795 resultados para non-parametric estimation


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Objectivo: Verificar os efeitos da prática da Dança Criativa (DC) em mulheres idosas, no peso (P), altura (A), índice de massa corporal (IMC), perímetro abdominal (PA), força, resistência e flexibilidade dos membros superiores e inferiores (F, R, FL-MS/MI), mobilidade física (MF) [agilidade (AG), velocidade (V), equilíbrio dinâmico (ED)], resistência aeróbia (RA) e satisfação com a vida (SV). Método: A amostra foi de 57 mulheres, entre os 65 e os 80 anos, tendo sido distribuídas aleatoriamente pelo grupo de controlo (GC) (n=25) e pelo grupo experimental (GE) (n=32). Este último frequentou aulas de DC durante 6 meses, 3 vezes por semana, com a duração de 50'. A análise estatística foi efectuada através do SPSS 17, b:mdo sido utilizadas técnicas não paramétricas. As variáveis funcionais foram avaliadas através da bateria funcional Fitness Test (Rikli & Jones, 1999) - Idosos e a SV através da Satisfaction with Live Scale (SWLS), (Diener, Larsen and Gri1fin, 1985). Resultados: Os resultados demonstraram diferenças significativas, para melhor, em todas as variáveis, excepto no P, no PA e na FLMS, entre o início e os 3 meses e entre o início E os 6 meses. No P e no PA foram observadas diferenças entre os 3 e os 15 meses. Na FRMS ambos os grupos apresentaram diferenças significativas, para melhor, e na FLMS só o GC apresentou diferenças significativas para pior. Não havia diferenças significativas entre o GE e o GC no início do estudo, excepto na RA. Conclusões: A DC promove melhorias no P; A; IMC; PA; F, R, FL-MI; MF; RA e SV em mulheres idosas. ABSTRACT: Objective: To test and verify the effects of the practice of Creative Dance in the weight, height, body mass, abdominal perimeter, strength, resistance and flexibility of the lower and upper limbs, as well as physical mobility (agility, velocity, dynamic balance), aerobic resistance and life satisfaction in elderly women. Method: 57 females constituted the sample analyzed within the ages of 65 and 80 years old randomly divided between the control group (25) and the experimental group (32). The experimental group attended 50 minutes’ classes prepared and orientated to the target core of this study during six months. The statistical analysis was processed with SPSS 17 software under non-parametric techniques. The functional battery Fitness Test (Rikli & Jones, 1999) was used to evaluate the functional variables and life satisfaction was accessed trough the Satisfaction with Live Scale (SWLS), (Diener, Larsen and Griffin, 1985). Results: The results defined positive significant differences in all variables evaluated, except weigh, abdominal perimeter and flexibility of the upper limbs between the beginning and the 3-month and the beginning and the 6- month. Differences were observed in weight and abdominal perimeter between the 3 and 6 months. 8oth groups showed considerable positive differences in the strength and resistance of the upper limbs and only the control group showed negative differences in flexibility of the upper limbs. At the beginning of the study there were no significant differences between the two groups, except in the aerobic resistance. Conclusions: Creative Dance promotes the improvement of weight, height, body mass index, abdominal perimeter, strength, resistance, flexibility of both upper and lower limbs in elderly women.

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Background: Knowing one’s own seropositivity status of HIV/AIDS is important. Seropositivity can be determined by a rapid HIV/AIDS test. Attitudes towards a rapid test of HIV/AIDS show a predisposition to perform the analysis. Objective: This study investigated, the attitudes of students and staff in a Portuguese university toward rapid HIV/AIDS test. Methods: In a convenience sample, the data was collected on campus in three consecutive years. A selfadministered structured questionnaire was used for data collection. A validated scale for Portuguese students was applied. A sample of 947 (86.3%) students and 150 (13.7%) teaching and non-teaching staff participated. The average age was 24.30 years-old (SD=8.64). Non-parametric tests were applied. Results: Attitudes of professors and non-teaching staff are more favorable in relation to the rapid test of HIV/AIDS, compared to students. Attitudes are also more favorable in the first year in which the study was conducted with both employees and students. The male students express more traditional attitudes. Students of nursing polo have expressed more favorable attitudes to the rapid test of HIV/AIDS. Conclusion: The attitudes towards rapid test of HIV/AIDS are generally favorable. It is necessary to conduct further research considering professors and other university staff. Improving favorable attitudes toward rapid HIV/AIDS test must be a positive fact for health.

