Studies on the corrosion behavior of cerium-implanted zircaloy-4 with GAXRD

In order to study the influence of cerium ion implantation on the aqueous corrosion behavior of zircaloy-4, specimens were implanted by cerium ions with a fluence range from 1×10¹⁶ to 1×10¹⁷ ions/cm² at maximum 150°C, using MEVVA source at an extracted voltage of 40 kV. The valence and elements penetration distribution of the surface layer were analyzed by X-ray photoelectron spectroscopy (XPS) and auger electron spectroscopy (AES) respectively. Glancing angle X-ray diffraction (GAXRD) was employed to examine the phase transformation due to the cerium ion implantation in the oxide films. Three-sweep potentiodynamic polarization measurement was employed to value the aqueous corrosion resistance of zircaloy-4 in a 1 N H₂SO₄ solution. It was found that a significant improvement in the aqueous corrosion behavior of zircaloy-4 implanted with cerium ions compared with that of the as-received zircaloy-4. The improvement effect will declined with raising the implantation fluence. The bigger is the fluence, the less is the improvement. Finally, the mechanism of the corrosion behavior of the cerium-implanted zircaloy-4 is discussed.     

高层印制线路板正面临的对位挑战

封装工业正在推动着印制线路板技术水平朝着半导体要求的方向发展。高密度印制线路板正广泛用于网络路由器、自动测试设备和服务器领域。高密度要求(>150 IO/cm~2)正成为客户的普通需求。为满足现有的高密度封装要求,由于线宽、线距和通孔孔径正接近传统制作极限,普遍的方法就是不断增加印制线路板的层数。这些特征正驱动着印制线路板在基材、图像转移、蚀刻、电镀、阻焊、测试流程和对位系统的变化。此文主要讲述了印制线路板特性的变化趋势和利用对位模式和雷利分布去预测满足高级对位要求的能力以及印制线路板各流程中有关对准度的控制要点。     

Speaker identification based on adaptive discriminative vector quantisation

A novel adaptive discriminative vector quantisation technique for speaker identification (ADVQSI) is introduced. In the training mode of ADVQSI, for each speaker, the speech feature vector space is divided into a number of subspaces. The feature space segmentation is based on the difference between the probability distribution of the speech feature vectors from each speaker and that from all speakers in the speaker identification (SI) group. Then, an optimal discriminative weight, which represents the subspace's role in SI, is calculated for each subspace of each speaker by employing adaptive techniques. The largest template differences between speakers in the SI group are achieved by using optimal discriminative weights. In the testing mode of ADVQSI, discriminative weighted average vector quantisation (VQ) distortions are used for SI decisions. The performance of ADVQSI is analysed and tested experimentally. The experimental results confirm the performance improvement employing the proposed technique in comparison with existing VQ techniques for SI and recently reported discriminative VQ techniques for SI (DVQSI)     

丙烯酸高碳醇酯的合成

介绍了降凝剂中间体丙烯酸高碳醇酯的合成和产品分离提纯方法。考察了合成条件对酯化反应的影响，结果表明，在原料丙烯酸与十八醇摩尔比1．2：1，阻聚剂对苯二酚用量占原料总量1．5％，催化剂对甲苯磺酸用量占原料总量1．5％，反应温度80-86℃，回流反应时间6h条件下，酯化率最高达89％。产品分离提纯方法与传统分离方法比较，所需分离时间短，洗涤用水量少，而产品收率远高于传统分离方法，达95％以上。     

苯部分加氢催化剂失活原因的研究

探讨了环己醇装置苯部分加氢催化剂失活的原因，分析了失活机理，并结合实例——母液置换法解决催化剂的氮化物中毒。     

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     

Analytical solution for the axisymmetric plane strain electroelastic dynamics of a special non-homogeneous piezoelectric hollow cylinder

By virtue of the introduction of a dependent variable and the separation of variables technique, the axisymmetric plane strain electroelastic dynamic problem of a special non-homogeneous piezoelectric hollow cylinder is transformed to a Volterra integral equation of the second kind about a function with respect to time, which can be solved successfully by means of the interpolation method. Then the solutions of displacements, stresses, electric displacements and electric potential are obtained. The present method is suitable for a piezoelectric hollow cylinder with an arbitrary thickness subjected to arbitrary mechanical and electrical loads. Numerical results are finally presented.     

Ultrafast Spectroscopy of La2−x Sr x CuO4 Single Crystals

We present measurements of the ultrafast optical response of La_2–x Sr _x CuO₄ single crystals at two different doping levels (x=0.15, 0.07) as a function of temperature. Owing to the 40-fs time resolution of our experiment, we are able to measure both the build-up and the decay of the ultrafast signal. We show for the first time that the temperature dependence of the transient reflectance amplitude tracks the thermal depletion of the superfluid density. At low temperature we identify a new regime characterized by an extremely long, temperature-dependent rise-time (3 ps). The doping dependence of the relaxation rate suggests that this is sensitive to the scattering of quasiparticles by low-energy spin excitations.     

短信服务误区的成因分析及其对策

短信市场巨额收入的刺激，再加上市场监管力度不够，使得一些服务提供商（SP）片在追求收益而忽视消费者需求，导致短信服务走入了一些误区，这已经引起一系列负面效应，要解决此问题，SP应树立服务理念，根据客户的需求来提供服务内容和服务方式；运营商需改进商业模式，应考虑对SP提供的业务内容和配套服务进行规范，用户要维护自身权益，政府则应加强监管能力。