Showing papers by "University of Maryland, College Park published in 1987"
Book•
01 Jan 1987TL;DR: The Sixth Edition of Designing the User Interface provides a comprehensive, authoritative, and up-to-date introduction to the dynamic field of human-computer interaction and user experience (UX) design.
Abstract: For courses in Human-Computer Interaction. The Sixth Edition of Designing the User Interface provides a comprehensive, authoritative, and up-to-date introduction to the dynamic field of human-computer interaction (HCI) and user experience (UX) design. This classic book has defined and charted the astonishing evolution of user interfaces for three decades. Students and professionals learn practical principles and guidelines needed to develop high quality interface designs that users can understand, predict, and control. The book covers theoretical foundations and design processes such as expert reviews and usability testing. By presenting current research andinnovations in human-computer interaction, the authors strive toinspire students, guide designers, and provoke researchers to seek solutions that improve the experiences of novice and expert users, while achieving universal usability. The authors also provide balanced presentations on controversial topics such as augmented and virtual reality, voice and natural language interfaces, and information visualization. Updates include current HCI design methods, new design examples, and totally revamped coverage of social media, search and voice interaction. Major revisions were made toEVERY chapter, changing almost every figure (170 new color figures) and substantially updating the references.
6,896 citations
TL;DR: A framework for understanding the etiology of organizational behavior is presented in this article, which is based on theory and research from interactional psychology, vocational psychology, I/O psychology, and organizational theory.
Abstract: A framework for understanding the etiology of organizational behavior is presented. The framework is based on theory and research from interactional psychology, vocational psychology, I/O psychology, and organizational theory. The framework proposes that organizations are functions of the kinds of people they contain and, further, that the people there are functions of an attraction-selection-attrition (ASA) cycle. The ASA cycle is proposed as an alternative model for understanding organizations and the causes of the structures, processes, and technology of organizations. First, the ASA framework is developed through a series of propositions. Then some implications of the model are outlined, including (1) the difficulty of bringing about change in organizations, (2) the utility of personality and interest measures for understanding organizational behavior, (3) the genesis of organizational climate and culture, (4) the importance of recruitment, and (5) the need for person-based theories of leadership and job attitudes. It is concluded that contemporary I/O psychology is overly dominated by situationist theories of the behavior of organizations and the people in them.
4,069 citations
TL;DR: In this article, the theory of first order Fermi acceleration at collisionless astrophysical shock fronts is reviewed and it is argued that the wave amplitude is probably non-linear within sufficiently strong astrophysical shocks.
1,881 citations
TL;DR: A concomitant increase in circulating monocytes bearing class II (HLA-DR) surface antigen suggested that the attacks induced during treatment were immunologically mediated, and IFN-gamma is unsuitable for treatment of MS.
1,069 citations
TL;DR: The authors reviewed the book "Social Foundations of Thought and Action: A Social-Cognitive View,” by Albert Bandura, and found it to be a good book to read.
Abstract: The article reviews the book “Social Foundations of Thought and Action: A Social-Cognitive View,” by Albert Bandura.
1,016 citations
01 Jan 1987
TL;DR: This paper outlines those features that distinguish the High Frequency (HF) Intra Task Force (ITF) Network from other packet radio networks, and presents a design concept for this network that encompasses organizational structure, waveform design, and channel access.
Abstract: The design of a packet radio network must reflect the operational requirements and environmental constraints to which it is subject. In this paper, we outline those features that distinguish the High Frequency (HF) Intra Task Force (ITF) Network from other packet radio networks, and we present a design concept for this network that encompasses organizational structure, waveform design, and channel access. Network survivability is achieved through the use of distributed network control and frequency hopping spread-spectrum signaling. We demonstrate how the execution of the fully distributed Linked Cluster Algorithm can enable a network to reconfigure itself when it is affected by connectivity changes such as those resulting from jamming. Additional resistance against jamming is provided by frequency hopping, which leads naturally to the use of code division mutiple access (CDMA) techniques that permit the simultaneous successful transmission by several users. Distributed algorithms that exploit CDMA properties have been developed to schedule contention-free transmissions for much of the channel access in this network. Contention-based channel access protocols can also be implemented in conjunction with the Linked Cluster network structure. The design concept presented in this paper provides a high degree of survivability and flexibility, to accommodate changing environmental conditions and user demands.
