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Breaking efficiency limit of thermal concentrators by conductivity couplings

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Science China(Physics,Mechanics & Astronomy) 2022年第11期65卷 68-77页

作者： pengfei zhuang Liujun Xu Peng Tan Xiaoping Ouyang Jiping Huang Department of Physics State Key Laboratory of Surface Physicsand Key Laboratory of Micro and Nano Photonic Structures(MOE)FudanUniversityShanghai200438China Department of Physics and State Key Laboratory of Surface Physics Fudan UniversityShanghai 200438China School of Materials Scienceand Engineering Xiangtan UniversityXiangtan 411105China

The concentrating efficiency of a thermal concentrator can be reflected in the ratio of its interior to exterior temperature gradients,which, however, has an upper limit in existing schemes. Here, we manage to break this upper limit by considering the couplings of thermal conductivities and improve the concentrating efficiency of thermal concentrators. For this purpose, we first discuss a monolayer scheme with an isotropic thermal conductivity, which can break the upper limit but is still restricted by its geometric configuration. To go further, we explore another degree of freedom by considering the monolayer scheme with an anisotropic thermal conductivity or by adding the second shell with an isotropic thermal conductivity, thereby making the concentrating efficiency completely free from the geometric configuration. Nevertheless, apparent negative thermal conductivities are required, and we resort to external heat sources realizing the same effect without violating the second law of thermodynamics. Finite-element simulations are performed to confirm the theoretical predictions, and experimental suggestions are also provided to improve feasibility. These results may have potential applications for thermal camouflage and provide guidance to other diffusive systems such as static magnetic fields and dc current fields for achieving similar behaviors.

关键词： thermal concentrator concentrating efficiency conductivity coupling apparent negative conductivity

Equal-time kinetic equations in a rotational field

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Chinese Physics C 2022年第2期46卷 149-159页

作者：陈诗乐王梓岳庄鹏飞 Physics Department Tsinghua UniversityBeijing 100084China

We investigate quantum kinetic theory for a massive fermion system under a rotational field.From theDirac equation in rotating frame we derive the complete set of kinetic equations for the spin components of the 8-and 7-dimensional Wigner functions.While the particles are no longer on a mass shell in the general case due to therotation-spin coupling,there are always only two independent components,which can be taken as the number andspin densities.With help from the off-shell constraint we obtain the closed transport equations for the two independent components in the classical limit and at the quantum level.The classical rotation-orbital coupling controls thedynamical evolution of the number density,but the quantum rotation-spin coupling explicitly changes the spin density.

关键词： equal-time transport rotation field kinetic theory

UA(1)symmetry restoration at high baryon density

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Chinese Physics C 2023年第10期47卷 120-129页

作者：李嘉宁桂进庄鹏飞 Department of Physics Tsinghua UniversityBeijing 100084China

We study the relation between chiral and UA(1)symmetries in the quark-meson model.Although quarks and mesons are described in mean field approximation,the topological susceptibility characterizing the UA(1)breaking comprises two components:one controlled by the condensate and the other by the meson fluctuation.The UA(1)restoration is governed by the competition of these components.In a hot medium,the condensates melt.However,the fluctuation is enhanced.Therefore,the UA(1)symmetry cannot be solely restored via the temperature effect.Nevertheless,the baryon density reduces the condensates and fluctuation,and thereby,the UA(1)symmetry can only be restored in a dense or dense and hot medium.The strange condensate plays a weak role in the susceptibility,and the chiral and UA(1)symmetry restorations occur almost at the same critical point.

关键词： UA(1)symmetry chiral phase transition finite temperature field theory

Synthesis, structure, and magnetic properties of a cyanide-bridged Fe(Ⅲ)-Cu(Ⅱ) bimetallic double-zigzag chain with slow relaxation of the magnetization

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Science China Chemistry 2012年第6期55卷 1018-1021页

作者： DONG DaPeng ZHENG Hui ZHAO Liang zhuang pengfei LIU Tao HE Cheng DUAN ChunYing State Key Laboratory of Fine Chemicals Dalian University of Technology Dalian 116012 China

Using Bu4N[Fe(Tp*)(CN)3]- (Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate) as the building block to react with CuII and N-methylimidazole, we obtained a one-dimensional (1D) heterobimetallic cyano-bridged chain, [Fe(Tp*)(CN)3]2Cu(N-methylimidazole)2·2H2O (1). The crystal structures and magnetic studies demonstrate that complex 1 exhibits slow relaxation of the magnetization due to strong intrachain ferromagnetic coupling and weak interchain interactions.

关键词：铁磁耦合晶体结构磁性能桥链磁化松弛双金属氰化物

Synthesis, structure, and magnetic properties of a cyanide-bridged Fe(Ⅲ)-Cu(Ⅱ) bimetallic double-zigzag chain with slow relaxation of the magnetization

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中国科学:化学 2012年第6期42卷 918-919页

作者： DONG DaPeng ZHENG Hui ZHAO Liang zhuang pengfei LIU Tao HE Cheng DUAN ChunYing State Key Laboratory of Fine Chemicals Dalian University of TechnologyDalian 116012Chin

Using Bu4N[Fe(Tp*)(CN)3]- (Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate) as the building block to react with CuII and N-methylimidazole, we obtained a one-dimensional (1D) heterobimetallic cyano-bridged chain, [Fe(Tp*)(CN)3]2Cu(N- methylimidazole)2·2H2O (1). The crystal structures and magnetic studies demonstrate that complex 1 exhibits slow relaxation of the magnetization due to strong intrachain ferromagnetic coupling and weak interchain interactions.

