431 research outputs found
MULTILEVEL ANT COLONY OPTIMIZATION TO SOLVE CONSTRAINED FOREST TRANSPORTATION PLANNING PROBLEMS
In this dissertation, we focus on solving forest transportation planning related problems, including constraints that consider negative environmental impacts and multi-objective optimizations that provide forest managers and road planers alternatives for making informed decisions. Along this line of study, several multilevel techniques and mataheuristic algorithms have been developed and investigated. The forest transportation planning problem is a fixed-charge problem and known to be NP-hard. The general idea of utilizing multilevel approach is to solve the original problem of which the computational cost maybe prohibitive by using a set of increasingly smaller problems of which the computational cost is cheaper.
The multilevel techniques are devised consisting of two parts. The first part is to recursively apply a graph coarsening heuristic to the original problem to produce a set of coarser level problems of which the sizes in terms of number of problem components such as edges and nodes are in decreasing order. The second part is to solve the set of the coarser level problems including the original problem bottom up, starting with the coarsest level. We propose that if coarser level problems inherit important properties (such as attribute value distribution) from their ancestor during the coarsening process, they can be treated as smaller versions of the original problem. Based on this hypothesis, the multilevel techniques use solutions obtained for the coarser level problems to solve the finer level problems.
Mainly, we develop multilevel techniques to address three problems, namely a constrained fixed-charge problem, parameter configuration problem, and a multi-objective transportation optimization problem in this study. The performance of the multilevel techniques is compared with other commonly used approaches. The statistical analyses on the experimental results indicate that the multilevel approach can reduce computing time significantly without sacrificing the solution quality
Metaheuristic Algorithms for Spatial Multi-Objective Decision Making
Spatial decision making is an everyday activity, common to individuals and organizations. However, recently there is an increasing interest in the importance of spatial decision-making systems, as more decision-makers with concerns about sustainability, social, economic, environmental, land use planning, and transportation issues discover the benefits of geographical information. Many spatial decision problems are regarded as optimization problems, which involve a large set of feasible alternatives, multiple conflicting objectives that are difficult and complex to solve. Hence, Multi-Objective Optimization methods (MOO)—metaheuristic algorithms integrated with Geographical Information Systems (GIS) are appealing to be powerful tools in these regards, yet their implementation in spatial context is still challenging. In this thesis, various metaheuristic algorithms are adopted and improved to solve complex spatial problems. Disaster management and urban planning are used as case studies of this thesis.These case studies are explored in the four papers that are part of this thesis. In paper I, four metaheuristic algorithms have been implemented on the same spatial multi-objective problem—evacuation planning, to investigate their performance and potential. The findings show that all tested algorithms were effective in solving the problem, although in general, some had higher performance, while others showed the potential of being flexible to be modified to fit better to the problem. In the same context, paper II identified the effectiveness of the Multi-objective Artificial Bee Colony (MOABC) algorithm when improved to solve the evacuation problem. In paper III, we proposed a multi-objective optimization approach for urban evacuation planning that considered three spatial objectives which were optimized using an improved Multi-Objective Cuckoo Search algorithm (MOCS). Both improved algorithms (MOABC and MOCS) proved to be efficient in solving evacuation planning when compared to their standard version and other algorithms. Moreover, Paper IV proposed an urban land-use allocation model that involved three spatial objectives and proposed an improved Non-dominated Sorting Biogeography-based Optimization algorithm (NSBBO) to solve the problem efficiently and effectively.Overall, the work in this thesis demonstrates that different metaheuristic algorithms have the potential to change the way spatial decision problems are structured and can improve the transparency and facilitate decision-makers to map solutions and interactively modify decision preferences through trade-offs between multiple objectives. Moreover, the obtained results can be used in a systematic way to develop policy recommendations. From the perspective of GIS - Multi-Criteria Decision Making (MCDM) research, the thesis contributes to spatial optimization modelling and extended knowledge on the application of metaheuristic algorithms. The insights from this thesis could also benefit the development and practical implementation of other Artificial Intelligence (AI) techniques to enhance the capabilities of GIS for tackling complex spatial multi-objective decision problems in the future
A robust solving strategy for the vehicle routing problem with multiple depots and multiple objectives
This document presents the development of a robust solving strategy for the Vehicle Routing Problem with Multiple Depots and Multiple Objectives (MO-MDVRP). The problem tackeled in this work is the problem to minimize the total cost and the load imbalance in vehicle routing plan for distribution of goods. This thesis presents a MILP mathematical model and a solution strategy based on a Hybrid Multi- Objective Scatter Search Algorithm. Several experiments using simulated instances were run proving that the proposed method is quite robust, this is shown in execution times (less than 4 minutes for an instance with 8 depots and 300 customers); also, the proposed method showed good results compared to the results found with the MILP model for small instances (up to 20 clients and 2 depots).MaestríaMagister en Ingeniería Industria
