Urban tree species provide various essential ecosystem services in cities,such as regulating urban temperatures,reducing noise,capturing carbon,and mitigating the urban heat island effect.The quality of these services...Urban tree species provide various essential ecosystem services in cities,such as regulating urban temperatures,reducing noise,capturing carbon,and mitigating the urban heat island effect.The quality of these services is influenced by species diversity,tree health,and the distribution and the composition of trees.Traditionally,data on urban trees has been collected through field surveys and manual interpretation of remote sensing images.In this study,we evaluated the effectiveness of multispectral airborne laser scanning(ALS)data in classifying 24 common urban roadside tree species in Espoo,Finland.Tree crown structure information,intensity features,and spectral data were used for classification.Eight different machine learning algorithms were tested,with the extra trees(ET)algorithm performing the best,achieving an overall accuracy of 71.7%using multispectral LiDAR data.This result highlights that integrating structural and spectral information within a single framework can improve the classification accuracy.Future research will focus on identifying the most important features for species classification and developing algorithms with greater efficiency and accuracy.展开更多
Airborne area-array whisk-broom imaging systems typically adopt constant-speed scanning schemes.For large-inertia scanning systems,constant-speed scanning requires substantial time to complete the reversal motion,redu...Airborne area-array whisk-broom imaging systems typically adopt constant-speed scanning schemes.For large-inertia scanning systems,constant-speed scanning requires substantial time to complete the reversal motion,reducing the system's adaptability to high-speed reversal scanning and decreasing scanning efficiency.This study proposes a novel sinusoidal variable-speed roll scanning strategy,which reduces abrupt changes in speed and acceleration,minimizing time loss during reversals.Based on the forward image motion compensation strategy in the pitch direction,we establish a line-of-sight(LOS)position calculation model with vertical flight path correction(VFPC),ensuring that the central LOS of the scanned image remains stable on the same horizontal line,facilitating accurate image stitching in whisk-broom imaging.Through theoretical analysis and simulation experiments,the proposed method improves the scanning efficiency by approximately 18.6%at a 90o whiskbroom imaging angle under the same speed height ratio conditions.The new VFPC method enables wide-field,high-resolution imaging,achieving single-line LOS horizontal stability with an accuracy of better than O.4 mrad.The research is of great significance to promote the further development of airborne area-array whisk-broom imaging technology toward wider fields of view,higher speed height ratios,and greater scanning efficiency.展开更多
The paper contains the results of investigation of interconnections between coals’vitrinite structural features,mode of its crushing under the cyclic nanoindentation with increasing peak load and coals’proneness to ...The paper contains the results of investigation of interconnections between coals’vitrinite structural features,mode of its crushing under the cyclic nanoindentation with increasing peak load and coals’proneness to formation of airborne respirable dust(ARD)with particles sized<10μm(PM10).A specific value of PM10 contents in coals normalized on a fines fraction(with particles sizes of less than 200μm)was used as a measure of proneness to ARD formation.It has been shown that the aforementioned parameter is predefined by the ratio of amorphous and crystalline carbon compounds in vitrinite and the mode of its crushing.Some preliminary investigation have been done in order to characterize the involvement of inertinite in ARD formation.It was proposed that the inertinite is not as actively involved in the processes of ARD formation of coals as vitrinite,having a more diverse structural features in terms of amorphous to crystalline carbon compounds ratio.展开更多
Site index(SI)is determined from the top height development and is a proxy for forest productivity,defined as the expected top height for a given species at a certain index age.In Norway,an index age of 40 years is us...Site index(SI)is determined from the top height development and is a proxy for forest productivity,defined as the expected top height for a given species at a certain index age.In Norway,an index age of 40 years is used.By using bi-temporal airborne laser scanning(ALS)data,SI can be determined using models estimated from SI observed on field plots(the direct approach)or from predicted top heights at two points in time(the height differential approach).Time series of ALS data may enhance SI determination compared to conventional methods used in operational forest inventory by providing more detailed information about the top height development.We used longitudinal data comprising spatially consistent field and ALS data collected from training plots in 1999,2010,and 2022 to determine SI using the direct and height differential approaches using all combinations of years and performed an external validation.We also evaluated the use of data assimilation.Values of root mean square error obtained from external validation were in the ranges of 16.3%–21.4%and 12.8%–20.6%of the mean fieldregistered SI for the direct approach and the height differential approach,respectively.There were no statistically significant effects of time series length or the number of points in time on the obtained accuracies.Data assimilation did not result in any substantial improvement in the obtained accuracies.Although a time series of ALS data did not yield greater accuracies compared to using only two points in time,a larger proportion of the study area could be used in ALS-based determination of SI when a time series was available.This was because areas that were unsuitable for SI determination between two points in time could be subject to SI determination based on data from another part of the time series.展开更多
