Influence of soft clays on the response spectra for structures in eastern Canada

The 1990 edition of the National Building Code of Canada (Associate Committee of the National Building Code, National Research Council, Ottawa, 1990) makes a clear distinction between eastern and western Canada in terms of seismic acceleration and velocity zones. While it is well established that ground motions can be amplified significantly through loose clay deposits, no results are available that take into consideration the typical high frequency content of ground motions in eastern Canada. This paper develops ground amplification curves for clays having depths between 10 and 70 m excited by typical eastern Canadian ground motions scaled to two different values of peak horizontal accelerations. Simplified free-field spectral design curves, which could be used by structural designers, are proposed. The curves show that maximum spectral accelerations occur for structural periods between 0.2 and 0.5 s. In addition, soil depth does not appear to be an important parameter controlling the response of typical clay deposits in eastern Canada.     

PROPAGATION OF 30—60 DAY LOW FREQUENCY OSCILLATIONS AND THEIR INFLUENCE UPON THE SUBTROPICAL WESTERLIES JET STREAM DURING NORTHERN HEMISPHERE WINTER

Based on daily ECMWF gridpoint data of two winters during 1981—1983 including an ENSOyear,propagation of low frequency oscillations(LFO)during Northern Hemisphere winters andtheir influences upon 30—60 day oscillations of the subtropical jet stream are studied with the sta-tistical methods as complex empirical orthogonal function(CEOF)and so on.Results show that inthe winter of a normal year(1981—1982),30—60 day oscillations in the subtropical zone aremainly in the northern and southern flanks of exit region of jet stream.In the ENSO year(1982—1983),they are mainly in the vicinity of entrance and exit regions of jet stream.Intraseasonalchanges of subtropical jet stream manifested themselves as latitudinal fluctuation or longitudinalprogression or regression of about 40 day period.There are marked differences between propagat-ing passages of low frequency modes responsible for changes of subtropical jet stream in the normalyear(1981—1982)and in the ENSO year(1982—1983).Changes of oscillation amplitude showobvious phases.In general,the one in late winter is stronger than that in early winter,strongestone occurs in February.     

A MESO-β SCALE SIMULATION OF THE EFFECTS OF BOREAL FOREST ECOSYSTEM ON THE LOWER ATMOSPHERE

Based on the Intensive Field Campaign(IFC-1)data of Boreal Ecosystem-Atmosphere Study(BOREAS).a three-dimensional meso-β scale model is used to simulate the effect of boreal forests onthe lower atmosphere.A fine horizontal resolution of 2 km×2 km is used in order to distinguish thevegetative heterogeneity in the boreal region.A total of 20×25 grid points cover the entire sub-modeling area in BOREAS' South Study Area(SSA).The ecosystem types and their coverage ineach grid square are extracted from the North American Land Cover Characteristics Data Base(NALCCD)generated by the U.S.Geographical Survey(USGS)and the University of Nebraska-Lincoln(UNL).The topography of the study area is taken from the Digital Elevation Map(DEM)of USGS.The model outputs include the components of the energy balance budget within the canopyand at the ground.the turbulence parameters in the atmospheric boundary layer and the wind.temperature and humidity profiles extending up to a height of 1500 m.In addition to the fine timeand spatial step,the unique feature of the present model is the incorporation of both dynamic andbiological effects of the Boreal forest into the model parameterization scheme.The model resultscompare favorably with BOREAS' IFC-1 data in 1994 when the forest was in the luxuriant growingperiod.     

