Le présent mémoire traite du débat qui a eu lieu au cours des dix dernières années sur le caractère scientifique du marketing. Après une mise en situation sur l'évolution historique du marketing, l'analyse aborde cette discipline selon trois dimensions: la nature et le champ de recherche du marketing, l'évaluation des règles méthodologiques utilisées et sa capacité à formuler des théories solides sur les problèmes abordés dans son champ de recherche. Sur ce dernier point, l'analyse du corpus théorique repose sur un de ses axes de recherche à savoir, le marketing stratégique. On constatera que, suite à une rupture épistémologique importante, la discipline actuelle du marketing a affermi le caractère scientifique de sa démarche et que la construction d'un édifice théorique reconnu par la communauté scientifique et utile pour les praticiens est davantage entravé par l'éparpillement de ses efforts plutôt que par des failles dans ses méthodes de travail.

This thesis presents the results obtained so far in an investigation concerning viscous effects in incompressible flows over airfoils. These effects are taken into account by assuming the existence of a boundary layer which interacts with an external inviscid flow. Numerical methods for solving the inviscid and boundary-layer flows are briefly described. The main objective of the investigation is the development of an interaction technique between both regions of flow. The method chosen for the interaction is the so-called semi-inverse procedure. This procedure is derived from a perturbation analysis of the linearized versions of the governing equations. The resulting method is subjected to a stability analysis, which shows that it will break down when used in conjunction with separated-flow boundary-layer solvers. The semi-inverse procedure is tested on several airfoils, using an attached-flow boundary-layer solver. Numerical results show that the method is sufficiently accurate for engineering purposes in the low-to-medium range of angles of attack, but its applicability is questionable when there is a large separation region. Finally, recommendations are made regarding future work to overcome the limitations of the present technique. / Master of Science

This thesis explores the PMU placement problem, that is, the placement of a minimal number of Phase Measurement Units (PMUs) on the nodes of a power system graph such that the entire graph is observed. The NP-completeness of PMU placement for planar bipartite graphs is shown. PMU placement algorithms are developed for graphs of bounded tree width, such as trees and outer planar graphs. Graph decompositions are used to develop efficient algorithms that produce minimal PMU covers. These algorithms are developed, analyzed, and compared theoretically. Algorithm animations were used in the study to develop insight into the problem and to understand algorithm behavior. / Master of Science

Full size wood joist floors were built and their frequencies were measured. Double tee-beam floors were built and also cut from the full size floors and their frequencies were measured. The floor joists investigated included: solid sawn, parallel chord floor trusses, and composite I -joists. The first natural frequency of each tee-beam floor was predicted after measuring the deflection under imposed loading. A design procedure is presented to predict the fundamental frequency of wood joist floors from tabulated material properties / Master of Science

Use of traditional gate level test generation techniques is prohibitively expensive and time consuming for VLSI chips. High level approaches to test generation have been proposed to improve the efficiency of test generation, e.g., the Behavioral Test Generator developed at Virginia Tech generates test vectors from high level Behavioral VHDL descriptions. To validate the utility of these test vectors, it needs to be established that they provide adequate coverage at the gate level. This thesis shows that test vectors obtained from the Behavioral Test Generator provide adequate coverage for the equivalent gate level circuit. A system that was developed to effectively evaluate the test vectors is presented. The implementation of Heuristic Test Generator to improve the coverage of the Behavioral Test Generator is explained. / Master of Science

Steady state and transient maneuver problems for a high performance fighter aircraft with and without thrust vectoring are investigated. The steady state aspect of these studies determines control combinations with and without thrust vectoring which optimize selected level-flight point performance criteria including minimum speed, maximum instantaneous range, and maximum sustained turn rate. The transient maneuvers are initiated from straight and level flight and include a longitudinal pitch-up to a desired fuselage pointing angle and a lateral-directional transition (wind-up) to a desired steady level turn rate. For the transient maneuvers, a full six-degree-of-freedom model of the aircraft is used with three conventional aerodynamic controls, throttle control and pitch and yaw thrust vectoring control. Each of the control time histories are parameterized so as to include both the rate and range limits of the controls. A nonlinear programming algorithm is used to determine the control parameter values which yield the minimum time to execute the prescribed maneuvers. Results indicate that thrust vectoring does not significantly change the steady state behavior in the scenarios investigated. However, flight times for the transient maneuvers are found to be reduced by up to 28%. The greatest effect of thrust vectoring occurs at low Mach number. / Master of Science

