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Gunnam, Kiran Kumar (Texas A&M University, September 30, 2004)[more][less]
Abstract: Spacecraft missions such as spacecraft docking and formation flying require high precision relative position and attitude data. Although Global Positioining Systems can provide this capability near the earth, deep space missions require the use of alternative technologies. One such technology is the vision-based navigation (VISNAV) sensor system developed at Texas A&M University. VISNAV comprises an electro-optical sensor combined with light sources or beacons. This patented sensor has an analog detector in the focal plane with a rise time of a few microseconds. Accuracies better than one part in 2000 of the field of view have been obtained. This research presents a new approach involving simultaneous activation of beacons with frequency division multiplexing as part of the VISNAV sensor system. In addition, it discusses the synchronous demodulation process using digital heterodyning and decimating filter banks on a low-power fixed point DSP, which improves the accuracy of the sensor measurements and the reliability of the system. This research also presents an optimal and computationally efficient six-degree-of-freedom estimation algorithm using a new measurement model based on the attitude representation of Modified Rodrigues Parameters. URI: http://handle.tamu.edu/1969.1/13 Files in this item: 1
GUNNAM-THESIS.pdf (564.3Kb) -
Webb, Michael Scott (Texas A&M University, September 30, 2004)[more][less]
Abstract: Intraspecific relationships among the anchialine cave shrimp Typhlatya mitchelli were examined by sequencing a total of 1505 bp from portions of three mitochondrial DNA genes. Cytochrome b, cytochrome oxidase I, and 16S rRNA were partially sequenced and analyzed for specimens from six different cenotes (water-filled caves) across the Yucatan Peninsula, Mexico. The conspecific Typhlatya pearsei that is sympatric with T. mitchelli was also sequenced and used as the outgroup. Comparisons among specimens of T. mitchelli yielded low sequence divergence values (0-1.7%), with the majority being less than 0.4%. Phylogenetic tree topologies reconstructed with neighbor-joining, maximum likelihood, and maximum parsimony were in agreement in regards of the resolution of deep branches. Also, there was no obvious geographic differentiation among the majority of T. mitchelli samples, with the exception of specimens from Cenote San Antonio Chiich (Yokdzonot, Yucatan, Mexico) which all clustered into an extremely well supported monophyletic group. The level of differentiation of this group, together with the nearly total absence of differentiation among T. mitchelli from distant cave systems, suggests that this is an Evolutionary Significant Unit (ESU), which may correspond to a new species. This unidentified Typhlatya from Cenote San Antonio Chiich was helpful in establishing a period in which the epigean ancestor colonized the cenotes. Based on pairwise distance data and previously published shrimp molecular clocks (Baldwin et al., 1998), T. mitchelli and the putative new Typhlatya species last shared a common ancestor between 3-5 million years ago (mya), during the mid-Pliocene era, while T. mitchelli and T. pearsei was approximately 7-10 mya (middle to late Miocene). The ancestor to T. mitchelli and the unidentified Typhlatya species abandoned its shallow coastal water existence in the early Pliocene and eventually expanded its range across the peninsula. Approximately 4 mya, Cenote San Antonio Chiich became isolated from the remaining gene pool thereby halting gene flow. As the regional water table fluctuated in response to the rise and fall of Pleistocene sea levels, T. mitchelli actively colonized the peninsula. The discovery of a single, continuous subterranean freshwater system provides for a better understanding of anchialine biogeography within the Yucatan Peninsula. URI: http://handle.tamu.edu/1969.1/14 Files in this item: 1
WEBB-THESIS.pdf (889.8Kb) -
Kim, Min Suk (Texas A&M University, September 30, 2004)[more][less]
Abstract: A numerical scheme, known as CABLE3D, originally developed for the simulation of dynamics of steel chain-wire mooring lines is extended to allow for the large elongation in a mooring line, the dependence of the modulus on tension, and energy dissipation of a polyester rope under mean and cyclic loads. The modified CABLE3D is then integrated into a numerical package, known as COUPLE6D, for computing the interaction between a floating structure and its hybrid polyester mooring system. The Deepstar Spar is chosen in this study to represent the floating structure. By considering large elongation in polyester ropes in numerical simulation, the static offset curve of a polyester mooring system is softer than that calculated under the assumption of small elongation. That is, about 10% reduction in restoring force at the mean offset position of the Spar under the impact of 100-year hurricane storm. The