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。     

数控螺纹车削的单步插补控制法

分析了运动控制芯片MCX34的控制原理及单步插补实现过程，提出了基于运动控制芯片MCX314实现螺纹切削的单步插补控制法，从而实现快速，高效的螺纹加工。该方法控制过程简单 ，同步实现锥螺纹，控制精度高（0.001mm），响应快（≤1.6MHz)，脉冲确保不丢失，解决了数控螺纹车削存在的一系列关键问题。     

基于混合遗传算法的树状注水管网拓扑优化

以投资最小为目标函数,以井间隶属关系的惟一性、连接注水井数量等限制为约束条件,建立了树状注水管网拓扑优化数学模型.根据模型特点,将优化问题分为分配层和几何层,分别采用遗传算法和非线性优化方法进行求解.并对遗传算法的操作过程进行了改进,调整了适应函数,采用随机多父辈适应函数值加权交叉和多种变异操作,结合了模拟退火算法,并给出了初温的确定方法,改进了选择复制操作,从而形成了混合遗传算法.该算法能够有效地提高收敛速度,避免早熟收敛.利用算例说明了该方法的有效性.     

柴胡皂苷的提取与鉴定

报道了大孔吸附层析分离提取柴胡皂苷的实验研究。结果表明。提取分离柴胡皂苷的最佳工艺是：30％乙醇洗杂质、70％的乙醇洗脱2个糖基或3个糖基的柴胡皂苷。柴胡总皂苷的提取率为1．96％。TLC、HPLC检测2个糖基的皂苷是柴胡皂苷b2，属于结构类型Ⅱ。     

Serially-connected series-stub resonators for narrowband coplanar-stripline bandpass filters

In this letter, a coplanar stripline (CPS) series resonator composed of serially-connected series-stubs is proposed. This kind of resonator provides two transmission zeros close to the resonant frequency. With the proposed structure, the reactance slope parameters of the resonators are significantly increased and adjustable by changing the length ratio of the two series stubs. This is useful for designing narrowband filters which is difficult to realize with conventional series CPS resonators. The structures of the resonators are optimized for a lower radiation loss and used to design a narrowband Chebyshev bandpass filter. The simulation and experimental results show that the proposed filter provides multiple transmission zeros and high selectivity.