Ein neuer Ansatz zur Fahrplanoptimierung im ÖPNV: Maximierung von zeitlichen Sicherheitabständen

Der Fahrplan bildet ein wichtiges Element der Verkehrsplanung. Er legt die Ankunfts- und Abfahrtszeiten der einzelnen Linien im Streckennetz fest. Die bislang verwendete Software hilft bei der manuellen Erstellung am Bildschirm und ermöglicht die Visualisierung und Simulation von Fahrplänen. Zur besseren Unterstützung des Planers fehlen jedoch Systeme zur automatischen Generierung zulässiger und in Hinblick auf die Zielvorstellung optimierter Fahrpläne. Die vorliegende Arbeit beschäftigt sich mit einem neuen Ansatz zur Optimierung von Fahrplänen. Das der Fahrplangestaltung zu Grunde liegende Streckennetzwerk besteht aus einer Menge von Stationen und Linien, denen Takte zugeordnet sind. Den Streckenabschnitten zwischen den Stationen sind Fahrzeiten zugeordnet. Das Ziel der Fahrplanoptimierung, die in dieser Arbeit betrachtet wird, besteht darin, die Abfahrtszeiten der Linien an den Anfangsstationen so festzulegen, dass die Ankunftszeiten an den einzelnen Stationen möglichst gleichmässig verteilt sind. Damit soll erreicht werden, dass kleine Störungen, wie sie häufig bei Nahverkehrssytemen auftreten, nur geringe, zeitlich begrenzte Auswirkungen auf den Linienverkehr haben. Im ersten Kapitel werden die einzelnen Planungsprozesse im öffentlichen Personennahverkehr (ÖPNV) erläutert und es wird ein überblick über einige aus der Literatur bekannte Ansätze zur Fahrplanoptimierung gegeben. Kapitel 2 stellt die Modellierung zur Fahrplanoptimierung, die in dieser Arbeit untersucht wird, dar. In Kapitel 3 werden Reduktionen des Streckennetzwerks präsentiert, mit deren Hilfe die Zielfunktion und obere Schranken schneller ermittelt werden können. Die Reduktionen nutzen Relationen, die auf der Menge der Stationen und auf der Menge der Kanten eines speziellen noch zu definierenden Multi-Linienkonflikt-Graphen, der aus dem Streckennetzwerk gebildet wird, definiert sind. Darüber hinaus enthält Kapitel 3 Ergebnisse zur Zeitkomplexität des hier untersuchten Fahrplanoptimierungsproblems. Ein Branch-and-Bound-Algorithmus zur Lösung des Fahrplanoptimierungsproblems wird in Kapitel 4 vorstellt. Es werden Heuristiken präsentiert, um mit deren Hilfe gute Anfangslösungen für den Branch-and-Bound-Algorithmus zu erhalten. Kapitel 4 enthält noch einen Ansatz zur Zerlegung des Streckennetzwerks in Teilnetze, so dass es ausreicht, optimale Fahrpläne für die Teilnetze zu berechnen, um daraus einen optimalen Fahrplan für das gesamte Streckennetzwerk zu erhalten. Dazu werden die zweifachen Zusammenhangskomponenten des Linienkonflikt-Graphen, der aus dem Streckennetzwerk gebildet wird, betrachtet. In Kapitel 5 wird das Fahrplanoptimierungsproblem als ganzzahliges lineares Programm dargestellt, um dann mittels CPLEX, einem Programmpaket zur Lösung linearer und gemischtganzzahliger Variablen, gelöst zu werden. Mit Hilfe von Reduktionen lässt sich die Zahl der Variablen und Gleichungen so verringern, dass CPLEX in vertretbarer Zeit gute Lösungen liefert. Kapitel 6 präsentiert experimentelle Ergebnisse zur Lösung des Fahrplanoptimierungsproblems, die mit einem Branch-and-Bound-Verfahren und mit CPLEX auf Basis der ganzzahligen LP-Formulierung anhand der Daten des Streckennetzwerks der Kölner Verkehrs-Betriebe (KVB) einerseits und auf künstlich erzeugten Streckennetzwerken andererseits, erzielt worden sind. Die Arbeit schliesst mit einer Zusammenfassung und einem Ausblick auf mögliche zukünftige Entwicklungen dieses Ansatzes

