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7,941 results on '"Zhi WEN"'

163. Rate-Splitting Multiple Access for Multigateway Multibeam Satellite Systems with Feeder Link Interference

Author

Si, Zhi Wen, Yin, Longfei, and Clerckx, Bruno

Subjects
Computer Science - Information Theory, Electrical Engineering and Systems Science - Signal Processing
Abstract

This paper studies the precoder design problem of achieving max-min fairness (MMF) amongst users in multigateway multibeam satellite communication systems with feeder link interference. We propose a beamforming strategy based on a newly introduced transmission scheme known as rate-splitting multiple access (RSMA). RSMA relies on multi-antenna rate-splitting at the transmitter and successive interference cancellation (SIC) at the receivers, such that the intended message for a user is split into a common part and a private part and the interference is partially decoded and partially treated as noise. In this paper, we formulate the MMF problem subject to per-antenna power constraints at the satellite for the system with imperfect channel state information at the transmitter (CSIT). We also consider the case of two-stage precoding which is assisted by on-board processing (OBP) at the satellite. Numerical results obtained through simulations for RSMA and the conventional linear precoding method are compared. When RSMA is used, MMF rate gain is promised and this gain increases when OBP is used. RSMA is proven to be promising for multigateway multibeam satellite systems whereby there are various practical challenges such as feeder link interference, CSIT uncertainty, per-antenna power constraints, uneven user distribution per beam and frame-based processing., Comment: Submitted for publication

Published
2021

165. Establishment and Research of Ecological Environment Assessment Method in Mining Area -- Taking Anshan Open-pit Mine as an Example

Author

Hu, Zhi-wen, Liao, Shun-bao, Qi, Yu-na, Li, Kan, Editor-in-Chief, Li, Qingyong, Associate Editor, Fournier-Viger, Philippe, Series Editor, Hong, Wei-Chiang, Series Editor, Liang, Xun, Series Editor, Wang, Long, Series Editor, Xu, Xuesong, Series Editor, Fernández-Viagas, Víctor, editor, Kandel, Bijay Kumar, editor, Valmohammadi, Changiz, editor, and Mallick, Hrushikesh, editor

Published
2023
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179. Association of hepatitis B virus DNA levels with efficacy and safety outcomes in patients with hepatitis B virus-associated advanced hepatocellular carcinoma receiving tyrosine kinase inhibitor plus anti-PD-1 antibody: a multicenter propensity-matched study

Author

Chen, Qing-Jing, Lin, Kong-Ying, Lin, Zhi-Wen, Zhang, Bing, Liu, Ming-Qiang, Zhang, Jian-Xi, Huang, Qi-Zhen, Lin, Ke-Can, Zhang, Jin-Yu, Wei, Fu-Qun, You, Peng-Hui, You, Song, Jiang, Ya-Bin, Zhang, Hui, Cheng, Zhi-Qing, Wang, Cong-Ren, and Zeng, Yong-Yi

Published
2023
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197. The existence and stability of the photon spheres and time-like circular orbits in the spacetime of magnetic Gauss-Bonnet black hole

Author

Ma, Chen, Zhang, Yu, and Lin, Zhi-Wen

Subjects
Orbits -- Observations, Black holes (Astronomy) -- Observations, Physics
Abstract

This paper was devoted to studying the structure of the photon spheres and time-like circular orbits in the magnetic GaussBonnet black hole space-time. Herein, the relationship between the photon spheres, the time-like circular orbits, and the black hole horizons was analyzed. We found that the photon sphere curve of the black hole ends at the horizon curve of the extreme black hole. The outer photon sphere is unstable and the inner photon sphere is stable. However, given that there is physically no inner photon sphere of the black hole inside the event horizon, the black hole has only one unstable photon sphere. Specifically, compact massive objects have at most two photon spheres, i.e., stable and unstable. Moreover, the curve of extremal stable time-like circular orbits ends at the coincidence of the inner and outer photon spheres, whereas the inner time-like circular orbits cannot be inside the photon spheres. Therefore, the extremal stable time-like circular orbits become multivalued, which is related to the existence of the photon sphere. When the photon sphere exists, the extremal stable timelike circular orbits behave as the innermost stable circular orbits. When the photon sphere does not exist, the extremal stable time-like circular orbits have both an innermost stable circular orbit and an outermost stable circular orbit. Key words: photon spheres, time-like cirular orbits, magnetic Gauss-Bonnet black hole, effective potential, orbital stability Ce travail etudie la structure des spheres de photons et les orbites circulaires de type temps dans un espace-temps de trou noir de Gauss-Bonnet magnetique. Ici, nous analysons la relation entre les spheres de photons, les orbites circulaires de type temps et les horizons du trou noir. Nous trouvons que la courbe de la sphere de photons du trou noir se termine a la courbe d'horizon du trou noir extremal. La sphere de photons exterieure est instable, alors que la sphere de photons interieure est stable. Cependant, etant donne qu'il n'y a physiquement aucune sphere de photons interieure a l'interieur de l'horizon des evenements, le trou noir n'a qu'une sphere de photons instable. Specifiquement, pour des objets compacts massifs, ils ont au maximum deux spheres de photons, l'une stable et l'autre instable. De plus, la courbe des orbites circulaires de type temps stables extremales se termine a la coincidence des spheres de photons interieure et exterieure, alors que les orbites circulaires de type temps interieures ne peuvent pas etre a l'interieur des spheres de photons. Par consequent, les orbites circulaires de type temps deviennent multivaluees, ce qui est relie a l'existence des spheres de photons. Lorsque la sphere de photons existe, les orbites circulaires de type temps stables extremales se comportent comme les orbites circulaires stables les plus profondes. Quand la sphere de photons n'existe pas, les orbites circulaires de type temps stables extremales ont, a la fois, une orbite circulaire stable au plus profond et une orbite circulaire stable au plus eloigne. [Traduit par la Redaction] Mots-cles : spheres de photons, orbite circulaire de type temps, trou noir de Gauss-Bonnet magnetique, potentiel effectif, stabilite orbitale, 1. Introduction Due to the latest developments in observing astronomy and gravitational waves, the calculate of black hole simulation has become more and more important. The Event Horizon Telescope [1], [...]

Published
2022
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