European policies on ship recycling: A stakeholder survey     

《Marine Policy》2017

After almost a decade of intensive regulatory activities focused on ship-recycling around the world, special reference is made to combating the problems of ship dismantling practices on the shores of Southern Asian countries. “The Hong Kong International Convention” was adopted in 2009, to provide a uniform shipbreaking management approach. However, in globalised maritime transport, with the majority of shipowners using Open Registries, the European Union has prepared a common approach considering the implementation of a new legal framework. Regulation 1257/2013 implemented by the EU on ship-recycling should be more rigorous than those in the rest of the world. In this article, stakeholder perceptions of this Regulation are presented, based on an online survey. The results show significantly different perceptions in the ship-recycling industry regarding the developing ship-recycling measures within the EU.  相似文献   

State estimation of tidal hydrodynamics using ensemble Kalman filter     

《Advances in water resources》2014

This paper presents a coupling of an ensemble Kalman filter (EnKF) with a discontinuous Galerkin-based, two-dimensional circulation model (DG ADCIRC-2DDI) to improve the state estimation of tidal hydrodynamics including water surface elevations and depth-integrated velocities. The methodology in this paper using EnKF perturbs the modeled hydrodynamics and bottom friction parameterization in the model while assimilating data with inherent error, and demonstrates a capability to apply EnKF within DG ADCIRC-2DDI for data assimilation. Parallel code development presents a unique aspect of the approach taken and is briefly described in the paper, followed by an application to a real estuarine system, the lower St. Johns River in north Florida, for the state estimation of tidal hydrodynamics. To test the value of gauge observations for improving state estimation, a tide modeling case study is performed for the lower St. Johns River successively using one of the four available tide gauging stations in model-data comparison. The results are improved simulations of water surface elevations and depth-integrated velocities using DG ADCIRC-2DDI with EnKF, both locally where data are available and non-locally where data are not available. The methodology, in general, is extensible to other modeling and data applications, for example, the use of remote sensing data, and specifically, can be readily applied as is to study other tidal systems.  相似文献   

Meridional circulation from differential rotation in an adiabatically stratified solar/stellar convection zone     

M. Dikpati 《地球物理与天体物理流体动力学》2014,108(2):222-235

Meridional circulation in stellar convection zones is not generally well observed, but may be critical for the workings of MHD dynamos operating in these domains. Coriolis forces from differential rotation play a large role in determining what the meridional circulation is. Here, we consider the question of whether a stellar differential rotation that is constant on cylinders concentric with the rotation axis can drive a meridional circulation. Conventional wisdom says that it can not. Using two related forms of the governing equations that respectively estimate the longitudinal components of the curl of the meridional mass flux and the vorticity, we show that such differential rotation will drive a meridional flow. This is because to satisfy anelastic mass conservation, non-spherically symmetric pressure contours must be present for all differential rotations, not just ones that depart from constancy on cylinders concentric with the rotation axis. Therefore, the fluid is always baroclinic if differential rotation is present. This is because, in anelastic systems, the perturbation pressure must satisfy a Poisson type equation, as well as an equation of state and a thermodynamic equation. We support our qualitative reasoning with numerical examples, and show that meridional circulation is sensitive to the magnitude and form of departures from rotation constant on cylinders. The effect should be present in 3D global anelastic convection simulations, particularly those for which the differential rotation driven by global convection is nearly cylindrical in profile. For solar-like differential rotation, Coriolis forces generally drive a two-celled circulation in each hemisphere, with a second, reversed flow at high latitudes. For solar like turbulent viscosities, the meridional circulation produced by Coriolis forces is much larger than observed on the Sun. Therefore, there must be at least one additional force, probably a buoyancy force, which opposes the meridional flow to bring its amplitude down to observed values.  相似文献   

3D Modeling of sediment movement by ships-generated wakes in confined shipping channel     

Shengcheng JI  Abdellatif OUAHSINE  Hassan SMAOUI 《国际泥沙研究》2014,29(1):49-58

Ship-generated waves and return currents are capable of re-suspending significant quantities of bottom and bank sediments.However,most of the previous studies done on the subject do not show how and where sediment is re-suspended by the wakes and the directions of net transport.In this paper,a 3D numerical model based on hydro-sedimentary coupling is presented to search the relationship between the sediment movement,and the pattern of ship-generated waves around and far away from the vessel and the return currents around the ships.The hydrodynamic model is based on 3D Navier-Stokes equations including the standard k-ε model for turbulence processes,and the sediment transport model is based on a 3D equation for the re-suspended sediment transport.The computation results show that the areas of sediment concentration and transport(whether by resuspension or by the bedload) depend mainly on the position,the speed of the ship in the waterways,the kinematics of ship-generated waves and on the return flows.Thus,a map of sediment distribution and the modes of sediment transport generated by the passage of the ship are presented.  相似文献   

The role of the International Maritime Organization in reducing vessel threat to whales: Process,options, action and effectiveness     

Gregory K. Silber  Angelia S.M. Vanderlaan  Ana Tejedor Arceredillo  Lindy Johnson  Christopher T. Taggart  Moira W. Brown  Shannon Bettridge  Ricardo Sagarminaga 《Marine Policy》2012

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日本记纪“船”神话的原始宗教信仰探源     

司志武 《广东海洋大学学报》2012,(2):9-13

日本古代民族来源复杂,但是中国大陆擅长舟楫的各个民族漂洋渡海到达日本列岛的事实早为人共识.作为东亚海洋文化的一个重要内容,中日舟船文化、民俗的交流的历史点滴被《古事记》《日本书纪》记录下来.日本记纪神话所涉及到的对芦苇、楠木、竹等植物的崇拜与中国原始宗教信仰密不可分.通过对上述日本“船”神话的研究,探讨了中日古代人民在涉及江河海洋以及船的信仰上的渊源与异同  相似文献   

