In dieser Arbeit werden zwei Klassen von Evolutionsgleichungen in einem Matrixraum-Setting studiert: Hyperbolische Erhaltungsgleichungen und aktive skalare Gleichungen. Für erstere wird untersucht, wann man Oszillationen mit Hilfe polykonvexen Maßen ausschließen kann; für Zweitere wird mit Hilfe von Oszillationen gezeigt, dass es unendlich viele periodische schwache Lösungen gibt.

The analysis of time-delayed dynamics on networks may help to understand many systems from physics, biology, and engineering, such as coupled laser arrays, gene-regulatory networks and complex ecosystems. Beside the complexity due to the network structure, the analysis is further complicated by the presence of the delays. Delay systems are in general infinite dimensional and thus can display complex dynamics as oscillations and chaos. The mathematical difficulties related to the delays hinders the analysis of delay networks. Thus, little is known yet about basic relations between network structure and delay dynamics. It has been shown that networks without delays can be studied efficiently with the generalized modeling approach, which analyzes the stability of an assumed steady state by a direct parametrization of the Jacobian matrix. In this thesis, I demonstrate the extension of the generalized modeling approach to delay networks and analyze networks of delay-coupled delay oscillators, with delayed auto-catalytic growth on the nodes and delayed transport between nodes. For degree-homogeneous networks (DHONs), in which each node has the same number of links, the bifurcation lines that border the stable areas can be calculated analytically, where the topology of the network is described only by the eigenvalues of the adjacency matrix. For undirected networks, the stability pattern in the parameter space of growth and transport delay is governed by two periodic sets of tongues of instability, which depend on the largest positive and the smallest negative eigenvalue. The direct relation between the eigenvalue and the bifurcation lines allows us to predict stability patterns for networks with certain topological properties. Thus, bipartite networks display a characteristic periodicity of tongues. In order to analyze the stability of degree-heterogeneous networks (DHENs), I apply a numerical sampling method based on Cauchy\'s Argument Principle. The stability patterns of these networks resembles the pattern of DHONs, which is governed by the two periodic sets. For networks with sufficiently many links, one set disappears, and the stability of DHENs can be approximates by the stability of a fully-connected network with the same average degree. However, random DHENs tend to be more stable than DHONs, and DHENs with a broad degree-distribution tend to be more stable than DHENs with a narrow distribution. Thus, such networks are more likely to give rise to amplitude death, i.e. the stabilization of an unstable steady state through diffusive coupling. The stability pattern of DHENs can be qualitatively different than the pattern in DHONs. However, for small growth delays, close to the critical delay of the single node system, the bifurcation lines of all DHENs with the same average degree coincide. This, is particularly interesting, because there the stability depends on a global property of the network, which suggests a diverging interaction length. In summary, the extension of generalized modeling to time-delay networks reveals basic relations between the delay dynamics and the topology. The generality of our model should allow to apply these results to a large class of real-world systems.

Die "Kontextsensitivität" genannte systematische Berücksichtigung von Umweltinformationen durch Anwendungssysteme kann als Querschnittsfunktion im betrieblichen Umfeld in vielen Bereichen einen Nutzen stiften. Wirklich praxistaugliche kontextsensitive Anwendungssysteme, die sich analog zu einem mitdenkenden menschlichen Assistenten harmonisch in die ablaufenden Vorgänge in der Realwelt einbringen, haben einen enormen Bedarf nach umfassenden, d.h. diverse Aspekte der Realwelt beschreibenden Kontextinformationen, die jedoch prinzipbedingt verteilt in verschiedenen Datenquellen, etwa Kontexterfassungssystemen, Endgeräten sowie prinzipiell auch in beliebigen anderen, z.T. bereits existierenden Anwendungen entstehen. Ziel dieser Arbeit ist die Verringerung der Komplexität des Beschaffungsvorganges von verteilten und heterogenen Kontextinformationen durch Bereitstellung einer einfach verwendbaren Methode zur Darstellung eines umfassenden, aus verteilten und heterogenen Datenquellen zusammengetragenen Kontextmodells. Im Besonderen werden durch diese Arbeit zwei Probleme