Thesis (doctoral)--Universität, Bern, 2001 entitled: Die Abbildung ausgewählter Verfahren des strategischen Kostenmanagements ...

Tübingen, Univ., Diss., 2007.

Techn. Hochsch., Diss., 2002--Aachen.

Gegenstand dieser Dissertation ist die numerische Untersuchung des ganzzahligen Quanten-Hall-Effekts (QHE). Im Mittelpunkt steht dabei der Übergang zwischen den charakteristischen Plateaus des Hall-Leitwertes. Die Beschreibung des Übergangs erfolgt im Rahmen des Chalker-Coddington-Netzwerkmodells, wobei zusätzlich ein Ortsraum-Renormierungsgruppenansatz (RG) angewendet wird um hohe Systemgrößen zu erreichen. Diese Vorgehensweise erlaubt eine einfache, aber statistisch sehr gute Beschreibung der starken charakteristischen Fluktuationen am Übergang im Rahmen von Verteilungsfunktionen. Die RG Resultate werden zunächst mit Ergebnissen anderer Methoden verglichen. Es werden die kritische Verteilungsfunktion des Leitwertes am QHE Übergang und deren Momente ermittelt. Aus dem Verhalten in der Nähe des Übergangs läßt sich der Wert des kritischen Exponenten der Lokalisierungslänge ableiten. Diese Ergebnisse stimmen sehr gut mit exakten numerischen Simulationen überein. Die RG Methode wird daraufhin zur Berechnung der Energieniveaustatistik (ENS) erweitert. Die kritische ENS der normierten Abstände von benachbarten Energieniveaus und der kritische Exponent werden bestimmt. Danach wird der Einfluß von makroskopischen Inhomogenitäten in Form von langreichweitiger korrelierter Unordnung auf die kritischen Eigenschaften des QHE Übergangs untersucht. Hierbei zeigt sich ein Anwachsen des Exponenten mit zunehmender Reichweite und Stärke der Unordnung. Abschließend wird die RG zur Berechnung des Hall-Widerstandes eingesetzt. Die kritische Verteilung des Hall-Widerstandes läßt auf sehr starke Fluktuationen am Übergang schließen. Abseits des Übergangs in Richtung Isolator wird divergentes Verhalten des Hall-Widerstandes gefunden. Zusammenfassend demonstrieren alle Ergebnisse die Robustheit universeller Eigenschaften am QHE Übergang.

