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16 results on '"Yang, Longshan"'

8. Nonlocal Band-Weighted Iterative Spectral Mixture Model for Hyperspectral Imagery Denoising

Author

Yang, Longshan, Xu, Linlin, Peng, Junhuan, Song, Yongze, Wong, Alexander, Clausi, David A, Yang, Longshan, Xu, Linlin, Peng, Junhuan, Song, Yongze, Wong, Alexander, and Clausi, David A

Abstract

Although efficient hyperspectral image (HSI) denoising relies on complete and accurate description and modeling the spatial-spectral signal in HSI, the current approaches do not fully account for key characteristics of HSI, i.e., the mixed spectra effect, the spatial nonstationarity effect, and noise variance heterogeneity effect. To address this issue, this article presents a linear spectral mixture model with nonlocal means constraint (LSMM-NLMC), with the following advantages. First, LSMM-NLMC can effectively learn the signal in mixed pixels in HSI by estimating clean endmembers and abundances for image restoration. Second, LSMM-NLMC can efficiently address nonstationary spatial correlation effect by imposing NLMC on the latent scene signal. Last, LSMM-NLMC provides accurate noise characterization by accounting for noise variance heterogeneity effect using a band-dependent noise model and a band-weighted Mahalanobis distance for similarity measurement. A novel optimization method based on the expectation-maximization (EM) algorithm and the purified means approach is used to efficiently solve the resulting maximum a posterior (MAP) problem. The experiments on both simulated and real HSI data sets demonstrate that the visual quality and denoising accuracy are significantly improved by the proposed LSMM-NLMC compared with previous methods.

Published
2020

16. Terminal trajectory of HbA 1c for 10 years supports the HbA 1c paradox: a longitudinal study using Health and Retirement Study data.

Author

Zhang Z, Yang L, and Cao H

Subjects
Humans, Female, Longitudinal Studies, Male, Aged, Middle Aged, Retirement, Mortality trends, Follow-Up Studies, Risk Factors, Glycated Hemoglobin analysis, Glycated Hemoglobin metabolism
Abstract

Objectives: We aimed to assess the potential time-varying associations between HbA 1c and mortality, as well as the terminal trajectory of HbA 1c in the elderly to reveal the underlying mechanisms., Design: The design is a longitudinal study using data from the Health and Retirement Study., Setting and Participants: Data were from the Health and Retirement Study. A total of 10,408 participants aged ≥50 years with available HbA 1c measurements at baseline (2006/2008) were included., Methods: Longitudinal HbA 1c measured at 2010/2012 and 2014/2016 were collected. HbA 1c values measured three times for their associations with all-cause mortality were assessed using Cox regression and restricted cubic splines. HbA 1c terminal trajectories over 10 years before death were analyzed using linear mixed-effect models with a backward time scale., Results: Women constitute 59.6% of the participants with a mean age of 69 years, with 3,070 decedents during the follow-up (8.9 years). The mortality rate during follow-up was 29.5%. Increased mortality risk became insignificant for the highest quartile of HbA 1c compared to the third quartile (aHR 1.148, 1.302, and 1.069 for a follow-up of 8.9, 6.5, and 3.2 years, respectively) with a shorter follow-up, while it became higher for the lowest quartile of HbA 1c (aHR 0.986, 1.068, and 1.439 for a follow-up of 8.9, 6.5, and 3.2 years, respectively). Accordingly, for both decedents with and without diabetes, an initial increase in HbA 1c was followed by an accelerating terminal decline starting 5-6 years before death., Conclusions and Implications: The time-varying association between HbA 1c and mortality mapped to the terminal trajectory in HbA 1c . High and low HbA 1c may have different clinical relationships with mortality. The HbA 1c paradox may be partially explained by reverse causation, namely, early manifestation of death., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Zhang, Yang and Cao.)

Published
2024
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