Numerical modeling of gravitational field lines – the effect of mass attraction on horizontal coordinates

There are two basic types of geodetic projections by which the points located on the Earth's surface can be projected onto a reference ellipsoid. Because of the different principles of Helmert's and Pizzetti's methods two sets of horizontal and vertical coordinates are obtained for the same set of surface points. The difference is investigated in terms of offsets of horizontal coordinates. For an estimation of the offsets the field lines going through topographic masses are determined by three different numerical methods in `flat Earth approximation' using a volume element model of the density distribution of the lithosphere in a part of central Europe. The maximum horizontal offset reaches 20 cm on the investigated area at the level of the geoid. Received: 28 October 1998 / Accepted: 16 August 1999     

基于遥感的城乡人口分布模拟——以松原市为例

利用遥感数据模拟基于居民地的人口空间分布,须解决两大难题：①居民地类型、面积、位置的精确获取;②居民地类型、面积与人口数量间的关系。本文根据地理意义和数学意义,对经典的城市人口-面积异速生长模型进行扩展,推导出城乡人口-面积统一模型。进而以松原市为例,以1∶5万地形图为辅助数据,建立居民地分类体系,利用ETM影像提取居民地信息,在以上模型的基础上采用“城乡人口分割”算法模拟城乡人口的空间分布。本研究方法可为中尺度人口分布的理论与应用研究借鉴。     

Study on the Thermal internal Boundary Layer and Dispersion of Air Pollutant

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Evaluation of substructuring method for seismic soil-structure interaction analysis of bridges

This paper evaluates the commonly used substructuring method for analysis of bridge systems where the bridge is divided into two sub-systems: the bridge superstructure and the substructure including the pile foundations, abutments, and soil. Modeling of the soil-structure interaction (SSI) in the system is simplified by replacing the pile foundations, abutments, and soil with sets of independent equivalent linear springs and dashpots at the base of the superstructure. The main objective of the paper is to examine how well the substructuring method simulates the seismic response of a bridge system. The baseline data required for the evaluation process is derived from analyzing a fully-coupled continuum bridge model, already validated for the instrumented two-span Meloland Road Overpass. The same bridge system is also simulated using the substructuring method. The results from both approaches are compared, and it is shown that the differences between them can be significant. The substructuring method consistently overestimates the pier base shear forces and bending moments and the pier top deflections. Moreover, the spectral response of the bridge structure is mispredicted. The analyses are repeated for a three-span bridge system subjected to several ground motions, leading to a similar observation as before. Hence, the current state of practice for simulating seismic SSI in bridges using the substructure model is shown to be too simplified to capture the major mechanisms involved in SSI.     

GRAPES-Meso模式浅对流云辐射效应的改进试验

在万子为等（2015）对GRAPES-Meso模式浅对流参数化改进的基础上,进一步引入了浅对流云量诊断计算,并设计旨在完善浅对流云辐射效应的浅云云量和云中水凝物的补偿方案,以改进模式低层云量偏少和浅对流云辐射效应不足的问题。通过对数值试验结果的诊断和对比分析以及与观测的比较,重点考察了浅对流云量计算与浅对流激发的协调性、浅对流云对低云补偿后所产生的辐射效应以及对模式地面要素预报的影响等,验证了改进方案的合理性与有效性。结果表明:（1）浅对流云量诊断计算合理,其云覆盖区与浅对流激发区相吻合,引入浅对流云量的计算可减小模式云量的计算偏差、使其向观测结果靠近;（2）改进方案在浅对流发生区低层0.5-4 km高度范围内,对影响模式云辐射过程的浅云云量和云中水凝物形成有效补偿,最明显的浅云补偿在1-1.5 km高度处,浅对流活跃时期浅对流过程对浅云水凝物（云水和雨水之和）的补偿量可达20%-55%;（3）云光学厚度对浅云水凝物的补偿响应合理,即水凝物的补偿引起云光学厚度增大,两者的变化特征在时空分布上十分相似,且云光学厚度之变化受云水补偿的影响比受雨水补偿的影响更明显;（4）在白天时段,浅云补偿所产生的辐射效应使模式地表太阳总辐射有所下降,缩小了与观测的偏差,进而使地表温度和地面2 m气温模拟偏差减小。改进方案在缓解模式云量偏少、地表太阳总辐射偏强和地面2 m气温偏高等方面的作用,在批量试验中得到了验证。      

降水对热带西南太平洋海温异常响应的数值试验

本文应用IAP9-AGCMⅡ九层大气环流数值模式，通过数值试验，研究了降水对热带西南太平洋SSTA(海温异常)的响应。结果表明：海温正异常下，夏季北半球热带中太平洋降水明显偏多；我国东部地区降水正常或偏多。海温负异常下，夏季赤道中太平洋降水偏少，我国大部地区降水正常或略偏少。当该区域SST异常时，从总体看降水对该异常响应最敏感的地区为北半球热带中太平洋、我国华中和西南、孟加拉湾和中南半岛。     

A simple displacement model for response analysis of EPS geofoam seismic buffers

A simple displacement-type block model is proposed to compute the compression–load–time response of an idealized seismic buffer placed against a rigid wall and used to attenuate earthquake-induced dynamic loads. The seismic buffer is modelled as a linear elastic material and the soil wedge shear surface by a stress-dependent linear spring. The model is shown to capture the trends observed in four physical reduced-scale model shaking table tests carried out with similar boundary conditions up to a base excitation level of about 0.7g. In most cases, quantitative predictions are in reasonable agreement with physical test results. The model is simple and provides a possible framework for the development of advanced models that can accommodate more complex constitutive laws for the component materials and a wider range of problem geometry.     

ACCURACY AND STABILITY OF FINITE DIFFERENCE EQUATIONS FOR SHALLOW WATER FLOWS IN ORTHOGOPNAL COORDINATES

IINTRODUCTIONNumericalmethodsasatooltosimulateflowsandpollutanttransportareincreasinglyimportantinhydraulicandenvironmentalengineering.AveryusefulapplicationofthenumericalmethodologyinengineeringproblemswouldbetosolvethesystemofZDdepth-integratedshallowwaterequations.ManysolutionsofthegoverningequationsarederivedusingtraditionalfinitedifferencemethodonCartesianregulargrids.ThedisadvantageofthismethodseemstobetheinflexibilityofCartesiangridstocomplywithirregularorcurvedperimeterswhichsur…