Evaluating design proposals for complex systems with work domain analysis

In this paper we propose a new framework for evaluating designs based on work domain analysis, the first phase of cognitive work analysis. We develop a rationale for a new approach to evaluation by describing the unique characteristics of complex systems and by showing that systems engineering techniques only partially accommodate these characteristics. We then present work domain analysis as a complementary framework for evaluation. We explain this technique by example by showing how the Australian Defence Force used work domain analysis to evaluate design proposals for a new system called Airborne Early Warning and Control. This case study also demonstrates that work domain analysis is a useful and feasible approach that complements standard techniques for evaluation and that promotes a central role for human factors professionals early in the system design and development process. Actual or potential applications of this research include the evaluation of designs for complex systems.

3D reconstruction and quantification of macropores using X-ray computed tomography and image analysis

Axial X-ray Computed tomography (CT) scanning provides a convenient means of recording the three-dimensional form of soil structure. The technique has been used for nearly two decades, but initial development has concentrated on qualitative description of images. More recently, increasing effort has been put into quantifying the geometry and topology of macropores likely to contribute to preferential now in soils. Here we describe a novel technique for tracing connected macropores in the CT scans. After object extraction, three-dimensional mathematical morphological filters are applied to quantify the reconstructed structure. These filters consist of sequences of so-called erosions and/or dilations of a 32-face structuring element to describe object distances and volumes of influence. The tracing and quantification methodologies were tested on a set of undisturbed soil cores collected in a Swiss pre-alpine meadow, where a new earthworm species (Aporrectodea nocturna) was accidentally introduced. Given the reduced number of samples analysed in this study, the results presented only illustrate the potential of the method to reconstruct and quantify macropores. Our results suggest that the introduction of the new species induced very limited chance to the soil structured for example, no difference in total macropore length or mean diameter was observed. However. in the zone colonised by, the new species. individual macropores tended to have a longer average length. be more vertical and be further apart at some depth. Overall, the approach proved well suited to the analysis of the three-dimensional architecture of macropores. It provides a framework for the analysis of complex structures, which are less satisfactorily observed and described using 2D imaging. (C) 2002 Elsevier Science B.V. All rights reserved.

Sequence analysis and expression of a virus-like particle protein,VLP2, from the parasitic wasp Venturia canescens

Endoparasitoid wasps produce maternal protein secretions, which are transported into the body of insect hosts at oviposition to regulate host physiology for successful development of their offspring. Venturia canescens calyx fluid contains so-called virus-like particles (VLPs) that are essential for immune evasion of the developing parasitoid inside the host. VLPs consist of four major proteins. In this paper, we describe the isolation and molecular cloning of a gene (vlp2) that is a constituent of VLPs and discuss its possible role in VLP structure and function.

Causes of communication problems at work: A qualitative analysis of supervisor-subordinate differences

This study provided information about how individual workers perceive, describe and interpret episodes of problematic communication. Sixteen full-time workers (5 males, 11 females) were interviewed in depth about specific incidents of problematic communication within their workplace. Their descriptions of the attributed causes of the incidents were coded using a categorisation scheme developed from Coupland, Wieman, and Giles' (1991) model of sources of problematic communication. Communication problems were most commonly attributed to individual deficiency and group membership, although there were differences depending on the direction of communication. The most negative attributions (to personality flaws, to lack of skills, and to negative stereotypes of the outgroup) were most commonly applied by individuals to their supervisors, whilst attributions applied to co-workers and subordinates tended to be less negative, or even positive in some instances (where individuals attributed the fault to themselves). Overall, results highlighted distinctions between the perceptions of communication problems with supervisors and with subordinates, and are interpreted with reference to social identity theory.

