The excellent response characteristics and detection sensitivity with much lower operational cost and the capability to discriminate between the isomer of some monoaromatic hydrocarbons （MAHCs） make differential opt...The excellent response characteristics and detection sensitivity with much lower operational cost and the capability to discriminate between the isomer of some monoaromatic hydrocarbons （MAHCs） make differential optical absorption spectroscopy （DOAS） a powerful tool to trace concentration variation of MAHCs. But due to the similarity in chemical structure, those MAHCs have the similar overlapped characteristic absorption structures, which make the selection of instrumental parameter critical to the accurate detection of MAHCs. Firstly, the spectral resolution used in DOAS system determines the nonlinear absorption of O2 and the mass dependence of characteristic absorption structure; thereby it determines the effect of elimination error of O2 absorption in the atmospheric spectra for the detection of MAHCs. Secondly, spectral resolution determines the differential absorption characteristics of twelve MAHCs representing major constituents in technical solvents used in the automobile industry and the interference of spectral overlapping. Thirdly, the spectral resolution determines the sensitivity, time resolution and linear range. So the spectral resolution range with the best ratio of signal to noise is used to determine the most suitable spectral resolution range, as well as the spectral resolution range that ensure the characteristic absorption structure of MAHCs and the minimization of O2 absorption interference. Finally, 0.15-0.16 nm （FWHM： full width at half maximum） is assumed to be closest to the optimum spectral resolution and it is confirmed by the results of practical measurement of MAHCs by DOAS.展开更多
High Spatial and Spectral Resolution(HSSR)remote-sensing images can provide rich spectral bands and detailed ground information,but there is a relative lack of research on this new type of remote-sensing data.Although...High Spatial and Spectral Resolution(HSSR)remote-sensing images can provide rich spectral bands and detailed ground information,but there is a relative lack of research on this new type of remote-sensing data.Although there are already some HSSR datasets for deep learning model training and testing,the data volume of these datasets is small,resulting in low classification accuracy and weak generalization ability of the trained models.In this paper,an HSSR dataset Luojia-HSSR is constructed based on aerial hyperspectral imagery of southern Shenyang City of Liaoning Province in China.To our knowledge,it is the largest HSSR dataset to date,with 6438 pairs of 256×256 sized samples(including 3480 pairs in the training set,2209 pairs in the test set,and 749 pairs in the validation set),covering area of 161 km2 with spatial resolution 0.75 m,249 Visible and Near-Infrared(VNIR)spectral bands,and corresponding to 23 classes of field-validated ground coverage.It is an ideal experimental data for spatial-spectral feature extraction.Furthermore,a new deep learning model 3D-HRNet for interpreting HSSR images is proposed.The conv-neck in HRNet is modified to better mine the spatial information of the images.Then,a 3D convolution module with attention mechanism is designed to capture the global-local fine spectral information simultaneously.Subsequently,the 3D convolution is inserted into the HRNet to optimize the performance.The experiments show that the 3D-HRNet model has good interpreting ability for the Luojia-HSSR dataset with the Frequency Weighted Intersection over Union(FWIoU)reaching 80.54%,indicating that the Luojia-HSSR dataset constructed in this paper and the proposed 3D-HRnet model have good applicable prospects for processing HSSR remote sensing images.展开更多
Purpose:Our study aims to compare speech understanding in noise and spectral-temporal resolution skills with regard to the degree of hearing loss,age,hearing aid use experience and gender of hearing aid users.Methods:...Purpose:Our study aims to compare speech understanding in noise and spectral-temporal resolution skills with regard to the degree of hearing loss,age,hearing aid use experience and gender of hearing aid users.Methods:Our study included sixty-eight hearing aid users aged between 40-70 years,with bilateral mild and moderate symmetrical sensorineural hearing loss.Random gap detection test,Turkish matrix test and spectral-temporally modulated ripple test were implemented on the participants with bilateral hearing aids.The test results acquired were compared statistically according to different variables and the correlations were examined.Results:No statistically significant differences were observed for speech-in-noise recognition,spectraltemporal resolution among older and younger adults in hearing aid users(p>0.05).There wasn’t found a statistically significant difference among test outcomes as regards different hearing loss degrees(p>0.05).Higher performances were obtained in terms of temporal resolution in male participants and participants with more hearing aid use experience(p<0.05).Significant correlations were obtained between the results of speech-in-noise recognition,temporal resolution and spectral resolution tests performed with hearing aids(p<0.05).Conclusion:Our study findings emphasized the importance of regular hearing aid use and it showed that some auditory skills can be improved with hearing aids.Observation of correlations among the speechin-noise recognition,temporal resolution and spectral resolution tests have revealed that these skills should be evaluated as a whole to maximize the patient’s communication abilities.展开更多
One of the crucial problems in study on the middle atmosphere is to determine the concentration and distribution of some trace gases.In this aspect,sounding methods with high spectral resolution have been developed by...One of the crucial problems in study on the middle atmosphere is to determine the concentration and distribution of some trace gases.In this aspect,sounding methods with high spectral resolution have been developed by many scientists.Some major trace gases and their spectral characteristics,space-borne limb method for determination of trace gases in the middle atmosphere are introduced,requirements for used methods and instruments,development and challenge encountered by sounding of trace gases with high spectral resolution are discussed in this paper.展开更多
Using infrared sensors to detect ice clouds in different atmospheric layers is still a challenge.The different scattering and absorption properties of longwave and shortwave infrared channels can be utilized to fulfil...Using infrared sensors to detect ice clouds in different atmospheric layers is still a challenge.The different scattering and absorption properties of longwave and shortwave infrared channels can be utilized to fulfill this purpose.In this study,the release of Suomi-NPP Cross-track Infrared Sounder(Cr IS)full spectrum resolution is used to select and pair channels from longwave(~15μm)and shortwave(~4.3μm)CO2 absorption bands under stricter conditions,so as to better detect ice clouds.Besides,the differences of the weighting function peaks and cloud insensitive level altitudes of the paired channels are both within 50 h Pa so that the variances due to atmospheric conditions can be minimized.The training data of clear sky are determined by Visible Infrared Imaging Radiometer Suite(VIIRS)cloud mask product and used to find the linear relationship between the paired longwave and shortwave CO2 absorption channels.From the linear relationship,the so-called cloud emission and scattering index(CESI)is derived to detect ice clouds.CESI clearly captures the center and the ice cloud features of the Super Typhoon Hato located above 415 h Pa.Moreover,the CESI distributions agree with cloud top pressure from the VIIRS in both daytime and nighttime in different atmospheric layers.展开更多
