Showing papers by "Virginia Tech published in 1982"

Self-Concept in Consumer Behavior: A Critical Review

Abstract: The self-concept literature in consumer behavior can be characterized as fragmented, incoherent, and highly diffuse. This paper critically reviews self-concept theory and research in consumer behavior and provides recommendations for future research.

Testing for Gaussianity and Linearity of a Stationary Time Series.

Abstract: : Stable autoregressive (AR) and autoregressive moving average (ARMA) processes belong to the class of stationary linear time series. A linear time series is Gaussian if the distribution of the independent innovations (sigma (t)) is normal. Assuming that E sigma (t) = 0, some of the third order cumulants sub c xxx (m,n) = Ex(t)x(t+m)x(t+n) will be non-zero if the sigma (t) are not normal and E sigma cube(t)=0. If the relationship between x(t) and sigma (t) is non-linear, then (x(t)) is non-Gaussian even if the sigma (t) are normal. This paper presents a simple estimator of the bispectrum, the Fourier transform of (sub c xxx (m,n)). This sample bispectrum is used to construct a statistic to test whether the bispectrum of (x(t)) is non-zero. A rejection of the null hypothesis implies a rejection of the hypothesis that (x(t)) is Gaussian. A related test statistic is then presented for testing the hypothesis that (x(t)) is linear. The asymptotic properties of the sample bispectrum are incorporated in these test statistics. The tests are consistent as the sample size (N approaches infinity.

The use of Focus Groups for Idea Generation: The Effects of Group Size, Acquaintanceship, and Moderator on Response Quantity and Quality:

Abstract: Assumptions about focus group interviewing were tested. Individual interviews generated more ideas than focus groups, eight-member groups generated significantly more ideas than four-member groups,...

Marketing, Strategic Planning and the Theory of the Firm

Abstract: The strategic planning process is inextricably linked with the issue of corporate goal formulation. It is argued that greater progress will be made in understanding marketing's participation in str...

Stiffness-reduction mechanisms in composite laminates

Abstract: It now is recognized widely that stiffness changes during the service loading of composite laminates can be significantly large, especially as those changes affect deflections, dimensional changes, vibration characteristics, and load or stress distributions. Several generic sources of stiffness change can be identified, in various degrees, in fibrous composite materials. The source which occurs quite early in the life of a specimen or component is matrix cracking, the subject of this paper. While most laboratories now report stiffness changes, very little systematic philosophy has been developed to account for and explain such stiffness changes. The complexity of this situation requires systematic study, and motivates the search for a model, or models, which can describe the behavior and predict unfamiliar response. The present paper reports the results of an experimental program and an analytical modelling exercise which indicate that much of the observed matrix cracking can be predicted and the effects on stiffness calculated with various degrees of accuracy depending upon the sophistication of the model used.

The room-temperature shapes of four-layer unsymmetric cross-ply laminates

Abstract: A geometrically nonlinear extension of classical lamination theory developed by Hyer (1981) for predicting the room-temperature shapes of unsymmetric laminates is reformulated using relaxed restrictions regarding the inplane strains The inplane residual strains of unsymmetric laminates which have cooled from curing into a cylindrical room-temperature shape are examined numerically Results show that the residual strains are compressive and practically independent of spatial location on the laminate In addition, the room temperature shapes of the four-layer unsymmetric cross-ply laminates are predicted, and it is shown that the temperature shapes are a strong function of their size and their stacking arrangement It is demonstrated that, depending on the parameters selected, the room-temperature shape of a four-layer cross-ply unsymmetric laminate can be a unique saddle shape, a unique cylindrical shape, or a cylindrical shape that can be snapped through to another cylindrical shape

Stream detritus dynamics: Regulation by invertebrate consumers

Abstract: Insecticide treatment of a small, Appalachian forest stream caused massive downstream insect drift and reduced aquatic insect densities to <10% of an adjacent untreated reference stream. Reduction in breakdown rates of leaf detritus was accompanied by differences in quantity and composition of benthic organic matter between the two streams. Following treatment, transport of particulate organic matter was significantly lower in the treated stream than in the reference stream whereas no significant differences existed prior to treatment. Our results indicate that macroinvertebrate consumers, primarily insects, are important in regulating rates of detritus processing and availability to downstream communities.

The Dyad as the Unit of Analysis: Conceptual and Methodological Issues

Abstract: This work assesses conceptual and methodological issues in the use of the dyad as the unit of analysis in family research. Illustrative examples from dyadic research and a table to aid researchers in the generation of dyadic studies using one or two informants are included. The focus of dyadic research is the relationship between two people. All components of a study must be at the level of the dyad and each stage of research must have the relationship as the object of study. Conceptualizing the pattern between two people is an essential first step. The pattern can take many forms reflecting different conceptual models of relationships and interactions. Individual properties such as values or needs must be distinguished from relationship properties such as norms or roles. Information about the partners individual characteristics or relationship may come from many sources and it is necessary to specify whose construction is under examination. Issues of subjectivity or objectivity self-report or observation and one informant or two relate to generalizability of information. How relationships are conceptualized must also be congruent with choice of sampling procedures. Two major weaknesses are common at the level of data analysis: data from both members of the dyad are aggregated rather than reflecting the pattern between the two or the conceptual basis of the constructed relationship pattern is not clear. The paper concludes with a discussion of the range of research questions that can appropriately be addressed using one or both partners as informants.

