Increased renewable energy integration and international power trades have led to the construction and development of new HVDC transmission systems.HVDC cables,in particular,play an important role in undersea power tr...Increased renewable energy integration and international power trades have led to the construction and development of new HVDC transmission systems.HVDC cables,in particular,play an important role in undersea power transmission and offshore renewable energy integration having lower losses and higher reliability.In this paper,the current commercial feasibility of HVDC cables and the development of different types of HVDC cables and accessories are reviewed.The non-uniform electric field distribution caused by the applied voltage,temperature dependent conductivity,and space charge accumulation is briefly discussed.Current research in HVDC cable for higher operation voltage level and larger power capacity is also reviewed with specific focus on the methodologies of space charge suppression for XLPE extruded cables.展开更多
A novel pseudo working-point control measurement scheme for the acoustic sensitivity of interferometric fiber-optic hydrophones is described and demonstrated. The measurement principle is introduced in detail. An expe...A novel pseudo working-point control measurement scheme for the acoustic sensitivity of interferometric fiber-optic hydrophones is described and demonstrated. The measurement principle is introduced in detail. An experimental system, which interrogates an interferometric fiber-optic hydrophone with this method, is designed. The acoustic pressure phase sensitivity of the fiber-optic hydrophone is measured over the frequency range of 20- 2500 Hz. The measured acoustic sensitivity is about -156.5 dB re 1 rad/μPa with a fluctuation lower than ±1.2 dB, which is in good agreement with the results obtained by the method of phase generated carrier. The experimental results testify the validity of this new method which has the advantages of no electric elements in the sensing head, the simplicity of signal processing, and wide working bandwidth.展开更多
A fiber Bragg grating （FBG） hydrophone with high sensitivity was demonstrated. This hydrophone used a rubber diaphragm and a copper hard core as the sensing element. To compensate the hydrostatic pressure, a capilla...A fiber Bragg grating （FBG） hydrophone with high sensitivity was demonstrated. This hydrophone used a rubber diaphragm and a copper hard core as the sensing element. To compensate the hydrostatic pressure, a capillary tube was fixed at the end of the hydrophone. Theoretical analysis of the acoustic pressure sensitivity was given in this letter. Experiments were carried out to test the frequency response of the hydrophone. The result shows that when the Young＇s modulus of the diaphragm is higher, a flatter frequency response will be obtained.展开更多
Nanomaterials integrated surface acoustic wave(SAW)gas sensing technology has emerged as a promising candidate for realtime toxic gas sensing applications for environmental and human health safety.However,the developm...Nanomaterials integrated surface acoustic wave(SAW)gas sensing technology has emerged as a promising candidate for realtime toxic gas sensing applications for environmental and human health safety.However,the development of novel chemical interface based on two-dimensional(2D)sensing materials for SAW sensors for the rapid and sensitive detection of NH_(3)gas at room temperature(RT)still remains challenging.Herein,we report a highly selective RT NH_(3)gas sensor based on sulfur-doped graphitic carbon nitride quantum dots(S@g-C_(3)N_(4)QD)coated langasite(LGS)SAW sensor with enhanced sensitivity and recovery rate under ultraviolet(UV)illumination.Fascinatingly,the sensitivity of the S@g-C_(3)N_(4)QD/LGS SAW sensor to NH_(3)(500 ppb)at RT is dramatically enhanced by~4.5-fold with a low detection limit(~85 ppb),high selectivity,excellent reproducibility,fast response/recovery time(70 s/79 s)under UV activation(365 nm)as compared to dark condition.Additionally,the proposed sensor exhibited augmented NH_(3)detection capability across the broad range of relative humidity(20%–80%).Such remarkable gas sensing performances of the as-prepared sensor to NH_(3)are attributed to the high surface area,enhanced functional groups,sulfur defects,UV photogenerated charge carriers,facile charge transfer in the S@g-C_(3)N_(4)QD sensing layer,which further helps to improve the gas molecules adsorption that causes the increase in conductivity,resulting in larger frequency responses.The gas sensing mechanism of S@g-C_(3)N_(4)QD/LGS SAW sensor is ascribed to the enhanced electroacoustic effect,which is supported by the correlation of resistive type and COMSOL Multiphysics simulation studies.We envisage that the present work paves a promising strategy to develop the next generation 2D g-C_(3)N_(4)based high responsive RT SAW gas sensors.展开更多
According to the World Health Organization (WHO), men and women older than 50 years present osteoporosis with reduced bone mass, this is one of the major impact morbidities causes in the world. It may be present in th...According to the World Health Organization (WHO), men and women older than 50 years present osteoporosis with reduced bone mass, this is one of the major impact morbidities causes in the world. It may be present in the hip, spine, and wrist. The gold standard technique for osteoporosis diagnosis is the Bone Densitometry (DXA). The evaluation of an electroacoustic device is as an alternative procedure for the validation and diagnosis of osteoporosis. Diagnosis of osteoporosis severity was carried out in 49 females by using the registers of the DEXA’s T-Score values. These were statistically compared with the measurements performed using the electroacoustic device. Non-Significative difference between measurements was found with ANOVA and Chi-square tests and the area for the ROC curve on electroacoustic devices was 0.551. The Bland Altman suggests an excellent concordance between both techniques. This is a non-invasive method that has a proper match with the gold standard. The study suggests that procedure measurements with the electroacoustic device could be implemented as an alternative clinical practice for osteoporosis diagnosis.展开更多
