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Articles 3541 - 3570 of 4180
Full-Text Articles in Engineering
Discrete Surface Solitons, Sergiy Suntsov
Discrete Surface Solitons, Sergiy Suntsov
Electronic Theses and Dissertations
Surface waves exist along the interfaces between two different media and are known to display properties that have no analogue in continuous systems. In years past, they have been the subject of many studies in a diverse collection of scientific disciplines. In optics, one of the mechanisms through which optical surface waves can exist is material nonlinearity. Until recently, most of the activity in this area was focused on interfaces between continuous media but no successful experiments have been reported. However, the growing interest that nonlinear discrete optics has attracted in the last two decades has raised the question of …
Design And Demonstration Of Meanderline Retarders At Infrared Frequencies, Jeffrey Scott Tharp
Design And Demonstration Of Meanderline Retarders At Infrared Frequencies, Jeffrey Scott Tharp
Electronic Theses and Dissertations
Meanderline structures are widely used as engineered birefringent materials for waveplates and retarders at radiofrequencies, and have been previously demonstrated at frequencies up to 90 GHz in the millimeter-wave band. In this dissertation, we present results related to the modeling, fabrication, and experimental characterization of meanderlines across the range from 30 to 100 THz, in the long-wave and mid-wave infrared bands. Specific issues addressed in these new designs include spectral dispersion and angular dependence of the retardance, as well as axial ratio and throughput. The impact resulting from the infrared properties of the metals and dielectrics is explicitly included throughout. …
Multivariate Discretization Of Continuous Valued Attributes., Ehab Ahmed El Sayed Ahmed 1978-
Multivariate Discretization Of Continuous Valued Attributes., Ehab Ahmed El Sayed Ahmed 1978-
Electronic Theses and Dissertations
The area of Knowledge discovery and data mining is growing rapidly. Feature Discretization is a crucial issue in Knowledge Discovery in Databases (KDD), or Data Mining because most data sets used in real world applications have features with continuously values. Discretization is performed as a preprocessing step of the data mining to make data mining techniques useful for these data sets. This thesis addresses discretization issue by proposing a multivariate discretization (MVD) algorithm. It begins withal number of common discretization algorithms like Equal width discretization, Equal frequency discretization, Naïve; Entropy based discretization, Chi square discretization, and orthogonal hyper planes. After …
Advancements In Frameworks For Educational Games Through Sound Software Engineering Principles., Christy M. Bogard
Advancements In Frameworks For Educational Games Through Sound Software Engineering Principles., Christy M. Bogard
Electronic Theses and Dissertations
Educational games have steadily entered classrooms as a means of challenging advanced students and tutoring those lacking comprehension. However, without adequate educational benefits, instructors are struggling to continually justify the marginal value added of using these programs. It is the intent of this thesis to demonstrate that sound software engineering principles can improve the framework of educational games. First, the core framework requirements of computer-based educational games are outlined. Current educational games are then evaluated based on their ability to meet these requirements. From this analysis, necessary architectural changes are recommended to best facilitate future game advancements. Finally, to demonstrate …
Initial In Vitro And In Vivo Characterization Of A Pediatric Cardiopulmonary Assist System., Jeffrey Michael Colyer
Initial In Vitro And In Vivo Characterization Of A Pediatric Cardiopulmonary Assist System., Jeffrey Michael Colyer
Electronic Theses and Dissertations
Historically in the area of pediatric heart failure, few options have been available that are specifically designed to provide pediatric circulatory support. Extracorporeal Membrane Oxygenation (ECMO) was the traditional method of choice, providing cardiopulmonary support (CPS) for a relatively short time of 3-7 days. The pediatric cardiopulmonary assist system (pCAS) examined in this paper is designed to be able to provide left ventricular assist (LVA), right ventricular assist (RVA), or cardiopulmonary assist to a pediatric patient for a period of 30 days, with the option of device replacement if needed. A specially designed controller allows for both continuous and pulsatile …
