基于广义点的相对定向和绝对定向

传统的摄影测量是基于测点的前方交会和后方交会,相对定向和绝对定向则基于同名像点共面的思想,而在工业计量测量和飞机姿态测量等领域,大量存在的是一些直线或者曲线,并不存在明确意义的点。因此,本文提出了基于广义点的相对定向和绝对定向的方法,解决了传统相对定向和绝对定向不能解决的问题,实践证明该方法是可行的。     

Isoparametric Boundary Element Method Applied to the Rectangular and Delta Hydrofoils near the Free Surface

In this paper, the hydrodynamic characteristics and flow field around rectangular and delta hydrofoils, moving with a constant speed beneath the free surface are numerically studied by means of isoparametric boundary element method (IBEM). The quantities (source and dipole strengths) and the geometry of the elements are represented by a linear distribution. Two types of three-dimensional hydrofoils (rectangular and delta) are selected with NACA4412 and symmetric Joukowski sections. Some numerical results of pressure distribution, lift, wave-making drag coefficients and velocity field around the hydrofoils are presented. Also, the wave pattern due to moving hydrofoil is predicted at different operational conditions. Comparisons are made between computational results obtained through this method and those from the experimental measurements and other numerical results which reveal good agreement.     

Hydroelastic Analysis of Very Large Floating Structures Using Plate Green Functions

1 .IntroductionRecentlygreatinteresthasbeenshowninthedevelopmentofverylargefloatingstructuressuchasMegaFloatofJapan (Isobe ,1 999)andMOBofUSA (Remmers ,1 999) .Owingtotheirextremelargesizeandgreatflexibility ,thecouplingbetweenthestructuraldeformationandfluidmotionissignifi cant.Thisisatypicalproblemofhydroelasticity .Efficientandaccurateestimationofthehydroelasticresponseofverylargefloatingstructuresinwavesisveryimportantfordesign .Manymethodshavebeenproposedinliteratureforthepredictiono…     

Two-Dimensional Large Deformation Finite Element Analysis for the Pulling-up of Plate Anchor

Based on mesh regeneration and stress interpolation from an old mesh to a new one, a large deformation finite element model is developed for the study of the behaviour of circular plate anchors subjected to uplift loading. For the deterruination of the distributions of stress components across a clay foundation, the Recovery by Equilibrium in Patches is extended to plastic analyses. ABAQUS, a commercial finite element package, is customized and linked into our program so as to keep automatic and efficient running of large deformation calculation. The quality of stress interpolation is testified by evaluations of Tresca stress and nodal reaction forces. The complete pulling-up processes of plate anchors buried in homogeneous clay arc simulated, and typical pulling force-displacement responses of a deep anchor and a shallow anchor are compared. Different from the results of previous studies, large deformation analysis is of the capability of estimating the breakaway between the anchor bottom and soils. For deep anchors, the variation of mobilized uplift resistance with anchor settlement is composed of three stages, and the initial buried depths of anchors affect the separation embedment slightly. The uplift bearing capacity of deep anchors is usually higher than that of shallow anchors.     

超大型浮体水弹性分析的平板格林函数法

采用Eatock Taylor ＆ Ohkusu提出的一种矩形平板的挠度格林函数进行超大型浮式结构物在波浪中的水弹性响应分析，计算结果与试验结果比较，相当吻合，证实此平板挠度格林函数可以用于超大型浮式结构物的水弹性分析。     

Uplift Pressure of Waves on A Horizontal Plate

1 .IntroductionOwingtotheneedfordevelopingoffshoreresources,moreandmorehollow trussedstructuresareconstructed ,suchasalongshorequays ,islandquays,artificialislands ,bollards ,maritimeplatforms ,etc .Thelargeentitypartofthosemaritimestructuresusuallyconsistsofahorizontalplateabovethestillwaterlevel,anditusuallysuffersfromwaveattacksandthuscaneasilybedestroyed .Toavoidsuchakindofaccidents ,themostimportantistoaccuratelyevaluatetheupliftpressuresofwavesontheplateundervariouswaveconditionsandbound…     

桶形基础平台三维有限元稳定性分析

以我国第一座桶形基础采油平台工程实例为原型，采用三维有限元计算方法对桶形基础稳定性分析。平台在波浪、风等荷载作用下，其稳定性不仅与平台的整体结构有关，而且与桶形基础及其周围土体相互作用相关。在计算中，利用薄层摩擦单元模拟土与结构间的相互作用，取得了很好的效果。分析结果表明桶形基础采油平台在设计条件下运行是较为稳定的。     

Interaction of Oblique Waves and A Rectangular Structure with An Opening Near A Vertical Wall

With the method of separation of variables and the eigenfunction expansion employed, an analytical solution is presented for the radiation and diffraction of a rectangular structure with an opening near a vertical wall in oblique seas, in which the unknown coefficients are determined by the boundary conditions and matching requirement on the interface. The effects of the width of the opening and the angle of incidence on the hydrodynamic characteristics of a rectangular structure with an opening near a vertical wall are mainly studied. The comparisons of the calculation results with wall-present and with wall-absent are also made. The results indicate that the variation trends of the heave added mass and excitation force with wall-present are almost the same as those with wall-absent, and that the peak values in the former case are obviously larger than those in the latter due to the reflection of the vertical wall.     

