This paper proposes a global optimization algorithm for solving a mixed (continuous/discrete) transportation network design problem (MNDP), which is generally expressed as a mathematical programming with equilibrium c...
详细信息
This paper proposes a global optimization algorithm for solving a mixed (continuous/discrete) transportation network design problem (MNDP), which is generally expressed as a mathematical programming with equilibrium constraint (MPEC). The upper level of the MNDP aims to optimize the network performance via both expansion of existing links and addition of new candidate links, whereas the lower level is a traditional Wardrop user equilibrium CUE) problem. In this paper, we first formulate the UE condition as a variational inequality (VI) problem, which is defined from a finite number of extreme points of a link-low feasible region. The MNDP is approximated as a piecewise-linearprogramming (P-LP) problem, which is then transformed into a mixed-integer linear programming (MILP) problem. A global optimization algorithm based on a cutting constraint method is developed for solving the MILP problem. Numerical examples are given to demonstrate the efficiency of the proposed method and to compare the results with alternative algorithms reported in the literature. (C) 2011 Elsevier Ltd. All rights reserved.
This paper addresses the problem of optimal Construction Supply Chain (CSC) design and integration in deterministic and stochastic environments by providing a family of models for the optimization of a dynamic, multi-...
详细信息
This paper addresses the problem of optimal Construction Supply Chain (CSC) design and integration in deterministic and stochastic environments by providing a family of models for the optimization of a dynamic, multi-product, multi-site contractor-led CSC. With the objective of minimizing the total CSC cost, optimal decisions are made on network design, production, inventory holding and transportation, while also considering discounts for bulk purchases, logistics centers, on-site shortages and an inventory-preparation phase. The models integrate the operations of temporal and project-based supply chains into a sustainable network with repetitive flows, large scope contracts and economies of scale to provide the main contractor with a versatile optimization framework which can account for different levels of uncertainty. The novelty of this paper lies in providing a flexible integrative optimization CSC tool that accounts for multiple CSC actors (suppliers and/or logistics centers), projects, products, time periods, operations, and different decision-making environments depending on the nature of the problem and the risk-attitude of the decision maker. This paper contributes to the fast-growing research field of stochastic CSC optimization showcasing stochastic transitions of a mixed-integer linear programming model to chance-constrained programming and two-stage programming and incorporating uncertainties with different types of probability distributions or scenarios, and even interdependent uncertainties-approaches that have not been explored extensively in the CSC context. The results reveal that the stochastic approaches sacrifice the minimum cost of deterministic solutions having average settings to obtain robust well-hedged solutions over the possible parameter variations and that the selection of a suitable method for modeling uncertainty is context-dependent.
Deep brain stimulation (DBS) programming remains a complex and time-consuming process, requiring manual selection of stimulation parameters to achieve therapeutic effects while minimizing adverse side-effects. This st...
详细信息
This note is concerned with the problem of crossing a target set between sample instants under the influence of bounded unknown disturbances. The proposed solution employs mixed-integer linear programming and is less ...
详细信息
This note is concerned with the problem of crossing a target set between sample instants under the influence of bounded unknown disturbances. The proposed solution employs mixed-integer linear programming and is less conservative compared with the standard approach of imposing pointwise-in-time constraints at the sample instants.
A single product maritime inventory routing problem is addressed in this paper by exploring the use of continuous and discrete time models. We first present a continuous time model based on time slots for single docks...
详细信息
A single product maritime inventory routing problem is addressed in this paper by exploring the use of continuous and discrete time models. We first present a continuous time model based on time slots for single docks, which is enhanced by reformulating the time assignment constraints. Next, we present a model based on event points to handle parallel docks. A discrete time is also presented based on a single commodity fixed-charge network flow problem (FCNF). All the models are solved for multiple randomly generated instances of different problems to compare their computational efficiency, and to illustrate the solutions obtained. (C) 2015 Elsevier Ltd. All rights reserved.
Draglines are among the largest earthmoving machines in surface mining, where they are used to remove the waste material (overburden) sitting above a target mineral or coal deposit. The effectiveness of their operatio...
