TCC Física - Bachareladohttp://repositorio.ufsm.br/handle/1/11912024-03-29T02:18:36Z2024-03-29T02:18:36ZEstudo da variabilidade da aeroluminescência noturna na alta atmosfera terrestreMachado, Cristiano Sarzihttp://repositorio.ufsm.br/handle/1/27112020-07-21T11:02:44Z2008-12-18T00:00:00ZEstudo da variabilidade da aeroluminescência noturna na alta atmosfera terrestre
Machado, Cristiano Sarzi
This work intends to study the airglow emissions in the Earth's upper atmosphere, between 70 and 300 km of altitude. The study implies a physical understanding of the processes involving airglow phenomenology and its applications in Aeronomy. Furthermore, some basic topics about the instrumentation used is also presented. A study on the monthly variability of the OI 557.7 nm and OI 630 nm airglow emissions was performed. The emissions have been monitored since 2001 at Southern Space Observatory, in São Martinho da Serra, RS. A comparative analysis was performed considering the nightglow emission measured in three different observational sites: Cachoeira Paulista, SP (22.7° S, 45° W), São Martinho da Serra, RS (29° S, 53° W) and Sao Joao do Cariri, PB (7.4° S, 36.6° W).
Universidade Federal de Santa Maria
Trabalho de Conclusão de Curso de Graduação
2008-12-18T00:00:00ZEstabilidade na camada limite atmosférica e intermitência nas pequenas escalasMartins, Luís Gustavo Nogueirahttp://repositorio.ufsm.br/handle/1/27102017-06-13T23:03:18Z2008-12-18T00:00:00ZEstabilidade na camada limite atmosférica e intermitência nas pequenas escalas
Martins, Luís Gustavo Nogueira
Although the understanding of turbulence is essential in many areas of science and technology, yet very little is known about its structure and its phenomenology. Since the first statistical models of decades of forty and sixty of the last century, few were really important contributions made to help qualitatively and quantitatively describe this phenomenon. The great complexity of turbulence is attributed to a characteristic phenomenon called intermittency, which is considered a "signature"of the turbulence and is associated with the variance of the rate of dissipation of energy distribution in different scales. The statistical parameter associated with this phenomenon is called the intermittency exponent (μ). The intermittency on small scales has been the main object of searches in turbulence over the past 46 years, so much effort has been applied in determining the parameter μ. The direct determination of the intermittency exponent with the use of experimental data is made by calculating the correlation of turbulent energy kinetic dissipation field (h(2(x + r)2(x)i ∼ r −μ ). Another method less accurate but also very popular, used to estimate indirectly μ is through the sixth order structure function (hu((x + r) − u(r)) 6 i ∼ r 2−μ ). However, to ensure a convergence statistics, these methods require long time series of high frequency and high quality provided by the hot wire anemometer, which require frequent calibrations. This type of anemometer are used mainly in the wind tunnel, where the experimental conditions are well controlled. Due to great the Atmospheric Boundary Layer (ABL) variations throughout the day, sonic anemometer are widely used in field experiments because they require much less frequently calibrations. However, the low sampling rate (∼ 10 a 30Hz) of sonic anemometer, plus the experimental difficulties results in a coarse and low resolution data series. In general, for a reliable direct estimation μ are needed tens of millions of points, which would require, in experiments in the CLA, a stationary signal of approximately 11 days (virtually impossible to acurr). Due to these implications, ( BASU; FOUFOULA-GEORGIOU; LASHERMES; ARNÉODO , 2007) proposed an alternative method for estimating the intermittency exponent for short and low frequency series using the Magnitude Cumulant Analysis together with the Surrogate Analysis. This methodology has been applied to ABL turbulent time series, which allowed us to estimate with good precision the intermittency exponent for these data. The results obtained through of the Magnitude Cumulantes Analysis are as precise as the values of μ estimated directly with wind tunnel data and ABL more elaborate experiments. The great importance to obtaining this exponent (μ) is that through of their behavior analysis in the presence of different conditions of atmospheric stability, was able to verify that the inertial range is affected by the large scale events, in this case, by different forcing generators of turbulence, contrary to classical idea where the inertial range is not influenced by large eddies anisotropy.
