The origin of the Kilometric Continuum(KC)is usually attributed to the linear mode conversion window theory,yet direct evidence has been lacking.Here we present an event where electrostatic waves,Z-mode,and KC were ob...The origin of the Kilometric Continuum(KC)is usually attributed to the linear mode conversion window theory,yet direct evidence has been lacking.Here we present an event where electrostatic waves,Z-mode,and KC were observed simultaneously near the magnetic equator by the Van Allen Probes.We identify the radio window(the region for mode conversion taking place)at L=4.059 by solving the fully-thermal dispersion relation.Ray tracing simulations show that the backward-propagating electrostatic mode can smoothly transition to Z-mode.Then,Z-mode can convert to KC when its direction shifts to parallel or anti-parallel propagation at the radio window,which aligns with observations.This study provides direct evidence that supports the linear mode conversion theory as an effective mechanism for KC generation.展开更多
In order to improve the performance of voice conversion, the fundamental frequency （F0） transformation methods are investigated, and an efficient F0 transformation algorithm is proposed. First, unlike the traditiona...In order to improve the performance of voice conversion, the fundamental frequency （F0） transformation methods are investigated, and an efficient F0 transformation algorithm is proposed. First, unlike the traditional linear transformation methods, the relationships between F0s and spectral parameters are explored. In each component of the Gaussian mixture model （GMM）, the F0s are predicted from the converted spectral parameters using the support vector regression （SVR） method. Then, in order to reduce the over- smoothing caused by the statistical average of the GMM, a mixed transformation method combining SVR with the traditional mean-variance linear （MVL） conversion is presented. Meanwhile, the adaptive median filter, prevalent in image processing, is adopted to solve the discontinuity problem caused by the frame-wise transformation. Objective and subjective experiments are carried out to evaluate the performance of the proposed method. The results demonstrate that the proposed method outperforms the traditional F0 transformation methods in terms of the similarity and the quality.展开更多
A novel linear ultrasonic motor based on d15 effect of piezoelectric materials was presented. The design idea aimed at the direct utilization of the shear-induced vibration modes of piezoelectric material. Firstly, th...A novel linear ultrasonic motor based on d15 effect of piezoelectric materials was presented. The design idea aimed at the direct utilization of the shear-induced vibration modes of piezoelectric material. Firstly, the inherent electromechanical coupling mechanism of piezoelectric material was investigated, and shear vibration modes of a piezoelectric shear block was specially designed. A driving point’s elliptical trajectory induced by shear vibration modes was discussed. Then a dynamic model for the piezoelectric shear stator was established with finite element（FE） method to conduct the parametric optimal design. Finally, a prototype based on d15 converse piezoelectric effect is manufactured, and the modal experiment of piezoelectric stator was conducted with laser doppler vibrometer. The experimental results show that the calculated shear-induced vibration modes can be excited completely, and the new linear ultrasonic motor reaches a speed 118 mm/s at noload, and maximal thrust 12.8 N.展开更多
In this paper,we propose an ultrabroadband chiral metasurface(CMS)composed of S-shaped resonator structures situated between two twisted subwavelength gratings and dielectric substrate.This innovative structure enable...In this paper,we propose an ultrabroadband chiral metasurface(CMS)composed of S-shaped resonator structures situated between two twisted subwavelength gratings and dielectric substrate.This innovative structure enables ultrabroadband and high-efficiency linear polarization(LP)conversion,as well as asymmetric transmission(AT)effect in the microwave region.The enhanced interference effect of the Fabry-Perot-like resonance cavity greatly expands the bandwidth and efficiency of LP conversion and AT effect.Through numerical simulations,it has been revealed that the cross-polarization transmission coefficients for normal forward(-z)and backward(+z)incidence exceed 0.8 in the frequency range of 4.13 to 17.34 GHz,accompanied by a polarization conversion ratio of over 99%.Furthermore,our microwave experimental results validate the consistency among simulation,theory,and measurement.Additionally,we elucidate the distinct characteristics of ultrabroadband LP conversion and significant AT effect through analysis of polarization azimuth rotation and ellipticity angles,total transmittance,AT coefficient,and electric field distribution.The proposed CMS structure shows excellent polarization conversion properties via AT effect and has potential applications in areas such as radar,remote sensing,and satellite communication.展开更多
In this Letter, we demonstrate a linear polarization conversion of transmitted terahertz wave with double-layer meta-grating surfaces, which integrated the frequency selectivity of a split ring resonator metasurface a...In this Letter, we demonstrate a linear polarization conversion of transmitted terahertz wave with double-layer meta-grating surfaces, which integrated the frequency selectivity of a split ring resonator metasurface and the polarization selectivity of a metallic grating surface. Since the double-layer can reduce the loss, and the Fabry- Perot like resonant effect between the two layers can improve the conversion efficiency, this converter can rotate the incident y-polarized terahertz wave into an x-polarized transmitted wave with relatively low loss and high efficiency. Experimental results show that an average conversion efficiency exceeding 75% from 0.25 to 0.65 THz with the highest efficiency of 90% at 0.43 THz with onlv -2 dB loss has been achieved.展开更多
