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Heterogeneities of grain boundary contact for simulation of laboratoryscale mechanical behavior of granitic rocks

Journal of Rock Mechanics and Geotechnical Engineering 2024年第7期16卷 2629-2644页

作者： Xiongyu hu Marte Gutierrez Zhiwei yan Key Laboratory of Transportation Tunnel Engineering Ministry of EducationSouthwest Jiaotong UniversityChengdu610031China University Transportation Center for Underground Transportation Infrastructure Colorado School of MinesGoldenUSA School of Civil Engineering Southwest Jiaotong UniversityChengdu610031China

From a practical point of view,grain structure heterogeneities are key parameters that control the rock response and still remains a challenge to incorporate in a quantitative *** of the less discussed topics in the context of the grain-based model(GBM)in the particle flow code(PFC)is the contact heterogeneities and the appropriate contact model to mimic the grain boundary ***,the smooth joint(SJ)model and linear parallel bond(LPB)model are used to simulate the grain boundary ***,the literature does not document the suitability of different models for specific *** challenge in implementing GBM in PFC is that only a single bonding parameter is used at the grain *** aim of this study is to investigate the responses of a laboratory-scale specimen with SJ and LPB models,considering grain boundary heterogeneous and homogeneous contact *** and biaxial compression tests are performed to calibrate the response of Creighton *** stressestrain curves,volumetric dilation,inter-crack(crack in the grain boundary),and intra-crack(crack within the grain)development,and failure patterns associated with different contact models are *** was found that both the SJ and LPB models can reproduce the pre-peak behavior observed for a granitic rock ***,the LPB model is unable to reproduce the post-peak *** to the large interlocking effect originating from the balls in contact and the ball size in the LPB model,local dilation is induced at the grain *** overestimates the volumetric dilation and residual shear *** LPB model tends to result in discontinuous inter-cracks and stress localization in the rock specimen,resulting in fine fragments at the rock surface during failure.

关键词： Grain boundary contact Smooth joint(SJ)model Linear parallel bond(LPB)model Contact heterogeneities Particle flow code(PFC) Granitic rock

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On complete convergence for Stout's type weighted sums of NOD sequence

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Applied Mathematics(A Journal of Chinese Universities) 2015年第3期30卷 340-346页

作者： YI yan-chun hu Di CHEN Ping-yan College of Mathematics and Statistics Hengyang Normal University Department of Mathematics Ji’nan University

In this paper, the complete convergence for the weighted sums of independent and identically distributed random variables in Stout [9] is improved and extended under NOD *** more optimal moment condition is given. The... 详细信息

关键词： NOD sequence Stout's type weighted sum complete convergence

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Reduced order model for unsteady aerodynamic performance of compressor cascade based on recursive RBF

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Chinese Journal of Aeronautics 2021年第4期34卷 341-351页

作者： Jiawei hu Hanru LIU yan'gang WANG Weixiong CHEN yan MA School of Power and Energy Northwestern Polytechnical UniversityXi'an 710072China yangtze River Delta Research Institute Northwestern Polytechnical UniversityTaicang 215400China

Based on Recursive Radial Basis Function(RRBF)neural network,the Reduced Order Model(ROM)of compressor cascade was established to meet the urgent demand of highly efficient prediction of unsteady aerodynamics performance of *** novel ROM called ASA-RRBF model based on Adaptive Simulated Annealing(ASA)algorithm was developed to enhance the generalization ability of the unsteady *** ROM was verified by predicting the unsteady aerodynamics performance of a highly-loaded compressor *** results show that the RRBF model has higher accuracy in identification of the dimensionless total pressure and dimensionless static pressure of compressor cascade under nonlinear and unsteady conditions,and the model behaves higher stability and computational ***,for the strong nonlinear characteristics of aerodynamic parameters,the RRBF model presents lower ***,the RRBF model predicts with a large error in the identification of aerodynamic parameters under linear and unsteady *** ASA-RRBF,by introducing a small-amplitude and highfrequency sinusoidal signal as validation sample,the width of the basis function of the RRBF model is optimized to improve the generalization ability of the ROM under linear unsteady ***,this model improves the predicting accuracy of dimensionless static pressure which has strong nonlinear *** ASA-RRBF model has higher prediction accuracy than RRBF model without significantly increasing the total time *** novel model can predict the linear hysteresis of dimensionless static pressure happened in the harmonic condition,but it cannot accurately predict the beat frequency of dimensionless total pressure.

