Showing papers by "University of Waterloo published in 1981"

Direct Experience And Attitude-Behavior Consistency

Abstract: Publisher Summary The chapter discusses the role of the manner of attitude formation. It focuses on the development of an attitude through direct behavioral experience with the attitude object and examines whether such attitudes better predict subsequent behavior than attitudes formed without behavioral experience. The chapter provides an overview of the attitude-behavior consistency problem and describes the effect of the manner of attitude formation through the “housing” study, the “puzzle” experiment, and the “subject pool” study. The prior-to-later behavior relation is also discussed in the chapter, wherein it has described the self-perception of past religious behaviors, attitudes and self-reports of subsequent behavior, an individual difference perspective, and a partial correlation analysis. The chapter discusses attitudinal qualities—namely, confidence and clarity, the persistence of the attitude, and resistance to attack. The reasons for the differential strength are also explored in the chapter—namely, the amount of information available, information processing, and attitude accessibility. The chapter briefly describes the attitude-behavior relationship, personality traits, and behavior.

Recursive Evaluation of a Family of Compound Distributions

Abstract: Compound dlstributmns such as the compound Pmsson and the compound negative binomial are used extensively m the theory of risk to model the distributmn off the total claims incurred m a fixed period of time The usual method of evaluating the dlqtributmn functmn requires the computatmn of many convolutions of the conditional d~atnbutmn of the amount of a claim given that a clmm has occurred When the expected number of claims is large, the computatmn can become unwmldy even with modern large scale electronic computers In tlus paper, a recurs|xe definitmn of the distribution of total clmms is developed for a family of claml numbel distnbutmns and arbitrary claim amount distributions When the clam1 amount is discrete, the recursive dehnitmn can be used to compute the distribution of total claims without the use of convolutions. This can reduce the number of required computations by several orders of magnitude for sufhcmntlv large portfolios Results for some spemfic dlatnbutmna have been prevmusly obtained using generating functions and Laplace transforms (see PANJER (1980) including dlscussmn). The simple algebraic proof of this paper yields all the previous results as special case~

Carbon isotope fractionation during microbial methane oxidation

Abstract: Methane, a common trace constituent of groundwaters, occasionally makes up more than 20% of the total carbon in groundwaters1,2. In aerobic environments CH4–rich waters can enable microbial food chain supporting a mixed culture of bacteria with methane oxidation as the primary energy source to develop3. Such processes may influence the isotopic composition of the residual methane and because 13C/12C analyses have been used to characterize the genesis of methanes found in different environments, an understanding of the magnitude of such effects is necessary. In addition, carbon dioxide produced by the methane-utilizing bacteria can be added to the inorganic carbon pool of affected groundwaters. We found carbon dioxide experimentally produced by methane-utilizing bacteria to be enriched in 12C by 5.0–29.6‰, relative to the residual methane. Where methane-bearing groundwaters discharged into aerobic environments microbial methane oxidation occurred, with the residual methane becoming progressively enriched in 13C. Various models have been proposed to explain the 13C/12C and 14C content of the dissolved inorganic carbon (DIC) of groundwaters in terms of additions or losses during flow in the subsurface4,5. The knowledge of both stable carbon isotope ratios in various pools and the magnitude of carbon isotope fractionation during various processes allows geochemists to use the 13C/12C ratio of the DIC along with water chemistry to estimate corrected 14C groundwater ages4,5. We show here that a knowledge of the carbon isotope fractionation between CH4 and CO2 during microbial methane-utilization could modify such models for application to groundwaters affected by microbial methane oxidation.

A modified strongly implicit procedure for the numerical solution of field problems

Abstract: A modified strongly implicit procedure for solving the system of algebraic equations that arise in the finite-difference or finite-analytic description of field problems is presented. The method is derived for a nine-point difference scheme and can readily be applied to the more conventional five-point scheme simply through the use of the five-point scheme coefficients. The method is demonstrated by application to several examples and a comparison is made between the performance of the modified procedure and that of the strongly implicit procedure, the alternating direction implicit method, and successive over-relaxation. In all cases examined the modified strongly implicit procedure offers superior results when the number of iterations required for convergence or the computational cost required for convergence is used as the measure of performance. The method is also less sensitive to control volume aspect ratio, relaxation parameters, and mesh subdivision than other available procedures. Savings in comp...

Expected Length of the Longest Probe Sequence in Hash Code Searching

Abstract: An investigation ts made of the expected value of the maximum number of accesses needed to locate any element m a hashing file under various colhston resoluuon schemes This differs from usual worst-case considerations winch, for hashmg, would be the largest sequence of accesses for the worst possible file Asymptotic expressxons of these expected values are found for full and partly full tables For the open addressing scheme with a clustering-free model these values are found to be 0.6315... x n for a full table and = -logan for a partly full table, where n ts the number of records, m is the size of the table, and a = n/m. For the open addressing scheme which reorders the insertions to minimize the worst case, the lower bounds In n + 1 077... and (-a-~in(l - a)) are found for full and partly full tables, respectively FmaUy, for the separate chaining (or direct chaining) method both expected values are found to be ~.F-t(n). These results show that for these schemes, the actual behawor of the worst case in hash tables is quite good on the average.

