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Statistics and dynamics of coherent structures in compressible wall-bounded turbulence

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Science China(Physics,Mechanics & Astronomy) 2024年

作者： Ming Yu siwei dong XianXu Yuan ChunXiao Xu State Key Laboratory of Aerodynamics Key Laboratory of Applied Mechanics Institute of Fluid Mechanics Department of Engineering Mechanics Tsinghua University

Compressible wall-bounded turbulence is ubiquitously encountered in modern aerospace and mechanical industries. In this review, we summarize the current state of the literature on the flow physics of compressible wall-bounded turbulence with simple flow geometry and boundary constraints, focusing on the statistics and dynamics of coherent structures, the seemingly organized flow patterns hidden amidst the nonlinear chaotic random processes. We summarize the conclusions brought by recent year studies regarding the influences of the Mach number and wall temperature on the velocity streaks, quasi-streamwise vortices and dilatational motions in the near-wall region, and the large-scale and very-large-scale motions in the outer region, from both statistical and dynamical point of view, with the primary concern of the similarities with and disparities from those in incompressible flows.

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宿舍排斥与大学生抑郁:自我肯定和家庭社会经济地位的作用

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心理研究 2024年第2期17卷 182-189页

作者：丁倩董思唯刘祎琳田俊信阳师范大学教育科学学院信阳464000 华中师范大学数学与统计学学院武汉430079

本研究基于抑郁的认知理论和社会阶层的社会认知理论,探讨宿舍排斥与大学生抑郁的关系,并在此基础上建构了一个有调节的中介模型,考察自我肯定的中介作用和家庭社会经济地位的调节作用。采用方便抽样法对湖北省和河南省各一所综合性大学... 详细信息

本研究基于抑郁的认知理论和社会阶层的社会认知理论,探讨宿舍排斥与大学生抑郁的关系,并在此基础上建构了一个有调节的中介模型,考察自我肯定的中介作用和家庭社会经济地位的调节作用。采用方便抽样法对湖北省和河南省各一所综合性大学608名学生进行问卷调查,结果显示:(1)宿舍排斥显著正向预测大学生抑郁;(2)自我肯定在宿舍排斥与大学生抑郁之间起中介作用,家庭社会经济地位调节该中介效应的前半路径。具体而言,相对于高家庭社会经济地位的大学生,间接效应对于低家庭社会经济地位的大学生作用更大。本研究结果揭示了宿舍排斥对大学生抑郁的影响及其作用机制,对大学生抑郁的干预具有一定的指导意义。

关键词：宿舍排斥自我肯定家庭社会经济地位抑郁

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高超声速有攻角锥裙直接数值模拟

航空学报 2024年第2期45卷 44-62页

作者：赖江范召林王乾董思卫童福林袁先旭中国空气动力研究与发展中心空气动力学国家重点实验室绵阳621000 中国空气动力研究与发展中心计算空气动力研究所绵阳621000 中国空气动力研究与发展中心绵阳621000

采用直接数值模拟方法对有攻角的高超声速7°~34°锥裙开展了数值研究,通过对比0°、90°、180°周向子午面,评估了三维横流效应对激波/边界层干扰的影响规律和作用机制,包括壁面压力、摩阻、热流分布,分离泡非定常运动,再附边界层演化... 详细信息

采用直接数值模拟方法对有攻角的高超声速7°~34°锥裙开展了数值研究,通过对比0°、90°、180°周向子午面,评估了三维横流效应对激波/边界层干扰的影响规律和作用机制,包括壁面压力、摩阻、热流分布,分离泡非定常运动,再附边界层演化等。研究发现,不同周向站位均出现流动分离,横流区、迎风区内复杂激波结构与边界层相互作用导致壁面压力、摩阻、热流显著升高。热流与压力的比值在干扰区上升后由于再附降低,而热流与摩阻的雷诺比拟关系在分离区则完全失效。分离泡面积脉动的功率谱结果表明,分离泡非定常膨胀/收缩运动呈低频特征,且分离泡呼吸与激波低频振荡在横流区密切相关,在迎风区存在迟滞,而在背风区不相关。速度脉动场的本征正交分解结果表明,分离区的低频特征与低阶模态相应的剪切层附近大尺度结构相关。对下游再附边界层演化分析指出,攻角的存在导致雷诺应力在再附点附近大幅增强,其流向分量的恢复最为迅速,雷诺应力分量的峰值位置在背风区沿流向持续外移,而在迎风区、横流区已迅速向内层恢复。此外,雷诺应力各向异性不变量分布进一步表明干扰下游的近壁区湍流各向异性峰值在背风区弱于迎风区。