In recent decades,materials science has experienced rapid development and posed increasingly high requirements for the characterizations of structures,properties,and performances.Herein,we report on our recent establi...In recent decades,materials science has experienced rapid development and posed increasingly high requirements for the characterizations of structures,properties,and performances.Herein,we report on our recent establishment of a multi-domain(energy,space,time)highresolution platform for integrated spectroscopy and microscopy characterizations,offering an unprecedented way to analyze materials in terms of spectral(energy)and spatial mapping as well as temporal evolution.We present several proof-of-principle results collected on this platform,including in-situ Raman imaging(high-resolution Raman,polarization Raman,low-wavenumber Raman),time-resolved photoluminescence imaging,and photoelectrical performance imaging.It can be envisioned that our newly established platform would be very powerful and effective in the multi-domain high-resolution characterizations of various materials of photoelectrochemical importance in the near future.展开更多
Integrated photonic spectrographs could provide a new generation of low-cost,highly integrated,high-performance optical terminal instruments for astronomical observations.However,these spectrographs still face the cha...Integrated photonic spectrographs could provide a new generation of low-cost,highly integrated,high-performance optical terminal instruments for astronomical observations.However,these spectrographs still face the challenge of high spectral resolution.In this Letter,we demonstrate a cascaded phase-modulated waveguide array(CPMWA)spectrograph,with designed and measured spectral resolutions of 100,000 and 68,000,respectively.A spectral reconstruction method is proposed to minimize the influence of the phase error induced during the chip fabrication process and increase the spectral contrast to 20 dB.This type of spectrograph demonstrates promising potential for high-resolution spectrum observations in astronomy.展开更多
At present, heavy metal pollution in food occurs frequently, which requires a novel method for rapid detection. Laser induced breakdown spectroscopy （LIBS） is a new technique for rapid and environmental friendly det...At present, heavy metal pollution in food occurs frequently, which requires a novel method for rapid detection. Laser induced breakdown spectroscopy （LIBS） is a new technique for rapid and environmental friendly detection, but it lacks high sensitivity and stability which restrict its development. In this study, Cr-polluted infant milk powder was used as experimental material to explore the feasibility of the application of LIBS technique in food safety detection. Aiming at improving the precision and accuracy of Cr detection by LIBS technique, LIBS spectra of samples were collected by a spectrometer with an intensified charge-cou- pled device （ICCD） using three gratings with different resolutions to comprehensively compare and analyze the stability, sensitivity and quantitative analysis accura- cy of LIBS detection. The results showed that average relative standard deviation （RSD） of LIBS spectral intensity was below 10%, indicating good stability. LIBS signals were collected by three gratings for quantitative analysis, and the results demonstrated that the linear correlation coefficient R2 of fitting curves was 0. 248 87, 0.903 12 and 0.992 81, respectively; the relative errors between actual and predicted concentrations were 38.23%, 8.84% and 7.43%, respectively, indicating that gratings with higher resolutions could lead to higher linear correlation coefficient and better detection accuracy. According to the results, high-resolu- tion spectrometer could significantly improve the accuracy of LIBS detection of Cr concentration in milk powder, suggesting that it is feasible to detect heavy metals in food by LIBS technique with the improvement of core device performance.展开更多
The primary goal of this report is to describe the operational concepts of NASA’s ACTIVATE mission. ACTIVATE hopes to improve the understanding of aerosol dispersion and models, provide accurate data for aerosols’ c...The primary goal of this report is to describe the operational concepts of NASA’s ACTIVATE mission. ACTIVATE hopes to improve the understanding of aerosol dispersion and models, provide accurate data for aerosols’ characterization and ozone profiles, and establish knowledge of the relationships between aerosols and water. ACTIVATE’s science objectives are to quantify Na-CCN-Nd relationships and reduce uncertainty in model cloud droplet activation parameterizations, improve process-level understanding and model representation of factors governing cloud micro/macro-physical properties and how they couple with cloud effects on aerosol, plus assess advanced remote sensing capabilities for retrieving aerosol and cloud properties related to aerosol-cloud interactions. ACTIVATE utilizes the fixed-wing B-200 King Air to collect data. Data collected by ACTIVATE is highly relevant for meteorologists and environmental scientists looking to understand more about aerosol-cloud formations. Finally, ACTIVATE is a 5-year mission spanning from January 2019 to December 2023 and has used, and will continue to use, instruments such as the High Spectral Resolution Lidar-2 (HSRL-2), the Research Scanning Polarimeter (RSP), and the Diode Laser Hygrometer (DLH).展开更多
Windowing applied to a given signal is a technique commonly used in signal processing in order to reduce spectral leakage in a signal with many data. Several windows are well known: hamming, hanning, beartlett, etc. T...Windowing applied to a given signal is a technique commonly used in signal processing in order to reduce spectral leakage in a signal with many data. Several windows are well known: hamming, hanning, beartlett, etc. The selection of a window is based on its spectral characteristics. Several papers that analyze the amplitude and width of the lobes that appear in the spectrum of various types of window have been published. This is very important because the lobes can hide information on the frequency components of the original signal, in particular when frequency components are very close to each other. In this paper it is shown that the size of the window can also have an impact in the spectral information. Until today, the size of a window has been chosen in a subjective way. As far as we know, there are no publications that show how to determine the minimum size of a window. In this work the frequency interval between two consecutive values of a Fourier Transform is considered. This interval determines if the sampling frequency and the number of samples are adequate to differentiate between two frequency components that are very close. From the analysis of this interval, a mathematical inequality is obtained, that determines in an objective way, the minimum size of a window. Two examples of the use of this criterion are presented. The results show that the hiding of information of a signal is due mainly to the wrong choice of the size of the window, but also to the relative amplitude of the frequency components and the type of window. Windowing is the main tool used in spectral analysis with nonparametric periodograms. Until now, optimization was based on the type of window. In this paper we show that the right choice of the size of a window assures on one hand that the number of data is enough to resolve the frequencies involved in the signal, and on the other, reduces the number of required data, and thus the processing time, when very long files are being analyzed.展开更多
