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Primary dendrite growth kinetics and rapid solidification mechanism of highly undercooled Ti-Al alloys

Journal of Materials Science & Technology 2020年第5期40卷 47-53页

作者： z.c.luo H.P.Wang Department of Applied Physics Northwestern Polytechnical UniversityXi’an 710072China

The rapid solidification processes of undercooled Ti-(47,50,54)at.%Al alloys were investigated by electromagnetic levitation(EML)method combined with a high-speed photoelectric detector.The maximum undercoolings of the three liquid alloys were 376 K,352 K and 316 K,respectively.Recalescence processes corresponding to the primary dendrite growth and subsequent phase transition were recorded at various undercoolings.The primary dendrite growth velocity V meets a double exponential relationship with the undercooling T.Besides,a novel formula with physical meaning is proposed to explain that the more ordered liquid metal atoms accelerate the primary dendrite growth.Three recalescences are found at all undercoolings for Ti-47 at.%Al alloy and at high undercoolings for Ti-50 at.%Al alloy.The microstructures of solidified Ti-47 at.%Al alloys successively appear as coarse lamellar dendrites and finally evolve to refined parallel lamellar dendrites with the increasing undercooling.When T rises,the microstructures of solidified Ti-50 at.%Al alloys appear from coarse primary dendrites and interdendritic dendrites to refined lamellar dendrites.In the process from low undercooling to high undercooling,the primary phase of undercooled Ti-54 at.%Al alloys changes from r-Ti(r)to r-TiAl(r)and the microstructures of solidified alloys evolve from spherical primary dendrites and matrix phases to cellular dendrite phases.Meanwhile,for the Ti-(47,50)at.%Al,the transformation temperature of metastable intermediateγphase decreases with the increase of undercooling.Moreover,the microhardness of the three solidified alloys reaches the maximum when the undercoolings are 185 K,270 K and 316 K,respectively.

关键词： Electromagnetic levitation Rapid solidification Dendrite growth Microstructure Microhardness

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Asymmetrical Fault current calculation Method and Influencing Factors Analysis of Droop-controlled Inverters

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cSEE Journal of Power and Energy Systems 2024年第2期10卷 562-573页

作者： Huimin zhao zhikang Shuai Jun Ge An luo Weimin Wu z.John Shen college of Electrical and Information Engineering Hunan UniversityChangsha 410006China Electrical Engineering Department Shanghai Maritime UniversityShanghai 201306China Department of Electrical and computer Engineering Ilinois Institute of TechnologyChicagoIL 60616 USA

Since the fault dynamic of droop-controlled inverter is different from synchronous generators (SGs), protection devices may become invalid, and the fault overcurrent may damage power electronic devices and threaten the safety of the microgrid. Therefore, it is imperative to conduct a comprehensive fault analysis of the inverter to guide the design of protection schemes. However, due to the complexity of droop control strategy, existing literatures have simplified asymmetric fault analysis of droop-controlled inverters to varying degrees. Therefore, accurate fault analysis of a droop-controlled inverter is needed. In this paper, by analyzing the control system, an accurate fault model is established. Based on this, a calculation method for instantaneous asymmetrical fault current is proposed. In addition, the current components and current characteristics are analyzed. It was determined that fault currents are affected by control loops, fault types, fault distance and nonlinear limiters. In particular, the influences of limiters on the fault model, fault current calculation and fault current characteristics were analyzed. Through detailed analysis, it was found that dynamics of the control loop cannot be ignored, the fault type and fault distance determine fault current level, and part of the limiters will totally change the fault current trend. Finally, calculation and experimental results verify the correctness of the proposed method.

关键词： Asymmetrical fault analysis droop control fault current calculation method limiter transient fault characteristics

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HI in High Gas-phase Metallicity Dwarf Galaxy WISEA J230615.06+143927.9

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Research in Astronomy and Astrophysics 2024年第1期24卷 292-299页

作者： Yan Guo c.Sengupta T.c.Scott P.Lagos Y.luo Purple Mountain Observatory Chinese Academy of SciencesNanjing 210023China School of Astronomy and Space Sciences University of Science and Technology of ChinaHefei 230026China Institute of Astrophysics and Space Sciences(IA Porto) Rua das Estrelas4150-762PortoPortugal

