The aerodynamic aspects of indirect thrust measurement by the impulse method have been studied both experimentally and numerically. The underlying basic aerodynamic principle is outlined, the phenomena in subsonic, su...The aerodynamic aspects of indirect thrust measurement by the impulse method have been studied both experimentally and numerically. The underlying basic aerodynamic principle is outlined, the phenomena in subsonic, supersonic and arc-heated jets are explored, and factors affecting the accuracy of the method are studied and discussed. Results show that the impulse method is reliable for indirect thrust measurement if certain basic requirements are met, and a simple guideline for its proper application is given.展开更多
The flow in a low-powered arc gas heater com- bined with a supersonic nozzle of throat diameter less than 1 mm is quite complicated and difficult to describe in quan- titative detail. Experiments on arc-heated superso...The flow in a low-powered arc gas heater com- bined with a supersonic nozzle of throat diameter less than 1 mm is quite complicated and difficult to describe in quan- titative detail. Experiments on arc-heated supersonic jet thrusters of monatomic gases argon and helium have been carried out and their performance measured. The flow charac- teristics are analyzed with the help of numerical simulation. Results show that the viscous effect is the most important factor causing the large difference between ideal and real performance. A large outer section of the exit flow is slow- moving. This is especially pronounced in helium, where 70 % of the exit area of the nozzle might be in subsonic flow. Fric- tion forces can be much larger than the net thrust, reaching several times higher in helium, resulting in very low efficien- cies. Other factors causing the differences between ideal and real flow include： complex flow in the throat region, electric arc extending to the nozzle expansion section, heat transfer to the inlet gas and from the hot plasma, and environmen- tal pressure in the vacuum chamber. It is recognized that the ordinary concepts of supersonic nozzle flow must be greatly modified when dealing with such complicated situations. The general concepts presented in this paper could be helpful in guiding the design and operation of this equipment.展开更多
This study aims to develop a method for isolating and purifying protoplasts/vacuoles from fresh leaves of the Cd hyperaccumulator plant species, Sedum alfredii. The results revealed that preheating cellulase and macer...This study aims to develop a method for isolating and purifying protoplasts/vacuoles from fresh leaves of the Cd hyperaccumulator plant species, Sedum alfredii. The results revealed that preheating cellulase and macerozyme at 50 ℃ for 5 rain significantly accel- erated the cell wall degradation. For the most optimal conditions for mesophyll protoplast isolation, the mixture of fresh leaves and cell lysates was followed by a 2-h-long vibration. The protoplast lysate for vacu- ole isolation was diluted, and 0.675 mmol/L was identi- fied as the most appropriate 3-[（3-cholamidopropyl） dimethylammonio]- 1 -propanesulfonic acid （CHAPS） level, in which S. alfredii large vacuoles are charac- terized by a high metal and malic acid content.展开更多
基金supported by the National Natural Science Foundation of China (50836007, 10921062, 10772016)
文摘The aerodynamic aspects of indirect thrust measurement by the impulse method have been studied both experimentally and numerically. The underlying basic aerodynamic principle is outlined, the phenomena in subsonic, supersonic and arc-heated jets are explored, and factors affecting the accuracy of the method are studied and discussed. Results show that the impulse method is reliable for indirect thrust measurement if certain basic requirements are met, and a simple guideline for its proper application is given.
基金supported by the National Natural Science Foundation of China(Grants 50836007,11475239,10921062,and 11275021)
文摘The flow in a low-powered arc gas heater com- bined with a supersonic nozzle of throat diameter less than 1 mm is quite complicated and difficult to describe in quan- titative detail. Experiments on arc-heated supersonic jet thrusters of monatomic gases argon and helium have been carried out and their performance measured. The flow charac- teristics are analyzed with the help of numerical simulation. Results show that the viscous effect is the most important factor causing the large difference between ideal and real performance. A large outer section of the exit flow is slow- moving. This is especially pronounced in helium, where 70 % of the exit area of the nozzle might be in subsonic flow. Fric- tion forces can be much larger than the net thrust, reaching several times higher in helium, resulting in very low efficien- cies. Other factors causing the differences between ideal and real flow include： complex flow in the throat region, electric arc extending to the nozzle expansion section, heat transfer to the inlet gas and from the hot plasma, and environmen- tal pressure in the vacuum chamber. It is recognized that the ordinary concepts of supersonic nozzle flow must be greatly modified when dealing with such complicated situations. The general concepts presented in this paper could be helpful in guiding the design and operation of this equipment.
基金Project supported by the National Natural Science Foundation of China(Nos.31370040 and 41401366)the Zhejiang Provincial Natural Science Foundation of China(No.LR14C150001)
文摘This study aims to develop a method for isolating and purifying protoplasts/vacuoles from fresh leaves of the Cd hyperaccumulator plant species, Sedum alfredii. The results revealed that preheating cellulase and macerozyme at 50 ℃ for 5 rain significantly accel- erated the cell wall degradation. For the most optimal conditions for mesophyll protoplast isolation, the mixture of fresh leaves and cell lysates was followed by a 2-h-long vibration. The protoplast lysate for vacu- ole isolation was diluted, and 0.675 mmol/L was identi- fied as the most appropriate 3-[（3-cholamidopropyl） dimethylammonio]- 1 -propanesulfonic acid （CHAPS） level, in which S. alfredii large vacuoles are charac- terized by a high metal and malic acid content.