Determination of Optimal Distribution and Transportation Network (Wood Transportation in Iran)
Today, transportation network optimization has become one of the significant aspects of supply
chain planning, and even a slight rise in productivity can significantly reduce costs of
distribution of wood in the transportation network. In the forest based industry, given that
transportation is the main cost of raw wood supply, using transportation planning, distribution
should be done in a way so as to minimize the overall wood displacement. Such planning
must meet the needs of all demand centers and the distribution supplier points must be used
to their full capacity. Accordingly, the present study strived to find an optimal solution for
transportation and distribution of raw wood from the main supplier points to small and large
centers of wood and paper industries in Iran. This optimization simultaneously focuses on
several products and is at the macroeconomic level of the country wood market. To achieve
this goal, linear programming – Transportation Simplex Algorithm was used. The results
show a significant fall in transportation costs and a more organized wood distribution network
than the current situation. This cost reduction can be attributed to decisions about the optimal
distribution of wood types, determining transport routes, and opting for the right type of truck
supplier based on load tonnage and distance. This plummet in transportation costs plunges
the cost of wood and wood products, which will surge competition in the business and will be
of interest to manufacturers, distributors, customers and stakeholders in general
A Polyhedral Study of Mixed 0-1 Set
We consider a variant of the well-known single node fixed charge network flow set with constant capacities. This set arises from the relaxation of more general mixed integer sets such as lot-sizing problems with multiple suppliers. We provide a complete polyhedral characterization of the convex hull of the given set
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Global supply chain optimization: a machine learning perspective to improve caterpillar's logistics operations
This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University London.Supply chain optimization is one of the key components for the effective management of a company with a complex manufacturing process and distribution network. Companies with a global presence in particular are motivated to optimize their distribution plans in order to keep their operating costs low and competitive. Changing condition in the global market and volatile energy prices increase the need for an automatic decision and optimization tool. In recent years, many techniques and applications have been proposed to address the
problem of supply chain optimization. However, such techniques are often too problemspecific or too knowledge-intensive to be implemented as in-expensive, and easy-to-use computer system. The effort required to implement an optimization system for a new instance of the problem appears to be quite significant. The development process necessitates the involvement of expert personnel and the level of automation is low. The aim of this project is to develop a set of strategies capable of increasing the level of
automation when developing a new optimization system. An increased level of automation is achieved by focusing on three areas: multi-objective optimization, optimization algorithm usability, and optimization model design. A literature review highlighted the great level of interest for the problem of multiobjective optimization in the research community. However, the review emphasized a lack of standardization in the area and insufficient understanding of the relationship between multi-objective strategies and problems. Experts in the area of optimization and artificial intelligence are interested in improving the usability of the most recent
optimization algorithms. They stated the concern that the large number of variants and parameters, which characterizes such algorithms, affect their potential applicability in real-world environments. Such characteristics are seen as the root cause for the low success of the most recent optimization algorithms in industrial applications. Crucial task for the development of an optimization system is the design of the optimization model. Such task is one of the most complex in the development process, however, it is still performed mostly manually. The importance and the complexity of the task strongly suggest the development of tools to aid the design of optimization models. In order to address such challenges, first the problem of multi-objective optimization is considered and the most widely adopted techniques to solve it are identified. Such techniques are analyzed and described in details to increase the level of standardization in the area. Empirical evidences are highlighted to suggest what type of relationship exists between strategies and problem instances. Regarding the optimization algorithm, a classification method is proposed to improve its usability and computational requirement by automatically tuning one of its key parameters, the termination condition. The algorithm understands the problem complexity and automatically assigns the best termination condition to minimize runtime. The runtime of the optimization system has been reduced by more than 60%. Arguably, the usability of the algorithm has been improved as well, as one of the key configuration tasks can now be completed automatically. Finally, a system is presented to aid the definition of the optimization model through regression analysis. The purpose of the method is to gather as much knowledge about the problem as possible so that the task of the optimization model definition requires a lower user involvement. The application of the proposed algorithm is estimated that could have saved almost 1000 man-weeks to complete the project. The developed strategies have been applied to the problem of Caterpillar’s global supply chain optimization. This thesis describes also the process of developing an optimization system for Caterpillar and highlights the challenges and research opportunities identified while undertaking this work. This thesis describes the optimization model designed for Caterpillar’s supply chain and the implementation details of the Ant Colony System, the algorithm selected to optimize the supply chain. The system is now used to design the distribution plans of more than 7,000 products. The system improved Caterpillar’s marginal profit on such products by a factor of 4.6% on average.Caterpillar Inc
