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一、引言考虑多重线性回归模型Y=Xβ ε,(1)其中,Y=(y_1,…y_n_)′为 n×p 观察矩阵,X=(x_1,…,x_n)′为 n×(k 1)列满秩设计矩阵,β=(β_0,β_1,…β_k)′为(k 1)×p 未知参数矩阵,ε=(ε_1,…ε_n)′为 n×p 随机误差矩阵,ε_1…,ε_n 相互独立. 相似文献
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本文研究了在阴离子表面活性剂十二烷基硫酸钠(简称SLS)存在下,铜(Ⅰ)与5[(3,5-二溴-2-吡啶)偶氮]-2,4-二氨基甲苯(简称3,5-二溴-PADAT)的显色反应和光度特性,试验了用该体系测定微量铜的条件和方法。 相似文献
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A new oxide CaCr_(0.5)Fe_(0.5)O_3 was prepared under high pressure and temperature conditions. It crystallizes in a B-site disordered Pbnm perovskite structure. The charge combination is determined to be Cr~(5+)/Fe~(3+) with the presence of unusual Cr~(5+) state in octahedral coordination, although Cr~(4+) and Fe~(4+) occur in the related perovskites CaCrO_3 and CaFeO_3.The randomly distributed Cr~(5+) and Fe~(3+) spins lead to short-range ferromagnetic coupling, whereas an antiferromagnetic phase transition takes place near 50 K due to the Fe~(3+)–O–Fe~(3+) interaction. In spite of the B-site Cr~(5+)/Fe~(3+) disorder,the compound exhibits electrical insulating behavior. First-principles calculations further demonstrate the formation of CaCr_(0.5)~(5+)Fe_(0.5)~(3+)O_3 charge combination, and the electron correlation effect of Fe~(3+) plays an important role for the insulting ground state. CaCr_(0.5)Fe_(0.5)O_3 provides the first Cr~(5+) perovskite system with octahedral coordination, opening a new avenue to explore novel transition-metal oxides with exotic charge states. 相似文献
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We synthesize LiTal-x FexO3-σ (LTFO) remain single phase up to x = 0.09 ceramics by the conventional solid-state reaction method. The samples The magnetic measurements show that the doping of Fe successfully realizes ferromagnetism of LTFO at room temperature. The dielectric measurements indicate that LTFO is ferroelectric, similarly to LiTaO3 (LTO), but its ferroelectric Curie temperature seems to decrease with the increasing Fe content. By means of doping Fe ions into LTO, the coexistence of spontaneous electric polarization and spontaneous magnetic moment is realized at room temperature. 相似文献
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Misfit-layered compound PbTiS3 with incommensurate modulation: Transmission electron microscopy analysis and transport properties
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The microstructural characteristic of the misfit-layered compound PbTiS3 has been studied with transmission electron microscopy. All the incommensurate modulation-induced satellite spots and main diffraction spots of basic sublattices can be indexed systematically with a superspace group method. Finally, the relationship between the electronic transport properties and the crystal structure is discussed. 相似文献
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总结了我们将原位技术和透射电子显微学分析方法相结合,针对纳米材料和器件的结构、形貌、成分以及电势分布等物理性质的动态行为所开展的综合物性表征和分析工作.主要成果有:揭示了C_(60)纳米晶须在焦耳热作用下的结构相变路径;观察到了电荷俘获存储器中的电荷存储位置以及栅极电压诱导的氧空位缺陷;研究了阻变存储器中氧空位通道的形成过程以及导电通道的开关机理.这些成果不但有助于深入理解纳米材料和器件相关功能的物理机理,改善其工作性能,更展示了透射电子显微学在微电子领域强大的研究能力. 相似文献
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