PARTICLE SIZE DISTRIBUTION CORRECTION METHOD USING A SIMULATED ANNEALING TECHNIQUE

The procedure for obtaining the particle size distribution by visual inspection of a sample involves stereological errors, given the cut of the sample. A cut particle, supposedly spherical, with radius R, will be counted as a circular particle with radius r, r≤R. The difference between r and R depends on how far from the center of the sphere the cut was performed. This introduces errors when the extrapolation of the properties from two to three dimensions during the analysis of a sample. The usual method is to correct the distribution by probabilistic functions, which have large errors. This paper presents a method to reduce the error inherent to this problem. The method is to compute a simulation of the preparation process in a sample whose structure can be described by non-penetrating spheres of various diameters which meet a known probability distribution function, for example, a log-logistic function, or even a constant function. For each distribution radius, a number of spheres is generated and virtually cut, generating a bi-dimensional (2D) distribution. The 2D curves of the spheres distribution obtained in this simulation are compared with that obtained by the experimental procedure and then the parameters of the threedimensional distribution function are adjusted until the 2D curves are similar to the experimental one using the optimization method Simulated Annealing for the curve-fitting. In future this method will be applied to the analysis of the oil reservoir rocks

Redesenho de agroecossistemas como inovação social para a construção da sustentabilidade local.

Resumo: A construção de uma nova perspectiva para o semiárido rural nordestino deverá estar amparada em abordagens com enfoque multidisciplinar, em que o contexto seja a referência e que promova o rompimento com o padrão convencional da modernização agrícola. Este estudo objetivou demonstrar aportes metodológicos de abordagem no meio rural, com a finalidade de construir elementos de resistência ao modelo tradicional por meio da mediação social para o redesenho de agroecossistemas. A metodologia foi orientada pela abordagem teórica da Perspectiva Orientada aos Atores. A pesquisa foi desenvolvida na comunidade Sítio Areias, Sobral, CE, local onde foi realizado o redesenho de um agroecossistema. A utilização da metodologia possibilitou a interface entre saberes, com o surgimento de novas práticas, com os agricultores familiares exercendo sua condição de agência na utilização de novos domínios para a produção de novidades referentes à construção de uma agricultura sustentável no semiárido. Tais inovações sociais poderão constituir elementos basilares para um novo processo de desenvolvimento rural sustentável e solidário, com novas formas de inovações no meio rural. Abstract: Building a new perspective to the rural northeastern semiarid should be supported by approaches with a multidisciplinary focus, that has the context as a reference and promotes rupture with the conventional pattern of agricultural modernization. This study aimed to demonstrate methodological contributions of approach in rural areas, with the aim of constructing elements of resistance to the traditional model through social mediation for the redesign of agroecosystems. The methodology was guided by the theoretical approach of the Oriented Perspective by Actors. The research was conducted in the community Sítio Areias, Sobral, CE, where was conducted the redesign of one agroecosystem. Using the methodology enabled the interface between knowledges, with the emergence of new practices, with family farmers exerting their agency conditions on the use of new domains for the novelty production relative the construction of sustainable agriculture in semiarid. These social innovations may constitute basic elements for a new process of sustainable rural development and solidarity, with new forms of innovation in rural areas

Supercurrent induced domain wall motion

We study the dynamics of a magnetic domain wall, inserted in, or juxtaposed to, a conventional superconductor, via the passage of a spin polarized current through a FSF junction. Solving the Landau-Lifshitz-Gilbert equation of motion for the magnetic moments we calculate the velocity of the domain wall and compare it with the case of a FNF junction. We find that in several regimes the domain wall velocity is larger when it is driven by a supercurrent.Comment: 10 pages, 8 figure

Intrapopulational chromosome number variation in Zephyranthes sylvatica Baker (Amaryllidaceae: Hippeastreae) from northeast Brazil.

