Showing papers by "University of Maryland, College Park published in 1976"
TL;DR: In this article, a generalization of Einstein's gravitational theory is discussed in which the spin of matter as well as its mass plays a dynamical role, and the theory which emerges from taking this coupling into account, the ${U}_{4}$ theory of gravitation, predicts, in addition to the usual infinite-range gravitational interaction medicated by the metric field, a new, very weak, spin contact interaction of gravitational origin.
Abstract: A generalization of Einstein's gravitational theory is discussed in which the spin of matter as well as its mass plays a dynamical role. The spin of matter couples to a non-Riemannian structure in space-time, Cartan's torsion tensor. The theory which emerges from taking this coupling into account, the ${U}_{4}$ theory of gravitation, predicts, in addition to the usual infinite-range gravitational interaction medicated by the metric field, a new, very weak, spin contact interaction of gravitational origin. We summarize here all the available theoretical evidence that argues for admitting spin and torsion into a relativistic gravitational theory. Not least among this evidence is the demonstration that the ${U}_{4}$ theory arises as a local gauge theory for the Poincar\'e group in space-time. The deviations of the ${U}_{4}$ theory from standard general relativity are estimated, and the prospects for further theoretical development are assessed.
2,421 citations
01 Jun 1976
TL;DR: This paper formulates the ambiguity-reduction process in terms of iterated parallel operations (i.e., relaxation operations) performed on an array of object, identification data.
Abstract: Given a set of objects in a scene whose identifications are ambiguous, it is often possible to use relationships among the objects to reduce or eliminate the ambiguity. A striking example of this approach was given by Waltz [13]. This paper formulates the ambiguity-reduction process in terms of iterated parallel operations (i.e., relaxation operations) performed on an array of (object, identification) data. Several different models of the process are developed, convergence properties of these models are established, and simple examples are given.
1,513 citations
01 Apr 1976
TL;DR: In this paper, three standard approaches to automatic texture classification make use of features based on the Fourier power spectrum, on second-order gray level statistics, and on first-order statistics of gray level differences, respectively.
Abstract: Three standard approaches to automatic texture classification make use of features based on the Fourier power spectrum, on second-order gray level statistics, and on first-order statistics of gray level differences, respectively. Feature sets of these types, all designed analogously, were used to classify two sets of terrain samples. It was found that the Fourier features generally performed more poorly, while the other feature sets all performned comparably.
1,379 citations
TL;DR: In this article, the spread of gonorrhea in a population is highly nonuniform and a mathematical model is proposed to split the population into n groups, and the asymptotic stability properties are studied.
Abstract: The spread of gonorrhea in a population is highly nonuniform. The mathematical model discussed takes this into account, splitting the population into n groups. The asymptotic stability properties are studied.
669 citations
TL;DR: Region growing systems and their role in pictorial segmentation are reviewed; developmental trends relating these systems are examined and a global initialization technique is suggested.
610 citations
TL;DR: In this article, a universal gauge theory based on E6 is suggested as a model for the unification of strong, electromagnetic and weak interactions, and the Weinberg angle and the R ratio are derived and the stability of the proton is discussed.
529 citations
TL;DR: In this article, nonlinear wave propagation in inhomogeneous media is studied analytically in the model of the nonlinear Schrodinger equation and exact solutions in the form of multisolitons, accelerated in the nonuniform medium are obtained.
Abstract: Nonlinear wave propagation in inhomogeneous media is studied analytically in the model of the nonlinear Schrodinger equation Exact solutions in the form of multisolitons, accelerated in the nonuniform medium, are obtained (AIP)
382 citations
TL;DR: In this article, it was shown that the solution of the Stokes problem has square integrable second derivatives provided that the domain is a convex polygon in the plane and the nonhomogeneous term is square integral.
293 citations
TL;DR: The concentrations of eighteen elements were determined by instrumental neutron activation analysis for samples of air particulates collected over a five month period in the Boston metropolitan area by the methods of common factor analysis and hierarchial aggregative cluster analysis.
244 citations
219 citations
TL;DR: There are several widely discussed proposals for changing the tax treatment of charitable contributions, including the complete abolition of the deduction, the substitution of a system of tax credits, the introduction of a "floor" with a deduction or credit only for contributions above that level, and various modifi-
TL;DR: Relationships among stress, coping behaviors, and performance were examined for 93 owner-manager s of small businesses damaged by hurricane floods and revealed an inverted-U relationship with perceived stress, while emotional coping behaviors displayed a positive linear relationship.
