Under deep and complex geological conditions,severe deformation occurs at intersection points of Y-type roadways with large cross sections during engineering projects in coal mines,especially at junction arches.Based ...Under deep and complex geological conditions,severe deformation occurs at intersection points of Y-type roadways with large cross sections during engineering projects in coal mines,especially at junction arches.Based on in-situ investigations and theoretical studies,we have summarized typical forms of destruction and identified high stress and unrestricted support at both sides of junction arch as its main causes.In this study,we also presented double-directional control bolt support technology for a large Y-type span intersection,applied to deep intersection engineering in the Jiahe Coal Mine,which has proved effective.展开更多
Three-dimensional （3D） five-directional braided （SiO2）/SiO2 composites were prepared by silicasol-infiltration-sintering （SIS） method. The flexural properties and microstructures were studied. The flexural stren...Three-dimensional （3D） five-directional braided （SiO2）/SiO2 composites were prepared by silicasol-infiltration-sintering （SIS） method. The flexural properties and microstructures were studied. The flexural strength and flexural elastic modulus were found to be 73 MPa and 12 GPa, respectively. The results of stress vs deflection curve and SEM examinations revealed that the fracture mechanism of 3D, five-directional braided （SiO2）/SiO2 composite was a mixture mode of ductile and brittle. The ductile mode was attributed to the weak bonding strength of fiber/matrix at low temperature. The brittle fracture might be caused by the propagation of micro defect or crack, which existed in the as-prepared composites for the ten-cycle process.展开更多
An Nb-14Si-22Ti-4Cr-2Al-2Hf-0.15Y(at.%) alloy was prepared by directional solidification(DS) with liquid metal cooling, and the withdrawal rates selected were 1.2, 6, and 18 mm·min-1, respectively. The Influence ...An Nb-14Si-22Ti-4Cr-2Al-2Hf-0.15Y(at.%) alloy was prepared by directional solidification(DS) with liquid metal cooling, and the withdrawal rates selected were 1.2, 6, and 18 mm·min-1, respectively. The Influence of withdrawal rate and heat treatment on the microstructural evolution, fracture toughness and tensile strength at room temperature were investigated. Results show that the directionally solidified microstructure is composed of primary(Nb, X)ss dendrites and(Nb, X)ss/α-(Nb, X)5Si3 eutectic cells aligning with the growth direction. The formation of bulk Nb3Si is suppressed. With an increase in withdrawal rate, the dendrite arm spacing of(Nb, X)ss decreases, and the(Nb, X)ss/α-(Nb, X)5Si3 eutectic cells become finer and distribute homogeneously. Directional solidification can significantly improve the room temperature fracture toughness, especially the alloy with a withdrawal rate of 6 mm·min-1; its average value reaches 14.1 MPa·m0.5, about 34% higher than that of the alloy without directional solidification. The withdrawal rate has obvious effect on tensile strength, and the tensile strength is improved from 200 MPa to 429 MPa as the withdrawal rate increases from 1.2 mm·min-1 to 1.8 mm·min-1. After heat treatment, the primary(Nb, X)ss branches become coarser; both the room temperature fracture toughness and tensile strength of the alloys solidified at 1.2 and 6 mm·min-1are somewhat lower than the corresponding values of the alloy without heat treatment, while they are higher than the corresponding values of the alloy without heat treatment when solidified at 18 mm·min-1.展开更多
针对目标函数中包含耦合函数H(x,y)的非凸非光滑极小化问题,提出了一种线性惯性交替乘子方向法(Linear Inertial Alternating Direction Method of Multipliers,LIADMM)。为了方便子问题的求解,对目标函数中的耦合函数H(x,y)进行线性化...针对目标函数中包含耦合函数H(x,y)的非凸非光滑极小化问题,提出了一种线性惯性交替乘子方向法(Linear Inertial Alternating Direction Method of Multipliers,LIADMM)。为了方便子问题的求解,对目标函数中的耦合函数H(x,y)进行线性化处理,并在x-子问题中引入惯性效应。在适当的假设条件下,建立了算法的全局收敛性;同时引入满足Kurdyka-Lojasiewicz不等式的辅助函数,验证了算法的强收敛性。通过两个数值实验表明,引入惯性效应的算法比没有惯性效应的算法收敛性能更好。展开更多
基金supported by the National Basic Research Program of China (No.2006CB202200)the Major Program of the National Natural Science Foundation of China (No.50490270)the Innovative Team Development Project of the Ministry of Education of China (No.IRT0656)
文摘Under deep and complex geological conditions,severe deformation occurs at intersection points of Y-type roadways with large cross sections during engineering projects in coal mines,especially at junction arches.Based on in-situ investigations and theoretical studies,we have summarized typical forms of destruction and identified high stress and unrestricted support at both sides of junction arch as its main causes.In this study,we also presented double-directional control bolt support technology for a large Y-type span intersection,applied to deep intersection engineering in the Jiahe Coal Mine,which has proved effective.
