1,277 research outputs found

    Epistemic and Conceptual Orphanhood in the Sustainability of Agroecosystems

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    The main problem in the analysis of sustainability of agroecosystems is precisely the lack of definition of both concepts. Above all agroecology has used the concept of agroecosystem in a nominal, ahistorical and atheoretical way; when it is possible to observe it as a system and at the frontier of complex systems. Thus, agroecology does not use, for example, the Thermodynamics of non-equilibrium, Theory of Catastrophes, Complex Networks, Theory of Chaos, among others. It is time to prompt agroecology agroecosystems out of the darkness of closed systems and bring them to the frontier of science systems. The objective of this document is precisely to make the field of agroecological studies expand towards the use of the theory of autopoietic social systems

    Modified geometry of spur gear drives for compensation of shaft deflections

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    One of the main problems when standard spur gears are in mesh is the appearance of edge contact on the gear tooth surfaces caused by misalignments. Those misalignments are caused partially by deflections of gear supporting shafts. As a result of an edge contact, a non-favorable condition of the bearing contact occurs, yielding high level of contact stresses. An intensive research and many practical solutions have been directed to modify the gear tooth surfaces in order to avoid edge contact. An innovative procedure is proposed here for: (1) determination of errors of alignment caused by shaft deflections, (2) compensation of predicted shaft deflections during generation of spur gears, and (3), obtaining a favorable function of transmission errors for the design load. A finite element model of a spur gear drive that comprises pinion and gear supporting shafts is used for the determination of errors of alignment along a cycle of meshing. Compensation of misalignments caused by shaft deflections in gear generation is then accomplished by modification of pinion tooth surfaces whereas the gear tooth surfaces are kept unmodified. Additional modifications of pinion tooth surfaces may be required for obtaining a favorable function of transmission errors. The effect of several misalignment compensations in the reduction of contact stresses has been investigated. Postprocessing of load intensity functions and loaded transmission errors is included. The developed approach is illustrated with numerical examples.The authors express their deep gratitude to the Spanish Ministry of Economy and Competitiveness (MINECO) for the financial support of research projects Refs. DPI2010-20388-C02-01 (financed jointly by FEDER), DPI2013- 47702-C2-1, and DPI2013-47702-C2-2

    The ancestral selection graph for a Λ\Lambda-asymmetric Moran model

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    Motivated by the question of the impact of selective advantage in populations with skewed reproduction mechanims, we study a Moran model with selection. We assume that there are two types of individuals, where the reproductive success of one type is larger than the other. The higher reproductive success may stem from either more frequent reproduction, or from larger numbers of offspring, and is encoded in a measure Λ\Lambda for each of the two types. Our approach consists of constructing a Λ\Lambda-asymmetric Moran model in which individuals of the two populations compete, rather than considering a Moran model for each population. Under certain conditions, that we call the ``partial order of adaptation'', we can couple these measures. This allows us to construct the central object of this paper, the Λ\Lambda-asymmetric ancestral selection graph, leading to a pathwise duality of the forward in time Λ\Lambda-asymmetric Moran model with its ancestral process. Interestingly, the construction also provides a connection to the theory of optimal transport. We apply the ancestral selection graph in order to obtain scaling limits of the forward and backward processes, and note that the frequency process converges to the solution of an SDE with discontinous paths. Finally, we derive a Griffiths representation for the generator of the SDE and use it to find a semi-explicit formula for the probability of fixation of the less beneficial of the two types

    Fenómenos meteorológicos y su semántica en el trópico mexicano

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    La comunicación de los fenómenos meteorológicos en los medios de comunicación masiva expresa principalmente una semántica distinta a la usada por los agricultores del trópico subhúmedo mexicano. En este sentido, el objetivo de este estudio fue comprender cómo los productores agropecuarios del trópico subhúmedo mexicano conceptúan ciertos fenómenos meteorológAutor icos, así como, las ideas que tienen sobre su duración, intensidad e impactos. El estudio se realizó en Paso de Ovejas, Veracruz; el diseño metodológico involucró una encuesta, entrevistas a profundidad y una revisión documental. La información fue analizada con técnicas estadísticas descriptivas y análisis de contenido. Los resultados indican que la conceptuación de nortes, suradas, vendavales, secas, temporales y lloviznas, así como, las ideas sobre su duración, intensidad e impactos derivan de una construcción semántica particular en el nivel local cuyo conocimiento debe ser utilizado como referencia en las estrategias de comunicación encaminadas a la adaptación de la actividad agropecuaria ante el cambio climático

