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Journal of Oceanology and Limnology 2024年第3期42卷 709-714页

作者： Xudong Zhang Xiaofeng LI Key Laboratory of Ocean Observation and Forecasting Key Laboratory of Ocean Circulation and WavesInstitute of OceanologyChinese Academy of SciencesQingdao 266071China

Internal solitary waves(ISW),characterized by large amplitude and long propagation distance,are widespread in global oceans.While remote sensing images have played an essential role in studying ISWs,they mainly exploit two-dimensional image information.However,with the launch of the surface water ocean topography(SWOT)satellite on December 16,2022,a unique opportunity has emerged to capture wide-swath three-dimensional ISW-induced sea surface information.In this study,we examine ISWs in the Andaman Sea using data from the Ka-band Radar Interferometer(KaRIN),a crucial sensor onboard SWOT.KaRIN not only provides backscattering satellite images but also employs synthetic aperture interferometry techniques to retrieve wide-swath two-dimensional sea surface height measurements.Our observations in the Andaman Sea revealed the presence of ISWs characterized by dark-bright strips and surface elevation solitons.The surface soliton has an amplitude of 0.32 m,resulting in an estimation of ISW amplitude of approximately 60 m.In contrast to traditional two-dimensional satellite images or nadir-looking altimetry data,the SWOT mission’s capability to capture threedimensional sea surface information represents a significant advancement.This breakthrough holds substantial promise for ISW studies,particularly in the context of ISW amplitude inversion.

关键词： internal solitary wave(ISW) surface water ocean topography(SWOT) altimeter

Oceanic internal waves generated by the Tongan volcano eruption

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Acta Oceanologica Sinica 2022年第8期41卷 1-4页

作者： Xudong Zhang Xiaofeng Li Key Laboratory of Ocean Circulation and Waves Institute of OceanologyChinese Academy of SciencesQingdao 266071China Center for Ocean Mega-Science Chinese Academy of SciencesQingdao 266071China

Internal waves(IW)are widely distributed at the marginal seas or continental shelves(Liu et al.,2013;Zhao and Alford,2006;Zheng et al.,2007).They have an amplitude of up to hundreds of meters and wave crests of severa... 详细信息

关键词： eruption environments ocean

Real‑Time Predictive Control of Path Following to Stabilize Autonomous Electric Vehicles Under Extreme Drive Conditions

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Automotive Innovation 2022年第4期5卷 453-470页

作者： Ningyuan Guo Xudong Zhang Yuan Zou Beijing Collaborative and Innovative Center for Electric Vehicle and School of Mechanical Engineering Beijing Institute of TechnologyNo.5 Zhongguancun South StreetHaidian DistrictBeijing 100081China School of Mechatronic Engineering and Automation Foshan UniversityFoshan 528225China

A novel real-time predictive control strategy is proposed for path following(PF)and vehicle stability of autonomous electric vehicles under extreme drive conditions.The investigated vehicle configuration is a distributed drive electric vehicle,which allows to independently control the torques of each in-wheel motor(IWM)for superior stability,but bringing control com-plexities.The control-oriented model is established by the Magic Formula tire function and the single-track vehicle model.For PF and direct yaw moment control,the nonlinear model predictive control(NMPC)strategy is developed to minimize PF tracking error and stabilize vehicle,outputting front tires’lateral force and external yaw moment.To mitigate the calcu-lation burdens,the continuation/general minimal residual algorithm is proposed for real-time optimization in NMPC.The relaxation function method is adopted to handle the inequality constraints.To prevent vehicle instability and improve steering capacity,the lateral velocity differential of the vehicle is considered in phase plane analysis,and the novel stable bounds of lateral forces are developed and online applied in the proposed NMPC controller.Additionally,the Lyapunov-based constraint is proposed to guarantee the closed-loop stability for the PF issue,and sufficient conditions regarding recursive feasibility and closed-loop stability are provided analytically.The target lateral force is transformed as front steering angle command by the inversive tire model,and the external yaw moment and total traction torque are distributed as the torque commands of IWMs by optimization.The validations prove the effectiveness of the proposed strategy in improved steering capacity,desirable PF effects,vehicle stabilization,and real-time applicability.