The surface vegetation condition has been operationally monitored from space for many years by the Advanced Very High Resolution Radiometer(AVHRR) and the Moderate Resolution Imaging Spectroradiometer(MODIS) instrumen...The surface vegetation condition has been operationally monitored from space for many years by the Advanced Very High Resolution Radiometer(AVHRR) and the Moderate Resolution Imaging Spectroradiometer(MODIS) instruments. As these instruments are close to the end of their design life, the surface vegetation products are required by many users from the new satellite missions. The MEdium Resolution Spectral Imager-Ⅱ(MERSI-Ⅱ) onboard the Fengyun(FY) satellite(FY-3 series;FY-3 D) is used to retrieve surface vegetation parameters. First, MERSI-Ⅱ solar channel measurements at the red and near-infrared(NIR) bands at the top of atmosphere(TOA) are corrected to the surface reflectances at the top of canopy(TOC) by removing the contributions of scattering and absorption of molecules and aerosols. The normalized difference vegetation index(NDVI) at both the TOA and TOC is then produced by using the same algorithms as the MODIS and AVHRR. The MERSI-Ⅱ enhanced VI(EVI) at the TOC is also developed. The MODIS technique of compositing the NDVI at various timescales is applied to MERSI-Ⅱ to generate the gridded products at different resolutions. The MERSI-Ⅱ VI products are consistent with the MODIS data without systematic biases. Compared to the current MERSI-Ⅱ EVI generated from the ground operational system, the MERSI-Ⅱ EVI from this study has a much better agreement with MODIS after atmospheric correction.展开更多
In this paper,a thin cloud removal method was put forward based on the linear relationships between the thin cloud reflectance in the channels from 0.4 μm to 1.0 μm and 1.38 μm.Channels of 0.66 μm,0.86 μm and 1....In this paper,a thin cloud removal method was put forward based on the linear relationships between the thin cloud reflectance in the channels from 0.4 μm to 1.0 μm and 1.38 μm.Channels of 0.66 μm,0.86 μm and 1.38 μm were chosen to extract the water body information under the thin cloud.Two study cases were selected to validate the thin cloud removal method.One case was applied with the Earth Observation System Moderate Resolution Imaging Spectroradiometer(EOS/MODIS) data,and the other with the Medium Resolution Spectral Imager(MERSI) and Visible and Infrared Radiometer(VIRR) data from Fengyun-3A(FY-3A).The test results showed that thin cloud removal method did not change the reflectivity of the ground surface under the clear sky.To the area contaminated by the thin cloud,the reflectance decreased to be closer to the reference reflectance under the clear sky after the thin cloud removal.The spatial distribution of the water body area could not be extracted before the thin cloud removal,while water information could be easily identified by using proper near infrared channel threshold after removing the thin cloud.The thin cloud removal method could improve the image quality and water body extraction precision effectively.展开更多
Obtaining continuous and high-quality soil moisture(SM) data is important in scientific research and applications,especially for agriculture, meteorology, and environmental monitoring. With the continuously increasing...Obtaining continuous and high-quality soil moisture(SM) data is important in scientific research and applications,especially for agriculture, meteorology, and environmental monitoring. With the continuously increasing number of artificial satellites in China, the acquisition of SM data from remote sensing images has received increasing attention.In this study, we constructed an SM inversion model by using a deep belief network(DBN) to extract SM data from Fengyun-3 D(FY-3 D) Medium Resolution Spectral Imager-Ⅱ(MERSI-Ⅱ) imagery;we named this model SM-DBN.The SM-DBN consists of two subnetworks: one for temperature and the other for SM. In the temperature subnetwork, bands 1, 2, 3, 4, 24, and 25 of the FY-3 D MERSI-Ⅱ imagery, which are relevant to temperature, were used as inputs while land surface temperatures(LST) obtained from ground stations were used as the expected output value when training the model. In the SM subnetwork, the input data included LSTs generated from the temperature subnetwork, normalized difference vegetation index(NDVI), and enhanced vegetation index(EVI);and the SM data obtained from ground stations were used as the expected outputs. We selected the Ningxia Hui Autonomous Region of China as the study area and used selected MERSI-Ⅱ images and in-situ observation station data from 2018 to 2019 to develop our dataset. The results of the SM-DBN were validated by using in-situ SM data as a reference, and its performance was also compared with those of the linear regression(LR) and back propagation(BP) neural network models. The overall accuracy of these models was measured by using the root mean square error(RMSE) of the differences between the model results and in-situ SM observation data. The RMSE of the LR, BP neural network, and SM-DBN models were 0.101, 0.083, and 0.032, respectively. These results suggest that the SM-DBN model significantly outperformed the other two models.展开更多
Xiao-Xu-Ming decoction（XXMD） was a traditional Chinese prescription and first recorded in ＂Bei Ji Qian Jin Yao Fang＂.It has been widely used to treat theoplegia and the sequel of theoplegia in China.In the present...Xiao-Xu-Ming decoction（XXMD） was a traditional Chinese prescription and first recorded in ＂Bei Ji Qian Jin Yao Fang＂.It has been widely used to treat theoplegia and the sequel of theoplegia in China.In the present work,high-performance liquid chromatography coupled with high resolution mass spectrometry（HPLC-HRMS） combined with the mass spectral tree similarity filter technique（MTSF）was used to rapidly discover and identify the compounds of the active fraction of XXMD.A total of 3362 compounds were automatically detected by HPLC-HRMS,and final 68 compounds were identified in the active fraction of XXMD.including 14 templated compounds（reference compounds）,50 related compounds fished by MTSF technique,and 4 unrelated compounds identified by manual method.This study successfully applied MTSF technology for the first time to discover and identify the components of Chinese prescription.The results demonstrated that MTSF technique should be useful to the discovery and identification of compounds in Chinese prescription.This study also proved that MTSF can be applied to the targeted phytochemical separation.展开更多
High-Q nanophotonic devices hold great importance in both fundamental research and engineering applications.Their ability to provide high spectral resolution and enhanced light-matter interactions makes them promising...High-Q nanophotonic devices hold great importance in both fundamental research and engineering applications.Their ability to provide high spectral resolution and enhanced light-matter interactions makes them promising in various fields such as sensing,filters,lasing,nonlinear optics,photodetection,coherent thermal emission,and laser stealth.While Q-factors as large as 109 have been achieved experimentally in on-chip microresonators,these modes are excited through near-field coupling of optical fibers.Exciting high-Q modes via free-space light presents a significant challenge primarily due to the larger fabrication area and more lossy channels associated with free-space nanophotonic devices.This Review provides a comprehensive overview of the methods employed to achieve high-Q modes,highlights recent research progress and applications,and discusses the existing challenges as well as the prospects in the field of free-space high-Q nanophotonics.展开更多
