Showing papers by "University of Minnesota published in 1988"
TL;DR: An overview of beamforming from a signal-processing perspective is provided, with an emphasis on recent research.
Abstract: An overview of beamforming from a signal-processing perspective is provided, with an emphasis on recent research. Data-independent, statistically optimum, adaptive, and partially adaptive beamforming are discussed. Basic notation, terminology, and concepts are included. Several beamformer implementations are briefly described. >
4,122 citations
15 Jun 1988
TL;DR: In this article, simple state-space formulas are presented for a controller solving a standard H∞-problem, where the controller has the same state-dimension as the plant, its computation involves only two Riccati equations, and it has a separation structure reminiscent of classical LQG theory.
Abstract: Simple state-space formulas are presented for a controller solving a standard H∞-problem. The controller has the same state-dimension as the plant, its computation involves only two Riccati equations, and it has a separation structure reminiscent of classical LQG (i.e., H2) theory. This paper is also intended to be of tutorial value, so a standard H2-solution is developed in parallel.
2,875 citations
TL;DR: In this article, the authors develop a theoretical extension to the basic transaction cost model by combining insights from dependence theory with the TCA approach, and introduce offsetting investments as a means of reducing transaction costs.
Abstract: The authors develop a theoretical extension to the basic transaction cost model by combining insights from dependence theory with the TCA approach. They introduce offsetting investments as a means ...
1,526 citations
TL;DR: Especially noteworthy among several differences in risk factor levels by demographic subgroup, were a higher body mass index among black than white women and much higher prevalence of cigarette smoking among persons with no more than a high school education than among those with more education.
1,486 citations
TL;DR: In this article, the melting of pure gallium in a rectangular cavity has been numerically investigated using the enthalpy-porosity approach for modeling combined convection-diffusion phase change.
Abstract: The melting of pure gallium in a rectangular cavity has been numerically investigated using the enthalpy-porosity approach for modeling combined convection-diffusion phase change. The major advantage of this technique is that it allows a fixed-grid solution of the coupled momentum and energy equations to be undertaken without resorting to variable transformations. In this work, a two-dimensional dynamic model is used and the influence of laminar natural-convection flow on the melting process is considered. Excellent agreement exists between the numerical predictions and experimental results available in the literature. The enthalpy-porosity approach has been found to converge rapidly, and is capable of producing accurate results for both the position and morphology of the melt front at different times with relatively modest computational requirements. These results may be taken to be a sound validation of this technique for modeling isothermal phase changes in metallurgical systems.
1,377 citations
TL;DR: In this article, the influence of protege characteristics, gender composition of the mentoring relationship, the quality of the relationship, and the amount of time the protege spent with the mentor on career and psychosocial benefits gained by a protege was examined.
Abstract: This study examined the influence of protege characteristics, gender composition of the mentoring relationship, the quality of the relationship, and the amount of time the protege spent with the mentor on career and psychosocial benefits gained by the protege. Proteges were assigned to mentors as part of a development program designed to facilitate personal and career development of educators. An instrument designed to assess the extent to which mentors provide career and psychosocial outcomes to proteges was developed. Protege gender, job involvement, and career planning activity was related to attainment of psychosocial outcomes. Implications and future directions for research regarding mentoring are discussed.
1,232 citations
TL;DR: The distinct element method has advanced to a stage where the complex mechanical interactions of a discontinuous system can be modelled in three dimensions and an efficient data structure is utilizes which permits the rapid calculation on a personal computer of systems involving several hundred particles.
1,020 citations
TL;DR: In this paper, a review of empirical studies demonstrates that effects of participation on satisfaction and performance vary according to form, and cast doubt on the conclusions of earlier reviews based on a unidimensional view of PDM.
Abstract: Participation in decision making (PDM) takes several distinct forms. A review of empirical studies demonstrates that effects of participation on satisfaction and performance vary according to form. The findings cast doubt on the conclusions of earlier reviews based on a unidimensional view of PDM and raise several issues for the study and practice of PDM.
780 citations
TL;DR: In this article, the vapor pressures of HNO3 and H2O have been measured over the trihydrate crystal formed by vapor deposit on a glass surface in the temperature range 190 to 205 K.
