碳化硅颗粒增强铝基复合材料颗粒表面改性技术研究现状

SiC颗粒增强铝基复合材料因具有高的比强度、比刚度、耐磨性及较好的高温稳定性而被广泛应用于航空航天、电子、医疗等领域,但由于SiC颗粒高熔点、高硬度的特点以及SiC颗粒与铝基体间存在界面反应,碳化硅铝基复合材料存在加工性差、界面结合力不足等问题,已无法满足航天等领域对材料性能更高的要求,因此开展如何改善基体与颗粒之间界面情况的研究对进一步提升复合材料综合性能具有重要的科学意义。结合国内外现有研究成果,总结了SiC颗粒与铝基体界面强化机制、界面反应特点、表面改性技术原理及数值建模的发展现状,结果表明,现有经单一表面改性方法处理后的增强颗粒对铝基复合材料性能的提升程度有限,因此如何采用新的手段使复合材料性能进一步提升将成为后续研究热点,且基于有限元数值模拟方法进行复合材料设计也是必然趋势。最后针对单一强化性能提升有限的问题,提出了基于表面改性的柔性颗粒多模式强化方法,同时针对现有的技术难点展望了后续的研究方向,以期为颗粒增强复合材料的制备提供理论参考。     

皮革涂饰助剂

除了皮革粘合剂和颜料,几乎任何涂饰配方都包含有助剂。这些助剂是涂饰工序所必需的,也对某些表面性质有一定调节作用。它们对工艺有好处,也常作表面改性剂。由于助剂及其应用范围很广泛,这里我仅从几个重要方面来谈。这类助剂中用于克服粘合剂的粘性和提高水性涂饰系统的流平性的产品是最重要的。     

Effect of protein content, casein–whey protein ratio and pH value on the foaming properties of skimmed milk

The average bubble diameter (ABD) and density of skimmed milk foam decreased with increasing protein content, up to 4%, while drainage was widely comparable. Samples with casein–whey protein ratios (C/W) of 94/6 and 7/93 showed smaller ABD than samples from mixtures with C/W ratios between 60/40 and 20/80. Foams prepared from samples with C/W of 20/80 exhibited the lowest drainage values after 10 min. Increasing pH from 6.4 to 7.0 led to increased overrun and ABD, while drainage was widely comparable, with a minimum value at pH 6.7. The protein composition of skimmed milk and foams prepared from this milk in relation to protein content, C/W ratio and pH value differed only slightly.     

不锈钢药芯焊丝中铁粉/长石对焊接烟尘中Cr(Ⅵ)的影响

采用汉诺威电弧质量分析仪、高速摄像机和激光粒度仪等研究了不锈钢药芯焊丝中铁粉/长石比对不锈钢药芯焊丝电弧稳定性、焊接烟尘平均颗粒尺寸、烟尘中Cr(Ⅵ)含量及其生成率.结果表明,短路过渡生成的焊接烟尘平均颗粒尺寸比粒状过渡小,烟尘中Cr(Ⅵ)/总Cr(n/N)的比值大;在同一焊接参数下,当药芯中铁粉/长石比例在1.8时,短路过渡时间最短为1033μs,焊接电弧稳定、焊接烟尘颗粒平均尺寸为1154 nm, Cr(Ⅵ)的含量及Cr(Ⅵ)/总Cr(n/N)的比最小,分别为1555.8 mg/kg和24%.     

电子束毛化对硼硅玻璃在可伐合金表面润湿性的影响

增加实际紧密接触面积能提高玻璃在金属表面的润湿性,文中提出了一种将可伐合金表面进行电子束毛化的方法来提高表面粗糙度. 采用座滴法研究了硼硅玻璃在毛化后可伐合金表面的润湿性. 结果表明,电子束毛化可以增大可伐合金表面的有效接触面积,促进熔融玻璃的润湿铺展,润湿角随着加热温度的升高和保温时间的延长而逐渐减小. 硼硅玻璃和氧化层之间的主要反应产物为Fe₂SiO₄,金属表面的高能束毛化和预氧化处理有效促进了玻璃-金属的机械-化学结合,有利于提高玻璃与金属的连接强度.     

TOWARDS THE IMPLEMENTATION OF RENEWABLE ENERGIES-A EUROPEAN PERSPECTIVE

The paper summarizes the rationale for an important development of the renewable energies in Europe and overseas. Possible instruments and actions for the development and market introduction of various forms of renewable energies and the associated technologies are reviewed. The progressive introduction of renewable energies in the future energy market requires that they first achieve economic competitiveness. A wide range of renewable energies are already cost-competitive today. The case for the renewables becomes even stronger when the macro-economic benefits are considered. This justifies ambitious implementation goals in the range of 20% penetration of renewable energies in Europe's energy consumption withing 20 to 30 years from now

Market introduction and development of renewable energies cannot be achieved solely with the conventional schemes currently employed for the existing product lines and conventional energy systems. New promotion schemes are reviewed among which an agressive R&D strategy will play a major role.     

THE TOTAL REPAIR COST IN A DEFECTIVE,COHERENT BINARY SYSTEM

Minimizing the repair cost in a coherent system leads to a sequencing process, which can terminate at every stage, components untested being replaced. The functional equation for the mean cost and an arbitrary policy are given. Minimization leads to a non-Markovian BELLMAN-equation. In certain situations it is obviously optimal to terminate. A criterion is stated for an optimal process not to terminate.

For non-terminating policies, considered henceforth, equations on the mean testing and replacement cost, mean numbers of tests and replacements, are given. Repair cost is decomposed into testing and replacement cost. Sufficient conditions for the repair cost to be minimized simultaneously with these quantities, respectively, are given.

The states of modules yield sufficient statistics. Inefficient components are detected and excluded. For two suboptimal policies, motivated by the non-Markovian problem, the corresponding upper bounds on the mean repair cost and number of tests are given.     

THE POLITICAL SYSTEM OF THE FIRM: TOWARD CONCEPTUAL CLARITY

Abstract

With this contribution to the political system of the Firm, Easton's politological analysis of the political system is confronted with the conception of business politics developed in the Institute for Business Politics at the Free University of Berlin.

The first part is therefore dealing with a heuristic analysis of Easton's model of a political system and, in a further step, the management's behavior in the political system of the firm is worked out. Based on the differentiation of primary goal-setting and of secondary goal-safeguarding managerial functions, an analysis is made of the business-politological possibilities and limitations of safeguarding the firm's goals against colliding ranges of action. In this connection the sources of power and means of power of the management, the alternatives and decision-criteria of conflict-handling as well as the effects of the determining actions are examined. Finally, the variables of the political system of the firm are discussed. Directions for further research are indicated.     

Miscibility Gaps in Alkali-Silicate Binaries—Data and Thermodynamic Interpretation

Measurements of the miscibility gaps in the Li₂O- and Na₂O-SiO₂ binaries are reported and compared to data of other workers. Heat treatments by brief immersion in liquid Sn were used for measuring the properties of glasses with a strong devitrification tendency. The miscibility-gap boundaries of both systems are successfully described by modified regular-mixing equations based on the concept that the thermodynamic mixing processes are controlled by complex but discrete molecular structures which exist in the melt. The assumptions and implications of the model are discussed.