Numerical Simulation of Bragg Reflection Based on Linear Waves Propagation over A Series of Rectangular Seabed

A numerical model, Evolution Equation of Mild-Slope Equation （EEMSE） developed by Hsu et al. （2003）, was applied to study the Bragg reflection of water waves over a series of rectangular seabed. Three key parameters of the Bragg reflection including the peak coefficient of primary Bragg reflection, its corresponding relative wavelength, and the bandwidth, have shown to be effective in describing the characteristics of the primary Bragg reflection. The characteristics of the Bragg reflection were investigated under the various conditions comprising number, height, and spacing interval of a series of rectangular seabed. The results reveal that the peak of Bragg reflection increases with the increase of rectangular seabed height and number, the bandwidth and the shift value of the Bragg reflection depend on the increase of the rectangular seabed height as well as the decrease of rectangular seabed number, and the relative rectangular seabed spacing in the rang of 3 and 4 could produce higher Bragg reflection. Finally, a correlative and regressive analysis is performed by use of the calculated data. Based on the results of the analysis, empirical equations were established. Our study results can provide an appropriate choice of a series of rectangular seabed field for a practical design.     

一种基于偏度平衡的LiDAR点云滤波方法

在地形起伏区域,针对免阈值的偏度平衡滤波方法存在利用高程难以满足算法假设条件、利用强度信息面临异物同强度等问题,提出基于高差的偏度平衡方法。该方法是在点云与初始地面TIN间高差计算的基础上,采用偏度平衡方法进行LiDAR点云滤波。利用ISPRS提供的测试数据对该方法进行实验,结果表明:在地形起伏区域,点云高差能够满足偏度平衡方法的假设条件,并且基于高差的偏度平衡方法滤波有效。     

精密单点定位的一种低动态解法

采用自适应选权滤波法,对低动态精密单点定位的解算方法进行研究,并编写了精密单点定位程序。通过合理选择自适应因子参数,对船载动态GPS测量数据进行了事后精密单点定位处理。结果表明:相对于经典卡尔曼滤波方法,采用自适应选权滤波法可大大提高低动态精密单点定位解的精度,X、Y、Z三个方向的RMS分别提高了79.9%、69.7%和92.0%。     

临淄地区包气带及地下水中酚、氰化物的污染迁移机理

依据环境水文地质条件、污染源的状况和酚、氰化物对地下水长期污染状况,综合临淄地区现场资料对酚、氰化物的污染特性及迁移机理作初步研究。研究表明,淄河沿岸区和冲沟内砂砾石分布区是酚、氰化物进入地下水的主要通道,大气降水是促进酚、氰化物解吸迁移的主要因素。虽然目前研究区域内已无含酚、氰化物的污水直接排放,但吸附于较厚细颗粒包气带土层中的酚、氰化物还将在较长时间内存在并缓慢进入地下水中,其含量将会随时间的推移而呈减少趋势。     

基于回归方程GPS单频精密单点定位算法

研究了单频GPS精密单点定位的算法,包括单频精密单点定位的回归方程及卡尔曼滤波用于单频精密单点定位,探讨卡尔曼滤波的观测方程和状态方程,给出了状态转移矩阵及系统噪声矩阵.通过算例验证了在1s采样率的情况下,定位达到了分米级的精度.     

Hydroelastic Response of A Circular Plate in Waves on A Two-Layer Fluid of Finite Depth

The hydroelastic response of a circular, very large floating structure (VLFS), idealized as a floating circular elastic thin plate, is investigated for the case of time-harmonic incident waves of the surface and interfacial wave modes, of a given wave frequency, on a two-layer fluid of finite and constant depth. In linear potential-flow theory, with the aid of angular eigenfunction expansions, the diffraction potentials can be expressed by the Bessel functions. A system of simultaneous equations is derived by matching the velocity and the pressure between the open-water and the plate-covered regions, while incorporating the edge conditions of the plate. Then the complex nested series are simplified by utilizing the orthogonality of the vertical eigenfunctions in the open-water region. Numerical computations are presented to investigate the effects of different physical quantities, such as the thickness of the plate, Young’s modulus, the ratios of the densities and of the layer depths, on the dispersion relations of the flexural-gravity waves for the two-layer fluid. Rapid convergence of the method is observed, but is slower at higher wave frequency. At high frequency, it is found that there is some energy transferred from the interfacial mode to the surface mode.     

