Search

ABSTRACTIn this paper, we study integrated strategies joining maintenance and quality. We consider an imperfect manufacturing system composed of a single machine subject to an increasing random failure rate and producing conforming (first and second choice) and non conforming items. In order to decrease the failure rate and its impact on teh quality of output products, a preventive maintenance (PM) policy, block type, with minimal reapair is applied. Indeed, two different strategies are developed: The first strategy consists on selling top quality products at the best price, selling products with substandard quality at a lower price and rejecting non-conforming items. For the second strategy, we propose reworking activities for products with substandard quality and non-conforming items in order to be sold at the best price. We aim to establish the optimal number of batches produced N* before each PM action maximizing the total profit per time unit. These two strategies are studied for both an infinite and finite horizon. A comparative study between these two strategies for an infinite horizon is developed in order to identify the most economical strategy. Numerical and sensitivity studies are developed, inspired from an industrial case, in order to illustrate the proposed models.

Depuis plus de 20 ans, une augmentation de l'incidence du cancer de la thyroïde de type papillaire et des carcinomes ≤20 mm a été observée en Algérie. Nous avons réalisé une étude afin de déterminer les effets sur les tendances observées de l’âge, de la période de diagnostic et de la cohorte de naissance, dans une cohorte de patients diagnostiqués avec un cancer papillaire confirmé dans le département d'Oran en Algérie, entre 1993 et 2013.

This paper deals with integrated models joining Non Quality effects and preventive maintenance (PM) policies. We consider a manufacturing system composed of a single machine subject to random failures and producing conforming and non conforming products. In order to decrease the random failure rate of our manufacturing system, we apply a preventive maintenance policy with minimal repair and non-negligible durations of maintenance actions. Our objective is to determine an optimal integrated maintenance-quality strategy taking into consideration the decreased quality of output products and the economic impact of reworking activities. In fact, we developed two different strategies: For the first strategy, we propose reworking activities for all non conforming products in order to improve their quality condition and to sell all batches at the best price Pmax. The aim of this strategy is to found the optimal number of batches produced and reworked N*before each preventive maintenance action, maximizing the total net profit per time unit PT1. For the second strategy, the same problem is studied but for a finite horizon. Two mathematical models are developed in order to find the optimal value of the decision variable N*for both strategies. Numerical examples are presented in order to illustrate proposed models and a sensitivity study is developed to evaluate the influence of the variation of models’ parameters.

The theory of regions has been recognized as a powerful method of control synthesis for obtaining maximally permissive and non-blocking controller. Although, the Petri net controller does not always exist, and in some cases, using the theory of regions becomes arduous when the reachability graph is sizable. We aimed in a previous work to reduce the resolution complexity of this theory by synthesizing minimal cuts that represent minimal zone in the reachability graph. In this work, we propose to design Petri net controller by dispossessing the reachability graph. To do so, we synthesize a set of canonic markings on which the theory of regions is applied to calculate the corresponding Petri net controller. Additionally, the Petri net supervisor will recognize and prohibit all event separation instances in order to ensure the maximal permissive behavior. To illustrate the presented policy, an application is implemented on the Flexible Manufacturing System (FMS) at the ENIM (National School of Engineering ofMetz), in FRANCE.

Past attempts to develop electronic laboratory notebooks (ELN) have not always met with the success expected of them. This may have been due to job aspects and the difficulties encountered in their practical application, insufficient support provided to users during the learning phase, application complexity, interfacing problems with preexisting information systems, and the necessary integration of regulatory and legal aspects. Sanofi-Synthelabo adopted a different approach by emphasizing practical application and user support while putting the regulatory aspects to one side. An ELN model was developed on the basis of initial user-derived specifications, and a prototype was then produced, known as Kalabie (Klee business software). This ELN is sufficiently flexible to be shaped for different specialized chemical development sectors (synthesis, automates, preparative chromatography) and interfaces with preexisting in-house Oracle and MDL databases, thus supporting multisite extensions as a user-friendly intranet application. Technicians, scientists, and managers were happy with Kalabie when it entered service. Work is ongoing to extend the use of the ELN and to integrate the regulatory aspects.

Abstract: Differential enthalpy analyses were performed on the binaryn-alkane systemn-C24H50-n-C26H54 with a Setaram DSC111 calorimeter of Tian Calvet type. The measurements provided enthalpy data from 260 to 260 K onn-tetracosane,n-hexacosane and 19 binary mixtures. An analytical expression, derived from the Einstein model, is proposed for every pure phase in its temperature domain, to represent the variation in the enthalpy with temperature. A general expression for the enthalpy as a function of temperature and composition is also given.

At "low temperatures", the binary mixtures of the consecutive [even-numbered: even-numbered]; [even-numbered: odd-numbered] and [odd-numbered: odd-numbered] n-alkanes (19 < n < 27) do not form a continuous homogeneous solid solution. This study shows the existence of terminal solid solutions which have the pure n-alkanes structures and many intermediate solid solutions, denoted β'n and β''n (n = 1 or 2): these intermediate phases have an orthorhombic cell as the odd-numbered n-alkanes, but they are not isostructural with the pure n-alkanes nor with their terminal solid solutions. On the basis of powder X-ray diffraction photographs, the phases and β'1 and β'2 are indistinguishable in all the binary systems. The X-ray behavior of the phases β''n is also identical. The succession of the solid solutions is described when varying the concentration. With increasing temperature, the intermediate phases undergo the same solid-solid transitions as the odd-numbered n-alkanes (n-tricosane), and the rotator phases appear at "high temperatures" below the solidus line. The phase diagrams of n-C22: n-C23 n-C23: n-C24 n-C22: n-C24 and n-C24: n-C26 are presented.

The shapes of the C22H46-C24H50and C23H48-C24H50binary phase diagrams were analyzed. In the C22H46-C24H50binary system the increased stability of the binary compounds with increasing temperature can be explained by the much larger heat capacity and entropy of the binary compounds compared to that of the components C22H46and C24H50. In the C23H48-C24H50system this effect is much less pronounced. The measured enthalpy data of n-alkanes C19H40to C24H50and of the binary system C22H46-C24H50were analyzed to obtain the ‘excess’ heat capacity per atom of carbon {[Cp/(Rm)]-3} (Rmbeing the number of carbon atoms). The ‘excess’ heat capacity per carbon atom is the value of the heat capacity above the Debye high temperature value of 3R. At low temperatures (below 280 K) one is in the Debye temperature θDregion. At higher temperatures the large ‘excess’ heat capacity of the solids explains the movements in the carbon chains. In the liquid the excess heat capacity is small and corresponds numerically to the anharmonic vibrations in low melting metals. In contrast to metals, where the difference in heat capacity between liquid and solid below the melting point is positive Cp(L-s)>0, in the alkanes studied it is strongly negative Cp(L-s)≪0. This explains the shape of the binary phase diagrams C22H46-C24H50, C24H50-C26H54, C22H46-C23H48and C23H48-C24H50.