Engineering Commons^™

Spectroscopic Investigation Of Palladium-Copper Bimetallic Systems For Pem Fuel Cell Catalysts, Timo Hofmann

UNLV Theses, Dissertations, Professional Papers, and Capstones

One of the main barriers to commercialization of polymer electrolyte membrane fuel cells systems is cost, which is largely due to the need of platinum (Pt)-containing catalysts. In this thesis we investigate bimetallic systems consisting of a base metal (copper) and a noble metal (palladium) that, as an alloy on the nanoscale, mimic the electronic properties that make Pt desirable as a catalyst.

We present a detailed investigation of the electronic structure of carbon-supported Pd/Cu nanoparticle catalysts, model bilayer thin film systems, alloys, and various metal reference samples. We have investigated the valence band structure of the catalysts using a …

Parametric Study Of Stimulus-Response Behavior Incorporating Vehicle Heterogeneity In Car-Following Models, Saidi Siuhi

UNLV Theses, Dissertations, Professional Papers, and Capstones

The objective of this study was to develop a family of car-following models that address the shortcomings of car-following models developed by General Motors (GM) in the 1950s. The developed models consist of separate models for acceleration, deceleration, and steady-state responses for congested freeway traffic conditions. The study calibrated the models using individual vehicle trajectory data collected on a segment of Interstate 101 in Los Angeles, California. Furthermore, the study validated the models using individual vehicle trajectory data collected on a segment of Interstate 80 in Emeryville, California. The study used nonlinear regression with robust standard errors to estimate the …

Effect Of Mechanical Vibrations On Light Emitting Diode Luminaires, Jayalakshmi Paladugu

UNLV Theses, Dissertations, Professional Papers, and Capstones

In this work, a LED and two types of Compact fluorescent lamps were investigated for the intensity variation due to mechanical vibrations in the range of 0 to 30 HZ. In general, subjecting the lamps to 24-hour vibration affects the total intensity percentage variations of peak intensities after vibrations is in the range of -25 to +15% compared to those of no vibrations for the light emitting diode luminaires. For the case of compact fluorescent lamps (Nuvue) the variations are in range from +10 to +35%, whereas for the Compact fluorescent lamps (Ecosmart) the intensity peaks range from -10 to …

Studying The Impacts Of Primary Incidents On Freeways To Identify Secondary Incidents, Rohit Reddy Saddi

UNLV Theses, Dissertations, Professional Papers, and Capstones

Freeway incidents are associated with different impacts such as traffic congestion, delays, fuel consumption, secondary incidents etc. Secondary incidents are caused due to primary incidents and require the same personnel who are already engaged. This thesis studies various impacts caused by primary incident in space and time occurring on the freeways and these results are applied to identify secondary incidents. Three types of impacts are identified and proposed in this study. Dynamic nature of queue length in the direction of accident is studied. Dynamic nature of congestion in the opposite direction of the freeway till the accident is cleared is …

Extents And Limits Of Radioscopic Detection Of Nuclear Materials In Cargo Containers With Two Megavoltage Energy Barriers, Vijay Kumar Mandava

UNLV Theses, Dissertations, Professional Papers, and Capstones

The megavoltage X-ray technology is utilized for detecting nuclear materials in cargo containers. Interlaced response is obtained by switching rapidly between 6MeV and 9 MeV beams. It is known that the ratio of penetration levels of cargo contents taken at nominal and dual energies provides the information about atomic numbers of materials, and thus can also indicate the threat group. However, the identification is not straightforward if combinations of materials are present. The latter can lead to misdetections. It is imperative to know what are the extent and the limit of the currently employed technology, and how to carry out …

Precise Measurement Of The Neutron Magnetic Form Factor Gnm In The Few-Gev² Region, Clas Collaboration, J. Lachniet, H. Bagdasaryan, S. Bültmann, N. Kalantarians, G. E. Dodge, T. A. Forest, G. Gavalian, C. E. Hyde-Wright, A. Klien, S. E. Kuhn, M. R. Niroula, R. A. Niyazov, L. M. Qin, L. B. Weinstein, J. Zhang

