Showing papers by "Virginia Tech published in 1992"
TL;DR: In contrast to the dominant multiattribute commodity view of outdoor recreation settings, wilderness users are described as having emotional and symbolic ties to the setting that are manifested as attachment to the site and the wilderness concept as mentioned in this paper.
Abstract: In contrast to the dominant multiattribute commodity view of outdoor recreation settings, wilderness users are described as having emotional and symbolic ties to the setting that are manifested as attachment to the site and the wilderness concept. Data from four wilderness areas show stronger place and wilderness attachment to be associated with previous visits, rural residence, a setting (as opposed to activity or group) focus, visiting alone and on weekdays, hunting in the area, and sensitivity to site impacts and horse encounters. Place attachment is also associated with a lack of nonwilderness substitutes and lower income and education. Wilderness attachment is associated with membership in wilderness and conservation organizations, visits to more wilderness areas, a preference for longer visits, participation in nature study, and sensitivity to sight and sound intrusions and hiker encounters. The importance of understanding emotional and symbolic values of natural resources is discussed in r...
1,251 citations
TL;DR: A group of practitioners and researchers discuss the role of parameter design and Taguchi's methodology for implementing it and the importance of parameter-design principles with well-established statistical techniques.
Abstract: It is more than a decade since Genichi Taguchi's ideas on quality improvement were inrroduced in the United States. His parameter-design approach for reducing variation in products and processes has generated a great deal of interest among both quality practitioners and statisticians. The statistical techniques used by Taguchi to implement parameter design have been the subject of much debate, however, and there has been considerable research aimed at integrating the parameter-design principles with well-established statistical techniques. On the other hand, Taguchi and his colleagues feel that these research efforts by statisticians are misguided and reflect a lack of understanding of the engineering principles underlying Taguchi's methodology. This panel discussion provides a forum for a technical discussion of these diverse views. A group of practitioners and researchers discuss the role of parameter design and Taguchi's methodology for implementing it. The topics covered include the importance of vari...
654 citations
TL;DR: In this paper, the use of a genetic algorithm to optimize the stacking sequence of a composite laminate for buckling load maximization is studied, and the advantage of the genetic algorithm in producing several near-optimal designs is discussed.
Abstract: The use of a genetic algorithm to optimize the stacking sequence of a composite laminate for buckling load maximization is studied. Various genetic parameters including the population size, the probability of mutation, and the probability of crossover are optimized by numerical experiments. A new genetic operator - permutation - is proposed and shown to be effective in reducing the cost of the genetic search. Results are obtained for a graphite-epoxy plate, first when only the buckling load is considered, and then when constraints on ply contiguity and strain failure are added. The influence on the genetic search of the penalty parameter enforcing the contiguity constraint is studied. The advantage of the genetic algorithm in producing several near-optimal designs is discussed.
576 citations
TL;DR: In this paper, the authors analyze a classroom lesson in which a student teacher was unsuccessful in providing a conceptually based justification for the standard divisionoffractions algorithm, and explain why the lesson failed, what it reveals about learning to teach, and what the implications are for mathematics teacher education.
Abstract: This article analyzes from several vantage points a classroom lesson in which a student teacher was unsuccessful in providing a conceptually based justification for the standard division-offractions algorithm. We attempt to understand why the lesson failed, what it reveals about learning to teach, and what the implications are for mathematics teacher education. We focus on (a) the student teacher's beliefs about good mathematics teaching, her knowledge related to division of fractions, and her beliefs about learning to teach; and (b) the treatment of division of fractions in the mathematics methods course she took. The student teacher's conception of good mathematics teaching included components compatible with current views of effective mathematics teaching. However, these beliefs are difficult to achieve without a stronger conceptual knowledge base and a greater commitment to use available resources and to engage in hard thinking than she possessed. Further, the mathematics methods course did not require the student teacher to reconsider her knowledge base, to confront the contradictions between her knowledge base and at least some of her beliefs, or to reassess her beliefs about how she would learn to teach. These findings suggest that mathematics teacher education programs should reconsider how they provide subject matter knowledge and opportunities to teach it, and whether and how they challenge student teachers' existing beliefs.
