Artificial intelligence(AI)has taken breathtaking leaps forward in recent years,evolving into a strategic technology for pioneering the future.The growing demand for computing power—especially in demanding inference ...Artificial intelligence(AI)has taken breathtaking leaps forward in recent years,evolving into a strategic technology for pioneering the future.The growing demand for computing power—especially in demanding inference tasks,exemplified by generative AI models such as ChatGPT—poses challenges for conventional electronic computing systems.Advances in photonics technology have ignited interest in investigating photonic computing as a promising AI computing modality.Through the profound fusion of AI and photonics technologies,intelligent photonics is developing as an emerging interdisciplinary field with significant potential to revolutionize practical applications.Deep learning,as a subset of AI,presents efficient avenues for optimizing photonic design,developing intelligent optical systems,and performing optical data processing and analysis.Employing AI in photonics can empower applications such as smartphone cameras,biomedical microscopy,and virtual and augmented reality displays.Conversely,leveraging photonics-based devices and systems for the physical implementation of neural networks enables high speed and low energy consumption.Applying photonics technology in AI computing is expected to have a transformative impact on diverse fields,including optical communications,automatic driving,and astronomical observation.Here,recent advances in intelligent photonics are presented from the perspective of the synergy between deep learning and metaphotonics,holography,and quantum photonics.This review also spotlights relevant applications and offers insights into challenges and prospects.展开更多
Dynamic tar simulator has been widely used in calibration and validation for star trackers.To achieve both high accuracy and large view field,a dynamic star simulatorbased on optical splicing technology with 2 1920 &#...Dynamic tar simulator has been widely used in calibration and validation for star trackers.To achieve both high accuracy and large view field,a dynamic star simulatorbased on optical splicing technology with 2 1920 × 1080- LCDs and a half-transmission and half- reflection prisms was proposed in this paper.The physical principal and error model due to the splicing structure has been discussed and analyzed in detail.Based on the Tsinghua Micro star tracker,the error effect and system accuracy has been carefully tested and calibrated.The result showed that this simulator can get the accuracy of 10.4 "(3sigma) within a field of view of,which can meet the simulating requirement of modern star tracker,whose accuracy can reach 3"(3sigma) 。展开更多
This study utilizes the All-phase Fast Fourier Transform(FFT)spectral analysis phase difference technique combined with a Kaiser-Hanning hybrid convolution window to enhance the displacement resolution of Swept Source...This study utilizes the All-phase Fast Fourier Transform(FFT)spectral analysis phase difference technique combined with a Kaiser-Hanning hybrid convolution window to enhance the displacement resolution of Swept Source Optical Coherence Tomography(SS-OCT),enabling sub-nanometer level micro-vibration measurements.By employing a designed ultrasmall Gradient Index(GRIN)fiber probe,the signal-to-noise ratio(SNR)is increased to 40 dB,and the frequency estimation error of the All-phase FFT phase difference method is reduced to 10^-4.An SS-OCT system incorporating the ultra-small GRIN probe is developed and applied to micro-vibration detection experiments.The system successfully captures vibration signals from a 0.8 mm diameter micro-motor shaft,showing an increase in vibration amplitude from 2μm to 6μm after damage.Experimental results demonstrate a displacement resolution of 1 nm under optimal conditions.These findings highlight the potential of the ultra-small GRIN fiber probe-based SS-OCT system for detecting micro-mechanical damage and the effectiveness of the All-phase FFT spectral analysis phase difference method in improving the system's displacement resolution,enabling the fiber-optic SS-OCT system to maintain sub-nanometerlevel measurement precision.展开更多
Graphene oxide(GO)is a two-dimensional carbon material with a graphene-like structure and many oxygen-containing functional groups,and in recent years from research into the unique optical properties of GO,GO-based co...Graphene oxide(GO)is a two-dimensional carbon material with a graphene-like structure and many oxygen-containing functional groups,and in recent years from research into the unique optical properties of GO,GO-based composite materials formed by combining with other materials have shown improved overall performance.Reported here is an investigation of how doping with Ni,Fe,and Ag nanoparticles affects the linear and nonlinear optical properties of GO films.The morphology and structure of films of GO,GO with Ni nanoparticles,GO with Fe nanoparticles,and GO with Ag nanoparticles were studied by laser scanning confocal microscopy,SEM,energy dispersive spectroscopy,XRD,and Raman spectroscopy.UV-visible absorption spectra were used to study the optical absorption properties,and the optical band gaps of GO and the composites were calculated from those spectra via Tauc plots.The results show that the band gaps of GO films can be effectively regulated by metal nanoparticles,and so the properties of GO composites can be manipulated.The nonlinear optical properties of GO and GO-metal-nanoparticle composite films were studied by femtosecond laser Z-scanning.The results show that the femtosecond laser power can be tuned to the optical limiting behavior of GO.The strong synergistic coupling effect between metal nanoparticles and GO enhances the nonlinear absorption and nonlinear refraction of composite thin films.The nonlinear absorption coefficient of the composite thin films is improved significantly,and the optical limiting properties are excellent.GO-metal-nanoparticle composite materials have potential applications and advantages in improving optical absorption,band-gap control,and optical limiting.They can promote the expansion of GO composite materials in various practical applications and are candidates for good optical materials,opening the way to GO photonics.展开更多
This study investigated the effects of high-energy-density femtosecond laser pulses on diamond under different pulse counts,revealing the resulting structural changes and defect-formation mechanisms.Raman spectroscopy...This study investigated the effects of high-energy-density femtosecond laser pulses on diamond under different pulse counts,revealing the resulting structural changes and defect-formation mechanisms.Raman spectroscopy and low-temperature fluorescence spectroscopy were used to examine the surface damage,stress,and defect evolution of diamond under varying numbers of pulses.The results revealed the generation of nitrogen-vacancy color centers in diamond under high-energy-density pulsed laser irradiation without requiring annealing treatment.Additionally,confocal spectroscopy provided a distribution model for the evolution of damage and defects in diamond after femtosecond laser processing.This research provides valuable insights into optimizing femtosecond laser processing techniques and improves our understanding of the structural changes and defect-formation mechanisms in diamond.展开更多
