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Journal of Materials Science & Technology 2020年第22期54卷 78-84页

作者： Ruihong Wang Shengyu Jiang Bao'an Chen Zhixiang Zhu School of Materials Science and Engineering Xi'an University of TechnologyXi'an710048PR China State Key Laboratory of Advanced Power Transmission Technology Global Energy Interconnection Research Institute Co.Ltd.Beijing102209PR China

A significant size effect is found in the Al3 Sc dispersoid-mediated precipitation in an Al-Mg-Si-Sc *** the Al3 Sc dispersoid size smaller than about 40 nm,β " precipitates nucleate directly on the coherent dispersoids and grow by sacrificing the *** the dispersoid size greater than^40 nm,Q' and U2 phases are additionally produced that nucleate on the dislocations induced by the semi-/incoherent *** and electrical properties are highly sensitive to the Al3 Sc dispersoid-tuned *** co-precipitation of β",Q' and U2 phases leads to an obvious improvement in hardness and simultaneously in electrical conductivity.

关键词： Al-Mg-Si-Sc alloy Al3Sc dispersoids Precipitation size effect Hardness and conductivity

size effect of sandstone after high temperature under uniaxial compression

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Journal of Central South University 2015年第5期22卷 1901-1908页

作者：苏海健靖洪文茅献彪赵洪辉尹乾王辰 State Key Laboratory for Geomechanics & Deep Underground Engineering(China University of Mining & Technology) School of Mechanics and Civil Engineering China University of Mining & Technology

Uniaxial compression tests on sandstone samples with five different sizes after high temperature processes were performed in order to investigate the size effect and its evolution. The test results show that the density, longitudinal wave velocity, peak strength, average modulus and secant modulus of sandstone decrease with the increase of temperature, however, peak strain increases gradually. With the increase of ratio of height to diameter, peak strength of sandstone decreases, which has an obvious size effect. A new theoretical model of size effect of sandstone material considering the influence of temperature is put forward, and with the increase of temperature, the size effect is more apparent. The threshold decreases gradually with the increase of temperature, and the deviations of the experimental values and the theoretical values are between 0.44% and 6.06%, which shows quite a credibility of the theoretical model.

关键词： high temperature process sandstone size effect threshold

size effect of deformation nanotwin bundles on their strengthening and toughening in heterogeneous nanostructured Cu

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Science China(Technological Sciences) 2021年第1期64卷 23-31页

作者： YOU ZeSheng LUO ShuSen LU Lei Herbert Gleiter Institute of Nanoscience Nanjing University of Science and TechnologyNanjing 210094China Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China

Herein, we fabricated a heterogeneous nanostructured Cu with deformation nanotwin bundles(NTBs) embedded in a matrix of nanograins by means of dynamic plastic deformation at liquid nitrogen temperature. We conducted fracture mechanical measurements to investigate the effect of longitudinal length of the NTBs on their strengthening and toughening. Results suggest that an increase in the NTB length had a marginal influence on the tensile strength;however, it remarkably promoted both fracture initiation toughness and crack growth toughness. Longer NTBs are more effective not only in intrinsically enhancing crack tip plasticity by suppressing the strain localization and void nucleation but also in serving as crack bridges behind the crack front to extrinsically resist the fracture by shielding the crack tip.

关键词： fracture toughness nanotwins J-integral size effect toughening mechanism

size effect of fullerene cages and encaged clusters in M3N@C2n

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Science China Chemistry 2009年第5期52卷 584-589页

作者： GAN LiHua School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, China School of Chemistry and Chemical Engineering Southwest University Chongqing China

Based on the calculated findings that the sizes of encaged clusters determine the structures and the stability of C80-based trimetallic nitride fullerenes (TNFs), more extensive density functional theory calculations were performed on M3N@C68, M3N@C78 and M3N@C80 (M=Sc, Y and La). The calculated results demonstrated that the structures and stability undergo a transition with the increasing of the sizes of the cages and clusters. Sc3N is planar inside the three considered cages, Y3N is slightly pyramidal inside C68-6140 and C78-5 and planar inside I h C80-7, however, La3N is pyramidal inside all the three cages. Those cages with pyramidal clusters inside deformed considerably, compared with their parent cages. In these cases, the bonding of metallic atoms toward the cages does not play an impor-tant role, and the encaged cluster tends to be located inside the cages with the largest M-M and M-C distances so that the strain energy can be released mostly. These calculations revealed the size effect of fullerene cages and encaged clusters, and can explain the position priority of M3N inside fullerene cages and the differences in yield of M3N@C2n.

