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The recirculation flow after different cross-section shaped high-rise buildings with applications to ventilation assessment and drag parameterization

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Building Simulation 2024年第4期17卷 509-524页

作者： Keyi chen Ziwei Mo jian Hang School of Atmospheric Sciences Sun Yat-sen University&Southern Marine Science and Engineering Guangdong LaboratoryZhuhai519082China Key Laboratory of Tropical Atmosphere-Ocean System Ministry of EducationZhuhai519000China

The building cross-section shape significantly affects the flow characteristics around buildings,especially the recirculation region behind the high-rise *** generic building shapes including square,triangle,octagon,T-shaped,cross-shaped,#-shaped,H-shaped and L-shaped are examined to elucidate their effects on the flow patterns,recirculation length L and areas A using computational fluid dynamics(CFD)simulations with Reynolds-averaged Navier-Stokes(RANS)*** sizes and positions of the vortexes behind the buildings are found to be substantially affected by the building shapes and subsequently changing the recirculation *** recirculation length L is in the range of 1.6b-2.6b with an average of *** maximum L is found for L-shaped building(2.6b)while the shortest behind octagon building(1.6b).The vertical recirculation area Av is in the range of 1.5b^(2)-3.2b^(2)and horizontal area Ah in 0.9b^(2)-2.2b^(2).The L,Av and Ah generally increase with increasing approaching frontal area when the wind direction changes but subject to the dent structures of the#-shaped and cross-shaped *** area-averaged wind velocity ratio(AVR),which is proposed to assess the ventilation performance,is in the range of 0.05 and 0.14,which is around a three-fold difference among the different building *** drag coefficient parameterized by Ah varies significantly,suggesting that previous models without accounting for building shape effect could result in large uncertainty in the drag *** findings provide important reference for improving pedestrian wind environment and shed some light on refining the urban canopy parameterization by considering the building shape effect.

关键词： recirculation region cross-section shape ventilation assessment drag parameterization computational fluid dynamics

Allelopathic potentials of surrounding vegetation on seedling establishment of alpine cushion Arenaria polytrichoides

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Journal of Plant Ecology 2024年第2期17卷 146-160页

作者： Xu-Fang chen Li-Shen Qian Hong-hua Shi Ya-Zhou Zhang Min-Shu Song Hang Sun jian-Guo chen Key Laboratory for Plant Diversity and Biogeography of East Asia Kunming Institute of BotanyChinese Academy of SciencesKunming 650201YunnanChina University of Chinese Academy of Sciences Beijing 101408China

When facilitating other species and sustaining plant community structures and biodiversity,alpine cushion plants simultaneously experience negative feedback effects from surrounding ***,the impact of surrounding vegetation on cushion dynamics remains poorly understood,particularly in terms of allelopathic *** investigate the allelopathic potentials of surrounding vegetation on seedling establishment of the typical cushion plant Arenaria polytrichoides *** an elevational gradient,we extracted potential allelopathic compounds and tested their impacts on seed germination and seedling growth of *** addition,exclusion experiments using activated carbon were conducted to further elucidate these *** results demonstrate that surrounding vegetation exhibits certain allelopathic potentials on *** seedling establishment,with variations observed based on elevation,source and concentration of allelopathy compounds,as well as growing ***,low-elevation vegetation exerts pronounced suppression on seedling ***,higher-elevation vegetation generally shows no effect on seed germination but stimulates seedling growth through allelopathy ***,aboveground vegetation predominantly inhibits both seed germination and seedling growth in low-elevation communities;however,the effects of belowground vegetation depend on elevation and extract concentration *** identifed allelopathic potentials of surrounding vegetation signifcantly infuence the population dynamics of cushion *** by potentially accelerating population degeneration in lower-elevation communities while ensuring consistent population recruitment and expansion in higher-elevation communities.

关键词： allelopathic potential community dynamic cushion plant seed germination seedling growth

Notably Accelerated Nano-Bainite Transformation via Increasing Undissolved Carbides Content on GCr15Si1Mo Bearing Steel

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Acta Metallurgica Sinica(English Letters) 2024年第4期37卷 703-712页

作者： Yan-Hui Wang hua-Qiang Sun Wen-Jing Feng Lei-Jie Zhao Xiang chen Qing-An chen Hai-Tao Sun jian-Jun Wang Zhi-Nan Yang Key Laboratory of Intelligent Industrial Equipment Technology of Hebei Province School of Mechanical and Equipment EngineeringHebei University of EngineeringHandan056038China Collaborative Innovation Center for Modern Equipment Manufacturing of Jinan New Area Hebei University of EngineeringHandan056038China School of Materials Science and Engineering Tsinghua UniversityBeijing100084China Avic Shang da Superalloys Company Limited Xingtai054800China National Engineering Research Center for Equipment and Technology of Cold Strip Rolling Yanshan UniversityQinhuangdao066004China

