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  • 1
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    Sensors, Vol. 14, Pages 2089-2109: Mobile Robot Self-Localization System Using Single Webcam Distance Measurement Technology in Indoor Environments (2014)
    MDPI Publishing
    In: Sensors
    Details
    Publikationsdatum: 2014-01-28
    Beschreibung: A single-webcam distance measurement technique for indoor robot localization is proposed in this paper. The proposed localization technique uses webcams that are available in an existing surveillance environment. The developed image-based distance measurement system (IBDMS) and parallel lines distance measurement system (PLDMS) have two merits. Firstly, only one webcam is required for estimating the distance. Secondly, the set-up of IBDMS and PLDMS is easy, which only one known-dimension rectangle pattern is needed, i.e., a ground tile. Some common and simple image processing techniques, i.e., background subtraction are used to capture the robot in real time. Thus, for the purposes of indoor robot localization, the proposed method does not need to use expensive high-resolution webcams and complicated pattern recognition methods but just few simple estimating formulas. From the experimental results, the proposed robot localization method is reliable and effective in an indoor environment.
    Digitale ISSN: 1424-8220
    Thema: Chemie und Pharmazie , Elektrotechnik, Elektronik, Nachrichtentechnik
    Publiziert von MDPI Publishing
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
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    Sensors, Vol. 12, Pages 4737-4763: Adapting an Ant Colony Metaphor for Multi-Robot Chemical Plume Tracing (2012)
    MDPI Publishing
    In: Sensors
    Details
    Publikationsdatum: 2012-05-03
    Beschreibung: We consider chemical plume tracing (CPT) in time-varying airflow environments using multiple mobile robots. The purpose of CPT is to approach a gas source with a previously unknown location in a given area. Therefore, the CPT could be considered as a dynamic optimization problem in continuous domains. The traditional ant colony optimization (ACO) algorithm has been successfully used for combinatorial optimization problems in discrete domains. To adapt the ant colony metaphor to the multi-robot CPT problem, the two-dimension continuous search area is discretized into grids and the virtual pheromone is updated according to both the gas concentration and wind information. To prevent the adapted ACO algorithm from being prematurely trapped in a local optimum, the upwind surge behavior is adopted by the robots with relatively higher gas concentration in order to explore more areas. The spiral surge (SS) algorithm is also examined for comparison. Experimental results using multiple real robots in two indoor natural ventilated airflow environments show that the proposed CPT method performs better than the SS algorithm. The simulation results for large-scale advection-diffusion plume environments show that the proposed method could also work in outdoor meandering plume environments.
    Digitale ISSN: 1424-8220
    Thema: Chemie und Pharmazie , Elektrotechnik, Elektronik, Nachrichtentechnik
    Publiziert von MDPI Publishing
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
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    Energies, Vol. 3, Pages 1622-1638: Hierarchical MAS Based Control Strategy for Microgrid (2011)
    MDPI Publishing
    In: Energies
    Details
    Publikationsdatum: 2011-01-14
    Beschreibung: Microgrids have become a hot topic driven by the dual pressures of environmental protection concerns and the energy crisis. In this paper, a challenge for the distributed control of a modern electric grid incorporating clusters of residential microgrids is elaborated and a hierarchical multi-agent system (MAS) is proposed as a solution. The issues of how to realize the hierarchical MAS and how to improve coordination and control strategies are discussed. Based on MATLAB and ZEUS platforms, bilateral switching between grid-connected mode and island mode is performed under control of the proposed MAS to enhance and support its effectiveness.
    Digitale ISSN: 1996-1073
    Thema: Energietechnik
    Publiziert von MDPI Publishing
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
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    Energies, Vol. 9, Pages 630: Coordinated Scheme of Under-Frequency Load Shedding with Intelligent Appliances in a Cyber Physical Power System (2016)
    MDPI Publishing
    In: Energies
    Details
    Publikationsdatum: 2016-08-11
    Beschreibung: The construction of a cyber physical system in a power grid provides more potential control strategies for the power grid. With the rapid employment of intelligent terminal equipment (e.g., smart meters and intelligent appliances) in the environment of a smart grid, abundant dynamic response information could be introduced to support a secure and stable power system. Combining demand response technology with the traditional under-frequency load shedding (UFLS) scheme, a new UFLS strategy-determining method involving intelligent appliances is put forward to achieve the coordinated control of quick response resources and the traditional control resources. Based on this method, intelligent appliances can be used to meet the regulatory requirements of system operation in advance and prevent significant frequency drop, thereby improving the flexibility and stability of the system. Time-domain simulation verifies the effectiveness of the scheme, which is able to mitigate frequency drop and reduce the amount of load shedding.
