浅谈旧桥承载能力可靠性评估

简要介绍了有关桥梁评估的内容、方法以及其研究方向。     

邮件内容过滤技术探讨

随着网络技术的发展,垃圾邮件日益猖獗,因此,众多邮件过滤技术也应运而生.介绍邮件内容过滤技术,并就内容过滤需要解决的难题进行探讨.     

基于动态贝叶斯的船舶中央冷却水系统状态推理

针对船舶中央冷却水系统日益复杂、处理这类信息时存在很大不确定性的问题，将动态贝叶斯网络运用于复杂管路系统的检测与控制中。通过全面分析某型船舶中央冷却水系统各个部件之间的相互关系以及评估参数，建立系统的动态贝叶斯网络模型，运用BK算法对系统的运行状态进行推理。使目标节点的各个特征因素以及不同时间片同一特征因素相互修正，克服系统检测时不确定性、数据不完整和主观性。通过仿真表明，动态贝叶斯网络在不确定环境和数据缺失的情况下可以考虑时间的因素进行有效的状态推理并实现有效的控制。     

Maritime accident risk estimation for sea lanes based on a dynamic Bayesian network

ABSTRACT

The safety of maritime transportation has become increasingly important with the development of international economics and trade. This paper introduces a dynamic Bayesian network (DBN) model to facilitate the estimation of the dynamic emergency risk in sea lanes. The DBN model is a novel model that can efficiently represent and infer complex stochastic knowledge. To construct this model, available data, which were collected from emergency investigation reports by the International Maritime Organization (IMO), are employed in conjunction with expert knowledge to develop and demonstrate a BN; an evidence theory approach is applied to calculate the prior probability with the help of historical data; the conditional probability is learned by the expectation maximization (EM) algorithm; and the transition probability is obtained by a Markov model. Finally, the Viterbi algorithm is adopted to estimate emergency risk. The emergencies that occurred in the Indian Ocean from 2009 to 2018 were used as a case study for risk estimation. Sensitivity analysis was conducted to identify significant influential factors. The results show that the sea lane risk in the Indian Ocean fluctuates within a small range, presenting an overall downward trend over time. These findings provide a reference for maritime stakeholders to make proper decisions.     

Inferring left behind passengers in congested metro systems from automated data

With subway systems around the world experiencing increasing demand, measures such as passengers left behind are becoming increasingly important. This paper proposes a methodology for inferring the probability distribution of the number of times a passenger is left behind at stations in congested metro systems using automated data. Maximum likelihood estimation (MLE) and Bayesian inference methods are used to estimate the left behind probability mass function (LBPMF) for a given station and time period. The model is applied using actual and synthetic data. The results show that the model is able to estimate the probability of being left behind fairly accurately.     

海船结构的总纵强度可靠性分析

本文在研究船舶结构总纵度强度的外载荷和结构能力的概率模型的基础上,应用结构可靠性原理中的全概率法和改进的一阶二次矩法编制了计算程序。通过对5艘实船的计算,分析了这些船舶的实际安全水平,特别,根据ZC规范要求的最小强度的最大载荷作了可靠性分析,得出了这5艘船的最低安全水平。在改进的一阶二次矩法计算的基础上,给出一种与传统的确定性设计方法形式相似但比其更为精确的安全设计条件及其相应的强度减小因子和载荷放大因子计算方法,供结构直接设计强度校核所用。     

两船在波浪中靠帮模型运动的试验预报

近来由于航道以及水域的限制，两船或多船定点靠帮进行装卸货物或补给越来越普遍，两船或多船之间相互影响也越来越引起工程师们的关注。通过两种船型（驳船和双体船）在4级上限和5级上限海况下分别与大船（panamax）进行靠帮的水池模型试验研究，给出它们的实船预报以及对应位置处的碰撞概率，分析两种船型在靠帮中运动的优劣，试验结果可为工程设计单位提供参考。     

斜拉桥结构损伤识别的概率可靠度法

基于静力响应测试数据,结合正则化技术和假设检验,提出了测试数据不完整且存在观测噪声条件下斜拉桥结构损伤识别的概率可靠度法。采用正则化技术降低斜拉桥结构损伤识别问题的不适定性和求解困难,综合利用参数估计和数据摄动技术获得结构参数的统计特征,在此基础上根据假设检验识别损伤位置和损伤程度。以一斜拉桥结构的损伤识别仿真分析验证了方法的正确性和有效性。研究表明,所提出的方法能够在测试数据存在观测噪声的情况下准确识别损伤。     

基于遗传算法的船用核动力装置故障诊断

介绍一种将概率因果模型和遗传算法相结合的核动力装置二回路凝给水系统的故障诊断方法,该方法将概率因果模型的似然函数作为遗传算法的适应函数,从而将复杂系统的故障诊断转化为最优问题。仿真结果表明,该方法能够适应诊断过程中出现的不确定性,并实现多故障诊断,具有较高的诊断可靠性和实用性。