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Essentially Commuting Truncated Toeplitz Operators

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Acta Mathematica Sinica,English Series 2024年第10期40卷 2453-2480页

作者： Xi zhao Tao yu School of Mathematics and Science Hebei GEO University School of Mathematical Sciences Dalian University of Technology

A model space is a subspace of the Hardy space which is invariant under the backward shift,and a truncated Toeplitz operator is the compression of a Toeplitz operator on some model space. In this paper we prove a necessary and sufficient condition for the commutator of two truncated Toeplitz operators on a model space to be compact.

关键词： 47B32 47B35 commutator compact operator maximal ideal space model space Truncated Toeplitz operator

Characteristics of a pre-combustion plasma jet igniter

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Chinese Journal of Aeronautics 2024年第7期37卷 178-189页

作者： Jinlu yu Baowen ZHANG Yang yu Bingbing {2. Lei ZHANG Aviation Engineering School Air Force Engineering UniversityXi’an 710038China Equipment Management and Unmanned Aerial Vehicle Engineering School Air Force Engineering UniversityXi’an 710038China

Plasma ignition technology has delivered good performance in the aerospace industry. In this study, a pre-combustion plasma jet igniter was designed, and its characteristics were examined from three aspects: the morphology, temperature, and discharge characteristics and process of ignition. Images of the OH distribution were obtained by using an OH Planar Laser-Induced Fluorescence(OH-PLIF) experimental system. Results have shown that the proposed plasma jet had a higher OH concentration, longer length, and larger area than those of a traditional igniter. The stability of discharge of the igniter was improved as the equivalence ratio φ was increased, and reducing gas flow reduced the pulsation of the plasma jet. When the input current was increased from 15A to 35 A, the highest average temperature increased from 512. K to 7987 K. An increase in the equivalence ratio reduced the region of arc ionization, but expanded the regions of the core combustion reaction and the outer flame. Herein, this study has obtained a deep understanding of the jet and ignition law and developed a new idea for the application of plasma in the ignition field.A pre-combustion plasma jet igniter can significantly improve the efficiency of ignition and shorten the ignition process compared with a traditional igniter.

关键词： Pre-combustion plasma igniter Plasma Jet temperature field Ignition process Arc Flame

Chord length sampling correction analysis for dispersion fuel in Monte Carlo simulation

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Nuclear Science and Techniques 2024年第4期35卷 57-64页

作者： zhao-yu Liang Ding She yu-Tong Wen Lei Shi Institute of Nuclear and New Energy Technology(INET) Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of EducationTsinghua UniversityBeijing 100084China

Dispersion fuels,knowned for their excellent safety performance,are widely used in advanced reactors,such as hightemperature gas-cooled *** with deterministic methods,the Monte Carlo method has more advantages in the geometric modeling of stochastic *** explicit modeling method has high computational accuracy and high computational *** chord length sampling(CLS)method can improve computational efficiency by sampling the chord length during neutron transport using the matrix chord length?s probability density *** study shows that the excluded-volume effect in realistic stochastic media can introduce certain deviations into the CLS.A chord length correction approach is proposed to obtain the chord length correction factor by developing the Particle code based on equivalent transmission *** numerical analysis against reference solutions from explicit modeling in the RMC code,it was demonstrated that CLS with the proposed correction method provides good accuracy for addressing the excludedvolume effect in realistic infinite stochastic media.

关键词： Stochastic media Monte Carlo Chord length sampling Excluded-volume effect Chord length correction

Mobility and dynamic erosion process of granular flow:insights from numerical investigation using material point method

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Journal of Mountain Science 2024年第8期21卷 2713-2738页

作者： yu Fangwei SU Lijun LI Xinpo zhao yu Institute of Mountain Hazards and Environment Chinese Academy of SciencesChengdu 610299China University of Chinese Academy of Sciences Beijing 100049China China-Pakistan Joint Research Center on Earth Sciences Islamabad 45320Pakistan Center for Excellence in Tibetan Plateau Earth Sciences Chinese Academy of SciencesBeijing 100101China College of Civil Engineering and Architecture Zhejiang UniversityHangzhou 310058China MOE Key Laboratory of Soft Soil and Geoenvironmental Engineering Zhejiang UniversityHangzhou 310058China

