A general solution framework for component commonality problems

Component commonality, the use of the same version of a component across multiple products, is increasingly considered as a promising way to offer high external variety while retaining low internal variety in operations. However, increasing commonality has both positive and negative cost effects, so that optimization approaches are required to identify an optimal commonality level. As a more or less of components influences nearly every process step along the supply chain, it is not astounding that a multitude of diverging commonality problems is investigated in literature, each of which developing a specific algorithm designed for the respective commonality problem considered. The paper on hand aims at a general framework, flexible and effcient enough to be applied to a wide range of commonality problems. Such a procedure basing on a two-stage graph approach is presented and tested. Finally, flexibility of the procedure is shown by customizing the framework to account for different types of commonality problems.Product variety, Component commonality, Optimization, Graph approach

The Car Resequencing Problem with Pull-Off Tables

The car sequencing problem determines sequences of different car models launched down a mixed-model assembly line. To avoid work overloads of workforce, car sequencing restricts the maximum occurrence of labor-intensive options, e.g., a sunroof, by applying sequencing rules. We consider this problem in a resequencing context, where a given number of buffers (denoted as pull-off tables) is available for rearranging a stirred sequence. The problem is formalized and suited solution procedures are developed. A lower bound and a dominance rule are introduced which both reduce the running time of our graph approach. Finally, a real-world resequencing setting is investigated.mixed-model assembly line, car sequencing, resequencing

Global imbalances after the financial crisis.

Finanzmarktkrise; Wirtschaftskrise; Leistungsbilanz; Zahlungsbilanzungleichgewicht; Welt;

Umschlagbahnhöfe aus entscheidungsorientierter Sicht

Trotz intensiver Fördermaßnahmen für die Bahn durch den Bund und die EU verlagert sich das Transportaufkommen immer weiter in Richtung der Straße. Nachteile der Bahn bestehen etwa in einer geringeren Durchschnittsgeschwindigkeit und Zuverlässigkeit sowie einer geringen Flexibilität. Durch die effiziente Planung des Containerumschlags in Umschlagbahnhöfen können die Nachteile der Bahn jedoch abgemildert werden. Dieser Beitrag beschreibt neben dem grundlegenden Aufbau von Umschlagbahnhöfen die wichtigsten strategischen, taktischen und operativen Planungsprobleme zur Ermöglichung eines effizienten Containerumschlags.

Design und Betrieb von Cross Docks

Die hohen Anforderungen an heutige Wertschöpfungsnetzwerke in Bezug auf Flexibilität und Lieferbereitschaft stellen die Distribution vor die Aufgabe, Güter immer häufiger und in immer kleineren Mengen ausliefern zu müssen. Ein Ansatz, diesen Forderungen auf möglichst wirtschaftliche Art und Weise gerecht zu werden, besteht darin, bestehende Distributionsnetze um sogenannte Cross Docks zu erweitern. In solchen lagerlosen Umschlagzentren können dann kleine Warensendungen mit ähnlicher Destination zu vollständig ausgelasteten Lkw-Transporten konsolidiert werden, um sogenannte "economies in transportation" realisieren zu können. Neben den strategischen Überlegungen für und wider die Einführung von Cross Docks stehen in diesem Aufsatz insbesondere die Planungsprobleme im Mittelpunkt, die es im Rahmen der Errichtung und der täglichen Prozessabläufe in einem Cross Docking Terminal zu lösen gilt.

Robotized sorting systems: Large-scale scheduling under real-time conditions with limited lookahead

A major drawback of most automated warehousing solutions is that fixedly installed hardware makes them inflexible and hardly scalable. In the recent years, numerous robotized warehousing solutions have been innovated, which are more adaptable to varying capacity situations. In this paper, we consider robotized sorting systems where autonomous mobile robots load individual pieces of stock keeping units (SKUs) at a loading station, drive to the collection points temporarily associated with the orders demanding the pieces, and autonomously release them, e.g., by tilting a tray mounted on top of each robot. In these systems, a huge number of products approach the loading station with an interarrival time of very few seconds, so that we face a very challenging scheduling environment in which the following operational decisions must be taken in real time: First, since pieces of the same SKU are interchangeable among orders with a demand for this specific SKU, we have to assign pieces to suitable orders. Furthermore, each order has to be temporarily assigned to a collection point. Finally, we have to match robots and transport jobs, where pieces have to be delivered between loading station and selected collection points. These interdependent decisions become even more involved, since we (typically) do not posses complete knowledge on the arrival sequence but have merely a restricted lookahead of the next approaching products. In this paper, we show that even in such a fierce environment sophisticated optimization, based on a novel two-step multiple-scenario approach applied under real-time conditions, can be a serviceable tool to significantly improve the sortation throughput

Costs of housing crises: International evidence

This analysis provides evidence for the costs housing crises induce in terms of GDP growth and under what circumstances these crises are particularly costly. Housing crises are often followed by recessions that are longer and deeper than other recessions. According to empirical estimates, a housing crisis reduces the GDP growth rate in the following year on average by 2.5 percentage points and has a further negative impact in the second year. One important channel transmitting the additional effect of housing crises works through the depression of the construction sector, while wealth effects play a minor role

Will global imbalances decrease or even increase?

Assessing the quantitative impact of the fiscal packages which have been adopted in the current financial crisis is extremely difficult. The studies which are presented in this paper show wide differences, both for short-term and for medium-term multipliers. Moreover, multipliers which are derived from past experience may not apply in the current financial crisis. There are three main reasons: the zero-bound for monetary policy which played almost no role in the past has become binding in many countries; the standard procedure of calculating multipliers on the assumption of being in an initial equilibrium position is hardly appropriate in the current deep recession; and the standard procedure of linearizing models is questionable as currently there is a substantial deviation from the equilibrium

The ugly and the bad: banking and housing crises strangle output permanently, ordinary recessions do not

This paper provides statistical evidence suggesting that in industrial countries, recessions that are associated with either banking crises or housing crises dampen output far more than ordinary recessions. Using a parametric panel framework that allows for a bounceback of the level of output in the course of the cyclical recovery, we find that ordinary recessions are followed by strong recoveries that make up for almost all the preceding shortfall in output. This bounceback tends to be significantly smaller following recessions associated with banking crises or housing crises. Our paper corroborates the practice of focusing exclusively on severe crises used in an emerging macroeconomic literature and integrates it with the earlier literature on recessions and recoveries