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Showing papers by "Virginia Tech published in 1991"


Journal ArticleDOI
TL;DR: In this article, the effects of price, brand, and store information on buyers' perceptions of product quality and value, as well as their willingness to buy Hypotheses are derived from a study of consumers.
Abstract: The authors report a study of the effects of price, brand, and store information on buyers’ perceptions of product quality and value, as well as their willingness to buy Hypotheses are derived fro

3,931 citations



Journal ArticleDOI
TL;DR: In this article, the impact response of continuous fiber-reinforced composites is reviewed and an attempt is made to draw together much of the work published in the literature and to identify the fundamental parameters determining the impact resistance of continuous fibre reinforced composite materials.

1,276 citations


Book
26 Jul 1991
TL;DR: In this article, Dirac operators and the spin group are used in the analysis of Euclidean spaces, where Dirac operator analysis is based on Clifford algebras.
Abstract: 1. Clifford algebras 2. Dirac operators and Clifford analyticity 3. Dirac operators and the spin group 4. Dirac operators in the analysis on Euclidean space 5. Dirac operators in representation theory 6. Dirac operators in analysis.

623 citations


Journal ArticleDOI
18 Oct 1991-Science
TL;DR: Electron diffraction patterns of the fullerene C60 in the gaseous state have been obtained by volatilizing it from a newly designed oven-nozzle at 730�C using least-squares refinement of a model incorporating all possible interatomic distances.
Abstract: Electron diffraction patterns of the fullerene C 60 in the gaseous state have been obtained by volatilizing it from a newly designed oven-nozzle at 730°C. The many peaks of the experimental radial distribution curve calculated from the scattered intensity are completely consistent with icosahedral symmetry for the free molecule. On the basis of this symmetry assumption, least-squares refinement of a model incorporating all possible interatomic distances led to the values r g (C 1 -C 2 ) = 1.458(6) angstroms (A) for the thermal average bond length within the five-member ring (that is, for the bond fusing five- and six-member rings) and r g (C 1 -C 6 ) = 1.401(10) A for that connecting five-member rings (the bond fusing six-member rings). The weighted average of the two bond lengths and the difference between them are the values 1.439(2) A and 0.057(6) A, respectively. The diameter of the icosahedral sphere is 7.113(10) A. The uncertainties in parentheses are estimated 2σ values.

591 citations


Journal ArticleDOI
TL;DR: In this article, the authors demonstrate that modes can be selectively excited and that the geometry of the actuator shape markedly affects the distribution of the response among modes, and that it is possible to tailor the shape of an actuator to either excite or suppress particular modes.
Abstract: The results demonstrate that modes can be selectively excited and that the geometry of the actuator shape markedly affects the distribution of the response among modes. It thus appears possible to tailor the shape of the actuator to either excite or suppress particular modes leading to improved control behavior

499 citations


Journal ArticleDOI
TL;DR: It is demonstrated the operation of a quadrature phase-shifted extrinsic Fabry-Perot fiber-optic sensor for the detection of the amplitude and the relative polarity of dynamically varying strain.
Abstract: We demonstrate the operation of a quadrature phase-shifted extrinsic Fabry–Perot fiber-optic sensor for the detection of the amplitude and the relative polarity of dynamically varying strain. Two laterally displaced single-mode fibers inserted within a hollow silica tube form the 90° phase-shifted sensing system. A multimode fiber, placed in the tube facing the two fibers, acts as a reflector, thereby creating an air gap that acts as a Fabry–Perot cavity. A theoretical description of the sensor is given, and its operation as a dynamically varying strain sensor is described. Strain sensitivities of 5.54° phase shift/microstrain cm−1 are obtained.

483 citations


Journal ArticleDOI
Kaye Kye Sung Chon1
TL;DR: This article examined how tourist destination image and tourist perceptions are modified and enhanced through travel to a tourist destination, using the traveller behaviour model presented by Gunn 1 in conjunction with an empirical analysis of American tourists travelling overseas, and found that first-time tourists to South Korea revealed a positive change in attitude to factors such as safety and scenery, as a result of the touristic experience.

464 citations


Journal ArticleDOI
John J. Tyson1
TL;DR: This work associates the steady state with metaphase arrest in unfertilized eggs, the spontaneous oscillations with rapid division cycles in early embryos, and the excitable switch with growth-controlled division cycles typical of nonembryonic cells.
Abstract: The proteins cdc2 and cyclin form a heterodimer (maturation promoting factor) that controls the major events of the cell cycle. A mathematical model for the interactions of cdc2 and cyclin is constructed. Simulation and analysis of the model show that the control system can operate in three modes: as a steady state with high maturation promoting factor activity, as a spontaneous oscillator, or as an excitable switch. We associate the steady state with metaphase arrest in unfertilized eggs, the spontaneous oscillations with rapid division cycles in early embryos, and the excitable switch with growth-controlled division cycles typical of nonembryonic cells.

