Effects of mechanical activation on the reduction behavior of hematite concentrate

The effect of mechanical activation on the reduction behavior of a hematite concentrate has been examined using a combination of simultaneous thermal analysis (STA), X-ray diffraction (XRD), scanning electron microscope (SEM) analysis, and laser diffraction. The samples were activated in vibratory and planetary mills.     

Can unbiased source be retrieved from anisotropic waveforms by using an isotropic model of the medium?

Anisotropy is frequently present in geological structures, but usually neglected when source parameters are determined through waveform inversion. Due to the coupling of propagation and source effects in the seismic waveforms, such neglect of anisotropy will lead to an error in the retrieved source. The distortion of the mechanism of a double-couple point source located in an anisotropic medium is investigated when inverting waveforms using isotropic Green's functions. The anisotropic medium is considered to be transversely isotropic with six levels of anisotropy ranging from a fairly weak to rather strong anisotropy, up to about 24% in P waves and 11% in S waves. Inversions are based on either only direct P waves or both direct P and S waves. Two different algorithms are employed: the direct parametrization (DIRPAR, a nonlinear algorithm) and the indirect parametrization (INPAR, a hybrid scheme including linear and nonlinear steps) of the source. The orientation of the double-couple mechanism appears to be robustly retrieved. The inclination of the resulting nodal planes is very small, within 10° and 20° from the original solution, even for the highest degree of anisotropy. However, the neglect of anisotropy results in the presence of spurious isotropic and compensated linear-vector dipole (CLVD) components in the moment tensor (MT). This questions the reliability of non-double-couple components reported for numerous earthquakes.     

直接铺管法适应性研究

直接铺管法是一种新的直接铺管的施工方法,其结合了现有顶管和水平定向钻进设备的技术优势。针对不同管道铺设方法的优缺点以及14个直接铺管法的工程案例分析,从施工长度、管径、地质、施工费用等多方面进行了对比,分析直接铺管法的适应性,确定直接铺管法的使用范围。     

Developing direct shipping across the Taiwan Straits

Direct shipping across the Taiwan Straits has been restricted since 1949 for political reasons. Goods for cross-Straits trade must be transshipped via a third place, such as Hong Kong or a Japanese port. Since commercial activities across the Straits have become increasingly prosperous in recent years, the demand for direct shipping across the Straits is growing critically important and attracts great attention from all sectors. Businessmen who are involved in cross-Straits trade have criticized the higher costs and longer transit time of transshipment. This article explores possible solutions for shipping directly across the Straits. It discusses the mode of negotiation for settling the discrepancies in viewpoints between the two sides, and aims to provide a reference for governments from both sides.     

Direct Current Measurements off Sanriku, East of Japan

One year records of four current meters moored at two sites off Sanriku (39°26′ N, 142°45′ E and 143°E) have been analyzed. Mean currents flowed southward to southwestward with velocity 2.5–7.8 cm s⁻¹. The geostrophic velocity appeared to be surface-intensified, and the flows at 500 m depth have a relationship with the 100 m depth temperature distribution, suggesting the influence of the upper layer flows. At a depth of 1500 m and 2500 m, southward to southwestward flows are thought to be a part of the current flowing southward on the western flank of the Japan Trench. This revised version was published online in July 2006 with corrections to the Cover Date.     

