We investigate a peculiar phenomenon by processing ZnO nanobelts with an atomic force microscope （AFM）. In the contact mode of AFM, peculiar bending occurs in meso-scale when the nanobelt is applied with force in la...We investigate a peculiar phenomenon by processing ZnO nanobelts with an atomic force microscope （AFM）. In the contact mode of AFM, peculiar bending occurs in meso-scale when the nanobelt is applied with force in lateral direction. We study the mechanical properties of ZnO nanobelts under the influence of small size effect, with finite element analysis and mathematical analysis by means of Matlab. Based on this abnormal effect, a novel measuring method is proposed, which allows the surface morphology and surface properties to be characterized at the same time.展开更多
Synchronous sampling is very essential in underwater multilinear array seismic exploration system in which every acquisition node(AN)samples analog signals by its own analog-digital converter(ADC).Aiming at the proble...Synchronous sampling is very essential in underwater multilinear array seismic exploration system in which every acquisition node(AN)samples analog signals by its own analog-digital converter(ADC).Aiming at the problems of complex synchronous sampling method and long locking time after varying sampling rate in traditional underwater seismic exploration system,an improved synchronous sampling model based on the master-slave synchronous model and local clock asynchronous drive with non phase locked loop(PLL)is built,and a high-precision synchronous sampling method is proposed,which combines the short-term stability of local asynchronous driving clock with the master-slave synchronous calibration of local sampling clock.Based on the improved synchronous sampling model,the influence of clock stability,transmission delay and phase jitter on synchronous sampling error is analyzed,and a high-precision calibration method of synchronous sampling error based on step-by-step compensation of transmission delay is proposed.The model and method effectively realize the immunity of phase jitter on synchronous sampling error in principle,and compensate the influence of signal transmission delay on synchronous sampling error.At the same time,it greatly reduces the complexity of software and hardware implementation of synchronous sampling,and solves the problem of long locking time after changing the sampling rate in traditional methods.The experimental system of synchronous sampling for dual linear array is built,and the synchronous sampling accuracy is better than 5 ns.展开更多
With the development of power plants towards high power and intelligent operation direction,the vibrations or failures of blades,especially the last stage blades in steam turbines,happen more frequently due to the uns...With the development of power plants towards high power and intelligent operation direction,the vibrations or failures of blades,especially the last stage blades in steam turbines,happen more frequently due to the unstable operating conditions brought by flexible operation.A vibration measuring method for the shrouded blades of a steam turbine based on eddy current sensors with high frequency response is proposed,meeting the requirements of non-contact heath monitoring.The eddy current sensors produce the signals which are related to the area changing of every blade’s shroud resulting from the rotation of stator.Then an improved blade tip timing(BTT)technique is proposed to detect the vibrations of shrouded blades by measuring the arrival time of each area changing signal.A structure of eddy current sensors is developed in steam turbines and an amplitude modulation/demodulation circuit is designed to improve the response bandwidth up to 250 kHz.Vibration tests for the last stage blades of a steam turbine were carried out and the results validate the efficiency of the improved BTT technique and the high frequency response of the eddy current sensors presented.展开更多
One of the biggest obstacles to reduce the uncertainty of the Avogadro constant NA is such that there will be an oxide layers on the surface of a silicon sphere. The thickness of this layer is measured by a modified s...One of the biggest obstacles to reduce the uncertainty of the Avogadro constant NA is such that there will be an oxide layers on the surface of a silicon sphere. The thickness of this layer is measured by a modified spectroscopic ellipsometer, which can eliminate the influence of the curved surface, and the results are calibrated by x-ray reflectivity. Fifty positions distributed nearly uniformly on the surface of the silicon sphere are measured twice. The results show that the mean thickness of the overall oxide layer is 3.75 nm with the standard uncertainty of 0.21 nm, which means that the relative uncertainty component of NA owing to this layer can be reduced to 1.2 × 10^-8.展开更多