The space-charge distributions of electric double-layer capacitors （EDLCs）, which are energy storage devices, were examined with the pulsed electroacoustic （PEA） method. It was found that the experimental results ...The space-charge distributions of electric double-layer capacitors （EDLCs）, which are energy storage devices, were examined with the pulsed electroacoustic （PEA） method. It was found that the experimental results could be influenced by the reflection and penetration of sound waves when the space-charge dis- tributions of EDLCs were measured with the PEA method. This is because EDLCs have a five-layer structure consisting of three materials （aluminum, cellulose, and activated carbon）. We calculated the reflection wave components that influenced the charge density through the acoustic impedance and the relative permittivity of the materials. In this way, we found that the changes in the space-charge distributions of EDLCs and their charge characteristics corresponded closely. We determined that measuring the space- charge distributions with the PEA method was effective for evaluating the charge accumulation of EDLCs. In this study, a polarized electrode was prepared for use in EDLCs. The ratio of the surface area to the average pore diameter of the polarized electrode was measured with the nitrogen adsorption method at 77 K. The relationship between the ratio of the surface area to the average pore size and the space-charge distributions of EDLCs is also discussed in this paper.展开更多
In order to reveal the conduction mechanism of ZnO varistor, the pulsed electroacoustic (PEA) measurement is employed to investigate the space charge distribution characteristics of ZnO varistors under different curre...In order to reveal the conduction mechanism of ZnO varistor, the pulsed electroacoustic (PEA) measurement is employed to investigate the space charge distribution characteristics of ZnO varistors under different current densities in this paper. Experimental results show that the relationship between the space charge and the current density is consistent with the voltage-current characteristics, and can reflect the nonlinear characteristics of ZnO varistor. The space charge increases linearly with the increase of the electric field strength and the current density in the small current region, this reflects the decrease of the surface states of the grain boundary and changes of the Schottky barrier. There exists a transition region between the small current and middle current regions, where the current is composed of the current by the emission of thermally activated electrons and the tunneling current. In the middle current region, the space charge will decrease as the current increases, and will disappear with the depletion layer decreasing to zero.展开更多
基金supported by the State Grid Corporation of China:Research on Key Technologies of Insulation Material and Accessories for 320 kV HVDC XLPE Cable System(SGRIZLJS(2014)888).
文摘Increased renewable energy integration and international power trades have led to the construction and development of new HVDC transmission systems.HVDC cables,in particular,play an important role in undersea power transmission and offshore renewable energy integration having lower losses and higher reliability.In this paper,the current commercial feasibility of HVDC cables and the development of different types of HVDC cables and accessories are reviewed.The non-uniform electric field distribution caused by the applied voltage,temperature dependent conductivity,and space charge accumulation is briefly discussed.Current research in HVDC cable for higher operation voltage level and larger power capacity is also reviewed with specific focus on the methodologies of space charge suppression for XLPE extruded cables.
基金the National High Tech-nology Program of China (No.2006AA09Z121)the Pro-gram for New Century Excellent Talents in Universities of China (No.NCET-06-0925)the Innovation Sci-ence and Technology Foundation of National University of Defense Technology of China (No.0623).
文摘A novel pseudo working-point control measurement scheme for the acoustic sensitivity of interferometric fiber-optic hydrophones is described and demonstrated. The measurement principle is introduced in detail. An experimental system, which interrogates an interferometric fiber-optic hydrophone with this method, is designed. The acoustic pressure phase sensitivity of the fiber-optic hydrophone is measured over the frequency range of 20- 2500 Hz. The measured acoustic sensitivity is about -156.5 dB re 1 rad/μPa with a fluctuation lower than ±1.2 dB, which is in good agreement with the results obtained by the method of phase generated carrier. The experimental results testify the validity of this new method which has the advantages of no electric elements in the sensing head, the simplicity of signal processing, and wide working bandwidth.
基金Key Projects Program of Chinese Acadelny of Sciences under Grant No.CXJJ-177.
文摘A fiber Bragg grating （FBG） hydrophone with high sensitivity was demonstrated. This hydrophone used a rubber diaphragm and a copper hard core as the sensing element. To compensate the hydrostatic pressure, a capillary tube was fixed at the end of the hydrophone. Theoretical analysis of the acoustic pressure sensitivity was given in this letter. Experiments were carried out to test the frequency response of the hydrophone. The result shows that when the Young＇s modulus of the diaphragm is higher, a flatter frequency response will be obtained.
基金the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.2020R1A2C2013385)Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(No.NRF-2020R1A6A1A03047771)Korea Institute of Planning and Evaluation for Technology in Food,Agriculture and Forestry(IPET),Korea Smart Farm Research and Development Foundation(KosFarm)through Smart Farm Innovation Technology Development Program,funded by Ministry of Agriculture,Food,and Rural Affairs(MAFRA)and Ministry of Science and ICT(MSIT),Rural Development Administration(RDA)(No.421029-4).