A cylindrical coordinate measuring machine for the detection of large-size rotational parts is introduced. The measuring machine can simultaneously measure the geometrical dimensions, form and position errors of the i...A cylindrical coordinate measuring machine for the detection of large-size rotational parts is introduced. The measuring machine can simultaneously measure the geometrical dimensions, form and position errors of the inner and outer surfaces. Since the maximum length of the workpiece can reach 2 000 mm , it is difficult to be clamped and adjusted and easy to produce clamping error. The eccentricity can be up to 1.5 mm, which has an interaction effect with the probe mounting offset. We mainly study the probe offset of the measuring machine and the influence of the workpiece clamping error on the measurement. A method of controlling the offset of the measuring probe is proposed. The effect of the clamping error is eliminated through the space coordinate transformation of the workpiece axis, and the axis is fitted by the least square method. Finally, a common fixture can be realized to meet the clamping requirements of the workpiece.展开更多
REVO?is a dynamic measuring head and probe system,which is designed and applied in orthogonal coordinatemeasuring machines(CMMs)to maximize measurement throughput whilst maintaining high system accuracy.A calibration ...REVO?is a dynamic measuring head and probe system,which is designed and applied in orthogonal coordinatemeasuring machines(CMMs)to maximize measurement throughput whilst maintaining high system accuracy.A calibration approachto the stylus deformation of REVO head is proposed and the scale value of each CMM axis is separated from the limiteddata returned from the measuring system according to the application of REVO head in non-orthogonal CMM.Experimentsshow that the calibration method presented and extraction of scale value are of effectiveness and correctness.Results demonstratethat the maximum measurement error has decreased from0.2021mm to0.0009mm and the variation of scale value ofeach CMM axis is two orders lower after the stylus deformation is compensated.展开更多
The orthogonally linearly polarized dual frequency Nd： YA G lasers with two quarter wave plates in laser resonator are proposed. The intra-cavity variable birefringence, which is caused by relative rotation of these ...The orthogonally linearly polarized dual frequency Nd： YA G lasers with two quarter wave plates in laser resonator are proposed. The intra-cavity variable birefringence, which is caused by relative rotation of these two wave plates in laser inner cavity, results in the frequency difference of the dual frequency laser also changeable. The theory model based on the Jones matrix is presented, as well as experimental results. The potential application of this phenomenon in precision roll-angle measurement is also discussed.展开更多
The ultraviolet（UV） photoresponses of ZnO nanorods directly grown on and between two micro Au-electrodes by using electric-field-assisted wet chemical method are measured comprehensively under different conditions, ...The ultraviolet（UV） photoresponses of ZnO nanorods directly grown on and between two micro Au-electrodes by using electric-field-assisted wet chemical method are measured comprehensively under different conditions, including ambient environment, applied bias voltage, gate voltage and temperature. Experimental results indicate that the photoresponses of the ZnO nanorods can be modulated by surface oxygen adsorptions, applied voltages, as well as temperatures. A model taking into account both surface adsorbed oxygen and electron-hole activities inside ZnO nanorods is proposed. The enhancement effect of the bias voltage on photoresponse is also analyzed. Experimental results shows that the UV response time（to 63%） of ZnO nanorods in air and at 59°C could be shortened from 34.8 s to 0.24 s with a bias of 4 V applied between anode and cathode.展开更多
The 3D characteristic diagram of acoustically induced surface vibration was employed to study the influence of different buried landmines on the acoustic detection signal. By using the vehicular experimental system fo...The 3D characteristic diagram of acoustically induced surface vibration was employed to study the influence of different buried landmines on the acoustic detection signal. By using the vehicular experimental system for acoustic landmine detection and the method of scanning detection, the 3D characteristic diagrams of surface vibration were measured when different objects were buried underground, including big plastic landmine, small plastic landmine, big metal landmine and bricks. The results show that, under the given conditions, the surface vibration amplitudes of big plastic landmine, big metal landmine, small plastic landmine and bricks decrease in turn. The 3D characteristic diagrams of surface vibration can be used to further identify the locations of buried landmines.展开更多
Cold atom clocks have made remarkable progresses in the last two decades and played critical roles in precision measurements. Primary Cs fountain frequency standards have achieved a total uncertainty of a few parts in...Cold atom clocks have made remarkable progresses in the last two decades and played critical roles in precision measurements. Primary Cs fountain frequency standards have achieved a total uncertainty of a few parts in 1016, and the best optical clock has reached a type B uncertainty below 10-18. Besides applications in the metrology, navigation, etc.,ultra-stable and ultra-accurate atomic clocks have also become powerful tools in the basic scientific investigations. In this paper, we focus on the recent developments in the high-performance cold atomic clocks which can be used as frequency standards to calibrate atomic time scales. The basic principles, performances, and limitations of fountain clocks and optical clocks based on signal trapped ion or neutral atoms are summarized. Their applications in metrology and other areas are briefly introduced.展开更多
