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Closed-form solutions for free vibration of rectangular fGM thin plates resting on elastic foundation

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Acta Mechanica Sinica 2016年第6期32卷 1088-1103页

作者： T. f. Xu Y. f. Xing Institute of Solid Mechanics Beihang UniversityBeijing 100191 China China Academy of Launch Vehicle Technology R&D Center Beijing 100076 China

This article presents closed-form solutions for the frequency analysis of rectangular functionally graded material (fGM) thin plates subjected to initially in-plane loads and with an elastic foundation. Based on classical thin plate theory, the governing differential equations are derived using Hamilton's principle. A neutral surface is used to eliminate stretching-bending coupling in fGM plates on the basis of the assumption of constant Poisson's ratio. The resulting governing equation of fGM thin plates has the same form as homogeneous thin plates. The separation-of-variables method is adopted to obtain solutions for the free vibration problems of rectangular fGM thin plates with separable boundary conditions, including, for example, clamped plates. The obtained normal modes and frequencies are in elegant closed forms, and present formulations and solutions are validated by comparing present results with those in the literature and finite element method results obtained by the authors. A parameter study reveals the effects of the power law index n and aspect ratio a/b on frequencies.

关键词： functionally graded material free vibration Rectangular plate Close form solutions Neutral surface

Determination of stress intensity factor with direct stress approach using finite element analysis

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Acta Mechanica Sinica 2017年第5期33卷 879-885页

作者： X.Ji f.Zhu P.f.He School of Aerospace Engineering and Applied Mechanics Tongji University

In this article, a direct stress approach based on finite element analysis to determine the stress intensity factor is improved. firstly, by comparing the rigorous solution against the asymptotic solution for a problem of an infinite plate embedded a central crack, we found that the stresses in a restrictive interval near the crack tip given by the rigorous solution can be used to determine the stress intensity factor, which is nearly equal to the stress intensity factor given by the asymptotic solution. Secondly, the crack problem is solved numerically by the finite element method. Depending on the modeling capability of the software, we designed an adaptive mesh model to simulate the stress singularity. Thus, the stress result in an appropriate interval near the crack tip is fairly approximated to the rigorous solution of the corresponding crack problem. Therefore, the stress intensity factor may be calculated from the stress distribution in the appropriate interval, with a high accuracy.

关键词： fracture mechanics Stress singularity Stress intensity factor finite element method Direct stress method

The role of AVDR in linear cascade testing

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航空动力学报 2007年第6期22卷 933-944页

作者： Wing f.Ng Department of Mechanical Engineering Virginia Polytechnic Instituteand State University

Linear cascade testing plays an important role in the research and development of turbomachinery and is widely used over the *** ideal cascade model of a turbomachinery blade row is *** actual linear cascade testing,the flow through the test section converges due to the development of the boundary layer and secondary flow along the sidewall surfaces of the test *** velocity density ratio(AVDR) is adopted to account for the deviation of the tested cascade flow from the ideal 2D *** numerous published cascade works,the influence of AVDR on cascade performance is seen to be complicated with many affecting factors,such as those related to cascade/blade geometry and flow ***,controlling AVDR is limited by the facility ***,real blade-to-blade flow in turbomachines is usually associated with AVDR greater than unity due to limited span of blades between the hub and shroud such that cascade testing without reducing AVDR could be favored *** these facets add complexity and diversification to the *** current paper reviews previous studies and results on *** understanding on the role of AVDR and recommendations on how to deal with it in linear cascade testing are provided.

关键词：线性叶栅试验轴向速度密度比空气流动叶栅特性

Competitive effect between roughness and mask pattern on charging phenomena during plasma etching

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Plasma Science and Technology 2022年第3期24卷 152-161页

作者： Peng ZHANG Ruvarashe f DAMBIRE School of Electronic Information Engineering Yangtze Normal UniversityChongqing 408100People's Republic of China School of Chemistry and Chemical Engineering Yangtze Normal UniversityChongqing 408100People's Republic of China

In the plasma etching process,the edge roughness and mask pattern usually play a significant role in the deformation of holes under the influence of the charging *** competitive effect between these two factors has been investigated,focusing on the surface charging in a hexagonal array,with various values of roughness parameters(amplitude(A)and wavelength(W))and distances between holes(L).A series of classical particle dynamic simulations of surface charging,surface etching and profile evolution were used to investigate the effect of roughness and pattern on *** study showed that various roughness and patterns(represented by different values of L)can significantly influence surface distributions of the electric-field(Efield)and the etching rates on the mask *** simulations also showed that(1)the shape of the pattern array influences the mask hole profile during the etching process,i.e.a hexagonal array pattern tends to deform the profile of a circular mask hole into a hexagonal hole;(2)pattern roughness is aggravated during the etching *** factors were found to be significant only at a small feature pitch and may be ignored at a large feature *** mechanisms of these results during the etching process are *** work sheds light on the ways to maintain pattern integrity and further improve the quality of the pattern transfer onto the substrate.

关键词： plasma etching pattern roughness

Experimental Investigation of Separation and Transition Processes on a High-Lift Low-Pressure Turbine Profile Under Steady and Unsteady Inflow at Low Reynolds Number

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Journal of Thermal Science 2010年第1期19卷 26-33页

作者： Satta f Simoni D Ubaldi M Zunino P Bertini f DIMSET-Università di Genova Via Montallegro 1I-16145 GenovaItaly Avio R&D V.I Maggio99 I-10040 Rivalta(TO)-Italy

The effects induced by the presence of incoming wakes on the boundary layer developing over a high-lift low-pressure turbine profile have been investigated in a linear cascade at *** tested Reynolds number is 70000,typical of the cruise operating *** results of the investigations performed under steady and unsteady inflow conditions are *** unsteady investigations have been performed at the reduced frequency of f+=0.62,representative of the real engine operating *** aerodynamic loadings as well as boundary layer velocity profiles have been measured to survey the separation and transition *** analysis has been also performed to better understand the phenomena associated with the transition process under steady *** the unsteady case,a phase-locked ensemble averaging technique has been employed to reconstruct the time-resolved boundary layer velocity distributions from the hot-wire instantaneous signal *** ensemble-averaging technique allowed a detailed analysis of the effects induced by incoming wakes-boundary layer interaction in separation ***-resolved results are presented in terms of mean velocity and unresolved unsteadiness time-space plots.

