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A Numerical Investigation of a Slow-Moving Convective Line in a Weakly Sheared Environment

Advances in Atmospheric Sciences 2005年第5期22卷 625-639页

作者： changhai liu National Center for Atmospheric Research Boulder Colorado 80307-3000 USA

A series of three-dimensional, cloud-resolving numerical simulations are performed to examine a slowpropagating, quasi-two-dimensional convective system in a weakly sheared environment during the Tropical Rainfall Measuring Mission Large-Scale Biosphere-Atmosphere （TRMM-LBA） field campaign. The focus is on the kinematics and thermodynamics, organization mechanisms, and dynamical effects of low-level shear, ice microphysics and tropospheric humidity. The control simulation, which is initialized with the observed sounding and includes full microphysics, successfully replicates many observed features of the convective system, such as the linear structure, spatial orientation, life cycle, and sluggish translation. The system at the mature stage displays a line-normal structure similar to that associated with squalltype convective systems, but the corresponding mesoscale circulation and thermodynamic modification are much weaker. Ice-phase microphysical processes are not necessary to the formation of the convective system, but they play a non-trivial role in the late evolution stage. In contrast, the low-level shear, albeit shallow and weak, is critical to the realistic realization of the convective line. The tropospheric moisture above the planetary boundary layer has an important impact on the behavior of convective organization. In particular, a dry layer in the lower troposphere significantly suppresses convective development and inhibits the generation of organized convection even though the convective available potential energy is substantial. The free-atmosphere humidity has received little attention in previous studies of organized convection and warrants further investigation.

关键词： mesoscale convective system cloud-resolving simulation

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Influence of Magnetic Reluctances of Magnetic Elements on Servo Valve Torque Motors

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Chinese Journal of Mechanical Engineering 2016年第1期29卷 136-144页

作者： liu changhai JIANG Hongzhou School of Mechatronics Engineering Harbin Institute of Technology

The current research of electro-hydraulic servo valves mainly focuses on the vibration, pressure oscillating and source of noise. Unfortunately, literatures relating to the study of the influence of the magnetic reluctances of the magnetic elements are rarely available. This paper aims to analyze the influence of the magnetic reluctances of the magnetic elements on torque motor. Considering these magnetic reluctances ignored in previous literatures, a new mathematical model of servo valve torque motor is developed and proposed based on the fundamental laws of electromagnetism. By using this new mathematical model and the previous models, electromagnetic torque constant and magnetic spring stiffness are evaluated for a given set of torque motor parameters. A computer simulation by using AMESim software is also performed for the same set of torque motor parameters to verify the proposed model. The theoretical results of electromagnetic torque constant and magnetic spring stiffness evaluated by the proposed model render closer agreement with the simulation results than those evaluated by the previous models. In addition, an experimental measurement of the magnetic flux densities in the air-gaps is carried out by using SFL218 servo valve torque motor. Compared with the theoretical results of the magnetic flux densities in the air-gaps evaluated by the previous models, the theoretical results evaluated by the proposed model also show better agreement with the experimental data. The proposed model shows the influence of the magnetic reluctances of the magnetic elements on the servo valve torque motor, and offers modified and analytical expressions to electromagnetic torque constant and magnetic spring stiffness. These modified and analytical expressions could provide guidance more accurately for a linear control design approach and sensitivity analysis on electro-hydraulic servo valves than the previous expressions.

关键词： servo valve torque motor magnetic reluctance electromagnetic torque constant magnetic spring stiffness

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A seventh-order model for dynamic response of an electro-hydraulic servo valve

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Chinese Journal of Aeronautics 2014年第6期27卷 1605-1611页

作者： liu changhai Jiang Hongzhou Department of Fluid Control and Automation Harbin Institute of Technology

In this paper, taking two degrees of freedom on the armature–flapper assembly into account, a seventh-order model is deduced and proposed for the dynamic response of a two-stage electro-hydraulic servo valve from nonlinear equations. These deductions are based on fundamental laws of electromagnetism, fluid, and general mechanics. The coefficients of the proposed seventhorder model are derived in terms of servo valve physical parameters and fluid properties *** validating the results of the proposed model, an AMESim simulation model based on physical laws and the existing low-order models validated by other researchers through experiments are used to compare with the seventh-order model. The results show that the seventh-order model can reflect the physical behavior of the servo valve more explicitly than the existing low-order models and it could provide guidance more easily for a linear control design approach and sensitivity analysis than the AMESim simulation model.