The burgeoning field of computational spectrometers is rapidly advancing,providing a pathway to highly miniaturized,on-chip systems for in-situ or portable measurements.The performance of these systems is typically li...The burgeoning field of computational spectrometers is rapidly advancing,providing a pathway to highly miniaturized,on-chip systems for in-situ or portable measurements.The performance of these systems is typically limited in its encoder section.The response matrix is largely compromised with redundancies,due to the periodic intensity or overly smooth responses.As such,the inherent interdependence among the physical size,resolution,and bandwidth of spectral encoders poses a challenge to further miniaturization progress.Achieving high spectral resolution necessitates a long optical path length,leading to a larger footprint required for sufficient spectral decorrelation,resulting in a limited detectable free-spectral range(FSR).Here,we report a groundbreaking ultraminiaturized disordered photonic molecule spectrometer that surpasses the resolution-bandwidth-footprint metric of current spectrometers.This computational spectrometer utilizes complicated electromagnetic coupling to determinately generate quasi-random spectral response matrices,a feature absents in other state-of-the-art systems,fundamentally overcoming limitations present in the current technologies.This configuration yields an effectively infinite FSR while upholding a high Q-factor(>7.74×10^(5)).Through dynamic manipulation of photon frequency,amplitude,and phase,a broad operational bandwidth exceeding 100 nm can be attained with an ultra-high spectral resolution of 8 pm,all encapsulated within an ultra-compact footprint measuring 70×50μm^(2).The disordered photonic molecule spectrometer is constructed on a CMOS-compatible integrated photonics platform,presenting a pioneering approach for high-performance and highly manufacturable miniaturized spectroscopy.展开更多
Dual-comb spectroscopy(DCS)with few-GHz tooth spacing that provides a better trade-off between spectral resolution and refresh rate is a powerful tool for measuring and analyzing rapidly evolving transient events.Desp...Dual-comb spectroscopy(DCS)with few-GHz tooth spacing that provides a better trade-off between spectral resolution and refresh rate is a powerful tool for measuring and analyzing rapidly evolving transient events.Despite such an exciting opportunity,existing technologies compromise either the spectral resolution or refresh rate,leaving few-GHz DCS with robust design largely unmet for frontier applications.In this work,we demonstrate a novel GHz DCS by exploring the multimode interference-mediated spectral filtering effect in an all-fiber ultrashort cavity configuration.The GHz single-cavity all-fiber dual-comb source is seeded by a dual-wavelength mode-locked fiber laser operating at fundamental repetition rates of about 1.0 GHz differing by 148 kHz,which has an excellent stability in the free-running state that the Allan deviation is only 101.7 mHz for an average time of 1 s.Thanks to the large repetition rate difference between the asynchronous dichromatic pulse trains,the GHz DCS enables a refresh time as short as 6.75μs,making it promising for studying nonrepeatable transient phenomena in real time.To this end,the practicality of the present GHz DCS is validated by successfully capturing the‘shock waves’of balloon and firecracker explosions outdoors.This GHz single-cavity all-fiber dual-comb system promises a noteworthy improvement in acquisition speed and reliability without sacrificing measurement accuracy,anticipated as a practical tool for high-speed applications.展开更多
In the domain of spectroscopy,miniaturization efforts often face significant challenges,particularly in achieving high spectral resolution and precise construction.Here,we introduce a computational spectrometer powere...In the domain of spectroscopy,miniaturization efforts often face significant challenges,particularly in achieving high spectral resolution and precise construction.Here,we introduce a computational spectrometer powered by a nonlinear photonic memristor with a WSe2 homojunction.This approach overcomes traditional limitations,such as constrained Fermi level tunability,persistent dark current,and limited photoresponse dimensionality through dynamic energy band modulation driven by palladium(Pd)ion migration.The critical role of Pd ion migration is thoroughly supported by first-principles calculations,numerical simulations,and experimental verification,demonstrating its effectiveness in enhancing device performance.Additionally,we integrate this dynamic modulation with a specialized nonlinear neural network tailored to address the memristor's inherent nonlinear photoresponse.This combination enables our spectrometer to achieve an exceptional peak wavelength accuracy of o.18 nm and a spectral resolution of 2 nm within the 630-640 nm range.This development marks a significant advancement in the creation of compact,high-effciency spectroscopic instruments and offers a versatile platform for applications across diverse material systems.展开更多
A new high spectral resolution crystal spectrometer is designed to measure very low emissive X-ray spectra of laser-produced plasma in 0.5-0.9 nm range. A large open aperture （30 ×20 （mm）） mica （002） spheri...A new high spectral resolution crystal spectrometer is designed to measure very low emissive X-ray spectra of laser-produced plasma in 0.5-0.9 nm range. A large open aperture （30 ×20 （mm）） mica （002） spherically bent crystal with curvature radius R = 380 mm is used as dispersive and focusing element. The imaging plate is employed to obtain high spectral resolution with effective area of 30 × 80 （mm）. The long designed path of the X-ray spectrometer beam is 980 mm from the source to the detector via the crystal. Experiment is carried out at a 20-J laser facility. X-ray spectra in an absolute intensity scale is obtained from Al laserproduced plasmas created by laser energy of 6.78 J. Samples of spectra obtained with spectral resolution of up to E/△E - 1500 are presented. The results clearly show that the device is good to diagnose laser high-density plasmas.展开更多
Knowledge of the temporal-spatial distribution of water content in atmosphere and water phase change in cloud is important for atmospheric study.For this purpose,we have developed a high resolution full-spectrum water...Knowledge of the temporal-spatial distribution of water content in atmosphere and water phase change in cloud is important for atmospheric study.For this purpose,we have developed a high resolution full-spectrum water Raman lidar that can collect Raman signals from ice,water droplets and water vapor simultaneously.A double-grating polychromator and a 32-channel photomultiplier-tube detector are used to obtain a spectral resolution of-0.19 nm in the full Raman spectrum range of water,Preliminary observations present the water Raman spectrum characteristics of both the mixed-phase cloud and humid air under cloudless condition.展开更多
文摘The excellent response characteristics and detection sensitivity with much lower operational cost and the capability to discriminate between the isomer of some monoaromatic hydrocarbons （MAHCs） make differential optical absorption spectroscopy （DOAS） a powerful tool to trace concentration variation of MAHCs. But due to the similarity in chemical structure, those MAHCs have the similar overlapped characteristic absorption structures, which make the selection of instrumental parameter critical to the accurate detection of MAHCs. Firstly, the spectral resolution used in DOAS system determines the nonlinear absorption of O2 and the mass dependence of characteristic absorption structure; thereby it determines the effect of elimination error of O2 absorption in the atmospheric spectra for the detection of MAHCs. Secondly, spectral resolution determines the differential absorption characteristics of twelve MAHCs representing major constituents in technical solvents used in the automobile industry and the interference of spectral overlapping. Thirdly, the spectral resolution determines the sensitivity, time resolution and linear range. So the spectral resolution range with the best ratio of signal to noise is used to determine the most suitable spectral resolution range, as well as the spectral resolution range that ensure the characteristic absorption structure of MAHCs and the minimization of O2 absorption interference. Finally, 0.15-0.16 nm （FWHM： full width at half maximum） is assumed to be closest to the optimum spectral resolution and it is confirmed by the results of practical measurement of MAHCs by DOAS.
