Engineering Commons^™

The Rheological Behavior Of Carbon Nanofiber-Reinforced Thermoplastic Composites, Qiang Zeng

Theses and Dissertations - UTB/UTPA

A rheological study of the thermoplastic HDPE filled with vapor grow carbon nanofiber (VGCNF) has been performed with a RheoStress 150 Tester. VGCNF having average 50 nm diameter were used. These nanofibers were purified to provide for an open network of high purity nanofibers. A rheomixer was used to disperse the nanofibers uniformly in the polyethylene matrix because of shear working conditions. The influence of fiber loading, frequency and temperature on the rheology was investigated. Studies were carried out in the temperature range of 160 to 210°C and frequency range of 0.062 to 628.3 rad/s. The rheological measurements show that …

Air Quality Impact Evaluation Of A Hypothetical Fire-Fighter Training Facility, William Glenn Fuller

Doctoral Dissertations

Human Health Risk Assessments (HHRAs) have become a required component in the permitting process for hazardous waste incinerators and boilers and for closure or evaluation of chemical and petroleum facilities. However, although not currently required, these evaluations are also essential for additional daily processes having the potential to adversely impact the environment. One such process includes emissions produced from a firefighter training facility. Firefighter training facilities perform scenarios to enhance the firefighting ability of the trainees. Three typical scenarios conducted at such a facility include air rescue and firefighting, building fire simulation, and propane system fires. During the course of …

Using Commercial Finite Element Code Called Abaqus In Modeling Hybrid Constrained Layers Damping Beam Structure And Quantitative Determination Of The Stability Of Implant-Bone Interface Using Resonance Frequency Analysis, Daniel Delgado Jr.

Theses and Dissertations - UTB/UTPA

In Chapter 1, it has been demonstrated that the damping treatments for beam and plate structures are effective, and the vibrational behaviors of the systems considered are influenced by many geometrical and material parameters. This has led to an interest in developing advanced “intelligent” structures. In the past, passive and active damping mechanisms have been used to reduce vibration. The uses of passive constrained layers are limited, but it has dissipative qualities for all the modes of the structure; and the uses of active constrained layers are limited to a single mode control. Recent published papers, many have suggested that …

Automated Robotic Inspection System For Electronic Manufacturing, Roberto Alejandro Balderas

Theses and Dissertations - UTB/UTPA

An automated robotic inspection system for electronic manufacturing has been developed to identify pin defects of IC packages mounted on printed circuit boards using surface mount technology. The automated robotic inspection system consists of two robots, a computer, a CCD camera with frame gabber for image acquisition, and a customized windows program using neural network for on-line defect identification. Gray scale images of the pins on IC packages are acquired using ambient light. The images are filtered and formatted to appropriate size, so that Matlab neural network tool could be used. The images are used to train neural networks using …

A Neural Network-Based Vision System For Automated Separation Of Onion From Clod Using Mechanical Harvester, Demian Morquin

Theses and Dissertations - UTB/UTPA

A neural network classifier for separating clods from onions during harvesting has been developed. The separator consists of a multi-layer feedforward network that maps textural features computed from gray-scale images of onions and clods into the correct object. Texture features were computed from co-occurrence matrices that specify the spatial relationship of pixel values in an image. The textural features selected for this application consist of homogeneity, contrast, variance, and energy. The network was trained using the back-propagation algorithm. Based on the textural features classification, the effect of changing the network configuration on separation effectiveness was investigated. Factors including network topology …

Postural Balance And Acceleration Threshold Detection For Anterior Horizontal Translation In Diabetic And Non-Diabetic Elderly, Venkatesh Balasubramanian

Doctoral Dissertations

Slips and falls, and even the fear of failing, can represent a major medical and functional deterrent to living independently, especially among the elderly population. Various groups of elders are at known risk for falling including, but not limited to, those with vestibular dysfunction, those with low visual acuity including visual neuropathies, and those with peripheral neuropathies. The first two groups are fairly well studied, but the relationship between the level of peripheral neuropathy and extent of falling has received relatively less attention.

In this study, using sliding linear investigative platform for analyzing lower limb stability (SLIP-FALLS), the psychophysical thresholds …

Mathematical Modeling For Fabricating A Microstructure With A Pre-Specified Geometry Using Laser -Induced Chemical Vapor Deposition, Chaoyang Zhang

Doctoral Dissertations

Laser-induced chemical vapor deposition (LCVD) is an emerging new technique with many practical applications. To optimize the system for fabricating a microstructure with a pre-specified geometry in pyrolytic LCVD, a three-dimensional mathematical model is developed for predicting temperature distributions and laser dwell times across the substrate scanned by the laser beam. A microstructure is fabricated layer by layer, and for each layer the laser beam moves from one pixel to the next. The complicated correlations among temperature distribution, deposit growth rate, and laser dwell time are investigated. A purely heterogeneous reaction is assumed and any gas-phase transport is ignored.

A …

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 …

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 …

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. …

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 …

An Empirical Investigation On The Impacts Of Ground-Level Ozone Concentrations On National Ambient Air Quality Standards: The Case Of Lake Charles, Louisiana, Benedict Nweke Nwokolo

Doctoral Dissertations

This study presents information upon which the state of Louisiana can base its ozone State Implementation Plans (SIPs) designed to achieve planned emissions reduction that are required by the Clean Air Act (CAAA) of 1990. The research investigation included an assessment survey on a number of Transportation Control Measures (TCMs) and their degree of acceptability by the residents of Lake Charles area of Louisiana, the research target area. The TCMS were first ranked on the basis of people's perception of each TCM and four TCMs were later analyzed for cost-effectiveness using computer mathematical models. The Traffic Flow Improvements TCM was …

An Analysis Of Sustained Collaborative Research Activities Between University Organized Research Units And Industry: A Case Study Of Three Institutions, Elizabeth Taraski Mcdonnell

Seton Hall University Dissertations and Theses (ETDs)

.

