scholarly journals Turnback Capacity Assessment and Delay Management at a Rail Transit Terminal with Two-Tail Tracks

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Zhibin Jiang ◽  
Yuyan Tan ◽  
Feng Wang ◽  
Lei Bu
Keyword(s):  
Positive Impact ◽  
Mixed Integer ◽  
Design Parameters ◽  
Rail Transit ◽  
Capacity Evaluation ◽  
Buffer Time ◽  
Study Results ◽  
And Performance ◽  
Allocation Strategies

Terminal capacity and performance have become a major concern for rail transit agencies in China due to the ever increasing passenger demand. This paper develops a mixed integer programming (MIP) optimization model to estimate the turnback capacity and performance of a rail transit terminal with two-tail tracks. The capacity evaluation and delay propagation are described and assessed as anN-track integrated model with minimal time span and train delay. Operations and design parameters such as tail track allocation strategies, maximum layover time, headway pattern, buffer time distribution scheme, and primary delay are also considered in this model. The effectiveness of the model is tested by a case study with computation results drawn from one terminal station in Shanghai, China. The case study results show that unfixed platform time and flexible tail track allocation strategies can improve the capacity of turnback operation, and the strategy of allowing swapping of the tail tracks has a significantly positive impact on delay absorption.

scholarly journals Perceived Trip Time Reliability and Its Cost in a Rail Transit Network

2021 ◽  
Vol 13 (13) ◽  
pp. 7504
Author(s):  
Jie Liu ◽  
Paul Schonfeld ◽  
Jinqu Chen ◽  
Yong Yin ◽  
Qiyuan Peng
Keyword(s):  
Regression Models ◽  
Influential Factors ◽  
Rail Transit ◽  
Linear Regression Models ◽  
Transit Network ◽  
Time Index ◽  
Trip Time ◽  
Buffer Time ◽  
Transfer Times

Time reliability in a Rail Transit Network (RTN) is usually measured according to clock-based trip time, while the travel conditions such as travel comfort and convenience cannot be reflected by clock-based trip time. Here, the crowding level of trains, seat availability, and transfer times are considered to compute passengers’ Perceived Trip Time (PTT). Compared with the average PTT, the extra PTT needed for arriving reliably, which equals the 95th percentile PTT minus the average PTT, is converted into the monetary cost for estimating Perceived Time Reliability Cost (PTRC). The ratio of extra PTT needed for arriving reliably to the average PTT referring to the buffer time index is proposed to measure Perceived Time Reliability (PTR). To overcome the difficulty of obtaining passengers’ PTT who travel among rail transit modes, a Monte Carlo simulation is applied to generated passengers’ PTT for computing PTR and PTRC. A case study of Chengdu’s RTN shows that the proposed metrics and method measure the PTR and PTRC in an RTN effectively. PTTR, PTRC, and influential factors have significant linear relations among them, and the obtained linear regression models among them can guide passengers to travel reliably.

scholarly journals Location Routing Problem with Consideration of CO2 Emissions Cost: A Case Study

2020 ◽  
Vol 21 (2) ◽  
pp. 225-234
Author(s):  
Ananda Noor Sholichah ◽  
Y Yuniaristanto ◽  
I Wayan Suletra
Keyword(s):  
Co2 Emissions ◽  
Time Windows ◽  
Optimal Solution ◽  
Mixed Integer ◽  
Distribution Centers ◽  
Location Routing Problem ◽  
Routing Problem ◽  
Location Routing ◽  
Study Results

Location and routing are the main critical problems investigated in a logistic. Location-Routing Problem (LRP) involves determining the location of facilities and vehicle routes to supply customer's demands. Determination of depots as distribution centers is one of the problems in LRP.  In LRP, carbon emissions need to be considered because these problems cause global warming and climate change. In this paper, a new mathematical model for LRP considering CO2 emissions minimization is proposed. This study developed a new  Mixed Integer Linear Programming (MILP)  model for LRP with time windows and considered the environmental impacts.  Finally, a case study was conducted in the province of Central Java, Indonesia. In this case study, there are three depot candidates. The study results indicated that using this method in existing conditions and constraints provides a more optimal solution than the company's actual route. A sensitivity analysis was also carried out in this case study.