A mathematical programming approach for determining oligopolistic market equilibrium

Abstract: During the past several years it has become increasingly common to use mathematical programming methods for deriving economic equilibria of supply and demand. Well-defined approaches exist for the case of a single firm (monopoly) and for the case of many firms (perfect competition). In this paper a certain family of convex programs is formulated to determine equilibria for the case of a few firms (oligopoly). Solutions to this family of convex programs are shown to be Nash equilibria in the formal sense ofN person games. This equivalence leads to a mathematical programming-based algorithm for determining an oligopolistic market equilibrium.

Sensitivity of Optimum Solutions of Problem Parameters

Abstract: Solution of the optimum sensitivity problem yields the values of derivatives of the optimal objective function and design variables with respect to those physical quantities which were kept constant as problem parameters during optimization. Examples of these sensitivity derivatives might include derivatives of cross-section al area and structural mass with respect to allowable stress and derivatives of fuel consumed and wing aspect ratio with respect to aircraft range. Derivation of the sensitivity equations that yield the sensitivity derivatives directly, which avoids the costly and inaccurate "perturb-and-reoptimize" approach, is discussed and solvability of the equations is examined. The equations apply to optimum solutions obtained by direct search methods as well as those generated by procedures of the sequential unconstrained minimization technique (SUMT) class. Applications are discussed for the use of the sensitivity derivatives in extrapolation of the optimal objective function and design variable values for incremented parameters, optimization with multiple objectives, and decomposition of large optimization problems. Several aspects of these applications and verification of the sensitivity equations are presented through numerical examples.

Stability of Goertler vortices in boundary layers

Abstract: A formal analysis of Goertler-type instability is presented. The boundary-layer and disturbance equations are formulated in a general, orthogonal, curvilinear system of coordinates constructed from the inviscid flow over a curved surface. Effects of curvature on the boundary-layer flow are analyzed. The basic approximation for the disturbance equations is presented and solved numerically. Previous analyses are discussed and compared with our analysis. It is shown that the general system of coordinates developed in this analysis and the correct order-of-magnitude analysis of the disturbance velocities with two velocity scales leads to a rational foundation for future work in Goertler vortices.

Ends of maps, II

Abstract: Versions of the finiteness obstruction and simple homotopy theory “within e overX” are developed. This provides a setting for obstructions to the map analogs of the end ands-cobordism theorems for manifolds. These are applied to study equivariant mapping cylinder neighborhoods in topological group actions, triangulations of locally triangulable spaces, and block bundle structures on approximate fibrations.

Alternation of sleeping groves by yellow baboons (Papio cynocephalus) as a strategy for parasite avoidance

Abstract: The primary locus of contact between free-living yellow baboons (Papio cynocephalus) in the Amboseli National Park of Kenya and the infective stages of their intestinal parasites is believed to be soil beneath sleeping trees contaminated by the baboons' own fecal emissions. In this report, we present evidence both that infective ova and larvae of intestinal parasites are found at very high densities in the soil beneath sleeping groves and that Amboseli baboons substantially reduce their contact with this reservoir of parasites by alternating periods of a few consecutive nights' use of any particular grove with much longer periods of avoidance of that grove. Although many factors other than the presence of parasite larvae also influence choice of sleeping groves, we propose as a working hypothesis that the temporal pattern of sleeping grove alternation shown by Amboseli baboons reflects a subtle behavioral strategy for parasite avoidance.

An Investigation of Cumulative Damage Development in Quasi-Isotropic Graphite/Epoxy Laminates

Abstract: Results of an experimental investigation of cumulative damage development in two unnotched quasi-isotropic graphite/epoxy laminates subjected to quasi-static tension and tension-tension fatigue are presented. Damage development in the form of transverse cracking in all off-axis laminae, longitudinal cracking, and delamination was monitored via the surface replication technique. Results of the study include a detailed description of the chronology of damage development prior to failure. Evidence also is presented in support of a damage model based on the concept of a characteristic damage state.

Effects of forest clearcutting on leaf breakdown in a southern Appalachian stream

Abstract: SUMMARY. Effects of forest clearcutting on rates of leaf breakdown were studied in Big Hurricane Branch, a second-order stream located at Coweeta Hydrologic Laboratory in the southern Appalachian Mountains of North Carolina, USA. Breakdown rates of leaves of three tree species were measured in the stream before, during and after the catchment was clearcut. Changes in the stream attributable to logging and associated activities—principally road building—were increased stream flow, increased sediment transport, elevated water temperatures, increased nitrate concentrations and decreased allochthonous organic inputs. Breakdown rates of all three leaf species were slowed during clearcutting and accelerated later. Following logging the breakdown rate of dogwood leaves was equal to the pre-treatment rate, and white oak and rhododendron leaves broke down faster than prior to treatment. We attribute the slow breakdown during treatment to burial of the leaf packs in sediment. Subsequent acceleration may have been due to a lack of alternative food sources for invertebrate detritivores.