    Digitale ISSN: 1996-1073
    Thema: Energietechnik
    Publiziert von MDPI Publishing
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 5
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    Sensors, Vol. 16, Pages 334: An Anchor-Based Pedestrian Navigation Approach Using Only Inertial Sensors (2016)
    MDPI Publishing
    In: Sensors
    Details
    Publikationsdatum: 2016-03-08
    Beschreibung: In inertial-based pedestrian navigation, anchors can effectively compensate the positioning errors originating from deviations of Inertial Measurement Units (IMUs), by putting constraints on pedestrians’ motions. However, these anchors often need to be deployed beforehand, which can greatly increase system complexity, rendering it unsuitable for emergency response missions. In this paper, we propose an anchor-based pedestrian navigation approach without any additional sensors. The anchors are defined as the intersection points of perpendicular corridors and are considered characteristics of building structures. In contrast to these real anchors, virtual anchors are extracted from the pedestrian’s trajectory and are considered as observations of real anchors, which can accordingly be regarded as inferred building structure characteristics. Then a Rao-Blackwellized particle filter (RBPF) is used to solve the joint estimation of positions (trajectory) and maps (anchors) problem. Compared with other building structure-based methods, our method has two advantages. The assumption on building structure is minimum and valid in most cases. Even if the assumption does not stand, the method will not lead to positioning failure. Several real-scenario experiments are conducted to validate the effectiveness and robustness of the proposed method.
    Digitale ISSN: 1424-8220
    Thema: Chemie und Pharmazie , Elektrotechnik, Elektronik, Nachrichtentechnik
    Publiziert von MDPI Publishing
    Standort Signatur Einschränkungen Verfügbarkeit
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    PAPER CURRENT
  • 6
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    Remote Sensing, Vol. 7, Pages 2302-2333: A Robust Photogrammetric Processing Method of Low-Altitude UAV Images (2015)
    MDPI Publishing
    Details
    Publikationsdatum: 2015-02-27
    Beschreibung: Low-altitude Unmanned Aerial Vehicles (UAV) images which include distortion, illumination variance, and large rotation angles are facing multiple challenges of image orientation and image processing. In this paper, a robust and convenient photogrammetric approach is proposed for processing low-altitude UAV images, involving a strip management method to automatically build a standardized regional aerial triangle (AT) network, a parallel inner orientation algorithm, a ground control points (GCPs) predicting method, and an improved Scale Invariant Feature Transform (SIFT) method to produce large number of evenly distributed reliable tie points for bundle adjustment (BA). A multi-view matching approach is improved to produce Digital Surface Models (DSM) and Digital Orthophoto Maps (DOM) for 3D visualization. Experimental results show that the proposed approach is robust and feasible for photogrammetric processing of low-altitude UAV images and 3D visualization of products.
    Digitale ISSN: 2072-4292
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geographie
    Publiziert von MDPI Publishing
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 7
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    Sensors, Vol. 12, Pages 12386-12404: Design of a Multi-Sensor Cooperation Travel Environment Perception System for Autonomous Vehicle (2012)
    MDPI Publishing
    In: Sensors
    Details
    Publikationsdatum: 2012-09-13
    Beschreibung: This paper describes the environment perception system designed for intelligent vehicle SmartV-II, which won the 2010 Future Challenge. This system utilizes the cooperation of multiple lasers and cameras to realize several necessary functions of autonomous navigation: road curb detection, lane detection and traffic sign recognition. Multiple single scan lasers are integrated to detect the road curb based on Z-variance method. Vision based lane detection is realized by two scans method combining with image model. Haar-like feature based method is applied for traffic sign detection and SURF matching method is used for sign classification. The results of experiments validate the effectiveness of the proposed algorithms and the whole system.