Object Association Across Multiple Moving Cameras In Planar Scenes, Yaser Sheikh
Object Association Across Multiple Moving Cameras In Planar Scenes, Yaser Sheikh
Electronic Theses and Dissertations
In this dissertation, we address the problem of object detection and object association across multiple cameras over large areas that are well modeled by planes. We present a unifying probabilistic framework that captures the underlying geometry of planar scenes, and present algorithms to estimate geometric relationships between different cameras, which are subsequently used for co-operative association of objects. We first present a local1 object detection scheme that has three fundamental innovations over existing approaches. First, the model of the intensities of image pixels as independent random variables is challenged and it is asserted that useful correlation exists in intensities of …
Polymer-Derived Si-Al-C-N Ceramics:Oxidation, Hot-Corrosion, And Structural Evolution, Yiguang Wang
Polymer-Derived Si-Al-C-N Ceramics:Oxidation, Hot-Corrosion, And Structural Evolution, Yiguang Wang
Electronic Theses and Dissertations
Polymer-derived ceramics are a new class of materials synthesized by thermal decomposition of polymer precursors. Previous studies have shown that the materials exhibit excellent thermo-mechanical properties and can be stable at temperatures up to 2000oC. Furthermore, the novel polymer-to-ceramics process enables the manipulation of the ceramic structures at the atomic/nano level by designing the chemistry of polymer precursors and controlling the pyrolysis conditions, thereby, the properties of ceramics. In this dissertation, oxidation/hot-corrosion behavior and the structural evolution of Si-Al-C-N ceramics have been studied. The structural evolution and crystallization behavior of the SiCN and SiAlCN ceramics are investigated using FT-IR, XRD, …
Unified Steady-State Computer Aided Model For Soft-Switching Dc-Dc Converters, Wisam Al-Hoor
Unified Steady-State Computer Aided Model For Soft-Switching Dc-Dc Converters, Wisam Al-Hoor
Electronic Theses and Dissertations
For many decades, engineers and students have heavily depended on simulation packages such as Pspice to run transit and steady-state simulation for their circuits. The majority of these circuits, such as soft switching cells, contain complicated modes of operations that require the Pspice simulation to run for a long time and, finally, it may not reach a convergent solution for these kinds of circuits. Also, there is a need for an educational tool that provides students with a better understanding of circuit modes of operation through state-plan figures and steady-state switching waveforms. The unified steady-state computer aided model proposes a …
A Derivation Of An Empirical Equation For Estimating The Acoustical Shadow Zone Length Of Roadway Noise Barriers, Wayne Arner
A Derivation Of An Empirical Equation For Estimating The Acoustical Shadow Zone Length Of Roadway Noise Barriers, Wayne Arner
Electronic Theses and Dissertations
The objective of this research was to derive an empirical equation that estimates the acoustical shadow zone length (SZL) of roadway noise barriers. The acoustical shadow zone is the area behind a noise barrier of reduced sound levels, generally to some stated level at or near background. The ability to predict the SZL can be used as a method to evaluate the performance, and possibly the design, of roadway noise barriers. The current federally required roadway noise model is the Federal Highway Administration (FHWA) Traffic Noise Model (TNM). TNM uses insertion loss (IL) to evaluate the effectiveness of a barrier. …
Annular Beam Shaping And Optical Trepanning, Danyong Zeng
Annular Beam Shaping And Optical Trepanning, Danyong Zeng
Electronic Theses and Dissertations
Percussion drilling and trepanning are two laser drilling methods. Percussion drilling is accomplished by focusing the laser beam to approximately the required diameter of the hole, exposing the material to one or a series of laser pulses at the same spot to melt and vaporize the material. Drilling by trepanning involves cutting a hole by rotating a laser beam with an optical element or an xy galvo-scanner. Optical trepanning is a new laser drilling method using an annular beam. The annular beams allow numerous irradiance profiles to supply laser energy to the workpiece and thus provide more flexibility in affecting …