We present resolved Giant Metrewave Radio Telescope H I observations of the high gas-phase metallicity dwarf galaxy WISEA J230615.06+143927.9(z = 0.005)(hereafter J2306) and investigate whether it could be a Tidal Dwarf Galaxy(TDG) candidate. TDGs are observed to have higher metallicities than normal dwarfs. J2306 has an unusual combination of a blue g-r color of 0.23 mag, irregular optical morphology and high-metallicity(12 +log(O/H) = 8.68 ± 0.14), making it an interesting galaxy to study in more detail. We find J2306 to be an H I rich galaxy with a large extended, unperturbed rotating H I disk. Using our H I data we estimated its dynamical mass and found the galaxy to be dark matter(DM) dominated within its H I radius. The quantity of DM, inferred from its dynamical mass, appears to rule out J2306 as an evolved TDG. A wide area environment search reveals J2306 to be isolated from any larger galaxies which could have been the source of its high gas metallicity. Additionally, the H I morphology and kinematics of the galaxy show no indication of a recent merger to explain the high-metallicity.Further detailed optical spectroscopic observations of J2306 might provide an answer to how a seemingly ordinary irregular dwarf galaxy achieved such a high level of metal enrichment.

关键词： galaxies:abundances galaxies:dwarf galaxies:irregular radio lines:galaxies radio lines:ISM

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New structure transistors for advanced technology node cMOS Ics

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National Science Review 2024年第3期11卷 24-41页

作者： Qingzhu zhang Yongkui zhang Yanna luo Huaxiang Yin Integrated circuit Advanced Process R&D center Institute of Microelectronics of Chinese Academy of Sciences(IMECAS) State key Lab of Fabrication Technologies for Integrated circuits Institute of Microelectronics of Chinese Academy of Sciences School of Integrated circuits University of Chinese Academy of Sciences

Over recent decades, advancements in complementary metal-oxide-semiconductor integrated circuits(Ics)have mainly relied on structural innovations in transistors. From planar transistors to the fin field-effect transistor(FinFET) and gate-all-around FET(GAAFET), more gate electrodes have been added to three-dimensional(3D) channels with enhanced control and carrier conductance to provide higher electrostatic integrity and higher operating currents within the same device footprint. Beyond the 1-nm node, Moore's law scaling is no longer expected to be applicable to geometrical shrinkage. Vertical transistor stacking, e.g. in complementary FETs(cFET), 3D stack(3DS) FETs and vertical-channel transistors(VFET), for enhanced density and variable circuit or system design represents a revolutionary scaling approach for sustained Ic development. Herein, innovative works on specific structures, key process breakthroughs, shrinking cell sizes and design methodologies for transistor structure research and development are reviewed. Perspectives on future innovations in advanced transistors with new channel materials and operating theories are also discussed.

关键词： transistor cMOS GAAFET cFET 3DS FET

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Reply to “Beyond microbial carbon use efficiency”

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National Science Review 2024年第4期11卷 35-37页

作者： Feng Tao Johannes Lehmann Ying-Ping Wang Lifen Jiang Bernhard Ahrens Kostiantyn Viatkin Stefano Manzoni Benjamin z.Houlton Yuanyuan Huang Xiaomeng Huang Yiqi luo Department of Ecology and Evolutionary Biology Cornell University Soil and crop Sciences Section School of Integrative Plant ScienceCornell University cSIRO Environment Max Planck Institute for Biogeochemistry Department of Physical Geography and Bolin centre for climate Research Stockholm University Department of Global Development Cornell University Key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Department of Earth System Science Ministry of Education Key Laboratory for Earth System Modelling Institute for Global Change Studies Tsinghua University

In their commentary, Xiao et al.[1]cautioned that the conclusions on the critical role of microbial carbon use efficiency (cUE) in global soil organic carbon (SOc) storage in the paper by Tao et al.[2] might be too simplistic.They claimed that Tao et al.’s study lacked mechanistic consideration of SOc formation and excluded important data sets.Xiao et al. brought up important points,which can be largely reconciled with our findings by understanding the differences in expressing processes in empirical studies and in models.

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Elevated brain temperature under severe heat exposure impairs cortical motor activity and executive function

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Journal of Sport and Health Science 2024年第2期13卷 233-244页

作者： Xiang Ren Tan Mary c.Stephenson Sharifah Badriyah Alhadad Kelvin W.z.Loh Tuck Wah Soong Jason K.W.Lee Ivan c.c.Low Health and Social Sciences Singapore Institute of TechnologySingapore 138683Singapore Human Potential Translational Research Programme Yong Loo Lin School of MedicineNational University of SingaporeSingapore 117597Singapore centre for Translational Magnetic Resonance Research Yong Loo Lin School of MedicineNational University of SingaporeSingapore 117549Singapore Department of Physiology Yong Loo Lin School of MedicineNational University of SingaporeSingapore 117593Singapore Heat Resilience and Performance centre Yong Loo Lin School of MedicineNational University of SingaporeSingapore 117510Singapore N.1 Institute for Health National University of SingaporeSingapore 117456Singapore campus for Research Excellence and Technological Enterprise(cREATE) Singapore 138602Singapore

