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Frequency domain based DC fault analysis for bipolar HVDC grids

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Journal of Modern Power Systems and Clean Energy 2017年第4期5卷 548-559页

作者： Mian WANG Jef BEERTEN dirk Van HERTEM EnergyVille/Electa Research Group Electrical Engineering Department ESATKU Leuven3001 HeverleeBelgium

This paper proposes a frequency domain based methodology to analyse the influence of High Voltage Direct Current(HVDC) configurations and system parameters on the travelling wave behaviour during a DC fault. The method allows us to gain deeper understanding of these influencing parameters. In the literature, the majority of DC protection algorithms essentially use thefirst travelling waves initiated by a DC fault for fault discrimination due to the stringent time constraint in DC grid protection. However, most protection algorithms up to now have been designed based on extensive time domain simulations using one specific test system. Therefore, general applicability or adaptability to different configurations and system changes is not by default ensured, and it is difficult to gain in-depth understanding of the influencing parameters through time domain simulations. In order to analyse the first travelling wave for meshed HVDC grids, voltage and current wave transfer functions with respect to the incident voltage wave are derived adopting Laplace domain based component models. The step responses obtained from the voltage transfer functions are validated by comparison against simulations using a detailed model implemented in PSCADTM. Then, the influences of system parameters such as the number of parallel branches, HVDC grid configurations and groundings on the first travelling wave are investigated by analysing the voltage and current transfer functions.

关键词： HVDC grids DC grid protection Travelling wave Frequency domain analysis Transfer function

Bean yellow disorder virus： Parameters of transmission by Bemisia tabaci and host plant range

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Insect Science 2011年第1期18卷 50-56页

作者： German Martin Isabel Maria Cuadrado dirk Janssen Instituto Andaluz de Investigacion y Formacion Agraria y Pesquera Centro La Mojonera Almeria Spain

Bean yellow disorder virus （BnYDV） was recently identified as the first crinivirus （family Closteroviridae） that infects members of the family Leguminosae. It was first observed during the autumn of 2003, causing heavy losses in French bean （Phaseolus vulgaris L.） grown commercially in Spain. The virus is transmitted by the sweetpotato whitefly, Bemisia tabaci （Hemiptera： Aleyrodidae） Q-biotype, and disease symptoms resemble nutritional disorders consisting of interveinal mottling and yellowing in leaves, combined with stiffness or brittleness, and are typically produced on the middle to lower parts of the plant. Transmission experiments showed that 50% and 100% of B. tabaci adults acquired the virus after a feeding period of 3 and 7 h, respectively. Viruliferous whiteflies infected 66% and 100% ofP. vulgaris plants after a feeding period of 12 and 24 h, respectively. The transmission efficiency of single whiteflies was 37% and persistence of BnYDV in the vector lasted up to 2 weeks with a half-life of 9 days. BnYDV was transmitted to P. vulgaris, Pisum sativum L., Lens culinaris Medik., and Vicia faba L., but not to Vigna unguiculata L., Glycine max （L.） Merr., Cicer arietum L., and to crop species belonging to families of the Solanaceae and Cucurbitaceae. No virus was detected in field samples collected from 30 different species from Boraginaceae, Asteraceae, Geraniaceae, Lamiaceae, Leguminosae, Malvaceae, Scrophulariaceae, Thymelaeaceae and Verbenaceae. The restricted host range and efficient management of crops regarding whitefly infestation may be key elements in the control of BnYDV.

关键词： bean Closteroviridae Crinivirus disease vector whiteflies

Predicting prognosis in colorectal liver metastases

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Hepatobiliary Surgery and Nutrition 2019年第6期8卷 643-645页

作者： dirk Grünhagen Erasmus MC Cancer Institute RotterdamThe Netherlands

Liver surgeons treating colorectal liver metastases(CRLM)are on the verge of fascinating *** one hand,there is a trend towards minimally invasive,or percutaneous,approaches of liver treatment,whereas on the other hand reports on maximally invasive surgery have come out that claim survival benefit for CRLM patients if treated *** order to choose between these different treatment philosophies,the surgeon,and equally importantly the patient,need *** that will tell whether the proposed treatment option will indeed be of benefit for the patient sitting in clinic in front of you.

