The polyhydroxy character of lignocellulosics and their natural abundance make them good candidates for the manufacture of polyurethanes. The cure characteristics of hydroxypropyl-cellulose and hydroxypropyl lignin (HPC and HPL, respectively) with polymeric methylene diphenyl diisocyanate (MDI) was studied via dynamic mechanical thermal analysis (DMTA). HPC/MDI and HPL/MDI resins flow at 30°C and proceed to cure at 50°C. The latter has excellent thermal stability over the former. Crosslinking of HPL and HPC with MDI follow an nth order kinetics, with an order of reaction of 2 and an apparent activation energy in the range of 12.9 kcal/mol - 14.7 kcal/mol. The rate of cure with time is higher in HPL-based polymers than HPC-based ones at the initial stage of cure; the difference vanishes at later stages. This demonstrates that the hydroxyl groups in HPC are less accessible to the NCO groups, and that cure rate might be dependent on diffusion limitations at later stages. Degree of cure, under all cure schedules, follows a parallel trend, and has to do with the fact that the hydroxyl groups of HPC are less accessible to isocyanate. Both HPL and HPC react with MDI at a reduced rate in comparison to a synthetic polyol: caprolactone triol. Time-glass transition temperature superposition was used to calculate times to vitrification of the HPL-based polymers, and is presented in a TTT cure diagram. This bio-based polymer displays the s-shaped vitrification pattern characteristics of thermosets. A similar approach did not work with HPC-based polymers. HPC- and HPL-based polymers did not display damping transitions, in isothermal cure, typical of gelation and vitrification. As the isocyanate to hydroxyl ratio (NCO:OH) increased, the glass transition temperature of the polymers increased, and the transition amplitude and width decreased and increased, respectively. In practical terms, this study illustrates that it is advantageous to use a) to use high isocyanate to hydroxyl ratios in order to produce polyurethanes which retain desirable damping behavior over a wider range of temperature. b) to use HPC/MDI resins in those situations where retention of stiffness at temperatures below 230° is required. c) to use HPL where rapid cure is desired. The study also reveals that the relative reactivity of water, HPL and HPC with isocyanate takes the form water > HPL > HPC. / Master of Science

Defects formed in solid rocket propellant during manufacturing, transportation, storage, and assembly can lead to alterations in the thrust time profiles and possibly catastrophic failure of the entire rocket. In order to determine the effects of temperature, loading rate, and thickness on this particulate composite, tests were conducted at three temperatures and two loading rates. Both uncracked and edge cracked "biaxial" specimens were produced from solid rocket propellant. The stress relaxation modulus and stress-strain data were obtained from load curves formed during "biaxial" tension tests. Near crack tip displacements and strains were calculated from photographs taken of a surface grating on the pre-cracked specimens during crack propagation. The effect of thickness, temperature, and loading rate on the stress intensity factor was also studied. Finally, by applying continuum theory the displacement singularity was determined at different stages of crack growth. From the stress strain data, it was found that temperature had a greater influence on behavior than loading rate over the ranges studied. The crack growth in the composite material consists of a series of crack opening, crack blunting, and crack growth/resharpening stages which are highly nonlinear. However, the thick specimen at low temperature did not follow this crack growth mechanism. At -65°F the thick specimen developed transverse constraints which caused a brittle fracture to occur when the specimen was loaded. Determination of the displacement singularity order for the sharp cracks was found to be consistent with the theoretical results predicted by Benthem. / Master of Science

Zinc gallate and Mn²⁺-activated zinc gallate were identified as potential low-voltage cathodoluminescent phosphors for use in vacuum fluorescent displays. The stability of these oxide phosphors in high-vacuum and absence of corrosive gas emission under electron bombardment, offer advantages over commonly used sulfide phosphors. A low-voltage cathodoluminescence spectrophotometer was developed for phosphor characterization. Sample brightness was measured as a function of anode voltage (10-300 VDC). The effects of activator concentration, phosphor layer thickness, deposition process, and internal pressure were examined. From photoluminescence measurements, absorption and emission centers were identified, the role of composition in the luminescence process explained, and host-to-activator, non-radiative energy transfer identified for ZnGa₂0₄:Mn²⁺. Samples of the general composition Zn_1-xMn_xGa₂O₄, with x ranging from 0 to 0.03, were synthesized by solid-state reaction techniques using oxide precursors fired in air, followed by reduction firing in 98%N₂, 2%H₂. The phase-pure ZnGa₂O₄ spinel structure of all the compositions was characterized by X-ray diffraction. / Master of Science

