Derivation of design soil coefficients (S) and response spectral shapes for Eurocode 8 using the European Strong-Motion Database

A revision is presently under way to upgrade the status of the `Designrecommendations for earthquake resistance of structures', commonlyreferred to as Eurocode 8 (or EC8). In order to improve the definition ofthe design elastic response spectra (ERS) as defined in the Eurocode 8 –Part 1 (Draft May 2001), the values of the soil amplification factors havebeen calculated for sites on sedimentary soils, both stiff (category B) andsoft (category C), with respect to rock sites (category A), such ascontemplated in EC8. The work was performed by a systematic study ofresponse spectra as a function of magnitude and site conditions, usingrecords from the European Strong-Motion Database.The results confirm the occurrence of systematic spectral amplification onsedimentary soils with respect to reference rock in a large set of Europeanstrong motion data. Such amplification has been quantified through ameasure derived from the Housner Spectrum Intensity definition.The values of the soil coefficients recommended in the current version ofEC 8 are shown to be realistic for category C, in the case of a moderateseismicity context. However the values for subsoil class B need to besignificantly increased both for the moderate and high seismicity context.     

A Ti L-edge X-ray absorption study of Ti-silicate glasses

 A series of titanium silicate glasses along the composition joins SiO₂–TiO₂, Na₂SiO₃–TiO₂, K₂SiO₃–TiO₂, and CaSiO₃–TiO₂ have been examined using titanium (Ti) L-edge X-ray absorption near-edge spectroscopy (XANES). XANES spectra were collected at the Canadian Synchrotron Radiation Facility (CSRF), University of Wisconsin, Madison, using the Spherical Grating Monochromator (SGM) beamline. Glass spectra were compared with spectra obtained from crystalline analogues with differing Ti coordination environments: β_rBa₂TiO₄ (^[4]Ti); fresnoite (^[5]Ti); and rutile and anatase (^[6]Ti). The Ti L-edge data indicate that for homogeneous TiO₂–SiO₂ glasses Ti coordination is ^[5]Ti at TiO₂ contents below 3.6 wt% but predominantly ^[4]Ti with some ^[5]Ti present above this content. There is no evidence for ^[6]Ti. For the Na₂ O-containing glasses the L-edge data indicate that Ti is ^[4]Ti with some ^[5]Ti at low TiO₂ contents, becomes a mix of ^[4]Ti and ^[5]Ti with increasing TiO₂ content, but is exclusively ^[5]Ti by 14.3 wt% TiO₂. The K₂O composition glasses exhibit similar behavior but contain a greater proportion of ^[4]Ti and less ^[5]Ti than the equivalent Na₂O-bearing glasses. These findings are consistent with previous Raman and XANES pre-edge studies. Alkaline-earth-containing glasses behave somewhat differently, with ^[5]Ti occurring in low TiO₂ content glasses, becoming a mix of ^[4]Ti and ^[5]Ti, and then gradually changing to predominantly ^[4]Ti at higher TiO₂ compositions. Finally, we have obtained data for a fresnoite composition (Ba₂TiSi₂O₈) glass. Previous pre-edge and Raman data had suggested that this composition glass contained ^[5]Ti; however, our Ti L-edge data indicate that Ti is almost exclusively ^[4]Ti, although some ^[5]Ti may also be present. Received: 20 December 2000 / Accepted: 10 July 2001     

我国新一代天气雷达网监测系统

简要介绍了我国正在布网的雷达的特点和功能以及雷达气象产品及其气象应用软件，给出了冰雹云识别和跟踪、中尺度气旋、暴雨等产品的个例。新一代天气雷达系统具有较强的对灾害性天气监测、预警能力，对较大范围内降水(台风)进行定量估测的能力，以及获取回波信号中风场信息的能力，是综合探测、分析、预测、预警功能为一体的智能型系统。     

