Digital Commons Network^™

Assessment Of Bivariate Normality, Pejmon Sadri

UNLV Retrospective Theses & Dissertations

There are three methods, which are most commonly used to assess the bivariate normality of paired data, two of which are also used to assess the multivariate normality. Nevertheless, none of the methods is very efficient or conclusive in their assessment of bivariate normality. In this thesis we are proposing a new method to test bivariate normality. This new method makes use of a set of if and only if conditions inherent in the theory of bivariate normal distribution. The proposed new method is highly efficient, accurate, and very easy to apply using any available standard statistical software.

The Randomized Server Problem, Qin Zhang

UNLV Retrospective Theses & Dissertations

In the k-server problem there are k ≥ 2 identical servers which are located at k points in a metric space M. If there is a request to a point r ∈ M, one of the servers must be moved to the request point in order to "serve" this request. The cost of this service is the distance between the points where the server "resided" before the service and after the service. A k-server algorithm A must decide which server should be moved at each step. The goal of A is to minimize the total service cost. Competitiveness makes sense …

Residual Stress Measurements And Analysis By Destructive And Non-Destructive Techniques, Satish Babu Dronavalli

UNLV Retrospective Theses & Dissertations

This investigation is focused on the evaluation of residual stresses resulting from cold deformation and welding in candidate target structural materials such as martensitic Alloys EP-823 and HT-9, and austenitic Type 304L stainless steel (SS). Measurements of residual stresses were performed by both destructive and nondestructive techniques including ring-core (RC), neutron diffraction (ND) and positron annihilation spectroscopy (PAS). The results obtained by the PAS method indicate that the residual stresses in the cold-worked specimens were significantly enhanced with increased level of cold reduction. Residual stress measurements by the RC method on welded specimens consisting of similar materials revealed tensile stresses …

Energy-Absorbing Sandwich Structures Under Blast Loading, Dong Kwan Lee

UNLV Retrospective Theses & Dissertations

An experimental study at the Army Research Laboratories shows that flat panels with foam or honeycomb faceplates transferred more energy to a structure under blast loading relative to a structure without an energy absorbing faceplate. The objective of this work is to simulate non-uniform response of sandwich panels subject to blast loaDing This involves an investigation into the optimum design of a square-celled sandwich structure for energy absorption. Variables under investigation are the core and face sheet thicknesses of the sandwich structure. Results of a design of experiments study are attained, which evaluate the relative contribution of panel variables to …

Non-Linear Optimized Cash Flow Model, Martin J Mack

UNLV Retrospective Theses & Dissertations

During construction of a lump-sum project, progress payments (cash inflow) are paid periodically to contractors for project performance. Contractors are required to pay the direct costs (cash outflow) during construction. The net difference between the cash inflow and outflow are the required overdraft, which the contractor financed from a bank. In order to increase profit margin, contractors look into alternate ways, such as front-end loading (unbalanced bid) and activities shifting. Usually, front-end loading and activities shifting are done in a linear, independent, and sequential method. This linear front-end loading and activity shifting formulation will likely not produce an ideal optimized …

Fabrication Of Nonlithographic Semiconductor Quantum Wire Infrared Photodetector, Pavan Kumar Singaraju Venkata Sai

UNLV Retrospective Theses & Dissertations

The thesis describes novel semiconductor quantum wire infrared photodetectors in the long- and very long-wavelength regions. The infrared photodetectors are based on intersubband transitions in semiconductor quantum wires and have the potential for higher operational temperature, increased signal-to-noise ratio, reduced dark current, wider spectral range and sensitivity to normal incident radiation. The quantum wire IR detectors were implemented using a nonlithographic nanostructure fabrication technique that is capable of producing large arrays of semiconductor quantum wires of a variety of materials and on different substrates. The operational principles, design procedure as well as the implementation of the quantum wire photodetectors using …

Comparative Analyses Of Residual Stresses In Target Sub-System Materials, Anand Venkatesh

