基于功能损伤的复杂电磁环境下炮兵目标毁伤评估

为适应复杂电磁环境,提高炮兵指挥员“科学决策,量敌用兵”的水平,依据目标在复杂电磁环境下的特点,综合利用了指数法和D-S理论等方法,分别对典型目标、电磁敏感目标和系统目标进行了功能损伤性毁伤评估。     

边坡稳定性分析的广义Bishop法

鉴于简化B ishop法作为一种简单实用且精度较高的极限平衡方法却仅限于分析圆弧破坏的缺陷,提出将B ishop法应用于任意滑裂面的广义方法.基于极限平衡理论和简化B ishop法的简化条件,推导其用于一般滑裂面破坏的边坡安全系数计算公式.通过实例分析考证比较该法的精度,并提出取矩中心的确定方法,以保证竖向力简化假设下的精度,为土坡稳定性分析提供了一种简单通用的方法.     

Analysis of velocity fluctuations and their intermittency properties in the surf zone using empirical mode decomposition

We consider here surf zone turbulence measurements, recorded in the Eastern English Channel using a sonic anemometer. In order to characterize the intermittent properties of their fluctuations at many time scales, we analyze the experimental time series using the Empirical Mode Decomposition (EMD) method. The series is decomposed into a sum of modes, each one narrow-banded, and we show that some modes are associated with the energy containing wave breaking scales, and other modes are associated with small-scale intermittent fluctuations. We use the EMD approach in association with a newly developed method based on Hilbert spectral analysis, representing the probability density function in an amplitude–frequency space. We then characterize the fluctuations in a stochastic framework using a cumulant generating function for all scales, and compare the results obtained from direct and classical structure function analysis, to EMD–Hilbert spectral analysis results, showing that the former method saturates at large scales, whereas the latter method is more precise in its scale approach. These results show the strength of the new EMD–Hilbert spectral analysis method for data presenting a strong forcing such as found in shallow water, wave dominated situations.     

有限元可靠度方法在桥梁工程中的应用

一次二阶矩法是目前求解结构可靠性分析的主要计算方法之一．该方法要求功能函数对随机变量的偏导运算。然而对于以有限元方法分析为主的桥梁结构．无法对其隐式功能函数进行显式求导．限制了一次二阶矩法的应用。本文给出了隐式功能函数可靠度的随机有限元解决方案．考虑了有限元方法和可靠度方法结合使用过程中,经典一次二阶矩法的改造问题。算例表明,该方法能够适用于基于有限元的结构可靠度分析,并在求解过程中给出随机变量的敏感系数。     

非稳态载荷对二维轮轨纯滚动接触应力和变形的影响

为了揭示轮轨波状表面与非稳态载荷的内在联系,利用有限元法,建立了二维弹塑性轮轨纯滚动接触计算模型,分析法向接触载荷波动值对钢轨残余应力、应变和变形的影响。模型中材料本构采用考虑棘轮效应的Jiang-Sehitoglu模型,非稳态仅考虑法向接触载荷的简谐变化,用弹塑性无限半空间表面上重复移动赫兹法向压力分布模拟反复纯滚动接触过程。发现非稳态法向接触载荷作用下产生同样波长的波状接触表面;随滚动次数的增加,残余应力增大,但很快趋于稳定,而残余应变也增大,但增大速率衰减;载荷波动值越大,波谷和波峰处的纵向残余应力越大,波谷处的轴向残余应力、残余剪应变和表面纵向位移越大,而波峰处的轴向残余应力、残余剪应变和表面纵向位移越小,波深越大。     

Predictive power of inspection outcomes for future shipping accidents – an empirical appraisal with special attention for human factor aspects

