Showing papers by "Virginia Tech published in 1981"

Structural Descriptions and Inexact Matching

Abstract: In this paper we formally define the structural description of an object and the concepts of exact and inexact matching of two structural descriptions We discuss the problems associated with a brute-force backtracking tree search for inexact matching and develop several different algorithms to make the tree search more efficient We develop the formula for the expected number of nodes in the tree for backtracking alone and with a forward checking algorithm Finally, we present experimental results showing that forward checking is the most efficient of the algorithms tested

Some Observations on the Cured Shape of Thin Unsymmetric Laminates

Abstract: This paper discusses the fact that the cured shape of thin unsymmetric laminates do not conform to the predictions of classical lamination theory. Rather than being saddle shaped, as predicted by the classical theory, the paper shows that thin unsymmetric laminates cure into a shape of a right circular cylinder. This anomalous behavior has been observed by many but the paper serves to quantify the effect and to inspire investigators to begin thinking about using the phenomenon to advantage. The paper indicates that the anomalous behavior is repeatable and that thicker laminates con form to the predictions of the classical theory. Laminates of the [0/902 /θ ]T, [02 /θ2 ] T and [04 /θ4 ] T families are investigated for this be havior and it is shown the principal curvature directions of the cylindrical shapes are predictable.

Black Consciousness and Political Participation: The Missing Link

Abstract: Recent research has demonstrated that black Americans are far more politically active than whites of similar socioeconomic status. The difference has been related to black consciousness. Yet the reasons for this relationship have not been adequately explained. Starting with the work of Gurin and Gamson, this article theorizes that black consciousness contributes to political mistrust and a sense of internal political efficacy which in turn encourages policy-related participation. The relationship between the two attitudes and policy-related behavior is demonstrated to be conditional. The conditions favor blacks more than whites. What I shall call the Gamson-Gurin thesis is supported by data from Verba's and Nie's 1967 survey of the American public. The thesis, and its derivations, prove useful in clarifying the scope and nature of black participation in the American political process as well as helping us to understand how individuals in general select one mode of participation over another and how the choice varies by race and social class.

Phanerozoic marine diversity and the fossil record

Abstract: Strong correlations between various local and global estimates of Phanerozoic marine diversity for taxa below the ordinal level indicate a single pattern of change underlying all data on fossil density. Geological time alone seems insufficient to explain all of the significant covariation among the data sets, and it is proposed that the common pattern in diversity reflects the signal from a real evolutionary phenomenon strong enough to overcome the biases inherent in the fossil record.

Calculations of the Room-Temperature Shapes of Unsymmetric Laminatestwo

Abstract: A theory explaining the characteristics of the cured shapes of unsymmetric laminates is presented. The theory is based on an extension of classical lamination theory which accounts for geometric nonlinearities. A Rayleigh-Ritz approach to minimizing the total potential energy is used to obtain quantitative information regarding the room temperature shapes of square T300/5208 (0(2)/90(2))T and (0(4)/90(4))T graphite-epoxy laminates. It is shown that, depending on the thickness of the laminate and the length of the side the square, the saddle shape configuration is actually unstable. For values of length and thickness that render the saddle shape unstable, it is shown that two stable cylindrical shapes exist. The predictions of the theory are compared with existing experimental data.

Consumer Perceptions of Comparative Price Advertisements

Abstract: The authors analyze the issue of comparative price advertising from a behavioral perspective. Because public policy recognizes that comparative pricing may lead to consumer misperceptions, the auth...

Strategies in Rater Training

Abstract: There is no evidence to support the belief that training raters to change rating distributions will increase accuracy or validity. Such training may merely promote a temporary and situation-specific response set. We call for a new emphasis in rater training programs on: (1) diary-keeping procedures to increase observational skills; (2) the establishment of a common rater frame of reference to enhance agreement on what constitutes effective job performance; and (3) mastery-based training to increase rater self-efficacy regarding negative appraisal situations.

Fault Diagnosis in a Boolean n Cube Array of Microprocessors

Abstract: Fault- tolerant characteristics of a Boolean n cube array of microprocessors are analyzed. Connectivity properties of the network graph are used to show that n processor or link failures are required to isolate a processor. For processor failures the network is shown to be n (one step) diagnosable. A testing algorithm is presented which can diagnose up to n processor failures.

