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We consider inferring transit route‐level origin–destination (OD) flows using large amounts of automatic passenger counter (APC) boarding and alighting data based on a statistical formulation. One critical problem is that we need to enumerate the OD flow matrices that are consistent with the APC data for each bus trip to evaluate the model likelihood function. The OD enumeration problem has not been addressed satisfactorily in the literature. Thus, we propose a novel sampler to avoid the need to enumerate OD flow matrices by generating them recursively from the first alighting stop to the last stop of the bus route of interest. A Markov chain Monte Carlo (MCMC) method that incorporates the proposed sampler is developed to simulate the posterior distributions of the OD flows. Numerical investigations on an operational bus route under a realistic OD structure demonstrate the superiority of the proposed MCMC method over an existing MCMC method and a state‐of‐the‐practice method. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
243.
This study tests the impact of Internal and External Environmental Management on performance in firms subject to the European Union’s Emissions Trading System (ETS). A conceptual model is drawn up based on the existing literature, and tested on a large sample of Italian firms. The unit of analysis is single firms subject to the ETS that are involved in Green Supply Chain Management (GSCM). The ETS mechanism has been shown to be marginally beneficial for some firms while supply chain relationships are also influenced by such system. Firms need to identify suitable practices to boost the effectiveness of their environmental strategies. We propose the implementation of a monitoring strategy as a useful practice for firms to be environmentally and economically better off. Our results show that firms subject to the ETS should rely on their own (internal) Environmental Management alone for improving environmental performance, as collaboration with suppliers only has a positive impact on economic performance. However, implementation of a monitoring strategy allows a firm subject to the ETS to partially offset the inefficiency created by the system. We show that environmental collaboration does not become more effective when a monitoring practice is put in place. 相似文献
244.
As current oil reserves start to deplete, companies are looking to exploit deeper deposits. At these greater depths composite risers, with their high strength-to-weight ratio, reduce the effective tensions and bending moments compared to steel risers. However, there is still limited research into their behaviour, with one key missing element being a comparison with traditional riser designs which accounts for variances in material properties and wave loads. This paper therefore conducts a strength-based reliability analysis of composite catenary risers operating between 1,500 m and 4,000 m. A static global catenary model is combined with Classical Laminate Theory to determine the extreme response and its performance is verified against FEA. This response is evaluated with the Tsai-Wu failure criterion to determine first-ply failure. The effect of laminate moisture absorption on the long-term reliability of submerged composite-based risers is also investigated as it can cause a significant reduction in the strength of composite risers. The reliability analysis is conducted using the Monte Carlo Method, revealing that the composite risers perform well at 4000 m. The degradation in performance from moisture absorption becomes increasingly important at greater depths and needs further investigation for these applications. 相似文献
245.
Channelized section spillover (CSS) is usually referred to the phenomenon of a traffic flow being blocked upstream and not being able to enter the downstream channelized section. CSS leads to extra delays, longer queues, and a biased detection of the flow rate. An estimation of CSS, including its occurrence and duration, is helpful for analysis of the state of traffic flow, as a basis for traffic evaluation and management. This has not been studied or reported in prior literature. A Bayesian model is developed through this research to estimate CSS, with its occurrence and duration formulated as a posterior distribution of given travel time and flow rate data. Basic properties of CSS are discussed initially, followed by a macroscopic model that explicitly models the CSS and encapsulates first-in-first-out (FIFO) behavior at an upstream section, with a goal of generating the prior distribution of CSS duration. Posterior distribution is then constructed using the detected flow rate and travel time vehicles samples. The Markov Chain Monte Carlo (MCMC) sampling method is used to solve this Bayesian model. The proposed model is implemented and tested in a channelized intersection and its modeling results are compared with Vissim simulation outputs, which demonstrated satisfactory results. 相似文献
247.
This paper compares the vehicle purchasing behaviors in Japan between before and after the eco-car (environmental friendly vehicle) promotion policy implemented. Consumer behaviors are modeled as a two-stage decision process: a consideration set formation stage and a choice-making stage. In the first stage, all available vehicle types are included in the choice set, and consumers are assumed to apply a conjunctive screening rule to construct consideration sets. In the second stage, consumers only evaluate the vehicles in the consideration set and choose the one with maximum utility. The applied Hierarchical Bayes model can avoid the issue of an indifferentiable and irregular likelihood surface caused by thresholds and discontinuities, and the data augmentation and Markov-Chain Monte Carlo estimation methods make it possible to estimate two stages simultaneously using only the information about the consumers’ actual choices. The estimations indicate that the change of consumer behavior during the formation of consideration sets after the policy implemented: more people preferred compact and hybrid vehicles because of their better fuel efficiency and more competitive prices under the tax reduction policy. The results show, however, that most of consumers who purchase hybrid vehicles after the policy implemented are only including hybrid vehicles in their consideration sets, and oil price and vehicle price still play important roles in the choice-making stage for these who consider both gasoline and hybrid vehicles. 相似文献
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249.
项正良;申永江;马菲;杨明;徐伟国 《铁道科学与工程学报》2017,14(5):1029-1036
基于概率的有限可加性提出一种结构时变可靠度计算方法,并采用Monte Carlo方法予以实现。通过编程计算将服从正态分布的单次活载转化为等效的服从极值分布的时段最大活载,再分别采用本文方法和文献方法计算同一结构的时变可靠度。研究结果表明：本文方法可较准确地计算结构的时变可靠度;随着服役期增大,结构时变可靠度与时不变可靠度相差越来越大,采用时不变可靠度方法进行结构设计偏于危险;增大抗力会提高结构时变可靠度,增大恒载和活载则会导致结构时变可靠度下降。 相似文献
250.
针对目前铁路运输客运量预测在精度方面的不足,提出一种无偏灰色组合动态预测模型,应用于现有铁路客运量的预测。通过借鉴无偏GM（1,1）模型直接建模思想,对传统的灰色Verhulst模型作出改进,即对原始序列作倒数生成,运用新生成的倒数序列建立无偏灰色Verhulst模型,以消除传统的灰色Verhulst模型自身的一些偏差;为进一步提高模型的拟合精度及收敛速度,引入马尔科夫链方法对无偏灰色Verhulst模型的拟合结果进行修正,同时兼顾数据序列具有一定的时效性,构建出无偏灰色组合动态客运量预测模型。以我国兰青铁路某区段2010—2019年共10年的客运量数据作为原始数据,验证模型的可靠性与准确性,并与传统EDGM（1,1）模型、灰色Verhulst模型和无偏灰色Verhulst模型作对比,结果表明,本文模型在预测精度方面更凸显优势,能有效提高预测结果的准确性。 相似文献