Numerical study on the effect of submerged depth on the horizontal plate wave energy converter

The growing search for clean and renewable energy sources has given rise to the studies of exploring sea wave energy. This paper is concerned with the numerical evaluation of the main operational principle of a submerged plate employed for the conversion of wave energy into electrical one. The numerical model used to solve the conservation equations of mass, momentum and transport of volume fraction is based on the finite volume method （FVM）. In order to tackle with the flow of mixture of air-water and its interaction with the device, the multiphase model volume of fluid （VOF） is employed. The purpose of this study is the evaluation of a numerical model for improvement of the knowledge about the submerged plate wave energy converter, as well as the investigation of the effect of the distance from the plate to the bottom of the sea （HP） on the performance of the converter. The simulations for several distances of the plate from the seabed show that the optimal efficiency is 64%, which is obtained for HP=0.53 m （88% of the depth）. This efficiency is 17% larger than that found in the worst case （HP=0.46 m, 77% of the depth）.     

湘东南中生代典型成矿花岗岩对比及成矿动力学

湘东南矿集区是南岭成矿带的重要组成部分。选取该矿集区内典型矿床的成矿花岗岩,利用成岩年龄、主量和微量元素组成、蛛网图及稀土元素配分模式等进行对比。结果表明:该矿集区内中生代成矿花岗岩的成岩年龄集中在150~165Ma。根据地球化学组成可将该矿集区内的成矿花岗岩分为2类:一类以骑田岭为代表,岩性以黑云母二长花岗岩为主,属于A型花岗岩,其分异程度较高,高w(Rb)/w(Sr)值,低w(K)/w(Rb)值,成矿元素以高温的W、Sn为主,具有富硅,富碱,贫P、Ti、Mg的特点,Ba、Sr、P、Eu、Ti负异常明显;另一类以宝山岩体为代表,其岩体产状为小岩株,岩性以花岗闪长岩为主,属于I型花岗岩,分异程度较低,低w(Rb)/w(Sr)值,高w(K)/w(Rb)值,Ba、Sr、P、Eu、Ti负异常不明显,其地球化学性质与岛弧岩浆类似,成矿元素以中低温的Cu、Pb、Zn等为主。黄沙坪花岗岩的成矿特征处于第一类与第二类岩体之间,属于过渡类型。结合矿集区所在的大地构造位置及其构造演化史,认为湘东南矿集区的形成与壳-幔相互作用密切相关,是后造山作用与大洋板块俯冲共同作用的结果。     

华北板块东缘金刚石成矿区域地质背景分析与成矿预测

对分布于华北板块东缘的辽宁铁岭、瓦房店及山东蒙阴等3个金伯利岩区的地质构造特征进行了研究,利用地层时代、构造行迹、古地磁以及同位素资料,对该区域金伯利岩的侵位时间进行了综合约束,认为该区域金伯利岩的侵位时间应该在250~300Ma之间。在此基础上,结合华北板块与扬子板块在古生代时的相互运移特征,对华北板块东缘金刚石的成矿区域地质背景进行了分析,并结合构造形迹的研究,对该区域金刚石原生矿进行了成矿预测。     

基于MATLAB图像处理的汽车牌照识别研究

汽车牌照识别是智能交通领域的重要研究课题,整个过程主要分为预处理、车牌定位、字符分割、字符识别4个环节。用MATLAB软件编写代码实现每一个过程,有效地解决恶劣环境下的车牌定位、字符倾斜、字符分割等复杂问题,结果表明MATLAB在彩色汽车牌照的识别中十分有效。     

Fractal characterization and frequency properties of near-fault ground motions

This study explores the irregularity and complexity of strong earthquake ground motions from the perspective of fractal geometry, and constructs a relation with the frequency content of the ground motions. The box-counting fractal dimensions and five representative period parameters of near-fault ground motions from the Chi-Chi and Northridge earthquakes are calculated and compared. Numerical results indicate that the acceleration and velocity time histories of ground motions present the statistical fractal property, and the dominant pulses of near-fault ground motions have a significant influence on their box dimensions and periods. Further, the average box dimension of near-fault impulsive ground motions is smaller, and their irregular degree of wave forms is lower. Moreover, the box dimensions of ground motions reflect their frequency properties to a large extent, and can be regarded as an alternative indicator to represent their frequency content. Finally, the box dimension D of the acceleration histories shows a considerably negative correlation with the mean period T. Meanwhile, the box dimension of the velocity histories Dye is negatively correlated with the characteristic period T and improved characteristic period Tgi.     