With the advancement of electronic countermeasures,airborne synthetic aperture radar(SAR)systems are facing increasing challenges in maintaining effective performance in hostile environments.In particular,high-power i...With the advancement of electronic countermeasures,airborne synthetic aperture radar(SAR)systems are facing increasing challenges in maintaining effective performance in hostile environments.In particular,high-power interference can severely degrade SAR imaging and signal processing,often rendering target detection impossible.This highlights the urgent need for robust anti-interference solutions in both the signal processing and image processing domains.While current methods address interference across various domains,techniques such as waveform modification and spatial filtering typically increase the system costs and complexity.To overcome these limitations,we propose a novel approach that leverages the multi-domain characteristics of interference to efficiently suppress narrowband interference and repeater modulation interference.Specifically,narrowband interference is mitigated using notch filtering,a signal processing technique that effectively filters out unwanted frequencies,while repeater modulation interference is addressed through strong signal amplitude normalization,which enhances both the signal and image processing quality.These methods were validated through tests on real SAR data,demonstrating significant improvements in the imaging performance and system robustness.Our approach offers valuable insights for advancing anti-interference technologies in SAR systems and provides a cost-effective solution to enhance their resilience in complex electronic warfare environments.展开更多
Airborne microorganisms(AM)have significant environmental and health implications.Extensive studies have been conducted to investigate the factors influencing the composition and diversity of AM.However,the knowledge ...Airborne microorganisms(AM)have significant environmental and health implications.Extensive studies have been conducted to investigate the factors influencing the composition and diversity of AM.However,the knowledge of AM with anthropogenic activities has not reach a consensus.In this study,we took advantage of the dramatic decline of outdoor anthropogenic activities resulting from COVID-19 lockdown to reveal their associations.We collected airborne particulate matter before and during the lockdown period in two cities.The results showed that it was fungal diversity and communities but not bacteria obviously different between pre-lockdownand lockdown samples,suggesting that airborne fungiwere more susceptible to anthropogenic activities than bacteria.However,after the implementation of lockdown,the co-occurrence networks of both bacterial and fungal community became more complex,whichmight be due to the variation of microbial sources.Furthermore,Mantel test and correlation analysis showed that air pollutants also partly contributed to microbial alterations.Airborne fungal community was more affected by air pollutants than bacterial community.Notably,some human pathogens like Nigrospora and Arthrinium were negatively correlated with air pollutants.Overall,our study highlighted the more impacts of anthropogenic activities on airborne fungal community than bacterial community and advanced the understanding of associations between anthropogenic activities and AM.展开更多
The adaptive filtering algorithm with a fixed projection order is unable to adjust its performance in response to changes in the external environment of airborne radars.To overcome this limitation,a new approach is in...The adaptive filtering algorithm with a fixed projection order is unable to adjust its performance in response to changes in the external environment of airborne radars.To overcome this limitation,a new approach is introduced,which is the variable projection order Ekblom norm-promoted adaptive algorithm(VPO-EPAA).The method begins by examining the mean squared deviation(MSD)of the EPAA,deriving a formula for its MSD.Next,it compares the MSD of EPAA at two different projection orders and selects the one that minimizes the MSD as the parameter for the current iteration.Furthermore,the algorithm’s computational complexity is analyzed theoretically.Simulation results from system identification and self-interference cancellation show that the proposed algorithm performs exceptionally well in airborne radar signal self-interference cancellation,even under various noise intensities and types of interference.展开更多
In this study,we discuss the methods and results for the tectonolayer of a hydrocarbon basin using airborne gravity and magnetic data in the Qijia-Gulong area of the Songliao Basin.Using the latest airborne gravity an...In this study,we discuss the methods and results for the tectonolayer of a hydrocarbon basin using airborne gravity and magnetic data in the Qijia-Gulong area of the Songliao Basin.Using the latest airborne gravity and magnetic data combined with seismic and drilling data,we determined the density and magnetic measurement data of strata(rocks)in the study area.Next,density and structural stratifications were conducted.The structural sections of the strata-structure-magmatic rocks in the shallow,middle,and deep strata of the basin were determined,and a three-dimensional framework with multiple levels of the basin was constructed.Combining qualitative analysis and quantitative calculation,we explained the depths of the bottom of the Cenozoic layer,the bottom of the Upper Cretaceous layer,the bottom of the Mesozoic layer,and the top of the magnetic basement.We also determined the thicknesses of the Cenozoic layer,the Upper Cretaceous layer,the Upper Jurassic-Lower Cretaceous layer,and the Upper Paleozoic layer.These provide important achievements for the new petroliferous strata survey of regional Upper Paleozoic and Upper Jurassic-Lower Cretaceous strata.At the same time,it provides a new exploration method for studying are as with magmatic rocks and unclear deep seismic reflections.The results show that the new Upper Paleozoic strata(with a thickness of 0-9200 m)are mainly distributed in the central and eastern regions but absent in the western region.This yields significant differences in different regions of the study area.The thickness and depth of the Upper Jurassic-lower Cretaceous layer were different between the eastern and western regions;thicker and deeper in the middle eastern region but thinner and shallower in the western region.展开更多