Fatigue behaviour has important implications for engineering composite structures in sectors ranging from automotive to aerospace.Optical sensing technology displays excellent performance in these fields for monitorin...Fatigue behaviour has important implications for engineering composite structures in sectors ranging from automotive to aerospace.Optical sensing technology displays excellent performance in these fields for monitoring.In this paper,temperature and residual strain during fatigue of a carbon fiber reinforced polymer(CFRP)are investigated.Four autoclaved CFRP beam specimens,with fiber Bragg grating(FBG)sensors and thermocouples embedded at selected locations,are subjected to three-point bending cyclic loading on the BOSE testing machine for fatigue testing.Thennocouples are used to measure the temperature while FBGs can sense the temperature and strain as well.Seven tests in total are conducted at different frequencies,and each test lasts for several days.From the experimental results,transient steep peaks of temperature increases(up to 2.3℃)are discovered at the beginning of the load.The following constant temperature increments are around 1.0℃,which is not relevant to frequencies from 0.1 Hz to 20 Hz and suspected due to fatigue.Residual strains of 1×10^-5-2×10^-5 during fatigue,fading away rapidly when unloading,are also reported.Embedded FBGs here are validated to sense temperature and strains in composite structures,which demonstrates promising potentials in structure monitoring fields.CFRP are verified to have an excellent performance during fatigue with low temperature increase and residual strain.展开更多
This paper has developed and characterized a method to produce a velocity-tunable ^87Rb cold atomic source for atomic interferometry application. Using a high speed fluorescence imaging technology, it reports that the...This paper has developed and characterized a method to produce a velocity-tunable ^87Rb cold atomic source for atomic interferometry application. Using a high speed fluorescence imaging technology, it reports that the dynamic process of the atomic source formation is observed and the source performances including the flux and the initial velocity are characterized. A tunable atomic source with the initial velocity of 1.4-2.6 m/s and the atomic source flux of 2× 10^8 - 6 × 10^9 atoms/s has been obtained with the built experimental setup.展开更多
The World Health Organization has declared COVID-19 a pandemic.The demand for devices or systems to diagnose and track COVID-19 infections noninvasively not only in hospitals but also in home settings has led to incre...The World Health Organization has declared COVID-19 a pandemic.The demand for devices or systems to diagnose and track COVID-19 infections noninvasively not only in hospitals but also in home settings has led to increased interest in consumer-grade wearables.A common symptom of COVID-19 is dyspnea,which may manifest as an increase in respiratory and heart rates.In this paper,a novel piezoelectric strain sensor is presented for real-time monitoring of respiratory and heartbeat signals.A highly sensitive and stretchable piezoelectric strain sensor is fabricated using a piezoelectric film with a serpentine layout.The thickness of the patterned PVDF flexible piezoelectric strain sensor is only 168μm,and the voltage sensitivity reaches 0.97 mV/με.The effective modulus is 13.5 MPa,which allows the device to fit to the skin and detect the small strain exhibited by the human body.Chest vibrations are captured by the piezoelectric sensor,which produces an electrical output voltage signal conformally mapped with respiratory–cardiac activities.The separate heart activity and respiratory signals are extracted from the mixed respiratory–cardiac signal by an empirical mode decomposition data processing algorithm.By detecting vital signals such as respiratory and heart rates,the proposed device can aid early diagnosis and monitoring of respiratory diseases such as COVID-19.展开更多
As actuator of the force-rebalanced servo loop,the electrostatic force generator of the micro-accelerometer shows high nonlinearity while the interpole of the micro-electro-mechanical system(MEMS)sensor is far away fr...As actuator of the force-rebalanced servo loop,the electrostatic force generator of the micro-accelerometer shows high nonlinearity while the interpole of the micro-electro-mechanical system(MEMS)sensor is far away from its balance position.The control system cannot rebalance itself with the limited bandwidth after an external long overload,because the characteristics of the force generator differ from normal case.Although for similar problems,solutions with cascading lead-lag blocks,with the anti-windup(AW)technology,or with the sliding-mode control,are widely reported,the problems such as performance loss or difficulty to synthesize a digital controller still remain.Based on existing researches,remedies are developed by analyzing the characteristic of the system not only near the balance position,but also corresponding to the whole moveable range of the interpole,and a new controller is proposed.The solution is compared with the common solutions of cascading lead-lag blocks method,AW methods,and sliding mode methods.Comparison results show that the proposed solution avoid performance loss,compared to cascading lead-lag blocks solution;the proposed solution is easily synthesized and implemented in the analog servo loop of the micro-accelerometer,compared to digital AW methods;at the same time,the proposed solution avoids suffering the chattering effect problem but just utilize it,compared to the sliding-mode control solution.Nevertheless,comparison results show the solution is lack of commonality,since the solution is only more suitable to micro electrostatic force-rebalance system.The SIMULINK models with and without the proposed solution,taking typical micro-accelerometer parameters,have been set up for simulation;corresponding experiments utilizing electrometric method are also conducted after the successful simulations.Simulation and experiment results verify that the micro-accelerometer will reliably return to normal operation after external long overload with the proposed solution.Therefore,it is expected to design the analog servo loop of high performance micro electrostatic force-rebalance system so as to ensure the rebalance after long overload without performance loss.展开更多
Alkaline phosphatase(ALP) plays an integral role in the metabolism of liver and development of the skeleton in humans. To date, the interactions between different-duration terahertz(THz) radiation and ALP activities, ...Alkaline phosphatase(ALP) plays an integral role in the metabolism of liver and development of the skeleton in humans. To date, the interactions between different-duration terahertz(THz) radiation and ALP activities, as well as the influence mechanism are still unclear. In this study, using the para-nitro-phenyl-phosphate(p NPP) method, we detect changes in ALP activities during 40-minute THz radiation(0.1 THz, 13 m W/cm^2). It is found that the activity of ALP decreases in the first 25 min, and subsequently increases in the later 15 min. Compared with the activity of ALP being heated, the results suggest that short-term terahertz radiation induces a decrease in enzyme activity through the non-thermal mechanism. In order to explore the non-thermal effects of THz radiation on ALP, we focus on the impacts of 0.1 THz radiation for 20 min on the activity of ALP in different concentrations. The results reveal that the activity of ALP decreases significantly after exposure to THz radiation. In addition, it could be deduced from fluorescence, ultraviolet-visible(UV-vis), and THz spectra results that THz radiation has induced changes in ALP structures. Our study unlocks non-thermal interactions between THz radiation and ALP, as well as suggests that THz spectroscopy is a promising technique to distinguish ALP structures.展开更多
