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A Case Study on the Rapid Rain-to-Snow Transition in Late Spring 2018 over Northern China:Effects of Return Flows and Topography

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Journal of Meteorological Research 2022年第1期36卷 107-127页

作者： Wenlong ZHANG Xiaopeng CUI Bolong DUAN Bo YU Runxia GUO haiwen liu Institute of Urban Meteorology China Meteorological AdministrationBeijing 100089 Key Laboratory of Cloud-Precipitation Physics and Severe Storms Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029 Lanzhou Central Meteorological Observatory Lanzhou 730020 Beijing Weather Forecast Center Beijing 100089 Department of Aviation Meteorology Civil Aviation University of ChinaTianjin 300300 University of Chinese Academy of Sciences Beijing 100049

Phase changes in the precipitation processes of early winter and late spring in midlatitude regions represent challenges when forecasting the timing and magnitude of snowfall.On 4 April 2018,a heavy snow process occurred in Beijing and northwestern Hebei Province,becoming the most delayed occurrence of heavy spring snow ever recorded over Beijing in the last 30 years.This paper uses observational and numerical simulation data to investigate the causes for the rapid rain-to-snow(RRTS)phase transition during this process.The following results are obtained.(1)Return flows(RFs),an interesting type of easterly wind,including those at 1000,925,and 800 hPa,played an important role in this heavy snow process and presented a characteristic"sandwich"structure.The RFs,complex topography,and snow particles that dominated the clouds,were the three key factors for the RRTS transition.(2)The RRTS transition in the plains was directly related to the RF at 925 hPa,which brought about advective cooling initiated approximately 4-6 h before the onset of precipitation.Then,the RF played a role of diabatic cooling when snow particles began to fall at the onset of precipitation.(3)The RRTS transition in the northern part of the Taihang Mountains was closely related to the relatively high altitude that led to a lower surface temperature owing to the vertical temperature lapse rate.Both immediately before and after the onset of precipitation,the snow particles in clouds entrained the middle-level cold air downward,causing the melting layer(from surface to the 0℃-isotherm level)to become very thin;and thus the snow particles did not have adequate time to melt before falling to the ground.(4)The rapid RRTS over the Yanqing mountainous area in the northwest of Beijing could have involved all the three concurrent mechanisms:the advective cooling of RF,the melting cooling of cloud snow particles,and the high-altitude effect.Compared with that in the plain area with less urbanization the duration of the RRTS in the plain area with significant

关键词： midlatitude heavy snow return flow phase transition Bohai Sea cold pool complex terrain numerical simulation

Moiréflat bands of twisted few-layer graphite

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Frontiers of physics 2023年第1期18卷 97-104页

作者： Zhen Ma Shuai Li Meng-Meng Xiao Ya-Wen Zheng Ming Lu haiwen liu Jin-Hua Gao XCXie School of Physics and Wuhan National High Magnetic Field Center Huazhong University of Science and TechnologyWuhan 430074China International Center for Quantum Materials School of PhysicsPeking UniversityBeijing 100871China Beijing Academy of Quantum Information Sciences Beijing 100193China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of SciencesBeijing 100190China Center for Advanced Quantum Studies Department of PhysicsBeijing Normal UniversityBeijing 100875China

We report that the twisted few layer graphite(tFL-graphite)is a new family of moiréheterostructures(MHSs),which has richer and highly tunable moiréflat band structures entirely distinct from all the known MHSs.A tFL-graphite is composed of two few-layer graphite(Bernal stacked multilayer graphene),which are stacked on each other with a small twisted angle.The moiréband structure of the tFL-graphite strongly depends on the layer number of its composed two van der Waals layers.Near the magic angle,a tFL-graphite always has two nearly flat bands coexisting with a few pairs of narrowed dispersive(parabolic or linear)bands at the Fermi level,thus,enhances the DOS at EF.This coexistence property may also enhance the possible superconductivity as been demonstrated in other multiband superconductivity systems.Therefore,we expect strong multiband correlation effects in tFL-graphite.Meanwhile,a proper perpendicular electric field can induce several isolated nearly flat bands with nonzero valley Chern number in some simple tFL-graphites,indicating that tFL-graphite is also a novel topological flat band system.