基金supported by the Major Program of the National Natural Science Foundation of China[grant number 92038301]The research was also supported by the National Natural Science Foundation of China[grant number 41971295]+1 种基金the Foundation for Innovative Research Groups of the Natural Science Foundation of Hubei Province[grant number 2020CFA003]the Special Fund of Hubei Luojia Laboratory.
文摘High Spatial and Spectral Resolution(HSSR)remote-sensing images can provide rich spectral bands and detailed ground information,but there is a relative lack of research on this new type of remote-sensing data.Although there are already some HSSR datasets for deep learning model training and testing,the data volume of these datasets is small,resulting in low classification accuracy and weak generalization ability of the trained models.In this paper,an HSSR dataset Luojia-HSSR is constructed based on aerial hyperspectral imagery of southern Shenyang City of Liaoning Province in China.To our knowledge,it is the largest HSSR dataset to date,with 6438 pairs of 256×256 sized samples(including 3480 pairs in the training set,2209 pairs in the test set,and 749 pairs in the validation set),covering area of 161 km2 with spatial resolution 0.75 m,249 Visible and Near-Infrared(VNIR)spectral bands,and corresponding to 23 classes of field-validated ground coverage.It is an ideal experimental data for spatial-spectral feature extraction.Furthermore,a new deep learning model 3D-HRNet for interpreting HSSR images is proposed.The conv-neck in HRNet is modified to better mine the spatial information of the images.Then,a 3D convolution module with attention mechanism is designed to capture the global-local fine spectral information simultaneously.Subsequently,the 3D convolution is inserted into the HRNet to optimize the performance.The experiments show that the 3D-HRNet model has good interpreting ability for the Luojia-HSSR dataset with the Frequency Weighted Intersection over Union(FWIoU)reaching 80.54%,indicating that the Luojia-HSSR dataset constructed in this paper and the proposed 3D-HRnet model have good applicable prospects for processing HSSR remote sensing images.
文摘Purpose:Our study aims to compare speech understanding in noise and spectral-temporal resolution skills with regard to the degree of hearing loss,age,hearing aid use experience and gender of hearing aid users.Methods:Our study included sixty-eight hearing aid users aged between 40-70 years,with bilateral mild and moderate symmetrical sensorineural hearing loss.Random gap detection test,Turkish matrix test and spectral-temporally modulated ripple test were implemented on the participants with bilateral hearing aids.The test results acquired were compared statistically according to different variables and the correlations were examined.Results:No statistically significant differences were observed for speech-in-noise recognition,spectraltemporal resolution among older and younger adults in hearing aid users(p>0.05).There wasn’t found a statistically significant difference among test outcomes as regards different hearing loss degrees(p>0.05).Higher performances were obtained in terms of temporal resolution in male participants and participants with more hearing aid use experience(p<0.05).Significant correlations were obtained between the results of speech-in-noise recognition,temporal resolution and spectral resolution tests performed with hearing aids(p<0.05).Conclusion:Our study findings emphasized the importance of regular hearing aid use and it showed that some auditory skills can be improved with hearing aids.Observation of correlations among the speechin-noise recognition,temporal resolution and spectral resolution tests have revealed that these skills should be evaluated as a whole to maximize the patient’s communication abilities.
文摘One of the crucial problems in study on the middle atmosphere is to determine the concentration and distribution of some trace gases.In this aspect,sounding methods with high spectral resolution have been developed by many scientists.Some major trace gases and their spectral characteristics,space-borne limb method for determination of trace gases in the middle atmosphere are introduced,requirements for used methods and instruments,development and challenge encountered by sounding of trace gases with high spectral resolution are discussed in this paper.
基金National Key R&D Program(2018YFC1506904)Natural Science Foundation of China(41590873,41705089)。
文摘Using infrared sensors to detect ice clouds in different atmospheric layers is still a challenge.The different scattering and absorption properties of longwave and shortwave infrared channels can be utilized to fulfill this purpose.In this study,the release of Suomi-NPP Cross-track Infrared Sounder(Cr IS)full spectrum resolution is used to select and pair channels from longwave(~15μm)and shortwave(~4.3μm)CO2 absorption bands under stricter conditions,so as to better detect ice clouds.Besides,the differences of the weighting function peaks and cloud insensitive level altitudes of the paired channels are both within 50 h Pa so that the variances due to atmospheric conditions can be minimized.The training data of clear sky are determined by Visible Infrared Imaging Radiometer Suite(VIIRS)cloud mask product and used to find the linear relationship between the paired longwave and shortwave CO2 absorption channels.From the linear relationship,the so-called cloud emission and scattering index(CESI)is derived to detect ice clouds.CESI clearly captures the center and the ice cloud features of the Super Typhoon Hato located above 415 h Pa.Moreover,the CESI distributions agree with cloud top pressure from the VIIRS in both daytime and nighttime in different atmospheric layers.
基金supported by the National Key Research and Development Program of China(No.2016YFA0200602,No.2017YFA0303500,and No.2018YFA0208702)the National Natural Science Foundation of China(No.21573211,No.21633007,No.21803067,and No.91950207)+1 种基金the Anhui Initiative in Quantum Information Technologies(AHY090200)the USTC-NSRL Joint Funds(UN2018LHJJ).
