Viscous MFD low Hartmann flow in an annular gap—a magnetic prandtl number expansion

The problem of a liquid conductor confined between two concentric cylindrical electrodes and driven electromagnetically is considered. The steady, three-dimensional viscous case is treated asymptotically in the limit of small magnetic Prandtl numbers. The zeroth-order solution to the coupled hydrodynamic and Maxwell equations yields the trivial solution of no motion in the limit of vanishing conductivity. Results for the first-order solution indicate two-dimensional effects in the electromagnetic field quantities while the first-order velocity is one dimensional in the circumferential direction. Due to secular effects the solution is limited to values of small Hartmann numbers. The formulation of the second order and a limited solution for the velocity distribution indicates that the velocity field is three-dimensional having a cell-type structure.     

Comparing Simple and Advanced Video Tools as Supports for Complex Collaborative Design Processes

Working with digital video technologies, particularly advanced video tools with editing capabilities, offers new prospects for meaningful learning through design. However, it is also possible that the additional complexity of such tools does not advance learning. We compared in an experiment the design processes and learning outcomes of 24 collaborating participant pairs (dyads) using 2 contrasting types of video tools for history learning. The advanced video tool WebDIVER supported segmenting, editing, and annotating capabilities. In the contrasting condition, students used a simple video playback tool with a word processor to perform the same design task. Results indicated that the advanced video editing tool was more effective in relation to (a) fostering student understanding of the topic and acquisition of cognitive skills, (b) the quality of student design products, and (c) the efficiency of dyad interactions. The implication of our experimental findings for constructivist design-based learning is that mediating functions of video tools may be used as cognitive and social supports, for example when students learn by solving design tasks in school.     

Workshop for Graduate Teaching Assistants

There are limited studies with conflicting results examining textbook use and student performance at the university level. To learn more, we surveyed instructors and over one thousand students in 12 undergraduate introductory science courses. The majority (77%) of the students reported reading the textbook either “often” (>75% of the assigned reading) or “sometimes” (25%–75% of the assigned reading). Those who read “often” had better final marks those who read “sometimes,” but surprisingly, those who reported “rarely” reading the textbook did as well as those who read “often.” Perceptions of the usefulness of the textbook were generally more favorable in courses in which some marks were based solely on the readings. We conclude that there appears to be different types of learners: some may need to read the textbook “often” to do well, while others do not.     

A differential-outcome effect in pigeons using spatial hedonically nondifferential outcomes

We examined the extent to which nonhedonically different differential outcomes involving feeder location control pigeons’ comparison choices in matching to sample. In Experiment 1, we showed that differential feeder location outcomes associated with each of two samples can facilitate delayed-matching accuracy. In Experiment 2, we found positive transfer following training on two matching tasks with differential feeder location outcomes when samples from one task were replaced by samples from the other task. In Experiment 3, we found that when differential-outcome expectations could no longer serve as the cues for comparison choice, sample stimuli continued to exert some control over choice of comparisons. The results indicate that differential outcomes (involving feeder location) that presumably do not differ in hedonic value are sufficient to control comparison choice. Thus, the differential hedonic value of the outcome elicited by the sample does not appear to be a requirement of the differential-outcome effect. Furthermore, these differential outcomes appear to augment matching accuracy, but they do not eliminate control by the samples.     

OPINION FORMATION IN MEDIATED CONFLICTS AND CRISES: A THEORY OF COGNITIVE-AFFECTIVE MEDIA EFFECTS

This paper analyzes opinion formation in the cases of threemediated conflicts using a complex model that evaluates therespondents' value systems, the coverage of the mass media used,the recipients' familiarity with specific events occurring inthe conflicts, and their positions on the issues. The modelpredicts that the recipients' long-term value systems influencetheir positions on the issue in two ways. Firstly, value systemshave a direct impact on the short-term positions on an issue.Secondly, value systems have an indirect impact on the positionsof issues by influencing the recipients' selection of news mediaand thus the type and amount of news information they are exposedto. The type and amount of news influences how knowledgeablethey are of the events related to the conflicts. The familiaritywith these events influences their positions on the issues.Value systems, media usage, familiarity and positions on theissues were measured in a survey. A parallel content analysisexamined the coverage of the conflicts in the German mass media(press, radio, television) during the six-month time frame priorto the survey. Both data sets were merged in order to give anestimate of the information each recipient was exposed to. Theresults of multiple regression analyses support the theoreticalmodel. Furthermore, this paper discusses the relevance of themodel for the analysis of opinion formation as well as the limitationsof the model.