scholarly journals Studying the Effects of Roads Geometry and Design Parameters on the Pavement Drainage System

2021 ◽  
Vol 7 (1) ◽  
pp. 49-58
Author(s):  
Mohammad Awwad
Keyword(s):  
Positive Impact ◽  
Drainage System ◽  
Road Construction ◽  
Design Parameters ◽  
Water Flow Velocity ◽  
The Road ◽  
Drainage Time ◽  
Operations And Maintenance ◽  
And Performance ◽  
Good Drainage

Background: Water floods have a considerable impact on roads sustainability by creating roads cracks, breaking down and holes, and failure for some other parts. The existence of good drainage system serviced the road and draining the water resulted from rain floods is crucial. These significant influences can be classified as positive or negative, low, moderate, or high. Aim and Objectives: This paper discusses the water floods and rainfall effects on roads and highways in Jordan as well as the drainage system on road sustainability and performance. The main aim of this paper is to investigate and analyse water as rainfall or floods affecting roads and highways in Jordan. The importance of this study is represented by studying and analysing the effects of rainfall and water floods on road construction and sustainability in Jordan after the latest high rain sizes of this winter and water floods, which affect the roads and highways in a good percentage. The other importance of the study is represented in offering solutions to problems caused by the environmental effects, specially floods and high rainfall rates. Methodology: all data and information about status of Jordanian roads during winter and floods are collected from real cases of about 40 main and semi-main roads in Jordan.  Results and Conclusions: A good drainage system and repair operations and maintenance generally have a positive impact on road sustainability and survival age. The effects of slopes of the road and surface of the asphalt, rainfall intensity, and water flow velocity on drainage length and drainage time and water depth are discussed here. Doi: 10.28991/cej-2021-03091636 Full Text: PDF

scholarly journals Freelancing Models for Fostering Innovation and Problem Solving in Software Startups: An Empirical Comparative Study

2020 ◽  
Vol 12 (23) ◽  
pp. 10106 ◽  
Author(s):  
Varun Gupta ◽  
Jose Maria Fernandez-Crehuet ◽  
Chetna Gupta ◽  
Thomas Hanne
Keyword(s):  
Software Development ◽  
Positive Impact ◽  
Empirical Studies ◽  
Competitive Advantages ◽  
Software Development Process ◽  
Model Framework ◽  
Study Results ◽  
Development Tasks

Context: freelancers and startups could provide each other with promising opportunities that lead to mutual growth, by improving software development metrics, such as cost, time, and quality. Niche skills processed by freelancers could help startups reduce uncertainties associated with developments and markets, with the ability to quickly address market issues (and with higher quality). This requires the associations between freelancers and startup to be long-term, based on trust, and promising agreements driven by motivations (leading to the growth of both parties). Freelancers could help startups foster innovations and undertake software development tasks in better ways than conducted in-house, if they are selected using informed decision-making. Objectives: the paper has three objectives, (1) to explore the strategies of startups to outsource software development tasks to freelancers (termed as freelancing association strategies); (2) to identify challenges in such outsourcings; and (3) to identify the impacts of outsourcing tasks to freelancers on overall project metrics. The overall objective is to understand the strategies for involving freelancers in the software development process, throughout the startup lifecycle, and the associated challenges and the impacts that help to foster innovation (to maintain competitive advantages). Method: this paper performs empirical studies through case studies of three software startups located in Italy, France, and India, followed by a survey of 54 freelancers. The results are analyzed and compared in the identification of association models, issues, challenges, and reported results arising because of such associations. The case study results are validated using members checking with the research participants, which shows a higher level of result agreements. Results: the results indicate that the freelancer association strategy is task based, panel based, or a hybrid. The associations are constrained by issues such as deciding pricing, setting deadlines, difficulty in getting good freelancers, quality issues with software artefacts, and efforts to access freelancer work submissions for reward. The associations have a positive impact on software development if there is availability of good freelancers (which lasts long for various tasks). The paper finally provides a freelancing model framework and recommends activities that could result in making the situation beneficial to both parties, and streamline such associations. Fostering innovation in startups is, thus, a trade-off situation, which is limited and supported by many conflicting parameters.

