In SiC/Ti composites, the physical-chemical behaviour at the interface at fabrication temperatures, is important. Ideally, only a thin bonding film is desired after fabrication with zero growth during the actual service conditions. In this study, two mechanisms which lower the growth rate of silicides about the SiC/Ti interface were investigated. Planar composites that incorporated Mo₅Si₃ or Al films, were compared with the uncoated SiC/Ti standards to investigate the "barrier" and "rejection" mechanisms respectively. Also, SiC/Ti₃Al/Ti composites were used to study the effectiveness of the two mechanisms combined, with the Ti₃Al acting as a barrier and with Ti(Al) retarding the reaction by rejection. Samples were vacuum-annealed at 875°C for various times and examined by X-ray diffraction techniques. The results from the SiC/Al/Ti and SiC/Ti₃Al/Ti composites indicated that silicide formation would be retarded in the presence of an Al saturated Ti matrix. Also, the formation of a Ti₃Al layer near the SiC/Ti interface serves as an effective barrier to diffusion of Si atoms. In the SiC/Mo₅Si₃/Ti composites however, the dissociation of the Mo₅Si₃ phase formed during sample preparation results in additional silicide formation at the interfaces. If stoichiometric Mo₅Si₃ films are sputter-deposited, they could be used as effective barrier. The inter-diffusion of Al films, sputter deposited on Ti substrates, at elevated temperatures have been analyzed. Samples were vacuum annealed at 635°C and 900°C for various times and then examined using X-ray diffraction. In each case, intensity bands from alpha-Ti and diffraction lines from an intermetallic compound have been observed. For subsequent annealing times, the integrated intensities from the compound decreased slightly, indicating that the compound partially decomposed and released Al into the alpha-Ti lattice. This resulted in an alpha-Ti diffracted intensity band that results from a range of compositions. Intensity bands from Ti(101) were used to obtain composition profiles for Al in alpha-Ti, by using X-ray diffraction techniques and computer simulations. In each case, mass conservation of Al atoms was used to determine the interface motion. It was assumed that the Al profiles extend continuously into the_disordered Ti₃Al and Ti₂Al composition regions. This assumption was verified by preparing a Ti₂Al (disordered) powder standard and obtaining accurate lattice parameters. An iterative solution was used to determine composition dependent diffusion coefficients of one-dimensional zones, for two-phase systems. Diffusion zones extending from a few tenths to several microns have been examined. Al diffusion coefficients in alpha-Ti and the Ti₃Al phase have been determined. Activation energies were calculated from the diffusion coefficients at 635°C and 900°C and compared with those obtained from a melting point correlation. Lower activation energies from the present investigation indicated that there was some grain boundary diffusion at these intermediate temperatures. / Ph. D.

The purpose of the research was to study the evolution of quilts in Floyd County, Virginia, as a means of documenting the life and culture of the county natives. Both documents and relics were examined and methods of qualitative and quantitative analysis were utilized. The relics were any existing quilts made in Floyd County, while the documents included not only those in traditionally written form, but those in the unwritten form--in this case, twenty-two oral interviews. A visual instrument was developed to substantiate subject responses to interview questions. Geographic, economic and cultural factors were shown to have played an important part in determining the characteristics of Floyd County quilts. County aesthetic values were determined to be closely related to nature. Design lines were moderately complex and color preferences fell in the primary and secondary color range. Due to the historic functional use of quilts, no relation was found between the women's craftsmanship and design ability. / Master of Science

This dissertation investigates the determinants of career commitment in an organizational setting. It utilizes the results of a mailed survey sent to a sample of Salvation Army officers in the United States. A major portion of the work involves the examination of the commitment concept as a dependent variable. The emphasis is on social psychological predictors with a view to developing a predictive model suitable for screening and applicant evaluation. A path analytic strategy is employed to analyze the multivariate relationships. Included in the analysis is the decomposition of the effect of the predictors on the commitment variable. A reduced model emerges from the preliminary analysis and is itself subjected to analytic scrutiny. / Ph. D.

