Showing papers by "University of Waterloo published in 1985"
01 Mar 1985-Graphical Models \/graphical Models and Image Processing \/computer Vision, Graphics, and Image Processing
TL;DR: Two methods of entropic thresholding proposed by Pun (Signal Process.,2, 1980, 223–237;Comput.16, 1981, 210–239) have been carefully and critically examined and a new method with a sound theoretical foundation is proposed.
Abstract: Two methods of entropic thresholding proposed by Pun (Signal Process.,2, 1980, 223–237;Comput. Graphics Image Process.16, 1981, 210–239) have been carefully and critically examined. A new method with a sound theoretical foundation is proposed. Examples are given on a number of real and artifically generated histograms.
3,551 citations
Book•
01 Jan 1985TL;DR: In this paper, the Schachter model of emotion was presented to the client, who was encouraged to view anxiety as a reaction involving negative self-statements and images and physiological arousal.
Abstract: Stress inoculation training originally referred to a relatively specific set of operations (Meichenbaum & Cameron, 1972) In order to evaluate the efficacy of a skills training approach to anxiety management, a study was conducted using phobia as a target problem Treatment involved three phases It began with an educational phase that clarified the cognitive, affective, and physiological concomitants of the client’s avoidant behavior The Schachter (1966) model of emotion was presented to the client, who was encouraged to view anxiety as a reaction involving negative self-statements and images and physiological arousal It was suggested that acquisition of two skills, namely, coping self-statements and self-directed relaxation, would help ameliorate the problem This initial phase was followed by a skills training phase: specific types of coping self-statements and relaxation skills were learned and rehearsed Finally, during an application phase, the client actually tested out the skills in a stressful laboratory situation (unpredictable electric shock was administered) This treatment was found to be more effective than imaginal systematic desensitization, then the standard treatment for phobia
1,149 citations
26 Sep 1985-Philosophical transactions - Royal Society. Mathematical, physical and engineering sciences
TL;DR: In this paper, the directional spectrum of wind-generated waves on deep water is determined by using a modification of Barber's (1963) method, and the results reveal that the frequency spectrum in the rear face is inversely proportional to the fourth power of the frequency.
Abstract: From observations of wind and of water surface elevation at 14 wave staffs in an array in Lake Ontario and in a large laboratory tank, the directional spectrum of wind-generated waves on deep water is determined by using a modification of Barber's (1963) method. Systematic investigations reveal the following: (a) the frequency spectrum in the rear face is inversely proportional to the fourth power of the frequency $\omega $, with the equilibrium range parameter and the peak enhancement factor clearly dependent on the ratio of wind speed to peak wave speed; (b) the angular spreading $\theta $ of the wave energy is of the form sech$^{2}$ ($\beta \theta $), where $\beta $ is a function of frequency relative to the peak; (c) depending on the gradient of the fetch, the direction of the waves at the spectral peak may differ from the mean wind direction by up to 50 degrees, but this observed difference is predictable by a similarity analysis; (d) under conditions of strong wind forcing, significant effects on the phase velocity caused by amplitude dispersion and the presence of bound harmonics are clearly observed and are in accordance with the Stokes theory, whereas (e) the waves under natural wind conditions show amplitude dispersion, but bound harmonics are too weak to be detected among the background of free waves.
983 citations
TL;DR: The Group Environment Questionnaire (GEQ) as discussed by the authors was developed to assess group cohesion in a sport team and is composed of four scales reflecting the constructs of group integration-task.
Abstract: The purpose of this paper was fourfold. The first purpose was to demonstrate the need to develop an instrument to assess group cohesion while the second was to outline a conceptual model of group cohesion upon which such an instrument could be based. This model reflected four related constructs which were the a priori basis for developing a large item pool and initial versions of the Group Environment Questionnaire (GEQ). The third purpose was to outline the four projects conducted to obtain construct-related information and to develop an initial version of the GEQ. The final purpose was to outline the two reliability and validity studies conducted with two different sport team samples. The results of these studies revealed that an 18-item version of the GEQ was internally consistent, reliable across studies, and content valid. Factor analyses with oblique rotation revealed preliminary evidence for construct validity. The GEQ is comprised of four scales reflecting the constructs of group integration-task,...
974 citations
TL;DR: In this article, the analysis of panel data under a continuous-time Markov model is presented, where the maximum likelihood estimates and associated asymptotic covariance matrices for transition intensity parameters in time homogeneous models, and for other process characteristics such as mean sojourn times and equilibrium distributions are proposed.
