The relatively fragile low-temperature stability of cryogen-free superconducting magnetic resonance imaging(MRI)magnets requires the careful management of exogenous heat sources.A strongly shielded gradient magnetic f...The relatively fragile low-temperature stability of cryogen-free superconducting magnetic resonance imaging(MRI)magnets requires the careful management of exogenous heat sources.A strongly shielded gradient magnetic field is important for the optimal operation of cryogen-free MRI systems.In this study,we present an enhanced shielding method incorporating a regionalized stray field constraining strategy.By optimizing the constraint parameters,we could develop engineering-feasible gradient coil schemes without increasing system complexity but with the stray field intensity reduced by half.In real measurement in an integrated MRI system,the developed gradient assembly demonstrated good performance and supported to output images of excellent quality.Our findings suggested that the proposed method could potentially form a useful design paradigm for cryogen-free MRI magnets.展开更多
Living system is a non-equilibrium open system having the function of self-organization and self-control. The study of energy principle of living system involves two principal parts: mechanics and thermodynamics. The ...Living system is a non-equilibrium open system having the function of self-organization and self-control. The study of energy principle of living system involves two principal parts: mechanics and thermodynamics. The classical infinitesimal deformation theory and thermodynamics of equilibrium state are not sufficient to explain the complex motion of living system. We aim in this paper to describe the mechanical energy principle of macroscopic motion of living body based on large deformation non-symmetry stress field theory. The principle of irreversible thermodynamics applied to living system will be left in another paper.展开更多
In this paper we deal with the second-order effect of an elastic circular shaft during torsion. The analysis is based on the method of co-moving coordinates and the strain-rotation decomposition theorem in the continu...In this paper we deal with the second-order effect of an elastic circular shaft during torsion. The analysis is based on the method of co-moving coordinates and the strain-rotation decomposition theorem in the continuum mechanics. By using asymptotic expansion methods, we comfirm that the effect of axial elongation and distortion of plane cross-section exists in an elastic circular shaft during large torsion and give the expressions of the axial force and the torque.展开更多
A new method of fringe multiplication is presented in this paper. The method is simple and applicable. Only one polarizer and one quarter-wave plate are adopted to get fringe multiplication by reflection.
基金This work is funded by the Magnetic Resonance Union of the Chinese Academy of Sciences(Grant No.2021gzl002)the International Partnership Program of Chinese Academy of Sciences(Grant No.182111KYSB20210014)+1 种基金the National Science Foundation of China(Grant No.52293423,Grant No.52277031)the Research and Development of Key Technologies and Equipment for Major Science and Technology Infrastructure of Development and Reform Commission of Shenzhen Municipality,China(Grant No.ZDKJ20190305002).
文摘The relatively fragile low-temperature stability of cryogen-free superconducting magnetic resonance imaging(MRI)magnets requires the careful management of exogenous heat sources.A strongly shielded gradient magnetic field is important for the optimal operation of cryogen-free MRI systems.In this study,we present an enhanced shielding method incorporating a regionalized stray field constraining strategy.By optimizing the constraint parameters,we could develop engineering-feasible gradient coil schemes without increasing system complexity but with the stray field intensity reduced by half.In real measurement in an integrated MRI system,the developed gradient assembly demonstrated good performance and supported to output images of excellent quality.Our findings suggested that the proposed method could potentially form a useful design paradigm for cryogen-free MRI magnets.
文摘Living system is a non-equilibrium open system having the function of self-organization and self-control. The study of energy principle of living system involves two principal parts: mechanics and thermodynamics. The classical infinitesimal deformation theory and thermodynamics of equilibrium state are not sufficient to explain the complex motion of living system. We aim in this paper to describe the mechanical energy principle of macroscopic motion of living body based on large deformation non-symmetry stress field theory. The principle of irreversible thermodynamics applied to living system will be left in another paper.
文摘In this paper we deal with the second-order effect of an elastic circular shaft during torsion. The analysis is based on the method of co-moving coordinates and the strain-rotation decomposition theorem in the continuum mechanics. By using asymptotic expansion methods, we comfirm that the effect of axial elongation and distortion of plane cross-section exists in an elastic circular shaft during large torsion and give the expressions of the axial force and the torque.
基金The work wins the finance of Huo Ying-dong educational foundation
文摘A new method of fringe multiplication is presented in this paper. The method is simple and applicable. Only one polarizer and one quarter-wave plate are adopted to get fringe multiplication by reflection.
