Enhanced Cross-Phase Modulation via Phase Control in a Quantum dot Nanostructure

A four-level quantum dot (QD) nanostructure interacting with four fields (two weak near-infrared (NIR) pulses and two control fields) forms the well-known double-cascade configuration. We investigate the cross-phase modulation (XPM) between the two NIR pulses. The results show, in such a closed-loop scheme, that the XPM can be greatly enhanced, while the linear absorption and two-photon absorption (gain) can be efficiently depressed by tuning the relative phase among the applied fields. This protocol may have potential applications in NIR all-optical switch design and quantum information processing with the solid-state materials.     

准连续调制激光吸收谱测量封闭室内O2浓度的研究

在开采煤矿的生产活动中,遇到煤矿爆炸或地震、地质等自然灾害,会导致坍塌、掩埋、堆积等情形,进而形成复杂的封闭环境。如果发生人员被困等突发情况,破灾救援、挽救生命工作显得至关重要。封闭环境中O₂的浓度随时间的变化直接威胁到被困人员的生命安全,及时掌握被困人员所处环境的O₂浓度变化对破灾救援机器人作业实施有着非常重要的指导意义。为准确测量O₂的浓度,以封闭室内O₂为研究对象,综合应用可调谐二极管激光吸收光谱(TDLAS)技术和波长调制光谱(WMS)技术,设计了一套准连续调制激光吸收谱实验测量O₂浓度系统,对24 h封闭室内O₂的浓度随时间变化情况进行测量研究。实验结果表明,封闭室内O₂的浓度受到室内人员活动的影响,准连续调制激光吸收谱测量方法可以准确测量封闭室内的氧气变化。     

Advanced electro-optic properties of nematic liquid crystal doped with high birefringence liquid crystal molecules

The study of fast response nematic liquid crystal display material mixture and synthesis about compounds has always been an important subject in recent years. In this article, one type of high birefringence liquid crystal based on phenyl-diacetylenes was synthesized by sonogashira coupling reaction. A research is conducted on the effect of electro-optic properties of a widely used nematic liquid crystal mixture doped with the prepared high birefringence liquid crystal molecule which concentrations ranging from 1% to 5 wt%. While the results show that the steepness of electro-optic curves first increase and then decrease with the prepared high birefringence liquid crystal molecule content increasing, when the content of high birefringence liquid crystal molecule reaches 3%, electro-optic properties of the mixture liquid crystals are excellent.     

新型吲嗪三联吡啶的合成及其荧光性能

以醋酸钯为催化剂,三环己基膦为配体,碳酸铯为碱,甲苯为溶剂,4-溴-三联吡啶和2-甲酸甲酯-吲嗪经Heck偶联反应合成了一个新型的吲嗪三联吡啶(3),其结构经¹H NMR, ¹³C NMR和HR-MS表征。并研究了3的荧光性能。结果表明：溶剂极性增加,3的荧光强度降低,最大发射波长红移;Cu²⁺可完全淬灭3的荧光;3的Cu²⁺, Cd²⁺, Zn²⁺配合物对部分氨基酸有荧光响应。     

Shock response of a heavy tungsten alloy

This article describes the results of shock wave experiments performed on a heavy tungsten alloy containing W, Ni, and Fe in the ratio of 92.85:4.9:2.25 by weight. These experiments provide information about the shear strength under compression and tensile strength, as measured by the spall threshold, of this alloy to 24 GPa. The results of these experiments show that: (i) the magnitude of its Hugoniot elastic limit (HEL) is 2.76±0.26 GPa; (ii) this alloy deforms plastically above its HEL and thus retains its shear strength to 24 GPa; (iii) the spall strength of the alloy is found to be 1.9±0.4 GPa and is independent of the impact stress and duration of the shock compression pulse; and (iv) the tensile impedance of the alloy, determined from a new experiment designed to measure this impedance, is 68±10 Gg/m² s.     

贴片晶振在冲击环境下的损伤边界

贴片式石英晶体振荡器广泛应用于各类电子和通信设备系统中。针对晶振在冲击环境中容易出现结构破坏而导致系统工作异常的问题,通过分析单自由度系统在不同频率冲击载荷作用下的响应特点,建立了结构的应力响应水平与相关冲击响应谱谱值之间的联系,获得了较已有结论更合理的损伤边界形式。根据典型晶振结构易损组件的力学特性建立对应的简化分析模型,得到了贴片晶振在大频率范围内的结构损伤边界。利用有限元仿真软件,对晶振结构在0.5~30 kHz频率范围内冲击载荷下的响应进行仿真分析,验证了该损伤边界的有效性。这也为以贴片晶振为代表的微小元器件在冲击环境下的可靠性研究提供了一种可行的方法。     

Android异常入侵检测中的主动响应系统

手机恶意程序有对智能手机用户造成经济损失、数据丢失及隐私泄露等危害。在现有的Android入侵检测系统框架基础上,提出异常入侵检测中的主动响应系统,及时减轻手机恶意软件对用户造成的危害。该主动响应系统采用C/S架构,其中客户端收集手机中应用的程序信息,负责最后的响应措施;服务器端及时静态分析由客户端发来的可执行文件,锁定导致手机出现异常状态的恶意程序。测试结果表明,该系统可以主动对手机上已发现的异常行为做出及时有效响应。     

基于DFT滤波器组的多载波调制系统设计

采用DFT滤波器组来代替OFDM系统中的IDFT/DFT模块,形成基于滤波器组的收发器。设计适于多经衰落信道的DFT滤波器组收发器。其均衡与OFDM系统一样,是在接收端采用单抽头的均衡器。实验采用随机多径信道,仿真结果表明所提出的滤波器组收发器可以获得较好的频谱特性,以及较满意的SIR（信号与干扰比值）。     

Loadrunner在Web系统性能测试中的应用

随着Web技术的不断发展,其应用的多样性和复杂性给性能测试工作带来了困难和挑战,介绍了如何借助于强大的工业级性能测试工具Loadrunner对Web系统性能进行测试,如何获取测试需求、制定测试计划、生成测试脚本、设计测试场景、监控系统性能,分析测试结果。     

“村村响”设备光功率过高干扰有线电视故障剖析

光缆网络改造增设光节点后,＂村村响＂广播难以采用原先射频插入的方式进行插播,改用光纤调频广播信号混合复用传输设备进行插播,调试过程中发生广播信号干扰有线电视信号的故障,就广播单频道调制度与有线电视多频道调制度之区别进行理论分析,剖析故障的具体原因。