关键词： trimetallic nitride fullerenes (TNFs) density functional theory (DFT) size effect stability

size effect of confined concrete subjected to axial compression

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Journal of Central South University 2014年第3期21卷 1217-1226页

作者：李振宝宋佳杜修力杨修广 College of Architecture and Civil Engineering Beijing University of Technology

In order to investigate the size effect and other effects on the stress-strain relationship of confined concrete, 42 specimens with different sizes and section shapes were placed under axial compression loading. effects of key parameters such as size of specimens, tie configuration, transverse reinforcement ratio, and concrete cover were studied. The results show that for specimens with the same configuration and the same volumetric ratio of the transverse reinforcement, along with the increasing specimen size, the peak stress, peak strain and deformation of the post-peak show a down trend, however, the volumetric ratio of the transverse reinforcement is lowered, the decreasing of the peak stress is accelerated, but the decreasing of the deformation is slow down. For specimens with the same volumetric ratio but different configurations of transverse reinforcement, though the transverse reinforcement configuration becomes more complicated, the peak stress of the large size specimen does not improve more than that of the small size. However, the deformation occurs before the stress declines to 85% of peak stress, and the improvement with the grid pattern tie configuration is much greater due to size effect.

关键词： confined concrete mechanical property size effect configuration type of transverse reinforcement volumetric ratio oftransverse reinforcement concrete cover

size effect of a Negatively Charged Exciton in a Two-Dimensional Quantum Dot

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Communications in Theoretical Physics 2009年第2期51卷 353-357页

作者： LIU Chao XIE Wen-Fang Department of Physics Guangzhou University Guangzhou 510006 China

In this paper we study a negatively charged exciton （NCE）, which is trapped by a two-dimensional （2D） parabolic potential. By using matrix diagonalization techniques, the correlation energies of the low-lying states with L=0, 1, and 2 are calculated as a function of confinement strength. We find that the size effects of different states are different. This phenomenon can be explained as a hidden symmetry, which is originated purely from symmetry. Based on symmetry, the features of the low-lying states are discussed in the influence of the 2D parabolic potential well. It is found that the confinement may cause accidental degeneracies between levels with different low-excited states. It is shown that the effect of quantum confinement on the binding energy of the heavy hole is stronger than that of a light hole.

关键词： quantum dot charged exciton size effect energy spectrum symmetry

size effect on compressive strength of reactive powder concrete

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Journal of China University of Mining and Technology 2008年第2期18卷 279-282页

作者： AN Ming-zhe ZHANG Li-jun YI Quan-xin Department of Civil Engineering and Architecture Beijing Jiaotong University Beijing 100044 China Wuzhou Engineering and Research Institute Beijing 100055 China Grace China Co. Ltd Beijing Branch Beijing 100176 China

In this paper the coefficient and law of the size effect of RPC were studied through experiments and theoretical analysis. The size-effect coefficients for the compressive strength of RPC are deduced through *** indicate that RPC without fiber behaves quite the same as normal or high strength *** size effect on compressive strength is more prominent in RPC containing ***'s size effect formula of compressive strength applies to RPC.A formula is given to predict the compressive strength of cubic RPC specimens 100 mm on a side where the fiber dosage ranges from 0-2%.

关键词： reactive powder concrete (RPC) compressive strength size effect influence factor forecast formula

‘size effect’ related bending formability of thin-walled aluminum alloy tube

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Chinese Journal of Aeronautics 2013年第1期26卷 230-241页

作者： Li Heng Yang He Zhang Zhiyong Wang Zekang State Key Laboratory of Solidification Processing School of Materials Science and Engineering Northwestern Polytechnical University