The continuous transformation of the industrial society into a service and knowledge society is accompanied by profound change of demand: Customer requests will increasingly focus on individual products, shorter delivery times and appropriate prices. To encounter these challenges under the conditions of dynamic global markets and inter-regional competition, the CRC 457 “Non-Hierarchical Regional Production-Networks” at the Chemnitz University of Technology focuses on SME and investigates ways to implement customer-oriented, temporary networking of smallest, autonomous units (“competence cells”) in the region of South-West-Saxony. As a partial result of this research we are able to present a model of competence cell based networking distinguishing between three levels of networking, each with its own logic of reproduction (cp. Figure 1): 1) According to a most general concept, networks can be seen as given in any social context. Regarding a specific region, one has to assume that there is a broad array of infra-structural, mental and communicative relations; that as a whole we call the Regional Network. This level can be seen as basic level of competence cell based networking, specific elements (competence cells) of this network can be seen as necessary resources of the following level. 2) The second level of networking we call Competence Network. The first continuous problem of this network is to select competence cells according to relevant parameters that may be defined by customer orders or, in view of new market entry, be generated by the Competence Network itself. The second problem is to arrange these cells along a product specific value chain and, by this means, to create temporary production networks. Concerning both of the problems, the third is to find a non-hierarchical mode of negotiation. 3) On the third level temporary alliances of basically autonomous competence cells can be observed. After executing their order, these Production Networks dissolve and the constituent cells reenter the second or even the first level of networking. Generalising our observation we now assume that every phenomena labelled as regional or industrial network or district should be investigated in view of (these) different levels of networking, especially if we are interested in dealing more efficiently with the problems of network management. Hence, we suggest to first answer the question “Which (of these) networks are we to manage?” before asking how. Concerning the latter, a synopsis on the discourse on managing networks shows three major approaches: 1) Networks are assumed to be uncontrollable (cp. e.g. Castells 2001), as they are self-organised systems selecting external control impulses only by their own criterias of relevance, so we have either to adapt the logic of the target system (which implies self-adaption) or to take the risk of being totally ignored. With this in mind we can’t speak of control in terms of causal logic. 2) Networks are assumed to be cultivable: According to Wenger and Snyder (2000) for example networks are uncontrollable, but - like a gardener - we are able to set adequate general conditions for their “growth” and continuity. 3) Networks are assumed to be controllable: For authors like Sydow (2000) networks are to be seen as hybrid forms of coordination recombining aspects of market and hierarchy. Thus, recombining the classical means of control will finally lead to the ability to manage networks. It will be to show that each of these approaches focuses on specific aspects of networking, thus, each of them is creating a self-contained concept of networks: Castells refers to networks as a basal nexus of (global) interconnectedness that, like the Regional Network in our case, obviously can’t be managed. Wenger and Snyder are interested in network-organisations that (like Competence Networks) also can’t be controlled but can be implemented by and embedded in other social systems (cp. Grabher 1993). Sydow finally observes networks of more or less autonomous organisations corresponding to our Production Networks, which are in deed more or less controllable. Not least because of their different theoretical assumptions, all these concepts seemed to be not only incommensurable but incompatible so far. Nonetheless, during our work in CRC 457 we were to manage all these concepts while approaching to one single objective of research. Therefore, we had to ask, how many perspectives on network are we to manage? The answer is: at least three. Integrating these, we generated a holistic life-cycle model of network, which we like to present as starting point for further research in the field network management.

Gegenstand dieser Dissertation ist die numerische Untersuchung des ganzzahligen Quanten-Hall-Effekts (QHE). Im Mittelpunkt steht dabei der Übergang zwischen den charakteristischen Plateaus des Hall-Leitwertes. Die Beschreibung des Übergangs erfolgt im Rahmen des Chalker-Coddington-Netzwerkmodells, wobei zusätzlich ein Ortsraum-Renormierungsgruppenansatz (RG) angewendet wird um hohe Systemgrößen zu erreichen. Diese Vorgehensweise erlaubt eine einfache, aber statistisch sehr gute Beschreibung der starken charakteristischen Fluktuationen am Übergang im Rahmen von Verteilungsfunktionen. Die RG Resultate werden zunächst mit Ergebnissen anderer Methoden verglichen. Es werden die kritische Verteilungsfunktion des Leitwertes am QHE Übergang und deren Momente ermittelt. Aus dem Verhalten in der Nähe des Übergangs läßt sich der Wert des kritischen Exponenten der Lokalisierungslänge ableiten. Diese Ergebnisse stimmen sehr gut mit exakten numerischen Simulationen überein. Die RG Methode wird daraufhin zur Berechnung der Energieniveaustatistik (ENS) erweitert. Die kritische ENS der normierten Abstände von benachbarten Energieniveaus und der kritische Exponent werden bestimmt. Danach wird der Einfluß von makroskopischen Inhomogenitäten in Form von langreichweitiger korrelierter Unordnung auf die kritischen Eigenschaften des QHE Übergangs untersucht. Hierbei zeigt sich ein Anwachsen des Exponenten mit zunehmender Reichweite und Stärke der Unordnung. Abschließend wird die RG zur Berechnung des Hall-Widerstandes eingesetzt. Die kritische Verteilung des Hall-Widerstandes läßt auf sehr starke Fluktuationen am Übergang schließen. Abseits des Übergangs in Richtung Isolator wird divergentes Verhalten des Hall-Widerstandes gefunden. Zusammenfassend demonstrieren alle Ergebnisse die Robustheit universeller Eigenschaften am QHE Übergang.