In order to understand the dynamics of granular flow on an erodible base soil,in this paper,a series of material point method-based granular column collapse tests were conducted to investigate numerically the mobility and dynamic erosion process of granular flow subjected to the complex settings,i.e.,the aspect ratio,granular mass,friction and dilatancy resistance,gravity and presence of water.A set of power scaling laws were proposed to describe the final deposit characteristics of granular flow by the relations of the normalized run-out distance and the normalized final height of granular flow against the aspect ratio,being greatly affected by the complex geological settings,e.g.,granular mass,the friction and dilatancy resistance of granular soil,and presence of water in granular *** index of the coefficient of friction of granular soil was defined as a ratio of the target coefficient of friction over the initial coefficient of friction to quantify the scaling extent of friction change(i.e.,friction strengthening or weakening).There is a characteristic aspect ratio of granular column corresponding to the maximum mobility of granular flow with the minimum index of the apparent coefficient of *** index of the repose coefficient of friction of granular flow decreased gradually with the increase in aspect ratio because higher potential energy of granular column at a larger aspect ratio causes a larger kinetic energy of granular soil to weaken the friction of granular soil as a kind of velocity-related friction *** increase in granular mass reduces gradually the indexes of the apparent and repose coefficients of friction of granular soil to enhance the mobility of granular *** mobility of granular flow increases gradually with the decrease in friction angle or increase in dilatancy angle of granular ***,the increase of gravity accelerates granular flow but showing the same final deposit profile without any dependence on ***

关键词： Column collapse Granular flow Granular soil Material point method Mobility Numerical tests

Deep kernel extreme learning machine classifier based on the improved sparrow search algorithm

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The Journal of China Universities of Posts and Telecommunications 2024年第3期31卷 15-29页

作者： zhao Guangyuan Lei yu School of Automation Xi'an University of Posts and TelecommunicationsXi'an 710000China

In the classification problem,deep kernel extreme learning machine(DKELM)has the characteristics of efficient processing and superior performance,but its parameters optimization is *** improve the classification accuracy of DKELM,a DKELM algorithm optimized by the improved sparrow search algorithm(ISSA),named as ISSA-DKELM,is proposed in this *** at the parameter selection problem of DKELM,the DKELM classifier is constructed by using the optimal parameters obtained by ISSA *** order to make up for the shortcomings of the basic sparrow search algorithm(SSA),the chaotic transformation is first applied to initialize the sparrow ***,the position of the discoverer sparrow population is dynamically adjusted.A learning operator in the teaching-learning-based algorithm is fused to improve the position update operation of the ***,the Gaussian mutation strategy is added in the later iteration of the algorithm to make the sparrow jump out of local *** experimental results show that the proposed DKELM classifier is feasible and effective,and compared with other classification algorithms,the proposed DKELM algorithm aciheves better test accuracy.

关键词： deep kernel extreme learning machine(DKELM) improved sparrow search algorithm(ISSA) classifier parameters optimization

Atomic Ni directional-substitution on ZnIn_(2.S_(4) nanosheet to achieve the equilibrium of elevated redox capacity and efficient carrier-kinetics performance in photocatalysis

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Journal of Energy Chemistry 2024年第1期88卷 272-281,I0007页

作者： Haibin Huang Guiyang yu Xingze zhao Boce Cui Jinshi yu Chenyang zhao Heyuan Liu Xiyou Li School of Materials Science and Engineering China University of Petroleum(East China)Qingdao 266580ShandongChina Key Laboratory of Optic-electric Sensing and Analytical Chemistry for Life Science(MOE) College of Chemistry and Molecular EngineeringQingdao University of Science and TechnologyQingdao 266042ShandongChina College of New Energy China University of Petroleum(East China)Qingdao 266580ShandongChina

It is a challenge to coordinate carrier-kinetics performance and the redox capacity of photogenerated charges synchronously at the atomic level for boosting photocatalytic ***,the atomic Ni was introduced into the lattice of hexagonal ZnIn_(2.S_(4) nanosheets(Ni/ZnIn_(2.S_(4))via directionalsubstituting Zn atom with the facile hydrothermal *** electronic structure calculations indicate that the introduction of Ni atom effectively extracts more electrons and acts as active site for subsequent reduction *** the optimized light absorption range,the elevation of Efand ECBendows Ni/ZnIn_(2.S_(4) photocatalyst with the increased electron concentration and the enhanced reduction ability for surface ***,ultrafast transient absorption spectroscopy,as well as a series of electrochemical tests,demonstrates that Ni/ZnIn_(2.S_(4) possesses 2.15 times longer lifetime of the excited charge carriers and an order of magnitude increase for carrier mobility and separation efficiency compared with pristine ZnIn_(2.S_(4).These efficient kinetics performances of charge carriers and enhanced redox capacity synergistically boost photocatalytic activity,in which a 3-times higher conversion efficiency of nitrobenzene reduction was achieved upon Ni/ZnIn_(2.S_(4).Our study not only provides in-depth insights into the effect of atomic directional-substitution on the kinetic behavior of photogenerated charges,but also opens an avenue to the synchronous optimization of redox capacity and carrier-kinetics performance for efficient solar energy conversion.

