@misc{vondemBussche2006,
  type      = {Master Thesis},
  author    = {von dem Bussche, Jens},
  title     = {Modelling the spatial distribution of blackbird (Turdus merula) and ring ouzel (Turdus torquatus) in Switzerland},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14012},
  school      = {Universit{\"a}t Potsdam},
  year      = {2006},
  abstract  = {To characterise the habitat preferences of ring ouzel (Turdus torquatus) and blackbird (T. merula) in Switzerland, we adopt species distribution modelling and predict the species' spatial distribution. We model on two different scales to analyse in how far downscaling leads to a different set of predictors to describe the realised habitat best. While the models on macroscale (grid of one square kilometre) cover the entire country, we select a set of smaller plots for modelling on territory scale. Whereas ring ouzels occur in altitudes above 1'000 m a.s.l. only, blackbirds occur from the lowlands up to the timber line. The altitudinal range overlap of the two species is up to 400 m. Despite both species coexist on macroscale, a direct niche overlap on territory scale is rare. Small-scale differences in vegetation cover and structure seem to play a dominant role for habitat selection. On macroscale however, we observe a high dependency on climatic variables mainly representing the altitudinal range and the related forest structure preferred by the two species. Applying the models for climate change scenarios, we predict a decline of suitable habitat for the ring ouzel with a simultaneous median altitudinal shift of +440 m until 2070. In contrast, the blackbird is predicted to benefit from higher temperatures and expand its range to higher elevations.},
  language  = {en}
}
@techreport{Gruševaja2006,
  type      = {Working Paper},
  author    = {Gruševaja, Marina},
  title     = {Do institutions matter?},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14485},
  year      = {2006},
  abstract  = {Contens 1 Introduction 2 Institutions and the Institutional Change 2.1 Institutions and Theoretical Concepts in Economics 2.2 Path Dependence 2.3 Inconsistence of Institutional Development 2.4 Determinants of Effectiveness 2.5 Efficiency of New Institutions 3 What is "Competition Policy"? 4 The Competition Policy in Russia as an Institution 4.1 Establishment of the Competition Policy as an Institution 4.2 Market Structure and Competition Policy 4.3 Measures of Competition Policy 4.3.1 Prohibition of Competition Restrictive Agreements or Concerted Actions 4.3.2 Abuse of Dominance 4.3.3 Merger Control 4.3.4 Restrictive Action to Competition of Administrative Bodies 4.4 Violations of the Competition Law 4.5 Problems of the Russian Competition Policy 5 Which Mistakes Russia has made with the Implementation of theCompetition Policy? 6 Is a Lacking Effectiveness of Transplanted Institutions Inevitable? 7 Concluding Remarks},
  language  = {en}
}
@techreport{BlienSanner2006,
  type      = {Working Paper},
  author    = {Blien, Uwe and Sanner, Helge},
  title     = {Structural change and regional employment dynamics},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14425},
  year      = {2006},
  abstract  = {A casual look at regional unemployment rates reveals that there are vast differences, which cannot be explained by different institutional settings. Our paper attempts to trace these differences in the labor market performance back to the regions' specialization in products that are more or less advanced in their product cycle. The model we develop shows how individual profit and utility maximization endogenously yields higher employment levels in the beginning. In later phases, however, employment decreases in the presence of process innovation. Our model suggests that the only way to escape from this vicious circle is to specialize in products that are at the beginning of their "economic life". The model is based on an interaction of demand and supply side forces.},
  language  = {en}
}
@techreport{Sanner2005,
  type      = {Working Paper},
  author    = {Sanner, Helge},
  title     = {Price responses to market entry with and without endogenous product choice},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14399},
  year      = {2005},
