Showing papers by "Virginia Tech published in 1983"

Curing of Epoxy Matrix Composites

Abstract: Models were developed which describe the curing process of composites constructed from continuous fiber-reinforced, thermosetting resin matrix prepreg materials. On the basis of the models, a computer code was developed, which for flat-plate composites cured by a specific cure cycle, provides the temperature distribution, the degree of cure of the resin, the resin viscosity inside the composite, the void sizes, the temperatures and pressures inside voids, and the residual stress distribution after the cure. In addition, the computer code can be used to determine the amount of resin flow out of the composite and the resin content of the composite and the bleeder.

Marketing, Scientific Progress, and Scientific Method:

Abstract: It is argued that the long debate concerning the scientific credentials of marketing has been couched in terms of an idealized notion of science as the ultimate source of objectively certified know...

A History of Nigeria

Abstract: Nigeria is Africa's most populous country and the world's eighth largest oil producer, but its success has been undermined in recent decades by ethnic and religious conflict, political instability, rampant official corruption and an ailing economy. Toyin Falola, a leading historian intimately acquainted with the region, and Matthew Heaton, who has worked extensively on African science and culture, combine their expertise to explain the context to Nigeria's recent troubles through an exploration of its pre-colonial and colonial past, and its journey from independence to statehood. By examining key themes such as colonialism, religion, slavery, nationalism and the economy, the authors show how Nigeria's history has been swayed by the vicissitudes of the world around it, and how Nigerians have adapted to meet these challenges. This book offers a unique portrayal of a resilient people living in a country with immense, but unrealized, potential.

Ridges and valleys on digital images

Abstract: Ridges and valleys on digital images are found by looking for zero crossings of the first directional derivative taken in a direction which extremizes the second directional derivative. Computation of the required directional derivative is accomplished by fitting a two-variable cubic polynomial to each neighborhood of the image. Results are shown for a face image and an airphoto scene. It indicates that the technique has a good ability to find ridges and valleys.

The Topographic Primal Sketch

Abstract: A complete mathematical treatment is given for describing the topographic primal sketch of the underlying gray tone intensity surface of a digital image. Each picture element is independently classified and assigned a unique descriptive label, invariant under monotonically increasing gray tone transformations from the set (peak, pit, ridge, ravine, saddle, flat, and hillside), with hillside having subcategories (inflection point, slope, convex hill, concave hill, and saddle hill). The topographic classification is based on the first and second directional derivatives of the estimated image- intensity surface. A local, facet model, two-dimensional, cubic polynomial fit is done to estimate the image-intensity surface. Zero-crossings of the first directional derivative are identified as locations of interest in the image.

A comparison of control techniques for large flexible systems

Abstract: Two broad approaches to the active control of large flexible systems are compared, namely, coupled control and independent modal-space control. The basic difference between the two approaches lies in the manner in which the feedback controls are designed. The two methods are compared qualitatively from design and computational viewpoints, and quantitatively through the work done, performance index, and spillover effects. The comparison shows the independent modal-space control method to possess many advantages over coupled control, as it permits easier design and implementation and requires less computational effort and control energy for implementation.

Cooperative Enterprise: An Alternative Conceptual Basis for Analyzing a Complex Institution

Abstract: A recent review of the theoretical literature on cooperative enterprise in agriculture concludes: "The formal treatment of agricultural co-operation is currently impoverished by a long period of neglect" (LeVay, p. 40). The years between the early 1940s and the early 1960s were a period of creative ferment among cooperative theorists, the most durable products of which were several variants of the model of the profit-seeking firm from neoclassical price theory, with the profit maximization objective replaced by other simple maximizing criteria (e.g., Enke, Helmberger and Hoos). Such models are capable of generating hypotheses about cooperative price and output levels, but more comprehensive theoretical analogues are necessary to investigate other important aspects of the modern, complex cooperative corporation in agriculture. It is the development of these latter that has suffered neglect. While the past two decades may have generated little progress in the futher development of cooperative theory, they have been productive years for the development of more comprehensive alternatives to the simple profitmaximization model to explain the behavior of the modem, complex investor-owned corporation. This development began with the ad hoc theorizing of the various "managerial theories of the firm," proceeded with the creation of a "new institutional economics" based on the concepts of transactions costs, property rights, and agency relationships, and is currently at the stage of integrating these previous developments into a generalized neoclassical theory of organizations (De Alessi). This paper is motivated by the belief that the evolving concepts of neoclassical organization theory hold considerable promise for the further productive development of cooperative theory. The purpose of the paper is to apply some of these concepts in cursory fashion to cooperative organizations and thereby suggest a framework for the eventual development of a more comprehensive organization theory of cooperatives.