The phase tuning characteristics of a double-longitudinal-mode He-Ne laser with optical feedback are demonstrated.The phase behaviors of the two adjacent longitudinal modes are studied with different laser cavity leng...The phase tuning characteristics of a double-longitudinal-mode He-Ne laser with optical feedback are demonstrated.The phase behaviors of the two adjacent longitudinal modes are studied with different laser cavity lengths at the weak feedback level,and it is found that the phase difference of the two modes can be 0 to 180°along with the changing of the length of external cavity.The high-density intensity fringes are obtained with asymmetric feedback cavity at a strong feedback level.In particular,the phase difference is also observed between the two high-density fringes of adjacent modes,which have the potential to develop a direction sensitive laser feedback interferometer with high resolution.A simple theoretical analysis is presented,which fits well with the experimental results.展开更多
In order to achieve high precision measurement of inductance in a wide frequency range,a method of inductance measurement based on double-excitation auto-balancing bridge is proposed.In this method,the direct digital ...In order to achieve high precision measurement of inductance in a wide frequency range,a method of inductance measurement based on double-excitation auto-balancing bridge is proposed.In this method,the direct digital synthesizer(DDS)as signal generator is used as the bridge excitation source,and the bridge is automatically balanced by adjusting and measuring the voltage ratio.Using standard resistors,the system can achieve high precision measurement of four-terminal pair inductors in the frequency range of 100Hz-100kHz.Aiming at the low efficiency of bridge balancing,an iterative balancing algorithm based on the steepest descent method is proposed.In order to suppress the interference caused by the initial phase change and non-integer periodic sampling,the high-precision measurement of the complex impedance of inductance is realized based on the all-phase fast Fourier transform(apFFT).Finally,the corresponding measurement system is built and the inductance measurement experiment is carried out.The experimental results show that the relative error of the system for inductance measurement can be as low as 0.009%,and the optimal relative measurement uncertainty of the system can reach 9.89×10^(-4)compared with 5×10^(-5)of commercial impedance analyzer.展开更多
We report a feasible method to realize tun able surface plasm on-polarit on(SPP)res onance in orga nic light-emitt ing devices(OLEDs)by emplo ying corrugated Ag-Al alloy electrodes.The excited SPP res onance in duced ...We report a feasible method to realize tun able surface plasm on-polarit on(SPP)res onance in orga nic light-emitt ing devices(OLEDs)by emplo ying corrugated Ag-Al alloy electrodes.The excited SPP res onance in duced by the periodic corrugations can be precisely tuned based on the composition ratios of the Ag-Al alloy electrodes.With an appropriate composition ratio of the corrugated alloy electrode,the photons trapped in SPP modes are recovered and extracted effectively.The 25%in creaseme nt in luminance and 21%enhan ceme nt in curre nt efficie ncy have bee n achieved by using the corrugated Ag-Al alloy electrodes in OLEDs.展开更多
The disguised covert detection method that imitates whale calls has received great attention in recent years because it can solve the traditional problem of the trade-off between long-range detection and covert detect...The disguised covert detection method that imitates whale calls has received great attention in recent years because it can solve the traditional problem of the trade-off between long-range detection and covert detection.However,under strong reverberation conditions,traditional echo signal processing methods based on matched filtering will be greatly disturbed.Based on this,a disguised sonar signal waveform design is proposed based on imitating whale calls and computationally efficient anti-reverberation echo signal processing method.Firstly,this article proposed a disguised sonar signal waveform design method based on imitating whale calls.This method uses linear frequency modulation(LFM)signals to replace LFM-like segments in real whale calls,and extracts the envelope of the real whale call’s LFM-like segment to modify the LFM signal.Secondly,this article proposed an echo signal processing method of fractional Fourier transform(FrFT)based on target echo locating of synchronization signals.This method uses the synchronization signal to locate the target echo,and determines the step-size interval of the FrFT based on the information carried by the synchronization signal.Compared with the traditional FrFT,this method effectively reduces the amount of calculation and also improves the anti-reverberation ability.Finally,the excellent performance of the proposed method is verified by simulation results.展开更多