  abstract  = {Textbook wisdom says that competition yields lower prices and higher consumer surplus than monopoly. We show in two versions of a simple location-product differentiation model with and without endogenous choice of products that these two results have to be qualified. In both models, more than half of the reasonable parameter values lead to higher prices with duopoly than with monopoly. If the product characteristics are exogenous to the firms, consumers may even be be better off with monopoly in average.},
  language  = {en}
}
@techreport{Kauffmann2005,
  type      = {Working Paper},
  author    = {Kauffmann, Albrecht},
  title     = {Structural change during transition},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14304},
  year      = {2005},
  abstract  = {This paper analyses the structural change in Russia during the transition from the planned to a market economy. With regard to the famous three sector hypothesis, broad economic sectors were formed as required by this theory. The computation of their shares at GNP at market prices using Input-Output tables, and the adjustment of results from distortions, generated as side effects of tax avoidance practices, shows results that clearly reject claims that Russia would be on the road to a post-industrial service economy. Instead, at least until 2001, a tendency of "primarisation" could be observed, that presents Russia closer to less-developed countries.},
  language  = {en}
}
@techreport{Sanner2005,
  type      = {Working Paper},
  author    = {Sanner, Helge},
  title     = {Instability in competition},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14299},
  year      = {2005},
  abstract  = {In this paper we show that Puu (2002) does not provide a stable solution to the location game, according to his own definition of stability. If the usual two-stage game is considered, where in the first stage a location is chosen once and forever, and in the second stage prices are determined, the equilibrium proves stable for a sizeable interval of parameters, however. Even though this procedure is most common in analyzing Hotelling's location problem, it is not satisfying because it exhibits an inconsistent informational structure. The search for a better concept of stability is imperative.},
  language  = {en}
}
@book{OPUS4-1294,
  title     = {Information structure in cross-linguistic corpora : annotation guidelines for phonology, morphology, syntax, semantics and information structure},
  editor    = {Dipper, Stefanie and Goetze, Michael and Skopeteas, Stavros},
  publisher = {Universit{\"a}tsverlag Potsdam},
  address   = {Potsdam},
  isbn      = {978-3-939469-66-7},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14199},
  publisher      = {Universit{\"a}t Potsdam},
  pages     = {210},
  year      = {2007},
  abstract  = {This volume presents annotation guidelines that have been developed in the context of the SFB 632, a collaborative research center entitled "Information Structure: the Linguistic Means for Structuring Utterances, Sentences and Texts". An important result of the SFB 632 are the SFB corpora from more than 20 typologically different languages, which have been annotated according to the guidelines presented here. The ultimate target of the data and its annotations is to support the study of Information Structure. Information Structure involves all levels of grammar and, hence, the present guidelines cover relevant aspects of all these levels: - Phonology - Morphology - Syntax - Semantics - Information Structure These levels are dealt with in individual chapters, containing tagset declarations with obligatory and optional tags, detailed annotation instructions, and illustrative examples. The volume also presents an evaluation of inter-annotator agreement of Syntax and Information Structural annotation.},
  language  = {en}
}
@techreport{Holzer2004,
  type      = {Working Paper},
  author    = {Holzer, Verena Le{\"i}la},
  title     = {Does the german renewable energies act fulfil sustainable development objectives?},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14189},
  year      = {2004},
  abstract  = {Table of contens 1 Introduction 2 The concept of sustainability 2.1 Ecological sustainability 2.2 Social sustainability 2.3 Economic sustainability 2.4 The sustainability strategy of the german government 3 Effects of energy use on the enviromment 4 Requirements of the SSGG for energy policy 4.1 Ecological implications of thr SSGG 4.2 Social and economic requirements of the SSGG 5 The German Renewable Energies Act 5.1 Objectives 5.2 Design and mechanisms 5.3 Fees-in tariffs 6 Does the EEG meet the sustainability requirements of the SSGG? 6.1 Management rules 6.2 Social sustainability 6.3 Economic sustainability 6.4 Development tendencis 7 Possible amendments for more sustainability 7.1 Changing the promotional system 7.2 A European regulation},
