scholarly journals Optimizing High-Speed Railroad Timetable with Passenger and Station Service Demands: A Case Study in the Wuhan-Guangzhou Corridor

2018 ◽  
Vol 2018 ◽  
pp. 1-18 ◽  
Author(s):  
Jin Wang ◽  
Leishan Zhou ◽  
Yixiang Yue ◽  
Jinjin Tang ◽  
Zixi Bai
Keyword(s):  
Lower Bound ◽  
High Speed ◽  
Programming Model ◽  
Optimal Solution ◽  
Travel Speed ◽  
Time Space ◽  
Proposed Model ◽  
Travel Efficiency ◽  
High Speed Railroad

This paper aims to optimize high-speed railroad timetables for a corridor. We propose an integer programming model using a time-space network-based approach to consider passenger service demands, train scheduling, and station service demands simultaneously. A modified branch-and-price algorithm is used for the computation. This algorithm solves the linear relaxation of all nodes in a branch-and-bound tree using a column generation algorithm to derive a lower-bound value (LB) and derive an upper-bound value (UB) using a rapid branching strategy. The optimal solution is derived by iteratively updating the upper- and lower-bound values. Three acceleration strategies, namely, initial solution iteration, delayed constraints, and column removal, were designed to accelerate the computation. The effectiveness and efficiency of the proposed model and algorithm were tested using Wuhan-Guangzhou high-speed railroad data. The results show that the proposed model and algorithm can quickly reduce the defined cost function by 38.2% and improve the average travel speed by 10.7 km/h, which indicates that our proposed model and algorithm can effectively improve the quality of a constructed train timetable and the travel efficiency for passengers.

scholarly journals Wind Farm Cable Connection Layout Optimization with Several Substations

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3615
Author(s):  
Adelaide Cerveira ◽  
Eduardo J. Solteiro Pires ◽  
José Baptista
Keyword(s):  
Energy Production ◽  
Wind Farm ◽  
Programming Model ◽  
Optimal Solution ◽  
Wind Farms ◽  
Green Energy ◽  
Fossil Energy ◽  
Proposed Model ◽  
Short Time ◽  
Cable Connection

Green energy has become a media issue due to climate changes, and consequently, the population has become more aware of pollution. Wind farms are an essential energy production alternative to fossil energy. The incentive to produce wind energy was a government policy some decades ago to decrease carbon emissions. In recent decades, wind farms were formed by a substation and a couple of turbines. Nowadays, wind farms are designed with hundreds of turbines requiring more than one substation. This paper formulates an integer linear programming model to design wind farms’ cable layout with several turbines. The proposed model obtains the optimal solution considering different cable types, infrastructure costs, and energy losses. An additional constraint was considered to limit the number of cables that cross a walkway, i.e., the number of connections between a set of wind turbines and the remaining wind farm. Furthermore, considering a discrete set of possible turbine locations, the model allows identifying those that should be present in the optimal solution, thereby addressing the optimal location of the substation(s) in the wind farm. The paper illustrates solutions and the associated costs of two wind farms, with up to 102 turbines and three substations in the optimal solution, selected among sixteen possible places. The optimal solutions are obtained in a short time.

scholarly journals A Study on the Practical Carrying Capacity of Large High-Speed Railway Stations considering Train Set Utilization

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Bin Guo ◽  
Leishan Zhou ◽  
Yixiang Yue ◽  
Jinjin Tang
Keyword(s):  
Carrying Capacity ◽  
High Speed ◽  
Programming Model ◽  
High Speed Railway ◽  
Railway Stations ◽  
China Studies ◽  
Important Nodes ◽  
Entire Network

Methods for solving the carrying capacity problem for High-Speed Railways (HSRs) have received increasing attention in the literature in the last few years. As important nodes in the High-Speed Railway (HSR) network, large stations are usually the carrying capacity bottlenecks of the entire network due to the presence of multiple connections in different directions and the complexity of train operations at these stations. This paper focuses on solving the station carrying capacity problem and considers train set utilization constraints, which are important influencing factors that have rarely been studied by previous researchers. An integer linear programming model is built, and the CPLEX v12.2 software is used to solve the model. The proposed approach is tested on a real-world case study of the Beijing South Railway Station (BS), which is one of the busiest and most complex stations in China. Studies of the impacts of different train set utilization constraints on the practical station carrying capacity are carried out, and some suggestions are then presented for enhancing the practical carrying capacity. Contrast tests indicate that both the efficiency of the solving process and the quality of the solution show huge breakthroughs compared with the heuristic approach.

scholarly journals Mixed Optimal Scheduling Model of Flexible Service System Based on Inverted Triangle

