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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.-3.2.^(2.and horizontal area Ah in 0.9b^(2.-2.2.^(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

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Recent progress in self-propelled particles

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Journal of Hydrodynamics 2024年第1期36卷 61-77页

作者： Zhen-yu Ouyang jian-zhong Lin Laboratory of Impact and Safety Engineering Ministry of EducationNingbo UniversityNingbo315201China Department of Mechanics State Key Laboratory of Fluid Power and Mechatronic SystemsZhejiang UniversityHangzhou310027China

Self-propelled particles are commonly found in a large number of planktonic organisms such as bacteria,fungi,and algae in nature,and researchers have taken a long interest in exploring their swimming mechanisms for more than a *** in the past 2. years,with the development of computational fluid dynamics and flow display technology,as well as the need for the design of synthetic self-propelled particles and micro-swimming devices,self-propelled particles have become the forefront and hotspot of current research in the field of fluid *** paper first introduces the swimming characteristics of common self-propelled particles,leading to a classic“squirmer”type self-propelled particle *** this basis,a systematic introduction and summary of the theoretical and numerical simulation research of“squirmer”will be ***,the main challenges and opportunities faced by the current research will be summarized.

关键词： Self-propelled particles multiphase flow hydrodynamic interaction

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Active Fault Tolerant Nonsingular Terminal Sliding Mode Control for Electromechanical System Based on Support Vector Machine

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Chinese Journal of Mechanical Engineering 2024年第3期37卷 189-203页

作者： jian Hu Zhengyin Yang jianyong Yao School of Mechanical Engineering Nanjing University of Science and TechnologyNanjing 210094China

Effective fault diagnosis and fault-tolerant control method for aeronautics electromechanical actuator is concerned in this *** borrowing the advantages of model-driven and data-driven methods,a fault tolerant nonsingular terminal sliding mode control method based on support vector machine(SVM)is proposed.A SVM is designed to estimate the fault by off-line learning from small sample data with solving convex quadratic programming method and is introduced into a high-gain observer,so as to improve the state estimation and fault detection accuracy when the fault *** state estimation value of the observer is used for state reconfiguration.A novel nonsingular terminal sliding mode surface is designed,and Lyapunov theorem is used to derive a parameter adaptation law and a control *** is guaranteed that the proposed controller can achieve asymptotical stability which is superior to many advanced fault-tolerant *** addition,the parameter estimation also can help to diagnose the system faults because the faults can be reflected by the parameters *** comparative simulation and experimental results illustrate the effectiveness and advancement of the proposed controller compared with several other main-stream controllers.

关键词： Aeronautics electromechanical actuator Fault tolerant control Support vector machine State observer Parametric uncertainty

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Accurate simulations of pure-viscoacoustic wave propagation in tilted transversely isotropic media

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Petroleum Science 2024年第2期21卷 866-884页

作者： Qiang Mao jian-Ping Huang Xin-Ru Mu Ji-Dong Yang Yu-jian Zhang Geosciences Department China University of Petroleum(East China)Qingdao266580ShandongChina Pilot National Laboratory for Marine Science and Technology(Qingdao) Qingdao266207ShandongChina

Forward modeling of seismic wave propagation is crucial for the realization of reverse time migration(RTM) and full waveform inversion(FWI) in attenuating transversely isotropic media. To describe the attenuation and anisotropy properties of subsurface media, the pure-viscoacoustic anisotropic wave equations are established for wavefield simulations, because they can provide clear and stable wavefields. However, due to the use of several approximations in deriving the wave equation and the introduction of a fractional Laplacian approximation in solving the derived equation, the wavefields simulated by the previous pure-viscoacoustic tilted transversely isotropic(TTI) wave equations has low accuracy. To accurately simulate wavefields in media with velocity anisotropy and attenuation anisotropy, we first derive a new pure-viscoacoustic TTI wave equation from the exact complex-valued dispersion formula in viscoelastic vertical transversely isotropic(VTI) media. Then, we present the hybrid finite-difference and low-rank decomposition(HFDLRD) method to accurately solve our proposed pure-viscoacoustic TTI wave equation. Theoretical analysis and numerical examples suggest that our pure-viscoacoustic TTI wave equation has higher accuracy than previous pure-viscoacoustic TTI wave equations in describing q P-wave kinematic and attenuation characteristics. Additionally, the numerical experiment in a simple two-layer model shows that the HFDLRD technique outperforms the hybrid finite-difference and pseudo-spectral(HFDPS) method in terms of accuracy of wavefield modeling.

