903 resultados para meta-analytical study
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HINDI
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HINDI
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HINDI
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HINDI
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Hindi
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The present dissertation is devoted to the construction of exact and approximate analytical solutions of the problem of light propagation in highly nonlinear media. It is demonstrated that for many experimental conditions, the problem can be studied under the geometrical optics approximation with a sufficient accuracy. Based on the renormalization group symmetry analysis, exact analytical solutions of the eikonal equations with a higher order refractive index are constructed. A new analytical approach to the construction of approximate solutions is suggested. Based on it, approximate solutions for various boundary conditions, nonlinear refractive indices and dimensions are constructed. Exact analytical expressions for the nonlinear self-focusing positions are deduced. On the basis of the obtained solutions a general rule for the single filament intensity is derived; it is demonstrated that the scaling law (the functional dependence of the self-focusing position on the peak beam intensity) is defined by a form of the nonlinear refractive index but not the beam shape at the boundary. Comparisons of the obtained solutions with results of experiments and numerical simulations are discussed.
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The characteristics of service independence and flexibility of ATM networks make the control problems of such networks very critical. One of the main challenges in ATM networks is to design traffic control mechanisms that enable both economically efficient use of the network resources and desired quality of service to higher layer applications. Window flow control mechanisms of traditional packet switched networks are not well suited to real time services, at the speeds envisaged for the future networks. In this work, the utilisation of the Probability of Congestion (PC) as a bandwidth decision parameter is presented. The validity of PC utilisation is compared with QOS parameters in buffer-less environments when only the cell loss ratio (CLR) parameter is relevant. The convolution algorithm is a good solution for CAC in ATM networks with small buffers. If the source characteristics are known, the actual CLR can be very well estimated. Furthermore, this estimation is always conservative, allowing the retention of the network performance guarantees. Several experiments have been carried out and investigated to explain the deviation between the proposed method and the simulation. Time parameters for burst length and different buffer sizes have been considered. Experiments to confine the limits of the burst length with respect to the buffer size conclude that a minimum buffer size is necessary to achieve adequate cell contention. Note that propagation delay is a no dismiss limit for long distance and interactive communications, then small buffer must be used in order to minimise delay. Under previous premises, the convolution approach is the most accurate method used in bandwidth allocation. This method gives enough accuracy in both homogeneous and heterogeneous networks. But, the convolution approach has a considerable computation cost and a high number of accumulated calculations. To overcome this drawbacks, a new method of evaluation is analysed: the Enhanced Convolution Approach (ECA). In ECA, traffic is grouped in classes of identical parameters. By using the multinomial distribution function instead of the formula-based convolution, a partial state corresponding to each class of traffic is obtained. Finally, the global state probabilities are evaluated by multi-convolution of the partial results. This method avoids accumulated calculations and saves storage requirements, specially in complex scenarios. Sorting is the dominant factor for the formula-based convolution, whereas cost evaluation is the dominant factor for the enhanced convolution. A set of cut-off mechanisms are introduced to reduce the complexity of the ECA evaluation. The ECA also computes the CLR for each j-class of traffic (CLRj), an expression for the CLRj evaluation is also presented. We can conclude that by combining the ECA method with cut-off mechanisms, utilisation of ECA in real-time CAC environments as a single level scheme is always possible.
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This study addresses the extent to which insecure and disorganized attachments increase risk for externalizing problems using meta-analysis. From 69 samples (N = 5,947), the association between insecurity and externalizing problems was significant, d = 0.31 (95% CI: 0.23, 0.40). Larger effects were found for boys (d = 0.35), clinical samples (d = 0.49), and from observation-based outcome assessments (d = 0.58). Larger effects were found for attachment assessments other than the Strange Situation. Overall, disorganized children appeared at elevated risk (d = 0.34, 95% CI: 0.18, 0.50), with weaker effects for avoidance (d = 0.12, 95% CI: 0.03, 0.21) and resistance (d = 0.11, 95% CI: −0.04, 0.26). The results are discussed in terms of the potential significance of attachment for mental health.
