The vibration characteristics of transverse oscillation of an axially moving beam with high velocity is in- vestigated. The vibration equation and boundary conditions of the free-free axially moving beam are derived u...The vibration characteristics of transverse oscillation of an axially moving beam with high velocity is in- vestigated. The vibration equation and boundary conditions of the free-free axially moving beam are derived using Hamilton＇s principle. Furthermore, the linearized equations are set up based on Galerkinl s method for the ap- proximation solution. Finally, three influencing factors on the vibration frequency of the beam are considered： （1） The axially moving speed. The first order natural frequency decreases as the axial velocity increases, so there is a critical velocity of the axially moving beam. （2） The mass loss. The changing of the mass density of some part of the beam increases the beam natural frequencies. （3） The thermal effect.＇ The temperature increase will decrease the beam elastic modulus and induce the vibration frequencies descending.展开更多
The supersonic duct flow with fixed back pressure to stagnation pressure ratio Pb/Po under heating is investigated analytically. A 'Flow Pattern Diagram' which consists of six pattern zones is developed.By thi...The supersonic duct flow with fixed back pressure to stagnation pressure ratio Pb/Po under heating is investigated analytically. A 'Flow Pattern Diagram' which consists of six pattern zones is developed.By this diagram the actual flow state in supersonic duct flow system can be determined conveniently when Pb/Po and heating intensity are known. It is impossible for flow with heavy heating to become supersonic, even though the pressure ratio is much smaller than the critical pressure ratio. Based on the analogy between viscous effect and heating effect a thermal drag factor has been defined, which can predict the flow property variation due to heating and the relative importance of viscous effect and heating effect.展开更多
For avoiding extra-damage to healthy tissues surrounding the focal point during high intensity focused ultrasound(HIFU) treatment in medical therapy, to reduce the ultrasonic intensity outside the focal point is expec...For avoiding extra-damage to healthy tissues surrounding the focal point during high intensity focused ultrasound(HIFU) treatment in medical therapy, to reduce the ultrasonic intensity outside the focal point is expected. Thus, the heating processes induced by moderate intensity focused ultrasound(MIFU) and enhanced by combined irradiation of laser pulses for bio-tissues are studied in details. For fresh bio-tissues, the enhanced thermal effects by pulsed laser combined with MIFU irradiation are observed experimentally. To explore the mechanisms of these effects, several tissue-mimicking materials composed of agar mixed with graphite powders are prepared and studied for comparison, but the laser-enhanced thermal effects in these mimicking materials are much less than that in the fresh bio-tissues. Therefore, it is suggested that the laser-enhanced thermal effects may be mainly attributed to bio-activities and related photo-bio-chemical effects of fresh tissues.展开更多
基金Supported by the National Natural Science Foundation of China(10972104)~~
文摘The vibration characteristics of transverse oscillation of an axially moving beam with high velocity is in- vestigated. The vibration equation and boundary conditions of the free-free axially moving beam are derived using Hamilton＇s principle. Furthermore, the linearized equations are set up based on Galerkinl s method for the ap- proximation solution. Finally, three influencing factors on the vibration frequency of the beam are considered： （1） The axially moving speed. The first order natural frequency decreases as the axial velocity increases, so there is a critical velocity of the axially moving beam. （2） The mass loss. The changing of the mass density of some part of the beam increases the beam natural frequencies. （3） The thermal effect.＇ The temperature increase will decrease the beam elastic modulus and induce the vibration frequencies descending.
文摘The supersonic duct flow with fixed back pressure to stagnation pressure ratio Pb/Po under heating is investigated analytically. A 'Flow Pattern Diagram' which consists of six pattern zones is developed.By this diagram the actual flow state in supersonic duct flow system can be determined conveniently when Pb/Po and heating intensity are known. It is impossible for flow with heavy heating to become supersonic, even though the pressure ratio is much smaller than the critical pressure ratio. Based on the analogy between viscous effect and heating effect a thermal drag factor has been defined, which can predict the flow property variation due to heating and the relative importance of viscous effect and heating effect.
基金supported by the Special Funds for Quality Supervision,Inspection and Quarantine Research in Public Interest of China(Grant No.201510068)
文摘For avoiding extra-damage to healthy tissues surrounding the focal point during high intensity focused ultrasound(HIFU) treatment in medical therapy, to reduce the ultrasonic intensity outside the focal point is expected. Thus, the heating processes induced by moderate intensity focused ultrasound(MIFU) and enhanced by combined irradiation of laser pulses for bio-tissues are studied in details. For fresh bio-tissues, the enhanced thermal effects by pulsed laser combined with MIFU irradiation are observed experimentally. To explore the mechanisms of these effects, several tissue-mimicking materials composed of agar mixed with graphite powders are prepared and studied for comparison, but the laser-enhanced thermal effects in these mimicking materials are much less than that in the fresh bio-tissues. Therefore, it is suggested that the laser-enhanced thermal effects may be mainly attributed to bio-activities and related photo-bio-chemical effects of fresh tissues.
