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791 results on '"Zhang, Chunhua"'

6. Developing an assessment tool for the healthy lifestyles of the occupational population in China: a modified Delphi-analytic hierarchy process study

Author

Zhang Min, Hu Bin, Zhou Wenjie, Li Tao, Meng Yi, Zhang Chunhua, and Yang Tong

Subjects
Healthy lifestyle, Occupational population, Delphi method, Analytic hierarchy process, Evaluation indicator system, Medicine, Science
Abstract

Abstract Lifestyle is an important factor affecting people's health. Evaluating and promoting healthy lifestyles among occupational population can not only improve work ability and efficiency, but also contribute to the prevention a variety of potential diseases. This study developed a preliminary index system based on literature review and group discussion. Two rounds of expert consultation were conducted on 12 experts using Delphi method. The questionnaire recovery rate of the two rounds of Delphi survey was over 85%, the expert authority coefficient was over 0.70, and Kendall W was 0.450 and 0.446, which were significant (P

Published
2024
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8. Central-moment discrete unified gas-kinetic scheme for incompressible two-phase flows with large density ratio

Author

Zhang, Chunhua, Wang, Lian-Ping, Liang, Hong, and Guo, Zhaoli

Subjects
Physics - Fluid Dynamics
Abstract

In this paper, we proposed a central moment discrete unified gas-kinetic scheme (DUGKS) for multiphase flows with large density ratio and high Reynolds number. Two sets of kinetic equations with central-moment-based multiple relaxation time collision operator are employed to approximate the incompressible Navier-Stokes equations and a conservative phase field equation for interface-capturing. In the framework of DUGKS, the first moment of the distribution function for the hydrodynamic equations is defined as velocity instead of momentum. Meanwhile, the zeroth moments of the distribution function and external force are also suitably defined such that a artificial pressure evolution equation can be recovered. Moreover, the Strang splitting technique for time integration is employed to avoid the calculation of spatial derivatives in the force term at cell faces. For the interface-capturing equation, two equivalent DUGKS methods that deal with the diffusion term differently using a source term as well as a modified equilibrium distribution function are presented. Several benchmark tests that cover a wide a range of density ratios (up to 1000) and Reynolds numbers (up to $10^5$) are subsequently carried out to demonstrate the capabilities of the proposed scheme. Numerical results are in good agreement with the reference and experimental data., Comment: 57 pages, 23 figures

Published
2022
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9. Discrete unified gas kinetic scheme for the conservative Allen-Cahn equation

Author

Zhang, Chunhua, Liang, Hong, Guo, Zhaoli, and Wang, Lian-Ping

Subjects
Computer Science - Computational Engineering, Finance, and Science, Mathematics - Numerical Analysis, Physics - Fluid Dynamics
Abstract

In this paper, the discrete unified gas kinetic scheme (DUGKS) with an improved microflux across the cell interface for the conservative Allen-Cahn equation (CACE) is proposed. In the context of DUGKS, the recovered kinetic equation from the flux evaluation with linear reconstruction in the previous DUGKS is analyzed. It is found that the calculated microflux across the cell interface is only the solution to the target kinetic equation with first order accuracy, which can result in an inaccurate CACE since the force term is involved or the first moment of the collision model has no conservation property. To correctly recover the kinetic equation up to the second order accuracy, the value of the distribution function that will propagate along the characteristic line with ending point at the cell interface is appropriated by the parabolic reconstruction instead of the linear reconstruction. To validate the accuracy of the present DUGKS for the CACE, several benchmark problems, including the diagonal translation of a circular interface, the rotation of a Zaleska disk and the deformation of a circular interface, have been simulated. Numerical results show that the present DUGKS scheme is able to capture the interface with improved accuracy when compared with the previous DUGKS., Comment: 31 pages,7 figures

Published
2022

10. Numerical study of three-dimensional single-mode Rayleigh-Taylor instability in turbulent mixing stage

Author

Liu, Bin, Zhang, Chunhua, Lou, Qin, and Liang, Hong

Subjects
Physics - Fluid Dynamics, Physics - Computational Physics
Abstract

Rayleigh-Taylor instability (RTI) as a multi-scale, strongly nonlinear physical phenomenon which plays an important role in the engineering applications and scientific research. In this paper, the mesoscopic lattice Boltzmann method is used to numerically study the late-time evolutional mechanism of three-dimensional (3D) single-mode RTI and the influences of extensive dimensionless Reynolds number and Atwood number on phase interfacial dynamics, spike and bubble growth are investigated in details. For a high Reynolds number, it is reported that the development of 3D single-mode RTI would undergo four different stages: linear growth stage, saturated velocity growth stage, reacceleration stage and turbulent mixing stage. A series of complex interfacial structures with large topological changes can be observed at the turbulent mixing stage, which always preserve the symmetries with respect to the middle axis at a low Atwood number, and the lines of symmetry within spike and bubble are broken as the Atwood number is increased. Five statistical methods for computing the spike and bubble growth rates are then analyzed to reveal the growth law of 3D single-mode RTI in turbulent mixing stage. It is found that the spike late-time growth rate shows an overall increase with the Atwood number, while the bubble growth rate seems to be independence of the Atwood number, approaching a constant of around 0.1. When the Reynolds number decreases, the later stages cannot be reached gradually and the evolution of phase interface presents a laminar flow state., Comment: 26 pages, 11 figures. arXiv admin note: text overlap with arXiv:2009.14655

Published
2022

20. Excess death and years of life lost of the residents in a town of Shanghai after the control of COVID-19 liberalized

Author

ZHANG Min, ZHOU Dongdong, ZHANG Chunhua, XUE Zhanying, and YAN Wenjuan

Subjects
covid-19, excess death, years of life lost, management and control, Medicine
Abstract

