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2,217 results on '"Zhang, Yunfei"'

53. Genomic dynamics of the Lower Yellow River Valley since the Early Neolithic

Author

Du, Panxin, Zhu, Kongyang, Wang, Minghui, Sun, Zhaofeng, Tan, Jingze, Sun, Bo, Wang, Peixiao, He, Guanglin, Xiong, Jianxue, Huang, Zixiao, Meng, Hailiang, Sun, Chang, Xie, Shouhua, Wang, Bangyan, Ge, Dong, Ma, Yongqiang, Sheng, Pengfei, Ren, Xiaoying, Tao, Yichen, Xu, Yiran, Qin, Xiaoli, Allen, Edward, Zhang, Baoshuai, Chang, Xin, Wang, Ke, Bao, Haoquan, Yu, Yao, Wang, Lingxiang, Ma, Xiaolin, Du, Zhenyuan, Guo, Jianxin, Yang, Xiaomin, Wang, Rui, Ma, Hao, Li, Dapeng, Pan, Yiling, Li, Bicheng, Zhang, Yunfei, Zheng, Xiaoqu, Han, Sheng, Jin, Li, Chen, Gang, Li, Hui, Wang, Chuan-Chao, and Wen, Shaoqing

Published
2024
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59. Simulation of pore-scale microscopic spontaneous imbibition of shale based on level-set method

Author

HAN Xiao, SONG Zhaojie, LI Peiyu, DENG Sen, SONG Yilei, ZHANG Yunfei, CAO Changxiao, YANG Zhicheng, and WU Jiapeng

Subjects
shale reservoirs, level-set method, pore-scale, spontaneous imbibition, oil and water two phase flow, imbibition efficiency, Chemical technology, TP1-1185, Petroleum refining. Petroleum products, TP690-692.5, Geology, QE1-996.5
Abstract

The core pore structure of the target shale oil block was finely characterized using scanning electron microscopy， and a microscopic numerical model of the pore-scale core was constructed to elucidate the intrinsic mechanisms and the main controlling factors of spontaneous imbibition of fracturing fluid within the complex pore space of shale. On this basis， research was conducted on spontaneous imbibition within the fracture-matrix system. The Navier-Stokes （N-S） equations were coupled with the level-set method to track changes in the oil and water interface， thus clarifying the oil and water two-phase flow characteristics and evaluating the efficiency of spontaneous imbibition under the influence of the wettability， viscosity ratio of oil and water， and interfacial tension. The research results revealed that large and small intercommunicating pores in shale form intricate microscopic displacement units under capillary action. When the rock wettability presents a water-wet state， water preferentially infiltrates from the fracture into the smaller pores， expelling oil from larger pores into the fracture， and the produced range of crude oil within the matrix pores is wider， resulting in higher spontaneous imbibition efficiency. When the rock wettability turns oil-wet， crude oil within the small pores cannot be produced during spontaneous imbibition， while the water invades from larger pores， causing crude oil to be displaced from other large pores. This results in a lower spontaneous imbibition efficiency and a small range of crude oil produced in the matrix pores. The spontaneous imbibition in the initial phase is faster but gradually slows over time. Stronger water wettability of shale indicates a lower viscosity ratio of oil and water and higher interfacial tension， resulting in a wider range of crude oil produced within the matrix pores and a cumulative efficiency of spontaneous imbibition of more than 15%.

Published
2024
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60. Continuous Cooling Phase Transformation Prediction Model of 20CrMnTiH

Author

Yang Ting, Duan Luzhao, Liu Xu, Bai Lijuan, Zhang Yunfei, Sun Li

Subjects
20crmntih steel； cct curves； phase transition dynamics； composition fluctuation； phase transition model, Materials of engineering and construction. Mechanics of materials, TA401-492, Technology
Abstract

The thermal expansion curves of 20CrMnTiH test steel with three compositions at different cooling rates were measured by DIL805 type quench deformation expansion instrument ， and the microstructures at room temperature were observed， the continuous cooling transition （CCT） curves were drawn. The test results show that the composition fluctuation mainly affects the cooling range of bainite and martensite phase transformation during the cooling transformation of 20CrMnTiH， and has little effect on the critical phase transformation temperature. The kinetic parameters of martensitic transformation of the three test steels were fitted by using K-M equation. Combined with the optimized Li empirical model and the regression equation of critical transition temperature， a prediction model of phase transformation prediction model of ferrite，pearlite and bainite during continuous cooling of 20CrMnTiH was established ，the influence of composition fluctuation on CCT curve of the test steels were predicted successfully. Furthermore， the end-quenching simulation model of 20CrMnTiH steel was established by finite element analysis method， which can better predict the influence of composition fluctuation on the hardenability of the test steel. This method can provide reference for the composition optimization design and material selection of gear steel.

