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Non-universal Fermi polaron in quasi two-dimensional quantum gases

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Chinese Physics B 2022年第8期31卷 246-251页

作者： Yue-Ran Shi jin-ge chen Kui-Yi Gao Wei Zhang Department of Physics Renmin University of ChinaBeijing 100872China Beijing Academy of Quantum Information Sciences Beijing 100193China Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices Renmin University of ChinaBeijing 100872China

We consider an impurity problem in a quasi-two-dimensional Fermi gas, where a spin-down impurity is immersed in a Fermi sea of N spin-up atoms. Using a variational approach and an effective two-channel model, we obtain the energy for a wide range of interaction strength and for various different mass ratios between the impurity and the background fermion in the context of heteronuclear mixture. We demonstrate that in a quasi-two-dimensional Fermi gas there exists a transition of the ground state from polaron in the weakly interacting region to molecule in the strongly interacting *** critical interaction strength of the polaron–molecule transition is non-universal and depends on the particle density of the background Fermi sea. We also investigate the excited repulsive polaron state, and find similar non-universal behavior.

关键词： Fermi gas polaron problem two-channel model

Fulde-Ferrell-Larkin-Ovchinnikov states in equally populated Fermi gases in a two-dimensional moving optical lattice

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Chinese Physics B 2021年第10期30卷 143-148页

作者： jin-ge chen Yue-Ran Shi Ren Zhang Kui-Yi Gao Wei Zhang Department of Physics Renmin University of ChinaBeijing 100872China School of Physics Xi’an Jiaotong UniversityXi’an 710049China Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices Renmin University of ChinaBeijing 100872China

We study the possibility of stabilizing a Fulde-Ferrell-Larkin-Ovchinnikov(FFLO)state in an equally populated two-component Fermi gas trapped in a moving two-dimensional optical *** a system with nearly half filling,we find that a finite pairing momentum perpendicular to the moving direction can be spontaneously induced for a proper choice of lattice *** a result,the total pairing momentum is tilted towards the nesting vector to take advantage of the significant enhancement of the density of states.

关键词： FFLO state optical lattice ultracold Fermi gas superfluid

Multiplicity of solutions for the semilinear subelliptic Dirichlet problem

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Science China Mathematics 2024年第3期67卷 475-504页

作者： Hua chen Hong-ge chen jin-Ning Li Xin Liao School of Mathematics and Statistics Wuhan UniversityWuhan 430072China Wuhan Institute of Physics and Mathematics Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhan 430071China

In this paper,we study the semilinear subelliptic equation{−△Xu=f(x,u)+g(x,u)inΩ,u=0 on∂Ω,where△X=−∑m i=1 Xi∗Xi is the self-adjoint Hormander operator associated with the vector fields X=(X_(1),X_(2),...,X_(m))satisfying the Hormander's condition,f(x,u)∈C(Ω×R),g(x,u)is a Carathéodory function onΩ×R,andΩis an open bounded domain in R~n with smooth *** the perturbation from the symmetry method with the approaches involving the eigenvalue estimate and the Morse index in estimating the minimax values,we obtain two kinds of existence results for multiple weak solutions to the problem ***,we discuss the difference between the eigenvalue estimate approach and the Morse index approach in degenerate *** with the classical elliptic cases,both approaches here have their own strengths in the degenerate *** new phenomenon implies that the results in general degenerate cases would be quite different from the situations in classical elliptic cases.

关键词： degenerate elliptic equations Hormander operators perturbation method Morse index

Meridional deflection of global eddy propagation derived from tandem altimetry: Mechanism and implication

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Science China Earth Sciences 2024年第3期67卷 811-825页

作者： ge chen Xiaoyan chen Frontiers Science Center for Deep Ocean Multispheres and Earth System School of Marine TechnologyOcean University of ChinaQindao 266100China Laboratory for Regional Oceanography and Numerical Modeling Laoshan LaboratoryQindao 266237China

A common view on meridional deflection of eddy propagation is poleward for cyclones and equatorward for anticyclones. This widely accepted polarity-sensitive pattern has been increasingly undermined given that it is systematically violated on both zonal and regional scales as recently reported. Here, we approach the problem by exploring these violations in terms of eddy effects of spatiotemporal geostrophy, thermal fading, and flow dragging, yielding the following main conclusions.(1) The polarity-dependent deflection discrepancy is a pseudo feature resulting from a biased fit to the normalized eddy tracks which are spatially asymmetric(though azimuthally symmetric) between the two signs;Instead, the primary pattern of eddy deflection appears to be geographically correlated and polarity independent.(2) geostrophic adjustment plays a critical role in defining the meridional movement of an eddy. Specifically, a consistent poleward(equatorward) trajectory bending of spatially(temporally) ageostrophic eddies is observed irrespective of their polarity.(3) The mechanism of eddy deflection is also determined by its zonal propagation direction. Westward propagating eddies are substantially affected by thermal fading, while opposite ones by flow dragging. A realistic and comprehensive understanding of eddy deflection mechanisms serves as a significant contribution to the prediction of eddy trajectory, and the protection of ocean environment.

