As a kind of multi-physics imaging approach integrating the advantages of electrical impedance tomography and ul- trasound imaging with the improved spatial resolution and image contrast, magneto-acoustic tomography w...As a kind of multi-physics imaging approach integrating the advantages of electrical impedance tomography and ul- trasound imaging with the improved spatial resolution and image contrast, magneto-acoustic tomography with magnetic induction （MAT-MI） is demonstrated to have the capability of electrical impedance contrast imaging for biological tissues with conductivity differences. By being detected with a strong directional transducer, abrupt pressure change is proved to be generated by the gradient of the induced Lorentz force along the force direction at conductivity boundary. A simplified boundary normal pressure （BNP）-based conductivity reconstruction algorithm is proposed and the formula for conductivity distribution inside the object with the clear physical meaning of pressure derivative, is derived. Numerical simulations of acoustic pressure and conductivity reconstruction are conducted based on a 2-layer eccentric cylindrical phantom model using Hilbert transform. The reconstructed two-dimensional conductivity images accord well with the model, thus success- fully making up the deficiency of only imaging conductivity boundary in traditional MAT-MI. The proposed method is also demonstrated to have a spatial resolution of one wavelength. This study provides a new method of reconstructing accurate electrical conductivity and suggests the potential applications of MAT-MI in imaging biological tissues with conductivity difference.展开更多
As a kind of special acoustic field, the helical wavefront of an acoustic vortex（AV） beam is demonstrated to have a pressure zero with phase singularity at the center in the transverse plane. The orbital angular mom...As a kind of special acoustic field, the helical wavefront of an acoustic vortex（AV） beam is demonstrated to have a pressure zero with phase singularity at the center in the transverse plane. The orbital angular momentum of AVs can be applied to the field of particle manipulation, which attracts more and more attention in acoustic researches. In this paper,by using the simplified circular array of point sources, dual coaxial AV beams are excited by the even-and odd-numbered sources with the topological charges of l_E and l_O based on the phase-coded approach, and the composite acoustic field with an on-axis center-AV and multiple off-axis sub-AVs can be generated by the superimposition of the AV beams for｜l_E｜ ≠ ｜l_O｜. The generation of edge phase dislocation is theoretically derived and numerically analyzed for l_E=-l_O. The numbers and the topological charges as well as the locations of the center-AV and sub-AVs are demonstrated, which are proved to be determined by the topological charges of the coaxial AV beams. The proposed approach breaks through the limit of only one on-axis AV with a single topological charge along the beam axis, and also provides the feasibility of off-axis particle trapping with multiple AVs in object manipulation.展开更多
Starting from the CD-Bonn potential, we have performed Gamow shell-model calculations for neutronrich oxygen isotopes, investigating excitation spectra and their resonant properties. The Gamow shell model is based on ...Starting from the CD-Bonn potential, we have performed Gamow shell-model calculations for neutronrich oxygen isotopes, investigating excitation spectra and their resonant properties. The Gamow shell model is based on the Berggren ensemble, which is capable of treating the continuum effect reasonably in weakly bound or unbound nuclei. To calculate heavier-mass oxygen isotopes, we choose ^16O as a frozen core in the Camow shell-model calculations. The first 2^＋ excitation energies of the even-even O isotopes are calculated, and compared with those obtained by the conventional shell model using the empirical USDB interaction. The continuum effect is proved to play an important role in the shell evolution near the drip line. We also discuss the effect of the Berggren contour choice. We improve the approximation in the contour choice to give more precise calculations of resonance widths.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11474166 and 11604156)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20161013)+1 种基金the Postdoctoral Science Foundation of China(Grant No.2016M591874)the Priority Academic Program Development of Jiangsu Provincial Higher Education Institutions,China
文摘As a kind of multi-physics imaging approach integrating the advantages of electrical impedance tomography and ul- trasound imaging with the improved spatial resolution and image contrast, magneto-acoustic tomography with magnetic induction （MAT-MI） is demonstrated to have the capability of electrical impedance contrast imaging for biological tissues with conductivity differences. By being detected with a strong directional transducer, abrupt pressure change is proved to be generated by the gradient of the induced Lorentz force along the force direction at conductivity boundary. A simplified boundary normal pressure （BNP）-based conductivity reconstruction algorithm is proposed and the formula for conductivity distribution inside the object with the clear physical meaning of pressure derivative, is derived. Numerical simulations of acoustic pressure and conductivity reconstruction are conducted based on a 2-layer eccentric cylindrical phantom model using Hilbert transform. The reconstructed two-dimensional conductivity images accord well with the model, thus success- fully making up the deficiency of only imaging conductivity boundary in traditional MAT-MI. The proposed method is also demonstrated to have a spatial resolution of one wavelength. This study provides a new method of reconstructing accurate electrical conductivity and suggests the potential applications of MAT-MI in imaging biological tissues with conductivity difference.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11474166 and 11604156)the Science and Technology Cooperation Projects of People’s Republic of China–Romania(Grant No.42-23)+2 种基金the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20161013)the Postdoctoral Science Foundation of China(Grant No.2016M591874)the Priority Academic Program Development of Jiangsu Higher Education Institutions,China
文摘As a kind of special acoustic field, the helical wavefront of an acoustic vortex（AV） beam is demonstrated to have a pressure zero with phase singularity at the center in the transverse plane. The orbital angular momentum of AVs can be applied to the field of particle manipulation, which attracts more and more attention in acoustic researches. In this paper,by using the simplified circular array of point sources, dual coaxial AV beams are excited by the even-and odd-numbered sources with the topological charges of l_E and l_O based on the phase-coded approach, and the composite acoustic field with an on-axis center-AV and multiple off-axis sub-AVs can be generated by the superimposition of the AV beams for｜l_E｜ ≠ ｜l_O｜. The generation of edge phase dislocation is theoretically derived and numerically analyzed for l_E=-l_O. The numbers and the topological charges as well as the locations of the center-AV and sub-AVs are demonstrated, which are proved to be determined by the topological charges of the coaxial AV beams. The proposed approach breaks through the limit of only one on-axis AV with a single topological charge along the beam axis, and also provides the feasibility of off-axis particle trapping with multiple AVs in object manipulation.
基金Supported by the National Key R&D Program of China(2018YFA0404401)the National Natural Science Foundation of China(11320101004,11575007)+2 种基金the China Postdoctoral Science Foundation(2018M630018)the CUSTIPEN(China U.S.Theory Institute for Physics with Exotic Nuclei)funded by the U.S.Department of Energy,Office of Science(DESC0009971)and High performance Computing Platform of Peking University
文摘Starting from the CD-Bonn potential, we have performed Gamow shell-model calculations for neutronrich oxygen isotopes, investigating excitation spectra and their resonant properties. The Gamow shell model is based on the Berggren ensemble, which is capable of treating the continuum effect reasonably in weakly bound or unbound nuclei. To calculate heavier-mass oxygen isotopes, we choose ^16O as a frozen core in the Camow shell-model calculations. The first 2^＋ excitation energies of the even-even O isotopes are calculated, and compared with those obtained by the conventional shell model using the empirical USDB interaction. The continuum effect is proved to play an important role in the shell evolution near the drip line. We also discuss the effect of the Berggren contour choice. We improve the approximation in the contour choice to give more precise calculations of resonance widths.