Evaluating Returns to Agricultural Research: A Review

Abstract: This paper reviews and compares the most common approaches used to evaluate public agricultural research investment. Ex post studies fall into two major groups: (a) consumer and producer surplus analyses, estimating average rates of return to research, and (b) production function analyses, estimating marginal rates of return to research. Ex ante studies fall into four groups: (a) those using scoring models to rank research activities, (b) those employing benefit-cost analysis to establish rates of return to research, (c) those using simulation models, and (d) those using mathematical programming to select an optimal mix of research activities.

Acorn dispersal by the blue jay (Cyanocitta cristata).

Abstract: Blue jays transported and cached 133,000 acorns from a stand of Quercus palustris trees in Blacksburg, Virginia, representing 54% of the total mast crop. A further 20% (49,000) of the mast crop was eaten by jays at the collecting site. A large proportion of the nuts remaining beneath the collecting trees was parasitized by curculionid larvae. The number of nuts transported per caching trip ranged from 1–5 with a mean of 2.2. Mean distance between seed trees and caches was 1.1 km (range: 100 m–1.9 km). Jays appeared to choose species with small- to medium-sized nuts (Quercus palustris, Q. phellos, Q. velutina, Fagus grandifolia) and avoided the larger nuts of Q. borealis and Q. alba. Nuts were cached singly within a few meters of each other and were always covered with debris. Covering may improve germination and early growth by protecting the nut and radicle from desiccation. The vegetation structure of most suburban caching sites was analogous to open, disturbed environments in more natural landscapes. The presence of numerous Quercus seedlings in jay caching sites and the tendency for jays to cache nuts in environments conducive to germination and early growth indicate that blue jays facilitate colonization of members of the Fagaceae.

An overview of the nonequilibrium behavior of polymer glasses

Abstract: It is pointed out that research efforts are at present being directed in two areas, one comprising experimental studies of this phenomenon in various glassy polymer systems and the other involving the development of a quantitative theory capable of satisfactorily predicting aging behavior for a variety of polymer materials under different conditions. Recent work in both these areas is surveyed. The basic principles of nonequilibrium behavior are outlined, with emphasis placed on changes in material properties with annealing below the glass transition temperature. Free volume theory and thermodynamic theory are discussed.

Carbonate ramp‐to‐deeper shale shelf transitions of an Upper Cambrian intrashelf basin, Nolichucky Formation, Southwest Virginia Appalachians

Abstract: The Nolichucky Formation (0–300 m thick) formed on the Cambrian pericratonic shelf in a shallow intrashelf basin bordered along strike and toward the regional shelf edge by shallow water carbonates and by nearshore clastics toward the craton. Lateral facies changes from shallow basinal rocks to peritidal carbonates suggest that the intrashelf basin was bordered by a gently sloping carbonate ramp. Peritidal facies of the regional shelf are cyclic, upward-shallowing stromatolitic carbonates. These grade toward the intrashelf basin into shallow ramp, cross-bedded, ooid and oncolitic, intraclast grain-stones that pass downslope into deeper ramp, subwave base, ribbon carbonates and thin limestone conglomerate. Ribbon limestones are layers and lenses of trilobite packstone, parallel and wave-ripple-laminated, quartzose calcisiltite, and lime mudstone arranged in storm-generated, fining upward sequences (1–5 cm thick) that may be burrowed. Shallow basin facies are storm generated, upward coarsening and upward fining sequences of green, calcareous shale with open marine biota; parallel to hummocky laminated calcareous siltstone; and intraformational flat pebble conglomerate. There are also rare debris-flow paraconglomerate (10–60 cm thick) and shaly packstone/wackestone with trace fossils, glauconite horizons and erosional surfaces/hardgrounds. A 15-m thick tongue of cyclic carbonates within the shale package contains subtidal digitate algal bioherms which developed during a period of shoaling in the basin. Understanding the Nolichucky facies within a ramp to intrashelf basin model provides a framework for understanding similar facies which are widely distributed in the Lower Palaeozoic elsewhere. The study demonstrates the widespread effects of storm processes on pericratonic shelf sedimentation. Finally, recognition of shallow basins located on pericratonic shelves is important because such basins influence the distribution of facies and reservoir rocks, whose trends may be unrelated to regional shelf-edge trends.

