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NDLTD Union Catalog (1.532.874 recursos)

The NDLTD Union Catalog is an OAICat server containing thesis and dissertation records harvested from registered NDLTD OAI repositories

Georgia Tech Electronic Thesis and Dissertation Archive

Mostrando recursos 1 - 20 de 3.280

  1. Analysis of Handling Stresses and Breakage of Thin Crystalline Silicon Wafers

    Brun, Xavier F
    Photovoltaic manufacturing is material intensive with the cost of crystalline silicon wafer, used as the substrate, representing 40% to 60% of the solar cell cost. Consequently, there is a growing trend to reduce the silicon wafer thickness leading to new technical challenges related to manufacturing. Specifically, wafer breakage during handling and/or transfer is a significant issue. Therefore improved methods for breakage-free handling are needed to address this problem. An important pre-requisite for realizing such methods is the need for fundamental understanding of the effect of handling device variables on the deformation, stresses, and fracture of crystalline silicon wafers. This knowledge is lacking...

  2. Aerodynamic Design Applying Automatic Differentiation and Using Robust Variable Fidelity Optimization

    Takemiya, Tetsushi
    In modern aerospace engineering, the physics-based computational design method is becoming more important. However, high-fidelity models require longer computational time, so the advantage of efficiency is partially lost. This problem has been overcome with the development of the approximation management framework (AMF). In the AMF, objective and constraint functions of a low-fidelity model are scaled at a design point so that the scaled functions, referred to as gsurrogate functions,h match those of a high-fidelity model. Since scaling functions and the low-fidelity model constitutes surrogate functions, evaluating the surrogate functions is faster than evaluating the high-fidelity model. Therefore, in the optimization process...

  3. Antibiotics in Water Treatment: The Role of Water Quality Conditions on their Fate and Removal during Chlorination and Nanofiltration

    Shah, Amisha D.
    Antibiotics are a group of compounds used in large quantities for both human therapy and animal food production. In recent years, antibiotics have been detected at low levels (up to μg/L) in wastewater effluents and surface waters in the US, Canada, and parts of Europe. The presence of such contaminants in the environment is of concern due to their potential to promote bacterial resistance as well as to trigger long-term adverse human health effects. Chemical disinfection, one of essential water treatment processes, may aid in their removal but may also form byproducts that can remain biologically active. Nanofiltration is another...

  4. Soft Margin Estimation for Automatic Speech Recognition

    Li, Jinyu
    In this study, a new discriminative learning framework, called soft margin estimation (SME), is proposed for estimating the parameters of continuous density hidden Markov models (HMMs). The proposed method makes direct use of the successful ideas of margin in support vector machines to improve generalization capability and decision feedback learning in discriminative training to enhance model separation in classifier design. SME directly maximizes the separation of competing models to enhance the testing samples to approach a correct decision if the deviation from training samples is within a safe margin. Frame and utterance selections are integrated into a unified framework to...

  5. X-Ray Structures of P22 c2 Repressor-DNA Complexes: The Mechansism of Direct and Indirect Readout

    Watkins, Jason Derrick
    The P22 c2 repressor protein (P22R) binds to DNA sequence-specifically and helps direct the temperate lambdoid bacteriophage P22 to the lysogenic developmental pathway. To gain insight into its DNA binding mechanism, we solved the 1.6 Å x-ray structure of the N-terminal domain (NTD) of P22R in a complex with a DNA fragment containing the synthetic operator sequence [d(ATTTAAGATATCTTAAAT)]2 This operator has an A-T at position 9L and T-A at position 9R and is termed DNA9T. Van der Waals interactions between protein and DNA appear to confer sequence-specificity. The structure of the P22R NTD DNA9T complex suggests that sequence-specificity arises substantially from...

  6. Characterization of Cement-Based Multiphase Materials Using Ultrasonic Wave Attenuation

    Treiber, Martin Paul
    Ultrasonic wave attenuation measurements have been used to successfully characterize the microstructure and material properties of inhomogeneous materials; these ultrasonic techniques have the potential to provide for the in situ characterization of heterogeneous, cement-based materials. Recent research has applied existing acoustic scattering models to predict ultrasonic attenuation in relatively simple cement-based materials with good results. The goal of the current research is to extend this past work and to investigate the influence of elastic inclusions in order to simulate a more realistic microstructure: a cement paste matrix material that contains both sand inclusions and air voids. The sand inclusions simulate...

