1,934 research outputs found

    Quantum Fokker-Planck models: the Lindblad and Wigner approaches

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    In this article we try to bridge the gap between the quantum dynamical semigroup and Wigner function approaches to quantum open systems. In particular we study stationary states and the long time asymptotics for the quantum Fokker-Planck equation. Our new results apply to open quantum systems in a harmonic confinement potential, perturbed by a (large) sub-quadratic term.Comment: 19 pages, corrected typos and quoted Theorem 6 more precisel

    PMMA Pyrolysis Simulation -- from Micro- to Real-Scale

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    In fire spread simulations, heat transfer and pyrolysis are processes to describe the thermal degradation of solid material. In general, the necessary material parameters cannot be directly measured. They are implicitly deduced from micro- and bench-scale experiments, i.e. thermogravimetric analysis (TGA), micro-combustion (MCC) and cone calorimetry. Using a complex fire model, an inverse modelling process (IMP) is capable to find parameter sets, which are able to reproduce the experimental results. In the real-scale, however, difficulties arise predicting the fire behaviour using the deduced parameter sets. Here, we show an improved model to fit data of multiple small scale experiment types. Primarily, a gas mixture is used to model an average heat of combustion for the surrogate fuel. The pyrolysis scheme is using multiple reactions to match the mass loss (TGA), as well as the energy release (MCC). Additionally, a radiative heat flux map, based on higher resolution simulations, is used in the cone calorimeter setup. With this method, polymethylmetacrylate (PMMA) micro-scale data can be reproduced well. For the bench-scale, IMP setups are used differing in cell size and targets, which all lead to similar and good results. Yet, they show significantly different performance in the real-scale parallel panel setup.Comment: The data is made publicly available: https://doi.org/10.5281/zenodo.706533

    Integrating the Cubesat Space Protocol into GSOC’s Multi-Mission Environment

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    CubeL is the first COTS cubesat to be operated by the German Space Operations Center (GSOC) utilizing cubesat space protocol (CSP). Scheduled for launch in summer 2020, it will initially be monitored and controlled via UHF using a compatible COTS ground segment to perform an IOD of “OSIRIS4CubeSat”, a miniaturized OSIRIS space-to-ground laser communication terminal developed by DLR-KN in cooperation with Tesat-Spacecom. Afterwards, CubeL will be integrated into the GSOC multi-mission environment and be operated via S-Band. The GSOC ground segment architecture and software focuses on institutionally standardized communication, such as CCSDS frame (132.0-B-2) and packet standards (133.0-B-1) and the ECSS packet utilization standard (E-ST-70-41C). At the core of GSOC\u27s multi-mission environment is the SCOS-2000 based monitoring and control system “GECCOS”, which supports all satellite missions currently operated by GSOC. CubeL however depends on CSP for most communication. This page briefly introduces the CubeL mission and ground segment design, presents relevant protocols and the subsequent tailoring of CCSDS protocol features before describing the required CSP to CCSDS adapter, to enable communication between CubeL and GECCOS. For concept validation a minimal prototype is tested against the CubeL engineering model. This work concludes with a critical review of the chosen approach

    Numerical Simulation of Current Sheet Formation in a Quasi-Separatrix Layer using Adaptive Mesh Refinement

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    The formation of a thin current sheet in a magnetic quasi-separatrix layer (QSL) is investigated by means of numerical simulation using a simplified ideal, low-β\beta, MHD model. The initial configuration and driving boundary conditions are relevant to phenomena observed in the solar corona and were studied earlier by Aulanier et al., A&A 444, 961 (2005). In extension to that work, we use the technique of adaptive mesh refinement (AMR) to significantly enhance the local spatial resolution of the current sheet during its formation, which enables us to follow the evolution into a later stage. Our simulations are in good agreement with the results of Aulanier et al. up to the calculated time in that work. In a later phase, we observe a basically unarrested collapse of the sheet to length scales that are more than one order of magnitude smaller than those reported earlier. The current density attains correspondingly larger maximum values within the sheet. During this thinning process, which is finally limited by lack of resolution even in the AMR studies, the current sheet moves upward, following a global expansion of the magnetic structure during the quasi-static evolution. The sheet is locally one-dimensional and the plasma flow in its vicinity, when transformed into a co-moving frame, qualitatively resembles a stagnation point flow. In conclusion, our simulations support the idea that extremely high current densities are generated in the vicinities of QSLs as a response to external perturbations, with no sign of saturation.Comment: 6 Figure

    Etablierung der VATS-Lobektomie im Stadium I und II des nicht-kleinzelligen Bronchialkarzinoms an ausgewählten Kliniken

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    Die Akzeptanz für die Anwendung minimal-invasiver Techniken in der Thoraxchirurgie ist momentan in Europa noch relativ gering. Allerdings scheint sich eine schrittweise Abkehr vom jahrzehntelang vorherrschenden Dogma der federführenden Thoraxchirurgen gegen den Einzug minimalinvasiver Technik in der Tumortherapie abzuzeichnen. Ziel dieser Arbeit ist die kritische Beleuchtung der VATS-Lobektomie als neu etabliertes, minimal-invasives Operationsverfahren in der Therapie des NSCLC im Stadium I und II im Operationsrepertoire dreier mitteldeutscher Kliniken. Das untersuchte Patientenkollektiv umfasste 197 VATS-lobektomierte Patienten mit der Diagnose eines primären Bronchialkarzinoms der Tumorstadien I und II. Prospektiv wurden vom 01.01.2011 bis zum 31.12.2013 Daten erhoben, welche retrospektiv ausgewertet wurden

    Automated urinalysis: first experiences and a comparison between the Iris iQ200 urine microscopy system, the Sysmex UF-100 flow cytometer and manual microscopic particle counting

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    Background: Automated analysis of insoluble urine components can reduce the workload of conventional microscopic examination of urine sediment and is possibly helpful for standardization. We compared the diagnostic performance of two automated urine sediment analyzers and combined dipstick/automated urine analysis with that of the traditional dipstick/microscopy algorithm. Methods: A total of 332 specimens were collected and analyzed for insoluble urine components by microscopy and automated analyzers, namely the Iris iQ200 (Iris Diagnostics) and the UF-100 flow cytometer (Sysmex). Results: The coefficients of variation for day-to-day quality control of the iQ200 and UF-100 analyzers were 6.5% and 5.5%, respectively, for red blood cells. We reached accuracy ranging from 68% (bacteria) to 97% (yeast) for the iQ200 and from 42% (bacteria) to 93% (yeast) for the UF-100. The combination of dipstick and automated urine sediment analysis increased the sensitivity of screening to approximately 98%. Conclusions: We conclude that automated urine sediment analysis is sufficiently precise and improves the workflow in a routine laboratory. In addition, it allows sediment analysis of all urine samples and thereby helps to detect pathological samples that would have been missed in the conventional two-step procedure according to the European guidelines. Although it is not a substitute for microscopic sediment examination, it can, when combined with dipstick testing, reduce the number of specimens submitted to microscopy. Visual microscopy is still required for some samples, namely, dysmorphic erythrocytes, yeasts, Trichomonas, oval fat bodies, differentiation of casts and certain crystals. Clin Chem Lab Med 2007;45:1251-
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