UNLV Retrospective Theses & Dissertations

Recent approaches to residual stress measurements in transmutation target structural materials using destructive and nondestructive techniques have been investigated in this research project. A major emphasis has been placed on the use of the Neutron Diffraction (ND) technique to determine the residual stresses in austenitic and martensitic stainless steels subjected to plastic deformation and welding operations. The resultant data have been compared to those obtained by other techniques including positron annihilation spectroscopy, x-ray diffraction and ring-core methods. Cold-worked (CW), three-point-bent (TPB) and welded specimens of similar and dissimilar materials were tested. ND measurements on CW specimens showed enhanced residual stresses …

Flux Profile Modeling Using Monte Carlo Simulation, Ramprasad Vijayagopal

UNLV Retrospective Theses & Dissertations

Molecular beam Epitaxy (MBE) is a process by which semiconductor films are grown on the substrate by physical vapor deposition of the source material in an ultra high vacuum environment. Spatial variations in flux are a result of the shape of the crucible and the geometry of the growth chamber. In this study a process simulation tool for MBE based on a phenomenological model is proposed and elaborated; Two different models based on physical principles are investigated. Model I includes the primary flux from the liquid surface and a secondary flux re-emitted from the crucible walls for the total flux …

Investigation Of Issues Related To The Revision Of Iso 10819, Erik Wolf

UNLV Retrospective Theses & Dissertations

This study has three main goals. The first is to evaluate a proposed change to the input spectra for the ISO 10819 antivibration glove tests. Secondly, this study investigates the effect of palm adapter geometry on linear transmissibility and mean corrected transmissibility values. Finally, the effect of test subject training is discussed and supporting data is shown; 30 rigid acrylic adapters were designed, fabricated, and tested. All adapters fell into one of four categories. Category 1 adapters passed the acceptability criteria. Category 2 adapters failed in the low frequency (16--40 Hz). Category 3 adapters failed in the high frequencies (1000--1600 …

Cfd Analysis Of Three-Dimensional Thermalhydraulics Flow Effects On Wall Concentration Gradient Profiles For Lbe Loop Fittings, Narain Armbya

UNLV Retrospective Theses & Dissertations

The objective of the thesis is to study the effects of thermalhydraulics flows on the wall concentration gradient profiles in LBE loop fittings. To that end detailed models of the fittings have been constructed to study these effects. These fittings include sudden expansion, sudden contraction, t-joint and elbow. The typical flow rates chosen for these simulations are typical of design criteria chosen for the Loop with Reynolds numbers expected around 200,000 and the usual axial temperature profiles which are being characterized in the DELTA loop at LANL. STAR-CD is the simulation package used to make these predictions, which include detailed …

Comparison Of The Performance Of Various Bootstrap Procedures For Gamma And Lognormal Distributions, Alex N Berejnoi

UNLV Retrospective Theses & Dissertations

The main objective of the present work is to study and compare the performance of the various bootstrap procedures (e.g., standard bootstrap method, bootstrap-t method, simple percentile bootstrap method, Hall's bootstrap method, and bias-corrected accelerated (BCA) bootstrap method (Efron and Tibshirani, 1993)) which may be used to compute a 95% UCL of the population mean based upon skewed distributions (e.g., gamma and lognormal); Monte Carlo simulation experiments have been performed to compare the performances of these methods. The comparison of the various methods has been evaluated in terms of the coverage probabilities achieved by the various 95% UCLs. Based upon …

Breaking Down The Wall: Hope And The Dialectical Nature Of Education, Ginger Clayton-Lee

UNLV Retrospective Theses & Dissertations

This paper will analyze the history of public education and its relationship to the industrial economy, education and curriculum reform literature and policies (both past and present) predominately within the theoretical framework proposed by Henry Giroux. Personal observations and experience as a teacher within this system will be used to provide insight into theoretical paradigms. Implemented programs will be assessed within the historical and theoretical framework outlined above in an effort to determine the impact of post-industrial economic needs on education and the potential for resistance. The predominant method of gathering data will be through literature reviews and within the …

