基于Betti-Rayleigh动力互易定理求解移动荷载引起的地基土振动

基于Betti-Rayleigh动力互易定理,论证了地基土Green函数的互易性,推导了移动荷载引起的地基土振动解析解,进而推证出移动常力荷载和移动简谐荷载作用下地基土表面振动在波数-频率域内和空间-时间域内的解析表达式,并采用Matlab对其进行数值计算。通过互易定理的使用将振源的移动问题变换为地面上受振点的移动问题,使移动荷载作用下地基土振动响应的解析表达式大大简化。最后结合某地基土参数对移动的单位常力荷载和单位简谐荷载作用下的地面振动进行算例分析,结果表明:移动常力荷载引起的地面振动属于典型的低频振动;移动简谐荷载作用下地基土表面出现波动的Doppler效应,且地面上受振点的振动频率范围由最上层地基土的Rayleigh波波速控制;地面上的受振点距振源较近时,地基土表面R波对振动的贡献明显高于P波和S波,而当受振点距振源较远时,P波对振动的影响较明显。

Painlevé Integrability of Nonlinear Schrdinger Equations with both Space-and Time-Dependent Coefficients

We investigate the Painleve integrabiiity of nonautonomous nonlinear Schr6dinger （NLS） equations with both space-and time-dependent dispersion, nonlinearity, and external potentials. The Painleve analysis is carried out without using the Kruskal＇s simplification, which results in more generalized form of inhomogeneous equations. The obtained equations are shown to be reducible to the standard NLS equation by using a point transformation. We also construct the corresponding Lax pair and carry out its Kundu-type reduction to the standard Lax pair. Special cases of equations from choosing limited form of coefficients coincide with the equations from the previous Painleve analyses and/or become unknown new equations.

SPATIAL DISTRIBUTION AND VARIATION TENDENCY OF DROUGHTS AND FLOODS IN HUNAN PROVINCE DURING THE PAST 36 YEARS

Using the 1970-2005 annual precipitation and evaporation data at 80 gauge stations across Hunan province,this work analyzes the spatial distribution and variation tendency of the local droughts and floods using linear regression,wavelet analysis,abrupt change,clusters,Empirical Orthogonal Function (EOF) and rotated EOF (REOF).Results show that there are four dry areas and three wet areas in Hunan.The whole province exhibits a moistening trend except some small areas in western,eastern and southern Hunan.The most prominent feature of annual precipitation is that the whole province basically displays a consistent variation tendency,as far as the dominant EOF mode is concerned.In addition,the spatial features of the other EOF modes include dry-wet differences,e.g.wet (or dry) in the north versus dry (or wet) in the south,wet (or dry) in the center and dry (or wet) in the surrounding areas.The distribution of the ratios of evaporation to precipitation exhibits both common features as well as spatial differences,which can be classified into four types:South Hunan,North Hunan,Northeast Hunan,and Central Hunan.There is an abrupt change from dry to wet patterns in the early 1990s.Generally,the drought-flood distribution presents variations of three periods.In the late 2000s,Hunan province will be in a period of drought,followed by a period of flood.

Temporal Data Mining Using Genetic Algorithm and Neural Network——A Case Study of Air Pollutant Forecasts

This paper integrates genetic algorithm and neura l network techniques to build new temporal predicting analysis tools for geographic information system (GIS). These new GIS tools can be readily applied in a practical and appropriate manner in spatial and temp oral research to patch the gaps in GIS data mining and knowledge discovery functions. The specific achievement here is the integration of related artificial intellig ent technologies into GIS software to establish a conceptual spatial and temporal analysis framework. And, by using this framework to develop an artificial intelligent spatial and tempor al information analyst (ASIA) system which then is fully utilized in the existin g GIS package. This study of air pollutants forecasting provides a geographical practical case to prove the rationalization and justness of the conceptual tempo ral analysis framework.