We propose and demonstrate a multi-wavelength converter using FP-LD with linear optical amplifier (LOA) which based on cross-gain modulation can convert an input signal to many wavelengths simultaneously for reconfigu...We propose and demonstrate a multi-wavelength converter using FP-LD with linear optical amplifier (LOA) which based on cross-gain modulation can convert an input signal to many wavelengths simultaneously for reconfigurable wavelength conversion in OXC and broadcasting in WDM systems.展开更多
The enhanced definition of Mechatronics involves the four underlying characteristics of integrated,unified,unique,and systematic approaches.In this realm,Mechatronics is not limited to electro-mechanical systems,in th...The enhanced definition of Mechatronics involves the four underlying characteristics of integrated,unified,unique,and systematic approaches.In this realm,Mechatronics is not limited to electro-mechanical systems,in the multi-physics sense,but involves other physical domains such as fluid and thermal.This paper summarizes the mechatronic approach to modeling.Linear graphs facilitate the development of state-space models of mechatronic systems,through this approach.The use of linear graphs in mechatronic modeling is outlined and an illustrative example of sound system modeling is given.Both time-domain and frequency-domain approaches are presented for the use of linear graphs.A mechatronic model of a multi-physics system may be simplified by converting all the physical domains into an equivalent single-domain system that is entirely in the output domain of the system.This approach of converting(transforming)physical domains is presented.An illustrative example of a pressure-controlled hydraulic actuator system that operates a mechanical load is given.展开更多
Dual-band photodetectors exhibit considerable advantages in target discrimination and navigation compared to single-band devices in complex circumstances.However,it remains a major challenge to overcome the limitation...Dual-band photodetectors exhibit considerable advantages in target discrimination and navigation compared to single-band devices in complex circumstances.However,it remains a major challenge to overcome the limitations of traditional devices in terms of their integration with multiple light-absorbing layers and complicated optical components.In this study,a visible and nearinfrared(NIR)dual-band polarimetric photodetector with a single lightabsorbing layer is constructed by utilizing the distinctive conversion of linear dichroism(LD)polarity in two-dimensional niobium trisulfide(NbS_(3)).The NbS_(3)photodetector exhibits selective detection behaviors in the visible and NIR bands,in which by switching the polarization angle of the incident light from 0°to 90°,photocurrent decreases in the visible region,and increases in the NIR region.Specifically,the degrees of linear polarization of photocurrent are 0.59 at 450 nm and-0.47 at 1300 nm,respectively.The opposite photoresponse in the visible and NIR bands of the photodetector significantly enhances the dual-band information recognition.Therefore,clear visible and NIR dual-band polarimetric imaging is accurately realized based on the NbS_(3)photodetector taking advantage of its fast response speed of 28μs.Such anisotropic materials,with unique LD conversion features,can facilitate selective modulation between the visible and NIR spectral ranges and promote the development of next-generation multi-dimensional photodetection for various applications,including com/puter vision,surveillance,and biomedical imaging.展开更多
Independent manipulation of orthogonal circularly polarized wavefronts is one of the important goals for metaoptics,and chiral nanophotonics is one of the crucial approaches.In this article,we propose a new scheme for...Independent manipulation of orthogonal circularly polarized wavefronts is one of the important goals for metaoptics,and chiral nanophotonics is one of the crucial approaches.In this article,we propose a new scheme for spin-dependent terahertz wavefront shaping based on chiral metasurfaces,which involves a hybrid design of the propagation phase,chirality induced phase,and Pancharatnam-Berry phase in all-silicon meta-atoms.A controllable linear polarization conversion effect in the transmitted wave is obtained via breaking the mirror symmetry and preserving the C_(2)symmetry of the resonator,which causes a different form of the Jones matrix.By simultaneously adjusting the in-plane geometric dimensions and azimuth angle of chiral units,and utilizing the evolution characteristics of circularly polarized components in parameter space and polarization space,spin-dependent phase responses have been observed.We provide the main theoretical analysis and demonstrate the functional design of circularly polarized multiplexed beam deflection or vortex beam generation,through the expected simulation and experimental results near the operating frequency of 0.6 THz.Our results may enrich the design of terahertz polarization-multiplexed devices.展开更多
基金supported by the National Natural Science Foundation of China grants 42074198,42230209 and 42374215the Scientific Research Fund of Hunan Provincial Education Department Grants 21A0212,Post-graduate Scientific Research Innovation Project of Hunan Province CX20240804.