A special wafer bonding method called the Silicon Direct Bonding technique is used to study the bonding of unipolar (n-type, <100> oriented) silicon wafers. The primary objective of this thesis project is to find an optimum surface preparation technique for subsequent silicon wafer bonding. Wafer cleaning and treatment methods are investigated to understand the correlation between a high quality wafer surface and the resulting high quality electrical conduction at the interface. Accordingly, in this project, a preference for hydrophobic (less polar Si-OH surface) wafers is given to ensure a minimized amount of oxide layer on the surface. Several key factors that govern the quality of the wafer surfaces, such as the degree of hydrophobicity, HF etching time, composition of HF etching solution and Dr water rinse, are examined with ellipsometric and XPS measurements. An HF etching followed by a sputter etching has been selected to pre-treat the wafer surfaces for bonding. A maximum allowable air exposure time (35 second) is also found which would allow bonding without significant re-growth of the oxide layer. Bonding is performed under vacuum with a special mechanical fixture and the resulting structures from a subsequent heat treatment process are examined with crack propagation testing. Bond strength after annealing is sufficient to withstand a pull test, however, with a 3 point bend testing, the crack propagated horizontally at the interface. / Master of Science

A homogeneous population of robots described as an Army-ant swarm is to be realized for material transportation. Robots envisioned in the Army-ant scenario are relatively small, independent autonomous mobile robots that can cooperatively carry palletized loads. In this thesis, the agents are treated as a self-organizing system of moving points. This characteristic makes the Army-ant swarm a modular, adaptive, and dynamic system. Several algorithms for the spatial self-organization of the robots are given. Self-organizing agents can arrange themselves geometrically in two- and three-dimensional space using only local information about teammates. The method is a distributed one: each agent uses only the information obtained by its own sensors. Algorithms are based on feasible assumptions. It is also shown possible to divide such a population into different groups around goals by communicating minimal data. Data transfer has a broadcast characteristic. Behavioral self-organization in the Army-ant scenario is also investigated. Activation and inhibition relations between robots determine the behavior (position in a behavioral space) of the agents, while in spatial self-organization force fields are in effect. Several problems which may be encountered and the solution to some of these problems are outlined. Methods for communication and cooperative decision systems — such as coupled van der Pol oscillators — in finding and carrying the pallets are proposed. Sensors and communication systems that may be used in the Army-ant scenario are also briefly discussed. / Master of Science

Historians have traditionally viewed the controversy between the ancients and moderns within the narrow scope of the title. However, in the seventeenth century the issue of learning and knowledge was a significant issue in the controversy. By 1600, the humanists were well established in the universities and applied the classical world view as an ideal for life. The humanists' emphasis on the classic world view along with their compatibility with scientific investigation strengthened their influence in university learning, which lasted until the mid-seventeenth century. From the 1640s onward, several groups explicitly criticized the prominence of humanist ideals in the universities. The sense of these criticisms and the humanists' responses indicate that the issue was not simply ancient against modern, but one world view against another. During the Civil War and Interregnum, radical puritans censured the use of human learning in the universities and alerted the humanists to future attacks on their domination of learning. After the Restoration of Charles II in 1660, the new philosophy emerged as a strong force in the quest for knowledge. The new philosophers' vitality encouraged them to denounce human learning and propose the subordination of human learning to the ever-advancing new philosophy. As a result, the humanists staunchly defended traditional learning and their standing in the universities. This thesis re-examines the ancient and modern controversy during the seventeenth century and views it as a continuing debate over which knowledge would best benefit English society. In this way, historians can better understand the motivations for humanists to the reactions of the humanists to the scientists. / Master of Arts