effects of the mean loads on the modulus of polyester ropes are much greater than those of the dynamic loads. Hence, the former is more important in the simulation of the response of floating structures. The energy dissipation in polyester ropes under cyclic loading does not play significant roles in the responses of the Spar and tensions in a polyester mooring system. The above findings, although observed based on the numerical simulation of a particular floating structure, namely Spar, may have implications to other floating offshore structures moored by a polyester mooring system. Two systems are simulated in two different met-ocean conditions: hurricane and loop current condition. To study the properties of polyester, numerical simulation were conducted in three ways. Those are related to the modulus based on mean load, mean and dynamic loads, and structural damping respectively. Through the simulation, statistics of motions of the hull and tension in the mooring lines are compared with those of a conventional steel mooring system. URI: http://handle.tamu.edu/1969.1/15 Files in this item: 1
KIM-THESIS.pdf (4.978Mb) -
Gamal Eldin, Ahmed Mohamed (Texas A&M University, September 30, 2004)[more][less]
Abstract: This thesis presents numerical predictions for the leakage and direct stiffness coefficients of pocket damper seals. Modifications made to earlier flow-prediction models are discussed. Leakage and static pressure measurements on straight-through and diverging configurations of eight-bladed and twelve-bladed seals were used for code validation and for calculation of seal discharge coefficients. Higher than expected leakage rates were measured in the case of the twelve-bladed seal, while the leakage rates for the eight-bladed seals were predicted reasonably accurately. Results are presented for shake tests conducted on the seals at pressures of up to 1000 Psi (6.90 MPa). Test variables included pressure drop across the seals and rotor speed. The experimentally obtained stiffness coefficients are compared to results of a rotordynamic damper seal code, which uses the corrected mass flow-rate calculation method. Results show that the code under-predicts the magnitude of the seal's stiffness for most test cases. However, general trends in the frequency dependency of the direct stiffness are more accurately predicted. The expectation of high values of negative stiffness in diverging seals is confirmed by the results, but the frequency at which the sign of the stiffness becomes positive is considerably lower than is predicted. In addition to presenting high-pressure test data, this thesis also attempts to provide some insight into how seal parameters can be modified to obtain desired changes in seal stiffness. URI: http://handle.tamu.edu/1969.1/16 Files in this item: 1
GAMAL-ELDIN-THESIS.pdf (743.4Kb) -
Park, Eungyu (Texas A&M University, September 30, 2004)[more][less]
Abstract: This dissertation is composed of three parts of major contributions. In Chapter II, we discuss analytical study of contaminant transport from a finite source in a finite-thickness aquifer. This chapter provides analytical solutions of contaminant transport from one-, two-, and three-dimensional finite sources in a finite-thickness aquifer using Green's function method. A library of unpublished analytical solutions with different finite source geometry is provided. A graphically integrated software CTINT is developed to calculate the temporal integrations in the analytical solutions and obtain the final solutions of concentration. In Chapter III, we obtained solutions of groundwater flow to a finite-diameter horizontal well including wellbore storage and skin effect in a three-dimensionally anisotropic leaky aquifer. These solutions improve previous line source solutions by considering realistic well geometry and offer better description of drawdown near the horizontal well. These solutions are derived on the basis of the separation of the source and the geometric functions. The graphically integrated computer program FINHOW is written to generate type curves of groundwater flow to a finite-diameter horizontal well. The influence of the finite-diameter of the well, the wellbore storage, the skin effect, the leakage parameter, and the aquifer anisotropy is thoroughly analyzed. In Chapter IV, a general theory of groundwater flow to a fractured or non-fractured aquifer considering wellbore storage and skin effect is provided. Solutions for both leaky confined and water table aquifers are provided. The fracture model used in this study is the standard double-porosity model. The storage of the aquitard (the leaky confining layer) is included in the formula. A program denoted FINHOW2 is written to facilitate the calculation. Sensitivity of the solution to the confined versus unconfined conditions, fractured versus non-fractured conditions, and wellbore storage and skin effects is analyzed. URI: http://handle.tamu.edu/1969.1/17 Files in this item: 1
PARK-DISSERTATION.pdf (1.084Mb) -