A Nonuniform Sampling Approach to Data Compression

Abstract: A nonuniform sampling approach to digital encoding of analog sources is proposed. The nonuniform sampler is basically a level crossing detector (LCD) which produces a sample whenever the input to the LCD crosses a threshold level. The information about the source signal is contained in the time intervals between level crossings and in the directions of level crossings. By assigning strings of the 2-tuple "00" to represent the time between level crossings and "01" and "10" to denote the directions of level crossings, the output binary sequence of the nonuniform sampling encoder (NSE) contains a high probability of the 0 symbol, which makes it suitable for further simple run-length encoding (RLE) to attain a "good" overall compression ratio. Introduction of prediction converts the NSE to a nonuniform sampling predictive coding (NSPC) scheme, which, depending on the source, can potentially improve the compression ratio. Results obtained in the encoding of a band-limied Gaussian source and a rasterscanned black and white still image reveal that an NSE/RLE or NSPC/ RLE system exhibits performance superior to that of an adaptive delta modulation system.

The splittance of a graph

Abstract: The splittance of an arbitrary graph is the minimum number of edges to be added or removed in order to produce a split graph (i.e. a graph whose vertex set can be partitioned into a clique and an independent set). The splittance is seen to depend only on the degree sequence of the graph, and an explicit formula for it is derived. This result allows to give a simple characterization of the degree sequences of split graphs. Worst cases for the splittance are determined for some classes of graphs (the class of all graphs, of all trees and of all planar graphs).

Errors in the use of isokinetic dynamometers.

Abstract: The use of constant velocity dynamometers in functional testing and in exercise and therapy programs has been increasing in the past few years. For movements in the horizontal plane there are no gravitational errors. However, in vertical movements the limbs are not only working against the dynamometer but also are either aided or opposed by gravity. Far too often these gravitational forces have not been taken into account, and the error involved can be quite large. 1. A study on four subjects using knee extension (against gravity) and flexion (with gravity) showed the error in mechanical work to vary from 26–43% in extension and from 55–510% in flexion. 2. A relatively simple solution is offered to overcome the problem by compensating for the gravitational errors over the full range of movement. The time course of the error is such as to cause erroneous magnitudes of recorded moments which are a maximum at low level contractions and minimum at high level contractions. 3. The effect of gravitational and other acceleration errors are such as to cause false early peaks in the muscle moment curves resulting in erroneous conclusions about muscle function.

The Exchange Process in Close Relationships

Abstract: Following years of apparent neglect, the study of close relationships is emerging as an important focus for social psychologists. Until a decade ago, research on the topic was typically confined to identifying predictors of marital harmony or discord (cf. Barry, 1970). The demographic characteristics of couples, such as education, status, and family background, were examined in order to portray relationships that were “at risk.” The large majority of studies used either self-ratings of satisfaction or divorce rates as reflections of troubled relationships. With the noteworthy exception of Levinger’s contribution (see Levinger & Snoek, 1972), the research was marked by a lack of concern with considerations of both process and theory. Recent contributions have demonstrated an interest in the theoretical development of models of intimate exchange and “pair cohesiveness” (e.g., Kelley, 1979; Moles & Levinger, 1976), though evidence of an emphasis on the process of conflict and estrangement is meagre (e.g., Hill, Rubin, & Peplau, 1976; Kelley, 1979; Passer, Kelley, & Michela, 1978).

Impression Management in the Job Interview When the Female Applicant Meets the Male (Chauvinist) Interviewer

Abstract: This study was conducted to determine the ways in which knowledge of a male interviewer's stereotyped beliefs about women would influence the behavior of female job applicants. In a two-cell design, female applicants were interviewed by a male confederate whose stereotype of the ideal female applicant conformed closely either to the traditional female stereotype or its opposite. The results indicated that applicants did present themselves in a more traditionally `feminine" manner when they knew the interviewer held traditional views of women. Interestingly, this pattern of results held not only for verbal and nonverbal measures but also for measures of physical appearance.

Message passing between sequential processes: The reply primitive and the administrator concept

Abstract: Message passing as a method of synchronizing and communicating among sequential processes is not as widely understood as monitors, and there is greater diversity in the semantics of what is meant by message passing. This paper surveys some of the issues on which there are differences and gives the rationale behind certain choices and some examples of experience with them. Paradigms are presented for process structuring found to be commonly useful.

Thermal Contact Correlations

Abstract: The theoretical relationships for determining contact, gap, and joint conductances are developed for conforming rough surfaces for first loading. The dimensionless conductances are functions of the relative contact pressure, surface parameters, conductivity ratio, and a fluid parameter which depends upon several gas and surface characteristics. The proposed conductance correlations are supported quantitatively

A Bayesian Study of the Error-in-Variables Model

Abstract: This article presents the results of a study of the functional case of the problem of parameter estimation when there is error in all the variables. There is consequently no distinction between independent and dependent variables. Posterior probability density functions are developed for the parameters with both linear and nonlinear, and possibly multiple, relations among the true values of the variables. There is no distinction between models that are linear or nonlinear in the parameters. The results are equivalent to generalizations of the work of some previous authors, but lead to new and efficient algorithms for finding point estimates and their precisions. For most of the results the error covariance matrix is assumed known, though a case is treated where it is known except for a scalar multiplier. The results are also shown to be valid if the covariance matrix is singular. Geometric interpretations are described.