抗差估计的初值选择

对L1 范估计的平差值和LS估计的平差值作为抗差估计的初值进行了比较 ,指出在 ρ函数是严凸函数时 ,二者无明显的区别。因为LS估计简单且易于计算 ,因此建议用LS估计的平差值作为抗差估计的初值。     

Energy flow in Branchiura sowerbyi (Oligochaeta: tubificidae) in a shallow macrophyte-dominated lake, Biandantang Lake

The energy flow ofBranchiura sowerbyi was studied for the first time in China in a shallow macrophytic lake, Biandantang Lake, Hubei Province. The energy flow was calculated from the measurement of flesh production (12.5241kJ/m²a), egestion (517.7302kJ/m²a), metabolism (38.3273 kJ/m²a), and excretion (4.3798kJ/m²a). The net growth efficiency of the species is about 22.7%, which accords well with the generally reported value for oligochaetes. In addition, the relationship between starvation respiration (R, mgO₂/ind·d), wet weight (Ww, mg) and temperature (T, °C) were also measured, with the regression function beingR=0.008Ww^0.736 e^0.050T. Project supported by NSFC (30270278, 3960019), the foundation of the government of Hubei Province (No. 2000J109), and the foundation of Ecological Station, CAS in the Institute of Hydrobiology.     

青藏块体东北缘地壳水平运动状态

应用青藏块体东北缘1999～2003年多期GPS观测资料，计算了不同时段GPS点水平运动速率。通过分析发现：甘青块体可分为东部块体和西部块体，东、西部块体的运动状态存在明显的差异；受2001年11月14日昆仑Ms8．1地震的影响，震后地壳运动状态发生了明显的改变。     

A stepwise method for determining the number of component distributions in a mixture

This paper considers the problem of estimatingm, the number of components in a finite mixture of distributions from a parametric family. A step-up procedure using the bootstrap method is proposed. Some properties of the procedure are illustrated with simulation studies. An example of the method, applied to orientation of beach clasts, is given.     

基于Chandra的活动星系核观测

活动星系核（AGN）是宇宙中最奇特的天体之一。它是真正意义上的全波天体，其中X射线波段的发射功率占到全波段功率的50％左右。AGN的X射线辐射研究涉及天体物理中的最基本问题，例如能量产生、辐射机制和宇宙论等，而Chandra X射线卫星的高分辨率图像和光谱对这一研究有着重要作用。以Chandra卫星的部分观测结果为例，简要介绍了几类不同类型AGN的X射线辐射研究进展：（1）宽吸收线类星体APM08279＋5255（z=3．91）的X射线谱分析，以及高红移类星体的观测概况；（2）Seyfert星系NGC 4151延展X射线发射问题的解决，及NGC 1068X射线辐射与光学波段的高激发态发射线（[OⅢ]λ5007）有很强相关性的发现；（3）6个BLLac天体样本的X射线环境分析；（4）射电星系X射线喷流的观测等。     

Study on numerical simulation to water lowering in an open coal mine digging

In view of the situation of excavation of open coal mine for the underground water disaster,we should carry out simulation studies for the numerical value of the water lowering project and improve the accuracy and the level of the water lowering project.On the basis of the hydrological geological conditions of certain open mine digging,a more reasonable seepage numerical model was built according to MODFLOW.It was simulated in advance that the process of the confined water level descending with the time,and combining with the actual observations to test the correctness of the model.The calculation showed that the results coincided well with the results of actual measurement.Based on this,different water lowering numerical simulations were built for the open coal mine digging.It could be simulated and forecast that the changes of the groundwater level in drainage process within and outside the mine pit,and it was quantitatively assessed that the possible water lowering result of the opencast water drainage process,which provide an important basis for the actual water lowering project and the possible project disposal.     

Speciation of trace metals in sediments of a tropical estuary

Axial surveys were performed in the two river tributaries of the Cochin estuary, SW India during November 1988. Surficial sediments were subjected to sequential chemical extractions to delineate five metal fractions, namely, exchangeable, carbonate bound, easily reducible, organic/sulfide bound, and residual. The results indicated selective accumulation of Mn and Ni in carbonate bound and organic/sulfide forms, along with marginal amounts of Co in the exchangeable fraction. Large portions of Fe and Cr occurred in the residual fraction, whereas composite fractionation of Zn species was noticed. The exchangeable fractions of Fe and Cr as well as of easily reducible cobalt were below detection limits. The levels of Cr and Zn indicate anthropogenic inputs in this estuary, whereas Co and Ni show regional contamination exceeding natural levels. The analytical speciation procedure helps to deduce the sedimental diagenetic processes in the estuarine environment.