Negative Poisson's Ratio in Modern Functional Materials

Materials with negative Poisson's ratio attract considerable attention due to their underlying intriguing physical properties and numerous promising applications, particularly in stringent environments such as aerospace and defense areas, because of their unconventional mechanical enhancements. Recent progress in materials with a negative Poisson's ratio are reviewed here, with the current state of research regarding both theory and experiment. The inter‐relationship between the underlying structure and a negative Poisson's ratio is discussed in functional materials, including macroscopic bulk, low‐dimensional nanoscale particles, films, sheets, or tubes. The coexistence and correlations with other negative indexes (such as negative compressibility and negative thermal expansion) are also addressed. Finally, open questions and future research opportunities are proposed for functional materials with negative Poisson's ratios.     

Mo2NiB2基金属陶瓷的研究进展

在金属陶瓷领域中,三元硼化物的研究已经取得了一系列的成果,但是对Mo_2NiB_2基金属陶瓷涂层的研究还比较少。主要论述了Mo_2NiB_2晶体结构、显微组织、Mo_2NiB_2基金属陶瓷的性能、Mo_2NiB_2基金属陶瓷的合金化、Mo_2NiB_2基金属陶瓷涂层研究进展,并且对Mo_2NiB_2基金属陶瓷的研究进行了展望。     

益新矿中心大空孔掏槽爆破扩腔过程数值分析

为了更好的应用中心大空孔掏槽爆破技术,根据益新煤矿爆破工况,运用有限元软件LS-DYNA,深入分析爆破过程中应力波的传播、有效应力和应力场的变化,研究其扩腔过程及岩石破碎机理。结果表明:爆炸应力波首先在炮孔连线方向相遇叠加并形成一条直线型的加强带,然后传至空孔并发生复杂的反射和叠加,最后在岩体中扩散;空孔外围的应力场分布呈现"圆形-菱形-圆形-方形"的变化规律;中心大空孔掏槽爆破有利于炸药能量的均匀分布和槽腔的形成与扩展。现场验证表明:该项技术大大提高了煤矿巷道的掘进速度,取得了较好的经济效益。     

Plasmon resonant amplification of a hot electron-driven photodiode

Nano Research - We report plasmon resonant excitation of hot electrons in a photodetector based on a metal/oxide/metal (Au/Al2O3/graphene) heterostructure. In this device, hot electrons, excited...     

Energy gap distribution of HgBa2CuO4+δ investigated by scanning tunneling microscopy/spectroscopy

The superconducting energy gap distribution of poly crystalline HgBa₂CuO₄₊ samples of differing oxygen doping levels (T_c = 94 K and T_c = 96 K) is determined by scanning tunneling spectroscopy (STS) using a low temperature scanning tunneling microscope (STM). From histograms of energy gap values the presence of two distinct energy gaps is inferred (₁=8.5±1.6meV and ₂=15.1±1.4meV). We attribute the different gaps to different crystallographic faces, implying a non-BCS electron-electron pairing mechanism.     

Scanning/friction force microscopy study of YBa2Cu3O7−δ single crystals grown in BaZrO3 crucibles

Very pure YBa₂Cu₃O_7– (YBCO) single crystals grown in BaZrO₃ crucibles are studied in the as-grown and the oxidized state by scanning force (SFM), friction force (FFM) and scanning tunneling microscopies (STM). The images show clean terraces with step-heights of one unit cell along YBCO(001), i.e. 1.2 nm. Only close to step edges is material contrast observed by FFM indicating traces af flux. Some crystal surfaces exhibit over-layer features, such as star-like, ribbon-like and checkerboard-like structures, which exhibit friction contrast implying the presence of different materials on the surface. Tunneling spectroscopy at 4.7 K in high vacuum reveals a superconducting energy gap of 2 26 me V.     

基于路由器反馈拥塞控制机制的研究

随着网络的不断发展,传统的TCP拥塞控制机制已经不能很好地适应现有的网络环境;文中在分析了不同反馈信息的价值的基础上提出了一种新的基于路由器反馈的拥塞控制机制RSCP,部署方便,不需要额外包头;该机制创造性地提出了信号包的方法与路由器交换信息,并以公平带宽和公平剩余带宽为反馈信息,在以公平带宽为基点的基础上根据公平剩余带宽的变化调整发送速率,同时采用快速启动机制使连接能够快速达到公平带宽;仿真实验证明RSCP在单瓶颈网络中能取得高利用率、低队列长度和零丢包以及良好的收敛性能.     

电动汽车参数检测及报警显示系统设计

为了避免电动汽车上发生车体漏电击晕乘客等事故,设计了一个参数检测和报警系统,利用传感器实时检测电压电流,对电动汽车不正常状态进行屏幕显示和语音报警;系统以ATMEGA 64芯片为核心,采用霍尔传感器采集电压和电流值,用光耦隔离检测车门开关状态,AD模块采用查询的方式采集数据,通过液晶显示和语音报警两种方式提醒司乘人员;系统采用串口与PC机通信,系统内部采用抗干扰性较强的CAN总线进行通信;通过实际的测试应用,该系统运行良好,能满足设计要求,已经在北京公交公司准无轨电车上应用。     

Measurement-based modeling of contact forces and textures for haptic rendering

Haptic texture represents the fine-grained attributes of an object's surface and is related to physical characteristics such as roughness and stiffness. We introduce an interactive and mobile scanning system for the acquisition and synthesis of haptic textures that consists of a visually tracked handheld touch probe. The most novel aspect of our work is an estimation method for the contact stiffness of an object based solely on the acceleration and forces measured during stroking of its surface with the handheld probe. We establish an experimental relationship between the estimated stiffness and the contact stiffness observed during compression. We also measure the height-displacement profile of an object's surface enabling us to generate haptic textures. We show an example of mapping the textures on to a coarse surface mesh obtained with an image-based technique, but the textures may also be combined with coarse surface meshes obtained by manual modeling.