Showing papers by "University of Maryland, College Park published in 1989"

The design and analysis of spatial data structures

Abstract: the design and analysis of spatial data structures addison the design and analysis of spatial data structures addison the design and analysis of spatial data structures addison the design and analysis of spatial data structures addison the design and analysis of spatial data structures addison applications of spatial data structures: computer graphics the design and analysis of spatial data structures (pdf editor: andrew s. glassner computer foundations of mathematics 10 by addison wesley bing the value of social media for predicting stock returns landscape architecture fourth edition a manual of land portland writing units grade 5 ekpbs samsung odin manual pdf pdf duckshost wheres the bee wire o journal wmcir document about oae special education 043 secrets study chapter 15 section 2 guided reading a worldwide depression private lemonade nfcqr songs made famous by tammy wynette mandv chapter 22 the great depression begins test answers shamrock cargo a story of the irish pota ekpbs tlia2050a learner guide ramonapropertymanagers 12. greene n., kass m., miller g. “hierarchical zbuffer the encyclopedia of the novel vmnlaw remembering and imagining palestine identity and service manual tc21da jupw websters new world basic dictionary of american english workshop manual for mercedes benz oligra

Socioeconomic Status and Obesity: A Review of the Literature

Abstract: A review of 144 published studies of the relationship between socioeconomic status (SES) and obesity reveals a strong inverse relationship among women in developed societies. The relationship is inconsistent for men and children in developed societies. In developing societies, however, a strong direct relationship exists between SES and obesity among men, women, and children. A review of social attitudes toward obesity and thinness reveals values congruent with the distribution of obesity by SES in different societies. Several variables may mediate the influence of attitudes toward obesity and thinness among women in developed societies that result in the inverse relationship between SES and obesity. They include dietary restraint, physical activity, social mobility, and inheritance.

Nucleosynthesis, neutrino bursts and gamma-rays from coalescing neutron stars

Abstract: It is pointed out here that neutron-star collisions should synthesize neutron-rich heavy elements, thought to be formed by rapid neutron capture (the r-process). Furthermore, these collisions should produce neutrino bursts and resultant bursts of gamma rays; the latter should comprise a subclass of observable gamma-ray bursts. It is argued that observed r-process abundances and gamma-ray burst rates predict rates for these collisions that are both significant and consistent with other estimates.

Hot Spots of Predatory Crime: Routine Activities and the Criminology of Place

Abstract: A leading sociological theory of crime is the “routine activities” approach (Cohen and Felson, 1979). The premise of this ecological theory is that criminal events result from likely offenders, suitable targets, and the absence of capable guardians against crime converging nonrandomly in time and space. Yet prior research has been unable to employ spatial data, relying instead on individual- and household-level data, to test that basic premise. This analysis supports the premise with spatial data on 323,979 calls to police over all 115,000 addresses and intersections in Minneapolis over 1 year. Relatively few “hot spots” produce most calls to Police (50% of calls in 3% of places) and calls reporting predatory crimes (all robberies at 2.2% of places, all rapes at 1.2% of places, and all auto thefts at 2.7% of places), because crime is both rare (only 3.6% of the city could have had a robbery with no repeat addresses) and concentrated, although the magnitude of concentration varies by offense type. These distributions all deviate significantly, and with ample magnitude, from the simple Poisson model of chance, which raises basic questions about the criminogenic nature of places, as distinct from neighborhoods or collectivities.

Digital topology: introduction and survey

Abstract: Digital topology deals with the topological properties of digital images: or, more generally, of discrete arrays in two or more dimensions. It provides the theoretical foundations for important image processing operations such as connected component labeling and counting, border following, contour filling, and thinning—and their generalizations to three- (or higher-) dimensional “images.” This paper reviews the fundamental concepts of digital topology and surveys the major theoretical results in the field. A bibliography of almost 140 references is included.

Skip Lists: A Probabilistic Alternative to Balanced Trees

Abstract: Skip lists are a practical, probabilistic data structure that can be used in place of balanced trees. Algorithms for insertion and deletion in skip lists are much simpler and significantly faster than equivalent algorithms for balanced trees. This paper describes and analyzes skip lists and presents new techniques for analyzing probabilistic algorithms.

