On the optimal characteristics of a memoryless power amplifier system

The performance of the piecewise linear limiter with multi-carrier input signal with arbitrary carrier amplitudes is analysed by using a simple, accurate and general approach. The limiter characteristic is expanded as an infinite Fourier series and convergent series expressions are obtained for the output carriers and intermodu-lation products. The special case of an input consisting of two equal-amplitude carriers is considered in detail and the results are found to be very accurate. This result will help in deciding whether the piecewise linear limiter will produce optimal or suboptimal results under specific traffic and criterion of optimality.     

Improvement in tensile properties of PVC–montmorillonite nanocomposites through controlled uniaxial stretching

In this paper we present the results exhibiting an improvement in the tensile properties of polyvinyl chloride (PVC)?Cmontmorillonite nanocomposites through uniaxial stretching. The clay was dispersed in PVC matrix with the help of dodecylamine. PVC?Cmontmorillonite nanocomposites films containing varying amounts of clay (0?C5%) were produced through solution elution technique. The films were stretched uniaxially at a constant temperature of 80?°C in three different steps using controlled loads. X-ray diffraction and stress?Cstrain curves were obtained for both unstretched and stretched films in order to determine the improvement in various properties. The controlled uniaxial stretching of films close to the softening temperature of PVC has resulted in enhancement in the degree of crystallinity in the nanocomposites. This improvement in the structural order has also imparted increase in tensile strength and Young??s modulus of the nanocomposite films.     

基于二象限APF的单相功率因数校正器

为消除单相整流装置产生的谐波,提出了一种基于二象限有源滤波器(APF)的单相功率因数校正器,包括其主回路拓扑与控制策略。使用T型拓扑可滤除高次谐波,在主回路加装二极管可削减有源滤波器电流峰值,并在控制回路中使用双前馈以实现快速响应。对该拓扑和控制方案进行了Matlab仿真,并设计了基于dsPIC33F系列数字控制器的实验样机。仿真和实验结果均表明该技术可在降低成本的情况下,仍将功率因数提升至99%。     

MWCNTs/SWCNTs Nanofluid Thin Film Flow over a Nonlinear Extending Disc: OHAM Solution

The aim of this research is the improvement towards the consumption of energy in the field of engineering and industry. The efforts have been paid to the enhancement of heat transmission and cooling process through a nanofluid coating of a nonlinear stretching disc. The combination of Water(H2 O) and multiple walled carbon nanotubes(MWCNT)/single walled carbon nanotubes(SWCNT) have been used as a nanofluid. The spreading of a thin nano-layer with variable thickness over a nonlinear and radially stretching surface has been considered. The estimated results of the problem have been accomplished using the Optimal Homotopy Analysis Method(OHAM). The residual errors of the OHAM method have been shown physically and numerically. The important physical parameters of skin friction and Nusselt number have been calculated and discussed. The other embedding parameters like generalized magnetic parameter, Prantl number, nanofluid volume fraction and Eckert number have been intended and discussed. The obtained results have been compared with the Numerical(ND-Solve) method for both sorts of CNTs. The closed agreement of both methods has been achieved.     

Plum Juice Quality Affected by Enzyme Treatment and Fining

Juice from six plum (Primus domestica L.) cultivars, Au Red, Abundance, Pobeda, Shiro, Peach Plum and Early Golden, was extracted using 0.2% Clarex® L pectinase. The juice was processed as high temperature-short time (HTST)-unfined juice, fined juice or HTST-fined juice, and analyzed for yield, clarity, pectin content, soluble solids, pH, titratable acidity, color, sugars, total anthocyanins and total phenolics. Pectinase treatment resulted in 41–214% increase in juice yields, with highest increase for Au Red. Enzyme-extracted juice averaged 54% lower pectin than controls, and fining further reduced pectin. Enzyme treatment also improved juice soluble solids and color. A consumer type sensory panel indicated juice from Abundance, Pobeda and Peach Plum had best flavor and acceptability.     

盐岩渗透特性的试验研究及其在深部储气库中的应用

为给深部盐岩地层(≥1 500 m)中所建天然气储库的稳定性和密闭性评价提供科学指导,针对取自江苏金坛的不同杂质含量盐岩试样,在荷兰乌德勒支大学HPT实验室开展了在三轴压缩条件下的瞬态法渗透率测试研究,揭示盐岩的变形特征与渗透率演化规律.试验研究表明:在围压20 MPa的常温测试条件下,随着偏应力从0～40MPa递增,损伤后的低含泥盐岩的渗透率从10-16 m2逐渐下降至10-21 m2以下,而损伤后的高含泥盐岩的渗透率则平均高出前者1～2个量级,推测表明损伤后的盐岩在加载下裂纹闭合、孔隙减小、逐渐压缩密实,进而渗透率快速降低,同时也表明外载压密作用对纯盐岩的裂纹压缩闭合、甚至损伤修复作用更显著.根据试验成果,并利用H.Alkan等[11]建立的盐岩压缩-扩容边界线对位于1 500～2 000 m深部的盐岩地层中的球形腔体的围岩应力状态分析显示,围岩几乎都位于扩容边界以下的安全区域,由此推知:即使在储气库低压运行条件下,围岩中较难发生扩容而导致密闭性失效事件发生,腔体的密闭性能极好.该研究为深部盐穴储气库的可行性和密闭性评价提供有利支撑.     

Microscopic model for chemical etchability along radiation damage paths in solids

It would be very interesting to develop a picture about removal of atoms from the radiation damaged paths or latent nuclear tracks and undamaged bulk material in track detectors. Here, theory of chemical etching is described briefly and a new model for chemical etching along radiation damaged paths in solids is developed based on basic scientific facts and valid assumptions. Dependence of chemical etching on radiation damage intensity and etching conditions is discussed. A new parameter for etching along radiation damaged paths is introduced, which is useful for investigation of relationship between chemical etchability and radiation damage in a solid. Results and discussion presented here are also useful for further development of nuclear waste immobilization.