关键词： Closed-loop stability Extreme drive conditions Fast optimization Nonlinear model predictive control Path following Vehicle stability bounds

Flow and thermal modeling of liquid metal in expanded microchannel heat sink

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Frontiers in Energy 2023年第6期17卷 796-810页

作者： Mingkuan zhang Xudong Zhang Luna GUO Xuan LI Wei RAO Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control School of Mechanical EngineeringTianjin University of TechnologyTianjin 300384China National Demonstration Center for Experimental Mechanical and Electrical Engineering Education Tianjin University of TechnologyTianjin 300384China Key Laboratory for Thermal Science and Power Engineering of the Ministry of Education Department of Engineering MechanicsTsinghua UniversityBeijing 100084China School of Mechanical Engineering Tianjin University of CommerceTianjin 300134China Institute of Refrigeration and Cryogenics Shanghai Jiao Tong UniversityShanghai 200240China Beijing Key Laboratory of CryoBiomedical Engineering and Key Laboratory of Cryogenics Beijing 100190China

Liquid metal-based microchannel heat sinks (MCHSs) suffer from the low heat capacity of coolant, resulting in an excessive temperature rise of coolant and heat sink when dealing with high-power heat dissipation. In this paper, it was found that expanded space at the top of fins could distribute the heat inside microchannels, reducing the temperature rise of coolant and heat sink. The orthogonal experiments revealed that expanding the top space of channels yielded similar temperature reductions to changing the channel width. The flow and thermal modeling of expanded microchannel heat sink (E-MCHS) were analyzed by both using the 3-dimensional (3D) numerical simulation and the 1-dimensional (1D) thermal resistance model. The fin efficiency of E-MCHS was derived to improve the accuracy of the 1D thermal resistance model. The heat conduction of liquid metal in Z direction and the heat convection between the top surface of fins and the liquid metal could reduce the total thermal resistance (Rt). The above process was effective for microchannels with low channel aspect ratio, low mean velocity (Um) or long heat sink length. The maximum thermal resistance reduction in the example of this paper reached 36.0%. The expanded space endowed the heat sink with lower pressure, which might further reduce the pumping power (P). This rule was feasible both when fins were truncated (h_(2) 0).

关键词： liquid metal cooling heat sink expanded microchannel flow and thermal modeling

Flavonoid scutellarin positively regulates root length through NUTCRACKER

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Plant Diversity 2021年第3期43卷 248-254页

作者： Xing Huang Weiqi Li Xudong Zhang Germplasm Bank of Wild Species Kunming Institute of BotanyChinese Academy of SciencesKunming650201China University of the Chinese Academy of Sciences Beijing100049China

Exploring approaches to regulate meristem is of special importance and broad interest.In this study,we found that the flavonoid scutellarin,which has a 6-hydroxyl and a 7-glucoside,increased root length through the transcription factor NUTCRACKER(NUC).This root lengthening disappeared in NUCknockout and reappeared in NUC-rescue plants.Scutellarin induced NUC expression and promoted the division of cortex/endodermal initials.In contrast,naringenin,which has same chemical backbone but without 6-hydroxyl and with 7-hydroxyl group,showed the opposite or no effects.Our results demonstrate that scutellarin promotes root length through NUC-mediated regulatory pathways and reveal that flavonoids with and without the 6-hydroxyl and 7-glucoside have positive and negative effects on meristem size,respectively。

关键词： Root length Meristem size Flavonoid Scutellarin Naringenin NUTCRACKER

Agonistic Memory,Compound Temporality and Expansion of Literary Space in Lu Xun

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Frontiers of Literary Studies in China-Selected Publications from Chinese Universities 2019年第2期13卷 200-261页

作者： Xudong Zhang Departments of Comparative Literature and East Asian Studies New York University New York NY 10003 USA

