Showing papers by "University of Maryland, College Park published in 1984"

Program Slicing

Abstract: Program slicing is a method for automatically decomposing programs by analyzing their data flow and control flow. Starting from a subset of a program's behavior, slicing reduces that program to a minimal form which still produces that behavior. The reduced program, called a ``slice,'' is an independent program guaranteed to represent faithfully the original program within the domain of the specified subset of behavior. Some properties of slices are presented. In particular, finding statement-minimal slices is in general unsolvable, but using data flow analysis is sufficient to find approximate slices. Potential applications include automatic slicing tools for debuggng and parallel processing of slices.

The Quadtree and Related Hierarchical Data Structures

Abstract: Apercu sur les quadarbres et les structures de donnees hierarchiques. Elles sont basees sur le principe de decomposition recursive. L'accentuation est mise sur la representation de donnees dans les applications de traitement d'images, d'infographie, les systemes d'informations geographiques et la robotique. On examine en detail un certain nombre d'operations dans lesquelles de telles structures de donnees trouvent leur utilisation

The Quality of Life Scale: An Instrument for Rating the Schizophrenic Deficit Syndrome

Abstract: There is growing interest in deficit symptoms in studies of the course and treatment response of schizophrenia. However, existing clinical assessment instruments focus primarily on productive symptoms. The authors describe the Quality of Life Scale (QLS), a 21-item scale based on a semistructured interview designed to assess deficit symptoms and thereby fill an important gap in the range of instruments now available. Data regarding reliability and training in the use of the QLS are presented. A factor analysis of the items yields results compatible with the conceptual model on which the scale is based. The factor analysis was also performed separately by sex and was fundamentally similar for men and women.

A Methodology for Collecting Valid Software Engineering Data

Abstract: An effective data collection method for evaluating software development methodologies and for studying the software development process is described. The method uses goal-directed data collection to evaluate methodologies with respect to the claims made for them. Such claims are used as a basis for defining the goals of the data collection, establishing a list of questions of interest to be answered by data analysis, defining a set of data categorization schemes, and designing a data collection form. The data to be collected are based on the changes made to the software during development, and are obtained when the changes are made. To ensure accuracy of the data, validation is performed concurrently with software development and data collection. Validation is based on interviews with those people supplying the data. Results from using the methodology show that data validation is a necessary part of change data collection. Without it, as much as 50 percent of the data may be erroneous. Feasibility of the data collection methodology was demonstrated by applying it to five different projects in two different environments. The application showed that the methodology was both feasible and useful.

A stable finite element for the stokes equations

Abstract: We present in this paper a new velocity-pressure finite element for the computation of Stokes flow. We discretize the velocity field with continuous piecewise linear functions enriched by bubble functions, and the pressure by piecewise linear functions. We show that this element satisfies the usual inf-sup condition and converges with first order for both velocities and pressure. Finally we relate this element to families of higer order elements and to the popular Taylor-Hood element.

Mood disorders in stroke patients: importance of location of lesion

Abstract: In a selected group of right-handed patients with single stroke lesions of either the right (n=14) or left (n=22) hemisphere and no predisposing factors for psychiatric disorder, we found that the severity of depression was significantly increased in patients with left anterior lesions as opposed to any other lesion location. In addition, the severity of depression correlated significantly with proximity of the lesion on CT scan to the frontal pole in the left anterior group. The right hemisphere lesion group showed the reverse trend: patients with right posterior lesions were more depressed than patients with right anterior lesions, who were unduly cheerful and apathetic. These findings suggest that intrahemispheric lesion location is in some way related to mood disorder in stroke patients and that there is a graded effect of lesion location on severity of mood change. The neuroanatomy of the biogenic amine-containing pathways in the cerebral cortex might explain this graded effect and provide a neurochemical basis for the mood change.

Effect of self-efficacy, goals, and task strategies on task performance.