关键词： boundary layer separation boundary layer transition wake-boundary layer interaction high-liftprofile low-pressure turbine

Bolstering integrity in environmental data science and machine learning requires understanding socioecological inequity

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frontiers of Environmental Science & Engineering 2024年第5期18卷 171-179页

作者： Joe f.Bozeman III School of Civil and Environmental Engineering Georgia Institute of TechnologyAtlantaGA30332USA School of Public Policy Georgia Institute of TechnologyAtlantaGA30332USA

Socioecological inequity in environmental data science—such as inequities deriving from data-driven approaches and machine learning(ML)—are current issues subject to debate and *** is growing consensus around embedding equity throughout all research and design domains—from inception to administration,while also addressing procedural,distributive,and recognitional ***,practically doing so may seem onerous or daunting to *** current perspective helps to alleviate these types of concerns by providing substantiation for the connection between environmental data science and socioecological inequity,using the Systemic Equity framework,and provides the foundation for a paradigmatic shift toward normalizing the use of equity-centered approaches in environmental data science and ML *** the integrity of environmental data science and ML is just beginning from an equity-centered tool development and rigorous application *** this end,this perspective also provides relevant future directions and challenges by overviewing some meaningful tools and strategies—such as applying the Wells-Du Bois Protocol,employing fairness metrics,and systematically addressing irreproducibility;emerging needs and proposals—such as addressing data-proxy bias and supporting convergence research;and establishes a ten-step path ***,the work that environmental scientists and engineers do ultimately affect the well-being of us all.

关键词： Equity Bias Machine Learning Data Science Justice Systemic Equity

A closed form of a kurtosis parameter of a hypergeometric-Gaussian type-Ⅱ beam

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Chinese Physics B 2016年第4期25卷 154-160页

作者： Khannous f Ebrahim A A A Belafhal A adida Morocco

Based on the irradiance moment definition and the analytical expression of waveform propagation for hypergeometric- Gaussian type-II beams passing through an ABCD system, the kurtosis parameter is derived analytically and illustrated numerically. The kurtosis parameters of the Gaussian beam, modified Bessel modulated Gaussian beam with quadrature radial and elegant Laguerre-Gaussian beams are obtained by treating them as special cases of the present treatment. The obtained results show that the kurtosis parameter depends on the change of the beam order m and the hollowness parameter p, such as its decrease with increasing m and increase with increasing p.

关键词： Kurtosis parameter hypergeometric-Gaussian type-II beams paraxial optical ABCD system

Phase Stability, Kinetic Diagrams and Diffusion Path in High Temperature Oxidation of Binary Solid-Solution Alloys

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Journal of Materials Science & Technology 2003年第6期19卷 545-552页

作者： YanNIU f.Gesmundo StateKeyLaboratoryforCorrosionandProtection InstituteofMetalResearchShenyang110016China DipartimentodiIngegneriaChimicaediProcesso UniversityofGenova16129GenovaItaly

The phase diagrams of ternary systems involving two metal components and one oxidant are considered first, the limitations to their use is discussed in relation to the high temperature oxidation of binary alloys. Kinetic diagrams, which are useful to predict the conditions for the stability of the two mutually insoluble oxides as the external scale, are then calculated on the basis of thermodynamic and kinetic data concerning both the alloys and the oxides, assuming the validity of the parabolic rate law. A combination of the two types of diagrams provides a more detail information about the oxidation behavior of binary alloys. The calculation of the diffusion paths, which relate the oxidant pressure to the composition of the system in terms of the alloy components both in the alloy and in the scale during an initial stage of the reaction in the presence of the parabolic rate law, is finally developed.

关键词： Binary alloys Oxidation Therniodynamic and kinetic diagrams Diffusion path

fifty years of character compatibility concepts at work

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植物分类学报 2008年第2期46卷 109-129页

作者： George f.ESTABROOK Department of Ecology and Evolutionary Biology The University of Michigan Ann Arbor MI 4809-1048 USA

In the mid 19th century, systematic biologists realized that observable similarities and differences among a group of related species could be the basis for hypotheses about the evolutionary relationships among the species and their ancestors. Such hypotheses can be expressed as characters. A character is comprised of two or more character states of species considered to be similar with respect to a basis for comparison. The states of a character may also be arranged into a character state tree to hypothesize speciation events associated with changes from one character state to another. In the mid 20th century, some systematists realized that sometimes pairs of characters （or character state trees） could be incompatible as hypotheses, i.e., they could not both be true. Through the 1950s, ＇60s and ＇70s, tests for, and ways to resolve, incompatibilities were used to estimate an ancestor rela-tion based on mutually compatible characters. An estimate was often shown as a diagram connecting ancestors to their immediate descendants （not quite correctly） called a phylogenetic tree. More recently, other applications of compatibility concepts have been developed, including： identify characters that appear to be random in the context of their data set; combine estimates of ancestor relations for subsets of taxa in a larger collection into a single estimate （a so-called supertree） for the whole collection; and interpret geographic patterns in an evolutionary context.

关键词： biogeography character compatibility character evaluation convex groups phylogenetic trees,reciprocal illumination speciation supertrees