The paper examines the ways in which memory is constructed in Lu Xun's writings, above all his essay (zawen) by means of an artistic staging of its antagonism with forgetting. The author emphasizes the primacy of forgetting, as opposed to recollection conventi on ally understood, as the centrality of Lu Xun's stressful, tragic principle of memory. The author argues that, by turning to forgetting as a register of and formal-spatial space for historical and political content, Lu Xun puts his signature stylistic maneuvers and mannerisms in full display. Hence,"memory for the sake of forgetting" must be understood literally, that is, as forgetting functioning as a heightened and intensified form of social protest, albeit in modernistic rather than realistic terms;and through this pressurized and agonistic inner space of convoluted temporality. Furthermore, the author seeks to show that forgetting also serves a representational function that goes hand-in-hand with Lu Xun's zawen as poetics and chronicle all at once.In Lu Xun's writing of reminiscence, that which fails to be repressed into silenee, despair and oblivion roars back from the depth of an existential void, and reorganizes historical experiences of chaos and danger into a more powerful and intimate encasement and mimesis of reality. Thus, in Lu Xun, a modernist intervention into nothingness makes palpable history's own structure of conflict, oppression and impasse which simultaneously stands for a metaphysics of defiance and hope.

关键词： memoire involontaire modernism the essay (zdwen) forgetting representation metaphysics of hope

Real‑Time Optimal Trajectory Planning for Autonomous Driving with Collision Avoidance Using Convex Optimization

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Automotive Innovation 2023年第3期6卷 481-491页

作者： Guoqiang Li Xudong Zhang Hongliang Guo Basilio Lenzo Ningyuan Guo School of Mechanical Engineering Beijing Institute of TechnologyBeijing 100081China Institute for Infocomm Research ASTARSingaporeSingapore Department of Industrial Engineering University of PadovaPaduaItaly

An online trajectory planning method for collision avoidance is proposed to improve vehicle driving safety and comfort simultaneously.The collision-free trajectory for autonomous driving is formulated as a nonlinear optimization problem.A novel approximate convex optimization approach is developed for the online optimal trajectory in both longitudinal and lateral directions.First,a dual variable is used to model the non-convex collision-free constraint for driving safety and is calculated by solving a dual problem of the relative distance between vehicles.Second,the trajectory is further optimized in a model predictive control framework considering the safety.It realizes continuous-time and dynamic feasible motion with collision avoidance.The geometry of object vehicles is described by polygons instead of circles or ellipses in traditional methods.In order to avoid aggressive maneuver in the longitudinal and lateral directions for driving comfort,rates of the acceleration and the steering angle are restricted.The final formulated optimization problem is convex,which can be solved by using quadratic programming solvers and is computationally efficient for online application.Simulation results show that this approach can obtain similar driving performance compared to a state-of-the-art nonlinear optimization method.Furthermore,various driving scenarios are tested to evaluate the robustness and the ability for handling complex driving tasks.

关键词： Trajectory planning Collision avoidance Model predictive control Autonomous driving

Analysis on fluid permeability of dendritic mushy zone during peritectic solidification in a temperature gradient

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Journal of Materials Science & Technology 2021年第12期71卷 169-176页

作者： Peng Peng Jinmian Yue Anqiao zhang Xudong Zhang Yuanli Xu Institute of Materials Science and Engineering Lanzhou UniversityLanzhou730000China School of Physical Science and Technology Lanzhou UniversityLanzhou730000China

Compared with the growing applications of peritectic alloys,none research on the fluid permeability K of dendritic network during peritectic solidification has been reported before.The fluid permeability K of dendritic network in the mushy zone during directional solidification of Sn-Ni peritectic alloy was investigated in this study.Examination on the experimental results demonstrates that both the temperature gradient zone melting(TGZM)and Gibbs-Thomson(G–T)effects have obvious influences on the morphology of dendritic network during directional solidification.This is realized through different stages of liquid diffusion within dendritic mushy zone by these effects during directional solidification.The TGZM effect is demonstrated to play a more important role as compared with the G–T effect during directional solidification.Besides,it is shown that the evolution of dendrite network is more complex during peritectic solidification due to the involvement of the peritectic phase.Through the specific surface SV,analytical expression based on the Carman–Kozeny model was proposed to analyze the fluid permeability of dendritic mushy zone in directionally solidified peritectic alloys.In addition,it is interesting to find a rise in permeability K after peritectic reaction in both theoretical predication and experimental results,which is different from that in other alloys.The theoretical predictions show that this rise in fluid permeability K after peritectic reaction is caused by the remelting/resolidification process on dendritic structure by the TGZM and G–T effects during peritectic solidification.

