The interfacial transition zone (ITZ) between the aggregates and the bulk paste is the weakest zone of ordinary concrete, which largely determines its mechanical and transporting properties. However, a complete unders...The interfacial transition zone (ITZ) between the aggregates and the bulk paste is the weakest zone of ordinary concrete, which largely determines its mechanical and transporting properties. However, a complete understanding and a quantitative modeling of ITZ are still lacking. Consequently, an integrated modeling and experimental study were conducted. First, the theoretical calculation model of the ITZ volume fraction about the rotary ellipsoidal aggregate particles was established based on the nearest surface function formula. Its calculation programs were written based on Visual Basic 6.0 language and achieved visualization and functionalization. Then, the influencing factors of ITZ volume fraction of the ellipsoidal aggregate particles and the overlapping degree between the ITZ were systematically analyzed. Finally, the calculation models of ITZ volume fraction on actual ellipsoidal aggregate were given, based on cobblestones or pebbles particles with naturally ellipsoidal shape. The results indicate that the calculation model proposed is highly reliable.展开更多
To investigate the transport characteristics of chloride ions in cement-based materials, the Mori-Tanaka (M-T) prediction scheme of the effective diffusion coefficient in composites containing single-phase and multi-p...To investigate the transport characteristics of chloride ions in cement-based materials, the Mori-Tanaka (M-T) prediction scheme of the effective diffusion coefficient in composites containing single-phase and multi-phase inclusions is systematically deduced based on the theory of composite mechanics and porous medium. The volume fraction, morphology and distribution of aggregates, as well as the interfacial transition zone (ITZ) are fully taken into consideration in this proposed model. The results show that the algorithm of M-T prediction scheme with high accuracy is relatively simple.展开更多
The dispersion behavior of the shear horizontal (SH) waves in the coupled structure consisting of a piezomagnetic substrate and an orthorhombic piezoelectric layer is investigated with different cut orientations. Th...The dispersion behavior of the shear horizontal (SH) waves in the coupled structure consisting of a piezomagnetic substrate and an orthorhombic piezoelectric layer is investigated with different cut orientations. The surface of the piezoelectric layer is mechanically free, electrically shorted, or open, while the surface of the piezomagnetic substrate is mechanically free, magnetically open, or shorted. The dispersion relations are derived for four electromagnetic boundary conditions. The dispersion characteristics are graphically illustrated for the layered structure with the PMN-PT layer perfectly bonded on the CoFe2O4 substrate. The effects of the PMN-PT cut orientations, the electromagnetic boundary conditions, and the thickness ratio of the layer to the substrate on the dispersion behavior are analyzed and discussed in detail. The results show that, (i) the effect of the cut orientation on the dispersion curves is very obvious, (ii) the electrical boundary conditions of the PMN-PT layer dominate the propagation feature of the SH waves, and (iii) the thickness ratio has a significant effect on the phase velocity when the wave number is small. The results of the present paper can provide valuable theoretical references to the applications of piezoelectric/piezomagnectic structure in acoustic wave devices.展开更多
According to the morphological characteristics of crushed stone,the sphericity was introduced to establish the theoretical calculation model of volume fraction of interfacial transition zone(ITZ)around crushed stone.T...According to the morphological characteristics of crushed stone,the sphericity was introduced to establish the theoretical calculation model of volume fraction of interfacial transition zone(ITZ)around crushed stone.The sphericity of crushed stone was obtained by image processing technology and numerical statistics.The experimental results show that when the maximum particle size of coarse aggregate is less than 31.5 mm,the practical sphericity is generally around 0.75,while the sphericity of sand is generally above 0.85.And the closer to 1 the practical sphericity is,the smaller the ITZ volume fraction(V_(ITZ))is,that is,the closer to spherical shape the aggregate is,the lower the ITZ content in concrete is.The V_(ITZ) and ITZ thickness in concrete and mortar have a linear relationship,and the ITZ content in concrete is lower than that in mortar at the same aggregate volume fraction.展开更多
In this paper we mainly study derivation algebras of n-Lie algebras. We give the detailed structural description of derivation algebras of n + 1 dimensional n-Lie algebras over the real field.