关键词： Mesoscale eddies Eddy propagation Eddy meridional deflection Satellite observation geostrophic adjustment

Overexpression of Kdm6b induces testicular differentiation in a temperature-dependent sex determination system

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Zoological Research 2024年第5期45卷 1108-1115页

作者： Qiran chen Wei Sun Lin jin Yingjie Zhou Fang Li Chutian ge College of Biological and Environmental Sciences Zhejiang Wanli UniversityNingboZhejiang 315100China Institute of Animal Sex and Development Zhejiang Wanli UniversityNingboZhejiang 315100China

In reptiles,such as the red-eared slider turtle(Trachemys scripta elegans),gonadal sex determination is highly dependent on the environmental temperature during embryonic *** complex process,which leads to differentiation into either testes or ovaries,is governed by the finely tuned expression of upstream genes,notably the testis-promoting gene Dmrt1 and the ovary-promoting gene *** studies have identified epigenetic regulation as a crucial factor in testis development,with the H3K27me3 demethylase KDM6B being essential for Dmrt1 expression in ***,whether KDM6B alone can induce testicular differentiation remains *** this study,we found that overexpression of Kdm6b in *** embryos induced the male development pathway,accompanied by a rapid increase in the gonadal expression of Dmrt1 at 31°C,a temperature typically resulting in female ***,this sex reversal could be entirely rescued by Dmrt1 *** findings demonstrate that Kdm6b is sufficient for commitment to the male pathway,underscoring its role as a critical epigenetic regulator in the sex determination of the red-eared slider turtle.

关键词： Temperature-dependent sex determination Sex reversal Kdm6b Dmrt1 T.s.elegans

Boundary slip and lubrication mechanisms of organic friction modifiers with effect of surface moisture

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Friction 2024年第7期12卷 1483-1498页

作者： Xiaobin YI Haiyu XU ge jin Yang LU Biqiang chen Shaofeng XU Junqin SHI Xiaoli FAN State Key Laboratory of Solidification Processing Center of Advanced Lubrication and Seal MaterialsNorthwestern Polytechnical UniversityXi’an 710072China Xi’an Thermal Power Research Institute Co. Ltd.Xi’an 710054China NingboTech University Ningbo 315000China

Surface moisture or humidity impacting the lubrication property is a ubiquitous phenomenon in tribological systems,which is demonstrated by a combination of molecular dynamics(MD)simulation and experiment for the organic friction modifier(OFM)-containing *** stearic acid and poly-α-olefin 4cSt(PAO4)were chosen as the OFM and base oil molecules,*** physical adsorption indicates that on the moist surface water molecules are preferentially adsorbed on friction surface,and even make OFM adsorption film thoroughly leave surface and mix with base *** shear process,the adsorption of water film and desorption OFM film are further enhanced,particularly under higher shear *** simulated friction coefficient(that is proportional to shear rate)increases firstly and then decreases with thickening water film,in good agreement with experiments,while the slip length shows a contrary *** wear increases with humidity due to tribochemistry revealing the continuous formation and removal of Si–O–Si *** tribological discrepancy of OFM-containing lubricant in dry and humid conditions is attributed to the slip plane’s transformation from the interface between OFM adsorption film and lubricant bulk to the interface between adsorbed water *** work provides a new thought to understand the boundary lubrication and failure of lubricant in humid environments,likely water is not always harmful in oil lubrication systems.

关键词： organic friction modifier(OFM) boundary lubrication boundary slip surface moisture

Bright InP quantum dots by Ga-doping for red emitters

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Nano Research 2024年第7期17卷 6721-6733页

作者： Kai-Zheng Song Xiao-Hang He Zhe-Yong chen ge Tang jin-Zhao Huang Feng-Lei Jiang College of Chemistry and Molecular Sciences Wuhan UniversityWuhan 430072China

