GOCE Gravity Field Processing Strategy

A processing strategy and the corresponding software architecture for the processing of GOCE (Gravity field and steady-state Ocean Circulation Explorer) observables is presented and described, with the major objective to compute a high-accuracy, high-resolution spherical harmonic model of the Earth's gravity field. The combination of two numerical solution strategies, i.e. the rigorous solution of the corresponding large normal equation systems applying parallel processing (on a PC cluster) as the core solver, and the fast semianalytic approach as a quick-look gravity field analysis (QL-GFA) tool, is proposed. Such a method fusion benefits from the advantages of the individual components: the rigorous inversion of the system providing also the full variance-covariance information, and the quickness enabling the consecutive production of intermediate gravity field solutions, for the purpose to analyse partial and incomplete data sets and to derive a diagnosis of the performance of the GOCE measurement system. The functionality and operability of the individual components are demonstrated in the framework of a closed loop simulation, which is based on a realistic mission scenario both in terms of the orbit configuration and the coloured measuring noise. Special concern is given to the accuracy of the recovered coefficients, the numerical behaviour, the required computing time, and the particular role of the individual modules within the processing chain. In the case of the core solver, it is demonstrated that the assembling and rigorous solution of large normal equation systems can be handled by using Beowulf clusters within a reasonable computing time. The application of the quick-look tool to partial data sets with short-term data gaps is demonstrated on the basis of several case studies. Additionally, the spectral analysis of the residuals of the adjustment is presented as a valuable tool for the verification of the noise characteristics of the GOCE gradiometer.     

Determination of S-wave velocity structure using microtremors and spac method applied in Thessaloniki (Greece)

Array measurements of microtremors at 16 sites in the city of Thessaloniki were performed to estimate the V_s velocity of soil formations for site effect analysis. The spatial autocorrelation method was used to determine phase velocity dispersion curves in the frequency range from 0.8–1.5 to 6–7 Hz. A Rayleigh wave inversion technique (stochastic method) was subsequently applied to determine the Vs profiles at all the examined sites. The determination of V_s profiles reached a depth of 320 m. Comparisons with V_s values from cross-hole tests at the same sites proved the reliability of the SPAC method. The accuracy of the V_s profiles, the ability to reach large penetration depths in densely populated urban areas and its low cost compared to conventional geophysical prospecting, make Mictrotremor Exploration Method very attractive and useful for microzonation and site effects studies. An example of its application for the site characterization in Thessaloniki is presented herein.     

具有空间分布裂缝岩石的随机介质模型

利用随机过程的谱展开理论以及Hudson等人的裂纹介质模型构造一种裂纹数密度是空间平稳随机过程的随机介质模型。这个模型可以将裂纹的微观参数(裂纹数密度)与裂纹介质的宏观性质(弹性常数)联系起来,能灵活、有效地描述实际非均匀裂纹介质。模型算例表明,弹性常数的空问分布特征与裂纹数密度的有差别,而且对不同的弹性常数影响不同。通过改编自相关长度的大小,可以模拟裂缝在两个坐标轴方向上具有不同分布尺度的情况。最后,利用高阶的交错网格有限差分方法,我们模拟了地震波在具有随机分布裂缝岩石中的传播特征。     

3-D rheologic model of earthquake preparation (II): Strain field and its applications

Introduction Based on the elastic theory of the hard inclusion (Dobrovolskii, 1991), we developed an inclusion theory of rheologic medium, and applied the results of bulk-strain field of a rheologic inclusion model to explain the spatial-temporal evolution process of earthquake precursors (SONG, et al, 2000). In the former paper (SONG, et al, 2003), we derived the viscoelastic displacement field of the rheologic inclusion model on the basis of the analytic expression of displacement field o…     

3-D finite element modeling for evolution of stress field and interaction among strong earthquakes in Sichuan-Yunnan region

Introduction Sichuan-Yunnan region is a major area with frequent strong earthquakes in Chinese mainland, especially the middle-southern segment of South-North Seismic Zone, where many strong earth-quakes occurred in history. In the past 30 years, Sichuan-Yunnan region has two seismically active periods: one is from Tonghai earthquake in 1970 to Longling-Songpan earthquake in 1976, the other is from Lancang earthquake in 1988 to now. During this two periods, the M=7.7 Tonghai, M=7.1 Dagua…     

