926 resultados para Three term recurrence relations
Resumo:
Compost, vermicompost and biochar amendments are thought to improve soil quality and plant yield. However, little is known about their long-term impact on crop yield and the environment in tropical agro-ecosystems. In this study we investigated the effect of organic amendments (buffalo manure, compost and verrnicompost) and biochar (applied alone or with vermicompost) on plant yield, soil fertility, soil erosion and water dynamics in a degraded Acrisol in Vietnam. Maize growth and yield, as well as weed growth, were examined for three years in terrestrial mesocosms under natural rainfall. Maize yield and growth showed high inter-annual variability depending on the organic amendment. Vermicompost improved maize growth and yield but its effect was rather small and was only significant when water availability was limited (year 2). This suggests that vermicompost could be a promising substrate for improving the resistance of agrosystems to water stress. When the vermicompost biochar mixture was applied, further growth and yield improvements were recorded in some cases. When applied alone, biochar had a positive influence on maize yield and growth, thus confirming its interest for improving long-term soil productivity. All organic amendments reduced water runoff, soil detachment and NH4+ and NO3- transfer to water. These effects were more significant with vermicompost than with buffalo manure and compost, highlighting that the beneficial influence of vermicompost is not limited to its influence on plant yield. In addition, this study showed for the first time that the combination of vermicompost and biochar may not only improve plant productivity but also reduce the negative impact of agriculture on water quality. (C) 2015 Elsevier B.V. All rights reserved.
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The central part of the Himalaya (Kumaun and Garhwal Provinces of India) is noted for its prolonged seismic quiescence, and therefore, developing a longer-term time series of past earthquakes to understand their recurrence pattern in this segment assumes importance. In addition to direct observations of offsets in stratigraphic exposures or other proxies like paleoliquefaction, deformation preserved within stalagmites (speleothems) in karst system can be analyzed to obtain continuous millennial scale time series of earthquakes. The Central Indian Himalaya hosts natural caves between major active thrusts forming potential storehouses for paleoseismological records. Here, we present results from the limestone caves in the Kumaun Himalaya and discuss the implications of growth perturbations identified in the stalagmites as possible earthquake recorders. This article focuses on three stalagmites from the Dharamjali Cave located in the eastern Kumaun Himalaya, although two other caves, one of them located in the foothills, were also examined for their suitability. The growth anomalies in stalagmites include abrupt tilting or rotation of growth axes, growth termination, and breakage followed by regrowth. The U-Th age data from three specimens allow us to constrain the intervals of growth anomalies, and these were dated at 4273 +/- 410 years BP (2673-1853 BC), 2782 +/- 79 years BP (851-693 BC), 2498 +/- 117 years BP (605-371 BC), 1503 +/- 245 years BP (262-752 AD), 1346 +/- 101 years BP (563-765 AD), and 687 +/- 147 years BP (1176-1470 AD). The dates may correspond to the timings of major/great earthquakes in the region and the youngest event (1176-1470 AD) shows chronological correspondence with either one of the great medieval earthquakes (1050-1250 and 1259-1433 AD) evident from trench excavations across the Himalayan Frontal Thrust.
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Based on the three-dimensional elastic inclusion model proposed by Dobrovolskii, we developed a rheological inclusion model to study earthquake preparation processes. By using the Corresponding Principle in the theory of rheologic mechanics, we derived the analytic expressions of viscoelastic displacement U(r, t) , V(r, t) and W(r, t), normal strains epsilon(xx) (r, t), epsilon(yy) (r, t) and epsilon(zz) (r, t) and the bulk strain theta (r, t) at an arbitrary point (x, y, z) in three directions of X axis, Y axis and Z axis produced by a three-dimensional inclusion in the semi-infinite rheologic medium defined by the standard linear rheologic model. Subsequent to the spatial-temporal variation of bulk strain being computed on the ground produced by such a spherical rheologic inclusion, interesting results are obtained, suggesting that the bulk strain produced by a hard inclusion change with time according to three stages (alpha, beta, gamma) with different characteristics, similar to that of geodetic deformation observations, but different with the results of a soft inclusion. These theoretical results can be used to explain the characteristics of spatial-temporal evolution, patterns, quadrant-distribution of earthquake precursors, the changeability, spontaneity and complexity of short-term and imminent-term precursors. It offers a theoretical base to build physical models for earthquake precursors and to predict the earthquakes.