Design of biochemical reactors mass transfer criteria for simple and complex systems

Abstract: Biochemical reactors are treated as heterogeneous catalytic reactors in which physical mass transfer completely or significantly controls the overall rate of the process being promoted in the reactor. The treatment used to develop basic design strategies takes into account the special constraints imposed by biological and biochemical phenomena on the systems.

Kd's — Can They Be Used to Describe Reversible Ion Sorption Reactions in Contaminant Migration?

Abstract: In considering reversible sorption processes in ground-water flow systems, it is important to determine whether the ground water is in steady-state or dynamic chemical evolution. In steady-state chemical evolution, the sorbed site populations at any point along the flow path are in equilibrium with the way in which ground water will evolve chemically due to mineral dissolution/precipitation, redox reactions, etc., during flow when it reaches this point. In dynamic chemical evolution it is not. In the steady-state case, a location in the flow system can be characterized by a constant distribution coefficient over time for an ionic species involved in reversible sorption reactions. In the dynamic case, the distribution coefficient can be expected to vary at a location in a flow system over time. Subsurface contaminant migration problems which confront hydrogeologists invariably are of the dynamic chemical evolution type and the notion of a constant distribution coefficient or Kd to describe reversible sorption processes cannot be entertained.

Optimization of Flow Passage Geometry for Air-Heating, Plate-Type Solar Collectors

Abstract: The effect of the choice of shape and dimensions of the air flow passages in plate-type, air-heating solar collectors is assessed. Particular examination is made of their effect on the overall heat transfer coefficient between the air stream and the plate, which has an important effect on collector efficiency. It is emphasized in this study that in comparing various designs of flow passage, they should be compared for the same pressure drop suffered by the air in passing through the collector, and for the same mass flow rate m per unit of collector area. 11 refs.

An Orthogonal Row Processing Algorithm for Power System Sequential State Estimation

Abstract: In this paper a sequential algorithm for power system state estimation based on the use of Givens rotations is investigated. The fact that the rotations are orthogonal transformations assures the numerical stability of the algorithm. The Jacobian matrix is processed one row at a time, and sparsity can be easily exploited. Also, the method presents some features which are advantageous from the point of view of bad data detection, identification and elimination. Both the description and the implementation of a fast version of the Givens rotations are presented. The method is applied to three different power systems, including real size networks, and the results are used to assess its performance.

A Robust Numerical Technique for Power System State Estimation

Abstract: It is well known in numerical analysis that the least-squares solution via the conventional Gauss' normal equation used in power system state estimation is prone to ill-conditioning problems by its own nature. Under unfavorable circumstances, this may be detrimental to the method's performance. This paper utilizes a numerically more reliable algorithm, known as Golub's method, to solve the least-squares problem as formulated in power system state estimation. Its improved numerical properties stem from the use of orthogonal transformations, which are perfectly conditioned. Details of the algorithm and its implementation are given, as well as results of its application to three different networks, including an actual 121-bus power system.

Grain refinement in magnetically stirred GTA welds of aluminum alloys

Abstract: The mechanisms of grain refinement have been examined for magnetically stirred gas tungsten arc (GTA) welds completely penetrating thin sheets of several aluminum alloys. Grain refinement in unstirred welds may be brought about by adding sufficient titanium to produce heterogeneous nucleation by Ti-rich particles. In some alloys magnetic stirring is shown to extend the range of welding conditions which produce a partially equiaxed structure, and to widen the equiaxed fraction of partially equiaxed welds. This is attributed to magnetic stirring lowering the temperature gradient, allowing nucleation and growth of Al-rich grains further ahead of the columnar interface growing in from the fusion boundaries. In alloys with low Ti levels, magnetic stirring may cause refinement by sweeping grains from the partially molten zone ahead of the advancing solidification interface. This mechanism requires that the partially molten zone be sufficiently wide, and that the grain size in this zone remain small.

Disruption of Candida utilis cells in high pressure flow devices

Abstract: The disruption of Candida utilis cells in suspensions subjected to different types of stress was investigated. Stresses caused by impingement of a high velocity jet of suspended cells against a stationary surface were found to be significantly more effective for disruption than either shear or normal stresses. The fraction of cells disrupted by impingement is a first order function of the number of passes through the disruptor and, over a prescribed range of operating pressures, is a power function of pressure. These results indicate that impingement is the predominant mechanism causing cells disruption in high pressure flow devices such as Manton–Gaulin homogenizers. The impingement results suggest that cells grown in cyclic batch culture are easier to disrupt than cells grown at a lower specific growth rate in continuous culture. In addition to determining the fraction of cells disrupted, the release of invertase activity was determined for the impingement experiments. The fraction of total invertase activity released was found to be somewhat greater than the fraction of cells disrupted.