Showing papers by "University of Michigan published in 1985"

The Nash bargaining solution in economic modelling

Abstract: This article establishes the relationship between the static axiomatic theory of bargaining and the sequential strategic approach to bargaining. We consider two strategic models of alternating offers. The models differ in the source of the incentive of the bargaining parties to reach agreement: the bargainers' time preference and the risk of breakdown of negotiations. Each of the models has a unique perfect equilibrium. When the motivation to reach agreement is made negligible, in each model the unique perfect equilibrium outcome approaches the Nash bargaining solution with utilities that reflect the incentive to settle and with the proper disagreement point chosen. The results provide a guide for the application of the Nash bargaining solution in economic modelling.

Microwave Dielectric Behavior of Wet Soil-Part II: Dielectric Mixing Models

Abstract: This paper is the second in a series evaluating the microwave dielectric behavior of soil-water mixtures as a function of water content and soil textural composition. Part II draws upon the data presented in Part 1 [13] to develop appropriate empirical and theoretical dielectric mixing models for the 1.4-to 18-GHz region. A semiempirical mixing model based upon the index of refraction is presented, requiring only easily ascertained soil physical parameters such as volumetric moisture and soil textural composition as inputs. In addition, a theoretical model accounting explicitly for the presence of a hydration layer of bound water adjacent to hydrophilic soil particle surfaces is presented. A four-component dielectric mixing model treats the soil-water system as a host medium of dry soil solids containing randomly distributed and randomly oriented disc-shaped inclusions of bound water, bulk water, and air. The bulk water component is considered to be dependent upon frequency, temperature, and salinity. The soil solution is differentiated by means of a soil physical model into 1) a bound component and 2) a bulk soil solution. The performance of each model is evaluated as a function of soil moisture, soil texture, and frequency, using the dielectric measurements of five soils ranging from sandy loam to silty clay (as presented in Part I [13]) at frequencies between 1.4 and 18 GHz. The semiempirical mixing model yields an excellent fit to the measured data at frequencies above 4 GHz. At 1.

Racial Attitudes in America: Trends and Interpretations

Abstract: Perspectives and Historical Background Problems in Studying Changes in Racial Attitudes Trends in White Racial Attitudes Sources of Change in White Racial Attitudes Trends in Black Racial Attitudes Theoretical Interpretations of White Trends Conclusions Appendix A: Locating and Selecting Trend Questions Appendix B: Statistical Testing Procedures Notes References Index of Survey Questions Index

Achieving Cooperation Under Anarchy: Strategies And Institutions

Abstract: Cooperation and discord in world politics are explained to a considerable extent by the three factors discussed in the Introduction: mutuality of interest, the shadow of the future, and the number of players. Yet the context of interaction, perceptions, and strategies is also important. Issues are linked to one another through multilevel games, which may be compatible or incompatible. Whether reciprocity constitutes an effective strategy depends both on linkages among issues and on the institutions within which negotiations take place. Perceptions are always significant and often decisive. Decision makers often actively seek to change the contexts within which they act by linking issues, trying to alter others' perceptions, establishing institutions, and promoting new norms. This finding suggests the importance of linking the upward-looking theory of strategy with the downward-looking theory of regimes.

Gender and health: an update on hypotheses and evidence.

Abstract: This is a "state of the issue" paper about gender and physical health. It organizes the hypotheses proposed for male-female differences in physical health status, therapeutic health behaviors, and longevity and it summarizes empirical research, especially sociological research, on the topic over the past 10-15 years. Capsule summaries of sex differentials in health and of recent trends in health and morality are also presented for American (U.S.) men and women. The central theoretical viewpoint of this paper is that sex differences in health are principally the outcome of differential risks acquiredfrom roles, stress, life styles, and preventive health practices. Psychosocial factors-how men and women perceive and evaluate symptoms, and their readiness and ability to take therapeutic actions-are important as well, but typically secondary to acquired risks. Other factors such as prior health care, biological risks, health reporting, and caretaker effects (for example, physician sex bias) have even smaller importance. We hypothesize that the relative weight of acquired risks and psychosocialfactors varies for different types of health problems as follows: (1) Psychosocial factors have their greatest weight in responses to chronic, nonfatal, or low severity diseases and injuries and (2) gender differences are also greatest in responses to these; that is, men and women differ more in their perception, evaluation, and treatment of prolonged, mild conditions than of acute, life-threatening, or severe ones. The paper suggests some strategies for social science research on male-female health differences in the next decade or two.

Social factors in psychopathology: stress, social support, and coping processes.

