中下地壳岩石弹性波各向异性的影响因素

地壳岩石成分及其构造的复杂性使得地壳弹性波各向异性的影响因素比较复杂。在地壳浅部,裂隙广泛发育,它们的定向排列对岩石各向异性起到了很重要的作用。在地壳深部,裂隙基本闭合,岩石的各向异性主要是由矿物晶格优选方位(LPO)和形态优选方位(SPO)决定的。云母和(或)角闪石含量较高且定向排列的地壳岩石通常具有较高的各向异性。熔体的定向排列(MPO)可以显著地加强地壳各向异性     

大连地震台地磁Z分量日变化特征初步分析

利用大连地震台地磁Z分量观测资料,对其日变幅度、低点时间和日变形态的年变化进行分析,由此初步总结地磁Z分量日变化的规律及特征,对识别地磁场异常变化或干扰变化具有一定参考意义。     

仿自然鱼道整体物理模型试验研究

仿自然鱼道不仅能满足多种鱼类的洄游需要,同时还增加了河道内鱼类生境的数量与多样性,近来越来越受到人们的重视。由于仿自然鱼道结构复杂,断面型式多变、边坡及底部材质粗糙,糙率估算困难等,目前尚无完善的研究方法。结合新干枢纽仿自然鱼道工程,建立了1∶12的整体物理模型试验,对鱼道初步设计方案的水流条件进行了论证。结果表明,采用常规鱼道的研究方法控制鱼道内底坡、底宽、池室长度、偏移率和透水率等参数,然后通过整体物理模型试验进行验证和优化,可有效地用于指导仿自然鱼道的设计。与常规鱼道相比,仿自然鱼道受断面型式及建造材料的尺寸误差等影响,鱼道线路内流速差异明显。特别是鱼道转弯段,偏移率受弯道影响,流速易出现较直线段高或低的情况。研究成果为工程的设计提供了参考依据,同时为仿自然鱼道的设计和研究提供了参考。     

未来20年印度资源需求预测及中国应对策略研究

印度已经成为全球重要的国家之一。文章系统分析了印度的人口、经济发展特点,印度在过去发展过程中能源、铁、铜、铝资源的消费历史。并选用了合理的经济分析模型、资源需求预测方法,参考权威机构的研究成果,如资源需求"S"形规律、"GDP增速‘钟’形规律"以及格罗宁根研究中心(简称GGDC)、世界银行等机构的数据,科学、合理地预测了印度人口、经济及资源需求。认为:1)在工业化的带动下,印度经济具有再创神话的潜力;2)印度对能源、铁、铜、铝的需求将随着工业化进程的推进而快速上升,印度将成为继中国后拉动全球资源需求的"新引擎";3)印度发展不仅带给我国产业升级带来了新机遇,同时也是我国强有力的竞争者,比如在资源获取方面的竞争。因此我国企业应加强自身的核心竞争力,在印度发展的过程中获得好的机会成长。     

Numerical study on mode curvature for damage detection of a drilling riser using transfer matrix technique

In order to prevent marine pipeline accidents caused by corrosion defect, crack or loose contact, the technique of non-destructive testing or examination (NDT or NDE) becomes great important in the flied of structural health monitoring (SHM) in ocean engineering. The objective of this study is to propose a numerical method to localize and size the structure damage of a drilling riser. One theoretical development is a simple and effective algorithm used for ocean risers’ mode extraction and damage detection based on the transfer matrix technique. The merits of the developed method are that damage of risers with different boundary conditions and variable cross-sections can be localized and sized. Additionally, the relationships between damage locations and modes are discussed by comparing mode shape difference, mode curvature and mode curvature difference. Numerical results show that mode curvature values of damaged elements have little influence on those of intact elements. Based on this fact, a damage index method is developed to evaluate damage severities and explore the influence of single and multiple damage severities on damage indexes. More importantly, the outcomes are verified to be accurate enough to indicate the feasibility and reliability of the numerical method by the standard FEM package.     

