Browsing Electronic Theses, Dissertations, and Records of Study (2002-present) by Title
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Jeon, Hyung-Joon (August 2009)[more][less]
Abstract: As demand for higher bandwidth I/O grows, the front end design of serial link becomes significant to overcome stringent timing requirements on noisy and bandwidthlimited channels. As a clock reconstructing module in a receiver, the recovered clock quality of Clock and Data Recovery is the main issue of the receiver performance. However, from unknown incoming jitter, it is difficult to optimize loop dynamics to minimize steady-state and dynamic jitter. In this thesis a 10 Gb/s adaptive loop bandwidth clock and data recovery circuit with on-chip loop filter is presented. The proposed system optimizes the loop bandwidth adaptively to minimize jitter so that it leads to an improved jitter tolerance performance. This architecture tunes the loop bandwidth by a factor of eight based on the phase information of incoming data. The resulting architecture performs as good as a maximum fixed loop bandwidth CDR while tracking high speed input jitter and as good as a minimum fixed bandwidth CDR while suppressing wide bandwidth steady-state jitter. By employing a mixed mode predictor, high updating rate loop bandwidth adaptation is achieved with low power consumption. Another relevant feature is that it integrates a typically large off-chip filter using a capacitance multiplication technique that employs dual charge pumps. The functionality of the proposed architecture has been verified through schematic and behavioral model simulations. In the simulation, the performance of jitter tolerance is confirmed that the proposed solution provides improved results and robustness to the variation of jitter profile. Its applicability to industrial standards is also verified by the jitter tolerance passing SONET OC-192 successfully.
URI: http://hdl.handle.net/1969.1/ETD-TAMU-2009-08-7183 Files in this item: 1
JEON-THESIS.pdf (1.808Mb) -
Edgar, Leslie Dawn (December 2007)[more][less]
Abstract: The field of agricultural education relies on multiple research journals to disseminate findings. This study focused on a 10-year content analysis of research published in premier journals in agricultural education. The study ascertained primary research themes, types of research conducted, prolifically published authors, frequently cited authors, and frequently cited referenced works, and discussed how the formation and usage of research in agricultural education has changed from 1997 to 2006. The study sought assistance from agricultural educators to narrow the focus of the study and to ensure study content validity. A conceptual model, based on a thorough review of literature and a focus on the peer discipline areas of agricultural education, guided the study. The study utilized a field study and employed descriptive statistics. Premier agricultural education (AGED) journals were identified: the Journal of Agricultural Education (93%); Journal of International Agricultural and Extension Education (67%); Journal of Extension (63%); North American Colleges and Teachers of Agriculture Journal (48%); Journal of Applied Communications (41%); and Journal of Leadership Education (41%). The study identified primary and secondary research themes, prolific authorship, research methods and types, and frequently cited authors and referenced works in each of the identified premier AGED journals. The research used compiled data, from each of the research journals, to analyze the frequencies and gaps identified in the National Research Agenda [NRA]: Agricultural Education and Communication 2007-2010 (2007). Agricultural education in domestic and international settings: Extension and outreach was the research priority area noted as the most frequently identified in past research and no gaps were identified in the NRA. To continue to strengthen the agricultural education discipline, research from this study should be used to adjust research priority areas in the NRA and on the regional and state levels.