Nonoxynol-9 spermicide for prevention of vaginally acquired HIV and other sexually transmitted infections: systematic review and meta-analysis of randomised controlled trials including more than 5000 women

We aimed to determine the effectiveness of the vaginally administered spermicide nonoxynol-9 (N-9) among women for the prevention of HIV and other sexually transmitted infections (STIs), We did a systematic review of randomised controlled trials, Nine such trials including 5096 women, predominantly sex workers, comparing N-9 with placebo or no treatment, were included. Primary outcomes were new HIV infection, new episodes of various STIs, and genital lesions. Five trials included HIV and nine included STI outcomes, and all but one (2% of the data) contributed to the meta-analysis. Overall, relative risks of HIV infection (1.12, 95% confidence interval 0.88-1.42), gonorrhoea (0.91, 0.67-1.24), chlamyclia (0.88, 0.77-1.01), cervical infection (1.01, 0.84-1-22), trichomoniasis (0.84, 0.69-1.02), bacterial vaginosis (0.88, 0.74-1.04) and candidiasis (0.97, 0.84-1.12) were not significantly different in the N-9 and placebo or no treatment groups. Genital lesions were more common in the N-9 group (1.18, 1.02-1.36). Our review has found no statistically significant reduction in risk of HIV and STIs, and the confidence intervals indicate that any protection that may exist is likely to be very small. There is some evidence of harm through genital lesions. N-9 cannot be recommended for HIV and STI prevention.

Undergraduate student experience in dental service delivery in rural South Australia: An analysis of costs and benefits

Background, Rural experience for dental students can provide valuable clinical education, change attitudes to rural practice, and make a valuable contribution to clinical service provision. The aim of this paper is to assess the costs and benefits of service delivery by students through rural training programmes Methods: Groups of two students worked in the public dental clinics in adjacent rural centres where there had been long-term difficulties in recruiting staff. The costs and benefits of the programme were assessed by the impact on waiting lists, the total cost per patient of, a course of care and by the marginal cost of adding service provision by students to existing arrangements. Results: The total costs of emergency and complete treatment provided by students were greater than the costs of treatment provided by public-sector dentists but less than the costs of private providers treating public patients. However, the value of services were greater when care was provided by students or private providers and the marginal cost of students providing services was 50-70 per cent of the cost of care provided by public dentists. Conclusion: This assessment suggests that the service benefits achieved compliment the primary objective of influencing the attitude of students to rural practice.

Analysis of steady-state heat transfer through mid-crustal vertical cracks with upward throughflow in hydrothermal systems

We conduct a theoretical analysis of steady-state heat transfer problems through mid-crustal vertical cracks with upward throughflow in hydrothermal systems. In particular, we derive analytical solutions for both the far field and near field of the system. In order to investigate the contribution of the forced advection to the total temperature of the system, two concepts, namely the critical Peclet number and the critical permeability of the system, have been presented and discussed in this paper. The analytical solution for the far field of the system indicates that if the pore-fluid pressure gradient in the crust is lithostatic, the critical permeability of the system can be used to determine whether or not the contribution of the forced advection to the total temperature of the system is negligible. Otherwise, the critical Peclet number should be used. For a crust of moderate thickness, the critical permeability is of the order of magnitude of 10(-20) m(2), under which heat conduction is the overwhelming mechanism to transfer heat energy, even though the pore-fluid pressure gradient in the crust is lithostatic. Furthermore, the lower bound analytical solution for the near field of the system demonstrates that the permeable vertical cracks in the middle crust can efficiently transfer heat energy from the lower crust to the upper crust of the Earth. Copyright (C) 2002 John Wiley Sons, Ltd.

Visualization of learning in multilayer perceptron networks using principal component analysis

This paper is concerned with the use of scientific visualization methods for the analysis of feedforward neural networks (NNs). Inevitably, the kinds of data associated with the design and implementation of neural networks are of very high dimensionality, presenting a major challenge for visualization. A method is described using the well-known statistical technique of principal component analysis (PCA). This is found to be an effective and useful method of visualizing the learning trajectories of many learning algorithms such as back-propagation and can also be used to provide insight into the learning process and the nature of the error surface.

Designing teams for first-of-a-kind, complex systems using the initial phases of cognitive work analysis: Case study

We present a technique for team design based on cognitive work analysis (CWA). We first develop a rationale for this technique by discussing the limitations of conventional approaches for team design in light of the special characteristics of first-of-a-kind, complex systems. We then introduce the CWA-based technique for team design and provide a case study of how we used this technique to design a team for a first-of-a-kind, complex military system during the early stages of its development. In addition to illustrating the CWA-based technique by example, the case study allows us to evaluate the technique. This case study demonstrates that the CWA-based technique for team design is both feasible and useful, although empirical validation of the technique is still necessary. Applications of this work include the design of teams for first-of-a-kind, complex systems in military, medical, and industrial domains.