462 citations


Journal ArticleDOI
TL;DR: A theoretical model is developed that explains the impact of the fit between top executive characteristics and strategic orientation on organizational performance and it was found that firms achieving a greater degree of alignment between their strategy and the profiles of top managers, generally realized superior performance outcomes.
Abstract: This paper develops a theoretical model that explains the impact of the fit between top executive characteristics and strategic orientation on organizational performance. Using the Miles and Snow typology as an integrative framework, the central propositions of the model were evaluated. The results of the empirical examination provided significant support for the administrative dimension, an aspect of the typology that has been largely overlooked thus far. Further, it was found that firms achieving a greater degree of alignment between their strategy and the profiles of top managers, generally realized superior performance outcomes.

432 citations


Journal ArticleDOI
TL;DR: In this paper, four studies were conducted to test the hypothesis that consumer behavior is more strongly predicted by functional congruity than by self-congruity, and functional con-gruity is influenced by selfcongruity.
Abstract: Four studies were conducted to test the hypothesis that (1) consumer behavior is more strongly predicted by functional congruity than by self-congruity, and (2) functional congruity is influenced by self-congruity. The pattern of the results provides support for hypotheses.

Journal ArticleDOI
Michael W. Hyer1, H.H. Lee1
TL;DR: In this article, the authors explored the gains in buckling performance that can be achieved by deviating from the conventional straightline fiber format and considering the situation whereby the fiber orientation in a layer, or a group of layers, can vary from point to point.

Journal ArticleDOI
TL;DR: In this article, the static and dynamic interaction between a bonded piezoelectric actuator and an underlying beam substructure is investigated using four different displacement-based finite element models all of which are derivable from the generalized laminate plate theory of Reddy.

Journal ArticleDOI
TL;DR: The acquisition by the uterus of responsiveness to oxytocin may determine when endogenous secretion of PGF2 alpha occurs during the estrous cycle, and the effects of progesterone ensure that PGF1 alpha is secreted only at the appropriate time to induce luteolysis.
Abstract: In recent years, considerable progress has been made in our understanding of the endocrine mechanisms that control the pattern and timing of uterine secretion of prostaglandin F2 alpha (PGF2 alpha) during luteolysis in ruminants. Oxytocin may be important in establishing a pulsatile pattern of secretion. Neurohypophyseal oxytocin appears to be released in a pulsatile fashion and may initiate each episode of PGF2 alpha secretion from the uterus. Uterine PGF2 alpha stimulates release of oxytocin from the corpus luteum. Luteal oxytocin further stimulates secretion of PGF2 alpha from the uterus and may induce a transient refractoriness of the uterus to subsequent stimulation with oxytocin. Uterine refractoriness subsides after approximately 6 h. A similar desensitization phenomenon occurs in response to PGF2 alpha at the level of the corpus luteum. Together, uterine and luteal refractoriness may account for the interval between pulses of PGF2 alpha observed during luteolysis. Uterine secretory responsiveness to oxytocin increases at luteolysis, when endogenous, pulsatile secretion of PGF2 alpha normally begins. Thus, the acquisition by the uterus of responsiveness to oxytocin may determine when endogenous secretion of PGF2 alpha occurs during the estrous cycle. Uterine secretory responsiveness to oxytocin develops slowly, in the presence of progesterone. Progesterone exerts two types of effects that contribute to the regulation of PGF2 alpha secretion. First, prolonged exposure to progesterone appears to promote uterine accumulation of arachidonic acid, prostaglandin endoperoxide synthase, and other substances needed for synthesis of PGF2 alpha. Second, progesterone exerts a suppressive effect on secretion, which wanes after prolonged exposure. Together, these effects of progesterone ensure that PGF2 alpha is secreted only at the appropriate time to induce luteolysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Journal ArticleDOI
TL;DR: This research develops both a planning and an operational computer-based tool through a particular location-allocation model that selects a set of candidate shelters from among a given set of admissible alternatives in a manner feasible to available resources and prescribes an evacuation plan which minimizes the total congestion-related evacuation time.
Abstract: The location of shelters in a region threatened by a hurricane can greatly influence the highway network clearance time, i.e. the time needed by evacuees to escape from origin points to safe areas. The studies conducted to date for developing hurricane plans have not implicitly considered the impact of shelter locations on evacuation times. The purpose of this research is to develop both a planning and an operational computer-based tool through a particular location-allocation model. This model selects a set of candidate shelters from among a given set of admissible alternatives in a manner feasible to available resources, and prescribes an evacuation plan which minimizes the total congestion-related evacuation time. An extraneous flow is also superimposed on the network in order to represent the traffic of evacuees not using the designated shelters as destinations. The model formulated is a nonlinear mixed-integer programming problem, for which we develop a heuristic and (two versions of) an exact implicit enumeration algorithm based on the generalized Benders' decomposition method. Computational experience is provided against a set of realistic test problems formulated on the Virginia Beach network. Potential avenues for future research are also explored.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the gains in structural efficiency that can be achieved by aligning the fibers in some or all of the layers in a laminate with the principal stress directions in those layers.
Abstract: 'I'his paper investigates the gains in structural efficiency that can be achieved by aligning the fibers in some or all of the layers in a laminate with the principal stress directions in those layers. The name curvilinear fiber format is given to this idea. The problem studied is a plate with a central circular hole subjected to a uniaxial tensile load. An iteration scheme is used to find the fiber directions at each point in the laminate. Two failure criteria are used to evaluate the tensile load capacity of the plates with a curvilinear format, and for comparison, counterpart plates with a conventional straightline fiber format. The curvilinear designs for improved tensile capacity are then checked for buckling resistance. It is concluded that gains in efficiency can be realized with the curvilinear format.