A Multi-Objective Ant Colony Optimization Algorithm for Infrastructure Routing
An algorithm is presented that is capable of producing Pareto-optimal solutions for multi-objective infrastructure routing problems: the Multi-Objective Ant Colony Optimization (MOACO). This algorithm offers a constructive search technique to develop solutions to different types of infrastructure routing problems on an open grid framework. The algorithm proposes unique functions such as graph pruning and path straightening to enhance both speed and performance. It also possesses features to solve issues unique to infrastructure routing not found in existing MOACO algorithms, such as problems with multiple end points or multiple possible start points. A literature review covering existing MOACO algorithms and the Ant Colony algorithms they are derived from is presented. Two case studies are developed to demonstrate the performance of the algorithm under different infrastructure routing scenarios. In the first case study the algorithm is implemented into the Ice Road Planning module within the North Slope Decision Support System (NSDSS). Using this ice road planning module a case study is developed of the White Hills Ice road to test the performance of the algorithm versus an as-built road. In the second case study, the algorithm is applied to a raw water transmission routing problem in the Region C planning zone of Texas. For both case studies the algorithm produces a set of results which are similar to the preliminary designs. By successfully applying the algorithm to two separate case studies the suitability of the algorithm to different types of infrastructure routing problems is demonstrated
Methodological review of multicriteria optimization techniques: aplications in water resources
Multi-criteria decision analysis (MCDA) is an umbrella approach that has been applied to a wide range of natural resource management situations. This report has two purposes. First, it aims to provide an overview of advancedmulticriteriaapproaches, methods and tools. The review seeks to layout the nature of the models, their inherent strengths and limitations. Analysis of their applicability in supporting real-life decision-making processes is provided with relation to requirements imposed by organizationally decentralized and economically specific spatial and temporal frameworks. Models are categorized based on different classification schemes and are reviewed by describing their general characteristics, approaches, and fundamental properties. A necessity of careful structuring of decision problems is discussed regarding planning, staging and control aspects within broader agricultural context, and in water management in particular. A special emphasis is given to the importance of manipulating decision elements by means ofhierarchingand clustering. The review goes beyond traditionalMCDAtechniques; it describes new modelling approaches. The second purpose is to describe newMCDAparadigms aimed at addressing the inherent complexity of managing water ecosystems, particularly with respect to multiple criteria integrated with biophysical models,multistakeholders, and lack of information. Comments about, and critical analysis of, the limitations of traditional models are made to point out the need for, and propose a call to, a new way of thinking aboutMCDAas they are applied to water and natural resources management planning. These new perspectives do not undermine the value of traditional methods; rather they point to a shift in emphasis from methods for problem solving to methods for problem structuring. Literature review show successfully integrations of watershed management optimization models to efficiently screen a broad range of technical, economic, and policy management options within a watershed system framework and select the optimal combination of management strategies and associated water allocations for designing a sustainable watershed management plan at least cost. Papers show applications in watershed management model that integrates both natural and human elements of a watershed system including the management of ground and surface water sources, water treatment and distribution systems, human demands,wastewatertreatment and collection systems, water reuse facilities,nonpotablewater distribution infrastructure, aquifer storage and recharge facilities, storm water, and land use
Advanced meta-heuristic approaches and their application to operational optimization in forest wildfire management