关键词： Hydraulic control systems Nozzle–flapper Servo valve Torque motor Transfer function

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Analysis of the Structure of Different Tibetan Plateau Vortex Types

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Journal of Meteorological Research 2017年第3期31卷 514-529页

作者： Xinyuan FENG changhai liu Guangzhou FAN Jie ZHANG College of Atmospheric Sciences Chengdu University of Information Technology/Plateau Atmosphere and Environment Key Laboratory of Sichuan Province National Center for Atmospheric Research Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science &Technology

Knowledge of the structure of the Tibetan Plateau vortex （TPV） is of considerable importance for understanding the generation and development mechanisms of this mesoscale system. However, our understanding of vortex struc- tures and our ability to classify them on a physical basis is limited due to insufficient observations. The high- resolution new-generation NCEP-CFSR （Climate Forecast System Reanalysis） dataset is used in the present paper to investigate the general structural features of various types of mature TPV through classification and composite struc- ture analysis. Results indicate that the dynamic and thermodynamic structures show regional and seasonal depend- ency, as well as being influenced by attributes of translation, associated precipitation, and the South Asian high （SAH）. The common precipitating TPV （type I）, frequently occurring in the west-east-oriented zonal region between 33° and 36°N, is a notably low-level baroclinic and asymmetric system. It resides within a large-scale confluent zone and preferentially travels eastward, potentially moving out of the plateau. The heavy rain vortex （type II） corresponds to a deep vortex circulation occurring in midsummer. The low-level baroclinic sub-category （type IIa） is associated with a low-level jet and mainly originates in the area 32°-35°N, 86°-94°E, preferentially moving east of 90°E and even away from the plateau; meanwhile, the nearly upright sub-category （type IIb）, which has a cold center at low levels and a warm center at mid-upper levels, is a quasi-stationary and quasi-symmetric system favorably occurring west of 92°E. A western-pattern SAH exists in the upper troposphere for these two sub-categories. The springtime dry vortex in the western plateau （type III） is warm and shallow （approximately 100 hPa deep）, and zonal circulation dominates the large-scale environmental flows in the middle and upper troposphere. The precipitating vortex in the southern plateau occurring during July-August

关键词： Tibetan Plateau vortex vortex structure composite analysis physical classification Climate ForecastSystem Reanalysis

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Overexpression of auxin/indole-3-acetic acid gene MdIAA24 enhances Glomerella leaf spot resistance in apple(Malus domestica)

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Horticultural Plant Journal 2024年第1期10卷 15-24页

作者： Qian Wang Dong Huang Wenyan Tu Fengwang Ma changhai liu State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple College of HorticultureNorthwest A&F UniversityYanglingShaanxi 712100China

Auxin is throughout the entire life process of plants and is involved in the crosstalk with other hormones,yet its role in apple disease resistance remains *** this study,we investigated the function of auxin/indole-3-acetic acid(IAA)gene Md IAA24 overexpression in enhancing apple resistance to Glomerella leaf spot(GLS)caused by Colletotrichum fructicola(Cf).Analysis revealed that,upon Cf infection,35S::Md IAA24 plants exhibited enhanced superoxide dismutase(SOD)and peroxidase(POD)activity,as well as a greater amount of glutathione(reduced form)and ascorbic acid accumulation,resulting in less H_(2)O_(2)and superoxide anion(O_(2)^(-))in apple ***,35S::Md IAA24 plants produced more protocatechuic acid,proanthocyanidins B1,proanthocyanidins B2 and chlorogenic acid when infected with *** Cf infection,35S::Md IAA24 plants presented lower levels of IAA and jasmonic acid(JA),but higher levels of salicylic acid(SA),along with the expression of related *** overexpression of Md IAA24 was observed to enhance the activity of chitinase andβ-1,3-glucanase in Cfinfected *** results indicated the ability of Md IAA24 to regulate the crosstalk between IAA,JA and SA,and to improve reactive oxygen species(ROS)scavenging and defense-related enzymes *** jointly contributed to GLS resistance in apple.