A Review of “Tectonic Faults: Agents of Change on a Dynamic Earth”

The fluvial system represents a nested hierarchy that reflects the relationship among different spatial and temporal scales. Within the hierarchy, larger scale variables influence the characteristics of the next lower nested scale. Ecoregions represent one of the largest scales in the fluvial hierarchy and are defined by recurring patterns of geology, climate, land use, soils, and potential natural vegetation. Watersheds, the next largest scale, are often nested into a single ecoregion and therefore have properties that are indicative of a given ecoregion. Differences in watershed morphology (relief, drainage density, circularity ratio, relief ratio, and ruggedness number) were evaluated among three ecoregions in eastern Oklahoma: Ozark Highlands, Boston Mountains, and Ouachita Mountains. These ecoregions were selected because of their high-quality stream resources and diverse aquatic communities and are of special management interest to the Oklahoma Department of Wildlife Conservation. One hundred thirty-four watersheds in first- through fourth-order streams were compared. Using a nonparametric, two-factor analysis of variance (α= 0.05) we concluded that the relief, drainage density, relief ratio, and ruggedness number all changed among ecoregion and stream order, whereas circularity ratio only changed with stream order. Our study shows that ecoregions can be used as a broad-scale framework for watershed management.     

基于多尺度分析方法的近断层地震动特性分析

近断层长周期地震动是一类较特殊的破坏性地震动.为了深入探讨近断层地震动的低频分量组成及其脉冲特性,基于小波理论中的多尺度分析方法提出了一种地震动分量分解方法,据此可将一条地震动分解成频率各不相同的多条分量.首先从频域、时域以及动态响应三个方面阐述了该分解方法的有效性和精确性.进而采用这种方法对近期12次大地震中的53条典型近断层地震动进行了分解,共获得266条地震动分量.分析了近断层地震动中的长周期分量随场地、断层距等影响因素的变化特征;再以卓越分量作为最大脉冲的简化模型,探讨了速度幅值和脉冲周期随震级、断层距的变化关系.结果表明：近断层长周期地震动主要由周期为0.2~2 s的分量组成;近断层土层场地地震动中的长周期分量比岩石场地多;在0~15 km的近断层区域,随断层距的增加,地震动中长周期分量的比重明显减小;卓越分量的速度幅值PGV_p约为原始地震动速度幅值PGV的0.6倍,且两者之间具有明显的线性关系;PGV_p随断层距的增大而减小,随震级的增大而增大;卓越分量周期T_p随震级的增大呈对数线性增大趋势.     

中美两国全球6级以上地震目录对比分析

中国地震台网中心(CENC)和美国国家地震信息中心(NEIC)提供的全球地震目录经常出现较大偏差.CENC发震时刻较早,CENC震源深度较深.2001年至2010年全球6.0级以上地震约11.67％存在明显目录偏差,印度洋板块北侧集中约70％有各类偏差地震.印度洋板块北侧各项误差统计占全世界同类地震约70％,表现出较好的一致性.这种现象应与震源过程有关,与该地区S波走时异常问题耦合,而不是算法或随机误差造成的.     

Modeling of spatially correlated,site-reflected,and nonstationary ground motions compatible with response spectrum

Seismic risk analysis and mitigation of spatially extended structures require the synthesis of spatially varying ground motions in the response history analysis of these structures. These synthetic motions are usually desired to be spatially correlated, site reflected, nonstationary, and compatible with target design response spectra. In this paper, a method is presented for simulating spatially varying ground motions considering the nonstationarity, local site effects, and compatibility of response spectra. The scheme for generating spatially varying and response spectra compatible ground motions is first established for spatial locations on the ground surface with varying site conditions. The design response spectrum is introduced as the “power” spectrum at the base rock. The site amplification approach is then derived based on the deterministic wave propagation theory, by assuming that the base rock motions consist of out-of-plane SH wave or in-plane combined P and SV waves propagating into the site with assumed incident angles, from which tri-directional spatial ground motions can be generated. The phase difference spectrum is employed to model ground motions exhibiting nonstationarity in both frequency and time domains with different site conditions. The proposed scheme is demonstrated with numerical examples.