Zephyranthes Herb. is a taxonomically complex and cytologically variable group, withabout 65 species of Neotropical distribution. Chromosome number variability in 32 individuals of a Zephyranthes sylvaticapopulation from Northeast Brazil was investigated. Three cytotypes were found: 2n = 12 (one metacentric, four submetacentricand one acrocentric pairs), in 24 individuals; 2n = 12 + 1B, in five and three individuals with 2n = 18, a triploid cytotype.All diploid individuals showed chromosomes with polymorphism in pair one and two, while in triploids this polymorphismwas observed in all chromosome triplets, generally with two homomorphic chromosomes and a higher or lower heteromorphicchromosome. All individuals had reticulated interfasic nucleus and a slightly asymmetric chromosome complement, withone metacentric chromosome pair and the others more submetacentric to acrocentric. These data confirm the cytologicalvariability previously registered for the genus. Mechanisms involved in karyotypic evolution in this population are discussed

Post-fire diversity and abundance in pine and eucalipt stands in Portugal: effects of biogeography, topography, forest type and post-fire management

This study concerned the mid-term regeneration of the woody understory vegetation of pure and mixed stands of Pinus pinaster Ait. and Eucalyptus globulus Labill. in northern and central Portugal following wildfires in 2005 and 2006. Pine and eucalypt stands are the most widespread and most fire-prone forest types in Portugal. The main aim was to investigate the importance of biogeography, topography, forest type and post-fire management operations in explaining the patterns in shrub diversity (species richness) and abundance (cover). To this end, 284 study sites in four distinct biogeographic regions were sampled 5 to 7 years following the last wildfire. At each site, the presence and cover of individual shrub species were estimated using 4 sub-plot of approximately 10 m2 each. The entire data set was analyzed by means of GLM using a total of seven explanatory variables: biogeographic region, forest type, three types post-fire management operations (soil tillage, tree harvesting, and shrub clearance), and two topographic variables (slope angle and elevation). The GLM analysis was also done for the individual biogeographic regions. Biogeographic region and slope steepness were key factors explaining shrub species richness, albeit the role of slope angle was possibly linked to the intensity of past land use. Biogeographic region equally played a significant role in explaining the cover of all shrubs together as well as of the shrubs of Leguminosae and Cistaceae. All three types of post-fire management operations appeared to hamper the recovery of resprouters and Leguminosae, whereas just tree harvesting and shrub clearance (but not soil tillage) negatively affected the cover of seeder species. These impacts of post-fire management operations had a noticeable region-specific component, being more relevant in the less productive biogeographic regions. Also the role of forest type depended strongly on biogeographic region. It was only significant in the South Mediterranean region, where pine plantations had a higher total shrub cover as well as higher covers of seeders and Cistaceae. Possibly, however, this significant role of forest type could be due to the lower incidence of shrub clearance in the pine standsinfo:eu-repo/semantics/publishedVersio

W/AlSiTiNx/SiAlTiOyNx/SiAlOx multilayered solar thermal selective absorber coating

Solar thermal energy has often been used as a renewable green energy source. Here we present a design composed of a highly selective solar thermal absorber coating that has been deposited by DC magnetron sputtering. This will consist of four layers: W/AlSiTiNx/SiAlTiOyNx/SiAlOx. The coating that was utilised revealed an excellent average solar thermal absorbance, (alpha = 95.5%) with very low emittance, (epsilon = 9.6% calculated for 500 degrees C) together with an excellent thermal stability after annealed at 500 degrees C, in air for 350 h, and at 630 degrees C in vacuum for 220 h.FCT in the framework of the Strategic Funding UID/FIS/04650/2013 and the financial support of FCT, POCI and PORL operational programs through the project POCI01-0145-FEDER-016907 (PTDC/CTM-ENE/2892/2014), co-financed by European community fund FEDER

Tailored graph ensembles as proxies or null models for real networks I: tools for quantifying structure

We study the tailoring of structured random graph ensembles to real networks, with the objective of generating precise and practical mathematical tools for quantifying and comparing network topologies macroscopically, beyond the level of degree statistics. Our family of ensembles can produce graphs with any prescribed degree distribution and any degree-degree correlation function, its control parameters can be calculated fully analytically, and as a result we can calculate (asymptotically) formulae for entropies and complexities, and for information-theoretic distances between networks, expressed directly and explicitly in terms of their measured degree distribution and degree correlations.Comment: 25 pages, 3 figure