486 research outputs found

    Efeito de doses e modos de aplicação de uréia na produção de feijão

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    The effect of rate and method of urea application on the yield of common beans (Phaseolus vulgaris L., cv. IPA-1) was evaluated on a Red-Yellow Latosol (Psamentic Haplortox) of Arapiraca and on a Solodic Planosol (Ustalf) of Igaci, both sandy-clay-loams located in the State of Alagoas, Brazil. Rates of 30,60 and 90 kg N/ha were applied placing the urea totally in the furrow at planting time; totally sidedressed twenty days after planting, mixed or not with the soil; or 1/3 of the amount in the furrow at planting plus 2/3 sidedressed twenty days after planting, mixed or not with the soil. Bean yield responses to nitrogen followed quadratic equations. In the Red-Yellow Latosol response to nitrogen occurred up to the rate of 66 kg N/ha, while in the Solodic Planosol the yield increased up to the highest applied rate of 90 kg N/ha. The relative yield increase for each site was 22% and 16%, respectively. Sidedressed application of the total amount of urea resulted in the lowest yields, whereas split application and furrow fertilization were the best and equally effective methods. No significant yield increase was observed by mixing the urea with the soil.O efeito de doses e modos de aplicação de uréia na produção de feijão (Phaseolus vulgaris L., cv. IPA-1) foi avaliado em um latossolo vermelho-amarelo de Arapiraca (AL) e em um planossolo solódico de Igaci (AL), ambos franco-argilo-arenosos. Doses de 30, 60 e 90 kg/ha de N foram aplicadas totalmente no sulco de plantio, totalmente em cobertura aos vinte dias após o plantio com ou sem incorporação, e 1/3 no sulco de plantio mais 2/3 em cobertura com ou sem incorporação. A produção de feijão aumentou com a dose de nitrogênio segundo equações quadrátricas. No latossolo vermelho-amarelo, o feijão respondeu à aplicação de nitrogênio até a dose de 66 kg/ha de N, enquanto no planossolo solódico a produção aumentou até a dose maior de 90 kg/ha de N. Os aumentos respectivos de produção em cada local foram de 22% e 16%. A aplicação de uréia de uma só vez em cobertura conferiu as menores produções, enquanto o fracionamento da dose em duas aplicações, bem como a adição única no plantio, foram os melhores métodos e igualmente efetivos. Não houve aumento significativo da produção de feijão com a incorporação da uréia no solo

    Shot noise in the presence of spin-flip scattering

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    Deforming tachyon kinks and tachyon potentials

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    In this paper we investigate deformation of tachyon potentials and tachyon kink solutions. We consider the deformation of a DBI type action with gauge and tachyon fields living on D1-brane and D3-brane world-volume. We deform tachyon potentials to get other consistent tachyon potentials by using properly a deformation function depending on the gauge field components. Resolutions of singular tachyon kinks via deformation and applications of deformed tachyon potentials to scalar cosmology scenario are discussed.Comment: To appear in JHEP, 19 pages, 5 eps figures, minor changes and one reference adde

    Ferramentas Educacionais e Análise Intervencional da Aprendizagem Significativa: Es tudos de Casos Aplicados no Ensino da Física Acústica na Disciplina de Conforto Ambiental

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    It is of fundamental importance the mastery of Physics contents for the understanding of Acoustic Comfort. In this sense, it is up to the teacher to become aware of students' prior knowledge, to give a new meaning to the cognitive structures that make it possible to transform their difficulties into learning potential. In this work, educational teaching / learning interventions were developed and focused on the Theory of Meaningful Learning. These case studies were carried out with several students in different classes in the same program. In addition to the pre- and post-intervention questionnaire, Computational Educational Tools were used in order to assess the previous concepts and the effectiveness and efficiency of the provided pedagogical intervention. Satisfactory results were obtained with a reduction of about 250% in terms of alternative conceptions to the scientific knowledge previously detected in the participating volunteer students. The analysis was based on the approach of Ausubel and collaborators' Meaningful Learning theories, contextualized to the content of Acoustic Physics and applied in the classes of the Environmental Comfort course in the Civil Engineering and Civil Construction Technology programs from 2012 to 2018

    Numerical Model of Constrained Wave Energy Hyperbaric Converter under Full-Scale Sea Wave Conditions

