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Generalized stress field in granular soils heap with RayleigheRitz method

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journal of Rock Mechanics and Geotechnical Engineering 2017年第1期9卷 135-149页

作者： Gang bi CH2M Inc. Englewood USA Chongqing Titan Architects-Multi-Disciplinary Practice Co. Chongqing China

The stress field in granular soils heap(including piled coal) will have a non-negligible impact on the settlement of the underlying soils. It is usually obtained by measurements and numerical *** the former method is not reliable as pressure cells instrumented on the interface between piled coal and the underlying soft soil do not work well, results from numerical methods alone are necessary to be doubly checked with one more method before they are extended to more complex cases. The generalized stress field in granular soils heap is analyzed with Rayleighe Ritz method. The problem is divided into two cases: case A without horizontal constraint on the base and case B with horizontal constraint on the base. In both cases, the displacement functions u(x, y) and v(x, y) are assumed to be cubic polynomials with 12 undetermined parameters, which will satisfy the Cauchy’s partial differential equations, generalized Hooke’s law and boundary equations. A function is built with the Rayleighe Ritz method according to the principle of minimum potential energy, and the problem is converted into solving two undetermined parameters through the variation of the function, while the other parameters are expressed in terms of these two parameters. By comparison of results from the Rayleighe Ritz method and numerical simulations, it is demonstrated that the Rayleighe Ritz method is feasible to study the generalized stress field in granular soils heap. Solutions from numerical methods are verified before being extended to more complicated cases.

关键词： Generalized stress field Rayleighe Ritz method Stress depression Variation of the function Principle of minimum potential energy

Time to most recent common ancestor for stationary continuous state branching processes with immigration

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Frontiers of Mathematics in China 2014年第2期9卷 239-260页

作者： Hongwei bi School of Mathematical Sciences Beijing Normal University Beijing 100875 China

Motivated by sample path decomposition of the stationary continuous state branching process with immigration, a general population model is considered using the idea of immortal individual. We compute the joint distribution of the random variables： the time to the most recent common ancestor （MRCA）, the size of the current population, and the size of the population just before MRCA. We obtain the bottleneck effect as well. The distribution of the number of the oldest families is also established. These generalize the results obtained by Y. T. Chen and j. F. Delmas.

关键词： Continuous state branching process with immigration (Cbi- processes) most recent common ancestor (MRCA) measured rooted real tree decomposition

Diffusion of an Extra Ga Atom in GaAs（001）（2×4） Rich-As Surface

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Chinese journal of Chemical Physics 2008年第1期21卷 69-75页

作者： Kun Li bi-cai Pan College of Physics and Engineering Qufu Normal University Qufu 273165 China Hefei National Laborator7 for Physical Sciences at Microscale Department of Physics University ofScience and Technology of China Hefei 230026 China

The potential energy surface for the migration of an extra Ga atom on the GaAs（001） β2（2×4） surfuce was mapped out by performing calculations at the level of analytical bond-order potential. Based on this calculations, we found some lower-energy sites for the adsorption of an extra Ga atom in the surface, which were in agreement with the experimental data. Moreover, many possible pathways for an extra Ga atom diffusing in this surface were revealed. According to the relative energies of the possible pathways, the individual Ga adatoms preferably keep their diffusion in two pathways parallel to the As dimers. This result can be understood using the strain caused by the diffusing Ga atom in the pathways. In addition, the simulated kinetic processes of the extra Ga atom diffusing in different pathways at finite temperatures support the prediction from our calculated potential energy surface.

关键词： Surface Adsorption Diffusion of an atom Molecular-dynamics simulation

On the Proper Holomorphic Mappings between Equidimensional Hartogs Domains over Hermitian Symmetric Manifolds

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Acta Mathematica Sinica,English Series 2024年第5期40卷 1215-1228页

作者： En Chao bi School of Mathematics and Statistics Qingdao UniversityQingdao 266071P.R.China

In this paper,we study a family of Hartogs domains fibred over Hermitian symmetric manifolds being a unit ball in C^(m).The aim of the present study is to establish the rigidity results about proper holomorphic mappings between two equidimensional Hartogs domains over Hermitian symmetric *** particular,we can fully determine its biholomorphic equivalence and automorphism group.

关键词： Proper holomorphic mapping Hartogs domains Hermitian symmetric manifolds

Strategic integration of 2D perovskite and chiral quantum dot hybrid heterostructures for superior CPL detection

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Science China Technological Sciences 2025年第1期 368-377页

作者： jiahe YAN Xi ZHANG Lei LIU Hualin bi Mengke WANG jing LI jun WANG Department of Chemistry College of SciencesNortheastern University Technical Institute of Physics and Chemistry Chinese Academy of Sciences

Circularly polarized light（CPL） detection has garnered significant research interest due to its extensive applications in optoelectronics and quantum *** perovskites possess CPL detection capabilities due to their inherent ***,incorporating organic amine spacers distorts the crystal lattice,resulting in defects that reduce the sensitivity of CPL *** study introduces the concept of chiral superposition for the first time,reporting two mixed heterostructures composed of two-dimensional（2D） chiral perovskite（R/S-MBA）2MAPb2I7（R/S）,chiral quantum dots（R/S-MBA）-CsPbBr3（R/SQD）,and chiral carbon dots（Ch-CDs）.The addition of chiral quantum dots/Ch-CDs fills the defects of the chiral perovskite films and reduces the electron-hole recombination rate in chiral hybrid perovskites,thereby significantly enhancing the circularly polarized sensitivity of the CPL *** adjusting the concentration of chiral quantum dots,controllability of spin electron transfer is achieved,which has a notable impact on circular dichroism（CD） and anisotropy factor *** anisotropy factor glhpof the mixed heterostructure R/S-R/SQD is approximately 21.58 times higher than that of single-phase chiral perovskites,and the asymmetry factor gCDincreases ***,this work opens up a new effective pathway for achieving high-sensitivity CPL detection,with promising applications in optoelectronic technologies such as spin information communication and quantum optics.