关键词： ZnIn_(2.S_(4) Substitution Carrier kinetics Redox capacity Photocatalysis

Probing the Kinematic Signatures of Planet Formation in the Gas Disk of MWC 480

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Research in Astronomy and Astrophysics 2024年第6期24卷 110-118页

作者： Min zhao Haochuan yu Zhengxiang Li Department of Astronomy Beijing Normal UniversityBeijing 100875China Sub-department of Astrophysics Department of PhysicsUniversity of OxfordOxfordOX13RHUK

The disk around MWC 480 has shown multiple substructures in both dust and gas observations,possibly suggesting ongoing planet formation in *** this paper,we explore the gas kinematics of the MWC 480 disk by analyzing the archival Atacama Large Millimeter/submillimeter Array observations of^(12.CO(J=2.1),^(13)CO(J=2.1),and C^(18)O(J=2.1).By modeling the line-of-sight velocities,inferred from the Doppler shifts of the emission lines,we are able to decompose the three-dimensional(3D)velocity field of the disk into rotational,radial,and vertical *** analysis reveals the presence of large-scale gas flows in the(r,z)***,we identify potential meridional flows across various heights as traced by all three CO isotopologues in the 80–12. au region,possibly associated with ongoing planet formation activities in this ***,we find upward flows near 2.0 au for all three CO isotopologues,which may point to the presence of disk winds.

关键词： protoplanetary disks planet-disk interactions planet-star interactions

A review on covalent organic frameworks for rechargeable zinc-ion batteries

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Chinese Chemical Letters 2024年第7期35卷 107-120页

作者： yunyu {2. Chuntao Yang Yingjian yu College of Physics Science and Technology Kunming UniversityKunming 650214China

In recent years,rechargeable zinc-ion batteries(ZIBs)are considered to be a promising alternative to lithium-ion batteries owing to their high safety and theoretical capacity with low ***,the in-depth development of rechargeable zinc-ion batteries is restricted by a sequence of issues,such as the dissolution and structure collapse of cathode materials,the formation of by-products,severe anode corrosion,passivation,and the growth of zinc *** covalent organic frameworks(COFs)can solve the above problems to a certain extent owing to their ideal characteristics,such as rigid structure,insolubility,high porosity,and abundant active ***,as advanced materials for ZIBs,have attracted researchers'*** this review,we systematically summarized the synthesis methods of COFs and discussed the application of several advanced characterization technologies in COFs,which would provide a reference for the in-depth research of *** addition,we elucidated the use of COFs as cathode materials and anode protective layers in rechargeable ***,we discussed the challenges and solutions in the development of COF materials,which would provide constructive insights into the future direction of COFs.

关键词： Covalent organic framework Zn-ion battery Zinc dendrite Anode Cathode

Simulation of nanofluid natural convection based on single-particle hydrodynamics in energy-conserving dissipative particle dynamics(eDPD)

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Applied Mathematics and Mechanics(English Edition) 2024年第8期45卷 1429-1446页

作者： Wei LU Shuo CHEN Zhiyuan yu Jiayi {2. School of Aerospace Engineering and Applied Mechanics Tongji UniversityShanghai 200092China Shanghai Key Laboratory of Vehicle Aerodynamics and Vehicle Thermal Management Systems Tongji UniversityShanghai 201804China School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China

In the present study,the nanofliud natural convection is investigated by the energy-conserving dissipative particle dynamics(eDPD)method,where the nanoparticles are considered at the single-particle *** thermal expansion coefficientβand the viscosityμof the simulated system containing nanoparticles are calculated and found to be in close alignment with the previous simulation *** single-particle hydrodynamics in e DPD enables simulations of nanofluid natural convection with higher Rayleigh numbers and greater nanoparticle volume ***,this approach is utilized to simulate the nanoparticle distribution during the enhanced heat transfer process in the nanofluid natural *** localized aggregation of nanoparticles enhances the heat transfer performance of the nanofluid under specific Rayleigh numbers and nanoparticles volume fractions.

关键词： single-particle hydrodynamics energy-conserving dissipative particle dynamics(eDPD) nanoparticle nanofluid heat transfer