499 citations
TL;DR: This article identified variables that influence teachers' commitment and job satisfaction among both general and special educators, and determined the extent to which these commitment and satisfaction variables influenced teachers' intent to stay in teaching.
Abstract: The primary purpose of this study was to identify variables that influence teachers' commitment and job satisfaction among both general and special educators. A secondary purpose was to determine the extent to which these commitment and satisfaction variables influence teachers' intent to stay in teaching. A questionnaire using primarily extant measures was sent to a random sample of 558 special educators and 589 general educators in Virginia. Completed questionnaires were received from 83% of both samples. Crossvalidated regression results suggest that workrelated variables, such as leadership support, role conflict, role ambiguity, and stress, are better predictors of commitment and job satisfaction than are demographic variables. Generally, the findings were similar for general and special educators. Implications for educational agencies are addressed.
437 citations
TL;DR: This paper is concerned with the development of an algorithm for general bilinear programming problems, and develops a new Reformulation-Linearization Technique (RLT) for this problem, and imbeds it within a provably convergent branch-and-bound algorithm.
Abstract: This paper is concerned with the development of an algorithm for general bilinear programming problems. Such problems find numerous applications in economics and game theory, location theory, nonlinear multi-commodity network flows, dynamic assignment and production, and various risk management problems. The proposed approach develops a new Reformulation-Linearization Technique (RLT) for this problem, and imbeds it within a provably convergent branch-and-bound algorithm. The method first reformulates the problem by constructing a set of nonnegative variable factors using the problem constraints, and suitably multiplies combinations of these factors with the original problem constraints to generate additional valid nonlinear constraints. The resulting nonlinear program is subsequently linearized by defining a new set of variables, one for each nonlinear term. This “RLT” process yields a linear programming problem whose optimal value provides a tight lower bound on the optimal value to the bilinear programming problem. Various implementation schemes and constraint generation procedures are investigated for the purpose of further tightening the resulting linearization. The lower bound thus produced theoretically dominates, and practically is far tighter, than that obtained by using convex envelopes over hyper-rectangles. In fact, for some special cases, this process is shown to yield an exact linear programming representation. For the associated branch-and-bound algorithm, various admissible branching schemes are discussed, including one in which branching is performed by partitioning the intervals for only one set of variables x or y, whichever are fewer in number. Computational experience is provided to demonstrate the viability of the algorithm. For a large number of test problems from the literature, the initial bounding linear program itself solves the underlying bilinear programming problem.
400 citations
TL;DR: In this article, the authors analyzed the thermal conductivity of the ZnS-diamond interface with different values of α, defined to be equal to the Kapitza radius divided by the particle radius.
Abstract: We have observed that the thernal conductivity of zincsulphide is increased by adding large particles of highly conducting diamond, but lowered by the addition of sub-micron size particles of diamond. This effect is explained in terms of the interfacial thermal resistance which becomes increasingly dominant as the particles becomes smaller (because that increases their surface to volume ratio). A phenomonological model in which the interface resistance is expressed as an effective Kapitza radius, ak, is presented. The conductivity of the composite is analyzed for different values of α, which is defined to be equal to the Kapitza radius divided by the particle radius. If α = 1, that is, the actual particle radius is equal to ak then the effective thermal conductivity of the particles is equal to that of the matrix. If α > 1, that is the particles are very small, then the contribution of the particles to the thermal conductivity of the composite is dominated by interfaces; if α < 1 then the bulk property of the particles is important. Our measurements yield ak ≈ 1.5 μm for the ZnS-diamond interface.
355 citations
TL;DR: Six hundred fourth-graders rated how much they liked to play with each of their classmates and then nominated their three best friends and their utility in identifying children at risk for later maladjustment is discussed.
