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Combined approach for analysing evolutionary power spectra of a track-soil system under moving random loads

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Acta Mechanica Sinica 2019年第3期35卷 674-690页

作者： Y.zhao L.T.Si h.Ouyang State Key Laboratory of Structural Analysis for Industrial Equipment Department of Engineering MechanicsInternational Center for Computational MechanicsDalian University of TechnologyDalian 116023Chin School of Engineering University of LiverpoolLiverpool L69 3GHUK

The pseudo-excitation method combined with the integral transform method (PEM-ITM) is presented to investigate the ground vibration of a coupled track-soil system induced by moving random loads. Commonly in the track model, the rail, sleepers, rail pads, and ballast are modelled as an infinite Euler beam, discretely distributed masses, discretely distributed vertical springs, and a viscoelastic layer, respectively. The soil is regarded as a homogenous isotropic half-space coupled with the track using the boundary condition at the surface of the ground. By introducing a pseudo-excitation, the random vibration analysis of the coupled system is converted into a harmonic analysis. The analytical form of evolutionary power spectral density responses of the simplified coupled track-soil system under a random moving load is derived in the frequency/wavenumber domain by PEM-ITM. In the numerical examples, the effects of different parameters, such as the moving speed, the soil properties, and the coherence of moving loads, on the ground response are investigated.

关键词： Track-soil system Moving random loads Evolutionary power spectrum Pseudo-excitation method Integral transform method Vibration transmission

Application of kernel ridge regression in predicting neutron-capture reaction cross-sections

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Communications in Theoretical Physics 2022年第9期74卷 98-104页

作者： T X huang X h Wu P W zhao State Key Laboratory of Nuclear Physics and Technology School of PhysicsPeking UniversityBeijing 100871China

This article provides the first application of the machine-learning approach in the study of the cross-sections for neutron-capture reactions with the kernel ridge regression(KRR)*** is found that the KRR approach can reduce the root-mean-square(rms)deviation of the relative errors between the experimental data of the Maxwellian-averaged(n,γ)cross-sections and the corresponding theoretical predictions from 69.8%to 35.4%.By including the data with different temperatures in the training set,the rms deviation can be further significantly reduced to 2.0%.Moreover,the extrapolation performance of the KRR approach along different temperatures is found to be effective and reliable.

关键词： kernel ridge regression machine learning neutron-capture reaction

Effect of interlayer addition on microstructure and mechanical properties of NiTi/stainless steel joint by electron beam welding

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Journal of Materials Science & Technology 2021年第2期61卷 16-24页

作者： h.Niu h.C.Jiang M.J.zhao L.J.Rong CAS Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of ScienceShenyang110016China School of Materials Science and Engineering University of Science and Technology of ChinaHefei230026China

NiTi/Stainless Steel(SS) sheets have been welded via a vacuum electron beam welding process, with three methods(offsetting electron beam to SS side without interlayer, adding Ni interlayer and adding Fe Ni interlayer), to promote mechanical properties of the Ni Ti/SS joints. The joints with different interlayers are all fractured in the weld zone near the Ni Ti side, which is attributed to the enrichment of intermetallic compounds including Fe2 Ti and Ni3 Ti. The fracture mechanisms of different joints are strongly dependent on the types of interlayers, and the joints without interlayer, adding Ni interlayer and adding Fe Ni interlayer exhibit cleavage fracture, intergranular fracture and mixed fracture composed of cleavage and tearing ridge, respectively. Compared with the brittle laves phase Fe2 Ti, Ni3 Ti phase can exhibit certain plasticity, block the crack propagation and change the direction of crack propagation. The composite structure of Ni3 Ti and Fe2 Ti will be formed when the Fe Ni alloy is taken as the interlayer, which provides the joint excellent mechanical properties, with rupture strength of 343 MPa.

