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Three-Dimensional Direct Numerical Simulation of Flow past A Near-Wall Circular Cylinder:Combined Effects of Gap Ratio and Boundary Layer Thickness on Flow Profiles and Pressure Distribution

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China Ocean Engineering 2023年第6期37卷 948-961页

作者： YING chao hua yang WEI Yu-han JI Chun-ning Zhejiang Institute of Hydraulics&Estuary(Zhejiang Institute of Marine Planning and Design) Hangzhou 310020China Shanghai Investigation Design&Research Institute Co.Ltd.Shanghai 200335China State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China

Three-dimensional direct numerical simulations of the wake flow downstream of a near-wall circular cylinder at different gap ratios and boundary layer thicknesses are carried out by using the iterative immersed boundary method.The non-dimensional gap between the cylinder and the wall,G/D=0.2,0.6 and 1.0,the non-dimensional boundary layer thickness,δ/D=0.0,0.7 and 1.6,the Reynolds number,Re=350,and the aspect ratio of the cylinder,L/D=25are adopted.High-resolution visualizations of the complex vortex structures at differentδ/D and G/D are presented.The transition of the streamwise vortex mode,the combined effects ofδ/D and G/D on the flow statistics,the pressure and shear stress distribution and the hydrodynamic forces are analyzed.Results show that with decreasing G/D and increasingδ/D,the gap flow and its vortex-shedding are significantly weakened,together with an elongated wake and an enlarged low-velocity area near the wall,leading to the wake mode transition from the two-sided to one-sided vortex-shedding.Different relative positions of the cylinder regarding the boundary layer alter the flow features of the shear layers.With an increase inδ/D,the front stagnation point shifts to the upper surface,and the distance between the flow divergence point and the maximum pressure position increases.The mean drag coefficient and r.***.s.values of drag and lift coefficients decrease with a decrease in G/D and an increase inδ/D,while the mean lift coefficient increases with decreasing G/D but decreases with increasingδ/D.

关键词： cylinder wake near-wall effect direct numerical simulation boundary layer thickness gap ratio

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Elevated intraspinal pressure in traumatic spinal cord injury is a promising therapeutic target

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Neural Regeneration Research 2022年第8期17卷 1703-1710页

作者： Chao-Hua Yang Zheng-Xue Quan Gao-Ju Wang Tao He Zhi-Yu Chen Qiao-Chu Li Jin yang Qing Wang Department of Orthopedics The Affiliated Hospital of Southwest Medical UniversityLuzhouSichuan ProvinceChina Department of Orthopedics The First Affiliated Hospital of Chongqing Medical UniversityChongqingChina

The currently recommended management for acute traumatic spinal cord injury aims to reduce the incidence of secondary injury and promote functional recovery.Elevated intraspinal pressure(ISP)likely plays an important role in the processes involved in secondary spinal cord injury,and should not be overlooked.However,the factors and detailed time course contributing to elevated ISP and its impact on pathophysiology after traumatic spinal cord injury have not been reviewed in the literature.Here,we review the etiology and progression of elevated ISP,as well as potential therapeutic measures that target elevated ISP.Elevated ISP is a time-dependent process that is mainly caused by hemorrhage,edema,and blood-spinal cord barrier destruction and peaks at 3 days after traumatic spinal cord injury.Duraplasty and hypertonic saline may be promising treatments for reducing ISP within this time window.Other potential treatments such as decompression,spinal cord incision,hemostasis,and methylprednisolone treatment require further validation.

关键词： blood-spinal cord barrier decompression duraplasty durotomy edema hemorrhage intraspinal pressure myelotomy spinal cord injury therapeutic target

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Microphysical Insights into a Tornadic Supercell from Dual-Polarization Radar Observations in Jiangsu, China on 14 May 2021

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Journal of Meteorological Research 2024年第2期38卷 303-320页

作者： chao YUAN yang BAI Pengfei SUN hua BAI Lu XIA China Meteorological Administration Tornado Key Laboratory Foshan 528315 Institute of Atmospheric Environment China Meteorological AdministrationShenyang 110166 Panjin National Climate Observatory Panjin 124010 yangzhou Meteorological Bureau of Jiangsu Province Yangzhou 225100 Yichun Meteorological Bureau of Heilongjiang Province Yichun 153000