A comprehensive study on the parameters setting in smoothed particle hydrodynamics (SPH) method applied to hydrodynamics problems     

《Computers and Geotechnics》2017

Smoothed particle hydrodynamics (SPH) is a meshfree, Lagrangian particle method which has advantages in handling solids with extremely large deformation. Like any other numerical methods, cares must be taken to ensure its desirable accuracy and stability through considering several correction techniques in calculation. The selection of values for parameters in those correction approaches is a key step in SPH simulation, which is always difficult for new beginners to deal well with effectively. This paper examines the common inconsistency and instability problems in SPH method and studies its computational efficiency when applied to hydrodynamics problems with material strength like soil column collapse. We analyzed in detail how the correction techniques mitigate these inconsistency and instability problems. Also, the numerical testing results associate with different values for the parameters used in the correction techniques are provided for better understanding the influence of these parameters and for finding out the desirable values. It is found that (1) the SPH method is easily subjected to an inconsistency problem in the boundary area due to the boundary deficiency, and it can be treated well by adopting “virtual particles” contributing to the particle summations. (2) The numerical oscillation in SPH simulation can be mitigated effectively by artificial viscosity with the suggested parameter values. (3) The tension cracking treatment, artificial viscosity and artificial stress work well in removing the tensile instability problem in SPH method. In addition, the nearest neighboring particle searching (NNPS) algorithm, spacing ratio, smoothing length and time step influence the efficiency and accuracy of SPH method significantly. It is shown that SPH method with suggested parameters values can produce a very good result compared with the experimental result.  相似文献   

Dispersion in the Yucatan coastal zone: Implications for red tide events     

Cecilia Enriquez  Ismael J Mariño-TapiaJorge A Herrera-Silveira 《Continental Shelf Research》2010

The mechanisms governing dispersion processes in the northern Yucatan coast are investigated using a barotropic numerical model of coastal circulation, which includes wind-generated and large scale currents (i.e. Yucatan Current). This work provides the foundations for studying the dispersion of harmful algal blooms (HABs) in the area. Modelling experiments include effects of climatic wind (from long term monthly mean NCEP reanalysis), short term wind events (from in situ point measurements), and Yucatan Current (YC) characteristics. Its magnitude was approximated from published reports, and its trajectory from geostrophic current fields derived from altimeter data. These provided a range of real and climatic conditions to study the routes in which phytoplankton blooms may travel. The 2-D model results show that a synthetic and conservative bloom seeded in the Cabo Catoche (CC) region (where it usually grows), moves along the coast to the west up to San Felipe (SF), where it can either move offshore, or carry on travelling westwards. The transport to the west up to SF is greatly influenced by the trajectory, intensity and proximity of the YC jet to the peninsula, which enhances the westward circulation in the Yucatan Shelf. Numerical experiments show that patch dispersion is consistently to the west even under the influence of northerly winds. When the YC flows westward towards the Campeche Bank, momentum transfer caused by the YC jet dominates the dispersion processes over wind stress. On the other hand, when it flows closer to Cuba, the local processes (i.e. wind and bathymetry) become dominant. Coastal orientation and the Coriolis force may be responsible for driving the patch offshore at SF if external forcing decreases.  相似文献   

Mode coupling analysis and differential rotation in a flow driven by a precessing cylindrical container     

Thierry Lehner  Waleed Mouhali  Jacques Leorat  Alex Mahalov 《地球物理与天体物理流体动力学》2013,107(4):369-401

We present a theoretical weakly nonlinear analysis of the dynamics of an inviscid flow submitted to both rotation and precession of an unbounded cylindrical container, by considering the coupling of two Kelvin (inertial) waves. The parametric centrifugal instability known for this system is shown to saturate when one expands the Navier–Stokes equation to higher order in the assumed small precession parameter (ratio of precession to rotation frequencies) with the derivation of two coupled Landau equations suitable to describe the dynamics of the modes. It is shown that an azimuthal mean flow with differential rotation is generated by this modes coupling. The time evolution of the associated dynamical system is studied. These theoretical results can be compared with water experiments and also to some numerical simulations where viscosity and finite length effects cannot be neglected.  相似文献   

Hydrodynamics and Thermodynamics of Newtonian Stars     

Ho-Young Kwak  Jung-Hwan Jun 《地球物理与天体物理流体动力学》2013,107(1):45-58

We investigated spherically symmetric solution for nonrelativistic cosmological fluid equations and thermodynamic equation of state for Newtonian stars. It was shown that the assumption of a polytropic equation, , at the center of the star only suffices to integrate the equations explicitly. Our exact solution yields many fruitful results such as stellar stability, spherical oscillation and collapses of stars. Pressure, temperature, and density profiles inside stars were obtained. Central densities, pressures and temperatures of the Newtonian stars such as Sun, Jupiter and Saturn were also calculated. Collapse and expansion mechanism was explained by the heat transfer mechanism inside star. The upper bound value of white dwarf mass obtained by the Newtonian cosmological fluid equations turns out to be comparable to the static limit of Chandrasekhar one. Motion of the Universe was also discussed within the framework of Newtonian mechanics. Our calculation results without considering nuclear reactions inside stars may be applicable to the formation of protostars.  相似文献