Expository Presentation Research Articles

Uniformization: Basics, extensions and applications

Uniformization, also referred to as randomization, is a well-known performance evaluation technique to model and analyse continuous-time Markov chains via an easier to performance measures via iteration of the one-step transition matrix of the discrete-time Markov chain. The number of iterations has a Poisson distribution with rate dominating the maximum exit rate from the states of the continuous-time Markov chain. This paper contains an expository presentation of uniformization techniques to increase awareness and to provide a formal and intuitive justification of several exact and approximate extensions, including: •exact uniformization for reward models,•exact uniformization for time-inhomogeneous rates,•a numerical comparison with simple time-discretization,•approximate uniformization for unbounded transition rates, and•exact uniformization for continuous state variables for non-exponential networks.Furthermore, several of these results are numerically illustrated for a processor sharing web server tandem model of practical interest.

Progress notes: Scenes of Subjection’s “actualization” dialectic

This essay explores Saidiya Hartman’s Scenes of Subjection’s actualization dialectic, its delicate balancing of identity and difference, as specifically mobilized through the study’s expository presentation of the event/non-event of Emancipation. It also examines Hartman’s relationship to Marx as it relates to the applicability of Marxian categories to think about New World slavery.

Listening to Narratives: An Experimental Examination of Storytelling in the Classroom

In an age of PowerPoint, much everyday public communication is semantically organized as an expository presentation. This contrasts with traditional approaches such as storytelling that are episodically organized and presented as narratives. The constructivist theory of narrative comprehension, along with other theoretical perspectives, suggests that a narrative form should present advantages related to listening retention. Further, it is argued that organization could interact with communication load in determining the likelihood of recalling information. In a controlled experiment, participants listened to videotaped instruction presented in either narrative or expository form and presented at either a normal or a moderately compressed rate. Results indicate a relationship between organization and retention such that audience members retain more information when it is presented in a narrative style and when it is presented at a normal presentation rate. Practically, the results suggest advantages for narrative form in the everyday practice of instructional communication. Theoretically, the results demonstrate that constructivist theory of narrative comprehension is relevant to contexts beyond written texts—to listening contexts.

Mini-workshop: Dirac Operators in Differential and Noncommutative Geometry

The mini-workshop, organized by Christian Bär and Andrzej Sitarz, had a very special character. The participating scientists came from two different mathematical communities: differential geometry (working mainly on problems related to the Dirac operator on spin manifolds) and noncommutative geometry (working mainly on concepts of Dirac operators in the framework of spectral geometry as postulated by Alain Connes). Spin geometry has become an established and very active subfield of Differential Geometry, after Lichnerowicz observed that the Index Theorem yields a topological obstruction against the existence of metrics with positive scalar curvature. The Dirac operator plays a key role in the deep work of Gromov, Lawson, Rosenberg, Stolz and others on manifolds admitting metrics with positive scalar curvature. The birth of noncommutative geometry offered completely new possibilities for extending some notions of differential geometry into the realm of operator algebras. In Connes' notion of spectral triples the Dirac operator was used to define a (possibly noncommutative) geometry itself rather than being an object derived from a geometry. Since then many interesting examples of noncommutative spaces and Dirac operators were studied. The equivalence theorem, allowing reconstruction of a spin manifold from a spectral geometry of a commutative algebra was proved only recently and the proof was presented at the workshop. The aim of the workshop was twofold: to show current interests, methods and results within each group and open the possibility for interaction between two groups. Due to the character of the meeting, first three days were devoted to the expository presentations, when we tried to cover the possibly broadest scope of topics from one subject presented for the participants from the other group. The remaining two days were devoted to talks on advanced current research problems and results, which had closer links to the topics of both groups. During problem sessions in the evenings various open questions were discussed some of which were solved during the week.

ZEROS OF REAL POLYNOMIALS ON BANACH SPACES

This paper is an expository presentation of a large part of the results, about zeros of real polynomials on Banach spaces, that have been obtained in recent years. Also new results, for or-thogonally additive polynomials on <TEX>$L_p$</TEX> spaces, are given.

