Time segmented least squares identification of base isolated buildings

In this article two new approaches are presented for time domain identification of base isolated buildings from recorded response during earthquakes: (1) a least squares technique with time segments is developed to identify the piece-wise linear system properties; and (2) an observer is used to estimate the unmeasured states and initial conditions of different time segments. In base isolated buildings changes in dynamic properties occur during earthquake response due to nonlinear behavior. Hence, a multi-input and multi-output technique using time segments is developed for piece-wise linear system identification. The primary advantage of the developed time segmented technique is that it can be applied to windows of time history instead of the entire duration of earthquake response. The developed technique (1) starts with identification using the entire duration of the earthquake response; (2) evaluation of time segments during which the identified response differs significantly from the recorded response to establish windows of time history during which refined identification is necessary; and (3) identification of the change in dynamic properties in the established windows using the observer based time segmented least squares approach. Only partial state measurements are usually available for identification. Hence, an observer is used to estimate the unmeasured states and initial conditions needed for different time segments. By comparing identified response with recorded response, of an actual base isolated building which experienced Northridge earthquake, it is shown that the change in dynamic system parameters, such as periods and damping ratios, due to nonlinear response, are reliably estimated using the presented technique.     

Les microbialites de l'Anti-Atlas occidental (Maroc) : marqueurs stratigraphiques et témoins des changements environnementaux au Cambrien inférieur

Three microbialite forms are recognized in the Lower-Cambrian succession of Irherm area in the western Anti-Atlas (Morocco). Stromatolites, which correspond to non-calcified shallow marine laminated microbialites, are well developed in the basal Lower-Cambrian succession. Occurrence of calcified microbial thrombolites, in the middle part of this succession, reflects an increasing sea level from the peritidal zone to the subtidal environment. In the upper part of this succession, a second increasing water depth event and the development of branching archaeocyathan reefal framework lead to dendritic microbialite emergence. To cite this article: M. Benssaou, N. Hamoumi, C. R. Geoscience 336 (2004).     

EPS98电子平板测图系统在建设项目用地勘测定界技术工作中的应用

本文介绍了应用北京清华山维新技术开发有限公司的EPS98电子平板测图系统进行建设用地勘测定界工作中的地籍测绘内业工作的方法和过程，给出了一个尤其适合于中小城市相关国土部门完成勘测定界工作的经济适用方案。多年的应用和实践证明了该方案的有效性和可靠性。     

TEQC软件对GPS数据质量的评定及软件界面的开发

本文主要介绍用于GPS数据转换、编辑和质量检查的共享软件TEQC(Translate／Edit／Quality Check)。作为例子，对一GPS数据进行质量检查。并针对TEQC软件人机交互性差的缺点，进行了软件界面程序的初步开发。     

GPS船体姿态测量技术研究

论述了应用GPS技术进行船体姿态解算的原理 ,介绍了基于当前技术的可行测量方法 ,对影响测量精度的几种误差源进行分析 ,并提出了系统软件设计的方案及系统设计时应注意的问题。     

主动式集成GPS滑坡监测系统的研制与监测实践

主动式集成GPS滑坡监测系统是GPS技术与电子全站仪技术的高度集成。本文叙述了主动式集成GPS滑坡监测系统的基本原理与工作过程。     

焦作市森林火险等级预报系统

利用1989～1999年焦作市逐日森林火险天气等级资料，分析了焦作地区森林火险与气象要素的关系，建立了焦作市火险等级预报系统。经2001～2002年实际应用，效果良好。     

Measuring Seismic Waves Induced by Large Earthquakes with GPS

Independent GPS position solutions at 1-sec interval, derived from the International GPS Service (IGS) data and orbit÷clock products, clearly show seismic waves generated by the magnitude 7.9 Denali Fault, Alaska earthquake of November 3, 2002. Surface seismic waves with periods of about 20 sec and amplitudes of up to 20 cm were detected up to 4,000 km from the epicenter. This confirms the previous findings reported by Larson et al. (2003); we use additional station data along with different processing software and strategies. The seismic waves from the May 26, 2003 magnitude 7.0 Japanese earthquake were also observed in the 1-sec position solution series at station MIZU, about 80 km from the epicenter. This earthquake, however, could not be detected by GPS at station USUD, about 410 km away. Similarly, the Algerian May 21, 2003 earthquake of magnitude 6.8 could not be detected by GPS at the nearest IGS station located approximately 800 km from the epicenter.     

无锡市数字遥测地震台网建设的体会

无锡市数字遥测地震台网是按照无锡市防震减灾十年目标纲要建设的，目前已正式投入运行。我局综合各方专家意见和资料，对台网的组成，台站的布局、选择、建设取得了一些经验。总结建设的体会，供其它台网建设时参考。     

Seismic response of isolated bridges with soil–structure interaction

The modern transportation facilities demand that the bridges are to be constructed across the gorges that are located in seismically active areas and at the same time the site conditions compel the engineers to rest the pier foundation on soil. The purpose of this study is to assess the effects of soil–structure interaction (SSI) on the peak responses of three-span continuous deck bridge seismically isolated by the elastomeric bearings. The emphasis has been placed on gauging the significance of physical parameters that affect the response of the system and identify the circumstances under which it is necessary to include the SSI effects in the design of seismically isolated bridges. The soil surrounding the foundation of pier is modelled by frequency independent coefficients and the complete dynamic analysis is carried out in time domain using complex modal analysis method. In order to quantify the effects of SSI, the peak responses of isolated and non-isolated bridge (i.e. bridge without isolation device) are compared with the corresponding bridge ignoring these effects. A parametric study is also conducted to investigate the effects of soil flexibility and bearing parameters (such as stiffness and damping) on the response of isolated bridge system. It is observed that the soil surrounding the pier has significant effects on the response of the isolated bridges and under certain circumstances the bearing displacements at abutment locations may be underestimated if the SSI effects are not considered in the response analysis of the system.