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method for studying diatomic rovibrational spectra at a given vibrational state

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Science China(Physics,Mechanics & Astronomy) 2019年第4期62卷 65-70页

作者： Yi Zhang WeiGuo Sun Jia Fu QunChao Fan Jie Ma LianTuan Xiao SuoTang Jia College of Advanced Interdisciplinary Studies National University of Defense Technology School of Science Research Center for Advanced Computation Xihua University Institute of Atomic and Molecular Physics Sichuan University State key Laboratory of Quantum Optics and Quantum Optics Devices Laser Spectroscopy LaboratoryShanxi University

An algebraic method for rotational energies at a given vibrational state(AMr(v)) is proposed in this study in order to obtain unknown high-lying rovibrational energies. Applications of this method to the ground electronic state X^1Σ^+of CO and the excited state C^1Σ^+of^(39)K^7Li molecules show the following:(1) the AMr(v) can give the rational upper limit J of a rotational quantum number of a diatomic electronic state;(2) the full AMr(v) rovibrational energies {E_(υJ)}_υ of given vibrational states not only reproduce all known experimental data excellently but also predict precisely the values of all high-lying rovibrational energies,which may not be available experimentally.

关键词： rovibrational energies diatomic systems algebraic method

method for Predicting the Fatigue Life of Geometrically Discontinuous Structures Under Combined Bending and Torsion

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Acta Mechanica Solida Sinica 2019年第3期32卷 367-377页

作者： Jianhui Liu Xuemei Pan Yaobing Wei Youliang Wang School of Mechanical and Electronical Engineering Lanzhou University of Technology Lanzhou 730050 China

The fatigue damage model based on theory of damage mechanics is capable of predicting the fatigue life under multiaxial loading. Meanwhile, the application of critical plane method in the prediction of multiaxial fatigue life has made certain progress. According to the law of thermodynamics, a new damage evolution equation is developed in the present study to predict the fatigue life of geometrically discontinuous structure under tension-torsion loading based on damage mechanics and the critical plane method. The essence of this approach is tha t the st rain parame ter of the uniaxial nonlinear fatigue damage model is replaced with the equivalent strain, which consists of the releva nt parame ters of the critical plane. However, it is difficult to calculate the stress-strain status and the critical plane position of geometrically dis? continuous structure by theoretical methods because of the existence of stress concentration and the multiaxial nonproportional characteristics. Therefore, a new numerical simulation method is proposed to determine the critical plane of geometrically discontinuous structure under multiaxial loading by means of the finite element method and MATLAB software. The fatigue life of notched specimens subjected to combined bending and torsion is predicted using the proposed met hod, and the result is compared with t hose from the experimen ts and the Manson-Cfiffin law. The comparisons show that the proposed method is superior to the Manson-Coffin law and is capable of reproducing the experimental results reasonably when the geometry of the structure is complex. It completely meets the needs of engineering practice.

关键词： Damage mechanics Critical plane method Geometrically discontinuous structure Finite element method

Univector field method-based multi-agent navigation for pursuit problem in obstacle environments

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Journal of Central South University 2017年第4期24卷 1002-1012页

作者： Le Pham Tuyen Hoang Huu Viet Sang Hyeok An Seung Gwan Lee Dong-Han Kim Tae Choong Chung Department of Computer Science and Engineering Kyung Hee University Yongin Gyeonggi 446-701 Korea Department of Information Technology Vinh University 182-Le Duan Vinh City Nghe An 461056 Vietnam Humanitas College Kyung Hee University Yongin Gyeonggi 446-701 Korea Department of Electronics and Radio Engineering Kyung Hee University Yongin Gyeonggi 446-701 Korea

The pursuit problem is a well-known problem in computer science. In this problem, a group of predator agents attempt to capture a prey agent in an environment with various obstacle types, partial observation, and an infinite grid-world. Predator agents are applied algorithms that use the univector field method to reach the prey agent, strategies for avoiding obstacles and strategies for cooperation between predator agents. Obstacle avoidance strategies are generalized and presented through strategies called hitting and following boundary(HFB); trapped and following shortest path(TFSP); and predicted and following shortest path(PFSP). In terms of cooperation, cooperation strategies are employed to more quickly reach and capture the prey agent. Experimental results are shown to illustrate the efficiency of the method in the pursuit problem.