Abstract: Our review has focused centrally on the etiologic significance of social factors in the development of psychopathology. Our implicit assumption has been that social factors in general, and stressors in particular, may play a causal role in the development of psychopathology. Yet the evidence is clear that the vast majority of people who are exposed to stressful life events or to chronic stress situations do not develop significant psychiatric impairments. For this reason, research interest over the past decade has shifted to factors like social support and coping strategies that may ameliorate the impact of stress. We have examined some of the important empirical results from recent studies of stress, support, and coping, and we have discussed ways in which these new understandings have informed long-standing attempts to explain group differences in emotional functioning. In each section of the review we have attempted not only to summarize existing results but also to provide some evaluation of the literature and suggestions for future research. It is important to recognize that the contributors to the work reviewed here do not all share a common research agenda. Some of them are primarily committed to unraveling the psychosocial determinants of a particular clinical disorder. Others are mainly concerned with the effects of a particular stressor. Still others are interested in the processes that link stress to health across a broad array of stress situations and health outcomes. In the face of these diverse interests, it is little wonder that our understanding of social factors in psychopathology is uneven. There is good reason to believe, however that these diverse strands of research are beginning to converge on a common conception of the stress process and on a common research design. The conception at present is only in rough form, but its outlines are nonetheless capable of description. At its center is the notion that stress exposure sets off a process of adaptation. It recognizes that this process unfolds over time, and it acknowledges that this process is modified by structural factors as well as by personal dispositions and vulnerabilities. There is growing recognition that the analysis of this process requires longitudinal methods. Also, it is becoming increasingly clear that experimental interventions are required to unravel the parts of this process that link stress and health. It is too early to know if this nascent convergence will lead to an integrative theory of adaptation, yet it is almost certain to promote methodological and conceptual rigor and facilitate replication and cumulation of findings.(ABSTRACT TRUNCATED AT 400 WORDS)

Microwave Dielectric Behavior of Wet Soil-Part 1: Empirical Models and Experimental Observations

Abstract: This is the first paper in a two-part sequence that evaluates the microwave dielectric behavior of soil-water mixtures as a function of water content, temperature, and soil textural composition. Part I presents the results of dielectric constant measurements conducted for five different soil types at frequencies between 1.4 and 18 GHz. Soil texture is shown to have an effect on dielectric behavior over the entire frequency range and is most pronounced at frequencies below 5 GHz. In addition, the dielectric properties of frozen soils suggest that a fraction of the soil water component remains liquid even at temperatures of -24° C. The dielectric data as measured at room temperature are summarized at each frequency by polynomial expressions dependent upon both the volumetric moisture content m and the percentage of sand and clay contained in the soil; separate polynomial expressions are given for the real and imaginary parts of the dielectric constant. In Part II, two dielectric mixing models will be presented to account for the observed behavior: 1) a semiempirical refractive mixing model that accurately describes the data and requires only volumetric moisture and soil texture as inputs, and 2) a theoretical four-component mixing model that explicitly accounts for the presence of bound water.

Three-dimensional object recognition

Abstract: A general-purpose computer vision system must be capable of recognizing three-dimensional (3-D) objects. This paper proposes a precise definition of the 3-D object recognition problem, discusses basic concepts associated with this problem, and reviews the relevant literature. Because range images (or depth maps) are often used as sensor input instead of intensity images, techniques for obtaining, processing, and characterizing range data are also surveyed.

Minimum-time control of robotic manipulators with geometric path constraints

Abstract: Conventionally, robot control algorithms are divided into two stages, namely, path or trajectory planning and path tracking (or path control). This division has been adopted mainly as a means of alleviating difficulties in dealing with complex, coupled manipulator dynamics. Trajectory planning usually determines the timing of manipulator position and velocity without considering its dynamics. Consequently, the simplicity obtained from the division comes at the expense of efficiency in utilizing robot's capabilities. To remove at least partially this inefficiency, this paper considers a solution to the problem of moving a manipulator in minimum time along a specified geometric path subject to input torque/force constraints. We first describe the manipulator dynamics using parametric functions which represent geometric path constraints to be honored for collision avoidance as well as task requirements. Second, constraints on input torques/ forces are converted to those on the parameters. Third, the minimum-time solution is deduced in an algorithm form using phase-plane techniques. Finally, numerical examples are presented to demonstrate utility of the trajectory planning method developed.

An evaluation of retrieval effectiveness for a full-text document-retrieval system

Abstract: An evaluation of a large, operational full-text document-retrieval system (containing roughly 350,000 pages of text) shows the system to be retrieving less than 20 percent of the documents relevant to a particular search. The findings are discussed in terms of the theory and practice of full-text document retrieval.