Risk-Averse Optimization for Resilience Enhancement Under Uncertainty

2020 ◽  
Author(s):  
Jiaxin Wu ◽  
Pingfeng Wang
Keyword(s):  
Large Scale ◽  
Risk Measure ◽  
Recovery Process ◽  
Recovery Phase ◽  
Mixed Integer ◽  
Network Systems ◽  
Additional Risk ◽  
Deterministic Equivalent ◽  
Study Results

Abstract With the growth of complexity and extent, large scale interconnected network systems, e.g., transportation networks or infrastructure networks, become more vulnerable towards external disturbances. Hence, managing potential disruptive events during design, operating, and recovery phase of an engineered system therefore improving the system’s resilience is an important yet challenging task. In order to ensure system resilience after the occurrence of failure events, this study proposes a mixed integer linear programming (MILP) based restoration framework using heterogenous dispatchable agents. Scenario based stochastic optimization (SO) technique is adopted to deal with the inherent uncertainties imposed on the recovery process from the nature. Moreover, different from conventional SO using deterministic equivalent formulations, additional risk measure is implemented for this study because of the temporal sparsity of the decision making in applications such as the recovery from extreme events. The resulting restoration framework involves with a large-scale MILP problem and thus an adequate decompaction technique, i.e., modified Langragian Relaxation, is also proposed in order to achieve tractable time complexity. Case study results based on the IEEE 37-buses test feeder demonstrate the benefits of using the proposed framework for resilience improvement as well as the advantages of adopting SO formulations.

A model for measuring the performance of the meat supply chain

2013 ◽  
Vol 115 (8) ◽  
pp. 1090-1111 ◽  
Author(s):  
Faranak Fattahi ◽  
Ali S. Nookabadi ◽  
Mahdi Kadivar
Keyword(s):  
Supply Chain ◽  
Case Study Research ◽  
Meat Industry ◽  
Performance Function ◽  
Content Type ◽  
Delphi Approach ◽  
Study Results ◽  
Overall Performance ◽  
And Performance

PurposeThe purpose of this paper is to analyze the characteristics and performance of the meat supply chain by focusing on developing a model for measuring the meat supply chain's performance in the province of Isfahan, Iran.Design/methodology/approachUsing a combination of literature review, Delphi approach and case study research, the paper examines part of the meat supply chain that consists of three industrial slaughterhouses, two cold rooms, three factories and more than 20 supermarkets and it then presents a framework to assess the performance of the industry in the region.FindingsThe methodology suggests indices for strategic and tactical levels in a meat industry as a case study. The proposed framework for the performance measurement of the chain was applied in strategic and tactical levels in which the ranking of indices are also among the achievements of this study. Results show that there are six main criteria required to measure the meat industry's performance.Originality/valueLiterature shows no record of an integrated measurement system for the entire food supply chain where indicators are combined into a performance function to assess the overall performance of the industry.

scholarly journals Study on the Influence of Psychological Intervention on Mood State and Coping Styles for High-Level Athletes: A Case Study for Wushu Sport in China

SAGE Open ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 215824402093251
Author(s):  
Hua Li
Keyword(s):  
Positive Impact ◽  
Mood State ◽  
Psychological Intervention ◽  
Coping Styles ◽  
Single Subject ◽  
Negative Coping ◽  
And Performance ◽  
High Level ◽  
And Coping

Psychological intervention has a positive impact on the competitive psychological ability and performance of athletes, while there are few studies on this subject. To improve the psychological ability of athletes’ mood and coping styles and promote the smooth progress of the competition, a single-subject experimental design model is used carry out psychological intervention on four high-level athletes for 8 months. According to the characteristics of Wushu routines, the psychological measurement and social validity evaluation are combined to explore the effect of psychological intervention. The results show that the mood state of four athletes improved obviously with the same trend. The coping styles showed a positive upward trend after psychological intervention. The results of three athletes also improved in the City Games. In addition, the results of “social validation” obtained from the coaches and athletes support the effectiveness of the intervention. Psychological intervention can effectively improve the bad mood and negative coping style of Wushu routine athletes so as to improve the competition of athletes.

