物理大地测量学的设置与教学法研究

论述了物理大地测量学的教学目的和在相关学科中的地位与作用,分析了其内容设置与学时安排,提出了课程教学方法和教学手段的具体建议.     

Comparative study on two methods for calculating the gravitational potential of a prism

The determination of the gravitational potential of a prism plays an important role in physical geodesy and geophysics. However, there are few literatures that provide accurate approaches for determining the gravitational potential of a prism. Discrete element method can be used to determine the gravitational potential of a prism, and can approximate the true gravitational potential values with sufficient accuracy (the smaller each element is, the more accurate the result is). Although Nagy’s approach provi...     

地震现场灾情信息反馈途径和集成软件

在破坏性地震作用下,可导致人员伤亡、建筑物及基础设施破坏、财产损失、社会与经济秩序的混乱及生产系统停止运行等,现场灾情信息是地震现场应急指挥决策的重要依据,迅速、全面对这些信息进行采集与集成是非常重要的。分析了当前地震应急指挥技术系统建设中在该方面存在的一些问题,阐述了地震现场灾情信息分类,同时就其收集反馈途径和集成技术实现进行了研究,并以青岛市地震应急指挥决策软件系统为例,说明了该方法的实用性。     

SURFACE DISPLACEMENTS OF A NON-HOMOGENEOUS ELASTIC HALF-SPACE SUBJECTED TO UNIFORM SURFACE TRACTIONS. PART I: LOADING ON ARBITRARILY SHAPED AREAS

A numerical technique is presented for the analysis of surface displacements of a non-homogeneous elastic half-space subjected to vertical and/or horizontal surface loads uniformly distributed over an arbitrarily shaped area. The non-homogeneity considered is a particular form of power variation of Young's modulus with depth. Since the exponent which determines the degree of non-homogeneity may vary from zero to unity, both the homogeneous half-space and the Gibson soil may be included as limiting cases in a single numerical scheme. In order to account for the arbitrary shape of the loading, the boundary of the loaded area is linearized piecemeal. This enables the modeling of any load pattern according to the desired degree of accuracy. Special attention is focused on the integration scheme, since the singularity associated with the Green's function becomes progressively more pronounced the greater the non-homogeneity parameter gets. The performance of the numerical procedure is studied using analytical solutions for rectangular shaped areas. Further comparisons with well-known solutions based on integral transform techniques for a uniformly distributed load acting on a circular area of the non-homogeneous soil mass show excellent agreement as well. © 1997 John Wiley & Sons, Ltd.     

A center-based modeling approach to solve the districting problem

This article deals with the districting problem arising in applications such as political districting, police patrol area delineation and sales territory design. The aim of districting is to group basic areal units into geographic districts such that some set of criteria are satisfied, with basic criteria being district balance, compactness and contiguity. This article proposes a center-based mixed-integer linear programming model to solve the districting problem. Given the central units of districts, the model optimizes weighted objectives of district balance and compactness while satisfying contiguous constraints on districts. The performance of the model was tested using three study areas with 297, 324 and 1297 areal units, respectively. Experimentation shows that, using the district centers identified by a multistart weighted K-medoids algorithm, the model instances can be solved optimally or near-optimally. Compared with local search-based algorithms, the center-based approach outperforms metaheuristics such as simulated annealing, variable neighborhood descent, iterative local search and old bachelor acceptance search in terms of solution quality.     

Modelling of a wave energy converter array with a nonlinear power take-off system in the frequency domain

This paper presents a nonlinear frequency domain model and uses this to assess the performance of a wave energy converter (WEC) array with a nonlinear power take-off (PTO). In this model, the nonlinear PTO forces are approximated by a truncated Fourier series, while the dynamics of the WEC array are described by a set of linear motion equations in the frequency domain, and the hydrodynamic coefficients are obtained with the boundary element method. A single heave absorber is firstly investigated to establish the accuracy of the new model in capturing the nonlinear behaviour of the pumping system. Subsequently, simulations of a 2D array with 18 WECs and a pillar in the centre (representing the tower of a wind turbine) are carried out to understand wave interference effects. Several optimisation strategies are proposed to improve the overall performance of the WEC array. These results demonstrate a computationally effective method for accounting for nonlinear effects in large WEC arrays. The proposed approach may potentially be applied for developing control algorithms for the adaptability of a 2D array to incoming wave excitation.     

顾及邻近五点的建筑物多边形化简方法

针对传统的建筑物化简算法无法准确保持建筑物局部细节几何特征,容易产生尖锐凸角等问题,提出了一种基于邻近五点的建筑物多边形化简方法。通过将多边形边界上的邻近五点定义为基本处理单元,实现对建筑物边界Z形平行、Z形不平行、U形平行、U形不平行的4类几何模式划分,进行渐进式化简,并针对化简过程中产生的尖角顾及角度约束对其削尖。对某地区部分1∶1万实际建筑物多边形数据进行试验,结果表明,所提算法在保持建筑物基本几何形态特征的基础上,能够尽可能地避免尖角的产生,化简结果更加符合人类的视觉认知。     

双层直立圆弧型防波堤上绕射波浪力的解析计算

基于微幅波绕射理论,应用特征函数展开法,推导了双层直立圆弧型透空防波堤的波浪绕射解析解,从而将已有的比例边界有限元法拓展为解析算法,并据此对外层与内层防波堤所受波浪载荷进行了解析计算。计算结果表明:应用本文方法对直立透空圆环柱的绕射波浪载荷进行验证计算,所得结果与现有的解析解完全吻合,说明方法可靠。双层堤较单层堤能更有效地减弱波浪作用。波浪的入射角度和特征参数、防波堤张角与半径、防波堤透空系数以及水深等因素的相对变化对双层堤的波浪作用均存在一定影响。     

钢筋混凝土结构基于地震损伤性能的设计

本文结合我国地震设防水准,在国内外有关地震损在量研究结果的基础上,提出钢筋混凝土结构地震损伤的“三水准”性能目标;其次,对于剪切型钢筋混凝土结构,提出了结构层间柱－压弯构件三线性恢复力模型参数确定和地震损伤计算方法;第三,提出了地震损伤直接验算和将地震损伤验算归结为变形验算的钢筋混凝土结构地震损伤性能设计方法;最后,通过设计例题说明了本文方法应用的可行性。     

Modern geostatistics: computational BME analysis in the light of uncertain physical knowledge – the Equus Beds study

This paper is concerned with a computational formulation of the Bayesian maximum entropy (BME) mapping method, which can handle rigorously and efficiently spatiotemporal applications of considerable practical importance. BME is a method of modern geostatistics that can integrate and process physical knowledge that belongs to two major bases: general knowledge (i.e., obtained from general principles and laws, summary statistics and background information), and specificatory knowledge (i.e., obtained through experience with the specific situation). BME allows considerable flexibility regarding the choice of an appropriate spatiotemporal map, offers a complete assessment of the mapping uncertainty and contributes to the scientific understanding of the underlying natural phenomenon. Valuable insight is gained by studying a spatiotemporal data set representing water-level elevations at the Equus Beds aquifer (Kansas). Numerical results show that, as was expected in theory, classical geostatistics analysis is obtained as a special case of the considerably more general BME approach. Moreover, modern geostatistical analysis in terms of BME offers more accurate and informative results in practice, by incorporating various sources of physical knowledge that cannot be processed by the classical methods.