关键词： few-layer graphite flat band moiréheterostructures

Impact of 1.5°C and 2.0°C global warming on aircraft takeoff performance in China

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Science Bulletin 2018年第11期63卷 700-707页

作者： Tianjun Zhou Liwen Ren haiwen liu Jingwen Lu LASG Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China University of Chinese Academy of Sciences Beijing 100049China Department of Aviation Meteorology Civil Aviation University of ChinaTianjin 300300China

Associated with global warming, climate extremes such as extreme temperature will significantly increase. Understanding how climate change will impact the airflights is important to the planning of future flight operations. In this study, the impacts of 1.5 and 2 degree's global warming on the aircraft takeoff performance in China are investigated using a unique climate projection data from an international collaboration project named HAPPI. It is found that the mean summer daily maximum temperature, which is a major factor that affects the flight through changing the aircraft's takeoff weight, will increase significantly with magnitude less than 1.5℃ over most parts of China except for the Tibetan Plateau. The half a degree additional global warming will lead to higher extreme temperature in the arid and semi-arid western China, the Tibetan Plateau and the northeastern China, while the change in eastern China is weak. Five airports including Beijing, Shanghai, Kunming, Lasa and Urumqi will see ～1.0°-2.0℃(1.4°-3.0℃) higher daily maximum temperature under 1.5℃(2.0℃) scenario. The half-degree additional warming will lead to a shift toward higher extreme temperature in these five sites. For both1.5° and 2.0℃ scenarios, the number of weight-restriction days will increase significantly at 3 airports including Beijing, Shanghai, and Lasa. Urumqi will witness an increase of weight-restriction days only in 2.0℃ future.

关键词：起飞性能中国温暖飞机极端温度气候变化飞行操作 Lasa

Double-frequency Aharonov-Bohm effect and non-Abelian braiding properties of Jackiw-Rebbi zero-mode

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National Science Review 2020年第3期7卷 572-578页

作者： Yijia Wu haiwen liu Jie liu Hua Jiang X.C.Xie International Center for Quantum Materials School of Physics Peking University Beijing Academy of Quantum Information Sciences Center for Advanced Quantum Studies Department of Physics Beijing Normal University School of Physical Science and Technology Soochow University Department of Applied Physics School of ScienceXi'an Jiaotong University CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences

Ever since its first proposal in 1976, Jackiw-Rebbi zero-mode has been drawing extensive attention for its charming properties including charge fractionalization, topologically protected zero-energy and possible non-Abelian statistics. We investigate these properties through the Jackiw-Rebbi zero-modes in quantum spin Hall insulators. Though charge fractionalization is not manifested, Jackiw-Rebbi zero-mode’s zero-energy nature leads to a double-frequency Aharonov-Bohm effect, implying that it can be viewed as a special case of Majorana zero-mode without particle-hole symmetry. Such relation is strengthened for Jackiw-Rebbi zero-modes also exhibiting non-Abelian properties in the absence of superconductivity.Furthermore, in the condition that the degeneracy of Jackiw-Rebbi zero-modes is lifted, we demonstrate a novel non-Abelian braiding with continuously tunable fusion rule, which is a generalization of Majorana zero-modes’ braiding properties.

关键词： Jackiw-Rebbi zero-mode Aharanov-Bohm effect non-Abelian statistics Majorana zero-mode

Tailoring the multiscale mechanics of tunable decellularized extracellular matrix (dECM) for wound healing through immunomodulation

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Bioactive Materials 2023年第10期28卷 95-111页

