测地主题正反解解算

由测地坐标系中大地线的微分方程式推导出其微分关系式，得出在地球椭球面上基于测地坐标进行正反解的算法和公式，它与大地主题解算公式相比，更为简捷明了。由实际计算数据表明，对于100km以下的距离解算，它亦能达到相当高的精度。因此测地坐标的点位表述不仅可用于DEM和GIS三维可视化，也可用于三维GIS建模以及空间度量和分析。     

Computing with certainty individual members of families of periodic orbits of a given period

The accurate computation of families of periodic orbits is very important in the analysis of various celestial mechanics systems. The main difficulty for the computation of a family of periodic orbits of a given period is the determination within a given region of an individual member of this family which corresponds to a periodic orbit. To compute with certainty accurate individual members of a specific family we apply an efficient method using the Poincaré map on a surface of section of the considered problem. This method converges rapidly, within relatively large regions of the initial conditions. It is also independent of the local dynamics near periodic orbits which is especially useful in the case of conservative dynamical systems that possess many periodic orbits, often of the same period, close to each other in phase space. The only computable information required by this method is the signs of various function evaluations carried out during the integration of the equations of motion. This method can be applied to any system of celestial mechanics. In this contribution we apply it to the photogravitational problem.     

长江河口的演变规律与水动力作用

本文应用流体运动的最小阻力原理导出了长江河口崇明岛发育长度的理论公式。论述了科里奥利力在河道分流中的作用与河口演变的混沌现象。文中指出,在未来当崇明岛归并北岸时南支可能发生的环境问题．     

从时空GIS视野来定量分析人类行为的思考

城市群体移动研究通常以网格为空间分析单元,其分析存在可塑性面积单元问题（modifiable area unit problem,MAUP）,目前的研究缺乏对不同大小的网格面积单元所忽略的城市群体移动规律的定量分析结论。对城市空间进行有限的不同大小的等间距格网划分并对城市群体移动忽略部分进行分析,发现格网内群体移动量随格网大小线性递增,格网间的群体移动量随格网大小线性递减,并以提取城市重要位置的空间分布和属性特征的不一致为例,表明应对忽略的短距离移动予以重视,避免决策上的偏差。与此同时,不同格网划分大小情况下格网内的移动量在住宅用地、工业用地上被忽略程度较为严重,建议根据实际研究的目的采取不均匀划分空间格网方法,避免过多忽略群体移动。     

Model identification and parameter estimation of elastoplastic constitutive model by data assimilation using the particle filter

Data assimilation, using the particle filter and incorporating the soil‐water coupled finite element method, is applied to identify the yield function of the elastoplastic constitutive model and corresponding parameters based on the sequential measurements of hypothetical soil tests and an actual construction sequence. In the proposed framework of the inverse analysis, the unknowns are both the particular parameter within the exponential contractancy model, n_E, which parameterizes various shapes for the yield function of the competing constitutive models, including the original/the modified Cam‐Clay models and in‐between models and the parameters of the corresponding constitutive model. An appropriate set, consisting of the yield function of the constitutive model and the parameters of the constitutive model, can be simultaneously identified by the particle filter to describe the most suitable soil behavior. To examine the validity of the proposed procedure, hypothetical and actual measurements for the displacements of a soil specimen were obtained for consolidated and undrained tests through a synthetic FEM computation and for consolidated and drained tests, respectively. After examining the applicability of the proposed procedure to these test results, the present paper then focuses on the actual measured data, ie, the settlement behavior including the lateral deformation of the Kobe Airport Island constructed on reclaimed land.     

四川省农业生态环境问题与对策

四川地处长江中上游地区，是全国三大林区之一和生态保护与建设的重点区域。搞好四川农业生态环境建设，对全国的生态保护与建设和长江中下游地区的经济发展有着十分重要的作用。该文全面分析评价了四川省农业生态环境的主要问题和演变趋势，提出了四川省农业生态环境恢复与重建的对策措施。     

Sinusoidal oscillations radiating from a cylindrical source in thermal conduction or groundwater flow: Closed‐form solutions

The diffusion equation governs thermal conduction and groundwater flow phenomena. In this paper, we study the two‐dimensional radial propagation of a sinusoidal perturbation radiating from a cylindrical source within an infinite slab of homogeneous material. The solution of this problem has several applications. For instance, it can be used to determine the hydraulic diffusivity of the subsurface based on measurements of the hydraulic head around a vertical well during its development. For thermal problems, it can be used to determine the thermal diffusivity based on measurements of the temperature distribution around a cylindrical heat source generating a sinusoidal power per unit length. In this paper, we present a comprehensive analytical solution of this problem and we compare these solutions with numerical solutions. Two approximate analytical solutions, which can be relevant in practice, are also presented. Finally, we give an upper bound for the survival time of the transient part of the solution and we provide an estimate of the radius of influence of the sinusoidal solicitation. Copyright © 2010 John Wiley & Sons, Ltd.     

Search for and study of nearly periodic orbits in the plane problem of three equal-mass bodies

We analyze nearly periodic solutions in the plane problem of three equal-mass bodies by numerically simulating the dynamics of triple systems. We identify families of orbits in which all three points are on one straight line (syzygy) at the initial time. In this case, at fixed total energy of a triple system, the set of initial conditions is a bounded region in four-dimensional parameter space. We scan this region and identify sets of trajectories in which the coordinates and velocities of all bodies are close to their initial values at certain times (which are approximately multiples of the period). We classify the nearly periodic orbits by the structure of trajectory loops over one period. We have found the families of orbits generated by von Schubart’s stable periodic orbit revealed in the rectilinear three-body problem. We have also found families of hierarchical, nearly periodic trajectories with prograde and retrograde motions. In the orbits with prograde motions, the trajectory loops of two close bodies form looplike structures. The trajectories with retrograde motions are characterized by leafed structures. Orbits with central and axial symmetries are identified among the families found.     

Collinear Central Configuration in Four-Body Problem

In the n-body problem a central configuration is formed if the position vector of each particle with respect to the center of mass is a common scalar multiple of its acceleration vector. We consider the problem: given a collinear configuration of four bodies, under what conditions is it possible to choose positive masses which make it central. We know it is always possible to choose three positive masses such that the given three positions with the masses form a central configuration. However for an arbitrary configuration of four bodies, it is not always possible to find positive masses forming a central configuration. In this paper, we establish an expression of four masses depending on the position x and the center of mass u, which gives a central configuration in the collinear four body problem. Specifically we show that there is a compact region in which no central configuration is possible for positive masses. Conversely, for any configuration in the complement of the compact region, it is always possible to choose positive masses to make the configuration central.     

The General Solution of the Planar Laplace Problem

The famous Laplace problem is the three-body, secular, planetary problem. Its plane version has the great theoretical advantage of being integrable (Ferraz-Mello, private correspondence, 2001) and Ferraz-Mello et al. (Chaotic World: from order to Disorder in Gravitational N-Body Systems, Kluwer Academic Publisher, 2004)). Nevertheless it remains a very complex problem with many singularities and many possibilities of collisions. Large eccentricities lead generally to large perturbations especially if the two planets have the same direction of revolution about their star.