关键词： colorectal metastases Liver

Tuning thermal release kinetics of soy oil from organic nanoparticles using variable synthesis conditions

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Particuology 2016年第3期14卷 54-65页

作者： Pieter Samyn Dieter Van Nieuwkerke Vibhore Rastogi dirk Stanssens University of Freiburg Freiburg Research Institute for Advances Studies (FRIAS) Faculty for Environment and Natural Resources Chair of Bio-based Materials Engineering Werthmannstrasse 6 D-79085 Freiburg Germany Ghent University Department of Textiles Technologiepark 907 B-9052 Zwijnaarde Belgium Topehim N.K Nijverheidsstraat 98 B-2160 Wommelgem Belgium

The thermal release properties of soy oil from poly（styrene-co-maleimide） nanoparticles containing 50 wt% encapsulated oil have been quantified as a function of temperature and time. The effects of dif- ferent synthesis conditions on the thermal stability of the nanoparticles and their oil release have been evaluated, i.e., by gradually increasing the amount of ammonium hydroxide used for the imidization of poly（styrene-co-maleic anhydride）. First, the intrinsic thermal properties of the oil-filled nanoparti- cles were analysed by differential scanning calorimetry, which revealed an exothermal reaction related to the oil release and a suppression of the glass transition that may be masked owing to the complex structure of the hybrid nanoparticles. The isothermal scans showed different rates of oil release after a post-imidization reaction. The oil release was better followed by dynamic mechanical analysis, which illustrated changes in visco-elastic properties expressed by the maximum in the loss factor that related to the amount of released oil. Depending on the amount of ammonium hydroxide, the oil started to release below the glass transition temperature at various rates. Thermal release profiles of the oil we re quantified by infrared and Raman spectrocopy after heating for 2 min to 6 h at 125 to 250 ℃, based on variations in oil-related and imide-related absorption bands. The oil release increased below and above the glass transition temperature, following a parabolic trend, and progressively decreased at higher ammonium hydroxide concentrations, in parallel with higher imide content and changes in imide conformation. The kinetics and mechanism of the oil release can be described by the Korsmeyer-Peppas model, suggesting a dominating diffusion mechanism that is influenced by further imidization of the polymer matrix during heating.

关键词： Soy oil Nanoparticle Encapsulation Release

Assessing global Sentinel-2 coverage dynamics and data availability for operational Earth observation(EO)applications using the EO-Compass

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International Journal of Digital Earth 2020年第7期13卷 768-784页

作者： Martin Sudmanns dirk Tiede Hannah Augustin Stefan Lang Department of Geoinformatics University of SalzburgSalzburgAustria

Sentinel-2 scenes are increasingly being used in operational Earth observation(EO)applications at regional,continental and global scales,in near-real time applications,and with multi-temporal *** a broader scale,they are therefore one of the most important facilitators of the Digital ***,the data quality and availability are not spatially and temporally homogeneous due to effects related to cloudiness,the position on the Earth or the acquisition *** spatiotemporal inhomogeneity of the underlying data may therefore affect any big remote sensing analysis and is important to *** study presents an assessment of the metadata for all accessible Sentinel-2 Level-1C scenes acquired in 2017,enabling the spatio-temporal coverage and availability to be quantified,including scene availability and *** exploratory analysis of the global,multi-temporal metadata also reveals that higher acquisition frequencies do not necessarily yield more cloud-free scenes and exposes metadata quality issues,*** incorrect cloud cover estimation in high,nonvegetated *** continuously updated datasets and analysis results are accessible as a Web application called *** contributes to a better understanding and selection of Sentinel-2 scenes,and improves the planning and interpretation of remote sensing analyses.

