船型参数对骑浪/横甩薄弱性衡准影响研究

骑浪/横甩是IMO船舶第二代完整稳性的五种失效模式之一,是一种基于概率的稳性衡准,制定规范的目的是更有效地保障船舶在实海域中的航行安全,确保不发生稳性失效情况.本研究中,以IMO有关成员国提出的最新版骑浪/横甩薄弱性衡准草案为基础,基于自主开发的骑浪/横甩薄弱性衡准校核软件,针对围网渔船开展了样船计算和比较分析,研究IMO正在制定的骑浪/横甩薄弱性衡准方法对该类船型的适用情况,分析船型参数对骑浪/横甩薄弱性衡准的影响,为我国参与国际法规制定,提出针对骑浪/横甩薄弱性衡准的提案提供技术支撑和依据.     

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.     

基于模糊聚类理论的TBM施工围岩可掘进性分级预测模型

文章针对硬岩掘进机(TBM)在复杂地质条件下的可掘进性,进行了系统及定量的研究;基于模糊聚类理论和施工样本数据分析,建立了以掘进速率为分级指标,包括岩石单轴抗压强度、岩石完整性系数、围岩结构面与隧道轴线夹角和渗水量四项性质指标的可掘进性分级预测模型,将TBM施工围岩可掘进性分为好、一般和差三个性能等级;并在此基础上进一步细化模型粒度,以提高模型的精度和地质适用性。将所建模型应用于西秦岭隧道和大伙房水库输水隧洞工程实际工程效果表明,TBM掘进速率与由模型预测的掘进速率基本相吻合,验证了掘进性分级预测模型的可行性、科学性和有效性,进而对TBM的选型、设计和施工提供了重要的理论依据。     

Guidelines for samplers: measuring a change in behaviour from before and after surveys

This paper addresses the issue of using before and after surveys to evaluate behavioural changes in response to transport policies and investments, a procedure that, we argue is done far too rarely in this profession. Further, it demonstrates very clearly that, in almost all conceivable cases, there are considerable economies to be obtained by using a panel (again, under-utilised in our profession) to undertake evaluation, rather than successive independent cross-sectional surveys. The paper also addresses the critical issue of sample size requirements for measuring changes of a relatively small magnitude in travel behaviour; i.e., to state, with 95% confidence, that if there is a ∂ percent change in behaviour for the sample, there is a ∂ percent ± e percent change in the behaviour of the population, where e is the sampling error. In this paper, we present a method for calculating such sample size requirements from first principles and demonstrate the applicability both hypothetically and then empirically using data from the Puget Sound Transportation Panel. The formulation enables designers of before and after surveys to investigate the trade-offs between the statistical accuracy of their predictions and the sample size requirements systematically, without the need to specify ∂ a priori. This latter point is crucial, we argue, because we have limited information on ∂, yet, as we explain here, it drives the sample size requirements using alternative, well-cited approaches for calculating sample sizes to assess behavioural change. The results have important ramifications both for those implementing transport policies intended to produce behavioural change, especially when a cost-benefit evaluation of the policy is desired, and for those interpreting the results reported in previous studies.     

潜艇大气污染物采样和样品处理技术

本文针对潜艇舱室空气中污染物的特点,介绍了潜艇舱室空气中污染物采样和样品处理常用的方法和技术,为开展潜艇大气污染物的检测提供参考依据。     

基于小波变换的交通流数据集成灵敏度分析

道路上的交通流数据通常是以20-30秒间隔采集并传递到交通管理中心的，为了使这些数据能够广泛地运用于各种交通用途，必须采用合理高效的集成方法对其进行处理。传统的数据集成方法基于数理统计的理论，该方法不能有效地去除数据中的噪音。近年来迅速发展的基于小波变换的交通流数据集成方法克服了这一缺点，通过对交通流数据的频率特性进行详细分析能够使集成更加高效，准确满足不同的交通用途对集成的需求。但该方法尚未作进一步的灵敏度分析，本文通过对数据集成中小波函数和数据样本量这两个重要参数的分析，从理论的角度探讨了这两个参数变化对数据集成的影响。然后以北京市三环上的交通流数据为例，计算得到了数据集成建议采用的小波族和小波阶数，以及合理的最小样本量。该结论对数据集成在将来的实际应用具有指导意义。     

关于沥青混合料密度测试计算方法的探讨

通过对沥青混合料设计方法的研究,提出了最大理论密度、压实沥青混合料试件与芯样密度的有效确定方法,并对沥青混合料老化时间的影响进行了分析。所得成果可为公路工程管理人员、路面设计工程师、沥青混合料设计工程师和施工工程师提供参考。     

基于人工神经网络的岩爆烈度预测研究

岩爆是高地应力岩石地下工程中的一种常见灾害,岩爆预测是岩爆研究中的重要研究课题。本文选取围岩最大切向应力与岩石抗压强度的比值σθ σc、岩石抗压和抗拉强度的比值σc σt和岩石弹性能量指数Wet作为评判指标,采用人工神经网络理论,根据给定的岩爆烈度分级标准构造学习样本集,建立了一种新的岩爆烈度预测模型。工程实例表明,所建议的模型预测精度高、通用性强,在岩爆烈度预测中具有良好的应用前景。     

Minimum sample size for extreme value statistics of flow-induced response

Extreme value statistics are one way to determine the maximum design loads for systems in extreme conditions, such as operational loads experienced by ships. Accurate predictions typically require large sample sizes, which are not always possible to obtain. Conversely, small sample sizes lead to more variation in the predictions. Increasing the sample size improves the variance to a desired range. The proposed method aimed to estimate a minimum sample size for an extreme value process by specifying and obtaining an acceptable variance. Minimum sample sizes for extreme value statistics depend on the distribution's behavior, so the method proposed here was designed for use before and during measurements. To test the proposed method, the response of a cantilever fin with a varying angle of attack was measured. The proposed method was able to estimate minimum sample sizes for several distributions. Accuracy was demonstrated by randomly drawing measured and simulated samples.     

道路交通网络中移动型检测器最小样本量优化方法研究

本文综合考虑交通流数据的质量及其成本等因素，对服务于ATMS的移动型检测器最小样本量的确定原则进行设计，建立一种基于行程时间估计最小样本量的确定方法，并利用微观仿真模拟软件对城市道路不同服务水平下的交通运行状态进行模拟分析。通过设置不同的检测器样本量方案，并利用优化方法对不同方案采集的交通流信息进行分析，确定合理的移动型检测器最小样本量。