固结过程中孔隙水压力计算中的吉布斯(Gibbs)现象及其消除   总被引：1，自引：0，他引：1  

包太  刘新荣  朱凡  朱可善 《水文地质工程地质》2006,33(1):23-26

一维固结过程中，孔隙水压力的计算在整个计算中占有重要的位置，其计算结果的准确性对于固结度及固结系数的确定均有一定的影响。目前，孔隙水压力的计算均采用级数计算，而由于级数计算中Gibbs现象的存在，使得孔隙水压力的计算中会出现振荡。针对这种情况，本文以误差函数作为基础，对孔隙水压力的计算进行了分析，发现在一定的精度范围内，采用误差函数可以有效地消除由于Gibbs现象带来的振荡。  相似文献   

Detection of model voids by identifying reverberation phenomena in GPR records   总被引：2，自引：1，他引：2  

Lev Kofman  Amit Ronen  Sam Frydman   《Journal of Applied Geophysics》2006,59(4):284-299

In order to improve the reliability of the ground penetrating radar (GPR) method in identifying subsurface sinkholes and karst cavities, laboratory investigations have been performed. The main objective of this work was to examine the relationship between horizontal/vertical voids dimensions and wavelengths of various antennas, and the corresponding GPR responses. Emphasis was given to the investigation of the factors that cause the appearance of reverberation phenomena in the signal pattern.The tests were conducted in 5 m × 10 m area by 2-m-deep trench filled with homogenous, dry sand. The voids models (empty fiberglass cylinders in diameters of 0.6 m, 1.0 m, 1.5 m and 2.4 m, with various heights) were buried vertically with their tops at depths of between 0.7 and 1.5 m. Investigations were performed for the various model conditions by towing 500, 300 and 100 MHz antennas along a pre-established grid, for the various model conditions.The GPR data collected using the 500 MHz bistatic antenna above the 1.0-m- and the 1.5-m-diameter cylinders, and using the 300 MHz bistatic antenna above the 1.5-m-diameter cylinder, confirmed the presence of a reverberation phenomenon, i.e. a strong convex signal pattern, containing a series of high amplitude extending oscillations with reduced frequency.Based on past practical GPR experience of void detection and presently obtained experimental data, two rules of thumbs may be adopted for the prediction of the appearance of resonant radar pictures:

1. The void diameter larger than the wavelength in air of the antenna used.

2. The vertical size of the empty void not significantly smaller than its horizontal dimension.

The strong reverberations generated by the inner surface of the void targets were found to approximate standing waves generated in cylindrical waveguides and waveguide resonators. The theoretical, experimental and practical results obtained concur.  相似文献   

对矿类专业毕业生“断层”现象的思考与对策     

张兴唐 《化工矿产地质》2006,28(2):121-123

在社会经济体制转型的过程中,矿类专业毕业生出现了人才的“断层”现象。通过对矿类专业人才“断层”现象形成的原因进行分析,认为缓解目前矿类专业人才短缺现象,要以矿山为主体采取内培外引、努力服务、“订单式”培养方式,长期克服类似的人才“断层”现象要以高校为主体,主动调整专业结构和招生规模,培养复合型人才校企合作,多形式、多渠道培养企业所需人才。  相似文献   

家用电器重复出现的地震前兆异常     

池谷元伺 《华南地震》1998,18(2):53-57

据有关报导,１９９５年神户地震前家用电器出现了奇怪的异常现象。我们在实验室中利用范德格拉夫静电发电机用磨擦生电的方法,证实了这些收音机和电视的噪音以及频道混乱现象的存在。  相似文献   

1989年3月特大电离层事件          下载免费PDF全文

何友文 《地球物理学报》1996,39(Z1):7-17

给出了１９８９年３月罕见的超级太阳活动区（ＮＯＡＡ，ＡＲ５３９５）的多次爆发，在远东地区诱发了一系列强烈的、甚至是首次观测到的电离层扰动事件：（１）重庆站以北地区ＴＥＣ增量达５５×１０^１６ｅｌ／ｍ^２的突增事件；同期武昌、仑坪和知本等站的ＴＥＣ负增量达６５×^１６ｅｌ／ｍ^２的突降事件；（２）兰州以南地区的强ＴＩＤ；（３）持续时间较长的Ｌａｃｕｎａ现象；（４）微粒Ｅ层事件等。作者结合同期远东和巴西地区的电离层扰动，多颗卫星探测结果和全球中低纬区极光的出现，对此次电离层事件的部分异常变化及其形成机制作了初步讨论，并指出东向电场剧增和粒子沉降可能是此次事件的主要因素。  相似文献   

