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Characteristic and Thermal Analysis of Permanent Magnet Eddy Current Brake

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Computer Modeling in Engineering & Sciences 2021年第3期126卷 1011-1031页

作者： jiahao li Guolai Yang Quanzhao Sun School of Mechanical Engineering Nanjing University of Science and TechnologyNanjing210094China

In this paper,the subdomain analysis model of the eddy current brake(ECB)is *** comparing with the finite element method,the accuracies of the subdomain model and the finite element model are ***,the resistance characteristics of radial,axial,andHalbach arrays under impact load are calculated and *** axial array has a large braking force coefficient but low critical *** radial array has a low braking force coefficient but high critical *** Halbach array has the advantages of the first two *** only the braking force coefficient is large,but also the critical speed is *** parameter analysis of the Halbach array is further carried *** inner tube thickness and air gap length are the sensitive factors of resistance *** demagnetization effect is significantly enhanced by the increase of the inner tube *** order to ensure that the ECB does not overheat,the electromagnetic-thermal coupling model is established based on the heat transfer *** temperature rise of the inner tube is obvious while that of the permanentmagnet is *** temperature rise of the inner tube is more than 20 K each time,and that of the permanent magnet is less than 1 K each time.

关键词： Eddy current brake Halbach array resistance characteristic temperature rise

Thermodynamic prediction of metastable phases of Ni-Ti system formed by ion beam mixing

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Science China(Technological Sciences) 2012年第4期55卷 921-926页

作者： ZHAO ShiZhen li jiahao liU BaiXin Advanced Materials Laboratory Department of Materials Science and EngineeringTsinghua UniversityBeijing 100084China

By taking into account the valence electron number and periodic number of constituting metals, a new method is first proposed to calculate the structural enthalpy in the Miedema's model and the modified Miedema's model is then used to predict the formation of metastable phases in Ni-Ti system. To testify the relevance of the present prediction, the multilayered films of Ni1-xTix (x=27.3, 30.5, 42.4, 83.1, 89) are prepared and irradiated by 200 keV xenon ions. Experiment results reveal that uniform amorphous phases are obtained in the Ni72.7Ti27.3, Ni69.5Ti30.5, and Ni57.6Ti42.4 films by increasing the irradiation dose. While for the Ni16.9Ti83.1 and Ni11Ti89 films, an hcp Ti-based solid solution phase and a bcc Ti-rich solid solution phase coexist upon irradiation dose higher than 6×1014 Xe+/cm2. The predictions of relative stabilities of metastable phases in Ni-Ti system by the modified Miedema's model match well with IBM experiments, thus justifying the modification proposed in the present study.

关键词： metallic glasses thermodynamics multilayer thin film ion-beam processing

Evolution of the rare earth trade network:A perspective of dependency and competition

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Geoscience Frontiers 2024年第3期15卷 183-191页

作者： Jilan Xu jiahao li Vincent Charles Xin Zhao School of Urban and Regional Science Shanghai University of Finance and EconomicsShanghai 200433China School of Business East China University of Science and TechnologyShanghai 200237China School of Management University of BradfordBradford BD71DPUnited Kingdom School of Statistics and Applied Mathematics Anhui University of Finance and EconomicsBengbu 233030China

As a global strategic reserve resource,rare earth has been widely used in important industries,such as military equipment and ***,existing analyses based solely on the total volume of rare earth trade fail to uncover the underlying competition and dependency *** address this gap,this paper employs the principles of trade preference and import similarity to construct dependency and competition *** network analysis is then employed to study the evolution of the global rare earth trade network from 2002 to *** main conclusions are as *** global rare earth trade follows the Pareto principle,and the trade network shows a scale-free *** has emerged as the world’s largest importer and exporter of rare earth since *** the dependency network,China has become the most dependent country since *** result of community division shows that China has separated from the American community and formed new communities with the Association of Southeast Asian Nations(ASEAN)*** United States of America has formed a super-strong community with European and Asian *** the competition network,the distribution of competition intensity follows a scale-free *** countries face low-intensity competition,but there are numerous competing *** competition related to China has increased ***,the competition source for the United States of America has shifted from Mexico to China,resulting in China,the USA,and Japan becoming the core participants in the competition network.