    Fenómenos meteorológicos y su semántica en el trópico mexicano

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    The communication of meteorological phenomena in the mass media mainly expresses a semantics different from that used by farmers in the Mexican sub-humid tropics. In this sense, the objective of this study was to understand how the agricultural producers of the Mexican sub-humid tropics conceptualize certain meteorological phenomena, as well as the ideas they have about their duration, intensity and impacts. The study was carried out in Paso de Ovejas, Veracruz; The methodological design involved a survey, in-depth interviews, and a desk review. The information was analyzed with statistical descriptive techniques and content analysis. The results indicate that the conception of north, south, wind, dry, temporal and drizzle, as well as the ideas about their duration, intensity and impacts derive from a particular semantic construction at the local level whose knowledge should be used as reference in the Communication strategies aimed at adapting agricultural activity to climate change.La comunicación de los fenómenos meteorológicos en los medios de comunicación masiva expresa principalmente una semántica distinta a la usada por los agricultores del trópico subhúmedo mexicano. En este sentido, el objetivo de este estudio fue comprender cómo los productores agropecuarios del trópico subhúmedo mexicano conceptúan ciertos fenómenos meteorológAutor icos, así como, las ideas que tienen sobre su duración, intensidad e impactos. El estudio se realizó en Paso de Ovejas, Veracruz; el diseño metodológico involucró una encuesta, entrevistas a profundidad y una revisión documental. La información fue analizada con técnicas estadísticas descriptivas y análisis de contenido. Los resultados indican que la conceptuación de nortes, suradas, vendavales, secas, temporales y lloviznas, así como, las ideas sobre su duración, intensidad e impactos derivan de una construcción semántica particular en el nivel local cuyo conocimiento debe ser utilizado como referencia en las estrategias de comunicación encaminadas a la adaptación de la actividad agropecuaria ante el cambio climático

    Melhoria da Atenção Às Pessoas com Hipertensão Arterial Sistêmica e Diabetes Mellitus na ESF Vitorino Nhoatto, Fontoura Xavier/RS

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    A Hipertensão Arterial Sistêmica é uma das doenças mais frequentes e silenciosas que afeta a nossa população e constitui um fator de risco principal, para doenças cardiovasculares, cerebrovasculares e Insuficiências Renais Crônicas e agudas. Por ser assintomático, às vezes seu diagnóstico e tratamento são frequentemente negligenciados, tanto pelo usuário como pelo profissional da saúde. A Diabetes Mellitus, também esta considerada como uma epidemia mundial e aqui no Brasil existe mais de seis milhões de pessoas que sofrem desta doença que junto a hipertensão, são responsáveis por um alto índice de mortalidade e hospitalizações. As ações de saúde encaminhadas a melhorar e modificar o estilo de vida da população é uma das terapêuticas mais importantes para diminuir a morbimortalidade destas doenças. Em nossa área de abrangência, este é uns dos principais problemas que atinge a nossa população, constatado durante a análise situacional, realizada na UBS. Como objetivo deste Projeto de Intervenção, traçamos melhorar a atenção de saúde dos usuários com hipertensão e diabetes da área de abrangência da unidade Vitorino Nhoatto, em Fontoura Xavier, no Rio Grande do Sul. As ações implementadas, foram desenvolvidas em um período de 12 semanas, abrangendo quatro eixos norteadores: Monitoramento e Avaliação; Organização e Gestão do Serviço; Engajamento Público e Qualificação da Prática Clínica. Nossa UBS atende uma população de 1682 pessoas, sendo que a estimativa da Planilha de Coleta de Dados, para os maiores de 20 anos, é de 1126 usuários, 256 com hipertensão e 63 com diabetes. Após intervenção se verificou que na área de abrangência temos um total de 262 usuários com hipertensão e 65 usuários com diabetes. Para capacitação da equipe e organização do serviço, foram utilizados os protocolos dos cadernos de atenção básica do Ministério da Saúde. Os registros e o monitoramento da intervenção foram realizados na ficha espelho e planilha de coleta de dados disponibilizada pelo curso. Dentro dos resultados obtidos, está o cadastrado e acompanhamento de 100% dos usuários, todos receberam atendimento clínico, realizaram exames laboratoriais, aderiram ao programa da farmácia popular, atendimento odontológico, busca ativa dos faltosos a consultas, através da visita domiciliar. Orientação sobre tabagismo, alimentação saudável, prática de exercícios físicos e saúde bucal por meio das palestras, as atividades de grupo e orientações individuais. Foram muitos os ganhos para a comunidade, a equipe e o serviço, obtidos com a intervenção. Entre eles, a organização no processo de trabalho da equipe, a integração dos membros da equipe com a comunidade e a qualidade nos atendimentos voltados aos usuários com hipertensão e/ou diabetes, intensificando as ações de prevenção e promoção da saúde na comunidade

    Predicting Wrist Joint Angles from the Kinematics of the Arm: Application to the Control of Upper Limb Prostheses

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    Automation of wrist rotations in upper limb prostheses allows simplification of the human–machine interface, reducing the user’s mental load and avoiding compensatory movements. This study explored the possibility of predicting wrist rotations in pick-and-place tasks based on kinematic information from the other arm joints. To do this, the position and orientation of the hand, forearm, arm, and back were recorded from five subjects during transport of a cylindrical and a spherical object between four different locations on a vertical shelf. The rotation angles in the arm joints were obtained from the records and used to train feed-forward neural networks (FFNNs) and time-delay neural networks (TDNNs) in order to predict wrist rotations (flexion/extension, abduction/adduction, and pronation/supination) based on the angles at the elbow and shoulder. Correlation coefficients between actual and predicted angles of 0.88 for the FFNN and 0.94 for the TDNN were obtained. These correlations improved when object information was added to the network or when it was trained separately for each object (0.94 for the FFNN, 0.96 for the TDNN). Similarly, it improved when the network was trained specifically for each subject. These results suggest that it would be feasible to reduce compensatory movements in prosthetic hands for specific tasks by using motorized wrists and automating their rotation based on kinematic information obtained with sensors appropriately positioned in the prosthesis and the subject’s body.This publication is part of the R&D project PID2020-118021RB-I00 funded by MICIN/AEI/ 10.13039/501100011033
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