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An embedded cell model is presented to obtain the effective elastic moduli and the elastic-plastic stress-strain relations of three-dimensional two-phase particulate composites. Each cell consists of an ellipsoidal inclusion surrounded by a finite ellipsoidal matrix that embedded in an infinite matrix. When both matrix and particle are elastic, the effective elastic moduli are derived which is an exact analytic formula without any simplified approximation that can be expressed in an explicit form. Further, the elastic-plastic stress-strain relations are obtained for spherical cells and oblate spheroid cells, in which the matrix is elastic and the particle is elastic-plastic. In addition, the macroscopic elastic-plastic constitutive relation of particle reinforced composites (PRC) is investigated by a systematic approach [1] in which the matrix is elastic-plastic and the particle is elastic.
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A fiber web is modeled as a three-dimensional random cylindrical fiber network. Nonlinear behavior of fluid flowing through the fiber network is numerically simulated by using the lattice Boltzmann (LB) method. A nonlinear relationship between the friction factor and the modified Reynolds number is clearly observed and analyzed by using the Fochheimer equation, which includes the quadratic term of velocity. We obtain a transition from linear to nonlinear region when the Reynolds numbers are sufficiently high, reflecting the inertial effect of the flows. The simulated permeability of such fiber network has relatively good agreement with the experimental results and finite element simulations.
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The authors report the growth of carbon nanowalls in freestanding, three-dimensional aggregates by microwave plasma-enhanced chemical vapor deposition. Carbon nanowalls extrude from plasma sites into three-dimensional space. The growth is catalyst-free and not limited by nucleating surfaces. The growth mechanism is discussed and compared with similar carbon nanomaterials. High surface area of as-grown carbon nanowalls indicates a potential for electrochemical applications. Field emission measurements show a low field turn-on and long-term stability. The results establish a scalable production method and possible applications using field emission or high surface area. © 2007 American Institute of Physics.
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Circadian clocks are 24-h timing devices that phase cellular responses; coordinate growth, physiology, and metabolism; and anticipate the day-night cycle. Here we report sensitivity of the Arabidopsis thaliana circadian oscillator to sucrose, providing evidence that plant metabolism can regulate circadian function. We found that the Arabidopsis circadian system is particularly sensitive to sucrose in the dark. These data suggest that there is a feedback between the molecular components that comprise the circadian oscillator and plant metabolism, with the circadian clock both regulating and being regulated by metabolism. We used also simulations within a three-loop mathematical model of the Arabidopsis circadian oscillator to identify components of the circadian clock sensitive to sucrose. The mathematical studies identified GIGANTEA (GI) as being associated with sucrose sensing. Experimental validation of this prediction demonstrated that GI is required for the full response of the circadian clock to sucrose. We demonstrate that GI acts as part of the sucrose-signaling network and propose this role permits metabolic input into circadian timing in Arabidopsis.
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Using US data for the period 1967:5-2002:4, this paper empirically investigates the performance of a Fed’s reaction function (FRF) that (i) allows for the presence of switching regimes, (ii) considers the long-short term spread in addition to the typical variables, (iii) uses an alternative monthly indicator of general economic activity suggested by Stock and Watson (1999), and (iv) considers interest rate smoothing. The estimation results show the existence of three switching regimes, two characterized by low volatility and the remaining regime by high volatility. Moreover, the scale of the responses of the Federal funds rate to movements in the rate of inflation and the economic activity index depends on the regime. The estimation results also show robust empirical evidence that the importance of the term spread in the FRF has increased over the sample period and the FRF has been more stable during the term of office of Chairman Greenspan than in the pre-Greenspan period.
