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Chinese Physics Letters 2024年第4期41卷 45-50页

作者：蓝志强李章顺徐浩然刘凡金钻明彭滟朱亦鸣 Terahertz Technology Innovation research institute Terahertz Spectrum and Imaging Technology Cooperative Innovation CenterShanghai Key Lab of Modern Optical SystemUniversity of Shanghai for Science and TechnologyShanghai 200093China

Using THz emission spectroscopy,we investigate the elementary spin dynamics in ferromagnetic single-layer Fe on a sub-picosecond *** demonstrate that THz radiation changes its polarity with reversal of the magnetization applied by the external magnetic *** addition,it is found that the sign of THz polarity excited from different sides is defined by the thickness of the Fe layer and Fe/dielectric *** on the thickness and symmetry dependences of THz emission,we experimentally distinguish between the two major contributions:ultrafast demagnetization and the anomalous Hall *** experimental results not only enrich understanding of THz electromagnetic generation induced by femtosecond laser pulses but also provide a practical way to access laser-induced ultrafast spin dynamics in magnetic structures.

关键词： magnetic magnetization polarity

Assessment of corrected time-step method for nominal ionospheric gradient calculation: A comparative analysis with spatial approaches

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Earth and Planetary Physics 2024年第4期8卷 641-649页

作者： Slamet Supriadi Prayitno Abadi Susumu Saito Harry Bangkit Dwiko Unggul Prabowo Adi Purwono Ginaldi Ari Nugroho research Center for Smart Mechatronics National Research and Innovation Agency(BRIN)BandungIndonesia research Center for Climate and atmosphere BRINBandungIndonesia School of Electrical Engineering Telkom UniversityKab.BandungIndonesia Electronic Navigation research institute National Institute of MaritimePort and Aviation TechnologyTokyoJapan research Center for Space BRINBandungIndonesia

The effect of ionospheric delay on the ground-based augmentation system under normal conditions can be mitigated by determining the value of the nominal ionospheric gradient(σvig).The nominal ionospheric gradient is generally obtained from Continuously Operating Reference Stations data by using the spatial single-difference method(mixed-pair,station-pair,or satellite-pair)or the temporal single-difference method(time-step).The time-step method uses only a single receiver,but it still contains ionospheric temporal *** introduce a corrected time-step method using a fixed-ionospheric pierce point from the geostationary equatorial orbit satellite and test it through simulations based on the global ionospheric *** also investigate the effect of satellite paths on the corrected time-step method in the region of the equator,which tends to be in a more north–south direction and to have less coverage for the east–west ionospheric *** study also addresses the limitations of temporal variation correction coverage and recommends using only the correction from *** processes are developed under simulations because observational data are still difficult to *** findings demonstrate that the corrected time-step method yieldsσvig values consistent with other approaches.

关键词： ground-based augmentation system nominal ionospheric gradient time-step correction global ionospheric model

Roles of Upper-Level Descending Inflow in Moat Development in Simulated Tropical Cyclones with Secondary Eyewall Formation

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Advances in Atmospheric Sciences 2024年第6期41卷 1100-1114页

作者： Nannan QIN Liguang WU Nanjing Joint institute for Atmospheric Sciences Nanjing 210041China Shanghai Typhoon institute China Meteorological AdministrationShanghai 200030China Department of Atmospheric and Oceanic Sciences and institute of Atmospheric Sciences Fudan UniversityShanghai 200438China Innovation Center of Ocean and atmosphere System Zhuhai Fudan Innovation Research InstituteZhuhai 518057China

This study investigated the effects of upper-level descending inflow(ULDI)associated with inner-eyewall convection on the formation of the moat in tropical cyclones(TCs)with secondary eyewall formation(SEF).In our numerical experiments,a clear moat with SEF occurred in TCs with a significant ULDI,while no SEF occurred in TCs without a significant *** eyewall convection developed more vigorously in the control run.A ULDI occurred outside the inner-eyewall convection,where it was symmetrically *** ULDI was initially triggered by the diabatic warming released by the inner eyewall and later enhanced by the cooling below the anvil *** ULDI penetrated the outer edge of the inner eyewall with relatively dry air and prevented excessive solid-phase hydrometeors from being advected further *** produced extensive sublimation cooling of falling hydrometeors between the eyewall and the outer *** sublimation cooling resulted in negative buoyancy and further induced strong subsidence between the eyewall and the outer *** a result,a clear moat was *** of the moat in the ongoing SEF prevented the outer rainband from moving farther inward,helping the outer rainband to symmetrize into an outer *** the sensitivity experiment,no significant ULDI formed since the eyewall convection was weaker,and the eyewall anvil developed relatively lower,meaning the formation of a moat and thus an outer eyewall was less *** study suggests that a better-represented simulation of inner-eyewall convective structures and distribution of the solid-phase hydrometeors is important to the prediction of SEF.

