161 resultados para quantization artifacts


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Pós-graduação em Ciências Biológicas (Zoologia) - IBB

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Pós-graduação em Design - FAAC

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Pós-graduação em Design - FAAC

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Sparse arrays have pitch larger than half-wavelength (lambda/2) and there is a reduced number of elements in comparison with a full-populated array. Consequently, there is a reduction in cost, data acquisition and processing. However, conventional beamforming techniques result in large side and grating lobes, and consequently in image artifacts. In this work the instantaneous phase of the signals is used in a beamforming technique instead of the instantaneous amplitudes to improve images obtained from sparse arrays configurations. A threshold based on a statistical analysis and the number of signals used for imaging is applied to each pixel, in order to determine if that pixel is related to a defect or not. Three sets of data are used to evaluate the technique, considering medical and non-destructive testing: a simulated point spread function, a medical phantom and an aluminum plate with 2 lambda-, 7 lambda- and lambda-pitch, respectively. The conventional amplitude image is superposed by the image improved by the instantaneous phase, increasing the reflectors detectability and reducing artifacts for all cases, as well as dead zone for the tested plate.

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

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Self-adaptive Software (SaS) presents specific characteristics compared to traditional ones, as it makes possible adaptations to be incorporated at runtime. These adaptations, when manually performed, normally become an onerous, error-prone activity. In this scenario, automated approaches have been proposed to support such adaptations; however, the development of SaS is not a trivial task. In parallel, reference architectures are reusable artifacts that aggregate the knowledge of architectures of software systems in specific domains. They have facilitated the development, standardization, and evolution of systems of those domains. In spite of their relevance, in the SaS domain, reference architectures that could support a more systematic development of SaS are not found yet. Considering this context, the main contribution of this paper is to present a reference architecture based on reflection for SaS, named RA4SaS (Reference Architecture for SaS). Its main purpose is to support the development of SaS that presents adaptations at runtime. To show the viability of this reference architecture, a case study is presented. As result, it has been observed that RA4SaS has presented good perspective to efficiently contribute to the area of SaS.

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

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The use of multimodal neuroimaging techniques has been helpful in the investigation of epileptogenic zone in patients with refractory epilepsies. This work aims to describe an ictal event during EEG-fMRI performed simultaneously in a 39-year-old man with refractory epilepsy. The EEG data were recorded at a sampling rate of 5 kHz, using a BrainAmp (BrainProducts, München, Germany) amplifier, with 64 MR (magnetic resonance) compatible Ag/AgCl electrodes. MR images were acquired using a 3T scanner in 3 sequences of 6 minutes of echo-planar images (EPIs), with TR = 2s, being the last sequence stopped after the ictal event. The EEG was corrected for gradient and pulse artifacts using the Brain Vision Analyzer2 software (BrainProducts), and the functional images were realigned, slice-timing corrected, normalized and smoothed. The start of the ictal changes was used for the evaluation of the BOLD response in MR images, using a t-test with a minimum cluster of 5 voxels, p <0.005 (T>2.5). The patient had a partial complex seizure, as noted by neurologist. The fMRI data showed positive BOLD responses (activation) in dysplastic areas, but showed the most significant activation outside the lesion, in areas compatible with secondary spread of the epileptic focus, probably caused by motor reaction also observed during the seizure. As a conclusion, we note that the technique of EEG-fMRI can detect the epileptogenic zone in patients with refractory epilepsy, but areas of dissemination of primary epileptogenic focus may show significant activation, introducing additional difficulties to the interpretation of the results

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In a world that is increasingly working with software, the need arises for effective approaches that encourage software reuse. The reuse practice must be aligned to a set of practices, procedures and methodologies that create a stable and high quality product. These questions produce new styles and approaches in the software engineering. In this way, this thesis aims to address concepts related to development and model-driven architecture. The model-driven approach provides significant aspects of the automated development, which helps it with produced models built in the specification phase. The definition of terms such as model, architecture and platform makes the focus becomes clearer, because for MDA and MDD is important to split between technical and business issues. Important processes are covered, so you can highlight the artifacts that are built into each stage of model-driven development. The stages of development: CSM, PIM, PSM and ISM, detailing the purpose of each phase in oriented models, making the end of each stage are gradually produced artifacts that may be specialized. The models are handled by different prospects for modeling, abstracting the concepts and building a set of details that portrays a specific scenario. This retraction can be a graphical or textual representation, however, in most cases is chosen a language modeling, for example, UML. In order to provide a practical view, this dissertation shows some tools that improve the construction of models and the code generate that assists in the development, keeping the documentation systemic. Finally, the paper presents a case study that refers to the theoretical aspects discussed throughout the dissertation, therefore it is expected that the architecture and the model-driven development may be able to explain important features to consider in software engineering