Abstract: Six hundred fourth-graders rated how much they liked to play with each of their classmates and then nominated their three best friends; 296 of the 600 children were assigned sociometric classifications of popular, neglected, average, controversial, or rejected status (the remaining 304 children failed to meet inclusion criteria). Five years later, 267 of the 296 classified children (90.2%) were evaluated on measures of academic performance, social behavior, and psychological adjustment. The number and type of contacts with the juvenile justice system were also determined. In general, children classified as rejected or controversial tended to fare more poorly on indices of long-term adjustment than did children classified as popular, neglected, or average. Results are discussed in terms of the predictive validity of sociometric rating and nomination procedures and their utility in identifying children at risk for later maladjustment.
354 citations
TL;DR: In this article, dietary fibers, starches, and Polydextrose® were incorporated into 5 and 10% fat hamburger for texture modification and comparison to 5, 10, 20, and 30% fat controls.
Abstract: Dietary fibers, starches, and Polydextrose® were incorporated unhydrated into 5 and 10% fat hamburger for texture modification and comparison to 5, 10, 20, and 30% fat controls. Levels for individual and total ingredients ranged from 0.5 to 4% and 3.5 to 6%, respectively. Treatments containing Polydextrose, starch, and fiber had cooking losses 20–40% less than controls. Patties containing three-way combinations of ingredients were more similar to 20% fat controls for texture traits than were those containing 1 or 2 ingredients: Patties with ingredients had less oily coating of the mouth, but were less juicy than controls. Beef flavor intensity scores were reduced slightly for low-fat patties with ingredients. Texture modification of low-fat ground beef is possible with food-grade ingredients.
348 citations
TL;DR: This paper is concerned with the development of an algorithm to solve continuous polynomial programming problems for which the objective function and the constraints are specified polynomials, and a linear programming relaxation is derived based on a Reformulation Linearization Technique.
Abstract: This paper is concerned with the development of an algorithm to solve continuous polynomial programming problems for which the objective function and the constraints are specified polynomials. A linear programming relaxation is derived for the problem based on a Reformulation Linearization Technique (RLT), which generates nonlinear (polynomial) implied constraints to be included in the original problem, and subsequently linearizes the resulting problem by defining new variables, one for each distinct polynomial term. This construct is then used to obtain lower bounds in the context of a proposed branch and bound scheme, which is proven to converge to a global optimal solution. A numerical example is presented to illustrate the proposed algorithm.
341 citations
TL;DR: In this article, the modes of crushing and their controlling mechanisms are described and the resulting crushing process and its efficiency are addressed, as well as its efficiency and its response is complex and depends on interaction between the different mechanisms that control the crushing process.
Abstract: Composite tubes can be reinforced with continuous fibers. When such tubes are subjected to crushing loads, the response is complex and depends on interaction between the different mechanisms that control the crushing process. The modes of crushing and their controlling mechanisms are described. Also, the resulting crushing process and its efficiency are addressed.
TL;DR: The authors examined the attributions of young adults about their relationships with their parents and intimate others and found that higher relationship quality was related to attributions in ways that were consistent with attributional theory.
Abstract: This study examined the attributions of young adults about their relationships with their parents and intimate others. In addition to their attributional reports, participants also provided information about the quality of their intimate relationships. The findings indicated that higher relationship quality was related to attributions in ways that were consistent with attributional theory. In addition, attributional differences between current and past relationships suggested relationship-sustaining versus relationship-terminating attributional patterns. Attributions about intimate relationships also were associated with attributions about relationships with parents. Specifically, (a) the attributions that individuals made about the positive aspects of their relationships with their mothers and (b) and the attributions about the negative aspects of their relationships with their fathers were related to their attributions in their intimate relationship. The findings suggest some refinements in attribution ...
TL;DR: The yeast and bacterial expression systems described here may be useful for further studies on the problem of expressing a biologically active peptide before scorpion toxins might be used for the genetic engineering of plants for insect resistance.