文摘The origin of the Kilometric Continuum(KC)is usually attributed to the linear mode conversion window theory,yet direct evidence has been lacking.Here we present an event where electrostatic waves,Z-mode,and KC were observed simultaneously near the magnetic equator by the Van Allen Probes.We identify the radio window(the region for mode conversion taking place)at L=4.059 by solving the fully-thermal dispersion relation.Ray tracing simulations show that the backward-propagating electrostatic mode can smoothly transition to Z-mode.Then,Z-mode can convert to KC when its direction shifts to parallel or anti-parallel propagation at the radio window,which aligns with observations.This study provides direct evidence that supports the linear mode conversion theory as an effective mechanism for KC generation.
基金The National Natural Science Foundation of China(No. 60975017)the Natural Science Foundation of Guangdong Province (No. 10252800001000001)the Natural Science Foundation of Higher Education Institutions of Jiangsu Province (No. 10KJB510005)
文摘In order to improve the performance of voice conversion, the fundamental frequency （F0） transformation methods are investigated, and an efficient F0 transformation algorithm is proposed. First, unlike the traditional linear transformation methods, the relationships between F0s and spectral parameters are explored. In each component of the Gaussian mixture model （GMM）, the F0s are predicted from the converted spectral parameters using the support vector regression （SVR） method. Then, in order to reduce the over- smoothing caused by the statistical average of the GMM, a mixed transformation method combining SVR with the traditional mean-variance linear （MVL） conversion is presented. Meanwhile, the adaptive median filter, prevalent in image processing, is adopted to solve the discontinuity problem caused by the frame-wise transformation. Objective and subjective experiments are carried out to evaluate the performance of the proposed method. The results demonstrate that the proposed method outperforms the traditional F0 transformation methods in terms of the similarity and the quality.
基金Funded by the National Basic Research Program of China(973 Program,No.2015CB057501)the National Natural Science Foundation of China(Nos.50975135,51275235)+1 种基金the Fundamental Research Funds for the Central Universities(No.NJ20140024)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘A novel linear ultrasonic motor based on d15 effect of piezoelectric materials was presented. The design idea aimed at the direct utilization of the shear-induced vibration modes of piezoelectric material. Firstly, the inherent electromechanical coupling mechanism of piezoelectric material was investigated, and shear vibration modes of a piezoelectric shear block was specially designed. A driving point’s elliptical trajectory induced by shear vibration modes was discussed. Then a dynamic model for the piezoelectric shear stator was established with finite element（FE） method to conduct the parametric optimal design. Finally, a prototype based on d15 converse piezoelectric effect is manufactured, and the modal experiment of piezoelectric stator was conducted with laser doppler vibrometer. The experimental results show that the calculated shear-induced vibration modes can be excited completely, and the new linear ultrasonic motor reaches a speed 118 mm/s at noload, and maximal thrust 12.8 N.
文摘In this paper,we propose an ultrabroadband chiral metasurface(CMS)composed of S-shaped resonator structures situated between two twisted subwavelength gratings and dielectric substrate.This innovative structure enables ultrabroadband and high-efficiency linear polarization(LP)conversion,as well as asymmetric transmission(AT)effect in the microwave region.The enhanced interference effect of the Fabry-Perot-like resonance cavity greatly expands the bandwidth and efficiency of LP conversion and AT effect.Through numerical simulations,it has been revealed that the cross-polarization transmission coefficients for normal forward(-z)and backward(+z)incidence exceed 0.8 in the frequency range of 4.13 to 17.34 GHz,accompanied by a polarization conversion ratio of over 99%.Furthermore,our microwave experimental results validate the consistency among simulation,theory,and measurement.Additionally,we elucidate the distinct characteristics of ultrabroadband LP conversion and significant AT effect through analysis of polarization azimuth rotation and ellipticity angles,total transmittance,AT coefficient,and electric field distribution.The proposed CMS structure shows excellent polarization conversion properties via AT effect and has potential applications in areas such as radar,remote sensing,and satellite communication.
基金supported by the National Natural Science Foundation of China(Nos.61531010,61270011,91438118,and 61501094)the National Key Basic Research Program of China(No.2014CB339806)
文摘In this Letter, we demonstrate a linear polarization conversion of transmitted terahertz wave with double-layer meta-grating surfaces, which integrated the frequency selectivity of a split ring resonator metasurface and the polarization selectivity of a metallic grating surface. Since the double-layer can reduce the loss, and the Fabry- Perot like resonant effect between the two layers can improve the conversion efficiency, this converter can rotate the incident y-polarized terahertz wave into an x-polarized transmitted wave with relatively low loss and high efficiency. Experimental results show that an average conversion efficiency exceeding 75% from 0.25 to 0.65 THz with the highest efficiency of 90% at 0.43 THz with onlv -2 dB loss has been achieved.
