Synthesis,characterization, and thermal properties of alternate copolymers containing N,N′‐bis(diphenylsilyl)tetraphenylcyclodisilazane

Hexamethyldisilazane was used as the starting material to synthesize N,N′‐bis(hydroxydiphenylsilanyl)tetraphenylcyclodisilazane (BHPTPC). By condensation polymerization of BHPTPC with α,ω‐bis(dialkylamino)dimethylsiloxane, a series of alternate copolymers containing N,N′‐bis(diphenylsilyl)tetraphenylcyclodisilazane was synthesized. GPC studies show that the highest molecular weight was obtained at a ratio of 1.005 : 1 (BHPTPC: α,ω‐bis(dimethyl amino)dimethylsiloxane). Data of DSC indicate that the temperature of glass transition (T_g) and temperature of melting point (T_m) decreased with the increasing of dimethylsiloxane segments units. Three stages of degradation were found in the thermogravimetric analysis curves. The activation energy of the copolymer (with m = 2, 3, and 7) was calculated by using Flynn–Wall–Ozawa method. The activation energy of the copolymer with m = 2, 3, and 7 at second stage is 214, 211, and 184 kJ/mol, respectively. Isothermal gravimetric analysis shows that for the same temperature and the same time, the weight loss of the alternate copolymer was greatly less than that of common polydimethylsiloxane. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 611–617, 2007     

Morphologies-Controlled Synthesis and Optical Properties of Bismuth Tungstate Nanocrystals by a Low-Temperature Molten Salt Method

Well-crystallized bismuth tungstate (Bi₂WO₆) powders with different morphologies were successfully synthesized via a low-temperature molten salt method. The powders were characterized by X-ray diffraction, transmission electron microscopy, and UV-Vis, respectively. It was found that the variation of morphology of the obtained Bi₂WO₆ powder mainly depends on the different reaction temperatures and the weight ratio of LiNO₃–NaNO₃ salt to precursor. In addition, the UV-Visible absorption spectra showed that the synthesized powders had strong light absorption properties not only in the ultraviolet light but also in the visible light region.     

A formal framework for service mashups with dynamic service selection

The service mashup programming paradigm is a blooming faction of service oriented Architecture for developing web applications. A mashup application constructs its functionality by combining data, presentation and functionalities obtained from online services published by service providers such as Google and Amazon. This paradigm significantly facilitates the implementation of application and reduces the workload. But it also makes the application rely on the availability and qualities of the online services which beyond its control in which case the robustness of the system requires more concern. This paper proposes a formal model to specify and analyze the behavior and robustness of service mashups under a certain environment where some services may become unavailable. The specification contains both system specification and environment situation. Refinement theory are employed to specify the correctness of dynamic service selection. The framework realizes the service selection by allowing virtual service requests to be handled by any online service having consistent interface and refined functionality. The framework provides a clear definition of the robustness of mashup systems and proposes several rules as well as approaches to preserve the robustness during the development and maintenance of the system.     

Structural topology optimization with constraints on multi-fastener joint loads

This paper addresses an important problem of design constraints on fastener joint loads that are well recognized in the design of assembled aircraft structures. To avoid the failure of fastener joints, standard topology optimization is extended not only to minimize the structural compliance but also to control shear loads intensities over fasteners. It is shown that the underlying design scheme is to ameliorate the stiffness distribution over the structure in accordance with the control of load distributions over fastener joints. Typical examples are studied by means of topology optimization with joint load constraints and the standard compliance design. The effects of joint load constraints are highlighted by comparing numerical optimization results obtained by both methods. Meanwhile, resin models of optimized designs are fabricated by rapid prototyping process for loading test experiments to make sure the effectiveness of the proposed method.     