In the fields of earth observation,deep space detection,laser communication,and directional energyweapon,the target needs to be observed and pointed at accurately.Acquisition,tracking,and pointing(ATP)systems are usua...In the fields of earth observation,deep space detection,laser communication,and directional energyweapon,the target needs to be observed and pointed at accurately.Acquisition,tracking,and pointing(ATP)systems are usually designed to stabilize the line of sight(LOS)within sub-micro radian levels.In the case of an ATP system mounted on a mobile platform,angular disturbances experienced by the mobile platform will seriously affect the LOS.To overcome the problemthat the sampling frequency of detectors is usually limited and achieving several hundreds of hertz is difficult,thewide-bandwidth inertial reference system(WBIRS)and fast steeringmirror are usually integrated into ATP systems to mitigate these angular disturbances.To reduce the structural stress,a flexible support providing two rotational degrees of freedomis usually adopted for the system.However,the occurrence of resonant points within the bandwidthwill be inevitable.Measurements have to be taken to compensate these low-frequency resonant points to realize a wide bandwidth and high precision.In this paper,the lowfrequency resonant points of a systemwere simulated using finite element analysis and tested by a systemidentification method.The results show that the first-order resonance happened at 34.5 Hz with a gain of 28 dB.An improved double-T notch filter was designed and applied in a real-time system to suppress the resonance at 34.5 Hz.The experimental results show that the resonance was significantly suppressed.In particular,the resonance peak was reduced by 79.37%.In addition,the closed-loop system settling time was reduced by 36.2%.展开更多
Electrochemical analysis is a promising technique for detecting biotoxic and non-biodegradable heavy metals.This article proposes a novel composite electrode based on a polyaniline(PANi)fra mework doped with bismuth n...Electrochemical analysis is a promising technique for detecting biotoxic and non-biodegradable heavy metals.This article proposes a novel composite electrode based on a polyaniline(PANi)fra mework doped with bismuth nanoparticle@graphene oxide multi-walled carbon nano tubes(Bi NPs@GO-MWCNTs)for the simultaneous detection of multiple heavy metal ions.Composite electrodes are prepared on screenprinted electrodes(SPCEs)using an efficient dispensing technique.We used a SM200 SX-3 A dispenser to load a laborato ry-specific ink with optimized viscosity and adhesion to draw a pattern on the work area.The SPCE was used as substrate to facilitate cost-effective and more convenient real-time detection technology.Electrochemical techniques,such as cyclic voltammetry and differential pulse voltammetry,were used to demonstrate the sensing capabilities of the proposed sensor,The sensitivity,limit of detection,and linear range of the PANi-Bi NPs@GO-MWCNT electrode are 2.57×10^(2)μA Lμmol^(-1) cm^-2,0.01 nmol/L,and 0.01 nmol/L-5 mmol/L and 0.15×10^(-1)μALμmol^(-1) cm^-2,0.5 nmol/L,and 0.5 nmol/L-5 mmol/L for mercury ion(Hg(Ⅱ))and copper ion(Cu(Ⅱ))detection,respectively.In addition,the electrode exhibits a good selectivity and repeatability for Hg(Ⅱ)and Cu(Ⅱ)sensing when tested in a complex heavy metal ion solution.The constructed electrode system exhibits a detection performance superior to similar methods and also increases the types of heavy metal ions that can be detected.Therefore,the proposed device can be used as an efficient sensor for the detection of multiple heavy metal ions in complex environments.展开更多
Based on the evaluation of advantages and disadvantages of high-precision digital time interval measuring algorithms, and combined with the principle of the typical time-difference ultrasonic flow measurement, the req...Based on the evaluation of advantages and disadvantages of high-precision digital time interval measuring algorithms, and combined with the principle of the typical time-difference ultrasonic flow measurement, the requirements for the measurement of echo time of flight put forward by the ultrasonic flow measurement are analyzed. A new high-precision time interval measurement algorithm is presented, which combines the pulse counting method with the phase delay interpolation. The pulse counting method is used to ensure a large dynamic measuring range, and a double-edge triggering counter is designed to improve the accuracy and reduce the counting quantization error. The phase delay interpolation is used to reduce the quantization error of pulse counting for further improving the time measurement resolution. Test data show that the systexn for the measurement of the ultrasonic echo time of flight based on this algorithm and implemented on an Field Programmable Gate Army（FleA） needs a relatively short time for measurement, and has a measurement error of less than 105 ps.展开更多
To compare mid-infrared(MIR)and near-infrared(NIR)spectroscopies for the determination of the fat and protein contents in milk,the same sample sets with varying concentrations of fat and protein were measured in the M...To compare mid-infrared(MIR)and near-infrared(NIR)spectroscopies for the determination of the fat and protein contents in milk,the same sample sets with varying concentrations of fat and protein were measured in the MIR range of 3 200-700 cm-1 and NIR range of 9 000-4 000 cm-1.The spectral features in the two regions were analyzed.The MIR spectra of milk were characteristic due to the MIR inherent molecular specificity,whereas the NIR spectra were relatively characterless due to the NIR low selectivity.Partial least squares(PLS)regression models for fat and protein were developed by using both MIR and NIR spectra.MIR data with no pretreatment gave better results than NIR data.The square correlation coefficient(R2)and the root mean square error of prediction(RMSEP)were 0.98 and 0.10 g/dL for fat and 0.97 and 0.11 g/dL for protein.With NIR techniques,satisfactory results were not obtained with raw data.However,NIR data after pretreatment gave similarly good results to the ones using MIR method.This paper indicates that either of the MIR and NIR spectral methods is reliable for the determination of the fat and protein contents.展开更多
基金supported by the National Natural Science Foundation of China(62035003 and 62235009).