ObjectiveTo understand the excess death and years of life lost of residents in a town in Shanghai after the control of COVID-19 liberalized.MethodsThe death information of the residents was obtained from the death registration report system， and the age specific population data was from the records of Shanghai Pudong public security registered residence system. The period from December 2015 to November 2022 was defined as before the liberalization， and the period from December 2022 to January 2023 was defined as after the liberalization. The SPSS 22.0 time series prediction expert modeler was used to estimate the expected number of deaths. For men and women under 60 years old， 60‒70， 70‒80， 80‒90， and over 90， the following parameters were calculated： expected number of deaths， actual number of deaths， number of excess deaths， excess rate， actual number of deaths， number of years of life lost， number of years of excess deaths， number of years of life lost， and number of years of life lost per capita of excess deaths.ResultsAfter the control of COVID-19 was liberalized， the expected deaths were 125， the actual deaths were 317， and the excess deaths were 192， with an excess rate of 153.60% （192/125）. The excess death accounted for 0.29% （192/66 703） of the total population. The highest excess rate was found in men over 90 years old （300.00%）， 70‒80 years old and women over 90 years old （283.33%， 258.82%， respectively）. Excess death increased with age. The life expectancy of the residents before the liberalization was 84.41 years， including 81.50 years for males and 87.36 years for females. After the liberalization， the life expectancy of residents was 79.88 years， including 77.24 years for men and 82.71 years for women. After the liberalization， the life expectancy of the residents decreased by 4.53 years， including 4.26 years for men and 4.65 years for women. After the liberalization， the average loss of life of the residents who died in excess was 11.60 years， including 11.91 years for men and 11.30 years for women.ConclusionAfter the control of COVID-19 was liberalized， more residents die， but most of them are elderly people over 70 years old.

Published
2023
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29. Decision Tree Ensembles for Smart Sewage Treatment: An Intelligent Dosing Model for Removing Phosphorus

Author

Zhang, Chunhua, Yuan, Fang, Xu, Wei, Cheng, Guojian, Angrisani, Leopoldo, Series Editor, Arteaga, Marco, Series Editor, Chakraborty, Samarjit, Series Editor, Chen, Jiming, Series Editor, Chen, Shanben, Series Editor, Chen, Tan Kay, Series Editor, Dillmann, Rüdiger, Series Editor, Duan, Haibin, Series Editor, Ferrari, Gianluigi, Series Editor, Ferre, Manuel, Series Editor, Jabbari, Faryar, Series Editor, Jia, Limin, Series Editor, Kacprzyk, Janusz, Series Editor, Khamis, Alaa, Series Editor, Kroeger, Torsten, Series Editor, Li, Yong, Series Editor, Liang, Qilian, Series Editor, Martín, Ferran, Series Editor, Ming, Tan Cher, Series Editor, Minker, Wolfgang, Series Editor, Misra, Pradeep, Series Editor, Mukhopadhyay, Subhas, Series Editor, Ning, Cun-Zheng, Series Editor, Nishida, Toyoaki, Series Editor, Oneto, Luca, Series Editor, Panigrahi, Bijaya Ketan, Series Editor, Pascucci, Federica, Series Editor, Qin, Yong, Series Editor, Seng, Gan Woon, Series Editor, Speidel, Joachim, Series Editor, Veiga, Germano, Series Editor, Wu, Haitao, Series Editor, Zamboni, Walter, Series Editor, Zhang, Junjie James, Series Editor, Tan, Kay Chen, Series Editor, Hu, Cungang, editor, and Cao, Wenping, editor

Published
2023
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40. Effect of Synergistic Fermentation of Different Beneficial Microorganisms on the Aroma Substances of Pu’er Tea

Author

YAN Xuehang, ZHAO Yuan, MAN Hongping, LUO Zijun, ZHOU Hongjie, SHAN Zhiguo, ZHANG Chunhua

Subjects
pu’er tea, beneficial microorganisms, collaborative fermentation, aroma substances, flowery and fruity aromas, Food processing and manufacture, TP368-456
Abstract

Ripened Pu’er tea was made from the sun-dried leave of large-leaf tea (Camellia sinensis (Linn.) var. assamica (Masters) Kitamura) by natural fermentation, pure culture fermentation with Rhizopus arrhizus, or mixed culture fermentation with Saccharomyces cerevisiae, R. arrhizus and Aspergillus niger in proportions of 2:1:2, 2:2:2 and 2:3:2. The composition and content of aroma substances in Pu’er tea were analyzed by simultaneous distillation extraction (SDE) coupled with gas chromatography-mass spectrometry (GC-MS). The results showed that there were significant differences in the types and relative contents of aroma substances among all tea samples. The relative contents of terpenols in the three co-fermented Pu’er tea samples were higher than that in the naturally or R. arrhizus fermented ones, and had unique flowery, fruity and caramel-like aromas. The relative content of alcohols in the co-fermented Pu’er tea with yeast, R. arrhizus and A. niger in a ratio of 2:1:2 was 47.32%, which was significantly higher than that in the other samples (P < 0.05). The relative content of methoxybenzene in Pu’er tea obtained by natural fermentation and pure culture fermentation, having an aged aroma, were higher than that obtained by the three collaborative fermentation methods. The relative content of methoxybenzene in Pu’er tea fermented with pure R. arrhizus was as high as 31.24%, which was significantly higher than that obtained by the other fermentation methods (P < 0.05). Therefore, co-fermentation with beneficial microorganisms can improve the quality of Pu’er tea and endow it with unique flowery and fruity aromas.

Published
2023
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