The time and state relationships in simulation modeling

Abstract: Time and state descriptions form the core of a simulation model representation. The historical influence of initial application areas and the exigencies of language implementations have created a muddled view of the time and state relationships. As a consequence, users of simulation programming languages work in relative isolation; model development, simulation application, model portability, and the communication of results are inhibited and simulation practice fails to contribute to the recognition of an underlying foundation or integrating structure. A model representation structure has been forged from a small set of basic definitions which carefully distinguish the state and time relationships. This paper focuses on the coordination of the time and state concepts using \"object\" as the link. In addition to clarifying the relationships, the structure relates the concept of \"state-sequenced simulation\" to the variations in time flow mechanisms. In conclusion, some speculations are offered regarding alternative algorithms for time flow mechanisms.

Mafic Silicates as Indicators of Intensive Variables in Granitic Magmas

Abstract: Reactions that involve biotites, amphiboles, pyroxenes and olivines place significant constraints on the intensive variables of magmas that crystallize to form granitic rocks. Fe2+-bearing minerals such as magnetite, il menite, olivine, pyroxene, amphibole, biotite, and allanite constrain oxygen and sulfur fugacities. All (OH)bearing phases place constraints on H2O fugacities, especially if anhydrous reactants are present. Exchange reactions of (OH)with halogens also place additional constraints on magma properties. Late stage subsolidus reactions commonly recrystallize these minerals and make interpretation more difficult. Intensive parameters change during the history of a given magma. Sequences of crystallization, coupled with the composition of minerals, can record devolatilization reactions, increases in volatile constituents, and tempera tures of magmas crystallizing to form plutons. The intrinsic properties of a magma may reflect the source region, but may also change significantly during the history of a given magma. Reactions involving hydrous minerals in the source region place strong constraints on the initial water content of magmas. In regions of repeated crustal melting, early granitic magmas will be more hydrous than subsequent ones. Introduction The relationship of mineral assemblages in granitic rocks to the intensive variables of the original magma is not always obvious. Many granitic plutons react with the magmatic fluids during cooling (e.g., CZAMANSKE and MIHALIK, 1972; CZAMANSKE and WONES, 1973), while others clearly react with metamorphic fluids (FERRY, 1979). The mafic silicates record much of the crystallization and cooling history of a given pluton, and can, used in conjunction with the oxides, sulfides, and feldspars, provide information about the original magma. TAKAHASHI et al. (1980) review the comparison of magnetiteand ilmenite-series granitoids (ISHIHARA, 1977) and Iand S-type granitoids (CHAPPELL and WHITE, 1974). EWART (1979), in a review of volcanic rocks and tectonic settings, pointed out that the relative oxidation states of volcanic rocks are related to tectonic setting. ISHIHARA et al. (1979) have stressed the importance of oxidation state on the origin of Sn-bearing granites. This paper reviews the relative stabilities of biotites and amphiboles in granitic magmas and suggests specific observations to be made on granitic rocks that aid in the interpretation of the initial magma. Stabilities of Hydrous Silicates The relative positions of dehydration reactions of amphiboles and biotites are shown in Figures 1 and 2 (see also ERNST, 1968). These data are taken from the references listed in Table 1, and are rephrased in log fH2O and 1/K in Figure 1, using the data of BURNHAM et al. (1969) for the properties of H2O. The fundamental reaction for each of these curves is: R2+(OH)2(amphibole, biotite) =R2+(silicate)+H2O As pointed out by HAZEN and WONES (1972, * Paper presented in the Symposium on Granitic Magmatism and Associated Mineralization in Japan and Korea, held in Tokyo on January 27, 1981. The manuscript received on March 3; accepted on June 29, 1981. ** Department of Geological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 U.S.A.

On the relationship between engineering properties and delamination of composite materials

Abstract: The influence of the coefficient of mutal influence, Poisson's ratio and coefficients of thermal and moisture expansion on delamination is studied. Engineering theories are compared to finite element and experimental results. It is shown that the mismatch in coefficients of mutual influence can have a strong influence on delamination with fiber angles in the 10-15 degree range being critical for adjacent layer combinations. The mismatch in coefficient of mutual influence is reduced by a factor of two and the interlaminar shear stress is reduced significantly when the + or - adjacent layers are interspersed between 0 and 90 degree layers. It is shown how the results can be used for design of composite laminates.

