Conductivities tomography with the interactions of magnetic field, electrical field, and ultrasound field is presented in this paper. We utilize a beam of ultrasound in scanning mode instead of the traditional ultraso...Conductivities tomography with the interactions of magnetic field, electrical field, and ultrasound field is presented in this paper. We utilize a beam of ultrasound in scanning mode instead of the traditional ultrasound field generated by point source. Many formulae for the reconstruction of conductivities are derived from the voltage signals detected by two electrodes arranged somewhere on tissue＇s surface. In a forward problem, the numerical solutions of ultrasound fields generated by the piston transducer are calculated using the angular spectrum method and its Green＇s function is designed approximately in far fields. In an inverse problems, the magneto-acousto-electrical voltage signals are proved to satisfy the wave equations if the voltage signals are extended to the whole region from the boundary locations of transducers. Thus the time-reversal method is applied to reconstructing the curl of the reciprocal current density. In addition, a least square iteration method of recovering conductivities from reciprocal current densities is discussed.展开更多
The presented research was focused on a comparison between different means of obtaining a Nusselt number distribution,in a situation where neither temperature nor heat flux density is constant.Two fundamentally differ...The presented research was focused on a comparison between different means of obtaining a Nusselt number distribution,in a situation where neither temperature nor heat flux density is constant.Two fundamentally different measurement techniques have been utilized,alongside a CFD simulation,in order to designate temperature distributions in a horizontal rod.Dry air under normal pressure,regarded as a perfect gas,was chosen as the working fluid,whereas the rod's cross-section was restricted to a ring.In this scenario heat exchange between the rod and the fluid is driven predominantly by natural convection,with a slight impact of thermal radiation,particularly at temperatures approaching the top end of the available range.Temperature margins achieved at the heated end of the rod ranged from 60 K up to 150 K,resulting in local Rayleigh numbers falling in-between 6.0xl03 and 2.6xl04.Reconstruction of Nusselt numbers from a discrete temperature distribution was possible thanks to a dedicated method implemented using a Scilab script.A segregated,steady-state solver based on the SIMPLE scheme was utilized for the purpose of numerical simulations on the fluid side,whereas a heat conduction equation was solved over solid domain in the considered conjugated heat transfer problem.A corresponding set of empirical data has been obtained,using both resistance temperature detectors and a thermal imaging camera,both for the sake of numerical model validation and comparison of individual methods.The Nusselt numbers resulting from each approach were compared against values computed using available correlations valid for horizontal configuration.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51137004,51277169,and 61271424)
文摘Conductivities tomography with the interactions of magnetic field, electrical field, and ultrasound field is presented in this paper. We utilize a beam of ultrasound in scanning mode instead of the traditional ultrasound field generated by point source. Many formulae for the reconstruction of conductivities are derived from the voltage signals detected by two electrodes arranged somewhere on tissue＇s surface. In a forward problem, the numerical solutions of ultrasound fields generated by the piston transducer are calculated using the angular spectrum method and its Green＇s function is designed approximately in far fields. In an inverse problems, the magneto-acousto-electrical voltage signals are proved to satisfy the wave equations if the voltage signals are extended to the whole region from the boundary locations of transducers. Thus the time-reversal method is applied to reconstructing the curl of the reciprocal current density. In addition, a least square iteration method of recovering conductivities from reciprocal current densities is discussed.
文摘The presented research was focused on a comparison between different means of obtaining a Nusselt number distribution,in a situation where neither temperature nor heat flux density is constant.Two fundamentally different measurement techniques have been utilized,alongside a CFD simulation,in order to designate temperature distributions in a horizontal rod.Dry air under normal pressure,regarded as a perfect gas,was chosen as the working fluid,whereas the rod's cross-section was restricted to a ring.In this scenario heat exchange between the rod and the fluid is driven predominantly by natural convection,with a slight impact of thermal radiation,particularly at temperatures approaching the top end of the available range.Temperature margins achieved at the heated end of the rod ranged from 60 K up to 150 K,resulting in local Rayleigh numbers falling in-between 6.0xl03 and 2.6xl04.Reconstruction of Nusselt numbers from a discrete temperature distribution was possible thanks to a dedicated method implemented using a Scilab script.A segregated,steady-state solver based on the SIMPLE scheme was utilized for the purpose of numerical simulations on the fluid side,whereas a heat conduction equation was solved over solid domain in the considered conjugated heat transfer problem.A corresponding set of empirical data has been obtained,using both resistance temperature detectors and a thermal imaging camera,both for the sake of numerical model validation and comparison of individual methods.The Nusselt numbers resulting from each approach were compared against values computed using available correlations valid for horizontal configuration.