In this study, a high-carbon nano-bainitic GCr15Si1Mo bearing steel was investigated. Specifically, the effects of content and size of undissolved carbides on the microstructure and transformation kinetics of nano-bainite were analyzed. The results demonstrated that after prolonged austempering at low temperatures, the mixed microstructure composed of nano-bainite (NB), undissolved carbides (UC), and retained austenite (RA) was obtained in GCr15SiMo steel. When the experimental steel was austenitized at 900 ℃, the undissolved carbides gradually dissolved until reaching a stable state with increasing holding time. Furthermore, at the same austempering temperature, despite different volume fractions of undissolved carbides in the substrate, the volume fractions of nano-bainite in the final microstructures remained essentially the same. Moreover, the higher the content of undissolved carbides in steel, the faster the transformation rate of nano-bainite and the shorter the total transformation time.

关键词： Nano-bainite Undissolved carbides Bainitic transformation kinetics Carbon concentration

Rasmussen＇s Encephalitis with Faciobrachial Dystonic Attacks and Bilateral Hemispheric Involvement

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Chinese Medical Journal 2016年第2期129卷 248-249页

作者： jian-hua chen Li-Ri Jin Xiao-hua Shi Di Yang Yi Guo Department of Neurology Peking Union Medical College Hospital Chinese Academy of Medical Sciences Beijing 100730 China Department of Pathology Peking Union Medical College Hospital Chinese Academy of Medical Sciences Beijing 100730 China Department of Neurosurgery Peking Union Medical College Hospital Chinese Academy of Medical Sciences Beijing 100730 China

To the Editor： Rasmussen＇s encephalitis （RE） is a rare but devastating unihemispheric brain disorder, usually affecting children and characterized by intractable seizures and progressive neurological deficits Characteristic magnetic resonance imaging （MRI） finding of RE is progressive unihemispheric focal cortical atrophy. Bilateral RE is very uncommon. Here, we report an RE patient with faciobrachial dystonic attacks and bilateral brain atrophy but without seizures.

关键词： encephalitis devastating unihemispheric seizures

Preparation of PVA/GO/h-BN Janus Film with High Thermal Conductivity and Excellent Flexibility via a Density Deposition Self-assembly Method

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Chinese Journal of Polymer Science 2024年第8期42卷 1217-1226页

作者： Fang-hua Luo Zhi-Tao Dong Guo-hua chen chen Ma huai-Yuan Wang College of Chemistry and Chemical Engineering Northeast Petroleum UniversityDaqing 163318China College of Materials Science and Engineering Huaqiao UniversityXiamen 361000China School of Chemical Engineering and Technology and State Key Laboratory for Chemical Engineering Tianjin UniversityTianjin 300350China

Janus films with asymmetric physical/chemical properties have attracted con siderable attention due to their promising applications in personal thermal management,electronic skin s,sensors,actuators,***,traditional methods for fabricating Janus films conventionally need the assistance of an interface or auxiliary equipment,which are usually complex and ***,flexible poly(vinyl alcohol)(PVA)/graphene oxide(GO)/h-BN(recorded as PVA/GO/h-BN)Janus films with thermally,optically,and electrically anisotropic properties are fabricated by a simple density deposition self-assem bly method,which just utilizes the density difference between GO and h-BN during water *** results show that the two sides of the acquired Janus films have obvious asymmetric *** the original state of the PVA/GO/h-BN Janus films,the thermal conductivity of the GO side(10.06 W·m^(-1)·K^(-1))is generally lower than that of the h-BN side(10.48W·m^(-1)·K^(-1)).But after GO is reduced,the thermal conductivity of the rGO side reaches 12.17 W·m^(-1)·K^(-1),surpassing that of the h-BN *** addition,the relative reflectance of the h-BN side of Janus film is also significantly higher than that of the rGO side,and the su rface resistance difference between the two sides is about 4 orders of *** prepared PVA/GO/h-BN Janus films show great application potential in human thermal management,light conversion switches,and electronic *** study provides a simple and versatile strategy for fabricating Janus films with multifunctional(such as thermal,optical,and electrical)anisotropies.