URI: http://hdl.handle.net/1969.1/ETD-TAMU-2413 Files in this item: 1
EDGAR-DISSERTATION.pdf (749.7Kb) -
York, Melissa Dawn (August 2007)[more][less]
Abstract: Renal cell carcinoma (RCC) accounts for 85% of kidney cancer incidence in the US. Since 1950 there has been a 126% increase in kidney cancer incidence in the US. Thirty percent of new patients present with a localized easily treatable carcinoma while 30% of patients present with a high-grade metastatic carcinoma. Five-year survival rates for metastatic RCC is 6-12 months (Lipworth et al, 2006). Current disease treatment options for metastasis include chemotherapy and radiation (8% response rate), immunotherapy (15-30% response rate) and newly developed angiogenesis inhibitors which are in phase III trials (Staehler et el, 2005). In RCC cells, it has been shown that PPARγ agonists inhibit cell proliferation, induce apoptosis, and induce anti-angiogenic effects in vitro. Unlike most tumor types, PPARγ is downregulated in tissue samples from 47 RCC patients. However, in cell culture studies PPARγ expression does not correlate with growth inhibitory or apoptotic effects of PPARγ agonists in renal cell lines indicating that PPARγ independent responses may play a large role in actions associated with the PPARγ agonists (Yuan et al, 2006). 1,1-Bis(3'-indolyl)-1-(p-substitutedphenyl)methanes containing p-trifluoromethyl, p-t-butyl and p-phenyl substituents activate peroxisome proliferator-activated receptor (PPAR) and inhibit growth of ACHN and 786-0 renal cell carcinoma cell lines. PPAR is overexpressed in ACHN cells and barely detectable in 786-0 cells, and treatment with the t-butyl analog (DIM-C-pPhtBu) induces cell cyle inhibition. DIM-C-pPhtBu also induced several common PPAR-independent proapoptotic responses in ACHN and 786-0 cells, including increased expression of nonsteroidal antiimflammatory drug-activated gene-1 (NAG-1) and endoplasmic reticulum stress which activates death receptor 5 and the extrinsic pathway of apoptosis. In addition, DIM-C-pPhtbu (40 mg/kg/d) also inhibited tumor growth in an orthotopic mouse model for renal carcinogenesis, and this was accompanied by induction of apoptosis in renal tumors treated with DIM-C-pPhtBu but not in tumors treated with the corn oil vehicle (control). Thus, DIM-C-pPhtBu and related compounds represent a novel class of mechanism-based drugs that have potential for treatment of renal adenocarcinoma for which there are currently limited options for successful chemotherapy.
URI: http://hdl.handle.net/1969.1/ETD-TAMU-1968 Files in this item: 1
YORK-THESIS.pdf (33.97Mb) -
11th Grade Students' English Reading Motivation, Language Problems and Reading Achievement in TaiwanSu, Jung-Hsuan (May 2012)[more][less]
Abstract: Motivation has been viewed as a very influential factor to successful reading for English as foreign language learners. Learners can be motivated to read English by extrinsic or intrinsic motivation, and the motivational orientations could also influence their reading achievement. However, language problems that EFL learners encounter while reading can affect their willingness to read as well as their reading achievement. The purpose of this study was to investigate Taiwanese EFL students’ English reading motivation and its relationship with perceived language problems and reading achievement. 302 11th grade students from an urban district in southern Taiwan participated in the study. Measures included an English reading comprehension test, an English reading motivation questionnaire, and a questionnaire regarding language problems in reading English. A factor analysis was used to determine the motivational orientations. Multiple regression and correlation analysis were performed to examine the relationship among reading motivation, language problems, and reading achievement. The results showed that: 1) Taiwanese senior high school students were largely motivated to read English by extrinsic motivation, specifically the importance and instrumental utility of reading English and the drive for recognition and competition, although they could also be motivated by intrinsic motivation to read English for knowledge and social purposes. Moreover, extrinsic motivation to read for compliance was significantly associated with their English reading scores. 2) While reading English, unknown idiomatic expressions and vocabulary were frequently reported language problems that influenced students’ willingness to read. Nevertheless, lack of grammar knowledge was generally not considered a big language problem to most of the students while reading. 3) Language problems in reading English and reading motivation were correlated, and motivation to read for compliance, grammar knowledge, and overall reading comprehension were significant predictors of students’ English reading scores. This study highlights the influential role of extrinsic motivation to EFL students in English reading and the importance of knowledge of vocabulary and idiomatic expressions in order to help understand the meaning of English texts. It provides implications for English teachers in designing appropriate curriculum that suits students’ needs and interests, and also suggestions for choosing proper reading materials.