Airborne microplastics(MPs)are important pollutants that have been present in the environment for many years and are characterized by their universality,persistence,and potential toxicity.This study investigated the e...Airborne microplastics(MPs)are important pollutants that have been present in the environment for many years and are characterized by their universality,persistence,and potential toxicity.This study investigated the effects of terrestrial and marine transport of MPs in the atmosphere of a coastal city and compared the difference between daytime and nighttime.Laser direct infrared imaging(LDIR)and polarized light microscopy were used to characterize the physical and chemical properties of MPs,including number concentration,chemical types,shape,and size.Backward trajectories were used to distinguish the air masses from marine and terrestrial transport.Twenty chemical types were detected by LDIR,with rubber(16.7%)and phenol-formaldehyde resin(PFR;14.8%)being major components.Three main morphological types of MPs were identified,and fragments(78.1%)are the dominant type.MPs in the atmosphere were concentrated in the small particle size segment(20-50μm).The concentration of MPs in the air mass from marine transport was 14.7 items/m^(3)-lower than that from terrestrial transport(32.0 items/m^(3)).The number concentration of airborne MPs was negatively correlated with relative humidity.MPs from terrestrial transport were mainly rubber(20.2%),while those from marine transport were mainly PFR(18%).MPs in the marine transport air mass were more aged and had a lower number concentration than those in the terrestrial transport air mass.The number concentration of airborne MPs is higher during the day than at night.These findings could contribute to the development of targeted control measures and methods to reduce MP pollution.展开更多
Airborne LiDAR(Light Detection and Ranging)is an evolving high-tech active remote sensing technology that has the capability to acquire large-area topographic data and can quickly generate DEM(Digital Elevation Model)...Airborne LiDAR(Light Detection and Ranging)is an evolving high-tech active remote sensing technology that has the capability to acquire large-area topographic data and can quickly generate DEM(Digital Elevation Model)products.Combined with image data,this technology can further enrich and extract spatial geographic information.However,practically,due to the limited operating range of airborne LiDAR and the large area of task,it would be necessary to perform registration and stitching process on point clouds of adjacent flight strips.By eliminating grow errors,the systematic errors in the data need to be effectively reduced.Thus,this paper conducts research on point cloud registration methods in urban building areas,aiming to improve the accuracy and processing efficiency of airborne LiDAR data.Meanwhile,an improved post-ICP(Iterative Closest Point)point cloud registration method was proposed in this study to determine the accurate registration and efficient stitching of point clouds,which capable to provide a potential technical support for applicants in related field.展开更多
Variogram has been utilized to exploring the spatial heterogeneity of remote sensing images,especially its association with spatial resolution.However,very few attentions have been drawn on evaluating the spatial hete...Variogram has been utilized to exploring the spatial heterogeneity of remote sensing images,especially its association with spatial resolution.However,very few attentions have been drawn on evaluating the spatial heterogeneity of multisensor airborne imagery and its relationship with spectral wavelength.Therefore,an investigation was carried out on multisensor airborne images to determine the relation between spatial heterogeneity and spectral wavelength for woodland,grass,and urban landscapes by applying variogram modeling.The airborne thematic mapper(ATM),compact airborne spectrographic imager(CASI),and Specim AISA Eagle airborne images at Harwood Forest,Monks wood,Cambridge,and River Frome areas,UK,were utilized.Results revealed that(1)the red band contained greater spatial variability than near-infrared wavelengths and other visible wavebands;(2)there was a steep gradient at the red edge in reference to its spatial variability of multisensor airborne images;(3)only for natural landscape such as woodland and grass,near-infrared waveband contains greater within-scene variations than the blue and green bands;(4)compared with the discrepancy of spatial resolution introduced by multisensor images(ATM,CASI,and Eagle),the specific landscape and spectral bands were more important in determining heterogeneity by means of original visible,near-infrared bands,and normalized difference vegetation index(NDVI).These findings remained us to be caution when combining and interpreting spatial variability and spatial structures derived from airborne images with different spatial resolution and spectral wavelength.Additionally,the outcomes of this study also have considerable implications in terms of designing and choosing suitable images for different applications.展开更多
Traditionally, airborne time-domain electromagnetic （ATEM） data are inverted to derive the earth model by iteration. However, the data are often highly correlated among channels and consequently cause ill-posed and ...Traditionally, airborne time-domain electromagnetic （ATEM） data are inverted to derive the earth model by iteration. However, the data are often highly correlated among channels and consequently cause ill-posed and over-determined problems in the inversion. The correlation complicates the mapping relation between the ATEM data and the earth parameters and thus increases the inversion complexity. To obviate this, we adopt principal component analysis to transform ATEM data into orthogonal principal components （PCs） to reduce the correlations and the data dimensionality and simultaneously suppress the unrelated noise. In this paper, we use an artificial neural network （ANN） to approach the PCs mapping relation with the earth model parameters, avoiding the calculation of Jacobian derivatives. The PC-based ANN algorithm is applied to synthetic data for layered models compared with data-based ANN for airborne time-domain electromagnetic inversion. The results demonstrate the PC-based ANN advantages of simpler network structure, less training steps, and better inversion results over data-based ANN, especially for contaminated data. Furthermore, the PC-based ANN algorithm effectiveness is examined by the inversion of the pseudo 2D model and comparison with data-based ANN and Zhody＇s methods. The results indicate that PC-based ANN inversion can achieve a better agreement with the true model and also proved that PC-based ANN is feasible to invert large ATEM datasets.展开更多