文摘Artificial intelligence(AI)has taken breathtaking leaps forward in recent years,evolving into a strategic technology for pioneering the future.The growing demand for computing power—especially in demanding inference tasks,exemplified by generative AI models such as ChatGPT—poses challenges for conventional electronic computing systems.Advances in photonics technology have ignited interest in investigating photonic computing as a promising AI computing modality.Through the profound fusion of AI and photonics technologies,intelligent photonics is developing as an emerging interdisciplinary field with significant potential to revolutionize practical applications.Deep learning,as a subset of AI,presents efficient avenues for optimizing photonic design,developing intelligent optical systems,and performing optical data processing and analysis.Employing AI in photonics can empower applications such as smartphone cameras,biomedical microscopy,and virtual and augmented reality displays.Conversely,leveraging photonics-based devices and systems for the physical implementation of neural networks enables high speed and low energy consumption.Applying photonics technology in AI computing is expected to have a transformative impact on diverse fields,including optical communications,automatic driving,and astronomical observation.Here,recent advances in intelligent photonics are presented from the perspective of the synergy between deep learning and metaphotonics,holography,and quantum photonics.This review also spotlights relevant applications and offers insights into challenges and prospects.
文摘Dynamic tar simulator has been widely used in calibration and validation for star trackers.To achieve both high accuracy and large view field,a dynamic star simulatorbased on optical splicing technology with 2 1920 × 1080- LCDs and a half-transmission and half- reflection prisms was proposed in this paper.The physical principal and error model due to the splicing structure has been discussed and analyzed in detail.Based on the Tsinghua Micro star tracker,the error effect and system accuracy has been carefully tested and calibrated.The result showed that this simulator can get the accuracy of 10.4 "(3sigma) within a field of view of,which can meet the simulating requirement of modern star tracker,whose accuracy can reach 3"(3sigma) 。
基金funded by the National Natural Science Foundation of China (NSFC)(62405174)State Key Laboratory of Precision Measurement Technology and Instruments (Pilab2402)Fundamental Research Funds for the Central Universities (3122016C010)。
文摘This study utilizes the All-phase Fast Fourier Transform(FFT)spectral analysis phase difference technique combined with a Kaiser-Hanning hybrid convolution window to enhance the displacement resolution of Swept Source Optical Coherence Tomography(SS-OCT),enabling sub-nanometer level micro-vibration measurements.By employing a designed ultrasmall Gradient Index(GRIN)fiber probe,the signal-to-noise ratio(SNR)is increased to 40 dB,and the frequency estimation error of the All-phase FFT phase difference method is reduced to 10^-4.An SS-OCT system incorporating the ultra-small GRIN probe is developed and applied to micro-vibration detection experiments.The system successfully captures vibration signals from a 0.8 mm diameter micro-motor shaft,showing an increase in vibration amplitude from 2μm to 6μm after damage.Experimental results demonstrate a displacement resolution of 1 nm under optimal conditions.These findings highlight the potential of the ultra-small GRIN fiber probe-based SS-OCT system for detecting micro-mechanical damage and the effectiveness of the All-phase FFT spectral analysis phase difference method in improving the system's displacement resolution,enabling the fiber-optic SS-OCT system to maintain sub-nanometerlevel measurement precision.
基金funded by the Henan Key Laboratory of Intelligent Manufacturing Equipment Integration for Superhard Materials(Grant No.JDKJ2022-01)the Key Lab of Modern Optical Technologies of Education Ministry of China,Soochow University。
文摘Graphene oxide(GO)is a two-dimensional carbon material with a graphene-like structure and many oxygen-containing functional groups,and in recent years from research into the unique optical properties of GO,GO-based composite materials formed by combining with other materials have shown improved overall performance.Reported here is an investigation of how doping with Ni,Fe,and Ag nanoparticles affects the linear and nonlinear optical properties of GO films.The morphology and structure of films of GO,GO with Ni nanoparticles,GO with Fe nanoparticles,and GO with Ag nanoparticles were studied by laser scanning confocal microscopy,SEM,energy dispersive spectroscopy,XRD,and Raman spectroscopy.UV-visible absorption spectra were used to study the optical absorption properties,and the optical band gaps of GO and the composites were calculated from those spectra via Tauc plots.The results show that the band gaps of GO films can be effectively regulated by metal nanoparticles,and so the properties of GO composites can be manipulated.The nonlinear optical properties of GO and GO-metal-nanoparticle composite films were studied by femtosecond laser Z-scanning.The results show that the femtosecond laser power can be tuned to the optical limiting behavior of GO.The strong synergistic coupling effect between metal nanoparticles and GO enhances the nonlinear absorption and nonlinear refraction of composite thin films.The nonlinear absorption coefficient of the composite thin films is improved significantly,and the optical limiting properties are excellent.GO-metal-nanoparticle composite materials have potential applications and advantages in improving optical absorption,band-gap control,and optical limiting.They can promote the expansion of GO composite materials in various practical applications and are candidates for good optical materials,opening the way to GO photonics.
基金funded by the Henan Key Laboratory of Intelligent Manufacturing Equipment Integration for Superhard Materials(Grant No.JDKJ2022-01)the Key Lab of Modern Optical Technologies of Education Ministry of China,Soochow University.