URI: http://hdl.handle.net/1969.1/ETD-TAMU-2012-05-11187 Files in this item: 1
SU-DISSERTATION.pdf (1.988Mb) -
Jung, Jae Won (Texas A&M University, May 2003)[more][less]
Abstract: A beta-emitting glass seed was proposed for the brachytherapy treatment of prostate cancer. Criteria for seed design were derived and several beta-emitting nuclides were examined for suitability. 142Pr was selected as the isotope of choice. Seeds 0.08 cm in diameter and 0.9 cm long were manufactured for testing. The seeds were activated in the Texas A&M University research reactor. The activity produced was as expected when considering the meta-stable state and epi-thermal neutron flux. The MCNP5 Monte Carlo code was used to calculate the quantitative dosimetric parameters suggested in the American Association of Physicists in Medicine (AAPM) TG-43/60. The Monte Carlo calculation results were compared with those from a dose point kernel code. The dose profiles agree well with each other. The gamma dose of 142Pr was evaluated. The gamma dose is 0.3 Gy at 1.0 cm with initial activity of 5.95 mCi and is insignificant to other organs. Measurements were performed to assess the 2-dimensional axial dose distributions using Gafchromic radiochromic film. The radiochromic film was calibrated using an X-ray machine calibrated against a National Institute of Standards and Technology (NIST) traceable ion chamber. A calibration curve was derived using a least squares fit of a second order polynomial. The measured dose distribution agrees well with results from the Monte Carlo simulation. The dose was 130.8 Gy at 6 mm from the seed center with initial activity of 5.95 mCi. AAPM TG-43/60 parameters were determined. The reference dose rate for 2 mm and 6 mm were 0.67 and 0.02 cGy/s/mCi, respectively. The geometry function, radial dose function and anisotropy function were generated.
URI: http://hdl.handle.net/1969.1/5738 Files in this item: 1
etd-tamu-2007A-NUEN-Jung.pdf (2.847Mb) -
McElhany, Katherine (December 2010)[more][less]
Abstract: Environmental microbiology has traditionally been performed using culture-based methods. However, in the last few decades, the emergence of molecular methods has changed the field considerably. The latest development in this area has been the introduction of next-generation sequencing, including pyrosequencing. These technologies allow the massively parallel sequencing of millions of DNA strands and represent a major development in sequencing technologies. The purpose of this study was to use both pyrosequencing and traditional culture-based techniques to investigate the diversity and dynamics of bacterial populations within milk and untreated sewage sludge samples. Pasteurized and raw milk samples were collected from grocery stores and dairies within Texas. Milk samples were analyzed by plating, pyrosequencing, and an assay for the presence of cell-cell signaling molecules. Samples were processed, stored, and then evaluated again for spoilage microflora. The results of this study showed that raw milk had a considerably higher bacterial load, more diversity between samples, and a significantly higher concentration of pathogens than pasteurized milk. Additionally, this study provided evidence for varying spoilage microflora between raw and pasteurized milk, as well as evidence for the production of cell-cell signaling molecules by bacterial organisms involved in milk spoilage. Four samplings of untreated sewage sludge were collected from wastewater treatment plants in seven different municipalities across the United States. Samples were subjected to quantification of selected bacterial organisms by culture and a pyrosequencing analysis was performed on extracted community DNA. The results of this study showed that untreated sewage sludge is inhabited by a huge diversity of microorganisms and that certain municipalities may have distinct bacterial populations that are conserved over time. Additionally, this study provided some evidence for seasonal differences in several of the major bacterial phyla. Lastly, this study emphasized the challenges of comparing results obtained by culture and pyrosequencing. In conclusion, this study showed that both milk and sewage are highly diverse, dynamic environments that can contain organisms of public health concern. The use of both culture-based methods and pyrosequencing in this study proved a complementary approach, providing a more comprehensive picture of both microbial environments.
