138 resultados para analysis of main components


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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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This work considers a problem of interest in several technological applications such as the thermal control of electronic equipment. It is also important to study the heat transfer performance of these components under off-normal conditions, such as during failure of cooling fans. The effect of natural convection on the flow and heat transfer in a cavity with two flush mounted heat sources on the left vertical wall, simulating electronic components, is studied numerically and experimentally. The influence of the power distribution, spacing between the heat sources and cavity aspect ratio have been investigated. An analysis of the average Nusselt number of the two heat sources was performed to investigate the behavior of the heat transfer coefficients. The results obtained numerically and experimentally, after an error analysis, showed a good agreement.

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A synaptonemal complex (SC) study of specimens of Nellore and Gyr breeds of Bos taurus indicus was performed with the main objective to identify and determinate the frequency of abnormalities of SC and the frequency of cells with abnormalities. All animals analyzed had 29 autosomal bivalents and one sexual bivalent. The Nellore breed had 30.00% of cells with SC abnormalities while the Gyr breed had only 11.11%. Statistical analyses showed that there were not significant differences for the number of cells with abnormalities among the breeds studied. The subspecies Bos taurus indicus had 16.92% of cells showing abnormalities, being 62.82% of these abnormalities in zygotene and 37.18% in pachytene. Some aspects regarding the frequency of cells with abnormalities and the fertility of Nellore and Gyr breeds are discussed.

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The model of development and evolution of complex morphological structures conceived by Atchley and Hall in 1991 (Biol. Rev. 66:101-157), which establishes that changes at the macroscopic, morphogenetic level can be statistically detected as variation in skeletal units at distinct scales, was applied in combination with the formalism of geometric morphometrics to study variation in mandible shape among populations of the rodent species Thrichomys apereoides. The thin-plate spline technique produced geometric descriptors of shape derived from anatomical landmarks in the mandible, which we used with graphical and inferential approaches to partition the contribution of global and localized components to the observed differentiation in mandible shape. A major pattern of morphological differentiation in T. apereoides is attributable to localized components of shape at smaller geometric scales associated with specific morphogenetic units of the mandible. On the other hand, a clinal trend of variation is associated primarily with localized components of shape at larger geometric scales. Morphogenetic mechanisms assumed to be operating to produce the observed differentiation in the specific units of the mandible include mesenchymal condensation differentiation, muscle hypertrophy, and tooth growth. Perspectives for the application of models of morphological evolution and geometric morphometrics to morphologically based systematic biology are considered.

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This paper analyzes the thermal storage characteristics of aluminum plates in furnaces during their heating for lamination under two sources of heat: an electrical resistance bank and a combustion process carried out with natural gas. The set of equations to model the furnace under operation with electrical energy, for air as the fluid, is presented. This supports the theoretical analysis for the system under operation with natural gas combustion products. A numerical procedure, using the software ANSYS, is applied to determine the convection heat transfer coefficients for heating by the air flow. Temperatures measured in a plate inside a real furnace are used as parameters to determine these coefficients. Then convection and radiation heat transfer coefficients are determined for the natural gas combustion products. Results are compared, indicating a possible gain of 5.5 h in relation to a 19.5 h period of conventional electrical heating per plate.

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This work presents an investigation into the use of the finite element method and artificial neural networks in the identification of defects in industrial plants metallic tubes, due to the aggressive actions of the fluids contained by them, and/or atmospheric agents. The methodology used in this study consists of simulating a very large number of defects in a metallic tube, using the finite element method. Both variations in width and height of the defects are considered. Then, the obtained results are used to generate a set of vectors for the training of a perceptron multilayer artificial neural network. Finally, the obtained neural network is used to classify a group of new defects, simulated by the finite element method, but that do not belong to the original dataset. The reached results demonstrate the efficiency of the proposed approach, and encourage future works on this subject.

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Chemical analyses of complete larvae of the first to third instar and cuticle, fat body and salivary glands extracts of fourth instar larvae using gas chromatography and gas chromatography-mass spectrometry, were performed upon Pachycondyla villosa. The results revealed that P. villosa larvae do not produce a pheromone, as only fatty acids and n-alkanes were detected. After quantifying the identified compounds, it was determined that the fat body is the main place of storage and/or production of the cuticular hydrocarbons. It was also observed that the absolute quantity of cuticular hydrocarbons increases progressively during larval development. Inferences about the transport behavior of matured larvae to the pupation place and the colony odor are discussed.

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Rain acidity may be ascribed to emissions from power station stacks, as well as emissions from other industry, biomass burning, maritime influences, agricultural influences, etc. Rain quality data are available for 30 sites in the South African interior, some from as early as 1985 for up to 14 rainfall seasons, while others only have relatively short records. The article examines trends over time in the raw and volume weighted concentrations of the parameters measured, separately for each of the sites for which sufficient data are available. The main thrust, however, is to examine the inter-relationship structure between the concentrations within each rain event (unweighted data), separately for each site, and to examine whether these inter-relationships have changed over time. The rain events at individual sites can be characterized by approximately eight combinations of rainfall parameters (or rain composition signatures), and these are common to all sites. Some sites will have more events from one signature than another, but there appear to be no signatures unique to a single site. Analysis via factor and cluster analysis, with a correspondence analysis of the results, also aid interpretation of the patterns. This spatio-temporal analysis, performed by pooling all rain event data, irrespective of site or time period, results in nine combinations of rainfall parameters being sufficient to characterize the rain events. The sites and rainfall seasons show patterns in these combinations of parameters, with some combinations appearing more frequently during certain rainfall seasons. In particular, the presence of the combination of low acetate and formate with high magnesium appears to be increasing in the later rainfall seasons, as does this combination together with calcium, sodium, chloride, potassium and fluoride. As expected, sites close together exhibit similar signatures. Copyright © 2002 John Wiley & Sons, Ltd.

