小口径涡轮钻具减速器非对称齿轮弯曲强度分析

小口径涡轮钻具减速器是小井眼深井钻探钻具的重要部件,具有体积小、承载大的特点。采用非对称齿轮代替传统齿轮是提高减速器承载能力的有效手段。非对称齿轮两侧的齿根圆角半径和压力角是区别于对称齿轮的关键参数,通过改变齿轮的齿形结构进而影响了齿轮的齿根弯曲强度。为了进一步研究齿根圆角半径和工作侧压力角对齿根弯曲应力的影响规律,以φ127 mm涡轮钻具减速器中太阳轮为研究对象,建立非对称齿轮的受力模型,基于平截面法得到非对称齿轮齿根弯曲应力的理论计算公式,并通过有限元法对对称齿轮和非对称齿轮进行对比分析,仿真结果表明：增大齿根圆角半径能增大齿轮齿根过渡曲线的曲率半径,从而改善齿根处的应力集中;工作侧压力角的增大能有效降低齿根弯曲应力,但压力角超过一定值时,齿根弯曲应力逐渐趋于稳定。理论分析和仿真结果基本吻合,研究结果可以为优化减速器非对称齿轮的主要参数提供依据和参考。     

Limit loads for an anchor/trapdoor embedded in an associative coulomb soil

A methodology for determining the plane strain limit load acting on an anchor or trapdoor buried within a purely associative Coulomb soil is presented. True lower bounds derived from a family of limiting stress fields appropriate to shallow horizontal trapdoors and anchors are shown to correlate to within less than 1 percent of upper bounds available in the literature, permitting the true limit load to be almost exactly defined. The solution form alters for deeply buried anchors and trapdoors resulting in poorer correlations. Methods by which the work may be extended to cover the more practical instances of non-associative Coulomb soils are indicated but are beyond the scope of the current paper. © 1998 John Wiley & Sons, Ltd.     

基坑围护结构水平位移监测常用方法比较

本文介绍了基坑围护结构水平位移监测的各种方法及新技术,重点讨论和分析了视准线法、极坐标法与角度交会法,结合误差传播定律分别对各方法监测点精度进行推算;在极坐标法的基础上,提出了监测精度更高的双极坐标法。论文结合具体基坑监测工程,分别利用每种方法对基坑围护结构水平位移监测进行精度估算,并分析不同监测方法的适用情况,为类似基坑水平位移监测方案设计提供理论参考。     

华南海滩剖面沉积物粒度特征影响因子分析

通过对2003年7月采集的华南沿海12条海滩剖面（3种海滩类型）的76个沉积物样品粒度分析,讨论了物质来源、地形地貌、风暴、水动力条件以及后滨向陆的极限高度等对海滩沉积物的性质与分布的影响．研究得出,后滨向陆的极限位置处于相对稳定的状态;后滨的极限高度随着滩面粒径的增大而增加．     

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地下掩埋管道及其地下建筑物压覆矿产边界的确定

地下掩埋管道及其地下建筑物压覆矿产边界,是由建设工程本身抗破坏能力、工程重要性以及矿体特征、开采方式、工程与矿体的相对位置等因素决定的。对于地下矿体,按围护带宽度、上覆各岩层移动角确定压覆矿产边界;对于地表非爆破性采矿,按围护带宽度和地表岩层移动角确定压覆矿产边界;对于地表爆破性采矿,安全爆破距离一般取50m。     

唐代试赋之“以题为韵”与“以题中字为韵”考述

"以题为韵"和"以题中字为韵"是试赋中的两种限韵类型,二者具有相通性。在以整题为韵类中,作者首先要将题目"字字叶之",同时还可以旁涉其他韵部。与其他试赋韵类相比,"以题为韵"和"以题中字为韵"介于宽严之间,但在注解题目方面,"以题为韵"和"以题中字为韵"就表现出了明显的不足。     

均匀弹性全空间中走滑断层产生的方向性速度脉冲研究

本文在均匀弹性全空间中对走滑断层附近方向性速度脉冲作了定性研究。研究表明,方向性速度脉冲主要与观测点和破裂起始点之间的一部分破裂面的破裂过程有关;方向性速度脉冲的周期随震源时间函数中的上升时间增大而增加。破裂速度对于方向性速度脉冲的峰值和周期有重要影响,一般而言,随着破裂速度的增加,方向性速度脉冲的周期减少,峰值增大。因此在统计脉冲的峰值和周期与矩震级的关系时,需要考虑破裂速度的影响。     

Cursory seismic drift assessment for buildings in moderate seismicity regions

This paper outlines a methodology to assess the seismic drift of reinforced concrete buildings with limited structural and geotechnical information. Based on the latest and the most advanced research on predicting potential near-field and far field earthquakes affecting Hong Kong, the engineering response spectra for both rock and soil sites are derived. A new step-by-step procedure for displacement-based seismic hazard assessment of building structures is proposed to determine the maximum inter-storey drift demand for reinforced concrete buildings. The primary information required for this assessment is only the depth of the soft soil above bedrock and the height of the building. This procedure is further extended to assess the maximum chord rotation angle demand for the coupling beam of coupled shear wall or frame wall structures, which may be very critical when subjected to earthquake forces. An example is provided to illustrate calibration of the assessment procedure by using actual engineering structural models.