943 citations
TL;DR: The authors examines the tourist and leisure experience from three perspectives: post-hoc satisfaction, immediate conscious experience, and immediate conscious tourist experience, concluding that tourist experience becomes leisure experience under certain conditions.
824 citations
TL;DR: In this paper, an effective center-of-gravity heuristic is presented that outperforms heuristics from the literature for orienteering, a sport in which start and end points are specified along with other locations.
Abstract: Orienteering is a sport in which start and end points are specified along with other locations. These other locations have associated scores. Competitors seek to visit, in a fixed amount of time, a subset of these locations on the way from the start point to the end point in order to maximize the total score. An effective center-of-gravity heuristic is presented that outperforms heuristics from the literature.
713 citations
TL;DR: In this article, the role of perceived certainty and severity of punishment in deterring criminal/deviant behavior was examined, and a thorough review of the perceptual deterrence literature from 1972-1986 was provided, which indicates that cross-sectional correlations between perceptions of sanction threats and self-reported criminal/evictive behavior are moderately negative for diverse offenses, consistent with the deterrence doctrine.
Abstract: This paper critically examines the role of the perceived certainty and severity of punishment in deterring criminal/deviant behavior. A thorough review of the perceptual deterrence literature from 1972–1986 is provided which indicates that cross-sectional correlations between perceptions of sanction threats and self-reported criminal/deviant behavior are moderately negative for diverse offenses, consistent with the deterrence doctrine. It is noted that rather than expressing the deterrent effect, these correlations probably indicate the effect of prior behavior on currently held perceptions—the experiential effect. In addition, since in many instances the reported correlations express simple bivariate relationships, the association may be spurious rather than causal. When researchers employing panel designs have estimated the deterrent relationship with variables in their correct temporal ordering and with more fully specified causal models, the moderate inverse effect for both perceived certainty and sev...
594 citations
TL;DR: In this article, the ability of satellite sensor systems to estimate area-averaged canopy photosynthetic and transpirative properties is evaluated, and the near linear relationship between the simple ratio (SR) and normalized difference (ND) and the surface biophysical properties of canopy photoynthetically active radiation (PAR) absorption, photosynthesis, and bulk stomatal resistance is studied.
575 citations
01 Oct 1987
TL;DR: Indefinite databases arise where, in general, the data consists of non-Horn clauses as discussed by the authors, i.e., a disjunction of literals in which more than one literal in the clause is positive.
Abstract: A database is said to be indefinite if there is an answer to a query of the form Pa V Pb where neither Pa nor Pb can be derived from the database. Indefinite databases arise where, in general, the data consists of non-Horn clauses. A clause is non-Horn if it is a disjunction of literals in which more than one literal in the clause is positive.
TL;DR: In this paper, a simple model of hyperbolic conservation laws with relaxation effects is presented and analyzed, and stability criteria for diffusion waves, expansion waves and traveling waves are justified nonlinearly.
Abstract: The effect of relaxation is important in many physical situations. It is present in the kinetic theory of gases, elasticity with memory, gas flow with thermo-non-equilibrium, water waves, etc. The governing equations often take the form of hyperbolic conservation laws with lower-order terms. In this article, we present and analyze a simple model of hyperbolic conservation laws with relaxation effects. Dynamic subcharacteristics governing the propagation of disturbances over strong wave forms are identified. Stability criteria for diffusion waves, expansion waves and traveling waves are found and justified nonlinearly. Time-asymptotic expansion and the energy method are used in the analysis. For dissipative waves, the expansion is similar in spirit to the Chapman-Enskog expansion in the kinetic theory. For shock waves, however, a different approach is needed.
TL;DR: This study applies an experimentation methodology to compare three state-of-the-practice software testing techniques: a) code reading by stepwise abstraction, b) functional testing using equivalence partitioning and boundary value analysis, and c) structural testing using 100 percent statement coverage criteria.
