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- Liu, Tianyou, et al.
(författare)
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Modeling the Duration of the Impact of Unplanned Disruptions on Passenger Trips Using Smartcard Data in Urban Rail Systems
- 2023
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Ingår i: URBAN RAIL TRANSIT. - : Springer Nature. - 2199-6687. ; 9:3, s. 266-279
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Tidskriftsartikel (refereegranskat)abstract
- Many urban rail systems operate near capacity given the rapid increase in passenger demand, and unplanned disruptions are unavoidable. From a passenger perspective, the duration of trip delays is a major concern, and passenger trip delays may be longer than the train delays. Several studies have focused on predicting train delays, but the research on the duration of the disruption impacts on passenger trips is limited given that the duration is not observed directly. This paper proposes a probabilistic method to estimate the disruption impact duration using smartcard data, explores statistical and machine learning models to predict the duration of impacts on passengers, and identifies influencing factors including incident characteristics, operating conditions, infrastructure, external factors, and demand. The results highlight that prediction accuracies are acceptable for multiple linear regression, accelerated failure time, and random forest models. Disruptions caused by power failures have longer impact durations than other causes, followed by platform screen doors. The fixed block signaling system leads to a larger disruption duration than the moving block system. The study provides, for the first time, a data-driven approach to understanding the duration of the impact of disruptions on passenger trips using smartcard data which can facilitate timely and informed decision-making under unplanned disruptions.
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| 2. |
- Xu, Guangfu, et al.
(författare)
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Evaluation of variable compression ratio (VCR)and variable valve timing (VVT)strategies in a heavy-duty diesel engine with reactivity controlled compression ignition (RCCI)combustion under a wide load range
- 2019
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 253, s. 114-128
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Tidskriftsartikel (refereegranskat)abstract
- Variable compression ratio (VCR)and variable valve timing (VVT)are two effective strategies to adjust the effective compression ratio, which is beneficial for controlling the combustion process of advanced combustion modes. In this study, systematic evaluation of the two strategies was conducted based on reactivity controlled compression ignition (RCCI)engine in terms of combustion process control, fuel efficiency, and emission characteristics. By coupling an updated KIVA-3V code with the genetic algorithm, the combustion of a heavy-duty RCCI engine with VCR and VVT strategies was respectively optimized, aiming to simultaneously realize high fuel efficiency and low emissions. The optimal VCR and VVT strategies were compared under a wide load range. The results indicate that, at low and mid loads, high effective compression ratio, large premix ratio, and early fuel injection can be utilized to realize Euro 6 nitrogen oxides (NO x )limit with ultra-low soot emissions and low fuel consumption for both VCR and VVT strategies. The increase of load from low to mid narrows the optimal range of exhaust gas recirculation (EGR)rate for VVT strategy whereas the range for VCR strategy is still wide. At high load, compared to VVT strategy, a further decreased effective compression ratio can be utilized for VCR strategy, which allows early fuel injection, leading to the improvements of fuel efficiency and soot emissions. This suggests that the VCR strategy is more practical for high-load operation of RCCI combustion and the commercialization the RCCI engine in the future compared to VVT strategy.
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