Changing National Images: International Public Relations and Media Agenda Setting

Abstract: Research within the agenda-setting framework has generally ignored the potential influence of purposive efforts by external actors (those outside the political system) to manipulate media coverage related to their interests. The present study uses interrupted time-series analysis to examine one such set of manipulative efforts, those undertaken by professional public relations consultants to influence the images of foreign nations as portrayed in the United States press. Data represent New York Times coverage of six nations that signed public relations contracts with American firms during the period from 1974 to 1978, and one nation that expressly rejected such a contract. The analysis identifies consistent patterns of improvement along two primary dimensions of national image, visibility and valence, which are associated in time with the public relations contracts.

Ecospace Utilization and Guilds in Marine Communities through the Phanerozoic

Abstract: Does the ecological theater influence the staging of the evolutionary play? What roles do biotic interactions have in influencing evolutionary patterns? This chapter presents a system of ecologic analysis for paleocommunities that reveals some relationships between the utilization of ecospace and change in diversity through time The analysis is restricted to marine shelf faunas The data base for marine faunas is the most voluminous available These faunas have been emphasized in community paleoecology because of the relatively complete fossil record of shallow marine habitats Recent studies summarizing diversity patterns for the Phanerozoic have also concentrated on the marine realm

A validated rating scale for global mental workload measurement applications

Abstract: The Cooper-Harper (1969) scale has been extensively used for evaluation of aircraft handling qualities and associated mental workload. The scale is a 10-point scale with a decision tree. A modified version of the scale, called the MCH scale, has been devised for the purpose of assessing workload in systems other than those where the human operator performs motor tasks; namely, where perceptual, mediational, and communications activity is preent. The MCH scale has been validated in three different experiments. The scale is recommended for applications in which overall mental workload is to be assessed.

A new connected components algorithm for virtual memory computers

Abstract: A new algorithm for calculating the connected components of a binary image is presented, and a proof of correctness is given. For a large image, this algorithm required 1 hour of CPU time while the standard technique used over 36 hours. The storage requirements for this new algorithm are appropriate for small minicomputers as well as for larger machines.

A simulation analysis of the japanese just‐in‐time technique (with kanbans) for a multiline, multistage production system

Abstract: The Japanese “just-in-time with kanban” technique reduces in-process inventory to absolute minimal levels, in concert with the Japanese belief that inventory is an unnecessary evil. Due to the success of Japanese firms that employ this type of system, American firms would like to import this technique and emulate Japanese successes. But this Japanese success may be attributable not only to the just-in-time with kanban technique but also to the production environment in which the technique is employed. This paper simulates the just-in-time with kanban technique for a multiline, multistage production system in order to determine its adaptability to an American production environment that might include such characteristics as variable processing times, variable master production scheduling, and imbalances between production stages. The results have practical implications for those firms considering adoption of the Japanese technique.

Are single species toxicity tests alone adequate for estimating environmental hazard

Abstract: Most biologists agree that at each succeeding level of biological organization new properties appear that would not have been evident even by the most intense and careful examination of lower levels of organization. These levels might be crudely characterized as subcellular, cellular, organ, organism, population, multispecies, community, and ecosystem. The field of ecology developed because even the most meticulous study of single species could not accurately predict how several such species might interact competitively or in predator-prey interactions and the like. Moreover, interactions of biotic and abiotic materials at the level of organization called ecosystem are so complex that they could not be predicted from a detailed examination of isolated component parts. This preamble may seem platitudinous to most biologists who have heard this many times before. This makes it all the more remarkable that in the field of toxicity testing an assumption is made that responses at levels of biological organization above single species can be reliably predicted with single species toxicity tests. Unfortunately, this assumption is rarely explicitly stated and, therefore, often passes unchallenged. When the assumption is challenged, a response is that single species tests have been used for years and no adverse ecosystem or multispecies effects were noted. This could be because single species tests are overly protective when coupled with an enormous application factor or that such effects were simply not detected because there were no systematic, scientifically sound studies carried out to detect them. Probably both of these possibilities occur. However, the important factor is that no scientifically justifiable evidence exists to indicate that degree of reliability with which one may use single species tests to predict responses at higher levels of biological organization. One might speculate that the absence of such information is due to the paucity of reliable tests at higher levels of organization. This situation certainly exists but does not explain the lack of pressure to develop such tests. The most pressing need in the field of toxicity testing is not further perfection of single species tests, but rather the development of parallel tests at higher levels of organization. These need not be inordinately expensive, time consuming, or require any more skilled professionals than single species tests. Higher level tests merely require a different type of biological background. Theoretical ecologists have been notoriously reluctant to contribute to this effort, and, as a consequence, such tests must be developed by associations of professional biologists and other organizations with similar interests.

