87 research outputs found

    Assessment Techniques to Ensure Reliable Electrical Insulation for More Electric Transportation

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    Partial discharge testing of complete, low-voltage induction machines and dry-type convertor transformers for the More Electric Transportation is discussed. The current standard (i.e. IEC 60034-18-41, 60317-0-1 and 61378\u20131) offers very few answers to the new challenges posed to the insulating systems reliability of these increasingly electrified electrical machines. Based on tests performed on different kind of specimens and the literature, the most promising assessment technique to ensure a reliable insulation is based on optical sensors. In addition, this work seeks to give some precise, but simple, indications on how to take into account the effect of altitude and high frequency in the qualification of an insulation system for More Electric Transportation and the limits of the different standards involved are highlighted

    Partial Discharge Phenomena in Electrical Machines for the More Electrical Aircraft. Part II: Impact of Reduced Pressures and Wide Bandgap Devices

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    This paper focuses on the inception of partial discharges within the insulation system of electrical actuators used for the More Electrical Aircraft (MEA). Since these machines should operate in the absence of Partial Discharges (PDs), the dependence of the PD Inception Voltage (PDIV) on voltage impulses typical of wide bandgap (SiC) devices is investigated at both 1 bar, reduced pressures close to those typical of aircraft cruising altitudes (150 mbar ‚Äď 200 mbar) or lower (down to 5 mbar). Propagation issues are not dealt with here as results were obtained working on insulation models consisting of couples of wires twisted together (twisted pairs), thus knowing exactly the potential differences between all points of the insulation model. The results show that the rise times and the switching frequencies associated with wide bandgap devices have little impact on the PDIV. A model able to predict the PDIV of the turn/turn insulation of random wound motors (the most vulnerable part of the insulation) at different pressures is proposed. The model is also able to deal with temperature changes, with limitations that depend on the type on insulation systems

    Partial Discharges in Electrical Machines for the More Electric Aircraft‚ÄĒPart I: A Comprehensive Modeling Tool for the Characterization of Electric Drives Based on Fast Switching Semiconductors

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    This paper proposed a modelling approach for the comprehensive analysis of high-frequency challenges in electrical drives designed for aerospace applications, in particular the overvoltage at the machine terminals and the voltage distribution within windings. After a separate description of the models for the estimation of these insulation stress sources, the combined model was detailed. The main benefit of developing a combined, flexible and comprehensive tool is that both overvoltage at machine terminals and uneven voltage distribution can be calculated simultaneously, without neglecting the voltage overshoot when estimating the voltage distribution (and vice versa). In fact, an accurate calculation of the terminal overvoltage is necessary to provide a good estimation of the voltage within winding turns since its waveform shape can be quite different with respect to the converter output, even with cables of a few meters. A case study based on a real aerospace application was considered to investigate the model validity and accuracy. Experimental results were performed on a complete system comprising a SiC-based converter, a connecting cable and a machine stator, proving the simulation model accuracy in terms of peak voltages of both the line-to-line terminal voltage and the turn voltage distribution across the first turns, which are the most relevant quantities for the sake of this study as well as for the investigations of the subsequent companion papers. In the forthcoming papers, the effects of different rise times and cable lengths on the inception of partial discharges will be investigated through fast parametric simulation carried out using the proposed combined model. The feasibility of using conventional insulation systems for aircraft applications using SiC drives fed by a ¬Ī270 V DC bus voltage will be discussed, with the aim of signaling and finding solutions to improve the overall reliability

    Growth rate fitting using the von Bertalanffy model: Analysis of natural populations of Drepanotrema spp. snails (Gastropoda: Planorbidae)

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    The genus Drepanotrema includes six species in Argentina. The life cycle in natural systems of Drepanotrema depressissimum, and D. lucidum has been little studied, except for some casual observations. The aim of this study is to analyze main population trends (age structures, recruitment periods, life span and curves of individual growth) in Paiva pond, Argentina. We explored growth model fitting and comparison methodologies between species and environments in Paiva pond and Isla Mart√≠n Garc√≠a (IMG), to determine interspecific patterns. Theoretical curves of von Bertalanffy's model for each population were contrasted with samplings using the Ōá2 test. Expected sizes were transformed into a percentage of maximum size and cohorts started from zero time, which allowed them to be independent of the real or estimated starting date and a comparison was possible. A similar time scale was used, because the k values proved to be sensitive to time scale. Maximum size reached by D. lucidum was 6.9 mm and by D. depressissimum 9.38 mm. Growth rates (k) fluctuated from 1.302 to 1.368 in the first and 1.339 to 1.509 in the second species. No statistically significant differences were found in growth curves among species inhabiting the Paiva pond and in the different IMG water bodies independent of the beginning of each cohort and maximum size. In general, no winter cohorts were observed, except in one population of D. kermatoides (IMG). Comparing circannual and biannual growth rhythms most of the species reached 60 % of their development during their first year, and 85 % or more during their second year.Museo de La Plat