Tornadoes are incredibly powerful and destructive natural events,yet the microphysical characteristics of the parent storm and its effects on tornadogenesis remain unclear.This study analyzed polarization radar data of a tornadic supercell that occurred in Jiangsu Province of China on 14 May 2021,in comparison with another tornadic supercell and two non-tornadic supercells that occurred in the same region in 2023.The two tornadic supercells exhibited lower differential reflectivity(ZDR)in the hook echo region compared with the non-tornadic supercells,indicating smaller median drop sizes.A distinct increase in ZDR from the melting of frozen hydrometeors,observed between2.5-and 4.0-km altitude in the non-tornadic storms,was absent in the tornadic cases.The non-tornadic supercells also displayed substantially higher specific differential phase(KDP)below the melting level,likely aroused from enhanced melting and cooling.These findings suggest fundamental microphysical contrasts between tornadic and nontornadic supercells.Specifically,tornadic supercells have smaller droplets and may reduce melting in hook echoes.Moreover,greater separation between the ZDR arc and the KDP foot was observed during tornadogenesis.The vertical gradient of KDP related to the cooling pool strength of the hook echo,regulating rear-flank downdraft thermodynamics.Despite the limited number of cases investigated,the findings of this study indicate that monitoring ZDR,KDP,and drop size distribution trends could assist with tornado prediction and warnings.

关键词： tornado polarimetric radar supercell hook echo drop size distribution

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Transient Stability Analysis of Large-scale Power Systems:A Survey

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CSEE Journal of Power and Energy Systems 2023年第4期9卷 1284-1300页

作者： Qing-hua Wu Yuqing Lin chao Hong Yinsheng Su Tianhao Wen yang Liu School of Electric Power Engineering South China University of TechnologyGuangzhou 510640China the Power Dispatching and Control Center China Southern Power GridGuangzhou 510530China

Transient stability analysis is a key problem in power system operation and planning.This paper aims at giving a comprehensive review on the modeling ideas and analysis methods for transient stability of large-scale power systems.For model construction,the general modeling of traditional power systems and special modeling for renewable generations and high-voltage direct-current transmissions are introduced.For transient stability analysis,Lyapunov based methods and non-Lyapunov based methods are thoroughly reviewed.In Lya-punov based methods,we focus on the energy function method,the sum-of-squares based method and decentralized stability analysis methods.Meanwhile,in non-Lyapunov based methods,the time-domain simulation,extended equal-area criterion and data-driven based methods are considered.The basic working principles,features and recent research progresses of all the above-mentioned methods are described in detail.In particular,their performances on several aspects,such as computational speed,conservativeness of stability region estimation or stability margin calculation,and adaptability to various types of system models,are mentioned.Finally,a brief discussion of potential directions for future research on transient stability analysis of large-scale power systems is included.Index Terms-connective stability,large-scale system analysis,Lyapunov functions,power systems,transient stability analysis.

关键词： connective stability large-scale system analysis Lyapunov functions power systems transient stability analysis

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Examining the influence of the loading path on the cracking characteristics of a pre-fractured rock specimen with discrete element method simulation

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2023年第4期24卷 332-349页

作者： Kang DUAN Ri-hua JIANG Xue-jian LI Lu-chao WANG Ze-ying yang School of Civil Engineering Shandong UniversityJinan 250061China

Damage in a rock mass is heavily dependent on the existence and growth of joints,which are also influenced by the complex stress states induced by human activities(e.g.,tunneling and excavation).A proper representation of the loading path is essential for understanding the mechanical behaviors of rock masses.Based on the discrete element method(DEM),the influence of the loading path on the cracking process of a rock specimen containing an open flaw is examined.The effectiveness of the model is confirmed by comparing the simulation results under a uniaxial compression test to existing research findings,where wing crack initiates first and secondary cracks contribute to the failure of the specimen.Simulation results confirm that the cracking process is dependent upon both the confining pressure and the loading path.Under the axial loading test,a higher confining pressure suppresses the development of tensile wing cracks and forces the formation of secondary cracks in the form of shear bands perpendicular to the flaw.Increase of confining pressure also decreases the influence of the loading path on the cracking process.Reduction of confining pressure during an unloading test amplifies the concentration of tensile stress and ultimately promotes the appearance of a tensile splitting fracture at meso-scale.Confining pressure at the failure stage is well predicted by the Hoek-Brown failure criterion under quasi-static conditions.