Environment-friendly indium phosphide(InP)-based quantum dots(QDs)with efficient red-emitting properties are sufficiently needed to satisfy the requirement of burgeoning display and lighting ***,the syntheses of InP QDs using tris(trimethylsilyl)phosphine as the precursor are highly toxic and ***,we successfully introduced gallium(Ga)ions into tris(dimethylamino)phosphine-based red InP cores through thermally-promoted cation exchange,and the obtained Ga-doped InP cores exhibited significantly increased photoluminescence quantum yields(PLQY)of up to 26%.The existence of Ga was directly confirmed by energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy,and the functions of Ga were systematically *** subsequent coating of Ga-doped InP cores with ZnSeS and ZnS shells,the resulting Ga-InP/ZnSeS/ZnS QDs achieved a high PLQY of 62%with an emission maximum at 640 *** contrast,without Ga-doping,the PLQY only attained 36%using the same synthetic *** indicated an approximate 1.7-fold increase in *** enhancement of photoluminescence was related to the Ga^(3+),as it not only passivated surface defects of InP cores but also reduced core–shell interface *** Ga-InP/ZnSeS/ZnS QDs exhibited good stability towards heat treatment and ultraviolet(UV)***,the red light-emitting diode(LED)based on Ga-InP/ZnSeS/ZnS QDs performed well in a wide injected current range of 2 to 200 mA,with a maximum power efficiency of 0.68 lm/*** work showcases Ga-doping through cation exchange as a promising strategy for enhancing the efficiency of InP-based red emitters.

关键词： indium phosphide gallium doping optical properties light emitting diode

Constraint Learning-based Optimal Power Dispatch for Active Distribution Networks with Extremely Imbalanced Data

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CSEE Journal of Power and Energy Systems 2024年第1期10卷 51-65页

作者： Yonghua Song ge chen Hongcai Zhang State Key Laboratory of Internet of Things for Smart City and Department of Electrical and Computer Engineering University of MacaoMacao 999078China School of Electrical and Computer Engineering Purdue UniversityWest LafayetteIN 47907 USA

Transition towards carbon-neutral power systems has necessitated optimization of power dispatch in active distribution networks(ADNs)to facilitate integration of distributed renewable *** to unavailability of network topology and line impedance in many distribution networks,physical model-based methods may not be applicable to their *** tackle this challenge,some studies have proposed constraint learning,which replicates physical models by training a neural network to evaluate feasibility of a decision(i.e.,whether a decision satisfies all critical constraints or not).To ensure accuracy of this trained neural network,training set should contain sufficient feasible and infeasible ***,since ADNs are mostly operated in a normal status,only very few historical samples are ***,the historical dataset is highly imbalanced,which poses a significant obstacle to neural network *** address this issue,we propose an enhanced constraint learning ***,it leverages constraint learning to train a neural network as surrogate of ADN's ***,it introduces Synthetic Minority Oversampling Technique to generate infeasible samples to mitigate imbalance of historical *** incorporating historical and synthetic samples into the training set,we can significantly improve accuracy of neural ***,we establish a trust region to constrain and thereafter enhance reliability of the *** confirm the benefits of the proposed method in achieving desirable optimality and feasibility while maintaining low computational complexity.

关键词： Deep learning demand response distribution networks imbalanced data optimal power flow

Laser powder bed fusion of NiTiFe shape memory alloy via premixed powder:microstructural evolution,mechanical and functional properties

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Rare Metals 2024年第5期43卷 2300-2316页

作者： Bo Yuan jin-Guo ge Liang Zhang Hong-Jun chen Long-Sha Wei Yu-Duo Zhou Run-Hua Song Institute of Intelligent Manufacturing Technology Shenzhen PolytechnicShenzhen 518055China School of Mechanical and Electrical Engineering Guilin University of Electronic TechnologyGuilin 541004China Guangdong Advanced Polymer Composite Engineering Technology Research Center Shenzhen Academy of Aerospace TechnologyShenzhen 518057China Jihua Laboratory Testing Center Jihua LaboratoryFoshan 528000China

High-cost pre-alloyed powder is the bottleneck problem that limits the widespread application of additivemanufactured shape memory *** this work,the lowcost ternary NiTiFe shape memory alloy is fabricated by laser powder bed fusion(LPBF)technique via mechanically mixed pre-alloy NiTi powder and varying contents pure Fe powder(1,2,3 wt%).All NiTiFe alloys show a relative density of up to 99.8%by optimizing the LPBF processing *** to the heterogeneous nucleation effect of micron-sized Fe particles,both grain refinement and texture weakening are generated in the NiTiFe alloys,accompanied by the reduction of dislocation *** the room-temperature mechanical properties,the NiTi-3Fe alloy shows the highest microhardness of HV370,but the fracture strength and elongation reduce to1701 MPa and 23%*** evolution of mechanical properties is attributed to the high internal defects,low dislocation density and the incoherent ***,the NiTi-3Fe alloy shows the quasi-linear superelasticity behavior;the superelastic recoverable strain of NiTi-1Fe and NiTi-2Fe decreased with the increase in Fe *** study provided a new-fangled insight for the development of multi-component NiTi-based shape memory alloys by additive manufacturing.

关键词： Additive manufacturing Shape memory alloy Metal matrix composite Microstructure Mechanical properties