DETERMINATION OF WEIBULL PARAMETERS FOR WIND APPLICATIONS IN TWO DIFFERENT REGIONS

In this work, the main objective is to determine the shape (k) and scale (c) parameters of the Weibull probability density function through four numerical methods, known as graphical method (GM), empirical method of Justus (EMJ), empirical method of Lysen (EML), and moment method (MM) in two distinct cities, Gravatá-PE and Osório-RS, under the influence of two wind regimes. To do that, it will be used the hourly wind data obtained through NASA's Meteonorm database, from 2006 to 2015. Statistical analyzes also will be used to determine the best method used to determine these parameters

A BRIEF REVIEW ON THE ADVANTAGES, HINDRANCES AND ECONOMIC FEASIBILITY OF STIRLING ENGINES AS A DISTRIBUTED GENERATION SOURCE AND COGENERATION TECHNOLOGY

The present paper aims to provide a brief review of the potentiality and economic feasibility of the Stirling engine as a distributed generation source and cogeneration technology. Another objective was the determination of hindrances which may be preventing the feasibility of the Stirling technology. With these intentions, a research based on a combination of preselected keywords was performed at the Metasearch of CAPES (Brazil's Higher Education Coordination of Personnel Perfecting). No filters in relation to the research period or to particular geographical regions were employed, thus publications until 2017’s middle were included and the research was conducted on a global level. Next, the selection of papers which contained some of the keywords was made, consisting initially of the read of the publications’ abstracts. The remaining ones were then further explored and had their relevant information incorporated, according to the scope of this work. It is worth mentioning that other accredited sources which dealt with important aspects of the topic were also included. Furthermore, a table containing some examples of products concerning the application of the Stirling engine as a distributed generation and cogeneration technology is presented. Ultimately, it is concluded that the Stirling technology, despite its advantages and suitability regarding the proposed applications, is not yet commercially feasible, having currently only a minor presence in the market. This scenario can be attributed to the need for further research and technical development as well as cost reduction

NOX EMISSION ON RECIPROCAL FILTRATION COMBUSTION OF BIOGAS: A CASE STUDY

Filtration combustion is an effective technique for dealing with low-calorific value fuels, such as derivative fuels from biomass, and simultaneously reducing pollutant emissions. In this study, combustion of biogas (22% of CO2) was investigated theoretically and experimentally by utilizing a reciprocal flow porous burner with heat exchangers inserted in the porous medium. Combustion of lean biogas-air mixtures is stabilized in a naturally transient process, in which a lean equivalence ratio range (0.1 ≤ Φ ≤ 0.9) and gas flow velocities of 0.2 and 0.3 m/s were employed, periodically switching gas flow direction. Reciprocal flow combustion has been compared with unidirectional combustion, using technical methane as reference gas. In this context, predicted temperature profiles inside the burner, as well as experimental results, have shown that the reciprocating system plays an important role in the combustion process, significantly improving flammability limits, efficiency, and emissions. As result, trapezoidal temperature distribution profiles have been obtained with peaks between 1200 and 1600 K, reaching high efficiency up to 90% and ultra-low emission of nitrogen oxides (≤ 2ppm)

Optical limiting behavior of bismuth oxide-based glass in the visible range

The authors report experimental results on the optical limiting behavior of a bismuth oxide-based glass by exciting the samples with nanosecond laser pulses at 532 and 598 nm. The results show that two-photon and free-carrier absorption processes contribute for the nonlinear absorption. Values for β, the two-photon absorption coefficient, and σe, the absorption cross section due to free carriers, were determined. The values for β and σe are dependent on the amount of bismuth oxide in the glass composition

Selection of species tolerant to the herbicide sulfentrazone with potential for phytoremediation of contaminated soils.

ABSTRACT: This paper aimed to select species with potential for phytoremediation of soils contaminated with the herbicide sulfentrazone. Eight species were evaluated: Arachis pintoi, Eleusine coracana, Crotalaria spectabilis, Crotalaria ochroleuca, Cajanus cajan, Leucaena leucocephala, Stizolobium cinereum, and Raphanus sativus. The experiment was set-up inside a greenhouse, using pots with a capacity of 6dm3 filled with soil samples collected at a depth of 0-20cm. The experimental design was arranged into randomised blocks in a factorial scheme (8 × 5) with four replications, which consisted of the combination between the species and five doses of sulfentrazone (0, 200, 400, 800, and 1,600g ha-1). The herbicide phytotoxicity, plant heights, and dry masses of shoots and roots were evaluated. The species Cajanus cajan and Leucaena leucocephala had a higher tolerance to sulfentrazone up to a dose of 400g ha-1, showing minor symptoms of phytotoxicity and smaller decreases in plant heights and in dry matter accumulation, both in the shoots and roots, when compared to the control treatment, indicating, thus, the potential to be used for further studies on phytoremediation of sulfentrazone in soil. RESUMO: Seleção de espécies tolerantes ao herbicida sulfentrazone com potencial para a fitorremediação de solos contaminados. Este trabalho teve como objetivo selecionar espécies com potencial para a fitorremediação de solos contaminados com o herbicida sulfentrazone. Foram avaliadas oito espécies: Arachis pintoi, Eleusine coracana, Crotalaria spectabilis, Crotalaria ochroleuca, Cajanus cajan, Leucaena leucocephala, Stizolobium cinereum e Raphanus sativus. O experimento foi instalado em casa de vegetação, com a utilização de vasos com capacidade para 6 dm3 preenchidos com porções de solo coletadas na profundidade de 0-20 cm. O delineamento experimental foi o de blocos casualizados em esquema fatorial 8 × 5, com quatro repetições, composto pela combinação entre as espécies e cinco doses do sulfentrazone (0, 200, 400, 800 e 1.600 g ha-1). Foram avaliadas a fitotoxicidade do herbicida, a altura de plantas e a massa da matéria seca da parte aérea e de raízes. As espécies Cajanus cajan e Leucaena leucocephala apresentaram maior tolerância ao sulfentrazone até a dose de 400 g ha-1, mostrando menores sintomas de fitotoxicidade e menores reduções na altura de plantas e no acúmulo de matéria seca, tanto na parte aérea como nas raízes, em relação ao tratamento controle, indicando, com isso, potencial de utilização para posteriores estudos de fitorremediação de sulfentrazone em solo

The monoclinic phase of PZT ceramics: Raman and phenomenological theory studies

This work reports on the first Raman detection of the tetragonal to monoclinic phase transition in PZT ceramics near morphotropic phase boundary at low temperatures. The transition is characterized by changes in the frequency of lattice modes with the temperature. The results presented here confirm the previous one recently reported by Noheda et al. using high-resolution synchrotron X-ray powder diffraction technique and dielectric measurements. The stability of the new phase is discussed within the framework of phenomenological Landau-Devonshire Theory.Comment: 6 pages including 4 figures, Latex, submitted to Applied Physics Letter