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RISS 인기검색어
- 검색키워드
- 저자 : Yunqing Gu (검색결과 5 건)
- 무료
- 기관 내 무료
- 유료
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Preparation and properties of the green-emitting phosphors NaCa0.98-xMgxPO4:
Bo Yue,Juan Gu,Guangfu Yin,Zhongbing Huang,Xiaoming Liao,Yadong Yao,Yunqing Kang,Panli You 한국물리학회 2010 Current Applied Physics Vol.10 No.4
In this study, a series of the green-emitting phosphors NaCa0.98-xMgxPO4:Eu2þ 0:02 was prepared through high temperature solid-state reaction. The structure and spectroscopic properties of these samples were characterized by XRD, FT-IR, reflectance spectra and photoluminescence (PL) spectra, respectively. The effect of Mg2+ co-doping concentration on the PL intensity of as-prepared samples was also investigated. The enhanced intensities of excitation and emission band of Eu2+ and a slight red-shift of the emission peak were observed due to Mg2+ co-doping. When the x value is 0.08, the phosphors possessed the maximum emission intensity monitored at 360 nm and the emission spectrum shows a single band centered at about 500 nm. The obtained phosphors had strong absorption in near-UV zone (350–400 nm), which can match the emission of near-UV light-emitting diodes. The prepared material is potential green phosphors for white LEDs.
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Denghao Wu,Yun Ren,Jiegang Mou,Yunqing Gu 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.5
Circulator pumps have wide engineering applications but the acoustics, vibration and unsteady flow structures of the circulator pump are still not fully understood. We investigated the noise and vibration characteristics and unsteady flow structures in a circulator pump at different flow rates. Three-dimensional, unsteady RANS equations were solved on high-quality structured meshes with SST k-ω turbulence model numerically. Measurements were made in a semi-anechoic chamber to get an overview of noise and vibration level of a pump at different flow rates. The 1/3 octave-band filter technique was applied to obtain the explicit frequency spectra of sound, pressure fluctuations and vibration signals and their principal frequencies were identified successfully. The air-borne noise level of the designed condition is lower than that of the off-design conditions, and the highest sound pressure level is found at part-load condition. The acoustic emission from the pump is mainly caused by unsteady flow structures and pressure fluctuations. In addition, both the link between airborne noise and pressure fluctuation, and the correlation between vibration and unsteady hydrodynamic forces, were quantitatively examined and verified. This work offers good data to understand noise and vibration characteristics of circulator pumps and the relationships among the noise, vibration and unsteady flow structures.
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Denghao Wu,Yun Ren,Jiegang Mou,Yunqing Gu 한국유체기계학회 2017 International journal of fluid machinery and syste Vol.10 No.4
The flow instabilities and pressure pulsations can be generated during the pump’s operation. However, it is even more serious under the part-load condition. Currently, the links between flow instabilities and pressure pulsations were still not fully understood. In the present study, the experimental investigation was performed on pressure pulsations by utilizing the dynamic pressure transducers and the internal unsteady flow structures were measured by PIV. The pressure pulsations were extracted at 6 different locations around the volute under different flow rates conditions ranging from 10% to 120% of the nominal flow rate. The study allowed relating the pressure pulsations and unsteady flow structures in a pump. It was noted that higher intensive broadband pressure pulsations can be found at the small flow rate together with the fully developed flow instabilities. This led to the preliminary conclusion that the broadband pressure pulsations are exclusively induced by the flow instabilities, especially the vortices in the flow passages of impeller.
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Wu, Denghao,Ren, Yun,Mou, Jiegang,Gu, Yunqing Korean Society for Fluid machinery 2017 International journal of fluid machinery and syste Vol.10 No.4
The flow instabilities and pressure pulsations can be generated during the pump's operation. However, it is even more serious under the part-load condition. Currently, the links between flow instabilities and pressure pulsations were still not fully understood. In the present study, the experimental investigation was performed on pressure pulsations by utilizing the dynamic pressure transducers and the internal unsteady flow structures were measured by PIV. The pressure pulsations were extracted at 6 different locations around the volute under different flow rates conditions ranging from 10% to 120% of the nominal flow rate. The study allowed relating the pressure pulsations and unsteady flow structures in a pump. It was noted that higher intensive broadband pressure pulsations can be found at the small flow rate together with the fully developed flow instabilities. This led to the preliminary conclusion that the broadband pressure pulsations are exclusively induced by the flow instabilities, especially the vortices in the flow passages of impeller.
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Probability Evaluation of Hydrodynamic Shear Damage for Fish Passing through Jet Fish Pumps
Maosen Xu,Jiegang Mou,Denghao Wu,Peijian Zhou,Yunqing Gu,Shuihua Zheng 한국유체기계학회 2020 International journal of fluid machinery and syste Vol.13 No.2
Jet fish pump is an efficient tool to transport fish. Due to the operation principle, shear flow cannot be avoided in jet fish pumps. Shear flow is a potential risk for fish damage in the fluid machinery. Therefore, it is valuable to evaluate the probability of hydrodynamic shear damage for fish passing through jet fish pumps. In the present study, the numerical investigation was performed on the distribution of dangerous region, where exposure strain rate was above 500 s-1, and probability of hydrodynamic shear damage for fish. Experiments were conducted to check the damage probability calculated by numerical simulation and the injury of fish was analyzed. The results showed that the dangerous region is usually distributed in the near wall region. As the rise of flow ratio, the range of dangerous region gradually became wider and the dangerous region extended into the throat. In the same inlet boundary conditions, the damage probability is lower for a jet fish pump with a bigger area ratio. With the increase of flow ratio, both probability of hydrodynamic shear damage and effect of area ratio grow. Compared with the results of experiments, the probability of hydrodynamic shear damage can be overestimated. The main reasons lie in the extremely short transit time for fish, independent movement of fish and the velocity difference between fish and flow.
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