关键词： Sentinel-2 metadata cloud cover scene coverage global analysis big Earth data digital earth

Semantic and syntactic interoperability in online processing of big Earth observation data

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International Journal of Digital Earth 2018年第1期11卷 95-112页

作者： Martin Sudmanns dirk Tiede Stefan Lang Andrea Baraldi Department of Geoinformatics–Z_GIS University of SalzburgSalzburgAustria Department of Agricultural and Food Sciences University of Naples FedericoⅡNapoliItaly

The challenge of enabling syntactic and semantic interoperability for comprehensive and reproducible online processing of big Earth observation(EO)data is still *** both types of interoperability is one of the requirements to efficiently extract valuable information from the large amount of available multi-temporal gridded data *** proposed system wraps world models,(semantic interoperability)into OGC Web Processing Services(syntactic interoperability)for semantic online *** models describe spatio-temporal entities and their relationships in a formal *** proposed system serves as enabler for(1)technical interoperability using a standardised interface to be used by all types of clients and(2)allowing experts from different domains to develop complex analyses together as collaborative *** are connecting the world models online to the data,which are maintained in a centralised storage as 3D spatio-temporal data *** allows also non-experts to extract valuable information from EO data because data management,low-level interactions or specific software issues can be *** discuss the concept of the proposed system,provide a technical implementation example and describe three use cases for extracting changes from EO images and demonstrate the usability also for non-EO,gridded,multitemporal data sets(CORINE land cover).

关键词： OGC WPS big Earth data time series large-scale processing model-driven semantic analyses

Long-term variability of air temperature and precipitation conditions in the Polish Carpathians

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Journal of Mountain Science 2018年第2期15卷 237-253页

作者： Agnieszka WYPYCH Zbigniew USTRNUL dirk R.SCHMATZ Department of Climatology Jagiellonian University Landscape Dynamics Unit Swiss Federal Research Institute WSL

Mountain regions are sensitive to climate changes, which make them good indicators of climate change. The aim of this study is to investigate the spatial and temporal variability of air temperature and precipitation in the Polish Carpathians. This study consists of climatological analyses for the historical period 1851-2010 and future projections for 2021-2100. The results confirm that there has been significant warming of the area and that this warming has been particularly pronounced over the last few decades and will continue in the oncoming *** change is most evident in the foothills;however, these are the highest summits which have experienced the most intensive increases in temperature during the recent period. Precipitation does not demonstrate any substantial trend and has high year-to-year variability. The distribution of the annual temperature contour lines modelled for selected periods provides evidence of the upward shift of vertical climate zones in the Polish Carpathians,which reach approximately 350 meters, on average,what indicates further ecological consequences as ecosystems expand or become extinct and when there are changes in the hydrological cycle.

关键词： Climate change Air temperature Precipitation Polish Carpathians

Impact of crystalline and amorphous iron-and aluminum hydroxides on mechanisms of phosphate adsorption and desorption

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Journal of Environmental Sciences 2018年第8期30卷 175-189页

作者： Stella Gypser Florian Hirsch Anja M.Schleicher dirk Freese Brandenburg University of Technology Cottbus-Senftenberg Faculty of Environment Process Engineering Biotechnology and Chemistry Department of Soil Protection and Recultivation Brandenburg University of Technology Cottbus-Senftenberg Faculty of Environment Process Engineering Biotechnology and Chemistry Department of Geopedology and Landscape Development German Research Centre for Geosciences Section 3.1 Inorganic and Isotope Geochchemistry