Resumo:
Based on the three-dimensional elastic inclusion model proposed by Dobrovolskii, we developed a rheological inclusion model to study earthquake preparation processes. By using the Corresponding Principle in the theory of rheologic mechanics, we derived the analytic expressions of viscoelastic displacement U(r, t) , V(r, t) and W(r, t), normal strains epsilon(xx) (r, t), epsilon(yy) (r, t) and epsilon(zz) (r, t) and the bulk strain theta (r, t) at an arbitrary point (x, y, z) in three directions of X axis, Y axis and Z axis produced by a three-dimensional inclusion in the semi-infinite rheologic medium defined by the standard linear rheologic model. Subsequent to the spatial-temporal variation of bulk strain being computed on the ground produced by such a spherical rheologic inclusion, interesting results are obtained, suggesting that the bulk strain produced by a hard inclusion change with time according to three stages (alpha, beta, gamma) with different characteristics, similar to that of geodetic deformation observations, but different with the results of a soft inclusion. These theoretical results can be used to explain the characteristics of spatial-temporal evolution, patterns, quadrant-distribution of earthquake precursors, the changeability, spontaneity and complexity of short-term and imminent-term precursors. It offers a theoretical base to build physical models for earthquake precursors and to predict the earthquakes.
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The divergence of properties from one location to another within a soil mass is termed spatial variability, which traditionally includes three parameters the mean, the standard deviation, and the scale of fluctuation, in order to stochastically describe a soil property. Among them, determining the scale of fluctuation in the evaluation of spatial variability of soil profiles is not easy due to soil condition complexity. A simplified procedure is presented in the paper to determine the scale of fluctuation combined recurrence averaging and weighted linear regression. The alternative approach utilizes widely usable spreadsheet to solve the problem more directly and efficiently.
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The magnitude evolution of ettringite and gypsum in hydrated Portland cement mortars due to sulfate attack was detected by X-ray powder diffraction. The influences of sulfate concentration and water-to-cement ratio on the evolution of ettringite and gypsum were investigated. Experimental results show that the magnitude of ettringite formation in sodium sulfate solution follows a three-stage process, namely, the 'penetration period', 'enhance period of strength', and 'macro-crack period'. The cracking of concrete materials is mainly attributed to the effect of ettringite. The gypsum formations occurred in two stages, the 'latent period' and the 'accelerated period'. The gypsum formation including ettringite formation was relative to the linear expansion of mortars to some extend. Both water-to-cement ratio and sulfate concentration play important roles in the evolution of ettringite and gypsum. (C) 2008 Elsevier Ltd. All rights reserved.
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This thesis is divided into three chapters. In the first chapter we study the smooth sets with respect to a Borel equivalence realtion E on a Polish space X. The collection of smooth sets forms σ-ideal. We think of smooth sets as analogs of countable sets and we show that an analog of the perfect set theorem for Σ11 sets holds in the context of smooth sets. We also show that the collection of Σ11 smooth sets is ∏11 on the codes. The analogs of thin sets are called sparse sets. We prove that there is a largest ∏11 sparse set and we give a characterization of it. We show that in L there is a ∏11 sparse set which is not smooth. These results are analogs of the results known for the ideal of countable sets, but it remains open to determine if large cardinal axioms imply that ∏11 sparse sets are smooth. Some more specific results are proved for the case of a countable Borel equivalence relation. We also study I(E), the σ-ideal of closed E-smooth sets. Among other things we prove that E is smooth iff I(E) is Borel.
In chapter 2 we study σ-ideals of compact sets. We are interested in the relationship between some descriptive set theoretic properties like thinness, strong calibration and the covering property. We also study products of σ-ideals from the same point of view. In chapter 3 we show that if a σ-ideal I has the covering property (which is an abstract version of the perfect set theorem for Σ11 sets), then there is a largest ∏11 set in Iint (i.e., every closed subset of it is in I). For σ-ideals on 2ω we present a characterization of this set in a similar way as for C1, the largest thin ∏11 set. As a corollary we get that if there are only countable many reals in L, then the covering property holds for Σ12 sets.
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The amphipod Gammarus lacustris, a regular representative of lacustrine communities, often plays a significant role in the transformation of matter and energy. The object of the present work was to clarify the quantitative side of the feeding of the amphipod under different conditions of habitation. Experimental works on determination of the rate of consumption of food and its dependence on body-weight were carried out in the summer periods 1975-1978 on three water-bodies of the Krasnoyarsk region, of different conditions of habitation for the amphipods.
