A Method for Reduced Finite Precision Effects in Parallel Filtering Echo Cancellation

The two-path algorithm is an adaptive filter algorithm based on a parallel filter structure, which has been found to be useful for line echo cancellation as well as for acoustic echo cancellation. It is well known that in finite precision arithmetic, the adaptation process of adaptive algorithms can be reduced or even halted due to finite precision effects. This paper proposes a variant of the two-path scheme where the effects of quantization are reduced, without any significant increase in complexity. The improvement is shown by simulations using bandlimited flat spectrum noise as well as real speech signals.     

Effect of Surface Roughness on the Magnetic Field Profile in the Meissner State of a Superconductor

It is well known that the London model (valid for a hard type II superconductor) predicts an externally applied magnetic field decays exponentially as a function of depth into the superconductor on a length scale λ. Direct measurements of the field profile using low energy μSR on high-Tc superconductors, such as YBa₂Cu₃ O _x measure deviations from a simple exponential decay. In particular, there is a short length scale δ close to the surface where the magnetic field does not decay. It has been proposed that this is due to surface roughness, which leads to a suppression of the order parameter near the surface. A model of surface roughness has been studied for the case of a sinusoidally modulated surface roughness on an isotropic superconductor showing that in some cases the profiles resulting from surface roughness may be qualitatively similar to the dead layer phenomena in that the field magnitude decay rate may be slowed near the surface relative to a flat interface but that for modest roughness, the quantitative value of the length over which the field decay is slowed is much smaller than the experiments measure. In this paper, we extend this work in two directions: firstly, by using atomic force microscopy data of YBa₂Cu₃ O _x crystals, we predict the expected field profiles within the context of the Isotropic London model of superconductivity given their actual surface geometry; and secondly, we consider how surface roughness could affect experimental values for λ and δ. The main finding is that roughness within an isotropic model does not produce the dead layers found in experiments on YBa₂Cu₃ O _x . However, we suggest that roughness in a highly anisotropic superconductor could account for the observed dead layer.     

Retrofit of Trangslet hydro power station

An accident in Trangslet Power Station in the fall of 1982 resulted in, among other things, flooding of the control equipment. Despite the effective cleaning up after the flooding, the reliability was not adequate and new equipment was needed. When assessing various options, Stora Power came to the conclusion that a computerized control system would be the best solution because of its ability to optimize the power production of the station. The authors describe the utility requirements for the distributed control system and experiences from implementation and operation. They also cover the control system philosophy and implemented functions. During the installed system's first four years of operation, the requirements set by Stora Power have been achieved     

Resonant tunneling permeable base transistors with high transconductance

A GaAs-based resonant tunneling permeable base transistor has been developed and evaluated at room temperature. The transistor is fabricated by overgrowing a tungsten gate placed next to an AlGaAs-GaAs-InGaAs resonant tunneling heterostructure. By changing the gate voltage, the effective conducting area of the tunnel diode can be modulated and the collector-emitter current thus controlled. Peak currents above 300 mA/mm and a maximum transconductance of 270 mS/mm have been obtained.     

The combustion toxicity controversy

As long as 20 years ago the need was considered to extend codes concerned with flammability and/or flame spread, to include combustion toxicity requirements. Due to the lack of suitable toxicity tests at that time, the added code requirements for combustion toxicity were not enforceable. Vinyl resin manufacturers have been cited as purveyors of hazardous materials which, when burned, generate a noxious toxic hazard due to the fumes they produce in a fire. Overlooked are such factors that commercial vinyl products have inherent low ignition and flame spread rates and only generate potentially toxic gases when quantities of other materials burning around them heat the vinyls to the decomposition point. In 1983 New York State commissioned a study by A. D. Little Inc. to assess the feasability of incorporating combustion toxicity requirements into building material and furnishing codes of New York State. This paper summarizes these findings, including evaluation and analysis of the data generated by the two tests selected as best meeting the seven critical criteria. Due to differnt combustion toxicity rankings provided by the two test methods, controversial and confusing interpretations reign. As a result, the author provides a four step set of recommendations.     

Genetic, genomic, and molecular tools for studying the protoploid yeast, L. waltii

Sequencing of the yeast Kluyveromyces waltii (recently renamed Lachancea waltii) provided evidence of a whole genome duplication event in the lineage leading to the well-studied Saccharomyces cerevisiae. While comparative genomic analyses of these yeasts have proven to be extremely instructive in modeling the loss or maintenance of gene duplicates, experimental tests of the ramifications following such genome alterations remain difficult. To transform L. waltii from an organism of the computational comparative genomic literature into an organism of the functional comparative genomic literature, we have developed genetic, molecular and genomic tools for working with L. waltii. In particular, we have characterized basic properties of L. waltii (growth, ploidy, molecular karyotype, mating type and the sexual cycle), developed transformation, cell cycle arrest and synchronization protocols, and have created centromeric and non-centromeric vectors as well as a genome browser for L. waltii. We hope that these tools will be used by the community to follow up on the ideas generated by sequence data and lead to a greater understanding of eukaryotic biology and genome evolution.     

Intermittent and daily smokers: two different socioeconomic patterns, and diverging influence of social participation

OBJECTIVE: To investigate socioeconomic differences in intermittent and daily smoking, and to assess the association between social participation and these two smoking behaviours. DESIGN/SETTING/PARTICIPANTS/MEASUREMENTS: A population of 11 837 individuals interviewed in 1992-94, aged 45-64 years, was investigated in this cross sectional study. A multivariate logistic regression model was used to assess socioeconomic differences in daily and intermittent smoking, adjusting for age, country of origin, previous/current diseases, and marital status. Finally, social participation as a measure of social capital was introduced in the multivariate model. RESULTS: When unskilled manual workers were compared to high level non-manual employees, odds ratios of 2.3 (95% confidence interval (CI) 1.7 to 3.0) for men and 1.9 (95% CI 1.4 to 2.5) for women were found in regard to daily smoking, but odd ratios of only 0.7 (95% CI 0.4 to 1.2) for men and 1.3 (95% CI 0.7 to 2.4) for women were found in regard to intermittent smoking. A decrease in the daily smoking odds ratios was found when social participation was introduced in the model, while the odds ratios regarding intermittent smoking were unaffected. CONCLUSIONS: There were no socioeconomic differences in intermittent smoking and no association with social participation, a result that contrasts sharply with the patterns of daily smoking. These findings have important implications for the discussion concerning social capital and preventive measures.     

Polyfluorinated compounds: past, present, and future

Interest and concern about polyfluorinated compounds (PFCs), such as perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), and an increasing number of other related compounds is growing as more is learned about these ubiquitous anthropogenic substances. Many of these compounds can be toxic, and they are regularly found in the blood of animals and humans worldwide. A great deal of research has been conducted in this area, but a surprising amount remains unknown about their distribution in the environment and how people ultimately become exposed. The utility of these compounds seems to ensure their continued use in one form or another for the foreseeable future, presenting a long-term challenge to scientists, industry leaders, and public health officials worldwide.