Abstract: Methods for the analysis of panel data under a continuous-time Markov model are proposed. We present procedures for obtaining maximum likelihood estimates and associated asymptotic covariance matrices for transition intensity parameters in time homogeneous models, and for other process characteristics such as mean sojourn times and equilibrium distributions. Generalizations to handle covariance analysis and to the fitting of certain nonhomogeneous models are presented, and an example based on a longitudinal study of the smoking habits of school children is discussed. Questions of embeddability and estimation are examined.
654 citations
TL;DR: A series of experiments revealed systematic effects of orientation on the time required to identify line drawings of natural objects, and suggested that novel depictions of a known class of objects may be identified by a process of mental rotation.
Abstract: A series of experiments revealed systematic effects of orientation on the time required to identify line drawings of natural objects. Naming time increases as patterns are rotated further from the upright. With practice, however, the effect of orientation is reduced considerably. Furthermore, the reduced orientation effect with practice on a set of objects does not transfer to a new set of objects, suggesting that the acquired ability to reduce the orientation effect is specific to particular patterns. Finally, for departures in orientation from the upright between 0° and 120°, the magnitude of the orientation effect on identification for patterns seen for the first time is equivalent to that found in a mental rotation task using the same patterns (making left/right decisions about rotated patterns). This final result suggests that novel depictions of a known class of objects may be identified by a process of mental rotation.
493 citations
TL;DR: For example, this paper found that women more frequently admit being lonely than men admit being depressed, while men tend to have higher self-labeling scores than women, while women tend to be more accepting of a lonely male than a lonely female.
Abstract: Earlier studies on gender differences in loneliness appear to have produced contradictory results. However, when 39 existing data sets were classified according to whether they used the UCLA scale (N = 28) or a self-labeling measure (N = II) of loneliness, the results revealed a clear pattern. Statistically significant sex differences are not usually found with the UCLA scale, but, when they are found, males typically have higher loneliness scores. In terms of self-labeling, women more frequently than men admit being lonely. Sex role factors may help explain these seemingly contradictory results. Of the various possible explanations of the gender differences in self-labeled loneliness, most assume that social influence processes play a crucial role. To test this viewpoint, an experiment was conducted. Subjects (N = 117) were presented with a case history of a lonely person, which varied only the target person's sex. The subjects were more rejecting of a lonely male than of a lonely female. These results s...
356 citations
TL;DR: This paper presents various theoretical and computational methods for estimating the domain of attraction of an autonomous nonlinear system based on the concept of a maximal Lyapunov function, which is introduced in this paper.
317 citations
TL;DR: To synthesize an ensemble of attributed graphs into the distribution of a random graph (or a set of distributions), this work proposes a distance measure between random graphs based on the minimum change of entropy before and after their merging.
Abstract: The notion of a random graph is formally defined. It deals with both the probabilistic and the structural aspects of relational data. By interpreting an ensemble of attributed graphs as the outcomes of a random graph, we can use its lower order distribution to characterize the ensemble. To reflect the variability of a random graph, Shannon's entropy measure is used. To synthesize an ensemble of attributed graphs into the distribution of a random graph (or a set of distributions), we propose a distance measure between random graphs based on the minimum change of entropy before and after their merging. When the ensemble contains more than one class of pattern graphs, the synthesis process yields distributions corresponding to various classes. This process corresponds to unsupervised learning in pattern classification. Using the maximum likelihood rule and the probability computed for the pattern graph, based on its matching with the random graph distributions of different classes, we can classify the pattern graph to a class.
307 citations
TL;DR: The relationship between riparian land use and environmental parameters that define the suitability of southern Ontario streams for trout were examined for 40 sites on 38 streams as discussed by the authors, and weekly observations of maximum and minimum temperature, coarse and line suspended matter, and discharge were made during June, July, and August 1980.
Abstract: The relationships between riparian land use and environmental parameters that define the suitability of southern Ontario streams for trout were examined for 40 sites on 38 streams. Weekly observations of maximum and minimum temperature, coarse and line suspended matter, and discharge were made during June, July, and August 1980. Land use was determined from aerial photographs of each stream. Fish were surveyed at each site during August by electrolishing and seining. The only environmental variable which clearly distinguished between trout and nontrout streams was weekly maximum water temperature: streams with trimean weekly maxima less than 22 C had trout; warmer streams had, at best, only marginal trout populations. Trout streams tended to have low concentrations of fine suspended solids and a more stable discharge, but so did many of the other streams. Water temperature, concentration of fine particulate matter, and variability of discharge were inversely related to the fraction of the upstrea...