    Primer aislamiento de <i>Enterobacter cloacae</i> productor de Nueva Delhi Metalobetalactamasa (NDM) en un felino de Argentina

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    La resistencia a carbapenemes es una preocupaci√≥n para la salud p√ļblica ya que estos antibi√≥ticos se consideran una de las √ļltimas terapias eficaces disponibles para tratar infecciones graves causadas por microorganismos multirresistentes. En 2009, se describe una metalo-ő≤-lactamasa Nueva Delhi (NDM), aislada en una persona hospitalizada en India. Estas enzimas, capaces de hidrolizar carbapenemes, se encuentran con frecuencia en elementos gen√©ticos m√≥viles y est√°n extendidas mundialmente. Enterobacter spp. constituye uno de los g√©neros donde se suele informar, aunque en muchos pa√≠ses no est√° bien documentado y, en animales, menos a√ļn. Reportamos el primer aislamiento cl√≠nico de Enterobacter cloacae, productor de NDM en mascota con infecci√≥n urinaria en CABA.Trabajo publicado en Cagliada, Maria del Pilar Lilia y Galosi, Cecilia M√≥nica (comps.). I Congreso de Microbiolog√≠a Veterinaria. Libro de res√ļmenes. La Plata: Facultad de Ciencias Veterinarias, 2021.Facultad de Ciencias Veterinaria

    Growth rate fitting using the von Bertalanffy model: Analysis of natural populations of Drepanotrema spp. snails (Gastropoda: Planorbidae)

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    The genus Drepanotrema includes six species in Argentina. The life cycle in natural systems of Drepanotrema depressissimum, and D. lucidum has been little studied, except for some casual observations. The aim of this study is to analyze main population trends (age structures, recruitment periods, life span and curves of individual growth) in Paiva pond, Argentina. We explored growth model fitting and comparison methodologies between species and environments in Paiva pond and Isla Mart√≠n Garc√≠a (IMG), to determine interspecific patterns. Theoretical curves of von Bertalanffy's model for each population were contrasted with samplings using the Ōá2 test. Expected sizes were transformed into a percentage of maximum size and cohorts started from zero time, which allowed them to be independent of the real or estimated starting date and a comparison was possible. A similar time scale was used, because the k values proved to be sensitive to time scale. Maximum size reached by D. lucidum was 6.9 mm and by D. depressissimum 9.38 mm. Growth rates (k) fluctuated from 1.302 to 1.368 in the first and 1.339 to 1.509 in the second species. No statistically significant differences were found in growth curves among species inhabiting the Paiva pond and in the different IMG water bodies independent of the beginning of each cohort and maximum size. In general, no winter cohorts were observed, except in one population of D. kermatoides (IMG). Comparing circannual and biannual growth rhythms most of the species reached 60 % of their development during their first year, and 85 % or more during their second year.Museo de La Plat

    Nemesny√°r kl√≥nok faanyagtani jellemzŇĎkh√∂z k√∂thetŇĎ g√©njeinek genetikai v√°ltozatoss√°ga = Allelic variation in candidate genes associated with wood properties of cultivated poplars

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    A nemesny√°rak kiemelkedŇĎ gazdas√°gi jelentŇĎs√©ggel b√≠rnak. A bemutatott vizsg√°lat legfŇĎbb c√©lja egy olyan kutat√°si metodika ismertet√©se, amely a faanyag tulajdons√°gai√©rt felelŇĎs kulcsenzimek k√≥dol√≥ r√©gi√≥inak azonos√≠t√°s√°b√≥l indul ki, bemutatva a genomikai alapokra helyezett nemes√≠t√©si technol√≥gi√°kban rejlŇĎ lehetŇĎs√©geket. A vizsg√°latunk elsŇĎ szakasz√°ban 24 k√ľl√∂nb√∂zŇĎ, a faanyagk√©pzŇĎd√©s szempontj√°b√≥l relev√°ns enzim k√≥dol√≥ r√©gi√≥j√°ra tervezt√ľnk primerp√°rokat. √Ėsszesen 55 saj√°t fejleszt√©sŇĪ primerp√°rt tesztelt√ľnk, 47,27%-os sikeress√©ggel. Ezut√°n nyolc enzimet v√°lasztottunk ki r√©szletesebb elemz√©sre h√©t ny√°rfaj √©s 11 hibrid kl√≥n bevon√°s√°val, √∂sszesen 23 ny√°r genot√≠pus vizsg√°lata r√©v√©n. A kiv√°lasztott enzimek egy r√©sze a lignifik√°ci√≥ folyamat√°ban vesz r√©szt (COMT, CCoAOMT, SAMS), egy m√°sik csoport a K+-f√ľggŇĎ xylogenezis sor√°n t√∂lt be kulcsszerepet (Kt, ptk2, SKOR), m√≠g a harmadik csoport (endo-1,4-b-xylanase, Araf-ase) a mikrofibrilla sz√∂g alakul√°s√°hoz k√∂thetŇĎ. A sikeresen amplifik√°lt √©s azonos√≠tott 13 markerr√©gi√≥ r√©v√©n √∂sszesen 188 szekvenci√°t elemezt√ľnk √©s 90 SNP-t azonos√≠tottunk. √Črt√©kelt√ľk a polimorf helyek sz√°m√°t, a nukleotid diverzit√°st, az inszerci√≥k/del√©ci√≥k sz√°m√°t, az SNP-k t√≠pus√°t, a rekombin√°ci√≥s esem√©nyek minim√°lis sz√°m√°t, illetve azonos√≠tottuk a konzervat√≠v szakaszokat. Eredm√©nyeink bemutat√°sa sor√°n r√©szletesen t√°rgyaljuk a vizsg√°latban rejlŇĎ alkalmaz√°si lehetŇĎs√©geket

