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2,243 results on '"Liu, YaJun"'

3. Sequential Change-point Detection for Compositional Time Series with Exogenous Variables

Author

Liu, Yajun and Andrews, Beth

Subjects
Statistics - Methodology, Mathematics - Statistics Theory
Abstract

Sequential change-point detection for time series enables us to sequentially check the hypothesis that the model still holds as more and more data are observed. It is widely used in data monitoring in practice. In this work, we consider sequential change-point detection for compositional time series, time series in which the observations are proportions. For fitting compositional time series, we propose a generalized Beta AR(1) model, which can incorporate exogenous variables upon which the time series observations are dependent. We show the compositional time series are strictly stationary and geometrically ergodic and consider maximum likelihood estimation for model parameters. We show the partial MLEs are consistent and asymptotically normal and propose a parametric sequential change-point detection method for the compositional time series model. The change-point detection method is illustrated using a time series of Covid-19 positivity rates.

Published
2024

4. Sequential Change-point Detection for Binomial Time Series with Exogenous Variables

Author

Liu, Yajun and Andrews, Beth

Subjects
Statistics - Methodology
Abstract

Sequential change-point detection for time series enables us to sequentially check the hypothesis that the model still holds as more and more data are observed. It's widely used in data monitoring in practice. Meanwhile, binomial time series, which depicts independent binary individual behaviors within a group when the individual behaviors are dependent on past observations of the whole group, is an important type of model in practice but hasn't been developed well. We first propose a Binomial AR($1$) model, and then consider a method for sequential change-point detection for the Binomial AR(1).

Published
2024

20. CT Images-Based Automatic Path Planning for Pedicle Screw Placement Incorporating Anatomical and Biomechanical Considerations

Author

Yang, Xintong, Wang, Yunning, Liu, Yajun, Ji, Xuquan, Guo, Anyi, Hu, Yan, Liu, Wenyong, Magjarević, Ratko, Series Editor, Ładyżyński, Piotr, Associate Editor, Ibrahim, Fatimah, Associate Editor, Lackovic, Igor, Associate Editor, Rock, Emilio Sacristan, Associate Editor, Wang, Guangzhi, editor, Yao, Dezhong, editor, Gu, Zhongze, editor, Peng, Yi, editor, Tong, Shanbao, editor, and Liu, Chengyu, editor

Published
2024
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39. Foam concrete for lightweight construction applications: A comprehensive review of the research development and material characteristics

Author

Liu Yajun, Zhao Zhilong, Amin Muhammad Nasir, Ahmed Bilal, Khan Kaffayatullah, Arifeen Siyab Ul, and Althoey Fadi

Subjects
foam concrete, mechanical and functional properties, lightweight material, Technology, Chemical technology, TP1-1185
Abstract

Foam concrete or foamcrete is a lightweight, porous material with a wide range of applications in the construction domain. This article focused on reviewing porosity, thermal conductivity, acoustic properties, compressive strength (f c′), elastic modulus (E), flexural strength (f y), stability, resistance to hostile environments, density, and fire resistance of foam concrete. A systematic literature analysis was conducted to identify relevant research trends on foam concrete. The challenges and limitations of foam concrete research were highlighted, including the lack of standardized testing methods and the need for more research on the long-term durability and structural performance of foam concrete. The analysis of the literature data revealed that there had been a growing interest in foamcrete research over the past decade. Foam concrete may be utilized in several construction applications due to its adaptability and wide range of uses. Its potential uses can be increased by developing new manufacturing methods and the inclusion of certain admixtures. The present research has the potential to be advantageous for scholars interested in collaborative advancement and the exchange of novel tactics and concepts, owing to the visual and statistical representation of the regions/countries and researchers that have contributed.

Published
2024
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