Journal ArticleDOI
TL;DR: In this paper, an orthotropic angle-ply laminate with an embedded piezoceramic patch is presented to show the coupling of bending and extension, and a comparison between the current work and that of Dimitriadis et al. is given.
Abstract: Classical laminated plate theory (CLPT) is applied to a laminate plate with induced strain actuators, such as piezoceramic patch, bonded to its surface or embedded within the laminate to develop an induced strain actuation theory that allows for the actuator patch to be spatially distributed. When piezoceramic patches are subjected to voltage fields, the equivalent external forces induced by piezoceramic patches can be determined upon the assumption of free constraint for the expansion or contraction of piezoceramic patches. This assumption is generally done in thermal expansion problem. Several examples, including pure bending and pure extension, are illustrated. For the case of pure bending, a comparison between the current work and that of Dimitriadis et al. (1989) is given. In addition, an orthotropic angle-ply laminate with an embedded piezoceramic patch is presented to show the coupling of bending and extension.

Journal ArticleDOI
TL;DR: The chemistry of the potent anticancer diterpenoid taxol is reviewed, with an emphasis on isolation and analysis, structural modifications, partial synthesis, and structure-activity relationships.

Journal ArticleDOI
TL;DR: The composition of microbiological floras of all periodontitis samples was statistically significantly different from that of subjects with healthy gingiva and that of active and control sites in AP subjects and the composition of microfloras of sites in subjects with naturally-occurring gingivitis was intermediate.
Abstract: 20 adult periodontitis (AP) subjects were examined every 2 to 4 months and microbiological samples were collected and cultured when 2 mm or more loss of attachment (active sites) was detected by 2 examiners. Similar sites in which no progressive destruction was observed (control sites) also were sampled in the same subjects. By lambda-analysis, there was no statistically significant difference in floras of active (42 sites from 12 subjects) and control (36 sites from 12 subjects) sites or between the floras of the active and control sites and of 63 samples from 22 AP subjects that were examined previously in a cross-sectional study. By paired t test, no microbial species had a significantly greater association with active than with control sites. The only species that were detected in one or more samples from all subjects with active sites were Wolinella recta, Fusobacterium nucleatum, and Peptostreptococcus micros. Porphyromonas gingivalis and 9 other taxa were isolated from one-half or more of the persons with active sites. The composition of microbiological floras of all periodontitis samples was statistically significantly different from that of subjects with healthy gingiva. The composition of microfloras of sites in subjects with naturally-occurring gingivitis was intermediate between that of subjects with healthy gingiva and that of active and control sites in AP subjects.