关键词： NiTi Stainless steel Electron beam welding Interlayer Mechanical property

Observability Analysis of Integrated Electricity and heating Systems with Thermal Quasi-dynamics in Pipelines

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CSEE Journal of Power and Energy Systems 2024年第3期10卷 1145-1158页

作者： Zhigang Li Wenjian Zheng Junbo zhao J.h.Zheng Q.h.Wu School of Electric Power Engineering South China University of TechnologyGuangzhou 510641China Fuzhou Changle District Power Supply Company of State Grid Fujian Electric Power Co. Ltd.Fuzhou 350000China Department of Electrical and Computer Engineering University of ConnecticutStorrsCT 06269USA CSEE IEEE

Observability analysis(OA)is vital to obtaining the available input measurements of state estimation(SE)in an integrated electricity and heating system(IEhS).Considering the thermal quasi-dynamics in pipelines,the measurement equations in heating systems are dependent on the estimated results,leading to an interdependency between OA and *** OA methods require measurement equations be known exactly before SE is performed,and they are not applicable to *** bridge this gap,a scenario-based OA scheme for IEhSs is devised that yields reliable analysis results for a predefined set of time-delay scenarios to cope with this *** its core procedure,the observable state identification and observability restoration are formulated in terms of integer linear *** tests are conducted to demonstrate the validity and superiority of the proposed formulation.

关键词： Integrated electricity and heating system measurement observability analysis state estimation thermal quasi-dynamics

The concentration and efflux of tree stem CO_(2) and the role of xylem sap flow

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Frontiers in Biology 2009年第1期4卷 47-54页

作者： Ping zhao Dirk hÖLSChER South China Institute of Botany Chinese Academy of SciencesGuangzhou 510650China 2 Department of Tropical Silviculture and Forest EcologyUniversity of Göttingen37077 GöttingenGermany

The accurate assessment of actual tree stem respiration and its relation with temperature plays a considerable role in investigating the forest carbon *** increasing number of research reports have indicated that tree stem respiration determined with the commonlyapplied chamber gas exchange measuring system does not follow expectations regarding temperature *** method is based on the nowadays widely-accepted theory that the respired CO_(2) in a tree stem would all diffuse outward into the ***,it neglects partial CO_(2) that is dissolved in the xylem sap and is carried away by the transpirational *** have started to realize that the respired CO_(2) measured with the chamber gas exchange method is only a portion of the total stem respiration(CO_(2) efflux),while the other portion,which is sometimes very substantial in quantity(thought to occupy maybe 15%-75%of the total stem respiration),is transported to the upper part of the stem and to the canopy by sap *** suggests that the CO_(2) produced by respiration is re-allocated within the ***,the change in CO_(2) efflux could be reflected in the rates of sap flow in addition to its dependence on *** methods and instruments are required to quantify the internal and external CO_(2) fluxes in the trunk and their interaction with related environmental factors.

关键词： sap flow rates respired CO_(2)in the stem retranslocation of stem respiration

A new thermodynamically stable Nb_(2)Ni intermetallic compound phase revealed by peritectoid transition within binary Nb-Ni alloy system

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Journal of Materials Science & Technology 2022年第5期100卷 246-253页

作者： J.F.zhao h.P.Wang B.Wei School of Physical Science and Technology Northwestern Polytechnical UniversityXi’an 710072China

A new intermetallic compound of thermodynamically stable Nb_(2)Ni phase is discovered within Nb-Ni binary system,refreshing the current situation that there are only three stable intermediate phases of Nb_(7)Ni_(6),NbNi_(3) and NbNi_(8).The new stable phase is generated from the peritectoid transition:(Nb)+Nb_(7)Ni_(6)→Nb_(2)Ni,and the transformation temperature is 1533 *** refreshes the current equilibrium Nb-Ni binary phase *** is confirmed by transmission electron microscopy and the annealing experiments,which is determined to be the FCC structure(Pearson:cF96,space grope:Fd-3m O2,a=11.888A).Furthermore,the equilibrium properties of Nb_(2)Ni phase are produced by density functional theory,including the formation energy,cohesive energy,bulk modulus and lattice constant.

