移动环境下一种缓存管理策略

移动计算环境中带宽具有非对称性,并且移动设备资源有限,传统的缓存管理策略需要占用大量的设备计算资源和网络带宽,有效的缓存管理技术能够极大提高移动计算的性能。对此提出一系列的针对移动计算的缓存管理策略。首先根据用户访问频率建立对应的具有生命周期的数据项缓存,然后使用自适应一致性维护策略维护缓存的一致性。通过实验分析,提出的管理策略能够很好地降低带宽占用,并且有效地减少对移动客户端的资源需求。     

聚苯乙烯／聚乙烯塑料合金的研究

以氢化SBS(SEBS)为相容剂,对聚苯乙烯/聚乙烯塑料合金进行了研究,着重讨论了体系中组成、相容剂含量、PS分子量以及合金制备条件对合金结构与性能的影响。     

Silica Nanoboxes as New Nano-structured Materials: Their Secondary Synthesis from Alumina-Rich Zeolites

Novel silica nanoboxes were prepared by controlled dealumination of Na-X and Ca-A type zeolites using ammonium hexafluorosilicate (AHFS). The silica-richer the parent zeolite, the smaller the average pore size produced and the narrower the pore size distribution obtained. This was due to the specific reactivity of the extracting agent with the zeolite framework aluminum atoms. High temperature calcination of the dealuminated X-zeolite (ammonium form) resulted in mesoporous materials exhibiting an ink-bottle shape, a quite high surface area (330 m²/g, no micropores), an average pore diameter of 4.5 nm with a quite narrow pore size distribution (± 1.0 nm) and finally, a pore opening diameter of 3.9 nm. The latter was determined by using the nitrogen sorption isotherms (BET technique) and related pore volume data. The sorption behavior also suggested the interconnecting character of the newly created nanoboxes. The periodicity of these nanoboxes throughout the mesoporous material was clearly shown by X-ray powder diffraction at very small angles. These materials, herein called monomodal nanoboxes because of the absence of micropores in the structure, were also thermally stable. Incorporation of orthosilicate into the obtained silica nanoboxes, in accordance with the recently developed technique for pore size engineering in zeolites, led to materials with smaller pore openings but having almost the same textural properties. Solid superacidic materials were prepared by incorporating a liquid superacid (triflic acid or trifluoromethanesulfonic acid) into the silica nanoboxes using the wet impregnation technique. The maximum triflic acid loading which did not significantly affect the mesoporous framework of the materials was 24 wt%. As a reference, the maximum loading of less acidic sulfuric acid was slightly lower. All this showed the high chemical stability of the silica nanoboxes for supporting very acidic species. Temperature-programmed desorption using a combined DTA/TGA system allowed the identification of the bound phases and some liquid phase of the loaded triflic acid.     

面向移动互联网的OSS服务能力开放架构设计与应用

在移动互联网环境下,实现OSS服务能力开放是增强电信企业运营支撑能力、提升客户感知的重要手段。从OSS服务能力开放需求分析入手,提出面向移动互联网的OSS服务能力开放架构,并通过实际业务场景进行验证。     

基于人脸特征和线积分卷积的肖像素描生成

为了更好地模拟素描的笔画和突显肖像素描中五官的部分,提出基于人脸特征和线积分卷积的肖像素描生成方法.首先进行人脸分割,由人脸特征点确定GrabCut算法中每个特征的初始trimap,然后根据分割结果使用线积分卷积算法绘制肖像素描.文中使用了基于分割结果的多分辨率白噪声和方向场,并提出了基于分割结果的自适应性边界提取算法.实验结果表明,该算法改善了肖像素描的生成效果.     