文摘This study investigated the effects of high-energy-density femtosecond laser pulses on diamond under different pulse counts,revealing the resulting structural changes and defect-formation mechanisms.Raman spectroscopy and low-temperature fluorescence spectroscopy were used to examine the surface damage,stress,and defect evolution of diamond under varying numbers of pulses.The results revealed the generation of nitrogen-vacancy color centers in diamond under high-energy-density pulsed laser irradiation without requiring annealing treatment.Additionally,confocal spectroscopy provided a distribution model for the evolution of damage and defects in diamond after femtosecond laser processing.This research provides valuable insights into optimizing femtosecond laser processing techniques and improves our understanding of the structural changes and defect-formation mechanisms in diamond.
基金National Natural Science Foundation of China(No.51375338)National Key R&D Program of China(No.2017YFF0108102)
文摘A cylindrical coordinate measuring machine for the detection of large-size rotational parts is introduced. The measuring machine can simultaneously measure the geometrical dimensions, form and position errors of the inner and outer surfaces. Since the maximum length of the workpiece can reach 2 000 mm , it is difficult to be clamped and adjusted and easy to produce clamping error. The eccentricity can be up to 1.5 mm, which has an interaction effect with the probe mounting offset. We mainly study the probe offset of the measuring machine and the influence of the workpiece clamping error on the measurement. A method of controlling the offset of the measuring probe is proposed. The effect of the clamping error is eliminated through the space coordinate transformation of the workpiece axis, and the axis is fitted by the least square method. Finally, a common fixture can be realized to meet the clamping requirements of the workpiece.
基金National Natural Science Foundation of China(No.51375338)
文摘REVO?is a dynamic measuring head and probe system,which is designed and applied in orthogonal coordinatemeasuring machines(CMMs)to maximize measurement throughput whilst maintaining high system accuracy.A calibration approachto the stylus deformation of REVO head is proposed and the scale value of each CMM axis is separated from the limiteddata returned from the measuring system according to the application of REVO head in non-orthogonal CMM.Experimentsshow that the calibration method presented and extraction of scale value are of effectiveness and correctness.Results demonstratethat the maximum measurement error has decreased from0.2021mm to0.0009mm and the variation of scale value ofeach CMM axis is two orders lower after the stylus deformation is compensated.
基金Supported by the National Natural Science Foundation of China under Grant No 50575110.
文摘The orthogonally linearly polarized dual frequency Nd： YA G lasers with two quarter wave plates in laser resonator are proposed. The intra-cavity variable birefringence, which is caused by relative rotation of these two wave plates in laser inner cavity, results in the frequency difference of the dual frequency laser also changeable. The theory model based on the Jones matrix is presented, as well as experimental results. The potential application of this phenomenon in precision roll-angle measurement is also discussed.
基金Project supported by the National Natural Science Foundation of China(Grant No.91123017)
文摘The ultraviolet（UV） photoresponses of ZnO nanorods directly grown on and between two micro Au-electrodes by using electric-field-assisted wet chemical method are measured comprehensively under different conditions, including ambient environment, applied bias voltage, gate voltage and temperature. Experimental results indicate that the photoresponses of the ZnO nanorods can be modulated by surface oxygen adsorptions, applied voltages, as well as temperatures. A model taking into account both surface adsorbed oxygen and electron-hole activities inside ZnO nanorods is proposed. The enhancement effect of the bias voltage on photoresponse is also analyzed. Experimental results shows that the UV response time（to 63%） of ZnO nanorods in air and at 59°C could be shortened from 34.8 s to 0.24 s with a bias of 4 V applied between anode and cathode.
基金Supported by the National Natural Science Foundation of China(No.61575119)Science and Technology on Near-Surface Detection Laboratory(No.TCGZ2015A005)State Key Laboratory of Precision Measuring Technology and Instruments(PIL1402)
文摘The 3D characteristic diagram of acoustically induced surface vibration was employed to study the influence of different buried landmines on the acoustic detection signal. By using the vehicular experimental system for acoustic landmine detection and the method of scanning detection, the 3D characteristic diagrams of surface vibration were measured when different objects were buried underground, including big plastic landmine, small plastic landmine, big metal landmine and bricks. The results show that, under the given conditions, the surface vibration amplitudes of big plastic landmine, big metal landmine, small plastic landmine and bricks decrease in turn. The 3D characteristic diagrams of surface vibration can be used to further identify the locations of buried landmines.
基金Project supported by the National Natural Science Foundation of China(Grant No.11873044)the National Key Research and Development Project of China(Grant No.2016YFF0200202)Consulting Research Project of Chinese Academy of Engineering(Grant No.2018-ZCQ-03)。
文摘Cold atom clocks have made remarkable progresses in the last two decades and played critical roles in precision measurements. Primary Cs fountain frequency standards have achieved a total uncertainty of a few parts in 1016, and the best optical clock has reached a type B uncertainty below 10-18. Besides applications in the metrology, navigation, etc.,ultra-stable and ultra-accurate atomic clocks have also become powerful tools in the basic scientific investigations. In this paper, we focus on the recent developments in the high-performance cold atomic clocks which can be used as frequency standards to calibrate atomic time scales. The basic principles, performances, and limitations of fountain clocks and optical clocks based on signal trapped ion or neutral atoms are summarized. Their applications in metrology and other areas are briefly introduced.
文摘Fatigue behaviour has important implications for engineering composite structures in sectors ranging from automotive to aerospace.Optical sensing technology displays excellent performance in these fields for monitoring.In this paper,temperature and residual strain during fatigue of a carbon fiber reinforced polymer(CFRP)are investigated.Four autoclaved CFRP beam specimens,with fiber Bragg grating(FBG)sensors and thermocouples embedded at selected locations,are subjected to three-point bending cyclic loading on the BOSE testing machine for fatigue testing.Thennocouples are used to measure the temperature while FBGs can sense the temperature and strain as well.Seven tests in total are conducted at different frequencies,and each test lasts for several days.From the experimental results,transient steep peaks of temperature increases(up to 2.3℃)are discovered at the beginning of the load.The following constant temperature increments are around 1.0℃,which is not relevant to frequencies from 0.1 Hz to 20 Hz and suspected due to fatigue.Residual strains of 1×10^-5-2×10^-5 during fatigue,fading away rapidly when unloading,are also reported.Embedded FBGs here are validated to sense temperature and strains in composite structures,which demonstrates promising potentials in structure monitoring fields.CFRP are verified to have an excellent performance during fatigue with low temperature increase and residual strain.
