Fuzzy Multi-Objective Linear Programming and Simulation Approach to the Development of Valid and Realistic Master Production Schedule

Master production schedule (MPS) plays an important role in an integrated production planning system. It converts the strategic planning defined in a production plan into the tactical operation execution. The MPS is also known as a tool for top management to control over manufacture resources and becomes input of the downstream planning levels such as material requirement planning (MRP) and capacity requirement planning (CRP). Hence, inappropriate decision on the MPS development may lead to infeasible execution, which ultimately causes poor delivery performance. One must ensure that the proposed MPS is valid and realistic for implementation before it is released to real manufacturing system. In practice, where production environment is stochastic in nature, the development of MPS is no longer simple task. The varying processing time, random event such as machine failure is just some of the underlying causes of uncertainty that may be hardly addressed at planning stage so that in the end the valid and realistic MPS is tough to be realized. The MPS creation problem becomes even more sophisticated as decision makers try to consider multi-objectives; minimizing inventory, maximizing customer satisfaction, and maximizing resource utilization. This study attempts to propose a methodology for MPS creation which is able to deal with those obstacles. This approach takes into account uncertainty and makes trade off among conflicting multi-objectives at the same time. It incorporates fuzzy multi-objective linear programming (FMOLP) and discrete event simulation (DES) for MPS development.

Ansätze zur Verbesserung von Qualität und Wirtschaftlichkeit bei generativen Verfahren durch Optimierung des Pre-Processes

Mittels generativer Fertigung ist es heute möglich die, Entwicklungszeit und Ferti-gungsdauer von Prototypen, Produkten und Werkzeugen zu verkürzen. Neben dieser Zeitersparnis sind die im Vergleich zu konventionellen Fertigungsverfahren unwe-sentlichen Geometriebeschränkungen für den Anwender von besonderem Interesse. Dieses Alleinstellungsmerkmal der generativen Fertigung macht es möglich auch komplexe Geometrie wirtschaftlich herzustellen. Voraussetzung für eine wirtschaftli-che und fehlerminimierte Fertigung ist hierbei eine möglichst optimale Prozessvorbe-reitung (Pre-Processing). Dabei sind insbesondere die Schritte der Bauteilorientie-rung, der Stützkonstruktionserzeugung, der Schichtzerlegung sowie der Bauraum-ausnutzung von Interesse. Auch wenn diese Punkte wesentlich zur Qualität und Wirtschaftlichkeit beitragen, sind die Erkenntnisse für den unerfahrenen Anwender nur unzureichend dokumentiert, wodurch eine möglichst effiziente Fertigung zu-nächst ausgeschlossen werden kann. Anhand unterschiedlicher Beispiele sollen dem Anwender hier die Möglichkeiten zur Optimierung dieser Pre-Processing Schritte er-läutert werden. In diesem Rahmen werden die aktuellen Forschungsergebnisse des Lehrstuhls Rechnereinsatz in der Konstruktion, Institut für Produkt Engineering der Universität Duisburg-Essen in Bezug auf die Optimierung der Bauteilorientierung, der variablen Schichtzerlegung und der Optimierung der Bauraumausnutzung vorgestellt.

Lean-Production-Methods for XXL-Products

This paper discusses the different characteristics used to describe XXL-products and, furthermore, presents fundamental aspects concerning the construction (e.g. principles, methods) of production systems. A survey of experts at XXL-producers is used to identify the most commonly implemented Lean-Production-Methods of production systems. The article presents the survey results and finally concludes with an outlook on further steps.

