Cargo Consolidation and Distribution Through a Terminals-Network: A Branch-And-Price Approach

Less-than-truckload is a transport modality that includes many practical variations to convey a number of transportation-requests from the origin locations to their destinations by using the possibility of goods-transshipments on the carrier?s terminals-network. In this way logistics companies are required to consolidate shipments from different suppliers in the outbound vehicles at a terminal of the network. We present a methodology for finding near-optimal solutions to a less-than-truckload shipping modality used for cargo consolidation and distribution through a terminals-network. The methodology uses column generation combined with an incomplete branch-and-price procedure.Fil: Dondo, Rodolfo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin

Cargo consolidation and distribution through a terminals-network : A branch-and-price approach

Less-than-truckload (LTL) is a transport modality that includes many practical variations to convey a number of transportation-requests from the origin locations to their destinations by using the possibility of goodstransshipments on the carrier’s terminals-network. In this way logistics companies are required to consolidate shipments from different suppliers in the outbound vehicles at a terminal of the network. We present a methodology for finding near-optimal solutions to a LTL shipping modality used for cargo consolidation and distribution through a terminals-network. The methodology uses column generation combined with an incomplete branch-and-price procedure.Sociedad Argentina de Informática e Investigación Operativa (SADIO

A branch-and-price method for the Vehicle Routing Problem with Cross-Docking and Time Windows

One important factor in supply chain management is to efficiently control the supply chain flows. Due to its importance, many companies are trying to develop efficient methods to increase customer satisfaction and reduce costs. Cross-docking is considered a good method to reduce inventory and improve responsiveness. The Vehicle Routing Problem with Cross-Docking and Time Windows (VRP-CD-TW) consists on designing the minimum-cost set of routes to serve a given set of transportation requests while respecting constraints on vehicles capacity, customer time windows and using transfers on a cross-docking base. Each customer must be visited just once and mixed tours comprising pick-up and delivery stops are not allowed. For a given vehicle, the designed pick-up tour must precede its delivery tour. In this work, we model the VRP-CD-TW assuming that all feasible orders are known in advance. We present a new mixed integer program to model the VRP-CD-TW and reformulate it via Dantzig–Wolfe decomposition to later develop a column generation procedure. The proposed branch-and-price algorithm shows encouraging results on solving some Solomon-based instances.Sociedad Argentina de Informática e Investigación Operativ

A Branch-and-price Method for the Vehicle Routing problem with Cross-docking and Time Windows

One important factor in supply chain management is to efficiently control the supply chain flows. Due to its importance, many companies are trying to develop efficient methods to increase customer satisfaction and reduce costs. Cross-docking is considered a good method to reduce inventory and improve responsiveness. The Vehicle Routing Problem with Cross-Docking and Time Windows (VRP-CD-TW) consists on designing the minimum-cost set of routes to serve a given set of transportation requests while respecting constraints on vehicles capacity, customer time windows and using transfers on a cross-docking base. Each customer must be visited just once and mixed tours comprising pick-up and delivery stops are not allowed. For a given vehicle, the designed pick-up tour must precede its delivery tour. In this work, we model the VRP-CD-TW assuming that all feasible orders are known in advance. We present a new mixed integer program to model the VRP-CD-TW and reformulate it via Dantzig-Wolfe decomposition to later develop a column generation procedure. The proposed branch-and-price algorithm shows encouraging results on solving some Solomon-based instances.Fil: Dondo, Rodolfo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentin

A new formulation to the shortest path problem with time windows and capacity constraints

The Shortest-path problem with timewindows and capacity constraints (SPPTWCC) is a problem used for solving vehicle-routing and crewscheduling applications. The SPPTWCC occurs as a sub-problem used to implicitly generate the set of all feasible routes and schedules in the columngeneration formulation of the vehicle routing problem with time windows (VRPTW) and its variations. The problem is NP-hard in the strong sense. Classical solution approaches are based on a nonelementary shortest-path problem with resource constraints using dynamic-programming labeling algorithms. In this way, numerous label-setting algorithms have been developed. Contrarily to this approach and with the aim to obtain elemental and optimal solutions, we propose a new mixed integerlinear formulation to the SPPTWCC. Some valid inequalities that can be used to strengthen the linear relaxation of the SPPTWCC are also proposed. Numerical experiments on some VRPTW instances taken from Solomon's benchmark problems show that (near) optimal solutions are easily obtained in spite of the considerable problem size. Also the number of generated columns is kept at a very low level.Fil: Dondo, Rodolfo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin

On Alternative Formulations to the Shortest Path Problem with Time Windows and Capacity Constraints

The elementary shortest-path problem with time-windows and capac-ity constraints is a problem used for solving vehicle-routing and crew-scheduling applications. It occurs as a sub-problem used to implicitly generate the set of all feasible routes and schedules in the column-generation formulation of the vehicle routing problem with time windows and its variations. In the problem there is a directed graph with a source node and a destination node, and each arc has a cost and a vector of weights specifying its requirements of a resource with a finite capacity. A minimum cost source–destination directed path is sought such that the total consumption of the resource does not exceed the capacity. The problem ins NP-hard in the strong sense. We review integer-linear formulation to the problem and compare them in order to study their computational efficiency.Sociedad Argentina de Informática e Investigación Operativ

On Alternative Formulations to the Shortest Path Problem with Time Windows and Capacity Constraints

The elementary shortest-path problem with time-windows and capac-ity constraints is a problem used for solving vehicle-routing and crew-scheduling applications. It occurs as a sub-problem used to implicitly generate the set of all feasible routes and schedules in the column-generation formulation of the vehicle routing problem with time windows and its variations. In the problem there is a directed graph with a source node and a destination node, and each arc has a cost and a vector of weights specifying its requirements of a resource with a finite capacity. A minimum cost source–destination directed path is sought such that the total consumption of the resource does not exceed the capacity. The problem ins NP-hard in the strong sense. We review integer-linear formulation to the problem and compare them in order to study their computational efficiency.Sociedad Argentina de Informática e Investigación Operativ

On Alternative Formulations to the Shortest Path Problem with Time Windows and Capacity Constraints

The elementary shortest-path problem with time-windows and capac-ity constraints is a problem used for solving vehicle-routing and crew-scheduling applications. It occurs as a sub-problem used to implicitly generate the set of all feasible routes and schedules in the column-generation formulation of the vehicle routing problem with time windows and its variations. In the problem there is a directed graph with a source node and a destination node, and each arc has a cost and a vector of weights specifying its requirements of a resource with a finite capacity. A minimum cost source–destination directed path is sought such that the total consumption of the resource does not exceed the capacity. The problem ins NP-hard in the strong sense. We review integer-linear formulation to the problem and compare them in order to study their computational efficiency.Sociedad Argentina de Informática e Investigación Operativ

Optimal control of a two stages process for ethanol production from lignocellulosic materials of sorghum

The production and purification of ethanol from sorghum lignocellulosic materials by a two stages process was modeled and optimized in the present work. The process involves a first stage for hydrolyzing sweet sorghum bagasse and simultaneously fermenting the generated sugars and a second stage for the separation of ethanol from the filtered culture. Kinetic and distillation equations were embedded into macroscopic balances in order to derive a mathematical model used to solve a two-stage optimal control problem. The aim was to maximize the productivity of the process by optimally managing the controlled flows and by optimally fixing the switching time between the fermentation phase and the separation phase.Sociedad Argentina de Informática e Investigación Operativ

Optimal control of a two stages process for ethanol production from lignocellulosic materials of sorghum

The production and purification of ethanol from sorghum lignocellulosic materials by a two stages process was modeled and optimized in the present work. The process involves a first stage for hydrolyzing sweet sorghum bagasse and simultaneously fermenting the generated sugars and a second stage for the separation of ethanol from the filtered culture. Kinetic and distillation equations were embedded into macroscopic balances in order to derive a mathematical model used to solve a two-stage optimal control problem. The aim was to maximize the productivity of the process by optimally managing the controlled flows and by optimally fixing the switching time between the fermentation phase and the separation phase.Sociedad Argentina de Informática e Investigación Operativ