Effects of ultrasonic vibration(UV)and mechanical vibration(MV)on the Mn-rich phase modification and mechanical properties of Al−12Si−4Cu−1Ni−1Mg−2Mn piston alloys were investigated.The results show that the UV and UV...Effects of ultrasonic vibration(UV)and mechanical vibration(MV)on the Mn-rich phase modification and mechanical properties of Al−12Si−4Cu−1Ni−1Mg−2Mn piston alloys were investigated.The results show that the UV and UV+MV treatments can significantly refine and fragmentize the microstructures.In addition,UV treatment can significantly passivate the primary Mn-rich Al15Mn3Si2 intermetallics.The formation mechanisms of refinement and passivation of the grains and non-dendrite particles were discussed.Compared with the gravity die-cast alloys,the UV and UV+MV treated alloys exhibit improved tensile and creep resistance at room and elevated temperatures.These results can be attributed to the refinement of theα(Al)grains and the secondary intermetallics,the increased proportion of refined heat-resistant precipitates,and the formation of nano-sized Si particles.The ultimate tensile strength of the UV treated alloys at 350℃ exceeds that of commercial piston alloys.This indicates the high application potential of the developed piston alloys in density diesel engines.展开更多
A dual transponder carrier ranging method can be used to measure inter-satellite distance with high precision by combining the reference and the to-and-fro measurements. Based on the differential techniques, the oscil...A dual transponder carrier ranging method can be used to measure inter-satellite distance with high precision by combining the reference and the to-and-fro measurements. Based on the differential techniques, the oscillator phase noise, which is the main error source for microwave ranging systems, can be significantly attenuated. Further, since the range measurements are derived on the same satellite, the dual transponder ranging system does not need a time tagging system to synchronize the two satellites. In view of the lack of oscillator noise analysis on the dual transponder ranging model, a comprehensive analysis of oscillator noise effects on ranging accuracy is provided. First, the dual transponder ranging system is described with emphasis on the detailed analysis of oscillator noise on measurement precision. Then, a high-fidelity numerical simulation approach based on the power spectrum density of an actual ultra-stable oscillator is carried out in both frequency domain and time domain to support the presented theoretical analysis. The simulation results under different conditions are consistent with the proposed concepts, which makes the results reliable. Besides, the results demonstrate that a high level of accuracy can be achieved by using this oscillator noise cancelation-oriented ranging method.展开更多
Although hydraulic drives have an advantage of high power density, volumetric shrinkage of hydraulic fluids due to pressure causes various disadvantages such as delay of hydraulic response and compression energy loss....Although hydraulic drives have an advantage of high power density, volumetric shrinkage of hydraulic fluids due to pressure causes various disadvantages such as delay of hydraulic response and compression energy loss. Hydraulic fluids of new concept, high bulk modulus oils, have been developed as a new approach to improve the performance of a hydraulic servo system and verified. In this paper, practical performances of high bulk modulus oil, such as oil temperature rise during pump test, air bubbles generation by ultrasonic wave vibration, oxidation stability and anti-wear property, were studied. And the new oil was confirmed to have excellent practical performances besides advantages in pressure response and volumetric efficiency of pumps. Various new applications of the new oil are promising.展开更多
Subsurface buoy systems,especially equipped with the vector sensor,have more and more extensive applications in military and civilian regions.However,their acoustic performances are constrained by the vibration result...Subsurface buoy systems,especially equipped with the vector sensor,have more and more extensive applications in military and civilian regions.However,their acoustic performances are constrained by the vibration resulting from the unavoidable ocean current in some degree.The influence of such vibrations is quantitatively analyzed by means of modeling the simplified models of two deployment configurations involving the positive buoyant buoy and neutral buoy system.The corresponding formulas are deduced respectively for the deployment configuration buoy systems in the motion state firstly.Then the simulation software is developed and some numerical simulations are put up via the Runge-Kutta method.The simulation results and theoretical analysis indicate that the neutral buoy will be an excellent design protocol in engineering application in comparison with the positive buoyant buoy.展开更多