URI: http://hdl.handle.net/1969.1/ETD-TAMU-2010-12-8933 Files in this item: 1
MCELHANY-THESIS.pdf (3.172Mb) -
Hoskins, Sara Grace (Texas A&M University, December 2003)[more][less]
Abstract: Within the collections of the Museu de Angra do Heroismo (Terceira Island, Azores, Portugal) are nine cast bronze guns from the 16th century. Most were raised from the seafloor between the 1960s and 1990s, but this study comprises the first in-depth research into their design and manufacture. The importance of this kind of study lies in the fact that ordnance is commonly found on shipwrecks of this time. A greater knowledge of guns will help provide information about the ships from which they came. Careful documentation and study of the Museu de Angra cannon will add greatly to their value as museum exhibits, by allowing museum patrons to better understand where the guns came from, how they were cast, and why they were important. This documentation adds to our knowledge of Western European gunfounding technology during the sixteenth century, as four different countries commissioned the guns: Portugal, Spain, France, and England. With detailed documentation and publication, the Museu de Angra bronze guns can be added to the bibliography of ordnance of this period, which will aid future researchers who encounter similar pieces. The Museu de Angra bronze guns, as symbols of the military and naval power of the countries that commissioned them, were sent aboard ships, into the field, and mounted on fortress walls. Bronze guns of this time period are particularly important, as bronze was an expensive commodity, and the demand for ordnance was increasing rapidly. Countries developed more effective ways to make use of iron for the founding of guns, and the use of bronze became more symbolic of wealth. The information that each gun contains includes both the cutting-edge military technology of the time and the artistic statement of the founder. Some of the finest metalwork of the period was displayed in cast bronze guns, and due to the founding techniques, no two are the same, making each an important piece of history.
URI: http://hdl.handle.net/1969.1/556 Files in this item: 1
etd-tamu-2003C-ANTH-Hoskins-1.pdf (10.11Mb) -
Stefanou, Nikolaos (Texas A&M University, May 2006)[more][less]
Abstract: Hard disk drive applications require a high Spurious Free Dynamic Range (SFDR), 6-bit Analog-to-Digital Converter (ADC) at conversion rates of 1GHz and beyond. This work proposes a robust, fault-tolerant scheme to achieve high SFDR in an av- eraging flash A/D converter using comparator chopping. Chopping of comparators in a flash A/D converter was never previously implemented due to lack of feasibility in implementing multiple, uncorrelated, high speed random number generators. This work proposes a novel array of uncorrelated truly binary random number generators working at 1GHz to chop all comparators. Chopping randomizes the residual offset left after averaging, further pushing the dynamic range of the converter. This enables higher accuracy and lower bit-error rate for high speed disk-drive read channels. Power consumption and area are reduced because of the relaxed design requirements for the same linearity. The technique has been verified in Matlab simulations for a 6-bit 1Gsamples/s flash ADC under case of process gradients with non-zero mean offsets as high as 60mV and potentially serious spot offset errors as high as 1V for a 2V peak to peak input signal. The proposed technique exhibits an improvement of over 15dB compared to pure averaging flash converters for all cases. The circuit-level simulation results, for a 1V peak to peak input signal, demon- strate superior performance. The reported ADC was fabricated in TSMC 0.18 ??mCMOS process. It occupies 8.79mm2 and consumes about 400mW from 1.8V power supply at 1GHz. The targeted SFDR performance for the fabricated chip is at least 45dB for a 256MHz input sine wave, sampled at 1GHz, about 10dB improvement on the 6-bit flash ADCs in the literature.
URI: http://hdl.handle.net/1969.1/2469 Files in this item: 1
etd-tamu-2005A-ENGR-Stefanou.pdf (1.120Mb) -
Bernhardt, Michelle Lee (December 2009)[more][less]
Abstract: The United States contains an estimated 100,000 miles (160000 km) of levees in which erosion related issues are the top priorities. Proper documentation of overtopping induced erosion is a complicated issue involving the collection and analysis of timesensitive field data and personal observations. This thesis is a study of the performance of the Midwest Levee system during the 2008 flooding events. The goal of the Midwest Levee investigation was to gather and analyze perishable data in an effort to provide a comprehensive overview at each breach location. To predict how a site will perform during a particular flood event, there are three main inputs: the flood conditions, the site conditions, and the soil properties. Site geometry and imperfections can greatly affect the performance of a levee system. Any low spots or potential seepage paths can concentrate the flow and be detrimental to the levee. The vegetative cover is the single most important condition at a site. As seen in the Brevator case, vegetative armor can prevent failure of a levee comprised of less resistant soils subjected to long periods of overtopping. Recommended grasses include: Switchgrass, Smooth Brome, Reed Canarygrass, and Tall Fescue. It is also recommended that grasses are kept at least 0.5 m tall during the flood season and to limit the presence of trees to 10 m beyond the levee toe. The erosion resistance of the materials comprising the levee is also important. From the correlations in this study, it was determined that erodibility is influenced by grain size, relative compaction, clay content, and activity. Devices like the Torvane and Pocket Erodometer can also be used to get a quick field estimate of erosion. While these correlations and field devices give insight into an erodibility value, they are no substitute for site specific analysis with laboratory equipment such as the Erosion Function Apparatus. Soil behavior is highly nonlinear and the entire erosion function is needed to get an accurate measure of the erodibility of a soil. By combining these properties in an erosion matrix, a prediction of whether a site will withstand a given flood event can be made.