Abstract: : This study examined the effect of self-efficacy, goals, and task strategies on goal choice and task performance Self-efficacy and task strategies were manipulated through training Ability, past performance and self-efficacy were the major predictors of goal choice Ability, self-efficacy, goals and task strategies were all related to task performance Self-efficacy was more strongly related to past performance than to future performance but was still a significant predictor of future performance when past performance was controlled Self-efficacy ratings for moderate to difficult levels of performance were the best predictors of future performance This finding was replicated when two previous goal setting studies, which had found no positive expectancy-performance relationship across goal groups, were re-analyzed It is suggested that the concept of self-efficacy might provide an integrating mechanism between the goal setting and social learning theory approaches to task performance

Multiple Resolution Texture Analysis and Classification

Abstract: Textures are classified based on the change in their properties with changing resolution The area of the gray level surface is measured at serveral resolutions This area decreases at coarser resolutions since fine details that contribute to the area disappear Fractal properties of the picture are computed from the rate of this decrease in area, and are used for texture comparison and classification The relation of a texture picture to its negative, and directional properties, are also discussed

Management accounting systems, perceived environmental uncertainty and organization structure: An empirical investigation☆

Abstract: The research reported in this study concerns the relationships among an organization's environment, structure and information system. Based on an empirical study it appears that information systems and organizational structures are both a function of the environment. However, after controlling for the effects of the environment, it does not appear that an organization's iinformation system and structure are significantly related to each other.

Logic and Databases: A Deductive Approach

Abstract: The purpose of this paper is to show that logic provides a convenient formalism for studying classical database problems. There are two main parts to the paper, devoted respectively to conventional databases and deductive databases. In the first part, we focus on query languages, integrity modeling and maintenance, query optimization, and data dependencies. The second part deals mainly with the representation and manipulation of deduced facts and incomplete information. Categories and Subject Descriptors: H.2.1 [Database Management]: Logical Design— data models; H.2.3 [Database Management]: Languages— query languages; H.2.4 [Database Management]: Systems— query processing General Terms: Deductive Databases, Indefinite Data, Logic and Databases, Null Values, Relational Databases

Determining conductivity by boundary measurements

Abstract: A. P. Calderon pose la question: est-il possible de determiner la conductivite thermique d'un objet a partir de mesures statiques de la temperature et du flux de chaleur a la limite? On demontre que ces mesures determinent de facon unique la conductivite thermique et toutes ses derivees a la limite

Chesapeake bay anoxia: origin, development, and significance.

Abstract: Anoxia occurs annually in deeper waters of the central portion of the Chesapeake Bay and presently extends from Baltimore to the mouth of the Potomac estuary. This condition, which encompasses some 5 billion cubic meters of water and lasts from May to September, is the result of increased stratification of the water column in early spring, with consequent curtailment of reoxygenation of the bottom waters across the halocline, and benthic decay of organic detritus accumulated from plankton blooms of the previous summer and fall. The Chesapeake Bay anoxia appears to have had significant ecological effects on many marine species, including several of economic importance.

Software errors and complexity: an empirical investigation0

Abstract: An analysis of the distributions and relationships derived from the change data collected during development of a medium-scale software project produces some surprising insights into the factors influencing software development. Among these are the tradeoffs between modifying an existing module as opposed to creating a new one, and the relationship between module size and error proneness.

Blacks in College: A Comparative Study of Students' Success in Black and in White Institutions

Abstract: (1986) Blacks in College: A Comparative Study of Students' Success in Black and in White Institutions The Journal of Higher Education: Vol 57, No 1, pp 111-113

Electron energy levels in GaAs- Ga 1 − x Al x As heterojunctions

Abstract: Calculated results for energy levels of electrons in GaAs-${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Al}}_{x}$ As heterojunctions are presented and their sensitivity to various parameters\char22{}including acceptor doping level in the GaAs, heterojunction barrier height, effective-mass and dielectric-constant discontinuities, interface grading, and ambient temperature\char22{}is examined.

Effects of Ultraviolet-B Irradiance on Soybean : V. The Dependence of Plant Sensitivity on the Photosynthetic Photon Flux Density during and after Leaf Expansion.

