10 research outputs found

    Fractal geometry for distribution grid topologies

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    This paper presents an application of fractal geometry in the design, development and expansion of distribution networks. In order to prove that electrical grids are fractal in form, the fractal dimension of distribution networks is measured using the box-counting algorithm. Then a two dimensional stochastic dielectric breakdown model (DBM) is utilized in order to generate virtual distribution networks. The fractal dimension of the simulated growth patterns varied depending on η which is the exponent of the breakdown probability distribution. By controlling the value of η, growth patterns similar to the actual distribution networks could be produced. Finally, some electrical characteristics (maximum voltage drop, total power losses) of the fractal generated networks are measured and compared with the real distribution networks

    Fractal geometry for distribution grid topologies

    No full text
    \u3cp\u3eThis paper presents an application of fractal geometry in the design, development and expansion of distribution networks. In order to prove that electrical grids are fractal in form, the fractal dimension of distribution networks is measured using the box-counting algorithm. Then a two dimensional stochastic dielectric breakdown model (DBM) is utilized in order to generate virtual distribution networks. The fractal dimension of the simulated growth patterns varied depending on η which is the exponent of the breakdown probability distribution. By controlling the value of η, growth patterns similar to the actual distribution networks could be produced. Finally, some electrical characteristics (maximum voltage drop, total power losses) of the fractal generated networks are measured and compared with the real distribution networks.\u3c/p\u3

    Aerosols in the Mediterranean Region and Their Role in Cloud Formation

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    The physical and chemical characteristics of aerosols are considered as critical for nucleation processes, cloud formation and evolution. The Mediterranean Region is well known for the mixture of aerosols from different origins such as desert dust, sea salt and anthropogenic and biomass burning. Sea salt is in relatively small quantities compared to dust amounts during episodes but its constant presence plays a key role in cloud formation, especially concerning the initial stage. In this work we discuss modeling results related to nucleation processes and cloud formation in the Eastern Mediterranean. Emphasis is given in the impact of sea salt on Marine Boundary Layer (MBL) and orographic cloud formation. The role of other sources of aerosols is also discussed. The modeling tool used for the simulations is the RAMS/ICLAMS fully-coupled modeling system. Satellite data and in situ measurements have been also used for a more comprehensive analysis

    Assessing the European offshore wind and wave energy resource for combined exploitation

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    The main concern when utilizing renewable energy resources is their intermittency and variability. One way to deal with this shortcoming is to harvest energy from complementary sources. In this study, wind and wave energy were selected as such and further analyzed in terms of availability, variability, coherence, correlation and potential impact from extreme values. This resource characterization was performed in different timescales, during a 10-year period, using high resolution numerical modeling systems. Based on the results of this analysis, the most suitable areas for combined exploitation were identified and the possible merits from this synergy were pin-pointed and discussed. It was indicated that the most suitable areas for combined use are the western offshore areas of Europe. The wind and wave fields in these open sea areas reveal the lowest correlation in the examined field in contrast to those located in semi-enclosed and enclosed basins that exhibit the highest ones. The joint exploitation in the former regions gives a less variable power output with considerable fewer hours of zero production. Moreover, the suitable energy conversion system for a specific area is strongly dependent on the local characteristics of the available resource. © 2016 Elsevier Lt

    A porous graphitized carbon LC-ESI/MS method for the quantitation of metronidazole and fluconazole in breast milk and human plasma

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    Information on drug transfer into the breast milk is essential to protect the infant from undesirable adverse effects of maternal consumption of drugs and to allow effective pharmacological treatment of breastfeeding mothers. Metronidazole and fluconazole are two drugs frequently used in nursing women to treat various infections, thus questioning infant's safety due to drug exposure through breast milk. In this article a porous graphitized carbon LC/ESI-MS assay was developed for the quantitation of metronidazole and fluconazole in breast milk and human plasma. The assay was based on the use of 150 μL of biological samples, following acetonitrile precipitation of proteins and filtration that enabled injection into the LC/ESI-MS system. All analytes and the internal standard, ropinirole, were separated by using a porous graphitized carbon analytical column (150 × 2.1 mm i.d., particle size 5 μm) with isocratic elution. The mobile phase consists of 55% acetonitrile in water acidified with 0.1% concentrated formic acid and pumped at a flow rate of 0.25 mL min−1. The assay was linear over a concentration range of 0.1 to 15 μg mL−1 for all analytes in both biological samples. Intermediate precision was found to be <8.4% over the tested concentration ranges. A run time of <5 min for each sample made it possible to analyze a large number of biological samples per day. The method is the first reported application for the analysis of metronidazole and fluconazole in both breast milk and human plasma and it can be used to support a wide range of clinical studies. © 2018 Elsevier B.V

    ASSURED Point-of-Need Food Safety Screening: A Critical Assessment of Portable Food Analyzers

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    Standard methods for chemical food safety testing in official laboratories rely largely on liquid or gas chromatography coupled with mass spectrometry. Although these methods are considered the gold standard for quantitative confirmatory analysis, they require sampling, transferring the samples to a central laboratory to be tested by highly trained personnel, and the use of expensive equipment. Therefore, there is an increasing demand for portable and handheld devices to provide rapid, efficient, and on-site screening of food contaminants. Recent technological advancements in the field include smartphone-based, microfluidic chip-based, and paper-based devices integrated with electrochemical and optical biosensing platforms. Furthermore, the potential application of portable mass spectrometers in food testing might bring the confirmatory analysis from the laboratory to the field in the future. Although such systems open new promising possibilities for portable food testing, few of these devices are commercially available. To understand why barriers remain, portable food analyzers reported in the literature over the last ten years were reviewed. To this end, the analytical performance of these devices and the extent they match the World Health Organization benchmark for diagnostic tests, i.e., the Affordable, Sensitive, Specific, User-friendly, Rapid and Robust, Equipment-free, and Deliverable to end-users (ASSURED) criteria, was evaluated critically. A five-star scoring system was used to assess their potential to be implemented as food safety testing systems. The main findings highlight the need for concentrated efforts towards combining the best features of different technologies, to bridge technological gaps and meet commercialization requirements
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