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136 results on '"Chen, Xuyu"'

1. An active-set based recursive approach for solving convex isotonic regression with generalized order restrictions

Author

Chen, Xuyu, Li, Xudong, and Su, Yangfeng

Subjects
Mathematics - Optimization and Control, Statistics - Computation
Abstract

This paper studies the convex isotonic regression with generalized order restrictions induced by a directed tree. The proposed model covers various intriguing optimization problems with shape or order restrictions, including the generalized nearly isotonic optimization and the total variation on a tree. Inspired by the success of the pool-adjacent-violator algorithm and its active-set interpretation, we propose an active-set based recursive approach for solving the underlying model. Unlike the brute-force approach that traverses an exponential number of possible active-set combinations, our algorithm has a polynomial time computational complexity under mild assumptions.

Published
2023

7. A dynamic programming approach for generalized nearly isotonic optimization

Author

Yu, Zhensheng, Chen, Xuyu, and Li, Xudong

Subjects
Mathematics - Optimization and Control, Statistics - Computation, 90C06, 90C25, 90C39
Abstract

Shape restricted statistical estimation problems have been extensively studied, with many important practical applications in signal processing, bioinformatics, and machine learning. In this paper, we propose and study a generalized nearly isotonic optimization (GNIO) model, which recovers, as special cases, many classic problems in shape constrained statistical regression, such as isotonic regression, nearly isotonic regression and unimodal regression problems. We develop an efficient and easy-to-implement dynamic programming algorithm for solving the proposed model whose recursion nature is carefully uncovered and exploited. For special $\ell_2$-GNIO problems, implementation details and the optimal ${\cal O}(n)$ running time analysis of our algorithm are discussed. Numerical experiments, including the comparisons among our approach, the powerful commercial solver Gurobi, and existing fast algorithms for solving $\ell_1$-GNIO and $\ell_2$-GNIO problems, on both simulated and real data sets, are presented to demonstrate the high efficiency and robustness of our proposed algorithm in solving large scale GNIO problems.

Published
2020

12. An Active-Set-Based Recursive Approach for Solving Convex Isotonic Regression with Generalized Order Restrictions.

Author

Chen, Xuyu, Li, Xudong, and Su, Yangfeng

Subjects
ISOTONIC regression, POLYNOMIAL time algorithms, TIME complexity, COMPUTATIONAL complexity, STRUCTURAL optimization
Abstract

This paper studies the convex isotonic regression with generalized order restrictions induced by a directed tree. The proposed model covers various intriguing optimization problems with shape or order restrictions, including the generalized nearly isotonic optimization and the total variation on a tree. Inspired by the success of the pool-adjacent-violator algorithm and its active-set interpretation, we propose an active-set-based recursive approach for solving the underlying model. Unlike the brute-force approach that traverses an exponential number of possible active-set combinations, our algorithm has a polynomial time computational complexity under mild assumptions. [ABSTRACT FROM AUTHOR]

Published
2024
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26. Risk for lung-related diseases associated with welding fumes in an occupational population: Evidence from a Cox model

Author

Li, Guangming, primary, Jiang, Jinfeng, additional, Liao, Yonggang, additional, Wan, Siyu, additional, Yao, Yong, additional, Luo, Yongbin, additional, Chen, Xuyu, additional, Qian, Huiling, additional, Dai, Xiayun, additional, Yin, Wenjun, additional, Min, Zhiteng, additional, Yi, Guilin, additional, and Tan, Xiaodong, additional

Published
2022
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32. Job satisfaction and associated factors among health care staff in township health centers——a cross-sectional survey in rural Central China.