TL;DR: The needle content and kinetic properties of GR, the increased activities of other enzymes, and the high substrate concentrations observed during the winter are consistent with the protective function this pathway may provide against photooxidative, winter injury.
Abstract: Antioxidant metabolites in eastern white pine (Pinus strobus L.) needles increased two- to fourfold from the summer to the winter season. Antioxidant enzymes in needle tissue increased between 2- and 122-fold during this same period. These seasonal changes were determined by monitoring ascorbate and glutathione concentrations and the activity of ascorbate peroxidase, glutathione reductase (GR), and superoxide dismutase. Levels of antioxidant metabolites and enzymes were observed always to be lowest during the summer, or active growing season, and highest during the winter, or dormant season. These data correlated well with the thermal kinetic window for purified GR obtained from summer needles. The minimum, apparent Km,NADPH for two isoforms of GR (GRA and GRB) occurred at 5 and 10°C, respectively. The upper limit of the thermal kinetic window (200% of the minimum Km) for GRA and GRB was 20 and 25°C, respectively, indicating that needle temperatures exceeding 25°C may result in impairment of antioxidant metabolism. The needle content and kinetic properties of GR, the increased activities of other enzymes, and the high substrate concentrations observed during the winter are consistent with the protective function this pathway may provide against photooxidative, winter injury.
TL;DR: The authors explored the influence of probability on risky choice, by proposing and estimating a parametric model of risky decision making, and found that the transformation differs for most subjects depending upon whether the risky outcomes are gains or losses.
Abstract: The appeal of expected utility theory as a basis for a descriptive model of risky decision making has diminished as a result of empirical evidence which suggests that individuals do not behave in a manner consistent with the prescriptive tenets of EUT. In this paper, we explore the influence of probability on risky choice, by proposing and estimating a parametric model of risky decision making. Our results suggest that models which provide for probability transformations are most appropriate for the majority of subjects. Further, we find that the transformation differs for most subjects depending upon whether the risky outcomes are gains or losses. Most subjects are considerably less sensitive to changes in mid-range probability than is proposed by the expected utility model and risk-seeking behavior over ‘long-shot’ odds is common.
TL;DR: In this article, the authors affirm the nature of their identities through a variety of mechanisms, including selection of and participation in leisure activities, and through leisure activities we are able to constrain and constrain ourselves.
Abstract: Individuals affirm the nature of their identities through a variety of mechanisms, including selection of and participation in leisure activities. Through leisure activities we are able to construc...
TL;DR: In this article, ground beef patties containing 5, 10, 15, 20, 25, and 30% fat were evaluated raw and after cooking to either 71 or 77°C.
Abstract: Ground beef patties containing 5, 10, 15, 20, 25, and 30% fat were evaluated raw and after cooking to either 71 or 77°C. Cooking losses were lowest for 5–20% fat patties (24.7-26.0%), intermediate for 25% fat patties (28.9%), and highest for 30% fat patties (32.1%). Low-fat patties (5 and 10%) were firmer in texture, more crumbly at end-of-chewing, less juicy and flavorful, and caused less oily coating of the mouth than 20–30% fat patties. Warner-Bratzler and Lee-Kramer shear forces decreased as fat increased. Instron texture profile analysis also indicated greater peak forces, springiness, and cohesiveness for low-fat patties. Cooking to 77 vs 71°C accentuated differences in palatability between low- and high-fat patties.
TL;DR: It was deduced that the processes leading to differentiation involved a combination of molecular events that include base substitutions and insertion/deletions, which demonstrate that indica rice is genetically more diverse than japonica type.