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The subfamily Tetragonopterinae is composed by a large number of species distributed in South and Central America. This subfamily has many taxonomic and phylogenetic problems, being considered by several authors as an artificial group. With the objective to better understanding the relationships among the components of this fish group, cytogenetic studies were conduced on five species of Tetragonopterinae. Astyanax janeiroensis had 2n=50 chromosomes (6M+14SM+14ST+16A), Hyphessobrycon reticulatus had 2n=50 chromosomes (14M+20SM+16ST), Hollandichthys multifasciatus had 2n=50 chromosomes (10M+12SM+28ST), Ctenobrycon hauxwellianus had 2n=50 chromosomes (10M+6SM+34ST), and Phenacogaster cf. pectinatus had 2n=46 chromosomes (12M+2ST+32A). Only A. janeiroensis had multiple NORs, while all other species had simple NORs. Small heterochromatic blocks were observed in the chromosomes of all species in a pericentromeric position. A. janeiroensis also had some chromosomes with large heterochromatic blocks in a terminal position and a pair with an interstitial block. The karyotypic evolution of each genus is discussed.

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This work aims at a better comprehension of the features of the solution surface of a dynamical system presenting a numerical procedure based on transient trajectories. For a given set of initial conditions an analysis is made, similar to that of a return map, looking for the new configuration of this set in the first Poincaré sections. The mentioned set of I.C. will result in a curve that can be fitted by a polynomial, i.e. an analytical expression that will be called initial function in the undamped case and transient function in the damped situation. Thus, it is possible to identify using analytical methods the main stable regions of the phase portrait without a long computational time, making easier a global comprehension of the nonlinear dynamics and the corresponding stability analysis of its solutions. This strategy allows foreseeing the dynamic behavior of the system close to the region of fundamental resonance, providing a better visualization of the structure of its phase portrait. The application chosen to present this methodology is a mechanical pendulum driven through a crankshaft that moves horizontally its suspension point.

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The Ag-NOR staining technique and image analysis were used to evaluate morphological parameters (area, perimeter and axis ratio) in nucleoli from normal thyroids and from thyroids bearing proliferating lesions (carcinomas, adenomas and hyperplasias). Regions with normal appearance located close to adenomatous and carcinomatous regions, in the thyroid of every patient, were also analyzed for comparison with the respective pathological regions and with normal thyroids. Statistical analysis of data for the nucleolar area and perimeter allowed the separation of adenomas and carcinomas from hyperplasias and normal tissue but not the two components in each of these two groups. However, if we look at the numbers, a sequence of increasing nucleolar mean areas in the order: normal, hyperplasia, adenoma and carcinoma may be observed, indicating the sequence of increasing rRNA requirements in these different kinds of cells. The axis ratio that denotes the nucleolar shape (round or oblong) did not show significant differences among tissues, suggesting that shape is not important in the characterization of these pathologies. Differences in nucleolar areas and perimeter between normal and affected regions from each patient were statistically significant for adenomas and carcinomas. When these normal regions were compared with the normal thyroids, significant differences were not obtained in the three evaluated parameters. The observations and their importance for histopathological diagnosis are discussed.

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A quantitative phase analysis was made of LixCoO2 powders obtained by two distinct chemical methodologies at different temperatures (from 400 to 700°C). A phase analysis was made using Rietveld refinements based on X-ray diffraction data, considering the Li xCoO2 powders as a multiphase system that simultaneously contained two main phases with distinct, layered and spinel-type structures. The results showed the coexistence of both structures in LixCoO 2 obtained at low temperature (400 and 500°C), although only the layered structure was detected at higher temperatures (600 and 700°C), regardless of the chemical powder process employed. The electrochemical performance, evaluated mainly by the cycling reversibility of Li xCoO2 in the form of cathode insertion electrodes, revealed that there is a close correlation between structural features and the electrochemical response, with one of the redox processes (3.3 v/3.9 v) associated only with the presence of the spinel-type structure. © 2003 Elsevier B.V. All rights reserved.

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Different cytogenetic techniques were used to analyze the chromosomes of Characidium gomesi with the main objective of comparing the base composition of ZZ/ZW sex-chromosomes, B-chromosomes and the heterochromatin of A-chromosomes. The results of digestion of chromosomes with AluI restriction endonuclease (RE), silver and CMA3 staining, C-banding and fluorescence in situ hybridization (FISH) with the 18S rDNA probe suggested the existence of compositional differences between the heterochromatin of ZZ/ZW sex-chromosomes, A- and B-chromosomes, and indicated the presence of different numbers and morphology of B-chromosomes in the samples of this population.

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Diplopods belonging to the subclass Helminthomorpha may present one or both leg pairs of the seventh diplosegment modified into structures that aid copulation, called gonopods. These structures are used as a taxonomic trait for the description of most species. In the genus Rhinocricus these structures are closely similar, so that it is difficult to distinguish species only on the basis of this trait. Two species, R. padbergi and R. varians, are found in the same habitat and present gonopods practically identical in shape; together they present a broad colour gradient, ranging from dark brown to light beige. Morphometric data for individuals of the experimental group were submitted to ANOVA and MANOVA, using Hotelling-Lawley Trace and generalized Mahalanobis distances (D 2) tests. The results demonstrated a relationship between size and colour, with darker individuals being larger. On the basis of this preliminary analysis, we may suggest that the two species are distinct since dark individuals are distant from medium- and light-coloured individuals according to the D 2 values. This seems to indicate a possible polymorphism of individuals belonging to R. padbergi which present close proximity in the values obtained. In all analyses, we observed that the main variables were diameter, length and telson size.