addressiert, zum einen daß ein Konsument von umfassenden Kontextinformationen mehrere Datenquellen sowohl kennen und zugreifen können und zum anderen über die zwischen den einzelnen Kontextinformationen in verschiedenen Datenquellen existierenden, zunächst nicht modellierten semantischen Verbindungen Bescheid wissen muß. Das dazu entwickelte Kontextinformationsintegrations- und -darstellungsverfahren kombiniert daher ein die Beschaffung und Integration von Kontextinformationen aus diversen Datenquellen modellierendes Informationsintegrationsmodell mit einem Kontextdarstellungsmodell, welches die abzubildende Realweltdomäne basierend auf ontologischen Informationen durch in problemspezifischer Weise erweiterte Verfahren des Semantic Web in einer möglichst intuitiven, wiederverwendbaren und modularen Weise modelliert. Nach einer fundierten Anforderungsanalyse des entwickelten Prinzips wird dessen Verwendung und Nutzen basierend auf der Skizzierung der wichtigsten allgemeinen Verwendungsmöglichkeiten von Kontextinformationen im betrieblichen Umfeld anhand eines komplexen betrieblichen Anwendungsszenarios demonstriert. Dieses beinhaltet ein Nutzerprofil, das von diversen Anwendungen, u.a. einem kontextsensitiven KFZ-Navigationssystem, einer Restaurantsuchanwendung sowie einem Touristenführer verwendet wird. Probleme hinsichtlich des Datenschutzes, der Integration in existierende Umgebungen und Abläufe sowie der Skalierbarkeit und Leistungsfähigkeit des Verfahrens werden ebenfalls diskutiert. / Context-awareness, which is the systematic consideration of information from the environment of applications, can provide significant benefits in the area of business and technology. To be really useful, i.e. harmonically support real-world processes as human assistants do it, practical applications need a comprehensive and detailed contextual information base that describes all relevant aspects of the real world. As a matter of principle, comprehensive contextual information arises in many places and data sources, e.g. in context-aware infrastructures as well as in "normal" applications, which may have knowledge about the context based on their functionality to support a certain process in the real world. This thesis facilitates the use of contextual information by reducing the complexity of the procurement process of distributed and heterogenous contextual information. Particularly, it addresses the two problems that a consumer of comprehensive contextual information needs to be aware of and able to access several different data sources and must know how to combine the contextual information taken from different and isolated data sources into a meaningful representation of the context. Especially the latter information cannot be modelled using the current state of the art. These problems are addressed by the development of an integration and representation model for contextual information that allows to compose comprehensive context models using information inside distributed and heterogeneous data sources. This model combines an information integration model for distributed and heterogenous information (which consists of an access model for heterogeneous data sources, an integration model and an information relation model) with a representation model for context that formalizes the representation of the respective real world domain, i.e. of the real world objects and their semantic relations in an intuitive, reusable and modular way based on ontologies. The resulting model consists of five layers that represent different aspects of the information integration solution. The achievement of the objectives is rated based on a requirement analysis of the problem domain. The technical feasibility and usefulness of the model is demonstrated by the implementation of an engine to support the approach as well as a complex application scenario consisting of a user profile that integrates information from several data sources and a couple of context-aware applications, e.g. a context-aware navigation system, a restaurant finder application as well as an enhanced tourist guide that use the user profile. Problems regarding security and social effects, the integration of this solution into existing environments and infrastructures as well as technical issues like the scalability and performance of this model are discussed too.

This volume contains contribution form the refereed “MobIS 2010” main program and selected papers of its tracks. The conference on information systems modeling was held in Dresden September 15-17, 2010. The guiding theme for MobIS 2010 focused on modeling topics between model-based management and component and service engineering.