Presley, Anna Lee (Texas A&M University, September 30, 2004)[more][less]
Abstract: The Tamaulipan Biotic Province (TBP) is an ecotonal community that has been characterized in the twentieth century as a mixture of plains, woodland, and desert-adapted mammalian taxa. Some authors have proposed that this heterogeneous mixture of animals is a result of human influence on the environment in the post-European contact period. Others have proposed that the characteristically disharmonious mixture of fauna has been present in south Texas since prehistory. By considering the presence of certain key taxa across the archaeological record of the area this thesis demonstrates that the fauna characteristic of the Tamaulipan Biotic Province can be followed back in time as far as the archaeological record allows. This work also provides complete lists of all vertebrate organisms present in the archaeological record of the area, organized by time period and also by archaeological site and citation. URI: http://handle.tamu.edu/1969.1/18 Files in this item: 1
PRESLEY-THESIS.pdf (1.516Mb) -
Bueso Ucles, Francisco Javier (Texas A&M University, September 30, 2004)[more][less]
Abstract: Antistaling properties of enzymes (xylanase, bacterial maltogenic and conventional a-amylases), CMC and vital wheat gluten on corn tortillas were evaluated during storage for up to 21 days. Effect of storage time (0-21 days) and temperature (-40, -20, 3, 10 and 21 oC) on tortilla staling was evaluated with or without additives. Addition of 275-1650 AU of ICS maltogenic amylase effectively reduced amylopectin retrogradation without reducing tortilla yields, but did not improve tortilla flexibility. The combination of 825 AU of ICS amylase (to interfere with intra-granular amylopectin re-crystallization) and 0.25% CMC (to create a more flexible inter-granular matrix than retrograded amylose) produced less stiff, equally flexible and less chewy tortillas than 0.5% CMC. Corn tortilla staling followed the basic laws that control aging in starch-based semi-crystalline systems such as starch gels, bread and other baked products. Amylopectin re-crystallization was the driving force behind the staling of corn tortillas. Increasing levels of re-crystallized amylopectin measured by DSC correlated significantly with increased tortilla stiffness and reduction in tortilla rollability, pliability and rupture distance during storage. Re-crystallization of amylopectin in fresh tortillas was not detected. It increased rapidly during the first 24 hr reaching a plateau after 7 days storage. The level of amylopectin re-crystallization on tortillas showed a bell-shaped trend along the evaluated storage temperature range with a maximum around 7 oC. However, a negative linear relationship of peak pasting viscosity with storage temperature of tortilla extracts without additives after 21 days suggests other compounds besides amylopectin affect tortilla staling. Thus, interfering with amylopectin re-crystallization is not the only way to retard staling. Further research is required to optimize the addition of maltogenic amylases in continuous processing lines that use fresh masa instead of nixtamalized corn flour, to determine how these amylases interfere with amylopectin re-crystallization and to elucidate if amylose retrogradation continues during storage and plays a role in tortilla staling. URI: http://handle.tamu.edu/1969.1/19 Files in this item: 1
BUESO-UCLES-DISSERTATION.pdf (2.684Mb) -
Wingfield, James (Texas A&M University, September 30, 2004)[more][less]
Abstract: This research pursues the use of powerful BDD-based functional circuit analysis to evaluate some approaches to test set generation. Functional representations of the circuit allow the measurement of information about faults that is not directly available through circuit simulation methods, such as probability of random detection and test-space overlap between faults. I have created a software tool that performs experiments to make such measurements and augments existing test generation strategies with this new information. Using this tool, I explored the relationship of fault model difficulty to test set length through fortuitous detection, and I experimented with the application of function-based methods to help reconcile the traditionally opposed goals of making test sets that are both smaller and more effective. URI: http://handle.tamu.edu/1969.1/20 Files in this item: 1
WINGFIELD-THESIS.pdf (261.6Kb) -
Lowitzsch, Svenja (Texas A&M University, September 30, 2004)[more][less]
