A study of the stability of subcycling algorithms in structural dynamics

Algorithms for explicit integration of structural dynamics problems with multiple time steps (subcycling) are investigated. Only one such algorithm, due to Smolinski and Sleith has proved to be stable in a classical sense. A simplified version of this algorithm that retains its stability is presented. However, as with the original version, it can be shown to sacrifice accuracy to achieve stability. Another algorithm in use is shown to be only statistically stable, in that a probability of stability can be assigned if appropriate time step limits are observed. This probability improves rapidly with the number of degrees of freedom in a finite element model. The stability problems are shown to be a property of the central difference method itself, which is modified to give the subcycling algorithm. A related problem is shown to arise when a constraint equation in time is introduced into a time-continuous space-time finite element model. (C) 1998 Elsevier Science S.A.

Anthropometric-based selection and sprint kayak training in children

A 12 week kayak training programme was evaluated in children who either had or did not have the anthropometric characteristics identified as being unique to senior elite sprint kayakers. Altogether, 234 male and female school children were screened to select 10 children with and 10 children without the identified key anthropometric characteristics. Before and after training, the children completed an all-out 2 min kayak ergometer simulation test; measures of oxygen consumption, plasma lactate and total work accomplished were recorded. In addition, a 500 m time trial was performed at weeks 3 and 12. The coaches were unaware which 20 children possessed those anthropometric characteristics deemed to favour development of kayak ability. All children improved in both the 2 min ergometer simulation test and 500 m time trial. However, boys who were selected according to favourable anthropometric characteristics showed greater improvement than those without such characteristics in the 2 min ergometer test only. In summary, in a small group of children selected according to anthropometric data unique to elite adult kayakers, 12 weeks of intensive kayak training did not influence the rate of improvement of on-water sprint kayak performance.

Extended GCD and Hermite normal form algorithms via lattice basis reduction

Extended gcd calculation has a long history and plays an important role in computational number theory and linear algebra. Recent results have shown that finding optimal multipliers in extended gcd calculations is difficult. We present an algorithm which uses lattice basis reduction to produce small integer multipliers x(1), ..., x(m) for the equation s = gcd (s(1), ..., s(m)) = x(1)s(1) + ... + x(m)s(m), where s1, ... , s(m) are given integers. The method generalises to produce small unimodular transformation matrices for computing the Hermite normal form of an integer matrix.

Effects of data characteristics on the results of reserve selection algorithms

We tested the effects of four data characteristics on the results of reserve selection algorithms. The data characteristics were nestedness of features (land types in this case), rarity of features, size variation of sites (potential reserves) and size of data sets (numbers of sites and features). We manipulated data sets to produce three levels, with replication, of each of these data characteristics while holding the other three characteristics constant. We then used an optimizing algorithm and three heuristic algorithms to select sites to solve several reservation problems. We measured efficiency as the number or total area of selected sites, indicating the relative cost of a reserve system. Higher nestedness increased the efficiency of all algorithms (reduced the total cost of new reserves). Higher rarity reduced the efficiency of all algorithms (increased the total cost of new reserves). More variation in site size increased the efficiency of all algorithms expressed in terms of total area of selected sites. We measured the suboptimality of heuristic algorithms as the percentage increase of their results over optimal (minimum possible) results. Suboptimality is a measure of the reliability of heuristics as indicative costing analyses. Higher rarity reduced the suboptimality of heuristics (increased their reliability) and there is some evidence that more size variation did the same for the total area of selected sites. We discuss the implications of these results for the use of reserve selection algorithms as indicative and real-world planning tools.

Work domain analysis for training-system definition and acquisition

Training-needs analysis is critical for defining and procuring effective training systems. However, traditional approaches to training-needs analysis are not suitable for capturing the demands of highly automated and computerized work domains. In this article, we propose that work domain analysis can identify the functional structure of a work domain that must be captured in a training system, so that workers can be trained to deal with unpredictable contingencies that cannot be handled by computer systems. To illustrate this argument, we outline a work domain analysis of a fighter aircraft that defines its functional structure in terms of its training objectives, measures of performance, basic training functions, physical functionality, and physical context. The functional structure or training needs identified by work domain analysis can then be used as a basis for developing functional specifications for training systems, specifically its design objectives, data collection capabilities, scenario generation capabilities, physical functionality, and physical attributes. Finally, work domain analysis also provides a useful framework for evaluating whether a tendered solution fulfills the training needs of a work domain.

Parent training skills and methadone maintenance: clinical opportunities and challenges

Children raised in substance abusing families show high rates of behavioural and emotional problems, in particular oppositional, defiant and non-compliant behaviours. While a range of social and individual factors correlate with poor parenting, it is often the quality of the parent-child relationship that mediates the effects of most other risk factors on child development. By addressing this relationship using behavioural family interventions, child behaviour problems have been reduced in multiple problem families. However, there has been little attempt to systematically evaluate such programs in substance abusing families. It is argued that methadone replacement programs provide a window of opportunity to deliver well-validated parent training programs that enhance the quality of parent-child relations. However, it is likely that such programs would need to be medium to long term and address issues beyond parent child relationships. How such interventions may be delivered and evaluated is discussed. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.

Syndrome packets and health worker training improve sexually transmitted disease case management in rural South Africa: randomized controlled trial

Background: Sexually transmitted diseases (STD) are important co-factors in HIV transmission. We studied the impact of health worker training and STD syndrome packets (containing recommended drugs, condoms, partner notification cards and information leaflets) on the quality of STD case management in primary care clinics in rural South Africa. Methods: A randomized controlled trial of five matched pairs of clinics compared the intervention with routine syndromic management. Outcomes were measured by simulated patients using standardized scripts, and included the proportion given recommended drugs; correctly case managed (given recommended drugs plus condoms and partner cards); adequately counselled; reporting good staff attitude; and consulted in privacy. Results: At baseline, the quality of STD case management was similarly poor in both groups. Only 36 and 46% of simulated patients visiting intervention and control clinics, respectively, were given recommended drugs. After the intervention, intervention clinics provided better case management than controls: 88 versus 50% (P < 0.01) received recommended drugs; 83 versus 12% (P < 0.005) were correctly case managed; 68 versus 46% (P = 0.06) were adequately counselled; 84 versus 58% experienced good staff attitude (P = 0.07); and 92 versus 86% (P = 0.4) were consulted privately. A syndrome packet cost US$1.50; the incremental cost was US$6.80. The total intervention cost equalled 0.3% of annual district health expenditure. Interpretation: A simple and affordable health service intervention achieved substantial improvements in STD case management. Although this is a critical component of STD control and can reduce HIV transmission, community-level interventions to influence health-seeking behaviour are also needed. (C) 2000 Lippincott Williams & Wilkins.