有限元分析在船舶轴系设计中的应用

使用Abaqus软件建立船舶轴系中间轴的模型，通过有限元方法计算轴法兰过渡处的应力集中系数，分析应力集中系数与轴系扭振计算结果之间的关系。相比于单圆弧过渡，三段式圆弧过渡将应力集中系数减小了20%，持续运转扭振许用应力提高了38%，瞬时运转扭振许用应力提高了17%。运用有限元分析方法检验校核了船舶轴系设计的合理性。     

索赔风险的模糊综合与辨识模型的应用

对工程各涉及方来讲,索赔风险的发现与识别既是索赔管理的首要任务,也是一个难点问题。运用索赔风险的模糊综合与辨识模型分析索赔风险,可以迅速而准确地解决这一难题。     

Fatigue damage induced by vortex-induced vibrations in oscillatory flow

Vortex-induced vibration (VIV) of a flexible cylinder in oscillatory flow was experimentally investigated in an ocean basin. An intermittent VIV was confirmed to have occurred during the tests. The fatigue damage caused by VIV was calculated based on rainflow counting and a standard S–N curve. There are 3 main observations for fatigue damage from VIV in oscillatory flow: 1) the damage varied significantly with the KC number, which is a unique feature for VIV in oscillatory flow. 2) Fatigue damage at small KC number cases was found to be larger compared to those at large KC numbers owing to the fact that number of vortex shedding cycles per half of the motion cycle is low, and damping within half of the motion cycle will hence become low. The fact that vortices from the previous cycle still are active during the next may also contribute to the large response at small KC numbers. 3) ‘Amplitude modulation’ and ‘mode transition’, two specific features for VIV in oscillatory flow, were found to have a strong influence on fatigue. Fatigue damage has also been calculated by an empirical VIV prediction model assuming that all cases have steady flow at an equivalent velocity. Finally, a simplified method for calculating fatigue damage from VIV in oscillatory flow based on steady flow conditions is proposed. A modification factor diagram is presented, but the scope of the present study is too limited to provide a good basis for a general model for this factor. A general model for how to apply results from constant current analysis to predict fatigue in oscillatory flow will therefore need further research.     

Effects of corruption on efficiency of the European airports

The effect of corruption on airport productive efficiency is analyzed using an unbalanced panel data of major European airports from 2003 to 2009. We first compute the residual (or net) variable factor productivity using the multilateral index number method and then apply robust cluster random effects model in order to evaluate the importance of corruption. We find strong evidence that corruption has negative impacts on airport operating efficiency; and the effects depend on the ownership form of the airport. The results suggest that airports under mixed public–private ownership with private majority achieve lower levels of efficiency when located in more corrupt countries. They even operate less efficiently than fully and/or majority government owned airports in high corruption environment. We control for economic regulation, competition level and other airports’ characteristics. Our empirical results survive several robustness checks including different control variables, three alternative corruption measures: International Country Risk Guide (ICRG) corruption index, Corruption Perception Index (CPI) and Control of Corruption Index (CCI). The empirical findings have important policy implications for management and ownership structuring of airports operating in countries that suffer from higher levels of corruption.     

高速公路车辆超速检测算法影响因素分析与对策研究

针对高速公路上车辆违章超速行为，给出了一种基于虚拟视频检测线的车辆速度检测与违章超速行为判定的实用算法。对影响该算法精度的各种影响因素进行了详细的分析，特别是针对检测线的数量与间距设置、图像采集卡的采集频率等对算法的影响进行了细致的讨论，并给出了算法条件下，所能检测的最高理论车速。对在应用中可能存在的漏检、误检情况，提出了解决办法。通过实验验证了该算法具有良好的适应性和较高的检测率。     