Abstract: Approximation and interpolation employing radial basis functions has found important applications since the early 1980's in areas such as signal processing, medical imaging, as well as neural networks. Several applications demand that certain physical properties be fulfilled, such as a function being divergence free. No such class of radial basis functions that reflects these physical properties was known until 1994, when Narcowich and Ward introduced a family of matrix-valued radial basis functions that are divergence free. They also obtained error bounds and stability estimates for interpolation by means of these functions. These divergence-free functions are very smooth, and have unbounded support. In this thesis we introduce a new class of matrix-valued radial basis functions that are divergence free as well as compactly supported. This leads to the possibility of applying fast solvers for inverting interpolation matrices, as these matrices are not only symmetric and positive definite, but also sparse because of this compact support. We develop error bounds and stability estimates which hold for a broad class of functions. We conclude with applications to the numerical solution of the Navier-Stokes equation for certain incompressible fluid flows. URI: http://handle.tamu.edu/1969.1/21 Files in this item: 1
LOWITZSCH-DISSERTATION.pdf (1.064Mb) -
Le Gia, Quoc Thong (Texas A&M University, September 30, 2004)[more][less]
Abstract: The theory of interpolation and approximation of solutions to differential and integral equations on spheres has attracted considerable interest in recent years; it has also been applied fruitfully in fields such as physical geodesy, potential theory, oceanography, and meteorology. In this dissertation we study the approximation of linear partial differential equations on spheres, namely a class of elliptic partial differential equations and the heat equation on the unit sphere. The shifts of a spherical basis function are used to construct the approximate solution. In the elliptic case, both the finite element method and the collocation method are discussed. In the heat equation, only the collocation method is considered. Error estimates in the supremum norms and the Sobolev norms are obtained when certain regularity conditions are imposed on the spherical basis functions. URI: http://handle.tamu.edu/1969.1/22 Files in this item: 1
LE-GIA-DISSERTATION.pdf (436.6Kb) -
Tian, Lu (Texas A&M University, September 30, 2004)[more][less]
Abstract: Epigenetic regulation is a mechanism by which heritable changes in gene expression are controlled by chromatin status rather than primary DNA sequence. Changes in chromatin structure affect accessibility of DNA elements to the transcriptional machinery and thus affect transcription activity of the gene. A key event in this process is reversible modification of core histones, which is catalyzed by histone acetyltransferases (HATs) and histone deacetylases (HDs, HDAs, or HDACs). In general, histone deacetylation is related to transcriptional gene silencing, whereas acetylation is associated with gene activation.To study the role of histone deacetylase in plant gene regulation and development, we generated constitutive antisense histone deacetylase 1 (CASH) transgenic plants. AtHD1 is a homolog of RPD3 protein, a global transcriptional regulator in yeast. Expression of the antisense AtHD1 caused dramatic reduction in endogenous AtHD1 transcription, resulting in accumulation of acetylated histones. Down-regulation of histone deacetylation caused a variety of growth and developmental abnormalities and ectopic expression of tissue-specific genes. However, changes in genomic DNA methylation were not detected in repetitive DNA sequences in the transgenic plants.We also identified a T-DNA insertion line in exon 2 of AtHD1 gene (athd1-t1), resulting in a null allele at the locus. The complete inhibition of the AtHD1 expression induced growth and developmental defects similar to those of CASH transgenic plants. The phenotypic abnormalities were heritable across the generations in the mutants. When the athd1-t1/athd1-t1 plants were crossed to wild-type plants, the mutant phenotype was corrected in the F1 hybrids, which correlated with the AtHD1 expression and reduction of histone H4 Lys12 acetylation. Microarray analysis was applied to determine genome-wide changes in transcriptional profiles in the athd1-t1 mutant. Approximately 6.7% (1,753) of the genes were differentially expressed in leaves between the wild-type (Ws) and the athd1-t1 mutant, whereas 4.8% (1,263) of the genes were up- or down-regulated in flower buds of the mutant. These affected genes were randomly distributed across five chromosomes of Arabidopsis and represented a wide range of biological functions. Chromatin immunoprecipitation assays indicated that the activation for a subset of genes was directly associated with changes in acetylation profiles. URI: http://handle.tamu.edu/1969.1/23 Files in this item: 1
TIAN-DISSERTATION.pdf (4.692Mb) -
McCleery, Robert Alan (Texas A&M University, September 30, 2004)[more][less]