碳氟磷灰石的位置群分析

本文借助于磷灰石的晶体结构资料,用位置群分析的方法,讨论了碳氟磷灰石的晶体结构与它的红外光谱间的关系,并从位置群的角度分析了CO_3~(2-)的存在形式及可能的位置对称。     

Influence of Site and Source Dependent Ground Motion Scenarios on the Seismic Safety of Long-span Bridges in Cologne, Germany

An overlap in frequency between the 1D resonance frequency of sediments and the vibrational frequencies of long-span bridges might lead to a strongly increased structural response of the latter. Interference of surface waves caused by reflections at dipping interfaces may introduce additional unfavourable amplifications. Therefore, the vulnerability of two bridges crossing the Rhine River in Cologne, Germany, was assessed using ground motion scenarios computed for four profiles crossing the Lower Rhine Embayment. Due to their vibrational frequencies being in the vicinity of resonant peaks in the response spectra, the Severinsbridge showed critical loading and the bridge Cologne-Deutz even exhibited grave failure according to the dynamic FE-simulations.     

一次冬季降雪过程的多普勒雷达资料特征分析

2005年2月17~18日青岛出现了一次大雪过程,通过对多普勒雷达资料的分析,发现多普勒雷达资料很好地揭示了本次降水过程的成因。降水初期,主要为暖湿气团从相对较暖的海面上移动到相对较冷的陆地上冷却凝结产生的降雪,所以强度很弱;在0~2.7km高度上,在倒槽上发展起来的以青岛为中心的中尺度气旋性风场的出现,预示着降水强度的迅速增强和降水量级的改变,该风场的破坏,则预示着降雪强度的迅速减弱;回波强度在30~35dbZ时,降雪强度即可达到较强。     

一种改进的电离层层析成像算法

针对电离层层析成像算法中确定相位积分常数以及合理选择迭代初值等关键问题,本文提出一种联合使用差分多普勒相位和差分多普勒频率数据的新算法,将相位积分常数的计算以及迭代初值的确定与图像的重建过程统一起来．该算法克服了单独计算相位积分常数的困难,初值的选择也较为合理,数值模拟反演与对实测数据反演的结果证明,本文提出的算法对电离层ＣＴ重建更为合理有效．     

黄河口邻近海域底栖动物粒径谱研究

首次建立了黄河口邻近海域4个站位底栖动物生物量粒径谱和标准化生物量粒径谱。生物量粒径谱模式为三峰模式,3峰分别由海洋线虫,其他小型底栖动物类群和大型底栖动物形成。研究站位标准化粒径谱斜率变化范围为-0.859至-0.664,截距为15.035至16.331,与东、黄海和南黄海研究结果一致,可有效地指示营养输入状况和总生物量。同时,需要指出的是截距对总生物量的指示作用需注意粒级选择的一致性。利用粒径谱方法计算了底栖动物次级生产力,结果显示,研究站位平均次级生产力为6.717 g.DW.m-2a-1,大型底栖动物次级生产力为4.509 g.DW.m-2a-1,小型底栖动物次级生产力为2.208 g.DW.m-2a-1。粒径谱方法计算结果与其他次级生产力计算方法基本一致。与其他方法相比,该方法更加简便,可避免因对生物特性的把握不准而引起的计算误差。     

2007年7月8日特大暴雨过程的中尺度特征

利用雷达、卫星、闪电定位仪及NCEP资料分析了2007年7月8日在安徽沿淮西部出现的特大暴雨过程的中尺度特征.分析结果表明:造成特大暴雨的强对流回波带与近地面层925hPa辐合区位置一致,而且回波单体移向与回波带走向一致,另外发现该中尺度对流雨团(rainstor ms)属于后向传播,其传播方向和单体的移动方向相反,使得强回波在特定区域保持相对静止,造成特大暴雨;逐时降水极值基本出现在对流发展旺盛和对流回波发生合并时.另外通过分析单多普勒雷达反演二维风场发现,中低层气旋性切变的维持是强降水形成和维持的重要条件.