Background:Excessive heat exposure can lead to hyperthermia in humans,which impairs physical performance and disrupts cognitive function.While heat is a known physiological stressor,it is unclear how severe heat stress affects brain physiology and function.Methods:Eleven healthy participants were subjected to heat stress from prolonged exercise or warm water immersion until their rectal temperatures(T_(re))attained 39.5℃,inducing exertional or passive hyperthermia,respectively.In a separate trial,blended ice was ingested before and during exercise as a cooling strategy.Data were compared to a control condition with seated rest(normothermic).Brain temperature(T_(br)),cerebral perfusion,and task-based brain activity were assessed using magnetic resonance imaging techniques.Results:T_(br)in motor cortex was found to be tightly regulated at rest(37.3℃±0.4℃(mean±SD))despite fluctuations in T_(re).With the development of hyperthermia,T_(br)increases and dovetails with the rising T_(re).Bilateral motor cortical activity was suppressed during high-intensity plantarflexion tasks,implying a reduced central motor drive in hyperthermic participants(T_(re)=38.5℃±0.1℃).Global gray matter perfusion and regional perfusion in sensorimotor cortex were reduced with passive hyperthermia.Executive function was poorer under a passive hyperthermic state,and this could relate to compromised visual processing as indicated by the reduced activation of left lateral-occipital cortex.conversely,ingestion of blended ice before and during exercise alleviated the rise in both T_(re)and T_(bc)and mitigated heat-related neural perturbations.conclusion:Severe heat exposure elevates T_(br),disrupts motor cortical activity and executive function,and this can lead to impairment of physical and cognitive performance.

关键词： Brain functional activity cognition Heat stress Hyperthermia Motor function

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Optimization of biofuel supply chain integrated with petroleum refineries under carbon trade policy

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Frontiers of chemical Science and Engineering 2024年第3期18卷 113-122页

作者： Wenhui zhang Yiqing luo Xigang Yuan chemical Engineering Research center School of Chemical Engineering and TechnologyTianjin UniversityTianjin300350China State Key Laboratory of chemical Engineering Tianjin UniversityTianjin300350China

The use of fossil fuels results in significant carbon dioxide emissions.Biofuels have been increasingly adopted as sustainable alternatives to fossil fuel to address this environmental issue.Integrating petroleum refineries into biofuel supply chains is an effective approach to mitigating greenhouse gas emissions and improving environmental sustainability.In this study,an integrated supply chain optimization framework was established,considering the carbon trade policy.In addition,a mixed-integer nonlinear programming model was developed to optimize the selection of biomass suppliers,construction of pretreatment plants and biorefineries,integration of petroleum refineries,and selection of transportation routes with the objective of minimizing the total annual cost.An example is presented to illustrate the applicability of the model.The optimization results show that integrating petroleum refineries into biofuel supply chains effectively mitigates carbon emissions.carbon trade policies can have a direct impact on the total annual cost and carbon emissions of the supply chain.

关键词： renewable energy biofuel supply chain carbon trade policy

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Effect of Axial Force on Seismic Performance of Prestressed High-strength concrete Piles

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Shenyang Jianzhu Daxue Xuebao (ziran Kexue Ban)/Journal of Shenyang Jianzhu University (Natural Science) 2024年第3期40卷 423-431页

作者： Yang z. Gai c. School of civil Engineering Shenyang Jianzhu University Shenyang 110168 China

To study the seismic performance of prestressed high-strength concrete pipe piles under axial force and reciprocating load,the finite element software ABAQUS is used to simulate the prestressed high-strength concrete pipe piles,and compared with existing experimental results. On the basis of verifying the accuracy of the model,the effects of axial compression ratio,the presence or absence of ordinary steel bars,and the diameter of ordinary steel bars on the hysteresis curve, skeleton curve,stiffness degradation,ductility,and energy dissipation capacity of prestressed high-strength concrete pipe piles are studied. The research results show that the configuration of ordinary steel bars can improve the bearing capacity and ductility of prestressed high-strength concrete pipe piles,with little impact on stiffness;as the axial compression ratio increases,the bearing capacity of prestressed high-strength concrete pipe piles gradually increases,but the ductility worsens. When the axial compression ratio is 0. 45,the prestressed high-strength concrete pipe piles undergo brittle failure,and the axial compression ratio of the prestressed high-strength concrete pipe piles should not exceed 0. 3. © 2024 Editorial Department of Journal of Shenyang Jianzhu University (Natural Sciences). All rights reserved.