Journal ArticleDOI
Paul L. Knox1
TL;DR: In this article, the authors address recent changes in the built environment of U.S. metropolitan areas and argue that the confluence of recent economic and sociocultural change has led to the emergence of distinctive new urban settings.
Abstract: This study addresses recent changes in the built environment of U.S. metropolitan areas. The confluence of recent economic and sociocultural change has led to the emergence of a number of distinctive new urban settings. This process is interpreted as part of a broader, epochal change in the dynamics of contemporary capitalism. The particular implications of this transformation for the supply and demand of elements of the built environment involve changes in the organization and product mix of developers and construction companies, in the roles and professional orientations of architects and planners, and in commodity aesthetics and patterns of consumption among a “new bourgeoisie.” The imprint of these changes on the built environment is illustrated with reference to the example of the Washington metropolitan area. Among the new settings and landscape elements identified here are private master-planned communities, high-tech corridors, mixed-use developments, “festival” settings, gentrified neigh...

Journal ArticleDOI
TL;DR: Results from model simulations suggest that inherent temperature thresholds in each life-stage help to synchronize population dynamics with seasonal climatic changes and facilitate both research and management endeavors aimed at reducing losses in lodgepole pine stands caused by mountain pine beetle infestations.
Abstract: Temperature-dependent development of the egg, larval, and pupal life-stages of the mountain pine beetle (Dendroctonus ponderosae Hopkins) was described using data from constant-temperature laboratory experiments A phenology model describing the effect of temperature on the temporal distribution of the life-stages was developed using these data Phloem temperatures recorded in a beetle-infested lodgepole pine (Pinus contorta Douglas) were used as input to run the model Results from model simulations suggest that inherent temperature thresholds in each life-stage help to synchronize population dynamics with seasonal climatic changes This basic phenological information and the developed model will facilitate both research and management endeavors aimed at reducing losses in lodgepole pine stands caused by mountain pine beetle infestations

Book ChapterDOI
01 Jan 1991
TL;DR: In this paper, the authors focused on correcting B, Cu, Fe, Mn, Mo, and Zn deficiencies in plants grown under diverse management regimes, and discussed various reasons for the current increased recognition of micronutrient needs in crop production.
Abstract: Increases in crop yields from application of B, Cu, Fe, Mn, Mo, and/or Zn occur in many parts of the world including numerous regions of the USA. There is growing awareness that micronutrient deficiencies may limit crop yields even though exceedingly small amounts are required by plants (Table 15-1). Various reasons can be provided to account for the current increased recognition of micronutrient needs in crop production. These include (i) improved soil test and tissue analysis methods for diagnosis of micronutrient deficiencies; (ii) accumulated data on crop responses to micronutrient applications on diverse soil types; (iii) micronutrient removal from long-term crop production; (iv) increased use of high-analysis fertilizers with low amounts of micronutrient impurities; (v) higher micronutrient requirements accompanying higher crop yields; (vi) less use of animal manures in crop production; and (vii) induction of micronutrient deficiencies by high P concentrations from long-term applications (Berger, 1962; Vitosh et al., 1981). Attention will be directed in this chapter toward correction of B, Cu, Fe, Mn, Mo, and Zn deficiencies in plants grown under diverse management regimes. Literature on Cl, Co, and Ni deficiencies also will be discussed.

Journal ArticleDOI
TL;DR: In this paper, the authors analyzed a mixed oligopoly with horizontal product differentiation, where firms choose their location and price in a model a la Hotelling with quadratic transport costs, and the solution-concept is a subgame perfect Nash equilibrium.

Journal ArticleDOI
TL;DR: In this paper, the authors find that almost 94 percent of the variation in loss rates within regions was due to banks having different loss rates on the same types of loans, and that banks with "adequate capital" in the preceding three years tended to have lower loss rates.
Abstract: Net loan chargeoffs and nonperforming loans reflect realized credit risks for banks. These risks arise from either external factors such as depressed economic conditions (e.g., the energy and farm belts of the United States in the 1980s) or internal factors such as poor lending decisions (including fraudulent ones) or both. For large commercial banks in 1987, we find that almost 94 percent of the variation in loss rates within regions was due to banks having different loss rates on the same types of loans. Our regression results indicate that loan-loss rates in 1987 were positively associated with loan rates, volatile funds, and loan volume from the preceding three years. In contrast, banks with “adequate capital” in the preceding three years tended to have lower loss rates.

Journal ArticleDOI
John Christman1
TL;DR: In this paper, the authors discuss autonomy and personal history in the context of Canadian Journal of Philosophy, Vol. 21, No. 1, pp. 1-24, 1991.
Abstract: (1991). Autonomy and Personal History. Canadian Journal of Philosophy: Vol. 21, No. 1, pp. 1-24.

