Terrestrial digital video broadcasting for mobile reception using OFDM

Performance of a system design for digital video broadcasting is examined with emphasis on mobile reception. Orthogonal frequency division multiplexing (OFDM) is used to achieve good bandwidth efficiency and to mitigate the intersymbol interference resulting from the channel delay spread. The resulting equivalent channel including OFDM can be modeled as a flat Rayleigh fading channel plus an interchannel interference (ICI) term due to the channel Doppler spread. This ICI term is analyzed and shown to result in an error floor. Performance improvements due to antenna diversity and trellis-coded modulation (TCM) are given. Finally, multiresolution modulation is discussed as a means of achieving graceful degradation and giving degrees of freedom for further performance improvement.This research was supported by the Multimedia Systems R & D Laboratory, Hitachi, Ltd.     

Metal dusting (catastrophic carburization) of a waste heat boiler tube

A waste-heat boiler at a chemical plant suffered an unusual tube failure. The boiler is part of the partial oxidation (POx) syngas production for a 2-ethyl hexanol unit. The syngas primarily consists of H₂, CO and CO₂ with trace amounts of CH₄. Steam is also reportedly injected into the process. The syngas enters the boiler at approximately 1800°F (980°C) on the internal side of the tube and is cooled, while generating approximately 640 psi (4.41 MPa) steam at 490°F (255°C) on the outside of the tube. The internal surface of the tube contained a region of metal loss that was approximately 1 inches long by inch wide (44.5 mm by 19 mm). The metal loss was very localized with little evidence of attack elsewhere on the tube's surface. Molten salt attack, sulfidation and metal dusting were considered as possible mechanisms for the metal loss. It was determined that metal dusting, also called catastrophic carburization, was the cause of the metal loss. The cause of the metal dusting was localized overheating of the tube, which developed because of water/steam flow disruption due to contact of the tube baffle with the tube. Approximately one year after this tube failure, the boiler suffered two more tube failures, which were also attributed to metal dusting.     

Typicality effects in attitudes toward social policies: A concept-mapping approach.

Social typicality effects occur when people apply their attitudes more consistently toward typical than toward atypical category members presumably because attitudes are directed toward the prototypic category member. Four studies tested whether individuals also apply social policy attitudes more consistently toward typical than toward atypical persons affected by the policy. Study 1 used attitude concept maps to assess how extensively individuals spontaneously reference the typical person affected by a social policy. Death penalty proponents did so more than did opponents; welfare proponents and opponents did so equally. In 3 other studies, death penalty proponents displayed greater typicality effects in sentencing "convicted murderers" than did opponents, welfare proponents and opponents displayed equal typicality effects in evaluating cases of suspected welfare fraud, and individuals whose attitude concept maps about welfare referred more to persons displayed greater typicality effects than did individuals whose maps referred more to principles. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The lexical nature of syntactic ambiguity resolution.

Ambiguity resolution is a central problem in language comprehension. Lexical and syntactic ambiguities are standardly assumed to involve different types of knowledge representations and be resolved by different mechanisms. An alternative account is provided in which both types of ambiguity derive from aspects of lexical representation and are resolved by the same processing mechanisms. Reinterpreting syntactic ambiguity resolution as a form of lexical ambiguity resolution obviates the need for special parsing principles to account for syntactic interpretation preferences, reconciles a number of apparently conflicting results concerning the roles of lexical and contextual information in sentence processing, explains differences among ambiguities in terms of ease of resolution, and provides a more unified account of language comprehension than was previously available. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial attention to arrays of multidimensional objects.

Encoding briefly displayed arrays of multidimensional objects appears to require selective attention, but this hypothesis is challenged by M. J. Nissen's (1985) finding that properties of an object are reported independently. Selective attention to some objects but not others should produce positive dependence. Theoretical analysis shows that deviations from independence would have been difficult to observe in Nissen's data because of high guessing rates and small sample sizes. Four new experiments showing strong positive dependence in property reports are described. Deviations from independence were highly significant for most Ss. Quantitative modeling shows that selective attention to subsets of objects would produce about the amount of dependence obtained. Rather than challenging attention theories, the amount of dependence in encoding multidimensional objects is consistent with selective attention to either objects or locations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social change and law.

Comments on D. R. Fox's (see record 1993-27200-001) call for reexamination of legal efforts made on behalf of organized psychology to accomplish social change. The author disagrees with the claim made by Fox that organized psychology's advocacy efforts are misdirected because they promote values consistent with those found in the law. It is argued here that the law remains the primary and most powerful mechanism through which social change is accomplished. Further, until it can be empirically shown otherwise, law is a proper venue for efforts directed by organized psychology toward social change. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Treatment of Posttraumatic Stress Disorder in Military and Veteran Populations.

While concerns about the psychological effects of war are not new, only recently has systematic attention been paid to such problems among past and present military personnel. There is increasing recognition that mental health has serious implications for operational performance, retention, and compensation. Although little controlled research exists with this population, preliminary evidence suggests that psychological treatments for posttraumatic stress disorder may be beneficial, albeit less so than for civilian populations. This article reviews evidence for each of several psychological treatment stages: stabilization and engagement, psychoeducation, symptom management, prolonged exposure, cognitive restructuring, and relapse prevention, with particular reference to the clinical issues raised by military personnel. Possible explanations for reduced treatment effects in this population compared with civilians are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Routine Highway Bridge Inspection Condition Documentation Accuracy and Reliability

Routine inspection is the most common form of highway bridge inspection to satisfy the requirements of the National Bridge Inspection Standards. The accuracy and reliability of documentation generated during these inspections are critical to the allocation of Department of Transportation construction, maintenance, and rehabilitation resources. Routine inspections are typically completed using only the visual inspection technique and rely heavily on subjective assessments made by bridge inspectors. In light of this, and given the fact that visual inspection may have other limitations that influence its reliability, the Federal Highway Administration initiated an investigation to examine the reliability of visual inspection as it is currently applied to bridges in the United States. This paper will summarize results from this study related to the accuracy and reliability of routine inspection documentation. A number of important conclusions were developed from the experimental study. Generally, it was found that all structural condition documentation is collected with significant variability. Specifically, 95% of primary element condition ratings for individual bridge components will vary within two rating points of the average and only 68% will vary within one point. Documentation generally collected to support condition ratings also has significant variability as exemplified by the number and types of field notes and photographs taken by inspectors. With respect to the use of element-level inspections, it was found that element usage was generally consistent with the Commonly Recognized Element Guide. However, there is significant variability in the condition state assignments of those elements and in some cases the condition states are not applied correctly to particular elements.     

Livsic theorems,maximizing measures and the stable norm

In this paper we consider two results motivated by Livsic's well-known theorem that, for a hyperbolic system, a Hölder continuous function is determined, up to a coboundary, by its values around closed orbits. The first result relates to negative values around orbits and the second result to values for finitely many orbits. We also present some new results on maximizing measures and the boundary of the unit ball in the stable norm for a surface.