Production of a TiN film with nanoscale particle size by a combined method of plasma-alloy reaction and spray deposition

On leave from: Honda Research and Development Co., Ltd, Wako 351-01, Japan.     

Variable-bit-rate speech transmission using punctured convolutionalcodes

Rate (n-1)/n punctured convolutional codes are very effective in conjunction with embedded differential pulse code modulation (EDPCM) in variable-bit-rate speech transmission. The authors investigate the performance of this variable-bit-rate EDPCM system in terms of probability of bit error and audio signal-to-noise ratio (SNR) versus channel SNR in an additive white Gaussian noise and Rayleigh fading channel using soft-decision decoding for specific sets of code generators of punctured convolutional codes. The results show that different sets of code generators affect the performance in terms of both the probability of bit error and the audio SNR. Improvements were obtained in the cases of Gaussian nonfading and Rayleigh fading channels using soft-decision decoding     

A refined statistical approach to thermal fatigue life prediction

Finding new applications for ceramic materials requires a better knowledge of thermal fatigue behaviour. However, result-scattering inherent to thermal fatigue and duration of a thermal fatigue cycle lead to a lack of experimental results. For these reasons, we have developed a new approach that permits the determination of a relevant stress intensity factor exponent n with a minimum testing sample number. From knowledge of the distribution function of artificial cracks, the analytical formula of the failure probability F(N) can be completely determined. Thus, it is possible to calculate n from a correlation of F(N) with experimental results obtained for only one temperature difference. Correlations between theoretical curves F(N) and experimental results, conducted for two temperature differences, lead to the same value of n. This and the good agreement between the experimental points and the theoretical curves validate this new approach.     

The use of probability theory in fracture mechanics—A case study

A probabilistic approach to fracture mechanics in the form of a typical case study is described wherein the integrity of a high-pressure water pipeline is assessed. An analysis methodology is discussed incorporating the probability density functions of defect sizes, the statistics of defect occurrences and the statistical distribution of material properties. This method enables the analyst to supply a very simple assessment of safety, based on the probability of failure (a single number) which may be compared to accepted industrial standards (e.g. 10⁻⁶ for nuclear applications). It is argued that this method often offers the only way to scientifically and economically assess the integrity of fracture prone structures.     

Stabilization of high-impact polystyrene/ polyethylene blends

Commercial poly(styrene-b-butadiene) copolymers (SBS) can act as effective compatibilizers in blends between high-impact polystyrene (HIPS) and polyethylene (PE), allowing a fine dispersion of PE in the polystyrene matrix, with a good balance of stiffness and impact strength. However, when processed under more severe conditions (e.g. in multiple extrusions, which simulate customer's product scrap recovery), the above blends show rather poor stability and their useful properties are rapidly lost. That undesirable effect is mainly due to cross-linking of SBS, which thus looses its compatibilizing activity. A correlation has been found between the time-to-cross-linking of SBS rubber in a Brabender mixer and the rapid decay of mechanical properties. The analysis of the mixing process and the morphology examinations of the final blend sample by TEM seem to support the above hypothesis. A significant reduction of block copolymer degradation has been achieved by means of a suitable stabilization.     

Periodic precipitation in multicomponent systems

Journal of Materials Science Letters -     

Numerical and asymptotic solutions for the thermal wall jet

This paper considers the evolution of the velocity and temperature fields within a jet of fluid on a thermally insulated wall. Numerical solutions are obtained for a range of Prandtl numbers and for a class of initial velocity and temperature profiles relevant to intrusion jets observed in certain thermal cavity flows. Numerical results are compared with asymptotic solutions which describe the initial structure of the jet and its subsequent diffusion at large distances downstream.     

Failure analysis of a hot extrusion die used for Al-Li alloy processing

Al-Li alloys being developed as lighter, substitutes for conventional high strength Al alloys are to be processed by routine methods. During extrusion of a 8090 Al-Li alloy, the extrusion die container failed causing some alarm. This failed die container was analysed to examine if the failure was caused by interaction of Li diffusing out of Al-Li alloy with the carbides of die steel. The evidence, although not conclusive, is sufficient to exercise caution during such processing.     

Recursive optimal pruning with applications to tree structuredvector quantizers

A pruning algorithm of P.A. Chou et al. (1989) for designing optimal tree structures identifies only those codebooks which lie on the convex hull of the original codebook's operational distortion rate function. The authors introduce a modified version of the original algorithm, which identifies a large number of codebooks having minimum average distortion, under the constraint that, in each step, only modes having no descendents are removed from the tree. All codebooks generated by the original algorithm are also generated by this algorithm. The new algorithm generates a much larger number of codebooks in the middle- and low-rate regions. The additional codebooks permit operation near the codebook's operational distortion rate function without time sharing by choosing from the increased number of available bit rates. Despite the statistical mismatch which occurs when coding data outside the training sequence, these pruned codebooks retain their performance advantage over full search vector quantizers (VQs) for a large range of rates.