  language  = {en}
}
@techreport{Wagner2004,
  type      = {Working Paper},
  author    = {Wagner, Wolfgang},
  title     = {A simulation of segregation in cities and its application for the analysis of rent control},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14177},
  year      = {2004},
  abstract  = {Social segregation in cities takes place where different household groups exist and when, according to Schelling, their location choice either minimizes the number of differing households in their neighborhood or maximizes their own group. In this contribution an evolutionary simulation based on a monocentric city model with externalities among households is used to discuss the spatial segregation patterns of four groups. The resulting complex spatial patterns can be shown as graphic animations. They can be applied as initial situation for the analysis of the effects a rent control has on segregation.},
  language  = {en}
}
@techreport{Wagner2004,
  type      = {Working Paper},
  author    = {Wagner, Wolfgang},
  title     = {Optimal spatial patterns of two, three and four segregated household groups in a monocentric city},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14165},
  year      = {2004},
  abstract  = {Usually, in monocentric city models the spatial patterns of segregated household groups are assumed to be ring-shaped, while early in the 1930ies Hoyt showed that wedge-shaped areas empirically predominate. This contribution presents a monocentric city model with different household groups generating positive externalities within the groups. At first, border length is founded as a criterion of optimality. Secondly, it is shown that mixed patterns of concentric and wedge-shaped areas represent multiple equilibria if more than two groups of households are being considered. The welfare optimal segregated pattern depends on the relative purchasing power of different household groups.},
  language  = {en}
}
@techreport{Wagner2004,
  type      = {Working Paper},
  author    = {Wagner, Wolfgang},
  title     = {Spatial patterns of segregation},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14153},
  year      = {2004},
  abstract  = {Usually, in monocentric city models, the spatial patterns of segregated ethnic groups are assumed to be ring-shaped, whereas in the 1930ies Hoyt showed that empirically wedge-shaped areas predominate. In contrast to Rose-Ackerman.s discussion of the in.uence within a ring-shaped pattern which the aversion which different households in the context of racism have, Yinger showed that, depending on the population mix, a wedge-shaped pattern may arise if it is border length which causes the spatial pattern. In this contribution, a simulation based on a monocentric city model with two or more different household groups is used to derive spatial patterns. Wedge-shaped segregation is shown to be the result of positive externalities among similar households. Differences between households only lead to ring-shaped patterns if the e\iect of a city center on spatial structure dominates neighborhood e\iects. If more than two groups of households are being considered, mixed patterns of concentric and wedge-shaped areas arise.},
  language  = {en}
}
@techreport{Sanner2004,
  type      = {Working Paper},
  author    = {Sanner, Helge},
  title     = {Economy vs. history},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14134},
  year      = {2004},
  abstract  = {The aim of this study is to examine in which cases economic forces or historical singularities prevail in the determination of the long-run distribution of firms. We develop a relatively general model of heterogenous firms' location choice in discrete space. The main force towards an agglomerated structure is the reduction of transaction costs for consumers if firms are located closely, whilst competition and transport costs work towards a more disperse structure. We then assess the importance of the initial conditions by simulating and comparing the resulting distribution of firms for identical economic parameters but varying initial settings. If the equilibrium distributions of firms are similar we conclude that economic forces have prevailed, while differences in the resulting distributions indicate that 'history' is more important. The (dis)similarity of distributions of firms is calculated by means of a measure, which exhibits a number of desirable features.},