The mechanical interaction between the induced seismic waves and landmines was analyzed according to acoustic-to-seismic coupling theory. And a geophone array based experimental system for landmine detection was devel...The mechanical interaction between the induced seismic waves and landmines was analyzed according to acoustic-to-seismic coupling theory. And a geophone array based experimental system for landmine detection was developed. By modeling a compliant mine and the soil on top of the mine as a mass-spring system, analytic method was adopted to study the resonance mechanism of the system. A loudspeaker was employed as energy source to excite a swept sine tone over the soil. We also used a geophone array to measure the vibration velocity of the ground surface. In order to analysis the landmine effect on the surface vibration, the magnitude spectra curves of the measured velocity values on-and-off mine were plotted. The results showed that the data measured on mine is much bigger than that off target and the proposed system can be applied to further investigation of acoustic landmines detection.展开更多
The small autonomous platform with a thin line array is an important tool for underwater acoustic mobile surveillance.Generally,only one-dimensional(1-D)direction-of-arrival(DOA)of the source signal can be estimated u...The small autonomous platform with a thin line array is an important tool for underwater acoustic mobile surveillance.Generally,only one-dimensional(1-D)direction-of-arrival(DOA)of the source signal can be estimated using a thin towed line array.In this work,the two-dimensional(2-D)DOA estimation is achieved by the thin line array towed by a small autonomous platform due to its flexible maneuver.Two perpendicular tow paths are formed through the fast turning of this array.An L-shaped array is formed by the same towed array on these two tow paths at different times.Using the array on these two straight paths,two 1-D DOAs of the source signal are obtained respectively,and then the 2-D DOA based on the formed L-shaped array can be estimated.The effectiveness of proposed approach is verified by numerical simulations and its theoretical error is analyzed.展开更多
1 Introduction 1.1 Advantages of DOE 1)High diffraction efficiency; 2)Dispersive; 3)More selectivity of designing parameters; 4)More selectivity of primary materials; 5)Can make components miniature,forming array and ...1 Introduction 1.1 Advantages of DOE 1)High diffraction efficiency; 2)Dispersive; 3)More selectivity of designing parameters; 4)More selectivity of primary materials; 5)Can make components miniature,forming array and integration. 1.2 1.3 megapixel triplet plastic mobile展开更多
Recently,all-optical memory and optical-computation properties of phase-change materials are receiving intensive attention.Because writing/erasing information in these devices is usually achieved by laser pulses,the i...Recently,all-optical memory and optical-computation properties of phase-change materials are receiving intensive attention.Because writing/erasing information in these devices is usually achieved by laser pulses,the interaction between the laser and the phase-change materials becomes a key issue for such new applications.In this work,by a time-dependent density-functional theory molecular-dynamics study,the physics underlying the optical excitation induced amorphization of Sc-Sb-Te is revealed,which goes back to superatom-like Sc-centered structural motifs.These motifs are found to be still robust under the excitation.展开更多
In order to improve the resolution of seismic acquisition,a new seismic acquisition system based on tangential laser Doppler effect with an optimized differential optical configuration is proposed.The relative movemen...In order to improve the resolution of seismic acquisition,a new seismic acquisition system based on tangential laser Doppler effect with an optimized differential optical configuration is proposed.The relative movement of the inertia object and the immobile frame is measured by laser Doppler effect,which can avoid the electromagnetic and thermometric interference,and the adoption of frequency-modulated (FM) transmission can improve the ability of anti-jamming.The frequency bandwidth is properly determined by analyzing the frequency of the Doppler signal.The velocity, displacement,acceleration, and frequency to be measured can be real-time acquired by frequency/velocity (F/V) converting the FM Doppler signal. A 100-dB dynamic range and the linear frequency range of 1.0 to 1000 Hz are realized.展开更多
We demonstrate a new fiber-based radio frequency （RF） dissemination scheme suitable for a star-shaped branching network. Without any phase controls on the RF signals or the use of active feedback-locking components,...We demonstrate a new fiber-based radio frequency （RF） dissemination scheme suitable for a star-shaped branching network. Without any phase controls on the RF signals or the use of active feedback-locking components, the highly stable reference frequency signal can be delivered to several remote sites simultaneously and independently. The relative frequency stabilities of 6 ×10^-15/s and 7×10^-17/10^4 s are obtained for a 10 km dissemination. This low cost and scalable method can be applied to a large-scale frequency synchroniza- tion network.展开更多
