Showing papers by "Concordia University published in 1997"

Corrective feedback and learner uptake

Abstract: This article presents a study of corrective feedback and learner uptake (i.e., responses to feedback) in four immersion classrooms at the primary level. Transcripts totaling 18.3 hours of classroom interaction taken from 14 subject-matter lessons and 13 French language arts lessons were analyzed using a model developed for the study and comprising the various moves in an error treatment sequence. Results include the frequency and distribution of the six different feedback types used by the four teachers, in addition to the frequency and distribution of different types of learner uptake following each feedback type. The findings indicate an overwhelming tendency for teachers to use recasts in spite of the latter's ineffectiveness at eliciting student-generated repair. Four other feedback types—elicitation, metalinguistic feedback, clarification requests, and repetition—lead to student-generated repair more successfully and are thus able to initiate what the authors characterize as the negotiation of form.

Current issues in recrystallization: a review

Abstract: The current understanding of the fundamentals of recrystallization is summarized. This includes understanding the as-deformed state. Several aspects of recrystallization are described: nucleation and growth, the development of misorientation during deformation, continuous, dynamic, and geometric dynamic recrystallization, particle effects, and texture. This article is authored by the leading experts in these areas. The subjects are discussed individually and recommendations for further study are listed in the final section.

Allometry for Sexual Size Dimorphism: Pattern and Process in the Coevolution of Body Size in Males and Females

Abstract: Sexual size dimorphism (SSD) is common in both plants and animals, and current evidence suggests that it reflects the adaptation of males and females to their different reproductive roles. When species are compared within a clade, SSD is frequently found to vary with body size. This allometry is detected as β ≠ 1, where β is the slope of a model II regression of log(male size) on log(female size). Most frequently, β exceeds 1, indicating that SSD increases with size where males are the larger sex, but decreases with size where females are larger, a trend formalized as “Rensch's rule.” Exceptions are uncommon and associated with female-biased SSD. These trends are derived from a sample of 40 independent clades of terrestrial animals, primarily vertebrates. Their extension to plants and aquatic animals awaits quantitative assessments of allometry for SSD within these groups. Many functional hypotheses have been proposed to explain the evolution of allometry for SSD, most featuring sexual selection on males ...

Application of majority voting to pattern recognition: an analysis of its behavior and performance

Abstract: It has been demonstrated that combining the decisions of several classifiers can lead to better recognition results. The combination can be implemented using a variety of strategies, among which majority vote is by far the simplest, and yet it has been found to be just as effective as more complicated schemes in improving the recognition results. This paper examines the mode of operation of the majority vote method in order to gain a deeper understanding of how and why it works, so that a more solid basis can be provided for its future applications to different data and/or domains. In the course of our research, we have analyzed this method from its foundations and obtained many new and original results regarding its behavior. Particular attention has been directed toward the changes in the correct and error rates when classifiers are added, and conditions are derived under which their addition/elimination would be valid for the specific objectives of the application. At the same time, our theoretical findings are compared against experimental results, and these results do reflect the trends predicted by the theoretical considerations.

ProbView: a flexible probabilistic database system

Abstract: Probability theory is mathematically the best understood paradigm for modeling and manipulating uncertain information. Probabilities of complex events can be computed from those of basic events on which they depend, using any of a number of strategies. Which strategy is appropriate depends very much on the known interdependencies among the events involved. Previous work on probabilistic databases has assumed a fixed and restrictivecombination strategy (e.g., assuming all events are pairwise independent). In this article, we characterize, using postulates, whole classes of strategies for conjunction, disjunction, and negation, meaningful from the viewpoint of probability theory. (1) We propose a probabilistic relational data model and a genericprobabilistic relational algebra that neatly captures various strategiessatisfying the postulates, within a single unified framework. (2) We show that as long as the chosen strategies can be computed in polynomial time, queries in the positive fragment of the probabilistic relational algebra have essentially the same data complexity as classical relational algebra. (3) We establish various containments and equivalences between algebraic expressions, similar in spirit to those in classical algebra. (4) We develop algorithms for maintaining materialized probabilistic views. (5) Based on these ideas, we have developed a prototype probabilistic database system called ProbView on top of Dbase V.0. We validate our complexity results with experiments and show that rewriting certain types of queries to other equivalent forms often yields substantial savings.