Fourier-transform infrared（FT-IR） spectroscopic experiments were carried out during phosphate adsorption on highly crystalline gibbsite, poorly crystalline 2-line-ferrihydrite and amorphous iron–aluminum–hydroxide mixtures in the molar ratio 1：0, 10：1, 5：1, 1：1, 1：5, 1：10 and 0：1. The OH stretching vibrational bands were utilized to analyze changes in structural and surface OH groups during adsorption, because the position of characteristic P／O vibrational bands can shift depending on reaction conditions, pH or adsorbed phosphate *** and desorption kinetics were studied at pH6 and different initial phosphate concentrations to achieve varying phosphate coverage on the mineral surfaces. For gibbsite the formation of AlHPO4 and Al2HPO4 can be assumed, while for ferrihydrite, a FeHPO4 or Fe2PO4 complex and the precipitation of FePO4 with longer equilibration time were ***2HPO4 or a Fe2PO4 surface complex was deduced for Fe-hydroxides, an AlH2PO4 surface complex was identified for Al-hydroxide, and both displayed either hydrogen bonds to neighboring hydroxyl groups or hydrogen bonds to outer-sphere complexes. Fe：Al-hydroxide mixtures with high Al ratios showed a low phosphate desorption rate, while ferrihydrite and the Fe：Al-hydroxide mixtures with high Fe ratios had almost negligible desorption rates. It was concluded that within the weakly associated amorphous FeO（OH） materials, FePO4 precipitated, which was bound by outer-sphere hydrogen bonds. With high Al ratios, desorption increased, which indicated weaker phosphate binding of both inner-sphere and outer-sphere complexes and hence, either no or minor quantities of precipitate. Ferrihydrite showed a more rigid structure and a lower extent of precipitation compared to amorphous Fe-hydroxide.

关键词： Phosphate Adsorption Desorption Surface complexation Precipitation FT-IR

Rates and processes affecting As speciation and mobility in lake sediments during aging

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Journal of Environmental Sciences 2018年第4期30卷 338-347页

作者： Alan Lock dirk Wallschlager Nelson Belzile Graeme Spiers Celine Gueguen Environmental and Life Sciences Graduate Program Trent University School of the Environment Department of Chemistry and Water Quality CentreTrent University Department of Chemistry Laurentian University School of the Environment Departments of Earth Sciences and BiologyLaurentian University School of the Environment and Chemistry Department Trent University

Sediments from an arsenic（As） contaminated groundwater vent site were used to investigate As（ Ⅲ） binding, transformation and redistribution in native and iron oxide amended lake sediments using aging spiked batch reactions and a sequential extraction procedure that maintains As（V） and As（ Ⅲ） speciation. In the native sediments, fractionation analysis revealed that 10% of the spiked As（ Ⅲ） remained intact after a 32-day aging experiment and was predominantly adsorbed to the strongly sorbed（NH4H2PO4 extractable） and amorphous Fe oxide bound（H3PO4 extractable） fractions. Kinetic modelling of the experimental results allowed identifying the dominant reaction path for depletion of dissolved As（ Ⅲ） to As（ Ⅲ）absorbed on to the solid phase, followed by oxidation in the solid phase. Arsenite was initially adsorbed primarily to the easily exchangeable fraction（（NH4）2SO4 extractable）, then rapidly transformed into As（V） and redistributed to the strongly sorbed and amorphous Fe oxide bound fractions. Oxidation of As（ Ⅲ） in recalcitrant fractions was less efficient. The iron oxide amendments illustrated the controls that iron oxides can have on As（ Ⅲ） binding and transformation rates. In goethite amended samples As（ Ⅲ） oxidation was faster and primarily occurred in the strongly sorbed and amorphous Fe oxide bound fractions. In these samples,19.3 μg Mn was redistributed（compared to the native sediment） from the easily exchangeable and crystalline Fe oxide bound fractions to the strongly sorbed and amorphous Fe oxide bound fractions, indicating that goethite may act as a catalyst for Mn（Ⅱ） oxidation, thereby producing sorbed Mn（ Ⅲ/Ⅳ ）, which then appears to be involved in rapidly oxidizing As（ Ⅲ）.

关键词： Arsenite Oxidation Fractionation Redistribution Modelling