51 research outputs found
Models and Algorithms for Inbound and Outbound Truck to Door Scheduling
Cross-docking is a logistic strategy that facilitates rapid movement of consolidated products between suppliers and retailers within a supply chain. It is also a warehousing strategy that aims at reducing or eliminating storage and order picking, two of which are known to be major costly operations of any typical warehouse. This strategy has been used in the retailing, manufacturing, and automotive industries. In a cross-dock, goods are unloaded from incoming trucks, consolidated according to their destinations, and then, loaded into outgoing trucks with little or no storage in between.
In this thesis, we address an integrated cross-dock door assignment and truck scheduling problem in which the assignment and sequencing of incoming trucks to strip doors and outgoing trucks to stack doors is optimized to minimize the total time to process all trucks. We present a mixed integer programming formulation to model this problem and some valid inequalities to strengthen the formulation. We also present two metaheuristics to obtain high quality solutions in reasonable CPU times. These algorithms use a mix of composite dispatching rules, constructive heuristics, local search heuristics which are embedded into a greedy randomized adaptive search procedure (GRASP) and an iterated local search (ILS). Results of computational experiments are presented to assess the performance of the proposed algorithms, in comparison with a general purpose solver
Optimization strategies for the integrated management of perishable supply chains: A literature review
Purpose: The main purpose of this article is to systematically review the papers published in the period 2005-2020 about the integration of production, inventory and distribution activities in perishable supply chains. Design/methodology/approach: The proposed research methodology is based on several steps. First, database and keywords are selected, with the aim to search and collect the main papers, dealing with the integration of production, inventory, distribution activities in perishable supply chains. Then, a bibliometric analysis is carried out, to detect: the main publishing sources, the chronological distribution, the most used keywords, the featured authors, about the selected papers. A five-dimension classification framework is proposed to carry out a content analysis, where the papers of the literature review are classified and discussed, according to: supply chain structure, objective, perishability type, solution approach, approach validation. Findings: Interest in the application of optimization models for integrated decision-making along perishable supply chains is strongly growing. Integrating multiple stages of the supply chain into a single framework is complex, especially when referring to perishable products. The vast majority of the problems addressed are then NP-Hard. Only a limited quantity of the selected papers aims to solve real-life case studies. There is a need for further research, which is capable of modeling and quantitatively improving existing supply chains. The potentials of Industry 4.0 are currently little explored. Originality/value: Based on the analysis of the papers published, this article outlines the current state of the art on the optimization strategies for the integrated management of perishable supply chains, which are very complex to be managed. Research trends and gaps are discussed, future challenges are presentedPeer Reviewe
Optimized Model Simulation of a Capacitated Vehicle Routing problem based on Firefly Algorithm
This paper presents an optimized solution to a capacitated vehicle routing (CVRP) model using firefly algorithm (FFA). The main objective of a CVRP is to obtain the minimum possible total travelled distance across a search space. The conventional model is a formal description involving mathematical equations formulated to simplify a more complex structure of logistic problems. These logistic problems are generalized as the vehicle routing problem (VRP). When the capacity of the vehicle is considered, the resulting formulation is termed the capacitated vehicle routing problem (CVRP). In a practical scenario, the complexity of CVRP increases when the number of pickup or drop-off points increase making it difficult to solve using exact methods. Thus, this paper employed the intelligent behavior of FFA for solving the CVRP model. Two instances of solid waste management and supply chain problems is used to evaluate the performance of the FFA approach. In comparison with particle swarm optimization and few other ascribed metaheuristic techniques for CVRP, results showed that this approach is very efficient in solving a CVRP model
Cost Factor Focused Scheduling and Sequencing: A Neoteric Literature Review
The hastily emergent concern from researchers in the application of scheduling and sequencing has urged the necessity for analysis of the latest research growth to construct a new outline. This paper focuses on the literature on cost minimization as a primary aim in scheduling problems represented with less significance as a whole in the past literature reviews. The purpose of this paper is to have an intensive study to clarify the development of cost-based scheduling and sequencing (CSS) by reviewing the work published over several parameters for improving the understanding in this field. Various parameters, such as scheduling models, algorithms, industries, journals, publishers, publication year, authors, countries, constraints, objectives, uncertainties, computational time, and programming languages and optimization software packages are considered. In this research, the literature review of CSS is done for thirteen years (2010-2022). Although CSS research originated in manufacturing, it has been observed that CSS research publications also addressed case studies based on health, transportation, railway, airport, steel, textile, education, ship, petrochemical, inspection, and construction projects. A detailed evaluation of the literature is followed by significant information found in the study, literature analysis, gaps identification, constraints of work done, and opportunities in future research for the researchers and experts from the industries in CSS
Synchronizing inventory and transport within supply chain management
The problem considers synchronized optimization of inventory and transport, and focuses on producer-distributor relations. Particular attention is paid to developing a mathematical model and an optimization problem that can be used to minimize the overall distribution cost by an appropriate placement of warehouses and cross-docking points. Solutions to this problem are explored using genetic algorithms and ideas from graph/network theory.
Note: there are three separate reports contained within the uploaded .pdf file
Two-Stage Vehicle Routing Problems with Profits and Buffers: Analysis and Metaheuristic Optimization Algorithms
This thesis considers the Two-Stage Vehicle Routing Problem (VRP) with Profits and Buffers, which generalizes various optimization problems that are relevant for practical applications, such as the Two-Machine Flow Shop with Buffers and the Orienteering Problem. Two optimization problems are considered for the Two-Stage VRP with Profits and Buffers, namely the minimization of total time while respecting a profit constraint and the maximization of total profit under a budget constraint. The former generalizes the makespan minimization problem for the Two-Machine Flow Shop with Buffers, whereas the latter is comparable to the problem of maximizing score in the Orienteering Problem.