Analytical study of the nonlinear behavior of a shape memory oscillator: Part II-resonance secondary
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Solubility and pH precipitation studies were carried out to obtain the binuclear complex {[TiO(C9H6NO)2][Sn(C9H6NO) 2]} involving 8-hydroxyquinoline as chelating agent. The compound, the individual mononuclear complexes and their physical mixture were evaluated by means of techniques such as TG, DTA, elemental analysis, X-ray diffraction, IR spectroscopy. The properties of the original compounds and also the thermoanalytical conditions exerted a great influence on the degree of crystallinity and on the crystalline phase of the mixed oxide obtained as final product of the thermal decomposition.
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This study at aims performing the stability analysis of the rotational motion to artificial satellites using quaternions to describe the satellite attitude (orientation on the space). In the system of rotational motion equations, which is composed by four kinematic equations of the quaternions and by the three Euler equations in terms of the rotational spin components. The influence of the gravity gradient and the direct solar radiation pressure torques have been considered. Equilibrium points were obtained through numerical simulations using the softwares Matlab and Octave, which are then analyzed by the Routh-Hurwitz Stability Criterion.
A meta-analysis of the feed intake and growth performance of broiler chickens challenged by bacteria
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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The significance of the works by Venezuelan-born composer Paul Desenne lies in his unique compositional style that incorporates elements of Latin American folk, pop, and traditional music within the framework of the Western European tradition. His works, though easily classified as art music, nevertheless gain much of their emotional and referential meaning through this rich borrowing. This document focuses on three of Desenne’s flute pieces: the Solo Flute Sonata (2001), Gurrufío for flute orchestra (1997), and Guasa Macabra for flute and clarinet (2003). It provides an analysis of the three works, examining formal, structural, motivic, and rhythmic aspects. Scores and interviews with the composer have been employed as primary sources. Bibliographical material closely related to his music and other secondary sources support this analytical approach. This document also provides an introduction and stylistic discussion of Desenne’s other pieces that incorporate the flute. Chapter one consists of an introduction to Desenne’s life and general considerations of his musical style. Each of the following three chapters focuses on one the three aforementioned flute works, including information about the composition and premiere of each piece as well as analysis and an examination of its incorporation of traditional folk elements. The final chapter presents an introduction to and stylistic discussion of the other flute pieces by this composer. This study intends to provide a basic understanding of Desenne’s flute music, including general characteristics of his musical style, paving the way for further investigation of Desenne’s music, and flute music in particular.
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Drying oils, and in particular linseed oil, were the most common binding media employed in painting between XVI and XIX centuries. Artists usually operated some pre-treatments on the oils to obtain binders with modified properties, such as different handling qualities or colour. Oil processing has a key role on the subsequent ageing of and degradation of linseed oil paints. In this thesis a multi-analytical approach was adopted to investigate the drying, polymerization and oxidative degradation of the linseed oil paints. In particular, thermogravimetry analysis (TGA), yielding information on the macromolecular scale, were compared with gas-chromatography mass-spectrometry (GC-MS) and direct exposure mass spectrometry (DEMS) providing information on the molecular scale. The study was performed on linseed oils and paint reconstructions prepared according to an accurate historical description of the painting techniques of the 19th century. TGA revealed that during ageing the molecular weight of the oils changes and that higher molecular weight fractions formed. TGA proved to be an excellent tool to compare the oils and paint reconstructions. This technique is able to highlight the different physical behaviour of oils that were processed using different methods and of paint layers on the basis of the different processed oil and /or the pigment used. GC/MS and DE-MS were used to characterise the soluble and non-polymeric fraction of the oils and paint reconstructions. GC/MS allowed us to calculate the ratios of palmitic to stearic acid (P/S), and azelaic to palmitic acid (A/P) and to evaluate effects produced by oil pre-treatments and the presence of different pigments. This helps to understand the role of the pre-treatments and of the pigments on the oxidative degradation undergone by siccative oils during ageing. DE-MS enabled the various molecular weight fractions of the samples to be simultaneously studied, and thus helped to highlight the presence of oxidation and hydrolysis reactions, and the formation of carboxylates that occur during ageing and with the changing of the oil pre-treatments and the pigments. The combination of thermal analysis with molecular techniques such as GC-MS, DEMS and FTIR enabled a model to be developed, for unravelling some crucial issues: 1) how oil pre-treatments produce binders with different physical-chemical qualities, and how this can influence the ageing of an oil paint film; 2) which is the role of the interaction between oil and pigments in the ageing and degradation process.