Seismoelectric wave propagation modeling in a borehole in water-saturated porous medium having an electrochemical interface

Water-saturated porous media often exhibit a seismoelectric effect due to the existence of an electrical double layer and a relative flow of pore fluid. Here we consider the seismoelectric waves in an open borehole surrounded by water-saturated porous formation which exhibits discontinuity of electrochemical properties at a cylindrical interface. We carefully analyze the seismoelectric interface response since these signals show sensitivity to contrasts in electrochemical properties across an interface. Both coupled and approximate methods are used to compute borehole seismoelectric fields. The simulation results show that the radiated electromagnetic wave from the electrochemical interface is generated due to the change of salinity in pore fluid in the porous formation. However, the elastic properties of the formation remain unchanged across such an electrochemical interface. As a result it is difficult to recognize such a change in electrochemical properties using only elastic waves. Therefore, the seismoelectric interface response is potentially used to detect the changes of the electrochemical properties in the formation.     

三维空间二阶精度流体体积界面重构方法

给出三维空间网格模板含81个单元的最小二乘流体体积界面重构方法,并和Youngs方法及网格模板含125个单元的最小二乘流体体积界面重构方法进行比较.静态和动态的测试例子均表明:该方法能精确重构任意方向的平面界面,对C²光滑曲面它能达到二阶收敛精度.和网格模板含125个单元的最小二乘流体体积界面重构方法相比,在达到同样网格精度的条件下,减少了计算量,节省了计算时间,提高了计算效率.     

超声空化引起界面湍动促进的传质机理

本文分析了超声空化引起界面湍动对传质过程的影响,提出了相界面上超声空化气泡析出增强边界层液体湍动并促进传质的机理,在传质理论和流体动力学原理的基础上,建立了超声空化引起界面湍动促进的传质机理模型,获得了超声空化引起界面湍动促进的传质系数表达式。实验结果验证了模型的合理性。该模型既证实了超声对传质有强化效应,又对传质过程有很好的预测功能,为工业化提供了理论依据。     

飞控系统控制信息自动采集处理模块与自测试设计

介绍一种机载飞控系统飞控计算机对各种控制信息（包括离散量、模拟量和串行数据）进行数字化控制、实时采集、监控和处理的接口模块设计方法,从工程应用角度出发,阐述了模块的设计思路以及工程实现,给出原理框图和测试流程。在某型飞机的实际应用中,实现了32路离散量输入输出、16路模拟量输入输出、6路ARINC429串行数据收发、4路ARINC422串行数据收发以及4路ARINC232串行数据收发的功能,自测试覆盖率达100%。因该模块的接口形式和接口数量可根据实际需要进行增减,故具有很强的典型性和通用性,可适用于各类型的机载飞控系统。     

有机半导体异质界面电荷传输解析模型研究

有机半导体多层薄膜器件的性质很大程度上由有机-有机界面的传输性质所决定，但是现有的关于有机-有机界面的分析模型很难适用于实际器件的模拟.以Miller-Abrahams跳跃传导理论为基础，充分考虑有机-有机界面和金属-有机界面性质的不同，建立了一个新的描述有机-有机异质界面电荷传输的解析模型.结果表明有机异质界面的载流子传输不仅取决于界面的肖特基势垒，而且还取决于界面附近两边的电场强度和载流子浓度.此模型可用于有机半导体多层薄膜器件的电流密度、电场分布和载流子浓度分布的自洽计算. 关键词： 有机半导体 界面 载流子传输     

Electrochemical characterization of poly(vinylidenefluoride)-zinc triflate gel polymer electrolyte and its application in solid-state zinc batteries

Gel polymer electrolyte (GPE) films comprising of poly(vinylidenefluoride), propylene carbonate, ethylene carbonate and zinc trifluoromethane sulfonate are prepared and characterized. The composition of GPE is optimized to contain minimum liquid components with a maximum specific conductivity of 3.94×10⁻³ S cm⁻¹ at (25±1) °C. A detailed investigation on the properties such as ionic conductivity, transport number, electrochemical stability window, reversibility of Zn/Zn²⁺ couple and Zn/gel electrolyte interfacial stability have been carried out. The ionic conductivity follows a VTF behaviour with an activation energy of about 0.0014 eV. Cationic transport number varies from 0.51 at 25 °C to 0.18 at 70 °C. Several cells have been assembled with GPE as the electrolyte, zinc as the anode, γ-MnO₂ as the cathode and their charge–discharge behaviour followed. Capacity values of 105, 82, 64 and 37 mAh/g of MnO₂ have been achieved at 10, 50, 100 and 200 μA/cm² discharge current densities, respectively. The discharge capacity values are almost constant for about 55 cycles for all values of current densities. Cyclic voltammetric study of MnO₂ electrode in Zn/GPE/MnO₂ cell clearly shows intercalation/deintercalation of Zn²⁺.     

Effects of charge and dipole on flatband voltage in an MOS device with a Gd-doped HfO_2 dielectric

Gd-doped HfO2 has drawn worldwide interest for its interesting features.It is considered to be a suitable material for N-type metal-oxide-semiconductor(MOS)devices due to a negative flatband voltage(Vfb)shift caused by the Gd doping.In this work,an anomalous positive shift was observed when Gd was doped into HfO2.The cause for such a phenomenon was systematically investigated by distinguishing the effects of different factors,such as Fermi level pinning(FLP),a dipole at the dielectric/SiO2interface,fixed interfacial charge,and bulk charge,on Vfb.It was found that the FLP and interfacial dipole could make Vfbnegatively shifted,which is in agreement with the conventional dipole theory.The increase in interfacial fixed charge resulting from Gd doping plays a major role in positive Vfbshift.     

LaAlO3/SrTiO3界面的电子结构及光学性质的第一性原理研究

采用基于密度泛函理论框架下的第一性原理平面波超软赝势方法,结合局域密度近似(LDA)研究了钙钛矿结构氧化物LaAlO3/SrTiO3界面的电子结构及光学性质.能带结构分析表明当形成(AlO2)-/(TiO2)0界面时其禁带宽度为1.888 eV,呈现绝缘体的性质,当形成(LaO)+/(SrO)0界面时其禁带宽度为0.021eV,呈现半导体或半金属性质.同时,对不同界面的光学性质也进行了研究,结果表明纯相的LaAlO3和SrTiO3的吸收系数、反射系数及能量损失谱强度明显高于由这两种单质形成不同界面的强度.     

On generation of electromagnetic waves in the terahertz frequency range in a multilayered open dielectric waveguide

We show that it is possible to produce terahertz wave generation in an open waveguide, which includes a multilayer dielectric plate. The plate consists of two dielectric layers with a corrugated interface. Electrons, drifting in the potential well, interact with the non-uniform electric field which is induced near the dielectric interface by the natural wave of the waveguide. The corrugated period and parameters of the electronic system are chosen in order to ensure the most effective interaction of electrons with a wave. Generation of electromagnetic waves is achieved by converting the electrons? energy into the electromagnetic wave energy.     

Interfacial characteristics of Al/Al2O3/ZnO/n-GaAs MOS capacitor

The interfacial characteristics of Al/Al2O3/ZnO/n-GaAs metal-oxide-semiconductor (MOS) capacitor are investigated. The results measured by X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM) show that the presence of ZnO can effectively suppress the formations of oxides at the interface between the GaAs and gate dielectric and gain smooth interface. The ZnO-passivated GaAs MOS capacitor exhibits a very small hysteresis and frequency dispersion. Using the Terman method, the interface trap density is extracted from C-V curves. It is found that the ZnO layer can effectively improve the interface quality.