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Full-Text Articles in Physical Sciences and Mathematics
Variational Approximations For Density Deconvolution, Yue Chang
Variational Approximations For Density Deconvolution, Yue Chang
Doctoral Dissertations
This thesis considers the problem of density estimation when the variables of interest are subject to measurement error. The measurement error is assumed to be additive and homoscedastic. We specify the density of interest by a Dirichlet Process Mixture Model and establish variational approximation approaches to the density deconvolution problem. Gaussian and Laplacian error distributions are considered, which are representatives of supersmooth and ordinary smooth distributions, respectively. We develop two variational approximation algorithms for Gaussian error deconvolution and one variational approximation algorithm for Laplacian error deconvolution. Their performances are compared to deconvoluting kernels and Monte Carlo Markov Chain method by …
Physical Activity Classification With Conditional Random Fields, Evan L. Ray
Physical Activity Classification With Conditional Random Fields, Evan L. Ray
Doctoral Dissertations
In this thesis we develop methods for classifying physical activity using accelerometer recordings. We cast this as a problem of classification in time series with moderate to high dimensional observations at each time point. Specifically, we observe a vector of summary statistics of the accelerometer signal at each point in time, and we wish to use these observations to estimate the type and intensity of physical activity the individual engaged in as it changes over time. Our methods are based on Conditional Random Fields, which allow us to capture temporal dependence in an individual’s physical activity type without requiring us …