IEEE Transactions on Antennas and Propagation, 2018
In high-frequency hybrid sky–surface wave radar, the echo characteristics of hybrid sky–surface w... more In high-frequency hybrid sky–surface wave radar, the echo characteristics of hybrid sky–surface wave propagation channel are extremely complex in spatial, time, and frequency domains, which seriously affect radar performance. The mechanisms and echo characteristics are theoretically and experimentally analyzed in this paper. Based on the hybrid sky–surface propagation model, the signal-to-noise ratio equation of the channel echo and ionospheric direct wave are initially derived. The simulation method is developed, which considers bistatic layout, ionospheric propagation, sea surface propagation, and radio noise. The echo characteristics by sweep frequency detection are simulated and analyzed. Using the newly developed hybrid sky–surface wave experimental system, the experimental results by sweep frequency detection are first achieved in China and abroad, which are consistent with the theoretical analysis, and the validity of the simulation is verified. Then, the characteristics of first-order sea clutter in different azimuths are theoretically and experimentally analyzed, and it is found that the bistatic layout and ionosphere play a significant role in the Doppler broadening and path distribution of the sea clutter. Finally, the experimental results by joint sweep and fixed frequency detections are analyzed. The echo characteristics are extremely complex with frequency. Specifically, owing to multimode echoes overlap, the spread of the sea clutter and ionospheric direct wave signals would seriously affect ship target detection in part of the operating frequency band. It is shown that the detection and diagnosis for hybrid sky–surface channel in spatial, time, and frequency domains are crucial for target detection performance. The research results on the propagation mechanisms and echo characteristics could provide important supporting function for layout design, frequency selection, target detection, and location of the radar.
Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 2016
The metal O-ring is effectively applied to extreme conditions and long-term uses for several deca... more The metal O-ring is effectively applied to extreme conditions and long-term uses for several decades, where conventional seals cannot meet the requirements. During the long-time service, the stress relaxation of the metal O-ring has been confirmed to be a potential damage to the sealing performance. By analyzing the sealing mechanism and the problem of the stress relaxation of the metal O-ring, a model has been developed to study its stress relaxation. The model includes the contact model, the stress–strain model, and the dynamic equation of stress relaxation. Based on the classical elastic-plastic model for two contact rough surfaces, the contact model of sealing zone is developed, by which the mechanical and geometric parameters of the sealing zone can be obtained for the initial state after the assembling. In the stress–strain model, the determination of stress and strain in the metal O-ring is performed by means of a simplified closed-form solution. The dynamic equation of stres...
Purpose – The purpose of this paper is to develop a leakage model of metallic static seals, which... more Purpose – The purpose of this paper is to develop a leakage model of metallic static seals, which can be used to accurately predict the leakage rate and study the corresponding seal characteristics. The metallic static seal is effectively applied to severe rugged environments where conventional seals cannot meet the needs. More research efforts for deepening the understanding of its seal characteristics are important for its effective and safe applications, of which the study about its leak is one key component. Design/methodology/approach – In the microscopic observations of the turning surface that is general in the processing of flange surfaces, it is found that the spiral morphology is dominant, which had been also obtained by other researches. There are two potential leakage paths for the flange surface of spiral morphology, one is the radial direction perpendicular to the spiral ridges and the other is the circumferential direction along the spiral groove. Based on the microge...
Foodborne illnesses have always been a serious problem that threats public health, so it is neces... more Foodborne illnesses have always been a serious problem that threats public health, so it is necessary to develop a method that can detect the pathogens rapidly and sensitively. In this study, we designed a magnetic controlled microfluidic device which integrated the dynamic magnetophoretic separation and stationary magnetic trap together for sensitive and selective detection of Salmonella typhimurium (S. typhimurium). Coupled with immunomagnetic nanospheres (IMNs), this device could separate and enrich the target pathogens and realize the sensitive detection of target pathogens on chip. Based on the principle of sandwich immunoassays, the trapped target pathogens identified by streptavidin modified QDs (SA-QDs) were detected under an inverted fluorescence microscopy. A linear range was exhibited at the concentration from 1.0×10(4) to 1.0×10(6)colony-forming units/mL (CFU/mL), the limit of detection (LOD) was as low as 5.4×10(3)CFU/mL in milk (considering the sample volume, the absol...