Calculating Basal Thermal Zones Beneath the Antarctic Ice Sheet

A procedure is presented for using a simple flowline model to calculate the fraction of the bed that is thawed beneath present-day ice sheets, and therefore for mapping thawed, frozen, melting and freezing basal thermal zones. The procedure is based on the proposition, easily demonstrated, that variations in surface slope along ice flowlines are due primarily to variations in bed topography and ice-bed coupling, where ice-bed coupling for sheet flow is represented by the basal thawed fraction. This procedure is then applied to the central flowlines of flow bands on the Antarctic ice sheet where accumulation rates, surface elevations and bed topography are mapped with sufficient accuracy, and where sheet flow rather than stream flow prevails. In East Antarctica, the usual condition is a low thawed fraction in subglacial highlands, but a high thawed fraction in subglacial basins and where ice converges on ice streams. This is consistent with a greater depression of the basal melting temperature and a slower rate of conducting basal heat to the surface where ice is thick, and greater basal frictional heat production where ice flow is fast, as expected for steady-state flow. This correlation is reduced or even reversed where steady-state flow has been disrupted recently, notably where ice-stream surges produced the Dibble and Dalton Iceberg Tongues, both of which are now stagnating. In West Antarctica, for ice draining into the Pine Island Bay polynya of the Amundsen Sea, the basal thawed fraction is consistent with a prolonged and ongoing surge of Pine Island Glacier and with a recently initiated surge of Thwaites Glacier. For ice draining into the Ross Ice Shelf, long ice streams extend nearly to the West Antarctic ice divide. Over the rugged bed topography near the ice divide, no correlation consistent with steady-state sheet flow exists between ice thickness and the basal thawed fraction. The bed is wholly thawed beneath ice streams, even where stream flow is slow. This is consistent with ongoing gravitational collapse of ice entering the Ross Sea embayment and with unstable flow in the ice streams.

Impact de la fabrication de charbon de bois sur la production et la disponibilité fourragère de pâturage en zone subaride, cas de la commune de Soalara-Sud, Toliara ll: Rapport final

Ce projet a pour objectif de (1) décrire la filière charbon dans un terroir de la commune de Soalara, (2) d’identifier les effets des activités de fabrication de charbon de bois sur la végétation des pâturages qui est un fourré épineux et (3) d’estimer la quantité maximale de charbon pouvant être produite sans causer sa dégradation irréversible. Pour ce faire, des enquêtes auprès de la population locale et des relevés écologiques ont été entrepris. La majorité des ménages enquêtés (>80% ; N=56) pratiquent la fabrication de charbon de bois. Environ 41 000 sacs de charbons ont été produits dans le terroir en 2009. L’impact socio-économique de la filière charbon est positif puisqu’elle génère des revenus importants pour ses agents (producteur, transporteur et collecteur). Par contre, l’impact écologique est plutôt négatif puisque les activités charbonnières contribuent à réduire la densité d’arbres et d’arbustes de la végétation des fourrés épineux et sa richesse spécifique même si elles n’affectent pas trop sa disponibilité fourragère. De plus, la quantité de charbon produite (environ 820 t en 2009) dépasse la productivité de la végétation, estimée à 218 t.an-1. Par conséquent, une dégradation du site de production actuel, se traduisant par la disparition des espèces charbonnières, arriverait dans 17 ans au plus tard, si le rythme de production actuel continue. Des mesures de réduction des pressions sur la végétation (professionnalisation des éleveurs, amélioration des rendements de carbonisation et réglementation et contrôle plus strict de la filière charbon) et d’augmentation de sa production et productivité (restauration) doivent être prises pour éviter cette dégradation irréversible qui à terme pourrait être dommageable à l’élevage de petits ruminants même si ce n’est pas encore le cas actuellement.

Special Tax Treatment as Trade Policy: A Database on Export Processing and Special Economic Zones

Many countries treat income generated via exports favourably, especially when production takes places in special zones known as export processing zones (EPZs). EPZs can be defined as specific, geographically defined zones or areas that are subject to special administration and that generally offer tax incentives, such as duty‐free imports when producing for export, exemption from other regulatory constraints linked to import for the domestic market, sometimes favourable treatment in terms of industrial regulation, and the streamlining of border clearing procedures. We describe a database of WTO Members that employ special economic zones as part of their industrial policy mix. This is based on WTO notification and monitoring through the WTO’s trade policy review mechanism (TPRM), supplemented with information from the ILO, World Bank, and primary sources. We also provide some rough analysis of the relationship between use of EPZs and the carbon intensity of exports, and relative levels of investment across countries with and without special zones.