Hill Instability Analysis Of Tlp Tether Subjected To Combined Platform Surge And Heave Motions

This paper presents the Hill instability analysis of Tension Leg Platform (TLP) tether it, deep sea. The 2-D nonlinear beam model which is Undergoing Coupled axial and transverse vibrations, is applied. The governing equations are reduced to nonlinear Hill equation by use of the Galerkin's method and the modes superposition principle. The Hill instability charted Lip to large parameters is obtained. An important parameter M is defined and can he expressed as the functions of tether length, the platform surge and heave motion amplitudes. Some example studies are performed for various environmental conditions. The results demonstrate that the nonlinear coupling between the axial and transverse vibrations has a significant effect on the response of structure.. It needs to be considered for the accurate dynamic analysis of long TLP tether subjected to the combined platform surge and heave motions.

Simulating a typhoon storm surge in the East Sea of China using a coupled model

A coupled numerical model with a 2' x 2' resolution grid has been developed and used to simulate five typical typhoon storm surges (5612, 7413, 7910, 8114, and 9711) in the East Sea of China. Three main driving forces have been considered in this coupled model: wave radiation stress, combined wave-current bottom shear stress and wave-state-dependent surface wind stress. This model has then been compared with in situ measurements of the storm set-up. The effect of different driving force components on the total storm surge has also been investigated. This study has found that the coupled model with high resolution is capable of simulating the five typical typhoons better than the uncoupled models, and that the wave-dependent surface wind stress plays an important role in typhoon storm surge-wave coupling in this area and can increase the storm set-up by 1 m. The study of the five typhoon cases has shown that the general coupling effects could increase storm set-up by 20-32%. Thus, it is suggested that to predict typhoon storm surges in the East Sea of China, a storm surge-wave coupled model be adopted. (C) 2008 National Natural Science Foundation of China and Chinese Academy of Sciences. Published by Elsevier Limited and Science in China Press. All rights reserved.

An analysis of the recent severe storm surge disaster events in China

The economic loss caused by the storm surge disasters is much higher than that caused by any other marine disaster in China, the loss from the severe storm surge disaster being the highest. Statistics show that there were 62 typhoon landings over the east-southeast coast of China since 1990, three of which, occurring in 1992, 1994 and 1997, respectively, caused the most severe damage. The direct economic losses due to these events are 9.3, 17.0 and 30 billion yuan (RMB, or about 1.7, 2.6 and 3.8 billion USD, respectively), which is much greater than the loss of 5.5 billion yuan (RMB) on an average every year during the 1989-1991 period. This paper makes a comparative analysis of the damage caused by the three events and presents an overview of progress of precautions against storm surge disaster in China. The suggested counter measures to mitigate the loss from the severe storm surge disasters in China is as follows: (1) Raise the whole society awareness of precaution against severe storm surge disaster; (2) Work out a new plan for building sea walls; (3) Improve and perfect the available warning and disaster relief command system; (4) Develop the insurance service in order to promptly mitigate the loss caused by severe storm surge disaster event.

Numerical Analysis on Intermittent Flow in a Longitudinal Section of Bingham Fluid along a Slope

The transition process of intermittent flow in a longitudinal section of Bingham fluid from initial distribution to fully developed state was numerically investigated in this paper. The influences of slope dimensionless runoff Q* and viscosity μ0* on the dimensionless surge speed U* were also presented in a wide range of parameters. By one typical example, the intermittent flow possessed wave characteristics and showed a supercritical flow conformation for a fully developed flow. The distributions of gravity and bed drag along the flow path and the velocity distribution of flow field were also analyzed.

Nonlinear Dynamic Responses of the Tensioned Tether under Parametric Excitations

The nonlinear dynamic responses of the tensioned tether subjected to combined surge and heave motions of floating platform are investigated using 2-D nonlinear beam model. It is shown that if the transverse-axial coupling of nonlinear beam model and the combined surge-heave motions of platform are considered, the governing equation is not Mathieu equation any more, it becomes nonlinear Hill equation. The Hill stability chart is obtained by using the Hill's infinite determinant and harmonic balance method. A parameter M, which is the function of tether length, the surge and heave amplitude of platform, is defined. The Hill stability chart is obviously different from Mathieu stability chart which is the specific case as M=0. Some case studies are performed by employing linear and nonlinear beam model respectively. It can be found that the results differences between nonlinear and linear model are apparent.

Observational evidence of the Yellow Sea warm current

The Yellow Sea Warm Current (YSWC) is one of the principal currents in the Yellow Sea in winter. Former examinations on current activity in the Yellow Sea have not observed a stable YSWC because of the positioning of current meters. To further understand the YSWC, a research cruise in the southern Yellow Sea was carried out in the winter of 2006/2007. Five moorings with bottom-mounted acoustic Doppler current profilers (ADCP) were deployed on the western side of the central trough of the Yellow Sea. The existence and distributional features of the YSWC were studied by analyzing three ADCP moorings in the path of the YSWC in conjunction with conductivity-temperature-depth (CTD) data over the observed area in the southern Yellow Sea. The results show the following. (1) The upper layer of the YSWC is strongly influenced by winter cold surge; its direction and speed often vary along a south-north axis when strong cold surges arrive from the north. (2) The YSWC near the bottom layer is a stable northwest flowing current with a speed of 4 to 10 cm/s. By combining the analyses of the CTD data, we speculate that the core of the YSWC may lie near the bottom. (3) On a monthly average timescale, the YSWC is stably oriented with northward flow from the sea surface to the sea floor.

一种水面救助机器人

本文介绍一种能在恶劣海况下 ,向遇险船舶送递导引缆绳和向落水人员快速送递救生圈的水面救助机器人 .该机器人具有抗涌浪能力强、体积小、重量轻、速度快以及机动灵活的特点 ,还可广泛应用于其他领域

8～12岁男孩的性激素与智力、人格的关系

Recently there emerged more and more researhes concerning about sex hormone-related cognitive ability and behaviours. Few were carried out in pre- to early adolescent children., and the objective of the current study is to investigate whether there are covariance between sex hormones, intelligence and personality in 232 pre- to early adolescent boys, including 62 gifted boys. Indexes of sex hormone levels were salivary testosterone and estradiol concentrations, the 2D:4D digit ratio ( a reliable pointer of prenatal sex hormone concentraions). The Cattell Culture Fair Intelligence Test and a Chinese version of Children’s Personality Questionaire was applied in the current study. The main findings are: 1) salivary sex hormone concentrations significantly positively correlated with intelligence performance in 10-year-old boys; 2) salivary testosterone negatively related to intelligence performance in 12-year-old boys; 3) gifted boys bears lower testosterone concentrations in both prenatal period and pre- to early adolescence; 4) for personality, higher salivary estradiol was related to extraversion and digit ratios correlated with several personality factors in 8-year-old boys. In conclusion, results in the current study suggested that for male early maturers, intelligence may be negatively influenced by early coming androgen surge. In contrast, male late matures may benefit from their lately and moderately increasing hormone. Besides, the results suggested that the relationship between 2D:4D digit ratio and personality may also be paid attention to.