能效设计指数EEDI功率曲线的直接计算方法

船舶能效规则强制生效后，所有适用船舶必须满足Attained EEDI≤Requied EEDI的条件，因此准确估算或预报功率曲线从而计算得到Attained EEDI将对适用船型具有极为重要的意义。根据国内外关于功率-转速-航速预报的最新进展，依据螺旋桨敞水性能图谱，采用KT/J^2系数，给出了功率曲线的直接计算方法，经实际算例验证，该方法相对传统的间接计算方法更为清晰简便，且结果准确可靠。     

区级海绵城市建设规划中指标管控方法探讨

针对区级海绵城市建设规划中管控单元划分和指标分解等关键环节,提出最小管控单元和管控指标源头-系统两级分解体系.上海市虹口区的案例表明,最小管控单元可有效衔接源头地块、控规单元和排水系统,管控指标源头-系统两级分解体系可有效体现系统性工程在海绵指标中的贡献,合理减轻源头项目的达标压力.     

浅析大客车气压制动装置制动失灵原因

介绍引起大客车制动失灵的一些故障，针对这些故障给出了预防措施和解决的方案。     

一种三角形网格自动生成技术

在研究总结目前流行的三角形网格自动生成法的基础上,提出前沿生成与Delaunay三角化组合起来的三角形自动生成方法。该方法解决了Delaunay法中离散点域的构造问题,不会产生重合点,不用进行点集排序和坏点剔除,同时避免了前沿生成法中过多的校验。该法计算效率高,对复杂边界适应性好,可实现三角形尺度的渐变过渡。应用该方法成功进行了三峡电站日调节数学模型计算域的自动剖分。     

粘土含量对粉沙质泥沙沉降速度的影响

通过对泥沙沉降试验结果进行统计整理和理论分析,研究了粘土含量对粉沙质泥沙沉降速度的影响。结果表明:泥沙沉降速度同时受泥沙中值粒径d50和粘土含量p0.004控制;沉降速度ω随泥沙中值粒径d50增大而增大;粘土含量较小时,沉速随p0.004增大而减小,粘土含量较大时,沉速随粘土含量增大而增大;粘土含量对泥沙沉速影响的分界点为20%~25%。     

Sampling of alternatives for route choice modeling

This paper presents a new paradigm for choice set generation in the context of route choice model estimation. We assume that the choice sets contain all paths connecting each origin–destination pair. Although this is behaviorally questionable, we make this assumption in order to avoid bias in the econometric model. These sets are in general impossible to generate explicitly. Therefore, we propose an importance sampling approach to generate subsets of paths suitable for model estimation. Using only a subset of alternatives requires the path utilities to be corrected according to the sampling protocol in order to obtain unbiased parameter estimates. We derive such a sampling correction for the proposed algorithm.Estimating models based on samples of alternatives is straightforward for some types of models, in particular the multinomial logit (MNL) model. In order to apply MNL for route choice, the utilities should also be corrected to account for the correlation using, for instance, a path size (PS) formulation. We argue that the PS attribute should be computed based on the full choice set. Again, this is not feasible in general, and we propose a new version of the PS attribute derived from the sampling protocol, called Expanded PS.Numerical results based on synthetic data show that models including a sampling correction are remarkably better than the ones that do not. Moreover, the Expanded PS shows good results and outperforms models with the original PS formulation.     

Experimental design influences on stated choice outputs: An empirical study in air travel choice

Discrete choice experiments are conducted in the transport field to obtain data for investigating travel behaviour and derived measures such as the value of travel time savings. The multinomial logit (MNL) and other more advanced discrete choice models (e.g., the mixed MNL model) have often been estimated on data from stated choice experiments and applied for planning and policy purposes. Determining efficient underlying experimental designs for these studies has become an increasingly important stream of research, in which the objective is to generate stated choice tasks that maximize the collected information, yielding more reliable parameter estimates. These theoretical advances have not been rigorously tested in practice, such that claims on whether the theoretical efficiency gains translate into practice cannot be made. Using an extensive empirical study of air travel choice behaviour, this paper presents for the first time results of different stated choice experimental design approaches, in which respective estimation results are compared. We show that D-efficient designs keep their promise in lowering standard errors in estimating, thereby requiring smaller sample sizes, ceteris paribus, compared to a more traditional orthogonal design. The parameter estimates found using an orthogonal design or an efficient design turn out to be statistically different in several cases, mainly attributed to more or less dominant alternatives existing in the orthogonal design. Furthermore, we found that small designs with a limited number of choice tasks performs just as good (or even better) than a large design. Finally, we show that theoretically predicted sample sizes using the so-called S-estimates provide a good lower bound. This paper will enable practitioners in better understanding the potential benefits of efficient designs, and enables policy makers to make decisions based on more reliable parameter estimates.     

沥青混合料汉堡车辙试验条件及评价指标研究

采用2种沥青、2种级配拌制4种混合料,分别在水浴和空气浴下进行50℃和60℃的汉堡车辙试验,分析了水和温度对车辙深度的影响;讨论了车辙深度和蠕变速率指标评价沥青混合料高温性能的不足,提出了车辙变形率指标.结果表明,水环境和提高温度都会加速车辙的产生,50℃水浴和60℃空气浴车辙深度的相关性好,50℃水浴汉堡车辙试验可以反映沥青混合料的抗车辙性能,建议B级沥青采用45℃,A级沥青采用50℃,改性沥青采用60℃的试验温度.     

带有压力补偿模块的容积式阀位指示器

文章分析了造成容积式阀位指示器在船舶液压阀门遥控系统中应用产生误差的因素,介绍了一种新颖的带有压力补偿模块的容积式阀位指示器.这种阀位指示器可在系统工作压力高、控制管路长的工况下有效提高阀位指示器的测量精度,可广泛应用于大型船舶液压阀门遥控系统.     

上海洋山港区的自然条件及泥沙来源分析

在现场水文测验、泥沙分析等资料整理分析的基础上 ,重点对该区水沙特性、沉积物质组成及盐度变化对泥沙沉速的影响及泥沙来源问题进行了探讨。