URI: http://hdl.handle.net/1969.1/ETD-TAMU-2009-12-7423 Files in this item: 1
BERNHARDT-THESIS.pdf (96.68Mb) -
Ayala, Julio Enqrique, II (Texas A&M University, December 2005)[more][less]
Abstract: Recently, there is a growing interest in applying electronic circuit design for biomedical applications, especially in the area of nuclear magnetic resonance (NMR). NMR has been used for many years as a spectroscopy technique for analytical chem- istry. Previous studies have demonstrated the design and fabrication of planar spiral inductors (microcoils) that serve as detectors for nuclear magnetic resonance mi- crospectroscopy. The goal of this research was to analyze, design, and test a prototype integrated sensor, which consisted of a similar microcoil detector with analog components to form a multiple-channel front-end for a magnetic resonance imaging (MRI) system to perform microspectroscopy. The research has succeeded in producing good function- ality for a multiple-channel sensor. The sensor met expectations compared to similar one-channel systems through experiments in channel separation and good signal-to- noise ratios.
URI: http://hdl.handle.net/1969.1/4729 Files in this item: 1
etd-tamu-2005C-ELEN-Ayala.pdf (1.933Mb) -
Gowan, Joshua Smith (May 2012)[more][less]
Abstract: Many scientific studies have been conducted on the Cretaceous-Paleogene boundary (KTB) in the Gulf coast region and, in particular, the Brazos River section in Falls County, Texas. Despite this, there remains much to be learned about the KTB and its depositional environment. Study of the KTB has been multidisciplinary, primarily in the fields of sedimentology and paleontology. Some researchers in these disciplines have questioned the consensus view of the placement of the KTB and subsequent interpretation of the timing of depositional events and mass extinction events. Geophysical methods have potential to provide additional understanding of the physical properties of the KTB. To date, study of the KTB has relied on point data and borehole information to create cross sections of the complex. Seismic refraction surveys can provide spatially continuous information on susburface horizons located adjacent to the KTB. In this study, seismic first-arrival traveltimes are processed with a tomographic modeling program to map the top of the hummocky cross-bedded sandstone (HCS), which is a key indicator of the deposition environment at the time of KTB boundary complex placement. The survey area is located at Cottonmouth Creek, a tributary of the Brazos River. Three seismic lines were surveyed, one across Cottonmouth Creek, and two parallel to the creek on either side. The data from the two parallel lines were processed using the 2-D seismic refraction tomography algorithm of Zelt and Smith. The reconstructed depth to the HCS in the survey area is approximately 6 m, with layer seismic velocities of 364, 1800, and 2200 m/s, respectively. Seismic tomography successfully mapped the HCS layer and reveals approximately 1 m amplitude undulations vertically and undulations on the order of several m horizontally. These variations are consistent with exposed surfaces of the HCS in the creek bed. Seismic refraction has been utilized successfully herein to map a key buried indicator, namely the top of the HCS layer, associated with the KTB complex. A detailed 3-D seismic refraction survey at this site is recommended to generate a high-resolution 2-D terrain map of the top of the HCS layer.