Ferroelectric memory is a promising candidate for next-generation nonvolatile memory owing to its outstanding performance such as low power consump-tion,fast speed,and high endurance.However,the ferroelectricity of co...Ferroelectric memory is a promising candidate for next-generation nonvolatile memory owing to its outstanding performance such as low power consump-tion,fast speed,and high endurance.However,the ferroelectricity of conven-tional ferroelectric materials will be eliminated by the depolarization field when the size drops to the nanometer scale.As a result,the miniaturization of ferroelectric devices was hindered,which makes ferroelectric memory unable to keep up with the development of integrated-circuit(IC)miniaturization.Recently,a two-dimensional(2D)In2Se3 was reported to maintain stable ferro-electricity at the ultrathin scale,which is expected to break through the bottle-neck of miniaturization.Soon,devices based on 2D In2Se3,including the ferroelectric field-effect transistor,ferroelectric channel transistor,synaptic fer-roelectric semiconductor junction,and ferroelectric memristor were demon-strated.However,a comprehensive understanding of the structures and the ferroelectric-switching mechanism of 2D In2Se3 is still lacking.Here,the atomic structures of different phases,the dynamic mechanism of ferroelectric switching,and the performance/functions of the latest devices of 2D In2Se3 are reviewed.Furthermore,the correlations among the structures,the properties,and the device performance are analyzed.Finally,several crucial problems or challenges and possible research directions are put forward.We hope that this review paper can provide timely knowledge and help for the research commu-nity to develop 2D In2Se3 based ferroelectric memory and computing technol-ogy for practical industrial applications.展开更多
文摘We investigate a peculiar phenomenon by processing ZnO nanobelts with an atomic force microscope （AFM）. In the contact mode of AFM, peculiar bending occurs in meso-scale when the nanobelt is applied with force in lateral direction. We study the mechanical properties of ZnO nanobelts under the influence of small size effect, with finite element analysis and mathematical analysis by means of Matlab. Based on this abnormal effect, a novel measuring method is proposed, which allows the surface morphology and surface properties to be characterized at the same time.
基金National Key Research and Development Program of China(No.2018YFE0208200)National Natural Science Foundation of China(Nos.61971307,61905175,51775377)+5 种基金National Key Research and Development Plan Project(No.2020YFB2010800)The Fok Ying Tung Education Foundation(No.171055)China Postdoctoral Science Foundation(No.2020M680878)Guangdong Province Key Research and Development Plan Project(No.2020B0404030001)Tianjin Science and Technology Plan Project(No.20YDTPJC01660)Project of Foreign Affairs Committee of China Aviation Development Sichuan Gas Turbine Research Institute(Nos.GJCZ-2020-0040,GJCZ-2020-0041)。
文摘Synchronous sampling is very essential in underwater multilinear array seismic exploration system in which every acquisition node(AN)samples analog signals by its own analog-digital converter(ADC).Aiming at the problems of complex synchronous sampling method and long locking time after varying sampling rate in traditional underwater seismic exploration system,an improved synchronous sampling model based on the master-slave synchronous model and local clock asynchronous drive with non phase locked loop(PLL)is built,and a high-precision synchronous sampling method is proposed,which combines the short-term stability of local asynchronous driving clock with the master-slave synchronous calibration of local sampling clock.Based on the improved synchronous sampling model,the influence of clock stability,transmission delay and phase jitter on synchronous sampling error is analyzed,and a high-precision calibration method of synchronous sampling error based on step-by-step compensation of transmission delay is proposed.The model and method effectively realize the immunity of phase jitter on synchronous sampling error in principle,and compensate the influence of signal transmission delay on synchronous sampling error.At the same time,it greatly reduces the complexity of software and hardware implementation of synchronous sampling,and solves the problem of long locking time after changing the sampling rate in traditional methods.The experimental system of synchronous sampling for dual linear array is built,and the synchronous sampling accuracy is better than 5 ns.