关键词： Rare earth Trade network Dependency Competition Complex network analysis

Structural stability and magnetism of metastable Ni-Pt intermetallic compounds studied by ab initio calculation

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Science China(Technological Sciences) 2009年第9期52卷 2681-2687页

作者： CHE XingLai li jiahao DAI Ye liU BaiXin Advanced Materials Laboratory Department of Materials Science and EngineeringTsinghua UniversityBeijing 100084China

The self-consistent electronic structure calculations were carried out with the accurate frozen-core full-potential projector augmented-wave method on 13 Ni-Pt intermetallic compounds of simple crystalline structures,i.e. A15,D019,D03 and L12 Ni3Pt and NiPt3,and α-NiAs,B1,B2,L2a,and L10 NiPt. The calculations reveal that the L12 Ni3Pt,L10 NiPt and L12 NiPt3 are energetically more stable than their respective competitive structures,indicating that the three structures may be formed in some appropriate conditions. The obtained results match well with the experimental observation or other theory predictions. It is found that there is hybridization between Ni 3d and Pt 5d states,which may significantly affect the structural stability and magnetism of metastable Ni-Pt intermetallic compounds.

关键词： ab initio study magnetism metastable phases

Formation of non-equilibrium phases and associated structural transition in the Pd-Ta system induced by ion beam mixing

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Science China(Technological Sciences) 2011年第3期54卷 676-681页

作者： ZHAO Man DAI Ye li jiahao liU BaiXin Advanced Materials Laboratory Department of Materials Science and Engineering Tsinghua University Beijing 100084 China

For the Pd-Ta system characterized by a negative heat of formation of -78 kJ/mol, 200 keV xenon ion beam mixing with nano-sized Pd-Ta multilayered films was conducted to study the non-equilibrium phase formation. The results showed that uniform amorphous alloys can be formed within a composition range of 25 at%-78 at% Ta, which falls in the maximum possible amorphization range of 22 at%-80 at% Ta predicted by the empirical model. Moreover, two metastable crystalline phases both of FCC structure, yet with different lattice constants were obtained. Interestingly, a self-assembled fractal pattern was observed in the Pd52Ta48 multilayered films after irradiation to a dose of 1×1015 Xe+/cm2 and its dimension was determined to be 1.75±0.05. The possible mechanisms for the formation of amorphous and metastable crystalline phases as well as for the growth of the fractal pattern were discussed.

关键词： amorphous phase Pd-Ta alloy ion beam mixing metastable crystalline phase fractal

Atomistic simulation study of favored compositions of Ni-Nb-Al metallic glasses

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Science China(Technological Sciences) 2018年第12期61卷 1829-1838页

作者： CAI Bei YANG MengHao liU JianBo li jiahao liU BaiXin Key Laboratory of Advanced Materials(MOE) School of Materials science and Engineering Tsinghua University

This study investigates the formation process of Ni-Nb-Al metallic glasses. To this end, a long-range n-body potential was constructed for the Ni-Nb-Al ternary metal system, and applied to atomistic simulations. The simulations not only showed the physical origins of the amorphous phase formation, but also quantitatively predicted a hexagonal compositional region that energetically favors the glass formation. The energy difference between the solid solution and metallic glass, which generates the amorphization driving force(ADF), was suggested to indicate the glass-formation ability(GFA) of each alloy. Based on the computed ADFs, the Ni55 Nb25 Al20 alloy exhibited the highest GFA among the Ni-Nb-Al members, implying that the glass formed by this amorphous alloy is more thermodynamically stable than other alloys in the system. In a Voronoi tessellation analysis, the knee point of the coordination-number distribution curve corresponded to the glass-formation region of the Ni-NbAl system.

关键词： interatomic potential atomistic simulation glass-formation ability Ni-Nb-Al system

Mechanism of nanoparticle aggregation in gas-liquid microfluidic mixing

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Chinese Chemical Letters 2024年第4期35卷 376-381页

作者： Hongxia li Xiyang Wang Du Qiao jiahao li Weiping Zhu Honglin li Key Laboratory for Precision&Non-traditional Machining Technology of Ministry of Education Dalian University of TechnologyDalian 116023China Shanghai Key Laboratory of New Drug Design School of PharmacyEast China University of Science and TechnologyShanghai 200237China