The Optimized Electrostatic Motor, Christopher Lee Rambin

Doctoral Dissertations

The most common means of electrically activated actuation is the electromagnetic motor. All electromagnetic motors have a low output to weight ratio and low energy efficiency. The motor's weight is due to the coils and magnets used to generate propulsion. The energy loss is mainly the result of Joule heating that is inherent with any current driven device. An electrostatic motor offers the potential of significantly less weight and higher energy efficiency. This lower weight characteristic is due to the epoxide material used to construct the major components of its propulsion unit. Greater efficiency results from the reduced Joule heating …

The Effect Of Pipe Bursting On Nearby Utilities, Pavement, And Structures, Alan Atalah

Doctoral Dissertations

This dissertation has involved field and analytical studies of ground movements, ground vibrations and other design issues associated with trenchless pipe replacement (or pipe bursting, as it is commonly known). The process is used to replace an existing underground service pipe with a completely new pipe but without the disturbance and cost of excavating a trench from the surface. The process typically involves the insertion of a tool into the existing pipe that has a maximum diameter that is slightly larger than the existing pipe. This tool is used to break the existing pipe into pieces and to displace the …

Two-Phase Flow In Microchannels, Roger Scott Stanley

Doctoral Dissertations

The purpose of this study was to investigate fluid mechanic and heat transfer characteristics of two-phase two-component flow in rectangular microchannels. Experiments were conducted using rectangular aluminum channels with hydraulic diameters ranging between 56 $\mu$m and 256 $\mu$m and aspect ratios which varied from 0.5 to 1.5. Both single- and two-phase tests were conducted using water and gaseous argon, helium, and nitrogen as the working fluids. The Reynolds number for both types of experiments ranged from approximately 50 to nearly 10,000. The Nusselt number ranged between 0.0002 and 70. The single- and two-phase experimental data were empirically correlated, using parameters …

Nitric Oxide Production: A Mechanism For Inhibition Of Chlamydia Trachomatis Replication, Bojun Chen

Electronic Theses and Dissertations

Chlamydia trachomatis (CT) replicates in macrophages, but is inhibited by IFN-$\gamma$ or LPS. IFN-$\gamma$ and/or LPS induced nitrite production in mouse peritoneal macrophages, macrophage cell lines (RAW264.7 and J774A.1) and McCoy cells. Kinetic studies indicated that peak production occurred 48 hours post-treatment. CT infection itself was insufficient to induce nitrite production, but resulted in enhancement of nitrite production in IFN-$\gamma$-treated cells. Treatment with IFN-$\gamma$ or LPS resulted in significant inhibition of CT replication in these cells. Strong correlation between nitrite production and inhibition of CT replication was observed in RAW264.7 and J774A.1 cells (correlation coefficients: $-$0.93 and $-$0.94, p $<$ 0.001). N$\sp{\rm g}$- monomethyl-L-arginine (L-NMMA) specifically inhibited nitrite production and partially reversed inhibition of CT replication in macrophage cell lines. NOS mRNA was measured in RAW264.7 cells by Northern blot and Dot blot hybridization. Strong correlation between NOS mRNA expression and inhibition of CT replication (correlation coefficient: $-$0.97, p $<$ 0.05) was observed. Anti-TNF-$\alpha$ antibody completely neutralized the biological activity of TNF-$\alpha$ secreted by LPS-treated RAW264.7 cells, yet the antibody neither reduced nitrite production nor restored CT replication. Combination of the antibody and L-NMMA significantly enhanced restoration of CT replication. In peritoneal macrophages, inhibition of CT replication induced by IFN-$\gamma$ was partially restored by L-NMMA or anti-TNF-$\alpha$ antibody. In McCoy cells, inhibition of CT replication induced by IFN-$\gamma$ and LPS was not significantly restored by L-NMMA. Great restoration of CT replication by 1 mM L-NMMA was observed in LPS-treated J774A.1 cells (31%), but not in IFN-$\gamma$-treated cells (5%). Our data indicate that (1) NO production is one of the mechanisms for inhibition of CT replication in IFN-$\gamma$-activated peritoneal macrophages and RAW264.7 cells; (2) NO plays a significant role in CT inhibition in LPS-treated macrophage cell lines, but not peritoneal macrophages; (3) TNF-$\alpha$ may be associated with inhibition, but the mechanism(s) may not involve NO production; (4) NO production may not be the mechanism for CT inhibition in McCoy cells treated with IFN-$\gamma$ and LPS.

Metabolism Of Arachidonate-Containing Phospholipid Molecular Species In The Murine Macrophage-Like Cell Line, P388d1, Crystal R. Waites

Electronic Theses and Dissertations

Glycerophospholipids of mammalian cells exist as chemically diverse structures with various fatty acids at the sn-1 and sn-2 positions. Arachidonic acid, a polyunsaturated fatty acid, which may be converted to biologically active eicosanoids such as prostaglandins, thromboxanes, and leukotrienes, is found predominantly in the sn-2 position of glycerophospholipids. The purpose of this study was to examine, at the level of the individual molecular species, the incorporation of arachidonate into phospholipids and its release from phospholipids during stimulation. In this way, the specificity of the enzymes controlling arachidonate metabolism could be examined in order to clarify the processes that control the …