Abstract: Development on the island of Key Largo, Florida, has isolated the Key Largo woodrat (KLWR, Neotoma floridana smalli) on approximately 850 ha of remaining habitat. The KLWR was listed as a federally endangered species in 1984, yet there is still only a limited amount of knowledge about its ecology and population dynamics. The objective of this study was to produce reliable information on KLWR ecology to aid in its management and recovery. Specifically, the study examined (1) the trend and status of the KLWR population, (2) KLWR habitat and nesting preferences, (3) the potential of a fatal disease on KLWR, (4) the movements and ranges of the KLWR, and (5) the viability of the KLWR population. I trapped on 60 (1-ha) grids from March to September 2002 and 10 (1-ha) grids in October 2002 and January, April, and July 2003. Additionally I radio-collared 17 KLWRs and tracked them from March to November 2002. I estimated the current population of KLWR to be between 26 and 106 individuals. I found KLWR selected young hammock (disturbed > 1971) over medium (disturbed between 1940-1971) and old hammock (disturbed < 1940). KLWRs selected garbage and rock piles in the young hammock for nesting sites. From the analysis of 64 raccoon (Procyon lotor) fecal samples, I have no evidence that the potentially fatal raccoon roundworm parasite (Baylisascaris procyonis) was present on Key Largo or had negative impact on the KLWR. Telemetry data indicated males have larger ranges than females. Females appear socially tolerant of one another and have significantly smaller ranges than males during the spring and summer breeding season. Results of a population viability analysis (PVA) using demographic parameters from previous studies and my study projected a high risk of extinction for the KLWR within the next 10 years. I recommend the creation of large continuous blocks of young (disturbed > 1971) habitat and the creation of nesting habitat for the KLWR within these areas. I would also advocate a large-scale captive breeding and augmentation of the population along with continued research on the limiting factors that are driving the KLWR toward extinction. URI: http://handle.tamu.edu/1969.1/24 Files in this item: 1
MCCLEERY-THESIS.pdf (424.0Kb) -
Bachhuber, Christoph Stephen (Texas A&M University, September 30, 2004)[more][less]
Abstract: The trade mechanisms joining the Mycenaean Aegean to the greater Levant have intrigued and eluded Bronze Age scholarship since the earliest discoveries of foreign objects in Mycenaean burials. In the past decade, topics of interregional trade in the eastern Mediterranean have enjoyed renewed discussions, inspired in no small part by the excavation of the Uluburun shipwreck. Data generated from the shipwreck is amounting to an extraordinary body of evidence for contact between the Aegean and the Near East. The proposed Mycenaean presence on board the Uluburun ship requires that the sum of evidence and hypotheses for trade between the two regions be re-examined. By attempting to demonstrate the role the Mycenaeans had performed on the last journey of the Uluburun ship, an important mechanism of trade may be revealed between the Aegean and Semitic worlds. URI: http://handle.tamu.edu/1969.1/25 Files in this item: 1
BACHHUBER-THESIS.pdf (1.488Mb) -
Palma Fanjul, Leonardo Manuel (Texas A&M University, September 30, 2004)[more][less]
Abstract: This thesis explores some new applications in power electronics for supercapacitors. This involves the design and development of dc-dc converters to interface the supercapacitor banks with the rest of the power electronic system. Two applications for supercapacitors are proposed and analyzed. The first application is aimed at high power applications such as motor drives. The proposed approach compensates the effect of voltage sags in the dc link of typical adjustable speed drives, thus reducing speed fluctuations in the motor and eliminating the possibility of nuisance tripping on the drive control board. The second approach presented in this thesis explores the use of supercapacitors to extend run-time for mobile devices such as laptop computers and hand held devices. Three possible approaches are explored: a) Supercapacitors connected directly across the battery; b) Battery-inductor-supercapacitor connection; and c) Supercapacitor, and battery connected via a DC-DC converter. Analytical models, simulation and experimental results on a typical laptop computer are presented. URI: http://handle.tamu.edu/1969.1/26 Files in this item: 1
PALMA-FANJUL-THESIS.pdf (5.842Mb) -
Mazingue-Desailly, Vincent Philippe Guillaume (Texas A&M University, September 30, 2004)[more][less]