Physics Faculty Publications

The neutron elastic magnetic form factor was extracted from quasielastic electron scattering on deuterium over the range Q² = 1.0–4.8  GeV² with the CLAS detector at Jefferson Lab. High precision was achieved with a ratio technique and a simultaneous in situ calibration of the neutron detection efficiency. Neutrons were detected with electromagnetic calorimeters and time-of-flight scintillators at two beam energies. The dipole parametrization gives a good description of the data

Using Extensible Modeling In Systems Engineering And Architectural Search, Jason Paul Dauby, Cihan H. Dagli

Engineering Management and Systems Engineering Faculty Research & Creative Works

The system architecting process is the hierarchical reduction of ambiguity associated with user needs and system design. Design allocation, and subsequent integration, implicitly requires a mechanism by which levels of detail can be added and removed from a decision scenario. This paper addresses the idea of engineering model sharing through the concept of vertical and horizontal extensibility as one mechanism by which hierarchical reduction in ambiguity can be facilitated. Extensible modeling introduces a systems architecting approach to the modeling community by identifying model interfaces and carefully decomposing the model domain. While the actual system hardware is not known at the …

Design Complexity And Its Relationship With Sn Ratio - Larger-The-Better Characteristics With Finite Target, Naresh K. Sharma, Elizabeth A. Cudney, Sonali Sharma

Engineering Management and Systems Engineering Faculty Research & Creative Works

The concept of complexity is an essential constituent of axiomatic design and axiomatic quality. a reciprocal transformation is used to compute quality loss for larger-the-better performance characteristics in Taguchi's methodology. El-Haik's work on connecting robust design and axiomatic design with the help of mathematical relationships also considers the reciprocal methodology for larger-the-better functional requirements. Because of reciprocal transformation axiomatic complexity formulation for larger-the-better performance characteristics is different from that for smaller-the-better and nominal-the-best characteristics. Second, the signal-to-noise ratio based on complexity is also different for the same reason. This paper shows that a simple linear transformation in which a finite …

Selection Of Pressure Equation For Preliminary Planing Hull Design Using Modified Analytical Hierarchy Process, Pamela Sue Fergen

Mechanical & Aerospace Engineering Theses & Dissertations

In the early stages of design when data availability is limited, engineers often times rely upon experience and regression analysis to select the most suitable design equation among many competitive ones. This study presents an alternative that applies a modified Analytical Hierarchy Process (AHP) to select the most suitable design equation. The Analytical Hierarchy Process, a multi-criteria decision making method, has been utilized in the business and management world to collect and evaluate experts' opinions in order to arrive at a final decision. The Analytical Hierarchy Process employed here will treat each of the design equations as an expert and …

Procedure To Validate Direct Numerical Simulations Of Wall-Bounded Turbulence Including Finite-Rate Reactions, Lian Duan, M. Pino Martín

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper first discusses the constitutive relations and surface catalytic model for direct numerical simulation of wall-bounded turbulence including finite-rate chemistry and gas-surface interaction and then provides a systematic procedure to test the validity of the simulations by dividing the whole problem into different components and testing each component separately. Namely, comparisons against similarity solutions and other established hypersonic boundary-layer solutions are used to test the validity of laminar mean flow with and without gas-phase chemical reactions; comparisons against the analytic solution for the one-dimensional diffusion equation are used to test the validity of the surface catalysis boundary condition; and …

System And Method For Quantitative Imaging Of Chemical Composition To Decompose Multiple Materials, Xin Liu, L. Yu, C. H. Mccollough

Nuclear Engineering and Radiation Science Faculty Research & Creative Works

The present invention provides a material decomposition method capable of determining the distribution of density and constituent material concentration throughout an imaged object. The concentration, in the form of a mass fraction, mass percent, weight fraction, or weight percent, is determined from CT images acquired at different energy levels. The ratio of attenuation coefficients associated with one energy level to attenuation coefficients associated with another energy level is determined and used as an index in a lookup table to determine the concentration of a given material throughout the imaged object.

