ESTIMATING THE NUMBER OF HOMELESS: Media Misrepresentation of an Urban Problen

ABSTRACT: In the 1980s several estimates were made of the size of the homeless population nationwide. An examination of these estimates shows that claims by advocacy groups that 2–3 million persons were homeless on any night were unjustified. Instead, social scientific studies agree that the number is probably about 300,000–500,000. This discrepancy tests the ability of the media to distinguish between good social science research and mere guesstimates. An examination of US magazines and newspapers found that, as a group, the media were more likely to cite high estimates than low estimates and this changed only slightly over time. Two factors seem to explain why journalists cannot distinguish between good and bad estimates: media bias and the process whereby information is gathered.     

NEW INTEGRATED SIMULATION TECHNIQUES FOR THE ELECTROMAGNETIC ANALYSIS OF MICROWAVE CIRCUITS USING THE TLM METHOD

A new methodology is presented which allows the integration of lumped elements into electromagnetic simulations, using the TLM method. It is shown that the new method retains the symmetrical condensed node algorithm structure, with the potential to be applied to all lumped elements. A new and accurate method for the extraction of circuit parameters from the impulse response of the TLM method is also presented. The method is simple and can be used for waveguide and planar structures. A study is carried out on the applications of various data windowing techniques during the postprocessing stages of an electromagnetic analysis. This has resulted in the realization of the need for careful selection of a particular window profile, according to the application and the nature of the required results.     

Development Aspects of an Integrated Pyroelectric Array Incorporating a Thin PZT Film and Radiation Collectors

Work is being undertaken to produce an uncooled pyroelectric infra-red detector array which incorporates within its structure, an array of radiation collectors made by the bulk micro-machining of silicon. Development aspects of the processing route are presented here.     

DIET-MEDIATED INTER-COLONIAL AGGRESSION IN THE FORMOSAN SUBTERRANEAN TERMITE <Emphasis Type="Italic">Coptotermes formosanus</Emphasis>

In most social insects, intercolonial and interspecific aggression are expressions of territoriality. In termites, cuticular hydrocarbons (CHCs) have been extensively studied for their role in nestmate recognition and aggressive discrimination of nonnest-mates. More recently, molecular genetic techniques have made it possible to determine relatedness between colonies and to investigate the influence of genetics on aggression. In the Formosan subterranean termite, Coptotermes formosanus, however, the role of CHCs and genetic relatedness in inter-colony aggression has been ambiguous, suggesting the involvement of additional factors in nest-mate recognition. In this study we assess the range of aggression in this termite species and characterize the influence of genetic relatedness, CHC profiles and diet on aggression levels. We collected four colonies of C. formosanus, feeding either on bald cypress or birch, from three locations in Louisiana. Inter-colony aggression ranged from low to high. Differences in CHC profiles, as well as genetic distances between colonies determined by using microsatellite DNA markers, showed no significant correlation with aggression. However, termite diet (host tree) played a significant role in determining the level of aggression. Thus, two distantly related colonies, each feeding on different diets, showed high aggression that significantly diminished if they were fed on the same wood in the laboratory (spruce). Using headspace solid phase microextraction, we found three compounds from workers fed on birch that were absent in workers fed on spruce. Such diet-derived chemicals may be involved in the complex determination of nest-mate recognition in C. formosanus.     

Heuristic improvement through triangulation

Abstract

This paper presents a method for improving heuristics using a triangulation technique. Instead of using a heuristic to directly estimate distance (X₁, X₂) between nodes X₁ and X₂, the proposed technique selects a reference node R_i applies the heuristic to (X₁,R_i) and (X₂,R_i), and uses the Euclidean distance formula to calculate a new heuristic value. If two nodes are close to each other, then they should also be approximately equidistant to a third reference node. Utilizing a set of many such reference nodes, node expansions can be reduced for a large class of heuristics. Very early results for this method, referred to as multi-dimensional heuristics, showed that fewer node expansions were needed when using the triangulation technique. New results in this paper include the development of a new learning procedure for selecting reference nodes, experimentation on reusing reference node sets for multiple goal instances, a comparison of multi-dimensional heuristics with weighting and how they dynamically weight states near the goal, and some observations which help explain how and why this technique improves heuristics.     

Sliding mode stabilization of uncertain systems using only output information

A practical procedure is presented for synthesizing output feedback controllers for uncertain systems based on sliding mode concepts. The class of systems to which the results apply is identified and includes the requirement that the nominal linear system is minimum phase. The procedure proposed for the design of the sliding surface uses established output feedback eigenvalue assignment results. It will be shown that all the assumptions imposed on the system pertain to the design of the sliding surface. The proposed controller, which guarantees attainment of a sliding mode despite the presence of uncertainty requires no additional assumptions.     

Viscosity and Thermal Expansion of Mixed-Alkali Sodium-Potassium Borate Glasses

The transformation-range viscosity and thermal expansion be-havior of sodium-potassium borate glasses were studied. The results indicate that negative deviations from additivity in the viscosity of these glasses are a function of the Na²O to K²O ratio and that the magnitude of these deviations increases with alkali oxide content. The thermal expansion coefficient exhibits a maximum deviation from additivity as a function of the Na²o to K²O ratio. The magnitude of this deviation increases with increasing total alkali oxide content. The results indicate that there is little, if any, interaction between the factors which lead to the mixed-alkali effect and the changes in the structure of the vitreous network which occur as the alkali oxide content of the glasses increases.