关键词： Compressor cascade Neural network Recursive radial basis function Reduced order model Unsteady flow

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Advanced glycation end products induce neural tube defects through elevating oxidative stress in mice

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Neural Regeneration Research 2018年第8期13卷 1368-1374页

作者： ru-Lin Li Wei-Wei Zhao Bing-yan Gao Laboratory for Development College of Life Sciences Northwest University

Our previous study showed an association between advanced glycation end products （AGEs） and neural tube defects （NTDs）. To understand the molecular mechanisms underlying the effect of AGEs on neural tube development, C57BL/6 female mice were fed for 4 weeks with com- mercial food containing 3% advanced glycation end product bovine serum albumin （AGE-BSA） or 3% bovine serum albumin （BSA） as a control. After mating mice, oxidative stress markers including malondialdehyde and H202 were measured at embryonic day 7.5 （E7.5） of ges- tation, and the level of intracellular reactive oxygen species （ROS） in embryonic cells was determined at E8.5. In addition to evaluating NTDs, an enzyme-linked immunosorbent assay was used to determine the effect of embryonic protein administration on the N-（carboxymethyl） lysine reactivity of acid and carboxyethyl lysine antibodies at E10.5. The results showed a remarkable increase in the incidence of NTDs at El0.5 in embryos of mice fed with AGE-BSA （no hyperglycemia） compared with control mice. Moreover, embryonic protein administration resulted in a noticeable increase in the reactivity of N-（carboxymethyl） lysine and N（ε）-（carboxyethyl） lysine antibodies. Malondialdehyde and H2O2 levels in embryonic cells were increased at E7.5, followed by increased intracellular ROS levels at E8.5. Vitamin E supplementation could partially recover these phenomena. Collectively, these results suggest that AGE-BSA could induce NTDs in the absence of hyperglycemia by an underlying mechanism that is at least partially associated with its capacity to increase embryonic oxidative stress levels.

关键词： nerve regeneration neural tube defects advanced glycation end products diabetic embryopathy oxidative stress N-(carboxymethyl)lysine malondiadehyde N(ε)-(carboxyethyl) lysine embryo H2O2 bovine serum albumin neural regeneration

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De novo assembly of white poplar genome and genetic diversity of white poplar population in Irtysh River basin in China

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Science China(Life Sciences) 2019年第5期62卷 609-618页

作者： yan-Jing Liu Xiao-ru Wang Qing-Yin Zeng State Key Laboratory of Tree Genetics and Breeding Chinese Academy of Forestry State Key Laboratory of Systematic and Evolutionary Botany Institute of BotanyChinese Academy of Sciences Department of Ecology and Environmental Science UPSCUmea University

The white poplar(Populus alba) is widely distributed in Central Asia and Europe. There are natural populations of white poplar in Irtysh River basin in China. It also can be cultivated and grown well in northern China. In this study, we sequenced the genome of P. alba by single-molecule real-time technology. De novo assembly of P. alba had a genome size of 415.99 Mb with a contig N50 of 1.18 Mb. A total of 32,963 protein-coding genes were identified. 45.16% of the genome was annotated as repetitive elements. Genome evolution analysis revealed that divergence between P. alba and Populus trichocarpa(black cottonwood)occurred ～5.0 Mya(3.0, 7.1). Fourfold synonymous third-codon transversion(4 DTV) and synonymous substitution rate(ks)distributions supported the occurrence of the salicoid WGD event(～ 65 Mya). Twelve natural populations of P. alba in the Irtysh River basin in China were sequenced to explore the genetic diversity. Average pooled heterozygosity value of P. alba populations was 0.170±0.014, which was lower than that in Italy(0.271±0.051) and hungary(0.264±0.054). Tajima's D values showed a negative distribution, which might signify an excess of low frequency polymorphisms and a bottleneck with later expansion of *** populations examined.

关键词： Populus alba de novo assembly genetic diversity population expansion

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Dynamic response to a moving load of a Timoshenko beam resting on a nonlinear viscoelastic foundation

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Acta Mechanica Sinica 2013年第5期29卷 718-727页

作者： yan yang hu Ding Li-Qun Chen Shanghai Institute of Applied Mathematics and Mechanics Shanghai Key Laboratory of Mechanics in Energy EngineeringShanghai University Department of Mechanics Shanghai University

The present paper investigates the dynamic response of finite Timoshenko beams resting on a sixparameter foundation subjected to a moving load. It is for the first time that the Galerkin method and its convergence are studied for the response of a Timoshenko beam supported by a nonlinear foundation. The nonlinear Pasternak foundation is assumed to be cubic. Therefore, the effects of the shear deformable beams and the shear deformation of foundations are considered at the same time. The Galerkin method is utilized for discretizing the nonlinear partial dif- ferential governing equations of the forced vibration. The dynamic responses of Timoshenko beams are determined via the fourth-order runge-Kutta method. Moreover, the effects of different truncation terms on the dynamic responses of a Timoshenko beam resting on a complex foundation are discussed. The numerical investigations shows that the dynamic response of Timoshenko beams supported by elastic foundations needs super high-order modes. Furthermore, the system parameters are compared to determine the dependence of the convergences of the Galerkin method.