Physics-Based Via And Trace Models For Efficient Link Simulation On Multilayer Structures Up To 40 Ghz, Renato Rimolo-Donadio, Xiaoxiong Gu, Young H. Kwark, Mark B. Ritter, Bruce Archambeault, Francesco De Paulis, Yaojiang Zhang, Jun Fan, Heinz Dietrich Brüns, Christian Schuster

Electrical and Computer Engineering Faculty Research & Creative Works

Analytical models for vias and traces are presented for simulation of multilayer interconnects at the package and printed circuit board levels. Vias are modeled using an analytical formulation for the parallel-plate impedance and capacitive elements, whereas the trace-via transitions are described by modal decomposition. It is shown that the models can be applied to efficiently simulate a wide range of structures. Different scenarios are analyzed including thru-hole and buried vias, power vias, and coupled traces routed into different layers. by virtue of the modal decomposition, the proposed method is general enough to handle structures with mixed reference planes. for the …

An Integrated Simulation Environment Combining Process-Driven And Event-Driven Models, Vishnu Sharma Kesaraju

Browse all Theses and Dissertations

A simulation framework that integrates process-driven and event-driven approaches offers a powerful combination of tools to the modeler. In process-driven simulation models, the system can be represented by block diagrams or system networks through which entities flow to mimic real life system objects. In event-driven models, the system can be represented by event graphs, which focus on the abstraction of the event rather than on observable physical entities. In this research, a simulation environment is proposed that integrates both the approaches, i.e. process and event. One of the main outcomes of working in such an environment is that modelers can …

Novel Intelligent Power Supply Using A Modified Pulse Width Modulator, Gary Richard Doss Jr.

Browse all Theses and Dissertations

The objective of this M.S. Thesis was to design, simulate, construct and test a pulse-width-modulated Buck DC-DC Converter and its compensated feedback system. Equations for the design and component selection of a buck converter have been obtained for operating the buck converter in the continuous conduction mode (CCM). A hardware version of the converter design has been implemented to demonstrate the functionality of the designed converter. Also, a digital buck converter control system has been designed and simulated. This digital buck converter led to the development of a proposed control scheme for Switched Mode Power Supplies (SMPS).

A novel hybrid …

Are Simulation Tools Developed And Used By Experts Appropriate Experimentation Tools For Educational Contexts?, Alejandra De Jesus Magana De Leon, George Bodner, Sean B. Brophy

School of Engineering Education Graduate Student Series

No abstract provided.

Rube Goldbergineering: Lessons In Teaching Engineering Design To Future Engineers, Shawn Jordan, Nielsen Pereira

School of Engineering Education Graduate Student Series

Hands-on learning experiences and interactive learning environments can be effective in teaching K-12 students. Design, in essence, is an interactive, hands-on experience. Engineering design can be taught in the classroom using innovative hands-on projects, such as designing and building serve to teach design, promote creativity, and provide opportunities for hands-on problem solving, in addition to giving students experience working in cooperative teams. In turn, these experiences could encourage students to consider future careers in engineering and science.

This paper explores findings from data collected during the authors’ recent experience teaching a group of fifteen 4th – 6th grade students enrolled …

Lean Six Sigma Principles In Capstone Aeronautical Engineering Technology Courses, Sergey Dubikovsky, Mary E. Johnson

School of Engineering Education Graduate Student Series

No abstract provided.

2009 Enacted Wheel Tax Rates (Lohut), Indiana Ltap

Indiana Local Technical Assistance Program (LTAP) Publications

This publication is a compilation of wheel tax rates using data provided by the Indiana Bureau of Motor Vehicles.

