According to the theory of phononic crystals, the hydraulic pipeline is designed to be a periodic structure composed of steel pipes and hoses to suppress the vibration of the hydraulic system with band gaps. We presen...According to the theory of phononic crystals, the hydraulic pipeline is designed to be a periodic structure composed of steel pipes and hoses to suppress the vibration of the hydraulic system with band gaps. We present theoretical and experimental investigations into the flexural vibration transfer properties of a high-pressure periodic pipe with the force on the inner pipe wall by oii pressure taken into consideration. The results show that the vibration attenuation of periodic pipe decreases along with the elevation of working pressure for the hydraulic system, and the band gaps in low frequency ranges move towards high frequency ranges. The periodic pipe has good vibration attenuation performance in the frequency range below 1000 Hz and the vibration of the hydraulic system is effectively suppressed. A11 the results are validated by experiment. The experimental results show a good agreement with the numerical calculations, thus the flexural vibration transfer properties of the high- pressure periodic pipe can be precisely calculated by taking the fluid structure interaction between the pipe and oil into consideration. This study provides an effective way for the vibration control of the hydraulic system.展开更多
The ground-state energy level (GEL) and electron distribution of GaAs pseudomorphic high-electron-mobility transistors (PHEMTs) are analyzed by a self-consistent solution to the Schrodinger-Poisson equations. The ...The ground-state energy level (GEL) and electron distribution of GaAs pseudomorphic high-electron-mobility transistors (PHEMTs) are analyzed by a self-consistent solution to the Schrodinger-Poisson equations. The indium composition and thickness of the InGaAs channel are optimized according to the GEL position. The GEL position is not in direct proportion to 1/d^2 (d is the channel thickness) by considering the influence of electron distribution in the InGaAs channel. Indium composition 0.22 and channel thickness 9 nm are obtained by considering the mismatch between InGaAs and AlGaAs. Several PHEMT samples are grown according to the theoretical results and mobility 6300 cm^2 /V.s is achieved.展开更多
A novel no-guide light pen type 3D-coordinate measurement system with three sets of position sensitive devices (PSDs) to realize intersection converge imaging is introduced. It is called as the light pen type measurem...A novel no-guide light pen type 3D-coordinate measurement system with three sets of position sensitive devices (PSDs) to realize intersection converge imaging is introduced. It is called as the light pen type measurement system, because the measuring head is shaped as a pen with several light sources on it. The structure design, measurement principle and experimental results are presented. The theoretical analysis and experimental results prove that this system has advanced features of simple structure, high automation, and high accuracy, and can be used in the measurement fields of mechanical manufacture, robot, auto, aviation and medicine effectively.展开更多
The evaporator is the main part of a quick-freeze equipment. There are many factors influencing the heat transfer coefficient of an evaporator. The most important factors among them are the fin shape, tube diameter, d...The evaporator is the main part of a quick-freeze equipment. There are many factors influencing the heat transfer coefficient of an evaporator. The most important factors among them are the fin shape, tube diameter, distance of fin space, frost, and velocity of air flow etc. They mainly influence the thermal efficiency of an evaporator, and therefore its thermal efficiency has direct relationship with the whole efficiency of the quick freeze plant. Evaporators with different structural types have different heat transfer efficiency, in order to obtain high efficiency structure of evaporator, 8 evaporator models with different fin shape, tube diameter and tube arrangement are analyzed and compared. The calculation results show that the integral waved fins, equilateral-triangle arranged small diameter tubes and varying fin-spacing has the highest heat transfer coefficient. The experimental result also shows that the evaporator with this type of structure has better thermal efficiency. The experimental result is in good agreement with the calculation result, it can instruct engineering design for usual designer. A real quick-freeze equipment is designed and put into production. The result shows that, compared with traditional domestic quick-freeze equipments, this equipment decreases by 40% in size and by 20% in energy consumption.展开更多
The underwater counter-rotation propeller non-cavitation noise has an obvious mod- ulation characteristic which is due to the interaction of flow and blade. A modulation mecha- nism is presented in this paper. A sound...The underwater counter-rotation propeller non-cavitation noise has an obvious mod- ulation characteristic which is due to the interaction of flow and blade. A modulation mecha- nism is presented in this paper. A sound pressure spectrum model is presented to describe its non-cavitation noise with application of generalized acoustic analogy method, the modulation mechanism is expressed with the improvement of sound pressure model. The power spectrum and modulation spectrum are presented by numerical simulation. Theoretical analysis and nu- merical simulation results are verified by the cavitation tunnel experiment. The modulation model of counter-rotation propeller is beneficial to the prediction modulation characteristics and identification of underwater high-speed vehicles.展开更多
The theoretical analysis and experimental research on Port/Starboard (P/S) discrimination in towed line array are proposed. Two methods resolving the P/S ambiguity with hydrophone triplets are introduced. By processi...The theoretical analysis and experimental research on Port/Starboard (P/S) discrimination in towed line array are proposed. Two methods resolving the P/S ambiguity with hydrophone triplets are introduced. By processing experimental data, the theoretical analysis is verified. The processing algorithm is extended to broadband signal. The research results show that the method based on optimum beamforming with triplets can be used to remove the port/starboard ambiguity. Also because of the simplicity of the method, it is expected to be implemented in practical towed line array sonar.展开更多
文摘According to the theory of phononic crystals, the hydraulic pipeline is designed to be a periodic structure composed of steel pipes and hoses to suppress the vibration of the hydraulic system with band gaps. We present theoretical and experimental investigations into the flexural vibration transfer properties of a high-pressure periodic pipe with the force on the inner pipe wall by oii pressure taken into consideration. The results show that the vibration attenuation of periodic pipe decreases along with the elevation of working pressure for the hydraulic system, and the band gaps in low frequency ranges move towards high frequency ranges. The periodic pipe has good vibration attenuation performance in the frequency range below 1000 Hz and the vibration of the hydraulic system is effectively suppressed. A11 the results are validated by experiment. The experimental results show a good agreement with the numerical calculations, thus the flexural vibration transfer properties of the high- pressure periodic pipe can be precisely calculated by taking the fluid structure interaction between the pipe and oil into consideration. This study provides an effective way for the vibration control of the hydraulic system.