The subject of the thesis is the investigation of asymptotic properties of solutions of the Cauchy problem for structurally damped sigma-evolution operators with time dependent, monotonous, dissipation term. An appropriate energy for solutions of the sigma-evolution equations is defined and some estimates for energies of higher order are proved. In the scale invariant case the optimality of these estimates is shown. Further, the influence of properties of the time dependent dissipation on L^p-L^q estimates for the energy with p and q bigger or equal to 2 and from the conjugate line is clarified. Also smoothing properties of the operators under consideration are investigated. The connection between the regularity of the data and the regularity of the solution in terms of L^2 based Gevrey spaces is considered. Finally, L^1-L^1-estimates in the special case delta = sigma/2 and decreasing dissipative coefficient. / Thema der vorliegenden Dissertation ist die Untersuchung asymptotischer Eigenschaften von Lösungen des Cauchy Problems für strukturell gedämpfte sigma-Evolutions-Operatoren mit zeitabhängigem, monotonen Dissipationskoeffizienten. Es wird eine geeignete Energie definiert und für diese Abschätzungen, auf für entsprechende Energien höherer Ordnung gezeigt. Darüber hinaus wird der Einfluss des Dissipationskoeffizienten auf L^p-L^q Abschätzungen auf und entfernt von der konjugierten Linie untersucht. Im skaleninvarianten Fall wird die Schärfe der Abschätzungen bewiesen. Weiterhin wird der Zusammenhang zwischen der Regularität der Daten und der der Lösung in Termen von L^2-basierten Gevrey-Räumen untersucht. Schließlich werden L^1-L^1-Abschätzungen für den Spezialfall delta = sigma/2 und monoton fallenden Dissipationskoeffizienten gezeigt.

Der Großteil des geschäftsrelevanten Wissens liegt heute als unstrukturierte Information in Form von Textdaten auf Internetseiten, in Office-Dokumenten oder Foreneinträgen vor. Zur Extraktion und Verwertung dieser unstrukturierten Informationen wurde eine Vielzahl von Text-Mining-Lösungen entwickelt. Viele dieser Systeme wurden in der jüngeren Vergangenheit als Webdienste zugänglich gemacht, um die Verwertung und Integration zu vereinfachen. Die Kombination verschiedener solcher Text-Mining-Dienste zur Lösung konkreter Extraktionsaufgaben erscheint vielversprechend, da so bestehende Stärken ausgenutzt, Schwächen der Systeme minimiert werden können und die Nutzung von Text-Mining-Lösungen vereinfacht werden kann. Die vorliegende Arbeit adressiert die flexible Kombination von Text-Mining-Diensten in einem serviceorientierten System und erweitert den Stand der Technik um gezielte Methoden zur Auswahl der Text-Mining-Dienste, zur Aggregation der Ergebnisse und zur Abbildung der eingesetzten Klassifikationsschemata. Zunächst wird die derzeit existierende Dienstlandschaft analysiert und aufbauend darauf eine Ontologie zur funktionalen Beschreibung der Dienste bereitgestellt, so dass die funktionsgesteuerte Auswahl und Kombination der Text-Mining-Dienste ermöglicht wird. Des Weiteren werden am Beispiel entitätsextrahierender Dienste Algorithmen zur qualitätssteigernden Kombination von Extraktionsergebnissen erarbeitet und umfangreich evaluiert. Die Arbeit wird durch zusätzliche Abbildungs- und Integrationsprozesse ergänzt, die eine Anwendbarkeit auch in heterogenen Dienstlandschaften, bei denen unterschiedliche Klassifikationsschemata zum Einsatz kommen, gewährleisten. Zudem werden Möglichkeiten der Übertragbarkeit auf andere Text-Mining-Methoden erörtert.

Die Dissertation untersucht, welche individuellen Einflussfaktoren Wissenschaftler zur Wissensteilung mittels Social Software motivieren. Dazu werden universitäre Wissenschaftler, ihre Stakeholder und typische Karrierewege sowie die Bereiche Open Science und Open Educational Resources beleuchtet. Im Anschluss wird die Anwendbarkeit existierender Theorien der Technologieakzeptanz und der Wissensteilung (insbesondere in virtuellen Communities) auf die Wissensteilung von Wissenschaftlern mittels Social Software untersucht. Darauf aufbauend werden potentielle Einflussfaktoren identifiziert und ein spezifisches Erklärungsmodell abgeleitet. Dieses wird mittels Online-Umfragen empirisch überprüft und verfeinert.

