1,721,095 research outputs found
The multi-path Traveling Salesman Problem with stochastic travel costs: A City Logistics computational study
No full textThe multi-path Traveling Salesman Problem with stochastic travel costs Models, methods and City Logistics applications
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A Multiclass Robust Twin Parametric Margin Support Vector Machine with an Application to Vehicles Emissions
No full textThis paper considers the problem of predicting vehicles smog rating by applying a novel Support Vector Machine (SVM) technique. Classical SVM-type models perform a binary classification of the training observations. However, in many real-world applications only two classifying categories may not be enough. For this reason, a new multiclass Twin Parametric Margin Support Vector Machine (TPMSVM) is designed. On the basis of different characteristics, such as engine size and fuel consumption, the model aims to assign each vehicle to a specific smog rating class. To protect the model against uncertainty arising in the measurement procedure, a robust optimization extension of the multiclass TPMSVM model is formulated. Spherical uncertainty sets are considered and a tractable robust counterpart of the model is derived. Experimental results on a real-world dataset show the good performance of the robust formulation
A rolling horizon approach for a multi-stage stochastic fixed-charge transportation problem with transshipment
No full textWe study a fixed-charge transportation problem under stochastic and dynamic demand. We propose a multi-stage mixed integer stochastic programming formulation, where the first-stage decision is the delivery from the supplier to the retailers, while transshipment is used, in addition to classical backordering as recourse decision. The objective is the minimization of the total expected cost. We prove that this problem is NP-hard and, through a worst-case analysis, that transshipment can provide significant cost savings. Extensive computational studies are carried out to evaluate the performance of a rolling horizon approach with respect to the optimal cost. Numerical results show that this heuristic provides effective solutions in short computational time. Managerial insights are finally drawn
The value of integration of full container load, less than container load and air freight shipments in vendor–managed inventory systems
No full textWe address a long–haul transportation problem of delivering a set of products from a producer to a customer, where Full Container Load (FCL) shipments on one side and Less than Container Load (LCL) or Air Freight shipments on the other side are integrated. A Vendor-Managed Inventory (VMI) approach is used: a decision-maker has to find a periodic shipping policy that minimizes the sum of transportation cost and inventory cost, both at the producer and at the customer. This problem is defined at the tactical level implying that the initial inventory levels at the producer and at the customer are not data, but decision variables. For this problem we formulate a Mixed Integer Linear Programming model and prove its computational complexity. Furthermore, we introduce the concept of Value of Integration of FCL and LCL/Air Freight shipments and prove performance bounds to show that the integration of FCL and LCL/Air Freight shipments can lead to significant cost savings, both in the worst case and on average. Systematic computational experiments are finally carried out
A Progressive Hedging method for the multi-path Traveling Salesman Problem with stochastic travel times
No full textBounds in Multistage Linear Stochastic Programming
No full textMultistage stochastic programs, which involve sequences of decisions over time, are usually hard to solve in realistically sized problems. Providing bounds for optimal solution may help in evaluating whether it is worth the additional computations for the stochastic program vs. simplified approaches. In this paper we generalize measures from the two-stage case, based on different levels of available information, to the multistage stochastic programming problems. A set of theorems providing chains of inequalities among the new quantities are proved. Numerical results on a case study related to a simple transportation problem illustrate the described relationships
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