1,721,058 research outputs found
New route relaxation and pricing strategies for the vehicle routing problem
No full textIn this paper, we describe an effective exact method for solving both the capacitated vehicle routing problem (cvrp) and the vehicle routing problem with time windows (vrptw) that improves the method proposed by Baldacci et al. [Baldacci, R., N. Christofides, A. Mingozzi. 2008. An exact algorithm for the vehicle routing problem based on the set partitioning formulation with additional cuts. Math. Programming 115(2) 351-385] for the cvrp. The proposed algorithm is based on the set partitioning (SP) formulation of the problem. We introduce a new route relaxation called ng-route, used by different dual ascent heuristics to find near-optimal dual solutions of the LP-relaxation of the SP model. We describe a column-and-cut generation algorithm strengthened by valid inequalities that uses a new strategy for solving the pricing problem. The new ng-route relaxation and the different dual solutions achieved allow us to generate a reduced SP problem containing all routes of any optimal solution that is finally solved by an integer programming solver. The proposed method solves four of the five open Solomon's vrptw instances and significantly improves the running times of state-of-the-art algorithms for both vrptw and cvrp. Subject classifications: vehicle routing; time windows; dual ascent heuristic; column-and-cut generation. Area of review: Transportation. History: Received March 2010; revision received September 2010; accepted November 2010. © 2011 INFORMS
Exact method for the vehicle routing problem with backhauls
No full textWe consider the problem in which a fleet of vehicles located at a central depot is to be optimally used to serve a set of customers partitioned into two subsets of linehaul and backhaul customers. Each route starts and ends at the depot and the backhaul customers must be visited after the linehaul customers. A new (0-1) integer programming formulation of this problem is presented. We describe a procedure that computes a valid lower bound to the optimal solution cost by combining different heuristic methods for solving the dual of the LP-relaxation of the exact formulation. An algorithm for the exact solution of the problem is presented. Computational tests on problems proposed in the literature show the effectiveness of the proposed algorithms in solving problems up to 100 customers
Optimizing Sustainable Production in the Readymade Garments Industry: A Multi-Objective Approach
No full textThe Readymade Garments (RMG) industry in Bangladesh is a significant economic driver but faces challenges concerning environmental sustainability. This research explores optimizing production processes to balance profit maximization with environmental impact minimization. A multi-objective optimization model is developed and applied to a case study involving ten commonly produced garments. The analysis confirms the inherent trade-off between economic and environmental objectives. Increased production leads to higher profits but also a heavier environmental footprint. A feasible production range is identified, with key insights provided on navigating the tradeoff between profit and environmental impact. This research proposes an implementation roadmap for RMG companies to utilize the developed multi-objective optimization model. This research demonstrates the potential of the model for promoting sustainable growth in the Bangladeshi RMG industry
QFD-based optimization model for mitigating sustainable supply chain management adoption challenges for Bangladeshi RMG industries
Full text linkIn response to heightened pressures from regulatory mandates, global competition, and evolving customer expectations, industries worldwide are compelled to prioritize environmental initiatives, often at the expense of economic considerations. The research gap addressed in this study is the lack of a comprehensive, data-driven optimization model for effectively mitigating sustainable supply chain management adoption challenges specific to the Bangladeshi Readymade Garments (RMG) industry. While previous studies often relied on single techniques, this research proposes a novel AHP integrated QFD-based MILP optimization model. This innovative approach empowers Bangladeshi RMG industries to make data-driven decisions for prioritizing sustainability challenges and selecting cost-effective mitigation strategies to promote the integration of sustainability initiatives within the sector. The study identifies and prioritizes 25 sustainable supply chain management adoption challenges and proposes 16 mitigation strategies. The model emphasizes the critical interplay between sustainability performance and implementation costs, achieving a sustainability performance score of 0.4511 while effectively implementing 12 out of 16 strategies within the expected budget. The optimal solution incorporates green strategies, technology integration, and aspects of Industry 5.0, demonstrating a holistic approach to sustainable supply chain management. The findings are crucial for Bangladeshi RMG industries aiming for global market competitiveness and contribute significantly to the academic field by introducing a robust, data-driven decisions for sustainable supply chain optimization. The implications extend beyond the RMG sector, offering a replicable model for other industries and regions facing similar sustainability challenges
Multimodel Simulations of Hydrogen Refueling Stations: Stock Levels, Infrastructure, and Performance Evaluation Under Stochastic Vehicle Inflows in the Gulf–Europe Corridor