Abstract: In the Permian Basin, strata of Leonardian age typically consist of interbedded carbonates and siliciclastics interpreted to be turbidite deposits. Happy Spraberry Field produces from a 100-foot thick carbonate section in the Lower Clear Fork Formation (Lower Leonardian) on the Eastern Shelf of the Midland Basin. Reservoir facies include oolitic- to-skeletal grainstones and packstones, rudstones and in situ Tubiphytes bindstones. Depositional environments vary from open marine reefs to shallow marine oolitic shoal mounds. Best reservoir rocks are found in the oolitic-skeletal packstones. Diagenesis occurred in several phases and includes (1) micritization, (2) stabilization of skeletal fragments, (3) recrystallization of lime mud, (4) intense and selective dissolution, (5) precipitation of four different stages of calcite cement, (6) mechanical compaction, (7) late formation of anhydrite and (8) saddle dolomite and (9) replacement by chalcedony. Oomoldic porosity is the dominant pore type in oolitic grainstones and packstones. Incomplete dissolution of some ooids left ring-shaped structures that indicate ooids were originally bi-mineralic. Bacterial sulfate reduction is suggested by the presence of (1) dissolved anhydrite, (2) saddle dolomite, (3) late-stage coarse-calcite cement and (4) small clusters of pyrite. Diagenetic overprinting on depositional porosity is clearly evident in all reservoir facies and is especially important in the less-cemented parts of the oolitic grainstones where partially-dissolved ooids were subjected to mechanical compaction resulting in "eggshell" remnants. Pore filling by late anhydrite is most extensive in zones where dissolution and compaction were intense. Finally, a porosity-permeability model was constructed to present variations in oolitic packstone- rudstone-bindstone reservoir rocks. The poroperm model could not be applied to oolitic grainstone intervals because no consistent trends in the spatial distribution of porosity and permeability were identified. Routine core analysis did not produce any reliable value of water saturation (Sw). An attempt to take advantage of wireline log data indicates that the saturation exponent (n) may be variable in this reservoir. URI: http://handle.tamu.edu/1969.1/27 Files in this item: 1
MAZINGUE-DESAILLY-THESIS.pdf (8.536Mb) -
Hudson, Jonathan Thomas (Texas A&M University, September 30, 2004)[more][less]
Abstract: The measurement of pain has had a growing importance in animals for both privately owned animals and those animals involved in clinical research. Lameness is considered to be 1 aspect of the pain experience. The ability of a veterinarian to assess lameness during a routine orthopedic examination can be difficult given the short amount of time in which the clinician can observe the animal, and the fact that the animal is in a stressful environment. Thus, the input of the owner concerning the animal's well-being over an extended time period may be extremely useful to the clinician in assessing the degree of lameness of the animal. It was the purpose of this study to establish an instrument that was both repeatable and valid in assessing the degree of lameness. The instrument used was a questionnaire containing 39 questions in a visual analog scale format. A force platform was used as the gold-standard for detecting mechanical lameness. Peak vertical, cranial-caudal, and their associated impulses were forces used to determine lameness, along with maximum slope in some cases. A test-retest measure of repeatability was conducted on a subset of 19 dogs that were confirmed to have less than a 10% change in vertical peak force. Nineteen of the 39 questions were found to be repeatable based on a Spearman rank correlation. These 19 questions were then used as predictor variables in several multiple regression models which predicted force plate measurements. The result was 3 different models each containing 7 independent variables that were thought to be valid representations of the forces measured (vertical peak, vertical impulse, and propulsion peak forces). Each reduced model was found to fit the data as well as the full model containing all 19 of the repeatable questions. The composite of 11 questions from the 3 different models was used to calculate a total score. This total score was found to be significantly correlated with force plate measurements. These 11 questions should be useful to a clinician in detecting the degree of lameness in the dog. URI: http://handle.tamu.edu/1969.1/28 Files in this item: 1
HUDSON-THESIS.pdf (411.1Kb) -
McDaniel, Brannon David (Texas A&M University, September 30, 2004)[more][less]
Abstract: There is a debate in the philosophy of time over the status of non-present entities. Do these things exist, and if so, what sorts of things are they? Recently, the debate has split into two groups, presentists and eternalists. Presentists hold that no past or future things exist now. Socrates does not now exist, though he did in the past; my future daughter does not now exist, though she may in the future. Ontologically, the present is distinct, serving to demarcate all that currently has existence. As far as the eternalist is concerned, all entities - whether past, present, or future - are equally real. If it was, is, or will be, it can be found in the eternalist picture of time. As such, there is no distinct present at which some entities exist while others do not; rather, everything enjoys the same ontological status. I will be concerned to offer an assessment of the presentist view. Common objections against presentism will be examined, amplified, and answered where appropriate. I will not examine the arguments in favor of the presentist view. Rather, I