大侧斜螺旋桨桨叶应力分析

采用求解RANS方程的方法对某大侧斜螺旋桨敞水流场进行模拟,计算得到的推力系数与力矩系数与试验值有很好的一致性.在此基础上,将计算得到的桨叶水动力载荷、离心力载荷和重力载荷导入有限元模型,求解大侧斜螺旋桨桨叶应力场分布.根据应力场分布特点,可知:桨叶除叶根有应力集中区域外,0.5倍半径靠近随边处还存在应力集中区域;在0.5倍半径桨叶切面处,桨叶压力面应力从导边至随边递增,桨叶吸力面应力从导边至随边存在波动.     

光谱分析技术在船舶燃料油与气缸油配伍研究中的应用

本文叙述了用原子吸收光谱分析方法研究船用重质燃料油与不同气缸油的配伍试验时使用 Bolnes 三缸柴油机和原子吸收光谱仪,通过测定废气缸油中铁、铬含量来确定气缸磨损情况,用磨损指数和清洁分散性系统地评价配伍效果。采用该方法,可在短期运行后不需停机,拆机,即可取样测定.原子吸收光谱分析法灵敏度高,精确度强,是一种有价值的方法.     

Statistical comparison of trace metal concentrations in wild mussels (Mytilus galloprovincialis) in selected sites of Galicia and Gulf of Biscay (Spain)

Concentrations of five trace metals (Cd, Hg, Pb, Cu and Zn) in wild mussels (Mytilus galloprovincialis) from the Galician and Gulf of Biscay areas in Spain were monitored from 2000 to 2004. A pool of mussel soft tissue was prepared using 50 or more individuals representing the available size range (35–60 mm) present at the sampling points (A Coruña, Pontevedra and Vigo–Galicia, NW of Spain—and Avilés, Bilbao and Santander–Gulf of Biscay). Metals were analysed by atomic absorption spectrometry, AAS, (flame–AAS: Cu and Zn; graphite furnace–AAS: Cd and Pb; flow injection-cold vapour–AAS: total Hg). Quality of the chemical analyses was assessed by participation in periodic QUASIMEME intercalibration exercises carried out from 2000 to 2004, while the present study was developed . Univariate statistical studies, Anova (Analysis of the Variance) and Principal Component Analysis (autoscaled data, Varimax rotation) were carried out. Differences between the two areas as well as certain temporal trends were found and, in general, the Gulf of Biscay samples showed higher metallic contents, mainly close to Avilés, where iron and steel factories thrown residues for years into a nearby coastal area.     

Sensitivity analysis of the probabilistic damage stability regulations for RoPax vessels

In the light of the newly developed harmonised probabilistic damage stability regulations, set to come into force in 2009, this article presents a systematic and thorough analysis of the sensitivity of the Attained Subdivision Index with reference to a wide range of related design parameters. The sensitivity of the probabilistic regulations was investigated for a typical large RoPax vessel, with variation of parameters, such as the number, positioning and local optimisation of transverse bulkheads; the presence and position of longitudinal bulkheads below the main vehicle deck; the presence of side casings; and the height of the main deck and double bottom. The effects of water on deck and of operational parameters (draught, centre of gravity and trim) were also investigated. The results of the study, presented in graphical form, can provide valuable assistance to the designer when determining subdivision characteristics at the very early stage of the design process, resulting in optimal, efficient and safe ships.     

几例船舶主机故障现象及其分析

船舶主机是船舶的动力核心,与主机相关的故障如果不能被及时发现和处理,将会造成严重的事故。文章就作者在船上的工作经历,介绍了船舶主机的几例故障现象,并对这些故障的原因进行了适当的分析,说明了有效的维护是船用设备可靠工作的必要保证。     

基于DEA模型的港口企业规模效率评估

根据数据包络分析的CRS、VRS、NIRS模型原理,建立评价港口企业规模效率的定量依据,并对扬州港2000-2006年的生产样本数据进行实证分析.通过扬州港各决策单元的DEA有效性和规模收益分析,对其各年份的生产情况进行评价,从而衡量扬州港的生产经营效率状况,有利于港口企业在发展中准确定位,也为港口的投资建设提供决策指导.     

船舶危险品运输的风险分析

船舶危险品安全运输是船舶运输安全的重要方面。它既取决于船上危险品本身的安全,又取决于船舶的航行安全。风险分析就是在识别其本身和船舶航行两个方面存在的潜在危险即风险源的基础上,通过定性、半定量或定量的分析方法,分析这些危险可能导致的后果和这些后果发生的可能性,从而得到相应的风险水平。文中在介绍风险分析的步骤和方法的基础上,阐述了适用于船舶危险品运输的风险分析方法。     

深基坑排水系统介绍

本文根据现场条件及雨量分析,介绍深基坑排水系统的布置。     

厦门湾悬沙分布的多时相遥感分析

利用厦门湾地区多时相遥感图像反演出表层悬沙浓度分布图,进而定性分析不同径流和潮流下悬沙分布规律。研究表明,九龙江河口湾为该地区悬沙浓度最高的区域,分布上具有西高东低的特征。全湾悬沙来源主要为两部分:径流来沙以及波浪和潮流掀沙。潮流运动是泥沙输送的主要动力,由于弗劳德数分布不同而引起的潮流挟沙力空间差异,是影响厦门湾悬沙分布的主导因素。利用实测泥沙资料将不同时相下瞬时悬沙浓度转换为全潮平均悬沙浓度以进行定量分析,结果表明悬沙浓度具有大潮大于小潮,枯季大于洪季的特征。     

神经网络模型在港口吞吐量预测中的应用与误差分析

应用神经网络BP算法对杭州港的吞吐量预测实例进行了详细分析。通过对网络各种参数的调试与组合得出,当隐含层节点数为15,训练控制误差为0.035,分级迭代级数为4级,平滑因子参数为0.2,学习速率参数为1.5时,网络性能最佳。将网络预测结果与时间序列和回归分析2种方法进行了比较,得出神经网络方法在短期预测中要优于传统方法。通过对模型预测误差产生原因的简要分析,得出神经网络方法并不适用于吞吐量长期预测。最后对其应用过程中可能存在的一些问题提出了建议。