Learned Helplessness and Victimization

Abstract: The learned helplessness phenomenon is proposed as a model for the emotional numbing and maladaptive passivity sometimes following victimization. Victims may learn during the victimization episode that responding is futile. This learning is represented as an expectation of future response-outcome independence (helplessness). Causal interpretations of the episode affect the chronicity and generality of deficits resulting from this expectation, as well as the involvement of self-esteem loss. We discuss several problems in applying the helplessness model to victimization, but we conclude that the theory may be useful in explaining why some victims become numb and passive.

Distribution, species composition and morphology of algal mats in Antarctic dry valley lakes

Abstract: Algal mats comprised primarily of the blue-green algae (cyanobacteria) Phormidium frigidum and Lyngbya martensiana, several species of pennate diatoms and heterotrophic bacteria occur abundantly th...

Attempts to promote residential water conservation with educational, behavioral and engineering strategies

Abstract: The water meters of 129 residences were read for 70 consecutive days. After five weeks of baseline, state-of-the-art education, feedback, and engineering interventions were applied according to the factorial design: 2(Education versus No Education) × 2(Daily Consumption Feedback versus No Feedback) × 2(Low Cost Conservation Devices versus No Devices). Significant water savings occurred following only the installation of low cost water conservation devices, although the amount of water saved with these devices (a daily average of 17 gallons) was much less than expected. The findings are discussed with reference to the development of cost-effective water conservation programs.

Metabolism of acetate, methanol, and methylated amines in intertidal sediments of lowes cove, maine.

Abstract: The fates and the rates of metabolism of acetate, trimethylamine, methylamine, and methanol were examined to determine the significance of these compounds as in situ methane precursors in surface sediments of an intertidal zone in Maine. Concentrations of these potential methane precursors were generally 8 h) and were characterized by formation of both 14CH4 and 14CO2. Ratios of 14CH4/14CO2 from [14C]trimethylamine and methylamine in uninhibited sediments indicated that a significant fraction of these substrates were catabolized via a non-methanogenic process. Data from inhibition experiments involving sodium molybdate and 2-bromoethanesulfonic acid supported this interpretation. [14C]methanol was oxidized relatively slowly compared with the other substrates and was catabolized mainly to 14CO2. Results from experiments with molybdate and 2-bromoethanesulfonic acid suggested that methanol was oxidized primarily through sulfate reduction. In Lowes Cove sediments, trimethylamine accounted for 35.1 to 61.1% of total methane production.

Preoperative predictors of postoperative pain

Abstract: This study attempted to predict postoperative pain from preoperative level of anxiety and the amount of information patients possessed regarding their surgery. Pain was assessed via the McGill Pain Questionnaire (MPQ) and a measure of pain complaints--number of analgesics taken. High levels of state anxiety and a high degree of information predicted the Present Pain Intensity measured of the MPQ, but did not predict the Pain Rating Index portion of the MPQ. The number of analgesics taken was predicted from the amount of information but not the level of presurgical anxiety. Biographical variables were unrelated to postoperative pain. The results were discussed in terms of State-Trait Anxiety theory, Janis' curvilinear prediction model and a contextual perspective of information imparting.

Stability of Stream Ecosystems

Abstract: The ability of ecosystems to recover from external disturbances, that is, their stability, is a fundamental property of these systems. Quantification of the ability for various ecosystems to recover and understanding of the mechanisms behind stability are currently areas of major ecological research. In this paper we present an overview of how the stability concept has been used in ecology and a more specific discussion of the application of these ideas to stream ecosystems. This is followed by a case study in which we have been observing the stability of small streams in response to watershed logging and comparing stream stability to stability of the adjacent forest ecosystem.

