An explicit representation of steady state response of a beam on an elastic foundation to moving harmonic line loads

A closed‐form deflection response of a beam rest is presented in this paper using the integral transform method. The theory of linear partial differential equations is used to represent the deflection of beam subjected to a moving harmonic line load in integration form. The solution is finally carried out using the inverse Fourier transform. To evaluate the integration analytically, poles of the integrand are identified with the help of algebraic equation theory. Residue theorem is then utilized to represent the integration as a contour integral in the complex plane. Closed‐form deflections and numerical results are provided for different combinations of load frequency and velocity. Copyright © 2002 John Wiley & Sons, Ltd.     

Transient‐state groundwater flow in various geometries with wells at arbitrary positions: analytical methods

We have developed a method for analytically solving the porous medium flow equation in many different geometries for horizontal (two‐dimensional), homogeneous and isotropic aquifers containing impermeable boundaries and any number of pumping or injection wells located at arbitrary positions within the system. Solutions and results are presented for rectangular and circular aquifers but the method presented here is easily extendible to many geometries. Results are also presented for systems where constant head boundary conditions can be emulated internal to the aquifer boundary. Recommendations for extensions of the present work are briefly discussed. Copyright © 2003 John Wiley & Sons, Ltd.     

Elastic solutions for stresses in a transversely isotropic half‐space subjected to three‐dimensional buried parabolic rectangular loads

In many areas of engineering practice, applied loads are not uniformly distributed but often concentrated towards the centre of a foundation. Thus, loads are more realistically depicted as distributed as linearly varying or as parabola of revolution. Solutions for stresses in a transversely isotropic half‐space caused by concave and convex parabolic loads that act on a rectangle have not been derived. This work proposes analytical solutions for stresses in a transversely isotropic half‐space, induced by three‐dimensional, buried, linearly varying/uniform/parabolic rectangular loads. Load types include an upwardly and a downwardly linearly varying load, a uniform load, a concave and a convex parabolic load, all distributed over a rectangular area. These solutions are obtained by integrating the point load solutions in a Cartesian co‐ordinate system for a transversely isotropic half‐space. The buried depth, the dimensions of the loaded area, the type and degree of material anisotropy and the loading type for transversely isotropic half‐spaces influence the proposed solutions. An illustrative example is presented to elucidate the effect of the dimensions of the loaded area, the type and degree of rock anisotropy, and the type of loading on the vertical stress in the isotropic/transversely isotropic rocks subjected to a linearly varying/uniform/parabolic rectangular load. Copyright © 2002 John Wiley & Sons, Ltd.     

A new stereo‐analytical method for determination of removal blocks in discontinuous rock masses

The paper provides a new stereo‐analytical method, which is a combination of the stereographic method and analytical methods, to separate finite removable blocks from the infinite and tapered blocks in discontinuous rock masses. The methodology has applicability to both convex and concave blocks. Application of the methodology is illustrated through examples. Addition of this method to the existing block theory procedures available in the literature improves the capability of block theory in solving practical problems in rock engineering. Copyright © 2003 John Wiley & Sons, Ltd.     

Dynamical friction force exerted on spherical bodies

We present a rigorous calculation of the dynamical friction force exerted on a spherical massive perturber moving through an infinite homogenous system of field stars. By calculating the shape and mass of the polarization cloud induced by the perturber in the background system, which decelerates the motion of the perturber, we recover Chandrasekhar's drag force law with a modified Coulomb logarithm. As concrete examples, we calculate the drag force exerted on a Plummer sphere or a sphere with the density distribution of a Hernquist profile. It is shown that the shape of the perturber only affects the exact form of the Coulomb logarithm. The latter converges on small scales because encounters of the test and field stars with impact parameters less than the size of the massive perturber become inefficient. We confirm in this way the earlier results based on the impulse approximation of small angle scatterings.     

