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All Library Books, journals and Electronic Records Telegrafenberg

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  • 1
    Publikationsdatum: 2016-01-23
    Beschreibung: The improvement of device performance of a recycling solar air heater featuring a wire mesh packing was investigated experimentally and theoretically. The application of the wire mesh packing and recycle-effect concept to the present study were proposed aiming to strengthen the convective heat-transfer coefficient due to increased turbulence. Comparisons were made among different designs, including the single-pass, flat-plate double-pass and recycling double-pass wire mesh packed operations. The collector efficiency of the recycling double-pass wire mesh packed solar air heater was much higher than that of the other configurations for various recycle ratios and mass flow rates scenarios. The power consumption increment due to implementing wire mesh in solar air heaters was also discussed considering the economic feasibility. A fairly good agreement between theoretical predictions and experimental measurements was achieved with an analyzed error of 1.07%–9.32%.
    Digitale ISSN: 1996-1073
    Thema: Energietechnik
    Publiziert von MDPI Publishing
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2019
    Beschreibung: With the rapid development of global positioning technologies and the pervasiveness of intelligent mobile terminals, trajectory data have shown a sharp growth trend both in terms of data volume and coverage. In recent years, increasing numbers of LBS (location based service) applications have provided us with trajectory data services such as traffic flow statistics and user behavior pattern analyses. However, the storage and query efficiency of massive trajectory data are increasingly creating a bottleneck for these applications, especially for large-scale spatiotemporal query scenarios. To solve this problem, we propose a new spatiotemporal indexing method to improve the query efficiency of massive trajectory data. First, the method extends the GeoSOT spatial partitioning scheme to the time dimension and forms a global space–time subdivision scheme. Second, a novel multilevel spatiotemporal grid index, called the GeoSOT ST-index, was constructed to organize trajectory data hierarchically. Finally, a spatiotemporal range query processing method is proposed based on the index. We implement and evaluate the index in MongoDB. By comparing the range query efficiency and scalability of our index with those of the other two space–time composite indexes, we found that our approach improves query efficiency levels by approximately 40% and has better scalability under different data volumes.
    Digitale ISSN: 2220-9964
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 3
    Publikationsdatum: 2016-03-19
    Beschreibung: System entropy describes the dispersal of a system’s energy and is an indication of the disorder of a physical system. Several system entropy measurement methods have been developed for dynamic systems. However, most real physical systems are always modeled using stochastic partial differential dynamic equations in the spatio-temporal domain. No efficient method currently exists that can calculate the system entropy of stochastic partial differential systems (SPDSs) in consideration of the effects of intrinsic random fluctuation and compartment diffusion. In this study, a novel indirect measurement method is proposed for calculating of system entropy of SPDSs using a Hamilton–Jacobi integral inequality (HJII)-constrained optimization method. In other words, we solve a nonlinear HJII-constrained optimization problem for measuring the system entropy of nonlinear stochastic partial differential systems (NSPDSs). To simplify the system entropy measurement of NSPDSs, the global linearization technique and finite difference scheme were employed to approximate the nonlinear stochastic spatial state space system. This allows the nonlinear HJII-constrained optimization problem for the system entropy measurement to be transformed to an equivalent linear matrix inequalities (LMIs)-constrained optimization problem, which can be easily solved using the MATLAB LMI-toolbox (MATLAB R2014a, version 8.3). Finally, several examples are presented to illustrate the system entropy measurement of SPDSs.
    Digitale ISSN: 1099-4300
    Thema: Chemie und Pharmazie , Physik
    Publiziert von MDPI Publishing
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Publikationsdatum: 2016-10-03
    Beschreibung: This paper presents an interleaved inductor-coupled converter for a fuel cell. It is designed to boost a low input voltage from a fuel cell to a specified voltage level for DC load or high voltage DC link, thus providing a high-voltage conversion ratio. The presented converter mainly involves coupled inductors and capacitor of voltage doublers for boosting purposes, but the voltage ratings of the involved power switches and diodes, in particular, remain unaffected as the output voltage is boosted. Using an interleaving trigger mechanism, this circuit configuration can not only suppress the input current ripple, but also reduce the current ratings of power switches. In simple terms, it is a low-cost but high-voltage gain converter due to a smaller number of required components and the lower current and voltage ratings of power switches. The operation principles and design steps are detailed herein, and the performance simulations are experimentally validated at the end of the work.
    Digitale ISSN: 1996-1073
    Thema: Energietechnik
    Publiziert von MDPI Publishing
    Standort Signatur Erwartet Verfügbarkeit
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