Trusted Next Generation Internet and Its Development

The ongoing research on secure and trustworthy issues in next generation Internet technology is still insufficient. China has achieved some progress in the field of the trusted next generation Internet. Under the support of the National High Technology Research and Development Program of China (863 Program), Tsinghua University and other units have completed the program named "Research on Critical Technologies and Demonstration Applications of the Trusted Next Generation Internet", which targets the secure and trustworthy problems existing in the current Internet. With focus on tackling the technical problem of authentic address access in the Internet, a prototype system for trusted Internet infrastructure, security service and typical applications are designed and implemented. It is expected that the trusted next generation Internet will support the trusted computer network, trusted telecom network and trusted broadcast & TV network applications.     

Calculation and analysis of thermal impedance of microelectronic structures from analytical models

This article deals with thermal impedances of microelectronic components that are useful in Simulation Programs with Integrated Circuit Emphasis (SPICE). In devices like heterojunction bipolar transistors, the active regions thicknesses are often much smaller than the substrates thicknesses. The devices can then be thermally assimilated to heat densities located on top of solid media. In addition to that, when the other dimensions of the heat sources are also much smaller than the substrates dimensions, it is reasonable to consider that the substrate is semi-infinite. First, the expression of the thermal impedance Z of a circular shape heat source centered on top of a half space is presented. For this purpose, the integral transform technique has been used to solve the tri-dimensional heat conduction equation in the frequency domain. The original expression is explicit, exact and allows obtaining results very quickly. After that, the case of a circular heat source on top of a cylinder is treated. A complete analysis of the substrate dimensions influence on the thermal impedance is done. It is based on the impedance decomposition into the one-dimensional impedance and the spreading impedance. By comparing these impedances with that obtained for the heat source on top of the semi-infinite medium, the threshold pulsation at which the thermal impedance of the finite medium differs from the thermal impedance of the half space is extracted. Moreover the geometrical criteria resulting in an error of less than 2% between the spreading impedance of the finite medium and the semi-infinite one are extracted. When these criteria are observed the impedance can be calculated using two perfectly known impedances: the spreading impedance of the semi-infinite medium and the one-dimensional impedance. The results are plotted on the Nyquist diagram, providing a compact representation. Finally the assumption of a circular shape heat source to approximate the thermal impedance of a square shape heat source is validated by evaluating the associated error. The calculation times have been compared to confirm the interest of using this hypothesis.     

InN薄膜的退火特性

对InN薄膜在氨气氛下的高温退火行为进行了研究.利用XRD,SEM和XPS对样品进行了分析.结果表明,InN薄膜的结晶质量和表面形貌并不随退火温度单调变化.由于高温退火时N原子的挥发,剩下的In原子在样品表面聚集形成In颗粒.当退火温度高于425℃时,In原子的脱吸附作用增加,从而导致样品表面的In颗粒在退火温度高于425℃时逐渐减少.XRD和SEM结果表明In颗粒密度最高的样品具有最差的结晶质量.这种现象可能是由于In颗粒隔离了其下面的InN与退火气氛的接触,同时,金属In和InN结构上的差异也可能在InN中导致了高密度的结构缺陷,从而降低了InN薄膜的结晶质量.     

WLAN技术与应用发展新趋势

提出WLAN的技术热点主要集中在VoWLAN,Mesh Wi-Fi和802.11n三个方面.具体阐述了VoWLAN和Mesh Wi-Fi的标准化进展、终端商用化进展以及对通信产业的影响.展望了VoWLAN和MeshWi-Fi的发展形势和机遇,分析了其面临的挑战.     

Quality-of-service provisioning and efficient resource utilization in CDMA cellular communications

One of the major challenges in supporting multimedia services over Internet protocol (IP)-based code-division multiple-access (CDMA) wireless networks is the quality-of-service (QoS) provisioning with efficient resource utilization. Compared with the circuit-switched voice service in the second-generation CDMA systems (i.e., IS-95), heterogeneous multimedia applications in future IP-based CDMA networks require more complex QoS provisioning and more sophisticated management of the scarce radio resources. This paper provides an overview of the CDMA-related QoS provisioning techniques in the avenues of packet scheduling, power allocation, and network coordination, summarizes state-of-the-art research results, and identifies further research issues.     

移动互联网背景下电信运营商创新产品应对策略

通过归纳移动互联网业务基本特征,分析其对电信运营商的冲击,进而结合典型移动互联网业务运作模式及中国联通传统项目管理的现状,提出中国联通针对移动互联网发展的创新产品应对策略。对移动互联网项目投资价值评估体系进行探讨,提出适合中国联通的创新产品管理体制。     

基于CAN总线的一体化两相步进电机驱动器的设计

设计了一种基于CAN总线接口的一体化步进电机驱动器,并描述了其详细的软硬件实现方法。采用高性能的STM32F103作为控制核心,接收CAN总线的控制命令,产生控制时序控制步进电机的运行。测试结果表明,系统具有结构简单、性能稳定等特点。     

532nm激光距离选通成像系统

实现了一套基于532 nm波长的距离选通成像系统,并选择了几种典型环境进行了相应的原理验证实验。采用532 nm的全固态调Q脉冲激光器作为主动照明激光,激光单脉冲能量可以在35~100 mJ之间调节,系统接收望远镜口径为200 mm。采用PIN探测器获得激光脉冲发射时间,并控制目标成像的曝光时刻。成像探测器采用ICCD(intensified CCD),最小曝光时间为2 ns。通过实验对比说明该系统能够在小雨天或者有烟雾的情况下正常工作,但是获得图像的信噪比会有所下降,同时能够在强光背景干扰的环境下获得目标的图像信息。该套系统的原理验证性实验能够为距离选通成像技术的进一步发展提供重要参考。     

Multifunctional Superelastic Cellulose Nanofibrils Aerogel by Dual Ice-Templating Assembly

A superelastic aerogel with fast shape recovery performance from large compressive strain is highly desired for numerous applications such as thermal insulation in clothing, high-sensitive sensors, and oil contaminant removal. Fabrication of superelastic cellulose nanofibrils (CNF) aerogels is challenging as the CNF can assemble into non-elastic sheet-like cell walls. Here, a dual ice-templating assembly (DITA) strategy is proposed that can control the assembly of CNF into sub-micrometer fibers by extremely low temperature freezing (–196 °C), which can further assemble into an elastic aerogel with interconnected sub-micron fibers by freezer freezing (−20 °C) and freeze drying. The CNF aerogel from the DITA process demonstrates isotropic superelastic behavior that can recover from over 80% compressive strain along both longitudinal and cross-sectional directions, even in an extremely cold liquid nitrogen environment. The elastic CNF aerogel can be easily modified by chemical vapor deposition of organosilane, demonstrating superhydrophobicity (164° water contact angle), high liquid absorption (489 g g⁻¹ of chloroform absorption capacity), self-cleaning, thermal insulating (0.023 W (mK)⁻¹), and infrared shielding properties. This new DITA strategy provides a facile design of superelastic aerogels from bio-based nanomaterials, and the derived high performance multifunctional elastic aerogel is expected to be useful for a wide-range of applications.     

播出系统中KII与PVS两代硬盘服务器的混合使用

目前Profile硬盘服务器的用户存在的现实问题是,在对系统进行升级改造时,在PDF和PVS系列硬盘服务器已经停产情况下,如何使KII系列与PDF或PVS系列安全高效地混合使用,温州市广播电视总台在这方面成功地解决了这个问题,通过近一年的使用,达到了预期的效果。简述KII与PVS在播出系统中的混用,希望能给Profile用户提供一些有益经验。