CLONGING AND THE EXPRESSION ANALYSIS OF CYP19A GENE cDNA DURING THE REPRODUCTIVE CYCLE OF SEBASTES SCHLEGELI

从许氏平鲐脑组织中克隆到细胞色素P450芳香化酶（P450aromB）（CYP19B）基因核心功能区cDNA。结果表明,许氏平铀CYP19B主要功能区片段编码369个氨基酸,包括I-螺旋区、Ozol’s肽区及部分芳香化酶特异性保守区。RT-PCR分析表明,CYP19B在雌鱼和雄鱼各组织中表达情况不同,在雌鱼中表达较丰富,但是两者都在性腺和脑中有表达,且脑中的表达量高于性腺。生殖季节表达结果表明,CYP19B在繁殖前期表达较为丰富,退化期未见有表达。CYP19B在精巢处于Ⅲ期的许氏平鲐脑组织中表达最为丰富,在精巢发育Ⅳ期的脑组织表达量最低。上述研究结果说明,CYP19B在雌性和雄性许氏平鲐繁殖周期中均发挥重要生理作用。     

斜带石斑鱼(Epinephelus coioides)两种催乳素受体基因的 cDNA 克隆和 mRNA 表达分析

采用RT-PCR方法克隆了斜带石斑鱼两种催乳素受体(Prolactin receptor,PRLR)的cDNA序列,序列分析表明:PRLR1开放阅读框为1947bp,共编码649个氨基酸,PRLR2开放阅读框为1749bp,共编码487个氨基酸,PRLR1与PRLR2的氨基酸同源性为40.4%。用Real-time RT-PCR方法研究了PRLR1和PRLR2在各组织和早期发育不同阶段的表达情况,结果表明:PRLR1和PRLR2在所检测的12种组织中均有表达,其中以鳃、肾、肠表达量较高;PRLR1在受精期表达最高,PRLR2在视囊形成期表达最高,而且除受精卵期外PRLR2在各时期的表达量均高于PRLR1。     

砂井联合水泥土搅拌桩复合地基固结解析解

砂井联合水泥土桩复合地基是一种新型的复合地基加固技术,既可以加快软土地基固结时间,又可以增强软土地基的强度。针对该组合型复合地基的布桩特点,该类复合地基可以简化成以水泥土搅拌桩为中心的轴对称固结模型,并假定孔隙水沿径向渗流到砂井体内的流量等同于砂井体内排出的水量,考虑砂井的涂抹效应,推导出该类型下砂井联合水泥土搅拌桩复合地基固结方程。根据实际工程荷载多数单级施加和地基附加应力呈梯形分布的特点,得出了砂井联合水泥土桩复合地基固结解析解。通过对单级荷载情况下的复合地基固结解析解的退化,得出了瞬时施加荷载下的解析解。最后分别针对井径比、加荷历时、桩-土模量比、砂井渗透系数等影响因素,对复合地基固结性状进行了分析。该解答对提高此类复合地基的设计和计算水平有一定的理论指导意义。     

北京西山南部构造序列初探

笔者利用解析构造学方法,初步确定了本区的构造序列。它反映了从下部构造层次到上部构造层次的系统变化,从早期的层内固态流变经压扁作用和弯曲作用到后期的剪切破裂变形过程中岩石韧性递减的系统演变。由于岩浆侵入而使其间增加了一个韧性再增强的变形期。     

锂同位素及其地质应用研究进展

锂同位素示踪是近几年发展起来的一门新兴的稳定同位素地球化学方法,锂有两个稳定同位素：^6Li和^7Li。自在界锂同位素的组成变化很大,其δ^6Li值变化幅度超过60‰,现代大洋水的δ^6Li值为－31．0‰,洋中脊玄武岩（BORB）的δ^6Li值为－4．7‰--3.7‰,由于锂同位素存在大的分馏和不同地质体中在截然不同的δ^6Li值,因此锂同位素地质应用前景十分广泛。目前,锂同位素在研究星云形成过程和宇宙事件,洋壳蚀变和海底热液活动,壳－幔物质循环和板块俯冲作用过程,判断卤水起源和演化等方面的研究中成效显著。