Abstract: This study applies an experimentation methodology to compare three state-of-the-practice software testing techniques: a) code reading by stepwise abstraction, b) functional testing using equivalence partitioning and boundary value analysis, and c) structural testing using 100 percent statement coverage criteria. The study compares the strategies in three aspects of software testing: fault detection effectiveness, fault detection cost, and classes of faults detected. Thirty-two professional programmers and 42 advanced students applied the three techniques to four unit-sized programs in a fractional factorial experimental design. The major results of this study are the following. 1) With the professional programmers, code reading detected more software faults and had a higher fault detection rate than did functional or structural testing, while functional testing detected more faults than did structural testing, but functional and structural testing were not different in fault detection rate. 2) In one advanced student subject group, code reading and functional testing were not different in faults found, but were both superior to structural testing, while in the other advanced student subject group there was no difference among the techniques. 3) With the advanced student subjects, the three techniques were not different in fault detection rate. 4) Number of faults observed, fault detection rate, and total effort in detection depended on the type of software tested. 5) Code reading detected more interface faults than did the other methods. 6) Functional testing detected more control faults than did the other methods.
TL;DR: Three types of changes that attractors can undergo as a system parameter is varied are considered, which are termed crises, where one (or more) chaotic attractors merge to form a single chaotic attractor and the merged attractor can be larger in phase-space extent than the union of the attractors before the change.
Abstract: We consider three types of changes that attractors can undergo as a system parameter is varied. The first type leads to the sudden destruction of a chaotic attractor. The second type leads to the sudden widening of a chaotic attractor. In the third type of change, which applies for many systems with symmetries, two (or more) chaotic attractors merge to form a single chaotic attractor and the merged attractor can be larger in phase-space extent than the union of the attractors before the change. All three of these types of changes are termed crises and are accompanied by a characteristic temporal behavior of orbits after the crisis. For the case where the chaotic attractor is destroyed, this characteristic behavior is the existence of chaotic transients. For the case where the chaotic attractor suddenly widens, the characteristic behavior is an intermittent bursting out of the phase-space region within which the attractor was confined before the crisis. For the case where the attractors suddenly merge, the characteristic behavior is an intermittent switching between behaviors characteristic of the attractors before merging.In all cases a time scale \ensuremath{\tau} can be defined which quantifies the observed post-crisis behavior: for attractor destruction, \ensuremath{\tau} is the average chaotic transient lifetime; for intermittent bursting, it is the mean time between bursts; for intermittent switching, it is the mean time between switches. The purpose of this paper is to examine the dependence of \ensuremath{\tau} on a system parameter (call it p) as this parameter passes through its crisis value p=${p}_{c}$. Our main result is that for an important class of systems the dependence of \ensuremath{\tau} on p is \ensuremath{\tau}\ensuremath{\sim}\ensuremath{\Vert}p-${p}_{c}$${\ensuremath{\Vert}}^{\mathrm{\ensuremath{-}}\ensuremath{\gamma}}$ for p close to ${p}_{c}$, and we develop a quantitative theory for the determination of the critical exponent \ensuremath{\gamma}. Illustrative numerical examples are given. In addition, applications to experimental situations, as well as generalizations to higher-dimensional cases, are discussed. Since the case of attractor destruction followed by chaotic transients has previously been illustrated with examples [C. Grebogi, E. Ott, and J. A. Yorke, Phys. Rev. Lett. 57, 1284 (1986)], the numerical experiments reported in this paper will be for crisis-induced intermittency (i.e., intermittent bursting and switching).
TL;DR: The authors were able to isolate Bacillus thuringiensis from environmental samples with a background of 10 bacteria per g of soil with a selection process differed significantly from classical selection methods which permit only the desired organism to grow.
Abstract: We were able to isolate Bacillus thuringiensis from environmental samples with a background of 109 bacteria per g of soil. Our selection process differed significantly from classical selection methods which permit only the desired organism to grow. In our process, germination of B. thuringiensis spores was selectively inhibited by sodium acetate, while most of the undesired sporeformers germinated. Next, all of the nonsporulated microbes were eliminated by heat treatment at 80°C for 3 min. The surviving spores were then plated on a rich agar medium and allowed to grow until they sporulated. Of random colonies picked from agar, 20 to 96% were crystal-forming Bacillus species. B. thuringiensis and B. sphaericus were routinely selected by this method.
