long and high purity ingots during OCC is possible before their purity diminishes to lower than the initial alloy purity.

Design And Construction Of Water Atomizer For Making Metal Powder, S Yenwiset, T Yenwiset

Journal of Metals, Materials and Minerals

Water Atomization for metal powder is an appropriate method for producing metal powder from different kinds of metal. Typically, a water atomizing machine is designed with a molten metal spraying chamber in a vertical or horizontal orientation depending on a nozzle design, a molten metal spraying chamber and related components. The main variables influencing the working condition of the water atomization process, which affect sizes, shapes and distribution of metal powder particles, are water pressure, water flow rate, a temperature higher than melting point of liquid metal and flow rate of liquid metal. The water atomizing machine in the study …

Effect Of Postweld Heat Treatment On Microstructures And Hardness Of Tig Weldment Between P22 And P91 Steels With Inconel 625 Filler Metal, N Tammasophon, W Homhrajai, G Lothongkum

Journal of Metals, Materials and Minerals

This research aims at searching for the optimal postweld heat treatment condition of the TIG weld joint between P22 (2.25Cr) and P91 (9Cr) steels using Inconel 625 as filler metal. The postweld heat treatment at 750C for 2, 4 and 6 hours was applied in order to reach the proper microstructure and hardness for high performance in mechanical properties at elevated temperatures. It is recommended that postweld heat treatment at 750C for 2 hours is the proper condition to reduce the hardness of heat affected zone (HAZ) of P91 steel.

Applying Computer Simulation In Improving Heat Treating Condition Of Thin High-Carbon Steel Parts, T Korad, M Polboon, N Chumchery, J Pearce

Journal of Metals, Materials and Minerals

The study was carried out using COSMOSFlowWorks to predict heat treatment conditions for AISI 1085 high-carbon steel sheet that is used to produce automotive parts that require wear resistance and stiffness resulting from controlled moderately high hardness levels. To achieve such properties, flat high-carbon steel parts need to be hardened to produce acicular matrix structures, and the most suitable heat treatment process to harden thin parts without distortion is austempering. In producing hard and stiff thin section parts in this company study the austempering process was performed by soaking at 830C and then quenching in a NaCl salt bath at …

Effect Of Nitrogen Partial Pressure On Characteristic And Mechanical Properties Of Hard Coating Tialn Film, C Chokwatvikul, S Larpkiattaworn, S Surinphong, C Busabok, P Termsuksawad

Journal of Metals, Materials and Minerals

(Ti,Al)N coating has been serving for the industry as cutting and forming tools. Compared with TiN film, TiAlN film significantly increases tool lifetime. Therefore, it reduces machine downtime and increases productivity. In this work, (Ti,Al)N film was deposited on cold-work tool steel (SKD 11) using PVD cathodic arc system. The sintered Ti-Al target with composition of (at%) 50 Ti and 50 Al was used as a cathode. The deposition bias voltage, bias arc current and deposition time were set at 100 V, 70 A and 90 minutes, respectively. Nitrogen gas was purged into the system with the applied pressure of …

Study Conditions Of Aluminum Billets For Relationship Between Precipitated Phases And Homogenizing Temperature With Different Cooling Methods, U Phongsophitanan, M Polboon, N Chumchery

Journal of Metals, Materials and Minerals

In producing cast aluminum billets for using in extruded profile production, homogenization is one of the significant steps of the process. This project examined a suitable homogenizing temperature for usage in manufacturing besides common condition. Computerized fluid dynamics and image analysis solution were techniques to identify the relationship between the area fraction of precipitated phases and homogenizing temperature with different cooling methods. Temperature gradient pattern revealed that soaking temperatures at 575C and 565C are suitable conditions to be used in manufacturing. Furthermore, area fraction calculation showed that the area fractions of precipitated phases of each cooling method were not significantly …

The Human Dimension Of Systemic Department-Level Change: A Change Agent’S Retrospective On A Case Of Reform, Linda Vanasupa

Materials Engineering

This paper represents a narrative of the process of department-level reform through the eyes of the initiating agent of change. Over the course of reform, our program has grown by 40%, primarily through retaining students. We exhibit a 10% net important rate of engineering students in the first two years of the curriculum relative to the college’s 5% mean export rate. Student freshmen SAT scores also indicate that we are attracting students with more balanced learning interests. The design of our Department Level Reform grant was to advance the knowledge of how to design engineering learning experiences that accomplish two …

Computational Microstructure Modeling Of Asphalt Mixtures Subjected To Rate-Dependent Fracture, Francisco Aragao

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

Computational microstructure models have been actively pursued by the pavement mechanics community as a promising and advantageous alternative to limited analytical and semi-empirical modeling approaches. The primary goal of this research is to develop a computational microstructure modeling framework that will eventually allow researchers and practitioners of the pavement mechanics community to evaluate the effects of constituents and mix design characteristics (some of the key factors directly affecting the quality of the pavement structures) on the mechanical responses of asphalt mixtures. To that end, the mixtures are modeled as heterogeneous materials with inelastic mechanical behavior. To account for the complex …