URI: http://hdl.handle.net/1969.1/ETD-TAMU-2012-05-11079 Files in this item: 1
GOWAN-THESIS.pdf (5.621Mb) -
Lopez-Rivera, Marcos L. (December 2009)[more][less]
Abstract: Recently, there is growing interest in high speed circuits for broadband communication, especially in wired networks. As the data rate increases beyond 1 GB/s conventional materials used as communication channels such as PCB traces, coaxial cables, and unshielded twisted pair (UTP) cables, etc. attenuate and distort the transmitted signal causing bit errors in the receiver end. Bit errors make the communication less reliable and in many cases even impossible. The goal of this work was to analyze, and design an channel equalizer capable of restoring the received signal back to the original transmitted signal. The equalizer was designed in a standard CMOS 0.18 µm process and it is capable of compensating up to 20 dB’s of attenuation at 1.5625 GHz for 15 and 20 meters of RG-58 A/U coaxial cables. The equalizer is able to remove 0.5 UI ( 160 ps ) of peak-to-peak jitter and output a signal with 0.1 UI ( 32 ps ) for 15 meters of cable at 3.125 Gb/s. The equalizer draws 18 mA from a 1.8 V power supply which is lower than publications [1, 2] for CMOS transversal equalizers.
URI: http://hdl.handle.net/1969.1/ETD-TAMU-2009-12-7529 Files in this item: 1
LOPEZ-RIVERA-THESIS.pdf (1.610Mb) -
Kaltenberg, Amanda May (Texas A&M University, December 2004)[more][less]
Abstract: A hull-mounted 38-kHz phased-array acoustic Doppler current profiler (ADCP) was used to acoustically survey the continental margin of the northern Gulf of Mexico (GOM) during 6 cruises in 2002-2003. This is the first backscatter survey with a 38-kHz ADCP in the Gulf of Mexico. ADCPs have been used as a proxy to measure the volume backscatter return from plankton in the water column, however previous studies were restricted to the upper 200 to 300 meters due to the relatively high frequency of operation (150-300 kHz) of the transducers. In addition to measuring deep water current velocities, the 38-kHz phased-array ADCP can measure Relative Acoustic Backscatter Intensity (RABI) as deep as 1000 meters. The daytime depth of the main deep scattering layer at 400 to 500 meters was resolved, and locally high backscatter intensity can be seen down to 800 meters. The objectives were to determine how to analyze RABI from the instrument to resolve scattering layers, and then to seek secondary deep scattering layers of potential prey species below the main deep scattering layer, from 600 to 800 meters in the feeding range for Gulf of Mexico sperm whales. Based on RABI from the 38-kHz ADCP, secondary DSLs in sperm whale diving range were more commonly recorded over the continental shelf than in the deep basin region of the Gulf of Mexico. The daytime depths of migrating plankton showed variation depending on physical circulation features (cyclone, anticyclone, proximity to Mississippi river, and Loop Current) present. Vertical migrations compared between concurrently running 38 and 153-kHz ADCPs showed an overlap of acoustic scatterers recorded by the two instruments, however the 153-kHz instrument has much finer vertical resolution. Vertical migration rates were calculated and simultaneous net tow samples from one of the cruises was used to compare abundance estimates by the two methods.
URI: http://hdl.handle.net/1969.1/1387 Files in this item: 1
etd-tamu-2004C-2-OCNG-Kaltenbe.pdf (1.442Mb) -
Sundar, Arun (December 2011)[more][less]
Abstract: The summing amplifier and the quantizer form two of the most critical blocks in a continuous time delta sigma (CT ΔΣ) analog-to-digital converter (ADC). Most of the conventional CT ΔΣ ADC designs incorporate a voltage summing amplifier and a voltage-mode quantizer. The high gain-bandwidth (GBW) requirement of the voltage summing amplifier increases the overall power consumption of the CT ΔΣ ADC. In this work, a novel method of performing the operations of summing and quantization is proposed. A current-mode summing stage is proposed in the place of a voltage summing amplifier. The summed signal, which is available in current domain, is then quantized with a 3-bit current mode flash ADC. This current mode summing approach offers considerable power reduction of about 80% compared to conventional solutions [2]. The total static power consumption of the summing stage and the quantizer is 5.3mW. The circuits were designed in IBM 90nm process. The static and dynamic characteristics of the quantizer are analyzed. The impact of process and temperature variation and mismatch tolerance as well as the impact of jitter, in the presence of an out-of-band blocker signal, on the performance of the quantizer is also studied.
