Influence of Polyalkylmethacrylate VII on Boundary Film Formation,Friction,Wear and Efficiency of Lubricants

1 Influence of PAMAon Boundary Fil mFormation and Friction1.1 Experi mental methodsUltra-thin optical interferometry has been used tostudy thinlubricating fil ms for more than a decade and theexperi mental details of this technique have been reportedpreviously[1].The principle of the test setup is shown inFigure1.A polished steel ball is loaded and rolled againstthe flat surface of a glass disc that is coated with a thinsemi-reflecting chromiumlayer and a silica spacer of about500nmthickne…     

热管传热性能对小型热管换热器散热效能影响

在零重力辅助下,小热管热阻是小型热管换热器散热效能的重要影响因素之一。基于集总参数法对于换热器系统数值计算的高效性思想,建立了热管、热管换热器的集总参数模型。对同一热管换热器选用不同传热性能的热管,在不同传热温差和流体质量流速下,就其散热效能进行了数值计算。计算结果表明,在零重力辅助下,热管换热器管内热阻存在一临界值Rcri。当热阻RHP≤Rcri时,管外热阻起主导作用,热管换热器的散热效能εh几乎不随热管管内热阻的值而变化。     

天然气吸附储存脱附过程的动态模拟

通过热动力学计算,认识了脱附过程当中储罐内温度剖面分布的典型特征:储罐轴心处的温度下降幅度最大。分析了脱附过程当中储罐壁的热交换、吸附剂的导热系数以及储罐内的初始压力对储罐内的温度剖面的影响。结论是加强储罐外壁的热交换、增大吸附剂的导热系数皆能改善吸附储罐内的温度剖面。     

600 A IGBT开关电路及其散热系统设计

采用IGBT开关电路，对大功率电阻带进行直流脉宽调制控制，实现了内燃机车大功率直流发电机负载实验中的负载大小的连续调节。为了避免在实验过程中IGBT器件的温度过高，采用独特的双管IGBT结构和双向强迫风冷的散热系统。实验表明该电路运行稳定、可靠。     

Non-resonant RF and microwave response: A novel technique for the characterization of superconducting materials

When examined using continuous wave electron paramagnetic resonance and nuclear magnetic resonance spectrometers, the highT _c superconductors give rise to intense, low field, ‘non-resonant’ absorption signals in the superconducting state. This phenomenon can be used as a highly sensitive, contactless technique for the detection and characterization of superconductivity even in samples containing only minute amounts of the superconducting phase. Further, it can also be applied to the determination of material parameters of interest such asJ _c andH _c2 in addition to being a powerful way of distinguishing between weak-link superconductivity and bulk superconductivity. The details of these aspects are discussed.     

声光效应拉曼-内斯方程矩阵级数解法及声光调制器优化设计

提出一种求解正常声光相互作用拉曼 内斯 (Raman Nath)方程的矩阵级数解法 ,该解法直观方便且具有普遍性。计算结果表明 ,对Q =4 1π ,Bragg衍射的效率只有 97 5 % ;对非对称入射 ,以往的Raman Nath近似解误差较大 ;指出提高Bragg衍射效率的有效途径在于提高声光频率比并给出计算声光器件最优长度的计算公式。     

Modeling of Diffusion in Capillary Porous Materials During the Drying Process

This paper presents a model of heterogenous diffusion in capillary porous materials during the process of drying. The governing heat and mass transfer equations have been established using the liquid as well as vapor flow. Two models have been presented. Model 1 does not consider the heat conduction while the model 2 has been established by considering the conduction. The developed models and the numerical solutions of the resulting differential equations can take into account the moisture and temperature dependent thermophysical properties of the product. All equations have been established in spherical coordinates but the programme written for the purpose of calculations can be used for other geometries also. Numerical calculations have been performed for gas concrete and tiles using model 1, while model 2 has been used for gas concrete only because of the lack of data for thermophysical properties of the tile. For gas concrete it was seen that conduction has only marginal effect on the drying process and the numerical predictions of the drying process were reasonably accurate.     

具有细小组织的高强度和高延性钢管的开发

介绍了日本川崎制铁公司技术研究所开发出的电焊钢管采用热张力减径工艺的特性 ,及这种钢管的高强度、高延性等基本特性。用这种钢管制造的汽车零部件 ,经弯曲、冲击和疲劳特性等实验 ,证明具有良好的机械加工性能 ,是制造汽车用零部件的优良材料。     

纳米级BaAl_2O_4微粉的制备和性质

分别用溶胶 -凝胶法、低温固相反应法 ,制得了纳米级BaAl2 O4微粉 ,用电镜观察了其形貌和粒径的大小 ,用X-射线衍射仪进行了物相分析 ,测定了其纯度与晶型 ,讨论了制备方法与粒度大小的相互影响     

换热器小浮头螺栓断裂失效分析

针对换热器小浮头螺栓发生断裂的情况进行失效分析，找出原因，提出处理措施及材质选择时应注意的问题。