文摘We propose and demonstrate a multi-wavelength converter using FP-LD with linear optical amplifier (LOA) which based on cross-gain modulation can convert an input signal to many wavelengths simultaneously for reconfigurable wavelength conversion in OXC and broadcasting in WDM systems.
基金supported by research grants from the Natural Sciences and Engineering Research Council(NSERC)of Canada
文摘The enhanced definition of Mechatronics involves the four underlying characteristics of integrated,unified,unique,and systematic approaches.In this realm,Mechatronics is not limited to electro-mechanical systems,in the multi-physics sense,but involves other physical domains such as fluid and thermal.This paper summarizes the mechatronic approach to modeling.Linear graphs facilitate the development of state-space models of mechatronic systems,through this approach.The use of linear graphs in mechatronic modeling is outlined and an illustrative example of sound system modeling is given.Both time-domain and frequency-domain approaches are presented for the use of linear graphs.A mechatronic model of a multi-physics system may be simplified by converting all the physical domains into an equivalent single-domain system that is entirely in the output domain of the system.This approach of converting(transforming)physical domains is presented.An illustrative example of a pressure-controlled hydraulic actuator system that operates a mechanical load is given.
基金supported by the National Natural Science Foundation of China(NSFC)-Research Grant Council of Hong Kong(RGC)Key International(Regional)Joint Research Program(NSFC Grant No.62261160574)NSFC Grant No.51872337+2 种基金the Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2024A1515010295,2022A1515110707,and 2021A1515012592)the China Postdoctoral Science Foundation(CPSF)(Grant Nos.2024M752105 and 2024T170580)Postdoctoral Fellowship Program of CPSF(GZB20230450).
文摘Dual-band photodetectors exhibit considerable advantages in target discrimination and navigation compared to single-band devices in complex circumstances.However,it remains a major challenge to overcome the limitations of traditional devices in terms of their integration with multiple light-absorbing layers and complicated optical components.In this study,a visible and nearinfrared(NIR)dual-band polarimetric photodetector with a single lightabsorbing layer is constructed by utilizing the distinctive conversion of linear dichroism(LD)polarity in two-dimensional niobium trisulfide(NbS_(3)).The NbS_(3)photodetector exhibits selective detection behaviors in the visible and NIR bands,in which by switching the polarization angle of the incident light from 0°to 90°,photocurrent decreases in the visible region,and increases in the NIR region.Specifically,the degrees of linear polarization of photocurrent are 0.59 at 450 nm and-0.47 at 1300 nm,respectively.The opposite photoresponse in the visible and NIR bands of the photodetector significantly enhances the dual-band information recognition.Therefore,clear visible and NIR dual-band polarimetric imaging is accurately realized based on the NbS_(3)photodetector taking advantage of its fast response speed of 28μs.Such anisotropic materials,with unique LD conversion features,can facilitate selective modulation between the visible and NIR spectral ranges and promote the development of next-generation multi-dimensional photodetection for various applications,including com/puter vision,surveillance,and biomedical imaging.
基金National Natural Science Foundation of China(12404484)Science and Technology Department of Sichuan Province(2025ZNSFSC0846,2025ZNSFSC0847,2022Z091,2023ZYD0175)+1 种基金Scientific Research Foundation of Chengdu University of Information Technology(KYTZ202245)Sichuan Meteorological Optoelectronic Sensor Technology and Application Engineering Research Center(2024GCZX001)。
文摘Independent manipulation of orthogonal circularly polarized wavefronts is one of the important goals for metaoptics,and chiral nanophotonics is one of the crucial approaches.In this article,we propose a new scheme for spin-dependent terahertz wavefront shaping based on chiral metasurfaces,which involves a hybrid design of the propagation phase,chirality induced phase,and Pancharatnam-Berry phase in all-silicon meta-atoms.A controllable linear polarization conversion effect in the transmitted wave is obtained via breaking the mirror symmetry and preserving the C_(2)symmetry of the resonator,which causes a different form of the Jones matrix.By simultaneously adjusting the in-plane geometric dimensions and azimuth angle of chiral units,and utilizing the evolution characteristics of circularly polarized components in parameter space and polarization space,spin-dependent phase responses have been observed.We provide the main theoretical analysis and demonstrate the functional design of circularly polarized multiplexed beam deflection or vortex beam generation,through the expected simulation and experimental results near the operating frequency of 0.6 THz.Our results may enrich the design of terahertz polarization-multiplexed devices.