    Digitale ISSN: 1424-8220
    Thema: Chemie und Pharmazie , Elektrotechnik, Elektronik, Nachrichtentechnik
    Publiziert von MDPI Publishing
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 8
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    IJERPH, Vol. 11, Pages 626-642: Residential Racial Composition and Black-White Obesity Risks: Differential Effects of Neighborhood Social and Built Environment (2014)
    MDPI Publishing
    Details
    Publikationsdatum: 2014-01-03
    Beschreibung: This study investigates the association between neighborhood racial composition and adult obesity risks by race and gender, and explores whether neighborhood social and built environment mediates the observed protective or detrimental effects of racial composition on obesity risks. Cross-sectional data from the 2006 and 2008 Southeastern Pennsylvania Household Health Survey are merged with census-tract profiles from 2005–2009 American Community Survey and Geographic Information System-based built-environment data. The analytical sample includes 12,730 whites and 4,290 blacks residing in 953 census tracts. Results from multilevel analysis suggest that black concentration is associated with higher obesity risks only for white women, and this association is mediated by lower neighborhood social cohesion and socioeconomic status (SES) in black-concentrated neighborhoods. After controlling for neighborhood SES, black concentration and street connectivity are associated with lower obesity risks for white men. No association between black concentration and obesity is found for blacks. The findings point to the intersections of race and gender in neighborhood effects on obesity risks, and highlight the importance of various aspects of neighborhood social and built environment and their complex roles in obesity prevention by socio-demographic groups.
    Print ISSN: 1661-7827
    Digitale ISSN: 1660-4601
    Thema: Energietechnik , Medizin
    Publiziert von MDPI Publishing
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 9
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    Energies, Vol. 10, Pages 1786: Universal Generating Function Based Probabilistic Production Simulation Approach Considering Wind Speed Correlation (2017)
    MDPI Publishing
    In: Energies
    Details
    Publikationsdatum: 2017-11-07
    Beschreibung: Energies, Vol. 10, Pages 1786: Universal Generating Function Based Probabilistic Production Simulation Approach Considering Wind Speed Correlation Energies doi: 10.3390/en10111786 Authors: Yan Li Ming Zhou Dawei Wang Yuehui Huang Zifen Han Due to the volatile and correlated nature of wind speed, a high share of wind power penetration poses challenges to power system production simulation. Existing power system probabilistic production simulation approaches are in short of considering the time-varying characteristics of wind power and load, as well as the correlation between wind speeds at the same time, which brings about some problems in planning and analysis for the power system with high wind power penetration. Based on universal generating function (UGF), this paper proposes a novel probabilistic production simulation approach considering wind speed correlation. UGF is utilized to develop the chronological models of wind power that characterizes wind speed correlation simultaneously, as well as the chronological models of conventional generation sources and load. The supply and demand are matched chronologically to not only obtain generation schedules, but also reliability indices both at each simulation interval and the whole period. The proposed approach has been tested on the improved IEEE-RTS 79 test system and is compared with the Monte Carlo approach and the sequence operation theory approach. The results verified the proposed approach with the merits of computation simplicity and accuracy.
    Digitale ISSN: 1996-1073
    Thema: Energietechnik
    Publiziert von MDPI Publishing
    Standort Signatur Einschränkungen Verfügbarkeit
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    PAPER CURRENT
  • 10
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    Energies, Vol. 11, Pages 2440: Effect of Ice Shedding on Discharge Characteristics of an Ice-Covered Insulator String during AC Flashover (2018)
    MDPI Publishing
    In: Energies
    Details
    Publikationsdatum: 2018-09-15
    Beschreibung: Energies, Vol. 11, Pages 2440: Effect of Ice Shedding on Discharge Characteristics of an Ice-Covered Insulator String during AC Flashover Energies doi: 10.3390/en11092440 Authors: Xiangxin Li Ming Zhou Yazhou Luo Gang Wang Lin Jia Considering the ice shedding phenomena on ice-covered outdoor insulators, this paper conducted the artificial experiments by using a five-unit suspension ceramic insulator string covered with wet-grown ice to investigate the effects of ice shedding on the icing discharge characteristics. According to IEEE Standard 1783/2009, the minimum flashover voltage (VMF), propagation of discharges to flashover and related leakage current (LC) were measured. It was found that VMF after ice shedding can be increased by about 17% as compared with that before ice shedding. The initiation and formation of discharge arcs across ice-free regions caused by ice shedding become difficult, showing an unstable propagating path, indeterminate arc shape and longer arc column. Although VMF under ice shedding conditions is higher than that without ice shedding, the fundamental component, and harmonics show lower amplitudes for the latter case. The ratios of harmonics to the fundamental are well in accordance with discharge characteristics during the flashover for which the ratios show a relatively stable varying tendency in the absence of ice shedding, but show changeable and indeterminate variation under ice shedding conditions. The obtained results are helpful to understand the icing state and its influence on surface discharges for preventing the icing flashovers.
    Digitale ISSN: 1996-1073
    Thema: Energietechnik
    Publiziert von MDPI Publishing
    Standort Signatur Einschränkungen Verfügbarkeit
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    PAPER CURRENT
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