Teoria De Inventarios

An Inventory Cost Model of a Government Owned
Facility using Fuzzy Set Theory
Derek M. Malstrom, Terry R. Collins, Ph.D., P.E., Heather L. Nachtmann, Ph.D.,
Manuel D. Rossetti, Ph.D., P.E
Department of Industrial Engineering
University of Arkansas
Fayetteville, AR 72701
Abstract
This project incorporates fuzzy set theory into developing a methodology for quantifying costs associated withperforming physical inventory procedures. While the project topic was developed through a direct application to a
particular facility, the paper extends this scope by presenting a methodology that is capable of being applied to most
warehouses or product distribution centers. Various methods of data collection are described, with a focus on
utilizing fuzzy set theory for areas where data isnot easily obtained.

Keywords
Physical inventory, Triangular fuzzy numbers, Time measurement

1. Introduction
Quantifying a total cost associated with physical inventorying procedures is often a difficult task. These costs are
frequently lumped into a single figure, and tracing the costs back to the activities that drive them requires detailed
analysis. The activities within physicalinventories consume resources at different rates, as some activities take
more time and effort than others do. Physical inventory procedures in the context of a warehouse or distribution
center often involve many activities and are not limited to simply conducting physical counts of stored merchandise.
A methodology to ascertain the cost associated with the physical inventorying process is needed toprovide
organizations with valuable information about their internal inventory procedures.
The topic originated as a research project conducted by the University of Arkansas and a government organization.
Due to the nature of the sensitive cost information, the name of this facility cannot be disclosed. The intent of the
paper is to outline the methodology used to develop a cost model thatrepresents all costs incurred through the daily
inventory operations. This methodology, while specific to the direct application, is then broadened to promote use
within similar types of facilities where inventory costs are not known with a high degree of precision. The first step
in this methodology is to identify the activities that consume resources, either of direct monetary value orexpenditures of physical labor with correlating costs. Depending upon the specific inventory activity to be
performed, various techniques can be implemented to collect data on the process. Traditional time measurement is
described and used when permissible by the activity, while fuzzy data collection is described for those activities
where a traditional time study is not feasible.
The majority ofhistorical data for the project application were recorded at the macroscopic level, but data that
depicted resource consumption at the activity level were not available. Analysis of the inventory activities that
consume resources was completed in efforts to outline procedures that could be used to collect data on each activity.
This process is described to promote use of this application to similartypes of facilities that routinely incur costs
from physical inventory procedures. It is expected that applying fuzzy set theory to gather data on physical
inventory procedures that possess inexact information will enable the proposed methodology to be applied to a
variety of similar circumstances in warehouses or distribution centers.

2. Literature Review
Relevant literature is reviewedto provide the reader with the types of applications of fuzzy set theory and physical
inventory procedures. Many such applications have been completed, with each providing unique insight on the
diverse range of instances where fuzzy set theory is deemed appropriate for the situation.

2.1 Physical Inventorying Procedures
Numerous industry experts have examined physical inventory costs by...