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Business angels provide both financing and managerial experience, which increase the likelihood of the survival of innovative start-ups. Over the last years, European countries with developing informal venture capital markets have seen governments support the creation of business angels networks (BANs) to increase and consolidate these markets. Using the Portuguese context to carry out the empirical work, this paper provides an assessment of value added provided by angels’ networks. A total of 88 useable responses were received and analysed using non-parametric statistical techniques. This paper demonstrates that is evidence of positive contribution of BANs in terms of bringing together investors and linking them with entrepreneur’s seeking finance. BANs played an important role in financing innovative start-ups also in peripheral regions. Results lead us to conclude that government support BANs would appear to be an effective mechanism to stimulate the angel market in developing informal venture capital markets. The conclusions of this paper are likely to have relevance for countries where there is growing interest in the potential of business angels as a means of financing innovative start-ups.

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Recently, attempts to improve decision making in species management have focussed on uncertainties associated with modelling temporal fluctuations in populations. Reducing model uncertainty is challenging; while larger samples improve estimation of species trajectories and reduce statistical errors, they typically amplify variability in observed trajectories. In particular, traditional modelling approaches aimed at estimating population trajectories usually do not account well for nonlinearities and uncertainties associated with multi-scale observations characteristic of large spatio-temporal surveys. We present a Bayesian semi-parametric hierarchical model for simultaneously quantifying uncertainties associated with model structure and parameters, and scale-specific variability over time. We estimate uncertainty across a four-tiered spatial hierarchy of coral cover from the Great Barrier Reef. Coral variability is well described; however, our results show that, in the absence of additional model specifications, conclusions regarding coral trajectories become highly uncertain when considering multiple reefs, suggesting that management should focus more at the scale of individual reefs. The approach presented facilitates the description and estimation of population trajectories and associated uncertainties when variability cannot be attributed to specific causes and origins. We argue that our model can unlock value contained in large-scale datasets, provide guidance for understanding sources of uncertainty, and support better informed decision making

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We discuss the estimation of the expected value of the quality-adjusted survival, based on multistate models. We generalize an earlier work, considering the sojourn times in health states are not identically distributed, for a given vector of covariates. Approaches based on semiparametric and parametric (exponential and Weibull distributions) methodologies are considered. A simulation study is conducted to evaluate the performance of the proposed estimator and the jackknife resampling method is used to estimate the variance of such estimator. An application to a real data set is also included.

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The position of a stationary target can be determined using triangulation in combination with time of arrival measurements at several sensors. In urban environments, none-line-of-sight (NLOS) propagation leads to biased time estimation and thus to inaccurate position estimates. Here, a semi-parametric approach is proposed to mitigate the effects of NLOS propagation. The degree of contamination by NLOS components in the observations, which result in asymmetric noise statistics, is determined and incorporated into the estimator. The proposed method is adequate for environments where the NLOS error plays a dominant role and outperforms previous approaches that assume a symmetric noise statistic.

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This paper investigates the use of time-frequency techniques to assist in the estimation of power system modes which are resolvable by a Digital Fourier Transform (DFT). The limitations of linear estimation techniques in the presence of large disturbances which excite system non-linearities, particularly the swing equation non-linearity are shown. Where a nonlinearity manifests itself as time varying modal frequencies the Wigner-Ville Distribution (WVD) is used to describe the variation in modal frequencies and construct a window over which standard linear estimation techniques can be used. The error obtained even in the presence of multiple resolvable modes is better than 2%.

