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Journal of Hydrodynamics 2024年第2期36卷 219-231页

作者： Chen Geng Zhao-hui Qian Ke-xin Zheng Wei-xiang Ye Xian-wu Luo State Key Laboratory of Hydroscience cand Engineering Deparment of Energy and Power EngineeringTsinghua UniversityBeijing 100084China Institute of Nuclear and New Energy Technology Tsinghua UniversityBeijing 100084China

In the present paper,the unsteady cavitating turbulent flow over the twisted NACA66 hydrofoil is investigated based on an modified shear stress transfer k-ωpartially averaged Navier-Stokes(MSST PANS)model,i.e.,new MSST PANS(NMSST PANS)model,where the production term of kinetic energy in the turbulence model is modified with *** with the experimental data,cavitation evolution and its characteristic frequency are satisfactorily predicted by the proposed NMSST PANS *** is revealed that the interaction among the main flow,the reentrant jets,and sheet cavitation causes the formation of the primary shedding cavity near the mid-span and the secondary shedding cavity at each side of the twisted hydrofoil,and further induces the remarkable pressure gradient around shedding *** with the development of the primary and the secondary shedding cavities,the great pressure gradient associated with large cavity volume variation promotes the vortical flow generation and the spatial deformation of vortex structure during cavitation evolution,and results in the primary and the secondary U-type ***,dynamic mode decomposition(DMD)analysis is utilized to confirm the interaction among the main flow,the main reentrant jet and two side reentrant jets,and *** results indicate that the proposed NMSST PANS model is suitable to simulate the complicated cavitating turbulent flow for various engineering applications.

关键词： Cavitating turbulent flow partially averaged Navier-Stokes(PANS)model hydrofoil numerical simulation

An extended social force model on unidirectional flow considering psychological and behavioral impacts of hazard source

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Chinese Physics B 2024年第2期33卷 567-576页

作者：邓凯丰李梦胡祥敏陈涛 Institute of Public Safety Research Department of Engineering PhysicsTsinghua UniversityBeijing 100084China Anhui Province Key Laboratory of Human Safety Hefei 230601China beijing Key Laboratory of Comprehensive Emergency Response Science Beijing 100084China

An accurate assessment of the evacuation efficiency in case of disasters is of vital importance to the safety design of buildings and street *** sources not only physically but psychologically affect the pedestrians,which may further alter their behavioral *** effect is especially significant in narrow spaces,such as corridors and *** study aims to integrate a non-spreading hazard source into the social force model following the results from a previous experiment and simulation,and to simulate unidirectional pedestrian flows over various crowd densities and clarity–intensity properties of the hazard *** integration include a virtual repulsion force from the hazard source and a decay on the social force *** simulations reveal(i)that the hazard source creates virtual bottlenecks that suppress the flow,(ii)that the inter-pedestrian push forms a stabilisation phase on the flow-density curve within medium-to-high densities,and(iii)that the pedestrians are prone to a less orderly and stable pattern of movement in low clarity–intensity scenarios,possibly with lateral collisions passing the hazard source.

关键词： evacuation social force model hazard source unidirectional pedestrian flow

Simultaneous dual-region two-photon imaging of biological dynamics spanning over 9 mm in vivo

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Photonics Research 2024年第3期12卷 456-464页

作者： CHI LIU CHENG JIN JUNHAO DENG JUNHAO LIANG LICHENG ZHANG LINGJIE KONG State Key Laboratory of Precision Measurement Technology and Instruments Department of Precision InstrumentTsinghua UniversityBeijing 100084China School of Life Sciences Tsinghua UniversityBeijing 100084China Senior Department of Orthopedics The Fourth Medical Center of Chinese PLA General HospitalBeijing 100853China IDG/McGovern Institute for Brain Research Tsinghua UniversityBeijing 100084China

Biodynamical processes,especially in system biology,that occur far apart in space may be highly *** study such biodynamics,simultaneous imaging over a large span at high spatio-temporal resolutions is highly *** example,large-scale recording of neural network activities over various brain regions is indispensable in ***,limited by the field-of-view(FoV)of conventional microscopes,simultaneous recording of laterally distant regions at high spatio-temporal resolutions is highly ***,we propose to extend the distance of simultaneous recording regions with a custom micro-mirror unit,taking advantage of the long working distance of the objective and spatio-temporal *** demonstrate simultaneous dual-region two-photon imaging,spanning as large as 9 mm,which is 4 times larger than the nominal FoV of the *** verify the system performance in in vivo imaging of neural activities and vascular dilations,simultaneously,at two regions in mouse brains as well as in spinal cords,*** adoption of our proposed scheme will promote the study of systematic biology,such as system neuroscience and system immunology.