A comparative analysis of allometry for sexual size dimorphism: assessing rensch's rule

Abstract: Rensch's rule states that sexual size dimorphism (SSD) increases with body size (hyperallometry) in taxa in which males are the larger sex and decreases with body size (hypoallometry) in those in which females are larger. We use the independent contrasts method to assess the validity and generality of Rensch's rule within 21 independent animal taxa. Allometry is estimated as the slope of the major axis regression of contrasts for log(female size) versus contrasts for log(male size). Allometry consistent with Rensch's rule is significant in 33% of the taxa examined across a diverse range of invertebrate and vertebrate taxa. Significant allometry inconsistent with Rensch's rule occurs in only one taxon. Meta-analysis of these results reveals that Rensch's rule is general and highly significant. Only owls have allometry inconsistent with this trend. Rensch's rule is also shown to be associated with male-biased SSD, which is consistent with the hypothesis that sexual selection acting on male size drives the e...

A Foundation for Multi-dimensional Databases

Abstract: We present a multi-dimensional database model, which we believe can serve as a conceptual model for On-Line Analytical Processing (OLAP)-based applications. Apart from providing the functionalities necessary for OLAP-based applications, the main feature of the model we propose is a clear separation between structural aspects and the contents. This separation of concerns allows us to define data manipulation languages in a reasonably simple, transparent way. In particular, we show that the data cube operator can be expressed easily. Concretely, we define an algebra and a calculus and show them to be equivalent. We conclude by comparing our approach to related work. The conceptual multi-dimensional database model developed here is orthogonal to its implementation, which is not a subject of the present paper.

Corticotropin-Releasing Factor, But Not Corticosterone, Is Involved in Stress-Induced Relapse to Heroin-Seeking in Rats

Abstract: We showed previously that brief footshock stress and priming injections of heroin reinstate heroin-seeking after prolonged drug-free periods. Here, we examined whether the adrenal hormone, corticosterone, and brain corticotropin-releasing factor (CRF) were involved in such reinstatement. We tested the effects of adrenalectomy, chronic exposure to the corticosterone synthesis inhibitor metyrapone (100 mg/kg, s.c., twice daily), acute exposure to metyrapone, acute intracerebroventricular injections of CRF (0.3 and 1.0 microgram), and intracerebroventricular injections of the CRF antagonist alpha-helical CRF (3 and 10 micrograms). Rats were trained to self-administer heroin (100 micrograms/kg/infusion, i.v.) for 12-14 d. Extinction sessions were given for 4-8 d (saline substituted for heroin). Tests for reinstatement were given after priming injections of saline and of heroin (0.25 mg/kg, s.c.), and after intermittent footshock (15 or 30 min, 0.5 mA). Adrenalectomy (performed after training) did not affect reinstatement by heroin but appeared to potentiate the reinstatement by footshock. Chronic exposure to metyrapone (from the beginning of extinction) or an acute injection of metyrapone (3 hr before testing) did not alter the reinstatement of heroin-seeking induced by footshock or heroin. Acute exposure to metyrapone alone potently reinstated heroin-seeking. In addition, acute exposure to CRF reinstated heroin-seeking, and the CRF antagonist alpha-helical CRF attenuated stress-induced relapse. The effect of the CRF antagonist on reinstatement by heroin was less consistent. These results suggest that CRF, a major brain peptide involved in stress, contributes to relapse to heroin-seeking induced by stressors.

Socio‐technical systems theory: an intervention strategy for organizational development

Abstract: Integrating organizational development (OD) and technological intervention into a total system is one of the more difficult tasks for an executive or consultant to execute. Organizations are profoundly affected by technological advancements and require a flexible customized change model to fit the social network of the specific organization into which technology is being introduced. Examines sociotechnical systems (STS) theory and presents classical organization theories of Burns and Stalker, Woodward, Perrow, Thompson and Trist to develop a contemporary OD intervention in terms of self‐regulating work groups (self‐leading or self‐managing teams) performing interrelated technological tasks. Finally, presents some pointers for executives and consultants in assessing STS interventions via 31 diagnostic questions intended to identify interactions among elements of the system.