Split and Migrate: Resource-Driven Placement and Discovery of Microservices at the Edge

Microservices architectures combine the use of fine-grained and independently-scalable services with lightweight communication protocols, such as REST calls over HTTP. Microservices bring flexibility to the development and deployment of application back-ends in the cloud. Applications such as collaborative editing tools require frequent interactions between the front-end running on users\u27 machines and a back-end formed of multiple microservices. User-perceived latencies depend on their connection to microservices, but also on the interaction patterns between these services and their databases. Placing services at the edge of the network, closer to the users, is necessary to reduce user-perceived latencies. It is however difficult to decide on the placement of complete stateful microservices at one specific core or edge location without trading between a latency reduction for some users and a latency increase for the others. We present how to dynamically deploy microservices on a combination of core and edge resources to systematically reduce user-perceived latencies. Our approach enables the split of stateful microservices, and the placement of the resulting splits on appropriate core and edge sites. Koala, a decentralized and resource-driven service discovery middleware, enables REST calls to reach and use the appropriate split, with only minimal changes to a legacy microservices application. Locality awareness using network coordinates further enables to automatically migrate services split and follow the location of the users. We confirm the effectiveness of our approach with a full prototype and an application to ShareLatex, a microservices-based collaborative editing application

Country Institutional Differences and Multinational Advantage in Banking

In this paper, we seek to answer the following questions : "Do country-level institutional differences affect benefits of multinationality? If so, how?" Focusing on resource and knowledge transfers as the key source of multinational advantage, we argue that the degree to which multinationals can benefit from such transfers depends on the extent to which knowledge or other resources are applicable across units. We further argue that the greater the institutional similarity across differrent countries in which the MNE is present, the greater the applicability and transferability of resources across its units. Hence, we claim that the greater the institutional similarity, the greater the firm performance and, further, the greater the effect of multinationality on performance. We test these arguments in a sample of 85 multinational banks using data from 2001-2002. We find that (1) institutional similarity significantly improves MNE performance, (2) multinationality does not have an independent effect on performance, and (3), contrary to our expectation, the positive effect of institutional similarity actually decrease with increasing levels of multinationality.country institution; multinational bank; banking

Investment Dynamics: Good News Principle

We study a dynamic Cournot game with capacity accumulation under demand uncertainty, in which the investment is perfectly divisible, irreversible, and productive with a lag. We characterize equilibrium investments under closed-loop and S-adapted open-loop information structures. Contrary to what is established usually in the dynamic games literature with deterministic demand, we find that the firms may invest at a higher level in the open-loop equilibrium (which in some cases coincides with Markov perfect equilibrium) than in the closed-loop Nash equilibrium. The rankings of the investment levels obtained in the two equilibria actually depend on the initial capacities and on the degree of asymmetry between the firms. We also observe, contrary to the bad news principle of investment, that firms may invest more as demand volatility increases and they invest as if high demand (i.e., good news) will unfold in the future.Capacity Investment, Dynamic Games, S-adapted Open-Loop Equilibrium, Closed-loop Equilibrium.