URI: http://hdl.handle.net/1969.1/ETD-TAMU-2011-12-10515 Files in this item: 1
SUNDAR-THESIS.pdf (2.862Mb) -
Zhuang, Wei (Texas A&M University, May 2003)[more][less]
Abstract: A three dimensional (3-D) capacitance extraction algorithm based on a kernel independent hierarchical method and geometric moments is described. Several techniques are incorporated, which leads to a better overall performance for arbitrary interconnect systems. First, the new algorithm hierarchically partitions the bounding box of all interconnect panels to build the partition tree. Then it uses simple shapes to match the low order moments of the geometry of each box in the partition tree. Finally, with the help of a fast matrix-vector product, GMRES is used to solve the linear system. Experimental results show that our algorithm reduces the linear system's size greatly and at the same time maintains a satisfying accuracy. Compared with FastCap, the running time of the new algorithm can be reduced more than a magnitude and the memory usage can be reduced more than thirty times.
URI: http://hdl.handle.net/1969.1/5794 Files in this item: 1
etd-tamu-2006A-CEEN-Zhuang.pdf (1.740Mb) -
Malagon Nieto, Camilo (Texas A&M University, May 2003)[more][less]
Abstract: The complex interrelations among the different physical processes involved in acid fracturing make it difficult to design, and later, to predict the outcome of stimulation jobs. Actual tendencies require the use of computational models to deal with the dynamic interaction of variables. This thesis presents a new study of acidized surface textures by means of a laser profilometer to improve our understanding of the remaining etched surface topography and its hydraulic response. Visualization plots generated by the profilometer identified hydrodynamic channels that could not be identified by the naked eye in acidized surfaces. The plots clarified the existence of rock heterogeneities and revealed how the processes of dissolution function in chalk rock. Experimental data showed clearly that the effect of dissolution depends on the type of rock and the fluid system; dolomite, for example, dissolves more rapidly but more roughly than limestone. Fluid leakoff rate and temperature also affect the dissolution. Further research is necessary to clarify the effects of conductivity.
URI: http://hdl.handle.net/1969.1/5771 Files in this item: 1
etd-tamu-2007A-PETE-Malagon.pdf (35.27Mb) -
Udphuay, Suwimon (December 2008)[more][less]
Abstract: Pointe du Hoc overlooking the English Channel in Normandy, France was host to one of the most important military engagements of World War II. While the site is a valuable historic cultural resource, it is vulnerable to cliff collapses that already have endangered the observation post and Rudder?s command post. The observation post has been closed to visitors for some time due to safety concerns. Geophysical techniques have been used increasingly in recent years for slope stability investigation purposes. The objective of this study is to apply advanced 3?D resistivity tomography toward a detailed site stability assessment with special attention to the two at-risk buildings. 3?D resistivity tomography datasets at Pointe du Hoc in the presence of extreme topography and dense cultural clutter have been successfully acquired, inverted, and interpreted. The cliff stability in the areas around the two at?risk buildings has been analyzed. A hazard assessment scheme has been designed in which regions of high resistivity are interpreted as zones of open, dry fractures with a moderate mass movement potential. Regions of low resistivity are zones of wet, clay?filled fractures with a high mass movement potential. The observation post tomography results indicate that the highest mass movement hazard appears to be associated with the marine caverns at the base of the cliff that are positioned at the point of strongest wave attack. These caverns likely occupy the future site of development of a sea arch which will definitely threaten the observation post building. A high probability of a soil wedge failure is on the east?facing cliff edge close to the observation post that could damage or destroy the building. The mass movement potential at the Rudder?s command post area is low to moderate. The greatest risk is associated with soil wedge failures at the top of the cliffs. The resistivity geophysical data add great value to the natural geohazard assessment at Pointe du Hoc and constitute an integral component of an interdisciplinary approach to the problem of cultural resource preservation at the site. Geophysics is a non?invasive and relatively inexpensive technology that provides unique constraints which are unobtainable using traditional engineering geology methods for site characterization. However, the technology is difficult to master and the inherent limitations must be carefully understood to ensure a reliable geotechnical interpretation.