详细信息
Draglines are among the largest earthmoving machines in surface mining, where they are used to remove the waste material (overburden) sitting above a target mineral or coal deposit. The effectiveness of their operation is highly dependent on decisions made by their operators, including the sequence of positions at which they operate and the bulk material movement (what to dig and where to dump) during excavation at each position. In this paper, we formulate a mixed-integerlinear program that captures the operational constraints imposed in dragline excavation to determine the optimal material movement for a prescribed sequence of dragline positions. Through a simulation study, we show that the dragline productivity can be improved by more effective assignment of material movement tasks to individual dragline positions. We find that the improvement made compared to using a greedy'digging and dumping strategy depends on the dragline positioning sequence and the terrain profile in the specific environment. The solutions in terms of what to dig and where to dump provide insights into the optimal digging and dumping patterns for different types of dragline positioning sequences, and contribute towards solving the overall dragline operation planning problem that includes the planning of the dragline positioning sequence.
A novel integerlinearprogramming (ILP) formulation of deploying base stations and repeaters to meet a target coverage of traffic points (TPs) with minimum cost is presented, where the number of discrete variables ap...
详细信息
A novel integerlinearprogramming (ILP) formulation of deploying base stations and repeaters to meet a target coverage of traffic points (TPs) with minimum cost is presented, where the number of discrete variables approximately equals the sum between the number of TPs and the number of backhaul links. The ILP is proved equivalent to a mixed-ILP (MILP) where the number of discrete variables is reduced by the number of TPs. Our MILP approach always yields optimal deployment solutions. A case study is presented to demonstrate the benefits of using repeaters based on the optimal solutions of the MILP.
This paper addresses resource-constrained project scheduling problem with mixed uncertainty of randomness and fuzziness (FS-RCPSP). The activity durations are considered to be fuzzy random variables. A resource flow n...
详细信息
This paper addresses resource-constrained project scheduling problem with mixed uncertainty of randomness and fuzziness (FS-RCPSP). The activity durations are considered to be fuzzy random variables. A resource flow network based mathematical model with fuzzy random variables is presented. Then, this model is transformed into a mixed-integer linear programming model with crisp variables. The CPLEX 12.6.0.1 solver in AIMMS (2014) is employed for applying the proposed model to solve 960 benchmark instances generated from the well-known sets J30 and J60 in PSPLIB. The computational results are encouraging and indicate the ability of the proposed model to handle the FS-RCPSP.
Multi-objective optimization problems (MOOP) reflect the complexity of many real-world decision problems where objectives are conflicting. The presence of more than one criterion makes finding the non-dominated (ND) p...
详细信息
Multi-objective optimization problems (MOOP) reflect the complexity of many real-world decision problems where objectives are conflicting. The presence of more than one criterion makes finding the non-dominated (ND) points a crucial issue in the decision making process. Tri-objective mixed-integerlinear programs (TOMILP) are an important subclass of MOOPs that are applicable to many problems in economics, business, science, and engineering including sustainable systems that must consider economic, environmental, and social concerns simultaneously. The literature on finding the ND points of TOMILPs is limited;there are only a few algorithms published in the literature that do not guarantee generating the entire ND points of TOMILPs. We present a new method, the Slicing with Adaptive Steps Search (SASS), to generate the ND points of TOMILPs. The result of SASS is primarily a superset of the set of ND points in the form of (partially) ND faces. We then perform a post-processing to eliminate the dominated parts of the partially ND faces. We provide a theoretical analysis of SASS and illustrate its effectiveness on a large set of instances.
This paper addresses a fuel-constrained, multiple vehicle routing problem (FCMVRP) in the presence of multiple refueling stations. We are given a set of targets, a set of refueling stations, and a depot where m vehicl...
详细信息
This paper addresses a fuel-constrained, multiple vehicle routing problem (FCMVRP) in the presence of multiple refueling stations. We are given a set of targets, a set of refueling stations, and a depot where m vehicles are stationed. The vehicles are allowed to refuel at any refueling station, and the objective of the problem is to determine a route for each vehicle starting and terminating at the depot, such that each target is visited by at least one vehicle, the vehicles never run out of fuel while traversing their routes, and the total travel cost of all the routes is a minimum. We present four new mixed-integer linear programming (MILP) formulations for the problem. These formulations are compared both analytically and empirically, and a branch-and-cut algorithm is developed to compute an optimal solution. Extensive computational results on a large class of test instances that corroborate the effectiveness of the algorithm are also presented.
暂无评论