Abstract: Genetic diversity and differentiation in indica and japonica groups of the cultivated rice (Oryza sativa L.) were studied by assaying DNA restriction fragment length polymorphisms of 12 indica and 14 japonica rice lines digested with three restriction endonucleases. A total of 49 probes were selected to represent the entire RFLP map at intervals of 20-30 cM. It was shown that 95 of the 145 possible probe/enzyme combinations, involving 43 probes and all three enzymes, detected restriction fragment length variation, and the degree of polymorphism varied greatly from one probe/enzyme combination to another. These results demonstrate that indica rice is genetically more diverse than japonica type. Significant differentiation between the two rice groups was detected by 33 probes representing 11 of the 12 rice chromosomes. It was deduced that the processes leading to differentiation involved a combination of molecular events that include base substitutions and insertion/deletions.
TL;DR: The current understanding of the methanogenic fermentation of acetate provides impressions of nature's novel solutions to problems of methyl transfer, electron transport, and energy conservation.
Abstract: The general features are known for the pathway by which most methane is produced in nature. All acetate-utilizing methanogenic microorganisms contain CODH which catalyzes the cleavage of acetyl-CoA; however, the pathway differs from all other acetate-utilizing anaerobes in that the methyl group is reduced to methane with electrons derived from oxidation of the carbonyl group of acetyl-CoA to CO2. The current understanding of the methanogenic fermentation of acetate provides impressions of nature's novel solutions to problems of methyl transfer, electron transport, and energy conservation. The pathway is now at a level of understanding that will permit productive investigations of these and other interesting questions in the near future.
TL;DR: A conceptual framework composed of eight categories of mentoring activities that address five domains of beginning teachers' concerns was developed based on the reported activities of 150 teachers who were lead mentors as discussed by the authors.
Abstract: A conceptual framework composed of eight categories of mentoring activities that address five domains of beginning teachers' concerns was developed based on the reported activities of 150 teachers who were lead mentors. The study suggests that experienced teachers possess an extensive repertoire of helping strategies and that, with opportunities for collaboration, teachers can develop and shape complex mentoring roles that meet beginning teachers' needs. Conditions that influence mentoring relationships include school context factors and mentor and beginning teacher characteristics. Mentoring programs thus should not attempt to rigidly specify mentoring roles. With support, experienced teachers can provide assistance tailored to the circumstances of beginning teachers in individual schools.
TL;DR: Findings support the conclusion that waters, soils, and aerosols of the acid, brown-water swamps of the southeastern United States coastal plain represent major environmental sources likely connected with the higher incidence of human infection in this region.
Abstract: Mycobacterium avium, Mycobacterium intracellulare, and Mycobacterium scrofulaceum (MAIS) organisms were isolated and identified from waters, soils, aerosols, and droplets ejected from water collected from four geographically separate aquatic environments (Okefenokee Swamp, GA; Dismal Swamp, VA; Claytor Lake, VA; and Cranberry Glades, WV) during several seasons. Recovery of MAIS was significantly higher from waters, soils, and aerosols collected from the two acid, brown-water swamps located in the southeastern coastal plain. High MAIS numbers correlated with warmer temperature, low pH, low dissolved oxygen, high soluble zinc, high humic acid, and high fulvic acid. This research, in relation to previous findings for the geographic distribution and physiologic ecology of MAIS, supports the conclusion that waters, soils, and aerosols of the acid, brown-water swamps of the southeastern United States coastal plain represent major environmental sources likely connected with the higher incidence of human infection in this region.
TL;DR: In this article, it is shown that the Shapley value of these projected games can be interpreted as an index that measures the power of the players in the permission structure, and that the collection of these games forms a subspace of the vector space of all games with side payments on a specified player set.
Abstract: This paper is devoted to the game theoretic analysis of decision situations, in which the players have veto power over the actions undertaken by certain other players. We give a full characterization of the dividends in these games with a permission structure. We find that the collection of these games forms a subspace of the vector space of all games with side payments on a specified player set. Two applications of these results are provided. The first one deals with the projection of additive games on a permission structure. It is shown that the Shapley value of these projected games can be interpreted as an index that measures the power of the players in the permission structure. The second application applies the derived results on games, where the organization structure can be analysed separately from the production capacities of the participating players.