关键词： Janus films PVA/GO/h-BN Density deposition self-assembly method

Advances in the application of hydrogel-based scaffolds for tendon repair

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Genes & Diseases 2024年第4期11卷 296-313页

作者： Renqiang chen Fanglin chen Kenian chen jian Xu Department of Orthopedics The First Affiliated HospitalZhejiang University School of MedicineHangzhouZhejiang 310003China Department of Orthopedics The Fourth Affiliated Hospital of Guangxi Medical UniversityLiuzhou Guangxi 545005China

Tendon injuries often lead to joint dysfunction due to the limited self-regeneration capacity of *** tendons is a major challenge for surgeons and imposes a signif-icant financial burden on ***,there is an urgent need to develop effective stra-tegies for repairing injured *** tissue engineering using hydrogels has emerged as a promising approach that has attracted considerable *** possess excellent biocompatibility and biodegradability,enabling them to create an extracellular matrix-like growth environment for *** can also serve as a carrier for cells or other substances to accelerate tendon *** the past decade,numerous studies have made significant prog-ress in the preparation of hydrogel scaffolds for tendon *** review aims to provide an overview of recent research on the materials of hydrogel-based scaffolds used for tendon tis-sue engineering and discusses the delivery systems based on them.

关键词： Application Hydrogel-based Repairscaffolds Review Tendon injury Tissue engineering

New-Onset Geriatric Epilepsy in China:A Single-Center Study

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Chinese Medical Journal 2018年第24期131卷 2915-2920页

作者： jian-hua chen Xiang-Qin Zhou Qiang Lu Li-Ri Jin Yan huang Department of Neurology Peking Union Medical College HospitalChinese Academy of Medical Sciences and Peking Union Medical College Beijing 100730China

Background:Few studies have been published on new-onset geriatric epilepsy especially in older Chinese *** study was to have a comprehensive understanding of new-onset geriatric epilepsy and find a more reasonable diagnosis and management of epilepsy in older people. Methods:One hundred and three patients with onset age 60 years and older were admitted between January 2008 and December 2016. Electronic medical records were reviewed to collect information. Results:There were 103 older patients with new-onset *** mean age of the patients was 68.5±6.4 years (range:60-89 years), and there were 67 (65%)men and 36 (35%)*** mean onset age was 67.9 ±6.2 years (range:60-89 years).The most common identifiable etiology of symptomatic seizures was autoimmune epilepsy in 43 (41.7%)*** second most common etiology was stroke in 15 (14.6%)*** (6.8%)older patients with acute seizures present with status epilepticus and 26 (25.2%)patients experienced clustered seizures (more than three events in 24 h)at seizure *** seizures (96.1%)were more common than generalized seizures (3.9%).Fifty-three (51.5%)patients had an abnormal brain magnetic resonance imaging (MRI)*** them, video-electroencephalogram findings in 31 (30.1%)patients correlated with MRI *** was the most used drugs before admission,in hospital,and during follow-up. Conclusions:Autoimmune encephalitis is becoming an increasing risk factor of subsequent epilepsy in older *** patients with new epilepsy are more likely to respond to antiepileptic drugs,and drug-resistant epilepsy is uncommon.

关键词： Elderly Electroencephalography Epilepsy Seizures

Data-Driven Active Disturbance Rejection Control of Plant-Protection Unmanned Ground Vehicle Prototype: A Fuzzy Indirect Iterative Learning Approach

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IEEE/CAA Journal of Automatica Sinica 2024年第8期11卷 1892-1894页

作者： Tao chen Ruiyuan Zhao jian chen Zichao Zhang College of Engineering China Agricultural UniversityBeijing 100083China Key Laboratory of Smart Agricultural Technology in Tropical South China Ministry of Agriculture and Rural AffairsGuangzhou 510642China

Dear Editor,This letter proposes a fuzzy indirect iterative learning(FIIL)active disturbance rejection control(ADRC)scheme to address the impact of uncertain factors of plant-protection unmanned ground vehicle(UGV),in which ADRC is a data-driven model-free control algorithm that only relies on the input and output data of the *** on the established nonlinear time-varying dynamic model including dynamic load(medicine box),the FIIL technology is adopted to turn the bandwidth and control channel gain online,in which the fuzzy logic system is used to update the gain parameters of iterative learning in real *** and experiment show the FIIL-ADRC scheme has better control performance.

关键词： Active scheme iterative

A REMARK ON THE RADIATION CONDITIONS

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Journal of Hydrodynamics 1991年第4期3卷 43-48页

作者： Wu jian-hua chen Yao-song Dept.of Mechanics,Peking Uuiversity,Beijing 100871,P.R.China

By studying stationary solution of the initial value problem of wave diffraction by a body moving with con- stant speed in waves,the boundary value problem of the stationary solution has been derived in this *** is proved that the free surface condition including a small damping μ,which may be seen as either real or fictitious, implies the radiation *** work may be seen as the mathematical proof of the Rayleigh stress and make one have more knowledge about the radiation condition.

关键词： A REMARK ON THE RADIATION CONDITIONS exp