Analysis of trophic and population ecology of an introduced (1968- 1969) alewife forage base and resident sportfishes (age 0 and older) indicated several negative trophic interactions within the community complex of Claytor Lake, Virginia. Alewife piscivority represents a potentially significant adverse impact on sportfish recruitment. Alewife consumed the young of at least four sport species. Larval alewife did not inhabit shallow coves and consequently were not a prey item of age 0 sportfish resident in that habitat. Dietary overlaps (Levins' equation) between adult alewife and young-of-year sportfishes indicated that competitive interactions may occur on a time/site-specific basis. Alewife were demonstrated to be highly size-selective planktivores, preferring zooplankters >1.0 mm length. Electivity determinations indicated the importance of considering size distribution of prey species in food-habit studies. Electivity values were often positive for zooplankters ≥1.0 mm and negative for those <1.0 mm length. Comparisons of the zooplankton community following an alewife die-off (1978) and after alewife recovery (1979) indicated that changes in abundance of predominate species were size-related with smaller forms dominating after alewife recovery. The sizes of Daphnia at onset of maturity were considerably smaller following alewife population recovery. Alewife-induced shifts in zooplankton composition toward small forms represent a potentially significant adverse impact on young-of-year sportfishes which are often size-dependent as well as size-selective planktivores. Electivity determinations of young-of-year sportfishes (<50 mm TL) indicated that only striped and white bass positively selected a zooplankton species (Leptodora kindtii) that was concurrently preferred by alewife. Partitioning of the food complex among cove-inhabiting young sportfishes was in evidence. Predation upon one another, as well as cannibalism appeared to be a more critical trophic interaction than competition with each other or alewife. Indirect trophic interactions between alewife and planktivorous sportfish stages may have affected first year growth rates of smallmouth bass, spotted bass, and white crappie which declined compared to results of a previous growth study made prior to alewife introduction. Following the alewife die-off, age 1 white bass and walleye growth rates significantly increased, perhaps in response to reduced competition with alewife. Utilization of alewife (age 0 and age 1 only) by pelagic sportfishes (walleye, striped bass, white bass) and predation of other prey by littoral black basses suggested partitioning of the forage base. In the spring following the alewife die-off, pelagic sportfishes switched to alternative prey and competition among limnetic and littoral-inhabiting piscivores presumably increased. Although alewife were shown to possess several negative traits for a forage fish, no forage species has proven ideal for southeastern reservoirs. Alewife introduction should be limited to systems too cold for threadfin shad, and that are managed primarily for pelagic predators with non-pelagic young or those that are maintained on a put-grow-take basis. Results of this study underscore the importance of assessing community impacts of an exotic species before wide-spread introduction. / Ph. D.

This investigation concerns the validity and feasibility of using moduli reduction to monitor the effect of fatigue damage in graphite epoxy composites. Five laminate orientations were considered, [O]₄, [90]₄, [±45]_s, [0,90]_s, [0,90,±45]_s, and four inplane-stiffness properties were monitored for each. The stiffness parameters were E_xx, E_yy, G_xy, and v_xy, and were measured using a longitudinal tension test, a rail shear test and a transverse bend test. Nondestructive testing techniques such as C-scan and edge replication were also performed to aid in the observation of damage development. Results describe the response of each laminate orientation in tension-tension fatigue, including a record of changes in the stiffness properties at intervals during fatigue. Longitudinal stiffness (E_xx) and shear stiffness (G_xy) were shown to significantly decrease for the [0,90,±45]_s, laminate following fatigue loading. The inplane stiffness properties for the other four laminates remain essentially unchanged following fatigue loading. Matrix cracking and delamination appears to contribute to the stiffness reductions that occur in the [0,90,±45]_s laminate. / Master of Science