关键词： pursuit problem predator agent prey agent univector field method multi-agent systems

A new method for deburring of servo valve core edge based on ultraprecision cutting with the designed monocrystalline diamond tool

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Science China(Technological Sciences) 2019年第10期62卷 1805-1815页

作者： AN QingLong DANG JiaQiang LIU GongYu Dong DaPeng MING WeiWei CHEN Ming State Key Laboratory of Mechanical System and Vibration School of Mechanical Engineering Shanghai Jiao Tong University

Deburring of high-precision components to their micrometer features without any damage is very important but of great difficulty as the burr-to-functionality size ratio increases. To this end, this paper proposes a new deburring method in which the micro burr should be directly removed based on ultraprecision cutting with the designed monocrystalline diamond tool. To determine the feasibility of the proposed method, this paper applies it for deburring of the precision working edge of the servo valve core. Firstly, the monocrystalline diamond tool is carefully designed by covering a variety of topics like rake angle,clearance angle, edge radius. Then, the finite element(FE) simulation was conducted to characterize the deburring performance during the removal of the micro burr produced by the single abrasive grinding. Finally, an innovative self-designed deburring system was introduced and the deburring process was evaluated in terms of cutting forces, temperatures, tool wear mechanisms and deburring quality of the working edges by experiments. The FE simulation results indicate the suitability of the proposed deburring method. Meanwhile, the experimental findings agree well with simulation results and show that ultraprecision cutting with the specialized monocrystalline diamond tool could be successfully used for deburring of servo valve core edge without any damage. This work can provide technical guidance for similar engineering applications, and thus brings an increase to the machining efficiency for the manufacture of precision components.

关键词： monocrystalline diamond tool FE simulation deburring method servo valve core edge ultraprecision cutting

Understanding roof deformation mechanics and parametric sensitivities of coal mine entries using the discrete element method

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International Journal of Mining Science and Technology 2020年第1期30卷 123-129页

作者： Rami Abousleiman Gabriel Walton Sankhaneel Sinha Department of Geology and Geological Engineering Colorado School of MinesGoldenCO 80218USA

Although conventional coal mine designs are conservative regarding pillar strength,local failures such as roof-falls and pillar bursts still affect mine safety and *** studies have identified that discontinuous,layered roof materials have some self-supporting *** research is a preliminary step towards understanding these mechanics in coal-measure *** others have considered broad conceptual models and simplified analogs for mine roof behavior,this study presents a unique numerical model that more completely represents in-situ roof *** discrete element method(DEM)is utilized to conduct a parametric analysis considering a range of in-situ stress ratios,material properties,and joint networks to determine the parameters controlling the stability of single-entries modeled in *** results are compared to empirical observations of roof-support effectiveness(ARBS)in the context of the coal mine roof rating(CMRR)*** such as immediate roof displacement,overall stability,and statistical relationships between model parameters and outcomes are presented *** practical applications of this line of research include:(1)roof-support optimization for a range of coal-measure rocks,(2)establishment of a relationship between roof stability and pillar stress,and(3)determination of which parameters are most critical to roof stability and therefore require concentrated evaluation.

关键词： Numerical modeling Discrete element method Coal mine roof rating Analysis of roof bolt systems Sensitivity analysis Strain softening ubiquitous joints Discrete fracture network

An improved boundary element method for modelling a self-reacting point absorber wave energy converter

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Acta Mechanica Sinica 2018年第6期34卷 1015-1034页

作者： Qian-Long Xu Ye Li Zhi-Liang Lin State Key Laboratory of Ocean Engineering Collaborative Innovation Center for Advanced Ship and Deep-Sea ExplorationMuti-function Towing TankKey Laboratory of Hydrodynamics(Ministry of Education)School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China

A numerical model based on a boundary element method (BEM) is developed to predict the performance of two-body selfreacting floating-point absorber (SRFPA) wave energy systems that operate predominantly in *** key numerical issues in applying the BEM are systematically *** particular,some improvements and simplifications in the numerical scheme are developed to evaluate the free surface Green's function,which is a main element of difficulty in the *** a locked SRFPA system,the present method is compared with the existing experiment and the Reynolds-averaged NavierStokes (RANS)-based method,where it is shown that the inviscid assumption leads to substantial over-prediction of the heave *** the unlocked SRFPA model we study in this paper,the additional viscous damping primarily induced by flow separation and vortex shedding,is modelled as a quadratic drag force,which is proportional to the square of body *** inclusion of viscous drag in present method significantly improves the prediction of the heave responses and the power absorption performance of the SRFPA system,obtaining results excellent agreement with experimental data and the RANS simulation results over a broad range of incident wave periods,except near resonance in larger wave height *** is found that the wave overtopping and the re-entering impact of out-of-water floating body are observed more frequently in larger waves,where these non-linear effects are the dominant damping sources and could significantly reduce the power output and the motion responses of the SRFPA system.