Research on the comprehensive traffic state evaluation model linked with drivers’ perception under the vehicle networking

Unified judgment standards and methods are often adopted to identify traffic state in certain road network based on traffic flow parameters. However, drivers often have different perceptions about the traffic state on different road sections, since their expectations on traffic state vary more or less from each other on different road sections. In particular, under the vehicle networking, out of considerations for safety and other relevant factors, requirements for the correlation and coordination of running vehicles have also raised significantly. Therefore, it is necessary to take driver’s perception about the driving conditions of certain road sections into consideration to adjust the release of traffic state. This paper has provided a comprehensive traffic state evaluation model linked with driver’s perception under the vehicle networking. The authors first establish an ANFIS model based on the T–S model and then conduct statistical analysis on drivers’ perceptions about certain traffic state. At last, the authors use the results of statistical analysis as regulatory factors to amend the parameters input through ANFIS. Through simulation, this paper has demonstrated that the model established has a high rate of convergence, a high identification precision and the generalization ability to conduct researches on the identification of traffic state.     

基于贪婪路由协议的动态单/多链路故障恢复策略

针对现有的贪婪方法不能有效处理拓扑结构中链路故障的问题,提出单链路故障和多链路故障本地化恢复策略。首先,通过利用克莱因伯格的贪婪嵌入给出单链路故障恢复策略;然后,将其扩展到多链路故障的情况;最后,在基于Python/C++的仿真环境下对提出的技术进行评估。实验结果表明,该技术仅需要非常有限的资源,且造成的路由质量损耗也有限,可以实现快速切换,可依网络生成树中链路数目扩展。该技术的可扩展性、简单性和低开销使其适合于大型网络。     

基于BPEL的MDO流程建模与调度系统设计和实现

在分析多学科设计优化特点的基础上,充分集成Web services技术和BPEL技术,设计一个基于BPEL的多学科设计优化的流程建模与调度系统。重点介绍该系统的两个模块即可视化流程建模工具模块和流程调度监控平台模块的设计和实现方法。最后给出一个优化实例说明该系统的可行性。     

The influence of monomer types on the colloidal stability in the miniemulsion copolymerization involving alkoxysilane monomer

Unlike conventional emulsion polymerization, monomer droplet nucleation becomes dominant in miniemulsion polymerization, offering the miniemulsion polymerization a great advantage over conventional emulsion polymerization when incorporating alkoxysilane monomer, which can easily undergo premature hydrolysis and condensation reactions, into polymer latex. The extensive premature hydrolysis and condensation can lead to the issue of the colloidal instability. In this article, the influence of monomer types on the colloidal stability in the miniemulsion co-(or ter-)polymerization was investigated when incorporating alkoxysilane monomer into styrene or acrylate latex. In the cases of butyl acrylate (BA)/γ-methacryoxypropytrimethoxysilane (MPMS), BA/methyl methyacrlate (MMA)/MPMS, and BA/styrene (St)/MPMS miniemulsion polymerization, nearly no coagulum was observed. The obtained latex had a long shelf life. However, the coagulum was formed in the late stage of MMA/MPMS and St/MPMS miniemulsion copolymerization. The shelf life of the corresponding latex was short. The selection of the main monomer, which can fast consume alkoxysilane comonomer, was critical to obtain the stable latex. In this way, the alkoxysilane groups were completely buried in particles thus the coagulation caused by condensation reactions derived from the alkoxysilane hydrolysis among particles was suppressed.     

己内酰胺生产的绿色化

己内酰胺生产的绿色化关键是环己酮肟贝克曼重排工艺路线替代的开发。重点介绍了代替浓硫酸催化该反应的固体酸催化剂、催化剂的失活与再生、反应器工业化的方法的进展。提出采用多相催化剂取代发烟硫酸使环己酮肟转化为己内酰胺的工艺 ,该催化剂具有转化率和选择性高 ,易处理再生 ,且可用于连续化工业生产     

CAU9901的高效液相色谱分析

报道了新型植物生长调节剂CAU9901的高效液相色谱分析方法。该方法快速简捷,精密度变异系数为0.49%,相关系数为1.000 4,准确度回收率在98.89%~100.1%之间。