Strain field measurements of rubber by image analysis and design criteria for laminated rubber bearings (LRB)

Although seismic isolation rubber bearings in bridges and buildings have proven to be a very effective passive method for reducing earthquake‐induced forces, a detailed mechanical modeling of the rubber that is used in bearings under large strains has not been established. Therefore, a 3D model of failure behavior and the design criteria for the safety evaluation of seismic isolation bearings have not yet been developed. This paper presents: (1) correlation‐based template‐matching algorithms to measure large strain fields of continua; (2) a failure criterion for rubber; and (3) the design criteria for the safety evaluation of laminated algorithms, data‐validation algorithms were developed and implemented to eliminate possible unrealistic displacement vectors present in the measured displacement field. The algorithms were successfully employed in the strain field measurement of LRB and rubber materials that are subjected to failure. The measured local strains for rubber material at failure were used to develop a failure criterion for rubber. The validity of the proposed criterion was evaluated by applying it to the LRB; the criterion was introduced into a 3D finite element model of LRB, compared with the experimental results of bearings failure, and verified. Finally, design criteria are proposed for LRB for the safety evaluation. Copyright © 2003 John Wiley & Sons, Ltd.     

Seismic response of a cable‐stayed bridge deck under multi‐component non‐stationary random ground motion

A Markov method of analysis is presented for obtaining the seismic response of cable‐stayed bridges to non‐stationary random ground motion. A uniformly modulated non‐stationary model of the random ground motion is assumed which is specified by the evolutionary r.m.s. ground acceleration. Both vertical and horizontal components of the motion are considered to act simultaneously at the bridge supports. The analysis duly takes into account the angle of incidence of the earthquake, the spatial correlation of ground motion and the quasi‐static excitation. A cable‐stayed bridge is analysed under a set of parametric variations in order to study the non‐stationary response of the bridge. The results of the numerical study indicate that (i) frequency domain spectral analysis with peak r.m.s. acceleration as input could provide more r.m.s. response than the peak r.m.s. response obtained by the non‐stationary analysis; (ii) the longitudinal component of the ground motion significantly influences the vertical vibration of the bridge; and (iii) the angle of incidence of the earthquake has considerable influence on the deck response. Copyright © 2003 John Wiley & Sons, Ltd.     

雾探测器现场对比试验方法研究

简单介绍了WT-1型雾探测器的结构和现场试验情况，对试验期间(2001年12月1日至2002年5月31日)所获取的数据进行了统计分析，计算了试验期间雾探测器数据的缺测率、与人工观测数据及芬兰同类产品的测量结果之间的相关系数，三者之间的相符率，以及数据随时间的变化趋势。以数据处理结果为依据，客观地阐述了雾探测器的优缺点，以及与目前世界上普遍认可的芬兰能见度仪之间的差距，同时也提出了雾探测器改进的一些建议。     

基于电场理论的主动防雷系统的初步设想

针对目前使用的传统雷电防护技术存在的问题，通过分析雷电原理和雷电触发机制，利用电场理论来设计一套主动防雷系统，即实现保护对象所在空间大气处于被激放电状态，并利用闪电将大气激活为自激放电状态。介绍了主动防雷系统的原理，并对其核心的“引而不发”理论进行阐述，在此基础上设计出主动防雷系统的模型。具体说明了构成主动防雷系统的阻塞系统、疏导系统和电源系统的构造和特征以及它们之间的关系。计算得到主动防雷系统所需的电场强度E=0．69kV／m。最后指出了存在问题与发展方向，在结论中总结了主动防雷系统的特点及其关键。     

中国稻田甲烷产生和排放研究 Ⅰ.产生和排放机理及其影响因子

综合论述了近 2 0年来中国稻田甲烷排放的研究状况 ,包括中国稻田甲烷排放通量的观测 ,稻田甲烷生成的生物学机理及产生、转化、传输的机理研究 ,稻田甲烷排放的影响因子 ,主要介绍了稻田甲烷产生和氧化过程、影响甲烷排放的因子