The effect of cooling rate and stacking sequence on fatigue behavior was analyzed for notched quasi-isotropic APC-2 laminates. The fatigue behavior of fast (475° F/min) and slow (1° F/min) cooled specimens of the following two layups was studied: Layup A of (-45/0/45/90), and Layup B of (45/90/-45/0),. All specimens were subjected to a load controlled, Tension - Tension fatigue loading with a stress ratio R = 0.1 at a frequency of 5 Hz. Parameters such as strain, temperature rise across the notch and number of cycles fatigued were continuously monitored during the fatigue tests. Damage was monitored by the reduction in modulus, penetrant enhanced X-ray radiography, and Scanning Acoustic Microscopy (SAM). Post failure analysis of the specimens was carried out by Scanning Electron Microscopy (SEM). A quasi-3D Finite Element Analysis was performed to compare the differences in the interlaminar stresses arising around the notch in the specimens of the two layups under study. The ultimate static strengths did not show any appreciable dependence on either cooling rate or stacking sequence. The maximum load in the fatigue cycle was selected as a fraction of the ultimate notched static tensile strength in each case. The fatigue lives showed appreciable difference between the two cooling rates in layup A when tested at the lower load levels. The fatigue behavior was vastly different between the two cooling rates for specimens of layup B. Also, specimens of layup B, both fast and slow cooled, had longer lives than their counterparts from layup A. A model, based on a constant strain-to-failure criterion, was developed for life prediction and the predicted lives are in good agreement with the experimental values. Fast cooled specimens of layup A showed a gradual degradation in the modulus till failure while slow cooled specimens of the same layup showed a more drastic reduction as they approached failure. No such distinguished behavior was observed in the specimens of layup B. Scanning Electron Micrographs of the fast cooled specimens indicate better fiber/matrix bonding conditions and more matrix plasticity as compared to the slow cooled specimens. A rotated stacking sequence technique was used for the calculation of the interlaminar stresses around the notch. No single stress seems to control failure but it is likely that failure occurs by the interaction of the different stresses since a three-dimensional stress state exists at the notch. Based on this reasoning, effective stresses were calculated at all those interfaces where one of the interlaminar (normal or shear) stresses has a maximum value. A comparison of the effective stresses calculated showed the layup A to be 1.7 times more prone to delamination than layup B. Damage analysis of the fatigued specimens by X-ray radiography and Scanning Acoustic Microscopy shows the specimens of layup A to be dominated by delaminations as compared to those of layup B. The interfaces predicted to be critical by FEA agreed well with the experimental observations, in general. / Master of Science

Three different time-dependent optimal reliability design models with a series-parallel system are formulated. An efficient heuristic procedure for each problem is elucidated, and the results are described. The redundancy optimization problem using the time-dependent reliability function is solved so that the system reliability exceeds the target reliability over a time period at a minimum cost. The number of the redundancies in the system is obtained to ensure that the target reliability can be matched with the system reliability, which is time-dependent, as closely as possible without violating a cost constraints. The system configuration is optimized so that the system reliability matches the target reliability as much as possible while maintaining the system reliability at certain level under a cost constraint. Various applications of simple and efficient heuristic algorithms for solving time-dependent redundancy optimization problems are also provided. These techniques are used and tested in systems containing a substantial number of subsystems. The heuristic approaches appear more successful than other optimization techniques in solving these problems, and can be applied to any constrained redundancy optimization problems without any tedious formulation and computation. / Master of Science

Thèse en cotutelle entre l'Université Laval, Québec, Canada et l'Université catholique de Louvain, Louvain-la-Neuve, Belgique / Notre thèse se donne pour tâche d'expliquer la critique, par Jonas, du rationalisme moderne à travers l'unité articulée de différentes phases de son travail intellectuel. Plaidant en faveur d'une rationalité dialectique, notre auteur a appris à critiquer Descartes à partir de Husserl et de Heidegger. Dans un premier temps, nous montrons la préfiguration de cette critique chez le jeune Jonas. Cette critique des Modernes est souterraine dans la démarche de Jonas qui rend compte de la dogmatisation de la dialectique paulinienne de la volonté par Augustin et applique l'analytique heideggérienne à la compréhension de l'existence gnostique. Sur le plan ontologique, la dialectique du vécu originaire, en tant que volo me velle, est brisée par l'objectivation qui la transforme en cogito (ou credo) me velle, puis en cogito me cogitare, à cause de la tendance de soi à la déchéance. Dans le mythe gnostique, la dialectique historique de la chute et de la délivrance s'accompagne de la dialectique de l'impuissance et de la puissance du soi comme mélange du divin et du monde. Cette double dialectique trouve également un vibrant écho dans la métaphysique d'Origène et dans celle de Plotin. Dans un deuxième temps, nous examinons la configuration de cette critique du rationalisme moderne à partir des Lettres d'apprentissage jusqu'aux recherches de New York. Jonas remet en question le dualisme cartésien qui fend la dialectique du réel, entraîne la science vers la géométrisation intégrale de la nature et conduit la théorie de l'organisme à l'impasse. En réalisant un saut décisif dans la compréhension de l'individualité et du conatus, Spinoza rétablit la dialectique de la vie et révolutionne le concept traditionnel de substance, au profit de la corrélation psychophysique à travers l'échelle infinie de l'individualité. Pour sa part, Leibniz propose la dialectique d'un ego perceptif et appétitif, selon laquelle chaque individu est une monade et la nature forme une échelle infinie de monades. Mais cette dialectique de la vie organique est mieux élucidée par Whitehead qui apparait, aux yeux de Jonas, comme la critique satisfaisante du rationalisme moderne. En troisième lieu, nous abordons la transfiguration de cette critique dans l'anthropologie et la philosophie de la nature de Jonas. Cette critique a donné une autre envergure à la thématique mobilisée dans les travaux de jeunesse et surtout aux concepts de nature et d'humain. D'une part, en formulant le projet d'un monisme intégral, Jonas examine la finalité spécifique à l'organisme et aux artefacts, en vue d'élaborer une phénoménologie du témoignage de la nature qui admet la dialectique entre la vie et le milieu et élargit son concept de liberté à toute l'échelle du vivant. D'autre part, l'anthropologie de l'homo pictor, mieux, de l'homo symbolicus met en évidence la constitution dialectique de la médiateté humaine d'où surgissent la métaphysique, la religion, l'éthique et le droit.

