关于先张法温差损失的探讨

我国混凝土结构设计规范（GBJ－89）对先张法预应力混凝土构件进行蒸汽养护时的温差损失，有明确的计算方法。从考虑钢筋和混凝土之间的线温度膨胀系数关系入手，对该项损失提出了不同的看法，供参考讨论。     

求机构速度瞬心的对心四边形法

本文阐述了求机构中不相邻两构件间速度瞬心的一种新方法,即“对心四边形法”,该法是将两不相邻构件和与它们相关的两构件组成封闭四边形,并用两封闭边的交点求得它们之间的速度瞬心的一种方法,此法比传统的三心定理法更为简便,可不受三心定理法求解瞬心顺序的限制,对求解平面多杆机构的速度瞬心是一种新的有效方法。     

基于熵权-层次分析的智能电能表关键元器件选型方法

智能电能表作为智能电网中近用户侧的量测终端,是智能电网高级量测体系中与用户交互的核心环节,其可靠性需要重点关注.针对现有智能电能表的核心部件-元器件的选型依据主观经验选型的不足之处,提出一种智能电能表关键元器件选型方法,攻克经验选型方法中严重依赖于主观的不足之处.采用层次分析法设定智能电能表中元器件选择模型;针对层次分...     

电沉积非晶态铬镀层的研究及其应用

对电沉积非晶态铬镀层的研究现状,非晶态铬镀层的组织与性能特点进行了全面的综述,指出了研究中尚未解决的问题,展望了非晶态铬镀层在工程中的应用前景.     

浅析微机测控装置软件抗干扰的措施

主要论述在单片机系统中应用较为广泛的几种典型软件抗干扰措施,并对目前在现场影响测控系统工作的干扰源、受干扰后的故障现象以及如何在测控装置软件设计中抑制干扰源的技术进行了分析,阐述了软件抗干扰技术在抑制电力系统现地干扰方面的作用。     

Mitral valve replacement with total preservation of native valve and subvalvular apparatus

BACKGROUND AND AIMS OF THE STUDY: Preservation of the mitral valve and subvalvular apparatus was introduced clinically in the early 1960s, but for two decades the technique for mitral valve replacement included excision of both leaflets and their attached chordae tendineae. Lately, emphasis has been replaced on retaining the mitral subvalvular apparatus during valve replacement because of its role in left ventricular function. Hence, during the past six years, when performing mitral valve replacement we have, when possible, preserved the valvular and sub-valvular mitral apparatus. METHODS: Between January 1990 and November 1996, complete retention of all mitral tissue in connection with mitral valve replacement was performed in 58 patients (23 women and 35 men). Mean age was 63 years (range: 23 years to 77 years). Coronary bypass was a concomitant procedure in 19 patients; both the mitral and aortic valve was replaced in four cases. Calcified and/or stenotic valves were not a contraindication for the procedure; calcified plaques were removed. Adhesion between anterior and posterior leaflets was treated with sharp dissection. Valve and subvalvular tissue were preserved. The leaflets were reefed within the valve-sutures and compressed between the sewing ring and the native annulus when implanting the valve prosthesis. Chordal tension on the ventricle is thus maintained and the chordae pulled away from the valve effluent. RESULTS: Six patients died in the postoperative period and three had transient neurological symptoms. In no patient was death or transient neurological symptoms a consequence of the retention of mitral leaflets with subvalvular apparatus. CONCLUSIONS: We find the described technique to be useful not only in valve insufficiency but also in valve stenosis when preserving the mitral leaflets with sub-valvular apparatus during valve replacement. The technique is without procedure-related complications and prevents obstruction of left ventricular outflow tract.     

染料调Q单纵模Nd：YAG环形激光器

染料调Ｑ单纵模Ｎｄ：ＹＡＧ环形激光器黄茂全，郑晋玲，潘庆，彭墀（山西大学光电研究所，太原０３０００６）提要应用调Ｑ染料可使环形腔处于单向行波运转并具有选模特性，研制成功染料调Ｑ单纵模Ｎｄ：ＹＡＧ环形激光器，输出稳定，选单纵模几率高达９０％以上．关键词...     

观音岩水电站拱坝的设计

观音岩水电站拦河坝高82．10m，为细石混凝土砌块石双曲薄拱坝．经多方案设计比较并结合结构模型试验，选用了双圆弧变厚度拱体形的双曲拱坝，使坝体厚度与应力分布的大小相适应，同时设置了内部及外部监测系统，以监视拱坝的运行状况。     

岩石爆破块度的分形研究

应用分形理论对岩石爆破块度的分形特征进行研究，进一步说明了岩石的爆破块度具有很好的分形结构，并建立了分维数D与爆破参数之间的关系式，从而为爆破参数优化进行块度预报提供了科学依据。