关键词： Apple MdIAA24 Glomerella leaf spot(GLS) Antioxidant capacity Auxin Salicylic acid Jasmonic acid

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Evaluation on the applicability of ERA5 reanalysis dataset to tropical cyclones affecting Shanghai

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Frontiers of Earth Science 2022年第4期16卷 1025-1039页

作者： Zhihui HAN Caijun YUE changhai liu Wen GU Yuqi TANG Yongyu LI Shanghai Ecological Forecasting&Remote Sensing Center Shanghai 200030China Shanghai Marine Meteorological Center Shanghai 200030China National Center for Atmospheric Research Boulder CO80305USA Shanghai Baoshan Meteorological Bureau Shanghai 201900China

Based on the 16 historical tropical cyclones(TCs)affecting Shanghai from 2007 to 2019,the suitability of ERA5 for studying TCs affecting Shanghai is systematically evaluated from the perspective of TC track,intensity,10-m and upper-level wind,using TC best-track data of China Meteorological Administration and surface observations and sounding *** to tropical storm(TS),strong tropical storm(STS),typhoon(TY),strong typhoon(STY)and super typhoon(SuperTY),the median TC track bias is 68.1,52.9,42.5,25.4,and 18.2 km,respectively,the median maximum 10-m wind speed(VMAX10m)bias is-3.7,-6.5,-11.4,-21.7,and-32.2 m·s-1,respectively,and the median minimum mean sea level pressure(MSLPmin)bias is 2.2,5.6,8.1,28.2,and 48.7 hPa,*** the increase of TC intensity,the median TC track bias decreases,while the median VMAX10m and MSLPmin bias *** general,VMAX10m in ERA5 is lower than observed,and MSLPmin is larger than *** influence of TS,STS,TY and STY,the median 10-m wind speed(V10m)bias in the city is 3.2,4.2,4.7,and 5.4 m·s-1,respectively,and is 4.4-5.2 m·s-1 near the east coast,respectively.V10m is mostly biased high,showing an"M"type pattern with the distance between TC and *** median 10 m wind direction(WD10m)bias is in a range of-7° to+7°.The median upper-level wind speed(Vupper)bias decreases with height,with a maximum of~5 m·s-1 at 975 *** 900 hPa Vupperin ERA5 is typically larger than the radiosonde observation,and its mean bias error(MBE)increases with TC *** upper-level wind direction(WDupper)matches the sounding data well,with a maximum bias of a few degrees *** results provide a reference for the application of ERA5 to coastal cities affected by TCs.

关键词： ERA5 reanalysis tropical cyclone wind field urban

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Carbon dots anchored NiAl-LDH@In_(2)O_(3) hierarchical nanotubes for promoting selective CO_(2) photoreduction into CH_(4)

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Chinese Chemical Letters 2024年第6期35卷 404-408页

作者： Xiuzheng Deng changhai liu Xiaotong Yan Jingshan Fan Qian Liang Zhongyu Li Advanced Catalysis and Green Manufacturing Collaborative Innovation Center CNPC-CZU Innovation AllianceSchool of Petrochemical EngineeringChangzhou UniversityChangzhou 213164China School of Materials Science&Engineering Changzhou UniversityChangzhou 213164China

The efficient conversion of CO_(2) into hydrocarbon fuels(CH_(4))with high selectivity is considered as a great challenge in photocatalysis owing to the multiple-electron transfer pathway and competitive H_(2) ***,we developed carbon dots(CDs)-modulated S-scheme heterojunction of CDs/NiAl-LDH@In_(2)O_(3)(C-DH@IN)through a facile in-situ hydrothermal *** to the multi-shell nanotube structure,the C-DH@IN shows an enhanced CH_(4) evolution rate of 10.67μmol h^(-1)g^(-1)and higher selectivity of CH_(4)(85.70%)compared with In_(2)O_(3) and Ni Al-LDH@In_(2)O_(3) binary catalyst in the pure water without sacrificial *** spin resonance(ESR)and in situ Fourier transform infrared spectra verify that the constructed S-scheme heterojunction can possess the strong redox capability and the HCOOand CH_(3)O-as critical intermediates play an important role in selective CO_(2) reduction to generate CH_(4).Furthermore,CDs with superior photoabsorption can boost the electron transfer and absorb H^(+),thus improving the integration of H^(+)and CO_(2) ***,this work emphasizes a facile strategy to achieve efficient CO_(2)-to-CH_(4) conversion based on construction of CDs-based heterojunction catalysts.

