自级联式感应电动机控制系统的研制

描述了自级联式感应电动机的数学模型及其控制系统的结构,研制成功该类电机矢量控制系统样机.根据实验结果,分析了其动态和静态品质,得出此种类型电机控制系统完全可以达到与直流电动机控制系统相同性能的结论,提出了自级联式感应电动机进一步的应用前景.     

新时期大学校长应具备的品质

我国正在逐步完善市场经济的运行机制,社会处于大变革时期,尤其是加入WTO后,高等教育国际化竞争趋势日益明显,高等学校面临着前所未有的严峻挑战.本文探讨了大学校长对高校的发展的重要性以及社会转型时期大学校长应具备的几点可贵品质.     

A rotating bottle culture method with continuous replacement of the gas phase

Summary A rotator culture method is described which provides a continuous flow of oxygenating gas to cultures in rotating bottles. The system maintains constant O₂ and CO₂ levels in the culture medium throughout the incubation period. It also provides a more stable pH than systems with sealed culture bottles.Acknowledgments. We would like to thank Mr B. Secker, Mr C. Hellon and Mr S. J. Ellis, of the Physiological Laboratory workshop, for constructing the rotator apparatus. We also thank the Medical Research Council, London, for financial support for the project.     

Ga原子对Fe-Ga合金原子磁矩的影响

研究了Fe-Ga合金中Ga原子对合金的平均原子磁矩的影响.Fe中掺入Ga原子后,并不是简单的"稀释"作用.与纯Fe的原子磁矩相比,Fe-Ga合金中平均原子磁矩减小的同时,在低Ga含量范围,Fe原子的磁矩随Ga含量的增加而增大;当Ga含量大于17%(原子分数)时,Fe原子磁矩随着Ga含量的增大而减小.     

How Stomaphis aphids use their giant proboscides

To penetrate tree bark, arboreal aphids of the genus Stomaphis Walk. (Hemiptera: Aphididae: Lachninae) have proboscides up to three times their body length. Our observations of S. quercus (L.) complement a recent analysis of the anatomy and function of these mouthparts by clarifying how these relatively short-legged aphids move their proboscides between the resting position, pointing back, and the prognathous working position. The absence of crumenae in Stomaphis aphids and their feeding technique are discussed.     

海泡石的物化特性

本文对海泡石进行了X射线衍射分析、化学全分析、热分析、红外光谱分析及电子显微分析,得出了有关的结构参数,同时测定了颗粒大小分布,表面参数和耐腐蚀性能.