We introduce, formulate, and solve the Generalized Median Tour Problem, which is motivated in the... more We introduce, formulate, and solve the Generalized Median Tour Problem, which is motivated in the health supplies distribution for urban and rural areas. A region comprises districts that must be served by a specialized vehicle visiting its health facilities. We propose a distribution strategy to serve these health facilities efficiently. A single tour is determined that visits a set of health facilities (nodes) composed of disjoint clusters. The tour must visit at least one facility within each cluster, and the unvisited facilities are assigned to the closest facility on the tour. We minimize the sum of the total tour distance and the access distance traveled by the unvisited facilities. Efficient formulations are proposed and several solution strategies are developed to avoid subtours based on branch & cut. We solve a set of test instances and a real-world instance to show the efficiency of our solution approaches.
A milk collection problem with blending is introduced. A firm collects milk from farms, and each ... more A milk collection problem with blending is introduced. A firm collects milk from farms, and each farm produces one out of three possible qualities of milk. The revenue increases with quality, and there is a minimum requirement at the plant for each quality. Different qual- ities of milk can be blended in the trucks, reducing revenues, but also transportation costs, resulting in higher profit. A mixed integer-programming model, a new cut, and a branch- and-cut algorithm are proposed to solve medium-sized instances. A three-stage heuristic is designed for large instances. Computational experience for test instances and a large-sized real case is presented.
... Obreque, C. and Marianov, V. 2004. A procedure for designing hierarchical path-tree networks ... more ... Obreque, C. and Marianov, V. 2004. A procedure for designing hierarchical path-tree networks and finding the optimal locations of the extremes of the main path , Santiago, Chile: Department of Electrical Engineering, Pontificia Universidad Católica de Chile. ...
The Single-Vehicle Routing Problem with Fixed Delivery and Optional Collections considers a set o... more The Single-Vehicle Routing Problem with Fixed Delivery and Optional Collections considers a set of delivery customers receiving goods from a depot and a set of collection customers sending goods to the same depot. All delivery customers must be visited by the vehicle, while a collection customer is visited only if the capacity of the vehicle is large enough to fit
... Duin and Volgenant (1990) provide a method for finding good upper and lower bounds for the so... more ... Duin and Volgenant (1990) provide a method for finding good upper and lower bounds for the solution; Pirkul et al. (1991) propose a heuristic based on a Lagrangean relaxation. Sancho (1995) finds a sub-optimal solution using a heuristic based on dynamic programming. ...
Abstract We address the p-cable-trench problem. In this problem, p facilities are located, a tren... more Abstract We address the p-cable-trench problem. In this problem, p facilities are located, a trench network is dug and cables are laid in the trenches, so that every customer-or demand-in the region is connected to a facility through a cable. The digging cost of the trenches, as ...
We introduce, formulate, and solve the Generalized Median Tour Problem, which is motivated in the... more We introduce, formulate, and solve the Generalized Median Tour Problem, which is motivated in the health supplies distribution for urban and rural areas. A region comprises districts that must be served by a specialized vehicle visiting its health facilities. We propose a distribution strategy to serve these health facilities efficiently. A single tour is determined that visits a set of health facilities (nodes) composed of disjoint clusters. The tour must visit at least one facility within each cluster, and the unvisited facilities are assigned to the closest facility on the tour. We minimize the sum of the total tour distance and the access distance traveled by the unvisited facilities. Efficient formulations are proposed and several solution strategies are developed to avoid subtours based on branch & cut. We solve a set of test instances and a real-world instance to show the efficiency of our solution approaches.
A milk collection problem with blending is introduced. A firm collects milk from farms, and each ... more A milk collection problem with blending is introduced. A firm collects milk from farms, and each farm produces one out of three possible qualities of milk. The revenue increases with quality, and there is a minimum requirement at the plant for each quality. Different qual- ities of milk can be blended in the trucks, reducing revenues, but also transportation costs, resulting in higher profit. A mixed integer-programming model, a new cut, and a branch- and-cut algorithm are proposed to solve medium-sized instances. A three-stage heuristic is designed for large instances. Computational experience for test instances and a large-sized real case is presented.
... Obreque, C. and Marianov, V. 2004. A procedure for designing hierarchical path-tree networks ... more ... Obreque, C. and Marianov, V. 2004. A procedure for designing hierarchical path-tree networks and finding the optimal locations of the extremes of the main path , Santiago, Chile: Department of Electrical Engineering, Pontificia Universidad Católica de Chile. ...
The Single-Vehicle Routing Problem with Fixed Delivery and Optional Collections considers a set o... more The Single-Vehicle Routing Problem with Fixed Delivery and Optional Collections considers a set of delivery customers receiving goods from a depot and a set of collection customers sending goods to the same depot. All delivery customers must be visited by the vehicle, while a collection customer is visited only if the capacity of the vehicle is large enough to fit
... Duin and Volgenant (1990) provide a method for finding good upper and lower bounds for the so... more ... Duin and Volgenant (1990) provide a method for finding good upper and lower bounds for the solution; Pirkul et al. (1991) propose a heuristic based on a Lagrangean relaxation. Sancho (1995) finds a sub-optimal solution using a heuristic based on dynamic programming. ...
Abstract We address the p-cable-trench problem. In this problem, p facilities are located, a tren... more Abstract We address the p-cable-trench problem. In this problem, p facilities are located, a trench network is dug and cables are laid in the trenches, so that every customer-or demand-in the region is connected to a facility through a cable. The digging cost of the trenches, as ...
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Papers by Carlos Obreque