An in-pixel histogramming time-to-digital converter(hTDC)based on octonary search and 4-tap phase detection is presented,aiming to improve frame rate while ensuring high precicion.The proposed hTDC is a 12-bit two-ste...An in-pixel histogramming time-to-digital converter(hTDC)based on octonary search and 4-tap phase detection is presented,aiming to improve frame rate while ensuring high precicion.The proposed hTDC is a 12-bit two-step converter consisting of a 6-bit coarse quantization and a 6-bit fine quantization,which supports a time resolution of 120 ps and multiphoton counting up to 2 GHz without a GHz reference frequency.The proposed hTDC is designed in 0.11μm CMOS process with an area consumption of 6900μm^(2).The data from a behavioral-level model is imported into the designed hTDC circuit for simulation verification.The post-simulation results show that the proposed hTDC achieves 0.8%depth precision in 9 m range for short-range system design specifications and 0.2%depth precision in 48 m range for long-range system design specifications.Under 30×10^(3) lux background light conditions,the proposed hTDC can be used for SPAD-based flash LiDAR sensor to achieve a frame rate to 40 fps with 200 ps resolution in 9 m range.展开更多
The availability of a tremendous amount of seismic data demands seismological researchers to analyze seismic phases efficiently.Recently,deep learning algorithms exhibit a powerful capability of detecting and picking ...The availability of a tremendous amount of seismic data demands seismological researchers to analyze seismic phases efficiently.Recently,deep learning algorithms exhibit a powerful capability of detecting and picking on P-and S-wave phases.However,it remains a challenge to effeciently process enormous teleseismic phases,which are crucial to probe Earth’s interior structures and their dynamics.In this study,we propose a scheme to detect and pick teleseismic phases,such as seismic phase that reflects off the core-mantle boundary(i.e.,PcP)and that reflects off the inner-core boundary(i.e.,PKiKP),from a seismic dataset in Japan.The scheme consists of three steps:1)latent phase traces are truncated from the whole seismogram with theoretical arrival times;2)latent phases are recognized and evaluated by convolutional neural network(CNN)models;3)arrivals of good or fair phase are picked with another CNN models.The testing detection result on 7386 seismograms shows that the scheme recognizes 92.15%and 94.13%of PcP and PKiKP phases.The testing picking result has a mean absolute error of 0.0742 s and 0.0636 s for the PcP and PKiKP phases,respectively.These seismograms were processed in just 5 min for phase detection and picking,demonstrating the efficiency of the proposed scheme in automatic teleseismic phase analysis.展开更多
Surface plasmon resonance (SPR) sensing is an optical method based on evanescent wave.SPR biosensor can detect interaction of label-free biomolecules in real-time.With further development,it can become a research ins...Surface plasmon resonance (SPR) sensing is an optical method based on evanescent wave.SPR biosensor can detect interaction of label-free biomolecules in real-time.With further development,it can become a research instrument in proteomics.SPR biosensor can be divided intensity measurement and phase measurement,and the latter possesses higher sensitivity than the former one.This paper attempts to summarize the SPR phase detection theory,discuss the major developments,compare the merits and deficiencies of various methods,and look forward to future prospects.展开更多
We developed an automatic seismic wave and phase detection software based on PhaseNet,an efficient and highly generalized deep learning neural network for P-and S-wave phase picking.The software organically combines m...We developed an automatic seismic wave and phase detection software based on PhaseNet,an efficient and highly generalized deep learning neural network for P-and S-wave phase picking.The software organically combines multiple modules including application terminal interface,docker container,data visualization,SSH protocol data transmission and other auxiliary modules.Characterized by a series of technologically powerful functions,the software is highly convenient for all users.To obtain the P-and S-wave picks,one only needs to prepare threecomponent seismic data as input and customize some parameters in the interface.In particular,the software can automatically identify complex waveforms(i.e.continuous or truncated waves)and support multiple types of input data such as SAC,MSEED,NumPy array,etc.A test on the dataset of the Wenchuan aftershocks shows the generalization ability and detection accuracy of the software.The software is expected to increase the efficiency and subjectivity in the manual processing of large amounts of seismic data,thereby providing convenience to regional network monitoring staffs and researchers in the study of Earth's interior.展开更多
The new generation particle accelerator requires a highly stable radio frequency（RF） system. The stability of the RF system is realized by the Low Level RF（LLRF） subsystem which controls the amplitude and phase of...The new generation particle accelerator requires a highly stable radio frequency（RF） system. The stability of the RF system is realized by the Low Level RF（LLRF） subsystem which controls the amplitude and phase of the RF signal. The detection of the RF signal＇s amplitude and phase is fundamental to LLRF controls. High-speed ADC（Analog to Digital Converter） ,DAC（Digital to Analog Converter） and FPGA（Field Programmable Gate Array） play very important roles in digital LLRF control systems. This paper describes the implementation of real-time amplitude and phase detection based of the FPGA with an analysis of the main factors that affect the detection accuracy such as jitter,algorithm＇s defects and non-linearity of devices,which is helpful for future work on high precision detection and control.展开更多
