Trevor S. Hale

Location Science Research: A Review

This document presents a broad review of facility location and location science research. The goal of this report is not to provide an exhaustive list of location science topics (an undertaking far beyond the scope of a single journal article), but rather to provide the reader with a more general review of the location science research landscape. This document starts with a short introduction to some of the more germane aspects of all location science research.

Improving supply chain disaster preparedness: A decision process for secure site location

Purpose – Terrorist attacks, natural disasters, and regional power outages from the past several years have all highlighted the low levels of disaster preparedness that exist at many firms. Supply chain disruptions caused by external events can have a significant financial and operational impact on firms not properly prepared. Therefore, improving disaster preparedness in supply chains is critical. One critical component of disaster management planning in supply chains is the storage of emergency supplies, equipment, and vital documents that will be needed in times of crisis. The goal of this paper is propose a decision process for establishing an efficient network of secure storage facilities that can effectively support multiple supply chain facilities.Design/methodology/approach – The authors use the five‐stage disaster management process for supply chains as the framework for a proposed decision process for secure site locations. The decision process combines recommendations from FEMAs Disaster Manag...

Closed form models for determining the optimal dwell point location in automated storage and retrieval systems

This paper examines the problem of where a storage/retrieval machine should reside, or dwell, when an automated storage and retrieval system (AS/RS) becomes idle to minimize the expected value of the next transaction time. After a review of the relevant literature on AS/RS dwell point strategies, this paper proposes several analytical models of these expected response times of the AS/RS based on the relative locations of the input and output ports of the AS/RS. It uses a continuous rack approximation to provide analytical models of the dwell point location problem. These models provide closed form solutions for the dwell point location in an AS/RS. Extensions are made to consider AS/RS with a variety of configurations including multiple input and output ports. These models not only provide solutions to the dwell point location problem, but they provide considerable insight into the nature of this problem, which is particularly valuable when the requirements facing the AS/RS are uncertain.

A continuous approximation procedure for determining inventory distribution schemas within supply chains

This paper presents an integrated inventory distribution optimization model that simultaneously incorporates the issues of location, production, inventory, and transportation within a supply chain. The objective is to determine the optimal number and size of shipments under varying but commonly practiced production and shipping scenarios. A continuous approximation procedure is proposed to determine the optimal number and size of shipments. Three production and shipping scenarios are investigated and closed form expressions for the optimal number of shipments for each scenario are obtained. A numerical example is presented to demonstrate the usefulness of the model. 2007 Elsevier B.V. All rights reserved.

A framework for an integrated distribution system optimisation model

This paper presents a framework for an integrated optimization model of supply chain functions in a multiplant, multi-product, multi-customer supply chain with deterministic demands. A mixed-binary integer programming model is proposed to integrate the capacitated location, production, and distribution (CLPD) functions within a supply chain. The integrated CLPD problem is formulated as a profit maximization model with capacity and demand constraints. The result is a framework from which to design entire supply chains from suppliers to customers. The proposed model is solved using OPL Studio 3.7 and solutions for four variations of the CLPD problem are presented to demonstrate the efficacy of the integrated approach. The main contribution of this research is a multi-echelon, supply chain design and modeling hierarchy. This study was motivated by a perceived gap in the literature on supply chain modeling methods and supply chain frameworks.

An improved facility layout construction method

This study presents a new distance-based facility layout construction technique. Given a two-dimensional (i.e. single-floor) facility layout construction problem in which the order of placement of individual departments is known (a challenging problem in itself), the technique presented herein proposes the use of sub-departments and expected distance functions instead of centroid-to-centroid distances for the placement of departments. In this paper an expected distance function is defined as the probabilistic expectation of the particular distance metric of interest (rectilinear, Euclidean, etc.) in which the parameters involved are defined by random vectors in 2-dimensional Euclidean space. This study presents an enhanced facility layout construction technique that incorporates several enhancements over the well-known systematic layout procedure (SLP). The goal herein is to minimise the error induced by the use of the centroid-to-centroid distances between the departments inherent to the SLP.

Closed form models for dwell point locations in automated storage carousel systems

This research focuses on determining the optimal dwell point location in an automated storage carousel system (ASCS) to minimise the expected response time for incoming service requests (storages and retrievals). This can be achieved by modelling the problem as a minisum location problem on a line segment with two-dimensional existing facilities (demands) using a continuous approximation of the individual storage locations of the ASCS. Closed form solutions of the associated dwell point location problem have been provided for the two different cases used to model this problem. These two cases arise from the two possible different configurations of the ASCS parameters; the travel times in circumference and height.

A methodology for estimating expected distances between nodes on a network

Transportation, distribution, and logistics professionals often need to estimate the distances that are used for the arc lengths between nodes on a network model. For example, a network model might be representative of roads and cities in which the actual distance from one city to the next may vary depending upon the actual source and destination within each of the respective cities. Hence, estimates for the arc lengths within the network model will contain error. This research presents two new models to estimate these inter-nodal distances for cases in which complete nodal representation of every source and destination is computationally prohibitive.

Closed form models for dwell point locations for overhead bridge cranes

This research presents a methodology for determining the optimal dwell point location for an overhead bridge crane to minimise the expected response times. The problem is modelled as a planar minisum location problem with both zero dimensional (point) and two-dimensional (planar) existing demands. These demands come in three forms: from the Input/Output (I/O) location into the service area (storage move), from the service area to the I/O (retrieval move); and, across the service area (intra-service area move). The result is a non-trivial solution to where the crane should dwell when it is idle. Results of an implementation are also presented.

The generalised dwell point location problem

This research presents a generalised procedure to determine the optimal dwell point location for an arbitrary service device within a defined region. Similar to some existing dwell point location research for material handling systems, this study models a generic system that responds to demands for service from a region defined by a bi-variate random vector over some predefined service region as well as from a particular point analogous to the Input/Output (I/O) location for an arbitrary material handling system. A step-by-step procedure is delineated for determining the optimal dwell point location for a generic system. Extensions to the model for systems with multiple point (I/O) locations as well as for systems with multiple service regions are also presented.