  language  = {en}
}
@phdthesis{Demircioglu2007,
  author    = {Demircioglu, Aydin},
  title     = {Reconstruction of deligne classes and cocycles},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-13755},
  school      = {Universit{\"a}t Potsdam},
  year      = {2007},
  abstract  = {In der vorliegenden Arbeit verallgemeinern wir im Wesentlichen zwei Theoreme von Mackaay-Picken und Picken (2002, 2004). Im ihrem Artikel zeigen Mackaay und Picken,dass es eine bijektive Korrespodenz zwischen Deligne 2-Klassen \$\xi \in \check{H}^2(M, \mathcal{D}^2)\$ und Holonomie Abbildungen von der zweiten d{\"u}nnen Homotopiegruppe \$\pi_2^2(M)\$ in die abelsche Gruppe \$U(1)\$ gibt. Im zweiten Artikel wird eine Verallgemeinerung dieses Theorems bewiesen: Picken zeigt, dass es eine Bijektion gibt zwischen Deligne 2-Kozykeln und gewissen 2-dimensionalen topologischen Quantenfeldtheorien. In dieser Arbeit zeigen wir, dass diese beiden Theoreme in allen Dimensionen gelten.Wir betrachten zun{\"a}chst den Holonomie Fall und k{\"o}nnen mittels simplizialen Methoden nachweisen, dass die Gruppe der glatten Deligne \$d\$-Klassen isomorph ist zu der Gruppe der glatten Holonomie Abbildungen von der \$d\$-ten d{\"u}nnen Homotopiegruppe \$\pi_d^d(M)\$ nach \$U(1)\$, sofern \$M\$ eine \$(d-1)\$-zusammenh{\"a}ngende Mannigfaltigkeit ist. Wir vergleichen dieses Resultat mit einem Satz von Gajer (1999). Gajer zeigte, dass jede Deligne \$d\$-Klasse durch eine andere Klasse von Holonomie-Abbildungen rekonstruiert werden kann, die aber nicht nur Holonomien entlang von Sph{\"a}ren, sondern auch entlang von allgemeinen \$d\$-Mannigfaltigkeiten in \$M\$ enth{\"a}lt. Dieser Zugang ben{\"o}tigt dann aber nicht, dass \$M\$ hoch-zusammenh{\"a}ngend ist. Wir zeigen, dass im Falle von flachen Deligne \$d\$-Klassen unser Rekonstruktionstheorem sich von Gajers unterscheidet, sofern \$M\$ nicht als \$(d-1)\$, sondern nur als \$(d-2)\$-zusammenh{\"a}ngend angenommen wird. Stiefel Mannigfaltigkeiten besitzen genau diese Eigenschaft, und wendet man unser Theorem auf diese an und vergleicht das Resultat mit dem von Gajer, so zeigt sich, dass es zuviele Deligne Klassen rekonstruiert. Dies bedeutet, dass unser Rekonstruktionsthreorem ohne die Zusatzbedingungen an die Mannigfaltigkeit M nicht auskommt, d.h. unsere Rekonstruktion ben{\"o}tigt zwar weniger Informationen {\"u}ber die Holonomie entlang von d-dimensionalen Mannigfaltigkeiten, aber daf{\"u}r muss M auch \$(d-1)\$-zusammenh{\"a}ngend angenommen werden. Wir zeigen dann, dass auch das zweite Theorem verallgemeinert werden kann: Indem wir das Konzept einer Picken topologischen Quantenfeldtheorie in beliebigen Dimensionen einf{\"u}hren, k{\"o}nnen wir nachweisen, dass jeder Deligne \$d\$-Kozykel eine solche \$d\$-dimensionale Feldtheorie mit zwei besonderen Eigenschaften, der d{\"u}nnen Invarianz und der Glattheit, induziert. Wir beweisen, dass jede \$d\$-dimensionale topologische Quantenfeldtheorie nach Picken mit diesen zwei Eigenschaften auch eine Deligne \$d\$-Klasse definiert und pr{\"u}fen nach, dass diese Konstruktion sowohl surjektiv als auch injektiv ist. Demzufolge sind beide Gruppen isomorph.},
  language  = {en}
}
@techreport{Do2004,
  type      = {Working Paper},
  author    = {Do, Truong Giang},
  title     = {Tariffs and export subsidies in a spatial economic model},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14071},
  year      = {2004},
  abstract  = {In the recent years there are many researchs discussing the effects of trade policy (tariffs, subsidies etc.) in international trade. The results are manifold. Some authors show that trade policy has negative effects on welfare, some spatial economists demonstrate that trade policy can have positive effects on welfare. This paper considers the effects of the trade policy made by both countries participating in international trade in a spatial economic model. It can be showed that trade policy of both trade partners (tariffs of one country and export subsidies of the other country) can improve the world welfare in comparison with free trade.},
  language  = {en}
}
@techreport{Holzer2004,
  type      = {Working Paper},
  author    = {Holzer, Verena Le{\"i}la},
  title     = {Ecological objectives and the energy sector},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14054},
  year      = {2004},