In recent years, surface-enhanced Raman spectroscopy （SERS） has developed rapidly and is used for the detection of molecules and biomolecules in liquids. However, few studies have focused on SERS using a water surfa...In recent years, surface-enhanced Raman spectroscopy （SERS） has developed rapidly and is used for the detection of molecules and biomolecules in liquids. However, few studies have focused on SERS using a water surface as the substrate. A floating metal film on water is desirable for an enhanced SERS performance. In this work, silver nanopartides （Ag NPs） encased in poly（vinylpyrrolidone） films （Ag-PVP films） were synthesized on the surface of an aqueous solution by room temperature electron reduction. A floating silver film on a water surface was thereby achieved and is reported for the first time. The synthesized Ag-PVP film is an excellent flexible substrate for SERS and has other potential appli- cations. Using the floating silver film as a flexible SERS substrate, 10-11 M of 4-aminothiophenol, 10^-6 M of riboflavin, 10^-9 M of 4-mercaptobenzoic acid, 10^-7 M of 4-mercaptophenol, and 10^-7 M of 4-aminobenzoic acid are identified, demonstrating potential use for the floating substrate in the liquid-phase detection of molecules.展开更多
A simple model of the phase-detection autofocus device based on the partially masked sensor pixels is described. The cross-correlation function of the half-images registered by the masked pixels is proposed as a focus...A simple model of the phase-detection autofocus device based on the partially masked sensor pixels is described. The cross-correlation function of the half-images registered by the masked pixels is proposed as a focus function. It is shown that—in such setting—focusing is equivalent to searching of the cross-correlation function maximum. Application of stochastic approximation algorithms to unimodal and non-unimodal focus functions is shortly discussed.展开更多
Aim to detect the characteristic weak magnetic field signal against the strong noises background. Methods In combination with a low-pass-filter, the correlation output of magne-* tic sensors between the magnetic field...Aim to detect the characteristic weak magnetic field signal against the strong noises background. Methods In combination with a low-pass-filter, the correlation output of magne-* tic sensors between the magnetic field and reference current was utilized to provide a DC output voltage proportional to the applied magnetic induction, computer simulation was* done to investigate the correlation output of the Hall-effect sensors. Results Some analysis results concerning the noise property, harmonic supppression and the sensitivity were given. Conclsion The minimum detection signal of the equipment evolved from the mentioned cor-* relation theory can be 10-6 T. In addition to the DC output, such sensors can also measure the phase of the detected magnetic induction and has good harmonic suppression as well as* noise elimination.展开更多
According to the time&space conversion relations and different frequency phase detection principle,an ultra-high precision time&frequency measurement method is proposed in this paper.The higher accuracy and st...According to the time&space conversion relations and different frequency phase detection principle,an ultra-high precision time&frequency measurement method is proposed in this paper.The higher accuracy and stability of the speed of light and electromagnetic signals during the transmission in space or a specific medium enable the measurement of short time interval which uses the coincidence detection of signal’s transmission delay in length.The measurement precision better than 10 picoseconds can be easily obtained.The method develops the length vernier utilizing the stability of signal’s transmission delay,minimizes the fuzzy region of phase coincidence between the standard frequency signal and the measured signal,approaches the best phase coincidences and therefore improves the measurement precision which is higher than the precision provided by the traditional methods based on frequency processing.Besides,the method costs less than the traditional methods and can also solve the problem of the measurement of super-high frequency.Experimental results show the method can improve the measurement precision to 10 12/s in the time&frequency domain.展开更多
In order to improve the performance of line spectrum detection,according to the feature that the underwater target radiated noise containing stable line spectrum,the differences of the phase difference between line sp...In order to improve the performance of line spectrum detection,according to the feature that the underwater target radiated noise containing stable line spectrum,the differences of the phase difference between line spectrum and background noise,a weighted line spectrum detection algorithm based on the phase variance is proposed in frequency domain.After phase difference alignment,the phase variance of line spectrum and the phase of background noise,respectively,are small and big in frequency domain,this method utilizes the weighted statistical algorithm to cumulate the frequency spectrum based on the phase variance,which can restrain the background noise disturbance,and enhance the signal to noise ratio（SNR）.The theory analysis and experimental results both verify that the proposed method can well enhance the energy of line spectrum,restrain the energy of background noise,and have better detection performance under lower SNR.展开更多
Glycerides are first separated to classes of triglycerides(TGs), diglycerides(DGs) and monoglycerides(MGs) by normal phase HPLC on silica gel column. Individual triglyceride separation is then achieved by non-aqueous ...Glycerides are first separated to classes of triglycerides(TGs), diglycerides(DGs) and monoglycerides(MGs) by normal phase HPLC on silica gel column. Individual triglyceride separation is then achieved by non-aqueous reversed phase(NARP) HPLC on C_(18) column with UV detection at 215nm.展开更多
