变速切削系统振动频率的变化特征

本文主要讨论变速切削系统中颤振频率随机床主轴转速变化的规律。理论分析和试验结果都证明在变速切削中颤振频率随转速呈分段线性锯齿状变化。试验在立式铣床和普通车床上进行。     

Functional evaluation in congenital and acquired heart disease

Conclusions Functional evaluation of the cardiovascular system using rapid imaging (spiral echo planar), chemical shift, and velocity mapping is capable of making the diagnosis in congenital and acquired cardiovascular disease which, between them, cause the largest number of deaths of any disease in the western world and massive morbidity and suffering. Furthermore, for the first time in the history of medicine, there is the opportunity to apply preventive measures to eardicate the epidemic of preventable arterial disease. There needs to be a change of emphasis and a switching of resources to apply to the most common diseases rather than to those which are most easily studied. There also needs to be proper training in cardiovascular MR, not so much for imagers as for cardiologists and experts in vascular disease.     

用屏蔽暂堵技术封堵水平井裂缝性漏层

克拉玛依油田HW702水平井的大斜度段和水平段,将穿越纵向裂缝发育的二叠系佳木河组储层。为安全钻进和保护油层,用超细碳酸钙和磺化沥青复配后加入复合离子钻井液中成屏蔽暂堵的堵漏钻井液。室内用岩心试验,屏蔽暂堵后渗透率可降为0,暂堵深度小于3cm,可用酸化和射孔解堵。现场使用效果也很好,使HW702水平井顺利完钻,并获得工业油气流。     

四川优质苧麻的结构和性能研究

本文采用扫描电镜、Ｘ射线衍射仪以及常规仪器分析的方法测试了四川优质麻－达县红皮小麻和大竹青白麻的形态结构，超分子结构和力学性能，并与棉纤维进行了对比．实验表明，精干麻表面光洁．有裂纹裂缝等结构不匀点，取向度高，结晶度高，断裂强度高，刚性和断裂比功大，而延伸小；纤维粗．在主要指标上，红皮小麻优于青白麻。     

多变量系统敏感性及鲁棒性综合最优的H∞解耦设计方法

本文利用H∞设计理论提出了一种多变量系统敏感性及鲁棒性综合最优的解耦设计方 法,证明了单变量系统所能达到的最优敏感性及鲁棒性指标值仅由被控对象右半平面的零极 点决定,而与左半平面的零极点无关.另外,本文对谱分解及模型匹配问题的求解算法作了改 进,给出了一个算例.