In this paper,we use high-precision airborne gravity and magnetic data to study the geophysical characteristics of the western slope of the Songliao Basin and its adjacent areas and evaluate the resource potential.We ...In this paper,we use high-precision airborne gravity and magnetic data to study the geophysical characteristics of the western slope of the Songliao Basin and its adjacent areas and evaluate the resource potential.We performed an in-depth analysis of three aspects of the basin characteristics:the characteristics of residual strata,the development characteristics of faults,and the distribution characteristics of magmatic rocks.Next,we analyzed the forming background of organic(oil and gas)resources and inorganic(uranium ore and hot dry rock)resources.The results showed that the new Upper Paleozoic strata have significant differences in different regions of the study area(with a thickness of 0–8000 m),mainly distributed in the eastern and northern regions but absent in the middle eastern and western regions.Furthermore,the thickness and depth of the Mesozoic layer varied between the eastern and western regions;it was thicker and deeper in the middle eastern region but thinner and shallower in the western region,and it is absent in most western regions.The main faults in the region are in the north–northeast(NNE)direction.Faults in the NE–NNE and NW directions jointly controlled the morphology of the secondary structural units.Magmatic rocks are relatively developed in the middle and eastern parts of the region.Most magmatic rocks are distributed along the faults and their sides,clearly reflecting the control of the faults on magmatic activities.The western slope of the Songliao basin and its surroundings have a favorable geological setting for the accumulation(mineralization)of oil,gas,shale oil,hot dry rock,and uranium ore.It is conducive to oil and gas exploration of deep new strata and collaborative exploration of multiple resources.展开更多
On the basis of a sinusoidal model of the disturbed horizontal acceleration,the spectrum characteristics of misaligned angle and horizontal acceleration correction are analyzed.In an airborne gravimetry test,the misal...On the basis of a sinusoidal model of the disturbed horizontal acceleration,the spectrum characteristics of misaligned angle and horizontal acceleration correction are analyzed.In an airborne gravimetry test,the misaligned angle of platform and horizontal acceleration correction are calculated.They are 5′and 3 mGal,respectively,when the flight is stable.展开更多
Aim To calculate and analyze the near field distribution of ariborne short wave antenna. Methods B-spline method was used to get the mathermatital model of a Boeing 707320Baircraft and simulate its short wave antenna ...Aim To calculate and analyze the near field distribution of ariborne short wave antenna. Methods B-spline method was used to get the mathermatital model of a Boeing 707320Baircraft and simulate its short wave antenna . FDTD (finite-difference time-domain) method are ed tO complete the calculation and analysis. Results The near field distributions on aircraft's surface were obtained, the curve and gray figures of the normalized near field value were shown. Conclusion These modeling and calculating methods can provide data foraircraft's EMC analysis and design.展开更多
Abstract The cross-coupling corrections for the LaCoste ＆ Romberg airborne gravimeter are computed as a linear combination of 5 so-called cross-coupling monitors. The weight factors （coefficients） determined from m...Abstract The cross-coupling corrections for the LaCoste ＆ Romberg airborne gravimeter are computed as a linear combination of 5 so-called cross-coupling monitors. The weight factors （coefficients） determined from marine gravity data by the factory are obviously not optimal for airborne application. These coefficients are recalibrated by minimizing the difference between airborne data and upward continued surface data （external calibration） and by minimizing the errors at line crossings （internal calibration） respectively. An integrating method to recalibrate the above-mentioned coefficients and the beam scale factor simultaneously is also presented. Experimental results show that the systemic errors in the airborne gravity anomalies can be greatly reduced by using any of the recalibrated coefficients. For example, the systemic error is reduced from 4.8 mGal to 1.8 mGal in Datong test.展开更多
Electrically anisotropic strata are abundant in nature, so their study can help our data interpretation and our understanding of the processes of geodynamics. However, current data processing generally assumes isotrop...Electrically anisotropic strata are abundant in nature, so their study can help our data interpretation and our understanding of the processes of geodynamics. However, current data processing generally assumes isotropic conditions when surveying anisotropic structures, which may cause discrepancies between reality and electromagnetic data interpretation. Moreover, the anisotropic interpretation of the time-domain airborne electromagnetic （TDAEM） method is still confined to one dimensional （1D） cases, and the corresponding three-dimensional （3D） numerical simulations are still in development. In this study, we expanded the 3D TDAEM modeling of arbitrarily anisotropic media. First, through coordinate rotation of isotropic conductivity, we obtained the conductivity tensor of an arbitrary anisotropic rock. Next, we incorporated this into Maxwell＇s equations, using a regular hexahedral grid of vector finite elements to subdivide the solution area. A direct solver software package provided the solution for the sparse linear equations that resulted. Analytical solutions were used to verify the accuracy and feasibility of the algorithm. The proven model was then applied to analyze the effects of arbitrary anisotropy in 3D TDAEM via the distribution of responses and amplitude changes, which revealed that different anisotropy situations strongly affected the responses of TDAEM.展开更多
Frequency-domain airborne electromagnetics is a proven geophysical exploration method.Presently,the interpretation is mainly based on resistivity-depth imaging and onedimensional layered inversion;nevertheless,it is d...Frequency-domain airborne electromagnetics is a proven geophysical exploration method.Presently,the interpretation is mainly based on resistivity-depth imaging and onedimensional layered inversion;nevertheless,it is difficult to obtain satisfactory results for two- or three-dimensional complex earth structures using 1D methods.3D forward modeling and inversion can be used but are hampered by computational limitations because of the large number of data.Thus,we developed a 2.5D frequency-domain airborne electromagnetic forward modeling and inversion algorithm.To eliminate the source singularities in the numerical simulations,we split the fields into primary and secondary fields.The primary fields are calculated using homogeneous or layered models with analytical solutions,and the secondary（scattered） fields are solved by the finite-element method.The linear system of equations is solved by using the large-scale sparse matrix parallel direct solver,which greatly improves the computational efficiency.The inversion algorithm was based on damping leastsquares and singular value decomposition and combined the pseudo forward modeling and reciprocity principle to compute the Jacobian matrix.Synthetic and field data were used to test the effectiveness of the proposed method.展开更多
