单电子晶体管I-V特性数学建模

基于正统单电子理论，提出了单电子晶体管的I-V特性数学模型。该模型的优点是：它由实际物理参数直接获得；支持双栅极工作，更利于逻辑电路应用。I-V特性和跨导仿真结果证实了它的准确性。     

Pulse-Width Dependence in Current-Driven Magnetization Reversal Using GaMnAs-Based Double-Barrier Magnetic Tunnel Junction

We have investigated the current pulse width dependence on current-driven magnetization reversal in double-barrier structures using GaMnAs-based magnetic tunneling junctions (MTJ) in order to clarify the origin of low threshold current density for current-driven magnetization reversal. Comparing with the case of single-barrier MTJ, the pulse-width dependence reveals that threshold current density is reduced by double-barrier MTJ. We confirmed that the threshold current density in the order of 10⁴ A/cm² is estimated considering the effect of current pulse width.     

Scale Transition in Steel-Concrete Interaction. II:?Applications

The proposed mode of consideration of the steel-concrete interaction (Part I) is applied to real-life engineering structures. Two structures recently investigated numerically at Vienna University of Technology are considered: (1) the reinforced concrete (RC) cooling tower III Ptolema?s SES (Greece) and (2) a part of the shotcrete tunnel lining installed at the Lainzer tunnel (Austria). In both examples, the uniaxial fracture criterion used in Part I is replaced by the maximum stress (Rankine) criterion. Together with the Drucker-Prager criterion, which is used for the simulation of compressive failure of concrete/shotcrete, it defines the space of admissible stress states in the framework of multisurface plasticity. For the simulation of early-age fracture of shotcrete, consideration of the steel-concrete interaction presented in Part I of this paper is extended towards young shotcrete. Similar to the benchmark problem investigated in Part I of this paper, several analyses with different degrees of consideration of the steel-concrete interaction are performed. The obtained results give insight into the influence of the steel-concrete interaction on the load-carrying behavior of the investigated structures.     

IPv6过渡技术中ISATAP隧道研究与应用

ISATAP是具有多种优点的自动隧道技术,适合用于校园网IPv4/IPv6过渡中。给出ISA-TAP隧道技术机制的分析,并结合校园网设计ISATAP隧道,解决将多个实验室的主机接入CERNET2的过渡问题,详细介绍配置过程,所实现的ISATAP隧道能很好地进行IPv6通信。     

基于防火墙构建VPN的远程气象连接方案

结合VPN技术在远程用户连入气象局域网中实现数据共享的应用,详细介绍了VPN技术特点、基本原理以及配置过程,为远程气象连接提供了一种新的手段。     

太赫兹共振隧穿二极管探测器研究进展及应用

太赫兹波独特的性质使其在物理学、生物学、医疗诊断、无损检测、无线通信等领域有着广阔的应用前景。共振隧穿二极管(RTD)是一种基于量子隧穿效应的半导体器件,利用其负微分电阻和直流非线性特性,可以分别实现太赫兹波的产生和探测,近年来获得越来越多的关注。基于RTD的太赫兹探测器具有可室温工作、体积小、易集成、灵敏度高等特点,使其在未来短距离、超高速的太赫兹无线通信及万物互联等场景具备优势。本文将重点介绍太赫兹RTD探测器的研究进展及其应用进展,并对后续技术发展进行展望。     

基于移动信息化的安全接入平台建设

为提高移动信息化接入的安全级别,保障组织内部业务的安全运作,在传统网络安全架构的基础上,使用第二层隧道协议和混合加密技术构建一个安全接入平台。根据平台的功能及其安全性,将移动信息化区域分为5类,并为每一类区域制定安全策略,使原本限制在内网中的业务系统可以安全地在移动终端上使用。实际应用结果表明,该平台可以保证用户身份的匿名性、数据机密性、数据完整性、数据新鲜性及不可抵赖性。     

Influence of Mesh Geometry on Three-Dimensional Finite-Element Analysis of Tunnel Excavation

Finite element (FE) analysis has become an important tool for predicting building response to tunnel-induced ground movement. Because tunnel construction is a three-dimensional (3D) process, the trend is to apply 3D FE analysis to tunnel-soil-building interaction problems instead of applying the plane-strain models that are commonly used in engineering practice. Since 3D FE analyses require large amounts of computational resources, the geometric dimensions of the 3D models are often kept to a minimum to reduce calculation time. There is, however, a lack of published information concerning appropriate mesh dimensions. This paper investigates the influence of the geometry and the dimension of a 3D FE model on tunnel-induced surface settlement predictions. The paper shows how the vertical boundaries can influence the results. It demonstrates that reasonable results can be obtained by increasing the length of incremental tunnel excavation and by scaling back the settlement values to give a required tunnel volume loss. This study therefore not only highlights the limitations of 3D modeling but also shows its potential for engineering practice.     

The RUB Tunneling Device – A newly developed test method to analyze and determine the wear of excavation tools in soils

The efficiency of a tunneling project is mainly associated with the abrasivity of the acting soil and the wear resistance of the cutting tools. Heavy wear can dull the cutting tool, which negatively affects the penetration rate and therefore the efficiency of a tunneling process. Completely worn tools with a short service life have to be replaced by newer ones. This circumstance results in unplanned machine shutdowns and higher maintenance costs. It is thus of high economic as well as technical interest to obtain a deeper understanding of soil/cutting tool interactions during tunneling. To meet this challenge, a large number of different testing devices to estimate the abrasivity of soils have been developed within the last two decades. An innovative and promising experimental setup is presented in this work. A horizontal implementation offers the possibility of simulating a tunneling process as well as the tribological system of a TBM tool. The interactions between all system components can be mapped and analyzed in detail. This method offers a unique setup, which allows wear prediction of TBM tools in a homogeneous soil with project-specific parameters (soil composition/condition, soil mechanics, tool material and machine/tunneling data).     

Experimental setup for non-destructive measurement of tunneling currents in semiconductor devices

A new experimental setup used to perform non-destructive measurement of electrical quantities on semiconductor devices is described in this paper. The particular case of tunneling current measurement in n-type semiconductor–oxide–semiconductor (SOS) capacitors, whose dielectrics play a crucial role in non-volatile memories, has been investigated. When the gates of such devices are polarized with a sufficient bias voltage while the other terminals are grounded, tunnel conduction of electrons through the thin oxide layer is allowed. Typical tunneling current measurements obtained with this advanced setup are presented and compared to the results yielded by older standard experimental protocols. An application to the experimental observation of the temperature dependence of the tunneling current is proposed. Conclusions about the benefits of this kind of electrical measurements are then drawn.