关键词： Carbon dots In_(2)O_(3) Layered double hydroxides Photocatalytic CO_(2) reduction S-scheme

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Modelling of low-temperature exhumation rate in Dabie Mountain based on (U-Th)/He and fission-track thermochronological data

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Science China Earth Sciences 2006年第10期49卷 1009-1019页

作者： DING Ruxin ZHOU Zuyi XU changhai liu Yuzhu CHENG Hao XU Fei State Key Laboratory of Marine Geology Tongji UniversityShanghai 200092China State Key Laboratory of Marine GeologyTongji UniversityShanghai 200092China State Key Laboratory of Marine GeologyTongji UniversityShanghai 200092China State Key Laboratory of Marine GeologyTongji UniversityShanghai 200092China State Key Laboratory of Marine GeologyTongji UniversityShanghai 200092China State Key Laboratory of Marine GeologyTongji UniversityShanghai 200092China

While the high-temperature exhumation process in the Dabie Mountain has been well documented, the low-temperature exhumation of this area since Cretaceous, especially since Late Cretaceous, is relatively less studied. Low-temperature thermochronology provides one of the important approaches to solve this problem. Based on the data of fission track and (U-Th)/He analysis of apaptites and zircons from the granitoid and metamorphic rocks in the Dabie Mountain, this paper applies Mancktelow’s and Braun’s methods to estimating the exhumation rates and to drawing the regional differential exhumation pattern since Cretaceous, especially since Late Cretaceous by taking into consideration factors such as heat transport, heat advection, topography and heat production, which could influence geothermal field in the shallow crust. Since Cretaceous, the exhumation rate (0.08-0.10 km/Ma) in the region around Tiantangzhai and in the south of Tanlu fault zone is larger than the rate (0.04-0.07 km/Ma) in other areas of the Dabie Mountain. The regional differential exhumation pattern might be related to the push-up effect caused by differential strike-slip movement along NNE-trending faults.

关键词： Dabie Mountain, fission track, (U-Th)/He, modelling, exhumation.

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Electromagnetic dispersion characteristics of a high energy electron beam guided with an ion channel

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Plasma Science and Technology 2017年第2期19卷 20-27页

作者： Jixiong XIAO Zhong ZENG Zhijiang WANG Donghui XIA changhai liu Institute of fusion and plasma research Huazhong University of Science and Technology Wuhan 430074 People＇s Republic of China

Taking self-fields into consideration, dispersion properties of two types of electromagnetic modes for a high energy electron beam guided with an ion channel are investigated by using the linear perturbation theory. The dependences of the dispersion frequencies of electromagnetic waves on the electron beam radius, betatron frequency and boundary current are revealed. It is found that the electron beam radius and betatron frequency have different influences on the electromagnetic waves dispersion behavior by compared with the previous works. As the boundary current is taken into account, the TM modes will have two branches and a lowfrequency branch emerged as the new branch in strong ion channel case. This new branch has similar dispersion behavior to the betatron modes. For TE modes, there are two branches and they have different dispersion behaviors in strong ion channel case. However, in weak ion channel case, the dispersion behaviors for both of the low frequency and high frequency branches are similar.

关键词： dispersion behavior electromagnetic eigenmodes betatron oscillation ion channel

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The m6A reader MhYTP2 regulates the stability of its target mRNAs contributing to low nitrogen tolerance in apple (Malus domestica)

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Horticulture Research 2023年第6期10卷 287-298页

作者： Tianli Guo Zehua Yang Ru Bao Xiaomin Fu Na Wang changhai liu Fengwang Ma State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple College of HorticultureNorthwest A&F UniversityYanglingShaanxi 712100China

Studies have shown that the m6A reader primarily affects genes expression by participating in the regulation of mRNA localization,splicing,degradation,translation,and other metabolic ***,we discovered that the apple(Malus domestica)m6A reader MhYTP2 bound with and destabilized m6A-modified MdMLO19 *** addition,it enhanced the translation efficiency of m6A-modified mRNA of MdGDH1L,encoding a glutamate dehydrogenase,which confers resistance to powdery *** this study,we report the function of MhYTP2 in the regulation of resistance to low nitrogen(N).The overexpression of MhYTP2 enhances the resistance of apple to low *** show that MhYTP2 binds with and stabilizes the mRNAs of MdALN,which participates in the allantoin catabolic process and cellular response to N starvation in apple;MdPIDL,which participates in root hair elongation;MdTTG1,which is involved in the differentiation process of trichomes;and MdATG8A,which is a core participant in the regulation of *** addition,MhYTP2 accelerates the degradation of MdRHD3 mRNA,which regulates root *** immunoprecipitation-seq and electrophoretic mobility shift assays show that the mRNAs of MdALN,MdATG8A,MdPIDL,MdTTG1,and MdRHD3 are the direct targets of *** or knocking down the above genes in MhYTP2 overexpressing plants dismisses the function of MhYTP2 under low N,suggesting the role of MhYTP2 is dependent on those ***,these results demonstrate that MhYTP2 enhances the resistance of apple to N deficiency by affecting the stability of the bound mRNAs.

关键词： dis translation expressing

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