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791.
工业闪光灯大量应用于智能交通工程,直接由交流220V供电,为达到宽场景、高亮度,需要使用较大电解电容,充电过程中限流电阻消耗功率较大,合适的电阻功率选取对于闪光灯可靠性和寿命有着决定性影响。由于输入信号是正弦波,半波充电过程非恒流或恒压,电阻功率计算比较复杂。通过积分方法,求得了闪光灯充电限流电阻的最大功率和最大电流,并得到了实物测量验证,产品可靠性得到了很好保证。 相似文献
792.
《Journal of Coordination Chemistry》2012,65(7):843-852
Four manganese(III) complexes, [Mn(salMeDPT)(O 2 CMe)] 1 , [Mn(salMeDPT)Cl]·MeCN 2 , [Mn(salEDPA)] Cl 3 and [Mn(salEDPA)](MeCO 2 ) 4 have been prepared, where the di-Schiff-base salMeDPT and salEDPA were from the (2 + 1) condensation of salicylaldehyde with 4-methyl-4-azaheptane-1,7-diamine and with 4,7-diazadecane-1,10-diamine, respectively. The four complexes have been characterized by elemental analyses and cyclic voltammetry, while complexes 1 - 3 have also been characterized by single-crystal x-ray diffraction, which reveals all the Mn(III) atoms in these complexes adopt slightly compressed octahedra with the Mn-O and Mn-N bond lengths in ranges 1.882(3)-1.890(3) and 2.021(4)-0.546(4) Å, respectively. The results of activity assay indicate that complexes 1 - 4 have moderate superoxide dismutase activities. 相似文献
793.
《Journal of Coordination Chemistry》2012,65(5):587-593
The rate constant for the basic hydrolysis of benzonitrile (PhCN) to benzamide (PhCONH2) in the [RuII(tpy)(bpy)] moiety (tpy = 2,2' : 6',2"-terpyridine, bpy = 2,2'-bipyridine) (kOH = 3.7 2 10-2 M-1s-1) is 5 2 103 times higher than that of the free ligand and two times higher than that corresponding to the analogous acetonitrile complex. This effect is unusual for a transition metal in the (II) oxidation state, and can be attributed to the π-electron acceptor properties of both the polypyridyl ligands and the phenyl group. Since amides, being poor π-acceptor ligands, are rapidly released from the coordination sphere of ruthenium(II), the final product of this process is the [Ru(tpy)(bpy)(OH)]+ complex. The activation parameters for this nitrile hydrolysis have been determined and compare reasonably well with other values for similar reactions. 相似文献
794.
在电路分析中,以经典电路理论探讨非线性电阻电路的问题。针对某些可以分段线性化的非线性电阻电路,当以曲线形式给出非线性电路的伏安特性时,探讨在凹电阻和凸电阻作基本积木块的方式下,依据电路KVL和KCL定律,运用串联分解法和并联分解法,分解拟合出满足分段线性要求的非线性电阻电路。通过对案例的仿真研究和误差分析,论证此方法在分析非线性电阻电路分段线性时,能比较方便地逆向解决以电路的伏安特性曲线完成实际电路的设计问题。 相似文献
795.
796.
通过对通信基站电源设备防护原理的介绍,系统地分析了当前通信基站普遍存在的季节性电源设备大量毁损的原因,同时,结合维护实践提出新的技术解决方案。 相似文献
797.
798.
从EPON承栽TDM业务的原理出发,结合CDMA基站业务承载的技术要求和现实需求,提出了通过EPON进行CDMA基站业务承载的方案,以解决CDMA基站业务承载、室内覆盖业务承载及今后Femtocell业务承载的需求. 相似文献
799.
Tuğba Horzum Erhan Ertekin 《International Journal of Mathematical Education in Science & Technology》2018,49(2):176-199
The purpose of this study is to analyze what kind of conceptions prospective mathematics teachers1(PMTs) have about the base concept2(BC). One-hundred and thirty-nine PMTs participated in the study. In this qualitative research, data were obtained through open-ended questions, the semi-structured interviews and pictures of geometric figures drawn by PMTs. As a result, it was determined that PMTs dealt with the BC in a broad range of seven different images. It was also determined that the base perception of PMTs was limited mostly to their usage in daily life and in this context, they have position-dependent and word-dependent images. It was also determined that PMTs named the base to explain the BC or paid attention to the naming of three-dimensional geometric figures through the statement: ‘objects are named according to their bases’. At the same time, it was also determined that PMTs had more than one concept images3which were contradicting with each other. According to these findings, potential explanations and advices were given. 相似文献
800.
We present the case of a Greek commercial enterprise facing the problem of managing the inventories of thousands of different items, supplied by more than 20 European and Asian manufacturers and sold to a large number of different-type customers. A key feature of the problem is that the demand for the vast majority of items is intermittent and lumpy, thus not allowing the use of the usual normal or Poisson distributions. The paper describes the solutions given to several practical problems in the course of developing an easy-to-use yet effective and all-encompassing inventory control system. Emphasis is placed on the accurate modeling of demand by means of a gamma distribution with a probability mass at zero or a package Poisson distribution for very-slow-moving items. Using those models and simple quantitative tools we develop an efficient procedure for approximate but quite accurate determination of the base stock levels that achieve the desired fill rates in the proposed periodic review system. We briefly describe the computerized implementation of the new system and the very encouraging results. 相似文献