作者： Pu Luo Ruoxuan Huang You Wu Xingchen liu Zhengjie Shan Li Gong Shudan Deng haiwen liu Jinghan Fang Shiyu Wu Xiayi Wu Quan liu Zetao Chen Kelvin W.K.Yeung Wei Qiao Shoucheng Chen Zhuofan Chen Hospital of Stomatology Sun Yat-sen UniversityGuangdong Provincial Key Laboratory of StomatologyGuangdong Research Center for Dental and Cranial Rehabilitation and Material EngineeringGuangzhou510055China Department of Orthopaedics and Traumatology Li Ka Shing Faculty of MedicineThe University of Hong KongHong Kong Special Administrative Region Instrumental Analysis Research Center Sun Yat-sen UniversityGuangzhou510275China Applied Oral Sciences and Community Dental Care Faculty of DentistryThe University of Hong KongHong Kong Special Administrative Region Shenzhen Key Laboratory for Innovative Technology in Orthopaedic Traum1 The University of Hong Kong-Shenzhen HospitalShenzhen518058China

With the discovery of the pivotal role of macrophages in tissue regeneration through shaping the tissue immune microenvironment, various immunomodulatory strategies have been proposed to modify traditional biomaterials. Decellularized extracellular matrix (dECM) has been extensively used in the clinical treatment of tissue injury due to its favorable biocompatibility and similarity to the native tissue environment. However, most reported decellularization protocols may cause damage to the native structure of dECM, which undermines its inherent advantages and potential clinical applications. Here, we introduce a mechanically tunable dECM prepared by optimizing the freeze-thaw cycles. We demonstrated that the alteration in micromechanical properties of dECM resulting from the cyclic freeze-thaw process contributes to distinct macrophage-mediated host immune responses to the materials, which are recently recognized to play a pivotal role in determining the outcome of tissue regeneration. Our sequencing data further revealed that the immunomodulatory effect of dECM was induced via the mechnotrasduction pathways in macrophages. Next, we tested the dECM in a rat skin injury model and found an enhanced micromechanical property of dECM achieved with three freeze-thaw cycles significantly promoted the M2 polarization of macrophages, leading to superior wound healing. These findings suggest that the immunomodulatory property of dECM can be efficiently manipulated by tailoring its inherent micromechanical properties during the decellularization process. Therefore, our mechanics-immunomodulation-based strategy provides new insights into the development of advanced biomaterials for wound healing.

关键词： Wound healing Decellularized extracellular matrix Freeze-thaw treatment Multiscale mechanics Macrophage polarization Immunomodulation Mechanotransduction

Effective spin dephasing mechanism in confined two-dimensional topological insulators

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Science China(Physics,Mechanics & Astronomy) 2016年第7期59卷 70-75页

作者： JunJie Qi haiwen liu Hua Jiang XinCheng Xie Institute of Physics Chinese Academy of Sciences Beijing 100190 China Center for Advanced Quantum Studies Department of Physics Beijing Normal University Beijing 100875 China College of Physics optoelectronics and Energy Soochow University Suzhou 215006 China International Center for Quantum Materials and School of Physics Peking University Beijing 100871 China Collaborative Innovation Center of Quantum Matter Beijing 100871 China

A Kramers pair of helical edge states in quantum spin Hall effect(QSHE) is robust against normal dephasing but not robust to spin dephasing. In our work, we provide an effective spin dephasing mechanism in the puddles of two-dimensional(2D) QSHE, which is simulated as quantum dots modeled by 2D massive Dirac Hamiltonian. We demonstrate that the spin dephasing effect can originate from the combination of the Rashba spin-orbit coupling and electron-phonon interaction, which gives rise to inelastic backscattering in edge states within the topological insulator quantum dots, although the time-reversal symmetry is preserved throughout. Finally,we discuss the tunneling between extended helical edge states and local edge states in the QSH quantum dots, which leads to backscattering in the extended edge states. These results can explain the more robust edge transport in In As/Ga Sb QSH systems.