Abstract: Vapor pressures of HNO3 and H2O have been measured over the trihydrate crystal, formed by vapor deposit on a glass surface. In the temperature range 190 to 205 K the two phase-equilibrium trihydrate/vapor was studied by adding and removing H2O. Coexistence equilibria vapor pressures of trihydrate/solid solutions of HNO3 in ice and of mono-/trihydrate were also measured. Results show that for typical mixing ratios of H2O and HNO3 found in the lower stratosphere (3 ppm H2O, 5 ppb HNO3) the trihydrate would start to form at temperatures about 7 K higher than the ice point. The pressure of atmospheric HNO3 would rapidly decrease as the atmosphere cools without large changes in partial pressures of H2O. These laboratory results provide information on the formation of polar stratospheric clouds containing H2O and HNO3.
778 citations
TL;DR: Meta-analysis predicted that a team of physicians and nonphysicians using multiple intervention modalities to deliver individualized advice on multiple occasions would produce the best result in controlled smoking cessation trials.
Abstract: Meta-analysis was used to examine 108 intervention comparisons in 39 controlled smoking cessation trials. Type of intervention (face-to-face advice being better than all others), type of intervenor (both physician and nonphysician counselors better than either alone), the number of reinforcing sessions, and the duration of reinforcing sessions were related to success six months after the initiation of intervention. The number of modalities used by the intervention predicted success with borderline statistical significance. Multivariate analysis predicted that a team of physicians and nonphysicians using multiple intervention modalities to deliver individualized advice on multiple occasions would produce the best result. Program success 12 months after the initiation of intervention was related to the type of intervention session (group and individual sessions combined better than either alone), the number of intervention modalities, and the number of reinforcing sessions. With multivariate adjustment for confounding, the number of intervention modalities alone had a positive association with intervention success. ( JAMA 1988;259:2882-2889)
761 citations
TL;DR: This paper applied particle-motion physics principles to the interpretation of stratigraphic charcoal data and found that the relationship between diameter and critical and deposition velocities results in fundamental aerodynamic differences between the sizes of particles quantified by the two methods.
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28 Mar 1988TL;DR: In this article, a comprehensive presentation of numerical methods suitable for the analysis of various heat transverse and fluid flow problems that occur in research, practice, and university instruction is given.
Abstract: A comprehensive presentation is given of virtually all numerical methods that are suitable for the analysis of the various heat transverse and fluid flow problems that occur in research, practice, and university instruction. After reviewing basic methodologies, the following topics are covered: finite difference and finite element methods for parabolic, elliptic, and hyperbolic systems; a comparative appraisal of finite difference versus finite element methods; integral and integrodifferential systems; perturbation methods; Monte Carlo methods; finite analytic methods; moving boundary problems; inverse problems; graphical display methods; grid generation methods; and programing methods for supercomputers.
TL;DR: In this article, the concept of an inertial manifold for nonlinear evolutionary equations, in particular for ordinary and partial differential equations, was introduced, which is an appropriate tool for the study of questions related to the long time behavior of solutions of the evolutionary equations.
TL;DR: In this paper, the role of family structure in mitigating income volatility in the absence of income insurance in low-income agricultural environments is discussed, and hypotheses concerning the relationship between the membership, size and composition of households and insurance-based income transfers are tested using longitudinal data from India.
Abstract: In this paper the role of family structure in mitigating income volatility in the absence of income insurance in low-income agricultural environments is discussed. Hypotheses concerning the relationship between the membership,
size and composition of households and insurance-based income transfers are tested using longitudinal data from India. A test is also performed of whether a household's ability to reduce risk ex post via family arrangements affects its willingness tobear risk ex ante through its selection of formal tenancy contracts. The results support these hypotheses concerning the risk-mitigating roles of both household structure and share contracts, and indicate as well the importance of heterogeneity in risk-aversion across households
TL;DR: Data sources used by the Nutrition Coordinating Center at the University of Minnesota for its nutrient database are identified and the procedures used to select and document nutrient values are described.