Journal ArticleDOI
01 Jan 1991-Polymer
TL;DR: In this article, bisphenol A-based epoxy resins were modified with either phenolic hydroxyl or aromatic amine functionally-terminated poly(arylene ether sulphone) oligomers and thermally cured with 4,4′ diaminodiphenyl sulphone.

Journal ArticleDOI
TL;DR: In this paper, the layer-wise laminate theory of Reddy is extended to account for multiple delaminations between layers, and the associated computational model is developed, which is validated through several numerical examples.

Book ChapterDOI
Kenneth Reifsnider1
01 Jan 1991
TL;DR: In this article, the authors present a continuum damage theory for composites and evaluate the damage in composite materials, showing that fiber-dominated fatigue damage is more prevalent in short fiber composites than in metal matrix composites.
Abstract: 1. Introduction (K.L. Reifsnider). 2. Damage and Damage Mechanics (K.L. Reifsnider). The fatigue effect in composite materials. The fatigue process. The mechanics of damage development. The mechanics of strength reduction. 3. Damage Characterization (R. Talreja). Damage in composite materials. Internal variable characterization of damage. Vectorial representation of composite damage. A continuum damage theory. Damage evaluation. 4. Fatigue Behaviour of Composite Laminates (W.W. Stinchcomb, C.E. Bakis). Loads, damage, and response - an example. The damage process. Mechanics of stress redistribution. Consequences of cyclic loading: strength, stiffness, and life. 5. Delamination of Composite Materials (T.K. O'Brien). Perspective. Mechanics of delamination. Delamination growth. Characterization of delamination resistance. Conclusions and future directions. 6. Fatigue of Metal Matrix Composites (W.S. Johnson). Matrix-dominated fatigue damage. Fiber-dominated fatigue damage. Self-similar fatigue damage growth. 7. Fatigue Behaviour of Short Fibre Composite Materials (J.F. Mandell). Fatigue lifeline trends. Aligned short fiber composites. Chopped strand composites. Injection molded composites. Summary and recommendations. 8. Viscoelastic Behaviour of Laminated Composite Materials (D.A. Dillard). Linear viscoelastic analysis. Non-linear viscoelasticity. Environmental and time effects. Viscoelastic design philosophy. 9. Moisture in Composites: Sorption and Damage (Y. Weitsman). Elementary considerations. Viscoelastic behaviour. Stress effects on diffusion. Moisture-induced damage. Chemical and physical effects and other observations. 10. Life Prediction for Resin-Matrix Composite Materials (G.P. Sendeckyj). Constant amplitude fatigue theories. Cumulative damage theories. Statistical interpretation of fatigue experiments. Discussion and recommendations. 11. Statistical Considerations (R. Talreja). Fatigue reliability: basic concepts. Fatigue reliability of composites. Probabilistic models for composite strength. Conclusions. References.

Journal ArticleDOI
TL;DR: Patterns of change of genetic correlations are caused by differences in development and physiology, an understanding of which appears to be necessary to predict the response to selection in natural, heterogeneous environments.
Abstract: Recent theory suggests that genetic correlations should help to predict the simultaneous response to selection of two or more traits, and much recent research has been directed towards understanding the sources of variation in genetic correlations. Genetic correlations can change from sample to sample, from species to species, from population to population, during the course of development and — within a population, at a fixed stage of development — from one environment to another. These are changes not only in magnitude but also in sign. Theory suggests that genetic correlations should not change sign when the two traits are tightly integrated by physiology or development. Patterns of change of genetic correlations are caused by differences in development and physiology, an understanding of which appears to be necessary to predict the response to selection in natural, heterogeneous environments.

Journal ArticleDOI
TL;DR: In this paper, the authors found that DuoFiber and oat fiber had beneficial effects on properties of low-fat, high added-water bologna, thus providing a way to alter product characteristics.
Abstract: Ingredients incorporated dry into 10% fat and 30% added-water bologna were: DuoFiber®, oat fiber, pea fiber, wheat starch, Firm-tex®, and isolated soy protein. Test bolognas were less firm than the high-fat control but more firm than the low-fat control. Fiber-containing bolognas were more grainy and less juicy than the high-fat control. Low-fat bolognas were darker red than high-fat bologna. DuoFiber and oat fiber had greater cooking losses than the low-fat control, but purge was reduced by all test ingredients, particularly Firm-tex. Lower vacuum level in packages also resulted in less purge. Test ingredients had beneficial effects on properties of low-fat, high added-water bologna, thus providing a way to alter product characteristics.