Three-Dimensional Cfd Simulations Of Natural And Forced Convection Solar Domestic Water Heating Systems, Sachin Sudhakar Deshmukh

UNLV Retrospective Theses & Dissertations

The objective of the thesis is to study the thermal performance of the open loop natural convection and closed loop forced convection solar water heating system. The 3 dimensional (3D) numerical models were made in the Computer aided design (CAD) package and were simulated for the 12 hours of day time. Analysis was performed using the Computational fluid dynamics (CFD) software package Star-CD. The physical system of natural convection can be used for the purpose of heating domestic hot water without the use of a circulating pump. The closed loop forced circulation system is simulated to study the numerical behavior …

Suppression Of Limit Cycle Oscillations In An Aeroelastic System Using Robust And Adaptive Control, Sushma Gujjula

UNLV Retrospective Theses & Dissertations

In this thesis control systems are designed for the flutter control of nonlinear aeroelastic system. The aeroelastic model describes the plunge and pitch motion of a wing. The model includes plunge and pitch nonlinearities, and has both leading and trailing edge control surfaces for the purpose of control. First the existence of limit cycle oscillations and domain of stability (attraction) of prototypical aeroelastic wing sections with pitch structural nonlinearity using the describing function method is determined. The model includes unsteady aerodynamics based on Theodorsen's theory. The dual-input describing functions of the nonlinearity are used for the limit cycle analysis. Interestingly …

Optical Character Recognition For Checkbox Detection, John Michael Istle

UNLV Retrospective Theses & Dissertations

Optical character recognition is the branch in computer science that involves reading text from paper and translating the images into a format that computers can manipulate. There are a lot of algorithms for finding letters and numbers, however checkboxes are often overlooked and very difficult to detect. To locate and determine if checkboxes are checked or unchecked is a very useful tool to use on forms. It is difficult to detect since there are so many ways a person can mark a checkbox. This thesis will describe a new algorithm for detecting checkboxes; Before checkboxes can be searched, certain preprocessing …

Characteristics Of The Mechanical Impedance Of The Hand-Arm System, Ahmed Moustafa

UNLV Retrospective Theses & Dissertations

The mechanical impedance of the human hand-arm system was measured within the frequency range of 5--1000 Hz. A handle specially designed for such measurements, was used. The studies were carried out on ten healthy male subjects during different experimental conditions defined by, three different vibration amplitudes (0.01, 0.005, and 0.001 m/s) different combinations of push (0--75 N) and grip (25--50 N) forces, and two different methods of handle mass subtraction (mathematical and electronic). The effect of test subjects' weight on the results was also studied. The outcome shows that the mechanical impedance of the hand-arm system depends on the frequency …

Current Video Compression Algorithms: Comparisons, Optimizations, And Improvements, Douglas Scott Price

UNLV Retrospective Theses & Dissertations

Compression algorithms have evolved significantly in recent years. Audio, still image, and video can be compressed significantly by taking advantage of the natural redundancies that occur within them. Video compression in particular has made significant advances. MPEG-1 and MPEG-2, two of the major video compression standards, allowed video to be compressed at very low bit rates compared to the original video. The compression ratio for video that is perceptually lossless (losses can't be visually perceived) can even be as high as 40 or 50 to 1 for certain videos. Videos with a small degradation in quality can be compressed at …

An Examination Of Interactions Between Computer Support Staff And End Users, Kim Mia Price

UNLV Retrospective Theses & Dissertations

For those employed as information technology support professionals, the message they are receiving is that communication skills are as important as any credential or certification they may possess in terms of staying competitive in the current job market. The goal of this study was to determine the importance of communication skills in interactions between information technology support staff and the end users they support in relation to factors such as stereotypes and expectations. The results of this study suggest that positive end user evaluations of these communication interactions do not rely solely upon the communication skills of the technician, but …

Handwritten Character Recognition Using A Gradient Based Feature Extraction, Ravi Kiran Reddy Veligati