In order to study the influence of parameters on airborne transmitted diseases in a hospital ward,a pollutant decay equation and a Wells-Riley model are adopted to study the relationship between the airborne infection...In order to study the influence of parameters on airborne transmitted diseases in a hospital ward,a pollutant decay equation and a Wells-Riley model are adopted to study the relationship between the airborne infection risk and the parameters such as the ventilation rate,the number of susceptible persons and the volume of the ward.The results show that the airborne infection risk can be reduced by increasing the ventilation rate.For two wards with the same air change per hour（ACH）but different volumes,the ventilation rate in a large room is higher than that in a small one.The number of the infected persons in the ward increases with the increase in the susceptible persons when the ACH is a constant.Therefore,the ventilation rate in the ward is not only estimated by the ACH but also related to the volume of the ward and the number of the susceptible persons.展开更多
Geohazard recognition and inventory mapping are absolutely the keys to the establishment of reliable susceptibility and hazard maps. However, it has been challenging to implement geohazards recognition and inventory m...Geohazard recognition and inventory mapping are absolutely the keys to the establishment of reliable susceptibility and hazard maps. However, it has been challenging to implement geohazards recognition and inventory mapping in mountainous areas with complex topography and vegetation cover. Progress in the light detection and ranging(Li DAR) technology provides a new possibility for geohazard recognition in such areas. Specifically, this study aims to evaluate the performances of the Li DAR technology in recognizing geohazard in the mountainous areas of Southwest China through visually analyzing airborne Li DAR DEM derivatives. Quasi-3 D relief image maps are generated based on the sky-view factor(SVF), which makes it feasible to interpret precisely the features of geohazard. A total of 146 geohazards are remotely mapped in the entire 135 km^(2) study area in Danba County, Southwest China, and classified as landslide, rock fall, debris flow based on morphologic characteristics interpreted from SVF visualization maps. Field validation indicate the success rate of Li DAR-derived DEM in recognition and mapping geohazard with higher precision and accuracy. These mapped geohazards lie along both sides of the river, and their spatial distributions are related highly to human engineering activities, such as road excavation and slope cutting. The minimum geohazard that can be recognized in the 0.5 m resolution DEM is about 900 m^(2). Meanwhile, the SVF visualization method is demonstrated to be a great alternative to the classical hillshaded DEM method when it comes to the determination of geomorphological properties of geohazard. Results of this study highlight the importance of Li DAR data for creating complete and accurate geohazard inventories, which can then be used for the production of reliable susceptibility and hazard maps and thus contribute to a better understanding of the movement processes and reducing related losses.展开更多
文摘Urban tree species provide various essential ecosystem services in cities,such as regulating urban temperatures,reducing noise,capturing carbon,and mitigating the urban heat island effect.The quality of these services is influenced by species diversity,tree health,and the distribution and the composition of trees.Traditionally,data on urban trees has been collected through field surveys and manual interpretation of remote sensing images.In this study,we evaluated the effectiveness of multispectral airborne laser scanning(ALS)data in classifying 24 common urban roadside tree species in Espoo,Finland.Tree crown structure information,intensity features,and spectral data were used for classification.Eight different machine learning algorithms were tested,with the extra trees(ET)algorithm performing the best,achieving an overall accuracy of 71.7%using multispectral LiDAR data.This result highlights that integrating structural and spectral information within a single framework can improve the classification accuracy.Future research will focus on identifying the most important features for species classification and developing algorithms with greater efficiency and accuracy.
基金Supported by the National Key Research and Development Program(2023YFC3107602)。
文摘Airborne area-array whisk-broom imaging systems typically adopt constant-speed scanning schemes.For large-inertia scanning systems,constant-speed scanning requires substantial time to complete the reversal motion,reducing the system's adaptability to high-speed reversal scanning and decreasing scanning efficiency.This study proposes a novel sinusoidal variable-speed roll scanning strategy,which reduces abrupt changes in speed and acceleration,minimizing time loss during reversals.Based on the forward image motion compensation strategy in the pitch direction,we establish a line-of-sight(LOS)position calculation model with vertical flight path correction(VFPC),ensuring that the central LOS of the scanned image remains stable on the same horizontal line,facilitating accurate image stitching in whisk-broom imaging.Through theoretical analysis and simulation experiments,the proposed method improves the scanning efficiency by approximately 18.6%at a 90o whiskbroom imaging angle under the same speed height ratio conditions.The new VFPC method enables wide-field,high-resolution imaging,achieving single-line LOS horizontal stability with an accuracy of better than O.4 mrad.The research is of great significance to promote the further development of airborne area-array whisk-broom imaging technology toward wider fields of view,higher speed height ratios,and greater scanning efficiency.
