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La problématique centrale de cette thèse est l'aliénation de l'homme moderne; son objectif: souligner la pertinence d'une éthique humaniste. Elle comporte quatre parties essentielles. La première énonce les concepts de base de l'éthique humaniste "vitaliste". La seconde situe cette éthique "biophile" par rapport aux tendances classiques et modernes pertinentes. La troisième revendique une vision "réaliste" du monde, grâce à une approche pluridisciplinaire, permettant une perception non dichotomique de celui-là. La dernière partie examine le statut philosophique de la réflexion humaniste dans la conjoncture actuelle, la confronte avec d'autres courants et analyse objectivement ses chances de réussite. La conclusion énonce le résultat atteint: l'humanisme semble être la seule orientation pouvant réhabiliter la philosophie et responsabiliser le philosophe, en leur prêtant un rôle décisif dans la destinée humaine.

In the past, various approaches to the high performance numerical computing problem have been explored. Recently, researchers have begun to explore the possibilities of using Field Programmable Gate Arrays (FPGAs) to solve numerically intensive problems. FPGAs offer the possibility of customization to any given application, while not sacrificing applicability to a wide problem domain. Further, the implementation of data flow graphs directly in silicon makes FPGAs very attractive for these types of problems. Unfortunately, current FPGAs suffer from a number of inadequacies with respect to the task. They have lower transistor densities than ASIC solutions, and hence less potential computational power per unit area. Routing overhead generally makes an FPGA solution slower than an ASIC design. Bit-oriented computational units make them unnecessarily inefficient for implementing tasks that are generally word-oriented. And finally, in large volumes, FPGAs tend to be more expensive per unit due to their lower transistor density. To combat these problems, researchers are now exploiting the unique advantage that FPGAs exhibit over ASICs: reconfigurability. By customizing the FPGA to the task at hand, as the application executes, it is hoped that the cost-performance product of an FPGA system can be shown to be a better solution than a system implemented by a collection of custom ASICs. Such a system is called a Configurable Computing Machine (CCM). Many aspects of the design of the FPGAs available today hinder the exploration of this field. This thesis addresses many of these problems and presents the embodiment of those solutions in the Colt CCM. By offering word grain reconfiguration and the ability to partially reconfigure at computational element resolution, the Colt can offer higher effective utilization over traditional FPGAs. Further, the majority of the pins of the Colt can be used for both normal I/O and for chip reconfiguration. This provides higher reconfiguration bandwidth contrasted with the low percentage of pins used for reconfiguration of FPGAs. Finally, Colt uses a distributed reconfiguration mechanism called Wormhole Run-Time Reconfiguration (RTR) that allows multiple data ports to simultaneously program different sections of the chip independently. Used as the primary example of Wormhole RTR in the patent application, Colt is the first system to employ this computing paradigm. / Ph. D.

Project Head Start, a federal child development program for low-income families,serves both the mother and her children. Previous studies have emphasized Head Start's influence on the child in terms of cognitive gains, social development, and social-emotional development. A continuing problem to understanding the extent of Head Start impact on families is the absence of reliable information about Head Start's influence on the mother and how that influence transfers to the family as they work toward self-sufficiency. This study investigated two issues: (1) the experiences, perceptions, and levels of involvement of mothers who participate in Head Start social services, and (2) how these mothers describe their benefits and relate these benefits to family experiences such as increased problem-solving, coping, and parenting skills. A multiple case study methodology was selected because of its flexibility to allow the researcher to follow new leads that emerged. Participants met three criteria: (1) enrollment in a Head Start social services program for at least six months, (2) willingness to sign an informed consent form and participate in three 90-minute interviews, and (3) having at least one child currently enrolled in Head Start. A participant pool of 17 African American mothers was constituted from parents enrolled in one of three Head Start programs in the Washington, D.C. area, and a sample of eight mothers was then selected for in-depth study. Each mother was interviewed three times, and data were drawn from these interviews. The findings of this study suggest that participation in Head Start social services may have important benefits for mothers and their children. Mothers had developed increased coping and problem-solving skills as well as increased leadership and organizational skills. The findings also suggest that participation in parent group meetings had an empowering influence that prompted several mothers to become involved in certain community activities and in their children's education. / Ph. D.

We investigate the dynamics of a three-state stochastic lattice gas, consisting of holes and two oppositely "charged" species of particles, under the influence of an "electric" field, at zero total charge. Interacting only through an excluded volume constraint, particles can hop to nearest neighbor empty sites, but particle-particle exchange between oppositely charged particles is also allowed on a separate time scale. Controlled by this relative time scale, particle density and drive, the system orders into a charge-segregated state. Using a combination of Monte Carlo simulations and continuum field theory techniques, we study the order of these transitions and map out the steady state phase diagram of the system. On a single sheet of transitions, a line of multicritical points is found, separating the first order and continuous transitions. Furthermore, we study the steady-state structure factors in the disordered phase where homogeneous configurations are stable against small harmonic perturbations. The average structure factors show a discontinuity singularity at the origin which in real space predicts an intricate crossover between power laws of different kinds. We also seek for generic statistical properties of these quantities. The probability distributions of the structure factors are universal asymmetric exponential distributions. This research was supported in part by grants from the National Science Foundation through the Division of Materials Research. / Ph. D.