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As relações sino-americanas passaram a desempenhar um papel ordenador fundamental na condução dos assuntos internacionais neste século XXI, ao ponto de alguns analistas criarem o termo G-2. A crise financeira de 2008, por representar um golpe profundo nos países desenvolvidos e nos direcionamentos de valores do estágio atual de desenvolvimento do sistema, levou a relação China-Estados Unidos a um outro patamar. Ao passo que os norte-americanos tiveram de se preocupar em resolver as turbulências causadas na economia doméstica, o país asiático passou a desempenhar um papel crucial no processo de recuperação da economia global. O presente trabalho tem o objetivo, então, de analisar de que forma a crise de 2008, também chamada de crise do subprime, impactou os ordenamentos centrais do Sistema Internacional neste período de recuperação e como as relações sino-americanas podem ser usadas para uma melhor compreensão deste fenômeno. Na busca por traçar respostas mais sólidas, a pesquisa delineia-se em três frentes principais de análise: as relações diretas entre China e Estados Unidos; as relações dos dois países com um terceiro ator, a saber, a África; e os posicionamentos adotados por ambas as partes nas instituições multilaterais. Para tal, primeiro buscou-se aliar análises qualitativas e quantitativas, baseadas em instrumentais matemáticos e também na Ciência Política, História e Economia Política Internacional, para alcançar os resultados definidos nos objetivos da pesquisa. A dissertação é dividida em cinco capítulos, onde os três primeiros tratam de introduzir o assunto estudado e as principais vertentes teóricas utilizadas ao longo do trabalho. Os últimos envolvem a aplicação prática dos conceitos interdisciplinares escolhidos como aliados do trabalho empírico e a apresentação dos resultados finais. Em linhas gerais, concluiu-se que a crise acentuou os aspectos de interdependência entre China e Estados Unidos em todas as frentes estudadas. Avaliando as relações sino-americanas e os rumos do sistema internacional pós-crise em três facetas, concluímos também que tal exercício analítico ofereceu recursos mais palpáveis no fornecimento das respostas procuradas pela dissertação.
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A formação de sujeitos cooperativos é uma demanda da sociedade contemporânea, que o Colégio Pedro II assumiu como compromisso em seu Projeto Político-Pedagógico, ao afirmar o aluno que pretende formar: cidadãos críticos, orientados para a cooperação igualitária, ética, mais fraterna e solidária. O modo como se investe na formação do sujeito cooperativo, nas práticas cotidianas do Colégio Pedro II, é o objeto deste estudo. O objetivo é analisar a formação do cidadão cooperativo, como um processo de produção de subjetividades, que tem início nas lógicas que circulam em nossa sociedade. O objetivo específico é investigar o lugar que a formação do sujeito cooperativo ocupa nas práticas de docentes e gestores do Colégio Pedro II, e em que medida elas são direcionadas pelas políticas públicas, como os Parâmetros Curriculares Nacionais, e pelo Projeto Político Pedagógico, do Colégio. A pesquisa se concentrou no Pedrinho, na Unidade São Cristóvão I, no período posterior à elaboração e publicação do atual Projeto Político Pedagógico, embora não seja possível descartar a história do Colégio, na busca de elementos que expliquem a realidade atual. A construção do campo de investigação se deu a partir da análise de documentos do Colégio, dos registros de oficinas de Jogos Cooperativos, reuniões pedagógicas e administrativas, bem como entrevistas com docentes que representaram a Unidade São Cristóvão I, na Congregação do CP II. Ao final, foi possível perceber que são múltiplos os caminhos, entre o documento e o investimento na formação do sujeito cooperativo, entre outros motivos porque são muitos os sentidos dados ao termo cooperação. Alem disso, há pelo menos, dois movimentos. Um que busca a orientação da conduta, a governamentalidade, pela atualização dos mecanismos disciplinares e de controle, utilizados desde a fundação do Imperial Colégio de Pedro II. Outro movimento busca produzir uma linha de fuga, uma alternativa, no Pedrinho, às relações competitivas e individualistas produzidas pela lógica capitalista, em nossa sociedade, e estabelecidas há quase três séculos no Colégio Pedro II. As políticas públicas de currículo produziram práticas pedagógicas, discursivas e não discursivas, no cotidiano escolar, e algumas dessas práticas podem contribuir para a produção de subjetividades cooperativas, mesmo que este não seja o foco da ação docente. Mas, sem dúvida, alguns docentes e gestores estão investindo na formação de cidadãos cooperativos, seja pensando em alunos e trabalhadores virtuosos ou apenas em pessoas mais felizes. Ainda há espaço para a produção de singularidades, na microfísica do cotidiano.