Phase is one of the most important parameters of electromagnetic waves. It is the phase distribution that determines the propagation, reflection, refraction, focusing, divergence, and coupling features of light, and f...Phase is one of the most important parameters of electromagnetic waves. It is the phase distribution that determines the propagation, reflection, refraction, focusing, divergence, and coupling features of light, and further affects the intensity distribution. In recent years, the designs of surface plasmon polariton （SPP） devices have mostly been based on the phase modulation and manipulation. Here we demonstrate a phase sensitive multi-parameter heterodyne scanning near-field opti- cal microscope （SNOM） with an aperture probe in the visible range, with which the near field optical phase and amplitude distributions can be simultaneously obtained. A novel architecture combining a spatial optical path and a fiber optical path is employed for stability and flexibility. Two kinds of typical nano-photonic devices are tested with the system. With the phase-sensitive SNOM, the phase and amplitude distributions of any nano-optical field and localized field generated with any SPP nano-structures and irregular phase modulation surfaces can be investigated. The phase distribution and the interference pattern will help us to gain a better understanding of how light interacts with SPP structures and how SPP waves generate, localize, convert, and propagate on an SPP surface. This will be a significant guidance on SPP nano-structure design and optimization.展开更多
Microseismic phase detection and arrival picking are critical steps in the processing of hydraulic fracturing microseismic monitoring data.As the signal-to-noise ratios of P-and S-waves diff er because of the infl uen...Microseismic phase detection and arrival picking are critical steps in the processing of hydraulic fracturing microseismic monitoring data.As the signal-to-noise ratios of P-and S-waves diff er because of the infl uence of focal mechanisms,geometry,and background noise,diffi culties are introduced in the eff ective discrimination of seismic phases and the accurate acquisition of arrivals in conventional processing methods.In this paper,we propose a method for identifying microseismic phase arrival time by comprehensively analyzing the variation of moveout curves and combining the intra-event waveform similarities with the energy ratio of multitrace signals.First,a curve-fi tting formula is constructed with perforation arrivals,and event detection is achieved by adopting an energy-weighted similarity coeffi cient that seeks plausible fi tting curves with a sliding time window in continuous microseismic recordings.Then,the P-and S-waves are separated by the fitting parameters.The known arrival time trend of the microseismic phase is employed to calculate residual time corrections.Finally,the accurate arrival results of the microseismic phases can be obtained by picking the arrivals of stacked traces.The reliability and eff ectiveness of the proposed method for microseismic phase detection and arrival picking were determined through tests using field data.Arrival results indicate that the proposed method can improve accuracy compared with the traditional energy ratio method.展开更多
Centrifugal microfluidic platforms are highly regarded for their potential in multiplexing and automation,as well as their wide range of applications,especially in separating blood plasma and manipulating two-phase fl...Centrifugal microfluidic platforms are highly regarded for their potential in multiplexing and automation,as well as their wide range of applications,especially in separating blood plasma and manipulating two-phase flows.However,the need to use stroboscopes or high-speed cameras for monitoring these tasks hinders the extensive use of these platforms in research and commercial settings.In this study,we introduce an innovative and cost-effective strategy for using an array of light-dependent resistors(LDRs)as optical sensors in microfluidic devices,particularly centrifugal platforms.While LDRs are attractive for their potential use as photodetectors,their bulky size frequently restricts their ability to provide high-resolution detection in microfluidic systems.Here,we use specific waveguides to direct light beams from narrow apertures onto the surface of LDRs.We integrated these LDRs into electrified Lab-on-a-Disc(eLOD)devices,with wireless connectivity to smartphones and laptops.This enables many applications,such as droplet/particle counting and velocity measurement,concentration analysis,fluidic interface detection in multiphase flows,real-time monitoring of sample volume on centrifugal platforms,and detection of blood plasma separation as an alternative to costly stroboscope devices,microscopes,and high-speed imaging.We used numerical simulations to evaluate various fluids and scenarios,which include rotation speeds of up to 50 rad/s and a range of droplet sizes.For the testbed,we used the developed eLOD device to analyze red blood cell(RBC)deformability and improve the automated detection of sickle cell anemia by monitoring differences in RBC deformability during centrifugation using the sensors’signals.In addition to sickle cell anemia,this device has the potential to facilitate low-cost automated detection of other medical conditions characterized by altered RBC deformability,such as thalassemia,malaria,and diabetes.展开更多