For receivers using the Global Positioning System (GPS), it is standard procedure to treat the receiver clock bias from GPS time as an unknown. This requires four range measurements to the satellites in order to solve for three dimensional position and clock offset. If the receiver clock could be synchronized with GPS time, the extra range measurement would not be necessary. To achieve this synchronization, a stable frequency reference must be incorporated into the GPS user set. This concept is known as clock aiding or clock augmentation of GPS receivers. Clock augmentation increases the availability of the navigation function because only three GPS satellites are required. Also, it is shown that clock augmentation improves vertical accuracy by reducing the vertical dilution of precision (VDOP), which is a unitless multiplier that translates range measurement error into vertical position error. This improvement in vertical accuracy is particularly beneficial for applications involving final approach and landing of aircraft using GPS, because GPS typically provides better horizontal accuracy than vertical accuracy. The benefits of atomic clock augmentation are limited by factors that cause a loss of synchronization either between the receiver and GPS time, or between ground station and airborne receivers processing GPS data in differential mode (DGPS). Among the error sources that cause a clock offset are antenna rotation, hardware drifts due to temperature variations, and relativistic effects for GPS receivers on moving platforms. Antenna rotation and temperature effects are addressed and supported by experimental data. It is shown that two particular relativity terms thought to be missing from GPS receiver algorithms are not evident in data collected during a flight test experiment. Upon addressing the error sources, the dissertation concludes with analysis of DGPS data collected during a flight test at the Federal Aviation Administration (FAA) Tech Center in Atlantic City, during which external rubidium oscillators were used by airborne (Boeing 757-B) and ground station GPS receivers. A new method of clock modeling is introduced, and this clock model is used to demonstrate the improvement in vertical accuracy, as well as three-satellite navigation. / Ph. D.

The purpose of this study was to determine factors impeding rapid completion of the dissertation. The population studied was 1990-95 graduates of the Department of Leadership and Policy Studies (formerly the Division of Administrative and Educational Services) of the College of Education at Virginia Tech. Two hundred ninety-four surveys were mailed. The total of potential eligible responses was 263. The total of returned, usable surveys was 192, for a return rate of 73 percent. There was one primary research question, with four sub-questions: Are there any student characteristics that can be used as flags for potential problems with completion of the dissertation? 1.Are there any personal characteristics associated with time to completion of the dissertation? 2.Are there any student situational conditions associated with time to completion of the dissertation? 3.Are there any research capabilities associated with time to completion of the dissertation? 4.Are there any aspects of committee dynamics associated with time to completion of the dissertation? Two statistical procedures were followed: linear regression analysis to determine predictors of time to completion of the dissertation, and Chi-square analysis of the independent variables against speed of completion to determine which variables are most closely associated with relative time on the dissertation. Regression analysis showed four significant predictors of time to complete the dissertation: how dissertation writing time was scheduled, computer skills at the beginning of the dissertation, perceived difficulties caused by job demands, and changes in advisor or committee membership. These predictors had a total r2 of 189. Chi-square analysis showed that the following variables were significantly associated with time to completion of the dissertation: perceived difficulties caused by lack of access to resources; whether the subject changed full-time employment or took a new full-time position; whether the subject was a member of the Counselor Education Program; emotional support from the subject's employer; perceived difficulties caused by job demands; whether subjects were on-campus or off-campus, and relative distance from resources; how writing of the dissertation was scheduled; and whether the subject was employed full-time during the dissertation. / Ph. D.

The applicability of restricted maximum likelihood (REML) in genetic analyses of categorical data was evaluated using simulation and field data. Four genetic models were used to simulate underlying phenotypic variates, which were derived as the sum of additive genetic and environmental effects (Model 1A and 1B) or additive genetic and permanent and temporary environmental effects (Model 2A and 2B). Fifty-eight replicates were simulated, each of which contained 5000 ewes by 500 sires and 5000 dams and with up to five records per ewe. The usual transformation of heritability estimated on the categorical scale to the normal scale for fertility and litter size performed better for a simple animal model than for a repeatability model. Genetic correlation estimates between the two categorical traits for Model 1B and 2B were .49 ± .01 and .48 ± .04, respectively, and were close to the expected value of .50. However, permanent and temporary environmental correlations whose input values were each .50 were underestimated with estimates of .41 ± .05 and .26 ± .03, respectively for Model 2B, and .33 ± .02 for the temporary environmental correlation for Model 1B. Bivariate genetic analyses of litter size with growth and fleece traits were carried out by REML for the data of Suffolk, Targhee and Polypay. Direct heritabilities for most growth traits in all the breeds were low (<.20). Maternal genetic and maternal permanent environmental effects were important for all body weights except for the weaning weight at 120 d for Polypay sheep. Estimates of heritability and permanent environmental effects for litter size for these breeds ranged from .09 to .12 and .00 to .05, respectively. Heritabilities for grease fleece weight and fiber diameter were high for Targhee and Polypay sheep. Direct genetic correlations between growth and litter size were favorable for Suffolk and Targhee but weak for Polypay sheep. Genetic correlations between maternal effects for growth and direct effects for litter size for the breeds were generally small. Within-trait maternal-direct genetic correlations for growth in the breeds were variable and generally negative. Direct genetic correlations of litter size with grease fleece weight and fiber diameter were variable across the breeds. / Ph. D.

With the increasing use of lightweight frame-type structures that span long distances, there is a need for a method to determine the probability that a structure having random initial geometric imperfections will become unstable at a load less than a specified fraction of the perfect critical load. The overall objective of this dissertation is to present such a method for frame-type structures that become unstable at limit points. The overall objective may be broken into three parts. The first part concerns the development of a three-dimensional total Lagrangian beam finite element that is used to determine the critical load for the structure. The second part deals with a least squares method for modeling the random initial imperfections using the mo de shapes from a linear buckling analysis, and a specified maximum allowable magnitude for the imperfection at any imperfect node in the structure. The third part deals with the calculation of the probability of failure using a combined response surface/ first-order second-moment method. Numerical results are presented for two example problems, and indicate that the proposed method is reasonably accurate. Several problems with the proposed method were noted during the course of this work and are discussed in the final chapter. / Ph. D.