关键词： recording vivo dynamics

Green manufacturing for achieving carbon neutrality goal requires innovative technologies:A bibliometric analysis from 1991 to 2022

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Journal of Environmental Sciences 2024年第6期140卷 255-269页

作者： Sheng Zhang Xintian Wang Jiayu Xu Qinqin Chen Meng Peng Jiming Hao School of Environment Tsinghua UniversityBeijing 100084China School of Environment&Natural Resources Renmin University of ChinaBeijing 100872China State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex Beijing 100084China

Recent years have seen a significant increase in interest in green manufacturing as a key driver of global carbon-neutral efforts and sustainable *** find the research hotspots of green manufacturing and reveal future research trends,this study reviewed and analyzed research articles from the Web of Science database on green manufacturing from1991 to 2022 using a bibliometric *** findings indicate a significant rise in the number of articles related to green manufacturing since the ***,there has been an increase in the involvement of scholars from developing countries such as China and India in this *** on the literature review and bibliometric cluster analysis on green manufacturing,we believed that future research may continue following the lines of intelligent technology integration,adoption of frontier engineering techniques,and industry development in line with carbon reduction targets.A framework for future green manufacturing development is proposed,with a focus on Chinese *** framework could provide policy implications for developing countries looking to pursue opportunities for development in green manufacturing.

关键词： Green manufacturing Carbon neutrality Sustainable development Innovative technologies China

Emerging probing perspective of two-dimensional materials physics:terahertz emission spectroscopy

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Light(Science & Applications) 2024年第7期13卷 1278-1298页

作者： Yifei Wu Yuqi Wang Di Bao Xiaonan Deng Simian Zhang Lin Yu-chun Shengxian Ke Jianing Liu Yingjie Liu Zeli Wang Pingren Ham Andrew Hanna Jiaming Pan Xinyue Hu Zhengcao Li Ji Zhou Chen Wang State Key Laboratory of New Ceramics and Fine Processing Key Laboratory of Advanced Materials of Ministry of EducationSchool of Materials Science and EngineeringTsinghua University100084 BeijingChina beijing Advanced Innovation Center for Integrated Circuits 100084 BeijingChina

Terahertz(THz)emission spectroscopy(TES)has emerged as a highly effective and versatile technique for investigating the photoelectric properties of diverse materials and nonlinear physical processes in the past few ***,research on two-dimensional(2D)materials has experienced substantial growth due to their atomically thin structures,exceptional mechanical and optoelectronic properties,and the potential for applications in flexible electronics,sensing,and ***,these materials offer advantages such as tunable bandgap,high carrier mobility,wideband optical absorption,and relatively short carrier *** applying TES to investigate the 2D materials,their interfaces and heterostructures,rich information about the interplay among photons,charges,phonons and spins can be unfolded,which provides fundamental understanding for future *** it is timely to review the nonlinear processes underlying THz emission in 2D materials including optical rectification,photon-drag,high-order harmonic generation and spin-to-charge conversion,showcasing the rich diversity of the TES employed to unravel the complex nature of these *** applications based on THz emissions,such as THz lasers,ultrafast imaging and biosensors,are also *** further,we analyzed the unique advantages of spintronic terahertz emitters and the future technological advancements in the development of new THz generation mechanisms leading to advanced THz sources characterized by wide bandwidth,high power and integration,suitable for industrial and commercial *** continuous advancement and integration of TES with the study of 2D materials and heterostructures promise to revolutionize research in different areas,including basic materials physics,novel optoelectronic devices,and chips for post-Moore’s era.

