Recognizing nullhomotopic maps into the classifying space of a Kac-Moody group

This paper extends certain characterizations of nullhomotopic maps between p-compact groups to maps with target the p-completed classifying space of a connected Kac-Moody group and source the classifying space of either a p-compact group or a connected Kac-Moody group. A well known inductive principle for p-compact groups is applied to obtain general, mapping space level results. An arithmetic fiber square computation shows that a null map from the classifying space of a connected compact Lie group to the classifying space of a connected topological Kac-Moody group can be detected by restricting to the maximal torus. Null maps between the classifying spaces of connected topological Kac-Moody groups cannot, in general, be detected by restricting to the maximal torus due to the nonvanishing of an explicit abelian group of obstructions described here. Nevertheless, partial results are obtained via the application of algebraic discrete Morse theory to higher derived limit calculations which show that such detection is possible in many cases of interest.Comment: References added, minor corrections; 29 pages, 4 figures, one tabl

Stereoscopic distance perception

Limited cue, open-loop tasks in which a human observer indicates distances or relations among distances are discussed. By open-loop tasks, it is meant tasks in which the observer gets no feedback as to the accuracy of the responses. What happens when cues are added and when the loop is closed are considered. The implications of this research for the effectiveness of visual displays is discussed. Errors in visual distance tasks do not necessarily mean that the percept is in error. The error could arise in transformations that intervene between the percept and the response. It is argued that the percept is in error. It is also argued that there exist post-perceptual transformations that may contribute to the error or be modified by feedback to correct for the error

Network Models

Networks can be combined in various ways, such as overlaying one on top of another or setting two side by side. We introduce "network models" to encode these ways of combining networks. Different network models describe different kinds of networks. We show that each network model gives rise to an operad, whose operations are ways of assembling a network of the given kind from smaller parts. Such operads, and their algebras, can serve as tools for designing networks. Technically, a network model is a lax symmetric monoidal functor from the free symmetric monoidal category on some set to $\mathbf{Cat}$, and the construction of the corresponding operad proceeds via a symmetric monoidal version of the Grothendieck construction.Comment: 46 page

A project and competition to design and build a simple heat exchanger

To address a declining interest in process engineering, a project to design and build a compact heat exchanger was initiated in the second year of a four-year, multidisciplinary degree programme in biotechnology. The heat exchangers had a double-pipe configuration and employed plastic outer pipes and copper inner pipes of various diameters. Designs produced ranged from coiled inner pipes to various multi-pass arrangements and were assessed on the basis of heat transfer achieved per unit mean temperature difference per unit cost. The project, which also formed the basis of a competition, was very well received by students and gave them hands-on experience of engineering design and construction, as well as team work, problem solving, engineering drawing and the use of simple tools. Based on the success of this project, a similar problem based learning approach will be initiated in the third year of the same degree programme and will focus on bioethanol production

Communicative planning theory and community initiatives

We evaluate lender discrimination during the mortgage default process. A telephone survey was conducted to evaluate the extent of lender discrimination in defaults that lead to foreclosure in New Orleans, Louisiana between 1985-1990. We use these data to estimate the independent effects of race and neighborhood characteristics on the extent of lender assistance or forbearance during the foreclosure process. Our analysis indicates that the proportion of black residents in the neighborhood where the property was foreclosed is a more significant predictor of forbearance than the race of the borrower. This is a foreboding indication of the possibility that recent gains in black home buying may be partially offset by the persistence of residential segregation in U.S. cities