基金supported in part by National Natural Science Foundation of China (Grant No 50775127/E0525)National Basic Research Specialized Program of China (Grant No 2007CB306504)
文摘This paper has developed and characterized a method to produce a velocity-tunable ^87Rb cold atomic source for atomic interferometry application. Using a high speed fluorescence imaging technology, it reports that the dynamic process of the atomic source formation is observed and the source performances including the flux and the initial velocity are characterized. A tunable atomic source with the initial velocity of 1.4-2.6 m/s and the atomic source flux of 2× 10^8 - 6 × 10^9 atoms/s has been obtained with the built experimental setup.
基金We are grateful for funding from the Natural Science Foundation of China(NSFC Grant No.62001322)the Tianjin Municipal Science and Technology Project(No.20JCQNJC011200)+1 种基金the National Key Research and Development Program(No.2020YFB2008801)the Nanchang Institute for Microtechnology of Tianjin University.
文摘The World Health Organization has declared COVID-19 a pandemic.The demand for devices or systems to diagnose and track COVID-19 infections noninvasively not only in hospitals but also in home settings has led to increased interest in consumer-grade wearables.A common symptom of COVID-19 is dyspnea,which may manifest as an increase in respiratory and heart rates.In this paper,a novel piezoelectric strain sensor is presented for real-time monitoring of respiratory and heartbeat signals.A highly sensitive and stretchable piezoelectric strain sensor is fabricated using a piezoelectric film with a serpentine layout.The thickness of the patterned PVDF flexible piezoelectric strain sensor is only 168μm,and the voltage sensitivity reaches 0.97 mV/με.The effective modulus is 13.5 MPa,which allows the device to fit to the skin and detect the small strain exhibited by the human body.Chest vibrations are captured by the piezoelectric sensor,which produces an electrical output voltage signal conformally mapped with respiratory–cardiac activities.The separate heart activity and respiratory signals are extracted from the mixed respiratory–cardiac signal by an empirical mode decomposition data processing algorithm.By detecting vital signals such as respiratory and heart rates,the proposed device can aid early diagnosis and monitoring of respiratory diseases such as COVID-19.
基金supported by National Key Technologies R&D Program of China during the 11th Five-Year Plan(Grant No.51309050208)
文摘As actuator of the force-rebalanced servo loop,the electrostatic force generator of the micro-accelerometer shows high nonlinearity while the interpole of the micro-electro-mechanical system(MEMS)sensor is far away from its balance position.The control system cannot rebalance itself with the limited bandwidth after an external long overload,because the characteristics of the force generator differ from normal case.Although for similar problems,solutions with cascading lead-lag blocks,with the anti-windup(AW)technology,or with the sliding-mode control,are widely reported,the problems such as performance loss or difficulty to synthesize a digital controller still remain.Based on existing researches,remedies are developed by analyzing the characteristic of the system not only near the balance position,but also corresponding to the whole moveable range of the interpole,and a new controller is proposed.The solution is compared with the common solutions of cascading lead-lag blocks method,AW methods,and sliding mode methods.Comparison results show that the proposed solution avoid performance loss,compared to cascading lead-lag blocks solution;the proposed solution is easily synthesized and implemented in the analog servo loop of the micro-accelerometer,compared to digital AW methods;at the same time,the proposed solution avoids suffering the chattering effect problem but just utilize it,compared to the sliding-mode control solution.Nevertheless,comparison results show the solution is lack of commonality,since the solution is only more suitable to micro electrostatic force-rebalance system.The SIMULINK models with and without the proposed solution,taking typical micro-accelerometer parameters,have been set up for simulation;corresponding experiments utilizing electrometric method are also conducted after the successful simulations.Simulation and experiment results verify that the micro-accelerometer will reliably return to normal operation after external long overload with the proposed solution.Therefore,it is expected to design the analog servo loop of high performance micro electrostatic force-rebalance system so as to ensure the rebalance after long overload without performance loss.
基金Project supported by the National Natural Science Foundation of China(Grant No.61675151)
文摘Alkaline phosphatase(ALP) plays an integral role in the metabolism of liver and development of the skeleton in humans. To date, the interactions between different-duration terahertz(THz) radiation and ALP activities, as well as the influence mechanism are still unclear. In this study, using the para-nitro-phenyl-phosphate(p NPP) method, we detect changes in ALP activities during 40-minute THz radiation(0.1 THz, 13 m W/cm^2). It is found that the activity of ALP decreases in the first 25 min, and subsequently increases in the later 15 min. Compared with the activity of ALP being heated, the results suggest that short-term terahertz radiation induces a decrease in enzyme activity through the non-thermal mechanism. In order to explore the non-thermal effects of THz radiation on ALP, we focus on the impacts of 0.1 THz radiation for 20 min on the activity of ALP in different concentrations. The results reveal that the activity of ALP decreases significantly after exposure to THz radiation. In addition, it could be deduced from fluorescence, ultraviolet-visible(UV-vis), and THz spectra results that THz radiation has induced changes in ALP structures. Our study unlocks non-thermal interactions between THz radiation and ALP, as well as suggests that THz spectroscopy is a promising technique to distinguish ALP structures.