No full textThis study employs multimodel simulations, including road traffic, process, and system dynamics modeling, to analyze hydrogen refueling stations (HRSs) in the Gulf–Europe corridor, also known as the Iraq’s development road project (DRP). It focuses on operational requirements, which consist of stock levels and infrastructure needs, along with refueling performance under stochastic vehicle inflows (SVIs) from the Gulf, European countries, and Iraq’s side roads (SRs). The research aims to identify key operational requirements and evaluate the refueling performance of an HRS for various stochastic vehicle inflow (SVI) scenarios, facilitating the efficient integration of hydrogen fuel cell vehicles (HFCVs) into freight networks. The study introduces novel multimodel simulations developed in the AnyLogic software environment to replicate real-world variability in vehicle inflows. Key findings reveal that SVIs significantly impact hydrogen stock level (HSL), infrastructure requirements (IRs), and refueling performance metrics (RPMs). For example, for a daily transportation demand of 30,000 tons of goods with 10%–20% side road (SR) vehicle entries, an HRS requires an IR-1 of 3, an IR-2 of 2, and an HSL of 44,391.6 kg, with performance reflected in refueling performance metric (RPM)-1 values of 73%, 72%, and 45%, and an RPM-2 range of 1.32–6.12 min. This proves that the HRS requirements and performance vary with SVIs for different transportation demands. Hence, we enhance the theoretical framework of refueling station design by integrating multimodel simulations to address stochastic inflows. It offers actionable insights for policymakers on optimizing HRS operations, improving scalability, and achieving United Nations sustainable development goals (SDGs)
Trade, economic growth, and transportation sustainability perspectives of the Gulf-Europe corridor in the GCC countries
Full text linkThe Gulf-Europe transportation project, also known as Iraq’s Development Road Project (DRP), is a transformative supply
chain initiative aimed at constructing a corridor from Al Faw Port in Iraq to Turkey, linking Gulf Cooperation Council (GCC)
countries with Europe. The project’s goal is to establish a robust transport corridor through the extensive construction
of roads and railways, facilitating the fast and seamless movement of goods between the East and the West. By creating
land-based direct transportation routes to complement traditional maritime pathways, the project seeks to reduce transit
times, lower shipping costs, increase trade flows, and improve regional integration. This study qualitatively examines how
the corridor will impact trade, the economy, and transportation sustainability in the Gulf nations. We explore potential
increases in trade volumes, foreign investments, logistics sustainability, and economic diversification within the region.
Additionally, we recommend the adoption of hydrogen fuel cell vehicles (HFCVs) and hydrogen-powered trains in the
corridor to align with the United Nations Sustainable Development Goals (SDGs). Furthermore, we suggest that the
corridor’s development will create opportunities for economic diversification and reduce the GCC countries’ reliance on
oil revenues. Finally, the study provides strategic recommendations for policymakers and stakeholders to maximize the
project’s benefits and address potential challenges, emphasizing its potential to drive long-term economic growth and
strengthen the GCC countries’ global trade positioning
Capacitated ring arborescence problems with profits
No full textIn this work, we introduce profit-oriented capacitated ring arborescence problems and present exact and heuristic algorithms. These combinatorial network design problems ask for optimized bi-level networks taking into account arc costs and node profits. Solutions combine circuits on the inner level with arborescences on the outer level of the networks. We consider the prize-collecting, the budget-constrained and the target-profit models and develop corresponding exact branch-and-cut algorithms based on mixed-integer formulations and valid inequalities. Iterated local search heuristics based on the exploration of problem-specific neighborhoods are elaborated to strengthen the upper bounds. For a set of hard literature derived instances with up to 51 nodes, we provide computational results which give evidence for the efficiency of the proposed approaches. Furthermore, we extensively analyze the performance of our methods, the obtained solution networks and the impact of the cutting planes on the obtained lower bounds
Recent exact algorithms for solving the vehicle routing problem under capacity and time window constraints
No full textThis paper provides a review of the recent developments that had a major impact on the current state-of-the-art exact algorithms for the vehicle routing problem (VRP). The paper reviews mathematical formulations, relaxations and recent exact methods for two of the most important variants of the VRP: the capacitated VRP (CVRP) and the VRP with time windows (VRPTW). The paper also reports a comparison of the computational performances of the different exact algorithms for the CVRP and VRPTW. © 2011 Elsevier B.V. All rights reserved
New pricing strategies and an effective exact solution framework for profit-oriented ring arborescence problems
No full textWe study novel solution methods for a class of network optimization problems that find application in strategic planning of telecommunication infrastructure. These directed network design models are used to compute centralized two-level networks under capacity constraints: Circuits on the inner level and directed trees in the periphery. We develop non-compact arc-based and set-packing formulations and integrate cuts to strengthen polyhedral descriptions of their relaxations. Theoretical results on polyhedral structure are provided that serve as the foundation of our branch-and-cut-and-price methods. For the column generation component, we introduce new relaxations of the pricing problem that are based on not necessarily elementary ring arborescences: q-d-Steiner-arb and ng-ring-Steiner-arbs. These models are related to q-arbs and ng-route relaxations known to be state-of-the-art for related network optimization models including vehicle routing. Our effective algorithmic framework incorporates iterated local search based primal heuristics and exact pricing strategies that can be applied to all considered model variants and related network design problems. The novel methods clearly outperform existing approaches from the literature regarding both solution time and solution quality. In a computational study, we show that our algorithms are capable of closing most optimality gaps for unsolved literature instances with up to 51 vertices. Furthermore, we provide results for new larger instances with up to 101 vertices
- …