A rapid, simple and selective method based on molecularly imprinted, spin column extraction coupled with fluorescence detection was successfully established for the determination of 2,4-dinitrophenol in serum samples....A rapid, simple and selective method based on molecularly imprinted, spin column extraction coupled with fluorescence detection was successfully established for the determination of 2,4-dinitrophenol in serum samples. The 2,4-dinitrophenol imprinted polymers exhibited highly selective recognition for the template molecule and the maximum adsorption capacity was 138.9 mg/g. The results indicated that when water is used as the loading solution, only 2,4-dinitrophenol could be adsorbed on the spin column without the remaining structural analogs（2-nitrophenol, 4-nitrophenol and phenol）. After eluting with acetonitrile/acetic acid（9/1, v/v）, 2,4-dinitrophenol in serum samples could be determined by using the fluorescence spectrometer, based on the fluorescence enhancement of fluorescein by the template molecule. Under the optimal conditions, the spiked recovery ranged from 95.8% to 103.4% and the detection limit was 1 nmol/L. The results confirmed the reliability and practicality of the protocol and revealed a good perspective of this method for biological sample analysis.展开更多
Fingerprint authentication system is used to verify users' identification according to the characteristics of their fingerprints.However,this system has some security and privacy problems.For example,some artifici...Fingerprint authentication system is used to verify users' identification according to the characteristics of their fingerprints.However,this system has some security and privacy problems.For example,some artificial fingerprints can trick the fingerprint authentication system and access information using real users' identification.Therefore,a fingerprint liveness detection algorithm needs to be designed to prevent illegal users from accessing privacy information.In this paper,a new software-based liveness detection approach using multi-scale local phase quantity(LPQ) and principal component analysis(PCA) is proposed.The feature vectors of a fingerprint are constructed through multi-scale LPQ.PCA technology is also introduced to reduce the dimensionality of the feature vectors and gain more effective features.Finally,a training model is gained using support vector machine classifier,and the liveness of a fingerprint is detected on the basis of the training model.Experimental results demonstrate that our proposed method can detect the liveness of users' fingerprints and achieve high recognition accuracy.This study also confirms that multi-resolution analysis is a useful method for texture feature extraction during fingerprint liveness detection.展开更多
For the isomers of amino benzoic acid, including o-, m-, p-amino benzoic acid, the beneficial effects of using the ionic liquid, l-butyl-3-methylimidazolium tetrafluoroborate （[BMIm][BF4]）, as mobile phase additives...For the isomers of amino benzoic acid, including o-, m-, p-amino benzoic acid, the beneficial effects of using the ionic liquid, l-butyl-3-methylimidazolium tetrafluoroborate （[BMIm][BF4]）, as mobile phase additives on retention behavior and separation were investigated. Chromatographic separation of the o-, m-, p-amino benzoic acid was performed on a reversed-phase C18 column by ultraviolet detection at 245 nm. The effects of several chromatographic parameters, concentrations and pH values of [BMIm][BF4] solutions, methanol concentration and length of alkyl chain on different ionic liquids, on the separation and determination of the isomers were evaluated. The optimized chromatographic conditions were established using an aqueous 0.5 mmol/L [BMIm][BF4] solution （pH 3.0）/methanol （40：60, v/v） as mobile phase without need of gradient eiution, with separation of three amino benzoic acids achieved within four min. The calibration curve showed good linearity over the tested range of 2 mg/L to 120 mg/L for the three isomers with a correlation coefficients of 0.9999. The recoveries of the three amino benzoic acids of spiked components were between 99.8% and 100%. The method has been successfully applied to the determination of p-amino benzoic acid in the pharmaceutical, Bromine Mitag Procaine Injection.展开更多
AIM: Variation in structure-related components in plant products prompted the trend to establish methods, using multiple or total analog analysis, for their effective quality control. However, the general use of routi...AIM: Variation in structure-related components in plant products prompted the trend to establish methods, using multiple or total analog analysis, for their effective quality control. However, the general use of routine quality control is restricted by the limited availability of reference substances. Using an easily available single marker as a reference standard to determine multiple or total analogs should be a practical option. METHOD: In this study, the Ultra-HPLC method was used for the baseline separation of the main components in ginseng extracts. Using a plant chemical component database, ginsenosides in ginseng extracts were identified by Ultra-HPLC-MS analysis. The charged aerosol detection(CAD) system with post-column compensation of the gradient generates a similar response for identical amounts of different analytes, and thus, the content of each ginsenoside in ginseng extracts was determined by comparing the analyte peak area with the reference standard(determination of total analogs by single marker, DTSM). The total ginsenoside content was determined by the summation of reference standard and other ginsenoside components. RESULTS: The results showed that DTSM approaches were available for the determination of total ginsenosides in a high purity ginseng extract because of the removal of impurities. In contrast, DTSM approaches might be suitable for determination of multiple ginsenosides without interference from impurities in the crude ginseng extract. CONCLUSION: Future practical studies similar to the present study should be conducted to verify that DTSM approaches based on CAD with post-column inverse gradient for uniform response are ideal for the quality control of plant products.展开更多
In this paper, we study the topological structure of the singular points of the third order phase locked loop equations with the character of detected phase being g(?) =(1+k)sin?/1+kcos?.