2019 ◽  
Vol 2019 ◽  
pp. 1-20 ◽  
Author(s):  
Shipei Hu ◽  
Yujun Sun
Keyword(s):  
Integer Programming ◽  
Programming Model ◽  
Optimal Solution ◽  
Working Hours ◽  
Binary Integer Programming ◽  
Scheduling Model ◽  
Programming Software ◽  
Working Day ◽  
Zhejiang Provincial

In the study presented in this paper, we built a nonlinear binary integer programming model of a flexible scheduling problem for the Department of Zhejiang Provincial Local Tax Services. One difference between our model and typical ones is that whereas in the latter the number of open windows within each working day is fixed, in our model it is not. We used a variety of integer programming software in an attempt to solve our scheduling model; however, unfortunately we could not find an optimal solution. Thus, we tested all the combinations of different numbers of employees to construct the optimal solution. When we tested our model in the tax office of Lishui City, China, the average waiting time of taxpayers was less than 15 min and the employees working hours were clearly reduced. Thus, a noteworthy improvement in the quality of the service is achieved by the model.

scholarly journals Global optimization approach for circular and chloroplast genome assembly

2017 ◽  
Author(s):  
Sebastien François ◽  
Rumen Andonov ◽  
Dominique Lavenier ◽  
Hristo Djidjev
Keyword(s):  
Global Optimization ◽  
Genome Assembly ◽  
Programming Model ◽  
Optimal Solution ◽  
Optimization Approach ◽  
Gap Filling ◽  
Insert Size ◽  
Genome Scaffolding ◽  
Additional Constraints

AbstractWe describe a global optimization approach for genome assembly where the steps of scaffolding, gap-filling, and scaffold extension are simultaneously solved in the framework of a common objective function. The approach is based on integer programming model for solving genome scaffolding as a problem of finding a long simple path in a specific graph that satisfies additional constraints encoding the insert-size information. The optimal solution of this problem allows one to obtain new kind of contigs that we call distance-based contig. We test the algorithm on a benchmark of chloroplasts and compare the quality of the results with recent scaffolders.

Stochastic Model of Train Running Time and Arrival Delay: A Case Study of Wuhan–Guangzhou High-Speed Rail

2018 ◽  
Vol 2672 (10) ◽  
pp. 215-223 ◽  
Author(s):  
Javad Lessan ◽  
Liping Fu ◽  
Chao Wen ◽  
Ping Huang ◽  
Chaozhe Jiang
Keyword(s):  
High Speed ◽  
Service Management ◽  
Empirical Distribution ◽  
Distribution Models ◽  
High Speed Rail ◽  
Proposed Model ◽  
Train Operation ◽  
Individual Track

Train operations are subject to stochastic variations, reducing service punctuality and thus the quality of service (QoS). Models of such variations are needed to evaluate and predict the potential impact of disturbances and to avoid service punctuality reduction in train service management and timetabling. In this paper, through a case study of the Wuhan–Guangzhou (WH–GZ) high-speed rail (HSR), we show how a wealth of train operation records can be used to model the stochastic nature of train operations at each level, section and station. Specifically, we examine different distribution models for running times of individual sections and show that the Log-logistic probability density function is the best distributional form to approximate the empirical distribution of running times on the specified line. Next, we show that the distribution of running times in each section can be used to accurately infer arrival delays. Consequently, we construct the underlying analytical model and derive the respective arrival delay distribution at the downstream stations. The results support the correctness of the model presented and show that the proposed model is suitable for constructing the distribution of arrival delays at every station of the specified line. We show that the integrated distribution models of running times and arrival delays, driven by empirical data, can also be used to evaluate the QoS at individual track sections.

scholarly journals Design of timetable for airport coach based on ‘time–space’ network and passenger’s trip chain

Transport ◽  
2015 ◽  
Vol 33 (1) ◽  
pp. 32-40
Author(s):  
Jing Lu ◽  
Zhongzhen Yang ◽  
Xiadan Dong ◽  
Xiaocong Zhu
Keyword(s):  
Practical Method ◽  
Unit Operation ◽  
Hub And Spoke ◽  
Space Network ◽  
Trip Chain ◽  
Time Space ◽  
Proposed Model ◽  
Access Service ◽  
Operation Cost

This paper designs the timetable for the airport coach which is a new access service provided by the airport with the purpose of attracting more passengers. Firstly, the ‘time–space’ network is constructed for analyzing the formation of the passengers’ trip chain; Secondly, the timetable design model is built with the aim to minimize the unit operation cost per transported passenger of the airport coach and a genetic algorithm with matrix coding is used for solving the model. In the model, the coach departure time and the flight schedule are connected with each other; the quality of the coach service and the passenger’s demand are both considered. Finally, the coach of Dalian airport in China is taken as an example to test the proposed method. Through solving the model and sensitivity analysis, we obtain a coach timetable for Dalian airport. The results show that the proposed model can provide a practical method to design the timetable for the airport coaches with ‘hub-and-spoke’ network.