scholarly journals Economic Management Based on Hybrid MPC for Microgrids: A Brazilian Energy Market Solution

Energies ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 3508 ◽  
Author(s):  
Eduardo Conte ◽  
Paulo R. C. Mendes ◽  
Julio E. Normey-Rico
Keyword(s):  
Predictive Control ◽  
Mixed Integer ◽  
Energy Market ◽  
High Fidelity ◽  
Management Problem ◽  
Economic Management ◽  
Central Controller ◽  
Energy Compensation ◽  
And Performance

This paper proposes a microgrid central controller (MGCC) solution to the energy management problem of a renewable energy-based microgrid (MG). This MG is a case study from the Brazilian energy market context and, thus, has some operational particularities and rules to be obeyed. The MGCC development was based on a hybrid model predictive control (HMPC) strategy using the mixed logical dynamic (MLD) approach to deal with logical constraints within the HMPC structure, which results in a mixed integer programming (MIP) problem. The development of the solution is done through economic and dynamic modeling of the MG components; furthermore, it also takes into account the energy compensation rules of the Brazilian energy market and the white energy tariff. These conditions are specified through a set of MLD constraints. The effectiveness and performance of the proposed solution are evaluated through high-fidelity numerical simulation.

Customer orientation and SME performance in Albania: A case study of the mediating role of innovativeness and innovation behavior

2019 ◽  
Vol 26 (1) ◽  
pp. 130-146 ◽  
Author(s):  
Shpresim Domi ◽  
Joan-Lluís Capelleras ◽  
Bari Musabelliu
Keyword(s):  
Customer Orientation ◽  
Positive Impact ◽  
Two Dimensions ◽  
Tourism Industry ◽  
Mediating Role ◽  
And Performance ◽  
The Relationship ◽  
Innovation Behavior

Although the tourism industry in Albania has had an impressive growth in the last years, it is currently facing several challenges. This study examines the determinants of Albanian tourism small and medium-sized enterprise (SME) performance. More specifically, the direct effects of customer orientation (CO) on performance and its indirect effects mediated by innovativeness and innovation behavior are investigated. Quantitative data from a survey conducted on 211 Albanian tourism SMEs, together with qualitative information gathered from personal interviews, are considered. Results indicate that CO has a direct positive impact not only on performance but also on both innovativeness and innovation behavior. However, none of these two dimensions of innovation play a mediating role in the relationship between CO and performance. Implications from these findings are discussed.

Enhancing construction project supply chains and performance evaluation methods: a case study of a bridge construction project

2010 ◽  
Vol 37 (8) ◽  
pp. 1094-1106 ◽  
Author(s):  
Nai-Hsin Pan ◽  
Yung-Yu Lin ◽  
Nang-Fei Pan
Keyword(s):  
Supply Chain ◽  
Performance Evaluation ◽  
Evaluation Method ◽  
Construction Project ◽  
Bridge Construction ◽  
Modeling Methodology ◽  
Scor Model ◽  
Study Results ◽  
And Performance

Construction supply chain management (cSCM) requires planning such that construction stages and logistics are coordinated and integrated to reduce costs, improve productivity, and generate a win–win situation for different parties. The supply chain operations reference (SCOR), which has been widely applied in other industries, is a standardized operational modeling methodology for analyzing supply chain processes. This study considers construction industry characteristics in applying the SCOR model to develop a dynamic cSCM model using computer simulation. Furthermore, this study developed a novel cSCM performance evaluation method using the SCOR method to evaluate cSCM performance and identify and solve cSCM problems. This study uses a bridge construction project as a case study, which determines the relationships among supply chain participants to enhance communication efficiency and identify problems related to materials management. The case study results demonstrate that the proposed hybrid modeling methodology helps construction supply chain participants identify their roles and communicate easily, helps project managers identify bottlenecks in a supply chain, and significantly improves cSCM performance.

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