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Difficulties in probing density dependent symmetry potential with the HBT interferometry

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Science China(Physics,Mechanics & Astronomy) 2009年第10期52卷 1530-1535页

作者： li qingfeng SHEN CaiWan School of Science Huzhou Teachers CollegeHuzhou 313000China

Based on the updated UrQMD transport model,the effect of the symmetry potential energy on the two-nucleon HBT correlation is investigated with the help of the coalescence program for constructing clusters,and the CRAB analyzing program of the two-particle HBT *** obvious nonlinear dependence of the neutron-proton(or neutron-neutron) HBT correlation function(Cnp,nn) at small relative momenta on the stiffness factor γ of the symmetry potential energy is found:when γ 0.8,Cnp,nn increases rapidly with increasing γ,while it starts to saturate if γ *** is also found that both the symmetry potential energy at low densities and the conditions of constructing clusters at the late stage of the whole process influence the two-nucleon HBT correlation with the same power.

关键词： density dependence of the symmetry energy sensitive observables HBT correlation

Machine learning transforms the inference of the nuclear equation of state

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Frontiers of physics 2023年第6期18卷 33-37页

作者： Yongjia Wang qingfeng li School of Science Huzhou UniversityHuzhou 313000China Institute of Modern Physics Chinese Academy of SciencesLanzhou 730000China School of Nuclear Science and Technology University of Chinese Academy of SciencesBeijing 100049China

Our knowledge of the properties of dense nuclear matter is usually obtained indirectly via nuclear experiments,astrophysical observations,and nuclear theory *** our understanding of the nuclear equation of state(EOS,which is one of the most important properties and of central interest in nuclear physics)has relied on various data produced from experiments and *** review how machine learning is revolutionizing the way we extract EOS from these data,and summarize the challenges and opportunities that come with the use of machine learning.

关键词： nuclear equation of state machine learning nuclear theory nuclear experiment

Control technology and coordination deformation mechanism of rise entry group with high ground stress

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International Journal of Mining Science and Technology 2012年第3期22卷 429-435页

作者： li qingfeng Zhu Quanqu Hunan Key Laboratory of Safe Mining Techniques of Coal Mines Hunan University of Sdence and Technology Xiangtan 411201 China School of Energy and Safety Engineering Hunan University of Science and Technology Xiangtan 411201 China

Based on engineering practices of Wuyang Coal Mine, we carried out X-ray diffract researches on No. 3 coal; and the rocks of its roof and floor by XRD meter, and simulated the interactive effect of the surrounding rock deformation by FLAC2DS.0 numerical simulation software under the condition of different tunneling method of multimine roadway in parallel. The internal structures of the surrounding rocks of 76 belt roadway were monitored by borehole observation instruments： and then, we analyzed the reason of fhilure and deformation of surrounding rocks of several rise entry, and proposed the technical mea- sures for controlling interactive effect of several rise entry surrounding rock deformation at last. For the thickness seam rise roadway, two conclusions were drawn： one is that the co-deformation among roadway groups mainly reflect on that both shear failure and deformation in coal pillar among roadways have decreased the width of pillar core region and clamping action of coal pillar to roof strata, increased the actual span of roof strata, intensified the flexural failure of roof strata and prized the bed separation of roof deep rock strata. The other conclusion is that the factors controlling the interactive deformation among roadways is obvious when appropriate re-adjustment in construction sequence of the tunneling of multimine parallel roadways because the construction sequence among roadways also has great effects on deformation of the surrounding rock in roadway.

