948 research outputs found

    Deconvolution Estimation of a Mixture Distribution with Boundary Effects Motivated by Mutation Effect Distribution

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    Density estimation in measurement error models has been widely studied. However, most existing methods consider only continuous target variables, hence they cannot be applied directly to many real problems. Motivated by an evolutionary biology study, we consider more general cases: the target distribution is a mixture of a continuous component and finite numbers of pointmasses, which can cover most of practical problems. In this dissertation, we approach the estimation of the distribution in three different ways under the framework of measurement error models. Our first proposal is of the Fourier type, which is obtained by generalizing Liu and Taylor. The proposed estimator has a closed form, and gives continuous and smooth density estimators for the continuous mixture component. In addition, its convergence rate is comparably fast. However, when the target distribution has non-smooth boundaries, it suffers from a strong boundary effect. This motivates us to to propose two other methods of the sieve type; one is based on maximum likelihood (ML), and the other uses least squares (LS). By easily reflecting the known boundary information, they remarkably reduce the boundary problems, which is another major contribution of this dissertation. Moreover, the use of penalization improves the smoothness of the resulting estimator, especially the ML based estimator, and reduces the estimation variance. For each estimator, some asymptotic properties are explored by mathematical computation, and finite sample performances are illustrated via simulation studies. In addition, the proposed estimators are applied to the virus lineage data in Burch et al., which originally motivates this study. In this application, we not only estimate the mutation effect distribution, but also visually validate the classical exponential assumption on the mutation effect distribution, using density envelope plots

    A narrative study on community practice through ESD (Education for sustainable development): A case study of high school teacher community

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    The purpose of this study is to create \u27ESD Community of Practice\u27 through the \u27ESD training experience\u27 in school and to narrate the \u27experience\u27 and the \u27story\u27 of the teachers who are teaching ESD classes in school

    Deconvolution estimation of mixture distributions with boundaries

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    In this paper, motivated by an important problem in evolutionary biology, we develop two sieve type estimators for distributions that are mixtures of a finite number of discrete atoms and continuous distributions under the framework of measurement error models. While there is a large literature on deconvolution problems, only two articles have previously addressed the problem taken up in our article, and they use relatively standard Fourier deconvolution. As a result the estimators suggested in those two articles are degraded seriously by boundary effects and negativity. A major contribution of our article is correct handling of boundary effects; our method is asymptotically unbiased at the boundaries, and also is guaranteed to be nonnegative. We use roughness penalization to improve the smoothness of the resulting estimator and reduce the estimation variance. We illustrate the performance of the proposed estimators via our real driving application in evolutionary biology and two simulation studies. Furthermore, we establish asymptotic properties of the proposed estimators

    High performance Ge nanowire anode sheathed with carbon for lithium rechargeable batteries

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    We present a single crystalline Ge nanowire anode material sheathed with carbon prepared by a solid-liquid solution method. The composite electrode composed of Ge nanowires shows impressive electrochemical properties, exhibiting a very high reversible charge capacity (after lithium removal) of 963 mA h g(-1) with a coulombic efficiency of 91%.close11810

    Highly controllable transparent and conducting thin films using layer-by-layer assembly of oppositely charged reduced graphene oxides

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    A new approach for the fabrication of reduced graphene oxide (rGO) multilayers which can be used for transparent and conducting thin films was developed. This was achieved by using layer-by-layer (LbL) assembly of positively and negatively charged rGO sheets, which could provide highly controllable thin films in terms of thickness, transmittance, and sheet resistance. In particular, the thickness of the multilayer thin films of rGO was able to be controlled precisely in the subnanometre scale by similar to 0.46 nm via simply varying the number of stacking layers. Therefore, this method enabled an excellent control of the rGO multilayers over the optical and electrical properties, which are related to the thickness. Furthermore, we demonstrated the application of the rGO multilayers for an OLED device.close585
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