The Consensus Glossary of Temporal Database Concepts - February 1998 Version.

Abstract: This document1 contains definitions of a wide range of concepts specific to and widely used within temporal databases. In addition to providing definitions, the document also includes explanations of concepts as well as discussions of the adopted names.

A bi-directional DC-DC converter topology for low power application

Abstract: This paper presents a bidirectional DC-DC converter for use in low power applications. The proposed topology is based on a half-bridge on the primary and a current-fed push-pull on the secondary side of a high frequency isolation transformer. Achieving bidirectional flow of power using the same power components provides a simple, efficient and galvanically isolated topology that is specially attractive for use in battery charge/discharge circuits in DC UPS. The DC mains (provided by the AC mains), when presented, powers the down stream load converters and the bidirectional converter which essentially operates in the buck mode to charge the battery to a nominal value of 48 V. On failure of the DC mains (derived from the AC mains), the converter operation is comparable to that of a boost and the battery regulates the bus voltage and thereby provides power to the downstream converters. Small signal and steady state analyses are presented for this specific application. The design of a laboratory prototype is included. Experimental results from the prototype, under different operating conditions, validate and evaluate the proposed topology. An efficiency of 86.6% is achieved in the battery charging mode and 90% when the battery provides load power. The converter exhibits good transient response under load variations and switchover from one mode of operation to another.

Disruptiveness, Friends' Characteristics, and Delinquency in Early Adolescence: A Test of Two Competing Models of Development

Abstract: This study tested 2 competing models of friends' influence on the development of delinquency in disruptive boys. In so doing, we examined whether highly disruptive, moderately disruptive, moderately conforming, and highly conforming boys' delinquency increased or decreased depending on their friends' characteristics. A sample of 868 boys was classified into the 4 groups according to teacher ratings at ages 11 and 12. Each group was then subdivided by mutual friends' peer-rated aggressiveness-disturbance at the same ages: aggressive-disturbing friends, average friends, nonaggressive-nondisturbing friends, and no friends. Subgroups were next compared on self-reported delinquency at age 13 while controlling for average self-reported delinquency and socioeconomic variables at ages 11 and 12. Results indicate that moderately disruptive boys with aggressive-disturbing friends were more delinquent at age 13 than other subgroups of moderately disruptive boys. Highly disruptive and conforming boys, however, were unaffected by their friends' characteristics. We conclude that the results partially support each theoretical model, suggesting that both individual characteristics and deviant peer association might play causal roles.

Socialization Tactics and Newcomer Information Acquisition

Abstract: Research on organizational socialization has usually focused on what organizations do to socialize newcomers or on what newcomers do to socialize themselves. The purpose of this study was to integrate these two perspectives of socialization by investigating the relationships between socialization tactics, newcomers' information acquisition (i.e. feedback and observation) and socialization outcomes. Consistent with previous research, socialization tactics and information acquisition were related to socialization outcomes. Furthermore, institutionalized socialization was positively related to the frequency of newcomers' feedback and observation and the frequency of newcomers' feedback and observation was found to mediate several of the relationships between socialization tactics and outcomes. These results suggest that what newcomers can do to socialize themselves (e.g. acquire information through feedback and observation) is partly a function of what organizations do to socialize newcomers (e.g. the use of specific socialization tactics). The implications of these findings are discussed for the development of a more complete and integrated theory of organizational socialization.