Over the past decade, ultraviolet(UV) detection has been a subject of major interest for both research scientists and engineers because of its important applications in both the civil and military fields. The rapid de...Over the past decade, ultraviolet(UV) detection has been a subject of major interest for both research scientists and engineers because of its important applications in both the civil and military fields. The rapid development of interdisciplinary research has enabled the realization of UV detectors based on a variety of principles. Among these devices, UV detectors based on surface acoustic wave(SAW) technology offer unique advantages of remote wireless operation capability and zero power consumption. This article provides a comprehensive review of the working principles, important parameters, and the acoustic wave and materials types used in SAW-based UV detectors. The research and development status of these detectors are discussed and the most commonly used methods to optimize device performance are also summarized. Novel types of acoustic UV detectors based on thin film bulk acoustic resonators(FBARs)and Lamb wave resonators(LMRs) are briefly introduced. Finally, future development challenges are proposed and suggestions for future directions are provided to aid the development of this important research field.展开更多
Laser phase noise （LPN） plays an important role in optical coherent systems. Based on the algorithm of Viterbi-Viterbi cartier phase estimation （CPE）, the effects of LPN imposed on the coherent receivers are inves...Laser phase noise （LPN） plays an important role in optical coherent systems. Based on the algorithm of Viterbi-Viterbi cartier phase estimation （CPE）, the effects of LPN imposed on the coherent receivers are investigated for quadrature phase shift keying （QPSK）, 8 phase shift keying （SPSK） and 16-quadrature amplitude modulation （16-QAM） optical coherent systems, respectively. The simulation results show that the optimal block length in the phase estimation algorithm is a tradeoffbetween LPN and additive white Gaussian noise （AWGN）, and depends on the level of modulation formats. The resolution requirements of analog to digital converter （ADC） in the coherent receivers are independent of LPN or the level of modulation formats. For the bit error rate （BER） of 10-3, the required bit number of ADC is 6, and the gain is marginal for the higher resolution.展开更多
基金the National Natural Science Foundation of China(No.52265043)Science and Technology Plan,Guizhou Province,China(No.ZK2021(267))+2 种基金Technology Achievements Application and Industrialization Project,Guizhou Province,China(No.2021(067))Cultivation Project of Guizhou University,China(No.2019(23))Lastly,we thank the Shanghai Synchrotron Radiation Facility(SSRF)for providing the synchrotron radiation beamtime.
文摘Effects of ultrasonic vibration(UV)and mechanical vibration(MV)on the Mn-rich phase modification and mechanical properties of Al−12Si−4Cu−1Ni−1Mg−2Mn piston alloys were investigated.The results show that the UV and UV+MV treatments can significantly refine and fragmentize the microstructures.In addition,UV treatment can significantly passivate the primary Mn-rich Al15Mn3Si2 intermetallics.The formation mechanisms of refinement and passivation of the grains and non-dendrite particles were discussed.Compared with the gravity die-cast alloys,the UV and UV+MV treated alloys exhibit improved tensile and creep resistance at room and elevated temperatures.These results can be attributed to the refinement of theα(Al)grains and the secondary intermetallics,the increased proportion of refined heat-resistant precipitates,and the formation of nano-sized Si particles.The ultimate tensile strength of the UV treated alloys at 350℃ exceeds that of commercial piston alloys.This indicates the high application potential of the developed piston alloys in density diesel engines.