The continuous transformation of the industrial society into a service and knowledge society is accompanied by profound change of demand: Customer requests will increasingly focus on individual products, shorter delivery times and appropriate prices. To encounter these challenges under the conditions of dynamic global markets and inter-regional competition, the CRC 457 “Non-Hierarchical Regional Production-Networks” at the Chemnitz University of Technology focuses on SME and investigates ways to implement customer-oriented, temporary networking of smallest, autonomous units (“competence cells”) in the region of South-West-Saxony. As a partial result of this research we are able to present a model of competence cell based networking distinguishing between three levels of networking, each with its own logic of reproduction (cp. Figure 1): 1) According to a most general concept, networks can be seen as given in any social context. Regarding a specific region, one has to assume that there is a broad array of infra-structural, mental and communicative relations; that as a whole we call the Regional Network. This level can be seen as basic level of competence cell based networking, specific elements (competence cells) of this network can be seen as necessary resources of the following level. 2) The second level of networking we call Competence Network. The first continuous problem of this network is to select competence cells according to relevant parameters that may be defined by customer orders or, in view of new market entry, be generated by the Competence Network itself. The second problem is to arrange these cells along a product specific value chain and, by this means, to create temporary production networks. Concerning both of the problems, the third is to find a non-hierarchical mode of negotiation. 3) On the third level temporary alliances of basically autonomous competence cells can be observed. After executing their order, these Production Networks dissolve and the constituent cells reenter the second or even the first level of networking. Generalising our observation we now assume that every phenomena labelled as regional or industrial network or district should be investigated in view of (these) different levels of networking, especially if we are interested in dealing more efficiently with the problems of network management. Hence, we suggest to first answer the question “Which (of these) networks are we to manage?” before asking how. Concerning the latter, a synopsis on the discourse on managing networks shows three major approaches: 1) Networks are assumed to be uncontrollable (cp. e.g. Castells 2001), as they are self-organised systems selecting external control impulses only by their own criterias of relevance, so we have either to adapt the logic of the target system (which implies self-adaption) or to take the risk of being totally ignored. With this in mind we can’t speak of control in terms of causal logic. 2) Networks are assumed to be cultivable: According to Wenger and Snyder (2000) for example networks are uncontrollable, but - like a gardener - we are able to set adequate general conditions for their “growth” and continuity. 3) Networks are assumed to be controllable: For authors like Sydow (2000) networks are to be seen as hybrid forms of coordination recombining aspects of market and hierarchy. Thus, recombining the classical means of control will finally lead to the ability to manage networks. It will be to show that each of these approaches focuses on specific aspects of networking, thus, each of them is creating a self-contained concept of networks: Castells refers to networks as a basal nexus of (global) interconnectedness that, like the Regional Network in our case, obviously can’t be managed. Wenger and Snyder are interested in network-organisations that (like Competence Networks) also can’t be controlled but can be implemented by and embedded in other social systems (cp. Grabher 1993). Sydow finally observes networks of more or less autonomous organisations corresponding to our Production Networks, which are in deed more or less controllable. Not least because of their different theoretical assumptions, all these concepts seemed to be not only incommensurable but incompatible so far. Nonetheless, during our work in CRC 457 we were to manage all these concepts while approaching to one single objective of research. Therefore, we had to ask, how many perspectives on network are we to manage? The answer is: at least three. Integrating these, we generated a holistic life-cycle model of network, which we like to present as starting point for further research in the field network management.

