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Ye Y.-L.,China Ship Scientific Research Center | Wu Y.-S.,China Ship Scientific Research Center | Tian C.,China Classification Society | You G.-H.,China Ship Scientific Research Center | Zou M.-S.,China Ship Scientific Research Center
Chuan Bo Li Xue/Journal of Ship Mechanics

The 3D hydroelastic analysis method is used for obtaining the vibration response characteristics of 1500t SWATH ship hull. The hull vibration response of navigating ship produced by generators is predicted, and the predicted design loads are compared with the ship test results. The comparisons illustrate the feasibility of the hydroelastic analysis method in hull vibration assessment of SWATH ships. Source

Li H.,Ocean University of China | Li P.,China Classification Society | Hu S.L.J.,University of Rhode Island
Applied Ocean Research

Accurate estimate of the modal parameters of an offshore structure is crucial to many practical engineering issues, such as finite element (FE) model updating/validation, damage detection, etc. Using noisy acceleration signals collected from a step-relaxation test of a jacket-type offshore platform, we estimate its modal frequencies and damping ratios by an extended Prony's method, which includes a noise removal procedure to yield filtered signals before implementing the classical Prony's method on the filtered signals. To validate the applicability of the proposed approach, numerical simulations were firstly performed. Investigating corrupted relaxation response signals simulated from a FE model of the test platform, we conclude that the proposed approach is very accurate on estimating the modal parameters. A significant improvement can be achieved when the filtered, rather than the originally measured, signals are used. Using sea test data measured from accelerometers mounted at three different locations of the test platform, we find that the modal parameters estimated from the filtered signals of the three locations separately are in excellent agreement. © 2012 Elsevier Ltd. Source

Zhu J.,Dalian Maritime University | Sun L.,China Classification Society | Yin J.,Dalian Maritime University | Li T.,Dalian Maritime University
Yingyong Jichu yu Gongcheng Kexue Xuebao/Journal of Basic Science and Engineering

An intelligent identification model for ship lights was established on the basis of back propagation (BP) neutral network. Parameters of visibility, average luminance of ship lights, average background luminance and glare were selected among various influence parameters, and were set as inputs of the ship lights identification model. The BP neural network model were established by means of Levenberg-Marquart (L-M) algorithm, momentum gradient descent algorithm, adaptive learning rate momentum gradient descent algorithm, and elastic back propagation algorithm respectively, and the L-M algorithm was selected as the optimal method and utilized for establishing the identification model. Results of ship lights identification simulation showed that the simulated results of the identification model were in accordance with the assessment results of experts in navigational field. The model realizes the prediction and the influence analysis of the identifiability of ship lights under complicated navigational luminous environments, and is of great importance for navigation safety at night. Source

Wu T.,Dalian Maritime University | Zhu J.,Dalian Maritime University | Sun L.,China Classification Society | He Q.,Dalian Maritime University
Journal of Applied Optics

In order to improve the recognizability of ship lights in the complex light environment to better protect the navigation safety of the ship at night, a new type of ship lights was designed according to the colorimetry and the emitting principle of semiconductor laser. Starboard light and masthead light of power-driven vessel with the length of no less than 50 m were selected as experimental objects. Starboard light and masthead light solid models were established in the three-dimensional solid modeling software (Lighttools) environment. Both of the lights'semiconductor laser spectral region, spectral weight, power, rays to trace, relative ray power threshold and other parameters were set to simulate the color properties at different reception distances. The simulation results show that: the color stimuli purity value of semiconductor laser starboard light is 1; the chromaticity coordinates of the semiconductor laser masthead light are close to the reference white (the chromaticity coordinates is (1/3, 1/3)); both of them meet the requirements of the International Regulations f or Preventing Collisions at Sea f or lights color properties. ©, 2015, Editorial Board, Journal of Applied Optics. All right reserved. Source

Wang X.L.,China Ship Scientific Research Center | Liu R.M.,China Classification Society | Hu J.J.,China Ship Scientific Research Center
Analysis and Design of Marine Structures - Proceedings of the 5th International Conference on Marine Structures, MARSTRUCT 2015

A bulk carrier is introduced in this paper to study its low- and high-frequency responses both in heading and following seas. Effects of four loading conditions on wave-induced responses are investigated by a 3-D hydroelasticity method. Moreover, experimental results of two loading conditions are also presented to test and verify the theoretical results of the 3-D method. It is shown that loading conditions have great influences on the wave-induced responses. Springing and whipping behaviors will be influenced obviously by high forward speeds. Small draft in ballast condition will cause high peak in 2-node vertical vibrations. 3-D hydroelasticity theory can make up the limitations in experiments because of the high cost and the capacity of facility. Results of this paper show the necessity of taking into adequate consideration of high-frequency vibrations on strength and fatigue damage of ship structure in the bulk carrier’s design stage. © 2015 Taylor & Francis Group, London. Source

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