TEM Studies of High Temperature Corrosion Behaviour of TiAl Intermetallics with Surface Modifications

The oxidation/sulphidation behaviour of a Ti‐46.7Al‐1.9W‐0.5Si alloy with a TiAl₃ diffusion coating was studied in an environment of H₂/H₂S/H₂O at 850^oC. The kinetic results demonstrate that the TiAl₃ coating significantly increased the high temperature corrosion resistance of Ti‐46.7Al‐1.9W‐0.5Si. The SEM, EDX, XRD and TEM analysis reveals that the formation of an Al₂O₃ scale on the surface of the TiAl₃‐coated sample was responsible for the enhancement of the corroison resistance. The Ti‐46.7Al‐1.9W‐0.5Si alloy was also modified by Nb ion implantation. The Nb ion implanted and as received sampels were subjected to cyclic oxidation in an open air at 800^oC. The Nb ion implantation not only increased the oxidation resistance but also substantially improved the adhesion of scale to the substrate.     

Fatigue crack growth in SiC particulates reinforced Al matrix graded composite

The SiC/Al graded composite was fabricated by powder metallurgy processing and its fatigue crack growth behavior was studied. The volume percentage of SiC particulates was distributed from 5 to 30% layer by layer on the cross section. Since the aluminium was dissolved together, there was no evident interface between the two layers with different volume fraction of SiC particulates. Fatigue crack growth was in direction of from 5 to 30% SiC layers under sinusoidal wave-form. The retardation of fatigue crack growth was found when crack propagated from low volume fraction of SiC to high volume fraction of SiC. The crack deflection and branching between two layers were observed, which decreased crack growth rates. In view of crack tip driving force, the plasticity mismatch between the layers shielded crack tip driving force, i.e. decreased the effective J-integral at the tip of the crack as the plastic zone of the crack tip spread from the weaker material into the stronger material.     

TD-SCDMA系统终端中的GMM功能实体研究

移动性管理(MM,MobilityManagement)是层3的一个子层,它主要完成与用户的移动性相关的一些功能。根据业务的分域划分,MM子层被分为支持CS模式的MM实体和支持PS模式的GMM实体。本文通过对GMM一般过程和特殊过程的描述,介绍了TD-SCDMA系统终端GMM实体的功能及其实现过程。     

天融信逾越中国企业"坎"

从去年年底的一段时间以来,尽管天融信备受外界关注,但除了宣布去年9月在天融信成立十周年之际,具有丰富国际企业运作和管理经验的金玉丹先生出任天融信公司的CEO和今年一月任命韦文为公司CTO以外,天融信通过正面渠道向外界发出的声音似乎并不多,大家听到更多的是通过小道消息或传闻,有人说天融信正在进行人事变动,也有人说天融信正在历经变革与调整,但都未得到正面证实。然而近期天     

SafeNet实现超强安全加密

安全加密产品的领导者SafeNet 公司,近日发布了新一代世界级高安全加密锁产品——圣天狗,以确保软件开发商的知识产权不被非法盗用。圣天狗(Sentinel Dog)是第一个也是唯一一个在市场上采用公钥技术、AES加密和内部验证机制的保护锁。它在提供超强安全加密性能的同时具有弹性化的授权模式。     

Adaptive agents and multiagent systems

New information systems and recent applications (grid computing, Web Services, and so on) are often distributed, large-scale, open, heterogeneous, and characterized by a dynamic environment. To model these complex systems, researchers have spent much effort during the last few years on multiagent systems. The aim is to model complex distributed systems as a set of (possibly organized) software agents that interact in a common environment. The decomposition of a system into a number of agents lets the system react and adapt better in a changing environment. Moreover, organized structures ("social" structures) can emerge from interactions between agents, which in turn constrain and coordinate the agents' behavior. A multiagent system takes its metaphors of interaction from social systems rather than using the metaphor of the isolated thinker that early artificial intelligence researchers preferred. An important issue when dealing with this increasing complexity is to build adaptive agents and multiagent systems. Agents and multiagent systems must be aware of their own capabilities and of changes to other agents and their environment. To remain effective, agents must be able to adapt their structures and knowledge while they execute.     

The First Template‐Free Growth of Crystalline Silicon Microtubes

A simple template‐free high‐temperature evaporation method was developed for the growth of crystalline Si microtubes for the first time. As‐grown Si microtubes were characterized using X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, and room‐temperature photoluminescence. The lengths of the Si tubes can reach several hundreds of micrometers; some of them have lengths on the order of millimeters. Each tube has a uniform outer diameter along its entire length, and the typical outer diameter is ≈ 2–3 μm. Most of the tubes have a wall thickness of ≈ 400–500 nm, though a considerable number of them exhibit a very thin wall thickness of ≈ 50 nm. Room‐temperature photoluminescence measurement shows the as‐synthesized Si microtubes have two strong emission peaks centered at ≈ 589 nm and ≈ 617 nm and a weak emission peak centered at ≈ 455 nm. A possible mechanism for the formation of these Si tubes is proposed. We believe that the present discovery of the crystalline Si microtubes will promote further experimental studies on their physical properties and smart applications.     

5Gb/s 0.25μm CMOS限幅放大器

采用TSMC 0.25μm CMOS技术设计实现了高速低功耗光纤通信用限幅放大器.该放大器采用有源电感负载技术和放大器直接耦合技术以提高增益,拓展带宽,降低功耗并保持了良好的噪声性能.电路采用3.3V单电源供电,电路增益可达50dB,输入动态范围小于5mVpp,最高工作速率可达7Gb/s,均方根抖动小于0.03UI.此外核心电路功耗小于40mW,芯片面积仅为0.70mm×0.70mm.可满足2.5,3.125和5Gb/s三个速率级的光纤通信系统的要求.