Modeling Of Subcontinuum Thermal Transport Across Semiconductor-Gas Interfaces, Dhruv Singh, Xiaohui Guo, Alina A. Alexeenko, Jayathi Y. Murthy, Timothy S. Fisher

School of Aeronautics and Astronautics Faculty Publications

A physically rigorous computational algorithm is developed and applied to calculate subcontinuum thermal transport in structures containing semiconductor-gas interfaces. The solution is based on a finite volume discretization of the Boltzmann equation for gas molecules (in the gas phase) and phonons (in the semiconductor). A partial equilibrium is assumed between gas molecules and phonons at the interface of the two media, and the degree of this equilibrium is determined by the accommodation coefficients of gas molecules and phonons on either side of the interface. Energy balance is imposed to obtain a value of the interface temperature. The classic problem of …

Numerical Investigation Of Power Transmission Efficiency In A Rf Plasma, Akshay Ashok, William Stein, Alina A. Alexeenko

School of Aeronautics and Astronautics Faculty Publications

Capacitively coupled radio frequency discharges are used in a variety of applications in which the power transmission efficiency of the discharge is an important performance parameter. While previous research addressed the discharge properties and discharge modeling, little analysis has been done on the dependence of the power transmission efficiency on main discharge paremeters such as applied voltage, operating frequency and pressure. To investigate the effects of a dual frequency waveform on the power transmission efficiency, Particle-InCell/Monte-Carlo Collison (PIC/MCC) methods are used to simulate RF co-axial plasma discharge. Plasma characteristics are studied for a range of operating pressures and radii, as …

Simulations And Measurements Of Gas-Droplet Flows In Supersonic Jets Expanding Into Vacuum, A Venkattraman, Alina A. Alexeenko

School of Aeronautics and Astronautics Faculty Publications

Simulations and measurements of gas-droplet multiphase flows in application to supersonic expansions into vacuum have been considered and compared with each other. The experiments involved exposing a control surface to a supersonic plume from two different nozzles and measuring the size distribution of droplets at various locations. The simulations are based on the direct simulation Monte Carlo modeling of vapor-phase flow with a one-way coupling of droplet momentum and energy. The droplet trajectories are computed for the experimental conditions for droplets originating at the throat and lip of two different nozzles. The maximum droplet radius reaching the control surface and …

Decision Making In First Year Engineering: Exploring How Students Decide About Future Studies And Career Pathways, Ida Ngambeki, Odesma Dalrymple, Demetra Evangelou Dr

School of Engineering Education Graduate Student Series

The number of students enrolling in engineering has declined steadily over the last fifteen years, and the number of engineers joining certain fields in engineering has decreased even more drastically. A number of studies have demonstrated a strong relationship between students’ interests and abilities and their persistence in engineering. It is therefore logical to assume that students who choose a major which makes the best use of their skills and engages their interest, are more likely to not only stay, but also thrive in the field of engineering which they choose. Students who make a poor choice, because of incomplete …

Unified Theory Of Gas Damping Of Flexible Microcantilevers At Low Ambient Pressures, Rahul A. Bidkar, Ryan C. Tung, Alina A. Alexeenko, Hartono Sumali, Arvind Raman

School of Aeronautics and Astronautics Faculty Publications

No abstract provided.

Modeling Of Viscous Shock Tube Using Es-Bgk Model Kinetic Equations, S Chigullapalli, A Venkattraman, Alina A. Alexeenko

School of Aeronautics and Astronautics Faculty Publications

The viscous effects on unsteady shock wave propagation are investigated by numerical solution of the Boltzmann model kinetic equations. The kinetic equations are solved for two unsteady non-equilibrium flow problems, namely, the one-dimensional Riemann problem and a two-dimensional viscous shock-tube. The numerical method comprises the discrete velocity method in the velocity space and the finite volume discretization in physical space using various flux schemes. The discrete version of H-theorem is applied for analysis of accuracy of the numerical solution as well as of the onset of non-equilibrium. Simulations show that the maximum entropy generation rate in viscous shock tube occurs …

Stabilizing Switched Linear Systems With Unstabilizable Subsystems, Wei Zhang, Jianghai Hu, Alessandro Abate

Department of Electrical and Computer Engineering Technical Reports

Abstract This paper studies the exponential stabilization problem for discrete-time switched linear systems based on a control-Lyapunov function approach. A number of versions of converse control-Lyapunov function theorems are proved and their connections to the switched LQR problem are derived. It is shown that the system is exponentially stabilizable if and only if there exists a finite integer N such that the N-horizon value function of the switched LQR problem is a control-Lyapunov function. An efficient algorithm is also proposed which is guaranteed to yield a control-Lyapunov function and a stabilizing strategy whenever the system is exponentially stabilizable.