On the problem of observation spillover in self-adjoint distributed-parameter systems

Abstract: The problem of observation spillover in self-adjoint distributed-parameter systems is investigated. Observation spillover occurs when the output of a limited number of sensors, located at various points on the distributed domain, cannot synthesize the modal coordinates exactly. To this end, two techniques of state estimation (namely, observers and modal filters) are described. Both techniques can be used to extract modal coordinates from the system output and to implement feedback controls. It is shown that, if the residual modes are included in the observer dynamics, observation spillover cannot lead to instability in the residual modes. The problem of the unmodeled modes does remain, however. It is also shown that the modal filters have some very attractive features. In particular, modal filters can be designed to estimate the modal coordinates with such accuracy that observation spillover can be virtually eliminated. In addition, when modal filters are used, in conjunction with a sufficiently large number of sensors, the entire infinity of the system modes can be regarded as modeled, which implies that actual distributed control of the system is possible. It is also demonstrated that modal filters are quite easy to design and are not plagued by instability problems.

Acetone, Isopropanol, and Butanol Production by Clostridium beijerinckii (syn. Clostridium butylicum) and Clostridium aurantibutyricum

Abstract: Thirty-four strains representing 15 species of anaerobic bacteria were screened for acetone, isopropanol, and n-butanol (solvent) production. Under our culture conditions, several strains of Clostridium beijerinckii and C. aurantibutyricum produced at least 40 mM n-butanol (C. acetobutylicum strains produced up to 41 mM n-butanol under similar conditions). Both solvent-producing and non-solvent-producing strains of C. beijerinckii have high DNA homology with a reference strain of C. beijerinckii. Strains labeled "Clostridium butylicum" are phenotypically similar to C. beijerinckii and showed at least 78% DNA homology to a reference strain of C. beijerinckii. Therefore, these "C. butylicum" strains are members of C. beijerinckii. An earlier DNA homology study has shown that C. beijerinckii, C. aurantibutyricum, and C. acetobutylicum are distinct species.

A New Computer-Based Flux-Restrained Current-Differential Relay for Power Transformer Protection

Abstract: The paper begins with a review of techniques for computer based protection of multi-winding three-phase power transformers. After reviewing the principles of harmonic-restraint and voltage-restraint current differential protection, the paper develops a technique which computes and uses flux-current relationship of the transformer to obtain. the restraint function. It is shown that this protection technique requires fewer computations as compared to the harmonic current computation, and hence can be implemented on a microcomputer of modest. capability. The principle has been tested. in the'laboratory on a model power transformer. The relay based on this flux-restraint principle performs well on all the system phenomena simulated in the laboratory. It is expected that a relay based on this principle will be tested in the field on a power transformer.

Geometrically nonlinear transient analysis of laminated composite plates

Abstract: Forced motions of laminated composite plates are investigated using a finite element that accounts for the transverse shear strains, rotary inertia, and large rotations (in the von Karman sense). The present results when specialized for isotropic plates are found to be in good agreement with those available in the literature. Numerical results of the nonlinear analysis of composite plates are presented showing the effects of plate thickness, lamination scheme, boundary conditions, and loading on the deflections and stresses. The new results for composite plates should serve as bench marks for future investigations. mation are assumed to remain straight and normal to the midsurface after deformation (i.e., transverse shear strains are zero), has been used to calculate frequencies, static response, and dynamic response under applied loads. Recent studies in the analysis of plates have shown that the effect of the transverse shear strains on the static and dynamic response of plates is significant. For example, the natural frequencies of vibration predicted by the classical plate theory are 25% higher, for plate side-to-thickness ratio of 10, than those predicted by a shear deformation theory (SDT). In transient analysis of plates the classical plate theory predicts unrealistically large phase velocities in the plate for shorter wavelengths. The Timoshenko beam theory,3 which includes transverse shear and rotary inertia effects, has been extended to isotropic plates by Reissner 4'5 and Mindlin,6 and to laminated anisotropic plates by Yang et al.7 A generalization of the von Karman nonlinear plate theory for isotropic plates to include the effects of transverse shear and rotary inertia in the theory of orthotropic plates is due to Medwadawski,8 and that for anisotropic plates is due to Ebcioglu.9 With the increased application of advanced fiber composite material to jet engine fan or compressor blades, and in high performance aircraft, studies involving transient response of plates made of such materials are needed to assess the capability of these materials to withstand the forces of impact due to foreign objects (e.g., the ingestion of stones, nuts and bolts, hailstones, or birds in jet engines). Previous in- vestigations into the linear transient analysis of composite plates include Moon's10'11 investigation of the response of infinite laminated plates subjected to transverse impact loads at the center of the plate; Chow's12 study of laminated plates (with transverse shear and rotary inertia) using the Laplace transform technique; the Wang et al. 13 investigation, by the method of characteristi cs, of unsymmetrical orthotropic laminated plates; and Sun and Whitney's14'15 study of plates under cylindrical bending. More recently, the present author16'17 investigated the linear transient response of layered anisotropic composite rectangular plates and presented extensive numerical results for center deflection and stresses.