文摘The ground-state energy level (GEL) and electron distribution of GaAs pseudomorphic high-electron-mobility transistors (PHEMTs) are analyzed by a self-consistent solution to the Schrodinger-Poisson equations. The indium composition and thickness of the InGaAs channel are optimized according to the GEL position. The GEL position is not in direct proportion to 1/d^2 (d is the channel thickness) by considering the influence of electron distribution in the InGaAs channel. Indium composition 0.22 and channel thickness 9 nm are obtained by considering the mismatch between InGaAs and AlGaAs. Several PHEMT samples are grown according to the theoretical results and mobility 6300 cm^2 /V.s is achieved.
基金This work was supported by the National Natural Science Foundation of China under Grant No. 59875066. X. Zhang's e-mail address is zhangxf@eyou.com.
文摘A novel no-guide light pen type 3D-coordinate measurement system with three sets of position sensitive devices (PSDs) to realize intersection converge imaging is introduced. It is called as the light pen type measurement system, because the measuring head is shaped as a pen with several light sources on it. The structure design, measurement principle and experimental results are presented. The theoretical analysis and experimental results prove that this system has advanced features of simple structure, high automation, and high accuracy, and can be used in the measurement fields of mechanical manufacture, robot, auto, aviation and medicine effectively.
基金This project is supported by National Key Technologies R&D Programme,China (No.2001BA501A22).
文摘The evaporator is the main part of a quick-freeze equipment. There are many factors influencing the heat transfer coefficient of an evaporator. The most important factors among them are the fin shape, tube diameter, distance of fin space, frost, and velocity of air flow etc. They mainly influence the thermal efficiency of an evaporator, and therefore its thermal efficiency has direct relationship with the whole efficiency of the quick freeze plant. Evaporators with different structural types have different heat transfer efficiency, in order to obtain high efficiency structure of evaporator, 8 evaporator models with different fin shape, tube diameter and tube arrangement are analyzed and compared. The calculation results show that the integral waved fins, equilateral-triangle arranged small diameter tubes and varying fin-spacing has the highest heat transfer coefficient. The experimental result also shows that the evaporator with this type of structure has better thermal efficiency. The experimental result is in good agreement with the calculation result, it can instruct engineering design for usual designer. A real quick-freeze equipment is designed and put into production. The result shows that, compared with traditional domestic quick-freeze equipments, this equipment decreases by 40% in size and by 20% in energy consumption.
基金supported by the National Natural Science Foundation of China(11704345)the Key Laboratory of Science and Technology for National Defence Foundation(9140C290304140C29133)
文摘The underwater counter-rotation propeller non-cavitation noise has an obvious mod- ulation characteristic which is due to the interaction of flow and blade. A modulation mecha- nism is presented in this paper. A sound pressure spectrum model is presented to describe its non-cavitation noise with application of generalized acoustic analogy method, the modulation mechanism is expressed with the improvement of sound pressure model. The power spectrum and modulation spectrum are presented by numerical simulation. Theoretical analysis and nu- merical simulation results are verified by the cavitation tunnel experiment. The modulation model of counter-rotation propeller is beneficial to the prediction modulation characteristics and identification of underwater high-speed vehicles.
文摘The theoretical analysis and experimental research on Port/Starboard (P/S) discrimination in towed line array are proposed. Two methods resolving the P/S ambiguity with hydrophone triplets are introduced. By processing experimental data, the theoretical analysis is verified. The processing algorithm is extended to broadband signal. The research results show that the method based on optimum beamforming with triplets can be used to remove the port/starboard ambiguity. Also because of the simplicity of the method, it is expected to be implemented in practical towed line array sonar.