A global collocation technique for the solution of opening mode crack problems

A review of various experimental and numerical techniques for determination of fracture mechanics calibration functions (i.e., the variation of K ₁ and CMOD with crack length) revealed that neither technique, employed independently, can determine K ₁, CMOD, and full field stresses in closed form over a wide range of crack lengths. To fill this void, a combined experimental/numerical collocation technique based on a series expansion of the modified Westergaard functions was developed. This technique uses both boundary conditions, known a priori, and interior stress field conditions, determined using a suitable experimental technique, for analysis of two dimensional, finite body, opening mode crack problems. This paper reports on an investigation of the accuracy of this technique and its sensitivity to errors in experimental data for a sample problem of practical interest.     

Preface.

In this issue of Health Psychology is a summary of discussions and presentations conducted at the National Working Conference on Research in Health and Behavior, Harpers Ferry, West Virginia, May 1988. Conceived by Richard Evans in 1985, the idea for this conference reflected both the substantial growth in this scientific endeavor and the recognition that the ways in which the field evolves are shaped in part by those active in it. The reports and summaries that appear in this issue do not reflect an exhaustive report of these deliberations. Rather, selected articles are presented along with task force (i.e., working group) reports in order to provide a hint of the context in which the task forces addressed their topics. Each of the keynote speakers (Richard Evans and Karen Matthews) was asked to provide a summary of remarks, and each panel agreed to provide one or more articles summarizing individual or group conclusions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Autonomic function in a cohort of children with diabetes

129 diabetic children in Avon County participated in a longitudinal study of the evolution of microvascular disease together with 129 age- and sex-matched controls. Diabetic children had mean (+/- SD) age 12.7 (+/- 3.4) years (range: 3.7-16.8), mean (+/- SD) diabetes duration 3.9 (+/- 3.2) years (range: 0.1-13.4) and mean (+/- SD) HbA1 11.1% (+/- 2.2) (range: 6.5-18.2). Cardiovascular autonomic function was studied by four heart rate (HR) tests using a computerized system of HR monitoring. As a group, diabetic children had higher mean HR (p = 0.0004) and reduced max/min HR ratio while standing (p = 0.001), compared with the control children. HR ratio while standing was the only variable related to diabetes duration (r = -0.20, p = 0.018), while no correlation of HR variables with glycaemic control was found. Twenty diabetic children (15.5%) had one abnormal HR test. Ten diabetic children (7.7%) demonstrated abnormality in two or more HR tests. When compared with the other diabetic children in the cohort, these ten children were found to be younger in age (mean age: 9.4 vs 12.0 yr, p = 0.05), but did not otherwise differ in terms of diabetes duration or glycaemic control. No pubertal or sex effect in the development of diabetic autonomic neuropathy was detected. These findings suggest that autonomic function may be impaired early in childhood diabetes, independent of the duration of the disease or the quality of glycaemic control.     

Erasure generation and interleaving for meteor-burst communicationswith fixed-rate and variable-rate coding

Erasure generation techniques are investigated in conjunction with symbol interleaving as methods to improve the performance of meteor-burst communication systems. Erasure generation via Viterbi's (1982) ratio-threshold test (RTT) and a Bayesian scheme are both considered. It is found that a system using fixed-rate coding, interleaving, and erasure generation can significantly outperform more complex variable-rate coding schemes which do not use erasures     

Preservation of diagnostic information in the synthesis of EKG signals of the Frank orthogonal system from those recorded by the standard lead system: The Washington Code criteria

The problem of synthesizing Frank orthogonal lead system signals from those recorded by the standard lead system is considered, to answer the important practical question: can the synthesized EKG signals be used in practice for their diagnostic classification in terms of the Washington Code?     

Book reviews

Urban Planning in a Multicultural Society

Michael A. Burayidi (ed.) Praeger, Westport, Conn., 2000 ISBN 0275961257 (hardback) 280 pp.; index RRP $123.85

The Community Planning Handbook: How People Can Shape Their Cities, Towns and Villages

Nick Wates (ed.) Earthscan, London, 2000 ISBN 1853836540 (paperback) 230 pp. RRP $42.85

City Against Suburb: The Culture Wars in an American Metropolis

Joseph A. Rodriguez Praeger, Westport, Conn., 1999 ISBN 027596406X (hardback) 144 pp.; bibliographic essay RRP $96.97

Community Development in the Market Economy

Jeremy McArdle Vista, Melbourne, 1999 ISBN 0958649677 (paperback) 117 pp.; bibliography RRP $16.50

Ethnicity and Housing: Accommodating Difference

Frederick W. Boal (ed.) Ashgate, Aldershot, 2000 ISBN 1859725961 (hardcover) 318 pp.; bibliography and index RRP $101.08

Computer-Aided Policymaking: Lessons from Strategic Planning Software

Ray Wyatt, E. & F. N. Spon, London, 1999 ISBN 0419244808 (paperback) 244 pp.; bibliography and index RRP $79.95

Making Common Ground: Public-Private Partnership in Land for Housing.

Geoffrey Payne (ed.). Intermediate Technology Publications, London, 1999. ISBN 1853394793 (paperback). 256 pp.; bibliography and index. RRP $45.86     

The effect of automatic gain control on serial, matched-filteracquisition in direct-sequence packet radio communications

The performance of a noncoherent serial acquisition technique is evaluated for direct-sequence spread-spectrum packet communications. The acquisition technique that is considered uses threshold crossing of a matched-filter output to detect a fixed-length preamble at the start of each packet. The analysis accounts for frequency mismatch between the transmitter and the receiver due to oscillator inaccuracies and mobility-induced Doppler shifts. It also accounts for the effects of automatic gain control (AGC) in the receiver. The role of the AGC system in determining the acquisition performance is examined. In addition, selection of the optimal acquisition threshold is considered, and a simple method for selection of a good suboptimal threshold is presented. It is shown that use of this threshold results in performance close to that obtained with the optimal threshold over a wide range of channels