关键词：铁磁耦合晶体结构磁学性质磁化松弛氰化物双金属 N-甲基咪唑

Heavy flavor dissociation in framework of multi-body Dirac equations

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Chinese Physics C 2020年第8期44卷 115-124页

作者：施舒哲赵佳星庄鹏飞 Physics Department Tsinghua UniversityBeijing 100084China Department of Physics McGill UniversityMontrealQC H3A 2T8Canada

We study heavy flavor properties at finite temperature in the framework of a relativistic potential model.Using an improved method to solve the three-body Dirac equation,we determine a universal set of model parameters for both mesons and baryons by fitting heavy flavor masses in vacuum.Taking heavy quark potential from lattice QCD simulations in hot medium,we systematically calculate heavy flavor binding energies and averaged sizes as functions of the temperature.The meson and baryons are separately sequentially dissociated in the quark-gluon plasma,and the mesons can survive at higher temperatures owing to the stronger potential between quark-antiquark pairs than that between quark-quark pairs.

关键词： heavy flavor hadron dissociation relativistic heavy-ion collision heavy flavor baryon

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高温高密度时的新物质形态

科学通报 2018年第24期63卷 2465-2473页

作者：姜寅马永亮庄鹏飞北京航空航天大学物理科学与核能工程学院清华大学物理系吉林大学物理学院

在高温高密条件下,夸克将解除禁闭形成全新的物质形态——夸克物质.本文从核物质的基本相互作用——量子色动力学(QCD)的基本对称性出发,首先简单介绍研究QCD相变的各种方法,阐述相变发生的物理机制和条件,然后着重讨论实现QCD相变的两... 详细信息

在高温高密条件下,夸克将解除禁闭形成全新的物质形态——夸克物质.本文从核物质的基本相互作用——量子色动力学(QCD)的基本对称性出发,首先简单介绍研究QCD相变的各种方法,阐述相变发生的物理机制和条件,然后着重讨论实现QCD相变的两种物理系统,即相对论重离子碰撞和致密星体.相对论重离子碰撞是制造高温环境的重要手段,核物质将形成全新的夸克胶子等离子体相(QGP).文中介绍了探测QGP的实验信号和高温环境特有的新奇物理现象.致密天体中的高密区则展现了极其丰富多彩的相结构.理论预示了与颜色和味道等自由度相联系的各类超导、超流态存在的可能性.相信在未来更大范围的束流能量扫描和对致密星体的精确观测中,我们将会对高温高密核物质的物态性质有着更加深入的认识.

关键词：量子色动力学相图相对论重离子碰撞致密星体对称性高温高密

Charmonium transverse momentum distribution and leakage effect in relativistic heavy ion collisions

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Charmonium transverse momentum distribution and leakage effe...

第五届中日双边核物理会议

作者： Xianglei Zhu and pengfei zhuang Physics Department, Tsinghua University, Beijing 100084, China

The charmonium suppression and transverse momentum distribution in heavy-ion collisions have been studied systematically in a transport approach. The suppression is caused by the nuclear absorption and dissociation via gluon-charmonium inelastic scattering in deconfined partonic medium and pion-charmonium inelastic scattering in hadronic medium. The evolution of the transverse distribution function of charmonium is described by the transport equation with leakge term and that of medium is described by a 1+1D relativistic hydrodynamics with Bjorken’s boost invariant condition. The adjustable parameters in the approach have been fixed by the J/ψand ψ’ suppression data at s = 17.3 AGeV Pb-Pb collisions at SPS. The as a function of transverse energy has been calculated and a good agreement with the data has been achieved. Larger charmonium suppression at central collisions and saturation in more peripheral collisions have been predicted for s=200 AGeV Au-Au collisions at RHIC. The elliptic flow v of J/ψat SPS and RHIC has also been calculated. The leakage effect has been shown to be essential in the consideration of the pt distribution related observables.

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等时量子输运理论及其应用

中国科学基金 2000年第5期14卷 305-307页

作者：庄鹏飞清华大学物理系北京100084

建立在Wigner算符基础上的输运理论被广泛用于讨论超相对论重离子碰撞和夸克胶子等离子体。Wigner算符可以在4维和3维动量空间表示,即(x,p)和(x,)。相应地,输运理论有协变和等时两种形式。除了具有明显的Lorentz协变性外,协变理论的另... 详细信息

建立在Wigner算符基础上的输运理论被广泛用于讨论超相对论重离子碰撞和夸克胶子等离子体。Wigner算符可以在4维和3维动量空间表示,即(x,p)和(x,)。相应地,输运理论有协变和等时两种形式。除了具有明显的Lorentz协变性外,协变理论的另一个优点是量子动力论方程可以分解为输运方程和反映离壳效应的约束方程。等时理论的最大优点是它能作为初始问题求解,因此。

关键词：输运理论等时量子输运重离子碰撞等离子体