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This article describes a Matlab toolbox for parametric identification of fluid-memory models associated with the radiation forces ships and offshore structures. Radiation forces are a key component of force-to-motion models used in simulators, motion control designs, and also for initial performance evaluation of wave-energy converters. The software described provides tools for preparing non-parmatric data and for identification with automatic model-order detection. The identification problem is considered in the frequency domain.

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The exchange of physical forces in both cell-cell and cell-matrix interactions play a significant role in a variety of physiological and pathological processes, such as cell migration, cancer metastasis, inflammation and wound healing. Therefore, great interest exists in accurately quantifying the forces that cells exert on their substrate during migration. Traction Force Microscopy (TFM) is the most widely used method for measuring cell traction forces. Several mathematical techniques have been developed to estimate forces from TFM experiments. However, certain simplifications are commonly assumed, such as linear elasticity of the materials and/or free geometries, which in some cases may lead to inaccurate results. Here, cellular forces are numerically estimated by solving a minimization problem that combines multiple non-linear FEM solutions. Our simulations, free from constraints on the geometrical and the mechanical conditions, show that forces are predicted with higher accuracy than when using the standard approaches.

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The issue of dynamic spectrum scene analysis in any cognitive radio network becomes extremely complex when low probability of intercept, spread spectrum systems are present in environment. The detection and estimation become more complex if frequency hopping spread spectrum is adaptive in nature. In this paper, we propose two phase approach for detection and estimation of frequency hoping signals. Polyphase filter bank has been proposed as the architecture of choice for detection phase to efficiently detect the presence of frequency hopping signal. Based on the modeling of frequency hopping signal it can be shown that parametric methods of line spectral analysis are well suited for estimation of frequency hopping signals if the issues of order estimation and time localization are resolved. An algorithm using line spectra parameter estimation and wavelet based transient detection has been proposed which resolves above issues in computationally efficient manner suitable for implementation in cognitive radio. The simulations show promising results proving that adaptive frequency hopping signals can be detected and demodulated in a non cooperative context, even at a very low signal to noise ratio in real time.

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Non-Gaussianity of signals/noise often results in significant performance degradation for systems, which are designed using the Gaussian assumption. So non-Gaussian signals/noise require a different modelling and processing approach. In this paper, we discuss a new Bayesian estimation technique for non-Gaussian signals corrupted by colored non Gaussian noise. The method is based on using zero mean finite Gaussian Mixture Models (GMMs) for signal and noise. The estimation is done using an adaptive non-causal nonlinear filtering technique. The method involves deriving an estimator in terms of the GMM parameters, which are in turn estimated using the EM algorithm. The proposed filter is of finite length and offers computational feasibility. The simulations show that the proposed method gives a significant improvement compared to the linear filter for a wide variety of noise conditions, including impulsive noise. We also claim that the estimation of signal using the correlation with past and future samples leads to reduced mean squared error as compared to signal estimation based on past samples only.

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In this paper, we propose a training-based channel estimation scheme for large non-orthogonal space-time block coded (STBC) MIMO systems.The proposed scheme employs a block transmission strategy where an N-t x N-t pilot matrix is sent (for training purposes) followed by several N-t x N-t square data STBC matrices, where Nt is the number of transmit antennas. At the receiver, we iterate between channel estimation (using an MMSE estimator) and detection (using a low-complexity likelihood ascent search (LAS) detector) till convergence or for a fixed number of iterations. Our simulation results show that excellent bit error rate and nearness-to-capacity performance are achieved by the proposed scheme at low complexities. The fact that we could show such good results for large STBCs (e.g., 16 x 16 STBC from cyclic division algebras) operating at spectral efficiencies in excess of 20 bps/Hz (even after accounting for the overheads meant for pilot-based channel estimation and turbo coding) establishes the effectiveness of the proposed scheme.