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Joint reliability importance (JRI) of components is the effect of a change of their reliability on the system reliability. The authors consider two coherent multi-component systems – a series-in-parallel (series subsystems arranged in parallel) and a parallel-in-series (parallel subsystems arranged in series) system. It is assumed that all the components in the subsystems are independent but not identically distributed. The subsystems do not have any component in common. The paper aims to discuss these issues.

For both the systems, the expressions for the JRI of two or more components are derived. The results are extended to include subsystems where some of the components are replicated.

The findings are illustrated by considering bridge structure as a series-in-parallel system wherein some of the components are repeated in different subsystems. Numerical results have also been provided for a series-in-parallel system with unreplicated components. JRI for various combinations of components for both the illustrations are given through tables or figures.

Chang and Jan (2006) and Gao et al. (2007) found the JRI of two components of series-in-parallel system when the components are identical and independently distributed. The authors derive the JRI of m=2 components for series-in-parallel and parallel-in-series systems when components are independent but need not be identically distributed. Expressions are obtained for the above-mentioned systems with replicated and unreplicated components in different subsystems. These results will be useful in analyzing the joint effect of reliability of several components on the system reliability. This will be of value to design engineers for designing systems that function more effectively and for a longer duration.

A least‐squares finite element analysis of viscous fluid flow together with a trajectory integration technique for tracers is formulated and provides a mechanism for investigating mixing. Tracer integration is carried out using an improved Heun predictor‐corrector. Results from our supporting numerical studies on the CRAY and Connection Machine (CM) closely resemble the patterns of mixing observed in experiments. A “box‐counting” scheme and other measures to characterize the level of mixing are developed and investigated. This measure is utilized in numerical experiments to determine an optimal forcing frequency for mixing by periodic boundary motion in a rectangular enclosure. Some details concerning the numerical schemes and vector‐parallel implementation are also included.

Presents the possibility of utilization of the textile heating element for designing protective clothing. Investigation of the textile heating element has been carried out and it has been found that a conductive woven fabric of specific resistance should not be higher than 4*10−2 (Ω*m). Physical behaviour of the heating element can be described according to Ohm's law. A number of variants of heating packs have been tested by means of thermovision. Attention was paid to the problem of ensuring an appropriate distribution of temperatures on the inner side of clothing and obtaining a possible low temperature on the outside of clothing. A model of the system, body/heated clothing/environment, has been developed, making assumptions related to: the structure and physiology of the body; the structure of clothing and properties of materials; outer climatic conditions. Clothing prototypes were subjected to laboratory tests to verify correctness of the assumptions concerning both the heating system construction and the active clothing designing. The laboratory and functional investigations of active clothing have been positively verified by the developed model. Garments so designed are absolutely safe for the user and protects him efficiently against cooling‐down during his stay in a low temperature environment.

The purpose of this paper is to report the system solution expressed in the form of a block diagram. In this paper, a multi-functional demonstrator of the interactive system designed to modelling, monitoring and validation of hybrid photovoltaic (PV) systems assisted by fuel cells and thermoelectric generators is presented. Technical parameters of demonstrator components such as: silicon PV modules, fuel cells, thermoelectric generators, gel batteries, control and monitoring systems are described.

The design shows the implementation of PV system modelling by four universal PV module simulators supported by two 65 W fuel cell and 12 modules, 6 W thermoelectric generators battery.

The paper provides practical proof that the combination of PV technology with both thermoelecric generators and fuel cells technologies shows promising results for the development of hybrid PV systems with increased effectiveness and efficiency.

The design idea can be developed for many applications gaining electricity from many distributed sources of wasted energy.

In practice, hybrid systems can be used to support the operation of classic PV systems, for example, working in various climatic conditions.

The proposed model demonstrates new technical solution leading to the enlargement of the PV systems application.

Are the learning procedures of genetic algorithms (GAs) able to generate optimal architectures for artificial neural networks (ANNs) in high frequency data? In this experimental study, GAs are used to identify the best architecture for ANNs. Additional learning is undertaken by the ANNs to forecast daily excess stock returns. No ANN architectures were able to outperform a random walk, despite the finding of non-linearity in the excess returns. This failure is attributed to the absence of suitable ANN structures and further implies that researchers need to be cautious when making inferences from ANN results that use high frequency data.

The purpose of this paper is to propose a stochastic optimisation model for integrating service and maintenance policies in order to solve the queuing problem and the cost of maintenance activities for public transport services, with a particular focus on urban ropeway system.

The authors adopt the following approaches: a discrete-event model that uses a set of interrelated queues for the formulation of the service problem using a cost-based expression; and a maintenance model consisting of preventive and corrective maintenance actions, which considers two different maintenance policies (periodic block-type and age-based).

The work shows that neither periodic block-type maintenance nor an age-based maintenance is necessarily the best maintenance strategy over a long system lifecycle; the optimal strategy must consider both policies.

The maintenance policies are then evaluated for their impact on the service and operation of the transport system. The authors conclude by applying the proposed optimisation model using an example concerning ropeway systems.

This is the first study to simultaneously consider maintenance policy and operational policy in an urban aerial ropeway system, taking up the problem of queuing with particular attention to the unique requirements public transport services.

The purpose of this paper is to present the use of the compensation theorem (CT), well known in the analysis of linear electric networks, to compute sensitivity of the performance functions used in the robust design or tolerance analysis of electromagnetic devices.

The CT is first illustrated in the case of a simple field analysis problem. Then, using numerical simulations, the effectiveness of compensation approach for assessing impact of the small modification of material properties is shown. The numerical simulations are performed with a finite elements code based on an integral formulation.

The complexity of additional computations to assess the effect of small variations involved in sensitivity analysis can be reduced.

The method can be applied only to linear systems; in addition, although compensation applies to any variations, the reduction of computational complexity is achieved only for small variations, giving localized effects.

The method proposed in the paper can speed up the computations of sensitivity arrays in the robust design and tolerance analysis of electromagnetic device, when numerical methods are applied.

The use of CT in field computations is not new, but its adoption in the sensitivity computation is new to the best knowledge of authors.

IN recent issues we have had contributionsion the future of Work Study as seen by Council members of the Institute of Industrial Technicians, the Society of Industrial Engineers and the Work Study Society.

A conceptual model of health care, a theory of quality improvement in health care and the role of patient, physician and employee judgements as part of organisation‐wide improvement are introduced. The conceptual model of health care shows how the practitioner, the locus of care‐giving and the social context interact to meet the needs of patients and highlights potential sources of unwanted variation in outcomes. This theory of quality improvement stresses the continuous improvement of processes throughout the entire organisation to meet the needs and expectations of customers. Basic building blocks for continuous improvement ‐ knowledge of customers, knowledge of work as processes, and statistical and scientific thinking ‐ are discussed along with the need to transform the entire organisation. A method for gaining customer knowledge and for monitoring hospital quality, based on measuring quality from patients′, physicians′, and employees′ judgements of quality, is introduced. The method, called the Hospital Quality Trend (HQT) family of quality measures, is described and its uses to promote organisation‐wide quality improvement are illustrated. Health care work is complex and unique. Careful analysis of the way that work is done and knowledge of the customers in defining and improving quality is essential for achieving better quality and value from the health care system.