Lab-on-a-Chip-Systeme sind mikrofluidische, portable Systeme mit denen bioanalytische Reaktionen und Auswertungen an kleinen Probenvolumina vor Ort durchführbar sind. In der vorliegenden Arbeit wird eine Entwurfsstrategie für das integrierte, resistive Heizen in einem solchen System auf Basis einer polymerbasierten, modularen Technologieplattform entwickelt. Dabei wird eine Modellierung als Feldmodell, die Ableitung eines reduzierten Makromodells sowie die experimentelle Untersuchung und Verifikation beschrieben. Verschiedene Ansätze für die Abbildung temperaturunabhängiger und -abhängiger elektrisch-thermischer Wandler sind berücksichtigt. Der Einflüsse von Aufbau, Widerstandsverhalten, Randbedingungen, sowie der elektrischen Ansteuerung auf die Temperatur der Biosensorfläche, in der die bioanalytische Reaktion erfolgt, werden dargelegt. / Lab on a chip systems are portable microfluidic systems which enable bioanalytical reactions and the appropriate analysis at the point of need using small sample volumes. In this publication a design strategy for integrated resistive heating in such a polymer based system is developed. The modelling comprises a field model, a derived reduced macro model and the experimental characterisation. Approaches to describe temperature dependent as well as independent electric-thermal converters are taken into account. The effects of the assembly, resistive behaviour, boundary conditions as well as the drive electronics on the temperature of the biosensor are presented.

Mit Hilfe eines variabel einsetzbaren Reaktornetzwerkmodells (RNM) wird in der vorliegenden Dissertation der Prozess der Vergasung von Brennstoffmischungen in der Fließbildsimulation beschrieben. Neben der Untersuchung von gestuften Prozessketten zur Veredelung von kohlenstoffhaltigen Energieträgern ist damit auch die differenzierte Analyse von Effekten während der Vergasung von binären und ternären Brennstoffmischungen möglich. Die Erstellung sowie Validierung des RNM wird anhand des PEFR-Vergasers, des SFGT-Vergasers und des Hybridwandvergaser vorgenommen. Die anschließende Analyse der Vergasung von Brennstoffmischungen zeigt, dass in ihren Eigenschaften sehr heterogene Brenn¬stoffmischungen Synergieeffekte bei der Vergasung hervorrufen. Diese sind in der Literatur schon oft beschrieben worden, eine systematische Analyse wird jedoch erst in der vorliegenden Dissertation durchgeführt. / Within this document the modeling and simulation of fuel blend gasification is investigated based on a variably applicable Reduced Order Model (ROM) developed for the flowsheet simulation of entrained-flow gasification reactors and processes. On one hand this enables the investigation of cascaded solid fuel conversion technologies and on the other hand effects during gasification of binary and ternary fuel blends are describable. The development as well as the validation of the ROM has been carried out for the SFGT gasifier, the PEFR gasifier and the hybrid-wall gasifier. The subsequent analysis of binary and ternary fuel blend gasification shows that fuel blends with very heterogeneous component properties induce synergy effects which have been reported in various peer review publications.

Hippocampal place-cell sequences observed during awake immobility often represent previous experience, suggesting a role in memory processes. However, recent reports of goals being overrepresented in sequential activity suggest a role in short-term planning, although a detailed understanding of the origins of hippocampal sequential activity and of its functional role is still lacking. In particular, it is unknown which mechanism could support efficient planning by generating place-cell sequences biased toward known goal locations, in an adaptive and constructive fashion. To address these questions, we propose a model of spatial learning and sequence generation as interdependent processes, integrating cortical contextual coding, synaptic plasticity and neuromodulatory mechanisms into a map-based approach. Following goal learning, sequential activity emerges from continuous attractor network dynamics biased by goal memory inputs. We apply Bayesian decoding on the resulting spike trains, allowing a direct comparison with experimental data. Simulations show that this model (1) explains the generation of never-experienced sequence trajectories in familiar environments, without requiring virtual self-motion signals, (2) accounts for the bias in place-cell sequences toward goal locations, (3) highlights their utility in flexible route planning, and (4) provides specific testable predictions.