关键词：激波/边界层干扰高超声速分离泡三维横流效应直接数值模拟

On the drag reduction mechanism of hypersonic turbulent boundary layers subject to heated wall blowing

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Advances in Aerodynamics 2023年第1期5卷 126-148页

作者： Qiang Liu Zhenbing Luo Yan Zhou Wei Xie siwei dong College of Aerospace Science and Engineering National University of Defense TechnologyChangsha 410073China State Key Laboratory of Aerodynamics Mianyang 621000China

Turbulence drag reduction is of great significance for the range increase of hypersonic flight *** proposed velocity-temperature coupling control method(Liu et al,Phys Rev Fluids 6:044603,2021)is further extended to the hypersonic turbulent boundary *** numerical simulation results of four comparative cases show that the heated wall blowing achieves a drag reduction rate of 10.58%,which is about the sum of wall blowing(5.27%)and wall heating(6.35%).By evaluating the control efficiency,however,it is found that heated wall blowing is not as good as wall blowing and cannot obtain net energy saving *** modified FIK decompositions of skin friction coefficient indicate that the cliffy decrease of the mean convection term is the primary contribution for the drag *** of the proposed control measure on turbu-lence statistics and coherent structures are also *** vortex is found to be away from the wall,thus leading to a lower friction drag.

关键词： Hypersonic turbulent boundary layer Turbulence drag reduction Velocity-temperature coupled control Turbulence statistics Turbulence structures Direct numerical simulations

Wall pressure beneath a transitional hypersonic boundary layer over an inclined straight circular cone

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Advances in Aerodynamics 2020年第1期2卷 597-616页

作者： siwei dong Jianqiang Chen Xianxu Yuan Xi Chen Guoliang Xu State Key Laboratory of Aerodynamics China Aerodynamics Research and Development Center621000 MianyangChina Computational Aerodynamics Institute China Aerodynamics Research and Development Center621000 MianyangChina

Properties of wall pressure beneath a transitional hypersonic boundary layer over a 7°half-angle blunt cone at angle of attack 6°are studied by Direct Numerical *** wall pressure has two distinct frequency *** low-frequency peak with f≈10−50 kHz is very likely the unsteady crossflow mode based on its convection direction,*** the axial direction and towards the windward symmetry *** peaks are roughly proportional to the local boundary layer *** the trajectories of stationary crossflow vortices,the location of intense high-frequency wall pressure moves from the bottom of trough where the boundary layer is thin to the bottom of shoulder where the boundary layer is *** comparing the pressure field with that inside a high-speed transitional swept-wing boundary layer dominated by the z-type secondary crossflow mode,we found that the high-frequency signal originates from the Mack mode and evolves into the secondary crossflow instability.

关键词： Wall pressure Mack mode Secondary crossflow instability Inclined cone 1 Introduction

High‑Entropy Layered Oxide Cathode Enabling High‑Rate for Solid‑State Sodium‑Ion Batteries

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Nano-Micro Letters 2024年第1期16卷 160-171页

作者： Tianxun Cai Mingzhi Cai Jinxiao Mu siwei Zhao Hui Bi Wei Zhao Wujie dong Fuqiang Huang State Key Laboratory of High Performance Ceramics and Superfine Microstructure Shanghai Institute of CeramicsChinese Academy of SciencesShanghai 200050People’s Republic of China State Key Laboratory of Rare Earth Materials Chemistry and Applications College of Chemistry and Molecular EngineeringPeking UniversityBeijing 100871People’s Republic of China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049People’s Republic of China Zhongke Institute of Strategic Emerging Materials Yixing 214213JiangsuPeople’s Republic of China

Na-ion O3-type layered oxides are prospective cathodes for Na-ion batteries due to high energy density and ***,such cathodes usually suffer from phase transitions,sluggish kinetics and air instability,making it difficult to achieve high performance solid-state sodium-ion ***,the high-entropy design and Li doping strategy alleviate lattice stress and enhance ionic conductivity,achieving high-rate performance,air stability and electrochemically thermal stability for Na_(0.95)Li_(0.06)Ni_(0.25)Cu_(0.05)Fe_(0.15)Mn_(0.49)O_(2).This cathode delivers a high reversible capacity(141 mAh g^(−1)at 0.2C),excellent rate capability(111 mAh g^(−1)at 8C,85 mAh g^(−1)even at 20C),and long-term stability(over 85%capacity retention after 1000 cycles),which is attributed to a rapid and reversible O3–P3 phase transition in regions of low voltage and suppresses phase ***,the compound remains unchanged over seven days and keeps thermal stability until 279℃.Remarkably,the polymer solid-state sodium battery assembled by this cathode provides a capacity of 92 mAh g^(−1)at 5C and keeps retention of 96%after 400 *** strategy inspires more rational designs and could be applied to a series of O3 cathodes to improve the performance of solid-state Na-ion batteries.