基金National Key Research and Development Program of China(2022YFB2804401)。
文摘An in-pixel histogramming time-to-digital converter(hTDC)based on octonary search and 4-tap phase detection is presented,aiming to improve frame rate while ensuring high precicion.The proposed hTDC is a 12-bit two-step converter consisting of a 6-bit coarse quantization and a 6-bit fine quantization,which supports a time resolution of 120 ps and multiphoton counting up to 2 GHz without a GHz reference frequency.The proposed hTDC is designed in 0.11μm CMOS process with an area consumption of 6900μm^(2).The data from a behavioral-level model is imported into the designed hTDC circuit for simulation verification.The post-simulation results show that the proposed hTDC achieves 0.8%depth precision in 9 m range for short-range system design specifications and 0.2%depth precision in 48 m range for long-range system design specifications.Under 30×10^(3) lux background light conditions,the proposed hTDC can be used for SPAD-based flash LiDAR sensor to achieve a frame rate to 40 fps with 200 ps resolution in 9 m range.
文摘The availability of a tremendous amount of seismic data demands seismological researchers to analyze seismic phases efficiently.Recently,deep learning algorithms exhibit a powerful capability of detecting and picking on P-and S-wave phases.However,it remains a challenge to effeciently process enormous teleseismic phases,which are crucial to probe Earth’s interior structures and their dynamics.In this study,we propose a scheme to detect and pick teleseismic phases,such as seismic phase that reflects off the core-mantle boundary(i.e.,PcP)and that reflects off the inner-core boundary(i.e.,PKiKP),from a seismic dataset in Japan.The scheme consists of three steps:1)latent phase traces are truncated from the whole seismogram with theoretical arrival times;2)latent phases are recognized and evaluated by convolutional neural network(CNN)models;3)arrivals of good or fair phase are picked with another CNN models.The testing detection result on 7386 seismograms shows that the scheme recognizes 92.15%and 94.13%of PcP and PKiKP phases.The testing picking result has a mean absolute error of 0.0742 s and 0.0636 s for the PcP and PKiKP phases,respectively.These seismograms were processed in just 5 min for phase detection and picking,demonstrating the efficiency of the proposed scheme in automatic teleseismic phase analysis.
文摘Surface plasmon resonance (SPR) sensing is an optical method based on evanescent wave.SPR biosensor can detect interaction of label-free biomolecules in real-time.With further development,it can become a research instrument in proteomics.SPR biosensor can be divided intensity measurement and phase measurement,and the latter possesses higher sensitivity than the former one.This paper attempts to summarize the SPR phase detection theory,discuss the major developments,compare the merits and deficiencies of various methods,and look forward to future prospects.
基金This study is jointly sponsored by the Basic Scientific Research Fee of Institute of Geophysics,China Earthquake Administration(DQJB19A0114)the National Natural Science Foundation of China(41804047).
文摘We developed an automatic seismic wave and phase detection software based on PhaseNet,an efficient and highly generalized deep learning neural network for P-and S-wave phase picking.The software organically combines multiple modules including application terminal interface,docker container,data visualization,SSH protocol data transmission and other auxiliary modules.Characterized by a series of technologically powerful functions,the software is highly convenient for all users.To obtain the P-and S-wave picks,one only needs to prepare threecomponent seismic data as input and customize some parameters in the interface.In particular,the software can automatically identify complex waveforms(i.e.continuous or truncated waves)and support multiple types of input data such as SAC,MSEED,NumPy array,etc.A test on the dataset of the Wenchuan aftershocks shows the generalization ability and detection accuracy of the software.The software is expected to increase the efficiency and subjectivity in the manual processing of large amounts of seismic data,thereby providing convenience to regional network monitoring staffs and researchers in the study of Earth's interior.
基金Supported by Knowledge Innovation Program of Chinese Academy of Sciences and National Natural Science Foundation of China (10675142)
文摘The new generation particle accelerator requires a highly stable radio frequency（RF） system. The stability of the RF system is realized by the Low Level RF（LLRF） subsystem which controls the amplitude and phase of the RF signal. The detection of the RF signal＇s amplitude and phase is fundamental to LLRF controls. High-speed ADC（Analog to Digital Converter） ,DAC（Digital to Analog Converter） and FPGA（Field Programmable Gate Array） play very important roles in digital LLRF control systems. This paper describes the implementation of real-time amplitude and phase detection based of the FPGA with an analysis of the main factors that affect the detection accuracy such as jitter,algorithm＇s defects and non-linearity of devices,which is helpful for future work on high precision detection and control.
基金This work was supported by the National Natural Science Foundation of China （No. 91334206）. The authors thank Dr. Jeanne Wynn for her help in the use of English and Dr. Tao Xue for Raman measurement. The authors declare no competing financial interests.