Multimedia design for communication of dynamic information

Computer-based multimedia technologies allow designers to construct interactive and animated graphical presentations to communicate dynamic information. The conventional wisdom is that such presentations are more effective than printed materials. This paper presents research that critically examines this assumption. Design guidelines and principles were derived from a cognitive process model of multimodal comprehension. These guidelines and principles were used to create several expository presentations in two domains—the concrete domain of mechanical systems and the abstract domain of computer algorithms. A series of experiments evaluated the efficacy of these presentations and compared them with other kinds of presentations such as books, CD-ROMs and animations. The experiments also compared computer-based interactive graphical presentations and static printed presentations containing the same information. Experimental results suggest that the communicative efficacy of multimodal presentations is more related to their match with comprehension processes than with the interactivity and dynamism of the presentation media. The results support a model-based approach to the design of multimodal expository presentations of dynamic information. The comprehension model and corresponding design guidance should aid designers in building interactive graphical presentations that are more effective than intuitive designs in communicating dynamic content.

Evaluating multimedia presentations

The paper reports the basis for a cognitive walkthrough method to support the evaluation of multimedia (MM) expository presentations (e.g. ‘how to do it’ type tasks). The walkthrough is founded upon an analysis of the cognitive processes and representations formed by the comprehension of an MM presentation. Issues include evaluation of attention, topic focus and information types. The walkthrough provides a series of guidelines for evaluation based on these cognitive models, such as the use of media, scripting and presentation techniques. The value of the guidelines is validated by several empirical studies. An eye tracking study is reported, providing evidence as to how visual attention responds to MM materials. A series of comprehension studies then investigate the effectiveness of a presentation before and after our guidelines were applied. The paper is illustrated with an example evaluation and studies of a commercially produced CD-ROM MM presentation ‘The Biology of Cancer’.

Instructional behaviors for clearer presentations in the classroom

Teachers spend a considerable amount of classroom time talking to students. Much of this talk revolves around expository presentations of information. Teachers claim the reason for the quantity of teacher talk is to clarify instruction to students. However, discrepancies can exist between what teachers assume are the benefits of their talk and how students learn from such talk. To match students' abilities to learn, teachers must produce clearer instructional presentations. This article proposes the importance of structure in developing sound teacher expository presentations. Nine instructional behaviors based on correlational and experimental research during the past two decades are presented in the form of teacher guidelines to maximise precision and structure in teacher talk in order to facilitate student achievement.

Comparison of models for the contact of rough surfaces

Numerical comparisons of the Greenwood-Williamson (GW) elastic microcontact model with two more general isotropic and anisotropic models suggest that the GW model gives good order-of-magnitude estimates of the number of contacts, real contact area fraction and nominal pressure that result at a given separation of a rough and a smooth flat plane. In effecting the comparisons, the three parameters of the GW model are related to the three spectral moments m 0, m 2 and m 4 of an isotropic or equivalently isotropic surface. It is shown that the real contact area at a given mean plane separation depends only on the bandwidth parameter α = m 0m 4 m 2 2 , while the elastically supported load depends on both α and m 2. On the basis of the comparisons it is suggested that the GW model be adopted by metrologists to relate measured microgeometry to physically more understandable quantities such as contact density, load, real area and plastic contact density. Accordingly, this paper includes an expository presentation of the GW model complete with tables and a detailed numerical example of their use.

The Effectiveness of Three Methods of Teaching Social Studies Concepts to Sixth-Grade Students