261 citations
TL;DR: In this paper, a finite sample optimal estimation of a discrete stochastic process is established for samples of finite size n, where n is the number of samples in the process.
Abstract: Generally, in the literature on stochastic processes, estimation is investigated in terms of asymptotic properties. In this paper we establish some finite sample optimal estimation. Let {Y1, Y2, ...} be a discrete stochastic process. Since we will be discussing results for samples of finite size n, we restrict the process to R'. In the following, the term 'parameter' is used in the same broad sense as by Godambe & Thompson (1984). Let Y be a class of probability distributions F on R' and 0 = 0(F), F E jZ be a real parameter. Let hi be a real function of y 1, yi and 0 be such that
TL;DR: Results show that a reasonably inexpensive approach in lifting task analysis is to measure the dynamic forces of the load on the hands and to use these in an otherwise static model, which results in a conservative assessment of the injury risk of lifts at least of the type reported in this study.
Proceedings Article•
18 Aug 1985TL;DR: A formal, model-theoretic characterisation of default reasoning is presented, which overcomes many of the problems which motivated non-normal defaults, and provides a semantics for correct inheritance in inheritance systems, where the authors want choose the result supported by the most specific knowledge.
Abstract: Default reasoning is reasoning with generalised knowledge which we want to use if there is no more specific knowledge also applicable. This paper presents a formal, model-theoretic characterisation of default reasoning. Defaults are treated as possible hypotheses in a "scientific" theory to explain the results. One of the problems with systems that reason with defaults occurs when two answers can be produced, and one is preferred. In terms of our default logic, we define a semantic characterisation of the notion of the more specific theory. This overcomes many of the problems which motivated non-normal defaults, and provides a semantics for correct inheritance in inheritance systems, where we want choose the result supported by the most specific knowledge. We also show how to produce a general computational mechanism in terms of normal first order predicate calculus deduction systems.
TL;DR: A deterministic model was developed and validated to calculate instantaneous ankle and knee moments during walking using processed EMG from representative muscles, instantaneous joint angle as a correlates of muscle length and angular velocity as a correlate of muscle velocity, and having available total instantaneous joint moments for derivation of certain model parameters.
25 Mar 1985
TL;DR: Using a multiloop version of the small gain theorem, robust trajectory tracking is shown under the assumption that the deviation of the model from the true system satisfies certain norm inequalities that lead to quantifiable bounds on the tracking error.
Abstract: The motion control of robotic manipulators is investigated using a recently developed approach to linear multivariable control known as the stable factorization approach. Given a nominal model of the manipulator dynamics, the control scheme consists of an approximate feedback linearizing control followed by a linear compensator design based on the stable factorization approach. Using a multiloop version of the small gain theorem, robust trajectory tracking is shown under the assumption that the deviation of the model from the true system satisfies certain norm inequalities. In turn, these norm inequalities lead to quantifiable bounds on the tracking error.
TL;DR: It is suggested that left-handers are a distinct subgroup of the population and skewed in the population as a whole, but the distributions can be adequately fitted by two normal curves.
TL;DR: The two major types of airlift contactors, concentric‐tube and external‐loop, were investigated for their gas holdup (riser and downcomer) and overall mass transfer characteristics.
Abstract: The two major types of airlift contactors, concentric-tube and external-loop, were investigated for their gas holdup (riser and downcomer) and overall mass transfer characteristics. Results obtained in batch charges of tap water and 0.15 kmol/m(3) NaCl solution are reported for external-loop airlift contactors having downcomer-to-riser cross-sectional area ratios, A(d)/A(r), ranging from 0.11
TL;DR: It is shown that every strongly stabilizable plant can be reliably stabilized; moreover, one of the two controllers can be specified arbitrarily, subject only to the constraint that it should be stable.
TL;DR: In this paper, the design of voltage- or current-controllable linear transconductance elements needed for the continuous-time CMOS active filters is explored in detail, and circuit configurations, techniques of achieving linearity, and temperature compensation using the controlling variable are outlined.
Abstract: This paper explores in detail the possible approaches to. the design of voltage- or current-controllable linear transconductance elements needed for the design of continuous-time CMOS active filters. The focus of the paper is on circuit configurations, techniques of achieving linearity, and temperature compensation using the controlling variable. Circuit techniques for obtaining small transductance values are outlined. Simulation results are presented.
TL;DR: A formula for the means response time of a given cycle and a lower bound for the mean response time for any cycle are derived and a design procedure is presented that yields a cycle withmean response time close to the theoretical lower bound.
TL;DR: The sociological implications of sport as a male preserve have been examined in this paper, where sport is defined as a gendered cultural form that has been dominated by men and masculinity.