Photophysics of Cyanine Dyes: Subnanosecond Relaxation Dynamics in Monomers, Dimers, and H- and J-Aggregates in Solution

Abstract: The photophysics of three cyanine dyes (i) 1,1‘-diethyl-2,2‘-cyanine iodide (pseudoisocyanine, PIC), (ii) 3,3‘-didodecyldithia-2,2‘-carbocyanine bromide (dye 1), and (iii) 3,3‘-diethyldithia-2,2‘-carbocyanine iodide (dye 2) have been examined by picosecond-laser photolysis in aqueous and methanolic-aqueous media. At moderately high concentration, solutions of PIC in 5 M NaCl/water contain monomers, H-aggregates, and J-aggregates; dye 1 water/methanol solutions consist mostly of monomers and H-aggregates (dimers and higher n-mers); aqueous dye 2 solutions contain only monomers and dimers. Photolysis of H- and/or J-aggregates in PIC and dye 1 cyanine solutions leads to photobleaching of the respective aggregate absorption bands and subsequently decays by biphasic kinetics. Two mechanisms are discussed for the deactivation of excited aggregates. In the first, nonradiative decay of the excited singlet states results in considerable heating of the aggregates together with their surrounding solvent shells causi...

Current-source converter on-line pattern generator switching frequency minimization

Abstract: On-line pulsewidth modulation (PWM) pattern generators for current-source rectifiers and inverters offer a number of control advantages over off-line optimized patterns. However, when implemented using the principles which apply to voltage-source inverter PWM pattern generators, the switching frequency is equal to: (1) the carrier frequency in standard carrier-based implementations and (2) a function of the cycle frequency, sequence of space vectors, and selection of the zero space vector in space vector implementations. This paper shows that this frequency can be reduced to one-half of the respective frequencies. Two pattern generators are investigated: (1) an analog on-line carrier-based technique, namely, the modified dead-band technique and (2) a digital on-line space vector-based technique, where advantage is taken of the extra zero state available in current-source converters. It is shown that the switching frequency reduction is achieved with no penalty in the line current harmonic distortion. Moreover, a significant reduction of AC line current distortion is obtained with the modified dead-band technique for modulation indexes greater than 0.4. The principles of operation of the proposed schemes are explained, Experimental results on a 5 kVA current-source rectifier and a 5 kVA current-source inverter confirm the feasibility and features of the proposed pattern generators.

Temporal and Spatial Information Diffusion in Real Estate Price Changes and Variances

Abstract: This article examines patterns of temporal and spatial diffusion of real estate price changes. In addition to means, changes in volatility are tracked in reaction to substantial new information, estimated with GARCH-M methods. The data covers towns in Connecticut and near San Francisco. There is evidence of negative feedback at short lags, contrary to previous research on housing and other assets. There is also evidence of a moving average error process which tends to reverse recent shocks. Significantly positive spatial information diffusion is found from neighboring towns in Connecticut but none in control tests on nonneighboring towns. The results also include evidence of a risk-reward tradeoff in housing price changes in the San Francisco area.

Effects of free-stream turbulence on surface pressure fluctuations in a separation bubble

Abstract: Wind-tunnel experiments were conducted to investigate the cause of large pressure fluctuations near leading edges of sharp-edged bluff bodies. Measurements obtained with a blunt flat plate showed that very low pressures occur in a narrow region located approximately 0.25XR from the leading edge, where XR defines the distance from the leading edge to the mean reattachment location. This phenomenon occurs in the undisturbed flow as well as turbulent flow, although the magnitude of peak pressure fluctuations increases with both turbulence intensity, σu/u, and turbulence scale, LX.Flow visualization experiments conducted with a high-speed cine-camera reveal the process that causes large pressure fluctuations in separation bubbles. This process is initiated when a perturbation in the approaching flow causes a roll-up of the separated shear layer, producing a strong vortex near the surface. Conditional sampling of pressure data was used to determine the spanwise length of the vortex. A significant increase in the spanwise correlation of pressure fluctuations occurs when the shear layer rolls up. Coherence measurements indicate that the spanwise length of vortices in the separation bubble is not directly related to longitudinal velocity fluctuations in the free-stream.

