The luminescence of magnesium tungstate dihydrate,MgWO4·2H2O

The luminescence of MgWO₄.2H₂O contains two emission bands, one due to the tungstate tetrahedron, and another one related to the hydrate group. The former is compared with the tungstate luminescence of anhydrous MGWO₄.     

Numerical aspects of a lagrangian particle model for atmospheric dispersion of heavy gases

The objective of the paper is to develop and analyze a numerical procedure, based on a Lagrangian particle model, for heavy gas dispersion. The paper discusses the numerical solution of the advection diffusion equation, with particular application to atmospheric dispersion of heavy gases. The discretization requirements to control numerical errors are examined for typical applications. The model is demonstrated to alleviate numerical diffusion errors which result from application of low-order finite difference methods, while allowing affordable discretization for heavy gas dispersion predictions of practical interest.     

变载荷Pxmtn作用于Ⅲ型裂纹面的动态扩展问题

采用复变函数论的方法,对变载荷Pxmtn作用于Ⅲ型裂纹面的动态扩展问题进行研究.利用自相似函数的方法获得应力、位移和动态应力强度因子的解析解.应用该法可以轻易地将所讨论的问题转化为Riemann——Hilbert问题,然后按照Muskhe lishvili方法即可得到问题的闭合解.利用这些解和叠加原理,即可求得任意复杂问题的解.     

Free vibrations of rotating small aspect ratio pretwisted blades

Free vibration characteristics of a rotating pretwisted small aspect ratio blade, mounted on a disc at a stagger angle, are determined using classical bending theory of thin shells. Differential geometry of the blade in curvilinear coordinates are analysed and strain-displacement relations are established. The strain and kinetic energies of the rotating and vibrating blade are determined and the Lagrangian function is set up. Following the Ritz procedure, natural frequencies and mode shapes of the blade are determined. The results obtained from the present analysis compare well with some of the experimental and finite element results available in literature. Variation of natural frequencies with various parameters like pretwist, speed of rotation, stagger angle and disc radius is studied and the results are presented in a nondimensional form.     

聚苯并双噁唑类聚合物的合成及改性

简述了聚对苯撑苯并双(?)唑(PBO)的合成方法,详述了直链烯烃型、稠环芳烃型、联苯取代基型、杂环型聚苯并双(?)唑类聚合物的合成方法。综述了等离子体处理法、偶联剂处理法、电晕处理法等一系列PBO纤维表面改性技术的研究进展,通过介绍PBO／碳纳米管复合材料和PBO／粘土复合材料的合成技术,简析了PBO的纳米改性的研究。指出聚苯并双(?)唑聚合物研究将集中在合成高相对分子质量的聚合物合成技术,通过纳米改性及表面改性提高其性能,扩大应用领域。     

新型真空关风器的研制

为实现连续真空干燥,开发了一种真空关风器。这种关风器采用弹性密封技术和复合耐磨、自润滑材料来减少关风器的漏气量。漏气率试验证明,该新型真空关风器达到了颗粒物塔式连续真空干燥设备的性能要求。     

深冷处理对W6Mo5Cr4V2高速钢性能的影响

对经-120℃和-150℃深冷工艺处理的W6Mo5Cr4V2高速钢进行了硬度及摩擦磨损性能测试,并用扫描电镜分析了其显微组织与磨损形貌。深冷处理使高速钢硬度和耐磨性能得到提高。随深冷温度的降低,性能改善明显,经循环深冷处理试样的性能均好于一次长时间深冷处理试样,-150℃温度下经3次1 h深冷处理试样的性能最优。结果表明,高速钢性能改善的主要原因是深冷处理可促进试样中残余奥氏体向马氏体转变,同时,高速钢组织中析出的大量碳化物在摩擦磨损过程中作为硬质颗粒可提高耐磨性能。循环深冷处理过程中过冷度一直存在,每次循环过程都可促进残余奥氏体转变为马氏体,促进基体马氏体上析出细小的碳化物,从而提高高速钢的性能。