Uv-b effects on terrestrial plants

Abstract: The potential impacts of an increase in solar UV-B radiation reaching the Earth's surface due to stratospheric ozone depletion have been investigated by several research groups during the last 15 years. Much of this research has centered on the effects of plant growth and physiology under artificial UV-B irradiation supplied to plants in growth chambers or greenhouses. Since these artificial sources do not precisely match the solar spectrum and due to the wavelength dependency of photobiol-ogical processes, weighting functions, based on action spectra for specific responses, have been developed to assess the biological effectiveness of the irradiation sources and of predicted ozone depletion. Recent experiments have also utilized artificially produced ozone cuvettes to filter natural solar radiation and simulate an environment of reduced UV-B for comparative purposes. Overall, the effectiveness of UV-B varies both among species and among cultivars of a given species. Sensitive plants often exhibit reduced growth (plant height, dry weight, leaf area, etc.), photosynthetic activity and flowering. Competitive interactions may also be altered indirectly by differential growth responses. Photosynthetic activity may be reduced by direct effects on photosynthetic enzymes, metabolic pathways or indirectly through effects on photosynthetic pigments or stomatal function. The fluence response of these changes has yet to be clearly demonstrated in most cases. Plants sensitive to UV-B may also respond by accumulating UV-absorbing compounds in their outer tissue layers, which presumably protect sensitive targets from UV damage. Several key enzymes in the biosynthetic pathways of these compounds have been shown to be specifically induced by UV-B irradiation. Few studies have documented the effects of UV-B on total plant yield under field conditions. One notable exception is a 6-yr study with soybean demonstrating harvestable yield reductions under a simulated 25% ozone depletion. These effects are further modified by prevailing microclimatic conditions. Plants tend to be less sensitive to UV-B radiation under drought or mineral deficiency, while sensitivity increases under low levels of visible light. Further studies are needed to understand the mechanisms of UV-B effects and the interactions with present stresses and future projected changes in the environment.

A Framework for Analyzing Customer Service Orientations in Manufacturing

Abstract: The proposed framework first clarifies the concept of customer service in a manufacturing context. Then the key strategic choices associated with emphasizing a customer service–oriented strategy are specified. Next, the organizational arrangements necessary to implement these strategic choices are described. Finally, alternative effective configurations of the strategic choices, organizational arrangements, and customer service activities are proposed. Research propositions are presented that focus on the relationship between central contingencies in the strategic management literature and customer service in manufacturing.

A Global Climatology of Albedo, Roughness Length and Stomatal Resistance for Atmospheric General Circulation Models as Represented by the Simple Biosphere Model (SiB)

Abstract: Components of the Simple Biosphere Model (SiB) of Sellers et al. (1986) were used to generate global monthly fields of surface albedo (0.4-4.0 microns), roughness length and minimum surface (stomatal) resistance. SiB consists of three submodels which describe the roles of radiative transfer, turbulent transfer and surface resistance in determining the energy balance of the vegetated land surface. These three submodels were detached from SiB and used on the SiB parameter set (total and green leaf area index, leaf angle orientation, canopy dimensions, etc.) to calculate global monthly fields of albedo, roughness length and minimum stomatal resistance at 1 x 1 deg resolution. Time series of various parameters are also displayed for each vegetation type for specified grid points. The SiB results compare reasonably well with appropriate measurements obtained from the literature and have the additional merit of being mutually consistent; the three submodels use many common parameters, which ensures that, for each grid area, the calculated surface properties are closely interrelated as is the case in nature. The derived fields provide a check on the operation of the submodels and the correctness of the parameter set. They can also be used as prescribed fields for GCMs that do not have biophysically based land surface parameterizations.

The validity of verbal protocols.

Abstract: The reactivity of a "think aloud" verbal protocol and the veridicality of different retrospective protocols were tested over four dissimilar tasks. Generating a concurrent protocol altered accuracy in two tasks, simple addition and a choice between two gambles, and generally prolonged response times. Such reactivity partially qualifies the dominant theory of protocol generation (Ericsson & Simon, 1984). Retrospective protocols yielded substantial forgetting or fabrication in all tasks, supporting the consensus on the nonveridicality of these methods. It is concluded that protocol validity should be based on an empirical check rather than on theory-based assurances.

The semantic conception of theories and scientific realism

Abstract: Frederick Suppe has come to enjoy a position of undisputed leadership in the post-positivistic philosophy of science. Students of the field will therefore welcome publication of the present account of his views. The fourteen chapters derive from papers published since 1971, but which have been subje

Metacognition: Answered and Unanswered Questions

Abstract: This article summarizes "facts" emerging from recent research and explanations of those facts arising from metacognitive theory. We suggest that the following four questions should be addressed empirically: (a) How can we measure "knowing about knowing" more accurately?, (b) How can we measure the effects of strategy instruction?, (c) What are the relations between content knowledge and strategy knowledge?, and (d) What is the role of achievement motivation in use of strategies?