关键词： tropical cyclone secondary eyewall formation upper-level descending inflow eyewall convection

Seasonal Variation of the Sea Surface Temperature Growth Rate of ENSO

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Advances in Atmospheric Sciences 2024年第3期41卷 465-477页

作者： Xinyi XING Xianghui FANG Da PANG Chaopeng JI Department of Atmospheric and Oceanic Sciences and institute of Atmospheric Sciences Fudan UniversityShanghai 200438China Shanghai Frontiers Science Center of atmosphere-Ocean Interaction Shanghai 200438China Shanghai Key Laboratory of Ocean-land-atmosphere Boundary Dynamics and Climate Change Fudan UniversityShanghai 200438China

El Ni?o–Southern Oscillation(ENSO) exhibits a distinctive phase-locking characteristic, first expressed during its onset in boreal spring, developing during summer and autumn, reaching its peak towards winter, and decaying over the next spring. Several studies have demonstrated that this feature arises as a result of seasonal variation in the growth rate of ENSO as expressed by the sea surface temperature(SST). The bias towards simulating the phase locking of ENSO by many state-of-the-art climate models is also attributed to the unrealistic depiction of the growth rate. In this study, the seasonal variation of SST growth rate in the Ni?o-3.4 region(5°S–5°N, 120°–170°W) is estimated in detail based on the mixed layer heat budget equation and recharge oscillator model during 1981–2020. It is suggested that the consideration of a variable mixed layer depth is essential to its diagnostic process. The estimated growth rate has a remarkable seasonal cycle with minimum rates occurring in spring and maximum rates evident in autumn. More specifically, the growth rate derived from the meridional advection(surface heat flux) is positive(negative) throughout the year. Vertical diffusion generally makes a negative contribution to the evolution of growth rate and the magnitude of vertical entrainment represents the smallest contributor. Analysis indicates that the zonal advective feedback is regulated by the meridional immigration of the intertropical convergence zone, which approaches its southernmost extent in February and progresses to its northernmost location in September, and dominates the seasonal variation of the SST growth rate.

关键词： SST growth rate intertropical convergence zone zonal advective feedback mixed layer depth ENSO seasonal variation

Are Solar Active Regions Born with Neutralized Currents?

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research in Astronomy and Astrophysics 2024年第7期24卷 82-91页

作者： Aiying Duan Yaoyu Xing Chaowei Jiang Planetary Environmental and Astrobiological research Laboratory (PEARL) School of Atmospheric SciencesSun Yat-sen University Yunnan Key Laboratory of the Solar Physics and Space Science Key Laboratory of Tropical atmosphere-Ocean System Sun Yat-sen UniversityMinistry of Education institute of Space Science and Applied Technology Harbin Institute of Technology

Solar active regions(ARs) are formed by the emergence of current-carrying magnetic flux tubes from below the photosphere. Although for an isolated flux tube the direct and return currents flowing along the tube should balance with each other, it remains controversial whether such a neutralization of currents is also maintained during the emergence process. Here we present a systematic survey of the degrees of the current neutralization in a large sample of flux-emerging ARs which appeared on the solar disk around the central meridian from 2010 to *** vector magnetograms taken by Helioseismic and Magnetic Imager onboard Solar Dynamic Observatory are employed to calculate the distributions of the vertical current density at the photosphere. Focusing on the main phase of flux emergence, i.e., the phase in which the total unsigned magnetic flux is continuously increased, we statistically examined the ratios of direct to return currents in all the ARs. Such a large-sample statistical study suggests that most of the ARs were born with currents close to neutralization. The degree of current neutralization seems to be not affected by the active-region size, the active-region growing rate, and the total unsigned *** only correlation of significance as found is that the stronger the magnetic field nonpotentiality is, the further the AR deviates from current neutrality, which supports previous event studies that eruption-productive ARs often have non-neutralized currents.

