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Interpretation of solar microwave C type burst spectra in terms of magnetic nonhomogeneity

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Science China Mathematics 1997年第12期40卷 1325-1330页

作者：姚金兴于兴凤魏奉思 Purple Mountain Observatory Chinese Academy of SciencesNanjing 210008China Laboratory of Numerical Study of Heliospheric Physics Chinese Academy of SciencesBeijing 100080China

The solar radio spectra of the gyro-synchrotron radiation without absorption from mildly relativistic non-thermal electron have been presented using the model with the spherical symmetric *** spectra have the following features: (i) Twists and turns of the spectra,which appear at the joint between the medium and high frequencies,(ii) Flux density drop at the lower *** if there are no absorption in the radio sources,flux density drop at the lower frequencies is still present because of magnetic nonhomogeneity.(iii) These theoretical spectra belong to C *** provides us a new interpretation for the observed solar burst C type spectra.

关键词： spherical symmetric nonhomogeneity gyro-synchrotron spectra twists and turns of spectra flux density drop at lower frequencies solar radio burst C type spectra.

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Light-induced nonhomogeneity and gradient bending in photochromic liquid crystal elastomers

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Science China(Physics,Mechanics & Astronomy) 2006年第5期49卷 553-563页

作者： JIN Lihua JIANG Xin HUO Yongzhong Department of Mechanics and Engineering Science Fudan UniversityShanghai 200433China Department of Mechanics and Engineering ScienceFudan UniversityShanghai 200433China Department of Mechanics and Engineering ScienceFudan UniversityShanghai 200433China

The recently reported opto-mechanical effect of some photochromic liquid crystal elastomers (LCEs) is studied. It is found that in such LCEs, material parameters such as the Young’s modulus and the stress-free strains will become nonhomogeneous under light irradiations. One may call them the light-induced functionally gradient materials. Analytical expressions for the dependence of the material parameters on the space varia- ble and possibly on the time variable are obtained. Exponential dependence can be derived under certain approximations. As an example, the light-induced bending of a beam is studied. Two neutral planes are found in the beam. Thus, along the thickness of the beam, there are extensions in the upper and lower parts and contractions in the middle.

关键词： opto-mechanical effect material nonhomogeneity functionally gradient materials light-induced bending

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Crack tip higher order stress fields for functionally graded materials with generalized form of gradation

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Journal of Central South University 2010年第6期17卷 1177-1184页

作者：燕秀发钱七虎卢红标王玮孙翱 Engineering Institute of Engineering Corps People's Liberation Army University of Science and Technology People's Liberation Army 91550 Unit

A generalized form of material gradation applicable to a more broad range of functionally graded materials(FGMs) was *** the material model,analytical expressions of crack tip higher order stress fields in a series form for opening mode and shear mode cracks under quasi-static loading were developed through the approach of asymptotic ***,a numerical experiment was conducted to verify the accuracy of the developed expressions for representing crack tip stress fields and their validity in full field data analysis by using them to extract the stress intensity factors from the results of a finite element analysis by local collocation and then comparing the estimations with the existing *** expressions show that nonhomogeneity parameters are embedded in the angular functions associated with higher terms in a recursive manner and at least the first three terms in the expansions must be considered to explicitly account for material nonhomogeneity effects on crack tip stress fields in the case of *** numerical experiment further confirms that the addition of the nonhomogeneity specific terms in the expressions not only improves estimates of stress intensity factor,but also gives consistent estimates as the distance away from the crack tip ***,the analytical expressions are suitable for the representation of crack tip stress fields and the analysis of full field data.

关键词： functionally graded materials crack tip nonhomogeneity asymptotic analysis higher order stress field

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Design equation for stability of a circular tunnel in anisotropic and heterogeneous clay

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Underground Space 2022年第1期7卷 76-93页

作者： Suraparb Keawsawasvong Boonchai Ukritchon Department of Civil Engineering Thammasat Engineering SchoolThammasat UniversityPathumthani 12120Thailand Centre of Excellence in Geotechnical and Geoenvironmental Engineering Department of Civil EngineeringFaculty of EngineeringChulalongkorn UniversityBangkok 10330Thailand Center of Excellence on Earthquake Engineering and Vibration Department of Civil EngineeringFaculty of EngineeringChulalongkorn UniversityBangkok 10330Thailand

The safety assessment of tunnel stability is critical to tunnel construction and requires accurate analysis to obtain a reliable *** anisotropy is an important aspect of clay behavior,but it is mostly neglected in practical stability *** this study,the effects of undrained strength anisotropy and strength nonhomogeneity on the stability of unlined circular tunnels in clays are *** static approach of lower-bound(LB)analysis using finite-element and second-order cone programming is employed to exam-ine the aforementioned *** anisotropic shear strength of clay is modeled by employing an elliptical yield function under plane strain conditions.A complete set of dimensionless parameters covering the cover depth ratios of tunnels,normalized overburden pressure ratios,normalized strength gradient ratios of clays,and anisotropic strength ratios,are systematically *** new LB solutions indicate that the stability load factor of the problem has a nonlinear relationship with the cover depth ratio and the anisotropic strength ratio,and there exists a linear relationship with the normalized overburden pressure and the normalized strength *** influ-ence on the predicted failure mechanism is parametrically evaluated.A statistically approximate stability equation of unlined circular tunnels in anisotropic and non-homogeneous clay is proposed for the first time,which contains four new stability factors,namely,con-stant undrained strength,linearly increasing strength gradient,undrained strength anisotropy,and soil unit weight,and it can serve as a fast and accurate tool for predicting the undrained stability of this problem in practice.

关键词： Circular tunnel Anisotropy nonhomogeneity Lower bound Second-order cone programming