The Psychology of Being "Right": The Problem of Accuracy in Social Perception and Cognition

Abstract: Several difficulties are noted with general questions psychologists have been asking about human accuracy, such as whether people are typically accurate or inaccurate, what the boundary conditions for accuracy are, or the general process whereby accuracy may be improved. Instead, a situationally specific approach to accuracy is adopted in which a central role is assigned to the judgmental process. Accordingly, two general paradigms are distinguished addressing accuracy from realistic and phenomenal perspectives. The realist paradigm focuses on subjects' judgments and the degree to which these correspond to an external criterion. The phenomenal paradigm focuses on subjects' internal criterion as well as their perceptions of the target judgment and the judgment-to-criterion correspondence. Research possibilities in each paradigm are noted. It is suggested that attention to judgmental factors may extend accuracy work in previously unexplored directions.

Identification of a neuropeptide hormone that regulates sex pheromone production in female moths.

Abstract: A pheromone biosynthesis activating neuropeptide (PBAN) hormone that controls sex pheromone production in female moths was identified from the brain-subesophageal ganglion complexes of the adult corn earworm, Heliothis zea. PBAN has 33 amino acid residues and a molecular weight of 3900. Its amino acid sequence has no significant homology with any of the fully characterized peptide hormones. The synthetic peptide, at a dose of between 2 and 4 picomoles, induced production of a normal quantity of sex pheromone in ligated H. zea females. The peptide also induced pheromone production in six other species of moths, thus indicating that this or similar peptides may be responsible for the regulation of pheromone production in moths.

The Labeling perspective and delinquency: An elaboration of the theory and an assessment of the evidence

Abstract: The labeling theory of deviance was extremely popular during the 1960s and 1970s. After a series of influential critiques, however, the validity of the theory had fallen into question by 1980 and was pronounced dead by 1985. In this paper we examine the application of the labeling perspective to one particular area, juvenile delinquency. We discuss the general theoretical origin of labeling theory in both conflict theory and symbolic interactionism, and use it to present two main labeling hypotheses: 1) that status attributes are influential in determining who is labeled (the “status characteristics hypothesis”) and 2) that labeling experiences are instrumental in producing problems of adjustment and in causing subsequent commitment to further deviance (the “secondary deviance hypothesis”). We note that what is often passed off as a critique of labeling theory itself is frequently a caricature of the theory. The major point of the paper is an elaboration of the full complexity of each labeling hypothesis,...

Components analysis of cognitive strategy instruction: Effects on learning disabled students' compositions and self-efficacy.

Abstract: 22 eleves de 10 a 13 ans en difficulte d'apprentissage (QI moyen de 95) et 11 eleves normaux pratiquent un entrainement aux strategies d'auto-instruction sur des tâches de composition On analyse les performances en termes de composantes dans la redaction d'une histoire, pour determiner l'impact de cet entrainement sur chacun des groupes

The Productivity Slowdown, Measurement Issues, and the Explosion of Computer Power

Abstract: No abstract is available for this paper.

Information-seeking strategies of novices using a full-text electronic encyclopedia

Abstract: An exploratory study was conducted of elementary school children searching a full-text electronic encyclopedia on CD-ROM. Twenty-eight third and fourth graders and 24 sixth graders conducted two assigned searches, one open-ended, the other one closed, after two demonstration sessions. Keystrokes captured by the computer and observer notes were used to examine user information-seeking strategies from a mental model perspective. Older searchers were more successful in finding required information, and took less time than younger searchers. No differences in total number of moves were found. Analysis of search patterns showed that novices used a heuristic, highly interactive search strategy. Searchers used sentence and phrase queries, indicating unique mental models for this search system. Most searchers accepted system defaults and used the AND connective in formulating queries. Transition matrix analyses showed that younger searchers generally favored query refining moves and older searchers favored examining title and text moves. Suggestions for system designers were made and future research questions were identified.

The perturbed test function method for viscosity solutions of nonlinear PDE

Abstract: The method of viscosity solutions for nonlinear partial differential equations (PDEs) justifies passages to limits by in effect using the maximum principle to convert to the corresponding limit problem for smooth test functions. We describe in this paper a “perturbed test function” device, which entails various modifications of the test functions by lower order correctors. Applications include homogenisation for quasilinear elliptic PDEs and approximation of quasilinear parabolic PDEs by systems of Hamilton-Jacobi equations.