关键词： Sun: corona Sun: coronal mass ejections (CMEs) Sun: flares Sun: magnetic fields

Physical mechanism of the rapid increase in intense and long-lived extreme heatwaves in the Northern Hemisphere since 1980

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Science China Earth Sciences 2024年第7期67卷 2103-2121页

作者： Yuqing WANG Wen ZHOU Chunzai WANG Key Laboratory of Polar atmosphere-ocean-ice System for Weather and Climate of the MOE Department of Atmospheric and Oceanic Sciences&Institute of Atmospheric SciencesFudan UniversityShanghai 200438China Key Laboratory for Polar Science of the MNR Polar Research Institute of ChinaShanghai 201209China State Key Laboratory of Tropical Oceanography South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China Global Ocean and Climate research Center South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China

Since 1980,both the intensity and duration of summer heatwaves in the middle and high latitudes of the Northern Hemisphere have significantly increased,leading this region to become a critical area for a significant increase in the frequency of intense and long-lived extreme *** found that stronger and more persistent high-pressure systems and lower soil moisture before the events were the main drivers of intense and long-lived extreme heatwaves in western Europe and the middle and high latitudes of North ***,in eastern Europe and Siberia,lower cloud cover before events is also a main driver of this type of extreme heatwave,in addition to the above *** factors are coupled with each other and can change heatwave intensity and duration by influencing surface radiation processes during *** the self-organizing map classification method,we found that 6 weather patterns with increased frequency,intensity,and duration were the main dynamic reasons leading to the increase in intense and long-lived extreme heatwaves after *** addition,the decrease in summer average soil moisture in most areas of the mid-high latitudes of the Northern Hemisphere and the decrease in average cloud cover in eastern Europe and Siberia are found to be the main thermodynamic reasons leading to the increase in these extreme heatwaves.

关键词： High intensity Long duration Extreme heatwaves High pressure system Soil moisture Cloud cover

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Effects of biodegradation on diamondoid distribution in crude oils from the Bongor Basin,Chad

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Energy Geoscience 2024年第2期5卷 120-128页

作者： Huanxin Song Menghan Chen Lirong Dou Dingsheng Cheng Zhigang Wen cooperative Innovation Center of Unconventional Oil and Gas Yangtze UniversityWuhanHubei430100China College of Resources and Environment Yangtze UniversityWuhanHubei430100China PetroChina research institute of Petroleum Exploration&Development Beijing100083China

The sensitivity of biodegradation on diamondoids was investigated using a series of biodegraded oil samples from the Ronier tectonic unit of Bongor Basin,*** results suggest that diamondoids,including adamantanes(As)and diamantanes(Ds),are relatively resistant to biodegradation and obvious biodegradation was observed in oils with a Peters-Moldowan(PM)biodegradation rank of 6 or ***,the sensibility of biodegradation on diamondoids is generally similar to hopanes and regular *** biodegradation evolves,the changes in concentration and components of diamondoids show that the biodegradation process is selective and *** significant increase of MD/MA and DMD/DMA for oils with a PM ranking 6t indicates that diamantanes are generally more resistant to biodegradation than *** similar trends of DMA/MA,EA/MA,MD/D,DMD/MD and other relevant indexes,show that higher alkylation homologs are more resistant to *** commonly used diamondoid ratios,such as MAI,EAI,MDI and DMID-1,are obviously affected by biodegradation at the stage of high-level biodegradation,which may indicate that these ratios should be used with caution in case of severely degraded oils.

关键词： Diamondoids Biodegradation Sensitivity Crude oil Bongor Basin Chad

Optimal search path planning of UUV in battlefeld ambush scene

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Defence Technology（防务技术） 2024年第2期32卷 541-552页

作者： Wei Feng Yan Ma Heng Li Haixiao Liu Xiangyao Meng Mo Zhou Naval research institute Beijing100161China

Aiming at the practical application of Unmanned Underwater Vehicle(UUV)in underwater combat,this paper proposes a battlefield ambush scene with UUV considering ocean ***,by establishing these mathematical models of ocean current environment,target movement,and sonar detection,the probability calculation methods of single UUV searching target and multiple UUV cooperatively searching target are given ***,based on the Hybrid Quantum-behaved Particle Swarm Optimization(HQPSO)algorithm,the path with the highest target search probability is ***,through simulation calculations,the influence of different UUV parameters and target parameters on the target search probability is analyzed,and the minimum number of UUVs that need to be deployed to complete the ambush task is demonstrated,and the optimal search path scheme is *** method proposed in this paper provides a theoretical basis for the practical application of UUV in the future combat.

