A reclaimer scheduling problem arising in coal stockyard management

We study a number of variants of an abstract scheduling problem inspired by the scheduling of reclaimers in the stockyard of a coal export terminal. We analyze the complexity of each of the variants, providing complexity proofs for some and polynomial algorithms for others. For one, especially interesting variant, we also develop a constant factor approximation algorithm.Comment: 26 page

The relevance of outsourcing and leagile strategies in performance optimization of an integrated process planning and scheduling

Over the past few years growing global competition has forced the manufacturing industries to upgrade their old production strategies with the modern day approaches. As a result, recent interest has been developed towards finding an appropriate policy that could enable them to compete with others, and facilitate them to emerge as a market winner. Keeping in mind the abovementioned facts, in this paper the authors have proposed an integrated process planning and scheduling model inheriting the salient features of outsourcing, and leagile principles to compete in the existing market scenario. The paper also proposes a model based on leagile principles, where the integrated planning management has been practiced. In the present work a scheduling problem has been considered and overall minimization of makespan has been aimed. The paper shows the relevance of both the strategies in performance enhancement of the industries, in terms of their reduced makespan. The authors have also proposed a new hybrid Enhanced Swift Converging Simulated Annealing (ESCSA) algorithm, to solve the complex real-time scheduling problems. The proposed algorithm inherits the prominent features of the Genetic Algorithm (GA), Simulated Annealing (SA), and the Fuzzy Logic Controller (FLC). The ESCSA algorithm reduces the makespan significantly in less computational time and number of iterations. The efficacy of the proposed algorithm has been shown by comparing the results with GA, SA, Tabu, and hybrid Tabu-SA optimization methods

Order Acceptance and Scheduling: A Taxonomy and Review

Over the past 20 years, the topic of order acceptance has attracted considerable attention from those who study scheduling and those who practice it. In a firm that strives to align its functions so that profit is maximized, the coordination of capacity with demand may require that business sometimes be turned away. In particular, there is a trade-off between the revenue brought in by a particular order, and all of its associated costs of processing. The present study focuses on the body of research that approaches this trade-off by considering two decisions: which orders to accept for processing, and how to schedule them. This paper presents a taxonomy and a review of this literature, catalogs its contributions and suggests opportunities for future research in this area

A survey of variants and extensions of the resource-constrained project scheduling problem

The resource-constrained project scheduling problem (RCPSP) consists of activities that must be scheduled subject to precedence and resource constraints such that the makespan is minimized. It has become a well-known standard problem in the context of project scheduling which has attracted numerous researchers who developed both exact and heuristic scheduling procedures. However, it is a rather basic model with assumptions that are too restrictive for many practical applications. Consequently, various extensions of the basic RCPSP have been developed. This paper gives an overview over these extensions. The extensions are classified according to the structure of the RCPSP. We summarize generalizations of the activity concept, of the precedence relations and of the resource constraints. Alternative objectives and approaches for scheduling multiple projects are discussed as well. In addition to popular variants and extensions such as multiple modes, minimal and maximal time lags, and net present value-based objectives, the paper also provides a survey of many less known concepts. --project scheduling,modeling,resource constraints,temporal constraints,networks

Unified Concept of Bottleneck

The term `bottleneck` has been extensively used in operations management literature. Management paradigms like the Theory of Constraints focus on the identification and exploitation of bottlenecks. Yet, we show that the term has not been rigorously defined. We provide a classification of bottleneck definitions available in literature and discuss several myths associated with the concept of bottleneck. The apparent diversity of definitions raises the question whether it is possible to have a single bottleneck definition which has as much applicability in high variety job shops as in mass production environments. The key to the formulation of an unified concept of bottleneck lies in relating the concept of bottleneck to the concept of shadow price of resources. We propose an universally applicable bottleneck definition based on the concept of average shadow price. We discuss the procedure for determination of bottleneck values for diverse production environments. The Law of Diminishing Returns is shown to be a sufficient but not necessary condition for the equivalence of the average and the marginal shadow price. The equivalence of these two prices is proved for several environments. Bottleneck identification is the first step in resource acquisition decisions faced by managers. The definition of bottleneck presented in the paper has the potential to not only reduce ambiguity regarding the meaning of the term but also open a new window to the formulation and analysis of a rich set of problems faced by managers.

Diseño y desarrollo del modelo óptimo de asignación y cronograma de remolques en el sistema de cadena de suministro con consideración de cross dock con planificación estocástica

Todays, transportation, and logistics engineering processes are among the important issues of organizations in the competitive market. Considering the logistical structure of the logistics engineering and the more attention paid to the logistical tools and, in particular, such as the use of these tools, such as containers (pallets, containers, etc.), transportation equipment (trailer, forklift trucks, etc.), and The art of building the supply and distribution network concerning the main warehouses, cross-dock, and temporary storage, is one of the most critical and contemplative cases. In fact, all these tools work together to maximize system efficiency in the field of logistics concerning the leading impact indicators, including the time of shipment (loading, disloading, the allocation of trailers, etc.). This paper's main goal is to present and develop a mathematical model of trailer schedule planning in possible conditions in the cross-dock. In fact, the main function of this mathematical model is to minimize the total time of the logistics process from the stage of emptying the pallets from the materials producers in the cross docks and assigning the trailer to the door, and finally reloading the pallets to be distributed to the production sites. To solve this model and to analyze the outputs, mixed integer programming was used by GAMS software.Hoy en día, los procesos de ingeniería de transporte y logística se encuentran entre los temas importantes de las organizaciones en el mercado competitivo. Teniendo en cuenta la estructura logística de la ingeniería logística y la mayor atención prestada a las herramientas logísticas y, en particular, como el uso de estas herramientas, como contenedores (pallets, contenedores, etc.), equipos de transporte (remolque, carretillas elevadoras, etc.), y El arte de construir la red de suministro y distribución con respecto a los almacenes principales, cross dock y almacenamiento temporal, es uno de los casos más importantes y contemplativos. De hecho, todas estas herramientas trabajan juntas para maximizar la eficiencia del sistema en el campo de la logística con respecto a los principales indicadores de impacto, incluido el tiempo de envío (carga, descarga, asignación de remolques, etc.). El objetivo principal de este artículo es presentar y desarrollar un modelo matemático de planificación de horarios de remolques en las posibles condiciones en el muelle de cruce. De hecho, la función principal de este modelo matemático es minimizar el tiempo total del proceso logístico desde la etapa de vaciado de los pallets de los productores de materiales en los cross docks y la asignación del remolque a la puerta y finalmente la recarga de los pallets a distribuir. a los sitios de producción. Para resolver este modelo y analizar las salidas, el software GAMS utilizó la programación de enteros mixtos

A linear programming-based method for job shop scheduling

We present a decomposition heuristic for a large class of job shop scheduling problems. This heuristic utilizes information from the linear programming formulation of the associated optimal timing problem to solve subproblems, can be used for any objective function whose associated optimal timing problem can be expressed as a linear program (LP), and is particularly effective for objectives that include a component that is a function of individual operation completion times. Using the proposed heuristic framework, we address job shop scheduling problems with a variety of objectives where intermediate holding costs need to be explicitly considered. In computational testing, we demonstrate the performance of our proposed solution approach