基金Project(61106113)supported by the National Natural Science Foundation of China
文摘A dual transponder carrier ranging method can be used to measure inter-satellite distance with high precision by combining the reference and the to-and-fro measurements. Based on the differential techniques, the oscillator phase noise, which is the main error source for microwave ranging systems, can be significantly attenuated. Further, since the range measurements are derived on the same satellite, the dual transponder ranging system does not need a time tagging system to synchronize the two satellites. In view of the lack of oscillator noise analysis on the dual transponder ranging model, a comprehensive analysis of oscillator noise effects on ranging accuracy is provided. First, the dual transponder ranging system is described with emphasis on the detailed analysis of oscillator noise on measurement precision. Then, a high-fidelity numerical simulation approach based on the power spectrum density of an actual ultra-stable oscillator is carried out in both frequency domain and time domain to support the presented theoretical analysis. The simulation results under different conditions are consistent with the proposed concepts, which makes the results reliable. Besides, the results demonstrate that a high level of accuracy can be achieved by using this oscillator noise cancelation-oriented ranging method.
文摘Although hydraulic drives have an advantage of high power density, volumetric shrinkage of hydraulic fluids due to pressure causes various disadvantages such as delay of hydraulic response and compression energy loss. Hydraulic fluids of new concept, high bulk modulus oils, have been developed as a new approach to improve the performance of a hydraulic servo system and verified. In this paper, practical performances of high bulk modulus oil, such as oil temperature rise during pump test, air bubbles generation by ultrasonic wave vibration, oxidation stability and anti-wear property, were studied. And the new oil was confirmed to have excellent practical performances besides advantages in pressure response and volumetric efficiency of pumps. Various new applications of the new oil are promising.
文摘Subsurface buoy systems,especially equipped with the vector sensor,have more and more extensive applications in military and civilian regions.However,their acoustic performances are constrained by the vibration resulting from the unavoidable ocean current in some degree.The influence of such vibrations is quantitatively analyzed by means of modeling the simplified models of two deployment configurations involving the positive buoyant buoy and neutral buoy system.The corresponding formulas are deduced respectively for the deployment configuration buoy systems in the motion state firstly.Then the simulation software is developed and some numerical simulations are put up via the Runge-Kutta method.The simulation results and theoretical analysis indicate that the neutral buoy will be an excellent design protocol in engineering application in comparison with the positive buoyant buoy.
基金This work was supported by China Scholarship Council,the National Natural Science Foundation of China(61974107)Hubei Provincial Major Program of Technological Innovation(2019AAA052,2017AAA121).
文摘Over the past decade, ultraviolet(UV) detection has been a subject of major interest for both research scientists and engineers because of its important applications in both the civil and military fields. The rapid development of interdisciplinary research has enabled the realization of UV detectors based on a variety of principles. Among these devices, UV detectors based on surface acoustic wave(SAW) technology offer unique advantages of remote wireless operation capability and zero power consumption. This article provides a comprehensive review of the working principles, important parameters, and the acoustic wave and materials types used in SAW-based UV detectors. The research and development status of these detectors are discussed and the most commonly used methods to optimize device performance are also summarized. Novel types of acoustic UV detectors based on thin film bulk acoustic resonators(FBARs)and Lamb wave resonators(LMRs) are briefly introduced. Finally, future development challenges are proposed and suggestions for future directions are provided to aid the development of this important research field.
基金supported by the Scientific Research Program Funded by Shaanxi Provincial Education Department (No.11JK1006)
文摘Laser phase noise （LPN） plays an important role in optical coherent systems. Based on the algorithm of Viterbi-Viterbi cartier phase estimation （CPE）, the effects of LPN imposed on the coherent receivers are investigated for quadrature phase shift keying （QPSK）, 8 phase shift keying （SPSK） and 16-quadrature amplitude modulation （16-QAM） optical coherent systems, respectively. The simulation results show that the optimal block length in the phase estimation algorithm is a tradeoffbetween LPN and additive white Gaussian noise （AWGN）, and depends on the level of modulation formats. The resolution requirements of analog to digital converter （ADC） in the coherent receivers are independent of LPN or the level of modulation formats. For the bit error rate （BER） of 10-3, the required bit number of ADC is 6, and the gain is marginal for the higher resolution.
