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41.
本文提供了除环上矩阵的一些子矩阵的秩的若干恒等式与不等式,出现在本文中的这些结果,在处理涉及某些应用方面的复矩阵(作为除环上矩阵的特例)问题以及某些纯数学问题将起重要作用。 相似文献
42.
应用ICP-AES法测定钨酸钇钾[kY(WO4)2]激光晶体中的Er和Nd。试样用磷酸分解,Tm被选作内标元素。Er和Nd的回收率分别为98.6%-105.3%和96.5%-105.8%,相对标准偏差分别为1.90%和1.60%。 相似文献
43.
Z.J. Li X.L. Chen H.J. Li Q.Y. Tu Z. Yang Y.P. Xu B.Q. Hu 《Applied Physics A: Materials Science & Processing》2001,72(5):629-632
Low-dimensional GaN materials, including nanorings, nanoribbons and smooth nanowires have been synthesized by reacting gallium
and ammonia using Ag particles as a catalyst on the substrate of MgO single crystals. They were characterized by field emission
scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). EDX, XRD indicated
that the low-dimensional nanomaterials were wurtzite GaN. New features are found in Raman scatterings for these low-dimensional
GaN materials, which are different from the previous observations of GaN materials.
Received: 16 November 2000 / Accepted: 17 November 2000 / Published online: 21 March 2001 相似文献
44.
45.
YongGuang Tu GuoNing Xu XiaoYu Yang YiFei Zhang ZhaoJie Li Rui Su DeYing Luo WenQiang Yang Ying Miao Rong Cai LuHua Jiang XiaoWei Du YanChu Yang QianShi Liu Yang Gao Shuai Zhao Wei Huang QiHuang Gong Rui Zhu 《中国科学:物理学 力学 天文学(英文版)》2019,(7)
<正>The metal halide perovskite materials demonstrate outstanding performance in photovoltaics because of their excellent optoelectronic properties [1-7]. The perovskite solar cells (PSCs) exhibiting outstanding efficiency [8,9], high power-per-weight [10], and excellent radiation resistance[11-13] are considered to be promising for developing the new-generation energy technology for space application.However, the extreme space environment would impose 相似文献
46.
Jun-Jie Tian Zhao-Ying Yang Xin-Shen Liang Ning Liu Chen-Yu Hu Xian-Shuang Tu Xiang Li Prof. Dr. Xiao-Chen Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(42):18610-18614
Herein, we report that highly chemoselective and enantioselective reduction of 2-vinyl-substituted pyridines has been achieved for the first time. The reaction, which uses chiral spiro-bicyclic bisboranes as catalysts and HBpin and an acidic amide as reducing reagents, proceeds through a cascade process involving 1,4-hydroboration followed by transfer hydrogenation of a dihydropyridine intermediate. The retained double bond in the reduction products permits their conversion to natural products and other useful heterocyclic compounds by simple transformations. 相似文献
47.
In order to investigate the influence of steam ingestion on the aerodynamic stability of a two-stage low-speed axial-flow compressor, multiphase flow numerical simulation and experiment were carried out. The total pressure ratio and stall margin of the compressor was decreased under steam ingestion. When the compressor worked at 40% and 53% of the nominal speed, the stall margin decreased, respectively, by 1.5% and 6.3%. The ingested steam reduced the inlet Mach number and increased the thickness of the boundary layer on the suction surface of the blade. The low-speed region around the trailing edge of the blade was increased, and the flow separation region of the boundary layer on the suction surface of the blade was expanded; thus, the compressor was more likely to enter the stall state. The higher the rotational speed, the more significant the negative influence of steam ingestion on the compressor stall margin. The entropy and temperature of air were increased by steam. The heat transfer between steam and air was continuous in compressor passages. The entropy of the air in the later stage was higher than that in the first stage; consequently, the flow loss in the second stage was more serious. Under the combined action of steam ingestion and counter-rotating bulk swirl distortion, the compressor stability margin loss was more obvious. When the rotor speed was 40% and 53% of the nominal speed, the stall margin decreased by 6.3% and 12.64%, respectively. 相似文献
48.
强流电子束泵浦XeCl准分子激光动力学模型由三部分组成,即电子束能量沉积的计算;电子温度、电子反应速率的计算和化学/激光动力学。这个模型可以准确地预报小信号增益、吸收等激光特征量的时间变化规律。 该模型是在文献[1]、[2]、[3]报导的动力学模型的基础上提出的。采用四阶龙格_库塔法在VAX—11/780机器上进行数值求解。 计算给出XeCl准分子激光反应过程中各种粒子浓度、小信号增益、吸收、输出光强、激发速率以及平均电子能量随时间的变化规律。计算结果表明本征效率是激发速率,电流密度和工作气体(Ne/Xe/HCl)的各分压比的函数。 该模型可为高功率准分子激光器的研制提供设计参数和最佳实验条件。 相似文献
49.
From measurements of the superconducting transition temperature and valence magnetic susceptibility ξv, of amorphous Cu100?xZrx (30? x ? 80), we find that ln Tc varies as (ξv)?1 implying that with changing x, Tc is controlled only by the electronic density of states. By contrast, thermal relaxation reduces Tc substantially, leaving ξv almost unaltered, implying that Tc is changed only by change in the effective electron-electron coupling. 相似文献
50.
时间序列中自相关与偏相关函数分析 总被引:9,自引:0,他引:9
相关函数表现出时间序列中任意两个值之间的相关性是如何随着时间间隔而改变的.自相关函数刻画了时间序列相邻变量之间的相关性,偏相关函数则是排除了其它中间变量的影响,真实地反映两个变量之间的相关性,并且二者紧密相连.同时两个相关图所反映的信息在时间序列分析各个方面发挥着关键作用. 相似文献