关键词：量子自旋退相干绝缘体二维拓扑机制电子-声子相互作用时间反演对称性

Log-periodic quantum oscillations in topological or Dirac materials

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Frontiers of physics 2019年第2期14卷 39-43页

作者： Huichao Wang Yanzhao liu haiwen liu Jian Wang International Center for Quantum Materials School of PhysicsPeking UniversityBeijing 100871China Collaborative Innovation Center of Quantum Matter Beijing 100871China Department of Applied Physics The Hong Kong Polytechnic UniversityKowloonHong KongChina Center for Advanced Quantum Studies Department of PhysicsBeijing Normal UniversityBeijing 100875China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of SciencesBeijing 100190China

As a manifestation of the underlying physical nature, quailtum oscillations with the applied magnetic field (B) are one of the most important topics in condensed matter physics. The research history can be tracked to 1930 when Lev Shubnikov and W. J. de Haas observed Shubnikov-de Haas (SdH) oscillations in the magnetoresistance (MR) of bismuth crystals. Since then, researchers have observed quantum oscillations in diverse materials, including metals, metallic compounds, semimetals, semiconductors and even insula tors, as well as in artificial mesoscopic microstructures . Nowadays, quantum oscillation detec ted by magneto transport investigation has been a powerful tool to detect the physical properties in solid-state systems.

关键词： Dirac materials Log-periodic quantum oscillations magnetoresistance (MR)

Amplification of the Solar Signal in the Summer Monsoon Rainband in China by Synergistic Actions of Different Dynamical Responses

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Journal of Meteorological Research 2017年第1期31卷 61-72页

作者： Liang ZHAO Jingsong WANG haiwen liu Ziniu XIAO State Key Laboratory of Numerical Modeling for Atmosphere Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 National Climate Center China Meteorological Administration Beijing 100081 China National Center for Space Weather Beijing 100081 Department of Aviation Meteorology Civil Aviation University of China Tianjin 300300

A rainband meridional shift index （RMSI） is defined and used to statistically prove that the East Asian summer monsoon rainband is usually significantly more northward in the early summer of solar maximum years than that of solar minimum years. By applying continuous wavelet transform, cross wavelet transform, and wavelet coherence, it is found that throughout most of the 20th century, the significant decadal oscillations of sunspot number （SSN） and the RMSI are phase-locked and since the 1960s, the SSN has led the RMSI slightly by approximately 1.4 yr. Wind and Eliassen-Palm （EP） flux analysis shows that the decadal meridional oscillation of the June rainband likely re- sults from both a stronger or earlier onset of the tropical monsoon and poleward shift of the subtropical westerly jet in high-solar months of May and June. The dynamical responses of the lower tropical monsoon and the upper subtropical westerly jet to the 11-yr solar cycle transmit bottom-up and top-down solar signals, respectively, and the synergistic actions between the monsoon and the jet likely amplify the solar signal at the northern boundary of the monsoon to some extent.

关键词： solar cycle rainband East Asian summer monsoon decadal variability EP flux precipitation

Quantum to classical crossover under dephasing effects in a two-dimensional percolation model

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Science China(Physics,Mechanics & Astronomy) 2020年第2期63卷 130-134页

作者： Junjie Qi haiwen liu Chui-Zhen Chen Hua Jiang X.C.Xie International Center for Quantum Materials and School of Physics Peking UniversityBeijing 100871China Collaborative Innovation Center of Quantum Matter Beijing 100871China Center for Advanced Quantum Studies Department of PhysicsBeijing Normal UniversityBeijing 100875China Institute for Advanced Study and School of Physical Science and Technology Soochow UniversitySuzhou 215006China

Scaling theory predicts complete localization in d = 2 in quantum systems belonging to the orthogonal class(i.e., with timereversal symmetry and spin-rotation symmetry). The conductance g behaves as g^exp(-L/l) with system size L and localization length l in the strong disorder limit. However, classical systems can always have metallic states in which Ohm’s law shows a constant g in d=2. We study a two-dimensional quantum percolation model by controlling dephasing effects. The numerical investigation of g aims at simulating a quantum-to-classical percolation evolution. An unexpected metallic phase, where g increases with L, generates immense interest before the system becomes completely classical. Furthermore, the analysis of the scaling plot of g indicates a metal-insulator crossover.

关键词： quantum percolation model dephasing effects metal-insulator crossover