TL;DR: A scheme based on the zinc‐binding site is proposed to classify metalloendopeptidases into five distinct families: thermolysin, astacin, serratia, matrixin, and snake venom metalloproteinases.
TL;DR: Results demonstrate that the mouse whey acidic protein gene contains regulatory elements that can direct cDNA expression at high levels in the pig mammary gland.
Abstract: Transgenic pigs were generated that produced human protein C in their milk at up to 1 g/liter. The gene construct was a fusion gene consisting of the cDNA for human protein C inserted into the first exon of the mouse whey acidic protein gene. These results demonstrate that the mouse whey acidic protein gene contains regulatory elements that can direct cDNA expression at high levels in the pig mammary gland. Recombinant human protein C that was produced at about 380 micrograms/ml per hr in transgenic pig milk possessed anticoagulant activity that was equivalent to that of protein C derived from human plasma. These studies provide evidence that gamma-carboxylation can occur at high levels in the mammary gland of a pig.
TL;DR: In this paper, a brief review of both the destructive and non-destructive techniques used for detecting and characterizing defects and damage is presented, and the ability of each technique to identify the various fracture mechanisms involved in the failure of long fibre reinforced composites is discussed and their overall suitability for damage detection evaluated.
Abstract: In this paper the various failure modes which occur in long fibre composites are described and discussed. The significance of each of these fracture mechanisms, in terms of their energy-dissipating capacity as well as their effect on the residual load-bearing properties, is considered. A brief review of both the destructive and non-destructive techniques used for detecting and characterizing defects and damage is presented. The ability of each technique to identify the various fracture mechanisms involved in the failure of long fibre reinforced composites is discussed and their overall suitability for damage detection evaluated.
TL;DR: Five models linking remarriage-induced attributes to an increased probability of a decline in marital quality and divorce are evaluated and all but socioeconomic status are found to explain declines in maritalquality and higher levels of marital instability.
Abstract: Using interview data from a national sample of married persons, the extent to which people in remarriages have attributes that adversely influence marital quality and stability is examined. Five models linking remarriage-induced attributes to an increased probability of a decline in marital quality and divorce are evaluated. Persons in remarriages are more likely to be poorly integrated with parents and in-laws, willing to leave the marriage, be poor marriage material, and to have lower socioeconomic status and age-heterogeneous marriages. All but socioeconomic status are found to explain declines in marital quality and higher levels of marital instability. Together the remaining four models explain major portions of the remarriage/marital-quality and remarriage/divorce relationships.
TL;DR: In this paper, the total photoproduction cross section was determined from a measurement of electroproduction with the ZEUS detector at HERA, and the Q2 values of the virtual photons were in the range 10−7
TL;DR: In this paper, the authors considered the tune optimal slewing problem of flexible spacecraft and solved it for a linearized model in reduced state space by parameter optimization, and verified the maximal principle.
Abstract: The tune optimal slewing problem of flexible spacecraft is considered. The system is discretized by the assumed modes method, and the problem is solved for a linearized model in reduced state space by parameter optimization. Optimality is verified by the maximal principle. The linear solution is further used to obtain time optimal solutions for the non-linear problem.
Posted Content•
TL;DR: The authors reviewed a program of research that traces the constructiveness of preferences to the use of multiple strategies in decision making, contingent on task demands, and argued that individuals often build strategies opportunistically, changing their processing on the spot depending upon the information they encounter during the course of solving the decision problem.
Abstract: A viewpoint that has recently emerged in decision research is that preferences for objects of any complexity are often constructed - not merely revealed - in generating a response to a judgment or choice task This paper reviews a program of research that traces the constructiveness of preferences to the use of multiple strategies in decision making, contingent on task demands It is argued that individuals often build strategies opportunistically, changing their processing on the spot depending upon the information they encounter during the course of solving the decision problem