Engineering Commons^™

A Characteristics Finite Element Algorithm For Computational Open Channel Flow Analysis, Zachariah Chambers

Doctoral Dissertations

For the reliable determination of open channel flows, a minimally dissipative flux jacobian decomposition finite element algorithm is developed for the one- and two-dimensional inviscid open channel flow equation systems. The modifed form of the parent kinetic flux divergence is biased by the characteristic speeds, i.e. eigenvalues of the kinetic flux divergence jacobian, to induce along all wavelike propogation directions a dissipation level proportional to the propogation speeds of the solution to the hyperbolic problem statement.

The analysis rigorously investigates the inviscid open channel equation system via non-linear, wave-like solutions and reveals linear dependency issues for the momentum equations in …

A Delay Model For Exclusive Right-Turn Lanes At Signalized Intersections With Uniform Arrivals And Right Turns On Red, Mohammad A. Qureshi

Doctoral Dissertations

Right turn on red (RTOR) is an established part of today’s driving patterns. However,despite several revisions of the Highway Capacity Manual (HCM), the procedures for estimating delay at signalized intersections do not adequately incorporate the effects of RTOR. The HCM currently removes RTOR from the analysis.

This dissertation has developed models of uniform delay that incorporate RTOR based on queuing theory. Queuing accumulation polygons (QAP) were developed that include RTOR. The research developed a classification system for describing any signal phasing into one of 4 classes based on the sequence of 3 red regimes and one green regime.

It was …

Formulation And Assessment Of A Customizable Procedure For Pavement Distress Index, Zongren Wang

Doctoral Dissertations

A customizable procedure for the formulation of Pavement Distress Index (PDI) based on human rating behavior is presented in this dissertation. This procedure formulates PDI as the maximum PDI value in a user-defined scale minus the Total Deduct Value (TDV), which is the sum of the product of each individual Deduct-Value (DV) and its corresponding weight. These weights, defined as a function of corresponding DV-percentages, i.e. individual DV over TDV, are identified using data simulated according to the studies by Sun and Yao (1991) and PAVER, a Pavement Management System (PMS) developed by the U. S. Army Corps of Engineers. …

Fluid Flow In Micro-Channels: A Stochastic Approach, Hilda Marino Black

Doctoral Dissertations

In this study free molecular flow in a micro-channel was modeled using a stochastic approach, namely the Kolmogorov forward equation in three dimensions. Model equations were discretized using Central Difference and Backward Difference methods and solved using the Jacobi method. Parameters were used that reflect the characteristic geometry of experimental work performed at the Louisiana Tech University Institute for Micromanufacturing.

The solution to the model equations provided the probability density function of the distance traveled by a particle in the micro-channel. From this distribution we obtained the distribution of the residence time of a particle in the micro-channel. Knowledge of …

Swarm Engineering, S. Kazadi '90

Doctoral Dissertations

Swarm engineering is the natural evolution of the use of swarm-based techniques in the accomplishment of high level tasks using a number of simple robots. In this approach, one seeks not to generate a class of behaviors designed to accomplish a given global goal, as is the approach typically found in mainstream robotics. Once the class of behaviors has been understood and decided upon, specific behaviors designed to accomplish this goal may be generated that will complete the desired task without any concern about whether or not the final goal will actually be completed. As long as the generated behaviors …

Evaluation Of Factors Affecting Earth Pressures On Buried Box Culverts, Michael Zhiqiang Yang

Doctoral Dissertations

Factors affecting the earth pressures acting on buried box culverts under deep embankments were evaluated by field instrumentation and numerical analyses. Two instrumented cast-in-place concrete culverts were designed and constructed differently. Long term earth pressures under constant embankment height were observed after the completion of construction. Both observed earth pressures and those predicted by numerical analyses were compared with the current AASHTO earth pressure recommendations, as well as the AASHTO design pressures in effect at the time a failed box culvert was designed in the mid 1970s. Field measurements suggested that the previous AAHSTO design pressure (1977, 12th edition) significantly …

Experimental Characterization Of Flow Patterns And Flow Characteristics In The Bulk Mercury Flow Field Of The Spallation Neutron Source Mercury Target, W. David Pointer

Doctoral Dissertations

The Spallation Neutron Source will provide an intense pulsed source of neutrons for neutron scattering research by focusing a high-energy pulsed proton beam on a liquid mercury target. Interactions between the protons and the nuclei of the mercury will result in the production of neutrons through a spallation reaction. The use of liquid mercury obviates concerns with radiation damage associated with solid targets, facilitates removal of the heat deposited in the target, and allows online processing of the target material to reduce the concentration of the products of the spallation reaction. These advantages allow the use of a much higher …

Orthogonal Grid Generation, Non-Reflecting Boundary Condition, And Parallel Computation For Fluid Flow, Shaopeng Sun

Doctoral Dissertations

The purpose of this study is to investigate one of the most interesting areas in computational fluid dynamics. The content of this paper is divided into three parts. The first part is the orthogonal grid generation. The second part is the non-reflecting boundary condition in curvilinear coordinates. The third part is parallel computation by Message Passing Interface.