TL;DR: Thunderstorms may transform local air pollution problems into regional or global atmospheric chemistry problems, and their concentrations were much greater in the outflow region of the storm, up to 11 kilometers in altitude, than in surrounding air.
Abstract: Acid deposition and photochemical smog are urban air pollution problems, and they remain localized as long as the sulfur, nitrogen, and hydrocarbon pollutants are confined to the lower troposphere (below about 1-kilometer altitude) where they are short-lived. If, however, the contaminants are rapidly transported to the upper troposphere, then their atmospheric residence times grow and their range of influence expands dramatically. Although this vertical transport ameliorates some of the effects of acid rain by diluting atmospheric acids, it exacerbates global tropospheric ozone production by redistributing the necessary nitrogen catalysts. Results of recent computer simulations suggest that thunderstorms are one means of rapid vertical transport. To test this hypothesis, several research aircraft near a midwestern thunderstrom measured carbon monoxide, hydrocarbons, ozone, and reactive nitrogen compounds. Their concentrations were much greater in the outflow region of the storm, up to 11 kilometers in altitude, than in surrounding air. Trace gas measurements can thus be used to track the motion of air in and around a cloud. Thunderstorms may transform local air pollution problems into regional or global atmospheric chemistry problems.
TL;DR: The capability of the closed-time-path formalism of dealing with Feynman, causal, and correlation functions on the same footing makes it a potentially powerful and versatile technique for treating nonequilibrium statistical properties of dynamical systems as in early-Universe quantum processes.
Abstract: We discuss the generalization to curved spacetime of a path-integral formalism of quantum field theory based on the sum over paths first going forward in time in the presence of one external source from an in vacuum to a state defined on a hypersurface of constant time in the future, and then backwards in time in the presence of a different source to the same in vacuum. This closed-time-path formalism which generalizes the conventional method based on in-out vacuum persistence amplitudes yields real and causal effective actions, field equations, and expectation values. We apply this method to two problems in semiclassical cosmology. First we study the back reaction of particle production in a radiation-filled Bianchi type-I universe with a conformal scalar field. Unlike the in-out formalism which yields complex geometries the real and causal effective action here yields equations for real effective geometries, with more readily interpretable results. It also provides a clear identification of particle production as a dissipative process in semiclassical theories. In the second problem we calculate the vacuum expectation value of the stress-energy tensor for a nonconformal massive \ensuremath{\lambda}${\ensuremath{\varphi}}^{4}$ theory in a Robertson-Walker universe. This study serves to illustrate the use of Feynman diagrams and higher-loop calculations in this formalism. It also demonstrates the economy of this method in the calculation of expectation values over the mode-sum Bogolubov transformation methods ordinarily applied to matrix elements calculated in the conventional in-out approach. The capability of the closed-time-path formalism of dealing with Feynman, causal, and correlation functions on the same footing makes it a potentially powerful and versatile technique for treating nonequilibrium statistical properties of dynamical systems as in early-Universe quantum processes.
TL;DR: In this paper, the authors investigated the magnitude of the thermal residual stresses by determining the difference of the yield stresses (Δσy) between tension and compression resulting from the residual stresses.
TL;DR: A reinterpretation of the equilibrium solution allows us to relate the dynamical transition to the equilibrium theory and the mathematical structure of the mean-field dynamical theory is closely related to certain recent dynamical theories of the structural glass transition.
Abstract: The static and the dynamical theories for the mean-field p-spin (pg2) interaction spin-glass model are studied. A broken-replica-symmetric equilibrium solution leads to a glass transition at a temperature ${T}_{g}^{\mathcal{'}}$ where the Edwards-Anderson order parameter is discontinuous but where there is no latent heat and there is a discontinuous specific heat. The dynamical theory leads to a continuous slowing down and predicts a glass transition at ${T}_{g}$g${T}_{g}^{\mathcal{'}}$. A reinterpretation of the equilibrium solution allows us to relate the dynamical transition to the equilibrium theory. The mathematical structure of the mean-field dynamical theory is closely related to certain recent dynamical theories of the structural glass transition.
