Use of the Precipitation Method in the Synthesis of Ceramic Pigments

The results of the synthesis of ceramic pigments using coprecipitation of hydroxides and difficultly soluble salts of multivalent metal ions are described. The specifics of the coprecipitation process and the effect of various factors on the production of the initial precipitates for subsequent synthesis of ceramic pigments are analyzed. The technology of pigment production is described. __________ Translated from Steklo i Keramika, No. 6, pp. 37 – 39, June, 2005.     

Thermal analysis of the architecture of old and new houses at Ghadames

The study suggests improvements in the design of new houses to conserve energy and enhance indoor thermal comfort. Summer temperature records show that a new house has an average indoor temperature of 35°C with the ambient average 31°C. The traditional house in the old city recorded 28°C for the same period. Winter temperatures in both types of houses were similar (12°C) when not occupied. Architectural features of the two houses were compared to identify those responsible for difference in the thermal performance. Larger exposed surface and window areas, higher overall heat transfer coefficient and weaker thermal coupling with the ground for the new houses seems to contribute to their inferior thermal performance.     

Materials technology for aerospace applications

Modern helicopter design depends on the successful combination of materials to fulfil a very wide range of critical functions. In the past few years demands from the aerospace industry have caused considerable enhancement in the favourable properties of both polymer based materials and metals. These are discussed in connection with the progressive technical evolution of helicopters and other advanced technological products from the Westland Group.     

A construction of codes with exponential error bounds on arbitrarydiscrete memoryless channels

This correspondence proposes an explicit construction of codes achieving capacity for arbitrary discrete memoryless channels. The proposed code is obtained by concatenating variable inner codes and an algebraic geometry code. Further, we clarify that the proposed code achieves the error exponent obtained by Forney for concatenated codes     

Characterisation and modelling of VBR video traffic

The impact of VBR video traffic characteristics on broadband network performance is analysed. In particular, the authors compare in a queue the behaviour of several models that adjust different statistical parameters of actual MPEG traces. It is proved that a good fit of the probability density function (PDF) is essential to approximate queuing behaviour while the effects of short range dependence (SRD) are of secondary importance and those of long range dependence (LRD) could be neglected for practical purposes if realistic scenarios, with strict QoS requirements, are considered     

Effect of rotor profiles on the torque of a switched-reluctancemotor

The authors examine effects on the torque that simple variations of the standard rotor pole face profile could have, basically from an elementary viewpoint of how the modified profiles affect the distribution and magnitude of the radial and tangential components of the flux density. It is observed that the average torque is mostly affected by changes that alter the dominant radial component, such as changes in the effective air gap length. The other observation that an increase in the average torque can also be obtained by a favorable shift in the torque versus angle characteristics by relatively simple changes of the rotor pole profile is not so well known. Such a shift that reduces the slope of the torque angle characteristic, skewing the curve towards the unaligned position, has two advantages: one is that the phase inductance is at its maximum positive slop and, hence, the maximum torque, when the phase is energized; second, the flatter inductance profile near the aligned position when the phase current is to be commutated would allow a faster drop off of the commutated current and, thus, a smaller negative torque