This dissertation concerns the synthesis of ultra-fine titania particles starting with titanium ethoxide as a precursor. The particle size and morphology was controlled using polymeric stabilizers which imparted in-situ steric stability during the particle growth. An attempt was made to elucidate the factors which govern the particle size and morphology by studying the solvent-polymer-particle surface interactions. For this purpose, the effects of polymer concentration, molecular weight, structure, and the solvent system were studied. Titanium dioxide particles were synthesized via the hydrolysis of tetraethylorthotitanate in ethanol in the presence of hydroxypropylcellulose, HPC, as an in-situ steric stabilizer. The effects of HPC concentration, molecular weight, and water concentration on TiO₂ particle size and morphology were determined along with the effect of HPC on the particle growth rate. The particle size decreased by ten-fold upon the addition of HPC at high water concentrations due to the combined effects of increased HPC adsorption and increased nucleation rates. Water was shown to segregate at the TiO₂ surface and to promote HPC adsorption through enhanced hydrogen bonding. Mean particle diameters as small as 70 nm were obtained. The particles grown with HPC had surface morphologies that suggest the particles aggregated by flocculating initially into a secondary energy minimum followed by condensation reactions that welded the aggregates together. Particle growth rate studies show that HPC can undergo an alcoholysis reaction with tetraethylorthotitanate when mixed in the absence of water. Electrophoresis measurements show the absence of any significant electrostatic stabilization effects under conditions giving the smallest particle sizes. In another related study, titanium dioxide particles were synthesized via the hydrolysis of tetraethylorthotitanate, TEOT, in mixtures of ethanol and tetrahydrofuran, THF, in the presence of hydroxypropylcellulose, HPC, as an in-situ steric stabilizer. The effects of THF concentration on the particle size and growth rate were studied at fixed concentrations of water, TEOT, and HPC. Particles grown in the absence of HPC were highly aggregated while the size of the primary particles comprising the aggregates decreased with THF concentration. The particle growth rate increased significantly with THF concentration due to the decrease in the hydrogen bonding capability of the solvent system which increased the activity of the water. In the presence of HPC, both the growth rate and the particle size decreased dramatically with increasing THF concentration. The decrease in the solubility of HPC with THF concentration presumably enhanced HPC adsorption at the particle surface which led to increased colloid stabilization. Particles as small as 50 nm in diameter were obtained when the particles were grown in 1:1 THF:ethanol volume mixtures. In an attempt to study the effect of polymer structure and structure on particle size and morphology, a low molecular weight (Mw = 2000) polymer with poly(propylene oxide) back-bone was end functionalized to make it a suitable in-situ steric stabilizer. Effects of polymer concentration, functionality at chain-ends, and molecular weight on the particle size were studied. The polymer functionalized at both ends imparted in-situ steric stability at C_p > 8 g/l. Particles having mean size of 0.2 microns were obtained at C_p = 16 g/l. This work demonstrated that end-functionalized low molecular weight polymers offer a novel way to synthesize in-situ steric stabilizers. An application of the synthesized ultra-fine titania particles was studied. For this purpose, novel thin films of ultra-fine titanium dioxide particles dispersed in a matrix of hydroxypropylcellulose polymer were made on quartz and silicon substrates. The TiO₂/HPC composite films were transparent in the visible region and completely blocked ultraviolet radiation at 300 nm. These films were crack-free and uniform in composition and thickness. Transparent films of amorphous TiO₂ were made by burning out the HPC at 500°C. These films were highly uniform and had no macroscopic cracks. X-ray diffraction revealed a transition to the anatase form upon sintering at 600°C. A film sintered at 700°C had a porosity of 38%. The crystalline films remained transparent until they densified at 800°C. / Ph. D.