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347 results on '"Zhang, Mengyun"'

1. On an age-structured model in moving boundaries: The effects of nonlocal diffusion and harvesting pulse

Author

Xu, Haiyan, Santos, Carlos Alberto, Zhang, Mengyun, and Lin, Zhigui

Subjects
Mathematics - Analysis of PDEs, 35R12, 35R35, 92D25
Abstract

In order to understand how nonlocal diffusion and pulse intervention affect dynamics of species, we focus on an age-structured nonlocal diffusion model in moving and heterogeneous environment, where nonlocal diffusion describes the long range dispersal of species itself and time-periodic harvesting pulse exacting on the adult reflects human intervention. A generalized principal eigenvalue involving harvesting rate used to identify the spreading and vanishing outcomes is firstly defined and the existence of the principal eigenvalue is given under some conditions. Subsequently, properties of the generalized principal eigenvalue and the principal eigenvalue related to harvesting rate and length of habitat interval are analyzed, respectively. The criteria to governing spreading or vanishing of the species are finally investigated, with sufficient conditions for spreading-vanishing established. Our results indicate that complexities can be induced by the internal long rang dispersal and expanding capacities of species, as well as external harvesting intervention of human. Specifically, appropriate harvesting rate and expanding capacities can even change the reciprocal outcomes of species from co-existence to co-extinction., Comment: 31 pages, 1 figure

Published
2024

28. Comparison of seven CD19 CAR designs in engineering NK cells for enhancing anti‐tumour activity

Author

Wang, Yao, primary, Li, Jianhuan, additional, Wang, Zhiqian, additional, Liu, Yanhong, additional, Wang, Tongjie, additional, Zhang, Mengyun, additional, Xia, Chengxiang, additional, Zhang, Fan, additional, Huang, Dehao, additional, Zhang, Leqiang, additional, Zhao, Yaoqin, additional, Liu, Lijuan, additional, Zhu, Yanping, additional, Qi, Hanmeng, additional, Zhu, Xiaofan, additional, Qian, Wenbin, additional, Hu, Fangxiao, additional, and Wang, Jinyong, additional

Published
2024
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37. The invasive dynamics of Aedes aegypti mosquito in a heterogenous environment

Author

Zhang, Mengyun, Ge, Jing, and Lin, Zhigui

Subjects
Mathematics - Analysis of PDEs, 35R35, 35K60
Abstract

A reaction-diffusion-advection model is proposed and investigated to understand the invasive dynamics of Aedes aegypti mosquitoes. The free boundary is introduced to model the expanding front of the invasive mosquitoes in a heterogenous environment. The threshold $R^D_0$ for the model with Dirichlet boundary condition is defined and the threshold $R^F_0(t)$ for the free boundary problem is introduced, and the long-time behavior of positive solutions to the reaction-diffusion-advection system is discussed. Sufficient conditions for the mosquitoes to be eradicated or to spread are given. We show that, if $R^F_0(\infty)\leq 1$, the mosquitoes always vanish, and if $R^F_0(t_0)\geq 1$ for some $t_0\geq 0$, the mosquitoes must spread, while if $R^F_0(0)<1

Published
2017

40. Spreading and vanishing in a West Nile virus model with expanding fronts

Author

Tarboush, Abdelrazig K., Lin, Zhigui, and Zhang, Mengyun

Subjects
Mathematics - Analysis of PDEs
Abstract

In this paper, we study a simplified version of a West Nile virus model discussed by Lewis et al. [28], which was considered as a first approximation for the spatial spread of WNv. The basic reproduction number $R_0$ for the non-spatial epidemic model is defined and a threshold parameter $R_0 ^D$ for the corresponding problem with null Dirichlet boundary condition is introduced. We consider a free boundary problem with coupled system, which describes the diffusion of birds by a PDE and the movement of mosquitoes by a ODE. The risk index $R_0^F (t)$ associated with the disease in spatial setting is represented. Sufficient conditions for the WNv to eradicate or to spread are given. The asymptotic behavior of the solution to system when the spreading occurs are considered. It is shown that the initial number of infected populations, the diffusion rate of birds and the length of initial habitat exhibit important impacts on the vanishing or spreading of the virus. Numerical simulations are presented to illustrate the analytical results., Comment: 28 pages, 4 figures. It has been accepted for publication in SCIENCE CHINA Mathematics

Published
2016
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41. Residual Mulching Film Detection in Seed Cotton Using Line Laser Imaging.

Author

Wang, Sanhui, Zhang, Mengyun, Wen, Zhiyu, Zhao, Zhenxuan, and Zhang, Ruoyu

Subjects
*LIGHT sources, *IMAGING systems, *IMAGE fusion, *SUPPORT vector machines, *FEATURE extraction, *COTTON quality
Abstract

Due to the widespread use of mulching film in cotton planting in China, residual mulching film mixed with machine-picked cotton poses a significant hazard to cotton processing. Detecting residual mulching film in seed cotton has become particularly challenging due to the film's semi-transparent nature. This study constructed an imaging system combining an area array camera and a line scan camera. A detection scheme was proposed that utilized features from both image types. To simulate online detection, samples were placed on a conveyor belt moving at 0.2 m/s, with line lasers at a wavelength of 650 nm as light sources. For area array images, feature extraction was performed to establish a partial least squares discriminant analysis (PLS-DA) model. For line scan images, texture feature analysis was used to build a support vector machine (SVM) classification model. Subsequently, image features from both cameras were merged to construct an SVM model. Experimental results indicated that detection methods based on area array and line scan images had accuracies of 75% and 79%, respectively, while the feature fusion method achieved an accuracy of 83%. This study demonstrated that the proposed method could effectively improve the accuracy of residual mulching film detection in seed cotton, providing a basis for reducing residual mulching film content during processing. [ABSTRACT FROM AUTHOR]

Published
2024
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42. Corporate financialisation, market attention and analyst tracking.

Author

Pu, Hongjing and Zhang, Mengyun

Subjects
FINANCIAL risk, FINANCIALIZATION, MARKETING research, VIRTUAL economy, INSTITUTIONAL investors, REAL estate business
Abstract

As an effective external governance factor, the effectiveness of analysts' governance and tracking options has been one of the most important topics of research. In recent years, there has been an influx of capital from real companies into finance, real estate and other industries related to the virtual economy, which has a significant impact on the financial position of companies and can also affect analysts' tracking choices. This paper takes A‐share listed companies from 2010 to 2021 as the research object and finds that as the financialisation of enterprises deepens, the number of analysts' tracking decreases; however, with the increase of market attention, the negative impact of the financialisation of enterprises on analysts' tracking will be weakened. Further research shows that, first, financial risk plays a mediating role between corporate financialisation and analyst tracking, in that corporate financialisation increases financial risk, which in turn leads to a decrease in the number of analyst tracking; second, as institutional investors have a greater influence on analysts, the impact of corporate financialisation on analyst tracking is weakened as the shareholding of institutional investors increases; finally, that holding two different types of financial assets, short‐term and long‐term, also has different consequences. The findings of this paper examine the impact of corporate financialisation from the analyst's perspective, confirming the identification and selection capabilities that analysts have. [ABSTRACT FROM AUTHOR]

Published
2024
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