TBM刀盘系统不确定工况下的动力学特性分析

为解决全断面岩石掘进机（TBM）刀盘系统由于掘进过程中工况不确定性造成的载荷不确定和动态特性预测难度大的问题,提出一种工况不确定性的动力学分析方法。首先,对4种典型掘进工况进行等效,采用区间理论将不同工况的等效载荷进行区间表示,并将工况的不确定性转化为载荷的不确定性; 然后,通过集中质量法建立刀盘多自由度耦合动力学模型,并结合得到的区间不确定载荷等效出不确定工况下的多自由度耦合动力学模型,求解得到不确定工况下的动力学响应; 最后,以现场实测数据对该方法进行验证。研究结果表明： TBM在设计时应充分考虑工况的差异性; 随着刀盘分块的增多,刀盘系统稳定性有所提高; 驱动齿轮均匀分布时,刀盘系统振动稳定性较好。     

Optimal reefer slot conversion for container freight transportation

Given a fleet of container ships of varying capacity, a cost-efficient approach for improving fleet utilization and reducing the number of delayed containers is to optimize the sequence of container ships in a given string, a problem which belongs to the large ship-deployment class. A string sequence with ‘uniformly’ distributed ship capacity is more likely to accommodate a random container shipment demand. The number of one’s total ship slots acts as a gauge of the capacity of the container ships. Meanwhile, there are two types of ship slots: dry slots and reefer slots. A dry slot only accommodates a dry container, while a reefer slot can accommodate either a dry or a reefer container. The numbers of dry and reefer slots for ships in a string are different. Therefore, in this study, we propose a model that considers both dry and reefer slots and use it to elucidate the optimal ship-deployment sequence. The objective is to minimize the delay of dry and reefer containers when the demand is uncertain. Furthermore, based on the optimal sequence deduced, the study also investigates the need to convert some dry slots to reefer slots for the container ships.     

Uncertainty analysis of the large zone economic module of the simple,efficient, elegant,and effective model (SE3M) of land use and transportation

Integrated land use and transportation forecasting models are used to assist decision-makers in the policy analysis and infrastructure capital improvement selection process. These models are typically given precise, point-estimate inputs that are mathematically linked, through a series of submodels, to forecasted model outputs. These point-estimate inputs represent an unrealistic level of precision and a growing body of research is focusing on statistical techniques to model uncertainty in model inputs and parameters and tracking the effects of this uncertainty through the various submodels to the model outputs. This paper presents an uncertainty analysis of the Large Zone Economic Module (LZEM) of the Simple, Efficient, Elegant, and Effective Model (SE³M) of land use and transportation. Three case-study implementations of the model are used to obtain a reasonably sound approximation of how uncertainty affects LZEM outputs: Guam, Puerto Rico, and Oahu, Hawaii. These case studies were the subject of an early transferability study with SE³M and were selected based on both their insularity and diverse physical, economic, and demographic geographies. The findings of this research demonstrate that LZEM has a robust framework, with the potential to estimate error both in the positive and negative direction under uncertain input/parameter conditions.     

气相色谱仪灵敏度的测量不确定度的评定

为了检定气相色谱仪数据的准确性,要考虑检定不确定度的影响.通过对气相色谱仪热导检测器(TCD)灵敏度进行校准过程中引入的不确定度分量进行了评定.TCD灵敏度的相对不确定度为2.1%,扩展不确定度为4.2%(k=2),所有检定项目中,标准样品进样量的不确定度是最大的.此方法简单、实用,可用于带色谱工作站的GC的校准.     