Emergency Logistics System Based on Bilevel Optimization Model

2013 ◽  
Vol 694-697 ◽  
pp. 3605-3609
Author(s):  
Bo Liu ◽  
Bo Li ◽  
Yan Li
Keyword(s):  
Genetic Algorithm ◽  
Bilevel Programming ◽  
Programming Model ◽  
Hybrid Genetic Algorithm ◽  
Optimal Solution ◽  
Bilevel Optimization ◽  
Logistics System ◽  
Emergency Logistics ◽  
Proposed Model ◽  
Bilevel Programming Model

A bilevel programming model is established to determine the emergency storage centers location and the resource supply plan of the provincial and municipal levels by the collaborative mode of the vertical supply and lateral transfer for the emergency logistics system in the unusual emergencies. And the optimal solution is obtained by the hybrid genetic algorithm. Finally, the case shows the effectiveness of the proposed model and its algorithm.

A Cooperative Scheduling Model for Subway Trains

2012 ◽  
Author(s):  
Xiang Li ◽  
Xin Yang ◽  
Hongwei Wang ◽  
Shuai Su ◽  
Wenzhe Sun
Keyword(s):  
Time Window ◽  
Programming Model ◽  
Electric Energy ◽  
Optimal Solution ◽  
Optimization Approach ◽  
Trip Time ◽  
Proposed Model ◽  
Time Window Constraints ◽  
Braking Phase ◽  
Cooperative Scheduling

For subway systems, the energy put into accelerating the trains can be reconverted into electric energy by using the motors as generators during braking phase. Generally speaking, except a small part is used for on-board purposes, most of the recovery energy is transmitted backwards along the conversion chain and fed back into the catenary. However, since the low catenary voltage DC systems, the transmission losses are very high. In order to improve the utilization of recovery energy, this paper proposes an optimization approach to cooperate the acceleration and brake times of successive trains such that the recovery energy from the braking train can be directly used by the accelerating train. First, we formulate a quadratic programming model to optimize the cooperative degree with trip time constraint and time window constraints. Furthermore, we solve the optimal solution by using the Kuhn-Tucker conditions. Finally, we present a numerical example based on the operation data from Beijing Yizhuang subway line of China, which illustrates that the proposed model can improve the cooperative degree by 9.08%.

scholarly journals Meta Learning for Image Captioning

2019 ◽  
Vol 33 ◽  
pp. 8626-8633
Author(s):  
Nannan Li ◽  
Zhenzhong Chen ◽  
Shan Liu
Keyword(s):  
Optimal Solution ◽  
Ground Truth ◽  
Propositional Content ◽  
Image Captioning ◽  
Reward Function ◽  
Proposed Model ◽  
New Learning ◽  
Meta Learning ◽  
Global Optimal

Reinforcement learning (RL) has shown its advantages in image captioning by optimizing the non-differentiable metric directly in the reward learning process. However, due to the reward hacking problem in RL, maximizing reward may not lead to better quality of the caption, especially from the aspects of propositional content and distinctiveness. In this work, we propose to use a new learning method, meta learning, to utilize supervision from the ground truth whilst optimizing the reward function in RL. To improve the propositional content and the distinctiveness of the generated captions, the proposed model provides the global optimal solution by taking different gradient steps towards the supervision task and the reinforcement task, simultaneously. Experimental results on MS COCO validate the effectiveness of our approach when compared with the state-of-the-art methods.

Variable-Capacity Operations with Modular Transits for Shared-Use Corridors

2020 ◽  
Vol 2674 (9) ◽  
pp. 230-244
Author(s):  
Xiaowei Shi ◽  
Zhiwei Chen ◽  
Mingyang Pei ◽  
Xiaopeng Li
Keyword(s):  
Programming Model ◽  
Optimal Solution ◽  
Operating Costs ◽  
Mixed Integer ◽  
Transit Systems ◽  
Persistent Problem ◽  
Proposed Model ◽  
Variable Capacity ◽  
New Perspective ◽  
In Transit

Since passenger demand in urban transit systems is asymmetrically distributed across different periods in a day and different geographic locations across the cities, the tradeoff between vehicle operating costs and service quality has been a persistent problem in transit operational design. The emerging modular vehicle technology offers us a new perspective to solve this problem. Based on this concept, we propose a variable-capacity operation approach with modular transits for shared-use corridors, in which both dispatch headway and vehicle capacity are decision variables. This problem is rigorously formulated as a mixed integer linear programming model that aims to minimize the overall system cost, including passenger waiting time costs and vehicle operating costs. Because the proposed model is linear, the state-of-the-art commercial solvers (e.g., Gurobi) can be used to obtain the optimal solution of the investigated problem. With numerical experiments, we demonstrate the feasibility of the mathematical model, verify the effectiveness of the proposed model in reducing overall system costs in transit systems, as well as the robustness of the proposed model with different parameter settings.

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