In vitro photochemical damage to DNA, RNA and their bases by an inorganic sunscreen agent on exposure to UVA and UVB radiation

Abstract: The fate of DNA, RNA and their pyrimidine and purine bases was examined on exposure to UVA and UVB radiation in the presence of a physical sunscreen agent (TiO2 anatase/rutile particles) to assess the potential damage that such an agent may cause on contact with such substrates DNA and RNA were partially decomposed and the bases were converted to carbon dioxide (nitrogen atoms to ammonia and nitrate ions) in a Pyrex reactor under conditions simulating UVA and UVB sunlight The physical and chemical damage inflicted on DNA and RNA was also confirmed by scanning electron microscopy and gel permeation chromatography

Transformational and adaptive learning within the learning organization: a framework for research and application

Abstract: States that organizational learning is currently a fashionable concept, and this is due to an attempt by many large organizations to develop structures and systems that are more adaptable and responsive to change. Reviews a framework for organizational learning and discusses the two main perspectives on the learning organization, that is, the focus on generative or transformational learning and the focus on incremental or adaptive learning. First, reviews a framework for organizational learning and examines the learning organization with regard to the twofold nature of organizational learning. Second, examines the generative or transformational perspective of the learning organization and how this has been developed in the literature. Third, looks at the incremental or adaptive perspective of the learning organization that has been presented in some recent literature. Examines a formula for a learning organization for application. Shows that this model integrates leadership vision, measurement of goals, internal/external data collection, inventiveness and proactive implementation to create a successful design. Concludes by integrating the two perspectives on the learning organization into the reviewed framework for congruence.

Mid-point siting of FACTS devices in transmission lines

Abstract: Many controllers of flexible AC transmission systems (FACTS), such as the STATCOM, the unified power flow controller (UPFC), the PWM asynchronous DC link, the thyristor-controlled series capacitor (TCSC) and the PWM series static VAr compensator have stabilized AC voltage support. Thus, they can be sited at the mid-point of the transmission line, which has been proven by the late E.W. Kimbark, as the optimum location for shunt capacitor compensation. This paper points out that the ability to double the power transfer of the uncompensated line applies also to the aforementioned FACTS devices. The mid-point siting also facilitates the independent control of reactive power at both ends of the transmission line.

Neuropsychological aspects of multiple sclerosis: A quantitative review

Abstract: Neuropsychological studies of multiple sclerosis (MS) from a 20-year period were reviewed using meta-analytic and vote-count techniques. Mean effect sizes comparing MS and healthy control groups on variables categorized by neuropsychological domain were small to moderate in magnitude; all were statistically significant (M r= .22 (.13) to .46 (.15), r w = .23 to .43, all p < .05). Interhemispheric transfer, general cognitive ability, and learning/memory were more highly related to MS than were visuoperceptual, visuospatial, and visuoconstructional ability, language and conceptual ability (all p < .05); other domains were generally intermediate. Despite previous reports to the contrary, disease subtype was not shown to be consistently related to neuropsychological status independently of other potential explanatory variables. Findings were interpreted with regard to future research and clinical activities involving patients with MS, including selection of tests for brief neuropsychological screenin...

Processes of formation of NH4+ and NO3− ions during the photocatalyzed oxidation of N-containing compounds at the titania/water interface

Abstract: Nitrogen-containing substrates such as amino acids, amides, succinimide, imidazole, hydroxylamine and urea were photodegraded in illuminated TiO2 suspensions, and the temporal course of formation of NH4+ and NO3− ions was monitored. The hydroxylated nitrogen moiety in a molecule was predominantly converted to NO3− ions, whereas a primary amine and/or an amide were exclusively transformed to NH4+ ions under the prevailing conditions. Heterocyclic nitrogen groups in imidazole were converted to both NH4+ and NO3− ions via the intermediates whose structures were the primary amine and hydroxylamine, respectively. The influence of chemical structure on formation of NH4+ and NO3− ions is discussed from the view point of adsorption behaviours of substrates onto the TiO2 surface.

The survivor syndrome: aftermath of downsizing

Abstract: Reports that the fundamental problem with corporate restructuring as it is practised today ‐ as an ongoing strategy even in profitable times, rather than as an emergency move ‐ is that it is based on a flawed vision of what makes people and organizations work well. Excessive downsizing experiences create a new psycho‐social problem: the “survivor syndrome”. Examines survivor syndrome, identifies its causes and suggests remedies that lead to rebuilding employee commitment to the new organization.