A Unified Method for Analyzing Mission Reliability for Fault Tolerant Computer Systems

A reliability model is proposed and evaluated for a fault tolerant computer system which consists of multiple classes of modules and allows for degraded modes of performance. Each module of a given class has both an active and a passive hazard rate; constant hazard rates are assumed for active and dormant failures, and the given class may operate either in N Modular Redundancy (NMR: n + 1 out of 2n + 1 = N) or as a standby sparing system. The model allows for mission-phase changes at deterministic time points when the numbers of modules per class can be changed. The analysis proceeds by generalizing the notions of standby and NMR redundancy, which for N = 3 is TMR (Triple Modular Redundancy), into a concept called hybrid-degraded redundancy. The probabilistic evaluation of the unified redundancy concept is then developed to yield, for a given modular class, the joint distribution of success and the number of nonfailed modules from that class, at special times. With this information, a Markov chain analysis gives the reliability of an entire sequence of phases (mission profile).     

Higher level programming and data abstractions—a case study using enhanced C

In this work the topological sort algorithm is programmed in EC, taking advantage of EC's set-oriented features and its macro-like data abstractions. The main issue was whether efficient run-time code could be achieved while maintaining program structure and readability. The main conclusion is that in this particular example such code was achieved. Program structure and readability were maintained despite changes in both the higher level program and the data abstractions. Other conclusions are the following: (1) The program design process requires dependent data abstractions; (2) it is iterative rather than strictly top down; choosing data abstractions for run-time efficiency requires insight into the properties of the algorithm. It is believed that global analysis can be used to enhance such insight.     

Theophylline induces diapause-like state in social wasps

Feeding of theophylline to hornet workers from their moment of eclosion during the summer results in the following effects on the hornets: loss of appetite for proteins, inhibited ovarial development, no cell-building activity, negative phototaxis, gradual slow-down of spontaneous motor activity, difficulty in flight and orientation, and an overall behavior pattern reminiscent of hornet queens in nature when they are in a state of winter diapause. These findings suggest that theophylline exerts anti-juvenile-hormone-like effects on hornets and raise the possibility of utilizing theophylline baits to suppress pest hornet populations.     

Software engineering: An example of misuse

Managers of programmers and designers are sometimes wont to adopt the new and shiny. This paper describes a situation in which managers at several levels grasped for the ‘new and shiny’ in the form of software engineering. This approach was not without its hidden dangers, especially when established guidelines were ignored or violated. The results of an experience with a large software project are reported. This project dealt with a sophisticated inventory control system. The effects on the project of ignorance and the violation of rules are described. Several measures of the final product are reported. Observations of the authors conclude the paper.     

Sandwich solutions

We review come of the latest developments in core materials and sandwich composite structures. Amanda Jacob reports.     

Cobra strikes out into industrial markets

Already a world leading manufacturer of watersports equipment, Cobra International Co Ltd is now translating its composites expertise into other markets and also aims to raise the profile of Thailand as a composites manufacturing centre. Amanda Jacob visited Cobra's headquarters in Chonburi, Thailand.     

Effect of Illite Clay and Divalent Cations on Bitumen Recovery

The adverse effect of illite clay on bitumen recovery was found to be related to its acidity. The addition of calcium or magnesium ions to the flotation deionized water had a marginal effect on bitumen recovery when measured using a Denver flotation cell. However, the co‐addition of illite clay and divalent cations caused a significant reduction in bitumen recovery. The effect was found to be compounded at a lower process temperature and low pH values. Zeta potential distributions of illite suspensions and bitumen emulsions were measured individually and as a mixture to investigate the effect of divalent cations on the interaction between bitumen and illite clay. The presence of 1 mM calcium or magnesium ions in deionized water had a significant effect on the interactions between bitumen and illite clay. Slime coating of illite onto bitumen was not observed in zeta potential distribution measurements performed in alkaline tailings water.     

International scene in remote sensing

A brief survey of the status of remote sensing or earth observations from space as applied to earth-bound resources management is made. Glimpses of space systems under execution and under planning are given. Utilisation of the remote sensing technology by developed and developing countries is reviewed, pointing out current problems and future potentials.     

A simplified buffer capacity model for sanitary landfill leachate

An initial simplified buffer capacity model for landfill leachate is postulated and compared to that of two different leachate samples from the same landfill. This equilibrium model is based on the products of anaerobic decomposition. The number of species is reduced by considering all organic acids as acetic acid. This simplification reduces the number and complexity of chemical analyses required to measure the species, and also, lessens the calculations involved.The model predicts maximum buffer capacity pH within a ΔpH = 0.35, and underpredicts the magnitude by 16%.