一种IPv6隧道环境下数据逃逸的防御策略

隧道技术是IPv4向IPv6过渡阶段的重要研究内容,为无IPv6物理接入的用户提供基于隧道的IPv6接入,使其可提前使用IPv6网络。为提高隧道网络的安全性,对隧道流量有关安全设备的影响进行了研究。指出隧道技术可被攻击者利用实施针对网络边界安全设备的数据逃逸,攻击网络内部主机。因此,提出了基于隧道分类的防御方法,通过在特定结构中增加外层包头的相关信息对不同流量进行分类,抵御上述攻击。实验表明,该方法具有较好的时间和空间复杂度,对系统负载影响较小。     

控制爆破技术在连拱隧道掘进应用的研究

九江至瑞昌高速公路A2标新合连拱隧道,穿越地层复杂,施工要求高。为保证工期和施工质量、安全,针对岩体特征及浅埋偏压段的实际,进行合理的超前支护;采用隧道光面爆破技术,经现场试验,对连拱隧道开挖爆破参数、装药结构和起爆网路进行优化设计;对钻爆、施工管理,提出了合理的质量要求和安全措施,实现了改善爆破效果、降低施工成本的目的。对类似隧道开挖施工具有一定的参考价值。     

重油隧道窑的红外温度测量

在分析重油隧道窑工况的基础上，分析了窑内烟气、燃烧物发射率、窑墙效应、环境温度对红外测温的影响以及热电偶测温的缺点，采取了相应的措施。利用中国发现专科实现了传感器输出信号的一致性。给出了传感器在重滑隧道窑现场使用２．５年后的复校数据。最后，估算出了用红外温度计替代热电偶测窑温产生的经济效益。     

单电子隧道结隧穿特性研究与仿真

基于单电子隧道结电压特征公式[1],借助Matlab拟合其隧穿特性曲线,给出了时不变和时变偏置电流作用下的I-V特性震荡曲线,并就仿真结果进行分析,将该模型应用于单电子盒进行仿真验证,出现了明显的库仑台阶,仿真曲线印证了理论分析结果.利用Matab强大的计算功能进行单电子器件特性仿真对单电子器件的应用研究有重要意义.     

深圳地铁9号线公用移动电话引入方案分析

基于地铁通信的特点,为促进公众移动电话系统与地铁专用通信系统更好的结合及合理布置。本文采用现场调研勘察,结合相关通信标准要求,对深圳地铁9号线公用移动电话引入设计方案进行研究。     

摩擦锚杆与砂浆锚杆锚固力的对比试验研究

本文介绍了在大冶铁矿进行的砂浆锚杆与摩擦锚杆锚固力的测试方法与结果 ,并用最大剪切理论和极限平衡原理评价了巷道围岩支护结构的承载能力。研究表明砂浆锚杆的锚固力较小且离散度较大 ;锚杆容易满足安全系数的校核却较难满足对锚杆长度可靠性的要求 ;两种锚杆混合支护可以在复杂困难条件下取得较好的支护效果     

Pipe Jacking Method for Long Curve Construction

The D301 pipe jacking method is the first to accomplish long spans, curves and high speed construction in the field of small diameter (300 mm) tunneling. The design of the system components are described: tunneling machine with directional control ability, jacking machine, power unit, and control unit which contains a microprocessor. As a result of field tests in about 100 m in length with a 200 curvature radius, the following capabilities are confirmed: the span length is up to 100 m, the curvature radius is down to 200 m, it is useable in either cohesive or sandy soils having N‐curves up to 10, and the construction speed is up to 3 m∕h.     

低时间晃动的重复脉冲单次化门电路

一、前言在有些物理实验中,需要从一重复脉冲序列中取出一个脉冲以作分析、测试之用。在利用微微秒高速扫描相机(即ps相机)测量北京正负电子对撞机(BEPC)贮存环上同步辐射光脉冲的时间结构时,便遇到了这一问题。在贮存环中单束团电子作周期运动,产生周期的同步辐射光脉冲。ps相机的斜坡电压扫描速度约为1kV/ns的量级,因此相机的光输入端与扫描部分必须有很好的同步以使得每当扫描电路被触发开启时,正好有一光脉冲进入相机。所以作触发的脉冲信号实际上是     

Simple Method for the Design of Jet Grouted Umbrellas in Tunneling

Tunnel excavation in cohesionless soils implies the use of a temporary supporting structure prior to lining installation. This temporary structure has to couple safety and economy, and can be conveniently realized using ground improvement techniques (for instance, by creating an arch of partially overlapped subhorizontal jet grouted columns). The adoption of ground improvement techniques results in structures far from having a perfect shape because they are intrinsically affected by defects (in both geometrical and mechanical characteristics), and therefore their design may hide unforeseen risks. As a consequence, this is the typical case in which sophisticated numerical analyses may just give the illusion of being refined, if possible defects are not correctly taken into account. In this paper a simple yet rational analytical method for the design of a nonclosed tunnel supporting structure that may be of some help to this aim is presented. It is done with reference to a simple two-dimensional scheme. In the first part of the paper, a design chart of optimal shape and minimum structural thickness of the cross section of the supporting structure is shown. In the second part, an iterative procedure to verify the stability or to design the minimum structural thickness of an existing supporting structure with a predefined shape is described. This method, coupled with the analysis of structural demand, allows one in principle to plot design charts. This approach can easily take into account structural defects with a semiprobabilistic approach and therefore with a chosen risk level, which is of great help to the designer at least in a preliminary design stage. The proposed semiprobabilistic procedure is applied to the case of a temporary supporting structure realized by partially overlapped subhorizontal jet grouted columns, intrinsically affected by defects in diameter and position. The variability of these geometrical parameters was considered based on the large quantity of experimental evidence collected in field trials by the writers and published elsewhere.     

Electrode Dependence of Tunneling Electroresistance and Switching Stability in Organic Ferroelectric P(VDF‐TrFE)‐Based Tunnel Junctions

Ferroelectric tunnel junctions (FTJs) are promising candidates for nonvolatile memories and memristor‐based computing circuits. Thus far, most research has focused on FTJs with a perovskite oxide ferroelectric tunnel barrier. As the need for high‐temperature epitaxial film growth challenges the technological application of such inorganic junctions, more easily processable organic ferroelectrics can serve as alternative if large tunneling electroresistance (TER) and good switching durability would persist. This study reports on the performance of FTJs with a spin‐coated ferroelectric P(VDF‐TrFE) copolymer tunnel barrier. The use of three different bottom electrodes, indium tin oxide (ITO), La_0.67Sr_0.33MnO₃, (LSMO), and Nb‐doped SrTiO₃ (STO) are compared and it is shown that the polarity and magnitude of the TER effect depend on their conductivity. The largest TER of up to 10⁷% at room temperature is measured on FTJs with a semiconducting Nb‐doped STO electrode. This large switching effect is attributed to the formation of an extra barrier over the space charge region in the substrate. The organic FTJs exhibit good resistance retention and switching endurance up to 380 K, which is just below the ferroelectric Curie temperature of the P(VDF‐TrFE) barrier.