    Freshwater gastropods from del Plata basin, Argentina : Checklist and new locality records

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    The greatest floral and faunal biodiversity estimated from Argentina -not including molluscs - is found in three subtropical forests belonging to the del Plata Basin, two of them at the northeastern part of Argentina (NEA). The aim of this study is to show new records as well as an update of the distribution of the freshwater Gastropoda species in the main NEA rivers: Iguaz√ļ, Paran√°, Paraguay, and Uruguay. At NEA, 66 species belonging to 9 families are known from literature records. According to the preferences of habitats in this area littoral and bottom species, could be recognized. The former includes 33 species belonging to Ampullariidae, Ancylidae, Lymnaeidae, Physidae, and Planorbidae, and the latter with 33 species of Lithoglyphidae, Cochliopidae, Thiaridae, and Chilinidae. In this paper, 30 species of 8 families were recorded, 25 of them are littoral whereas only 5 species inhabiting the bottom were found, because of the high level of the rivers. Two new records were registered for the country, both belonging to Ancylidae: Gundlachia ticaga and the genus Laevapex. Thus, now there are 68 species at NEA. Twenty-three species increase the number of localities. Planorbidae was the family with more collected species (13). No Thiaridae species were found.Facultad de Ciencias Naturales y Muse

    Estado actual del conocimiento de las parasitosis del molusco invasor Achatina fulica en la Argentina: su importancia como posible vector de angiostrongiliasis

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    Achatina fulica (Bowdich, 1822) (Achatinidae) es un gaster√≥podo terrestre originario de √Āfrica oriental como Kenia y Tanzania y de varios pa√≠ses al sur del Sahara y centro del continente donde se lo utiliza como alimento. Se lo conoce como caracol gigante de √Āfrica. En √°reas agr√≠colas esta especie puede convertirse en plaga, produciendo un gran impacto en la salud del ecosistema y generando competencia con las especies de moluscos nativas. Achatina fulica posee tambi√©n importancia m√©dica y veterinaria ya que act√ļa como hospedador intermediario de nematodes de inter√©s sanitario, entre los que se encuentra Angiostrongylus cantonensis (Chen, 1935) un nematode que puede causar meningoencefalitis eosinof√≠lica en humanos. Este molusco se comporta adem√°s como hospedador intermediario de otros Metastrongylidos como Angiostrongylus costaricensis (Morera y C√©spedes 1971) causante de la angiostrongiliasis abdominal, una enfermedad que se extiende desde el sur de Estados Unidos hasta el norte de Argentina (15), as√≠ como Angiostrongylus vasorum (Baillet, 1866) y Aelurostrongylus abstrusus (Railliet, 1898) de patolog√≠a incierta. Las especies de Angiostrongylus y Aelurostrongylus pertenecen a la Familia Metatastrongyloidea, la mayor√≠a de los cuales son par√°sitos pulmonares de mam√≠feros (hospedadores definitivos) y los gaster√≥podos son sus hospedadores intermediarios con muy pocas excepciones. Adem√°s de A. fulica otros g√©neros y especies de moluscos fueron reportadas como hospedadores intermediarios de A. cantonensis (e. g. Pomacea spp., Subulina octona, Pila spp. y Ampullarium canaliculatus).Trabajos presentados en el taller ‚ÄúMoluscos de inter√©s sanitario en la Argentina‚ÄĚ Instituto Nacional de Medicina Tropical (Misiones, 1 de agosto de 2012)Centro de Estudios Parasitol√≥gicos y de Vectore
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