The existence of strange attractors for dynamical systems with three variables is discussed. The structure and dimensionality of these attractors are observed with computer packages that have three dimensional viewing capabilities. The importance of visualizing these attractors is discussed. Some new visual tools developed for this purpose are introduced. These tools are then used to observe strange attractors for the Lorenz, Rossler, and Silnikov systems of equations. The solutions to the Lorenz equations are followed in detail for certain parameter values. Figures of the attractors are included to attempt to show the benefits of the new tools. There is an accompanying video that contains visualizations of the strange attractors to illustrate the three dimensional capability of the new tools. A comparison is made of current methods used to view attractors with the new tools. It is concluded that the three dimensional visualization of the structures is very important and beneficial for learning about the attractors. / Master of Science

The goal of this thesis is to develop a set of standards for use in calibrating heat flux gages at elevated temperatures in a radiant heat transfer environment by comparing several "trial" standards. Ideally, the same incident heat flux is derived from each standard when exposed to the same heat source. Three heat flux standards are proposed and evaluated. The standards are based on temperature measurements, material properties, and electrical measurements. The theory and design of each standard are described, as are the calibration procedures used. For experimental comparisons, two standards are simultaneously exposed to heat fluxes of up to 220 W/cm² by placing one standard on each side of a graphite flat plate heater. The temperature measurement based standard derives incident heat flux from the temperature of a blackbody heat source and the Stefan-Boltzmann law. The heat flux gage employed in this standard is a water-cooled Gardon gage. This standard does not operate at high temperatures. The calibration of this standard produced highly repeatable results. / Master of Science

A common practice in reliability studies is to model the failure process of systems with a single distribution. This thesis investigates this practice for modeling the failure distribution of systems subject to a finite number of independent failure mechanisms experiencing age acceleration. The models of systems during component age acceleration and the models of the residual lives of systems surviving component age acceleration are investigated. The fit of a single distribution to represent the failure time distribution of such systems is investigated for both modeling environments. More importantly, the assumption of time scale compression, and the resulting effect of parameter stability in the single Weibull and lognormal distribution models, is investigated for systems experiencing both differential component age acceleration and uniform component age acceleration. The analysis in this thesis shows that single distribution models are biased when modeling systems with non-identical components. Also, parameter stability in the single distribution models does not occur when the components experience differential age acceleration. The bias in the models leads systems with uniform age acceleration to experience parameter instability because of data dependency due to the bias. / Master of Science

Plant β-glucosidases (β-D-glucoside glucohydrolases, E.C. 3.2.1.21) are known to function in defense in cyanogenic systems, and may also function in the metabolism of phytohormone glucosides and glucosides of other secondary plant products. Maize (Zea mays L.) β-glucosidase is a homodimer of 60 KD monomers and occurs in the plastid. Numerous glycosides were tested as substrates and K_m's and V_m's were determined. Various compounds were also tested as inhibitors and K_i's and/or K_i’ 's were estimated. 4- methylumbelliferyl-β-D-glucoside was the best substrate (K_m=0.14 mM) for which kinetic data were obtained. Monosaccharides were poor inhibitors. The best competitive inhibitors were D-gluconic acid lactone, dhurrin, and 2,4- dihydroxy-7-methoxy-2H-1, 4-benzoxazin-3(4H)-one (DIMBOA) (K_i's< 1 mM). The enzyme had broad substrate specificity and could cleave many glycosides with hydrophobic aglycones. One major substrate, the hydroxamic acid 2,4-dihydroxy-7- methoxy-1, 4-benzoxazin-3-one-8-D-glucopyranoside (DIMBOA-glc), was found in methanolic maize extracts. Increasing DIMBOA levels are associated with increasing resistance to several pests. The highest levels of enzyme activity and hydroxamic acids along K55 and H95 shoot length were found near the node. Tissue distribution of hydroxamic acids and β-glucosidase activity was also determined. In K55, both were found in the stele of the mesocotyl, the young leaves, and associated with the vascular bundles of the coleoptile. A major function of the enzyme is to mediate insect and pathogen resistance via the release of the toxic aglycone DIMBOA. / Master of Science