Evaluation Of Alternative Water Resources For Cape Coast And Its Environs In Ghana, Alex Kumah
Evaluation Of Alternative Water Resources For Cape Coast And Its Environs In Ghana, Alex Kumah
Electronic Theses and Dissertations
Cape Coast once a national capital of Ghana and its environs in recent years have constantly suffered perennial acute water shortage. The Brimsu dam which takes its supplies from the Kakum River with current production capacity of 1.4 × 104 m3/day cannot meet the water needs of the study area. The operating levels of the dam during crisis have reduced from 7.3 meters to 4.7 meters over the years with subsequent reduction in water production by 35%. Recently, the operating level has reduced further to about 3.5 meters with 60% reduction in water supply. This study evaluated alternative water resources …
Study Of Discharge Coefficient And Trends In Film Cooling Effectiveness Of Conical Holes With Increasing Diffusion Angles, Humberto Zuniga,
Study Of Discharge Coefficient And Trends In Film Cooling Effectiveness Of Conical Holes With Increasing Diffusion Angles, Humberto Zuniga,
Electronic Theses and Dissertations
Previous studies indicate that increasing the diffusion angle in conical film-cooling holes leads to an improvement in their film cooling effectiveness. Discharge coefficient and film cooling effectiveness measurements are conducted to characterize this behavior. Part of the focus of this investigation is to find out how this trend develops and attempt to ascertain the optimum cone angle, if possible. Six test plates, each with one row of eight conical-shaped cooling holes of equal diffusion angles of 0, 1, 2, 3, 6, or 8 [degrees], with respect to the hole axis are used in this study. The ratios of the hole …
Efficient Large Scale Transient Heat Conduction Analysis Using A Parallelized Boundary Element Method, Kevin Erhart
Efficient Large Scale Transient Heat Conduction Analysis Using A Parallelized Boundary Element Method, Kevin Erhart
Electronic Theses and Dissertations
A parallel domain decomposition Laplace transform Boundary Element Method, BEM, algorithm for the solution of large-scale transient heat conduction problems will be developed. This is accomplished by building on previous work by the author and including several new additions (most note-worthy is the extension to 3-D) aimed at extending the scope and improving the efficiency of this technique for large-scale problems. A Laplace transform method is utilized to avoid time marching and a Proper Orthogonal Decomposition, POD, interpolation scheme is used to improve the efficiency of the numerical Laplace inversion process. A detailed analysis of the Stehfest Transform (numerical Laplace …
Meta-Raps: Parameter Setting And New Applications, Seyhun Hepdogan
Meta-Raps: Parameter Setting And New Applications, Seyhun Hepdogan
Electronic Theses and Dissertations
Recently meta-heuristics have become a popular solution methodology, in terms of both research and application, for solving combinatorial optimization problems. Meta-heuristic methods guide simple heuristics or priority rules designed to solve a particular problem. Meta-heuristics enhance these simple heuristics by using a higher level strategy. The advantage of using meta-heuristics over conventional optimization methods is meta-heuristics are able to find good (near optimal) solutions within a reasonable computation time. Investigating this line of research is justified because in most practical cases with medium to large scale problems, the use of meta-heuristics is necessary to be able to find a solution …
Prediction And Allocation Of Live To Virtual Communication Bridging Resources, Stephanie Lackey
Prediction And Allocation Of Live To Virtual Communication Bridging Resources, Stephanie Lackey
Electronic Theses and Dissertations
This document summarizes a research effort focused on improving live-to-virtual (L-V) communication systems. The purpose of this work is to address a significant challenge facing the tactical communications training community through the development of the Live-to-Virtual Relay Radio Prediction Algorithm and implementation of the algorithm into an Integrated Live-to-Virtual Communications Server prototype device. The motivation for the work and the challenges of integrating live and virtual communications are presented. Details surrounding the formulation of the prediction algorithm and a description of the prototype system, hardware, and software architectures are shared. Experimental results from discrete event simulation analysis and prototype functionality …