Abstract: Relationships among stress, coping behaviors, and performance were examined for 93 owner-manager s of small businesses damaged by hurricane floods. It was hypothesized that (a) perceived stress and performance display an inverted-U relationship, and (b) emotional coping mechanisms increase under higher stress. Subjects were interviewed regarding their handling of critical incidents under stress and completed the Subjective Stress Scale. Type of recovery effort following the flood was recorded, organizational performance was rated on a 5-point scale, and final loss data were acquired. Perceived stress and organization performance displayed a curvilinear, nearly inverted-U relationship. Actual financial loss (or stress level) did not account for performance differences. Problem-solving coping behaviors revealed an inverted-U relationship with perceived stress, while emotional coping behaviors displayed a positive linear relationship. Implications for improving performance under stress are discussed. Previous studies of psychological stress indicate that there is an optimum amount of stress in terms of its effects on performance. Stress that is higher or lower than this amount results in steadily decreasing performance. Performance under stress, then, follows an inverted-U-shaped function. This type of relationship between stress and performance, called the Yerkes-Dodson law, has been demonstrated in a number of laboratory studies under different types of experimental conditions. However there appears to be no research demonstrating a similar relationship between stress and performance in a field organizational setting. Several explanations have been advanced for this inverted-U-shaped relationship with emphasis placed on the amount of motivation generated by the stressing agent. For example, Vroom (1964), in reviewing a number of studies that demonstrate this type of relationship between stress and performance, pro
TL;DR: In this paper, the authors report that shells of shell-eating gastropods living on intertidal open rocky surfaces exhibit various shell features which can be interpreted as adaptations against such shell-breaking predators as fishes, spiny lobsters, and crabs.
Abstract: SHELLED gastropods living on intertidal open rocky surfaces exhibit various shell features which can be interpreted as adaptations against such shell-breaking predators as fishes, spiny lobsters, and crabs. These anti-predatory devices include strong external shell sculpture, elongate or dentate apertures and low spires1. Not only are these characteristics more common among tropical species compared with ecologically similar cold-water forms, but within the tropics they are more prevalent and better developed in the Pacific and Indian Oceans than in the Atlantic1,2. Any or all of three conditions must obtain in areas with a high incidence and strong development of anti-predatory armour compared with areas where such armour is reduced: the prey are stronger, that is, the criteria needed by the prey to avoid being crushed are more stringent; the predators are stronger; and shell-breaking predators account for relatively greater mortality. Here I report data confirming the first two of these possibilities.
TL;DR: In this article, it was shown that probability amplitudes and transition matrix elements are gauge-invariant for a nonrelativistic spinless, spinless charged particle.
TL;DR: In this article, the effect of adiabatic focussing along with scattering on charged particles propagating along diverging lines of force of a spatially inhomogeneous guiding field was considered as they are scattered by random fields.
Abstract: Charged particles propagating along the diverging lines of force of a spatially inhomogeneous guiding field were considered as they are scattered by random fields. Their longitudinal transport is described in terms of the eigenfunctions of a Sturm-Liouville operator incorporating the effect of adiabatic focussing along with that of scattering. The relaxation times and characteristic velocities are graphed and tabulated. The particle density is evaluated as a function of space and time for two different regimes. In the first regime (relatively weak focussing), a diffusive mode of propagation is dominant but coherent modes are also dominant. In the second regime (strong focussing), diffusion does not occur and the propagation is purely coherent. This supercoherent mode corresponds exactly to the so-called scatter-free propagation of kilovolt solar flare electrons. On a larger scale, focussed transport provides an interpretation of many observed characteristics of extragalactic radio sources.
TL;DR: In this paper, it was shown that a shock satisfies condition (E) if and only if the shock is admissible, that is, it is the limit of progressive wave solutions of the associated viscosity equations.
TL;DR: In this paper, a method for computing a nested sequence of orthonormal bases for the dominant invariant subspaces of a non-Hermitian matrix is described, which is particularly suited to large sparse eigenvalue problems, since it requires only that one can form the product of the matrix in question with a vector.
Abstract: This paper describes a simultaneous iteration technique for computing a nested sequence of orthonormal bases for the dominant invariant subspaces of a non-Hermitian matrix. The method is particularly suited to large sparse eigenvalue problems, since it requires only that one be able to form the product of the matrix in question with a vector. A convergence theory for the method is developed and practical details are discussed.
TL;DR: Psychiatrists were most often assaulted in the early stages of their career or while they were working in high-risk settings such as prisons or emergency rooms, and it is recommended that clinicians learn techniques for managing potentially assaultive patients.