关键词： Several rise entryCoordination deformationNumerical simulationConstruction sequence

Transport model analysis of the pion interferometry in Au+Au collisions at Ebeam=1.23 GeV/nucleon

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Science China(Physics,Mechanics & Astronomy) 2023年第2期66卷 51-58页

作者： Pengcheng li Yongjia Wang qingfeng li Hongfei Zhang School of Science Huzhou UniversityHuzhou 313000China School of Nuclear Scienceand Technology Lanzhou UniversityLanzhou730oooChina Institut für Theoretische Physik Goethe Universitat FrankfurtFrankfurt am Main 60438Germany Institute of Modern Physics Chinese Academyof SciencesLanzhou730000China School of Physics Xi'an JiaotongUniversityXi'an710049China

Within the framework of the Ultra-relativistic Quantum Molecular Dynamics model,the effects of resonance decay widths,inmedium nucleon-nucleon(in)elastic cross sections,and potentials on the pion Hanbury-Brown-Twiss(HBT)intensity interferometry in central Au+Au collisions at Ebeam=1.23 GeV/nucleon are *** results show that the pion emission source is visibly influenced by theΔparticles with small invariant masses,i.e.,with long resonance ***,the pion HBT radii are found to be insensitive to the nucleon-nucleon(in)elastic cross sections,while the measured rapidity distributions of the charged pions are sensitive to the nucleon-nucleon(in)elastic cross sections and can be much better reproduced by considering a reduction factor on the nucleon-nucleon inelastic cross *** observed charge-sign difference of the source radii,especially in outward and sideward directions,can be qualitatively explained by simulations with the potential contributions,especially including the Coulomb potential of *** present work demonstrates that the potential updates play important roles in describing the measured HBT radii and duration-time-related radii ratios when understanding the dynamics in relativistic heavy-ion collisions at~GeV beam energies.

关键词： interferometry beam relativistic

Analysis of a two-grid method for semiconductor device problem

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Applied Mathematics and Mechanics(English Edition) 2021年第1期42卷 143-158页

作者： Ying liU Yanping CHEN Yunqing HUANG qingfeng li School of Mathematics and Computational Science Hunan Key Laboratory for Computation and Simulation in Science and EngineeringXiangtan UniversityXiangtan 411105Hunan ProvinceChina College of Information and Intelligence Hunan Agricultural UniversityChangsha 410128China School of Mathematical Sciences South China Normal UniversityGuangzhou 510631China

The mathematical model of a semiconductor device is governed by a system of quasi-linear partial differential *** electric potential equation is approximated by a mixed finite element method,and the concentration equations are approximated by a standard Galerkin *** estimate the error of the numerical solutions in the sense of the *** linearize the full discrete scheme of the problem,we present an efficient two-grid method based on the idea of Newton *** main procedures are to solve the small scaled nonlinear equations on the coarse grid and then deal with the linear equations on the fine *** estimation for the two-grid solutions is analyzed in *** is shown that this method still achieves asymptotically optimal approximations as long as a mesh size satisfies H=O(h^1/2).Numerical experiments are given to illustrate the efficiency of the two-grid method.

关键词： two-grid method semiconductor device mixed finite element method Galerkin method L^q error estimate

Study on the growth of platinum nanowires as cathode catalysts in proton exchange membrane fuel cells

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Frontiers of Chemical Science and Engineering 2022年第3期16卷 364-375页

作者： Ruiqing Wang Xiaolan Cao Sheng Sui Bing li qingfeng li Institute of Fuel Cells Shanghai Jiao Tong UniversityShanghai200240China School of Mechanical and Power Engineering East China University of Science and TechnologyShanghai200237China Department of Energy Conversion and Storage Technical University of Denmark2800LyngbyCopenhagenDenmark

The platinum nanowires have been verified to be a promising catalyst to promote the performance of proton exchange membrane fuel *** this paper,accurately controlled growth of nanowires in a carbon matrix is achieved for reducing Pt *** effects of formic acid concentration and reaction temperature on the morphology and size of the Pt nanowires,as well as their electrochemical performances in a single cell,are *** results showed that the increase in the formic acid concentration results in a volcano trend with the length of Pt *** increasing reduction temperature,the diameter of Pt nanowires increases while Pt particles evolve from one-dimensional to zero-dimensional up to 40°C.A mechanism of the Pt nanowires growth is *** optimized Pt nanowires electrode exhibits a power density(based on electrochemical active surface area)79%higher than conventional Pt/C *** control strategy obtained contributes to the design and control of novel nanostructures in nano-synthesis and catalyst applications.

