In order to establish a new method for measuring the dimensions of coarse aggregates, five different-size flat and elongated (F&E) coarse aggregates were glued into two specimens by epoxy resin, respectively, and ...In order to establish a new method for measuring the dimensions of coarse aggregates, five different-size flat and elongated (F&E) coarse aggregates were glued into two specimens by epoxy resin, respectively, and slice images were obtained by X-ray CT, then the aggregates were extracted by the fuzzy c-means clustering algorithm. Attributions of the particle on different cross-sections were determined by the ‘overlap area method’. And unified three-dimensional Cartesian coordinate system was established based on continuous slice images. The coefficient values of spherical harmonics descriptor representing particles surface profile were gained, then each scanned particle was represented by 60×120 discrete points conformably with spherical harmonics descriptor. The chord length and direction angles were determined by the calculation. With the major axis (L) and orthogonal axis (W and T), the calculated results were compared with those measured by caliper. It is concluded that the new L, W, and T dimension measuring method is able to take the place of the present manual measurement.展开更多
Over the past 2 decades,tight restriction has been imposed on strength criteria of concrete by the combination of plasticity and damage in one theory.The present study aims at constructing plastic/damage loading funct...Over the past 2 decades,tight restriction has been imposed on strength criteria of concrete by the combination of plasticity and damage in one theory.The present study aims at constructing plastic/damage loading functions for elastoplastic damage models for concrete that can perform more satisfactorily in 3D stress states.Numerous strength criteria of concrete are reorganized according to their simplest representations as Cartesian,cylindrical,mixed cylindrical-Cartesian,and other forms,and the homogeneity of loading functions discussed.It is found that under certain supplementary conditions from physical meanings,an unambiguous definition of the cohesion in a strength criterion,which is demanded in an elastoplastic damage model,is usually available in an explicit or implicit form,and in each case the loading function is still homogeneous.To apply and validate the presented theory,we construct the respective homogeneous damage and plastic loading functions and implant them into some widely used elastoplastic damage models for concrete,and their performances in triaxial compression prove to have improved significantly.展开更多
The effects of isotope substitution on stereodynamic properties for the reactions C^+ + H_2/HD/HT →CH^+ + H/D/T have been studied applying a quasi classical trajectory method occurring on the new ground state CH_2^+ ...The effects of isotope substitution on stereodynamic properties for the reactions C^+ + H_2/HD/HT →CH^+ + H/D/T have been studied applying a quasi classical trajectory method occurring on the new ground state CH_2^+ potential energy surface [J. Chem. Phys. 142(2015) 124302]. In the center of mass coordinates applying the quasi classical trajectory method to investigate the orientation and the alignment of the product molecule. Differential cross section and three angle distribution functions P(θ_r), P(ф_r), P(θ_r, ф_r) on the potential energy surface that fixed the collision energy with a value is 40 kcal/mol have been studied. The isotope effect becomes more and more important with the reagent molecules H_2 changing into HD and HT. P(θ_r, ф_r) as the joint probability density function of both polar angles θ_r and ф_r, which can illustrate more detailed dynamics information. The isotope effect is obvious influence on the properties of stereodynamics in the reactions of C^+ + H_2/HD/HT → CH^+ + H/D/T.展开更多
基金Project(51038004) supported by the National Natural Science Foundation of ChinaProject(2009318000078) supported by the Western China Communications Construction and Technology Program, China
文摘In order to establish a new method for measuring the dimensions of coarse aggregates, five different-size flat and elongated (F&E) coarse aggregates were glued into two specimens by epoxy resin, respectively, and slice images were obtained by X-ray CT, then the aggregates were extracted by the fuzzy c-means clustering algorithm. Attributions of the particle on different cross-sections were determined by the ‘overlap area method’. And unified three-dimensional Cartesian coordinate system was established based on continuous slice images. The coefficient values of spherical harmonics descriptor representing particles surface profile were gained, then each scanned particle was represented by 60×120 discrete points conformably with spherical harmonics descriptor. The chord length and direction angles were determined by the calculation. With the major axis (L) and orthogonal axis (W and T), the calculated results were compared with those measured by caliper. It is concluded that the new L, W, and T dimension measuring method is able to take the place of the present manual measurement.
基金supported by the National Natural Science Foundation of China-National Science Foundation Joint Project(Grant No.51261120374)the National Natural Science Foundation of China(Grant Nos.51108336 and 51378377)
文摘Over the past 2 decades,tight restriction has been imposed on strength criteria of concrete by the combination of plasticity and damage in one theory.The present study aims at constructing plastic/damage loading functions for elastoplastic damage models for concrete that can perform more satisfactorily in 3D stress states.Numerous strength criteria of concrete are reorganized according to their simplest representations as Cartesian,cylindrical,mixed cylindrical-Cartesian,and other forms,and the homogeneity of loading functions discussed.It is found that under certain supplementary conditions from physical meanings,an unambiguous definition of the cohesion in a strength criterion,which is demanded in an elastoplastic damage model,is usually available in an explicit or implicit form,and in each case the loading function is still homogeneous.To apply and validate the presented theory,we construct the respective homogeneous damage and plastic loading functions and implant them into some widely used elastoplastic damage models for concrete,and their performances in triaxial compression prove to have improved significantly.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11474141,11274149,11544015the Program for Liaoning Excellent Talents in University under Grant No.LJQ2015040the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry(2014-1685)
文摘The effects of isotope substitution on stereodynamic properties for the reactions C^+ + H_2/HD/HT →CH^+ + H/D/T have been studied applying a quasi classical trajectory method occurring on the new ground state CH_2^+ potential energy surface [J. Chem. Phys. 142(2015) 124302]. In the center of mass coordinates applying the quasi classical trajectory method to investigate the orientation and the alignment of the product molecule. Differential cross section and three angle distribution functions P(θ_r), P(ф_r), P(θ_r, ф_r) on the potential energy surface that fixed the collision energy with a value is 40 kcal/mol have been studied. The isotope effect becomes more and more important with the reagent molecules H_2 changing into HD and HT. P(θ_r, ф_r) as the joint probability density function of both polar angles θ_r and ф_r, which can illustrate more detailed dynamics information. The isotope effect is obvious influence on the properties of stereodynamics in the reactions of C^+ + H_2/HD/HT → CH^+ + H/D/T.