基金funding from the Strategic project‘Technologies of Sustainable Development’of Program of strategic academic leadership‘Priority 2030’of NUST MISIS.
文摘The paper contains the results of investigation of interconnections between coals’vitrinite structural features,mode of its crushing under the cyclic nanoindentation with increasing peak load and coals’proneness to formation of airborne respirable dust(ARD)with particles sized<10μm(PM10).A specific value of PM10 contents in coals normalized on a fines fraction(with particles sizes of less than 200μm)was used as a measure of proneness to ARD formation.It has been shown that the aforementioned parameter is predefined by the ratio of amorphous and crystalline carbon compounds in vitrinite and the mode of its crushing.Some preliminary investigation have been done in order to characterize the involvement of inertinite in ARD formation.It was proposed that the inertinite is not as actively involved in the processes of ARD formation of coals as vitrinite,having a more diverse structural features in terms of amorphous to crystalline carbon compounds ratio.
基金part of the Centre for Research-based Innovation SmartForest:Bringing Industry 4.0 to the Norwegian forest sector(NFR SFI project no.309671,smartforest.no)。
文摘Site index(SI)is determined from the top height development and is a proxy for forest productivity,defined as the expected top height for a given species at a certain index age.In Norway,an index age of 40 years is used.By using bi-temporal airborne laser scanning(ALS)data,SI can be determined using models estimated from SI observed on field plots(the direct approach)or from predicted top heights at two points in time(the height differential approach).Time series of ALS data may enhance SI determination compared to conventional methods used in operational forest inventory by providing more detailed information about the top height development.We used longitudinal data comprising spatially consistent field and ALS data collected from training plots in 1999,2010,and 2022 to determine SI using the direct and height differential approaches using all combinations of years and performed an external validation.We also evaluated the use of data assimilation.Values of root mean square error obtained from external validation were in the ranges of 16.3%–21.4%and 12.8%–20.6%of the mean fieldregistered SI for the direct approach and the height differential approach,respectively.There were no statistically significant effects of time series length or the number of points in time on the obtained accuracies.Data assimilation did not result in any substantial improvement in the obtained accuracies.Although a time series of ALS data did not yield greater accuracies compared to using only two points in time,a larger proportion of the study area could be used in ALS-based determination of SI when a time series was available.This was because areas that were unsuitable for SI determination between two points in time could be subject to SI determination based on data from another part of the time series.
文摘With the advancement of electronic countermeasures,airborne synthetic aperture radar(SAR)systems are facing increasing challenges in maintaining effective performance in hostile environments.In particular,high-power interference can severely degrade SAR imaging and signal processing,often rendering target detection impossible.This highlights the urgent need for robust anti-interference solutions in both the signal processing and image processing domains.While current methods address interference across various domains,techniques such as waveform modification and spatial filtering typically increase the system costs and complexity.To overcome these limitations,we propose a novel approach that leverages the multi-domain characteristics of interference to efficiently suppress narrowband interference and repeater modulation interference.Specifically,narrowband interference is mitigated using notch filtering,a signal processing technique that effectively filters out unwanted frequencies,while repeater modulation interference is addressed through strong signal amplitude normalization,which enhances both the signal and image processing quality.These methods were validated through tests on real SAR data,demonstrating significant improvements in the imaging performance and system robustness.Our approach offers valuable insights for advancing anti-interference technologies in SAR systems and provides a cost-effective solution to enhance their resilience in complex electronic warfare environments.
基金supported by the National Natural Science Foundation of China(No.31900106)the East China University of Technology Practical Teaching Construction Project(No.DHSY-202261)。
文摘Airborne microorganisms(AM)have significant environmental and health implications.Extensive studies have been conducted to investigate the factors influencing the composition and diversity of AM.However,the knowledge of AM with anthropogenic activities has not reach a consensus.In this study,we took advantage of the dramatic decline of outdoor anthropogenic activities resulting from COVID-19 lockdown to reveal their associations.We collected airborne particulate matter before and during the lockdown period in two cities.The results showed that it was fungal diversity and communities but not bacteria obviously different between pre-lockdownand lockdown samples,suggesting that airborne fungiwere more susceptible to anthropogenic activities than bacteria.However,after the implementation of lockdown,the co-occurrence networks of both bacterial and fungal community became more complex,whichmight be due to the variation of microbial sources.Furthermore,Mantel test and correlation analysis showed that air pollutants also partly contributed to microbial alterations.Airborne fungal community was more affected by air pollutants than bacterial community.Notably,some human pathogens like Nigrospora and Arthrinium were negatively correlated with air pollutants.Overall,our study highlighted the more impacts of anthropogenic activities on airborne fungal community than bacterial community and advanced the understanding of associations between anthropogenic activities and AM.
基金supported by the Shan⁃dong Provincial Natural Science Foundation(No.ZR2022MF314).
文摘The adaptive filtering algorithm with a fixed projection order is unable to adjust its performance in response to changes in the external environment of airborne radars.To overcome this limitation,a new approach is introduced,which is the variable projection order Ekblom norm-promoted adaptive algorithm(VPO-EPAA).The method begins by examining the mean squared deviation(MSD)of the EPAA,deriving a formula for its MSD.Next,it compares the MSD of EPAA at two different projection orders and selects the one that minimizes the MSD as the parameter for the current iteration.Furthermore,the algorithm’s computational complexity is analyzed theoretically.Simulation results from system identification and self-interference cancellation show that the proposed algorithm performs exceptionally well in airborne radar signal self-interference cancellation,even under various noise intensities and types of interference.