关键词： Alloys Diffusion behaviour Directional solidification Peritecticm icrostructures Solid/liquid interface

Macrosegregation and thermosolutal convection-induced freckle formation in dendritic mushy zone of directionally solidified Sn-Ni peritectic alloy

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Journal of Materials Science & Technology 2021年第16期75卷 21-26页

作者： Peng Peng Anqiao zhang Jinmian Yue Xudong Zhang Yuanli Xu Institute of Materials Science and Engineering Lanzhou UniversityLanzhou730000China School of Physical Science and Technology Lanzhou UniversityLanzhou730000China

Compared with the growing applications of peritectic alloy,none research on the freckle formation during peritectic solidification has been reported before.Observation on the dendritic mushy zone of Sn-36 at.%Ni peritectic alloy during directional solidification at different growth velocities shows that the freckles are formed in two different regions:region I before peritectic reaction and region II after peritectic reaction.In addition,more freckles can be observed at lower growth velocities.Examination on the experimental results demonstrates that both the temperature gradient zone melting(TGZM)and Gibbs-Thomson(G–T)effects have obvious influences on the morphology of dendritic network during directional solidification.The current theories onKI Rayleigh number Racharacterizing the thermosolutal convection of dendritic mushy zone to predict freckle formation through the maximum of Ra can only explain the existence of region I while the appearance of region II after peritectic reaction cannot be predicted.Thus,a new Rayleigh number RaP is proposed in consideration of evolution of dendritic mushy zone by both effects and peritectic reaction.Theoretical prediction of RaPalso shows a maximum after peritectic reaction in addition to that before peritectic reaction,thus,agreeing well with the freckle formation in region II.In addition,more severe thermosolutal convection can be predicted by the new Rayleigh number RaP at lower growth velocities,which further demonstrates the reliability of RaP in describing the dependence of freckle formation on growth velocity.

关键词： Directional solidification Thermosolutal convection Dendritic solidification Peritectic microstructures

Identification of ring current proton precipitation driven by scattering of electromagnetic ion cyclotron waves

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Fundamental Research 2023年第2期3卷 257-264页

作者： Binbin Ni Yang zhang xudong Gu Department of Space Physics School of Electronic InformationWuhan UniversityWuhanHubei 430072China CAS Center for Excellence in Comparative Planetology Hefei 230026China MNR Key Laboratory for Polar Science Polar Research Institute of ChinaShanghai 200136China

Among the most intense emissions in the Earth's magnetosphere,electromagnetic ion cyclotron(EMIC)waves are regarded as a critical candidate contributing to the precipitation losses of ring current protons,which however lacks direct multi-point observations to establish the underlying physical connection.Based upon a robust conjunction between the satellite pair of Van Allen Probe B and NOAA-19,we perform a detailed analysis to capture simultaneous enhancements of EMIC waves and ring current proton precipitation.By assuming that the ring current proton precipitation is mainly caused by EMIC wave scattering,we establish a physical model between the wave-driven proton diffusion and the ratio of precipitated-to-trapped proton count rates,which is subsequently applied to infer the intensity of EMIC waves required to cause the observed proton precipitation.Our simulations indicate that the model results of EMIC wave intensity,obtained using either the observed or empirical Gaussian wave frequency spectrum,are consistent with the wave observations,within a factor of 1.5.Our study therefore strongly supports the dominant contribution of EMIC waves to the ring current proton precipitation,and offers a valuable means to construct the global profile of EMIC wave intensity using low-altitude NOAA POES proton measurements,which generally have a broad L-shell coverage and high time resolution in favor of near-real-time conversion of the global EMIC wave distribution.

关键词： Electromagnetic ion cyclotron waves Ring current protons Wave-particle interactions Conjugate observations Precipitation losses