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Distribution Problems (distribution + problem)

Distribution by Scientific Domains

Mathematics and Statistics	50%

Selected Abstracts

A tabu search procedure for coordinating production, inventory and distribution routing problems

INTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH, Issue 2 2010
André Luís Shiguemoto
Abstract This paper addresses the problem of optimally coordinating a production-distribution system over a multi-period finite horizon, where a facility production produces several items that are distributed to a set of customers by a fleet of homogeneous vehicles. The demand for each item at each customer is known over the horizon. The production planning determines how much to produce of each item in every period, while the distribution planning defines when customers should be visited, the amount of each item that should be delivered to customers and the vehicle routes. The objective is to minimize the sum of production and inventory costs at the facility, inventory costs at the customers and distribution costs. We also consider a related problem of inventory routing, where a supplier receives or produces known quantities of items in each period and has to solve the distribution problem. We propose a tabu search procedure for solving such problems, and this approach is compared with vendor managed policies proposed in the literature, in which the facility knows the inventory levels of the customers and determines the replenishment policies. [source]

Integer programming solution approach for inventory-production,distribution problems with direct shipments

INTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH, Issue 3 2008
Miguel A. Lejeune
Abstract We construct an integrated multi-period inventory,production,distribution replenishment plan for three-stage supply chains. The supply chain maintains close relationships with a small group of suppliers, and the nature of the products (bulk, chemical, etc.) makes it more economical to rely upon a direct shipment, full-truck load distribution policy between supply chain nodes. In this paper, we formulate the problem as an integer linear program that proves challenging to solve due to the general integer variables associated with the distribution requirements. We propose new families of valid cover inequalities, and we derive a practical closed-form expression for generating them, upon the determination of a single parameter. We study their performances through benchmarking several branch-and-bound and branch-and-cut approaches. Computational testing is performed using a large-scale planning problem faced by a North American company. [source]

Flexibility and complexity in periodic distribution problems

NAVAL RESEARCH LOGISTICS: AN INTERNATIONAL JOURNAL, Issue 2 2007
Peter Francis
Abstract In this paper, we explore trade-offs between operational flexibility and operational complexity in periodic distribution problems. We consider the gains from operational flexibility in terms of vehicle routing costs and customer service benefits, as well as the costs of operational complexity in terms of modeling, solution methods, and implementation challenges for drivers and customers. The period vehicle routing problem (PVRP) is a variation of the classic vehicle routing problem in which delivery routes are constructed for a period of time; the PVRP with service choice (PVRP-SC) extends the PVRP to allow service (visit) frequency to become a decision of the model. For the periodic distribution problems represented by PVRP and PVRP-SC, we introduce operational flexibility levers and a set of quantitative measures to evaluate the trade-offs between flexibility and complexity. We develop a Tabu Search heuristic to incorporate a range of operational flexibility options. We analyze the potential value and the increased operational complexity of the flexibility levers. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2007 [source]

Edge assembly-based memetic algorithm for the capacitated vehicle routing problem

NETWORKS: AN INTERNATIONAL JOURNAL, Issue 4 2009
Yuichi Nagata
Abstract Vehicle routing problems are at the heart of most decision support systems for real-life distribution problems. In vehicle routing problem a set of routes must be determined at lowest total cost for a number of resources (i.e., fleet of vehicles) located at one or several points (e.g., depots, warehouses) to efficiently service a number of demand or supply points. In this article a new memetic algorithm is suggested for the standard capacitated vehicle routing problem. The proposed algorithm combines the edge assembly (EAX) crossover with well-known local searches and allows for infeasible solutions with respect to capacity and route duration constraints after invoking the crossover. To address the constraint violation, an efficient modification algorithm is also suggested. Experimental tests on 47 standard benchmarks demonstrate that the suggested method is robust and competitive, finding new best-known solution to 20 well-studied instances and repeating the existing best-known solution for 24 problems in a reasonable computing time. © 2009 Wiley Periodicals, Inc. NETWORKS, 2009 [source]

Selective precipitation-assisted recovery of immunoglobulins from bovine serum using controlled-fouling crossflow membrane microfiltration

BIOTECHNOLOGY & BIOENGINEERING, Issue 5 2008
Adith Venkiteshwaran
Abstract Efficient and economic recovery of immunoglobulins (Igs) from complex biological fluids such as serum, cell culture supernatant or fermentation cell lysate or supernatant, represents a substantial challenge in biotechnology. Methods such as protein A affinity chromatography and anion exchange chromatography are limited by cost and selectivity, respectively, while membrane chromatography is limited by low adsorptive area, flow distribution problems and scale-up difficulties. By combining the traditional salt-assisted precipitation process for selective removal of Igs from serum followed by constant-permeate flux membrane microfiltration for low fouling, we demonstrate an exciting new, efficient and economic hybrid method. The high selectivity of an ammonium sulfate-induced precipitation step was used to precipitate the Igs leaving the major undesirable impurity, the bovine serum albumin (BSA), in solution. Crossflow membrane microfiltration in diafiltration mode was then employed to retain the precipitate, while using axial flow rates to optimize removal of residual soluble BSA to the permeate. The selectivity between immunoglobulin G (IgG) and BSA obtained from the precipitation step was ,36, with 97% removal of the BSA with diafiltration in 5 diavolumes with resulting purity of the IgG of ,93% after the membrane microfiltration step. Complete resolubilization of the IgG was obtained without any aggregation at the concentrations of ammonium sulfate employed in this work. Further, membrane pore size and axial Reynolds number (recirculation rate) were shown to be important for minimizing fouling and loss of protein precipitate. Biotechnol. Bioeng. © 2008 Wiley Periodicals, Inc. [source]