This book is devoted to the study of operators on discrete structures. The operators are supposed to be self-adjoint and obey a certain translation invariance property. The discrete structures are given as Cayley graphs via finitely generated groups. Here, sofic groups and amenable groups are in the center of our considerations. Note that every finitely generated amenable group is sofic. We investigate the spectrum of a discrete self-adjoint operator by studying a sequence of finite dimensional analogues of these operators. In the setting of amenable groups we obtain these approximating operators by restricting the operator in question to finite subsets Qn , n ∈ N. These finite dimensional operators are self-adjoint and therefore admit a well-defined normalized eigenvalue counting function. The limit of the normalized eigenvalue counting functions when |Qn | → ∞ (if it exists) is called the integrated density of states (IDS). It is a distribution function of a probability measure encoding the distribution of the spectrum of the operator in question on the real axis. We prove the existence of the IDS in various geometric settings and for different types of operators. The models we consider include deterministic as well as random situations. Depending on the specific setting, we prove existence of the IDS as a weak limit of distribution functions or even as a uniform limit. Moreover, in certain situations we are able to express the IDS via a semi-explicit formula using the trace of the spectral projection of the original operator. This is sometimes referred to as the validity of the Pastur-Shubin trace formula. In the most general geometric setting we study, the operators are defined on Cayley graphs of sofic groups. Here we prove weak convergence of the eigenvalue counting functions and verify the validity of the Pastur-Shubin trace formula for random and non-random operators . These results apply to operators which not necessarily bounded or of finite hopping range. The methods are based on resolvent techniques. This theory is established without having an ergodic theorem for sofic groups at hand. Note that ergodic theory is the usual tool used in the proof of convergence results of this type. Specifying to operators on amenable groups we are able to prove stronger results. In the discrete case, we show that the IDS exists uniformly for a certain class of finite hopping range operators. This is obtained by using a Banach space-valued ergodic theorem. We show that this applies to eigenvalue counting functions, which implies their convergence with respect to the Banach space norm, in this case the supremum norm. Thus, the heart of this theory is the verification of the Banach space-valued ergodic theorem. Proceeding in two steps we first prove this result for so-called ST-amenable groups. Then, using results from the theory of ε-quasi tilings, we prove a version of the Banach space-valued ergodic theorem which is valid for all amenable groups. Focusing on random operators on amenable groups, we prove uniform existence of the IDS without the assumption that the operator needs to be of finite hopping range or bounded. Moreover, we verify the Pastur-Shubin trace formula. Here we present different techniques. First we show uniform convergence of the normalized eigenvalue counting functions adapting the technique of the Banach space-valued ergodic theorem from the deterministic setting. In a second approach we use weak convergence of the eigenvalue counting functions and additionally obtain control over the convergence at the jumps of the IDS. These ingredients are applied to verify uniform existence of the IDS. In both situations we employ results from the theory of large deviations, in order to deal with long-range interactions.

A social media stream allows users to share user-generated content as well as aggregate different external sources into one single stream. In Enterprise 2.0 such social media streams empower co-workers to share their information and to work efficiently and effectively together while replacing email communication. As more users share information it becomes impossible to read the complete stream leading to an information overload. Therefore, it is crucial to provide the users a personalized stream that suggests important and unread messages. The main characteristic of an Enterprise 2.0 social media stream is that co-workers work together on projects represented by topics: the stream is topic-centered and not user-centered as in public streams such as Facebook or Twitter. A lot of work has been done dealing with recommendation in a stream or for news recommendation. However, none of the current research approaches deal with the characteristics of an Enterprise 2.0 social media stream to recommend messages. The existing systems described in the research mainly deal with news recommendation for public streams and lack the applicability for Enterprise 2.0 social media streams. In this thesis a recommender concept is developed that allows the recommendation of messages in an Enterprise 2.0 social media stream. The basic idea is to extract features from a new message and use those features to compute a relevance score for a user. Additionally, those features are used to learn a user model and then use the user model for scoring new messages. This idea works without using explicit user feedback and assures a high user acceptance because no intense rating of messages is necessary. With this idea a content-based and collaborative-based approach is developed. To reflect the topic-centered streams a topic-specific user model is introduced which learns a user model independently for each topic. There are constantly new terms that occur in the stream of messages. For improving the quality of the recommendation (by finding more relevant messages) the recommender should be able to handle the new terms. Therefore, an approach is developed which adapts a user model if unknown terms occur by using terms of similar users or topics. Also, a short- and long-term approach is developed which tries to detect short-term interests of users. Only if the interest of a user occurs repeatedly over a certain time span are terms transferred to the long-term user model. The approaches are evaluated against a dataset obtained through an Enterprise 2.0 social media stream application. The evaluation shows the overall applicability of the concept. Specifically the evaluation shows that a topic-specific user model outperforms a global user model and also that adapting the user model according to similar users leads to an increase in the quality of the recommendation. Interestingly, the collaborative-based approach cannot reach the quality of the content-based approach.

