A fuzzy approach for the earned value management

The earned value technique is a crucial technique in analyzing and controlling the performance of a project which allows a more accurate measurement of both the performance and the progress of a project. This paper presents a new fuzzy-based earned value model with the advantage of developing and analyzing the earned value indices, and the time and the cost estimates at completion under uncertainty. As the uncertainty is inherent in real-life activities, the developed model is very useful in evaluating the progress of a project where uncertainty arises. A small example illustrates how the new model can be implemented in reality. © 2010 Elsevier Ltd and IPMA

Economic Production Quantity in Reworkable Production Systems with Inspection Errors, Scraps and Backlogging

ABSTRACT The classical economic production quantity (EPQ) model is a well-known and commonly used inventory control technique. Common assumptions in this model are that all units produced are of perfect quality and shortage is not allowed, since in practice shortage, non-conforming product or scrap items are possible, these assumptions will underestimate the actual required quantity. The objective of this paper is to provide a framework to integrate production of imperfect quality items, inspection errors, rework, scrap items and backlogging into a single EPQ model. To achieve this objective a suitable mathematical model is developed and the optimal production lot size which minimizes the total cost is derived. The sensitivity analysis results indicate the model is very sensitive to shortage cost per unit shortage and type-I error of inspection. While findings of this study show that the model is very sensitive to parameters type-I error of inspection, proportion of defectives in production process and shortage cost per unit short, it is much less sensitive to parameters like proportion of scraps in rework process and Type-II error of inspection. If the existence of such error and shortages are ignored, then the obtained results may differ considerably from the optimal outcome. This will impose additional costs to the system

A closed-loop IGBT non-destructive tester

Non-destructive testing capability is a very important aspect of power device technology evolution towards more robust and reliable products. This paper proposes a closed-loop non-destructive tester for high power multi-chip IGBT modules. Other than proposed elsewhere in the past, the solution put forward here includes the possibility to be used in closed-loop, by proper identification and monitoring of representative pre-failure signatures to automatically trigger the activation of a protective switch and prevent the failure of the device under test. The advantage is that devices of different characteristics (e.g., voltage range, type) can be tested without having to set a specific intervention delay for the protection circuit. © 2012 Elsevier Ltd. All rights reserved