铁路桥梁浅基础设计变量的不确定性分析

设计变量不确定性的计算分析是可靠性理论修订规范的基础工作。本文对铁路桥梁浅基础可靠度设计中各种变量的不确定性 进行了分析计算，推导了其作用荷载和地基土抗力的变异系数的计算表达式，可供可靠度理论规范改革时参考和作用。     

Capacity investment model for airport facilities under demand uncertainty

This paper addresses strategic airport facility planning under demand uncertainty. Existing studies are improved by (1) allowing capacity contraction and (2) adopting more flexible delay functions. A mixed‐integer nonlinear program, which incorporates scale economies in construction, time value of money, nonlinear congestion effect, and other factors, is proposed for optimizing the capacity expansion/contraction decisions over time for multiple airport components. The stochastic problem is converted into its deterministic equivalent because the number of demand scenarios considered is finite. A discrete approximation technique is used to remove the nonlinearities. Numerical studies are presented to demonstrate the capability of the proposed model and the computational efficiency of the solution method. The “Flaw of Averages” due to faulty decisions based on the average future condition is illustrated, and trade‐offs among various costs are discussed in the numerical analyses. Copyright © 2016 John Wiley & Sons, Ltd.     

Drivers’ parking location choice under uncertain parking availability and search times: A stated preference experiment

To assess parking pricing policies and parking information and reservation systems, it is essential to understand how drivers choose their parking location. A key aspect is how drivers’ behave towards uncertainties towards associated search times and finding a vacant parking spot. This study presents the results from a stated preference experiment on the choice behaviour of drivers, in light of these uncertainties. The attribute set was selected based on a literature review, and appended with the probabilities of finding a vacant parking spot upon arrival and after 8 min (and initially also after 4 min, but later dropped to reduce the survey complexity). Efficient Designs were used to create the survey design, where two rounds of pilot studies were conducted to estimate prior coefficients. Data was successfully collected from 397 respondents. Various random utility maximisation (RUM) choice models were estimated, including multinomial logit, nested logit, and mixed logit, as well as models accounting for panel effects. These model analyses show how drivers appear to accept spending time on searching for a vacant parking spot, where parking availability after 8 min ranks second most important factor in determining drivers’ parking decisions, whilst parking availability upon arrival ranks fourth. Furthermore, the inclusion of heterogeneity in preferences and inter-driver differences is found to increase the predictive power of the parking location choice model. The study concludes with an outlook of how these insights into drivers’ parking behaviour can be incorporated into traffic assignment models and used to support parking systems.     

Uncertainty modeling for bus selection and allocation in a private transportation system

ABSTRACT

This paper describes the development of a probabilistic formulation that provides global optimum selection and allocation of a fleet of buses in a private transportation system of an organization where a third party is hired to provide transportation for its employees and their dependents. In this private transportation system, a fleet of buses is to be selected and allocated to serve employees and their independents on different prescheduled trips along different routes from the organization’s headquarters and residential compound where round-trip times of scheduled trips are subject to uncertainty due to random delays. We propose a probabilistic approach based on 0-1 integer programming for the selection and allocation to determine the optimal number and size of buses assigned to a set of prescheduled trips in a particular time interval. Examples and a case study are presented to illustrate the applicability and suitability of the proposed approach.     

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区域公交调度是未来城市公共交通的发展趋势,主要解决如何合理统一安排最初分布于不同车场的车辆完成所有线路固定时刻表对应班次任务,从而减少车队规模和降低营运成本.考虑现实中许多突发事件干扰车辆按时完成班次,借助双层规划模型,本文探讨区域公交车辆调度和购车计划之间的有机联系,在满足多车型、车场容量限制、燃料限制等现实因素基础上,设计求解上下层模型的遗传算法,引入满意解的概念,将下层规划产生的一组满意解供上层规划比选,进而生成最佳公交车调度方案,以及与之对应的购车计划.最后给出了一个实例,验证模型和算法的正确性和有效性.     

基于区间矩阵的时态关系的简化方法

用区间代数能表示不确定的时态关系,可以方便地应用于时态推理,表达能力强。将区间代数及区间矩阵中有端点相等的基本关系去掉,只保留现实世界中真正可能发生的基本关系,大大降低了问题的复杂性,然后,对每个原子矩阵建立一个特征集,用特征集的并运算来取代矩阵的复合运算,提高了计算效率。