基于 K-Medoid 聚类算法的 GPS 坐标转换研究

对GPS网约束平差时,GPS控制网的精度与坐标系统转换控制点的位置选择有关。通过实验分析得出,整个网的检核点与相应的转换控制点总距离越远,坐标转换后网的精度越低。在此基础上,提出使用K-Medoid聚类算法,通过计算机程序自动寻找用于计算坐标系统转换参数的最佳控制点,并将文中方法运用于某大桥GPS控制网的控制点选取,通过工程实例验证了基于K-Medoid聚类方法的GPS坐标系统转换的可行性。     

三维物体上二阶波浪绕射的实时模拟

采用二阶时域理论对非线性波浪在任意三维物体周围的绕射问题进行了研究，对自由表面边界条件进行Taylor级数展开，应用摄动展开可以建立相应的边值问题，而且此边值问题的计算域不随时间变化，运用基于B－样条的边界元方法求解每一时刻的波浪场，二阶自由表面边界条件在时间上进行数值积分，在自由表面加了一个人工阻尼层以避免波浪的反射，速度势分解为已知的入射势和未知的散射势，初始条件采用二阶Stokes波浪场，通过加入物体表面边界条件，得到散射势在时间和空间上的发展，本文对圆柱所受规则波的二阶波浪力和波浪爬高进行了计算，数值结果表明此理论计算准确，效率高，数值稳定。     

EFFECTS OF PHOTOPERIOD AND SALINITY ON GROWTH AND UPTAKE OF 60Co AND 137Cs FOR CHLORELLA SP.

The effects of three photoperiods (24 hr illumination, 12 hr illumination + 12 hr darkness and 24 hr darkness) and three salinities (20‰, 30‰ and 35‰) on the uptake of 60Co and 137Cs for Chlorella sp. and on the growth of its algae are studied. The uptake of 60Co for the algae is two orders of magnitude higher than that of 137Cs. Of factorial effects, the effect of photoperiod is most significant either on the uptake of the radionuclides or on the growth of the algae; the effect of salinity comes next in order and that of their interaction remains with the last. The uptake of the two radionuclides increases with extended photoperiod while the uptake of 137Cs declines with increasing of salinity. The growth of the algae appears to be the best under the conditions of 24 hr illumination and 30‰ salinity.     

一个新的非恒定型不规则波缓坡方程

缓坡方程由Ｂｅｒｋｈｏｆ所推导并在规则波折射绕射问题的研究上有着广泛的应用。然而对于不规则波折射绕射问题研究，缓坡方程还处于发展研究阶段，本文采用Ｐａｄｅ近似并仿Ｋｕｂｏ方法对缓坡波动方程进行了推导，得到了一个含有时间高阶导数项的不规则波缓坡方程，随即采用ＷＫＢ方法对这个不规则波的缓坡方程进行了简化，推导出一个较为实用的含有一阶时间导数的不规则波缓坡的波动方程。通过数值手段对所推导的不规则波缓坡方程进行了数值模拟，其结果与物模实验较为一致     

考虑桩土作用独桩海洋平台横向振动特性研究

采用动Winkler弹性地基梁模型模拟桩土问动力相互作用，并考虑了流体与桩问相互作用，通过组合成层土中、水中桩单元的刚度阵，推得了独桩海洋平台连续系统横向振动的动刚度阵及在波浪力作用下平台甲板处的频率响应函数，进而求得了在确定性波浪力及随机波浪力作用下桩身任意点的位移响应。最后，通过算例研究和分析了在随机波浪力作用下成层土参数、甲板上重量及冲刷淘深等因素对平台振动响应的影响。     

Experimental and Theoretical Investigation of Wave Forces on A Partially-Perforated Caisson Breakwater with A Rock-Filled Core

1.IntroductionVertical breakwaters are widely used for harbor and coastline protection in coastal engineering.Recently,perforated breakwaters have been often used in practice as they can effectively reduce thewaveforces actingon,the wave reflectionfromand…     

Simulation of T-bar penetration in soft clay with adhesive contact

Abstract

To model the deep penetration process of T-bar in soft clay, an adhesive contact algorithm was developed in conjunction with the Coupled Eulerian–Lagrangian approach with consideration of the effect of strain softening. Numerical results show the simulated penetration resistance agrees well with the previous centrifuge experimental data. The failure mechanisms of the clay around the T-bar can be divided into three stages, including shallow penetration stage with global failure mechanism, partially and fully back-flow stages with local failure mechanism. Fluctuations of the penetration resistance can be explained by the formation and evolution of shear bands around the T-bar. Newly formed shear bands would intersect the previously formed shear bands in the partially back-flow stage, which results in the formation of “ear-shaped” areas rotating anticlockwise around the T-bar. The evolution of shear bands would form a similar fabric structure in the fully back-flow stage.     

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.     

The New Form of Time-Dependent Mild Slope Equation for Random Waves

The mild-slope equation derived by Berkhoff (1972), has widely been used in the numerical calculation of refraction and diffraction of regular waves. However, it is well known that the random sea waves has a significant effect in the refraction and diffraction problems. In this paper, a new form of time-dependent mild slope equation for irregular waves was derived with Fade approximation and Kubo's time series concept. The equation was simplified using WKB method, and simple and practical irregular mild slope equation was obtained. Results of numerical calculations are compared with those of laboratory experiments.     

Wave Action on Structures of Combined Cylinders

1.Introduction Owingtoitssignificanteffectofreductionofwaveloadsandwaverun up,theperforatedwallon anarrayofcylindricalstructureshasreceivedconsiderableattentioninrecentyears.Manyresearches havebeencarriedoutinthisfield.Anexactsolutionforthediffractionoflinearwaterwaveswithan arrayofimpermeablecylinderswasfirstgivenbySpringandMonkmeyer(1974)usinganeigenfunction expansionapproach.Subsequently,LintonandEvans(1990)madeamajorsimplificationtothetheo ry,whichallowedthenear fieldquantitiessuchasload…