基于损失函数法的船舶操纵水动力导数灵敏度分析

船舶操纵水动力导数的灵敏度分析是简化和重建船舶操纵运动数学模型的主要手段。本文使用平方损失函数方法对船舶操纵水动力导数进行灵敏度分析,并基于灵敏度分析结果对Mariner船的操纵运动数学模型进行简化。通过基于简化模型和原始数学模型的操纵运动仿真对比,验证了基于损失函数法的船舶操纵水动力导数灵敏度分析方法的有效性。     

气垫船操纵性能理论分析

研讨了全垫升气垫船垫态航行时的操纵性.利用所建立的气垫船六自由度仿真系统和航向保持控制系统使气垫船进入稳定直航后,进行了操舵回转特性和螺距差回转特性仿真试验研究,并进行了验证气垫船直线稳定性的回舵试验和航向保持能力的Z形机动试验.最后,对仿真试验结果进行了详细分析,并对气垫船的操纵特点进行了论述.     

操纵运动潜艇水动力计算研究

采用FLUENT软件对一模型艇在不同漂角下运动的升沉力系数和表面压力分布进行计算,验证了该软件解决此类问题的有效性。在此基础上,对作操纵运动的潜艇主体和带附体的全艇体,在一定攻角和漂角下的垂向力、俯仰力矩和横向力、纵倾力矩进行计算,取得了工程上较为满意、实用的精度,为解决潜艇操纵运动水动力预报的困难做出了有益的探索。     

Improved calibration of simulation models in railway dynamics: application of a parameter identification process to the multi-body model of a TGV train

This paper aims at estimating the vehicle suspension parameters of a TGV (Train à Grande Vitesse) train from measurement data. A better knowledge of these parameters is required for virtual certification or condition monitoring applications. The estimation of the parameter values is performed by minimising a misfit function describing the distance between the measured and the simulated vehicle response. Due to the unsteady excitation from the real track irregularities and nonlinear effects in the vehicle behaviour, the misfit function is defined in the time domain using a least squares estimation. Then an optimisation algorithm is applied in order to find the best parameter values within the defined constraints. The complexity of the solution surface with many local minima requires the use of global optimisation methods. The results show that the model can be improved by this approach providing a response of the simulation model closer to the measurements.     

操纵运动船艇水动力计算方法研究

船艇水动力的计算方法目前主要有模型实验法、理论经验估算法和计算机模拟法.为了更好地预报船艇水动力性能,运用不同方法对2种典型船艇在不同漂角下运动时横向力进行计算,并对各自结果进行了对比分析,得出各种计算方法的优缺点.研究表明,流体计算软件(Fluent)精度较高,计算速度快,能解决人脑有时不能解决的问题.同时,Fluent计算软件为船艇水动力性能的预报等研究提供良好的方法和有益的探讨.     

Identification and interpretation of spatial–temporal mismatch between taxi demand and supply using global positioning system data

Taxis provide a type of on-demand mobility service in urban transportation. There are growing concerns regarding the level of service of taxis in satisfying residents’ mobility demand. However, the mismatch between demand and supply of taxi services has not been resolved even with the introduction of app-based vehicle services. In this study, three indicators are constructed using the Shanghai taxi global positioning system (GPS) dataset to reveal the spatial–temporal mismatch pattern. The issue is further analyzed via a case study, in which seven regions with frequent mismatch patterns are identified in the time period from 21:00 to 22:00. Then, a multinomial logistic regression model is employed to identify the demographic and built-environment factors contributing to the taxi mismatch problem. The study results show that population density, residential areas, the number of points of interest, and road density have significant relationships with the taxi undersupply. In contrast, the areas of commercial lands, as well as the other two transportation-related factors, that is, the number of bus stops and the distance to nearest subway station, are observed to be statistically significant for both “oversupply” and “undersupply” conditions. This study provides valuable insights for identifying mismatch patterns and interpreting the mismatch problem as a function of spatially explicit factors that are of great use for urban governance, especially in the improvement of taxi efficiency, taxi management, and urban planning.     

基于成本费用的铁路无线通信基站设计优化研究

目前,我国铁路无线通信系统设计从整体上考虑优化困难,这在一定程度上制约了铁路的长远发展。在成本结构分析的基础上,以总费用最小、基站数最少为目标,以满足基站无线信号覆盖为主要约束,建立铁路无线通信系统优化模型,并以国内某条已有铁路线为例求得模型的最优解。与已有方案对比表明,新方案不仅大大降低设计费用,而且具有普遍适用性。     

全球变暖潜能值的计算及其演变

全面论述了政府间气候变化专门委员会自1990年至2007年的四次评估报告中有关全球变暖潜能值的计算及其数值的演变。指出全球变暖潜能值是变量,而且同一制冷剂的全球变暖潜能值在各种资料和评估中不尽相同,因此建议在引述全球变暖潜能值时应标注其数据来源。     

潜艇攻击机动目标武器使用有关问题的研究

对潜艇攻击机动目标情况下武器使用涉及的有关问题进行研究。可能的潜射攻击机动目标的武器包括线导鱼雷、声自导鱼雷、尾流自导鱼雷、直航鱼雷以及反舰导弹等。分别分析这些武器用于攻击机动目标时所具有的特点,探讨这些武器在攻击机动目标作战背景下的射击使用方法、存在的问题、注意事项等。结果表明,这些武器用于机动目标攻击作战各有所长的同时也都有不足之处,程度不同而已,关键是射击使用中对其特点的科学合理把握,以及通过严格射击训练达成的熟练运用。     

圆筒形生活平台总体强度分析

参考挪威船级社海工规范要求,分析平台极限载荷状态下的总体结构强度.应用海工规范公式对主船体结构中的板和筋进行规范校核,对主船体双层壳内的环形梁进行屈服和局部屈曲的强度校核,对大的板架结构开展针对各种屈曲类型的校核,结果表明,该生活平台在目标海况下的结构承载能力满足船级社的规范要求.