Universidade Federal de Santa Maria
Trabalho de Conclusão de Curso de Graduação
2008-12-18T00:00:00ZPropriedades eletrônicas e estruturais de impureza substitucional de silício em nanotubos de BC2NRupp, Caroline Jaskulskihttp://repositorio.ufsm.br/handle/1/26662020-07-21T11:10:31Z2008-12-10T00:00:00ZPropriedades eletrônicas e estruturais de impureza substitucional de silício em nanotubos de BC2N
Rupp, Caroline Jaskulski
Spin polarized density functional theory (SP-DFT) is used to investigate the incorporation of substitutional Si atoms in the zigzag (5,0) and in the armchair (3,3) BC2N nanotubes (NTs). Our results show that the Si impurities in BC2N NTs have lower formation energy as compared with Si in carbon nanotubes (CNTs) and boron nitride nanotubes (BNNTs). For both nanotubes studied, the Si impurity in the boron site (SiB) show a spin splitting and introduce a empty (spin down) electronic level near to the bottom of the conduction band giving rise to a net spin magnetic moment of 1 μB . Silicon in the nitrogen site (SiN), depending on the tube chirality, introduce electronic levels near or resonant with the top of the valence band leaving the system to exhibit acceptor properties, suggesting the formation of defect induced type-p BC2N NTs. Whereas, for Si in the two non equivalent carbon atoms (SiCI and SiCII), the defective levels are resonant with the valence and conduction bands, respectively. The calculated formation energies for Si impurities in BC2N nanotubos show that the SiCII is the most like defect (lower formation energy). However, when we consider the growth process in the B-rich and N-rich conditions, SiB is the most likely and SiN is the most unlike (higher formation energy) defects.
Universidade Federal de Santa Maria
Trabalho de Conclusão de Curso de Graduação
2008-12-10T00:00:00ZConstruindo árvores filogenéticas com o uso de caminhadas aleatórias e geometria fractalOliveira, Luciana Renata dehttp://repositorio.ufsm.br/handle/1/26652020-07-21T11:20:50Z2008-11-28T00:00:00ZConstruindo árvores filogenéticas com o uso de caminhadas aleatórias e geometria fractal
Oliveira, Luciana Renata de
The purpose of this study is to propose an alternative method to build phylogenetic trees using the fractal dimension calculated from (pseudo) random walks on mitochondrial DNA and ribosomal RNA of some species of living beings. The walks are are performed attributing coordinates to each of the nitrogenous bases of DNA or RNA. The generated figures show complex morphologies and therefore we use parameters such as fractal dimension to characterize the different morphologies found. The obtained fractal dimensions of these figures are grouped to generate distance trees (dendograms) using the method of hierarchical clustering. We use the software Mathematica 6.0 to program the routines that build the random walks and calculates the values of fractal dimension and we also use the routine of the software that does the clustering and generates the dendograms. We have chosen ten eukaryotic species for the study: Anopheles gambiae (malaria mosquito), Arabidopsis thaliana (a plant), Danio rerio (zebra fish), Drosophila melanogaster (the fruit fly), Homo sapiens (human), Mus musculus (mouse), Pan troglodytes (chimpanzee), Rattus norvegicus (laboratory rat), Strongylocentrotus purpuratus (sea hedgehog), Xenopus laevis (a species of frog). We found that for these organisms our method can distinguish kingdoms, e.g. the plant from the animals. Among the animals, it distinguishes vertebrates from invertebrates. Among invertebrates, it distinguishes insects (fly and mosquito) from echinoderms (hedgehog). Among the vertebrates, it distinguishes the amphibian from mammals and fish. We conclude that the method generates results consistent with those predicted by the traditional phylogeny.
Universidade Federal de Santa Maria
Trabalho de Conclusão de Curso de Graduação
2008-11-28T00:00:00Z