Abstract: A nutrient database that contains current, reliable data is a prerequisite for accurate calculation of dietary intakes. Most nutrient databases are expanded from data supplied by the U.S. Department of Agriculture and may include additional foods or nutrients or data from more recent analyses, food manufacturers, or foreign food tables. Guidelines must be established for selection of reliable values from appropriate sources. A system for precise documentation of data sources provides a means for determining whether individual nutrient values were derived from chemical analyses, recipe calculations, or imputations. This article identifies data sources used by the Nutrition Coordinating Center at the University of Minnesota for its nutrient database and describes the procedures used to select and document nutrient values.
TL;DR: For des fonctions positives u and v, on considere le systeme D 1 Δu-χ⊇•(u⊆logv)=0, D 2 Δv-av+bu=0 dans Ω; ∂u/∂n=∂v/οn=0 sur ∂Ω, |Ω| −1 ∫ Ω u(x)dx=ū, ou |Φ| est le volume de Ω et ū>0 est une constante don
TL;DR: In this paper, the authors present a typology that posits a reciprocal interdependence between a firm's business strategy and its human resources strategy Implications for research and practice are discussed.
Abstract: Past efforts to relate the management of human resources to a firm's business strategy have taken three approaches: matching managerial style or personnel activities with strategies, forecasting manpower requirements given certain strategic objectives or environmental conditions, and presenting means for integrating human resource management into the overall effort to match strategy and structure. In this article, the literature on each of these approaches is reviewed, and a typology is presented that posits a reciprocal interdependence between a firm's business strategy and its human resources strategy Implications for research and practice are discussed.
TL;DR: In this paper, the individual and organizational factors that may inhibit the development of mentoring relationships for women are discussed, and an agenda for research on the development and dynamics of relationships is proposed.
Abstract: Mentoring provides career guidance and psychological support to employees. However, women may have difficulty establishing a mentoring relationship. This paper describes the individual and organizational factors that may inhibit the development of mentorships for women. An agenda for research on the development and dynamics of mentoring relationships is proposed.
TL;DR: Abused mothers who were able to break the abusive cycle were significantly more likely to have received emotional support from a nonabusive adult during childhood, participated in therapy during any period of their lives, and to have had aNonabusive and more stable, emotionally supportive, and satisfying relationship with a mate.
Abstract: The aim of this study was to identify variables that distinguish mothers who broke the cycle of abuse from mothers who were abused as children and who also abused their own children. Based on maternal interviews and questionnaires completed over a 64-month period, measures of mothers' past and current relationship experiences, stressful life events, and personality characteristics were obtained. Abused mothers who were able to break the abusive cycle were significantly more likely to have received emotional support from a nonabusive adult during childhood, participated in therapy during any period of their lives, and to have had a nonabusive and more stable, emotionally supportive, and satisfying relationship with a mate. Abused mothers who reenacted their maltreatment with their own children experienced significantly more life stress and were more anxious, dependent, immature, and depressed.
TL;DR: The controlled environment vitrification system (CEVS) is described and the value of the technique is illustrated with TEM micrographs of surfactant microstructures in which specimen preparation artifacts were avoided.
Abstract: The controlled environment vitrification system (CEVS) permits cryofixation of hydrated biological and colloidal dispersions and aggregates from a temperature- and saturation-controlled environment. Otherwise, specimens prepared in an uncontrolled laboratory atmosphere are subject to evaporation and heat transfer, which may introduce artifacts caused by concentration, pH, ionic strength, and temperature changes. Moreover, it is difficult to fix and examine the microstructure of systems at temperatures other than ambient (e.g., biological systems at in vivo conditions and colloidal systems above room temperature). A system has been developed that ensures that a liquid or partially liquid specimen is maintained in its original state while it is being prepared before vitrification and, once prepared, is vitrified with little alteration of its microstructure. A controlled environment is provided within a chamber where temperature and chemical activity of volatile components can be controlled while the specimen is being prepared. The specimen grid is mounted on a plunger, and a synchronous shutter is opened almost simultaneously with the release of the plunger, so that the specimen is propelled abruptly through the shutter opening into a cryogenic bath. We describe the system and its use and illustrate the value of the technique with TEM micrographs of surfactant microstructures in which specimen preparation artifacts were avoided. We also discuss applications to other instruments like SEM, to other techniques like freeze-fracture, and to novel "on the grid" experiments that make it possible to freeze successive instants of dynamic processes such as membrane fusion, chemical reactions, and phase transitions.