西南极菲尔德斯半岛岩浆作用非平衡过程的自组织现象          下载免费PDF全文

李兆鼐  李汉声  尚如相 《极地研究》1996,8(1):12-23

对西南极菲尔德斯半岛早第三纪火山岩岩石学、地球化学特征及岩浆作用过程的具体分析表明，其岩浆演化过程是岩浆系统与周围环境（介质）进行能量和物质交换的热能耗散过程，具有动态平衡和阶段性的特点。岩浆结晶的多级复合结构和高位岩浆房中的分带构造，是岩浆作用非平衡过程的自组织现象。这种自组织现象也称作耗散结构  相似文献   

伪权现象及抗差估计   总被引：1，自引：0，他引：1  

靳奉祥  王同孝 《测绘工程》1997,6(4):16-20

讨论了权与平差结果的关系，指出了残差向量与权之间不一定存在的一一对应的关系，对现行常用抗差估计方案用实例进行了研究，并建议抗差方案设计应对权函数的取值加以限制，以保证平差系统的稳健性。  相似文献   

Seismic Design of Symmetric Structures for Accidental Torsion   总被引：5，自引：0，他引：5  

Silvia L. Dimova  Ilia Alashki 《Bulletin of Earthquake Engineering》2003,1(2):303-320

The paper presents an analytical estimation of the dynamic effects, caused by the shifting of the centre of mass with accidental eccentricity in symmetric structures. The approximate analytical solution proves, that even under small accidental eccentricities the symmetric structures exhibit “irregular behaviour” and the accidental torsional effects cannot be described properly by static application of torsional moments. The prescribed application rule by Eurocode 8 for multimodal analysis underestimates the accidental torsional effects up to 21% for 5% eccentricity for the structures considered in the paper. An expression for the correction of member responses is derived. It is proved by numerical simulations of the dynamic response of three-dimensional models of symmetric structures, that the proposed correction coefficient gives accurate results in cases of single-storey and multi-storey structures. It gives a convenient way for the design practice to estimate accurately the accidental torsional effects on planar and 3-D models of symmetric structures. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Multiple‐tuned liquid column dampers for torsional vibration control of structures: theoretical investigation     

Y. L. Xu  K. M. Shum 《地震工程与结构动力学》2003,32(2):309-328

This paper presents a theoretical investigation on the performance of multiple‐tuned liquid column dampers (MTLCD) for reducing torsional vibration of structures in comparison with single‐tuned liquid column dampers (STLCD). The analytical model is first developed for torsional vibration of a structure with an MTLCD under either harmonic excitation or white noise excitation. The experimental results are then used to verify the analytical model for coupled MTLCD‐structure systems under harmonic excitation. The performance of an MTLCD and its beneficial parameters for achieving the maximum torsional response reduction to white noise excitation are finally investigated through an extensive parametric study in terms of the distance from the centre line of the MTLCD to the rotational axis of the structure, the ratio of the horizontal length to the total length of liquid column, frequency bandwidth, head‐loss coefficient, the number of TLCD units in an MTLCD, frequency‐turning ratio and the spectral level of excitation moment. The results show that there is an optimal head‐loss coefficient and an optimal frequency bandwidth for an MTLCD to achieve the maximum torsional response reduction. It is also demonstrated that the sensitivity of an optimized MTLCD to the frequency‐tuning ratio is less than that of an optimized STLCD, and it can be further improved by increasing the bandwidth but at the cost of less torsional vibration reduction. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

浅谈地下流体宏观异常的落实     

杨世英  范玉俊  孟彩菊  黄春玲 《山西地震》2003,(2):32-34

落实宏观异常是地震台站的一项重要工作，为了识别宏观异常是否是地震前兆异常，对近年来山西省地震局夏县中心地震台参与落实地下流体异常的工作进行了总结，对地下流体出现的类型、原因等进行了分析。指出，应充分认识落实宏观异常的意义，应根据当时、当地的实际情况分区、分片、分段、分项目地进行宏观异常的分析，这样才能对各类宏观异常做出科学合理的解释。  相似文献