Microchannel heat sink with high heat transfer coefficients has been extensively investigated due to its wide application prospective in electronic cooling. However, this cooling system requires a separate pump to dri...Microchannel heat sink with high heat transfer coefficients has been extensively investigated due to its wide application prospective in electronic cooling. However, this cooling system requires a separate pump to drive the fluid transfer, which is uneasy to minimize and reduces their reliability and applicability of the whole system. In order to avoid these problems, valveless piezoelectric pump with fractal-like Y-shape branching tubes is proposed. Fractal-like Y-shape branching tube used in microchannel heat sinks is exploited as no-moving-part valve of the valveless piezoelectric pump. In order to obtain flow characteristics of the pump, the relationship between tube structure and flow rate of the pump is studied. Specifically, the flow resistances of fractal-like Y-shape branching tubes and flow rate of the pump are analyzed by using fractal theory. Then, finite element software is employed to simulate the flow field of the tube, and the relationships between pressure drop and flow rate along merging and dividing flows are obtained. Finally, valveless piezoelectric pumps with fractal-like Y-shape branching tubes with different fractal dimensions of diameter distribution are fabricated, and flow rate experiment is conducted. The experimental results show that the flow rate of the pump increases with the rise of fractal dimension of the tube diameter. When fractal dimension is 3, the maximum flow rate of the valveless pump is 29.16 mL/min under 100 V peak to peak （13 Hz） power supply, which reveals the relationship between flow rate and fractal dimensions of tube diameter distribution. This paper investigates the flow characteristics of valveless piezoelectric pump with fractal-like Y-shape branching tubes, which provides certain references for valveless piezoelectric pump with fractal-like Y-shape branching tubes in application on electronic chip cooling.展开更多
Branched CdTe nanocrystals with zinc blende structure were directly synthesized in the early growth stage at a high initial concentration of cadmium precursor and a high molar ratio of Cd precursor to Te precuesor. Ac...Branched CdTe nanocrystals with zinc blende structure were directly synthesized in the early growth stage at a high initial concentration of cadmium precursor and a high molar ratio of Cd precursor to Te precuesor. Activation of the cadmium precursor by octadecylamine was found to be critical for the formation of branched CdTe nanocrystals. Furthermore, these as-prepared CdTe nanocrystals can evolve into nearly monodisperse dots through Ostwald ripening and still keep strong photoluminescence. These results manifest a new route to synthesize branch- and dot-shaped CdTe nanocrystals with zinc blende structure.展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.51275235,51375227)Major Research Plan of National Natural Science Foundation of China(Grant No.91223201)Independent Projects Fund of State Key Lab of Mechanics and Control of Mechanical Structures of China(Grant No.0313G01)
文摘Microchannel heat sink with high heat transfer coefficients has been extensively investigated due to its wide application prospective in electronic cooling. However, this cooling system requires a separate pump to drive the fluid transfer, which is uneasy to minimize and reduces their reliability and applicability of the whole system. In order to avoid these problems, valveless piezoelectric pump with fractal-like Y-shape branching tubes is proposed. Fractal-like Y-shape branching tube used in microchannel heat sinks is exploited as no-moving-part valve of the valveless piezoelectric pump. In order to obtain flow characteristics of the pump, the relationship between tube structure and flow rate of the pump is studied. Specifically, the flow resistances of fractal-like Y-shape branching tubes and flow rate of the pump are analyzed by using fractal theory. Then, finite element software is employed to simulate the flow field of the tube, and the relationships between pressure drop and flow rate along merging and dividing flows are obtained. Finally, valveless piezoelectric pumps with fractal-like Y-shape branching tubes with different fractal dimensions of diameter distribution are fabricated, and flow rate experiment is conducted. The experimental results show that the flow rate of the pump increases with the rise of fractal dimension of the tube diameter. When fractal dimension is 3, the maximum flow rate of the valveless pump is 29.16 mL/min under 100 V peak to peak （13 Hz） power supply, which reveals the relationship between flow rate and fractal dimensions of tube diameter distribution. This paper investigates the flow characteristics of valveless piezoelectric pump with fractal-like Y-shape branching tubes, which provides certain references for valveless piezoelectric pump with fractal-like Y-shape branching tubes in application on electronic chip cooling.
基金Supported by the National Natural Science Foundation of China(No.20771035)
文摘Branched CdTe nanocrystals with zinc blende structure were directly synthesized in the early growth stage at a high initial concentration of cadmium precursor and a high molar ratio of Cd precursor to Te precuesor. Activation of the cadmium precursor by octadecylamine was found to be critical for the formation of branched CdTe nanocrystals. Furthermore, these as-prepared CdTe nanocrystals can evolve into nearly monodisperse dots through Ostwald ripening and still keep strong photoluminescence. These results manifest a new route to synthesize branch- and dot-shaped CdTe nanocrystals with zinc blende structure.
