舰船目标一维距离像多姿态角相关匹配识别

为提高高分辨雷达目标识别率,对多姿态角舰船目标一维距离像的相关匹配识别方法进行了研究。提出了一种以相关匹配法为基础,求取目标各姿态角一维距离像与模板之间的最大滑动相关系数,并与识别率建立对应联系,通过引入联合概率计算提高目标识别率的方法。这种方法较为贴近实际应用,在一定程度上提高了识别率,为目标识别提供了一条较为有效地途径。     

超宽“海上渔场”海运砰击数值模拟与分析

考虑到半潜船海上运输超宽悬垂货物过程中可能发生波浪砰击,提出利用波浪势流理论及超宽悬垂货物海运过程中砰击控制条件的数值模拟方法,以半潜式“海上渔场”载运为例,利用OCTOPUS软件建立计算模型,模拟海运过程中不同海况、航行吃水及航速情况下,船舶横摇、纵摇、垂荡、“海上渔场”砰击发生概率及砰击载荷的变化情况,“海上渔场”海运过程砰击数值模拟结果与工程实际数据十分吻合,验证了数值模拟方法的合理、可行。     

Prediction of capsizing probability for a ship with trapped water on deck

The authors have already examined a method for evaluating the capsizing probability of a ship in the dead ship condition based on a piecewise linear approximation of the restoring arm. Here, this method is extended to ships with trapped water on deck. This is because the stability of ships having a relatively high bulwark, such as fishing vessels, could substantially deteriorate due to trapped water on deck. First, the mean amount of water trapped on deck was estimated as a function of the significant wave height and the mean wave period using a model experiment in irregular beam seas. Second, the restoring arm curve with trapped water on deck was calculated hydrostatically and then approximated with a piecewise linear curve. Third, the roll angle was estimated using a nonlinear and uncoupled equation of absolute roll angle under stochastic wave and wind exciting moments. The short-term and long-term capsizing probabilities were calculated for a fishing vessel operating off Kyushu. Numerical results quantitatively demonstrated that the effect on capsizing probability of trapped water on deck cannot be ignored when accurately evaluating the stability of fishing vessels.     

Methods for probabilistic safety assessments of ships

 At the 62nd MSC conference (MSC62) in 1993, the UK proposed a new methodology for the consideration of safety regulations. This method is called formal safety assessment (FSA). FSA is an application of probabilistic safety assessment (PSA). Risk is used as an index of safety. One of the most important parts of FSA is to evaluate the risk to a ship when it is equipped with the safety measures recommended by the proposed safety regulations. The National Maritime Research Institute (NMRI, formerly the Ship Research Institute) has been developing a method which allows the risk to be obtained holistically by utilizing a scientific method. To obtain the risk, the probability and consequences of every accident must be evaluated. This paper examines the following points: (a) a holistic methodology for risk evaluation; (b) a method used in the process of estimating the probability of collision; (c) a method to reduce the numbers of fire escalation scenarios; (d) a trial risk evaluation of cabin fire. Received: January 10, 2002 / Accepted: April 18, 2002     

流动式起重机抗倾覆稳定性的可靠性验算

在研究流动式起重机倾覆力矩及复原力矩的概率分布特性和干涉模型的基础上,导出不倾覆事件概率的解析解,提出流动式起重机稳定性的可靠性验算方法和验算准则.采用该验算方法和验算准则,可有效地判断流动式起重机的抗倾覆稳定性是否符合实际工况要求.     

LPG发动机缸内Nox分布及其排放的预测研究

借助CFD软件Star-CD,将基于β函数的概率密度函数方法应用于描述LPG发动机缸内不同区域的温度来模拟NOx的生成,同时考虑了缸内湍流场中组份和温度场的脉动。给出了在火花点火的燃烧方式下,LPG发动机在不同曲轴转角下缸内NOx的时空分布。计算和试验结果吻合良好。与其它PDF方法相比更趋理性,为研究和改善发动机的排放提供了参考。     

基于纵弯曲强度可靠性分析的船舶中剖面优化

研究基于船舶纵弯曲强度可靠性分析的全概率方法,以通过波浪载荷直接计算软件和船舶剖面强度信息计算得到的纵弯曲强度失效概率为目标函数,以相关规范对剖面构件的尺寸要求和剖面面积上限作为约束条件,通过MATLAB建立优化模型。并结合MATLAB集成的遗传算法工具箱对船舶中剖面进行优化设计。算例结果表明在剖面面积减小了0.38%的情况下,纵弯曲强度失效概率由原来的7.22×10-5降低为1.32×10-5,表明此方法用于船舶中剖面结构优化是行之有效的。     

悬浮式拦截弹拦截鱼雷概率分析

悬浮式拦截弹是水面舰艇拦截鱼雷的常用武器,首先从直航雷的相遇三角形命中目标条件出发,推导出鱼雷相对舰艇的正常提前角,从而确定鱼雷在被发现点的最大航向角范围。以此为基础,确定悬浮式拦截弹阵布放中心位置,最后得出悬浮式拦截弹拦截鱼雷概率计算公式,为如何提高拦截概率提供了理论依据。     

水面舰艇编队成员对潜攻击命中概率数据库研究

基于潜艇对水面舰艇编队威胁判断的需要,针对命中概率数据实时取得较为困难的问题,采用较成熟的DBMS平台,分数据库建立必要性和可行性分析、数据库组成和数据库建立流程三个方面,对水面舰艇编队成员对潜攻击命中概率数据库的建立进行探讨。     

Determinants of the probability of default: the case of the internationally listed shipping corporations

In this study, we use a sample of 192 listed shipping companies and employ a logit model in order to investigate the determinants of the probability of default. We enhance our analysis by isolating not only the cases of company liquidations but also those cases where companies had to change their legal status due to warning liquidity signals. Our key findings are in line with prior research and moreover we depict a changing trend in the marginal effects of relevant variables, on the probability of default. We further show, through an empirical application, how the obtained results can be used in a managerial decision-making process and in a bank credit underwriting process in order to assess the creditworthiness of a shipping company.