Since the mid-1960's women have been moving into previously male-dominated professions; one exception, however, has been the administrative hierarchies of universities throughout the United States. Within these institutions of higher education, women continue to hold a low proportion of the top-level administrative positions. Their low representation is often justified on the basis that women have little interest in assuming positions of leadership in college and university administration. The purpose of this study was to determine if women faculty aspire to administrative positions in higher education in the same proportions as do men faculty. The study also sought to compare administrative levels to which both groups aspire and to compare the reasons they have for their interest, or lack of interest, in obtaining an administrative position. In addition, the variables of age, marital status, tenure status, year of tenure review, academic rank, years of teaching experience in higher education, previous administrative experience, and previous encouragement to apply for an administrative position were studied to determine whether they interacted with sex to produce an effect upon administrative aspirations. The study involved all of the land-grant universities established by law in 1862 in the contiguous 48 states. The population included all professors with the rank of assistant or above from 18 departments typically found within Colleges of Arts and Sciences. From each university ten professors, six men and four women, were selected for the study sample. A four-part, four page questionnaire was developed for data collection. A 76 percent response rate provided a usable sample of 331, of which 192 were men and 139 were women. The results of this study showed that men's and women's interests in assuming an administrative position did not differ statistically, however, a slightly higher proportion of women expressed administrative aspirations than did men. There was no difference in the administrative levels to which men and women aspired. While some professors were willing to begin at an assistant or staff position, most men and women sought a line office as their ultimate administrative goal. Generally, men and women respondents held similar reasons for their interest in administration. Both men and women ranked the same three reasons in the same order of importance. They indicated that the primary reasons for their administrative interests were that (1) they would like the challenge of the decision-making aspect of an administrative position, (2) they felt they could ultimately help more people reach their educational goals, and (3) they believed that they could be a more effective administrator than many they knew. Two out of eight personal and academic descriptor variables were found to have had a significant effect on the administrative interests of men and women respondents. Within the variable of age, men, ages 45-65, expressed little interest in an administrative position, while the women indicated a greater interest at this age level than any other age group of men or women. Within the marital status variable, the administrative interests of married men were not as great as the interests of married women. Respondents who reported that they had no interest in an administrative post often stated that they preferred continuing their work as teachers, researchers and/or writers. The second most strongly held position was that respondents did not like administrative responsibilities and/or the people who tended to serve as administrators. Even though some statistical differences were reported, the consistent theme throughout the responses was one of similarity between men and women in their interests in acquiring positions of leadership on university campuses, thereby conclusively laying to rest the assumption that the low representation of women in top level administrative positions in land-grant universities results from a lack of interested female candidates. / Ed. D.

M. S.

Carte géographique dans une pochette.

Cette thèse présente les principes d'apprentissage considérés comme fondamentaux par Staats (1975) dans son paradigme du behaviorisme social. L'approche qu'il propose inclut une intégration des conditionnements classique et instrumental qui sont les deux principaux types d'apprentissage. De plus, cette approche accorde une importance considérable à l'étude et au développement théorique et expérimental du comportement humain complexe. Le chapitre premier décrit les principes des conditionnements classique et instrumental; le chapitre II en développe les sous-principes, alors que le chapitre III met en évidence 1'interrelation entre ces deux types de conditionnement. Le chapitre IV traite des stimuli et des réponses manifestes et voilés. Le chapitre V expose les différents types de mécanismes S-R. / Québec Université Laval, Bibliothèque 2014

A partir des données écrites et des objets de collection, l'auteur a décrit et montré l'évolution du chauffage de la maison au Canada depuis la période des premiers contacts entre les Européens et les Amérindiens du XVIe siècle jusqu'à l'industrialisation du pays, choisissant comme date limite 1867. Cet ensemble de traits culturels si importants dans un climat rigoureux comme le Canada a été d'abord regroupé en six points couvrant tout le champ du chauffage domestique: combustibles, production du feu, conservation et transport du feu, appareils de chauffage, accessoires des appareils de chauffage, et chauffage et milieu humain. Cette classification générale a servi de base aux trois premières parties de l'ouvrage auxquelles est venue s'ajouter une quatrième partie plus descriptive. La première partie porte sur le chauffage domestique chez les Amérindiens de l'est du Canada, i.e., ceux qui ont été le plus en contact avec les nouveaux venus français dans la vallée du Saint-Laurent. Pour le moment, â cause des données incomplètes sur le sujet, l'étude néglige les données archéologiques se rapportant à ces populations au moment des premiers contacts et se limite â l'interprétation des données écrites. La deuxième partie porte sur le chauffage domestique en Nouvelle-France. On essaie d'y démontrer comment les Français, abordant cette nouvelle terre d’Amérique, cet environnement physique et biologique, y ont adapté et transformé les traits culturels se rapportant au chauffage. Avec l'arrivée des Britanniques â la Conquête, nous assistons à l'infusion d'idées et de traits culturels nouveaux et surtout â une confrontation d'idées différentes avec la population autochtone qui vont faire que tout ce complexe culturel que constitue le chauffage domestique s'en trouvera profondément modifié au XIXe siècle. Ceci constitue la troisième partie. Enfin, dans le but de faire de cette thèse un véritable ouvrage de références utile aux chercheurs dans le domaine et même aux amateurs, antiquaires et autres personnes intéressées, on a inclu, dans une quatrième partie, toutes les données accumulées au long de la recherche sur les fabricants d'appareils de chauffage du Québec, de l'Ontario et même sur les appareils importés. Ces répertoires, organisés par ordre alphabétique de fabricants ou de manufacturiers, comprennent aussi des index de modèles d'appareils et de noms de personnes et de manufactures. / Québec Université Laval, Bibliothèque 2012