关键词： Intermetallic compound Peritectoid transition Transmission electron microscopy Density functional theory Nb alloy

Frequency equations of nonlocal elastic micro/nanobeams with the consideration of the surface effects

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Applied Mathematics and Mechanics(English Edition) 2018年第8期39卷 1089-1102页

作者： h.S.zhao Y.ZhANG S.T.LIE School of Civil and Environmental Engineering Nanyang Technological University

A nonlocal elastic micro/nanobeam is theoretically modeled with the consideration of the surface elasticity, the residual surface stress, and the rotatory inertia,in which the nonlocal and surface effects are considered. Three types of boundary conditions, i.e., hinged-hinged, clamped-clamped, and clamped-hinged ends, are examined. For a hinged-hinged beam, an exact and explicit natural frequency equation is derived based on the established mathematical model. The Fredholm integral equation is adopted to deduce the approximate fundamental frequency equations for the clamped-clamped and clamped-hinged beams. In sum, the explicit frequency equations for the micro/nanobeam under three types of boundary conditions are proposed to reveal the dependence of the natural frequency on the effects of the nonlocal elasticity, the surface elasticity, the residual surface stress, and the rotatory inertia, providing a more convenient means in comparison with numerical computations.

关键词： Fredholm integral equation micro/nanobeam natural frequency nonlocal elasticity surface effect

Photodetachment of a homo-Nuclear Linear Tetra-Atomic Negative Molecular Ion

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Chinese Physics Letters 2012年第4期29卷 61-64页

作者： A.Rahman Iftikhar Ahmad A.Afaq h.J.zhao Department of Physics Hazara UniversityMansehraPakistan Department of Physics University of MalakandChakdaraPakistan Centre of Excellence in Solid State Physics University of the PunjabQuid-e-Azam CampusLahore-54590Pakistan School of Physics and Information Science Shanxi Normal UniversityLinfen 041004

The photodetachment of a homo-nuclear linear tetra-atomic negative molecular ion is studied theoretically for an arbitrary laser *** expression for the total cross section is obtained by using an extended version of the two center model,where each center acts as a source of coherent photodetached-electron *** oscillations on observation plane,placed at a large distance from the ion,are *** amplitude of these oscillations is maximum when the laser polarization is parallel to the molecular ***,the amplitude decreases as the angle between the laser polarization and molecular axis increases and consequently vanishes when they are perpendicular to each *** is also found that if the distance between the adjacent centers is very small or very large,then the ampplitude of oscillations is negligibly small.

关键词： Strong centers polarization

Preparation of textile preform with sewing machines and bending properties of stitched woven glass fibre fabrics

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中国有色金属学会会刊：英文版 2005年第2期15卷 221-224页

作者： zhao Nuo-ping h.Rdel C.herzberg Institute of Textile and Clothing Technology Technische Universitt Dresden 01069 Dresden GermanyInstitute of Textile and Clothing Technology Technische Universitt Dresden 01069 Dresden GermanyInstitute of Textile and Clothing Technology Technische Universitt Dresden 01069 Dresden Germany

With the increasing demand of light structure composite in industry, carbon and glass fibres are more and more used, because of their light mass, high strength, high temperature endurance and erosion resistance. This paper focuses on the process of forming a preform. Up to the finished preform, the multilayer reinforced fabrics are subjected to the following procedures: pattern design, cutting and sewing. Considering the fabric properties, the 3-dimensional CAD software and sewing machines, which are generally used in the clothing industry, are also suitable for the processing of the reinforced fabrics. This study aims also to the changes of property arising from the sewing process. Bending stiffness and changes of thickness after sewing are studied. These properties will provide input data for CAD pattern design.

关键词：三维加固织物粗加工弯曲硬度 CAD 光结构复合材料玻璃纤维