The grid generation method is presented by solving elliptic partial difference equations. The elliptic grid generation method is based on the use of composite mapping, which consists of a non-linear algebraic transformation and an elliptic transformation. The elliptic transformation is based on the …

Computational Investigation Of Stress, Contact Conditions, And Buckling Of Thin-Walled Pipe Liners, Meihuan Zhu

Doctoral Dissertations

Thin walled polymeric liners are often used to rehabilitate deteriorated pipe lines. The host pipes into which these liners are installed are typically assumed to be structurally sound, and the liner is only expected to carry the external pressure exerted by the groundwater. This external pressure will induce creep deformation and radial deflections that may eventually result in collapse of the liner within the host pipe. The aim of this work is use computational modeling to better understand the evolution of conditions leading up to collapse so that improved liner design models can be developed. Emphasis is placed on a …

A Hybrid Finite Element-Finite Difference Method For Thermal Analysis In A Double-Layered Thin Film, Teng Zhu

Doctoral Dissertations

Thin film technology is of vital importance in microtechnology applications. For instance, thin films of metals, of dielectrics such as SiO2, or Si semiconductors are important components of microelectronic devices. The reduction of the device size to the microscale has the advantage of enhancing the switching speed of the device. The reduction, on the other hand, increases the rate of heat generation that leads to a high thermal load on the microdevice. Heat transfer at the microscale with an ultrafast pulsed-laser is also a very important process for thin films. Hence, studying the thermal behavior of thin films or of …

Bulk Micromachining Of Silicon For Moems Prototype, Sung-Dong Suh

Doctoral Dissertations

In this dissertation, the optical application of silicon micromachining technology was investigated in order to create the three-dimensional microstructures that can be used as the components for the MOEMS prototype. These microstructures were designed and fabricated by utilizing corner compensation techniques and silicon bulk micromachining technologies. The fabricated microstructures are silicon mirror arrays that have a 1250 μm etch depth and through-holes across the OE-MCM substrate that has sixteen-fan-out OCDN on front side and a 1mm thickness.

Guided-wave OCDN on MCMs are designed and fabricated to meet the high-speed clocking requirements of next-generation digital systems through a realization of superior …

Kinetics Of Laser Chemical Vapor Deposition Of Carbon And Refractory Metals, Feng Gao

Doctoral Dissertations

Three-dimensional laser chemical vapor deposition (3D-LCVD) has been used to grow rods of carbon, tungsten, titanium, and hafnium from a variety of hydrocarbons and metal halide-based precursors. A novel computerized 3D-LCVD system was designed and successfully used in the experiments. A focused Nd:Yag laser beam (λ = 1.06 μm) was utilized to locally heat up a substrate to deposition temperature. The rods, which grew along the axis of the laser beam, had a typical diameter of 30–80 μm and a length of about 1 mm. The precursors for carbon deposition were the alkynes: propyne, butyne, pentyne, hexyne, and octyne. Propyne …

Efficient Algorithms And Implementations For Signal Processing, Changbai Xiao

Doctoral Dissertations

A scheme is presented to regain a finite number of lost samples from a Nyquist-rate-sampled band-limited signal f of finite energy by replenishing new sample values of the same number. The result can also be viewed as the solution to a special non-uniform sampling problem.

A scheme is also presented to recover a band-limited function f of finite energy from its sampling values on real sequences with an accumulation point. The result given here can also be viewed as an approach to the extrapolation problem of determination a band-limited function in terms of its given values on a finite interval. …

Cramer-Rao Bound And Optimal Amplitude Estimator Of Superimposed Sinusoidal Signals With Unknown Frequencies, Shaohui Jia

Doctoral Dissertations

This dissertation addresses optimally estimating the amplitudes of superimposed sinusoidal signals with unknown frequencies. The Cramer-Rao Bound of estimating the amplitudes in white Gaussian noise is given, and the maximum likelihood estimator of the amplitudes in this case is shown to be asymptotically efficient at high signal to noise ratio but finite sample size. Applying the theoretical results to signal resolutions, it is shown that the optimal resolution of multiple signals using a finite sample is given by the maximum likelihood estimator of the amplitudes of signals.

Bottom-Up Design Of Artificial Neural Network For Single-Lead Electrocardiogram Beat And Rhythm Classification, Srikanth Thiagarajan

Doctoral Dissertations

Performance improvement in computerized Electrocardiogram (ECG) classification is vital to improve reliability in this life-saving technology. The non-linearly overlapping nature of the ECG classification task prevents the statistical and the syntactic procedures from reaching the maximum performance. A new approach, a neural network-based classification scheme, has been implemented in clinical ECG problems with much success. The focus, however, has been on narrow clinical problem domains and the implementations lacked engineering precision. An optimal utilization of frequency information was missing. This dissertation attempts to improve the accuracy of neural network-based single-lead (lead-II) ECG beat and rhythm classification. A bottom-up approach defined …

Integration Of Battery Energy Storage With Flexible Ac Transmission System Devices, Zhiping Yang

Doctoral Dissertations

"This dissertation, consisting of five papers, presents the results of research on the incorporation of battery energy storage into a Static Synchronous Compensator (StatCom). The main contribution of this body of work is the establishment of the modeling and control of the StatCom/BESS in power system dynamic applications. The first paper is focused on the steady state characteristics of the StatCom and StatCom/BESS. The characteristic curves of output voltage and output power were proposed and used in comparing the functionality of the StatCom and StatCom/BESS. In the second paper, a StatCom model was proposed and used in power flow analysis. …