  abstract  = {Table of contents 1 Introduction 2 Ecological regulation and cost effectiveness 2.1 Climate policy 2.2 Promotion of renewable energies 3 Ecological regulation and security of supply 3.1 Climate policy 3.2 Promotion of renewable energies 4 The German Renewable Energies Act (EEG) 4.1 Objectives 4.2 Design and mechanisms 5 The European emissions trading system (EETS) 5.1 Objectives 5.2 Framework 6 The EEG and the EETS: trade off between ecological objectivesand cost effectiveness, innovation and security of supply? 6.1 EEG 6.2 EETS 6.3 Comparison between the approaches of the EEG and the EETS 7 Conclusions and outlook},
  language  = {en}
}
@techreport{Sanner2003,
  type      = {Working Paper},
  author    = {Sanner, Helge},
  title     = {Imperfect goods and labor markets, regulation, and spillover effects},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-13951},
  year      = {2003},
  abstract  = {(De)regulatory interventions frequently have unintended cross- market effects, which may or may not be desirable. We assess the effects of three policies on aggregate variables, in particular real income, from a theoretical perspective. Our results suggest that instruments acting upon wages have only a weak impact on real income, whereas the distribution of income is affected strongly. In contrast, a policy that enhances product market competition is fostering real income, but also impacts strongly on union wages and the distribution of income.},
  language  = {en}
}
@techreport{Sanner2003,
  type      = {Working Paper},
  author    = {Sanner, Helge},
  title     = {Imperfect goods and labor markets, and the union wage gap},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-13949},
  year      = {2003},
  abstract  = {Existing theoretical literature fails to explain the differences between the pay of workers that are covered by union agreements and others who are not. This study aims at closing this gap by a single general- equilibrium approach that integrates a dual labor market and a two- sector product market. Our results suggest that the so­ called 'union wage gap' is largely determined by the degree of centralization of the bargains, and, to a somewhat lesser extent, by the expenditure share of the unionized sector's goods.},
  language  = {en}
}
@misc{Wickert2007,
  type      = {Master Thesis},
  author    = {Wickert, Claudia},
  title     = {Breeding white storks in former East Prussia : comparing predicted relative occurrences across scales and time using a stochastic gradient boosting method (TreeNet), GIS and public data},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-13532},
  school      = {Universit{\"a}t Potsdam},
  year      = {2007},
  abstract  = {In dieser Arbeit wurden verschiedene GIS-basierte Habitatmodelle f{\"u}r den Weißstorch (Ciconia ciconia) im Gebiet der ehemaligen deutschen Provinz Ostpreußen (ca. Gebiet der russischen Exklave Kaliningrad und der polnischen Woiwodschaft Ermland-Masuren) erstellt. Zur Charakterisierung der Beziehung zwischen dem Weißstorch und der Beschaffenheit seiner Umwelt wurden verschiedene historische Datens{\"a}tze {\"u}ber den Bestand des Weißstorches in den 1930er Jahren sowie ausgew{\"a}hlte Variablen zur Habitat-Beschreibung genutzt. Die Aufbereitung und Modellierung der verwendeten Datens{\"a}tze erfolgte mit Hilfe eines geographischen Informationssystems (ArcGIS) und einer statistisch-mathematischen Methode aus den Bereichen „Machine Learning" und „Data-Mining" (TreeNet, Salford Systems Ltd.). Unter Verwendung der historischen Habitat-Parameter sowie der Daten zum Vorkommen des Weißstorches wurden quantitative Modelle auf zwei Maßstabs-Ebenen erstellt: (i) auf Punktskala unter Verwendung eines Rasters mit einer Zellgr{\"o}ße von 1 km und (ii) auf Verwaltungs-Kreisebene basierend auf der Gliederung der Provinz Ostpreußen in ihre Landkreise. Die Auswertung der erstellten Modelle zeigt, dass das Vorkommen von Storchennestern im ehemaligen Ostpreußen, unter Ber{\"u}cksichtigung der hier verwendeten Variablen, maßgeblich durch die Variablen ‚forest', ‚settlement area', ‚pasture land' und ‚coastline' bestimmt wird. Folglich l{\"a}sst sich davon ausgehen, dass eine gute Nahrungsverf{\"u}gbarkeit, wie der Weißstorch sie auf Wiesen und Weiden findet, sowie die N{\"a}he zu menschlichen Siedlungen ausschlaggebend f{\"u}r die Nistplatzwahl des Weißstorches in Ostpreußen sind. Geschlossene Waldgebiete zeigen sich in den Modellen als Standorte f{\"u}r Horste des Weißstorches ungeeignet. Der starke Einfluss der Variable ‚coastline' l{\"a}sst sich h{\"o}chstwahrscheinlich durch die starke naturr{\"a}umliche Gliederung