Η Εύβοια είναι το δεύτερο μεγαλύτερο σε έκταση νησί της Ελλάδας, στο οποίο απαντάται μεγάλη ποικιλομορφία αναγλύφου, γεωλογικού υποστρώματος και υψομέτρου, ιδιαίτερα στο βόρειο τμήμα του. Σε συνδυασμό με το κλίμα που επικρατεί, δημιουργούνται κατάλληλες συνθήκες, οι οποίες ευνοούν την ανάπτυξη σπανίων ή απειλούμενων φυτικών ειδών και υποειδών μεγάλου επιστημονικού ενδιαφέροντος. Το Quercus trojana subsp. euboica, η ευβοϊκή δρυς όπως ονομάζεται κοινώς, είναι ένα από τα ιδιαίτερα ενδιαφέροντα φυτικά taxa, τα οποία φύονται στη βόρεια Εύβοια. Μάλιστα, είναι ένα από τα στενότοπα ενδημικά taxa της Εύβοιας και ταυτόχρονα το μοναδικό ενδημικό υποείδος του γένους Quercus στην Ελλάδα. Έχει χαρακτηριστεί ως Τρωτό (VU) βάσει της κατηγοριοποίησης της IUCN (2001) σύμφωνα με το κριτήριο C1, όμως οι περιοχές εξάπλωσής του δεν υπόκεινται ακόμη σε καθεστώς νομικής προστασίας. Υφίσταται πιέσεις από ανθρωπογενείς επιδράσεις όπως πυρκαγιές, βόσκηση και υλοτομίες. Στο πλαίσιο της παρούσας εργασίας ξεκίνησε η διαδικασία παρακολούθησης (monitoring) της κατάστασης στη φύση του ενδημικού taxon Quercus trojana subsp. euboica. Ως “monitoring” ορίζονται οι επανειλημμένες μετρήσεις διαφόρων παραγόντων και μεταβλητών (αριθμός ατόμων εκάστοτε taxon, ύψος-διάμετρος κορμού, εδαφοκάλυψη, ανθοφορία, καρποφορία, φυτρωτικότητα ατόμων, βιωσιμότητα αρτιφύτρων κ.ά.) σε βάθος χρόνου και σε έκταση. Τοποθετήθηκαν δέκα συνολικά επιφάνειες παρακολούθησης επιφάνειας 25 m2 η καθεμία στις περιοχές εξάπλωσής του, με επιμέρους υποτετράγωνα 1 m2. Πραγματοποιήθηκε έρευνα επί τρία έτη και καθ’ όλη τη διάρκεια του έτους. Πάρθηκαν ποικίλες μετρήσεις (γεωγραφικό μήκος-πλάτος, υψόμετρο, κλίση-έκθεση, εδαφολογικές παρατηρήσεις), ενώ συλλέχθηκαν φυτικά δείγματα για την πλήρη χλωριδική ανάλυση και φωτογραφήθηκε λεπτομερώς κάθε επιφάνεια. Πραγματοποιήθηκε ταξινομικός προσδιορισμός των δειγμάτων βάσει της πλέον πρόσφατης βιβλιογραφίας, έγινε προσδιορισμός των βιομορφών, διάκριση των χωρολογικών στοιχείων και φυτοκοινωνιολογική ανάλυση σύμφωνα με τη μέθοδο Braun-Blanquet. Έτσι, βρέθηκαν 93 taxa στις περιοχές εξάπλωσης της ευβοϊκής δρυός, με κυρίαρχες οικογένειες την Asteraceae (17%) και την Poaceae (6%). Τα Ημικρυπτόφυτα αποτελούν σχεδόν το 41% του συνόλου, ενώ το 44,1% είναι Μεσογειακά taxa. Επίσης, παρατηρήθηκαν 18 ελληνικά ενδημικά taxa, εκ των οποίων τα 6 είναι στενότοπα ενδημικά. Έπειτα, όλες οι δειγματοληπτικές επιφάνειες καταχωρήθηκαν στη βάση δεδομένων Turboveg και χρησιμοποιήθηκε το πρόγραμμα TWINSPAN (two-way indicator species analysis) για να ομαδοποιηθούν οι φυτοληψίες. Ακόμη, χρησιμοποιήθηκε η μέθοδος DCA (Detrended Correspondence Analysis-DECORANA) για τη δημιουργία γραφικής απεικόνισης του πίνακα των φυτοκοινωνιολογικών δεδομένων. Επιπλέον, χρησιμοποιώντας το πρόγραμμα SPSS 13.0 πραγματοποιήθηκε Ανάλυση Ομαδοποίησης (Cluster Analysis) με τη μέθοδο Σύνδεσης Γειτόνων (Neighbor Joining) για τις δέκα επιφάνειες παρακολούθησης. Ο δείκτης που χρησιμοποιήθηκε είναι αυτός της παρουσίας-απουσίας ειδών Jaccard. Όπως προκύπτει από τη μελέτη αυτή, οι περιοχές εξάπλωσης της ευβοϊκής δρυός φαίνεται να έχουν υποστεί συρρίκνωση από την πυρκαγιά του 1977, ενώ οι πληθυσμοί της κινδυνεύουν από τη διαρκή πίεση της βόσκησης. Τέλος, προτείνονται