用于铁路轨道不平顺预测的综合因子法

根据轨道结构存在的不平顺特征及其形成原因,提出基于数字统计理论、信号处理理论和轨道不平顺检测数据的综合因子法,对各类轨道不平顺的发展趋势进行预测,为铁路线路的维修提供参考依据。方法的核心思想是基于对同一地段轨道不平顺变化规律相近的认知,即轨道在线路脆弱的地方会更脆弱,在不平顺幅值较大的地方其不平顺发展也相应较大。综合考虑影响轨道不平顺发展的众多因素,如轨道系统各部件的材料影响、铁路施工以及各种运营条件、环境因素等,将这些影响因素共同作用后的整体效果反映在构建的预测模型中,给出相应的综合因子和随机量的参数矩阵,并建立轨道不平顺管理的分级概念。计算结果表明,综合因子法能够较好地预测轨道不平顺的变化。     

φ840D货车车轮辐板孔疲劳裂纹扩展特性研究

针对目前840D货车车轮辐板孔裂纹故障增多及其可能带来的隐患,本文首先采用有限元方法数值模拟了不同运用条件下车轮的机械应力和制动热应力,其次根据线弹性断裂力学理论研究了辐板孔边裂纹的应力强度因子,最后结合Forman疲劳裂纹扩展方程及裂纹扩展门槛值,得到不同运用工况下辐板孔裂纹扩展的基本特性及规律,从而分析出了导致裂纹扩展的载荷条件。分析结果表明:辐板孔裂纹是典型的疲劳裂纹,是由萌生于辐板孔内侧的微细裂纹逐渐扩展而来的,它是由热负荷和机械载荷的综合效应造成的。单纯的机械载荷不会直接导致孔边裂纹的萌生和扩展;坡道制动与机械载荷的叠加才是导致辐板孔裂纹萌生与扩展的最主要的载荷工况。这对预防车轮疲劳失效、优化车轮设计,保障行车安全,具有重要意义。     

76 000 dwt散货船发电机容量的确定

从介绍76 000 dwt散货船的电力负荷估算书着手,阐述了确定该船发电机容量的方法。     

基于最大裂纹张口位移计算应力强度因子的方法研究

文章提出了基于最大裂纹张口位移计算I型应力强度因子的新方法,该方法适用于复合载荷(均匀拉伸和纯弯曲载荷组合)作用下的具有半椭圆表面裂纹的有限平板模型。首先,理论推导了具有埋藏裂纹的无限大平板受均匀拉伸载荷作用时应力强度因子与裂纹最大张口位移的对应关系,再应用有限元数值模拟技术,考虑了表面效应、模型尺寸效应及载荷形式的影响,然后基于有限元模拟结果,根据多元多次最小二乘法原理拟合出对应修正系数表达式,最终建立了复合载荷作用下有限平板裂纹尖端应力强度因子与最大张口位移的函数关系,实现了由容易获得的最大裂纹张口位移确定应力强度因子的方法。该方法避免了对裂纹尖端的应力场、位移场的分析,为实际应用中应力强度因子的获得提供了新的方法。     

Methodologies to monetize the variations in load factor and GHG emissions per passenger-mile of airlines

Global GHG emissions from air travel are currently at 3% and it could increase to 15% of the total GHG emissions by 2050. To curb the growth of GHG emissions from air travel, the U.S. Federal Aviation Administration (FAA) has created a policy to achieve carbon neutral growth by 2020 relative to the 2005 baseline. If the airline industry is to both grow and meet the objectives set by this policy, new and innovative aircraft designs, operational efficiencies, and widespread use of alternate fuels are required. To accomplish this would require large research and development investment. The federal government and state governments have passed legislations that provide tax breaks and other incentives to encourage investments in new technologies. One such tax policies is cap and trade system. This had partial success in reducing GHG emissions in certain industries but was not successful in the airline industry. This paper presents alternate methods to raise capital to invest in GHG emissions reduction projects in the airline sector. The four methodologies presented here monetizes the GHG emissions resulting from differences in load factor (ratio of number of passengers to number of seats) and GHG emissions per passenger-mile among different airlines, among different flight sectors, etc. to raise the capital. Based on 2012 air travel data, these methodologies could raise more than $300 million dollars annually to invest in GHG emissions reduction projects.