关键词： Boundary element method Floating-point absorber Heave Green's function Viscous drag

Free vibration of non-uniform axially functionally graded beams using the asymptotic development method

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Applied Mathematics and Mechanics(English Edition) 2019年第1期40卷 85-96页

作者： Dongxing CAO Yanhui GAO College of Mechanical Engineering Beijing University of Technology Beijing Key Laboratory of Nonlinear Vibrations and Strength of Mechanical Structures

The asymptotic development method is applied to analyze the free vibration of non-uniform axially functionally graded(AFG) beams, of which the governing equations are differential equations with variable coefficients. By decomposing the variable flexural stiffness and mass per unit length into reference invariant and variant parts, the perturbation theory is introduced to obtain an approximate analytical formula of the natural frequencies of the non-uniform AFG beams with different boundary ***, assuming polynomial distributions of Young's modulus and the mass density, the numerical results of the AFG beams with various taper ratios are obtained and compared with the published literature results. The discussion results illustrate that the proposed method yields an effective estimate of the first three order natural frequencies for the AFG tapered beams. However, the errors increase with the increase in the mode orders especially for the cases with variable heights. In brief, the asymptotic development method is verified to be simple and efficient to analytically study the free vibration of non-uniform AFG beams, and it could be used to analyze any tapered beams with an arbitrary varying cross width.

关键词： axially functionally graded(AFG)beam non-uniform natural frequency asymptotic development method

Microstructure and magnetic properties of sintered Nd-Fe-B magnets with Ce substitution for Nd by intergranular-alloy method

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Rare Metals 2020年第1期39卷 62-69页

作者： Jian-Xin Huang Ying Liu Jun Li Wei Zhao Qi Shi College of Materials Science and Engineering Sichuan UniversityChengdu610065China Key Laboratory of Advanced Special Material and Technology Ministry of EducationChengdu610065China

Aiming at the comprehensive utilization of the rare-earth resources and the preparation of the high-performance low-cost Nd-Fe-B magnets,sintered magnets with different Ce substitution amounts of 17.2 wt%,24.8 wt%and 31.8 wt%were prepared by intergranularalloy *** influence of substitution of Ce for Nd on their microstructure and magnetic properties in this work was detailedly *** results indicated that the remanence(Br)and the maximum energy product((BH)max)of the sintered magnets decreased monotonic ally with the increase in Ce ***,the obvious enhancement of coercivity(Hcj)was also observed,which was mainly due to the improvement of microstructure and the smooth,continuous grain boundary(GB).It can be found that a reasonable Ce substitution of 24.8 wt%for the sintered magnets could promote the refinement of microstructure,leading to the realization of superior magnetic *** is expected that the investigations could be beneficial to offer a feasible method for preparing the high-performance low-cost Ce-doped magnets.

关键词： Microstructure Sintered magnets Ce substitution Intergranular-alloy method

Microstructure evolution and crystallography of directionally solidified Al2O3/Y3Al5O12 eutectic ceramics prepared by the modified Bridgman method

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Journal of Materials Science & Technology 2019年第9期35卷 1982-1988页

作者： Xu Wang Nan Zhang Yujie Zhong BailingJiang Langhong Lou Jian Zhang Jingyang Wang Shool of Material Science and Engineering Xi'an University of TechnologyXi'an710048China School of Materials Science and Engineering Xi'an Shiyou UniversityXi'an710065China Institute of Metal Research. Chinese Academy of Sciences Shenyang110016China

Large size,high-density(99.97%)and well-organized Al2O3/Y3Al5O12(YAG)eutectic ceramics were prepared by the modified Bridgman *** evolution of the three dimensional microstructure and micropores were *** diameter of the micro-pores and the porosity decreased during directional *** average equivalent diam eter of the micro-pores was 2.41μm in the well-prepared eutectic *** of the pores(98.07%)were smaller than 4μ*** data are comparable to those prepared by the optical floating zone *** as-grown eutectic ceramics were polycrystalline,but the interfaces were well-bonded and there were no amorphous phases in the *** misfits of the different crystallographic relationships were calculated,and the bottleneck of the single-crystal preparation was *** results could provide theoretical guidance for the preparation of large,single-crystal Al2O3/YAG eutectic ceramics by the modified Bridgman method.

关键词： Al2O3/YAG eutectic ceramics Crystallography Interfaces Bridgman method