3,943 research outputs found

    BCS theory in the weak magnetic field regime for systems with nonzero flux and exponential estimates on the adiabatic theorem in extended quantum lattice systems

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    In the main part of this PhD thesis, we consider a periodically realized microscopic superconductor described by BCS theory, which is subject to external electromagnetic fields. We show that the superconductor is properly described by Ginzburg--Landau theory in the macroscopic and weak magnetic field limit. The main novelty of our results is to allow for a non-vanishing magnetic flux through the unit cell of the lattice of periodicity. These main results are supplemented by various unpublished notes in the field of BCS theory. Furthermore, we preface the presentation of these results with a comprehensive introduction suitable for master's or PhD students. Thereby, we hope to contribute to filling the gap of missing introductory literature in the field. The thesis comprises a second topic, in which we provide ideas for setting up quantum lattice systems in order to prove exponential estimates for the adiabatic theorem. These notes are the result of studies in this field, which have been conducted during a research stay at the University of British Columbia (UBC) in Vancouver, Canada.Comment: PhD thesi

    Fork bending self-oscillation on bicycles influencing braking performance

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    This work deals with a fork bending oscillation phenomenon observed during hard braking on bicycles. The observed oscillation is described with experimental data and an attempt is made to understand the underlying root cause. Therefore, a multibody model consisting of the front wheel and the fork is employed to simulate a braking maneuver. The self-oscillation is replicated in simulation and implications on the brake process are derived from it. Fork and tire oscillations on bicycles are rarely described in scientific literature. An oscillation due to tire resonance on high-speed motorcycles was described by Cossalter [1]. However, the mentioned speed dependence is not found in the present case under investigation. Klug et al. [2] were the first to report an oscillation of the fork inclination angle during braking. They noticed oscillations in the front wheel speed signals measured with a speed encoder mounted on the fork. Measurements of accelerometers and gyroscopes placed on the fork near the hub showed these oscillations on the forks inclination angular rate and vertical acceleration as well. This makes the phenomenon relevant for suspension and braking control. They also described the distorting effect of fork bending on the wheel speed signal and the wheel slip calculation derived from it. This work tries to identify a root cause of the fork bending oscillation and investigates its influence on the stopping performance

    Are Pedelec crashes different to bicycle crashes?: A comparison of national accident data in Germany

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    Since 2014, a distinction between Pedelec (electrical support up to 25 km/h) and bicycle crashes is made in official police reported accidents with personal injuries in Germany. Yet, no comparative analysis using national data is available, moreover some estimation was done how Pedelec crashes may look like based on bicycle crashes. Hence, the present study aims to compare real-world crashes with personal injuries with both vehicle types - Pedelec and bicycle and show similarities and differences of the vehicle classes. Nearly a decade of reporting allows furthermore to have a closer look at the accident figures in a time series and to estimate possible trends

    Development of a Generic Framework to Assess Asset Management Maturity within Organisations

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    With the comprehensive Lean Smart Maintenance philosophy and its associated maturity model, organisations were given a tool to reach asset and maintenance excellence. This paper discusses the approach used to transfer the scientifically based methods and concepts of the Lean Smart Maintenance Maturity Model into an assessment structure to generate a generic tool to collect the complete and correct information necessary to determine an organisation\u27s maturity level. Research results show that a standardised assessment process combined with continuous improvement cycles, a more accurate assessment of the company\u27s maturity is possible. A well-structured MM assessment supports less experienced assessors whereby experienced assessors will not need a full questionnaire but only a well-structured list of items and their maturity levels

    Evolution of a Lean Smart Maintenance Maturity Model towards the new Age of Industry 4.0

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    Over the last few years, the complexity of asset and maintenance management of industrial plants and machinery in the producing industry has risen due to higher competition and volatile environments. Smart factories, Internet of Things (IoT) and the underlying digitisation of a significant number of processes are changing the way we have to think and work in terms of asset management. Existing Lean Smart Maintenance (LSM) philosophy, which focuses on the cost-efficient (lean) and the learning organisation (smart) perspectives enables a value-oriented, dynamic, and smart maintenance/asset management. The associated LSM maturity model is the evaluation tool that contains the normative, strategic, and operational aspects of industrial asset management, based on which numerous reorganisation projects have already been carried out in industrial companies. However, due to the ever-increasing development of Industry 4.0 (I4.0), it is necessary to extend the model by selected aspects of digitisation and digitalisation. Based on a structured literature review (SLR) of state of the art I4.0 maturity models, we were able to investigate the essential maturity items for I4.0. To restructure and expand the existing LSM maturity model, the principle of design science research (DSR) was used. The architecture of the LSM maturity model was based on the structure of the Capability Maturity Model Integration (CMMI). Further development of a Lean Smart Maintenance maturity model thus covers the future requirements of I4.0 and data science. It was possible to enhance existing categories with new artefacts from the I4.0 range to represent the influence of cyber-physical systems (CPS), (big) data and information management, condition monitoring (CM) and more. Furthermore, the originally defined LSM-Model was restructured for a more simplified application in industrial use cases

    Validation of a Lean Smart Maintenance Maturity Model

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    Rising complexity in industrial asset and maintenance management due to more volatile business environments and megatrends like Industry 4.0 has led to the need for a new perspective on these management domains. The Lean Smart Maintenance (LSM) philosophy, which focuses on both the efficient (lean) and the learning (smart) organization was introduced during the past few years, and a corresponding maturity model (MM) has been developed to guide organizations on their way to asset and maintenance excellence. This paper discusses use cases, in which the usability and the generic aspect of the LSM MM are validated by using data from three different asset management assessment projects in organizations with different types of production. Research results show that the LSM MM can be used as a basis for management system improvement, independent of production types such as one-of-a-kind industry, mass production and continuous production

    Modellbasierte Entwicklung eines aktiven Sicherheitssystems für elektrifizierte Fahrräder

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    Die bei elektrifizierten Fahrrädern vorhandene elektrische Energie bietet neue funktionale Möglichkeiten wie zum Beispiel ein aktives Sicherheitssystem zur Unterstützung des Fahrers beim Bremsvorgang. Im Rahmen dieser Arbeit wird durch einen fahrbaren Prototypen die Machbarkeit eines solchen Systems nachgewiesen, welches die Vorderradblockade als auch den Überschlag (um die Fahrzeugquerachse) verhindert
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