文摘In recent years, surface-enhanced Raman spectroscopy （SERS） has developed rapidly and is used for the detection of molecules and biomolecules in liquids. However, few studies have focused on SERS using a water surface as the substrate. A floating metal film on water is desirable for an enhanced SERS performance. In this work, silver nanopartides （Ag NPs） encased in poly（vinylpyrrolidone） films （Ag-PVP films） were synthesized on the surface of an aqueous solution by room temperature electron reduction. A floating silver film on a water surface was thereby achieved and is reported for the first time. The synthesized Ag-PVP film is an excellent flexible substrate for SERS and has other potential appli- cations. Using the floating silver film as a flexible SERS substrate, 10-11 M of 4-aminothiophenol, 10^-6 M of riboflavin, 10^-9 M of 4-mercaptobenzoic acid, 10^-7 M of 4-mercaptophenol, and 10^-7 M of 4-aminobenzoic acid are identified, demonstrating potential use for the floating substrate in the liquid-phase detection of molecules.
基金supported by the NCN grant UMO-2011/01/B/ST7/00666.
文摘A simple model of the phase-detection autofocus device based on the partially masked sensor pixels is described. The cross-correlation function of the half-images registered by the masked pixels is proposed as a focus function. It is shown that—in such setting—focusing is equivalent to searching of the cross-correlation function maximum. Application of stochastic approximation algorithms to unimodal and non-unimodal focus functions is shortly discussed.
文摘Aim to detect the characteristic weak magnetic field signal against the strong noises background. Methods In combination with a low-pass-filter, the correlation output of magne-* tic sensors between the magnetic field and reference current was utilized to provide a DC output voltage proportional to the applied magnetic induction, computer simulation was* done to investigate the correlation output of the Hall-effect sensors. Results Some analysis results concerning the noise property, harmonic supppression and the sensitivity were given. Conclsion The minimum detection signal of the equipment evolved from the mentioned cor-* relation theory can be 10-6 T. In addition to the DC output, such sensors can also measure the phase of the detected magnetic induction and has good harmonic suppression as well as* noise elimination.
基金supported by the National Natural Science Foundation of China (Grant No. U1304618)the Open Fund of Key Laboratory of Precision Navigation and Timing Technology of Chinese Academy of Sciences(Grant No. 2012PNTT01)+5 种基金the Postdoctoral Grant of China (Grant Nos. 2011M501446, 2012T50798)the Basic and Advanced Technology Research Foundation of Henan Province under Grant (Grant No. 122300410169)The Key Science and Technology Foundation of Henan Province under Grant (Grant No. 132102210180)the Doctor Fund of Zhengzhou University of Light Industry under (Grant No. 2011BSJJ031)the Scientific Research Fund of Zhengzhou University of Light Industry under (Grant No. 2012XJJ009)the Fundamental Research Funds for the Central Universities(Grant No. K5051204003)
文摘According to the time&space conversion relations and different frequency phase detection principle,an ultra-high precision time&frequency measurement method is proposed in this paper.The higher accuracy and stability of the speed of light and electromagnetic signals during the transmission in space or a specific medium enable the measurement of short time interval which uses the coincidence detection of signal’s transmission delay in length.The measurement precision better than 10 picoseconds can be easily obtained.The method develops the length vernier utilizing the stability of signal’s transmission delay,minimizes the fuzzy region of phase coincidence between the standard frequency signal and the measured signal,approaches the best phase coincidences and therefore improves the measurement precision which is higher than the precision provided by the traditional methods based on frequency processing.Besides,the method costs less than the traditional methods and can also solve the problem of the measurement of super-high frequency.Experimental results show the method can improve the measurement precision to 10 12/s in the time&frequency domain.
基金supported by the National Natural Science Foundation of China(61372180)the Young Talent Frontier Project of Institute of Acoustics of Chinese Academy of Sciences(Y454341261)
文摘In order to improve the performance of line spectrum detection,according to the feature that the underwater target radiated noise containing stable line spectrum,the differences of the phase difference between line spectrum and background noise,a weighted line spectrum detection algorithm based on the phase variance is proposed in frequency domain.After phase difference alignment,the phase variance of line spectrum and the phase of background noise,respectively,are small and big in frequency domain,this method utilizes the weighted statistical algorithm to cumulate the frequency spectrum based on the phase variance,which can restrain the background noise disturbance,and enhance the signal to noise ratio（SNR）.The theory analysis and experimental results both verify that the proposed method can well enhance the energy of line spectrum,restrain the energy of background noise,and have better detection performance under lower SNR.
文摘Glycerides are first separated to classes of triglycerides(TGs), diglycerides(DGs) and monoglycerides(MGs) by normal phase HPLC on silica gel column. Individual triglyceride separation is then achieved by non-aqueous reversed phase(NARP) HPLC on C_(18) column with UV detection at 215nm.