A Common Component-Based Software Architecture For Military And Commercial Pc-Based Virtual Simulation, Joshua Lewis
A Common Component-Based Software Architecture For Military And Commercial Pc-Based Virtual Simulation, Joshua Lewis
Electronic Theses and Dissertations
Commercially available military-themed virtual simulations have been developed and sold for entertainment since the beginning of the personal computing era. There exists an intense interest by various branches of the military to leverage the technological advances of the personal computing and video game industries to provide low cost military training. By nature of the content of the commercial military-themed virtual simulations, a large overlap has grown between the interests, resources, standards, and technology of the computer entertainment industry and military training branches. This research attempts to identify these commonalities with the purpose of systematically designing and evaluating a common component-based …
A Sparse Program Dependence Graph For Object Oriented Programming Languages, Keith Garfield
A Sparse Program Dependence Graph For Object Oriented Programming Languages, Keith Garfield
Electronic Theses and Dissertations
The Program Dependence Graph (PDG) has achieved widespread acceptance as a useful tool for software engineering, program analysis, and automated compiler optimizations. This thesis presents the Sparse Object Oriented Program Dependence Graph (SOOPDG), a formalism that contains elements of traditional PDG's adapted to compactly represent programs written in object-oriented languages such as Java. This formalism is called sparse because, in contrast to other OO and Java-specific adaptations of PDG's, it introduces few node types and no new edge types beyond those used in traditional dependence-based representations. This results in correct program representations using smaller graph structures and simpler semantics when …
Analysis Of Complexity And Coupling Metrics Of Subsystems In Large Scale Software Systems, Harish Ramakrishnan
Analysis Of Complexity And Coupling Metrics Of Subsystems In Large Scale Software Systems, Harish Ramakrishnan
Electronic Theses and Dissertations
Dealing with the complexity of large-scale systems can be a challenge for even the most experienced software architects and developers. Large-scale software systems can contain millions of elements, which interact to achieve the system functionality. Managing and representing the complexity involved in the interaction of these elements is a difficult task. We propose an approach for analyzing the reusability, maintainability and complexity of such a complex large-scale software system. Reducing the dependencies between the subsystems increase the reusability and decrease the efforts needed to maintain the system thus reducing the complexity of the system. Coupling is an attribute that summarizes …
The Effects On Operator Performance And Workload When Gunnery And Robotic Control Tasks Are Performed Concurrently, Carla Joyner
The Effects On Operator Performance And Workload When Gunnery And Robotic Control Tasks Are Performed Concurrently, Carla Joyner
Electronic Theses and Dissertations
The purpose of this research was to examine operator workload and performance in a high risk, multi-task environment. Specifically, the research examined if a gunner of a Future Combat System, such as a Mounted Combat System, could effectively detect targets in the immediate environment while concurrently operating robotic assets in a remote environment. It also analyzed possible effects of individual difference factors, such as spatial ability and attentional control, on operator performance and workload. The experimental conditions included a gunner baseline and concurrent task conditions where participants simultaneously performed gunnery tasks and one of the following tasks: monitor an unmanned …
Design And Fabrication Of A Full-Featured Labscale Hybrid Rocket Engine, Kyle Platt
Design And Fabrication Of A Full-Featured Labscale Hybrid Rocket Engine, Kyle Platt
Electronic Theses and Dissertations
The design, development, integration and testing of a full-featured, Lab-Scale Hybrid Rocket Engine was not only envisioned to be the chosen method of putting student payloads into space, but to be an invaluable teaching resource. The subject of the present thesis is the analysis, design, development, integration and demonstration of a lab-scale hybrid rocket motor. The overarching goal of this project was to establish a working developmental lab model from which further research can be accomplished. The lab model was specifically designed to use a fuel source that could be studied in normal laboratory conditions. As such, the rocket engine …