合肥市地壳浅部三维速度结构及城市沉积环境初探

合肥市位于合肥盆地东南缘,东侧紧邻郯庐断裂带,多条大型隐伏断裂穿过市区.为进一步认识合肥城市下方隐伏断裂的空间展布、性质,以及城市复杂的沉积环境,本文利用布设在合肥市区的58套三分量短周期地震仪组成的台阵,获得了37天的三分量连续波形数据,通过基于射线追踪的面波走时直接成像方法反演得到了合肥市地壳浅部0.6~3.6 km的三维剪切波速度结构,速度结构图像展现了地壳浅部的横向不均匀性和纵向成层性,揭示出NNE、NWW和近EW三组不同走向的隐伏断裂在城市地下浅部的构造特征.取得以下认识：（1）合肥市南、北方向在浅地表（2 km以内）存在显著速度差异,速度分界线位置与已知的近EW向的蜀山断裂一致,断裂南侧呈现低速凹陷,北侧则为高速隆起.低速中心深度达2~3 km,速度异常与该断裂在合肥盆地东部演化过程中的构造反转沉积了不同地层有关;（2）合肥市区存在明显的高速异常带,其走向、位置与穿过该区域的郯庐断裂带西支主干断裂相符,其中五河—合肥断裂在市区北部以东呈现低速凹陷特征,低速区范围与肥东凹陷晚白垩纪以来的沉积构造边界一致,认为肥东凹陷的最大沉积厚度可达2 km以上;（3）合肥市中心跨郯庐断裂带西支主干断裂之间呈现明显的凹、隆相间的复杂构造,推测其是在多组断裂的共同拉伸作用下形成的小型沉积盆地,沉积中心位于郯庐断裂带内部,最大厚度可达3~4 km.由于其展布方向在不同深度与该区域断裂的走向具有明显的相关性,推测不同深度的沉积形态与郯庐断裂带在不同时期的构造演化过程有关.     

基于GAMIT的基线解算应用探究

GAMIT基线解算是GPS数据分析和处理的重要方法。本文主要介绍利用虚拟的linux系统,以GAMIT软件进行精确定位、基线解算的批处理过程。对GAMIT软件安装过程进行详细的介绍,并利用基站的数据信息进行基线解算,对结算结果进行分析并得出结论,其目的在于解算后能形成模块以进行不同点的精确定位。     

Direct displacement-based design for seismic retrofit of existing buildings using nonlinear viscous dampers

This paper presents a direct displacement-based design procedure for seismic retrofit of existing buildings using nonlinear viscous dampers according to equivalent linear systems. Unlike conventional methods, the equivalent linear viscous damping provided by the nonlinear viscous dampers is derived based on the assumption that the average energy dissipated between the linear and the nonlinear viscous dampers is equal. Also, the equivalent period and viscous damping for the equivalent linear systems which are used for representing the behavior of bare frames (the buildings without dampers) are derived from the concept of average storage energy and average dissipated energy, respectively. It is shown from nonlinear time-history analyses that the nonlinear action of the retrofitted structures can be reasonably captured by the presented direct displacement-based procedure.     

有限元直接迭代算法及其在线源频率域电磁响应计算中的应用

采用有限元直接迭代算法实现了线源频率域测深电磁响应的二维正演计算. 首先给出了线源正演问题的有限元直接迭代格式,然后由迭代法进行求解. 在处理奇异源问题上,采用向内递推的组合网格技巧,在源点附近可进行局部加密,并实现粗细网格的对接,从而较好地解决了奇异源附近的计算问题. 还提出一种迭代求取全区视电阻率的方法,避免了远近区的划分. 通过对均匀半空间、层状介质和二维模型电磁响应的计算,获得了与大地电磁测深相似的视电阻率曲线,验证了算法的正确性;通过对计算结果的分析,在理论上说明了线源频率域近区测深的可行性.     

Hydroelastic analysis of floating structures with liquid tanks and comparison with experimental tests

In this study, we develop a numerical method for a 3D linear hydroelastic analysis of floating structures with liquid tanks subjected to surface regular water waves and compare the numerical results with experimental tests. Considering direct couplings among structural motion, sloshing, and water waves, a mathematical formulation and a numerical method extended from a recent work [1] are developed. The finite element method is employed for the floating structure and internal fluid in tanks, and the boundary element method is used for the external fluid. The resulting formulation completely incorporates all the interaction terms including hydrostatic stiffness and the irregular frequency effect is removed by introducing the extended boundary integral equations. Through various numerical tests, we verify the proposed numerical method. We also performed 3D hydroelastic experimental tests of a floating production unit (FPU) model in an ocean basin. The measured dynamic motions are compared with the numerical results obtained using the proposed method.