关键词： Cracking process Loading path Fractured rock mass Discrete element method(DEM) Local stress concentration

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Exogenous brain-derived neurotrophic factor attenuates cognitive impairment induced by okadaic acid in a rat model of Alzheimer's disease

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Neural Regeneration Research 2018年第12期13卷 2173-2181页

作者： Ai-hua Xu yang yang Yong-Xin Sun chao-Dong Zhang Department of Rehabilitation Medicine the First Affiliated Hospital of China Medical University Department of Neurology the First Affiliated Hospital of China Medical University

Decreased expression of brain-derived neurotrophic factor（BDNF） plays an important role in the pathogenesis of Alzheimer＇s disease, and a typical pathological change in Alzheimer＇s disease is neurofibrillary tangles caused by hyperphosphorylation of tau. An in vivo model of Alzheimer＇s disease was developed by injecting okadaic acid（2 μL） and exogenous BDNF（2 μL） into the hippocampi of adult male Wister rats. Spatial learning and memory abilities were assessed using the Morris water maze. The expression levels of protein phosphatase 2 A（PP2 A）, PP2 Ac-Yp307, p-tau（Thr231）, and p-tau（Ser396/404） were detected by western blot assay. The expression levels of BDNF, TrkB, and synaptophysin mRNA were measured by quantitative real-time polymerase chain reaction. Our results indicated that BDNF expression was suppressed in the hippocampus of OA-treated rats, which resulted in learning and memory deficits. Intra-hippocampal injection of BDNF attenuated this OA-induced cognitive impairment. Finally, our findings indicated an involvement of the PI3 K/GSK-3β/AKT pathway in the mechanism of BDNF in regulating cognitive function. These results indicate that BDNF has beneficial effect on Alzheimer＇s disease, and highlight the potential of BDNF as a drug target for treatment of Alzheimer＇s disease.

关键词： nerve regeneration Alzheimer＇s disease exogenous brain-derived neurotrophic factor Tau protein okadaic acid phosphorylation PP2A- Y307 glycogen synthase kinase-3~ TrkB cognitive function brain protection neural regeneration

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Numerical study of fluid resonance of a two-dimensional heaving-free moonpool in a wide range of incident waves

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Journal of Hydrodynamics 2022年第4期34卷 647-664页

作者： Peng-lin Jing Guang-hua He Zheng-xiao Luan chao-gang Liu Hao yang School of Mechatronics Engineering Harbin Institute of TechnologyHarbin 150001China School of Ocean Engineering Harbin Institute of TechnologyWeihaiWeihai 264209China Shandong Institute of Shipbuilding Technology Weihai 264209China

The fluid resonance of a moonpool freely heaving in a beam sea is studied by an in-house constrained interpolation profile(CIP)code.Generally,the moonpool behaves as in the piston mode with a narrow opening.The numerical studies are carried out for a wide range of the incident waves,and a new secondary resonant region is identified in the low frequency region of the incident waves,besides the ordinary main resonant region.Numerical results demonstrate that the horizontal wave forces are significant in the secondary resonant region,although the resonant wave elevations are less remarkable than those of the main resonant region.It is concluded that the fluid resonance of the low frequency is excited mainly by the heave motion of the moonpool.Parameter studies of the moonpool draft and the gap width of the moonpool based on the fluid resonance are also performed.

关键词： Gap resonance low-frequency incident wave heave motion constrained interpolation profile(CIP)

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Boost activation of peroxymonosulfate by iron doped K_(2-x)Mn_(8)O_(16):Mechanism and properties

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Chinese Journal of Chemical Engineering 2023年第5期57卷 88-97页

作者： Linlin Su Meijun Chen Li Gong hua yang chao Chen Jun Wu Ling Luo Gang yang Lulu Long Institute of Ecological and Environmental Sciences Sichuan Agricultural UniversityChengdu 611130China Sichuan Keyuan Testing Center of Engineering Technology Chengdu 610091China

