The giant magnetoresistance (GMR) in magnetic multilayers with current in the plane of the layers is studied by using the quantum-statistical Green's function approach, in which the effects of the interfacial roug...The giant magnetoresistance (GMR) in magnetic multilayers with current in the plane of the layers is studied by using the quantum-statistical Green's function approach, in which the effects of the interfacial roughness and magnetization configuration on the GMR are included. It is shown that the maximal GMR first increases and then decreases with increasing interfacial roughness, exhibiting a peak at an optimum value of interfacial roughness. An approximately linear dependence of GMR on is obtained, where is the angle between magnetizations of the two successive ferromagnetic layers. Furthermore, the maximal GMR is found to increase with increasing the number of bilayers.展开更多
A reasonable strength criterion should reflect the hydrostatic pressure effect, minimum principal stress effect,and intermediate principal stress effect. The former two effects can be described by the meridian curves,...A reasonable strength criterion should reflect the hydrostatic pressure effect, minimum principal stress effect,and intermediate principal stress effect. The former two effects can be described by the meridian curves, and the last one mainly depends on the Lode angle dependence function. Among three conventional strength criteria, i.e.Mohr–Coulomb(MC), Hoek–Brown(HB), and Exponent(EP) criteria, the difference between generalized compression and extension strength of EP criterion experience a firstly increase then decrease process, and tends to be zero when hydrostatic pressure is big enough. This is in accordance with intrinsic rock strength characterization. Moreover, the critical hydrostatic pressure Icorresponding to the maximum difference of between generalized compression and extension strength can be easily adjusted by minimum principal stress influence parameter K. So, the exponent function is a more reasonable meridian curves, which well reflects the hydrostatic pressure effect and is employed to describe the generalized compression and extension strength.Meanwhile, three Lode angle dependence functions of L,L, and L, which unconditionally satisfy the convexity and differential requirements, are employed to represent the intermediate principal stress effect. Realizing the actual strength surface should be located between the generalized compression and extension surface, new true-triaxial criteria are proposed by combining the two states of EP criterion by Lode angle dependence function with a same lode angle. The proposed new true-triaxial criteria have the same strength parameters as EP criterion. Finally, 14 groups of triaxial test data are employed to validate the proposed criteria. The results show that the three new true-triaxial exponent criteria,especially the Exponent Willam-Warnke criterion(EPWW)criterion, give much lower misfits, which illustrates that the EP criterion and Lhave more reasonable meridian and deviatoric function form, respectively. The proposed new true-triaxial strength criteria can provide theoretical foundation for stability analysis and optimization of support design of rock engineering.展开更多
An engineering-feasible design and fabrication procedure for REB2aCu3O7-x(REBCO)magnets based on the strong Ic angle dependence at moderate temperatures(40–77 K)was developed.In this procedure,the Ic value of every R...An engineering-feasible design and fabrication procedure for REB2aCu3O7-x(REBCO)magnets based on the strong Ic angle dependence at moderate temperatures(40–77 K)was developed.In this procedure,the Ic value of every REBCO coil of the magnet is calculated from the Ic(B,θ)data of REBCO tape at operating temperature with different applied fields,which is called the“full field-angle dependent Ic method.”This approach has significantly higher accuracy than the conventional method,which only focuses on the Ic value at the coil with the highest perpendicular field component.Additionally,the fitted lift factor at 45 K with different applied fields was closely related to the minimum Ic value at 77 K and 0.5 T.The engineering-feasible design and fabrication procedure for the REBCO magnet was developed on the basis of the Ic values calculated via the“full field-angle dependent Ic method”and lifting-factor fitted method,and it had a design error of<5%.The proposed technique is a more accurate method for the design and fabrication of cooling REBCO coils and will improve the applicability of REBCO magnets in this temperature range.展开更多
文摘The giant magnetoresistance (GMR) in magnetic multilayers with current in the plane of the layers is studied by using the quantum-statistical Green's function approach, in which the effects of the interfacial roughness and magnetization configuration on the GMR are included. It is shown that the maximal GMR first increases and then decreases with increasing interfacial roughness, exhibiting a peak at an optimum value of interfacial roughness. An approximately linear dependence of GMR on is obtained, where is the angle between magnetizations of the two successive ferromagnetic layers. Furthermore, the maximal GMR is found to increase with increasing the number of bilayers.
基金supported by the National Natural Science Foundation of China (Grants 51204168, 51579239)the China Postdoctoral Science Foundation funded project (Grants 2013M531424, 2015M580493)+1 种基金the National Basic Research 973 Program of China (Grants 2013CB036003, 2014CB046306)the Fundamental Research Funds for the Central Universities (Grant 2012QNB23)
文摘A reasonable strength criterion should reflect the hydrostatic pressure effect, minimum principal stress effect,and intermediate principal stress effect. The former two effects can be described by the meridian curves, and the last one mainly depends on the Lode angle dependence function. Among three conventional strength criteria, i.e.Mohr–Coulomb(MC), Hoek–Brown(HB), and Exponent(EP) criteria, the difference between generalized compression and extension strength of EP criterion experience a firstly increase then decrease process, and tends to be zero when hydrostatic pressure is big enough. This is in accordance with intrinsic rock strength characterization. Moreover, the critical hydrostatic pressure Icorresponding to the maximum difference of between generalized compression and extension strength can be easily adjusted by minimum principal stress influence parameter K. So, the exponent function is a more reasonable meridian curves, which well reflects the hydrostatic pressure effect and is employed to describe the generalized compression and extension strength.Meanwhile, three Lode angle dependence functions of L,L, and L, which unconditionally satisfy the convexity and differential requirements, are employed to represent the intermediate principal stress effect. Realizing the actual strength surface should be located between the generalized compression and extension surface, new true-triaxial criteria are proposed by combining the two states of EP criterion by Lode angle dependence function with a same lode angle. The proposed new true-triaxial criteria have the same strength parameters as EP criterion. Finally, 14 groups of triaxial test data are employed to validate the proposed criteria. The results show that the three new true-triaxial exponent criteria,especially the Exponent Willam-Warnke criterion(EPWW)criterion, give much lower misfits, which illustrates that the EP criterion and Lhave more reasonable meridian and deviatoric function form, respectively. The proposed new true-triaxial strength criteria can provide theoretical foundation for stability analysis and optimization of support design of rock engineering.
基金the National Key R&D Program of China(2018YFF0109401)Magnetic Resonance Union of Chinese Academy of Sciences(2020GZL001)+1 种基金National Natural Science Foundation of China(51807191,12042506)Key Research Program of Frontier Sciences,CAS,(ZDBS-LY-JSC039).
文摘An engineering-feasible design and fabrication procedure for REB2aCu3O7-x(REBCO)magnets based on the strong Ic angle dependence at moderate temperatures(40–77 K)was developed.In this procedure,the Ic value of every REBCO coil of the magnet is calculated from the Ic(B,θ)data of REBCO tape at operating temperature with different applied fields,which is called the“full field-angle dependent Ic method.”This approach has significantly higher accuracy than the conventional method,which only focuses on the Ic value at the coil with the highest perpendicular field component.Additionally,the fitted lift factor at 45 K with different applied fields was closely related to the minimum Ic value at 77 K and 0.5 T.The engineering-feasible design and fabrication procedure for the REBCO magnet was developed on the basis of the Ic values calculated via the“full field-angle dependent Ic method”and lifting-factor fitted method,and it had a design error of<5%.The proposed technique is a more accurate method for the design and fabrication of cooling REBCO coils and will improve the applicability of REBCO magnets in this temperature range.
