Stress-deformable state of isotropic double curved shell with internal cracks and a circular hole

This work is devoted to the stress–strain state of isotropic double curved shell with defect system. The construction is weakened by two non-through thickness (internal) cracks of different length and by a circular hole located between cracks. In this study we use the line-spring model. Within the framework of this model cracks are modeled as mathematical cuts of shell’s middle surface. This leads to a two-dimensional problem. The problem is reduced to a system of eight boundary integral equations. To ensure the uniqueness of solution an additional equation is added. In the numerical solution of the problem special quadrature formulas for singular integrals of Cauchy type and the finite difference method are applied. The influence of defects on each other for double curved shell has been investigated. The given theoretical results can be used for the calculation of structural elements with holes, cracks on the strength and fracture toughness in various branches of engineering.     

美国固体照明技术进展概况

介绍了美国能源部于2002年开始实施的固体照明(SSL)技术的"下一代照明计划".同时对美国SSL技术的研发、生产和使用现状以及召开学术会议的情况做了叙述.     

Microstructure study of Sm,Mn-modified PbTiO3 piezoelectric ceramics by XRD profile-fitting technique

By using the X-ray diffraction profile-fitting technique, the microstructures of Sm, Mn-modified PbTiO₃ piezoelectric ceramic discs, including ferroelectric domain sizes, microstrains, and their variations with the poling strength have been quantitatively investigated. The results manifest that the modified PbTiO₃ ceramics contain a high density of domain walls due to the presence of finely-divided coherent domain structures (tens of nanometres in dimension). The poling treament can evidently influence the domain-size distribution, with a more homogeneous microstructure being developed; however, it simultaneously causes high anisotropic microstrains within the structure which, together with the high density of domain walls, is expected to be responsible for the unusual high electromechanical coupling properties possessed by this material.     

反应温度对聚苯胺薄膜生长的影响

在不同反应温度条件下采用原位聚合法在石英基片上制备了聚苯胺薄膜．对薄膜样品进行了紫外光谱、SEM、电性能表征。实验结果表明，过高的合成温度会加速聚合反应过程，抑制膜厚的增长，引起薄膜的热降解，进而对样品的导电性产生不良影响。根据生长速率与合成温度的依赖关系，估算了聚合反应的活化能Ea=34.4kJ/mol。     

材料化学工程科学内涵及方法初探:从介观尺度界面流体行为出发认知材料

作为一门新兴的交叉学科,材料化学工程科学内涵的进一步凝练和方法论的建立显得十分重要和迫切。介观尺度下界面流体的研究对于材料化学工程具有重要意义,材料化学工程的科学内涵在于通过认识介观尺度下界面处流体行为来"认知"材料,以期建立材料结构、性能(应用)与制备(生产)三者之间的关系。其中,弄清介观尺度下复杂作用和复杂结构对界面流体行为的影响,是"认知"材料的关键。分子模拟技术作为单因素遴选介观尺度各影响因素的有效手段,在实际应用中存在两大难点:如何同时获得界面流体反应和传递两个方面的信息;如何实现分子层面认识在材料应用层面的转化。基于此,初步讨论了材料化学工程研究方法的发展趋势。     

改性压实水泥抗压强度影响因素的研究

采用ＤＳＰ原理和压实技术相结合，掺加硅灰和ＣａＣＯ３等细颗粒矿物外加剂改变压实水泥材料基质。研究了成型压力、细粉掺量、养护制度等因素对压实水泥强度的影响。结果表明，掺加适量硅灰和提高成型压力可显著提高压实水泥的抗压强度，掺加ＣａＣＯ３对强度无明显影响；压实水泥存在最佳养护龄期，超过此龄期强度倒缩。     

Synthesis, characterization of bimetallic Sn-Zn-MCM41 and its catalytic performance in the hydroxylation of phenol

A series of Sn-Zn modified-MCM41 has been synthesized by direct hydrothermal method and characterized using ICP, XRD, TG/DTA, FT-IR, HRTEM and N_2-adsorption techniques. Catalytic performances of the obtained materials were evaluated in the hydroxylation of phenol with H₂O₂. Results indicated that all the samples exhibited typical hexagonal arrangement of mesoporous structure with high surface area and the heteroatoms were probably incorporated into the framework of MCM41. Catalytic tests revealed that the bimetallic incorporated materials were effective catalysts in the hydroxylation of phenol. The conversion of phenol could be reach to 56.8% for the catalysts with Sn: Zn: Si = 2.69: 4.57: 100 (molar ratio) under the optimized reaction conditions. Moreover, the materials containing Sn and Zn exhibited higher catalytic activity than monometallic Sn and Zn modified MCM41.     

2-乙基-2- 唑啉的阳离子开环聚合及聚合物的表征

以对甲苯磺酸甲酯为引发剂进行２乙基２唑啉阳离子开环聚合研究，主要考察了不同的单体／引发剂配比、聚合温度和聚合时间对聚合转化率和聚合物分子量的影响。聚合物通过ＩＲ、１Ｈ核磁共振、ＤＳＣ进行表征，并考察了聚（２乙基２唑啉）与部分聚合物和共聚物的共混性能。     

氧化锌对高胶凝性水泥熟料矿物形成及强度的影响

采用工业原料配料，对以硅酸三钙（C3S，C=CaO，S=SiO2）、硫铝酸钙（C4A3 S^-，C=CaO，A=Al2O3，S^-=SO4^2-）为主导矿物的含C4A3 S^-矿物硅酸盐水泥熟料的矿物形成及其强度进行了研究。借助X射线衍射和热重一差热分析研究了矿物形成过程；探讨了微量元素ZnO对熟料性能的影响及在熟料体系中的固溶情况。研究结果表明：生料中掺入ZnO可使C4A3 S^-和CaS等矿物通过低温反应形成，共存于同一熟料体系中，并可提高熟料的强度；过高的ZnO含量亦会降低C4A3 S^-矿物的分解温度。     

一步法合成5-甲基海因

以氰化钠、碳酸铵、乙醛等为原料，常压下一步反应得到５甲基海因，总收率７０２％。其最佳操作条件为：反应温度７５℃，反应时间３ｈ，原料碳酸铵与氰化钠之比为２∶１，酸化回流ｐＨ值为２，酸化回流时间２ｈ。