This paper investigates whether deficiencies detected during port state control (PSC) inspections have predictive power for future accident risk, in addition to other vessel-specific risk factors like ship type, age, size, flag, and owner. The empirical analysis links accidents to past inspection outcomes and is based on data from all around the globe of PSC regimes using harmonized deficiency codes. These codes are aggregated into eight groups related to human factor aspects like crew qualifications, working and living conditions, and fatigue and safety management. This information is integrated by principal components into a single overall deficiency index, which is related to future accident risk by means of logit models. The factor by which accident risk increases for vessels with above average compared to below average deficiency scores is about 6 for total loss, 2 for very serious, 1.5 for serious, and 1.3 for less-serious accidents. Relations between deficiency scores and accident risk are presented in graphical format. The results may be of interest to PSC authorities for targeting inspection areas, to maritime administrations for improving asset allocation based on prediction scenarios connected with vessel traffic data, and to maritime insurers for refining their premium strategies.     

基于HMM-SVR的船舶动力设备故障模式识别与状态预测研究

船舶动力设备因故障监测信号样本少、变化缓慢且数据特征呈非线性,使得设备故障模式的准确识别和状态预测比较难。鉴于此,文章研究了基于隐马尔科夫模型的故障模式识别方法,利用该模型将微弱变化的信号特征转换为变化较大的对数似然概率对故障模式实现有效识别。在此基础上进一步提出基于HMM-SVR的设备状态预测模型,将遗传算法用于支持向量回归模型参数寻优,并结合隐马尔科夫模型,实现对设备状态的预测。对船用柴油机进行仿真,结果表明上述模型具有较高的识别率,能准确预测船舶动力设备的当前状态。     

基于指数函数非线性反馈的船舶航向保持控制

为研究船舶航向保持控制问题,本文以“育鹏”轮为研究对象,建立了其非线性Nomoto船舶模型,设计了基于闭环增益成形算法的指数函数非线性反馈控制器,并以“育鹏”轮的非线性模型为被控制对象,用Matlab的Simulink工具箱进行系统仿真研究。系统仿真结果表明,建立的非线性Nomoto数学模型精度良好,设计的控制器进行船舶航向保持控制时效果优异,并且更节能。使用这种方法设计的控制器,可以很好地进行船舶航向保持控制,对今后的船舶运动仿真和控制器的设计具有重要意义。     

安装状态对扭矩扳子检定结果的影响

针对日常使用及检测扭矩扳子的过程中发现的不同安装状态对被检扭矩扳子的示值误差影响很大这一问题,通过大量的试验数据和经验数据相结合的方法,客观评估安装状态对扭矩扳子测量结果的影响。其中,扳手的水平安装状态及安装同轴度对检定结果影响较大。文章旨在帮助检定测试人员得到相对准确的数据。     

How do economies of density in container handling operations affect ships’ time and emissions in port? Evidence from Norwegian container terminals

Efficient port services are prerequisites for competitive and sustainable maritime transports. This paper makes advances in studying the determinants of the time that ships spend in port and the associated emissions to air. We estimate a production model for cargo handling based on a unique dataset containing each port of call at the largest container terminals in Norway in 2014. In turn, we use auxiliary engine emission factors to estimate particulate matter and nitrogen oxide emissions from ships at berth, to determine how the corresponding damage costs of air pollution vary with container throughput, location, and terminal investments. We find that Norwegian container terminals operate under increasing returns to density. Small ships that unload few containers are far from reaping economies of density, leading to high marginal time requirements for container handling and consequently high marginal external costs. From a Pigouvian taxation perspective, port charges should therefore be regressive in the number of containers handled. Moreover, we find that the external costs of maritime transports are severely understated when port operations are ignored. Our model allows determining the marginal productivities of port facilities. Thereby, it is instrumental in designing port charges that are diversified according to the quantity of containers handled and the service quality (i.e., the speed of handling operations). Regarding contextual factors, we find that establishing high-frequent liner services improves the ship working rate, while simultaneous calls at a terminal impede productivity. The type of container (loading/unloading; empty/laden) also appears to influence the duration of ship working.