基于DES方法的螺旋桨尾涡演化数值研究

采用分离涡模拟(DES)方法对多工况下螺旋桨的尾流场特性及尾涡结构进行数值研究,应用滑移网格技术完成螺旋桨敞水试验模拟,采用Spalart-Allmaras湍流模型封闭N-S方程组。数值计算结果显示:采用DES方法得到的水动力特性结果与模型试验结果吻合度高,DES方法能够较好地捕捉到螺旋桨尾流场中复杂的尾涡结构,螺旋桨不同桨叶产生的梢涡之间的自诱导和相互诱导作用引起尾涡结构形态变化,4叶桨梢涡结构之间会产生2次融合重组,毂涡振荡与梢涡演化之间存在相互干扰作用,不同进速系数下尾涡演化规律基本一致。     

同步洒布摊铺机的研制与开发

超薄磨耗层养护技术被欧美列为高速公路第一养护方案,在国内也已经开始推广应用。文章介绍了国产超薄磨耗层施工专用设备的研制过程,通过对国内高速公路养护市场的分析以及与德国福格勒公司的进口设备对比,认为国内同步洒布摊铺机的研制与开发具有广阔的市场前景。     

Benchmarking road safety performance by grouping local territories: A study in the Netherlands

The method of benchmarking provides an opportunity to learn from better performing territories to improve the effectiveness and efficiency of activities in a particular field of interest. Such a field of interest could be road safety. Road safety benchmarking can include several indicators, ranging from performance indicated by crash statistics, to indicators that also account for consequences in costs or the underlying state of the road safety system and relevant organisation and processes at actor level. The structure and culture of a territory is identified as a basic context of road safety performance. This is regarded as important information to use in grouping of territories to get more homogenous or equal and comparable conditions to learn from ‘the best in class’.The main aim of this study is to assess the usability of different groupings using the physical structure for benchmarking road safety performance at local territorial level. A traditional grouping of municipalities in the Netherlands was compared with a simple grouping of these municipalities based on their level of urbanisation and an advanced grouping in which more indicators such as differences in demography, growth and road structure were taken into account. As in other studies, urbanisation showed to be the most predominant structural factor for grouping local territories and related to differences in road safety performance. However, if information would be needed for specific target groups, other factors like age and gender distribution or the distribution of the road network can provide valuable additional insight and better homogenous starting points for benchmarking. Especially benchmarking of rural territories may profit from such extra distinctive characteristics.     

Development of driving cycles for electric vehicles in the context of the city of Florence

Strong efforts are spent in automotive engineering for the creation of so called Driving Cycles (DCs). Vehicle DC development has been a topic under research over the last thirty years, since it is a key activity both from an authority and from an industrial research point of view. Considering the innovative characteristics of Electric Vehicles (EVs) and their diffusion on certain contexts (e.g. city centers), the demand for tailored cycles arises. A proposal for driving data analysis and synthesis has been developed through the review and the selection of known literature experiences, having as a goal the application on a EVs focused case study. The measurement campaign has been conducted in the city of Florence, which includes limited traffic areas accessible to EVs. A fleet of EVs has been monitored through a non-invasive data logging system. After data acquisition, time-speed data series have been processed for filtering and grouping. The main product of the activity is a set of DCs obtained by pseudo-randomized selection of original data. The similarity of synthetic DCs to acquired data has been verified through the validation of cycle parameters. Finally, the new DCs and a selection of existing ones are compared on the basis of relevant kinematic parameters and expected energy consumption. The method followed for the creation of DCs has been implemented in a software package. It can be used to generate cycles and, under certain boundary conditions, to get a filtered access to the measured data and provide integration within simulation environment.     

论未来的船舶生产管理模式

在对船舶生产特点进行分析的基础上，提出了船舶生产管理３Ｉ新模式设想，即船舶制造壳舾涂一体化；船舶产品和制造过一体化设计及造船工程管理一体化。     

铁路路基填料分类深化研究

根据泰波最大干密度理论和粒子干涉理论,分析不均匀系数取值范围及其对孔隙率的影响,提出颗粒级配的改进方案:当不均匀系数大于或等于10且曲率系数为1～3时,定义填料的颗粒级配为良好级配;当不均匀系数大于或等于10且曲率系数小于1或大于3时,定义填料的颗粒级配为间断级配;当不均匀系数小于10时,定义填料的颗粒级配为均匀级配。通过对影响填料工程性能因素的分析,并结合工程实践,提出填料分类分组的建议方案:在巨粒土和粗粒土中,细粒含量按5%,15%和30%分界;将细粒含量大于或等于15%的巨粒土和粗粒土划分为粉土块石、黏土块石、多粉土块石和多黏土块石等;对于细粒土,在粗粒含量大于或等于30%的条件下,将砾石含量大于或等于25%的细粒土定义为含砾液限土,否则定义为含砂液限土;巨粒土和粗粒土母岩的饱水抗压强度应大于或等于20MPa;在砾石类土划分中增加5mm粒组界限。     

混合P2P分组网络研究及其在教学系统中的应用

在现今网络教育中,协同化教育模式也成为其核心模式.然而传统的教育系统存在许多问题,系统可靠性和扩展性差,不能充分利用客户端资源,而且协同化不高.基于Agent的P2P协作模型恰好弥补了传统系统的缺陷.以此模型为基础设计出一套网络教学系统.     

Long-term approach for assessment of sloshing loads in LNG carrier,part II: Grouping method

Assessing the sloshing loads has been a significant issue in designing the cargo containment system (CCS) of a liquefied natural gas carrier (LNGC). The sloshing problem contains numerous physical and technical uncertainties. The long-term approach has been suggested to reduce the possible uncertainties, but it has not been a feasible option owing to the incalculable number of experimental cases. Daewoo Shipbuilding and Marine Engineering Co., Ltd., Hyundai Heavy Industry Co., Ltd., Samsung Heavy Industry Co., Ltd., Korean Register, and Seoul National University conducted extensive sloshing model tests for the 174 K S-LNGC. To consider the long-term approach, Part I describes the differences between short- and long-term approaches based on the guidelines of different classification societies. To address the significant number of experimental conditions required for the long-term approach, a grouping method is investigated (Part II). Although this grouping method is typically used in practical design, it has not been validated, and its applicability is yet to be determined. In Part II, the sea states are classified using 16 different grouping methods. The long-term exceedance probabilities and pressures are obtained individually and then compared with the results obtained from fully considering all sea states. After performing the general sloshing model test of the shipbuilding industry, the sloshing impact pressure of a liquefied natural gas cargo model is measured via 6DoF irregular simulations, where the upper section of the cargo hold structure is considered. Long-term pressures are locally and globally investigated and compared among 16 different sea states and all the sea states. Based on the results, the best grouping method is suggested for the long-term approach.