TL;DR: It is suggested that anterior subcortical structures may play an important but lateralized role in the production or regulation of mood in patients with poststroke mood disorders.
Abstract: Patients with single stroke lesions, verified by computerized tomography, involving either cortical tissue or restricted entirely to subcortical structures were examined for mood disorders Those with left anterior lesions, either cortical or subcortical, had significantly greater frequency and severity of depression than patients with any other lesion location A strong correlation between the severity of depression and proximity of the lesion to the frontal pole was observed for both left cortical and subcortical groups Right hemisphere lesions did not show the same correlation with depression but were associated with a significantly higher incidence of undue cheerfulness These findings demonstrate the importance of the location of subcortical lesions in poststroke mood disorders and suggest that anterior subcortical structures may play an important but lateralized role in the production or regulation of mood
TL;DR: Basic developments in the field of chaotic dynamics of dissipative systems are reviewed, Topics covered include strange attractors, how chaos comes about with variation of a system parameter, universality, fractal basin boundaries and their effect on predictability, and applications to physical systems.
Abstract: Recently research has shown that many simple nonlinear deterministic systems can behave in an apparently unpredictable and chaotic manner. This realization has broad implications for many fields of science. Basic developments in the field of chaotic dynamics of dissipative systems are reviewed in this article. Topics covered include strange attractors, how chaos comes about with variation of a system parameter, universality, fractal basin boundaries and their effect on predictability, and applications to physical systems.
TL;DR: It is suggested that female choice is a mechanism for the evolution of color patterns in guppies and may have contributed to the distinctive color pattern of the Paria population.
Abstract: This study tested the effect of differences in the extent of orange pigment in the color pattern of male guppies on the sexual responsiveness of females. Fish used in this study were descendants of a single natural population from the Paria River of Trinidad. Males from this population have unusually large, brilliant orange spots. I used three experimental approaches to test for discrimination by females among males based on the relative area of orange in color patterns: 1) the time to mating when a male was presented to a virgin female; 2) the frequency of sexual responses of females to passing, nondisplaying males; and 3) the proportion of a male's courtship displays that elicited a female sexual response. In all three experiments, females appeared to discriminate against males with less-than-average amounts of orange in their color patterns. In at least one experiment, however, the increase in female responsiveness with increasing amounts of orange leveled off and possibly decreased at high levels of orangeness. This suggests that there may be no advantage of increased amounts of orange above a certain level. These results suggest that female choice is a mechanism for the evolution of color patterns in guppies and may have contributed to the distinctive color pattern of the Paria population.
TL;DR: The technique permits the construction of complex strains with many directed mutations without the introduction of a corresponding number of antibiotic resistance markers and should prove useful, for example, in exploring the role of the multiple pel genes in E. chrysanthemi.
Posted Content•
TL;DR: The authors showed that workers in longer jobs earn more throughout than workers in a series of shorter jobs and that the measured positive cross-sectional return seniority is largely a statistical artifact due to the correlation of seniority with an omitted variable representing the quality of the worker, the job, or the worker-employer match.
Abstract: An important stylized fact about labor markets is that workers with longer seniority with their current employer have higher earnings than other workers with the same total labor market experience. This study shows that workers in longer jobs earn more throughout than workers in a series of shorter jobs and that the measured positive cross-sectional return seniority is largely a statistical artifact due to the correlation of seniority with an omitted variable representing the quality of the worker, the job, or the worker-employer match. The implication is tha t earnings do not, in fact, rise very much with seniority. Copyright 1987 by American Economic Association.
TL;DR: It is shown that this optimal design of the zero-memory quantization of memoryless sources could result in substantial performance improvements, more noticeable at high bit rates and for broad-tailed densities.