wish to describe why it is that the eternalist feels compelled to deny presentism. Ultimately, my goal will be to show that although presentism survives some of the current objections raised against it, it does not survive them all. Presentism is an interesting, but ultimately unsatisfactory view. There is a modified form of presentism (call it presentism*) that can meet the objections raised against the original position, and after noting some of the objections raised against presentism, I will sketch the outlines of presentism* in some detail. I intend to show that presentism* is able to retain what is most valuable about presentism, while also withstanding certain objections that the latter view could not. URI: http://handle.tamu.edu/1969.1/29 Files in this item: 1
MCDANIEL-THESIS.pdf (207.1Kb) -
Brown, Laura Ann (Texas A&M University, September 30, 2004)[more][less]
Abstract: The number of subsea production systems placed in deepwater locations in the Gulf of Mexico (GOM) has increased significantly in the last ten to fifteen years. Currently, API-RP2A (2000 a,b) designates the GOM as a low seismic zone, and thus does not require seismic effects to be considered during the design process. However, there have been a number of seismic events with Richter magnitudes between 3.0 and 4.9 that have occurred in this region. As a result, questions have been raised regarding the seismic performance of deepwater subsea systems. This thesis presents an analytical parametric study where a prototype subsea structure was selected based on a survey of subsea systems. The baseline analytical model consisted of a single casing embedded in soft clay soils, which supported a lumped mass at a cantilevered height above the soil. A number of the model characteristics were varied in the parametric study to simulate the structural response of a range of subsea structures. This thesis discusses the impact of API-RP2A Zone 1 and 2 design seismic demands for the performance of subsea structures. The results from the subsequent analyses show that the stresses and deflections produced by the Zone 1 and 2 peak ground accelerations fall within the allowable limits. URI: http://handle.tamu.edu/1969.1/30 Files in this item: 1
BROWN-THESIS.pdf (2.678Mb) -
Szakaly, Frank Joseph (Texas A&M University, September 30, 2004)[more][less]
Abstract: The purpose of this work is to investigate the implementation of nitride fuels containing little or no uranium in a fast-spectrum nuclear reactor to reduce the amount of plutonium and minor actinides in spent nuclear fuel destined for the Yucca Mountain Repository. A two tier recycling strategy is proposed. Thermal spectrum transmutation systems converted from the existing LWR fleet were modeled for the first tier, and the Japanese fast reactor MONJU was used for the fast-spectrum transmutation. The modeling was performed with the Monteburns code. Transmutation performance was investigated as well as delayed neutron fraction, heat generation rates, and radioactivity of the spent material in the short and long term for the different transmutation fuel cycles. A two-tier recycling strategy incorporating fast and thermal transmutation with uranium-free nitride fuel was shown to reduce the long-term heat generation rates and radioactivity of the spent nuclear fuel inventory. URI: http://handle.tamu.edu/1969.1/31 Files in this item: 1
SZAKALY-THESIS.pdf (1.164Mb) -
Ustun, Selen (Texas A&M University, September 30, 2004)[more][less]
Abstract: With the wide-spread adoption of hypermedia systems and the World Wide Web (WWW) in particular, these systems have evolved from simple systems with only textual content to those that incorporate a large content base, which consists of a wide variety of document types. Also, with the increase in the number of users, there has grown a need for these systems to be accessible to a wider range of users. Consequently, the growth of the systems along with the number and variety of users require new presentation and navigation mechanisms for a wider audience. One of the new presentation methods is the audio-only presentation of hypertext content and this research proposes a novel solution to this problem for complex and dynamic systems. The hypothesis is that the proposed Audio Browser is an efficient tool for presenting hypertext in audio format, which will prove to be useful for several applications including browsers for visually-impaired and remote users. The Audio Browser provides audio-only browsing of contents in a Petri-based hypertext system called Context-Aware Trellis (caT). It uses a combination of synthesized speech and pre-recorded speech to allow its user to listen to contents of documents, follow links, and get information about the navigation process. It also has mechanisms for navigating within documents in order to allow users to view contents more quickly. URI: http://handle.tamu.edu/1969.1/33 Files in this item: 1
USTUN-THESIS.pdf (782.3Kb)
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