Abstract: The authors describe the results of a survey of 115 psychiatrists regarding assaults by patients. Forty-eight psychiatrists stated that they had been assaulted; a total of 68 assaults was reported. Psychiatrists were most often assaulted in the early stages of their career or while they were working in high-risk settings such as prisons or emergency rooms. Many reported retrospectively that they might have had a role in provoking the assault and that they could have anticipated it. The authors believe that psychiatrists avoid dealing with the issue of violence by patients for a variety of reasons, and they recommend that clinicians learn techniques for managing potentially assaultive patients.
TL;DR: The history and definitions common to data-base technology are discussed, important concepts are discusses, and terminology for use by other papers in this issue is defined.
Abstract: This paper deals with the history and definitions common to data-base technology It delimits the objectives of data-base management systems, discusses important concepts, and defines terminology for use by other papers in this issue, traces the development of data-base systems methodology, gives a uniform example, and presents some trends and issues
TL;DR: Through this transformational stage, the statistical approach to texture is shown to be a generalization of the structural approach in the same way that random variables are ageneralization of deterministic variables.
TL;DR: Using an airborne mounted UV tunable laser system, natural tropospheric OH radical concentrations at 7 and 11.5 km are reported for the first time in this article, where the technique employed was that of Laser Induced Fluorescence where the OH radicals were excited at 2820.6A with the fluorescence being monitored at ∼3095A.
Abstract: Using an airborne mounted UV tunable laser system, natural tropospheric OH radical concentrations at 7 and 11.5 km are here reported for the first time. The technique employed was that of Laser Induced Fluorescence where the OH radicals were excited at 2820.6A with the fluorescence being monitored at ∼3095A. Sampling of the OH was carried out continuously using a laminar flow intake manifold in which the UV laser beam (7mm diameter) was passed through the center core of the gas stream. Measurements at 32° north latitude and 21° north latitude at 7 and 11.5 km revealed significant latitude and altitude variations of the OH radical during the month of October 1975. Details on the importance of these measurements to tropospheric chemistry are discussed.
TL;DR: A simple formula is derived for the distance between two points on a hexagonal grid, in terms of coordinates with respect to a pair of oblique axes.
Abstract: A simple formula is derived for the distance between two points on a hexagonal grid, in terms of coordinates with respect to a pair of oblique axes.
TL;DR: In this article, a probabilistic model for the validation of behavioral hierarchies is presented, which is by means of iterative convergence to maximum likelihood estimates, and two approaches to assess the fit of the model to sample data are discussed.
Abstract: A probabilistic model for the validation of behavioral hierarchies is presented. Estimation is by means of iterative convergence to maximum likelihood estimates, and two approaches to assessing the fit of the model to sample data are discussed. The relation of this general probabilistic model to other more restricted models which have been presented previously is explored and three cases of the general model are applied to exemplary data.
TL;DR: In this paper, a comprehensive model of career development in early adulthood is proposed, which suggests hypotheses to test it, and outlines ways in which it can be translated into operational terms for further research.
TL;DR: In this article, the in-stack particulate material in the stack effluent of a coal-fired power plant was collected and fractionated with an in stack cascade impactor.
01 Jan 1976
TL;DR: Homogenization is an approach which studies the macrobehaviour of a medium by its microproperties as discussed by the authors, which is related to the question of a replacement of the heterogenous material by an equivalent homogenous one.
Abstract: Homogenization is an approach which studies the macrobehaviour of a medium by its microproperties. The origin of this word is related to the question of a replacement of the heterogenous material by an “equivalent” homogenous one.
TL;DR: From both a chemical as well as biological point of view the polyphosphates appear to be the most plausible general prebiotic condensing agent.
Abstract: Biopolymers are formed by dehydration-type condensation reactions. In aqueous solutions dehydration reactions are very unlikely to happen spontaneously. However, coupling of dehydration-condensation to the hydrolysis of condensing agents could facilitate the synthesis of biopolymers in an aqueous solution. The literature shows that the peptides, nucleosides, nucleotides and oligonucleotides can be formed in this way. A careful study of the literature pertaining to prebiotic condensing agents was conducted in order to determine the most plausible prebiotic synthesis of biopolymers. The condensing agents taken into consideration are cyanamide, carbodimide, dicyanamide, dicyandiamide, hydrogen-cyanide-tetramer, cyanogen and the linear- and cyclic polyphosphates. From both a chemical as well as biological point of view the polyphosphates appear to be the most plausible general prebiotic condensing agent.