文摘Nanomaterials integrated surface acoustic wave(SAW)gas sensing technology has emerged as a promising candidate for realtime toxic gas sensing applications for environmental and human health safety.However,the development of novel chemical interface based on two-dimensional(2D)sensing materials for SAW sensors for the rapid and sensitive detection of NH_(3)gas at room temperature(RT)still remains challenging.Herein,we report a highly selective RT NH_(3)gas sensor based on sulfur-doped graphitic carbon nitride quantum dots(S@g-C_(3)N_(4)QD)coated langasite(LGS)SAW sensor with enhanced sensitivity and recovery rate under ultraviolet(UV)illumination.Fascinatingly,the sensitivity of the S@g-C_(3)N_(4)QD/LGS SAW sensor to NH_(3)(500 ppb)at RT is dramatically enhanced by~4.5-fold with a low detection limit(~85 ppb),high selectivity,excellent reproducibility,fast response/recovery time(70 s/79 s)under UV activation(365 nm)as compared to dark condition.Additionally,the proposed sensor exhibited augmented NH_(3)detection capability across the broad range of relative humidity(20%–80%).Such remarkable gas sensing performances of the as-prepared sensor to NH_(3)are attributed to the high surface area,enhanced functional groups,sulfur defects,UV photogenerated charge carriers,facile charge transfer in the S@g-C_(3)N_(4)QD sensing layer,which further helps to improve the gas molecules adsorption that causes the increase in conductivity,resulting in larger frequency responses.The gas sensing mechanism of S@g-C_(3)N_(4)QD/LGS SAW sensor is ascribed to the enhanced electroacoustic effect,which is supported by the correlation of resistive type and COMSOL Multiphysics simulation studies.We envisage that the present work paves a promising strategy to develop the next generation 2D g-C_(3)N_(4)based high responsive RT SAW gas sensors.
文摘According to the World Health Organization (WHO), men and women older than 50 years present osteoporosis with reduced bone mass, this is one of the major impact morbidities causes in the world. It may be present in the hip, spine, and wrist. The gold standard technique for osteoporosis diagnosis is the Bone Densitometry (DXA). The evaluation of an electroacoustic device is as an alternative procedure for the validation and diagnosis of osteoporosis. Diagnosis of osteoporosis severity was carried out in 49 females by using the registers of the DEXA’s T-Score values. These were statistically compared with the measurements performed using the electroacoustic device. Non-Significative difference between measurements was found with ANOVA and Chi-square tests and the area for the ROC curve on electroacoustic devices was 0.551. The Bland Altman suggests an excellent concordance between both techniques. This is a non-invasive method that has a proper match with the gold standard. The study suggests that procedure measurements with the electroacoustic device could be implemented as an alternative clinical practice for osteoporosis diagnosis.
基金supported by a Scientific Research Grant from the Japan Society for the Promotion of Science and the Special Coordination Fund for Promoting Science and Technology from the Japanese Ministry of Education, Culture, Sports, Science and Technology and a grant for Scientific Research on Priority Areas from the University of Miyazaki
文摘The space-charge distributions of electric double-layer capacitors （EDLCs）, which are energy storage devices, were examined with the pulsed electroacoustic （PEA） method. It was found that the experimental results could be influenced by the reflection and penetration of sound waves when the space-charge dis- tributions of EDLCs were measured with the PEA method. This is because EDLCs have a five-layer structure consisting of three materials （aluminum, cellulose, and activated carbon）. We calculated the reflection wave components that influenced the charge density through the acoustic impedance and the relative permittivity of the materials. In this way, we found that the changes in the space-charge distributions of EDLCs and their charge characteristics corresponded closely. We determined that measuring the space- charge distributions with the PEA method was effective for evaluating the charge accumulation of EDLCs. In this study, a polarized electrode was prepared for use in EDLCs. The ratio of the surface area to the average pore diameter of the polarized electrode was measured with the nitrogen adsorption method at 77 K. The relationship between the ratio of the surface area to the average pore size and the space-charge distributions of EDLCs is also discussed in this paper.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50577021, 50877025)the Doctoral Program Foundation of Institutions of Higher Education of China (Grant No. 200800790004)
文摘In order to reveal the conduction mechanism of ZnO varistor, the pulsed electroacoustic (PEA) measurement is employed to investigate the space charge distribution characteristics of ZnO varistors under different current densities in this paper. Experimental results show that the relationship between the space charge and the current density is consistent with the voltage-current characteristics, and can reflect the nonlinear characteristics of ZnO varistor. The space charge increases linearly with the increase of the electric field strength and the current density in the small current region, this reflects the decrease of the surface states of the grain boundary and changes of the Schottky barrier. There exists a transition region between the small current and middle current regions, where the current is composed of the current by the emission of thermally activated electrons and the tunneling current. In the middle current region, the space charge will decrease as the current increases, and will disappear with the depletion layer decreasing to zero.