01 Jan 1988
TL;DR: A good deal of attention from researchers in several disciplines, including economics, marketing, and law, has been paid to the recent rise in prominence of the transaction costs analysis (TCA) of vertical integration as mentioned in this paper.
Abstract: The issue of forward vertical integration has attracted a good deal of attention from researchers in several disciplines, including economics, marketing, and law. Many explanations have been offered for this phenomenon, including technological interrelationships involving economies of scale and scope (Chandler), uncertainty and risk considerations (Arrow, 1969), information externalities (Green), and strategic purposes. Blair and Kaserman (1983) offer an extensive survey of the extant literature in this area. Of particular note, however, is the recent rise in prominence of the transaction costs analysis (TCA) of vertical integration. This approach consists of a blend of institutional economics, organizational theory, and contract law, and has been developed primarily by Oliver Williamson (1979, 1985). He views vertical integration as a response to the inability of arms-length market relationships to govern exchange efficiently under particular circumstances. The level of specialized assets' required to support the exchange, the uncertainty2 surrounding the exchange, and the frequency3 of exchange are
TL;DR: The classification and prevalence of amelogenesis imperfecta is updated based upon new information in the literature and problems with the currently used classification of inherited dentin defects are discussed.
Abstract: The classification and prevalence of amelogenesis imperfecta is updated based upon new information in the literature. Problems with the currently used classification of inherited dentin defects are discussed.
TL;DR: In this paper, a three-dimensional formulation of the distinct element method is embodied in computer program 3DEC, which has been adapted to run on a personal computer, based on a dynamic (time domain) solution algorithm.
TL;DR: This paper examined several grounds for doubting the value of much of the special attention recently devoted to unit root econometrics and showed that unit root hypotheses are less well connected to economic theory than is often suggested or assumed.
TL;DR: Anderson and Shannon argue that effec tive mentoring programs must be grounded on a clear and strong concep tual foundation as discussed by the authors, such a foundation in cludes a carefully articulated approach to mentorin...
Abstract: Anderson and Shannon argue that effec tive mentoring programs must be grounded on a clear and strong concep tual foundation. Such a foundation in cludes a carefully articulated approach to mentorin...
TL;DR: In this article, it was shown that large, outsized clasts can be transported along a rheological interface which develops within the flow, and the clasts "glide" along the top of an underlying, pseudolaminar inertia-flow layer, partly submerged in it, and are driven by the downflow component of turbulent shear-stresses transmitted from the overlying, faster-moving turbulent layer.
TL;DR: B cell lymphoproliferative disorders developed in eight patients following bone marrow transplantation for leukemia or immunodeficiency, and seven patients died despite aggressive attempts at therapy with combinations of antiviral, immunologic, and chemotherapeutic agents.
TL;DR: It is suggested that the relations of stress exposure to competence vary as a function of individual differences as well as the competence criterion, and boys were less socially competent than girls and, when stress was high, appeared to be less protected by positive family qualities.
Abstract: This study examined the associations of stress exposure to various aspects of school-based competence in a normative sample of 205 children aged 8–13. Potential moderators of these relations, including child attributes of sex and IQ, and environmental attributes of socioeconomic status (SES) and family qualities, were also studied. Stress exposure was indexed by a life event questionnaire. Competence was assessed by teacher ratings, peer assessments and school record data. Family attributes were derived from a set of rating scales completed by interviewers after 6 hours of interviews with a parent. Results suggest that the relations of stress exposure to competence vary as a function of individual differences as well as the competence criterion. Disadvantaged children, with lower IQ and SES, and less positive family qualities, were generally less competent and more likely to be disruptive at high stress levels. Advantaged children were more competent, and with stress were less positively engaged in school, but were not likely to be disruptive. Boys were less socially competent than girls and, when stress was high, appeared to be less protected by positive family qualities. Causal hypotheses for future research in this area are discussed.