Blind source separation by nonstationarity of variance: acumulant-based approach

Blind separation of source signals usually relies either on the nonGaussianity of the signals or on their linear autocorrelations. A third approach was introduced by Matsuoka et al. (1995), who showed that source separation can be performed by using the nonstationarity of the signals, in particular the nonstationarity of their variances. In this paper, we show how to interpret the nonstationarity due to a smoothly changing variance in terms of higher order cross-cumulants. This is based on the time-correlation of the squares (energies) of the signals and leads to a simple optimization criterion. Using this criterion, we construct a fixed-point algorithm that is computationally very efficient.     

Characterizing Mold Problem Buildings – Concentrations And Flora Of Viable Fungi

The purpose of this study was to characterize mold problem buildings by determining concentrations and flora of viable fungi. The composition and concentrations of fungal flora in mold problem (n = 9) and reference buildings (n = 9) were determined by means of four different sampling methods: six-stage impactor (Andersen sampler), sedimentation plate, surface and house dust samples. Samples were taken in the fall and in the winter, and the concentrations and flora in mold problem buildings were compared with those of matched reference buildings. The differences between mold problem and reference buildings were most clearly seen with the impactor samples. The total concentrations of airborne fungi were higher in moldy buildings. In addition, the concentrations of the genera Aspergillus and Oidiodendron in the fall and the concentrations of Aspergillus and Penicillium in the winter were higher in mold problem than in reference buildings. In the winter, certain fungal genera (Stachybotrys, Acremonium, Oedocephalum and Botryosporium) were detected only in the problem buildings in impactor samples. These results indicate that there may be an unusual composition of fungal flora in mold problem buildings. The results of the sedimentation plate samples showed a trend similar to that of impactor samples in the winter. In addition, the results of surface samples supported the data on the fungal flora in the winter-time air samples. The house dust samples did not reveal any differences between mold problem and matched reference buildings.     

奥托昆普湿法炼铜法

奥托昆普公司提出了由硫化铜精矿湿法炼铜的新工艺,即:用氢氧化钠由净化后的浸出母液中沉淀出氧化亚铜;在氯—碱电解槽中再生氢氧化钠;氯碱电解的其它产物(Cl2、H2)也在工艺中循环利用:氯气送精矿浸出,氢气送氧化亚铜的还原,将氧化亚铜还原为金属铜。从氯化物溶液中电积铜容易形成树枝状的铜结晶,一定程度上使得隔膜电解槽的操作变得复杂。奥托昆普湿法炼铜工艺克服了这个缺陷。     

Fast and robust fixed-point algorithms for independent componentanalysis

Independent component analysis (ICA) is a statistical method for transforming an observed multidimensional random vector into components that are statistically as independent from each other as possible. We use a combination of two different approaches for linear ICA: Comon's information theoretic approach and the projection pursuit approach. Using maximum entropy approximations of differential entropy, we introduce a family of new contrast functions for ICA. These contrast functions enable both the estimation of the whole decomposition by minimizing mutual information, and estimation of individual independent components as projection pursuit directions. The statistical properties of the estimators based on such contrast functions are analyzed under the assumption of the linear mixture model, and it is shown how to choose contrast functions that are robust and/or of minimum variance. Finally, we introduce simple fixed-point algorithms for practical optimization of the contrast functions     

Temperature rises in an OFAF transformer at OFAN cooling mode in service

In order to properly assess operating conditions of a 40 MVA, oil-forced air-forced (OFAF) transformer unit in service the permanent online monitoring system has been upgraded. Dissolved gas analysis laboratory measurements are also applied. The hot-spot temperature and the top-oil temperature responses predicted by two different thermal methods are compared to measured values.