Automated Adaptive Data Center Generation For Meshless Methods, Eric Mitteff
Automated Adaptive Data Center Generation For Meshless Methods, Eric Mitteff
Electronic Theses and Dissertations
Meshless methods have recently received much attention but are yet to reach their full potential as the required problem setup (i.e. collocation point distribution) is still significant and far from automated. The distribution of points still closely resembles the nodes of finite volume-type meshes and the free parameter, c, of the radial-basis expansion functions (RBF) still must be tailored specifically to a problem. The localized meshless collocation method investigated requires a local influence region, or topology, used as the expansion medium to produce the required field derivatives. Tests have shown a regular cartesian point distribution produces optimal results, however, in …
Analyis Of Airborne Microwave Polarimetric Radiometer Measurements In The Presence Of Dynamic Platform Attitude Errors, Jean Yves Kabore
Analyis Of Airborne Microwave Polarimetric Radiometer Measurements In The Presence Of Dynamic Platform Attitude Errors, Jean Yves Kabore
Electronic Theses and Dissertations
There are numerous applications for airborne imaging systems in remote sensing, and this thesis deals with a new microwave polarimetric radiometer technique for inferring ocean surface wind direction [3, 5, 7]. This technique is based upon the anisotropy of the polarized ocean blackbody emissions at microwave frequencies relative to the azimuth angle between the microwave radiometer antenna "look" direction and the direction of the wind. Because of the weak wind direction signature, it is important that all systematic brightness temperature (Tb) errors be eliminated, especially those that vary with the radiometer antenna scan position (look direction). This can be accomplished …
Polymer-Derived Ceramics: Electronic Properties And Application, Weixing Xu
Polymer-Derived Ceramics: Electronic Properties And Application, Weixing Xu
Electronic Theses and Dissertations
In this work, we studied the electronic behavior of polymer-derived ceramics (PDCs) and applied them for the synthesis of carbon nanotube reinforced ceramic nanocomposites and ceramic MEMS (Micro-Electro-Mechanical Systems) structures. Polymer-derived SiCN ceramics were synthesized by pyrolysis of a liquid polyureasilazane with dicumyl peroxide as thermal initiator. The structural evolution during pyrolysis and post-annealing was studied using FTIR, solid state NMR and Raman. The results revealed that the resultant ceramics consisted of SiCxNx-4 as major building units. These units were connected with each other through C-C/C=C bonds or by shearing N/C. The amount of sp2 free carbon strongly depends on …
Demonstrating Reflectarray Behavior At Infrared, James Ginn
Demonstrating Reflectarray Behavior At Infrared, James Ginn
Electronic Theses and Dissertations
Reflectarrays are traditionally passive, planar microstrip antenna devices designed for reflected phase manipulation at each individual antenna element making up the array. By varying the phase response across the surface with the antenna elements, reflectarrays allows a planar surface to exhibit electromagnetically an arbitrary geometry, such as a spherical surface. Initially proposed as a low-cost replacement for bulky parabolic reflectors, reflectarrays have been successfully developed and utilized at both RF and millimeter-wave frequencies. From the standpoint of an optical systems designer, adapting low-frequency reflectarray technology to develop a sub-millimeter and infrared reflectarray (SMIR) would provide a highly desirable alternative to …
Framework For Cost Modeling A Supply Chain, Nabeel Yousef
Framework For Cost Modeling A Supply Chain, Nabeel Yousef
Electronic Theses and Dissertations
Researchers are interested in value chain analysis to identify the different opportunities for cost savings. The literature have been narrow in scope and addressed specific problems; however none has addressed the need for a general framework that can be used as a standard template in the supply chain cost management and optimization, though Dekker and Goor (2000) said that the goal was to develop a model that would allow direct comparison of specific activities between firms, such as warehousing activities costs. There was no indication in the literature of a cost model that can identify all costs and cost drivers …