基金supported by the National Natural Science Foundation of China(Grant Nos.61177089,61227014,and 60978047)
文摘Phase is one of the most important parameters of electromagnetic waves. It is the phase distribution that determines the propagation, reflection, refraction, focusing, divergence, and coupling features of light, and further affects the intensity distribution. In recent years, the designs of surface plasmon polariton （SPP） devices have mostly been based on the phase modulation and manipulation. Here we demonstrate a phase sensitive multi-parameter heterodyne scanning near-field opti- cal microscope （SNOM） with an aperture probe in the visible range, with which the near field optical phase and amplitude distributions can be simultaneously obtained. A novel architecture combining a spatial optical path and a fiber optical path is employed for stability and flexibility. Two kinds of typical nano-photonic devices are tested with the system. With the phase-sensitive SNOM, the phase and amplitude distributions of any nano-optical field and localized field generated with any SPP nano-structures and irregular phase modulation surfaces can be investigated. The phase distribution and the interference pattern will help us to gain a better understanding of how light interacts with SPP structures and how SPP waves generate, localize, convert, and propagate on an SPP surface. This will be a significant guidance on SPP nano-structure design and optimization.
基金This work has been funded by the National Key Research and Development Project(2017YFC0307605,2017YFC0307702),National Science and Technology Major Project of China(No.2017ZX05008-008)and State Key Project(2016ZX05051004).The authors also thank Sinopec Oilfield Service Jianghan Corporation for providing the data and support and express their gratitude to the reviewers for their constructive comments.
文摘Microseismic phase detection and arrival picking are critical steps in the processing of hydraulic fracturing microseismic monitoring data.As the signal-to-noise ratios of P-and S-waves diff er because of the infl uence of focal mechanisms,geometry,and background noise,diffi culties are introduced in the eff ective discrimination of seismic phases and the accurate acquisition of arrivals in conventional processing methods.In this paper,we propose a method for identifying microseismic phase arrival time by comprehensively analyzing the variation of moveout curves and combining the intra-event waveform similarities with the energy ratio of multitrace signals.First,a curve-fi tting formula is constructed with perforation arrivals,and event detection is achieved by adopting an energy-weighted similarity coeffi cient that seeks plausible fi tting curves with a sliding time window in continuous microseismic recordings.Then,the P-and S-waves are separated by the fitting parameters.The known arrival time trend of the microseismic phase is employed to calculate residual time corrections.Finally,the accurate arrival results of the microseismic phases can be obtained by picking the arrivals of stacked traces.The reliability and eff ectiveness of the proposed method for microseismic phase detection and arrival picking were determined through tests using field data.Arrival results indicate that the proposed method can improve accuracy compared with the traditional energy ratio method.
基金funding from CONAHCYT in the form of a scholarship as a member of the National System of Researchers(CVU:969467)the financial support of the FEMSA foundation.
文摘Centrifugal microfluidic platforms are highly regarded for their potential in multiplexing and automation,as well as their wide range of applications,especially in separating blood plasma and manipulating two-phase flows.However,the need to use stroboscopes or high-speed cameras for monitoring these tasks hinders the extensive use of these platforms in research and commercial settings.In this study,we introduce an innovative and cost-effective strategy for using an array of light-dependent resistors(LDRs)as optical sensors in microfluidic devices,particularly centrifugal platforms.While LDRs are attractive for their potential use as photodetectors,their bulky size frequently restricts their ability to provide high-resolution detection in microfluidic systems.Here,we use specific waveguides to direct light beams from narrow apertures onto the surface of LDRs.We integrated these LDRs into electrified Lab-on-a-Disc(eLOD)devices,with wireless connectivity to smartphones and laptops.This enables many applications,such as droplet/particle counting and velocity measurement,concentration analysis,fluidic interface detection in multiphase flows,real-time monitoring of sample volume on centrifugal platforms,and detection of blood plasma separation as an alternative to costly stroboscope devices,microscopes,and high-speed imaging.We used numerical simulations to evaluate various fluids and scenarios,which include rotation speeds of up to 50 rad/s and a range of droplet sizes.For the testbed,we used the developed eLOD device to analyze red blood cell(RBC)deformability and improve the automated detection of sickle cell anemia by monitoring differences in RBC deformability during centrifugation using the sensors’signals.In addition to sickle cell anemia,this device has the potential to facilitate low-cost automated detection of other medical conditions characterized by altered RBC deformability,such as thalassemia,malaria,and diabetes.