La última década ha sido testigo de un aumento vertiginoso de la cantidad y frecuencia de desastres a gran escala, principalmente debido a los fenómenos devastadores derivados de paradigmas climatológicos y ambientales a gran escala como el calentamiento global. De entre ellos son las inundaciones, huracanes y terremotos los desastres de mayor frecuencia de aparición y fatales consecuencias durante este período, tal como certifican los más de 20.000 muertos a consecuencia de un terremoto en la región de Gujarat (India) en 2001, o las 230.000 y 316.000 pérdidas humanas de los terremotos de Indonesia y Haití en 2004 y 2010, respectivamente. En este contexto, el enfoque de esta tesis se centra en una casuística concreta de desastre a media-gran escala cuya frecuencia y severidad han crecido de manera igualmente preocupante en los últimos tiempos: los incendios, definidos como un fuego de grandes dimensiones no voluntariamente iniciado por el ser humano, y que afecta a aquello que no está destinado a quemarse. Pese a la diversidad de iniciativas, campañas y procedimientos orientados a la minimización del impacto y las consecuencias de los incendios, varios sucesos fatales acontecidos en los últimos años han puesto en duda la efectividad de las políticas actuales de gestión de recursos contra incendios como aeronaves, vehículos terrestres, equipamiento de comunicaciones radio, logística de abastecimiento y las brigadas desplegadas en el área afectada. Un ejemplo manifiesto de esta falta de eficacia es la muerte de once bomberos ocurrida en un incendio de 130 kilómetros cuadrados en la zona de Guadalajara (España) en 2005, oficialmente atribuida a una deficiente coordinación entre el puesto de mando y los equipos de extinción debida, fundamentalmente, a problemas de cobertura en los sistemas de radiocomunicación. Aunque la causa de esta falta de coordinación ha sido cuestionada por las autoridades y los agentes involucrados desde entonces, lo cierto es que este suceso supone un ejemplo evidente de la necesidad de estudiar y desarrollar herramientas algorítmicas que ayuden al personal de comandancia a ejecutar óptimamente sus tareas de coordinación y control. Desafortunadamente la coyuntura de crisis económica mundial que azota con especial fuerza los países del Sur de Europa ha mermado dramáticamente las partidas presupuestarias para la prevención y extinción de incendios en beneficio de programas nacionales de reducción de déficit. A consecuencia de estos recortes, el coste ha irrumpido con fuerza como un criterio de extrema relevancia en la planificación operativa de este tipo de desastres: desde la perspectiva de un problema de optimización, los recursos contra incendios son actualmente gestionados con el objetivo fundamental de maximizar su efectividad contra incendios, sujeto a la restricción de que el coste agregado asociado a las decisiones tomadas no supere un determinado umbral presupuestario. Pese a que estas restricciones de coste están bien acotadas, en la práctica la mayoría de los procedimientos de gestión de recursos contra incendios están fuertemente determinados por la capacidad limitada del ser humano para tomar decisiones ágiles en escenarios de elevada complejidad y heterogeneidad. Por los motivos anteriormente expuestos, la presente Tesis doctoral propone la adopción de algoritmos meta-heurísticos para solventar eficientemente problemas de optimización que modelan procesos de gestión de recursos contra incendios. Esta familia de algoritmos de optimización es capaz de explorar el espacio solución de un problema dado merced a la aplicación iterativa de mecanismos inteligentes de búsqueda explorativa y explotativa, produciendo soluciones que sacrifican calidad por una complejidad computacional menor en comparación con la resultante de procesos determinísticos de búsqueda exhaustiva. En particular la Tesis plantea la búsqueda por harmonía (del inglés Harmony Search) como la técnica meta-heurística de optimización común a las herramientas diseñadas para la gestión de recursos en dos escenarios diferentes: ? El primer escenario analizado contempla el despliegue óptimo de redes de comunicación inalámbrica para la coordinación de equipos de extinción en incendios forestales de gran escala. Desde el punto de vista formal, el problema del despliegue dinámico de retransmisores que caracteriza matemáticamente este escenario consiste en estimar el número y localización de los retransmisores radio que deben ser desplegados en el área afectada por el incendio, de tal modo que el número de nodos móviles (i.e. recursos) con cobertura radio es maximizado a un coste del despliegue mínimo. A fin de reflejar la diversidad de equipamiento de retransmisión radio existente en la realidad, este problema es reformulado para considerar modelos de retransmisor con diferentes características de cobertura y coste. El problema resultante es resuelto de manera eficiente mediante sendos algoritmos mono- y bi-objetivo que conjugan 1) la Búsqueda por Harmonía como método de búsqueda global; y 2) una versión modificada del algoritmo de agrupación K-means como técnica de búsqueda local. El desempeño de los métodos propuestos es evaluado mediante experimentos numéricos basados en datos estadísticos reales de la Comunidad de Castilla la Mancha (España), merced a cuyos resultados queda certificada su practicidad a la hora de desplegar infraestructura de comunicación en este tipo de desastres. ? El segundo escenario bajo estudio se concentra en el despliegue y planificación óptima de vehículos aéreos de extinción de incendios basados en estimaciones predictivas del riesgo de incendio de una cierta área geográfica. De manera enunciativa, el problema subyacente busca la asignación de recursos a aeródromos y aeropuertos con restricciones de capacidad que maximice la utilidad de dichos recursos en relación al riesgo de incendio y minimice, a su vez, el coste de ejecutar dicha asignación. La formulación de este problema también considera, dentro de la definición de dicha función de utilidad, la distancia relativa entre aeropuerto, punto de potencial riesgo de incendio y el recurso acuífero (lago, río o mar) más cercano. Para su resolución eficiente se propone el uso de algoritmos de optimización basados, de nuevo, en la Búsqueda por Harmonía, incorporando además métodos voraces de reparación capacitiva. La aplicabilidad práctica de estos métodos es validada mediante experimentos numéricos en escenarios sintéticos y un caso práctico que incluye valores reales del riesgo de incendio, posiciones de recursos acuíferos e instalaciones aeroportuarias. En resumen, esta Tesis evidencia, desde un punto de vista práctico, que la meta-heurística moderna supone una solución algorítmica computacionalmente eficiente para tratar problemas de gestión de recursos contra incendios sujetos a restricciones de coste
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