Aluminum alloy （Al-alloy） thin-walled （D/t ＆gt; 20, diameter D, wall thickness t） bent tubes have attracted increasing applications in many industries with mass quantities and diverse specifications due to satisfying high strength to weigh ratio requirements of product manufacturing. However, due to nonlinear nature of bending with coupling effects of multiple factors, the similarity theory seems not applicable and there occurs a challenge for efficient and reliable evaluation of the bending formability of thin-walled tube with various bending specifications. Considering the unequal deformation and three major instabilities, the bending formability of thin-walled Al-alloy tube in changing tube sizes such as D and t are clarified via both the analytical and FE modeling/ simulations. The experiments of rotary draw bending are conducted to validate the theoretical models and further confirm ＇size effect＇ related bending formability. The major results show that （1） The anti-wrinkling capability of tube decreases with the larger D and smaller t, and the effect significance of t is larger than that of D even under rigid supports; （2） The wall thinning increases with the larger D and smaller t, and this tendency becomes much more obvious under rigid supports; （3） The cross-section deformation increases with the larger D and smaller t according to the analytical model obtained intrinsic relationship, while this tendency becomes opposite due to the nonlinear role of mandrel die; （4） The size factor D/t can be used as a nondimensional index to evaluate both the bending formability regarding the wall thinning and cross-section deformation.

关键词： Al-alloy Bending formability Flattening size effect Tube bending Wall thinning Wrinkling

Characterization of size effect of natural convection in melting process of phase change material in square cavity

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Chinese Physics B 2021年第10期30卷 400-409页

作者： Shi-Hao Cao Hui Wang College of Civil Engineering Henan University of TechnologyZhengzhou 450001China School of Civil Engineering and Architecture Hainan UniversityHaikou 570228China

The accelerating effect of natural convection on the melting of phase change material(PCM)has been extensively ***,such an influence is directly dependent on the size and shape of domain in which phase change happens,and how to quantitatively describe such an influence is still *** the other hand,the simulation of natural convection process is considerably difficult,involving complex fluid flow in a region changing with time,and is typically not operable in *** overcome these obstacles,the present study aims to quantitatively investigate the size effect of natural convection in the melting process of PCM paraffin filled in a square latent heat storage system through experiment and simulation,and ultimately a correlation equation to represent its contribution is ***,the paraffin melting experiment is conducted to validate the two-dimensional finite element model based on the enthalpy ***,a comprehensive investigation is performed numerically for various domain *** results show that the melting behavior of paraffin is dominated by the thermal *** the melting time exceeds 50 s,a whirlpoor flow caused by natural convection appears in the upper liquid phase region close to the heating wall,and then its influencing range gradually increases to accelerate the melting of ***,its intensity gradually decreases as the distance between the melting front and the heating wall ***,it is found that the correlation between the total melting time and the domain size approximately exhibits a power *** the domain size is less than 2 mm,the accelerating effect of natural convection becomes very weak and can be ignored in ***,in order to simplify the complex calculation of natural convection,the equivalent thermal conductivity concept is proposed to include the contribution of natural convection to the total melting time,and an empirical correlation is given fo

关键词： phase change material natural convection size effect equivalent thermal conductivity

Performance Optimization of Irreversible Air Heat Pumps Considering size effect

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Journal of Thermal Science 2018年第3期27卷 223-229页

作者： BI Yuehong CHEN Lingen DING Zemin SUN Fengrui Institute of Civil & Architectural Engineering Beijing University of Technology Beijing 100124 China Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology Beijing 100124 China Institute of Thermal Science and Power Engineering Naval University of Engineering Wuhan 430033 China

Considering the size of an irreversible air heat pump （AHP）, heating load density （HLD） is taken as thermodynamic opt/mization objective by using finite-time thermodynamics. Based on an irreversible AHP with infinite reservoir thermal-capacitance rate model, the expression of HLD of AHP is put forward. The HLD opti-mization processes are studied analytically and numerically, which consist of two aspects：（1） to choose pressure ratio; （2） to distribute heat-exchanger inventory. Heat reservoir temperatures, heat transfer performance of heat exchangers as well as irreversibility during compression and expansion processes are important factors influenc-ing on the performance of an irreversible AHP, which are characterized with temperature ratio, heat exchanger inventory as well as isentropic efficiencies, respectively. Those impacts of parameters on the maximum HLD are thoroughly studied. The research results show that HLD optimization can make the size of the AHP system smaller and improve the compactness of system.

关键词： Irreversible Air Heat Pump Thermodynamic Optimization Heating Load Density size effect Finite Time Thermodynamics