基于多孔介质热弹性理论的井壁诱导缝成因

常规纯弹性理论通常把钻井过程中直井井壁诱导缝的形成归结为钻井液密度过高或者水平主应力差值过大,然而该理论却并不能完全合理地解释深井井壁诱导缝的成因。为揭示井壁诱导拉伸缝形成机理,考虑钻井液循环期间低温钻井液与高温井壁围岩的热交换,基于多孔介质热弹性力学理论,建立了适于深部地层的井壁稳定分析模型,研究了流固热耦合作用下的井周周向有效应力、孔隙压力与温度分布计算模型。计算结果表明:(1)在最大水平地应力方位,井眼钻开初期多孔弹性作用居于主导,孔隙压力在近井壁地带出现谷值,对诱导缝的形成起到了抑制作用;(2)然而随着钻井液与地层热交换的进行,钻井液的冷却作用愈加重要,井周周向有效应力由挤压状态逐渐转变为拉伸状态,从而导致近井壁地带诱导缝的形成。结论认为,为避免诱导缝的形成,在工程上一方面需加强钻井液的封堵性,控制液柱压力向井周的扩散;另一方面也可以通过调整优化钻井液密度与流变性能,控制井底钻井液当量密度(ECD)。     

Deflection behaviour of plate girders loaded in shear at elevated temperatures

This paper presents a theoretical investigation about out-of-plane and in-plane deflection behaviour of plate girders loaded in shear at elevated temperatures at the pre- and post-buckling stages. Theoretical elastic analysis of plate out-of-plane deflection employs an approximate approach using a combination of classical plate theory and Galerkin’s method. Effects from initial out-of-plane imperfections have been addressed, with the considerations of various varying degrees of thermal restraint. These elastic analytical solutions are compared with experimental results and numerical predictions. In addition to an out-of-plane deflection investigation, a combination of shear strength theory for plate girders and energy method is adopted to describe the in-plane vertical deflection of plate girders. The advantages and implementations of these methods are also discussed.     

我国城市空间可持续利用问题探析

该文从城市空间基本经济属性入手,在我国城市空间急剧膨胀的前提下,分析我国实现城市空间可持续利用的诸多动因,指出城市空间可持续利用是我国城市化可持续进行的重要内容。     

Hiding data: a high-capacity distortionless approach

The widespread use of 3D models has become an interest in steganography. In this paper, we present a novel data hiding method for 3D models. Based on the representation information, the key idea is to consider the vertex index as a message block. A message consists of three types of message blocks, namely, unique, repeated and 1-bit or 0-bit repetitions blocks. Three embedding methods, namely, vertex index embedding (VIE), dynamic-length bit-string mapping (DBM), and repeated bits embedding (RBE), each best for a respective type of message block are devised. All message vertices are then arranged in the light of proposed vertex order and output as the stego-model. The message block is extracted from the vertex of the stego-model by the order of vertex sequence and its index in the ordered vertex list. While integrating the proposed methods our scheme gains high capacity compared to existing techniques while preserving reasonable robustness. In addition, our method is efficient, 25 times faster than previous techniques. With high capacity, several novel applications like content annotation for large documents, 3D meta model for related resources, etc., becomes possible, making the 3D model as an excellent data container.     

我国纺织工业技术进步状况的分析

本文系统地分析了我国纺织工业,纺织工业内部各行业、重要纺织工业基地的技术进步状况并测算了它们技术进步的速度,及技术进步对经济增长贡献的比重。并提出了加快纺织工业技术进步的对策。     

Ca替代Y对YBa_2Cu_3O_(7-δ)超导电性的影响

用固相反应方法制备了Y_(1-x)Ca_xBa_2Cu_3O_y(x=0.0,0.02,0.05,0.10,0.15,0.20,0.50)系列样品,发现超导转变温度随x增加而呈线性下降。粉末x-射线衍射结果表明,在x≤0.15范围内,体系呈现出很好的正交单相性,晶格参数无明显变化。用碘滴定方法测量了体系的氧含量,发现随着x的增加,Cu的平均价态降低,氧含量减少。把上述结果同Y_(1-x)Pr_xBa_2Cu_3O_y作比较,表明氧含量和Cu的平均价态均不是决定Tc的直接因素。讨论了氧含量改变的可能位置和引起超导电性发生变化的原因。     

产品设计造型系统—PLAGE

PLAGE是32位微型计算机上运行的,用以进行平面构形及三维实体造型,生成产品的两维及三维零件图和装配图的系统。文中介绍了两维图形生成及三维几何造型系统的结构,在两维中介绍了三种两维图形的生成方法——图形描述、几何作图、几何图形的集合运算;两维图形编辑系统及尺寸字符标注方法。在三维中介绍了用长方体、圆柱、圆锥、球、环、一般扫描体、变形扫描体经几何变换及集合运算的实体造型、凸包树差分割算法;变形扫描的特点;自由曲面与函数曲面求交等。     

文献检索与利用课的实践与探讨

笔者通过自己的教学实践,对文献检索与利用课的教学方法进行了探讨。提出在高等院校,应该针对不同学科专业,合理安排教学内容,选择适当的检索工具书,联系实际,注重实践,提高学生的情报意识和能力。     

水轮机转轮叶片的数据拟合研究与工程应用

本文介绍一种用于水轮机转轮叶片的曲面拟合方法——B样条空间曲面拟合法,用该方法编制了叶片的曲面拟合及水轮机转轮的流场、强度、振动等问题的有限元分析网格的形成程序。最后给出了某电站转轮叶片的有限元分析网格的图形。     

不同比转速(n_(s_1)、n_(s_2))泵叶轮的同轴串联试验研究

本文论述了不同比转速(n:1、n:2)泵叶轮进行同轴串联的有关问题。通过对性能参数的选择与匹配计算、水力设计问题的处理,样机试验及真机的运行考核,其问题得到了满意的解决。