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    Funding Information: This research was funded by Fundação para a Ciência e a Tecnologia (FCT.IP) through the grant UIDB/00667/2020 (UNIDEMI). This work was also supported by the project SURVIWEC PID2020-113245RB-I00 and by the project ED431C 2021/44 “Programa de Consolidación e Estructuración de Unidades de Investigación Competitivas”. This study forms part of the Marine Science programme (ThinkInAzul) supported by Ministerio de Ciencia e Innovación and Xunta de Galicia with funding from the European Union NextGenerationEU (PRTR-C17.I1) and European Maritime and Fisheries Fund. Funding Information: The authors acknowledge Fundação para a Ciência e a Tecnologia (FCT.IP) for its financial support through the grant UIDB/00667/2020 (UNIDEMI). This work was also supported by the project SURVIWEC PID2020-113245RB-I00 financed by MCIN/AEI/10.13039/501100011033 and by the project ED431C 2021/44 ”Programa de Consolidación e Estructuración de Unidades de Investigación Competitivas” financed by Xunta de Galicia, Consellería de Cultura, Educación e Universidade. This study forms part of the Marine Science programme (ThinkInAzul) supported by Ministerio de Ciencia e Innovación and Xunta de Galicia with funding from the European Union NextGenerationEU (PRTR-C17.I1) and European Maritime and Fisheries Fund. Publisher Copyright: © 2022 by the authors.A 2D numerical investigation of the power absorption of a constrained wave energy hyperbaric converter (WEHC) under full-scale sea wave conditions is presented. A fully non-linear numerical model DualSPHysics, based on the coupling of a smoothed particle hydrodynamics (SPH) fluid solver with a multibody dynamics solver, is used to model the interaction between wave and WEHC sub-systems. The numerical model was first validated against experimental data for a similar device, with a good accordance between PTO position and velocity. The model is then employed to study the hydrodynamics of a constrained WEHC considering several sea states, different hydraulic power take-off (PTO) damping and breakwater geometries. It is observed that the capture width ratio (CWR) is particularly sensitive to variations in the PTO damping, although the CWR absolute maximum is less sensitive considering mild variations applied to the PTO damping. Both wave height and wave period have an important effect on the CWR. The breakwater geometry is also essential for the performance of the WEHC, with a decrease in maximum CWR of about 15% for porous breakwater. These results are necessary to understand the full-scale behaviour of WEHC.publishersversionpublishe

    The role of lubricant feeding conditions on the performance improvement and friction reduction of journal bearings

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    Most conventional hydrodynamic journal bearing performance tools can not suitably assess the effect of lubricant feeding conditions on bearing performance, even though these conditions are known to affect important performance parameters such as eccentricity and powerloss. A thermohydrodynamic analysis suitable to deal with realistic feeding conditions has been proposed. Special attention was given to the treatment of phenomena taking place within grooves and their vicinity,as well as to the ruptured film region. The effec to flubricant feeding pressure and temperature, groove length ratio,width ratio and number (single/twin) on bearing performance has been analyzed for a broad range of conditions.It was found that a careful tuning of the feeding conditions may indeed improve bearing performance.FCT - POCTI/EME/39202/200

    A survey on Anthozoa and its habitats along the Northwest African coast and some islands: new records, descriptions of new taxa and biogeographical, ecological and taxonomical comments. Part I

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    Varias especies de Actiniarios y Escleractinias han sido recolectadas y estudiadas a lo largo de la costa noroeste africana y algunos de sus archipiélagos. Esta es la primera parte de un artículo más extenso que está centrado en Marruecos y Cabo Verde pero que también incluye información de otras zonas geográficas (Islas Canarias, Madeira, Gabón y Mauritania). La segunda parte incluirá bastante material del Golfo de Guinea. Cuatro nuevas especies y un nuevo género son descritos además de cinco nuevos registros de especies para la región estudiada. Bellactis caeruleus, Tubastrea caboverdiana, Thalamophyllia wirtzi y Africana wirtzi son las cuatro especies y el nuevo género descrito para la ciencia. Se han completado algunas descripciones de especies que de una forma y otra no estaban bien estudiadas.Several species of Actiniaria and Scleractinia have been searched and collected along the Western African coast and some of its archipelagos. This paper constitutes the first part of an extensive paper and it is focused on Morocco and Cape Verde, although some material and images from other spots (Canary Islands, Madeira, Gabon or even Mauritania) are included. The second part will also include some material from Gulf of Guinea. Four new species and a new genus are described, and five new records are also included in the paper. Bellactis caeruleus, Tubastrea caboverdiana, Thalamophyllia wirtzi and Africana wirtzi are the four new species and the new genus described. Some species, due to previous lack of good descriptions, are presented more deeply from the point of view of the descriptive aspect

    Sliding blocks with random friction and absorbing random walks

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    With the purpose of explaining recent experimental findings, we study the distribution A(λ)A(\lambda) of distances λ\lambda traversed by a block that slides on an inclined plane and stops due to friction. A simple model in which the friction coefficient μ\mu is a random function of position is considered. The problem of finding A(λ)A(\lambda) is equivalent to a First-Passage-Time problem for a one-dimensional random walk with nonzero drift, whose exact solution is well-known. From the exact solution of this problem we conclude that: a) for inclination angles θ\theta less than \theta_c=\tan(\av{\mu}) the average traversed distance \av{\lambda} is finite, and diverges when θθc\theta \to \theta_c^{-} as \av{\lambda} \sim (\theta_c-\theta)^{-1}; b) at the critical angle a power-law distribution of slidings is obtained: A(λ)λ3/2A(\lambda) \sim \lambda^{-3/2}. Our analytical results are confirmed by numerical simulation, and are in partial agreement with the reported experimental results. We discuss the possible reasons for the remaining discrepancies.Comment: 8 pages, 8 figures, submitted to Phys. Rev.
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