URI: http://hdl.handle.net/1969.1/ETD-TAMU-2008-12-155 Files in this item: 1
UDPHUAY-DISSERTATION.pdf (15.45Mb) -
Anderson, Christopher Dean (Texas A&M University, December 2003)[more][less]
Abstract: The purpose of this project is to develop a software framework, a 3D engine, which will generate images to be projected onto facets of a spatially immersive display (SID). The goal is to develop a software library to support the creation of images of specified 3D environments which are specific to the display geometries of a polyhedral class of SIDs. Part of this goal is developing auxiliary software to allow this library to be thoroughly tested. When properly working, the images being displayed on adjoining faces of the SID appear spatially and temporally consistent with one another, creating the illusion that the user is within a surrounding three-dimensional space.
URI: http://hdl.handle.net/1969.1/1307 Files in this item: 1
etd-tamu-2003C-VIZA-Anderson-1.pdf (2.118Mb) -
Zou, Le (August 2007)[more][less]
Abstract: In this dissertation, we focus on two related parts of a 3D face recognition system with wireless transportation. In the first part, the core components of the system, namely, the feature extraction and classification component, are introduced. In the feature extraction component, range images are taken as inputs and processed in order to extract features. The classification component uses the extracted features as inputs and makes classification decisions based on trained classifiers. In the second part, we consider the wireless transportation problem of range images, which are captured by scattered sensor nodes from target objects and are forwarded to the core components (i.e., feature extraction and classification components) of the face recognition system. Contrary to the conventional definition of being a transducer, a sensor node can be a person, a vehicle, etc. The wireless transportation component not only brings flexibility to the system but also makes the “proactive” face recognition possible. For the feature extraction component, we first introduce the 3D Morphable Model. Then a 3D feature extraction algorithm based on the 3D Morphable Model is presented. The algorithm is insensitive to facial expression. Experimental results show that it can accurately extract features. Following that, we discuss the generic face warping algorithm that can quickly extract features with high accuracy. The proposed algorithm is robust to holes, facial expressions and hair. Furthermore, our experimental results show that the generated features can highly differentiate facial images. For the classification component, a classifier based on Mahalanobis distance is introduced. Based on the classifier, recognition performances of the extracted features are given. The classification results demonstrate the advantage of the features from the generic face warping algorithm. For the wireless transportation of the captured images, we consider the location-based wireless sensor networks (WSN). In order to achieve efficient routing perfor¬mance, a set of distributed stateless routing protocols (PAGER) are proposed for wireless sensor networks. The loop-free and delivery-guaranty properties of the static version (PAGER-S) are proved. Then the performance of PAGER protocols are compared with other well-known routing schemes using network simulator 2 (NS2). Simulation results demonstrate the advantages of PAGER.
URI: http://hdl.handle.net/1969.1/ETD-TAMU-1448 Files in this item: 1
ZOU-DISSERTATION.pdf (3.490Mb) -
Lau, Ryan (Texas A&M University, May 2003)[more][less]
Abstract: Relatively little is known about marine controlled-source electromagnetic surveys (MCSEM) used to detect hydrocarbon reservoirs. Typical MCSEM require the use of inversion to generate a model of the subsurface. We utilize a 3D finite-element forward model to simulate a MCSEM survey. With the results we were able to determine the strengths and weaknesses of each transmitter and receiver configuration that would best detect a shallow hydrocarbon target. Careful selection of the correct configuration is important as we have found that incorrect transmitter orientation, offset and receiver measurement component can yield misleading results. Using the ideal configuration we were able to directly image the hydrocarbon target without the use of inversion modeling. The direct image is able to show the hydrocarbon target's shape and edges without any ambiguity. The direct image of the target can potentially be used to refine 3D inversion modeling, or be used in conjunction with seismic profiles to refine seismic picks.
URI: http://hdl.handle.net/1969.1/5790 Files in this item: 1
etd-tamu-2006A-GEOP-Lau.pdf (384.0Kb)
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