Multimarket Contact in Vertically Related Markets

We analyze collusion in two comparable market structures. In the first market structure only one firm is vertically integrated; there is one more independent firm in the upstream industry and another independent firm in the downstream industry. In the second market structure, there are only two vertically integrated firms that can trade among themselves in the intermediate good market. The second market structure mimics markets like the California gasoline market where firms vertically integrated through refinery, and retail markets. We rank these two market structures in terms of ease of collusion and show that while under some circumstances collusion is not possible in the market with one vertically integrated firm, collusion is possible in the market structure with two vertically integrated firms. We conclude that vertical (multimarket) contact facilitates collusion and vertical mergers suspected to lead to subsequent vertical mergers in an industry should receive higher antitrust scrutiny relative to single isolated vertical mergers.Multimarket; collusion; vertical integration; gasoline markets

Dynamic Competition in Electricity Markets: Hydroelectric and Thermal Generation

We study competition between hydro and thermal electricity generators that face uncertainty over demand and water flows where the hydro generator is constrained by water flows and the thermal generator by capacity. We compute the Feedback equilibrium for the in?nite horizon game and show that there can be strategic withholding of water by the hydro generator. When water inflow is relatively low, however, the hydro generator may use more water than efficient as it faces an inefficiently low shadow price of water in this case. The inefficiency of the market outcome is tempered by the capacity constraints: for a large range of possible thermal production capacities and water flow levels, welfare loss under the duopoly market structure is much less than would occur in the absence of water and capacity constraints.Electricity markets; Electricity markets; Hydroelectricity; Imperfect Competition

Religious education in two secular multicultural societies. The Turkish and Dutch case compared

In this paper we present in the first section the historical antecedents of the Turkish and Dutch educational system regarding religion(s) in education. In the second section we will outline the different approaches in religious education in both countries. In the third section the focus is on the relationship between state and church. In the fourth section the issue is how in both countries curricula and textbooks for religious education are constructed, checked and approved. Finally, we will summarize the most remarkable points of comparison between the Dutch and the Turkish case regarding religion(s) in education. © 2011 Published by Elsevier Ltd

Investment in Electricity Markets with Asymmetric Technologies

We study competition between hydro and thermal electricity generators under de- mand uncertainty. Producers compete in quantities and each is constrained: the ther- mal generator by capacity and the hydro generator by water availability. We analyze a two-period game emphasizing the incentives for capacity investments by the ther- mal generator. We characterize both Markov perfect and open-loop equilibria. In the Markov perfect equilibrium, investment is discontinuous in initial capacity and higher than it is in the open-loop equilibrium. However, since there are two distortions in the model, equilibrium investment can be either higher or lower than the ecient investment.Electricity markets; Dynamic game; Duopoly; Capacity investment.

Trade, diaspora and migration to New Zealand

NZIER has always had a strong interest in understanding the way in which the New Zealand economy interacts with the rest of the world. We have a long history of producing research into trade liberalisation and globalisation. As the global economy becomes ever more complex, we are now turning our attention to issues such as services, investment, technology transfer and the role of people movement in promoting economic growth and productivity. NZIER is delighted to continue this tradition by funding this important and innovative piece of research by David Law, Murat Gen and John Bryant into the links between trade flows and the movement of people across borders. This research was funded by NZIER in celebration of our 50th Anniversary in 2008. During this very challenging period for the global economy, there has been a tendency for policy makers to implement inwards-focused policies aimed to protecting domestic jobs and promoting domestic economic activity. Such policies are politically popular, but can be economically inefficient and often come at the expense of deeper economic integration between countries. One particularly topical area of policy discussion is the role of immigration in promoting economic growth. New Zealand has long been reliant on immigration to boost its population and to fill gaps in the labour market. And many Kiwis love to travel overseas to gain life and work experience. Given these continual inflows and outflows, it is interesting to consider how people movements might affect the New Zealands exports and imports of goods and services, and thus how immigration policy might be used as a policy lever to boost our international linkages. The paper uses empirical techniques to investigate the links between trade, migration and New Zealands diaspora. It clearly shows that inwards and outwards migration has a positive effect on goods and tourism trade. This suggests that policy makers could design immigration policy with these links in mind in order to maximise the economic potential of migrants. If trade follows migration flows, then an important avenue for boosting New Zealands integration with the global economy may be encouraging migrants from important trading partners.Diaspora, trade, Migration, New Zealand, economic growth