This paper presents a piezoelectric-metal structure called a drum transducer. An equation for calculating the resonance frequency of the drum transducer is obtained based on thin plate elastic theory of piezoelectric ...This paper presents a piezoelectric-metal structure called a drum transducer. An equation for calculating the resonance frequency of the drum transducer is obtained based on thin plate elastic theory of piezoelectric and metal material combined with the Rayleigh-Ritz method. The finite element method (FEM) was used to predict the excitation frequency of the drum transducer. To verify the theoretical analysis, the input impedance characteristic of the drum transducer was measured using an experimental method. The results obtained from theoretical analysis were in very good agreement with those from the FEM and experimental results. The effect of geometrical changes to the thick-walled steel ring of the drum transducer at the first resonance frequency is also described. The calculated results were found to be in good agreement with the FEM results. The results indicate that the first resonance frequency of the drum decreases with the increasing inner diameter of the thick-walled steel ring.展开更多
In this paper,the interrupted and ruptured creep tests were carried out in a novel second generation single crystal superalloy named DD11 at 1100℃/130 MPa.The alloy exhibited typical creep curve including primary,ste...In this paper,the interrupted and ruptured creep tests were carried out in a novel second generation single crystal superalloy named DD11 at 1100℃/130 MPa.The alloy exhibited typical creep curve including primary,steady,and tertiary three creep stages.The microstructural evolution at different stages of the creep were analyzed by scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The results show that theγ′phases transform into rafted structure at the early stage of the steady creep and keep stable during the steady creep stage.As the creep goes on,the rafted structure further coarsens and the topological inversion occurs.In addition,at the primary creep,the dislocations mainly move in theγmatrix and pile up in theγ/γ′interface since the matrix channels widen slightly.The formation of the regular interfacial dislocation networks occurs at the early stage of the steady creep.Under the low stress,the dominated deformation mechanism during steady creep stage is the climbing of the〈010〉type edge dislocation.Furthermore,the effect of the deformation mechanism on creep property was discussed in detail.展开更多
Conventional radiotherapy has a good killing effect on femoral echinococcosis.However,the sciatic nerve around the lesion is irreversibly damaged owing to bystander effects.Although intensity-modulated radiation thera...Conventional radiotherapy has a good killing effect on femoral echinococcosis.However,the sciatic nerve around the lesion is irreversibly damaged owing to bystander effects.Although intensity-modulated radiation therapy shows great advantages for precise dose distribution into lesions,it is unknown whether intensity-modulated radiation therapy can perfectly protect the surrounding sciatic nerve on the basis of good killing of femoral echinococcosis foci.Therefore,this study comparatively analyzed differences between intensity-modulated radiation therapy and conventional radiotherapy on the basis of safety to peripheral nerves.Pure-breed Meriones meridiani with bilateral femoral echinococcosis were selected as the research object.Intensity-modulated radiation therapy was used to treat left femoral echinococcosis of Meriones meridianus,while conventional radiotherapy was used to treat right femoral echinococcosis of the same Meriones meridianus.The total radiation dose was 40 Gy.To understand whether intensity-modulated radiation therapy and conventional radiotherapy can kill femoral echinococcosis,trypan blue staining was used to detect pathological changes of bone Echinococcus granulosus and protoscolex death after radiotherapy.Additionally,enzyme histochemical staining was utilized to measure acid phosphatase activity in the protoscolex after radiotherapy.One week after radiotherapy,the overall structure of echinococcosis in bilateral femurs of Meriones meridiani treated by intensity-modulated radiation therapy disappeared.There was no significant difference in the mortality rate of protoscoleces of Echinococcus granulosus between the bilateral femurs of Meriones meridiani.Moreover,there was no significant difference in acid phosphatase activity in the protoscolex of Echinococcus granulosus between bilateral femurs.To understand the injury of sciatic nerve surrounding the foci of femoral echinococcosis caused by intensity-modulated radiation therapy and conventional radiotherapy,the ultrastructure of sciatic ner展开更多
基金Project supported by the National Natural Science Foundation of China (No. 50875057)the Natural Scientific Research Innova-tion Foundation in Harbin Institute of Technology,China (No. HIT. NSRIF.2008.50)
文摘This paper presents a piezoelectric-metal structure called a drum transducer. An equation for calculating the resonance frequency of the drum transducer is obtained based on thin plate elastic theory of piezoelectric and metal material combined with the Rayleigh-Ritz method. The finite element method (FEM) was used to predict the excitation frequency of the drum transducer. To verify the theoretical analysis, the input impedance characteristic of the drum transducer was measured using an experimental method. The results obtained from theoretical analysis were in very good agreement with those from the FEM and experimental results. The effect of geometrical changes to the thick-walled steel ring of the drum transducer at the first resonance frequency is also described. The calculated results were found to be in good agreement with the FEM results. The results indicate that the first resonance frequency of the drum decreases with the increasing inner diameter of the thick-walled steel ring.