Author

Chen, Xuyu, Yao, Hui, Ran, Li, and Tan, Xiaodong

Subjects
*WORK environment, *CROSS-sectional method, *COMMUNITY health services, *PEARSON correlation (Statistics), *JOB satisfaction, *DESCRIPTIVE statistics, *QUESTIONNAIRES, *CHI-squared test, *STATISTICAL sampling, *SOCIODEMOGRAPHIC factors, *LOGISTIC regression analysis
Abstract

Township health centers play a cornerstone role in the primary healthcare in China while it's development is largely limited by the brain drain. Job satisfaction is closely related to brain drain, investigating the relevant factors of job satisfaction can provide strategies to reduce brain drain. This research was conducted in Huangpi, China. Convenience sampling methods and self-administereded questionnaires were used. We collected 1370 valid samples, with an effective rate of 97.72%. Descriptive statistics are used to describe sociodemographic information. The Pearson Chi-square statistical was used to test the binary association between job satisfaction and another categorical variable. All the sociodemographic information was applied to the binary logistic regression model using the stepwise selection method. The mean age was 36.98 (SD = 9.84), factors that affect job satisfaction include educational background (x2 = 7.99, p< 0.05), marital status (x2 = 8.96, p< 0.05, monthly income (x2 = 51.43, p< 0.01), hire form (x2 = 7.64, p< 0.05), hours worked per week (x2 = 33.48, p< 0.01), parent had a stable job (x2 = 10.65, p< 0.01). Government and management should consider the impact of current policies on job satisfaction. Increasing the welfare of healthcare staff and promoting equity are potential strategies for improving low levels of job satisfaction. [ABSTRACT FROM AUTHOR]

Published
2022
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47. Agarwood Formation Induced by Fermentation Liquid of Lasiodiplodia theobromae, the Dominating Fungus in Wounded Wood of Aquilaria sinensis

Author

Yun Yang, Yang-Yang Liu, Chen Xuyu, Peiwei Liu, Jianhe Wei, Chun Sui, and Zheng Zhang

Subjects
0106 biological sciences, 0301 basic medicine, Aquilaria sinensis, Fungus, engineering.material, DNA, Ribosomal, 01 natural sciences, Applied Microbiology and Biotechnology, Microbiology, 03 medical and health sciences, Ascomycota, Botany, Aquilaria, biology, General Medicine, Dothideomycetes, Sordariomycetes, Agarwood, biology.organism_classification, Wood, 030104 developmental biology, Thymelaeaceae, Fermentation, engineering, Fusarium solani, 010606 plant biology & botany, Lasiodiplodia theobromae
Abstract

Agarwood is broadly used in incense and medicine. Traditionally, agarwood formation is induced by wounding the trunks and branches of some species of Aquilaria spp., including A. sinensis. As recently evidenced, some fungi or their fermentation liquid may have the potential of inducing agarwood formation. The present study aimed to analyze the fungi isolated from an agarwood-producing A. sinensis tree and subsequently identify the fungi capable of promoting agarwood formation. We identified a total of 110 fungi isolates based on their morphological characteristics and rDNA ITS sequences. These isolates came from four different layers (namely the decomposing layer, agarwood layer, transition layer, and normal layer) near the agarwood formation site of the trunk. According to the experimental results, most of them belonged to Dothideomycetes (81.82%), while the others to Sordariomycetes (13.64%) or Eurotiomycetes (4.55%). Of note, 88 isolates were shown belonging to the species of Lasiodiplodia theobromae that are most frequently isolated from different layers. In addition, when the fermentation liquid of two isolates of L. theobromae (AF4 and AF12) and one isolate of Fusarium solani (AF21) was inoculated into the A. sinensis wood using the Agar-Wit technique, promoted agarwood formation was observed; however, the effect of AF21 did not keep stable in the later test, while AF4 and AF12 still functioned 1 year later. This study may lay a foundation for exploring the underlying mechanism of agarwood formation as well as fungi application in agarwood production.

Published
2017

48. Health Summits in Global Health Governance

Author

Ma Mengdi, Chen Xuyu, Zhang Yanan, Tan Xiaodong, and Xie Qian

Subjects
musculoskeletal diseases, Gerontology, Rasch model, Corporate governance, Interpretation (philosophy), Global health, General Medicine, Psychology, humanities, Oswestry Disability Index
Abstract

Our purposes were to: (a) examine the psychometric properties of 10-item Oswestry Disability Index 2.0 (ODI) (0-100) questionnaire using the Rasch analysis, and (b) develop a functional staging approach to guide clinical interpretation of the patient’s improvement by interpreting ODI scores...

Published
2018

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