Morphology and characterization of conductive films based on polyaniline‐coated polystyrene latexes

The polyaniline (PANI)‐coated polystyrene (PS) latexes were synthesized, and the electrically conductive films were prepared thereafter. The weight ratio of PANI was 5%. Thermal analysis of the latices was performed using DSC and TGA. In this study, the electrically conductive films were prepared above the PS glass transition temperature (T_g). During the film formation, the effects of the annealing temperature and atmosphere (air or N₂) on the film resistance were investigated. In addition, the film morphology was observed utilizing scanning electron microscopy. The film resistance decreased in the initial heating stage due to the increasing temperature and the compaction of film. Then the film resistance increased with further annealing due to the aging of PANI. Typically, the film resistance was about 6000 Ω/sq, and the conductivity was 0.3 S/cm. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5406–5413, 2006     

Aromatization of n-butane over new LD-HBS catalysts. Effect of the gallium oxide support

It is shown that even pure quartz, other silicas or aluminas can enhance the aromatization activity of a ZSM-5 zeolite. Incorporation of gallium oxide onto these supports increases further the production of aromatics. The use of supported gallium oxide co-catalyst obtained by co-evaporation of a colloidal silica and a Ga salt has led to extremely high aromatization performance for the hybrid catalyst.     

Studies on crystal morphology and crystallization kinetics of polypropylene filled with CaCO3 of different size and size distribution

Changes in the crystal morphology, crystallinity, and the melting temperature of thermoplastics resulted in significant changes in the mechanical behavior of composites containing them. For this reason, the research of crystal morphology and crystallization kinetics in thermoplastic composites became an important requirement. The thermoplastic filled with the filler of different size gradation was a new method for improving processability of thermoplastic composites. We have previously reported that the melt viscosity of polypropylene (PP) composites, which were filled with 30 wt % CaCO₃ of effective size gradation, could be evidently declined. In this study, two sizes of CaCO₃, 325 meshes and 1500 meshes, were blended by different proportions and filled into PP matrix with 30 wt %. Crystal morphology and isothermal crystallization kinetics of a series of composites were characterized by differential scanning calorimeter (DSC) and polarizing microscope. The results showed that composites filled with CaCO₃ of effective size gradation leaded to a well‐crystalline order and a large crystal size, while their isothermal crystallization kinetics and crystallization rate constant (k) were declined, and their Avrami exponents (n) and crystallization half‐life (t_1/2) were increased compared with the composites filled with single size CaCO₃. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2437–2444, 2006     

聚合物流变性能对共注射成型的影响

在共注射成型多相分层流动充模成型机理的基础上，揭示了芯壳层熔体对共注射成型的分层界面形貌和芯层熔体前沿突破的影响，并模拟了芯壳层熔体粘度比对共注射成型的影响，建立了芯壳层熔体粘度与分层界面和前沿移动界面菜貌的关系。本文的模拟研究结果与一些文献的实验结果相吻合。     

Nonisothermal crystallization kinetics of poly(butylene terephthalate)/montmorillonite nanocomposites

The melt intercalation method was employed to prepare poly(butylene terephthalate) (PBT)/montmorillonite (MMT) nanocomposites, and the microstructures were characterized with X‐ray diffraction and transmission electron microscopy. Then, the nonisothermal crystallization behavior of the nanocomposites was studied with differential scanning calorimetry (DSC). The DSC results showed that the exothermic peaks for the nanocomposites distinctly shifted to lower temperatures at various cooling rates in comparison with that for pure PBT, and with increasing MMT content, the peak crystallization temperature of the PBT/MMT hybrids declined gradually. The nonisothermal crystallization kinetics were analyzed by the Avrami, Jeziorny, Ozawa, and Mo methods on the basis of the DSC data. The results revealed that very small amounts of clay (1 wt %) could accelerate the crystallization process, whereas higher clay loadings reduced the rate of crystallization. In addition, the activation energy for the transport of the macromolecular segments to the growing surface was determined by the Kissinger method. The results clearly indicated that the hybrids with small amounts of clay presented lower activation energy than PBT, whereas those with higher clay loadings showed higher activation energy. The MMT content and the crystallization conditions as well as the nature of the matrix itself affected the crystallization behavior of the hybrids. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3257–3265, 2006