基金This study was financially supported by the National Natural Science Foundation of China(No.51471014).
文摘In this paper,the interrupted and ruptured creep tests were carried out in a novel second generation single crystal superalloy named DD11 at 1100℃/130 MPa.The alloy exhibited typical creep curve including primary,steady,and tertiary three creep stages.The microstructural evolution at different stages of the creep were analyzed by scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The results show that theγ′phases transform into rafted structure at the early stage of the steady creep and keep stable during the steady creep stage.As the creep goes on,the rafted structure further coarsens and the topological inversion occurs.In addition,at the primary creep,the dislocations mainly move in theγmatrix and pile up in theγ/γ′interface since the matrix channels widen slightly.The formation of the regular interfacial dislocation networks occurs at the early stage of the steady creep.Under the low stress,the dominated deformation mechanism during steady creep stage is the climbing of the〈010〉type edge dislocation.Furthermore,the effect of the deformation mechanism on creep property was discussed in detail.
基金supported by the China Postdoctoral Science Foundation,No.2019M652397(to WLX)。
文摘Conventional radiotherapy has a good killing effect on femoral echinococcosis.However,the sciatic nerve around the lesion is irreversibly damaged owing to bystander effects.Although intensity-modulated radiation therapy shows great advantages for precise dose distribution into lesions,it is unknown whether intensity-modulated radiation therapy can perfectly protect the surrounding sciatic nerve on the basis of good killing of femoral echinococcosis foci.Therefore,this study comparatively analyzed differences between intensity-modulated radiation therapy and conventional radiotherapy on the basis of safety to peripheral nerves.Pure-breed Meriones meridiani with bilateral femoral echinococcosis were selected as the research object.Intensity-modulated radiation therapy was used to treat left femoral echinococcosis of Meriones meridianus,while conventional radiotherapy was used to treat right femoral echinococcosis of the same Meriones meridianus.The total radiation dose was 40 Gy.To understand whether intensity-modulated radiation therapy and conventional radiotherapy can kill femoral echinococcosis,trypan blue staining was used to detect pathological changes of bone Echinococcus granulosus and protoscolex death after radiotherapy.Additionally,enzyme histochemical staining was utilized to measure acid phosphatase activity in the protoscolex after radiotherapy.One week after radiotherapy,the overall structure of echinococcosis in bilateral femurs of Meriones meridiani treated by intensity-modulated radiation therapy disappeared.There was no significant difference in the mortality rate of protoscoleces of Echinococcus granulosus between the bilateral femurs of Meriones meridiani.Moreover,there was no significant difference in acid phosphatase activity in the protoscolex of Echinococcus granulosus between bilateral femurs.To understand the injury of sciatic nerve surrounding the foci of femoral echinococcosis caused by intensity-modulated radiation therapy and conventional radiotherapy,the ultrastructure of sciatic ner