关键词： optoelectronic versatile exceptional

Deep learning-based optical aberration estimation enables offline digital adaptive optics and super-resolution imaging

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Photonics Research 2024年第3期12卷 474-484页

作者： CHANG QIAO HAOYU CHEN RUN WANG TAO JIANG YUWANG WANG DONG LI Department of Automation Tsinghua UniversityBeijing 100084China Institute for Brain and Cognitive Sciences Tsinghua UniversityBeijing 100084China National Laboratory of Biomacromolecules New Cornerstone Science LaboratoryCAS Center for Excellence in BiomacromoleculesInstitute of BiophysicsChinese Academy of SciencesBeijing 100101China College of Life Sciences University of Chinese Academy of SciencesBeijing 100049China beijing National Research Center for Information Science and Technology Tsinghua UniversityBeijing 100084China

Optical aberrations degrade the performance of fluorescence *** adaptive optics(AO)leverages specific devices,such as the Shack–Hartmann wavefront sensor and deformable mirror,to measure and correct optical ***,conventional AO requires either additional hardware or a more complicated imaging procedure,resulting in higher cost or a lower acquisition *** this study,we proposed a novel space-frequency encoding network(SFE-Net)that can directly estimate the aberrated point spread functions(PSFs)from biological images,enabling fast optical aberration estimation with high accuracy without engaging extra optics and image *** showed that with the estimated PSFs,the optical aberration can be computationally removed by the deconvolution ***,to fully exploit the benefits of SFE-Net,we incorporated the estimated PSF with neural network architecture design to devise an aberration-aware deeplearning super-resolution model,dubbed *** demonstrated that the combination of SFE-Net and SFT-DFCAN enables instant digital AO and optical aberration-aware super-resolution reconstruction for live-cell imaging.

关键词： optics resolution enable

Hydrothermal hydrogenation/deoxygenation of palmitic acid to alkanes over Ni/activated carbon catalyst

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Chinese Journal of Chemical Engineering 2024年第2期66卷 8-18页

作者： Min Lin Yuhao Yan Xiaoxian Li Rui Li Yulong Wu MOE Engineering Center of Forestry Biomass Materials and Bioenergy Beijing Forestry UniversityBeijing 100083China Institute of Nuclear and New Energy Technology Tsinghua UniversityBeijing 100084China Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education Tsinghua UniversityBeijing 100084China

To produce paraffin from hydrogenation/deoxygenation of palmitic acid,model compound of bio-oil obtained by hydrothermal liquefaction(HTL)of microalgae has been an attractive focus in recent *** order to avoid energy-intensive separation process of water and bio-oil,it is of importance that deoxygenation upgrading of fatty acids under hydrothermal conditions similar to HTL ***,it is the first time to explore the application of activated carbon(AC)-supported non-noble-metal catalysts,such as Ni,Co,and Mo,and so on,in the hydrothermal hydrogenation/deoxygenation of long-chain fatty acids,and the obtained Ni/AC-H(the Ni/AC was further H_(2)pre-reduced)is one of the best *** addition,it is found that the catalytic activity can be further improved by H_(2)pre-reduction of *** results that are more low valences of nickel and oxygen vacancy can be obtained after H_(2)pre-reduction,thus significant promoting the deoxygenation especially the decarbonylation pathway of fatty *** total alkanes yield can reaches 95.9%at optimal conditions(280℃,360 min).This work confirmed that the low-priced AC-supported non-noble-metal catalysts have great potential compared with the noble-metal catalyst,in hydrothermal upgrading of bio-oil.

关键词： Bio-oil Fatty acids Deoxygenation Hydrothermal upgrading

Effect of Interface Form on Creep Failure and Life of Dissimilar Metal Welds Involving Nickel-Based Weld Metal and Ferritic Base Metal

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Chinese Journal of Mechanical Engineering 2024年第1期37卷 265-285页

作者： Xiaogang Li Junfeng Nie Xin Wang Kejian Li Haiquan Zhang Institute of Nuclear and New Energy Technology Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of EducationTsinghua UniversityBeijing 100084China Department of Mechanical Engineering Tsinghua UniversityBeijing 100084China