基金Funded by the National Natural Science Foundations of China(Nos.51478278 and 51408380)the Natural Science Foundation of Hebei Province(No.E2014210149)Higher Education Science and Technology Research Project of Hebei Province(No.ZD2016065)
文摘The interfacial transition zone (ITZ) between the aggregates and the bulk paste is the weakest zone of ordinary concrete, which largely determines its mechanical and transporting properties. However, a complete understanding and a quantitative modeling of ITZ are still lacking. Consequently, an integrated modeling and experimental study were conducted. First, the theoretical calculation model of the ITZ volume fraction about the rotary ellipsoidal aggregate particles was established based on the nearest surface function formula. Its calculation programs were written based on Visual Basic 6.0 language and achieved visualization and functionalization. Then, the influencing factors of ITZ volume fraction of the ellipsoidal aggregate particles and the overlapping degree between the ITZ were systematically analyzed. Finally, the calculation models of ITZ volume fraction on actual ellipsoidal aggregate were given, based on cobblestones or pebbles particles with naturally ellipsoidal shape. The results indicate that the calculation model proposed is highly reliable.
基金Funded by the National Natural Science Foundations of China(Nos.51778378,51478278)。
文摘To investigate the transport characteristics of chloride ions in cement-based materials, the Mori-Tanaka (M-T) prediction scheme of the effective diffusion coefficient in composites containing single-phase and multi-phase inclusions is systematically deduced based on the theory of composite mechanics and porous medium. The volume fraction, morphology and distribution of aggregates, as well as the interfacial transition zone (ITZ) are fully taken into consideration in this proposed model. The results show that the algorithm of M-T prediction scheme with high accuracy is relatively simple.
基金supported by the National Natural Science Foundation of China(No.11272222)the Key Project of Hebei Provincial Education Department of China(No.ZD2017072)
文摘The dispersion behavior of the shear horizontal (SH) waves in the coupled structure consisting of a piezomagnetic substrate and an orthorhombic piezoelectric layer is investigated with different cut orientations. The surface of the piezoelectric layer is mechanically free, electrically shorted, or open, while the surface of the piezomagnetic substrate is mechanically free, magnetically open, or shorted. The dispersion relations are derived for four electromagnetic boundary conditions. The dispersion characteristics are graphically illustrated for the layered structure with the PMN-PT layer perfectly bonded on the CoFe2O4 substrate. The effects of the PMN-PT cut orientations, the electromagnetic boundary conditions, and the thickness ratio of the layer to the substrate on the dispersion behavior are analyzed and discussed in detail. The results show that, (i) the effect of the cut orientation on the dispersion curves is very obvious, (ii) the electrical boundary conditions of the PMN-PT layer dominate the propagation feature of the SH waves, and (iii) the thickness ratio has a significant effect on the phase velocity when the wave number is small. The results of the present paper can provide valuable theoretical references to the applications of piezoelectric/piezomagnectic structure in acoustic wave devices.
基金Funded by the National Natural Science Foundations of China(No.52178237)the Graduate Innovation Fund of Shijiazhuang Tie Dao University(YC2021064)。
文摘According to the morphological characteristics of crushed stone,the sphericity was introduced to establish the theoretical calculation model of volume fraction of interfacial transition zone(ITZ)around crushed stone.The sphericity of crushed stone was obtained by image processing technology and numerical statistics.The experimental results show that when the maximum particle size of coarse aggregate is less than 31.5 mm,the practical sphericity is generally around 0.75,while the sphericity of sand is generally above 0.85.And the closer to 1 the practical sphericity is,the smaller the ITZ volume fraction(V_(ITZ))is,that is,the closer to spherical shape the aggregate is,the lower the ITZ content in concrete is.The V_(ITZ) and ITZ thickness in concrete and mortar have a linear relationship,and the ITZ content in concrete is lower than that in mortar at the same aggregate volume fraction.
基金the National Natural Science Foundation of China (No. 10871192) and the Natural Science Foundation of Hebei Province (No. A2007000138).
文摘In this paper we mainly study derivation algebras of n-Lie algebras. We give the detailed structural description of derivation algebras of n + 1 dimensional n-Lie algebras over the real field.