基金supported by National Key Technology R&D Program in the 11th Five-Year Plan of China(No.2009BADB9B02)
文摘A rapid, simple and selective method based on molecularly imprinted, spin column extraction coupled with fluorescence detection was successfully established for the determination of 2,4-dinitrophenol in serum samples. The 2,4-dinitrophenol imprinted polymers exhibited highly selective recognition for the template molecule and the maximum adsorption capacity was 138.9 mg/g. The results indicated that when water is used as the loading solution, only 2,4-dinitrophenol could be adsorbed on the spin column without the remaining structural analogs（2-nitrophenol, 4-nitrophenol and phenol）. After eluting with acetonitrile/acetic acid（9/1, v/v）, 2,4-dinitrophenol in serum samples could be determined by using the fluorescence spectrometer, based on the fluorescence enhancement of fluorescein by the template molecule. Under the optimal conditions, the spiked recovery ranged from 95.8% to 103.4% and the detection limit was 1 nmol/L. The results confirmed the reliability and practicality of the protocol and revealed a good perspective of this method for biological sample analysis.
基金supported by the NSFC (U1536206,61232016,U1405254,61373133, 61502242)BK20150925the PAPD fund
文摘Fingerprint authentication system is used to verify users' identification according to the characteristics of their fingerprints.However,this system has some security and privacy problems.For example,some artificial fingerprints can trick the fingerprint authentication system and access information using real users' identification.Therefore,a fingerprint liveness detection algorithm needs to be designed to prevent illegal users from accessing privacy information.In this paper,a new software-based liveness detection approach using multi-scale local phase quantity(LPQ) and principal component analysis(PCA) is proposed.The feature vectors of a fingerprint are constructed through multi-scale LPQ.PCA technology is also introduced to reduce the dimensionality of the feature vectors and gain more effective features.Finally,a training model is gained using support vector machine classifier,and the liveness of a fingerprint is detected on the basis of the training model.Experimental results demonstrate that our proposed method can detect the liveness of users' fingerprints and achieve high recognition accuracy.This study also confirms that multi-resolution analysis is a useful method for texture feature extraction during fingerprint liveness detection.
基金supported by the Natural Science Foundation of Heilongjiang Province (No. B201307)
文摘For the isomers of amino benzoic acid, including o-, m-, p-amino benzoic acid, the beneficial effects of using the ionic liquid, l-butyl-3-methylimidazolium tetrafluoroborate （[BMIm][BF4]）, as mobile phase additives on retention behavior and separation were investigated. Chromatographic separation of the o-, m-, p-amino benzoic acid was performed on a reversed-phase C18 column by ultraviolet detection at 245 nm. The effects of several chromatographic parameters, concentrations and pH values of [BMIm][BF4] solutions, methanol concentration and length of alkyl chain on different ionic liquids, on the separation and determination of the isomers were evaluated. The optimized chromatographic conditions were established using an aqueous 0.5 mmol/L [BMIm][BF4] solution （pH 3.0）/methanol （40：60, v/v） as mobile phase without need of gradient eiution, with separation of three amino benzoic acids achieved within four min. The calibration curve showed good linearity over the tested range of 2 mg/L to 120 mg/L for the three isomers with a correlation coefficients of 0.9999. The recoveries of the three amino benzoic acids of spiked components were between 99.8% and 100%. The method has been successfully applied to the determination of p-amino benzoic acid in the pharmaceutical, Bromine Mitag Procaine Injection.
基金supported by the National Natural Science Foundation of China(81303246)the Jiangsu Provincial Natural Science Foundation of China(BK2011815)+1 种基金the ‘Qing Lan’ Project from Jiangsu Provincial Framework Teacher Support Schemethe Projects of priority-discipline for colleges and universities of Jiangsu Province
文摘AIM: Variation in structure-related components in plant products prompted the trend to establish methods, using multiple or total analog analysis, for their effective quality control. However, the general use of routine quality control is restricted by the limited availability of reference substances. Using an easily available single marker as a reference standard to determine multiple or total analogs should be a practical option. METHOD: In this study, the Ultra-HPLC method was used for the baseline separation of the main components in ginseng extracts. Using a plant chemical component database, ginsenosides in ginseng extracts were identified by Ultra-HPLC-MS analysis. The charged aerosol detection(CAD) system with post-column compensation of the gradient generates a similar response for identical amounts of different analytes, and thus, the content of each ginsenoside in ginseng extracts was determined by comparing the analyte peak area with the reference standard(determination of total analogs by single marker, DTSM). The total ginsenoside content was determined by the summation of reference standard and other ginsenoside components. RESULTS: The results showed that DTSM approaches were available for the determination of total ginsenosides in a high purity ginseng extract because of the removal of impurities. In contrast, DTSM approaches might be suitable for determination of multiple ginsenosides without interference from impurities in the crude ginseng extract. CONCLUSION: Future practical studies similar to the present study should be conducted to verify that DTSM approaches based on CAD with post-column inverse gradient for uniform response are ideal for the quality control of plant products.
文摘In this paper, we study the topological structure of the singular points of the third order phase locked loop equations with the character of detected phase being g(?) =(1+k)sin?/1+kcos?.