Filterpave Systems, Purdue Ect Team

ECT Fact Sheets Archive

The need for hard-surfaced porous pavements has grown over the past few years as the market accepts PPS technology as a viable solution, as regulations leave few other options and as frequency of use increases. The FilterPave system is a unique porous pavement system that uses post-consumer recycled glass as the open-graded aggregate. Approximately 90 glass beverage bottles are used in just one square foot of pavement, making constructive use of abundant recycled materials that are traditionally sent to the landfill and used as daily cover.

Quantitative Prediction Of Body Surface Potentials From Myocardial Action Potentials Using A Summed Dipole Model, Charles F. Babbs

Weldon School of Biomedical Engineering Faculty Publications

This paper demonstrates quantitatively, using streamlined mathematics, how the transmembrane ionic currents in individual cardiac muscle cells act to produce the body surface potentials of the electrocardiogram (ECG). From fundamental principles of electrostatics, anatomy, and physiology, one can characterize the strength of apparent dipoles along a wavefront of depolarization in a local volume of myocardium. Net transmembrane flow of ionic current in actively depolarizing or repolarizing tissue induces extracellular current flow, which sets up a field of electrical potential that resembles that of a dipole. The local dipole strength depends upon the tissue cross section, the tissue resistivity, the resting …

The Effect Of Polydispersivity On The Thermal Conductivity Of Particulate Thermal Interface Materials, Sasanka Kanuparthi, Ganesh Subbarayan, Thomas Siegmund, Bahgat Sammakia

School of Mechanical Engineering Faculty Publications

A critical need in developing thermal interface materials (TIMs) is an understanding of the effect of particle/matrix conductivities, volume loading of the particles, the size distribution, and the random arrangement of the particles in the matrix on the homogenized thermal conductivity. Commonly, TIM systems contain random spatial distributions of particles of a polydisperse (usually bimodal) nature. A detailed analysis of the microstructural characteristics that influence the effective thermal conductivity of TIMs is the goal of this paper. Random microstructural arrangements consisting of lognormal size-distributions of alumina particles in silicone matrix were generated using a drop-fall-shake algorithm. The generated microstructures were …

Influence Of Dimensionality On Thermoelectric Device Performance, Raseong Kim, Supriyo Datta, Mark S. Lundstrom

Department of Electrical and Computer Engineering Faculty Publications

The role of dimensionality on the electronic performance of thermoelectric devices is clarified using the Landauer formalism, which shows that the thermoelectric coefficients are related to the transmission, T(E)T(E), and how the conducting channels, M(E)M(E), are distributed in energy. The Landauer formalism applies from the ballistic to diffusive limits and provides a clear way to compare performance in different dimensions. It also provides a physical interpretation of the “transport distribution,” a quantity that arises in the Boltzmann transport equation approach. Quantitative comparison of thermoelectric coefficients in one, two, and three dimensions shows that the channels are utilized more effectively in …

Remote Sensing Methods By Compressive Sensing, Atul Divekar, Okan Ersoy

Department of Electrical and Computer Engineering Technical Reports

Compressive Sensing is a recently developed technique that exploits the sparsity of naturally occurring signals and images to solve inverse problems when the number of samples is less than the size of the original signal. We apply this technique to solve underdetermined inverse problems that commonly occur in remote sensing, including superresolution, image fusion and deconvolution. We use l1-minimization to develop algorithms that perform as well as or better than conventional methods for these problems. Our algorithms use a library of samples from similar images or a model for the image to be reconstructed to express the image as a …