关键词： Nonlinear Timoshenko beam Pasternak foun- dation Galerkin method Convergence

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Comparison of Chain Structures between High-speed Extrusion Coating Polyethylene Resins by Preparative Temperature Rising Elution Fractionation and Cross-fractionation

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Chinese Journal of Polymer Science 2015年第11期33卷 1586-1597页

作者： yan-hu Xue Shu-qin Bo 姬相玲 State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied ChemistryChinese Academy of Sciences

Two polyethylene（PE） resins（samples A and B） are synthesized as high-speed extrusion coatings with similar minimum coating thickness and neck-in performance but different maximum coating speeds. Both samples are separated into seven fractions using preparative temperature rising elution fractionation. The microstructures of the original samples and their fractions are studied by high-temperature gel permeation chromatography, Fourier transform infrared spectroscopy, 13 C nuclear magnetic resonance spectroscopy, differential scanning calorimetry, and successive self-nucleation/annealing thermal fractionation. Compared with sample B, sample A has a broader MWD, more LCB contents, and less SCB contents. Moreover, sample A contains slightly more 30 ℃ and 50 ℃ fractions with lower molecular weights, and more fractions at 75 ℃ and 85 ℃ with higher molecular weight. The chain structure and its distribution in the two PE resins are studied in detail, and the relationship between the chain structure and resin properties is also discussed.

关键词： Polyethylene High-speed extrusion coating Chain structure TREF Cross-fractionation

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Hot deformation behavior and microstructure evolution of as-cast AZ91D magnesium alloy without pre-homogenization treatment

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Rare Metals 2013年第4期32卷 338-346页

作者： yan Xu Lian-Xi hu Yu Sun School of Materials Science and Engineering Harbin Institute of Technology School of Mechanical Engineering Beihua University

The deformation behavior and the microstruc-ture evolution of as-cast AZ91D magnesium alloy without pre-homogenization treatment were systematically inves-tigated. The flow stress behavior was studied by com-pression tests in strain rate range of 0.001-1.000 s^-1 and deformation temperature range of 220-380 ℃ with a maximum deformation strain of 60 %. The dependence of flow stress on deformation temperature and strain rate was described by hyperbolic sine constitutive equation. Through regression analysis, the average apparent activa- tion energy and coefficient of strain rate sensitivity were estimated to be 181.98 ***^-1 and 0.14, respectively. The results also reveal that the variation of peak stress depends on strain rate and deformation temperature. Microstructure observation shows that, at temperatures higher than 300 ℃ and strain rates lower than 0.01 s^-1, DRX developed extensively at the grain boundaries and in the core of coarse grains, resulting in a more homogeneous microstructure. Furthermore, the effects of strain, defor-mation temperature, strain rate, and eutectic β phase on the microstructure evolution of as-cast AZ91D magnesium alloy were discussed.

关键词： AZ91D magnesium alloy Isothermalcompression Constitutive equation Peak stress Microstructure evolution

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Effect of Ti contents on interfacial bonding,mechanical and thermal properties of Mo-Cu composites

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Tungsten 2024年第3期6卷 549-554页

作者： Jian-ru Chu Xiao-Song Jiang Tian-yan Liu Key Laboratory of Advanced Technologies of Materials Ministry of EducationChengdu 610031China School of Materials Science and Engineering Southwest Jiaotong UniversityChengdu 610031China Reactor Engineering Research Sub-Institute Nuclear Power Institute of ChinaChengdu 610005China

Mo-Cu composites are widely used in electronic packaging,vacuum technology,microwave devices and other fields due to their excellent properties,such as excellent electrical and thermal conductivity,low adjustable coef... 详细信息

关键词： composites thermal properties

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Deployment dynamics of a simplified spinning IKAROS solar sail via absolute coordinate based method

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Acta Mechanica Sinica 2013年第1期29卷 132-142页

作者： Jing Zhao Hai-yan hu Qiang Tian State Key Lab of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and Astronautics School of Aerospace Engineering Beijing Institute of Technology

The spinning solar sail of large scale has been well developed in recent years. Such a solar sail can be considered as a rigid-flexible multibody system mainly composed of a spinning central rigid hub, a number of flexible thin tethers, sail membranes, and tip masses. A simplified interplanetary kite-craft accelerated by radiation of the Sun （IKAROS） model is established in this study by using the absolute-coordinate-based （ACB） method that combines the natural coordinate formulation （NCF） describing the central rigid hub and the absolute nodal coordinate formulation （ANCF） describing flexible parts. The initial configuration of the system in the second-stage deployment is determined through both dynamic and static analyses. The huge set of stiff equations of system dynamics is solved by using the generalized-alpha method, and thus the deployment dynamics of the system can be well understood.

关键词： Solar sail · Spinning deployment - Natural coordinate formulation Absolute nodal coordinate formulation

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