The microstructure evolution and phase transformation of Cu-20Ni-20Mn（mass fraction,%） alloy at 450 °C were investigated by X-ray diffraction and transmission electron microscopy（TEM）.The variations of tensil...The microstructure evolution and phase transformation of Cu-20Ni-20Mn（mass fraction,%） alloy at 450 °C were investigated by X-ray diffraction and transmission electron microscopy（TEM）.The variations of tensile strength,yield strength and hardness of this alloy during aging process were also analyzed.The results show that no significant variations of hardness and strength in the initial stage of aging,with a long incubation period,are observed at 450 °C.Subsequently,the ordered face-centered tetragonal（FCT） Ni Mn phase nucleates and grows up with prolonging the aging time.The hardness and tensile strength of the alloy increase up to their maximum values with increasing the ordered particle size,i.e.,the strength of the alloy reaches 942 MPa after being aged at 450°C for 40h.The main cause of the age-hardening is considered to be precipitation strengthening due to the ordered FCT-Ni Mn particles.展开更多
To describe strategies for addressing technical aspects of computational modeling of leg tissue with the finite element （FE） method, a patient＇s leg sample was selected and scanned by CT at the direction parallel t...To describe strategies for addressing technical aspects of computational modeling of leg tissue with the finite element （FE） method, a patient＇s leg sample was selected and scanned by CT at the direction parallel to the Frankfort Horizontal plane. A three-dimensional （3D） finite element model of the human leg was developed using the actual geometry of the leg skeleton and soft tissues, which were obtained from 3D reconstruction of CT images. All joints were defined as contact surfaces, which allow relative articulating movement. The major ligaments were simulated using tension-only truss elements by connecting the corresponding attachment points on the bone surfaces. The bony and ligamentous structures were embedded in a volume of soft tissues. The muscles were defined as non-linear viscoelastic material, and the skin, ligaments and tendons were defined as hyperelastic, while the bony structures were assumed to be linearly elastic. The muhilayer FEM model containing thighbone, tibia, fibula, kneecap, soft tissue was formed after meshing. Diverse forces were imposed on the FEM model. The results show that the multilayer FEM model can represent tissue deformation more accurately.展开更多
A ring R is Zhou nil-clean if every element in R is the sum of two tripotents and a nilpotent that commute. Homomorphic images of Zhou nil-clean rings are explored. We prove that a ring R is Zhou nil-clean if and only...A ring R is Zhou nil-clean if every element in R is the sum of two tripotents and a nilpotent that commute. Homomorphic images of Zhou nil-clean rings are explored. We prove that a ring R is Zhou nil-clean if and only if 30 ∈ R is nilpotent and R/30R is Zhou nil-clean, if and only if R/BM（R） is 5-potent and BM（R） is nil, if and only if J（R） is nil and R/J（R） is isomorphic to a Boolean ring, a Yaqub ring, a Bell ring or a direct product of such rings. By means of homomorphic images, we completely determine when the generalized matrix ring is Zhou nil-clean. We prove that the generalized matrix ring Mn（R; s） is Zhou nil-clean if and only if R is Zhou nil-clean and s ∈ J（R）.展开更多
基金Project(51401026)supported by the National Natural Science Foundation of China
文摘The microstructure evolution and phase transformation of Cu-20Ni-20Mn（mass fraction,%） alloy at 450 °C were investigated by X-ray diffraction and transmission electron microscopy（TEM）.The variations of tensile strength,yield strength and hardness of this alloy during aging process were also analyzed.The results show that no significant variations of hardness and strength in the initial stage of aging,with a long incubation period,are observed at 450 °C.Subsequently,the ordered face-centered tetragonal（FCT） Ni Mn phase nucleates and grows up with prolonging the aging time.The hardness and tensile strength of the alloy increase up to their maximum values with increasing the ordered particle size,i.e.,the strength of the alloy reaches 942 MPa after being aged at 450°C for 40h.The main cause of the age-hardening is considered to be precipitation strengthening due to the ordered FCT-Ni Mn particles.
基金Sponsored by the Natural Science Foundation of Heilongjiang Province of China(Grant No.200815)the Research Foundation for Talented Scholars ofHarbin (Grant No.2008RFQXS061)
文摘To describe strategies for addressing technical aspects of computational modeling of leg tissue with the finite element （FE） method, a patient＇s leg sample was selected and scanned by CT at the direction parallel to the Frankfort Horizontal plane. A three-dimensional （3D） finite element model of the human leg was developed using the actual geometry of the leg skeleton and soft tissues, which were obtained from 3D reconstruction of CT images. All joints were defined as contact surfaces, which allow relative articulating movement. The major ligaments were simulated using tension-only truss elements by connecting the corresponding attachment points on the bone surfaces. The bony and ligamentous structures were embedded in a volume of soft tissues. The muscles were defined as non-linear viscoelastic material, and the skin, ligaments and tendons were defined as hyperelastic, while the bony structures were assumed to be linearly elastic. The muhilayer FEM model containing thighbone, tibia, fibula, kneecap, soft tissue was formed after meshing. Diverse forces were imposed on the FEM model. The results show that the multilayer FEM model can represent tissue deformation more accurately.
基金The authors are grateful to the referee for his/her careful the paper, and for the invaluable comments which improve our presentation reading of author H.Y. Chen was supported by the Natural Science Foundation of Zhejiang （No. LY17A010018）, China. The first Province
文摘A ring R is Zhou nil-clean if every element in R is the sum of two tripotents and a nilpotent that commute. Homomorphic images of Zhou nil-clean rings are explored. We prove that a ring R is Zhou nil-clean if and only if 30 ∈ R is nilpotent and R/30R is Zhou nil-clean, if and only if R/BM（R） is 5-potent and BM（R） is nil, if and only if J（R） is nil and R/J（R） is isomorphic to a Boolean ring, a Yaqub ring, a Bell ring or a direct product of such rings. By means of homomorphic images, we completely determine when the generalized matrix ring is Zhou nil-clean. We prove that the generalized matrix ring Mn（R; s） is Zhou nil-clean if and only if R is Zhou nil-clean and s ∈ J（R）.