Published
2024
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61. Rate Splitting for General Multicast

Author

Zhao, Lingzhi, Cui, Ying, Yang, Sheng, Shamai, Shlomo, Han, Yunbo, and Zhang, Yunfei

Subjects
Computer Science - Information Theory
Abstract

Immersive video, such as virtual reality (VR) and multi-view videos, is growing in popularity. Its wireless streaming is an instance of general multicast, extending conventional unicast and multicast, whose effective design is still open. This paper investigates the optimization of general rate splitting with linear beamforming for general multicast. Specifically, we consider a multi-carrier single-cell wireless network where a multi-antenna base station (BS) communicates to multiple single-antenna users via general multicast. Linear beamforming is adopted at the BS, and joint decoding is adopted at each user. We consider the maximization of the weighted sum rate, which is a challenging nonconvex problem. Then, we propose an iterative algorithm for the problem to obtain a KKT point using the concave-convex procedure (CCCP). The proposed optimization framework generalizes the existing ones for rate splitting for various types of services. Finally, we numerically show substantial gains of the proposed solutions over existing schemes and reveal the design insights of general rate splitting for general multicast., Comment: 6 pages, 7 figures, to appear in IEEE ICC 2022. arXiv admin note: substantial text overlap with arXiv:2201.07386

Published
2022

91. Adaptive Streaming of 360 Videos with Perfect, Imperfect, and Unknown FoV Viewing Probabilities in Wireless Networks

Author

Zhao, Lingzhi, Cui, Ying, Liu, Zhi, Zhang, Yunfei, and Yang, Sheng

Subjects
Computer Science - Multimedia
Abstract

This paper investigates adaptive streaming of one or multiple tiled 360 videos from a multi-antenna base station (BS) to one or multiple single-antenna users, respectively, in a multi-carrier wireless system. We aim to maximize the video quality while keeping rebuffering time small via encoding rate adaptation at each group of pictures (GOP) and transmission adaptation at each (transmission) slot. To capture the impact of field-of-view (FoV) prediction, we consider three cases of FoV viewing probability distributions, i.e., perfect, imperfect, and unknown FoV viewing probability distributions, and use the average total utility, worst average total utility, and worst total utility as the respective performance metrics. In the single-user scenario, we optimize the encoding rates of the tiles, encoding rates of the FoVs, and transmission beamforming vectors for all subcarriers to maximize the total utility in each case. In the multi-user scenario, we adopt rate splitting with successive decoding and optimize the encoding rates of the tiles, encoding rates of the FoVs, rates of the common and private messages, and transmission beamforming vectors for all subcarriers to maximize the total utility in each case. Then, we separate the challenging optimization problem into multiple tractable problems in each scenario. In the single-user scenario, we obtain a globally optimal solution of each problem using transformation techniques and the Karush-Kuhn-Tucker (KKT) conditions. In the multi-user scenario, we obtain a KKT point of each problem using the concave-convex procedure (CCCP). Finally, numerical results demonstrate that the proposed solutions achieve notable gains over existing schemes in all three cases. To the best of our knowledge, this is the first work revealing the impact of FoV prediction on the performance of adaptive streaming of tiled 360 videos., Comment: 18 pages, 20 figures, to appear in Trans. Image Process. arXiv admin note: text overlap with arXiv:2009.01753

Published
2021
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92. WDR38, a novel equatorial segment protein, interacts with the GTPase protein RAB19 and Golgi protein GM130 to play roles in acrosome biogenesis

Author

Gao Qiujie, Liu Gang, Huang Lihua, Zhang Yunfei, Zhang Xinxing, Song Xiaoyue, and Xing Xiaowei

Subjects
WDR38, RAB19, GM130, acrosome biogenesis, equatorial segment, Biochemistry, QD415-436, Genetics, QH426-470
Abstract

The WD40-repeat containing (WDR) proteins are enriched in the testis and play important roles in spermatogenesis. In the present study, we investigate the expression profile of WDR38, a novel member of the WDR protein family, in humans and mice. RT-qPCR (reverse transcription-quantitative polymerase chain reaction) results demonstrate that WDR38 mRNA is abundantly expressed in both the human and mouse testis. The expression of mouse Wdr38 is strictly regulated during development. Further immunofluorescence staining results show that WDR38 is located in the equatorial segment of the acrosome in human and mouse mature spermatozoa and is involved in acrosome biogenesis. Subcellular localization analysis reveals that the mouse Wdr38 protein is distributed in the perinuclear cytoplasm of transfected cells and colocalizes with the GTPase protein Rab19 and Golgi protein GM130. Coimmunoprecipitation (co-IP) assays demonstrate that Wdr38, Rab19 and GM130 interact with each other in the mouse testis and in HEK293T cells. In acrosome biogenesis, Wdr38, Rab19 and GM130 aggregate at the nuclear membrane to form large vesicles, and GM130 then detaches and moves towards the caudal region of the nucleus, whereas the Wdr38/Rab19 complex spreads along the dorsal nuclear edge and finally docks to the equatorial segment. These results indicate that WDR38 is a novel equatorial segment protein that interacts with the GTPase protein RAB19 and Golgi protein GM130 to play roles in acrosome biogenesis.

Published
2023
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