Sex and friendship in baboons

Abstract: This work analyzes male-female relationships outside the context of mating in a troop of wild baboons. Barbara Smuts used long-term friendships between males and females, documented over a two-year period, to show how social interactions between members of friendly pairs differed from those of other troop mates, Her findings, now enhanced by 15 years of field studies, suggest that the evolution of male reproductive strategies in baboons can only be understood by considering the relationship between sex and friendship: female baboons prefer to mate with males who have previously engaged in friendly interaction with them and their offspring. Smuts suggests that female choice may promote male investment in other species, and she explores the relevance of her findings for the evolution of male-female relationships in humans.

Right half plane poles and zeros and design tradeoffs in feedback systems

Abstract: This paper expresses limitations imposed by right half plane poles and zeros of the open-loop system directly in terms of the sensitivity and complementary sensitivity functions of the closed-loop system. The limitations are determined by integral relationships which must be satisfied by these functions. The integral relationships are interpreted in the context of feedback design.

Evidence of hierarchies in cognitive maps.

Abstract: Previous research suggested that the apparent hierarchical organization of landmarks in an environment will influence subjects’ judgments about spatial characteristics of that environment. We extended this previous work to a natural environment that has no predetermined, well-defined hierarchical structure. Using an algorithm that generates a hierarchy of landmarks from recall protocols, we constructed hypothesized clusterings of landmarks for a set of subjects familiar with the space. Then we tested these hypothesized clusters in a series of tasks, all of which required judgments about distances in the space. The results of these tests suggest that subjects do cluster landmarks on the basis of nonspatial attributes, and that the clusters have consequences for performance in various tasks that require access to spatial information.

Extracorporeal circulation in neonatal respiratory failure: a prospective randomized study.

Abstract: A prospective controlled randomized study of the use of extracorporeal membrane oxygenation to treat newborns with respiratory failure was carried out using the "randomized play-the-winner" statistical method. In this method the chance of randomly assigning an infant to one treatment or the other is influenced by the outcome of treatment of each patient in the study. If one treatment is more successful, more patients are randomly assigned to that treatment. A group of 12 infants with birth weight greater than 2 kg met objective criteria for high mortality risk. One patient was randomly assigned to conventional treatment (that patient died); 11 patients were randomly chosen for extracorporeal membrane oxygenation (all survived). Intracerebral hemorrhage occurred in one of 11 surviving children. Extracorporeal membrane oxygenation allows lung rest and improves survival compared to conventional ventilator therapy in newborn infants with severe respiratory failure.

Sources of Market Pioneer Advantages in Consumer Goods Industries

Abstract: In a broad cross section of consumer goods businesses, market pioneers generally have substantially higher market shares than late entrants. In fact, the empirical association between order of entr...

Decomposition and Partitioning Methods for Multistage Stochastic Linear Programs

Abstract: Multistage stochastic linear programs model problems in financial planning, dynamic traffic assignment, economic policy analysis, and many other applications. Equivalent representations of such problems as deterministic linear programs are, however, excessively large. This paper develops decomposition and partitioning methods for solving these problems and reports on computational results on a set of practical test problems.

Quasiperiodic GaAs-AlAs Heterostructures

Abstract: We report the first realization of a quasiperiodic (incommensurate) superlattice. The sample, grown by molecular-beam epitaxy, consists of alternating layers of GaAs and AlAs to form a Fibonacci sequence in which the ratio of incommensurate periods is equal to the golden mean $\ensuremath{\tau}$. X-ray and Raman scattering measurements are presented that reveal some of the unique properties of these novel structures.

Choline acetyltransferase activity in striatum of neonatal rats increased by nerve growth factor

Abstract: Some neurodegenerative disorders may be caused by abnormal synthesis or utilization of trophic molecules required to support neuronal survival. A test of this hypothesis requires that trophic agents specific for the affected neurons be identified. Cholinergic neurons in the corpus striatum of neonatal rats were found to respond to intracerebroventricular administration of nerve growth factor with prominent, dose-dependent, selective increases in choline acetyltransferase activity. Cholinergic neurons in the basal forebrain also respond to nerve growth factor in this way. These actions of nerve growth factor may indicate its involvement in the normal function of forebrain cholinergic neurons as well as in neurodegenerative disorders involving such cells.

Oxidative Autoactivation of Latent Collagenase by Human Neutrophils

Abstract: The pathological destruction of collagen plays a key role in the development of inflammatory disease states affecting every organ system in the human body. Neutrophils localized at inflammatory sites can potentially degrade collagen by releasing a metalloenzyme, collagenase, which is stored in a latent inactive form. Triggered human neutrophils were shown to release and simultaneously activate their latent collagenase. The activation of the latent enzyme was coupled to an oxidative process that required the generation of a highly reactive oxygen metabolite, hypochlorous acid. Oxidative regulation of latent collagenase activity may be important in the pathogenesis of connective tissue damage in vivo.