基金National Natural Science Foundation of China(No.51775377)National Key Research and Development Plan(No.2017YFF0204800)+2 种基金Natural Science Foundation of TianJin City(No.17JCQNJC01100)Young Elite Scientists Sponsorship Program by Cast of China(No.2016QNRC001)Open Project of Key Laboratory of Underwater Information and Control(No.6142218081811)
文摘With the development of power plants towards high power and intelligent operation direction,the vibrations or failures of blades,especially the last stage blades in steam turbines,happen more frequently due to the unstable operating conditions brought by flexible operation.A vibration measuring method for the shrouded blades of a steam turbine based on eddy current sensors with high frequency response is proposed,meeting the requirements of non-contact heath monitoring.The eddy current sensors produce the signals which are related to the area changing of every blade’s shroud resulting from the rotation of stator.Then an improved blade tip timing(BTT)technique is proposed to detect the vibrations of shrouded blades by measuring the arrival time of each area changing signal.A structure of eddy current sensors is developed in steam turbines and an amplitude modulation/demodulation circuit is designed to improve the response bandwidth up to 250 kHz.Vibration tests for the last stage blades of a steam turbine were carried out and the results validate the efficiency of the improved BTT technique and the high frequency response of the eddy current sensors presented.
文摘One of the biggest obstacles to reduce the uncertainty of the Avogadro constant NA is such that there will be an oxide layers on the surface of a silicon sphere. The thickness of this layer is measured by a modified spectroscopic ellipsometer, which can eliminate the influence of the curved surface, and the results are calibrated by x-ray reflectivity. Fifty positions distributed nearly uniformly on the surface of the silicon sphere are measured twice. The results show that the mean thickness of the overall oxide layer is 3.75 nm with the standard uncertainty of 0.21 nm, which means that the relative uncertainty component of NA owing to this layer can be reduced to 1.2 × 10^-8.
基金Supported by the National Natural Science Foundation of China under Grant No 60827006.
文摘The phase tuning characteristics of a double-longitudinal-mode He-Ne laser with optical feedback are demonstrated.The phase behaviors of the two adjacent longitudinal modes are studied with different laser cavity lengths at the weak feedback level,and it is found that the phase difference of the two modes can be 0 to 180°along with the changing of the length of external cavity.The high-density intensity fringes are obtained with asymmetric feedback cavity at a strong feedback level.In particular,the phase difference is also observed between the two high-density fringes of adjacent modes,which have the potential to develop a direction sensitive laser feedback interferometer with high resolution.A simple theoretical analysis is presented,which fits well with the experimental results.
基金National Key Research and Development Plan Project(No.2020YFB2010800)National Natural Science Foundation of China(Nos.61905175,51775377,61971307)+4 种基金Fok Ying Tung Education Foundation(No.171055)China Postdoctoral Science Foundation(No.2020M680878)Guangdong Province Key Research and Development Plan Project(No.2020B0404030001)Tianjin Science and Technology Plan Project(No.20YDTPJC01660)Project of Foreign Affairs Committee of China Aviation Development Sichuan Gas Turbine Research Institute(Nos.GJCZ-2020-0040,GJCZ-2020-0041)。
文摘In order to achieve high precision measurement of inductance in a wide frequency range,a method of inductance measurement based on double-excitation auto-balancing bridge is proposed.In this method,the direct digital synthesizer(DDS)as signal generator is used as the bridge excitation source,and the bridge is automatically balanced by adjusting and measuring the voltage ratio.Using standard resistors,the system can achieve high precision measurement of four-terminal pair inductors in the frequency range of 100Hz-100kHz.Aiming at the low efficiency of bridge balancing,an iterative balancing algorithm based on the steepest descent method is proposed.In order to suppress the interference caused by the initial phase change and non-integer periodic sampling,the high-precision measurement of the complex impedance of inductance is realized based on the all-phase fast Fourier transform(apFFT).Finally,the corresponding measurement system is built and the inductance measurement experiment is carried out.The experimental results show that the relative error of the system for inductance measurement can be as low as 0.009%,and the optimal relative measurement uncertainty of the system can reach 9.89×10^(-4)compared with 5×10^(-5)of commercial impedance analyzer.