基金supported by the Research on Key Problems of Wide-band Inertial Reference Based on Magnetohydrodynamics (Grant number 61733012)National Natural Science Foundation of China Youth Project (Grant number 61703303)+2 种基金Tianjin Natural Science Foundation Youth Project (Grant number No. 17JCQNJCo4100)State Key Laboratory of Precision Testing Technology and Instruments Open Project (Grant number No. PILAB1705)2017 Tianjin Education Commission Research Project (Grant number 2017KJ086)
文摘In the fields of earth observation,deep space detection,laser communication,and directional energyweapon,the target needs to be observed and pointed at accurately.Acquisition,tracking,and pointing(ATP)systems are usually designed to stabilize the line of sight(LOS)within sub-micro radian levels.In the case of an ATP system mounted on a mobile platform,angular disturbances experienced by the mobile platform will seriously affect the LOS.To overcome the problemthat the sampling frequency of detectors is usually limited and achieving several hundreds of hertz is difficult,thewide-bandwidth inertial reference system(WBIRS)and fast steeringmirror are usually integrated into ATP systems to mitigate these angular disturbances.To reduce the structural stress,a flexible support providing two rotational degrees of freedomis usually adopted for the system.However,the occurrence of resonant points within the bandwidthwill be inevitable.Measurements have to be taken to compensate these low-frequency resonant points to realize a wide bandwidth and high precision.In this paper,the lowfrequency resonant points of a systemwere simulated using finite element analysis and tested by a systemidentification method.The results show that the first-order resonance happened at 34.5 Hz with a gain of 28 dB.An improved double-T notch filter was designed and applied in a real-time system to suppress the resonance at 34.5 Hz.The experimental results show that the resonance was significantly suppressed.In particular,the resonance peak was reduced by 79.37%.In addition,the closed-loop system settling time was reduced by 36.2%.
基金the Tianjin Natural Science Foundation(Nos.18JCZDJC998007JCQNJC00900)+4 种基金National Natural Science Foundation of China(No.51502203)Tianjin Young Overseas High-level Talent Plans(No.01001502)Tianjin Science and Technology Foundation(No.17ZXZNGX00090)Tianjin Distinguished Professor Foundation of Young ResearchersTianjin Development Program for Innovation and Entrepreneurship。
文摘Electrochemical analysis is a promising technique for detecting biotoxic and non-biodegradable heavy metals.This article proposes a novel composite electrode based on a polyaniline(PANi)fra mework doped with bismuth nanoparticle@graphene oxide multi-walled carbon nano tubes(Bi NPs@GO-MWCNTs)for the simultaneous detection of multiple heavy metal ions.Composite electrodes are prepared on screenprinted electrodes(SPCEs)using an efficient dispensing technique.We used a SM200 SX-3 A dispenser to load a laborato ry-specific ink with optimized viscosity and adhesion to draw a pattern on the work area.The SPCE was used as substrate to facilitate cost-effective and more convenient real-time detection technology.Electrochemical techniques,such as cyclic voltammetry and differential pulse voltammetry,were used to demonstrate the sensing capabilities of the proposed sensor,The sensitivity,limit of detection,and linear range of the PANi-Bi NPs@GO-MWCNT electrode are 2.57×10^(2)μA Lμmol^(-1) cm^-2,0.01 nmol/L,and 0.01 nmol/L-5 mmol/L and 0.15×10^(-1)μALμmol^(-1) cm^-2,0.5 nmol/L,and 0.5 nmol/L-5 mmol/L for mercury ion(Hg(Ⅱ))and copper ion(Cu(Ⅱ))detection,respectively.In addition,the electrode exhibits a good selectivity and repeatability for Hg(Ⅱ)and Cu(Ⅱ)sensing when tested in a complex heavy metal ion solution.The constructed electrode system exhibits a detection performance superior to similar methods and also increases the types of heavy metal ions that can be detected.Therefore,the proposed device can be used as an efficient sensor for the detection of multiple heavy metal ions in complex environments.
基金supported by the National 863 Program(No.2008AA042207)
文摘Based on the evaluation of advantages and disadvantages of high-precision digital time interval measuring algorithms, and combined with the principle of the typical time-difference ultrasonic flow measurement, the requirements for the measurement of echo time of flight put forward by the ultrasonic flow measurement are analyzed. A new high-precision time interval measurement algorithm is presented, which combines the pulse counting method with the phase delay interpolation. The pulse counting method is used to ensure a large dynamic measuring range, and a double-edge triggering counter is designed to improve the accuracy and reduce the counting quantization error. The phase delay interpolation is used to reduce the quantization error of pulse counting for further improving the time measurement resolution. Test data show that the systexn for the measurement of the ultrasonic echo time of flight based on this algorithm and implemented on an Field Programmable Gate Army（FleA） needs a relatively short time for measurement, and has a measurement error of less than 105 ps.
基金Supported by National Natural Science Foundation of China(No.30170261)the 10th Five-Year Plan of China(No.2004BA706B12).
文摘To compare mid-infrared(MIR)and near-infrared(NIR)spectroscopies for the determination of the fat and protein contents in milk,the same sample sets with varying concentrations of fat and protein were measured in the MIR range of 3 200-700 cm-1 and NIR range of 9 000-4 000 cm-1.The spectral features in the two regions were analyzed.The MIR spectra of milk were characteristic due to the MIR inherent molecular specificity,whereas the NIR spectra were relatively characterless due to the NIR low selectivity.Partial least squares(PLS)regression models for fat and protein were developed by using both MIR and NIR spectra.MIR data with no pretreatment gave better results than NIR data.The square correlation coefficient(R2)and the root mean square error of prediction(RMSEP)were 0.98 and 0.10 g/dL for fat and 0.97 and 0.11 g/dL for protein.With NIR techniques,satisfactory results were not obtained with raw data.However,NIR data after pretreatment gave similarly good results to the ones using MIR method.This paper indicates that either of the MIR and NIR spectral methods is reliable for the determination of the fat and protein contents.