关键词： Pure-viscoacoustic TTI wave equation Attenuation anisotropy Seismic modeling Low-rank decomposition method

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A product version of the Hilton-Milner-Frankl theorem

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Science China Mathematics 2024年第2期67卷 455-474页

作者： Peter Frankl jian Wang Alfréd Rényi Institute of Mathematics Hungarian Academy of SciencesBudapest H-1053Hungary Department of Mathematics Taiyuan University of TechnologyTaiyuan 030024China

Two families F and G of k-subsets of {1, 2...., n} are called non-trivial cross t-intersecting if|F ∩ G|≥t for all F ∈ F, G ∈ G and | ∩ {F : F ∈ F}| < t, | ∩ {G : G ∈ G}| < t. In the present paper,we determine... 详细信息

Two families F and G of k-subsets of {1, 2...., n} are called non-trivial cross t-intersecting if|F ∩ G|≥t for all F ∈ F, G ∈ G and | ∩ {F : F ∈ F}| 2...., n} for n≥4(t + 2.2.2. k≥5, which is a product version of the Hilton-Milner-Frankl theorem.

关键词： extremal set theory cross t-intersecting family product version non-trivial

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Burden of gastrointestinal cancers among working-age population over past thirty years in China

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World Journal of Gastrointestinal Oncology 2024年第9期16卷 3955-3979页

作者： Yu Dong Zhuan-Zhuan Fan Wen-Ting Li jian kang Yan Zhang Yue Guan Hui-Qing Xu Jie Yuan Fei Xu Department of Gastroenterology Nanjing First HospitalNanjing Medical UniversityNanjing 210006Jiangsu ProvinceChina Department of Primary Healthcare Management Nanjing Municipal Center for Disease Control and PreventionNanjing 210003Jiangsu ProvinceChina Department of Emergency The First Affiliated Hospital with Nanjing Medical UniversityNanjing 210029Jiangsu ProvinceChina Department of Epidemiology Nanjing Medical University School of Public HealthNanjing 211116Jiangsu ProvinceChina

BACKGROUND Although gastrointestinal(GI)cancers have been becoming a great public health concern in China,there is currently a lack of comprehensive literature on the overall burden and changing trends of GI cancers in the working-age *** To assess the burden of GI cancers and to examine the overall,age-and genderspecific trends among the working-age population in China from 1990 to *** Data were extracted from the Global Burden of Disease Study *** burden of GI cancers was indicated by incidence,mortality,disability-adjusted life-years(DALYs),age-standardized incidence rate(ASIR),age-standardized mortality rate,and age-standardized DALYs *** in the burden of GI cancers from 1990 to 2.19 were examined using annual percent change and average annual percent change with Joinpoint regression *** For overall GI cancers,a declining trend was observed in the ASIR,age-standardized mortality rate,and agestandardized DALYs rate,with reductions of 0.74%,2.2.%,and 2.2.%,respectively,from 1999 to 2.19 in the Chinese working-age ***,an increasing trend was observed in the ASIR for overall GI cancers from *** number of either incident cases,mortality cases,and DALYs was higher for colon/rectum cancer and liver cancer in younger participants but lower for esophageal,gallbladder,biliary tract,pancreatic,and stomach cancer among older ***,sex disparity in the GI cancers burden was also examined over 30 *** The total burden of GI cancers remained heavy among the working-age population in China,although declining trends were observed from 1999 to *** in the GI cancers burden existed between sexes,age groups,and cancer ***-based precision prevention strategies are needed to tackle GI cancers among working-age individuals,considering the age,sex,and cancer type disparities in China.

关键词： Gastrointestinal cancer Working-age population Disease burden Disability-adjusted life-years Chinese

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Pd-catalyzed asymmetric carbonyl alkynylation:Synthesis of axial chiral ynones

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Chinese Chemical Letters 2024年第6期35卷 293-297页

作者： Long Jin jian Han Dongmei Fang Min Wang jian Liao Natural Products Research Center Chengdu Institute of BiologyChinese Academy of SciencesChengdu 610041China College of Chemical Engineering Sichuan UniversityChengdu 610065China University of Chinese Academy of Sciences Beijing 100049China

Ynones are important skeletons in bioactive molecules and valuable building blocks for organic synthesis,thus great efforts have been devoted to their ***,introducing prochiral substrates to construct ynones bearing a chiral framework is unrealized to ***,we reported the first example of Pd/SOP-catalyzed asymmetric carbonylative alkynylation via a non-classical carbonylative Sonogashiratype approach(acyl-Pd(Ⅱ)species generated from nucleophiles).By using cyclic diaryliodonium salts as prochiral substrates,various axial chiral ynones with good functional group tolerance(39 examples),satisfied yields(71%-96%)and excellent enantioselectivities(generally 94%-99%ee)were *** of bioactive compounds,scale-up experiment and useful transformations were also conducted to demonstrate the utility of this process.