The Effect of Conductor Academic Task Presentation, Conductor Reinforcement, and Ensemble Practice on Performers' Musical Achievement, Attentiveness, and Attitude

Abstract: This study examined the effect of conductor academic task presentation, reinforcement, and student performance on attentiveness, achievement, and attitude of members of a university symphonic band. The band rehearsed five times under three treatment conditions: A—directions followed by ensemble performance; B—academic task presentations followed by directions and ensemble performance; and C—academic task presentations, directions, and ensemble performance, followed by conductor reinforcement. Results indicated attentiveness was a function of both performance time and treatment. All treatments resulted in gains for music achievement, with Treatment B resulting in the smallest and Treatment C resulting in the largest gains. Student attitudes were related significantly to music, conductors, and their interaction. Student ratings of rehearsal enjoyment and conductor as a good teacher were significantly related to treatments, with Treatment C consistently rated the highest.

Nucleon-nucleon partial-wave analysis to 1100 MeV.

Abstract: Comprehensive analyses of nucleon-nucleon elastic-scattering data below 1100 MeV laboratory kinetic energy are presented. The data base from which an energy-dependent solution and 22 single-energy solutions are obtained consists of 7223 pp and 5474 np data. A resonancelike structure is found to occur in the $^{1}\mathrm{D}_{2}$, $^{3}\mathrm{F}_{3}$, $^{3}\mathrm{P}_{2}$${\mathrm{\ensuremath{-}}}^{3}$${\mathrm{F}}_{2}$, and $^{3}\mathrm{F}_{4}$${\mathrm{\ensuremath{-}}}^{3}$${\mathrm{H}}_{4}$ partial waves; this behavior is associated with poles in the complex energy plane. The pole positions and residues are obtained by analytic continuation of the ``production'' piece of the T matrix obtained in the energy-dependent solution. The new phases differ somewhat from previously published VPI solutions, especially in I=0 waves above 500 MeV, where np data are very sparse. The partial waves are, however, based upon a significantly larger data base and reflect correspondingly smaller errors. The full data base and solution files can be obtained through a computer scattering analysis interactive dial-in (SAID) system at VPI, which also exists at many institutions around the world and which can be transferred to any site with a suitable computer system. The SAID system can be used to modify solutions, plan experiments, and obtain any of the multitude of predictions which derive from partial-wave analyses of the world data base.

Isolation and Characterization of a Methylotrophic Marine Methanogen, Methanococcoides methylutens gen. nov., sp. nov.

Abstract: A new genus of marine methanogenic bacteria is described that utilizes trimethylamine, diethylamine, monomethylamine, and methanol as substrates for growth and methanogenesis. Methane was not produced from H2-CO2, sodium formate, or sodium acetate. Growth on trimethylamine was stimulated by yeast extract, Trypticase (BBL Microbiology Systems, Cockeysville, Md.), rumen fluid, or B vitamins. The optimal growth temperature was 30 to 35°C. The maximum growth rate was between pH 7.0 and 7.5. Na+ (0.4 M) and MgSO4 (0.05 M) were required for maximum growth. Colonies of the type strain, TMA-10, were yellow, circular, and convex with entire edges. Cells were nonmotile, nonsporeforming, irregular cocci 1 μm in diameter which stained gram negative and occurred singly or in pairs. Micrographs of thin sections revealed a monolayered cell wall approximately 10-nm thick which consisted of protein. Cells were lysed in 0.01% sodium dodecyl sulfate or 0.001% Triton X-100. The DNA base composition was 42 mol% guanine plus cytosine. Methanococcoides is the proposed genus and Methanococcoides methylutens is the type species. TMA-10 is the type strain (ATCC 33938). Images

Interdependence and Coordination in Organizations: A Role-System Analysis

Abstract: The relations between interdependence and coordination in organizations are investigated. Results from a study of 127 work units in 33 organizations indicate that as the level of interdependence in...