排序方式: 共有118条查询结果,搜索用时 15 毫秒
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从ZnO和SrTiO3的不同晶体结构和烧结工艺出发,论述了CoO在这两种晶体中所处的位置和不同的作用机理。实验结果证实同一种原子在不同的材料和烧结工艺中起着不同的作用。通过分析晶体点缺陷和烧结气氛的关系解释了实验结果:在氧化气氛中,CoO的主要缺陷是金属空位,增加晶界受主态密度;在还原气氛中,CoO的主要缺陷是氧空位,减少受主态密度。 相似文献
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测试了国产和美国Cree公司生产的n型6H-SiC低温下的电学参数,包括电阻率、迁移率和自由载流子浓度,并用FCCS软件数据拟合分析得到两种SiC的杂质浓度和能级.实验结果表明:杂质浓度和补偿度对低温下SiC的电性能有很大影响,轻度补偿的掺氮6H-SiC是施主氮的两个能级共同起作用;而重度补偿的6H-SiC在低温时则是受主能级起作用,并且后者迁移率随温度变化曲线的峰值降低并右移.同时发现重度补偿的SiC在较低温度时由n型转变成了p型,并从理论上分析了产生这种现象的原因. 相似文献
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由于快关汽门的控制量受汽门关闭速度的限制,因此,采用线性最优控制理论 来解决快关汽门问题存在缺陷。本文根据庞特里雅金最大值原理提出了一种快 关汽门最优控制方法。该方法考虑了快关汽门中控制量的非线性。此外,由其 求得的控制规律满足断续型暂稳紧急控制的要求。本文控制方法不存在奇异现 象。通过三个系统的计算证明该方法正确。 相似文献
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Predictive model based on artificial neural net for purity of perovskite-type SrTiO3 nanocrystalline
A three-layer structure back-propagation network model based on the non-linear relationship between the purity of the perovskite-type SrTiO3 nano-crystal samples and the technology factors, such as reaction time, reaction temperature, raw material adding amount of NaOH and SrCl2, and the rate of TiCl4/H1, was established. The input variables were pretreated by using the main component analysis firstly. Moreover, the momentum terms were introduced so as to accelerate the converging rate and avoid the non-converging situation. At the same time, the variable learning speed was adopted. The results show that the improved back propagation neural network model is very efficient for the prediction of the perovskite-type SrTiO3 nano-crystal sample purity. 相似文献
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YAl3 (BO3)4: Eu^3+ phosphors were prepared by the conventional solid state reaction. The phase structure and morphology were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). Doping YAl3(BO3)4: Eu^3+ phosphors with concentration of Eu^3+ ions of 0, 2, 5, 8 and 10 mol% were studied and their luminescent properties at room temperature were discussed. The excitation spectrum of Y0.95Eu0.05Al3(BO3)4 was composed of a broad band centered at about 252 nm and a group of lines in the longer wavelength region. In the emission spectra, the peak wavelength was about 614 nm under a 252 nm UV excitation. The optimal doping concentration of Eu^3+ ions in YAl3(BO3)4: Eu^3+ phosphors was 8 mol%. 相似文献
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为了提高ZnO压敏电阻器的性能,采用Sol-Gel法制备复合纳米添加剂.用该复合添加剂、ZnO及SiO2混合球磨后的粉体制备了Φ10 mm×1 mm氧化锌压敏电阻器元件,并对其性能进行了测试、分析.结果表明:Sol-Gel方法制成的元件具有粉体掺杂均匀、晶粒粒径小、分布均匀,其电性能也较传统工艺有很大提高,8/20 μs通流能力达到了2 700 A,2 ms方波能量耐受能力超过705.6 J/cm^3,漏电流约为0.3 μA,非线性系数为53. 相似文献