Influences of the Helical Strake Cross-Section Shape on Vortex-Induced Vibrations Suppression for A Long Flexible Cylinder

An experimental study on a bare flexible cylinder as well as cylinders fitted with two types of cross-sectioned helical strakes was carried out in a towing tank. The main purpose of this paper is to investigate the effects of strakes’ cross-section on the vortex-induced vibrations (VIV) suppression of a flexible cylinder. The square-sectioned and round-sectioned helical strakes were selected in the experimental tests. The uniform current was generated by towing the cylinder models along the tank using a towing carriage. The Reynolds number was in the range of 800–16000. The strain responses were measured by the strain gages in cross-flow (CF) and in-line (IL) directions. A modal analysis method was adopted to obtain the displacement responses using the strain signals in different measurement positions. The comparison of the experimental results among the bare cylinder, square-sectioned straked cylinder and round-sectioned straked cylinder was performed. The helical strakes can effectively reduce the strain amplitude, displacement amplitude, response frequencies and dominant modes of a flexible cylinder excited by VIV. And the mean drag coefficients of straked cylinders were approximately consistent with each other. In addition, the square-sectioned and round-sectioned strakes nearly share the similar VIV reduction behaviors. Sometimes, the strakes with round-section represent more excellent effects on the VIV suppression of response frequency than those with square-section.     

Experimental study on the hydraulic conductivity of calcareous sand in South China Sea

Characterization of the hydraulic property of a specific geomaterial is of fundamental importance in engineering design and application. This paper reports an experimental investigation to the hydraulic conductivity of a typical marine sand, i.e., calcareous sand, which becomes increasingly popular as sea-filling material for land reclamation or construction of artificial islands. A series of permeability tests have been performed using the calcareous sand collected from Nansha islands in South China Sea. Using the home-made permeability test apparatus (so-called velocity-controlled pressure-differential acquisition flow apparatus), the relationship between flow velocity and hydraulic gradient was obtained and the hydraulic conductivity of calcareous sand was then determined accordingly. The effects of important parameters, including particle shape and particle size distribution on the hydraulic conductivity of calcareous sand, were assessed. To investigate the effect of particle size distribution on the hydraulic conductivity of calcareous sand, two often-used parameters, i.e., nonuniformity coefficient and curvature coefficient were considered in this study. To quantitatively evaluate the irregularity of soil particle, a particle-shape parameter was introduced and it was able to consider sphericity and circularity of highly irregular particle. Two materials, namely, Fujian quartz sand and glass beads consisting of particles of characteristic shape, were also used in the permeability tests, and they were used to compare with calcareous sand. Through the comparison, the effect of particle shape of calcareous sand on its hydraulic conductivity was examined based on the newly introduced particle shape parameter. The test results indicate that the particle size distribution has a significant influence on the hydraulic conductivity of calcareous sand. The quite irregular particle shape is able to reduce the hydraulic conductivity of the calcareous sand. A comparative study of hydraulic conductivity between the theoretical prediction and experimental measurement was performed, and it is concluded that an improvement of theoretical model for prediction of the hydraulic conductivity of the porous media consisting of particles with highly irregular shapes, such as the calcareous sand, is still required.     

水泥土结构特性的定量化研究

采用电阻率测试技术,通过测试水泥土在强度增长以及压缩过程中的竖向、水平向电阻,探求水泥土在强度增长过程和压缩过程中电阻率特性参数--平均结构因子F、平均形状因子f以及各向异性系数A变化的基本规律,分析了F, f, A与水泥土物理力学特性之间的关系,证实了这3个参数能对土的结构性进行定量分析。     

地球质心偏移与各圈层形变

地幔结构的地震层析图象显示热心南偏和质心北偏可能是地球南北反对称的动力基础。建立了南北半球密度反对称分布的数学模型，计算结果表明：地壳地幔南北半球的密度不均匀分布可使地核偏离地球质心１～３公里，完全符合张焕志１９８２年的计算结果。质心偏移将造成地球各圈层相同数量级的等位移动与等位变形，从而产生大幅度的全球海平面变化和地壳形变。     

SHAPE INDICES: USEFUL MEASURES OR RED HERRINGS?

Considerable attention has been devoted to shape analysis in geography with few fruitful results. We ask whether or not shape analysis is worth pursuing, referring to papers by Griffith and Lo. The methodology utilizes a two-step procedure. First, Lo's analysis is reconstructed to include indices reported in Griffith. Second, findings from the investigations are compared. Similar results are obtained from both studies, but the failure to extract any one-to-one correspondence between a shape and its associated index value(s) continues to cast doubt on the utility for subsequent studies.