基金This work was supported by the National Key Research and Development Program of China and the National Natural Science Foundation of China(NSFC)under Grants No.2020YFA0715000 and No.61825402.
文摘We report a feasible method to realize tun able surface plasm on-polarit on(SPP)res onance in orga nic light-emitt ing devices(OLEDs)by emplo ying corrugated Ag-Al alloy electrodes.The excited SPP res onance in duced by the periodic corrugations can be precisely tuned based on the composition ratios of the Ag-Al alloy electrodes.With an appropriate composition ratio of the corrugated alloy electrode,the photons trapped in SPP modes are recovered and extracted effectively.The 25%in creaseme nt in luminance and 21%enhan ceme nt in curre nt efficie ncy have bee n achieved by using the corrugated Ag-Al alloy electrodes in OLEDs.
基金National Natural Science Foundations of China under Grant(Nos.61971307,61905175,51775377)National Key Research and Development Plan Project(No.2020YFB2010800)+5 种基金Fok Ying Tung Education Foundation(No.171055)China Postdoctoral Science Foundation(No.2020M680878)Guangdong Province Key Research and Development Plan Project(No.2020B0404030001)Tianjin Science and Technology Plan Project(No.20YDTPJC01660)Foreign Affairs Committee of China Aviation Development Sichuan Gas Turbine Research Institute(Nos.GJCZ-2020-0040,GJCZ-2020-0041)Science and Technology on Underwater Information and Control Laboratory under Grant(No.6142218081811)。
文摘The disguised covert detection method that imitates whale calls has received great attention in recent years because it can solve the traditional problem of the trade-off between long-range detection and covert detection.However,under strong reverberation conditions,traditional echo signal processing methods based on matched filtering will be greatly disturbed.Based on this,a disguised sonar signal waveform design is proposed based on imitating whale calls and computationally efficient anti-reverberation echo signal processing method.Firstly,this article proposed a disguised sonar signal waveform design method based on imitating whale calls.This method uses linear frequency modulation(LFM)signals to replace LFM-like segments in real whale calls,and extracts the envelope of the real whale call’s LFM-like segment to modify the LFM signal.Secondly,this article proposed an echo signal processing method of fractional Fourier transform(FrFT)based on target echo locating of synchronization signals.This method uses the synchronization signal to locate the target echo,and determines the step-size interval of the FrFT based on the information carried by the synchronization signal.Compared with the traditional FrFT,this method effectively reduces the amount of calculation and also improves the anti-reverberation ability.Finally,the excellent performance of the proposed method is verified by simulation results.
文摘The mechanical interaction between the induced seismic waves and landmines was analyzed according to acoustic-to-seismic coupling theory. And a geophone array based experimental system for landmine detection was developed. By modeling a compliant mine and the soil on top of the mine as a mass-spring system, analytic method was adopted to study the resonance mechanism of the system. A loudspeaker was employed as energy source to excite a swept sine tone over the soil. We also used a geophone array to measure the vibration velocity of the ground surface. In order to analysis the landmine effect on the surface vibration, the magnitude spectra curves of the measured velocity values on-and-off mine were plotted. The results showed that the data measured on mine is much bigger than that off target and the proposed system can be applied to further investigation of acoustic landmines detection.
基金National Key Research and Development Plan Project(No.2020YFB2010800)National Natural Science Foundation of China(Nos.61971307,61905175,51775377)。
文摘The small autonomous platform with a thin line array is an important tool for underwater acoustic mobile surveillance.Generally,only one-dimensional(1-D)direction-of-arrival(DOA)of the source signal can be estimated using a thin towed line array.In this work,the two-dimensional(2-D)DOA estimation is achieved by the thin line array towed by a small autonomous platform due to its flexible maneuver.Two perpendicular tow paths are formed through the fast turning of this array.An L-shaped array is formed by the same towed array on these two tow paths at different times.Using the array on these two straight paths,two 1-D DOAs of the source signal are obtained respectively,and then the 2-D DOA based on the formed L-shaped array can be estimated.The effectiveness of proposed approach is verified by numerical simulations and its theoretical error is analyzed.