For the three problems, a theoretical analysis is performed regarding computational complexity, existence of optimal permutation schedules (where all vehicles traverse the same nodes in the same order) and potential gaps in attainable solution quality between permutation schedules and non-permutation schedules. The obtained theoretical results are visualized in a table that gives an overview of various subproblems belonging to the Two-Stage VRP with Profits and Buffers, their theoretical properties and how they are connected.
For the Two-Machine Flow Shop with Buffers and the Orienteering Problem, two metaheuristics 2BF-ILS and VNSOP are presented that obtain favorable results in computational experiments when compared to other state-of-the-art algorithms. For the Two-Stage VRP with Profits and Buffers, an algorithmic framework for Iterative Search Algorithms with Variable Neighborhoods (ISAVaN) is proposed that generalizes aspects from 2BF-ILS as well as VNSOP. Various algorithms derived from that framework are evaluated in an experimental study. The evaluation methodology used for all computational experiments in this thesis takes the performance during the run time into account and demonstrates that algorithms for structurally different problems, which are encompassed by the Two-Stage VRP with Profits and Buffers, can be evaluated with similar methods.
The results show that the most suitable choice for the components in these algorithms is dependent on the properties of the problem and the considered evaluation criteria. However, a number of similarities to algorithms that perform well for the Two-Machine Flow Shop with Buffers and the Orienteering Problem can be identified. The framework unifies these characteristics, providing a spectrum of algorithms that can be adapted to the specifics of the considered Vehicle Routing Problem.:1 Introduction
2 Background
2.1 Problem Motivation
2.2 Formal Definition of the Two-Stage VRP with Profits and Buffers
2.3 Review of Literature on Related Vehicle Routing Problems
2.3.1 Two-Stage Vehicle Routing Problems
2.3.2 Vehicle Routing Problems with Profits
2.3.3 Vehicle Routing Problems with Capacity- or Resource-based Restrictions
2.4 Preliminary Remarks on Subsequent Chapters
3 The Two-Machine Flow Shop Problem with Buffers
3.1 Review of Literature on Flow Shop Problems with Buffers
3.1.1 Algorithms and Metaheuristics for Flow Shops with Buffers
3.1.2 Two-Machine Flow Shop Problems with Buffers
3.1.3 Blocking Flow Shops
3.1.4 Non-Permutation Schedules
3.1.5 Other Extensions and Variations of Flow Shop Problems
3.2 Theoretical Properties
3.2.1 Computational Complexity
3.2.2 The Existence of Optimal Permutation Schedules
3.2.3 The Gap Between Permutation Schedules an Non-Permutation
3.3 A Modification of the NEH Heuristic
3.4 An Iterated Local Search for the Two-Machine Flow Shop Problem with Buffers
3.5 Computational Evaluation
3.5.1 Algorithms for Comparison
3.5.2 Generation of Problem Instances
3.5.3 Parameter Values
3.5.4 Comparison of 2BF-ILS with other Metaheuristics
3.5.5 Comparison of 2BF-OPT with NEH
3.6 Summary
4 The Orienteering Problem
4.1 Review of Literature on Orienteering Problems
4.2 Theoretical Properties
4.3 A Variable Neighborhood Search for the Orienteering Problem
4.4 Computational Evaluation
4.4.1 Measurement of Algorithm Performance
4.4.2 Choice of Algorithms for Comparison
4.4.3 Problem Instances
4.4.4 Parameter Values
4.4.5 Experimental Setup
4.4.6 Comparison of VNSOP with other Metaheuristics
4.5 Summary
5 The Two-Stage Vehicle Routing Problem with Profits and Buffers
5.1 Theoretical Properties of the Two-Stage VRP with Profits and Buffers
5.1.1 Computational Complexity of the General Problem
5.1.2 Existence of Permutation Schedules in the Set of Optimal Solutions
5.1.3 The Gap Between Permutation Schedules an Non-Permutation Schedules
5.1.4 Remarks on Restricted Cases
5.1.5 Overview of Theoretical Results
5.2 A Metaheuristic Framework for the Two-Stage VRP with Profits and Buffers
5.3 Experimental Results
5.3.1 Problem Instances
5.3.2 Experimental Results for O_{max R, Cmax≤B}
5.3.3 Experimental Results for O_{min Cmax, R≥Q}
5.4 Summary
Bibliography
List of Figures
List of Tables
List of Algorithm
Application of exact and multi-heuristic approaches to a sustainable closed loop supply chain network design
Closed-loop supply chains (CLSC) are gaining popularity due to their efficiency in addressing economic, environmental, and social concerns. An important point to ponder in the distribution of CLSC is that imperfect refrigeration and bad road conditions may result in product non-conformance during the transit and thus such products are to be returned to the supply node. This may hinder the level of customer satisfaction. This paper presents a sustainable closed-loop supply chain framework coupled with cross-docking subject to product non-conformance. A cost model is proposed to investigate the economic and environmental aspects of such systems. The transportation cost is analyzed in terms of total carbon emissions. A set of metaheuristics are administered to solve the model and a novel lower bound is proposed to relax the complexity of the proposed model. The results of different size problems are compared with the branch and bound approach and the proposed lower bound. The results indicate that the proposed research framework, mathe-matical model, and heuristic schemes can aid the decision-makers in a closed-loop supply chain context
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