基于第一性原理计算ReB2的点阵动力学

为了研究新型超硬材料ReB2的低温超导特性,利用基于密度泛函理论平面波赝势法的第一性原理计算,研究了过渡金属化合物ReB2的点阵动力学性质,并分析了不同原子对电声耦合作用的贡献.计算结果表明,对于相同原子振动模式的频率,沿c方向振动的频率总是大于在a-b平面内振动的频率.轻原子B对电声耦合作用的贡献最大,而总的电声耦合...     

The simulation of electrostatic coupling intra body communication based on the finite element method

In this paper, investigation has been done in the computer simulation of the electrostatic coupling IBC by using the developed finite-element models, in which a.the incidence and reflection of electronic signal in the upper arm model were analyzed by using the theory of electromagnetic wave;b.the finite-element models of electrostatic coupling IBC were developed by using the electromagnetic analysis package of ANSYS software;c.the signal attenuation of electrostatic coupling IBC were simulated under the conditions of different signal frequencies, electrodes directions, electrodes sizes and transmission distances. Finally, some important conclusions are deduced on the basis of simulation results.     

新型三氮烯试剂的合成及其性质

在稀盐酸存在下,对硝基苯胺经亚硝酸正丁酯重氮化生成重氮化试剂,再与芳胺发生氮偶联反应,合成了一种三氮烯类新试剂.通过质谱分析、红外光谱和核磁共振数据证实产物为三氮烯类化合物.实验结果表明,新合成的三氮烯试剂与微量金属离子Cu2+,Ag+,Zn2+,pd2+等的显色反应具有很高的灵敏度.     

Development and Performance Study of CaCO3 Modified PP Spun-Bonded Nonwovens

The manufacturing process of CaCO3 modified Polypropylene (PP) spun-bonded nonwovens was studied.Then the effect of the additive amount of CaCO3 on mechanical properties of the product was analyzed,and a compatible mechanism between CaCO3 partides and the main component of PP was established.In the end,the mechanical performance of the products was studied when the natural light degradation was changed.The experiment results show that after adding CaCO3 to the PP spun-bonded nonwovens and through the application of complex coupling agent and organic modification,hardcore of rigid particles and polymer composite elastomers can be combined together tightly and disperse rapidly and evenly in the main part of PP.In addition,CaCO3 can catalyze the light degradation of PP spun-bonded nonwovens.The larger the content of CaCO3 is,the faster the light degradation will be.     

地震作用对钢桁梁桥车桥系统耦合振动的影响分析

为了研究地震对车桥系统耦合振动的影响,采用最小二乘法对地震加速度进行校正拟合,消除位移时程因直接对加速度时程积分出现的漂移现象。根据弹性系统动力学总势能不变值原理及形成矩阵的对号入座法则,将轨道不平顺作为系统的自激激励源,地震作为外部激励,建立考虑地震作用的车桥系统耦合振动方程。并以某钢桁梁桥为例,采用计算机模拟的方法,建立列车和桥梁动力分析的有限元模型,研究地震对车桥系统耦合振动的影响。研究结果表明:在地震作用下,桥梁的动力响应主要取决于地震力,横向地震波对车辆与桥梁的横向动力响应具有非常重要的影响;竖向地震波主要影响车桥系统的竖向振动,对横向振动影响很小;但是,竖向地震波对脱轨系数、轮重减载率、车体竖向加速度的影响较显著,因此,在评判桥上列车的运行安全性时必须考虑竖向地震波的影响。     

高速电主轴的电压解耦与负载特性

为了研究高速电主轴动态数学模型中耦合回路对高速电主轴负载特性的影响,根据控制理论的不变性原理,在高速电主轴给定电流和反馈电流的偏差处引入外部解耦支路来消除耦合电压的影响,研究解耦后高速电主轴的励磁电流和转矩电流在负载变化时对主轴磁通、电磁转矩以及负载特性的影响方式,并利用高速电主轴性能测试试验平台进行负载特性测试.理论分析和试验结果表明:高速电主轴的解耦效果会直接影响主轴磁通的稳定性和转矩电流对负载的线性跟踪能力,并通过不同频率下机械特性曲线的平行度、电磁转矩脉动程度、主轴的载荷能力、功率因素和效率等特性参数直接体现.因此,可以根据包含上述特征信息的机械特性曲线、功率因素曲线和效率曲线的变化趋势,判断高速电主轴的实际解耦效果,并预测高速电主轴在该控制方式下的动态性能.     

静电放电电磁脉冲辐照效应研究

基于传输线理论研究了静电放电电磁脉冲(ESD EMP)对电路的辐照效应机理,并建立了相关的数学模型.参照IEC61000-4-2标准,进行了ESD EMP辐照效应实验,同时实测了耦合板周围电场强度,实验结果表明,当受试设备电路板平行于水平耦合板(HCP)放置时,在电场强度类似的情况下,对水平耦合板(HCP)放电时的感应干扰电压普遍比对垂直耦合板(VCP)放电时高.将实验结果与模型分析比较,结果吻合良好,因此可以用此模型来研究静电放电产生的电磁脉冲场与电子系统的能量耦合问题.本文研究也表明现行的IEC61000-4-2标准存在不足,水平耦合金属板会改变静电放电电磁脉冲辐射场的入射方向,对测试结果影响较大,需要对被测设备(EUT)的摆放位置作进一步的规范.     

Land-atmosphere coupling amplifies hot extremes over China

Climate extremes, such as extreme hot temperatures and heat waves, can have dramatic societal, economic, and ecological consequences. China has experienced remarkable interannual and decadal changes in hot extremes during the last several decades. However, the underlying mechanisms responsible for changes in the hot extremes over China have not been clearly identified. In this study, we investigate the role of land-atmosphere coupling for hot days and heat waves during summer over China using two long-term Weather Research and Forecasting model simulations with and without interactive soil moisture. Results indicate that land-atmosphere coupling mainly amplifies hot extremes over China. In particular, significant amplifying effects appear over most of eastern and southwestern China. Over these areas, land-atmosphere coupling generally accounts for 30%-70% of the numbers of hot days and heat waves. This study highlights the critical importance of land-atmosphere interactions for the occurrence of hot extremes over China.     

泛函积分与sine-Gordon-Thirring模型的统计平均值

根据泛函积分方法研究了杂质耦合sine-Gordon-Thirring模型的统计物理性质,通过辅助玻色场技巧推导了弱耦合模型的有效势,由泛函行列式微扰展开获得了模型的自由能.另外,在弱耦合情况下计算了两个杂质和凝聚项的4阶统计平均值,还给出了有效势和统计平均值的图形表示.     

Optical properties of amorphous thin film of Se-Te-Ag system prepared by using thermal evaporation technique

Zn_(0.95)Co_(0.05)O and Zn_(0.91)Co_(0.05)Cu_(0.04)O thin films were fabricated on Si(111) substrate by the reactive magnetron sputtering method at different O-Ar ratios.Detailed characterizations by X-ray diffractometry(XRD),X-ray photo-electronic spectrum(XPS), and electron paramagnetic resonance(EPR) indicate that the doped Cu ions substitute the Zn~(2+) ions in the ZnO lattice.The doped Cu ions are in Cu~+ and Cu~(2+) mixture valence states.The ferromagnetism of the Zn_(0.91)Co_(0.05)Cu_(0.04)O film ...