Altered Tissue Content and Cytosol Distribution of Trace Metals in Experimental Diabetes

Abstract: An insulin-dependent diabetic condition was induced in male Sprague-Dawley rats by streptozotocin injection. Ten days after administration of the diabetogenic drug, tissue levels of copper, zinc, iron and manganese were determined and compared to control animals. Increased quantities of hepatic copper, zinc and manganese, renal copper and zinc and plasma zinc were observed in the diabetic group. Intestinal, muscle and spleen contents of the metals were similar in control and diabetic rats. Elevated levels of zinc- and copper-metallothionein were found in liver and kidney of diabetic rats. The distribution of zinc among soluble proteins in the diabetic liver was also content of tissues, intracellular distribution of zinc and the quantity of zinc-and copper-metallothionein to normal levels. Pair-feeding copper, zinc, iron and manganese to diabetic and control groups demonstrated that the enhanced food consumption of the diabetic rat was not a significant factor in the observed accumulation of trace metals in liver and kidney. These data suggest that the hormonal imbalance characteristic of the insulin-dependent diabetic condition influences trace metal metabolism. These studies also demonstrate the usefulness of the streptozotocin-diabetic rat as an animal model for investigations concerning hormone-mediated regulation of trace metal metabolism.

Fatigue Damage Evaluation through Stiffness Measurements in Boron-Epoxy Laminates:

Abstract: Stiffness reductions, resulting from fatigue damage, were measured for unnotched [±45]s, [0/90] s, and [0/90/ ±45 ] s boron/epoxy laminates. Deg radation in the various in-plane stiffnesses (Exx, Byy, Gxy) were measured using a combination of uniaxial tension, rail shear, and flexure tests. An attempt was made to predict stiffness loss at failure from a secant modulus criterion. Damage growth and stiffness loss were load-history dependent, hence, the secant modulus criterion is not a valid criterion for general application.

Race, residence, and leisure style: some policy implications.

Abstract: The relationships between race, residence, and leisure style are examined to ascertain if leisure differences are a consequence of subcultural diversity (ethnicity) or differential allocation of recreational resources (marginality). Findings obtained from a sample of urban blacks and whites indicate that ethnicity is a factor that should be considered in the planning and placement of public recreation programs. However, for blacks living in predominantly white residential settings, as opposed to an ethnic community, ethnicity does not appear to be an issue. Expectations of leisure needs are higher for this group, perhaps illustrating anticipatory socialization or compensation for limited informal leisure involvement. It is suggested that both the theoretical and policy implications of the marginality and ethnicity perspectives be re‐examined.

Temperature‐growth responses of algal isolates from antarctic oases1

Abstract: Thirty-five taxa (128 clonal cultures) of Antarctic algae isolated from various habitats were assayed for growth over a range of 2–34°C. Isolates, all unialgal and two axenic, varied markedly in their temperature-growth responses. Only four taxa belonging to either the Chlamydomonadaceae or Ulotrichaceae were obligately cold-adapted and incapable of growth at ≥20°C. All isolates grew at temperatures ranging from 7.5 to 18°C, and a few were incapable of growth at ≤5°C. Over one-third of the isolates grew at 30°C, but none grew at 34°C. Percentages of cold-adapted clones correlated well with the more stable low temperature habitats. Four chlamydomonad isolates displayed optimum temperatures for growth near their maximum temperatures for growth, both temperatures being well above those of the native habitats. This temperature-growth response suggests a closer relationship to algae from more moderate thermal regions than one might have supposed. However, the ability to grow at low temperatures and the inability to grow at 34°C suggest that these Antarctic algae are cold temperature adapted. Growth capability at low in situ temperatures is considered more useful ecologically than physiologically-defined categories for algae based on their maximum temperature for growth.

Some Neighborhood Operators

Abstract: In this paper we review a variety of neighborhood operators in a way which emphasizes their common form. These operators are useful for image segmentation tasks as well as for the construction of primitives involved in structural image analysis. The common form of the operators suggests the possibility of a large scale integration hardware implementation in the VLSI device technology.

On the Substructure Synthesis Method

Abstract: Substructure synthesis is a model reduction method whereby a complex structure is regarded as an assemblage of substructures. The motion of each of the substructures is represented by a series of admissible functions (vectors), and the substructures are made to act as a single structure by imposing certain geometric compatibility conditions at the boundary between any two adjacent substructures. Because the series of admissible functions (vectors) represents the motion of the substructures only approximately and because the geometric compatibility conditions are only approximations of the true conditions, the computed eigensolution is only an approximation of the actual one. Convergence of computed eigenvalues to actual eigenvalues requires two limiting processes, one in which the number of admissible functions (vectors) is increased and the other in which the number of geometric compatibility conditions is increased.