Using gas-liquid segmented micromixers to prepare nanoparticles that have a homogeneous particle size, controllable shape, and monodispersity advantages. Although nanoparticle aggregation within a microfluid has been shown to be affected by the shear effect, the shear effect triggering conditions in gasliquid two-phase flow is unclear and the aggregation behavior of nanoparticles under the shear effect is difficult to predict, resulting in uncontrollable physical and chemical properties of nanoparticle aggregates. In this study, a numerical simulation of nanoparticle aggregation in gas-liquid two-phase flow under the shear effect is performed using the CFD-DEM method. Then, the effects of total flow rate,gas-liquid two-phase flow ratio, and particle volume fraction on particle aggregation were analyzed to achieve control of particle aggregation shape and size. Meanwhile, the triggering mechanism of the shear effect and the mechanism of the shear effect on the aggregation of nanoparticles were clarified. The results show that increasing the total flow rate or decreasing the gas-liquid two-phase flow rate ratio can induce the shear effect, which reduces the particle aggregation size and makes the morphology tend to be spherical. Moreover, increasing the particle volume fraction, and total flow rate or decreasing the gas-liquid two-phase flow rate ratio also increases the number of particle collisions and induce interparticle adhesion. Hence, particle adhesion and the shear effect compete with each other and together affect particle aggregation.

关键词： Microfluidic Gas-liquid segmented micromixer Nanoparticle aggregation Shear effect Numerical calculation

An Incremental Model for Defect Production upon Cascade Overlapping

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Chinese Physics Letters 2020年第1期37卷 43-47页

作者： Yi Wang Wensheng Lai jiahao li The Key Laboratory of Advanced Materials(MOE) School of Materials Science and EngineeringTsinghua UniversityBeijing 100084

An analytic incremental model is proposed to predict the defect production upon cascade *** resolving the coupled annealing events during cascade overlapping,this model handles cascade overlapping with multiple pre-existing defects of different sizes and number *** model is first parameterized and then applied to *** proposed model satisfyingly reproduces the defect production obtained by molecular dynamics simulations with various radiation damage levels and defect cluster size *** present model provides an essential description of the primary source of radiation damage,especially for high dose irradiation,and could be used in conjunction with reactive diffusion models for better understanding of radiation damage.

关键词： damage handle sizes

A superior strength-ductility synergy of Al_(0.1)CrFeCoNi high-entropy alloy with fully recrystallized ultrafine grains and annealing twins

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Journal of Materials Science & Technology 2022年第36期131卷 185-194页

作者： jiahao li Kejie Lu Xiaojun Zhao Xinkai Ma Fuguo li Hongbo Pan Jieming Chen Key Laboratory of Advanced Technologies of Materials Ministry of EducationSchool of Materials Science and EngineeringSouthwest Jiaotong UniversityChengdu 610031China Shenzhen Institute of Southwest Jiaotong University Shenzhen 518000China State Key Laboratory of Solidification Processing School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi’an 710072China Anhui Province Key Laboratory of Metallurgical Engineering&Resources Recycling(Anhui University of Technology) 243002 MaanshanChina Luoyang Ship Material Research Institute Luoyang 471023China

Grain refinement usually makes the materials stronger,while ductility has a dramatic ***,a superior tensile strength–ductility synergy in a fully recrystallized ultrafine-grained(UFG)Al_(0.1)CrFeCoNi with abundant annealing twins was achieved by cold rolling at room temperature and short-time *** microstructure characterization using electron backscattered scattering diffraction demonstrates that abundant geometrically necessary dislocations(GNDs)gather around the grain boundaries and twin boundaries after tensile *** coarse-grained(CG)samples undergo a larger plastic deformation than UFG samples,the GND density decreases with grain size ranging from UFG to *** electron microscopy results reveal that the annealing twin boundary,which effectively hinders the dislocation slip and stores dislocation in grain interior,and the activation of multiple deformation twins are responsible for the superior strength–ductility synergy and work hardening *** addition,the yield strength of fully recrystallized Al_(0.1)CrFeCoNi follows a Hall–Petch relationship(σ_y=24+676d^(–1/2)),where d takes into account both grain boundaries and annealing twin *** strengthening effects of grain boundaries and annealing twin boundaries were also evaluated separately.

关键词： High-entropy alloy Ultrafine grains Annealing twins Strength Ductility