基金funded by National Key Research and Development Program of China(no.2023YFB3907703)Project of Aviation Gravity and Magnetism Comprehensive Investigation in Xinjiang Awulale IronResource Base(no.DD20240205003).
文摘In this study,we discuss the methods and results for the tectonolayer of a hydrocarbon basin using airborne gravity and magnetic data in the Qijia-Gulong area of the Songliao Basin.Using the latest airborne gravity and magnetic data combined with seismic and drilling data,we determined the density and magnetic measurement data of strata(rocks)in the study area.Next,density and structural stratifications were conducted.The structural sections of the strata-structure-magmatic rocks in the shallow,middle,and deep strata of the basin were determined,and a three-dimensional framework with multiple levels of the basin was constructed.Combining qualitative analysis and quantitative calculation,we explained the depths of the bottom of the Cenozoic layer,the bottom of the Upper Cretaceous layer,the bottom of the Mesozoic layer,and the top of the magnetic basement.We also determined the thicknesses of the Cenozoic layer,the Upper Cretaceous layer,the Upper Jurassic-Lower Cretaceous layer,and the Upper Paleozoic layer.These provide important achievements for the new petroliferous strata survey of regional Upper Paleozoic and Upper Jurassic-Lower Cretaceous strata.At the same time,it provides a new exploration method for studying are as with magmatic rocks and unclear deep seismic reflections.The results show that the new Upper Paleozoic strata(with a thickness of 0-9200 m)are mainly distributed in the central and eastern regions but absent in the western region.This yields significant differences in different regions of the study area.The thickness and depth of the Upper Jurassic-lower Cretaceous layer were different between the eastern and western regions;thicker and deeper in the middle eastern region but thinner and shallower in the western region.
基金supported by the National Natural Science Foundation of China (No.42075107)the Fundamental Research Funds for the Central Universities (No.2022YJSDC05)+1 种基金the China Scholarship Council (No.202206430058)the Yueqi Scholar Fund of China University of Mining and Technology (Beijing).
文摘Airborne microplastics(MPs)are important pollutants that have been present in the environment for many years and are characterized by their universality,persistence,and potential toxicity.This study investigated the effects of terrestrial and marine transport of MPs in the atmosphere of a coastal city and compared the difference between daytime and nighttime.Laser direct infrared imaging(LDIR)and polarized light microscopy were used to characterize the physical and chemical properties of MPs,including number concentration,chemical types,shape,and size.Backward trajectories were used to distinguish the air masses from marine and terrestrial transport.Twenty chemical types were detected by LDIR,with rubber(16.7%)and phenol-formaldehyde resin(PFR;14.8%)being major components.Three main morphological types of MPs were identified,and fragments(78.1%)are the dominant type.MPs in the atmosphere were concentrated in the small particle size segment(20-50μm).The concentration of MPs in the air mass from marine transport was 14.7 items/m^(3)-lower than that from terrestrial transport(32.0 items/m^(3)).The number concentration of airborne MPs was negatively correlated with relative humidity.MPs from terrestrial transport were mainly rubber(20.2%),while those from marine transport were mainly PFR(18%).MPs in the marine transport air mass were more aged and had a lower number concentration than those in the terrestrial transport air mass.The number concentration of airborne MPs is higher during the day than at night.These findings could contribute to the development of targeted control measures and methods to reduce MP pollution.
基金Guangxi Key Laboratory of Spatial Information and Geomatics(21-238-21-12)Guangxi Young and Middle-aged Teachers’Research Fundamental Ability Enhancement Project(2023KY1196).
文摘Airborne LiDAR(Light Detection and Ranging)is an evolving high-tech active remote sensing technology that has the capability to acquire large-area topographic data and can quickly generate DEM(Digital Elevation Model)products.Combined with image data,this technology can further enrich and extract spatial geographic information.However,practically,due to the limited operating range of airborne LiDAR and the large area of task,it would be necessary to perform registration and stitching process on point clouds of adjacent flight strips.By eliminating grow errors,the systematic errors in the data need to be effectively reduced.Thus,this paper conducts research on point cloud registration methods in urban building areas,aiming to improve the accuracy and processing efficiency of airborne LiDAR data.Meanwhile,an improved post-ICP(Iterative Closest Point)point cloud registration method was proposed in this study to determine the accurate registration and efficient stitching of point clouds,which capable to provide a potential technical support for applicants in related field.
基金The authors gratefully acknowledge the financial support received for this work from the National Natural Science Foundation of China[grant numbers 41471362 and 41071267]the Scientific Research Foundation for Returned Scholars,Ministry of Education of China(LXKQ201202)+1 种基金the Science and Technology Department of Fujian Province of China[grant numbers 2012I0005 and 2012J01167]The authors would like to thank the Natural Environment Research Council of UK for the provision of the airborne remote sensing data,and Ben Taylor and Gabriel Amable who kindly offered help in processing these data.