  7. Sustainability Studies in Recycling Post Consumer Carpet

    Subbiah, Valli
    This thesis presents some novel techniques to process Post Consumer Carpet waste and provides detailed cost comparisons between setting up and running small-scale decentralized units and large-scale centralized chemical facilities. The techniques presented include: a decentralized underlay manufacturing process which does not distinguish between the types of face fiber, a decentralized facility with twin screw extruder to depolymerize nylon 6 face fiber with a concurrent underlay manufacturing facility, a decentralized pallet production facility, and a centralized facility for chemically depolymerizing nylon 6, and nylon 6,6 with a concurrent underlay manufacturing facility The limiting factors to recycling are the collection of significant volumes of material and...

  8. SPATIAL MEMORY RECALL IN THE GIANT PANDA (AILUROPODA MELANOLEUCA)

    Perdue, Bonnie Marie
    The giant panda (Ailuropoda melanoleuca) is an endangered species and many efforts are being made to ensure its survival, including numerous research studies. However, there has been little investigation of spatial memory in the giant panda. Spatial memory is an important mechanism for survival in the wild, allowing an animal to find and remember the location of food, mates, den sites and avoid predators. Memory assessment in non-human species typically involves the use of recognition, as opposed to recall tasks. The current study tested spatial memory recall in 1.1 giant pandas using a delayed response memory task. The design required...

  9. Conversion of Hardwoods to Ethanol: Design and Economics of Delignification and Enzyme Recycling

    Paruchuri, Divya
    The objective of this study was to investigate the possibility of recycling enzymes during saccharification of cellulose for the production of ethanol from woodchips. To make enzyme recycling feasible and economical when woodchips are processed for ethanol, the lignin in the wood is to be removed before the enzymes are added. Since enzymes constitute a major part of the input costs, second only to the feedstock, the ability to reuse the enzymes could lead to a considerable decrease in the production cost of ethanol. Tulip poplar woodchips were selected as the feedstock. Different delignification methods with recovery of byproducts were...

  10. Study of algorithms for analysis of XRF spectra to automate inspection of carpets

    Mahuteau, Laurent
    The objective of this thesis is to categorize carpet types according to their XRF spectra and verify if further classification of carpets is possible for use of an XRF analysis system in the carpet manufacturing line. This thesis consists of (1) implementing and studying effective algorithms for automated analysis of X-ray spectra, (2) comparing known algorithms for X-ray spectra analysis, and (3) implementing our own algorithm for classification of carpets spectra obtained for further fluorine online analysis of XRF inspected carpets. This research is intended for quick and accurate automated analysis of raw XRF spectra and matching analysis results to...

  11. Human-in-the-Loop Neural Network Control of a Planetary Rover on Harsh Terrain

    Livianu, Mathew Joseph
    Wheel slip is a common problem in planetary rover exploration tasks. During the current Mars Exploration Rover (MER) mission, the Spirit rover almost became trapped on a dune because of wheel slip. As rover missions on harsh terrains expand in scope, mission success will depend not only on rover safety, but also alacrity in task completion. Speed combined with exploration of varied and difficult terrains, the risk of slip increases dramatically. We first characterize slip performance of a rover on harsh terrains by implementing a novel High Fidelity Traversability Analysis (HFTA) algorithm in order to provide slip prediction and detection...

  12. Development of a Novel Organ Culture System Allowing Independent Control of Local Mechanical Variables and its Implementation in Studying the Effects of Axial Stress on Arterial Remodeling

    Dominguez, Zachary
    Arterial remodeling is a process by which arteries respond to sustained changes in their mechanical environment. This process occurs in a way such that an arterys local mechanical environment (circumferential, shear, and axial stress) is maintained at a homeostatic level. However, most studies utilize a methodology that controls the global parameters (pressure, flow rate, and axial stretch). This approach often confounds the results since the actual drivers of remodeling are not independently isolated. This research involved developing a methodology and system capable of independently controlling each of the local parameters and examining the effect of axial stress on remodeling. An organ...

  13. Boundary Layer Models of Hydrothermal Circulation on Earth and Mars

    Craft, Kathleen L.
    Continental and submarine hydrothermal systems are commonly found around the world. Similar systems that sustain water or other fluids are also likely to exist in planetary bodies throughout the solar system. Also, terrestrial submarine systems have been suggested as the locations of the first life on Earth and may, therefore, provide indications of where to find life on other planetary bodies. The study of these systems is vital to the understanding of planetary heat transfer, chemical cycling, and biological processes; hence hydrothermal processes play a fundamental role in planetary evolution. In this thesis, three particular types of hydrothermal systems are investigated...