This study examined the effectiveness of three methods of teaching concepts: reading-recitation method, a presentation of examples and non-examples only, and Merrill and Tennyson's model. Sixth-grade students (TV = 95) were randomly assigned to one of three experimental treat ment groups. Two social studies concepts, arable land and ter tiary production, were the topics of the lessons. Results of a 3 x 3 x 2 factorial ANOVA indicated that the Merrill and Tennyson model was more effective than either Gagne's model or the reading-recitation method. No significant aptitude treatment interactions were found. Merrill and Tennyson have designed a model for teachi g concepts which s based upon a set of propositions derived from prior research (Merrill & Tennyson, 1977; Tennyson, 1973; Tennyson, Chao, & Youngers, 1981; Tennyson & Park, 1980; Tennyson, Steve, & Boutwell, 1975; Tennyson, Wooley, & Merrill, 1973). Their model includes: (a) a definition expressed in terms of critical attributes; (b) an expository presen tation of examples and non-examples, where matched means similarity of variable attributes; and (c) an inquisitory practice during which students are required to differentiate between unfamiliar examples and non-examples and to justify their choices in terms of the definition of the concept. The Merrill and Tennyson model also specifies that examples/non examples in the expository presentation should be se quenced from easy to difficult and should be divergent. This model is admirable as a serious attempt to build theory which can guide instructional practice. The research evidence for the design, however, is question able on at least four grounds. First, most of the evidence has been generated through studies directed by the per sons who developed the instructional design. Second, most of the relevant studies have failed to report the amount of time allocated to each of the treatments. Since a presentation consisting of either a definition and/or examples may require much less time than a presentation utilizing the full model, the results of these studies might simply reflect amount of time allocated to each treatment. Third, the kinds of treatment (computer-assisted instruction) administered in most of the studies cited above raise questions of external valid ity. Although we are not opposed to the use of com puters in the classroom, our experience has led us to believe that most teachers generally use some type of reading-recitation when teaching concepts. Fourth, Tennyson and his associates have failed to compare the effectiveness of their model against other commonly recommended models such as the Gagne (1965) model and the more typical textbook approach. This study was an attempt to replicate the findings of a previous study conducted by three of the authors (McKinney, Lar kins, & Peddicord, 1982). McKinney, Lar kins, and Peddicord (1982) compared the effective ness of Merrill and Tennyson's model, Gagne's model, and a reading-recitation method. Gagne's model was chosen because of its simplicity and popularity with some social studies educators. The reading-recitation method was included because of its popularity with classroom teachers. Subjects (N = 102) were selected from four sections of fourth-grade social studies classes and were randomly assigned to one of the three treat ment groups or to a control group. The topic of the lessons was the concept *'cultural diffusion. They reported no significant differences between or among the three treatment groups. All three treatment groups Address correspondence to C. Warren McKinney, Depart ment of Curriculum and Instruction, University of Southern Mississippi, Southern Station /Box 8220, Hattiesburg, MS 39406.

Number Patterns: Discovery versus Reception Learning

Subjects were randomly assigned to one of three treatment groups that differed in terms of the manner in which initial learning of number patterns took place. In one group, the presentation was expository. In the other two, discovery learning--either in groups or individually--was the mode. Results were assessed in terms of immediate recall, longer-term retention, and transfer. Data analyses indicated that the expository presentation was the most effective for immediate recall. In terms of retention and transfer, however, the group discovery approach was clearly superior to both other treatments.

An analysis of alpha-beta pruning

The alpha-beta technique for searching game trees is analyzed, in an attempt to provide some insight into its behavior. The first portion of this paper is an expository presentation of the method together with a proof of its correctness and a historical discussion. The alpha-beta procedure is shown to be optimal in a certain sense, and bounds are obtained for its running time with various kinds of random data.

A Study of Discovery and Expository Presentation: Implications for Teaching

A Study of Discovery and Expository Presentation: Implications for Teaching

Interpretation and Application of Statistical Analysis for Random Physical Phenomena

This paper is an expository presentation on 1) mathematical and statistical concepts deemed to be important in analyzing the nature of random physical phenomena, 2) development of over-all procedures for evaluating single records and a collection of records, and 3) particular details on interpreting and applying probability density functions, correlation functions, and power spectral density functions. The discussion is directed towards a general audience to help bring about a wider understanding of these ideas for application to many problems such as: vibration in space vehicles, meteorological or oceanographic prediction, electrical noise properties, biomedical research, etc.

Quality Control in Business

A SERIES of six articles by Mr. William B. Rice on quality control in business production and administration have been separately reprinted from Western Industry, the Journal of the American Statistical Association and the Accounting Review, and provides a useful introductory account for anyone interested in the application of statistical methods in business. Mr. Rice, who is the director of the Department of Statistics and Reports of the Plomb Tool Company of Los Angeles, writes with first-hand experience of the methods he describes and drives home his points with a wealth of practical illustration. The first four of his articles deal with the control of quality of a manufactured product on fairly familiar lines—an expository presentation which should do much to arouse interest among manufacturers. In the remaining two he extends the technique to business administration and office accounting, showing, for example, how excessive overtime costs in a department of an engineering plant were tracked down and eliminated, and how administrative charges in a business were brought under control. This is quite a recent development of the subject, and provides an interesting illustration of the growth of scientific methods in the most ordinary commercial operations.