关键词： axial compression ratio hysteresis curve prestressed high-strength concrete pipe pile seismic performance

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Enhanced photocatalytic performance of Bi_(2)O_(2)cO_(3)/Bi_(4)O_(5)Br_(2)/reduced graphene oxide z-schemehe terojunction via a one-pot room-temperature synthesis

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Journal of Environmental Sciences 2024年第4期138卷 418-427页

作者： Xiaoge Wu Lei Yan Rongrong Qin Qikai zhang Wei Yang Xiaozhi Wang Yongcai zhang Min luo Jianhua Hou college of Environmental Science and Engineering Yangzhou UniversityYangzhouJiangsu 225009China Jiangsu collaborative Innovation center for Solid Organic Waste Resource Utilization Nanjing 210095China Beijing Xinfeng Aerospace Equipment co. Ltd.Beijing 100854China Beijing System Design Institute of Electro-Mechanic Engineering Beijing 100005China college of chemistry and chemical Engineering Ningxia UniversityYinchuanNingxia 750021China

Bi_(2)O_(2)cO_(3)(BOc)/Bi_(4)O_5Br_(2)(BOB)/reduced graphene oxide(rGO)z-scheme heterojunction with promising photocatalytic properties was synthesized via a facile one-pot room-temperature method.Ultra-thin nanosheets of BOc and BOB were grown in situ on r GO.The formed 2D/2D direct z-scheme heterojunction of BOc/BOB with oxygen vacancies(OVs)effectively leads to lower negative electron reduction potential of BOB as well as higher positive hole oxidation potential of BOc,showing improved reduction/oxidation ability.Particularly,rGO is an acceptor of the electrons from the conduction band of BOc.Its dual roles significantly improve the transfer performance of photo-induced charge carriers and accelerate their separation.With layered nanosheet structure,rich OVs,high specific surface area,and increased utilization efficiency of visible light,the multiple synergistic effects of BOc/BOB/rGO can achieve effective generation and separation of the electron-holes,thereby generating more·O_(2)^(-)and h^(+).The photocatalytic reduction efficiency of cO_(2)to cO(12.91μmol/(g·hr))is three times higher than that of BOc(4.18μmol/(g·hr)).Moreover,it also achieved almost 100%removal of Rhodamine B and cyanobacterial cells within 2 hours.

关键词： Bi_(2)O_(2)cO_(3) Bi_(4)O_(5)Br_(2) Reduced graphene oxide z-scheme heterojunction Photocatalysis cO_(2)reduction

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AWells-Riley/based cOVID-19 infectiousrisk assessment model combining both short rangeandroom scale effects

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Building Simulation 2024年第1期17卷 93-111页

作者： Yinshuai Feng Yifan Fan Xiaoyu luo Jian Ge college of civil Engineering and Architecture Zhejiang UniversityHangzhouChina center for Balance Architecture Zhejiang UniversityHangzhouChina International Research center for Green Building and Low-carbon city International CampusZhejiang UniversityHainingChina

There is growing evidence of the high transmission potential of cOVID-19 through virus-laden aerosols.Because aerosols are inhaled in various concentrations,an overall assessment of transmission risks at different indoor scales is crucial.However,a comprehensive risk assessment method that evaluates the direct link between short-range and room-scale zones is stl lacking.In this paper,a risk assessment model combining both short-range and room-scale effects is developed to obtain effective reproduction number in confined indoor environments,called Turbulent Jet Wells Riley(TJWR)model.combined with the viral load data and aerosol generation data of different human respiratory activities,the Monte carlo simulation method is applied to calculate the quanta emission rate,which further provides the input parameters of the TJWR model.Three known outbreaks(Hangzhou banquet hall X,Guangzhou restaurant Y,and Hong Kong restaurant z,china)are chosen to validate the TJWR model.Results show that the TJWR model is more efficient than the original Wells-Riley model.The average relative error of the TJWR model ranges between 9%and 44%,while for the Wells-Riley model,it ranges between 57%and 78%.The TJWR model also proves that infection risk assessments using the well-mixed assumption can systematically underestimate the transmission risk for those close to the source.Additionally,there is a significant positive linear correlation between the total number of exposed individuals at the short-range and the effective reproduction number.This newly developed TJWR model has great potential for rapid and real-time overall airborne transmission risk assessment in buildings and cities.

关键词： cOVID-19 airborne transmission infection risk Wells-Riley model Monte carlo simulation

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