基于VPN技术的第二层隧道协议L2TP

随着Internat的商业化,大量的企业内部网与Internat连接,如何为企业外部用户提供安全经济的接入方式成为一个技术问题。虚拟专用网在这样的背景下产生了,虚拟专用网（VPN）即通过隧道技术构建了企业局域网与外界用户的一种经济有效的接入方式。本文着重分析了L2TP第二层隧道协议实现原理,和利用IPSec第三层隧道协议增强L2TP安全性的方法。     

基于EEMD-HHT方法的隧洞爆破网路延时分析

由于非电毫秒雷管本身存在起爆误差,造成网路理论延时与实际延时存在较大误差。为更深入研究网路实际延时时间,以黄河上游某水电站引水发电隧洞工程实测爆破振动信号为分析对象,使用EEMD方法求出爆破信号IMF分量,进行Hilbert变换求出各分量能量,并对能量最大分量进行Hilbert变换求出包络线,再对包络线峰值进行分析得到网路的各段非电雷管的实际起爆时刻分别为49,74,178,235,350,469,609ms,从而准确求得网路中各段间的实际延时时间为25,104,57,115,119,140ms。对网路的理论与实际延时时间进行对比分析,发现理论与实际延时时间存在较大精度误差,这说明采用EEMD-HHT方法识别网路的延时精度是可行的。     

Nanofabrication of magnetic tunnel junctions by using side-edge thin film deposition

Nanostructured double ferromagnetic tunnel junctions (MTJs) are indispensable for investigation of spin-dependent single-electron transport at low temperature. A new fabrication process that enables us to reduce the size of MTJs down to nanometer scale by using the side edge of a patterned film were developed. The multilayers of MTJ partially replaced by thick Al₂O₃/Cu double layer were prepared by using electron beam lithography and lift-off, then Pt film was vacuum-evaporated onto the side edge of Al₂O₃/Cu film, which masked MTJ during following Ar ion milling. As a result, the double MTJs with the dimension of 10 nm £ 10 mm were formed beneath the Pt film. The large tunnel magnetoresistive ratio of 35% and symmetrical I–V characteristics were obtained at room temperature.     

坑道口部内爆炸冲击波传播速度规律的数值分析

准确计算坑道口部内爆炸条件下冲击波传播速度的变化,是确定坑道内主动消波设备时间响应指标的关键。为此,基于AutoDyn进行5种不同工况的坑道内爆炸计算。采用量纲分析构建了冲击波传播速度的工程模型,通过对数值计算结果的拟合确定了模型的系数。与坑道化爆实验的实测值进行分析比较表明,所拟合的坑道内冲击波传播速度的经验模型最大误差为15%,作为一种工程方法而言具有较强适用性。     

数量工程技术在南京长江隧道工程中风险 辨别及事故防范的应用研究

以南京长江隧道工程为背景,提出了基于数量工程技术的风险提示及事故防范方法,即运用数值仿真方法,借助超级计算机的并行计算能力,建立盾构机进出洞,盾构机穿越长江大堤及穿越江中最浅覆土层,两台盾构机同时施工影响,盾构机穿越复合土层等工程关键问题的数量分析模型。基于该模型,对地表沉降过大、盾构机姿态偏移、开挖面失稳等工程风险进行了提示;分析了风险产生的机理、后果;提出了事故防范的措施,评价和验证了防范措施的有效性和合理性。     

具有无线通讯功能的挖掘机器人的设计与实现

介绍了具有无线通讯、智能寻径等功能的挖掘机器人的设计与制作;该挖掘机器人以玩具小车为车体,直流电机及其控制电路为整个系统的驱动部分,采用上、下位机分级控制模式作为挖掘机器人智能控制系统的组成方式,利用PTR2000实现上位机和单片机之间的无线数据传输,并加以多种传感器以实现挖掘机器人的智能寻径与自主挖掘等功能;测试结果表明,在该控制系统下,挖掘机器人工作准确可靠,该系统可作为智能机器人进一步研究的平台.     

Electrical properties of ultra-thin oxynitrided layer using N2O plasma in inductively coupled plasma chemical vapor deposition for non-volatile memory on glass

In this work, the silicon oxynitride layer was studied as a tunneling layer for non-volatile memory application by fabricating low temperature polysilicon thin film transistors on glass. Silicon wafers were oxynitrided by only nitrous oxide plasma under different radio frequency powers and plasma treatment times. Plasma oxynitridation was performed in RF plasma using inductively coupled plasma chemical vapor deposition. The X-ray energy dispersive spectroscopy was employed to analyze the atomic concentration ratio of nitrogen/oxygen in oxynitride layer. The oxynitrided layer formed under radio frequency power of 150 W and substrate temperature of 623 K was found to contain the atomic concentration ratio of nitrogen/oxygen as high as 1.57. The advantage of high nitrogen concentration in silicon oxide layer formed by using nitrous oxide plasma was investigated by capacitance-voltage measurement. The analysis of capacitance-voltage characteristics demonstrated that the ultra-thin oxynitride layers of 2 nm thickness formed by only nitrous oxide plasma have good properties as tunneling layer for non-volatile memory device.     

Efficiency of mechano-catalytic water-splitting system

Input energy to mechano-catalytic water-splitting system is transferred partly to organize the frictional electric condenser (FEC) system, which motivates the water-splitting, and partly to rotate the slurry. A part of the rotational energy is regained as a feedback, while the remainder is wasted to the dispersion loss through the viscous motion. The mechanism of the cyclic transfer of charge between the stirrer (Teflon), the vessel wall (Pyrex glass) and the semiconductor particles (NiO, etc.) is discussed. System efficiency, dynamic efficiency, energy conversions and the dispersion processes are analyzed. System design of the cell and the stability of FEC system are discussed as well.     

大直径扩底灌注桩设计若干问题分析

分析了大直径底灌注桩的受力特点,根据有关规范,结合工程实际对人工挖孔桩承载的计算,桩身计算,桩的检测进行了论述,供设计人员参考。     

当前长江采砂执法中的问题与对策

长江采砂管理是近几年水利工作的一个热点,长江大规模非法采砂状况现虽已得到改变,但仍面临较多的问题.文章有针对性地提出了对策,并指出执法实践中的注意事项,对所涉及的若干难点法律问题进行了探讨.