Among the numerous transition metal catalysts,manganese-based compounds are considered as promising peroxymonosulfate(PMS)catalysts due to their low cost and environmental friendliness,such as cryptomelane manganese oxide(K_(2-x)Mn_(8)O_(16):abbreviation KMnO).However,the limited catalytic performance of KMnO limits its practical application.In this work,iron-doped KMnO(Fe-KMnO)was prepared by one-step hydrothermal method to optimize its catalytic performance.Compared with KMnO/PMS system,Fe-KMnO/PMS system possessed more excellent removal efficiency of tetracycline(TC).Meanwhile,the Fe-KMnO/PMS system also exhibited good practical application potential and excellent stability.The mechanism of Fe-KMnO activation of PMS was further analyzed in detail.It was found that Fe participated in the redox of high-valent Mn,which promoted the activation of PMS.Moreover,The Fe site as an adsorption site enhanced the TC enrichment ability of the catalyst,reducing the mass transfer resistance and further enhancing the TC removal ability of Fe-KMnO/PMS system.This work not only provides an excellent PMS catalyst,but also offers new insights into the mechanism of PMS activation by bimetallic manganese-based catalysts.

关键词： Catalyst Environment Waste water Peroxymonosulfate K_(2-x)Mn_(8)O_(16) Iron doping

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Variable solution structure can be helpful in evolutionary optimization

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Science China(Information Sciences) 2015年第11期58卷 145-161页

作者： QIAN chao YU yang ZHOU Zhi-hua National Key Laboratory for Novel Software Technology Nanjing University Collaborative Innovation Center of Novel Software Technology and Industrialization

Evolutionary algorithms are a family of powerful heuristic optimization algorithms where various representations have been used for solutions. Previous empirical studies have shown that for achieving a better efficiency of evolutionary optimization, it is often helpful to adopt rich representations(e.g., trees and graphs)rather than ordinary representations(e.g., binary coding). Such a recognition, however, has little theoretical justifications. In this paper, we present a running time analysis on genetic programming. In contrast to previous theoretical efforts focused on simple synthetic problems, we study two classical combinatorial problems, the maximum matching and the minimum spanning tree problems. Our theoretical analysis shows that evolving tree-structured solutions is much more efficient than evolving binary vector encoded solutions, which is also verified by experiments. The analysis discloses that variable solution structure might be helpful in evolutionary optimization when the solution complexity can be well controlled.

关键词： evolutionary algorithms genetic programming maximum matching minimum spanning tree running time computational complexity

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Effects of Acupuncture on Alzheimer’s Disease: Evidence from Neuroimaging Studies

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Chinese Journal of Integrative Medicine 2019年第8期25卷 631-640页

作者： YU chao-chao MA chao-yang WANG hua KONG Li-hong ZHAO Yan SHEN Feng WU Miao College of Acupuncture and Orthopedics Hubei University of Chinese Medicine Wuhan (430061)China Department of Rehabilitation Wuhan Central Hospital Affiliated to Tongji Medical College Huazhong University of Science and Technology Wuhan (430014) China Hubei Provincial Collaborative Innovation Center of Preventive Treatment by Acupuncture and Moxibustion Hubei University of Chinese Medicine Wuhan (430061)China Hubei Provincial Hospital of Traditional Chinese Medicine Wuhan (430061)China Hubei Province Academy of Traditional Chinese Medicine Wuhan (430074)China

As the worldwide population ages, the prevalence of Alzheimer's disease (AD) increases. However, the results of promising medications have been unsatisfactory. Chinese acupuncture has a long history of treating dementia, but lack of evidence from well-designed randomized controlled trials that validate its efficacy and safety, as well as its lack of clear underlying mechanisms, contribute to its limited application in clinical practice. In recent years, brain imaging technologies, such as functional magnetic resonance imaging and positron emission tomography, have been used to assess brain responses to acupuncture in a dynamic, visual, and objective way. These techniques are frequently used to explore neurological mechanisms of responses to acupuncture in AD and provide neuroimaging evidence as well as starting points to elucidate the possible mechanisms. This review summarizes the existing brain imaging evidence that explains the effects of acupuncture for AD and analyzes brain responses to acupuncture at cognitive-related acupoints [Baihui (GV 20), Shenmen (HT 7), Zusanli (ST 36), Neiguan (PC 6), and Taixi (KI 3)] from perspectives of acupoint specificity and acupoint combinations. Key issues and directions to consider in future studies are also put forward. This review should deepen our understanding of how brain imaging studies can be used to explore the underlying mechanisms of acupuncture in AD.

关键词： acupuncture Alzheimer's disease brain response acupoint specificity neuroimaging

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