AIS航标标识符探讨

AIS航标在纸质海图、ECDIS等媒介上显示符号各不相同,严重影响其使用。本世纪初,IMO决定将制定AIS航标新符号提上议事日程,责成MSC下辖的NAV分委会负责,制定一套简单直观的AIS航标标识符。文中通过对AIS航标标识符的应用现状以及相关国际组织和国家的提案进行总结分析,提出相关设计原则和一套适用于纸质海图和电子海图的AIS航标标识符,并分析其对我国航运业的影响。     

A study on dynamic response of cable-seabed interaction

A numerical method is developed to investigate the dynamic response of cable-seabed interaction in this paper. The motion of cable is described by the Lumped Parameter Method, while the seabed, unlike the prevailing simplified model of elastic foundation, is modeled as an irregular continuous rigid surface with rebound and friction existing, and the forces exerted by the seabed consist of normal counterforce and isotropic tangential Coulomb friction resistance. To describe the detailed dynamic response, two coefficients are introduced by analogy with the theory of rigid body collision with friction. The cable-seabed kinematic and dynamic contact conditions are formulated subsequently, and are used to incorporate the seabed effect into the cable dynamics to produce a set of ordinary differential governing equations. In this paper, we employ 4th order Runge-Kutta method to solve these equations. Several simulation cases are presented to illustrate the seabed effect. The results show that friction and impact have a prominent influence on the statics and dynamics of the cable.