文摘1 Introduction 1.1 Advantages of DOE 1)High diffraction efficiency; 2)Dispersive; 3)More selectivity of designing parameters; 4)More selectivity of primary materials; 5)Can make components miniature,forming array and integration. 1.2 1.3 megapixel triplet plastic mobile
基金Work in China was supported by the National Natural Science Foundation of China(No.61922035,No.11904118,No.11874171)S.B.Z.was supported by the Department of Energy under Grant No.DE-SC0002623J.B.was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF-2018R1D1A1B07044564).
文摘Recently,all-optical memory and optical-computation properties of phase-change materials are receiving intensive attention.Because writing/erasing information in these devices is usually achieved by laser pulses,the interaction between the laser and the phase-change materials becomes a key issue for such new applications.In this work,by a time-dependent density-functional theory molecular-dynamics study,the physics underlying the optical excitation induced amorphization of Sc-Sb-Te is revealed,which goes back to superatom-like Sc-centered structural motifs.These motifs are found to be still robust under the excitation.
基金This work was supported by the National Natural Science Foundation of China under Grant No. 40274046.
文摘In order to improve the resolution of seismic acquisition,a new seismic acquisition system based on tangential laser Doppler effect with an optimized differential optical configuration is proposed.The relative movement of the inertia object and the immobile frame is measured by laser Doppler effect,which can avoid the electromagnetic and thermometric interference,and the adoption of frequency-modulated (FM) transmission can improve the ability of anti-jamming.The frequency bandwidth is properly determined by analyzing the frequency of the Doppler signal.The velocity, displacement,acceleration, and frequency to be measured can be real-time acquired by frequency/velocity (F/V) converting the FM Doppler signal. A 100-dB dynamic range and the linear frequency range of 1.0 to 1000 Hz are realized.
基金supported by the National Key Scientific Instrument and Equipment Development Project under Grant No. 2013YQ09094303.
文摘We demonstrate a new fiber-based radio frequency （RF） dissemination scheme suitable for a star-shaped branching network. Without any phase controls on the RF signals or the use of active feedback-locking components, the highly stable reference frequency signal can be delivered to several remote sites simultaneously and independently. The relative frequency stabilities of 6 ×10^-15/s and 7×10^-17/10^4 s are obtained for a 10 km dissemination. This low cost and scalable method can be applied to a large-scale frequency synchroniza- tion network.
基金China Postdoctoral Science Foundation,Grant/Award Number:2019M661200National Natural Science Foundation of China,Grant/Award Numbers:11874171,11904118,61922035Fundamental Research Funds for the Central Universities。
文摘Ferroelectric memory is a promising candidate for next-generation nonvolatile memory owing to its outstanding performance such as low power consump-tion,fast speed,and high endurance.However,the ferroelectricity of conven-tional ferroelectric materials will be eliminated by the depolarization field when the size drops to the nanometer scale.As a result,the miniaturization of ferroelectric devices was hindered,which makes ferroelectric memory unable to keep up with the development of integrated-circuit(IC)miniaturization.Recently,a two-dimensional(2D)In2Se3 was reported to maintain stable ferro-electricity at the ultrathin scale,which is expected to break through the bottle-neck of miniaturization.Soon,devices based on 2D In2Se3,including the ferroelectric field-effect transistor,ferroelectric channel transistor,synaptic fer-roelectric semiconductor junction,and ferroelectric memristor were demon-strated.However,a comprehensive understanding of the structures and the ferroelectric-switching mechanism of 2D In2Se3 is still lacking.Here,the atomic structures of different phases,the dynamic mechanism of ferroelectric switching,and the performance/functions of the latest devices of 2D In2Se3 are reviewed.Furthermore,the correlations among the structures,the properties,and the device performance are analyzed.Finally,several crucial problems or challenges and possible research directions are put forward.We hope that this review paper can provide timely knowledge and help for the research commu-nity to develop 2D In2Se3 based ferroelectric memory and computing technol-ogy for practical industrial applications.