UNLV Retrospective Theses & Dissertations

Handwriting Recognition is the task of transforming a language that is represented in its spatial form of graphical marks into its symbolic representation. In Offline Handwriting Recognition, there are three steps: preprocessing of the image, segmentation of words into characters and recognition of the characters. In this thesis I implemented two methods for character recognition, which is the most important step in Offline Handwriting Recognition. The heart of character recognition is the features that are extracted from the character image. The accuracy of the classification of the character image depends on the quality of the features extracted from the image. …

Power Quality Issues Related To Variable-Frequency Drives, Mahesh M Venkateswaran

UNLV Retrospective Theses & Dissertations

Variable Frequency Drives (VFDs) are widely used in industrial and commercial applications due to their ability to reduce energy demand. A VFD, however, is not only sensitive to poor power quality (e.g., voltage transients, sags, and swells), but is also considered as a source of harmonic pollution. Harmonic currents generated by VFDs are often blocked by passive shunt or series filters. The impact of line reactors on voltage disturbances originating from the utility side is not fully explored. Other issues like the use of output reactors with long motor leads and grounding of the power distribution system are also important …

Lower Limb Bone Shape And Structure Among Populations Of Differing Lifestyles: Effects Of Biomechanical Stress And Inferences Of Activity, Michele Marcela Bleuze

UNLV Retrospective Theses & Dissertations

It is known that activity-related stresses and mechanical loadings affect adult bone morphology. The purpose of this study is to examine how well presumed subsistence-related activities correlate with bone morphology; In addition, this study will investigate the degree to which sex differences can be explained by differences in mechanical loaDing If such differences in expression are apparent between males and females within a population, then it can be speculated that the sexes were participating in different activities---or at least in activities that yielded different mechanical loadings; Although there have been several biomechanical studies that have looked at the relationship between …

Evaluation Of The Perceptual Magnet Effect And Categorical Perception For Musical Timbre, Melissa Kay Griffith

UNLV Retrospective Theses & Dissertations

Recent auditory research has raised fundamental questions about the perceptual magnet effect (PME), where discrimination performance is poorer for stimuli that approach best exemplars of a phonetic category. It has been suggested that the effect reflects inter-categorical comparisons, and might not generalize to nonspeech. Three experiments addressed these concerns. In Experiment 1 prototype and non-prototype stimuli were determined from goodness ratings of synthesized (violin) timbres varying in center frequencies of F1 and F2 formants. Experiment 2 evaluated for a PME using discrimination data, and influences from other categories by comparing goodness ratings from stimuli in prototype, non-prototype, and no context …

Three-Dimensional Modeling And Simulation Of Manufacturing Processes For Transmuter Fuel Fabrication, Richard Arthur Silva

UNLV Retrospective Theses & Dissertations

A proposed method of converting long-lived radionuclides contained within spent nuclear fuel into shorter-lived radionuclides is known as transmutation. The feasibility assessment of fuel manufacturing for transmutation is necessary for the overall success of the transmutation project. As part of that assessment, this paper reviews current methodologies for handling spent nuclear fuel and other highly radioactive material. While not exhaustive, the review encompassed facilities within the U.S. Department of Energy, international operations, as well as, work performed collegiately; The manufacturing of fuel for transmutation will certainly utilize automation and robotics. A simplified 3-D model of a fuel handling operation was …

Metricizing' Non-Metric Craniofacial Traits: Application Of Three Dimensional Geometric Morphometric Analysis To Ancestral Identification, Summer Joy Decker

UNLV Retrospective Theses & Dissertations

Non-metric traits are commonly used by anthropologists to distinguish between groups for such things as age, sex, and even ancestry. However, many non-metric traits cannot be measured with traditional osteological tools. While these traditional methods are useful, they do not take individual variation into account. This thesis uses geometric morphometric coordinate data to 'metricize' such traits and to evaluate their accuracy of correctly assigning unknown individuals to statistically defined groups; A 3-D digitizer was used to collect data from 39 craniofacial landmarks to capture the form of several phenotypic facial characteristics. The sample consisted of individuals from four different geographic …