Ostpreußens parallel zur K{\"u}stenlinie erkl{\"a}ren. In einem zweiten Schritt konnte unter Verwendung der in dieser Arbeit erstellten Modelle auf beiden Skalen Vorhersagen f{\"u}r den Zeitraum 1981-1993 getroffen werden. Dabei wurde auf dem Punktmaßstab eine Abnahme an potentiellem Bruthabitat vorhergesagt. Im Gegensatz dazu steigt die vorhergesagte Weißstorchdichte unter Verwendung des Modells auf Verwaltungs-Kreisebene. Der Unterschied zwischen beiden Vorhersagen beruht vermutlich auf der Verwendung unterschiedlicher Skalen und von zum Teil voneinander verschiedenen erkl{\"a}renden Variablen. Weiterf{\"u}hrende Untersuchungen sind notwendig, um diesen Sachverhalt zu kl{\"a}ren. Des Weiteren konnten die Modellvorhersagen f{\"u}r den Zeitraum 1981-1993 mit den vorliegenden Bestandserfassungen aus dieser Zeit deskriptiv verglichen werden. Es zeigt sich hierbei, dass die hier vorhergesagten Bestandszahlen h{\"o}her sind als die in den Z{\"a}hlungen ermittelten. Die hier erstellten Modelle beschreiben somit vielmehr die Kapazit{\"a}t des Habitats. Andere Faktoren, die die Gr{\"o}ße der Weißstorch-Population bestimmen, wie z.B. Bruterfolg oder Mortalit{\"a}t sollten in zuk{\"u}nftige Untersuchungen mit einbezogen werden. Es wurde ein m{\"o}glicher Ansatz aufgezeigt, wie man mit den hier vorgestellten Methoden und unter Verwendung historischer Daten wertvolle Habitatmodelle erstellen sowie die Auswirkung von Landnutzungs{\"a}nderungen auf den Weißstorch beurteilen kann. Die hier erstellten Modelle sind als erste Grundlage zu sehen und lassen sich mit Hilfe weitere Daten hinsichtlich Habitatstruktur und mit exakteren r{\"a}umlich expliziten Angaben zu Neststandorten des Weißstorches weiter verfeinern. In einem weiteren Schritt sollte außerdem ein Habitatmodell f{\"u}r die heutige Zeit erstellt werden. Dadurch w{\"a}re ein besserer Vergleich m{\"o}glich hinsichtlich erdenklicher Auswirkungen von {\"A}nderungen der Landnutzung und relevanten Umweltbedingungen auf den Weißstorch im Gebiet des ehemaligen Ostpreußens sowie in seinem gesamten Verbreitungsgebiet.},
  language  = {en}
}
@unpublished{Seehafer1995,
  author    = {Seehafer, Norbert},
  title     = {Nature of the α effect in magnetohydrodynamics},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-13919},
  year      = {1995},
  abstract  = {It is shown that the ff effect of mean-field magnetohydrodynamics, which consists in the generation of a mean electromotive force along the mean magnetic field by turbulently fluctuating parts of velocity and magnetic field, is equivalent to the simultaneous generation of both turbulent and mean-field magnetic helicities, the generation rates being equal in magnitude and opposite in sign. In the particular case of statistically stationary and homogeneous fluctuations this implies that the ff effect can increase the energy in the mean magnetic field only under the condition that also magnetic helicity is accumulated there.},
  language  = {en}
}
@unpublished{FeudelSeehafer1995,
  author    = {Feudel, Fred and Seehafer, Norbert},
  title     = {Bifurcations and pattern formation in a 2D Navier-Stokes fluid},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-13907},
  year      = {1995},
  abstract  = {We report on bifurcation studies for the incompressible Navier-Stokes equations in two space dimensions with periodic boundary conditions and an external forcing of the Kolmogorov type. Fourier representations of velocity and pressure have been used to approximate the original partial differential equations by a finite-dimensional system of ordinary differential equations, which then has been studied by means of bifurcation-analysis techniques. A special route into chaos observed for increasing Reynolds number or strength of the imposed forcing is described. It includes several steady states, traveling waves, modulated traveling waves, periodic and torus solutions, as well as a period-doubling cascade for a torus solution. Lyapunov exponents and Kaplan-Yorke dimensions have been calculated to characterize the chaotic branch. While studying the dynamics of the system in Fourier space, we also have transformed solutions to real space and examined the relation between the different bifurcations in Fourier space and toplogical changes of the streamline portrait. In particular, the time-dependent solutions, such as, e.g., traveling waves, torus, and chaotic solutions, have been characterized by the associated fluid-particle motion (Lagrangian dynamics).},
  language  = {en}
}