文摘In recent decades,materials science has experienced rapid development and posed increasingly high requirements for the characterizations of structures,properties,and performances.Herein,we report on our recent establishment of a multi-domain(energy,space,time)highresolution platform for integrated spectroscopy and microscopy characterizations,offering an unprecedented way to analyze materials in terms of spectral(energy)and spatial mapping as well as temporal evolution.We present several proof-of-principle results collected on this platform,including in-situ Raman imaging(high-resolution Raman,polarization Raman,low-wavenumber Raman),time-resolved photoluminescence imaging,and photoelectrical performance imaging.It can be envisioned that our newly established platform would be very powerful and effective in the multi-domain high-resolution characterizations of various materials of photoelectrochemical importance in the near future.
基金supported by the National Natural Science Foundation of China(Nos.11973009,11933005,U23A20381,11904232,11774235,and 61705130)the Jiangsu Provincial Key Research and Development Program(No.BE2023080)+3 种基金the Chinese Academy of Sciences(No.KGFZD-145-23-04-03)the National Key Research and Development Program of China(No.2022YFE0107400)the Science and Technology Commission of Shanghai Municipality(Nos.23010503600 and 23530730500)the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning(No.GZ2020015).
文摘Integrated photonic spectrographs could provide a new generation of low-cost,highly integrated,high-performance optical terminal instruments for astronomical observations.However,these spectrographs still face the challenge of high spectral resolution.In this Letter,we demonstrate a cascaded phase-modulated waveguide array(CPMWA)spectrograph,with designed and measured spectral resolutions of 100,000 and 68,000,respectively.A spectral reconstruction method is proposed to minimize the influence of the phase error induced during the chip fabrication process and increase the spectral contrast to 20 dB.This type of spectrograph demonstrates promising potential for high-resolution spectrum observations in astronomy.
文摘At present, heavy metal pollution in food occurs frequently, which requires a novel method for rapid detection. Laser induced breakdown spectroscopy （LIBS） is a new technique for rapid and environmental friendly detection, but it lacks high sensitivity and stability which restrict its development. In this study, Cr-polluted infant milk powder was used as experimental material to explore the feasibility of the application of LIBS technique in food safety detection. Aiming at improving the precision and accuracy of Cr detection by LIBS technique, LIBS spectra of samples were collected by a spectrometer with an intensified charge-cou- pled device （ICCD） using three gratings with different resolutions to comprehensively compare and analyze the stability, sensitivity and quantitative analysis accura- cy of LIBS detection. The results showed that average relative standard deviation （RSD） of LIBS spectral intensity was below 10%, indicating good stability. LIBS signals were collected by three gratings for quantitative analysis, and the results demonstrated that the linear correlation coefficient R2 of fitting curves was 0. 248 87, 0.903 12 and 0.992 81, respectively; the relative errors between actual and predicted concentrations were 38.23%, 8.84% and 7.43%, respectively, indicating that gratings with higher resolutions could lead to higher linear correlation coefficient and better detection accuracy. According to the results, high-resolu- tion spectrometer could significantly improve the accuracy of LIBS detection of Cr concentration in milk powder, suggesting that it is feasible to detect heavy metals in food by LIBS technique with the improvement of core device performance.
文摘The primary goal of this report is to describe the operational concepts of NASA’s ACTIVATE mission. ACTIVATE hopes to improve the understanding of aerosol dispersion and models, provide accurate data for aerosols’ characterization and ozone profiles, and establish knowledge of the relationships between aerosols and water. ACTIVATE’s science objectives are to quantify Na-CCN-Nd relationships and reduce uncertainty in model cloud droplet activation parameterizations, improve process-level understanding and model representation of factors governing cloud micro/macro-physical properties and how they couple with cloud effects on aerosol, plus assess advanced remote sensing capabilities for retrieving aerosol and cloud properties related to aerosol-cloud interactions. ACTIVATE utilizes the fixed-wing B-200 King Air to collect data. Data collected by ACTIVATE is highly relevant for meteorologists and environmental scientists looking to understand more about aerosol-cloud formations. Finally, ACTIVATE is a 5-year mission spanning from January 2019 to December 2023 and has used, and will continue to use, instruments such as the High Spectral Resolution Lidar-2 (HSRL-2), the Research Scanning Polarimeter (RSP), and the Diode Laser Hygrometer (DLH).
文摘Windowing applied to a given signal is a technique commonly used in signal processing in order to reduce spectral leakage in a signal with many data. Several windows are well known: hamming, hanning, beartlett, etc. The selection of a window is based on its spectral characteristics. Several papers that analyze the amplitude and width of the lobes that appear in the spectrum of various types of window have been published. This is very important because the lobes can hide information on the frequency components of the original signal, in particular when frequency components are very close to each other. In this paper it is shown that the size of the window can also have an impact in the spectral information. Until today, the size of a window has been chosen in a subjective way. As far as we know, there are no publications that show how to determine the minimum size of a window. In this work the frequency interval between two consecutive values of a Fourier Transform is considered. This interval determines if the sampling frequency and the number of samples are adequate to differentiate between two frequency components that are very close. From the analysis of this interval, a mathematical inequality is obtained, that determines in an objective way, the minimum size of a window. Two examples of the use of this criterion are presented. The results show that the hiding of information of a signal is due mainly to the wrong choice of the size of the window, but also to the relative amplitude of the frequency components and the type of window. Windowing is the main tool used in spectral analysis with nonparametric periodograms. Until now, optimization was based on the type of window. In this paper we show that the right choice of the size of a window assures on one hand that the number of data is enough to resolve the frequencies involved in the signal, and on the other, reduces the number of required data, and thus the processing time, when very long files are being analyzed.