关键词： Pd-catalyzed Axial chiral ynones Cyclic diaryliodonium High-valent palladium catalyzed Asymmetric carbonyl alkynylation

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Recent progress in carbene-catalyzed fluoroalkylation

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Science China Chemistry 2024年第8期67卷 2448-2460页

作者： Bei Zhang Xuan Zhang jian Wang jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control Collaborative Innovation Center of Atmospheric Environment and Equipment TechnologySchool of Environmental Science and EngineeringNanjing University of Information Science and TechnologyNanjing 210044China School of Pharmaceutical Sciences Tsinghua UniversityBeijing 100084China

The fluoroalkyl fragment plays a vital role in various fields such as pharmaceuticals and materials science, and has a significant impact on human life not only on the present but also in the future. The insertion of fluoroalkyl groups into the chemical skeletons can cause considerable alternations in the chemical, physical and biological properties of molecules, which has attracted numerous scientists from different fields. This review focuses on N-heterocyclic carbene(NHC)-catalyzed fluoroalkylation reactions, providing a detailed analysis and summary of the achievements in the past two decades. Many successful examples clearly indicate that NHCs can catalyze the tranformation of fluoroalkylation reagents with various electronic characteristics, whether electrophilic, nucleophilic, or radical precursors. Herein, the fluoroalkylation reactions are classified based on different catalytic modes of NHCs: Lewis base catalysis, Umploung catalysis, radical catalysis and others. Meanwhile, by refining and systematically studying the contribution of NHC catalysis in fluoroalkylation reactions, this review is expected to provide valuable insights and enlightenment for related fields.

关键词： N-heterocyclic carbene fluoroalkylation radical catalysis

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Direct numerical simulation of shock wave/boundary layer interaction controlled by steady microjet in a compression ramp

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Chinese Journal of Aeronautics 2024年第10期37卷 83-102页

作者： Ruoye XIAO Dong SUN jian YU School of Aeronautic Science and Engineering Beihang UniversityBeijing 100191China State Key Laboratory of Aerodynamics Mianyang 621000China

Shock wave/boundary layer interaction in a 2.°turning angle of the compression ramp at Mach number 2.9 controlled by steady microjet is investigated using direct numerical *** different jet spacings which are termed as sparse,moderate and dense are considered,and the induced vortex system and shock structures are compared.A moderate jet spacing configuration is found to generate counter-rotating vortex pairs that transport high-momentum fluid towards the vicinity of wall and strengthen the boundary layer to resist separation,reducing the separation *** dense jet spacing configuration creates a larger momentum deficit region,reducing the friction downstream of the *** of pressure and pressure gradient reveals that dense jet spacing configuration reduces the intensity of separation *** impact of varying jet spacings on the turbulent kinetic energy transport mechanism is also investigated by decomposing the budget terms in the transport ***,the spectral characteristics of the separation region are studied using power spectral density and dynamic mode decomposition methods,revealing that moderate jet spacing configuration suppresses low-frequency fluctuations in the separation region.

关键词： Shock wave/boundary layer interaction Compression ramp Steady microjet Different jet spacings Direct numerical simulation

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A compact multi-pixel superconducting nanowire single-photon detector array supporting gigabit space-to-ground communications

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Light(Science & Applications) 2024年第2期13卷 254-266页

作者： Hao Hao Qing-Yuan Zhao Yang-Hui Huang Jie Deng Fan Yang Sai-Ying Ru Zhen Liu Chao Wan Hao Liu Zhi-jian Li Hua-Bing Wang Xue-Cou Tu La-Bao Zhang Xiao-Qing Jia Xing-Long Wu jian Chen Lin {2. Pei-Heng Wu Research Institute of Superconductor Electronics(RISE) School of Electronic Science and EngineeringNanjing UniversityNanjingJiangsu 210023China Purple Mountain Laboratories NanjingJiangsu 211111China Hefei National Laboratory HefeiAnhui 230088China National Laboratory of Solid State Microstructures and Department of Physics Nanjing UniversityNanjing 210023China

Classical and quantum space-to-ground communications necessitate highly sensitive receivers capable of extracting information from modulated photons to extend the communication distance from near-earth orbits to deep space *** achieve gigabit data rates while mitigating strong background noise photons and beam drift in a highly attenuated free-space channel,a comprehensive design of a multi-functional detector is *** this study,we present an innovative compact multi-pixel superconducting nanowire single-photon detector array that integrates near-unity detection efficiency(91.6%),high photon counting rate(1.61 Gcps),large dynamic range for resolving different photon numbers(1-2.),and four-quadrant position sensing function all within one ***,we have constructed a communication testbed to validate the advantages offered by such an *** 8-PPM(pulse position modulation)format communication experiments,we have achieved an impressive maximum data rate of 1.5 Gbps,demonstrating sensitivities surpassing previous benchmarks at respective *** incorporating photon number information into error correction codes,the receiver can tolerate maximum background noise levels equivalent to 0.8 photons/slot at a data rate of 12. Mbps—showcasing a great potential for daylight operation ***,preliminary beam tracking tests were conducted through open-loop scanning techniques,which revealed clear quantitative dependence indicating sensitivity variations based on beam *** on the device characterizations and communication results,we anticipate that this device architecture,along with its corresponding signal processing and coding techniques,will be applicable in future space-to-ground communication tasks.

关键词： photon supporting correction

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