关键词： Battlefield ambush Optimal search path planning UUV path Planning Probability of cooperative search

Factor analysis of recent major heatwaves in East Asia

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Geoscience Frontiers 2024年第1期15卷 374-383页

作者： Arim Yoon Jeongwon Kim Jooyeop Lee Hyun Min Sung Je-Woo Hong Seung-Ki Min Junhong Lee Jinkyu Hong Ecosystem-atmosphere Process Laboratory Department of Atmospheric SciencesYonsei UniversitySeoul 03722Republic of Korea National institute of Meteorological Sciences Jeju 63568Republic of Korea Korea Adaptation Center for Climate Korea Environment InstituteSejong 30121Republic of Korea Division of Environmental Science and Engineering Pohang University of Science and TechnologyPohang 37673Republic of Korea Max Planck institute for Meteorology Hamburg 20146Germany institute for Convergence research and Education in Advanced Technology Yonsei UniversitySeoulRepublic of Korea

Heatwaves(HWs)present a major hazard to our society and more extreme heatwaves are expected with future climatic ***,it is important to improve our understanding of the underlying processes that drive HWs,in order to boost our socioeconomic-ecological *** this study,we quantified the influences of key driving factors(large-scale atmospheric circulation,soil moisture,and sea surface temperature)and their synergies on recent heatwaves in East *** conducted a factor separation analysis for three recent HW events by constraining the key factors in the regional Weather research and Forecasting model with their climatologies or pseudo-observations in different *** study showed distinct spatial variations in the HW-controlling factors in East *** synergistic interaction of large-scale circulation and soil moisture was the most important factors in the 2013 Chinese *** the 2018 HWs in Korea and Japan,the same stagnant large-scale atmospheric circulation played a dominant role in driving the HW *** land-atmosphere coupling via soil moisture,its interaction with circulation,and SST exhibited stronger influences during the Korean HW than the Japanese *** analysis also revealed temporal variations in the factors driving Korean and Chinese HWs due to typhoon passage and other multiple processes over heterogeneous surfaces(i.e.,topographically induced Foehn winds,large-scale warm advection from the warm ocean,spatial differences in soil moisture).Our findings suggest that future heatwave-related studies should consider interactive contributions of key factors,their interplay with surface heterogeneities of complex terrain.

关键词： Heatwave East Asia Large-scale circulation Soil moisture Sea surface temperature Synergistic impacts

Multi-UAVs Collaborative Path Planning in the Cramped Environment

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IEEE/CAA Journal of Automatica Sinica 2024年第2期11卷 529-538页

作者： Siyuan Feng Linzhi Zeng Jining Liu Yi Yang Wenjie Song School of Automation Beijing Institute of TechnologyNanjing 210039China Nanjing research institute of Electronics Technology Nanjing 210039China Yichang Testing Technique research institute Yichang 443003China IEEE

Due to its flexibility and complementarity, the multiUAVs system is well adapted to complex and cramped workspaces, with great application potential in the search and rescue(SAR) and indoor goods delivery fields. However, safe and effective path planning of multiple unmanned aerial vehicles(UAVs)in the cramped environment is always challenging: conflicts with each other are frequent because of high-density flight paths, collision probability increases because of space constraints, and the search space increases significantly, including time scale, 3D scale and model scale. Thus, this paper proposes a hierarchical collaborative planning framework with a conflict avoidance module at the high level and a path generation module at the low level. The enhanced conflict-base search(ECBS) in our framework is improved to handle the conflicts in the global path planning and avoid the occurrence of local deadlock. And both the collision and kinematic models of UAVs are considered to improve path smoothness and flight safety. Moreover, we specifically designed and published the cramped environment test set containing various unique obstacles to evaluating our framework performance thoroughly. Experiments are carried out relying on Rviz, with multiple flight missions: random, opposite, and staggered, which showed that the proposed method can generate smooth cooperative paths without conflict for at least 60 UAVs in a few *** benchmark and source code are released in https://***/inin-xingtian/multi-UAVs-path-planner.

关键词： Collision avoidance conflict resolution multi-unmanned aerial vehicles(UAVs)system path planning