2,873 research outputs found
On the space of generalized fluxes for loop quantum gravity
We show that the space of generalized fluxes - momentum space - for loop quantum gravity cannot be constructed by Fourier transforming the projective limit construction of the space of generalized connections - position space - due to the non-abelianess of the gauge group SU(2). From the abelianization of SU(2), U(1)^3, we learn that the space of generalized fluxes turns out to be an inductive limit, and we determine the consistency conditions the fluxes should satisfy under coarse-graining of the underlying graphs. We comment on the applications to loop quantum cosmology, in particular, how the characterization of the Bohr compactification of the real line as a projective limit opens the way for a similar analysis for LQC
Modeling extreme wave heights from laboratory experiments with the nonlinear Schrödinger equation
Spatial variation of nonlinear wave groups with different initial envelope
shapes is theoretically studied first, confirming that the simplest nonlinear
theoretical model is capable of describing the evolution of propagating wave
packets in deep water. Moreover, three groups of laboratory experiments run
in the wave basin of CEHIPAR (Canal de Experiencias Hidrodinámicas de El
Pardo, known also as El Pardo Model Basin) was founded in 1928 by the Spanish
Navy. are systematically compared with the numerical simulations of the
nonlinear Schrödinger equation. Although a little overestimation is
detected, especially in the set of experiments characterized by higher
initial wave steepness, the numerical simulation still displays a high degree
of agreement with the laboratory experiments. Therefore, the nonlinear
Schrödinger equation catches the essential characteristics of the extreme
waves and provides an important physical insight into their generation. The
modulation instability, resulting from the quasi-resonant four-wave
interaction in a unidirectional sea state, can be indicated by the
coefficient of kurtosis, which shows an appreciable correlation with the
extreme wave height and hence is used in the modified Edgeworth–Rayleigh
distribution. Finally, some statistical properties on the maximum wave
heights in different sea states have been related with the initial
Benjamin–Feir index
Modelling of the temporal and spatial evolutions of weakly nonlinear random directional waves with the modified nonlinear Schrödinger equations
Variações anuais na produção de frutos de castanha-da-amazônia no sul do Amapá.
A castanha-da-amazônia é uma espécie típica da região. Além da sua importância para o setor alimentício e de cosméticos, também é considerada alimento funcional e pode prevenir algumas enfermidades. Com isso, tem aumentado a demanda pela produção de castanha. Todavia, estudos sobre a variação anual na oferta de castanha ainda são incipientes. Assim, o objetivo do presente estudo foi avaliar a produção de frutos da castanheira, ao longo dos anos e em diferentes ambientes no sul do Amapá
Estudos CTS e construções em agroecologia: expansão de comunidade epistêmica ou processos transepistêmicos?
Apresenta e discute a obra Ciência, tecnologia e sociedade (CTS) para a construção da Agroecologia, publicada pela Editora da UnB em 2014, uma coletânea de 14 capítulos sequenciais que se destinam a um público abrangente, das ciências sociais aplicadas aos campos dos estudos sociais da ciência e da tecnologia e, sobretudo, a formuladores, operadores e avaliadores de políticas agrícolas, de C&T, inovação e desenvolvimento social.Obra resenhada: NEDER, R. T.; COSTA, F. M. P. (Org.). Ciência tecnologia sociedade (CTS) para a construção da agroecologia. Brasília, DF: Ed. da UnB, 2014 . 261 p. il. (Cadernos construção social da tecnologia, série 1, número 7, primeira versão, 4)
Estudo preliminar de fitoplâncton e análise comparativa de parâmetros físico-químicos do rio Falsino e igarapés adjacentes, FLONA-AP.
A genetic algorithm for resizing and sampling reduction of non-stationary soil chemical attributes optimizing spatial prediction
Aim of study: To evaluate the influence of the parameters of the geostatistical model and the initial sample configuration used in the optimization process; and to propose and evaluate the resizing of a sample configuration, reducing its sample size, for simulated data and for the study of the spatial variability of soil chemical attributes under a non-stationary with drift process from a commercial soybean cultivation area.Area of study: Cascavel, BrazilMaterial and methods: For both, the simulated data and the soil chemical attributes, the Genetic Algorithm was used for sample resizing, maximizing the overall accuracy measure.Main results: The results obtained from the simulated data showed that the practical range did not influence in a relevant way the optimization process. Moreover, the local variations, such as variance or sampling errors (nugget effect), had a direct relationship with the reduction of the sample size, mainly for the smaller nugget effect. For the soil chemical attributes, the Genetic Algorithm was efficient in resizing the sampling configuration, since it generated sampling configurations with 30 to 35 points, corresponding to 29.41% to 34.31% of the initial configuration, respectively. In addition, comparing the optimized and initial configurations, similarities were obtained regarding spatial dependence structure and characterization of spatial variability of soil chemical attributes in the study area.Research highlights: The optimization process showed that it is possible to reduce the sample size, allowing for lesser financial investments with data collection and laboratory analysis of soil samples in future experiments
Desenvolvimento e eficiência de um fungicita triazol a partir do líquido da casca da castanha (LCC) do cajueiro.
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