Redundant configuration of automated flow lines based on “Industry 4.0”-technologies

Over the past decades, robots have been heavily used for flow lines to increase productivity and product quality and to relieve workers of repetitive and dangerous tasks. However, despite continuous improvement of robots, the occurrence of failures remains a significant challenge in the operation of automated flow lines. Due to the connection of the stations in a flow line via a material handling system, failures at one station can quickly lead to throughput losses due to blocking and starving of upstream and downstream stations, respectively. To some extent, these throughput losses can be reduced by installing buffers between the stations. However, the installation of buffers requires considerable investments and scarce factory space. Therefore, the minimization of the total number of buffers is one of the primary objectives in flow line planning. Due to the advances of manufacturing technologies that form the foundation of “Industry 4.0”, new solutions to reduce throughput losses caused by equipment failures open up. One solution is a redundant configuration, in which downstream stations automatically take over the operations of failed stations in the event of failure. The throughput loss in these situations mainly depends on the level of redundancy designed into the system. Based on existing methods for the design of automated flow lines, we present two line balancing formulations for the configuration of automated flow lines under consideration of redundancies. The first formulation aims at maximizing the lines’ level of redundancy. The second formulation aims at a balanced allocation of redundancies along the line. To evaluate the presented formulations, we compare the performance with an existing line balancing approach for automated lines. With respect to this approach, improvements of the throughput rate between 3 % and 7 % are achieved.     

The Performance of MRP Purchase Lot-Size Procedures Under Actual Multiple Purchase Discount Conditions

Several heuristic procedures for purchase lot sizing in material requirements planning (MRP) systems were tested with actual data from manufacturing companies. Information provided by the companies for each purchased item included the estimated requirements and costs, the price discount structure from the vendor, and the actual company ordering policy. Simulation tests for each purchased item involved comparisons of several purchase lot-size procedures from the research literature along with the actual procedure used by the company providing the data. Results indicate that one of the heuristic lot-size procedures from the literature consistently outperformed the company policies as well as all other models tested. Another noteworthy result is that, in some cases, the actual company order policy was more cost-effective than some of the models from the research literature.     

Struktur und Entwicklung der Controllingforschung — Eine Zitations-und Kozitationsanalyse von Controllingbeiträgen in deutschsprachigen wissenschaftlichen Zeitschriften von 1970 bis 2003

Zusammenfassung  Controlling ist eine vergleichsweise junge Teildisziplin der Betriebswirtschaftslehre, die sich mittlerweile in Praxis und Wissenschaft etabliert hat. Das Wissen über seine Entwicklung ist in weiten Teilen noch unscharf und weitgehend durch „anecdotal evidence” bestimmt. Die Autoren verfolgen daher in ihrem Aufsatz das Ziel, einen Beitrag zum besseren Verst?ndnis der Strukturen und Entwicklung der deutschsprachigen Controllingforschung zu leisten. Hierfür analysieren sie die Zitations-und Kozitationsstrukturen in 643 Beitr?gen zu Controllingthemen, die im Zeitraum von 1970 bis 2003 in sechs führenden wissenschaftlichen Zeitschriften im deutschen Sprachraum ver?ffentlicht wurden. Diese Beitr?ge enthalten insgesamt 18.125 Quellen. Im Ergebnis der Analysen zeigt sich, dass das Zitierverhalten in der Controllingforschung im Vergleich zu anderen betriebswirtschaftlichen Teildisziplinen durch eine Reihe von Besonderheiten gepr?gt ist und dass sich die Strukturen der deutschsprachigen Controllingforschung über die Zeit stark ver?ndert haben.

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Structure and development of research on controlling — a citation analysis papers on controlling in German speaking journals from 1970 through 2003

Summary  Controlling is a relatively young discipline in the field of business administration, which has now established itself in practice as well as in theory. Our knowledge about its development is for the most part still diffuse and dominated by anecdotal evidence. In their paper, the authors pursue the goal of contributing to a better understanding of the structures and the development of the German-speaking research in controlling. For this purpose, they analyze the citations-and co-citations structures of 643 articles, focusing on controlling aspects published in six leading Germanic academic journals between 1970 and 2003. These papers comprise a total of 18,125 sources. The results of the analyses show that the attitude to cite in controlling research, compared to other disciplines in business administration, is characterized by a number of features. Furthermore, the structures of German controlling research have changed significantly over time.

     

Income tax schedule and redistribution in direct democracies – the Swiss case

This study examines redistribution policy through personal income taxes in Swiss cantons over the period 1995–2011. In a first step, redistribution measures are estimated with the help of exhaustive administrative data. Redistribution is decomposed into average tax rate and tax progression. In a second step, we investigate the impact of direct democratic institutions and their usage on tax policy and redistribution. The results suggest that the effect of direct democracy on income tax redistribution is a multilayered process. First, the theoretical availability of direct democracy tools does not seem to have the same impact as the effective use of them. Second, fiscal referendums may – in the short term –reduce redistribution through lower tax rates and lead to less tax progression. Third, an increasing number of ballots on initiatives leads to more tax progression and more redistribution in the long run. It seems that the short-term dampening effects of fiscal referendums on redistribution may be overridden in the long run by the expansive effect of popular initiatives.     

Analyzing event stream dynamics in two-mode networks: An exploratory analysis of private communication in a question and answer community

Information about social networks can often be collected as event stream data. However, most methods in social network analysis are defined for static network snapshots or for panel data. We propose an actor oriented Markov process framework to analyze the structural dynamics in event streams. Estimated parameters are similar to what is known from exponential random graph models or stochastic actor oriented models as implemented in SIENA. We apply the methodology on a question and answer web community and show how the relevance of different kinds of one- and two-mode network structures can be tested using a new software.     

Policy evaluation and economic policy advice

Arguably, one of the most important developments in the field of applied economics during the last few decades has been the emergence of systematic policy evaluation, with its distinct focus on the establishment of causality. By contrast to the natural sciences, the objects of our scientific interest typically exert some influence on their treatment status under the policy to be evaluated and on their economic outcomes. Thus, economic policy advice can only be successful, if it is based on an appropriate study design, experimental or observational. It will strive in societies that provide liberal access to data, accept the merits of randomized assignment and guard the independence of research institutions.