Flammability and thermal stability studies of ABS/Montmorillonite nanocomposite

Acrylonitrile–butadiene–styrene (ABS)/montmorillonite nanocomposites have been prepared using a direct melt intercalation technique by blending ABS and organophilic clay of two different particle sizes: OMTa (5 µm) and OMTb (38 µm). Their structure and flammability properties were characterized by X‐ray diffraction, high resolution electronic microscopy (HREM), thermogravimetric analysis (TGA) and cone calorimeter experiments. The results of HREM showed that ABS/5 wt% OMTa nanocomposite was a kind of intercalated–delaminated structure, while ABS/5 wt% OMTb nanocomposite was mainly an intercalated structure. The nanocomposites showed a lower heat release rate peak and higher thermal stability than the original ABS by TGA and cone calorimeter experiments. Also, the intercalated nanocomposite was more effective than an exfoliated–intercalated nanocomposite in fire retardancy. Copyright © 2003 Society of Chemical Industry     

电子商务中信息传输与共享

电子商务中信息传输与共享技术是电子商务的核心技术 ,电子商务是以Internet为基础的新兴产业 ,保护信息的安全无疑是十分重要的 ,人们越来越多地使用计算机网络来传送对安全敏感的信息 ,所以在信息传输域共享中 ,认证业务、保密业务、数据完整性业务、不可否认业务是当前电子商务急需解决的关键技术 ,本文对这方面做了一些探讨并提出自己的看法     

The Content Driven Mobile Internet

The development of future mobile networks will be driven, in large part, by content and web based services. In this paper, we examine several performance, scalability and architectural challenges faced by future mobile web applications and how advanced mobile content delivery techniques can address these challenges. We review existing content delivery using a taxonomy that consists of three categories: network scaling, end system acceleration, and content and protocol optimization. While wireline content delivery focuses on network and server scalability, mobile content delivery will likely benefit most from optimizing radio link usage. We also present our ongoing work in this area, which extends the functionality of edge caching to the terminal, uses user interest correlation information to maintain low terminal power consumption and adds a new dimension to radio resource management. This revised version was published online in August 2006 with corrections to the Cover Date.     

Laser-assisted sealing and testing for ceramic packaging of MEMS devices

In this work, a CO/sub 2/ laser-assisted silicon lid sealing process, utilizing Au80/Sn20 solder, for encapsulating gas breakdown test micro-electro-mechanical structures (MEMS) in a ceramic quad flatpack (CQFP) was studied. Wire bonded MEMS dies were sealed into CQFPs under various gas media, such as air, nitrogen, helium and vacuum. The gas breakdown test results showed a significantly higher breakdown voltage for vacuum packaged parts compared to those packaged in other various gas environments. Hermeticity testing according to MIL-STD-883E showed that the leak rate of the package was below 10/sup -8/ atm cc/s. The bonding was uniform and the bonding strength is believed to be comparable to the tensile strength of Au80/Sn20 solder.     

Phase Transition VO2 Thin Films for Optical Switches

This paper presents a method to make vanadium dioxide (VO₂) crystallites on silicon substrates by reactive ion beam sputtering. The thickness of the thin film is about 100nm. The phase transition temperature of VO₂ is 65°C. The transmittance of the semiconducting phase VO₂ is about 50% and it is reduced to as low as 3% in metal phase at the infrared wavelenghth spectrum. The extinction ratio of the optical switches is 12dB. and the insertion loss is of 1-2dB. The switching time is about 1ms.     

27keV Ar~+斜入射时的Cu-Au合金溅射实验角分布

用27keV Ar~+分别在垂直和倾斜入射情况下,轰击了Cu-Au(30wt％)合金样品,测量了Cu和Au原子的溅射角分布。角分布是用卢瑟福背散射(RBS)技术分析Al捕获膜上的Cu-Au沉积成分而定量得到的。结果表明:(1)在Ar~+倾斜(θ=40°)入射时,Cu原子择优发射,且程度比垂直入射(θ_r=O°)时增强:(2)倾斜入射时,Cu原子的角分布显示出在接近于样品表面法线方向的发射角范围内(θ<45°),发射机率比垂直入射时减小。     

傅立叶变换在虚拟仪器LabVIE中的应用

文中介绍了LabVIEW环境下用NI公司高级分析库里的信号处理工具包的Real FFT.vi傅立叶变换,采用此种方法对某型飞机起落架液压测试系统采样信号进行频谱分析,实验证明其效果良好.     

铸造铝合金(ZL109)激光表面处理

采用功率为2kW级CO_2连续可调式横流激光光源,对不同涂层的ZL109试样表面进行了激光熔凝的实验研究。     

A vectorial boundary element method analysis of integrated optical waveguides

In this paper, a new vectorial boundary element method is introduced and applied to the modal analysis of dielectric waveguides with piecewise homogeneous refractive indexes. The procedure, which is free of spurious modes, determines the full field distribution from the longitudinal fields at the refractive index boundaries. Singular kernels are evaluated through series solutions while the electric field discontinuity at corners is accommodated through either a grid refinement technique or a semianalytic approach. Our formalism generates propagation constants and modal field distributions for several representative refractive index profiles with far higher accuracy than standard finite-difference or finite-element procedures.