关键词： High-entropy High-rate performance Li-TM interaction Air stability O3 layered oxide cathode

Introduction to AVS2 Scene Video Coding Techniques

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ZTE Communications 2016年第1期14卷 50-53页

作者： Jiaying Yan siwei dong Yonghong Tian Tiejun Huang National Engineering Laboratory for Video Technology School of EE & CS Peking University School of Electronic and Computer Engineering Shenzhen Graduate School Peking University Cooperative Medianet Innovation Center

The second generation Audio Video Coding Standard (AVS2) is the most recent video coding standard. By introducing several new coding techniques, AVS2 can provide more efficient compression for scene videos such as surveillance videos, conference videos, etc. Due to the limited scenes, scene videos have great redundancy especially in background region. The new scene video coding techniques applied in AVS2 mainly focus on reducing redundancy in order to achieve higher compression. This paper introduces several important AVS2 scene video coding techniques. Experimental results show that with scene video coding tools, AVS2 can save nearly 40%BD?rate (Bj?ntegaard?Delta bit?rate) on scene videos.

关键词： AVS2 scene videos coding background prediction

Research on the Campus Cultural Landscape of the Tibetan-Yi Corridor:Taking the Middle and Primary Schools in Meigu County of Liangshan Yi Autonomous Prefecture as an Example

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Journal of Architectural Research and Development 2024年第3期8卷 98-103页

作者： Xueli Wang Hangchuan dong Xi Pan siwei Yu School of Arts and Design Leshan Normal UniversityLeshan 614000China

In view of rural revitalization,the Meigu area,as a key region of the Tibetan-Yi Corridor,faces challenges in educational development and the construction of campus cultural *** landscape culture,as the foundation of campus culture,is one of the important factors affecting the quality of campus *** traditional cultural elements such as Yi patterns and totems into the design can effectively enhance the aesthetic of the campus,promote the local ethnic characteristic culture,and inject new vitality into rural ***,this paper applies traditional Yi cultural elements to the design of campus cultural *** is of great significance for improving the rural school environment and enhancing students’enthusiasm for learning and cultural ***,it provides an alternative for the preservation and development of local culture.

关键词： Campus landscape design Tibetan-Yi culture Rural revitalization

Baicalein suppresses Coxsackievirus B3 replication by inhibiting caspase-1 and viral protease 2A

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Virologica Sinica 2024年第4期39卷 685-693页

作者： Yanyan dong Enze Shao siwei Li Ruiqi Wang Dan Wang Lixin Wang Hong Yang Yingxia He Tian Luan Yang Chen Yao Wang Lexun Lin Yan Wang Zhaohua Zhong Wenran Zhao Department of Cell Biology Harbin Medical UniversityHarbin 150081China Department of Microbiology Harbin Medical UniversityHarbin 150081China

Myocarditis is an inflammatory disease of the cardiac muscle and one of the primary causes of dilated *** B coxsackievirus(CVB)is one of the leading causative pathogens of viral myocarditis,which primarily affects children and young *** to the lack of vaccines,the development of antiviral medicines is crucial to controlling CVB infection and the progression of *** this study,we investigated the antiviral effect of baicalein,a flavonoid extracted from Scutellaria *** results demonstrated that baicalein treatment significantly reduced cytopathic effect and increased cell viability in CVB3-infected *** addition,significant reductions in viral protein 3D,viral RNA,and viral particles were observed in CVB3-infected cells treated with *** found that baicalein exerted its inhibitory effect in the early stages of CVB3 *** also suppressed viral replication in the myocardium and effectively alleviated myocarditis induced by CVB3 *** study revealed that baicalein exerts its antiviral effect by inhibiting the activity of caspase-1 and viral protease *** together,our findings demonstrate that baicalein has antiviral activity against CVB3 infection and may serve as a potential therapeutic option for the myocarditis caused by enterovirus infection.

关键词： Baicalein Coxsackievirus B(CVB) Myocarditis 2A protease Caspase-1