基金Supported by the National Key Research and Development Program of China(2018YFC1506500)。
文摘The surface vegetation condition has been operationally monitored from space for many years by the Advanced Very High Resolution Radiometer(AVHRR) and the Moderate Resolution Imaging Spectroradiometer(MODIS) instruments. As these instruments are close to the end of their design life, the surface vegetation products are required by many users from the new satellite missions. The MEdium Resolution Spectral Imager-Ⅱ(MERSI-Ⅱ) onboard the Fengyun(FY) satellite(FY-3 series;FY-3 D) is used to retrieve surface vegetation parameters. First, MERSI-Ⅱ solar channel measurements at the red and near-infrared(NIR) bands at the top of atmosphere(TOA) are corrected to the surface reflectances at the top of canopy(TOC) by removing the contributions of scattering and absorption of molecules and aerosols. The normalized difference vegetation index(NDVI) at both the TOA and TOC is then produced by using the same algorithms as the MODIS and AVHRR. The MERSI-Ⅱ enhanced VI(EVI) at the TOC is also developed. The MODIS technique of compositing the NDVI at various timescales is applied to MERSI-Ⅱ to generate the gridded products at different resolutions. The MERSI-Ⅱ VI products are consistent with the MODIS data without systematic biases. Compared to the current MERSI-Ⅱ EVI generated from the ground operational system, the MERSI-Ⅱ EVI from this study has a much better agreement with MODIS after atmospheric correction.
基金Under the auspices of National Nature Science Foundation of China(No.40901231,41101517)
文摘In this paper,a thin cloud removal method was put forward based on the linear relationships between the thin cloud reflectance in the channels from 0.4 μm to 1.0 μm and 1.38 μm.Channels of 0.66 μm,0.86 μm and 1.38 μm were chosen to extract the water body information under the thin cloud.Two study cases were selected to validate the thin cloud removal method.One case was applied with the Earth Observation System Moderate Resolution Imaging Spectroradiometer(EOS/MODIS) data,and the other with the Medium Resolution Spectral Imager(MERSI) and Visible and Infrared Radiometer(VIRR) data from Fengyun-3A(FY-3A).The test results showed that thin cloud removal method did not change the reflectivity of the ground surface under the clear sky.To the area contaminated by the thin cloud,the reflectance decreased to be closer to the reference reflectance under the clear sky after the thin cloud removal.The spatial distribution of the water body area could not be extracted before the thin cloud removal,while water information could be easily identified by using proper near infrared channel threshold after removing the thin cloud.The thin cloud removal method could improve the image quality and water body extraction precision effectively.
基金Supported by the Science Foundation of Shandong(ZR2017MD018)Key Research and Development Program of Ningxia(2019BEH03008)+3 种基金Open Research Project of the Key Laboratory for Meteorological Disaster MonitoringEarly Warning and Risk Management of Characteristic Agriculture in Arid Regions(CAMF-201701 and CAMF-201803)Arid Meteorological Science Research Fund Project by the Key Open Laboratory of Arid Climate Change and Disaster Reduction of China Metrological Administration(IAM201801)Science Foundation of Ningxia(NZ12278)。
文摘Obtaining continuous and high-quality soil moisture(SM) data is important in scientific research and applications,especially for agriculture, meteorology, and environmental monitoring. With the continuously increasing number of artificial satellites in China, the acquisition of SM data from remote sensing images has received increasing attention.In this study, we constructed an SM inversion model by using a deep belief network(DBN) to extract SM data from Fengyun-3 D(FY-3 D) Medium Resolution Spectral Imager-Ⅱ(MERSI-Ⅱ) imagery;we named this model SM-DBN.The SM-DBN consists of two subnetworks: one for temperature and the other for SM. In the temperature subnetwork, bands 1, 2, 3, 4, 24, and 25 of the FY-3 D MERSI-Ⅱ imagery, which are relevant to temperature, were used as inputs while land surface temperatures(LST) obtained from ground stations were used as the expected output value when training the model. In the SM subnetwork, the input data included LSTs generated from the temperature subnetwork, normalized difference vegetation index(NDVI), and enhanced vegetation index(EVI);and the SM data obtained from ground stations were used as the expected outputs. We selected the Ningxia Hui Autonomous Region of China as the study area and used selected MERSI-Ⅱ images and in-situ observation station data from 2018 to 2019 to develop our dataset. The results of the SM-DBN were validated by using in-situ SM data as a reference, and its performance was also compared with those of the linear regression(LR) and back propagation(BP) neural network models. The overall accuracy of these models was measured by using the root mean square error(RMSE) of the differences between the model results and in-situ SM observation data. The RMSE of the LR, BP neural network, and SM-DBN models were 0.101, 0.083, and 0.032, respectively. These results suggest that the SM-DBN model significantly outperformed the other two models.
基金the Natural Science Foundation of Beijing(No.7133252) for financial support of this work
文摘Xiao-Xu-Ming decoction（XXMD） was a traditional Chinese prescription and first recorded in ＂Bei Ji Qian Jin Yao Fang＂.It has been widely used to treat theoplegia and the sequel of theoplegia in China.In the present work,high-performance liquid chromatography coupled with high resolution mass spectrometry（HPLC-HRMS） combined with the mass spectral tree similarity filter technique（MTSF）was used to rapidly discover and identify the compounds of the active fraction of XXMD.A total of 3362 compounds were automatically detected by HPLC-HRMS,and final 68 compounds were identified in the active fraction of XXMD.including 14 templated compounds（reference compounds）,50 related compounds fished by MTSF technique,and 4 unrelated compounds identified by manual method.This study successfully applied MTSF technology for the first time to discover and identify the components of Chinese prescription.The results demonstrated that MTSF technique should be useful to the discovery and identification of compounds in Chinese prescription.This study also proved that MTSF can be applied to the targeted phytochemical separation.
基金supported by the National Natural Science Foundation of China(U2341225 and 62375242).
文摘High-Q nanophotonic devices hold great importance in both fundamental research and engineering applications.Their ability to provide high spectral resolution and enhanced light-matter interactions makes them promising in various fields such as sensing,filters,lasing,nonlinear optics,photodetection,coherent thermal emission,and laser stealth.While Q-factors as large as 109 have been achieved experimentally in on-chip microresonators,these modes are excited through near-field coupling of optical fibers.Exciting high-Q modes via free-space light presents a significant challenge primarily due to the larger fabrication area and more lossy channels associated with free-space nanophotonic devices.This Review provides a comprehensive overview of the methods employed to achieve high-Q modes,highlights recent research progress and applications,and discusses the existing challenges as well as the prospects in the field of free-space high-Q nanophotonics.
基金supports from National Key R&D Program of China(2021YFB2800404)Natural Science Foundation of China(62175151,62341508)+1 种基金Shanghai Municipal Science and Technology Major Project(BH0300071)a Leverhulme Trust Early Career Fellowship grant,reference ECF-2022-711.