Differential Space Frequency Mapping Schemes and Norm Criterion

This paper proposed four types of differential modulation to map the unitary code into the orthogonal frequency division multiplexing(OFDM) signal. The time-varying channel model is established and the norm of detection metric is deduced. The norm is the inherent interference of the time-varying channel, so it can be used as criterion to evaluate the performance of the mapping schemes. The simulation results agree with the analytic conclusion.

Remote sensing needs and capabilities in West Africa

The greatest advantage of remote sensing over conventional measurements lies in the opportunity to carry out detailed spatio-temporal analysis of land and ocean features on a very frequent basis. This paper analyses the contribution of satellite imagery to atmospheric, geophysical and ocean studies and management in West Africa since the early 1980s. The detailed application of data from optical sensors (e.g. Meteosat,NOAA/AVHRR, SPOT, Landsat TM, etc.) for weather prediction, hydrogeologicah landuse/cover and cartographic studies has been acknowledged. However, the use of microwave (e.g. SAR) and optical data for ocean monitoring and studies in the sub-region is still very limited. Even though sufficient remote sensing expertise and infrastructure is perceived in the region, no clearly defined networking or database exists.

Statistical Analysis of Influencing Factors of Temporal and Spatial Variation Patterns of Decadal Accumulative Heavy Rainfall in China

Daily precipitation analyses for 659 Chinese meteorological stations from 1951 to 2010 show that the rapid urbanization may have triggered the significant increase of heavy rainfall in China. During the last decades, HRAs （Heavy Rainfall Amounts）, HRDs （Heavy Rainfall Days） and HRI （Heavy Rainfall Intensity） in China have increased. Impressively, the upward trends are not randomly observed among stations, but of robust consistency with quite large regional scale over large widely and significantly. Compared to the 1950s, the HRA, HRD, and HRI increased by 68.71%, 60.15% and 11.52% during the 2000s. The significant increase of accumulative heavy rainfall appears firstly in the southeastern coasts in the early period, and then gradually expands to the central, southwest, north and northeast China. Rapid urbanization is very likely the main cause of large-scale heavy rainfall increase in China. The urbanization indicators including the industrial production output （GDP2）, UP （Urban Population） and annual average HDs （Haze Days） are in good agreement with the heavy rainfall variations, and these indicators can statistically explain the variance of HRA, HRD and HRI by 61.54%, 58.48% and 65.54%, respectively. Meanwhile, the explained variance by leading climate indices including WPSH （Western Pacific Subtropical High）, ENSO （El Nino-Southern Oscillation）, AMO （Atlantic Multi-decadal Oscillation） and AAO （Antarctic Oscillation） are respectively 24.30%, 26.23% and 21.92%, being only about 1/3 of the urbanization-related variance. Panel data analysis of county-level total population and annual average visibility days less than 10 km also show that these two indicators have significant correlation with decadal HRA, HRD ＆ HRI and the spatial correlation coefficient increases gradually with time. These consistent temporal and spatial features strongly suggest that rapid urbanization most likely triggered the steady increase of heavy rainfall over China during the recent decades.

基于遥感与地理信息技术的登革热环境风险因子标识

目的通过分析广州市2002年登革热疫情数据,采用遥感以及地理信息系统技术标识与登革热(DF)的流行风险相关的地表景观种类。方法首先,通过基于泊松模型的回顾式空间-时间分析方法获取疫情数据的时空聚集状况。其后,从MODIS卫星图像中提取地表景观信息,并逐月逐区计算各地类所占对应研究区的面积比例。最终,由广义线性模型分析确定DF病例的存在与否与地表景观种类面积比例的关系,并使用二态逻辑回归分析建立预测模型。结果最有可能的登革热聚集圈中心位于东山区,同时覆盖越秀区以及荔湾区,其时间窗为8月至10月。最佳预测模型对"某行政区在气候条件允许下是否存在登革热病例"的预测达到了91.1%的准确度。结论开放水域,以沼泽和湿地为主的湿草场,以水稻为主的农田以及开发用地被标识为与登革热病例存在与否最为相关的地类因子。