μέτρα για την καλύτερη πρoστασία του Quercus trojana subsp. euboica. / Evvia is the second largest greek island, which is characterized by a great variety of terrain, geologic substrate and altitude, especially in its northern part. In combination with the climate, the appropriate conditions are met that favor the evolvement of rare or endangered plant species and subspecies of great scientific interest. Quercus trojana subsp. euboica, the euboean oak as it is commonly reffered to, is one of the most interesting plant taxa that grow in northern Evvia. Not only is it one of the local endemic taxa of northern Evvia, but it is the unique endemic subspecies of the Quercus genus in Greece. It has been characterized as vulnerable (VU) according to the IUCN (2001) categories and the C1 criteria, though it has yet not been included in a protectin law regime. It has been under the constant pressure of human impact such as fire, browsing and timbering. During this study, monitoring the status of the endemic taxon Quercus trojana subsp. euboica has begun. The monitoring process involves the repeated measurement of multiple factors and variables (such as measurement of height/diameter, soil-coverage, florescence, fruition, germination/viability of individuals etc.) in a length of time and area extent. A number of ten monitoring plots was set, each plot occupying a surface of 25 m2 in total, with 25 subplots of 1 m2. The study lasted three years and was conducted throughout the year. Multiple measurements took place (geographic length and width, altitude, gradient, exposure etc.), while plant samples were collected in the framework of a full floristic analysis and each monitoring plot was thoroughly photographed. A taxonomic assessment of the plant samples was conducted according to the latest bibliography, as well as a distinction of biomorphs and geographic elements. Moreover, a phytosociologic analysis was conducted according to the Braun-Blanquet method. Thus, 93 different taxa were found in the vicinity of the territories that Quercus trojana subsp. euboica takes up. Asteraceae and Poaceae families were found to be dominant in the plots with a percentage of 17% and 6% respectively. Hemicryptophyts represent 41%, while the Mediterranean elements dominate with a percentage of 44,1%. Nevertheless, 18 greek endemic plant taxa were found, 6 of which are local endemics of Evvia. Thereinafter, all of the monitoring plots were registered in the TurboVeg database and the TWINSPAN (Two-way indicator species analysis) program was used in order to group the plots. Furthermore, the DCA method (Detrended Correspondence Analysis-DECORANA) was used for the creation of a graphic display of the phytosociologic data index. The SPSS 13.0 program was used so that a Cluster Analysis was conducted, using the Neighbor Joining Method for the 10 plots. The Jaccard presence-absence indicator was used. In a nutshell, this study showed that Quercus trojana subsp. euboica territories of appearance have been reduced after the 1977 wildfire, while the taxon’s population is in danger due to the constant pressure of goat grazing. Concluding, measures for better protection of the taxon are proposed.