文摘The burgeoning field of computational spectrometers is rapidly advancing,providing a pathway to highly miniaturized,on-chip systems for in-situ or portable measurements.The performance of these systems is typically limited in its encoder section.The response matrix is largely compromised with redundancies,due to the periodic intensity or overly smooth responses.As such,the inherent interdependence among the physical size,resolution,and bandwidth of spectral encoders poses a challenge to further miniaturization progress.Achieving high spectral resolution necessitates a long optical path length,leading to a larger footprint required for sufficient spectral decorrelation,resulting in a limited detectable free-spectral range(FSR).Here,we report a groundbreaking ultraminiaturized disordered photonic molecule spectrometer that surpasses the resolution-bandwidth-footprint metric of current spectrometers.This computational spectrometer utilizes complicated electromagnetic coupling to determinately generate quasi-random spectral response matrices,a feature absents in other state-of-the-art systems,fundamentally overcoming limitations present in the current technologies.This configuration yields an effectively infinite FSR while upholding a high Q-factor(>7.74×10^(5)).Through dynamic manipulation of photon frequency,amplitude,and phase,a broad operational bandwidth exceeding 100 nm can be attained with an ultra-high spectral resolution of 8 pm,all encapsulated within an ultra-compact footprint measuring 70×50μm^(2).The disordered photonic molecule spectrometer is constructed on a CMOS-compatible integrated photonics platform,presenting a pioneering approach for high-performance and highly manufacturable miniaturized spectroscopy.
基金partially supported by National Natural Science Foundation of China(NSFC)(62375087)Key-Area Research and Development Program of Guangdong Province(2023B0909010002)+2 种基金NSFC Development of National Major Scientific Research Instrument(61927816)Introduced Innovative Team Project of Guangdong Pearl River Talents Program(2021ZT09Z109)Natural Science Foundation of Guangdong Province(2021B1515020074).
文摘Dual-comb spectroscopy(DCS)with few-GHz tooth spacing that provides a better trade-off between spectral resolution and refresh rate is a powerful tool for measuring and analyzing rapidly evolving transient events.Despite such an exciting opportunity,existing technologies compromise either the spectral resolution or refresh rate,leaving few-GHz DCS with robust design largely unmet for frontier applications.In this work,we demonstrate a novel GHz DCS by exploring the multimode interference-mediated spectral filtering effect in an all-fiber ultrashort cavity configuration.The GHz single-cavity all-fiber dual-comb source is seeded by a dual-wavelength mode-locked fiber laser operating at fundamental repetition rates of about 1.0 GHz differing by 148 kHz,which has an excellent stability in the free-running state that the Allan deviation is only 101.7 mHz for an average time of 1 s.Thanks to the large repetition rate difference between the asynchronous dichromatic pulse trains,the GHz DCS enables a refresh time as short as 6.75μs,making it promising for studying nonrepeatable transient phenomena in real time.To this end,the practicality of the present GHz DCS is validated by successfully capturing the‘shock waves’of balloon and firecracker explosions outdoors.This GHz single-cavity all-fiber dual-comb system promises a noteworthy improvement in acquisition speed and reliability without sacrificing measurement accuracy,anticipated as a practical tool for high-speed applications.
基金supported by National Key Research and Development Program of China(2023YFA1406900)Strategic Priority Research Program(B)of Chinese Academy of Sciences(XDB0580000,XDB43010200,GJ0090406)+7 种基金National Natural Science Foundation of China(62222514,62350073,U2341226,61991440,12227901)Shanghai Science and Technology Committee(23ZR1482000,22JC1402900)Natural Science Foundation of Zhejiang Province(LR22F050004)Shanghai Municipal Science and Technology Major Project(2019SHZDZX01)Youth Innovation Promotion Association(Y2021070)International Partnership Program(112GJHZ2022002FN)of Chinese Academy of SciencesShanghai Human Resources and Social Security Bureau(2022670)China Postdoctoral Science Foundation(2023T160661,2022TQ0353and 2022M713261).
文摘In the domain of spectroscopy,miniaturization efforts often face significant challenges,particularly in achieving high spectral resolution and precise construction.Here,we introduce a computational spectrometer powered by a nonlinear photonic memristor with a WSe2 homojunction.This approach overcomes traditional limitations,such as constrained Fermi level tunability,persistent dark current,and limited photoresponse dimensionality through dynamic energy band modulation driven by palladium(Pd)ion migration.The critical role of Pd ion migration is thoroughly supported by first-principles calculations,numerical simulations,and experimental verification,demonstrating its effectiveness in enhancing device performance.Additionally,we integrate this dynamic modulation with a specialized nonlinear neural network tailored to address the memristor's inherent nonlinear photoresponse.This combination enables our spectrometer to achieve an exceptional peak wavelength accuracy of o.18 nm and a spectral resolution of 2 nm within the 630-640 nm range.This development marks a significant advancement in the creation of compact,high-effciency spectroscopic instruments and offers a versatile platform for applications across diverse material systems.
基金supported by the National Natural Science Foundation of China under Grant No.10576041
文摘A new high spectral resolution crystal spectrometer is designed to measure very low emissive X-ray spectra of laser-produced plasma in 0.5-0.9 nm range. A large open aperture （30 ×20 （mm）） mica （002） spherically bent crystal with curvature radius R = 380 mm is used as dispersive and focusing element. The imaging plate is employed to obtain high spectral resolution with effective area of 30 × 80 （mm）. The long designed path of the X-ray spectrometer beam is 980 mm from the source to the detector via the crystal. Experiment is carried out at a 20-J laser facility. X-ray spectra in an absolute intensity scale is obtained from Al laserproduced plasmas created by laser energy of 6.78 J. Samples of spectra obtained with spectral resolution of up to E/△E - 1500 are presented. The results clearly show that the device is good to diagnose laser high-density plasmas.
基金supported by the National Natural Science Foundation of China (Grant No. 40731055)
文摘Knowledge of the temporal-spatial distribution of water content in atmosphere and water phase change in cloud is important for atmospheric study.For this purpose,we have developed a high resolution full-spectrum water Raman lidar that can collect Raman signals from ice,water droplets and water vapor simultaneously.A double-grating polychromator and a 32-channel photomultiplier-tube detector are used to obtain a spectral resolution of-0.19 nm in the full Raman spectrum range of water,Preliminary observations present the water Raman spectrum characteristics of both the mixed-phase cloud and humid air under cloudless condition.