基金Funded by the Basic Research Project of Science and Technology of Jiangsu Province(No.BK2009002)the National Natural ScienceFoundation of China(No.61176062)the Fundamental Research Funds for the Central Universities(No.NS2013061)
文摘Three-dimensional （3D） five-directional braided （SiO2）/SiO2 composites were prepared by silicasol-infiltration-sintering （SIS） method. The flexural properties and microstructures were studied. The flexural strength and flexural elastic modulus were found to be 73 MPa and 12 GPa, respectively. The results of stress vs deflection curve and SEM examinations revealed that the fracture mechanism of 3D, five-directional braided （SiO2）/SiO2 composite was a mixture mode of ductile and brittle. The ductile mode was attributed to the weak bonding strength of fiber/matrix at low temperature. The brittle fracture might be caused by the propagation of micro defect or crack, which existed in the as-prepared composites for the ten-cycle process.
基金financially supported by the National Natural Science Foundation of China(No.51101005)
文摘An Nb-14Si-22Ti-4Cr-2Al-2Hf-0.15Y(at.%) alloy was prepared by directional solidification(DS) with liquid metal cooling, and the withdrawal rates selected were 1.2, 6, and 18 mm·min-1, respectively. The Influence of withdrawal rate and heat treatment on the microstructural evolution, fracture toughness and tensile strength at room temperature were investigated. Results show that the directionally solidified microstructure is composed of primary(Nb, X)ss dendrites and(Nb, X)ss/α-(Nb, X)5Si3 eutectic cells aligning with the growth direction. The formation of bulk Nb3Si is suppressed. With an increase in withdrawal rate, the dendrite arm spacing of(Nb, X)ss decreases, and the(Nb, X)ss/α-(Nb, X)5Si3 eutectic cells become finer and distribute homogeneously. Directional solidification can significantly improve the room temperature fracture toughness, especially the alloy with a withdrawal rate of 6 mm·min-1; its average value reaches 14.1 MPa·m0.5, about 34% higher than that of the alloy without directional solidification. The withdrawal rate has obvious effect on tensile strength, and the tensile strength is improved from 200 MPa to 429 MPa as the withdrawal rate increases from 1.2 mm·min-1 to 1.8 mm·min-1. After heat treatment, the primary(Nb, X)ss branches become coarser; both the room temperature fracture toughness and tensile strength of the alloys solidified at 1.2 and 6 mm·min-1are somewhat lower than the corresponding values of the alloy without heat treatment, while they are higher than the corresponding values of the alloy without heat treatment when solidified at 18 mm·min-1.
文摘针对目标函数中包含耦合函数H(x,y)的非凸非光滑极小化问题,提出了一种线性惯性交替乘子方向法(Linear Inertial Alternating Direction Method of Multipliers,LIADMM)。为了方便子问题的求解,对目标函数中的耦合函数H(x,y)进行线性化处理,并在x-子问题中引入惯性效应。在适当的假设条件下,建立了算法的全局收敛性;同时引入满足Kurdyka-Lojasiewicz不等式的辅助函数,验证了算法的强收敛性。通过两个数值实验表明,引入惯性效应的算法比没有惯性效应的算法收敛性能更好。