Abstract: This paper examines the sociological implications of sport as a male preserve. Sport is a gendered cultural form that has been dominated by men and masculinity. The effects of this domination upon broader patterns of social relations have been misrepresented in much of the literature on sport and gender, where sport is often conceptualized as a static fact, rather than as a dynamic social practice. Analysis of sport as social practice directs attention to the manner in which sport gives meaning to broader patterns of social relations. In the case of gender relations, sport as a male preserve has contributed to the oppression of women through the objectification and dornination of their physicality and sexuality. A feminist alternative to sport as a male preserve challenges gender inequality by challenging sexual stereotypes and patriarchal control of women's bodies.
TL;DR: The timing of EMG activity was closely related to the normalized stride time and remained invariant at different cadence, and the shape of the EMG patterns generally remained similar at the different cadences.
TL;DR: It is shown that even for these simple models, lot splitting may occur and that these batching decisions may have a dramatic impact on the manufacturing lead time of items to be processed.
TL;DR: In this paper, two task characteristics task size, and similarity of loan profiles describing alternatives were varied in a bank loan decision context, and the effect that changes in task characteristics had on loan officers' decision strategies.
Abstract: Research on decision-making behavior has shown that decision strategies used by individuals are contingent upon the characteristics of the task. For example, as the task size i.e., the number of alternatives and/or the number of dimensions describing each alternative increases, individuals tend to quickly eliminate alternatives that do not meet a criterion level for any dimension i.e., they adopt a noncompensatory decision strategy, in which a high value on one dimension cannot offset or compensate for a low value on another dimension. Most of this research has involved consumers making buying decisions. The purpose of the research reported here was to determine if contingent decision behavior extends to experts experienced bank loan officers making business decisions loan decisions. In this study two task characteristics task size, and similarity of loan profiles describing alternatives were varied in a bank loan decision context. Two process tracing methods information boards and think-aloud verbal protocol analysis were used to obtain evidence of how eleven bank loan officers made choices among alternative loan candidates. Of particular interest was the effect that changes in task characteristics had on loan officers' decision strategies. The results indicated that when faced with tasks of increasing size, loan officers adapted their behavior in a manner consistent with an increased use of noncompensatory decision strategies. In contrast, when the loan profiles of candidate companies were similar loan officers exhibited an increased use of compensatory strategies. It was also found that when both the task size and similarity of alternatives were varied loan officers adapted their behavior as if they processed these characteristics serially. These results indicate that contingent behavior associated with the two types of task characteristics may be quite different. A priori, there was reason to believe that expert loan officers would not exhibit contingent decision behavior. The fact that their decision strategies were contingent upon task characteristics has important implications for managerial practice and research. First, the results have design implications for information and decision support systems for lending institutions. Second, future research should investigate the consequences of serial processing of task characteristics.
TL;DR: Goyder et al. as discussed by the authors developed a correlational design for assessing the typical response difference between these two forms of data collection, after controlling for other factors known to affect survey response.
Abstract: Traditionally, as reflected in methodology textbook reviews of the survey nonresponse literature, interviews have been thought to achieve substantially higher response rates than mailed questionnaires. The paper describes a correlational design for assessing the typical response difference between these two forms of data collection, after controls for other factors known to affect survey response. Attention is given to change over time in the response difference between interviews and questionnaires. In the primary data set, the net response due to data collection amounts to some 7.5 percentage points, in the middle (30-70) range of survey response. The analysis quantifies the decline over time in interview response, and shows mailed questionnaires to be free from decline. A second data set reproduces the essential findings. John Goyder is Associate Professor, Department of Sociology, University of Waterloo, Ontario, Canada N2L 3G1. The work reported herein was supported by a Canada Council Leave Fellowship held by the author during a stay at Cambridge University in 1978, and by a UW-SSHRC grant awarded in 1981. The author is greatly indebted to Cathie Marsh and others at the Social and Political Sciences Committee, Cambridge, for hospitality and research resources. Research Assistants were Norleen Heyzer and Kerry Davies at Cambridge and Jean Leiper and Olorunfe Taylor-Cole at Waterloo. Public Opinion Quarterly Vol. 49:234-252 ?) by the Trustees of Columbia University Published by Elsevier Science Publishing Co., Inc 0033-362X/85/0049-234/$2.50 This content downloaded from 157.55.39.181 on Thu, 29 Sep 2016 05:51:04 UTC All use subject to http://about.jstor.org/terms INTERVIEWS AND