Effects of 'Seductive Details' on Macroprocessing and Microprocessing in Adults and Children

Abstract: Twenty adults were asked to read a three-paragraph expository text on differences among insects. Information in the text had been rated for importance and interestingness. Half of the adults read the text with "seductive details" (propositions presenting interesting, but unimportant, information), half without. After reading, the adults recalled the important information (a macroprocessing task), rated the text for overall interestingness, reported the single most interesting piece of information read, and matched pictures of animals on the basis of differences mentioned in text (a microprocessing task). The adults presented with seductive details in text were significantly less adept than their peers at including three main ideas in their recall protocols. Microprocessing performance and interestingness ratings were unaffected by text condition. In a second study, with 36 seventh graders, macroprocessing performance in general was weak. Students presented with seductive details in text were significantly...

Fractals for secondary key retrieval

Abstract: In this paper we propose the use of fractals and especially the Hilbert curve, in order to design good distance-preserving mappings. Such mappings improve the performance of secondary-key- and spatial- access methods, where multi-dimensional points have to be stored on an 1-dimensional medium (e.g., disk). Good clustering reduces the number of disk accesses on retrieval, improving the response time. Our experiments on range queries and nearest neighbor queries showed that the proposed Hilbert curve achieves better clustering than older methods (“bit-shuffling”, or Peano curve), for every situation we tried.

Estimation of Soil Water Retention and Hydraulic Properties

Abstract: Water flow in soils can be characterized, in principle, for many boundary and initial conditions by solving the proper governing differential equations. There are several reasons why this state-of-the-art technology is not yet fully utilized. One reason may be complexity and expense of computer based numerical solutions. However, a more important reason is the difficulty of obtaining the primary input which is the relationship between matrix potential and hydraulic conductivity as a function of soil water content. Approximate water flow models based on physical principles or empirical results may simplify the computational requirements; however, soil property inputs are still required.

The changing solar ultraviolet climate and the ecological consequences for higher plants

Abstract: There is compelling evidence that a general erosion of the global ozone layer is occurring. Since ozone in the stratosphere absorbs much of the shortwave solar ultraviolet radiation (UV-B), diminished ozone means that more UV-B of a very specific wavelength composition will be received at the earth's surface. Evaluating the implications for vegetation involves consideration of the wavelength specificity of biological photochemical reactions and their sensitivity to the extant and future solar spectrum. Recent research suggests the occurrence of direct damaging reactions and of indirect morphological and chemical responses with implications at the community and ecosystem levels.

Petri-net-based hypertext: document structure with browsing semantics

Abstract: We present a formal definition of the Trellis model of hypertext and describe an authoring and browsing prototype called aTrellis that is based on the model. The Trellis model not only represents the relationships that tie individual pieces of information together into a document (i.e., the adjacencies), but specifies the browsing semantics to be associated with the hypertext as well (i.e., the manner in which the information is to be visited and presented). The model is based on Petri nets, and is a generalization of existing directed graph-based forms of hypertext. The Petri net basis permits more powerful specification of what is to be displayed when a hypertext is browsed and permits application of previously developed Petri net analysis techniques to verify properties of the hypertext. A number of useful hypertext constructs, easily described in the Trellis model, are presented. These include the synchronization of simultaneous traversals of separate paths through a hypertext, the incorporation of access controls into a hypertext (i.e., specifying nodes that can be proven to be accessible only to certain classes of browsers), and construction of multiple specialized (tailored) versions from a single hypertext.

Detection of H 3 + on Jupiter

Abstract: SINCE their detection in the high latitudes of Jupiter, first by the Voyager Ultraviolet Spectrometer (UVS) experiment1,2, then by the International Ultraviolet Explorer (IDE) satellite3, the auroral particle precipitations have been associated with various phenomena in the jovian environment. In the magnetosphere, the H+3 ion, probably of ionospheric origin, was detected in situ by the Voyagers4. Infrared emissions were observed in spectral bands characteristic of CH4 (ref. 5) and of other hydrocarbons6,7, localized in two auroral spots5,8. Here we present high-resolution spectra at a wavelength of 2 μm, in the southern auroral region of Jupiter, recorded at the Canada–France–Hawaii Telescope (CFHT), which we believe to be the first astronomical spectroscopic detection of H3+. The derived rotational temperature of H3+ is in the range 1,000–1,200 K. Such strong H3+ lines could be used in future ground-based monitoring of the jovian auroral activity and to search for this molecular ion in the interstellar medium.