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41.
提出了一种微波衰减器脉冲功率容量的测试方法,该方法可概括为利用定向耦合器组测试比对法,测试系统主要由微波源、定向耦合器组、衰减器、检波器及示波器等器件及设备组成。选取了广泛应用于高功率微波测试系统的波导衰减器及同轴衰减器进行了功率容量测试。初步测试结果表明:在X波段,对于μs量级脉冲宽度的单脉冲,衰减材料为羟基铁的BJ-100矩形波导式衰减器的脉冲功率容量可达50 kW,厚膜电阻为衰减材料的N型接头的同轴式衰减器的功率容量可达10 kW以上。 相似文献
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针对产业集群创新能力评价的一些复杂方法,以文献中的基于BP神经网络的产业集群创新能力评价模型作为比较对象,提出了两种评价模型:组合评价模型和主成分指数模型.前者将变异系数法和Topsis法组合使用,用以评价产业集群创业能力;后者则是对所有参评样本的评价指标进行主成分分析,以主成分的方差贡献率为权重,构建主成分综合指数,从而形成产业集群创新能力的综合评价指数模型.对这两个模型用来自比较对象模型的同一数据进行了验证,三个模型都得出了非常相近的结果,而这两种模型更具可操作性且易于解释,这两者相比,主成分分析的方法则更为简单易行. 相似文献
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Owing to high-energy density of rechargeable lithium-ion batteries (LIBs), they have been investigated as an efficient electrochemical power sources for various energy applications. High theoretical capacities of tin oxide (SnO2) anodes have led us a path to meet the ever-growing demands in the development of high-performance electrode materials for LIBs. In this paper, a facile approach is described for the synthesis of porous low-dimensional nanoparticles and nanorods of SnO2 for application in LIBs with the help of Tween-80 as a surfactant. The SnO2 samples synthesized at different reaction temperatures produced porous nanoparticles and nanorods with average diameters of ~7–10 nm and ~70–110 nm, respectively. The SnO2 nanoparticle electrodes exhibit a high reversible charge capacity of 641.1 mAh/g at 200 mA/g after 50 cycles, and a capacity of 340 mAh/g even at a high current density of 1000 mA/g during the rate tests, whereas the porous nanorod electrodes delivers only 526.3 mAh/g at 200 mA/g after 50 cycles and 309.4 mAh/g at 1000 mA/g. It is believed that finer sized SnO2 nanoparticles are much more favorable to trap more Li+ ion during electrochemical cycling, resulting in a large irreversible capacity. In contrast, rapid capacity fading was observed for the porous nanorods, which is the result of their pulverization resulting from repeated cycling. 相似文献
45.
通过溶胶-凝胶和高温固相掺杂反应可控合成了形貌均匀、结晶性好的尖晶石型LiMn1.9Al0.1O3.95F0.05正极材料,探究了Al部分取代Mn、F部分取代O后对结构的影响,测试并比较了电极材料的倍率性能和循环充放电性能. 结果表明,尖晶石型LiMn1.9Al0.1O3.95F0.05和LiMn2O4有同样的晶型,但电极较传统的LiMn2O4电极倍率稳定性有显著提高. 在连续混合(如0.1C、0.5C和1C)充放电150次后,LiMn1.9Al0.1O3.95F0.05电极的容量仍能保持90%以上. 相似文献
46.
20单元双压电片变形镜对Zernike像差空间拟合能力的实验研究 总被引:1,自引:1,他引:0
利用20单元双压电片变形镜和13×13阵列哈特曼波前传感器所构成的闭环自适应光学系统,实验测试了双压电片变形镜对3~20项静态Zernike像差的空间校正能力,并将实验结果与仿真计算结果进行了对比.最后分析了哈特曼传感器与双压电片变形镜之间的对准误差对实验结果的影响.研究表明,除了少数几项外,双压电片变形镜对3~20项Zernike像差的拟合误差都小于0.5,各项Zernike仿真和实验结果之差平均小于0.1.计算表明,与严格对准的理想情况相比,双压电片变形镜对3~20项Zernike像差中大多数项的拟合误差都随着失配程度的增加而增大,对准精度对于高阶像差拟合效果的影响尤其严重. 相似文献
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Thyreostatic compounds could be illegally administered to animals in order to obtain a weight gain due to a higher retention of water in the edible tissue and the gastro-intestinal tract. In the European Union their use for animal production is banned since 1981. Recently a highly sensitive method exploiting the determination of thyreostats with 3-iodobenzylbromide prior to purification to determine thyreostats in urine and other matrices was reported. For the first time, the UPLC instrumentation was used to separate the 3-iodobenzyl derivatives of various thyreostats. The deuterated internal standards tapazole-d3 and propylthiouracil-d5 were for the first time used for the quantification of tapazole, thiouracil, methylthiouracil, propylthiouracil, phenylthiouracil and mercaptobenzimidazole. The confirmative quantitative liquid chromatographic tandem mass spectrometric (LC–MS/MS) method was validated according to Commission Decision 2002/657/EC. The decision limit (CCα) and the detection capability (CCβ) were found to be for all compounds below the recommended value of 10 μg kg−1. 相似文献
50.
Over the years, numerous process capability indices (PCIs) have been proposed to the manufacturing industry to provide numerical measures of process performance. Most research efforts have focused on developing and investigating PCIs that assess process capability by precise measurements of output quality. However, real observations of continuous quantities are not precise numbers; in practice, they are more or less imprecise. Since observations of continuous random variables are imprecise the values of related test statistics become imprecise. Therefore, decision rules for statistical tests have to be adapted to this situation. This article presents a set of confidence intervals that produces triangular fuzzy numbers for the estimation of Cpk index using Buckley’s approach with some modification. Additionally, a three-decision testing rule and step-by-step procedure are developed to assess process performance based on fuzzy critical values and fuzzy p-values. This concept is also illustrated with an example for testing process performance. 相似文献