For dissimilar metal welds(DMWs)involving nickel-based weld metal(WM)and ferritic heat resistant steel base metal(BM)in power plants,there must be an interface between WM and BM,and this interface suffers mechanical and microstructure mismatches and is often the rupture location of premature *** this study,a new form of WM/BM interface form,namely double Y-type interface was designed for the *** behaviors and life of DMWs containing double Y-type interface and conventional I-type interface were compared by finite element analysis and creep tests,and creep failure mechanisms were investigated by stress-strain analysis and microstructure *** applying double Y-type interface instead of conventional I-type interface,failure location of DMW could be shifted from the WM/ferritic heat-affected zone(HAZ)interface into the ferritic HAZ or even the ferritic BM,and the failure mode change improved the creep life of *** interface premature failure of I-type interface DMW was related to the coupling effect of microstructure degradation,stress and strain concentrations,and oxide notch on the WM/HAZ *** creep failure of double Y-type interface DMW was the result of Type IV fracture due to the creep voids and micro-cracks on fine-grain boundaries in HAZ,which was a result of the matrix softening of HAZ and lack of precipitate pinning at fine-grain *** double Y-type interface form separated the stress and strain concentrations in DMW from the WM/HAZ interface,preventing the trigger effect of oxide notch on interface failure and inhibiting the interfacial microstructure *** is a novel scheme to prolong creep life and enhance reliability of DMW,by means of optimizing the interface form,decoupling the damage factors from WM/HAZ interface,and then changing the failure mechanism and shifting the failure location.

关键词： Dissimilar metal weld Nickel-based weld metal Ferritic heat resistant steel Interface Creep strain Microstructure Failure mechanism Creep life

Large-disturbance Stability Analysis of Power Systems with Synchronous Generator and Converter-interfaced Generation

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Journal of Modern Power Systems and Clean Energy 2024年第3期12卷 997-1002页

作者： Lei Chen Yong Min Liangshuai Hao Guangzheng Xing Yalou Li Shiyun Xu Department of Electrical Engineering Tsinghua UniversityBeijing 100084China China Electric Power Research Institute Beijing 100192China

This letter studies large-disturbance stability of the power system with a synchronous generator(SG)and a converter-interfaced generation(CIG)connected to infinite *** power system is multi-timescale and first *** is shown that the boundary of region of attraction(ROA)of the simplified model is composed of stable manifolds of unstable equilibrium point(UEP)or semi-singular point(SSP),named anchor points,and singular surface *** type of anchor point determines the dominant instability pattern of the power *** the anchor point is UEP or SSP,the dominant instability pattern is the instability of rotor angle of SG or the instability of phase-locked loop and outer control loop(OCL)of CIG,*** of dominant instability pattern can be analyzed with the relative position relationship between UEP and *** effect of OCL is *** the OCL is activated,the ROA becomes smaller and the system is more prone to instability of *** is necessary to consider the OCL when studying the large-disturbance stability of the power system.

关键词： Converter-interfaced generation large-disturbance stability outer control loop phase-locked loop synchronous generator voltage source converter

Novel self-assembled porous yolk-shell NiO nanospheres with excellent electrochromic performance for smart windows

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Particuology 2024年第1期84卷 72-80页

作者： Baoshun Wang Ya Huang Siming Zhao Run Li Di Gao Hairong Jiang Rufan Zhang beijing Key Laboratory of Green Chemical Reaction Engineering and Technology Department of Chemical EngineeringTsinghua UniversityBeijing100084China

With the rapid development of optoelectronics,electrochromic(EC)materials(ECMs)with the advan-tages of low power consumption,easy viewing,high contrast ratio,etc have attached more and more attention from the fields of smart windows,electronic billboards,emerging wearable and portable electronics,and other next-generation *** oxide(NiO)is a promising candidate for high-performance ECMs because of its neutral-colored states and low ***,NiO-based ECMs still face the problem of slow switching speed due to their low electrical conductivity and small lattice ***-organic frameworks(MOFs)are promising candidates to fabricate hollow and porous transition metal oxides(TMOs)with high ion transport efficiency,excellent specific capacitance,and electrochemical *** this work,porous yolk-shell NiO nanospheres(PYS-NiO NSs)were syn-thesized via a solvothermal and subsequent calcination process of Ni-MOF,which exhibited outstanding EC *** the large specific surface areas and hollow porous nanostructures were conducive to ionic transport,PYS-NiO NSs exhibited a fast coloring/bleaching speed(3.6/3.9 s per one coloring/bleaching cycle)and excellent cycling stability(82%of capacity retention after 3000 cycles).These superior EC properties indicated that the PYS-NiO NSs was a promising candidate for high-performance EC *** work provides a new and feasible strategy for the efficient preparation of TMOs ECMs with good EC performance,especially fast switching speed.

关键词： Electrochromic Nickel oxide Metal-organic frameworks Hollow structure Smart windows