Abstract: Soybeans (Glycine max [L.] Merr. cv Essex) were grown in a green-house, and the first trifoliate leaf was either allowed to expand under a high photosynthetic photon flux density (PPFD) (1.4 millimoles per square meter per second) or a low PPFD (0.8 millimoles per square meter per second). After full leaf expansion, plants from each treatment were placed into a factorial design experiment with two levels of ultraviolet-B (UV-B) radiation (0 and 80 milliwatts per square meter biologically effective UV-B) and two levels of concomitant PPFD (0.8 and 1.4 millimoles per square meter per second) resulting in a total of eight treatments. Measurements of net photosynthesis and the associated diffusion conductances, ribulose-1,5-bisphosphate carboxylase activity, chlorophyll and flavonoid concentrations, and leaf anatomy were examined for all treatments. Leaves expanded in the high PPFD were unaffected by UV-B radiation while those expanded in the low PPFD were sensitive to UV-B-induced damage. Likewise, plants which were UV-B irradiated concomitantly with the high PPFD were resistant to UV-B damage, while plants irradiated under the low PPFD were sensitive. The results of this study indicate that both anatomical/morphological and physiological/biochemical factors contribute toward plant sensitivity to UV-B radiation.

Cyclical Unemployment: Sectoral Shifts or Aggregate Disturbances?

Abstract: Recent work by David Lilien has argued that the existence of a strong positive correlation between the dispersion of employment growth rates across sectors (G) and the unemployment rate implies that shifts in demand from some sectors to others are responsible for a substantial fraction of cyclical variation in unemployment. This paper demonstrates that, under certain empirically satisfied conditions, aggregate demand movements alone can produce a positive correlation between G and the unemployment rate. Two tests are developed which permit one to distinquish between a pure sectoral shift interpretation and a pure aggregate demand interpretation of this positive correlation. The finding that G and the volume of help wanted advertising are negatively related and the finding that G is directly associated with the change in unemployment rather than with the level of unemployment both support an aggregate demand interpretation. A proxy for sectoral shifts that is purged of the influence of aggregate demand is then developed. Models which allow sectoral shifts in the composition of demand and fluctuations in the aggregate level of demand to affect the unemployment rate independently are estimated using this proxy. The results support the view that pure sectoral shifts have not been an important source of cyclical fluctuations in unemployment.

The coupling of nitrification and denitrification in two estuarine sediments1,2

Abstract: Nitrification and denitrification in estuarine sediments were measured by /sup 15/N isotopic tracer techniques at two stations in the Patuxent River estuary for April and August. A close coupling of the two processes was demonstrated directly from the evolution of labeled N/sub 2/ following /sup 15/NH/sub 4//sup +/ amendments during spring experiments. In contrast, this coupled nitrification-denitrification was decreased by two orders of magnitude in the summer, even though the capacity for denitrification remained similar to spring levels. This pattern of sharply seasonal nitrification was corroborated with measurements of bacterial relative abundance. Ambient rates of nitrification-denitrification were inferred from /sup 15/N experiments in these sediments.

AUDIENCE ACTIVITY AND GRATIFICATIONS A Conceptual Clarification and Exploration

Abstract: Certain aspects of the concept of an “active” mass media audience are explored and two dimensions of audience activity identified. The first activity dimension centers on the qualitative orientation of audiences toward the communication process. Audiences are seen as being “selective,”“involved,” or in a “using” relationship to communications. The second activity dimension relates to specific phases in the communication sequence and includes a preexposure period, exposure itself, and a postexposure time. Based on these two dimensions (audience orientation and temporal sequence), a typology of nine audience “activities” is developed. Empirical measures of three types of activity are derived and tested, with audiences found to vary considerably with regard to their “activeness.” A model that links audience activity to uses and gratifications and to exposure is then proposed.

PEERS: A new mixed finite element for plane elasticity

Abstract: A mixed finite element procedure for plane elasticity is introduced and analyzed. The symmetry of the stress tensor is enforced through the introduction of a Lagrange multiplier. An additional Lagrange multiplier is introduced to simplify the linear algebraic system. Applications are made to incompressible elastic problems and to plasticity problems.