关键词： Pt nanowires morphology structure control in situ growth mechanism proton exchange membrane fuel cells

Factors affecting the dynamic response of pre-stressed anchors after transient excitation

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Mining Science and Technology 2011年第3期21卷 395-399页

作者： Xu Huijun li qingfeng School of Materials Science and Engineering China University of Mining ＆ Technology Xuzhou 221008 China Shenhua Group Corporation limited Beijing 100011 China School of Energy and Safety Engneering Hunan University of Sdence and Technology Xianootan 411201 China

The wide application of pre-stressed bolting technology in coal mine tunnels has made the nondestructive stress wave reflection method of determining bolting quality an important one. The effect of the support plate on the dynamic response of the pre-stressed anchor is of particular interest. A theoretical analysis and numerical simulations are used to identify the factors affecting the contact stress between the support plate and the rock wall. A formula allowing the calculation of contact stress is presented. Stress wave propagation through the nut, support plate, and rock wall are predicted. The dynamic response signals were measured in the field using prestressed anchors pre-tightened to different torques. The effects from the support plate on the dynamic response were recorded and the results compared to the predictions of pre-stressed anchor. This work provides a theoretical reference for the signal processing of dynamic reflected wave signals in anchor bolts.

关键词： Support plate effectContact stressPre-stressed anchorDynamic response

Characteristics of the induced voltage between deep brain stimulation(DBS) device electrodes by a transcranial magnetic stimulation(TMS) device

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Science China(Technological Sciences) 2015年第6期58卷 1062-1071页

作者： li qingfeng CHEN ShaoBo WANG WeiMing HAO HongWei li LuMing School of Aerospace Tsinghua University National Engineering Laboratory for Neuromodulation Center of Epilepsy Beijing Institute for Brain Disorders

The combination of deep brain stimulation(DBS) and transcranial magnetic stimulation(TMS) is expected to provide additional insights into the pathophysiology of some brain diseases. However, when using TMS in patients with DBS implants, the induced voltage between DBS electrodes presents the greatest risk of brain damage. This paper describes the characteristics of the induced DBS electrode voltage due to TMS. We first examined the TMS stimulus signal and the DBS output impedance characteristics, and then experimentally investigated the induced DBS electrode voltage for various DBS and TMS conditions. The results show that many factors impact the induced electrode voltage. The induced electrode voltage with DBS device working in the unipolar mode is greater than that with DBS device working in the bipolar mode. No matter DBS device is turned on or turned off, the induced electrode voltage is almost the same, but it can provide a significant addition to the original stimulus waveform. There are no significant differences in the induced DBS electrode voltage when the DBS system is working at different stimulus intensities. Lowering the TMS stimulus intensity could effectively reduce the induced DBS electrode voltage. The induced electrode voltage is also strongly related to the position of the TMS coil relative to the DBS lead. This study provides further information about the characteristics of the induced DBS electrode voltage in TMS applications and a reference for the combined use of DBS and TMS.

关键词： deep brain stimulation transcranial magnetic stimulation induced electrode voltage signal characteristics electromagneticcompatibility

The effect of Lorentz-like force on collective flows of K+in Au+Au collisions at 1.5 Ge V/nucleon

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Science China(Physics,Mechanics & Astronomy) 2018年第6期61卷 24-29页

作者： YuShan Du YongJia Wang qingfeng li ling liu School of Science Huzhou University School of Physics science and Technology Shenyang Normal University Institute of Modern Physics Chinese Academy of Sciences

Producing kaon mesons in heavy-ion collisions at beam energies below their threshold energy is an important way to investigate the properties of dense nuclear matter. In this study, based on the newly updated version of the ultrarelativistic quantum molecular dynamics model, we introduce the kaon-nucleon(KN) potential, including both the scalar and vector(also dubbed Lorentz-like)aspects. We revisit the influence of the KN potential on the collective flow of K+mesons produced in Au+Au collisions at Elab= 1.5 Ge V/nucleon and find that the contribution of the newly included Lorentz-like force is very important, particulary for describing the directed flow of K+. Finally, the corresponding Kao S data of both directed and elliptic flows can be simultaneously reproduced well.

关键词： kaon flow heavy-ion collision transport model kaon-nucleon potential