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21.
Makikazu Takehana Tomomichi Nishino Katsuyasu Sugawara Takuo Sugawara 《Korean Journal of Chemical Engineering》1996,13(5):538-543
Cobalt-, praseodymium-added zinc oxide varistor was prepared through a wet chemical method followed by sintering with or without
calcination. Changes in grain size, compact density, additives distribution, and voltagecurrent/ capacitance-voltage relations
were investigated for the characterization of the samples sintered at temperatures from 1473 to 1573 K without calcination
or with calcination at 773 K for 2 h. The electrical properties were compared with nhose of samples prepared by two types
of ball mill methods. The wet chemical method provided almost the same additives-distribution profile and less impurities
in comparison with the ball grinding method carried out for 10–100 h. The donor concentration and the potential-barrier height
for the samples were evaluated by Double Schottky Barrier Model. Addition of small amount of both cobalt and praseodymium
in preparation by the wet chemical method was effective for a better nonlinearity relation between voltage and current, which
has potential for a smaller sized varistor. 相似文献
22.
A scheme to randomly generate dust points on the surface of a three-dimensional (3D) object is proposed. This scheme will potentially eliminate the bias of a density of points which are approximately equally spaced on the surface, as well as eliminate possible weighting requirements for areas of higher density. This method has the potential to reduce computational effort, as fewer points might be required to define the surface area. The global trial function vector can be assigned to these dust points and then entered into the complex variable boundary element method (CVBEM) commercial code. This scheme can be applied to each piece of a system that is comprised of a connected multiple geometry. A noticeable benefit of this approach is that the same problem can be studied several times, using a new random distribution of surface points each time. The smallest error can then be determined and that run selected. The Mathematica code used to generate the scheme is attached as an appendix. 相似文献
23.
The three-parameter and two-parameter Weibull distributions are compared using 26 mechanical property data sets of fiber-reinforced polymeric (FRP) composite materials manufactured by the pultrusion process. Both strength and stiffness properties were examined. The probability distributions were compared on the basis of goodness of fit, nominal design values, and allowable load to achieve uniform reliability. It is recommended that the two-parameter Weibull distribution be used to characterize FRP composite material properties. The primary basis for this recommendation is small differences in nominal design values and small differences in allowable loads between the two-parameter and three-parameter Weibull distributions. Other supporting reasons for the recommendation are similar observed significance levels in distribution fitting, computational efficiency, and the fact that the location parameter of the three-parameter Weibull distribution is near the first order statistic. 相似文献
24.
S. A. Halsey 《Journal of the Institute of Brewing》1985,91(5):306-312
Both transmission and transflectance near infrared spectroscopy have been evaluated for the rapid analysis of beer components. Results of sufficient accuracy have been obtained for ethanol content and Original Gravity. Application of a first derivative mathematical treatment on the spectral data improved calibration equations. Better accuracy was achieved using the transmission mode compared to that using the transflectance mode. 相似文献
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26.
文章对国内外开展微区薄层电阻测试的方法进行了综述,特别对改进范德堡四探针技术方法的测试原理、测试过程与测试结果进行了论述与分析,对微区电阻测试方法的进一步发展提出了一种可操作的方法,并研制出新型四探针测试样机。 相似文献
27.
莫灿林 《浙江理工大学学报》1992,(1)
根据空间RSCR四杆机构出现特殊位置的几何特征,运用旋转变换把空间问题转换为平面问题,对实现两特殊位置运动的空间RSCR曲柄摇杆机构的图解综合法进行了探讨。 相似文献
28.
农村电网的无功功率补偿 总被引:1,自引:0,他引:1
张晓琴 《重庆科技学院学报(社会科学版)》2002,17(3):35-37
阐述农村电网无功补偿的意义 .针对农村电网和农村用户的特点 ,提出在农网改造中 ,对各级电力线路 ,以提高农村电网的功率因数 ,保证农网安全、可靠和经济运行 .和电力用户进行无功补偿的方法 相似文献
29.
30.
讨论比较了现有内燃机节油率计算方法的优缺点、产生误差的原因,提出了采用曲线拟合的方法求取率的新方法。文中给出了计算公式和计算步骤,通过编制计算机程序,计算了几种典型发动机的节油率指标,并传统的按度试验数据逐点计算方法进行了对比,证明此方法是一种比较客观、科学的节油率指标计算方法。 相似文献