The resonant behaviors of an ultra-sonic gas atomization nozzle with a zero mass-flux jet actuator were numerically investigated with FLUENT software by using a double precision unsteady two-dimensional pressure-based...The resonant behaviors of an ultra-sonic gas atomization nozzle with a zero mass-flux jet actuator were numerically investigated with FLUENT software by using a double precision unsteady two-dimensional pressure-based solver. The Spalart-Allmaras turbulence model was adopted in the simulations. Numerical results indicated that the oscillation properties of the gas efflux were effectively improved. Several resonatory frequencies corresponding to different vibration modes of gas were distinguished in the nozzle. With the changing of nozzle geometric parameters, different characters among those modes were elucidated by analyzing the propagations of pressure waves.展开更多
We report a unique case of communicating gastric duplication associated with pancreas divisum,diagnosed with a multidisciplinary approach,including X-rays,computed tomography,magnetic resonance imaging,esophagogastro ...We report a unique case of communicating gastric duplication associated with pancreas divisum,diagnosed with a multidisciplinary approach,including X-rays,computed tomography,magnetic resonance imaging,esophagogastro duodenoscopy,ultrasound endoscopy and histology. We believe that this approach constitutes a fuller diagnostic evaluation,resulting in better and safer surgery.展开更多
The ultra-sonic gas atomization （USGA） nozzle is an important apparatus in the metal liquid air-blast atomization process. It can generate oscillating supersonic gas effiux, which is proved to be effective to enforc...The ultra-sonic gas atomization （USGA） nozzle is an important apparatus in the metal liquid air-blast atomization process. It can generate oscillating supersonic gas effiux, which is proved to be effective to enforce the atomization and produce narrow-band particle distributions. A double-actuator ultra-sonic gas nozzle is proposed in the present paper by joining up two active signals at the ends of the resonance tubes. Numerical sim- ulations axe adopted to study the effects of the flow development on the acoustic resonant properties inside the Haxtmann resonance cavity with/without actuators. Comparisons show that the strength and the onset process of oscillation are enhanced remarkably with the actuators. The multiple oscillating amplitude peaks are found on the response curves, and two kinds of typical behaviors, i.e., the Hartmann mode and the global mode, are discussed for the corresponding frequencies. The results for two driving actuators are also investigated. When the amplitudes, the frequencies, or the phase difference of the input signals of the actuators are changed, the oscillating amplitudes of gas effiux can be altered effectively.展开更多
Ti-6Al-4V alloy is used extensively in aerospace and aircraft because of its excellent comprehensive properties and outstanding machinability. Ti-6Al-4V alloy was welded by conventional tungsten iner-gas arc welding (...Ti-6Al-4V alloy is used extensively in aerospace and aircraft because of its excellent comprehensive properties and outstanding machinability. Ti-6Al-4V alloy was welded by conventional tungsten iner-gas arc welding (TIG) and ultra-sonic frequency pulse TIG welding (U-TIG) respectively. The welding quality was tested by X-ray, and the mechanical properties of welded joint were tested , the microstructure and the fracture appearance of welded joint were observed by means of optical microscope and SEM .The results show that the joints were welded successfully by U-TIG welding, U-TIG welding could reduced pores defects of welded joint. With the increment of ultra-sonic pulse frequency, the microstructure became more and more fine and was inclined to equiaxed crystal. Moreover, the properties of joint by U-TIG welding were improved compared with that of conventional TIG. Tensile fractures of joints by TIG welding and U-TIG welding all presented character of quasi-cleavage crack, but the cellular dendrite depredation was not observed obviously in U-TIG joint.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.10772107, 10702038)the Shanghai Municipal Key Projects on Basic Research (Grant No.08JC1409800)+1 种基金the Innovation Project of Shanghai Municipal Education Commission (Grant No.08YZ10)the Shanghai Municipal Science and Technology Commission (Grant No.09DZ1141502)
文摘The resonant behaviors of an ultra-sonic gas atomization nozzle with a zero mass-flux jet actuator were numerically investigated with FLUENT software by using a double precision unsteady two-dimensional pressure-based solver. The Spalart-Allmaras turbulence model was adopted in the simulations. Numerical results indicated that the oscillation properties of the gas efflux were effectively improved. Several resonatory frequencies corresponding to different vibration modes of gas were distinguished in the nozzle. With the changing of nozzle geometric parameters, different characters among those modes were elucidated by analyzing the propagations of pressure waves.
文摘We report a unique case of communicating gastric duplication associated with pancreas divisum,diagnosed with a multidisciplinary approach,including X-rays,computed tomography,magnetic resonance imaging,esophagogastro duodenoscopy,ultrasound endoscopy and histology. We believe that this approach constitutes a fuller diagnostic evaluation,resulting in better and safer surgery.
基金Project supported by the National Natural Science Foundation of China (Nos. 10772107,10702038,and 11172163)the E-Institutes of Shanghai Municipal Education Commission,and the Shanghai Program for Innovative Research Team in Universities
文摘The ultra-sonic gas atomization （USGA） nozzle is an important apparatus in the metal liquid air-blast atomization process. It can generate oscillating supersonic gas effiux, which is proved to be effective to enforce the atomization and produce narrow-band particle distributions. A double-actuator ultra-sonic gas nozzle is proposed in the present paper by joining up two active signals at the ends of the resonance tubes. Numerical sim- ulations axe adopted to study the effects of the flow development on the acoustic resonant properties inside the Haxtmann resonance cavity with/without actuators. Comparisons show that the strength and the onset process of oscillation are enhanced remarkably with the actuators. The multiple oscillating amplitude peaks are found on the response curves, and two kinds of typical behaviors, i.e., the Hartmann mode and the global mode, are discussed for the corresponding frequencies. The results for two driving actuators are also investigated. When the amplitudes, the frequencies, or the phase difference of the input signals of the actuators are changed, the oscillating amplitudes of gas effiux can be altered effectively.
基金Defense Advance Research Program of China (2006137-2)
文摘Ti-6Al-4V alloy is used extensively in aerospace and aircraft because of its excellent comprehensive properties and outstanding machinability. Ti-6Al-4V alloy was welded by conventional tungsten iner-gas arc welding (TIG) and ultra-sonic frequency pulse TIG welding (U-TIG) respectively. The welding quality was tested by X-ray, and the mechanical properties of welded joint were tested , the microstructure and the fracture appearance of welded joint were observed by means of optical microscope and SEM .The results show that the joints were welded successfully by U-TIG welding, U-TIG welding could reduced pores defects of welded joint. With the increment of ultra-sonic pulse frequency, the microstructure became more and more fine and was inclined to equiaxed crystal. Moreover, the properties of joint by U-TIG welding were improved compared with that of conventional TIG. Tensile fractures of joints by TIG welding and U-TIG welding all presented character of quasi-cleavage crack, but the cellular dendrite depredation was not observed obviously in U-TIG joint.