A Finite Element Method for Cracked Components of Structures

1 .IntroductionOffshoreplatformsarelargescalesteelorconcretestructures.Theyexperiencevariouskindsofdamagessuchasdents ,corrosionpits ,cracks ,deformation ,etc .,afteryearsofenvironmentalimpactofwinds ,waves ,currents ,soilreactions ,earthquakesandice (DuanandLiu ,1 995) .Thesafetyofthestructureshasalwaysbeenthemostimportantissueconcerned ,anditdependsontheassessmentoftheintegrityofthestructures,orspecificallyontheassessmentofthedamagesinthestructures .Riclesetal.( 1 994)experimentallyinvestig…     

同伦内点方法求解无界域上的非线性规划问题

冯果忱等人提出了同伦内点方法,在可行域有界的条件下求解一类非线性规划问题,并且还猜想此结果能够推广到无界可行域上。本文提出1个无界性条件,在此基础上,部分解决了该猜想。最后给出2个数值例子来进一步验证结果的有效性。     

三维点云数据拼接中ICP及其改进算法综述

ICP算法是三维点云数据精确拼接过程中的主流算法.文章对目前国内外ICP及其各种改进算法的发展现状进行了系统地分析与研究.将ICP算法分为4个主要阶段:(1) 对原始点云数据进行采样;(2) 确定初始对应点集;(3) 去除错误对应点对;(4) 坐标变换的求解.分别对各个阶段中典型方法的基本思想和关键技术进行了分类与分析,并在精度与效率等方面对这些算法进行了比较.最后对目前算法研究中的难点问题及未来的研究重点进行了展望.     

A Finite Element Solution of Wave Forces on Submerged Horizontal Circular Cylinders

In this paper, a numerical model is established for estimating the wave forces on a submerged horizontal circular cylinder. For predicting the wave motion, a set of two-dimensional Navier-Stokes equations is solved numerically with a finite element method. In order to track the moving non-linear wave surface boundary, the Navier-Stokes equations are discretized in a moving mesh system. After each computational time step, the mesh is modified according to the changed wave surface boundary. In order to stabilize the numerical procedure, a three-step finite element method is applied in the time integration. The water sloshing in a tank and wave propagation over a submerged bar are simulated for the first time to validate the present model. The computational results agree well with the analytical solution and the experimental data.Finally, the model is applied to the simulation of interaction between waves and a submerged horizontal circular cylinder.The effects of the KC number and the cylinder depth on the wave forces are studied.     

Computation of Viscous Uniform and Shear Flow over A Circular Cylinder by A Finite Element Method

The incompressible viscous uniform and shear flow past a circular cylinder is studied. The two-dimensional Navier-Stokes equations are solved by a finite element method. The governing equations are discretized by a weighted residual method in space. The stable three-step scheme is applied to the momentum equations in the time integration. The numerical model is firstly applied to the computation of the lid-driven cavity flow for its validation. The computed results agree well with the measured data and other numerical results. Then, it is used to simulate the viscous uniform and shear flow over a circular cylinder for Reynolds numbers from lO0 to lO00. The transient time interval before the vortex shedding occurs is shortened considerably by introduction of artificial perturbation. The computed Strouhal number, drag and lift coefficients agree well with the experimental data. The computation shows that the finite element model can be successfully applied to the viscous flow problem.     

渤、黄、东海M2和K1分潮潮流场的有限元模拟

使用有限元模式(QUODDY)数值模拟了渤、黄、东海浅水区的M2和K1分潮潮流场。对于M2分潮潮流场,东分量和北分量的潮流调和常数与16个测站观测资料的平均绝对误差分别为8.23 cm/s,23.74°();7.36 cm/s,27.78(°)。对于K1分潮潮流场,则分别为8.39 cm/s,36.48(°);9.40 cm/s,38.04(°)。文中得到的M2分潮流在模拟海区共有9个圆流点(秦皇岛附近1个,莱州湾口1个,山东半岛北部海域2个,黄海北部2个,苏北辐射沙洲的外侧1个,舟山群岛东南海域2个)。K1分潮流在模拟海域也存在9个圆流点(秦皇岛附近1个,莱州湾口1个,北黄海2个,南黄海1个,苏北辐射沙洲的外侧1个,济州岛东南海域3个),其中黄海北部偏北的圆流点(39°25′N,123°05′E)和济州岛东南海域最东南的圆流点(32°50′N,127°50′E)以前未见过报道。