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Inconel 617 and Stellite 6 alloys for tooling in thixoforming of steels

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Transactions of Nonferrous Metals Society of China 2010年第9期20卷 1656-1662页

作者： Y.bi ROL Materials Institute Marmara Research Centre

Thermal fatigue and high temperature wear are the two principle failure mechanisms for thixoforming dies. Samples of Inconel 617 and Stellite 6 alloys were submitted to thermal cycling under conditions which approximate thixoforming of steels and to sliding wear tests at 750 ℃. The experimental results thus obtained were compared with those of the X32CrMoV33 hot work tool steel. The Inconel 617 and Stellite 6 samples are much more resistant to oxidation and to softening than the hot work tool steel, providing a superior resistance to thermal fatigue cracking. The wear resistance of the Inconel 617 and Stellite 6 alloys at 750 ℃ is also markedly superior. The adhesive oxides growing slowly on Inconel 617 and Stellite 6 alloys sustain the wear action without spalling and are claimed to be responsible for the superior wear resistance of these alloys at 750 ℃.

关键词： steel thixoforming tooling thermal fatigue wear

Adaptive learning algorithm based on mixture Gaussian background

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journal of Systems Engineering and Electronics 2007年第2期18卷 369-376页

作者： Zha Yufei bi Duyan Signal and Information Processing Lab Engineering Coll. of Air Force Engineering Univ. Xi'an 710038 P. R. China

The key problem of the adaptive mixture background model is that the parameters can adaptively change according to the input data. To address the problem, a new method is proposed. Firstly, the recursive equations are inferred based on the maximum likelihood rule. Secondly, the forgetting factor and learning rate factor are redefined, and their still more general formulations are obtained by analyzing their practical functions. Lastly, the convergence of the proposed algorithm is proved to enable the estimation converge to a local maximum of the data likelihood function according to the stochastic approximation theory. The experiments show that the proposed learning algorithm excels the formers both in converging rate and accuracy.

关键词： Mixture Gaussian model Background model, Learning algorithm.

The study of disturbance sources energy size identification based on free energy theory

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Science China(Technological Sciences) 2018年第2期61卷 242-249页

作者： bi tianshu qin junda state key laboratory of alternate electrical power system with renewable energy sources north china electric power universityBeijing 102206China

The influence of power system disturbance on safety and stability is serious. Therefore, it is very important to identify the disturbance quickly and accurately. However, until now there is no unilbrm standard evaluation of disturbances on the energy impact strength, also no appropriate method to quantitatively and quickly assess the size of the disturbance energy. In this paper, the relationship between energy enthalpy and free energy in thermodynamics field is introduced into the description of disturbance free energy. And a new method based on energy entropy theory is proposed. In order to analyze the energy characteristics of various types of disturbances in power systems, an amended method of energy entropy is proposed. The free energy of each disturbance is described. Finally, the proposed theory is validated using the standard IEEE 39-bus system. The disturbance free energy is calculated under 5 kinds of disturbances. The proposed method provides a new idea to analyze the disturbance propagation and describe the impact strength of disturbance.

关键词： free energy disturbance identification energy identification energy entropy

Effect of Spanwise Flexibility on Propulsion Performance of a Flapping Hydrofoil at Low Reynolds Number

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Chinese journal of Mechanical Engineering 2012年第1期25卷 12-19页

作者： bi Shusheng CAI Yueri Robotics Institute Beihang UniversityBeijing 100191China

Spanwise flexibility is a key factor influencing propulsion performance of pectoral foils. Performances of bionic fish with oscillating pectoral foils can be enhanced by properly selecting the spanwise flexibility. The influence law of spanwise flexibility on thrust generation and propulsion efficiency of a rectangular hydro-foil is discussed. Series foils constructed by the two-component silicon rubber are developed. NACA0015 shape of chordwise cross-section is employed. The foils are strengthened by fin rays of different rigidity to realize variant spanwise rigidity and almost the same chordwise flexibility. Experiments on a towing platform developed are carried out at low Reynolds numbers of 10 000, 15 000, and 20 000 and Strouhal numbers from 0.1 to 1. The following experimental results are achieved: (1) The average forward thrust increases with the St number increased; (2) Certain degree of spanwise flexibility is beneficial to the forward thrust generation, but the thrust gap is not large for the fins of different spanwise rigidity; (3) The fin of the maximal spanwise flexibility owns the highest propulsion efficiency; (4) Effect of the Reynolds number on the propulsion efficiency is significant. The experimental results can be utilized as a reference in deciding the spanwise flexibility of bionic pectoral fins in designing of robotic fish prototype propelled by flapping-wing.

关键词： spanwise flexibility flapping motion thrust generation propulsion efficiency low Reynolds number