Electrospinning of poly(dimethyl siloxane) by sol–gel method

Crosslinked poly(dimethyl siloxane) (PDMS) fibers were fabricated by electrospinning in combination with a sol–gel process followed by heat treatment. Before and after heat treatment, the changes in the chemical and thermal properties of the electrospun PDMS fibers were examined by differential scanning calorimetry (DSC), equilibrium swelling tests, and contact angle measurements. There was no significant change in morphology and average diameter of the as‐spun PDMS fibers after heat treatment. The tensile properties of the as‐spun PDMS fibers mat increased with increasing heat treatment temperature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Mass Transfer Enhancement in Double‐Pass,Parallel‐Plate Mass Exchangers under Asymmetric Wall Fluxes

A device involving mass exchangers with a permeable membrane inserted to divide the open duct into two subchannels for conducting double‐pass laminar countercurrent operations under asymmetric wall mass fluxes, which results in a substantial improvement of the mass transfer, has been developed and investigated theoretically. The resultant partial differential equations for such a double‐pass forced‐convection mass transfer problem are referred to as conjugated Graetz problems and solved analytically in this work by using an eigenfunction expansion in terms of power series for the homogeneous part and an asymptotic solution for the inhomogeneous part. The theoretical predictions of mass transfer efficiency improvement in double‐pass, parallel‐plate mass exchangers are obtained by suitably adjusting the permeable membrane location. They are represented graphically and compared with the results from an open duct of a single‐pass operation (without a permeable membrane inserted). The increment of power consumption is also discussed.     

人工神经网络和模式识别

80年代重新兴起的人工神经网络已成为世界人工智能研究的热门课题之一。本文介绍了人工神经网络的一般结构及其算法,着重介绍人工神经网络在模式识别方面的作用及用作模式识别的人工神经网络分类器。希望能给读者了解这一当今世界科学前沿热门课题起一介绍作用。     

盐酸直接浸取钛铁矿制取人造金红石

研究了盐酸直接浸取钛铁矿制取金红石的方法，探讨了搅拌条件、盐酸浓度、浸取时间、温度、矿粉粒度对浸取效果的影响，利用Ｘ－粉末衍射证明所得产物实现了由锐钛型至金红石型的转型，得到了浸取过程的最佳工艺条件为盐酸浓度６．２７ｍｏｌ／Ｌ；浸取温度１１０℃；液固比４：１（质量）；颗粒粒径３００目以下     

体心立方Ising模型的Green函数方法处理

本文利用Ｇｒｅｅｎ函数技术，严格处理了体心立方Ｉｓｉｎｇ模型的Ｈａｍｉｌｔｏｎ量，得到了可以递推的自旋综合平均值的代数方程。根据该方程，并利用前文的递推原则和切断近似，可以得到体心立方Ｉｓｉｎｇ模型的转变温度、自发磁化等。     

An acoustic diagnostic technique for use with electric machineinsulation

Many of the electrical failures of large electric machines have mechanical precursors. This premise has led to the attempts described here to detect mechanical changes, such as groundwall delamination, by acoustic methods as a means of early detection of incipient failure. By optimally launching an ultrasonic wave into a stator bar and using the conductor as a waveguide, it has been shown possible to interrogate the groundwall insulation and the critical interface region adjacent to the conductor. Laboratory studies using an epoxy mica stator bar subjected to thermal cycling have demonstrated that the acoustic signatures obtained with this method are mirrored by conventional corona spectroscopy conducted simultaneously, although earlier damage is clearly discernible. Based on the results of this study, the acoustic technique appears to have substantial promise as an advanced detection tool     

TECHNOLOGICAL RESEARCH OF THE SYNTHESIS OF BaTiO_3 POWDERS BY TI(O~nBu)_4-Ba(OAc)_3HYDROLYSIS

The paper stresses to study the process andparameters of preparation in the synthisis of high pure and ul-trafine BaTiO_3 powders by Ti(O~nBu)_4—Ba(OAc)_2 hydrolysis.Characters of BaTiO_3 powdrs synthesised in differential condi-tions are tested and analysed by mean of TG-DAT,XRD,TEM,SAXS and ICP-AES.Their laws are discovered.TheBaTiO_3 powders with Purity of 99.80wt% and surface area of68m~2/g,primary particles of awerage diameter of 46.7nm,sec-ondary particles(laggregates)of diameter ranging between 20～30nm are prepared by the method.     

C_2液相加氢用固定床鼓泡反应器的适宜操作区

本文以氢气为气相介质、甲苯为液相介质。研究了:气液通过φ39固定床鼓泡反应器时。反应器内流体的流动状态,确定了适宜的操作区,以便应用于碳二液相催化选择性加氢脱炔工艺研究。     

Determination of longitudinal dispersion coefficient and net advection in the tidal hudson river with a large-scale,high resolution SF6 tracer release experiment

Physical processes such as advection, dispersion, and air-water gas exchange play important roles in determining the movement and change in concentration of contaminants discharged into rivers. In the following, we report results from a large-scale SF6 tracer release experiment conducted in the tidal Hudson Riverto examine longitudinal dispersion and net advection. SF6 was injected into the Hudson River near Newburgh, NY, and surveyed for 13 days using a new, fully automated, high-resolution SF6 sampling and analysis system. Net down river advection of the water body originally tagged with SF6 was slow, averaging mean displacement rates of about 0.5 +/- 0.2 km d(-1). In contrast, spreading of the tracer was driven by tidal movement, causing rapid mixing of the water up and down river. By examining the change in the second moment of the tracer distribution with time, we determined the mean longitudinal dispersion coefficient to be 70.1 +/- 4.3 m2 s(-1). Temporal evolution of the SF6 inventory indicates an average gas transfer velocity over the period of the experiment of 6.5 +/- 0.5 cm h(-1) (1.56 +/- 0.12 m d(-1)). Vertical profiles show that mixing into the bottom layers of the river, in places reaching more than 53 m, seemed to be rapid.     

Hematological changes of children exposed to volatile organic compounds containing low levels of benzene

A high performance liquid chromatographic (HPLC) method was developed to determine the concentration of diflubenzuron, a delousing agent used in fish farming, in marine mud and shell sand. The recovery of diflubenzuron from mud was 100.8+/-1.1% and 105.5+/-4.3% for shell sand. The limit of quantitation was found to be 0.1 microg g(-1). The stability of diflubenzuron was studied under laboratory conditions in marine sediments at different temperatures (4 and 14 degrees C). No degradation of diflubenzuron occurred in the organic rich mud sediment or in the shell sand sediment during the experimental period of 204 days. Increasing the temperature from 4 to 14 degrees C had no effect on the stability. Furthermore, diflubenzuron showed to be persistent in both mud and shell sand sediment since no detectable diffusion from the sediment to the water phase occurred during the experimental period of 204 days. Increasing the water current in the tanks had no effect on the persistence. Under field conditions, the concentrations of diflubenzuron found in the organic material from sediment traps placed 2 m from the bottom under the cage in a fish farm during medication were high and ranged from 71 to 259 microg g(-1). The concentrations of diflubenzuron in the sediment under the fish farm were, however, low, with a maximum concentration of 5.4 microg g(-1). The dispersion of diflubenzuron to the sediment was limited to less than 20 m from the edge of the cage in every direction. Fifteen months following the medication, only traces (< 0.1 microg g(-1)) of diflubenzuron were detected in the sediment under the fish farm. Possible explanations for this decrease are resuspension and redistribution of sediment and/or oxic degradation of the drug.