Abstract: We present an analysis of the zero-memory quantization of memoryless sources when the quantizer output is to be encoded and transmitted across a noisy channel. Necessary conditions for the joint optimization of the quantizer and the encoder/decoder pair are presented, and an iterative algorithm for obtaining a locally optimum system is developed. The performance of this locally optimal system, obtained for the class of generalized Gaussian distributions and the binary symmetric channel, is compared against the optimum performance theoretically attainable (using rate-distortion theoretic arguments), as well as against the performance of Lloyd-Max quantizers encoded using the natural binary code and the folded binary code. It is shown that this optimal design could result in substantial performance improvements. The performance improvements are more noticeable at high bit rates and for broad-tailed densities.
TL;DR: In this article, four studies were conducted to examine the relationship between academic self-efficacy and performance in college courses, and measures of academic grade goals and ability were also obtained.
Abstract: Four studies were conducted to examine the relationship between academic self-efficacy and performance in college courses. Measures of academic grade goals and ability were also obtained. The first study was used to select valid items from a larger pool of self-efficacy measures. The items were further revised and the new item set was then tested out on the sample from study 4. A final set of items was selected and the resulting self-efficacy scale replicated on two other samples (studies 2 and 3). Self-efficacy was found to be significantly related to academic performance and to self-set academic grade goals. Grade goals and ability were also related to course performance. These results are consistent with laboratory studies of the relation of self-efficacy and goals to task performance.
TL;DR: In this article, the authors examined the effects of strategic business units' strategies on the utility of various states of corporate-SBU relations and found that openness and subjectivity in performance assessment were positively associated with effectiveness.
Abstract: In a departure from earlier studies focusing only on the effects of corporate strategies, this study examined the effects of strategic business units' (SBUs') strategies on the utility of various states of corporate-SBU relations. For SBUs trying to build market share or to pursue differentiation as a competitive strategy, openness in corporate-SBU relations and subjectivity in performance assessment were found to be positively associated with effectiveness; for SBUs trying lo maximize short-term earnings or to pursue low cost as a competitive strategy, the corresponding associations were found to be negative. In contrast, corporate-SBU decentralization emerged as positively associated with SBUs' effectiveness irrespective of their strategic contexts; although SBUs' competitive strategies moderated the magnitude of that association, their strategic missions did not.
TL;DR: This paper investigated how different methods of text production affect the writing processes and products of LD students, and found that handwritten and word processed stories did not differ on any of the product measures, including length, quality, story structure, mechanical or grammatical errors, vocabulary, or mean T-unit length.
Abstract: The purpose of this study was to investigate how different methods of text production affect the writing processes and products of LD students. Eleven fifth and sixth grade LD students, selected for their experience with word processing, composed and revised stories using handwriting, dictation, and word processing. Dictated stories were significantly longer, were of higher quality, and had fewer grammatical errors than handwritten or word processed stories. The handwritten and word processed stories did not differ on any of the product measures, including length, quality, story structure, mechanical or grammatical errors, vocabulary, or mean T-unit length. However, differences between handwriting and word processing were found on the process measures of composing rate and revisions. Implications for writing in struction with LD students are discussed.
01 Apr 1987
TL;DR: Results support the notion that nutrient replete Synechococcus have the capacity to grow at maximal growth rates in brightly lit oceanic surface mixed layers.
Abstract: We grew Synechococcus WH7803 at rates exceeding 1.4 d −1 at irradiances from 200 to 2000 μE m −2 s −1 under continuous light in nutrient replete media with no evidence of photoinhibition. Concentrations of the photosynthetic pigments phycoerythrin, phycocyanin, and chlorophyll a , were inversely related to growth irradiance. Phycoerythrin exhibited the greatest plasticity with the concentration in cells adapted to 30 μE m −2 s −1 being ca . 20 times greater than that in cells adapted to 700 μE m −2 s −1 . Changes in the phycoerythrin: phycocyanin ratio as well as their respective concentrations indicate that phycobilisomes underwent changes in size at irradiances which saturated or nearly saturated growth and underwent changes in number at irradiances which limited growth. Phycoerythrin in high light adapted cells contained 20% in light limited cells. Results support the notion that nutrient replete Synechococcus have the capacity to grow at maximal growth rates in brightly lit oceanic surface mixed layers.