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351.
稀土正铁氧体YFeO3呈正交钙钛矿结构,其晶体和纳米晶材料在电极材料、 传感器和光催化领域具有重要的应用价值.用平面波赝势方法,采用广义梯度近似、改进的Perdew-Burke-Emzerhof交换-关联势、 实空间超软赝势计算方案,研究了YFeO3晶体的几何结构、电子结构和光学性质. 计算得到的晶格参量与报道的实验结果一致.通过对能带结构、态密度、介电函数、吸收系数和光电导率的计算和分析, 确定YFeO3是直接能隙半导体,能隙Eg约为2.22 eV,阐明了YFeO3晶体和纳米晶具有较好的可见光催化性能. 相似文献
352.
Yifei Chen Qinggong SongHuiyu Yan Tong WeiXiong Yang 《Physica B: Condensed Matter》2012,407(3):519-522
Using first-principles calculations based on density functional theory, we investigated systematically the electronic structures and magnetic properties of Fe16N2 system and their unit cell volume dependence. It has been found that total magnetic moment increases as increasing unit cell volume of Fe16N2. In addition, it also has been found that the d electron number on Fe I, Fe II and Fe III atoms decreases as increasing unit cell volume and the local magnetic moment on Fe atoms increases with the decrease of d electron number. The present study provides a clear insight into the numerous conflicting experimental results on the magnetic properties of Fe16N2 system. 相似文献
353.
Chuan-zhen Zhao Na-Na Li Tong Wei Sha-Sha Wang Ke-Qing Lu Zi-Li Xie 《Physica B: Condensed Matter》2012,407(24):4823-4825
In this paper, a model for the band gap energy of the N-rich GaNAs (0<x≤0.07) and the As-rich GaNAs (0.95<x≤1) is developed. For the N-rich GaNAs, The parameters describing the variation of the CBM and the VBM in the N-rich GaNAs are obtained by fitting the experimental data. For the As-rich GaNAs, the parameters in the model are obtained by fitting the experimental data of the band gap energy. It is found that the band gap evolution of the N-rich energy is different from that of the As-rich band gap energy. The model may be used to calculate the band gap energy of other dilute group III-N–V nitrides. 相似文献
354.
355.
Yuzhao Ma 《Optical Review》2012,19(3):125-130
In the present work the propagation of a partially coherent radially polarized beam through aligned and misaligned ABCD optical systems is discussed. The elements of the beam coherence-polarization matrix for a partially coherent radially polarized beam propagating through these systems are derived for the first time. Using the derived analytical results the intensity distribution of the focused partially coherent radially polarized beam after a low-NA lens is investigated. It is shown that the coherence of the light source affects the beam intensity profile at the focal plane significantly, while for the given coherence of the light source the focal length of the used lens does not affect the beam intensity profile at the focal plane. This is consistent with the case of a partially coherent Hermite-Gaussian beam, as expected. 相似文献
356.
Qingjun Zhou Tong Wei Yihua Shi Songqing Guo Yan Li Jingxin Su Huan Ren Yin Zhu 《Current Applied Physics》2012,12(4):1092-1095
The SrCo0.9Ta0.1O3-δ (SCT) perovskite-type oxide is synthesized by the conventional solid state reaction method and examined as an alternative cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs). The electrical conductivity of SCT sample reaches 250–152 S cm?1 in the temperature range 600–800 °C. SCT exhibits good chemical compatibility with the intermediate-temperature electrolyte material Sm0.2Ce0.8O1.9 (SDC). The average thermal expansion coefficient of SCT is 21.4 × 10?6 K?1. The cathode area specific resistance (ASR) of SCT is only 0.095 Ω cm2 at 750 °C and it decreases to 0.068 Ω cm2 when SDC is added to form a SCT-SDC composite cathode. The results indicate that the SCT can be a promising alternative cathode material for IT-SOFCs. 相似文献
357.
介绍了电磁场与微波技术课程改革中的3种特色教学手段:将与电磁场、微波有关的物理现象与日常生活实际联系起来,引入电磁场仿真软件以及将课程教学内容与我校民航专业人才培养目标结合起来.这3种手段在教学过程中的运用不仅使难教难学的理论知识变得简单有趣,为学生毕业后快速适应工作岗位打下良好的基础,而且对教师本人科研与教学的结合也起到了促进作用. 相似文献
358.
由于风险投资的高不确定性和风险性,使得人们难以准确预测风险投资项目的收益和状态概率,而只能得到其大致的区间范围。鉴于这种情况,本文将投资项目收益和状态概率描述为模糊变量,利用模糊变量的均值和方差建立了模糊风险投资决策模型,并给出利用模糊模拟方法计算的实例。 相似文献
359.
利用高压直流正负极同电场静电纺丝方法, 制备了聚(3-羟基丁酸-co-4-羟基丁酸酯)共聚物的超细纤维, 实验发现, 正负极同时工作, 形成的宏观纤维形貌与单极相比截然不同, 纤维形态呈现出“蜘蛛网”的变化趋势. 用电磁学理论建立了数学模型. 电压控制在8.0 kV, 溶液质量分数为20%, 电导率控制在0.002—46.7 μS/cm时, 正负极同电场工作时纺丝速率比单极高十几倍; 纤维拉伸取向好于单极纺丝, 该方法为静电纺丝产业化提供了新的思路. 相似文献
360.
Haifeng Ji Gaojie Yan Dr. Peng Zou Han Wang Mengke Li Dr. Yi Feng Prof. Dr. Xiongwei Qu Dr. Dongling Geng Dr. Jingjing Shi Prof. Dr. Xiaojie Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2023,29(1):e202202787
The development of new vinylene-linked covalent organic frameworks (COFs) with special ionic structure and high stability is challenging. Herein, we report a facile, general method for constructing ionic vinylene-linked thiopyrylium-based COFs from 2,4,6-trimethylpyrylium tetrafluoroborate and other common reagents by means of acid-catalyzed Aldol condensation. Besides, pyrylium-, and pyridinium-based COFs also can be prepared from the same monomer under slightly different reaction conditions. The COFs exhibited uniform nanofibrous morphologies with excellent crystallinities, special ionic structures, well-defined nanochannels, and high specific surface areas. 相似文献