  14. A Virtualized Quality of Service Packet Scheduler Accelerator

    Chuang, Kangtao Kendall
    Resource virtualization is emerging as a technology to enable the management and sharing of hardware resources including multiple core processors and accelerators such as Digital Signal Processors (DSP), Graphics Processing Units (GPU), and Field Programmable Gate Arrays (FPGA). Accelerators present unique problems for virtualization and sharing due to their specialized architectures and interaction modes. This thesis explores and proposes solutions for the virtualized operation of high performance, quality of service (QoS) packet scheduling accelerators. It specifically concentrates on challenges to meet 10Gbps Ethernet wire speeds. The packet scheduling accelerator is realized in a FPGA and implements the Sharestreams-V architecture. ShareStreams-V implements...

  15. Production of Dielectric Materials

    Blandin, Christopher
    Dielectric materials are used as spacers in antennas. The design of the dielectric determines the properties of the antenna. The insertion of high dielectric materials in a specific pattern into a low dielectric matrix material is one means to accomplish this. This thesis studies the means to insert metal cylinders (wire or nails) into polymer foams to produce such a material. Depending on the antenna properties desired, the patterns and number of nails varies tremendously. To decrease the manufacturing time and, therefore, the cost of creating these materials, an automatic machine capable of rapidly inserting wires to a predetermined pattern...

  16. Electro-kinetically Enhanced Nano-metric Material Removal

    Blackburn, Travis Lee
    This project is a fundamental proof of concept to look at the feasibility of using field activated abrasive particles to achieve material removal on a substrate. There are a few different goals for this project. The first goal is to prove through visualization that particle movement can be influenced and controlled by changes in electric field. The second goal is to fundamentally prove that particles controlled by electric field can remove material from a substrate. Third, it should be shown that changes in electric field can control the amount of material being removed in a given amount of time. A...

  17. AUTOMATIC SOFT PLAQUE DETECTION FROM CTA

    Arumuganainar, Ponnappan
    This thesis explores two possible ways of detecting soft plaque present in the coronary arteries, using CTA imagery. The coronary arteries are vessels that supply oxidized blood to the cardiac muscle and are thus important for the proper functioning of heart. Cholesterol or reactive oxygen species from cigarette smoke and other toxins may get adhered to the walls of coronary arteries and trigger chronic inflammation that leads to formation of the soft plaque. When the soft plaque grows bigger in volume, it occludes the blood flow to the cardiac muscle and finally results in ischemic heart attack. Moreover, smaller plaque...

  18. Quality Inspection and Reliability Study of Solder Bumps in Packaged Electronic Devices: Using Laser Ultrasound and Finite Element Methods

    Yang, Jin
    Consumer demands are driving the current trend in the microelectronics industry to make electronic products that are miniature, fast, compact, high-density, reliable and low-cost. The use of surface mount devices (SMDs) has helped to decrease the size of electronic packages through the use of solder bump interconnections between the devices and the substrates/printed wiring boards (PWBs). Solder bumps act as not only mechanical, but also electrical interconnections between the device and the substrate/PWB. Common manufacturing defects ¨C such as open, cracked, missing, and misaligned solder bumps ¨C are difficult to detect because solder bumps are hidden between the device and...

  19. Simultaneous Approach to Model Building and Process Design using Experimental Design: Application to Chemical Vapor Deposition

    Wissmann, Paul J
    In this thesis a tool to be used in experimental design for batch processes is presented. Specifically, this method is to aid in the development of a process model. Currently, experimental design methods are either empirical in nature which need very little understanding of the underlying phenomena and without the objective of more fundamental understanding of the process. Other methods are model based which assume the model is correct and attempt to better define the model parameters or discriminate between models. This new paradigm for experimental design allows for process optimization and process model development to occur simultaneously. The methodology specifically...

  20. Selective Surface Activation of Motor Circuitry in the Injured Spinal Cord

    Meacham, Kathleen Williams
    Access to and subsequent control of spinal cord function are critical considerations for design of optimal therapeutic strategies for SCI patients. Electrical stimulation of the spinal cord is capable of activating behaviorally-relevant populations of neurons for recovery of function, and is therefore an attractive target for potential devices. A promising method for accessing these spinal circuits is through their axons, which are organized as longitudinal columns of white matter funiculi along the cord exterior. For this thesis, I hypothesized that these funiculi can be selectively recruited via electrodes appropriately placed on the surface of the spinal cord, for functional activation...

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