Traveling-wave thermoacoustic electricity generator is a new external-combustion type device capa... more Traveling-wave thermoacoustic electricity generator is a new external-combustion type device capable of converting heat such as solar energy into electric power. In this paper, a 1 kW solar-powered traveling-wave thermoacoustic electricity generation system is designed and fabricated. The system consists of a traveling-wave thermoacoustic electricity generator, a solar dish collector and a heat receiver. In the preliminary tests, using electric cartridge heaters to simulate the solar energy, a maximum electric power of 481 W and a maximum thermal-to-electric efficiency of 15.0% were achieved with 3.5 MPa pressurized helium and 74 Hz working frequency. Then, after integrating the traveling-wave thermoacoustic electricity generator with the solar dish collector and the heat receiver, the solar-powered experiments were performed. In the experiments, a maximum electric power of about 200 W was obtained. However, due to the solar dish collector problems, the heating temperature of the receiver was much lower than expected. Optimizations of the collector and the heat receiver are under way.
In this paper, an experimental investigation of a traveling-wave thermoacoustic electricity gener... more In this paper, an experimental investigation of a traveling-wave thermoacoustic electricity generator, which consists of a traveling-wave thermoacoustic heat engine and a linear alternator driven by that engine, is presented. Using the results of previous theoretical and experimental research, we designed and fabricated a traveling-wave thermoacoustic heat engine and a linear alternator. In the experiments, 450.9 W of electrical power was obtained with a maximum thermal-to-electrical efficiency of 15.03%, and a maximum electrical power of 481.0 W was achieved with 12.65% thermal-to-electrical efficiency.
IEEE Transactions on Antennas and Propagation, 2018
In high-frequency hybrid sky–surface wave radar, the echo characteristics of hybrid sky–surface w... more In high-frequency hybrid sky–surface wave radar, the echo characteristics of hybrid sky–surface wave propagation channel are extremely complex in spatial, time, and frequency domains, which seriously affect radar performance. The mechanisms and echo characteristics are theoretically and experimentally analyzed in this paper. Based on the hybrid sky–surface propagation model, the signal-to-noise ratio equation of the channel echo and ionospheric direct wave are initially derived. The simulation method is developed, which considers bistatic layout, ionospheric propagation, sea surface propagation, and radio noise. The echo characteristics by sweep frequency detection are simulated and analyzed. Using the newly developed hybrid sky–surface wave experimental system, the experimental results by sweep frequency detection are first achieved in China and abroad, which are consistent with the theoretical analysis, and the validity of the simulation is verified. Then, the characteristics of first-order sea clutter in different azimuths are theoretically and experimentally analyzed, and it is found that the bistatic layout and ionosphere play a significant role in the Doppler broadening and path distribution of the sea clutter. Finally, the experimental results by joint sweep and fixed frequency detections are analyzed. The echo characteristics are extremely complex with frequency. Specifically, owing to multimode echoes overlap, the spread of the sea clutter and ionospheric direct wave signals would seriously affect ship target detection in part of the operating frequency band. It is shown that the detection and diagnosis for hybrid sky–surface channel in spatial, time, and frequency domains are crucial for target detection performance. The research results on the propagation mechanisms and echo characteristics could provide important supporting function for layout design, frequency selection, target detection, and location of the radar.
Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 2016
The metal O-ring is effectively applied to extreme conditions and long-term uses for several deca... more The metal O-ring is effectively applied to extreme conditions and long-term uses for several decades, where conventional seals cannot meet the requirements. During the long-time service, the stress relaxation of the metal O-ring has been confirmed to be a potential damage to the sealing performance. By analyzing the sealing mechanism and the problem of the stress relaxation of the metal O-ring, a model has been developed to study its stress relaxation. The model includes the contact model, the stress–strain model, and the dynamic equation of stress relaxation. Based on the classical elastic-plastic model for two contact rough surfaces, the contact model of sealing zone is developed, by which the mechanical and geometric parameters of the sealing zone can be obtained for the initial state after the assembling. In the stress–strain model, the determination of stress and strain in the metal O-ring is performed by means of a simplified closed-form solution. The dynamic equation of stres...
Purpose – The purpose of this paper is to develop a leakage model of metallic static seals, which... more Purpose – The purpose of this paper is to develop a leakage model of metallic static seals, which can be used to accurately predict the leakage rate and study the corresponding seal characteristics. The metallic static seal is effectively applied to severe rugged environments where conventional seals cannot meet the needs. More research efforts for deepening the understanding of its seal characteristics are important for its effective and safe applications, of which the study about its leak is one key component. Design/methodology/approach – In the microscopic observations of the turning surface that is general in the processing of flange surfaces, it is found that the spiral morphology is dominant, which had been also obtained by other researches. There are two potential leakage paths for the flange surface of spiral morphology, one is the radial direction perpendicular to the spiral ridges and the other is the circumferential direction along the spiral groove. Based on the microge...
Foodborne illnesses have always been a serious problem that threats public health, so it is neces... more Foodborne illnesses have always been a serious problem that threats public health, so it is necessary to develop a method that can detect the pathogens rapidly and sensitively. In this study, we designed a magnetic controlled microfluidic device which integrated the dynamic magnetophoretic separation and stationary magnetic trap together for sensitive and selective detection of Salmonella typhimurium (S. typhimurium). Coupled with immunomagnetic nanospheres (IMNs), this device could separate and enrich the target pathogens and realize the sensitive detection of target pathogens on chip. Based on the principle of sandwich immunoassays, the trapped target pathogens identified by streptavidin modified QDs (SA-QDs) were detected under an inverted fluorescence microscopy. A linear range was exhibited at the concentration from 1.0×10(4) to 1.0×10(6)colony-forming units/mL (CFU/mL), the limit of detection (LOD) was as low as 5.4×10(3)CFU/mL in milk (considering the sample volume, the absol...
Traveling-wave thermoacoustic electricity generator is a new external-combustion type device capa... more Traveling-wave thermoacoustic electricity generator is a new external-combustion type device capable of converting heat such as solar energy into electric power. In this paper, a 1 kW solar-powered traveling-wave thermoacoustic electricity generation system is designed and fabricated. The system consists of a traveling-wave thermoacoustic electricity generator, a solar dish collector and a heat receiver. In the preliminary tests, using electric cartridge heaters to simulate the solar energy, a maximum electric power of 481 W and a maximum thermal-to-electric efficiency of 15.0% were achieved with 3.5 MPa pressurized helium and 74 Hz working frequency. Then, after integrating the traveling-wave thermoacoustic electricity generator with the solar dish collector and the heat receiver, the solar-powered experiments were performed. In the experiments, a maximum electric power of about 200 W was obtained. However, due to the solar dish collector problems, the heating temperature of the receiver was much lower than expected. Optimizations of the collector and the heat receiver are under way.
In this paper, an experimental investigation of a traveling-wave thermoacoustic electricity gener... more In this paper, an experimental investigation of a traveling-wave thermoacoustic electricity generator, which consists of a traveling-wave thermoacoustic heat engine and a linear alternator driven by that engine, is presented. Using the results of previous theoretical and experimental research, we designed and fabricated a traveling-wave thermoacoustic heat engine and a linear alternator. In the experiments, 450.9 W of electrical power was obtained with a maximum thermal-to-electrical efficiency of 15.03%, and a maximum electrical power of 481.0 W was achieved with 12.65% thermal-to-electrical efficiency.
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