The Use Of Pc Based Simulation Systems In The Training Of Army Infantry Officers - An Evaluation Of The Rapid Decision Trainer, Thomas Lucario
The Use Of Pc Based Simulation Systems In The Training Of Army Infantry Officers - An Evaluation Of The Rapid Decision Trainer, Thomas Lucario
Electronic Theses and Dissertations
This research considers two modes of training Army infantry officers in initial training to conduct a platoon live fire exercise. Leaders from groups that were training with the current classroom training methods were compared to leaders from groups whose training was augmented with a PC based training system known as the Rapid Decision Trainer (RDT). The RDT was developed by the US Army Research Development and Engineering Command for the purpose of aiding in the training of tactical decision making and troop leading procedures of officers in the initial levels of training to become rifle platoon leaders. The RDT allows …
Laser Metallization And Doping For Silicon Carbide Diode Fabrication And Endotaxy, Zhaoxu Tian
Laser Metallization And Doping For Silicon Carbide Diode Fabrication And Endotaxy, Zhaoxu Tian
Electronic Theses and Dissertations
Silicon carbide is a promising semiconductor material for high voltage, high frequency and high temperature devices due to its wide bandgap, high breakdown electric field strength, highly saturated drift velocity of electrons and outstanding thermal conductivity. With the aim of overcoming some challenges in metallization and doping during the fabrication of silicon carbide devices, a novel laser-based process is provided to direct metallize the surface of silicon carbide without metal deposition and dope in silicon carbide without high temperature annealing, as an alternative to the conventional ion implantation, and find applications of this laser direct write metallization and doping technique …
Development Of Thermally Processed Nanocomposites With Controlled Surfaces, Petya Georgieva
Development Of Thermally Processed Nanocomposites With Controlled Surfaces, Petya Georgieva
Electronic Theses and Dissertations
The ever increasing need for technology development requires the integration of inexpensive, light weight and high strength materials which are able to meet the high standards and specifications for various engineering applications. The intention of this work is to show that the suitable material selection and the utilization of plasma spray processing can be of potential interest to a large number of industrial, biomedical and everyday life applications. This research demonstrates also that plasma processing is a promising engineering tool for multifunctional coatings and near-net-shape manufacturing. Further, the theoretical and experimental results are combined in order to explain the mechanisms …
Nonparametric Multivariate Statistical Process Control Using Principal Component Analysis And Simplicial Depth, Luis Beltran
Nonparametric Multivariate Statistical Process Control Using Principal Component Analysis And Simplicial Depth, Luis Beltran
Electronic Theses and Dissertations
Although there has been progress in the area of Multivariate Statistical Process Control (MSPC), there are numerous limitations as well as unanswered questions with the current techniques. MSPC charts plotting Hotelling's T2 require the normality assumption for the joint distribution among the process variables, which is not feasible in many industrial settings, hence the motivation to investigate nonparametric techniques for multivariate data in quality control. In this research, the goal will be to create a systematic distribution-free approach by extending current developments and focusing on the dimensionality reduction using Principal Component Analysis. The proposed technique is different from current approaches …
High Speed Turbo Tcm Ofdm For Uwb And Powerline System, Yanxia Wang
High Speed Turbo Tcm Ofdm For Uwb And Powerline System, Yanxia Wang
Electronic Theses and Dissertations
Turbo Trellis-Coded Modulation (TTCM) is an attractive scheme for higher data rate transmission, since it combines the impressive near Shannon limit error correcting ability of turbo codes with the high spectral efficiency property of TCM codes. We build a punctured parity-concatenated trellis codes in which a TCM code is used as the inner code and a simple parity-check code is used as the outer code. It can be constructed by simple repetition, interleavers, and TCM and functions as standard TTCM but with much lower complexity regarding real world implementation. An iterative bit MAP decoding algorithm is associated with the coding …