On penalty function methods in the finite‐element analysis of flow problems

Abstract: In this paper the penalty function method is reviewed in the general context of solving constrained minimization problems. Mathematical properties, such as the existence of a solution to the penalty problem and convergence of the solution of a penalty problem to the solution of the original problem, are studied for the general case. Then the results are extended to a penalty function formulation of the Stokes and Navier-Stokes equations. Conditions for the equivalence of two penalty-finite element models of fluid flow are established, and the theoretical error estimates are verified in the case of Stokes's problem.

Determination of Saturated Values of Rotating Machinery Incremental and Apparent Inductances by an Energy Perturbation Method

Abstract: Energy and winding current perturbations form the basis of a method for calculation of the saturated apparent and incremental inductances of rotating machinery as functions of rotor position and machine winding excitation currents. The method is totally general and utilizes numerical field calculation techniques in obtaining stored energy in the magnetic circuits of such machines. Thus, it can be applied to a wide class of machinery with practically any cross-sectional contours and number of windings. It can be used at any given set of excitations (any loads). This method was applied to the calculation of the apparent and incremental inductances of a 15 hp samarium cobalt permanent magnet synchronous machine. The necessary-numerical field soluitions were obtained by finite elements at both rated and no load conditions. The calculated inductances, at various rotor positions, were compared with those obtained during laboratory measurements and the agreement between calculated and measured values was consistently very good. The advantage of this method over the more traditional calculations of only the direct and quadrature axes inductances (or reactances, including transient and subtransient components) is that the entire n > n matrix of incremental inductances that truely govern the dynamic performance of an n winding machine can be determined regardless of the validity of a rotating d-q-o frame of reference.

The effects of videotape modeling and daily feedback on residential electricity conservation, home temperature and humidity, perceived comfort, and clothing worn: winter and summer

Abstract: Two studies were conducted in all-electric townhouses and apartments in the winter (N = 83) and summer (N = 54) to ascertain how energy conservation strategies focusing on thermostat change and set-backs and other low-cost/no-cost approaches would affect overall electricity use and electricity used for heating and cooling, the home thermal environment, the perceived comfort of participants, and clothing that was worn. The studies assessed the effectiveness of videotape modeling programs that demonstrated these conservation strategies when used alone or combined with daily feedback on electricity use. In the winter, the results indicated that videotape modeling and/or feedback were effective relative to baseline and to a control group in reducing overall electricity use by about 15% and electricity used for heating by about 25%. Hygrothermographs, which accurately and continuously recorded temperature and humidity in the homes, indicated that participants were able to live with no reported loss in comfort and no change in attire at a mean temperature of about 62°F when home and about 59°F when asleep. The results were highly discrepant with prior laboratory studies indicating comfort at 75°F with the insulation value of the clothing worn by participants in this study. In the summer, a combination of strategies designed to keep a home cool with minimal or no air conditioning, in conjunction with videotape modeling and/or daily feedback, resulted in overall electricity reductions of about 15% with reductions on electricity for cooling of about 34%, but with feedback, and feedback and modeling more effective than modeling alone. Despite these electricity savings, hygrothermograph recordings indicated minimal temperature change in the homes, with no change in perceived comfort or clothing worn. The results are discussed in terms of discrepancies with laboratory studies, optimal combinations of video-media and personal contact to promote behavior change, and energy policies that may be mislabeled as sacrificial and underestimate the effectiveness of conservation strategies such as those investigated in these studies.

Removal of organic and inorganic matter from antarctic lakes by aerial escape of bluegreen algal mats1

Abstract: Field studies on three perennially ice-covered Antarctic oasis lakes with little or no outflow disclosed a unique biological phenomenon. Benthic algal mats dominated by the prokaryotic Phormidium frigidum Fritsch and several pennate diatoms growing in shallower, more brightly illuminated areas beneath 4 to 5.5 m of ice accumulate and entrap bubbles of photosynthetically produced oxygen. Clumps of this gas-filled mat tear loose from the gravelly substrate, lift off and float to the bottom of the lake ice. Some of these floating mat pieces become frozen into newly forming ice with the onset of winter. Through the combination of ablation of ice from the upper surface and the formation of new ice from below, algal mat pieces reach the upper lake surface in 5–10 years. Here, they are lyophilized by polar winds and dispersed in at least a partially viable state. The process of mat lift-off and escape is important in removing nutrients and salts from these lakes and helps to perpetuate their oligotrophic state. Neutron activation and X-ray dispersive analyses of elements in the algal mats along with other analyses, field observations, and calculations suggest that significant quantities of organic matter, select minerals and salts are lost from the lakes annually through this process whose magnitude has not been recognized previously.