Flux Profile Modelling Using Numerical Methods, Bharat Reddy Pemmireddy

UNLV Retrospective Theses & Dissertations

Molecular beam Epitaxy (MBE) is a physical vapor deposition system, used to grow semiconductor layers (epilayers). In order to increase the economics of MBE, the industry has increased the size and number of wafers processed in one stage. This lead to, non-uniformity in thickness of material grown. In this work a process simulation tool based on numerical methods was developed to study different parameters which affect the thickness. The process of emission in open cells was identified as free evaporation and for computer simulation of these types of cells Model I was developed. The process of emission in closed cells …

Kytoon Observations Of The Lake Mead Boundary Layer, Daron J Tanko

UNLV Retrospective Theses & Dissertations

On July 14--16, 1997 nearly 60 hours of kytoon sampling of the boundary layer at Lake Mead was done through a cooperative effort among the U.S. Geological Survey, National Oceanic Atmospheric Administration, and U.S. Bureau of Reclamation. Micrometeorological data (MET) were analyzed to find boundary layer characteristics of height, precipitable water content, and precipitable water content residence time. In addition, the boundary layer precipitable water content was compared to tributary inflows in an approximated Lake Mead water compariSon The kytoon data was unique and indicated the boundary layer at Lake Mead maintained an inversion during day and night and in …

Performance Characteristics Of Beamline 6.3.1 From 200 Ev To 2000 Ev At The Advanced Light Source, Ponnusamy Nachimuthu, J. H. Underwood, C. D. Kemp, Eric M. Gullikson, Dennis W. Lindle, David K. Shuh, Rupert C. Perera

Chemistry and Biochemistry Faculty Research

Bend magnet beamline 6.3.1 at the Advanced Light Source operates from 200 eV to 2000 eV, primarily used for x-ray absorption fine structure investigations. The beamline optics consist of a compact, entrance-slitless, Hettrick-Underwood type variable-line-spacing plane-grating monochromator and refocusing mirrors to provide a 25 μm × 500 μm spot at the focal point in the reflectometer end station. Wavelength is scanned by the simple rotation of the grating and illuminates a fixed exit slit. The LabView based beamline control and data acquisition computer code has been implemented to provide a convenient interface to the user. The dedicated end station is …

Design And Analysis Of A Process For Melt Casting Metallic Fuel Pins Incorporating Volatile Actinides, Yitung Chen, Darrell Pepper, Randy Clarksean

Fuels Campaign (TRP)

The goal of this project is to investigate the casting processes for metallic fuels to help design a process that minimizes the loss of the volatile actinide elements from the fuel. The research effort centers on the development of advanced numerical models to assess conditions that significantly impact the transport of volatile actinides during the melt casting process and represents a joint effort between researchers at UNLV and Argonne National Laboratory (ANL). Assessing critical equipment and process variables is required to build a successful system that will operate efficiently.

Design And Evaluation Of Processes For Fuel Fabrication, Georg F. Mauer

Fuels Campaign (TRP)

The goal of this research project is to provide technical support to process designers working on the development of the fuel cycles for transmutation applications. Detailed process models are developed to better define the impact of fuel choice on the transmuter fuel cycle, including relative process losses, waste generation, and plant capital cost. These process models provide insight regarding required plant size and number of plants needed to mesh with the fuel recycling line. They also determine requirements for automation.

Manufacturing models for large-scale production in a hot cell environment are also developed. Combined, these two models allow the assessment …

Interaction Between Metal Fission Products And Triso Coating Materials: A Study Of Chemical Bonding And Interdiffusion, Clemens Heske

Fuels Campaign (TRP)

The goal of this project is to elucidate the chemical bonding and interface formation of metal fission products with the coating materials used in state-of-the-art TRISO fuel particles. Particular emphasis is placed on an analysis of intermediate chemical phases at the interface, the intermixing/diffusion behavior, and the electronic interface structure as a function of material choice (metal and coating materials), temperature, and external stress. Furthermore, we intend to assess the chemical state of some of the metal fission products. The findings are expected to give valuable information about failure mechanisms of TRISO particles and fission product transport. Secondly, through simulating …