MAILED QUESTIONNAIRES 235 (1981:150), the 50 percent ceiling holds true even allowing for follow-ups. Others, however, set the upper limit markedly higher. Fitzgerald and Cox (1975:53), for example, choose 60 percent, while, for True (1983: 218), "estimates of likely return rates range to 70 percent," a maximum also reported in Goode and Hatt (1952:173) and Cole (1980:62). Sanders and Pinhey (1983:152-53) cite 60 percent as an average and note that "some researchers have reported returns of 80 percent and more." Consistent 70 percent returns from general populations are not unrealistic, argue Weisberg and Bowen (1977:58), given energetic follow-ups (also Miller, 1977:79-81). Estimated typical completion rate on interview surveys is 70-80 percent for Kidder (1981:150), 80-85 percent for Babbie (1973:171), 80-90 percent for Orenstein and Phillips (1978:229), over 90 percent according to Parten (1950:351), "about 95 percent" for Nachmias and Nachmias (1976:107), and "as much as 85 percent" for Sanders and Pinhey (1983: 154). Weisberg and Bowen (1977:36), introducing a factor to be emphasized herein, quote 90 percent interview response as "typical" during the 1950s, with rates "in the 80 percent range" common today. The greater response due to data collection by interview rather than by questionnaire could, from the above estimates, amount to anywhere from zero to some 60 percentage points. In noting the variability of the textbook estimates, we do not deny that the accumulated wisdom on survey methodology presents a broad consensus that interview response is generally greater than mailed questionnaire returns, nor that each of the typical response figures cited by different authors accurately reflects at least some aspect of reality. The review of textbooks is effective, however, in emphasizing the variability in survey response according to both form of data collection and other factors. A "typical" survey response rate exists only insofar as there is a typical salience level of topic, sponsor, target population, and set of field procedures. In the unsystematic comparisons of questionnaire and interview response presented in methodology textbooks, these various factors have varied haphazardly. The argument in this paper is that the survey methodology literature is now in a position to establish a net effect for form of data collection, controlling for other determinants of survey response by means of multivariate analysis. We develop this methodology herein, and establish the net margin between interviews and questionnaires, both as averaged over the history of survey research and as mediated over time.
TL;DR: The results suggest that being alone is not a wholley negative experience for this age group, especially for those who have the regular companionship of a spouse.
Abstract: This research investigates the quantity and quality of time alone or "solitude" in the daily lives of older adults. A sample of 92 retired adults carried electronic pagers for 1 week and filled out self-reports on their companionship and internal states in response to signals received at random times. Analysis of the 3,412 reports indicates that those who were unmarried and living alone spent a majority of their waking hours alone and experienced low affect and arousal when in this dominant part of their lives. For the married, solitude was also a major part of daily life, filling 40% of their time, but, although it was related with somewhat lower affect, it was also related with higher arousal. These results suggest that being alone is not a wholley negative experience for this age group, especially for those who have the regular companionship of a spouse.
TL;DR: In this paper, mean monthly flows from thirty rivers in North and South America are used to test the short-term forecasting ability of seasonal ARIMA, deseasonalized ARMA, and periodic autoregressive models.
TL;DR: In this paper, the authors compared the consistency of the consistent and the lumped Galerkin finite element schemes and found that the consistency can be maintained throughout the simulation period while allowing the time step length to grow.
TL;DR: Different sets of conditions allow this examination to take place when null-space, range-space or Lagrangian methods are used to find stationary points for the quadratic program.
Abstract: We present practical conditions under which the existence and uniqueness of a finite solution to a given equality quadratic program may be examined. Different sets of conditions allow this examination to take place when null-space, range-space or Lagrangian methods are used to find stationary points for the quadratic program.
TL;DR: The findings of this study imply that embryo survival models based on substrate size composition may not be entirely suitable for assessing the quality of spawning beds in groundwater-fed streams.
Abstract: Several measures of the size composition of spawning substrates were used to describe the survival of preemergent embryos of rainbow trout Salmo gairdneri in a groundwater-fed streambed. Survival was not significantly related (P > 0.05) to the percentage of sediments smaller than 2.0 mm in diameter, the geometric-mean particle size, or fredle indices of substrate quality. However, survival strongly depended on the mean dissolved oxygen content and velocity of groundwater in redds. Dissolved oxygen concentrations were not related (P > 0.05) to measures of substrate size composition, and these variables accounted for only a limited proportion of the variance among redds in seepage velocities. These factors account for the lack of any significant association between survival and substrate size composition. The findings of this study imply that embryo survival models based on substrate size composition may not be entirely suitable for assessing the quality of spawning beds in groundwater-fed streams.