文摘Variogram has been utilized to exploring the spatial heterogeneity of remote sensing images,especially its association with spatial resolution.However,very few attentions have been drawn on evaluating the spatial heterogeneity of multisensor airborne imagery and its relationship with spectral wavelength.Therefore,an investigation was carried out on multisensor airborne images to determine the relation between spatial heterogeneity and spectral wavelength for woodland,grass,and urban landscapes by applying variogram modeling.The airborne thematic mapper(ATM),compact airborne spectrographic imager(CASI),and Specim AISA Eagle airborne images at Harwood Forest,Monks wood,Cambridge,and River Frome areas,UK,were utilized.Results revealed that(1)the red band contained greater spatial variability than near-infrared wavelengths and other visible wavebands;(2)there was a steep gradient at the red edge in reference to its spatial variability of multisensor airborne images;(3)only for natural landscape such as woodland and grass,near-infrared waveband contains greater within-scene variations than the blue and green bands;(4)compared with the discrepancy of spatial resolution introduced by multisensor images(ATM,CASI,and Eagle),the specific landscape and spectral bands were more important in determining heterogeneity by means of original visible,near-infrared bands,and normalized difference vegetation index(NDVI).These findings remained us to be caution when combining and interpreting spatial variability and spatial structures derived from airborne images with different spatial resolution and spectral wavelength.Additionally,the outcomes of this study also have considerable implications in terms of designing and choosing suitable images for different applications.
基金supported by the National Natural Science Foundation of China (Grant No. 40974039)High-Tech Research and Development Program of China (Grant No.2006AA06205)Leading Strategic Project of Science and Technology, Chinese Academy of Sciences (XDA08020500)
文摘Traditionally, airborne time-domain electromagnetic （ATEM） data are inverted to derive the earth model by iteration. However, the data are often highly correlated among channels and consequently cause ill-posed and over-determined problems in the inversion. The correlation complicates the mapping relation between the ATEM data and the earth parameters and thus increases the inversion complexity. To obviate this, we adopt principal component analysis to transform ATEM data into orthogonal principal components （PCs） to reduce the correlations and the data dimensionality and simultaneously suppress the unrelated noise. In this paper, we use an artificial neural network （ANN） to approach the PCs mapping relation with the earth model parameters, avoiding the calculation of Jacobian derivatives. The PC-based ANN algorithm is applied to synthetic data for layered models compared with data-based ANN for airborne time-domain electromagnetic inversion. The results demonstrate the PC-based ANN advantages of simpler network structure, less training steps, and better inversion results over data-based ANN, especially for contaminated data. Furthermore, the PC-based ANN algorithm effectiveness is examined by the inversion of the pseudo 2D model and comparison with data-based ANN and Zhody＇s methods. The results indicate that PC-based ANN inversion can achieve a better agreement with the true model and also proved that PC-based ANN is feasible to invert large ATEM datasets.
基金funded by the national geological and mineral resources and environment investigation project (no. DD20190028)。
文摘In this paper,we use high-precision airborne gravity and magnetic data to study the geophysical characteristics of the western slope of the Songliao Basin and its adjacent areas and evaluate the resource potential.We performed an in-depth analysis of three aspects of the basin characteristics:the characteristics of residual strata,the development characteristics of faults,and the distribution characteristics of magmatic rocks.Next,we analyzed the forming background of organic(oil and gas)resources and inorganic(uranium ore and hot dry rock)resources.The results showed that the new Upper Paleozoic strata have significant differences in different regions of the study area(with a thickness of 0–8000 m),mainly distributed in the eastern and northern regions but absent in the middle eastern and western regions.Furthermore,the thickness and depth of the Mesozoic layer varied between the eastern and western regions;it was thicker and deeper in the middle eastern region but thinner and shallower in the western region,and it is absent in most western regions.The main faults in the region are in the north–northeast(NNE)direction.Faults in the NE–NNE and NW directions jointly controlled the morphology of the secondary structural units.Magmatic rocks are relatively developed in the middle and eastern parts of the region.Most magmatic rocks are distributed along the faults and their sides,clearly reflecting the control of the faults on magmatic activities.The western slope of the Songliao basin and its surroundings have a favorable geological setting for the accumulation(mineralization)of oil,gas,shale oil,hot dry rock,and uranium ore.It is conducive to oil and gas exploration of deep new strata and collaborative exploration of multiple resources.
文摘On the basis of a sinusoidal model of the disturbed horizontal acceleration,the spectrum characteristics of misaligned angle and horizontal acceleration correction are analyzed.In an airborne gravimetry test,the misaligned angle of platform and horizontal acceleration correction are calculated.They are 5′and 3 mGal,respectively,when the flight is stable.
文摘Aim To calculate and analyze the near field distribution of ariborne short wave antenna. Methods B-spline method was used to get the mathermatital model of a Boeing 707320Baircraft and simulate its short wave antenna . FDTD (finite-difference time-domain) method are ed tO complete the calculation and analysis. Results The near field distributions on aircraft's surface were obtained, the curve and gray figures of the normalized near field value were shown. Conclusion These modeling and calculating methods can provide data foraircraft's EMC analysis and design.
文摘Abstract The cross-coupling corrections for the LaCoste ＆ Romberg airborne gravimeter are computed as a linear combination of 5 so-called cross-coupling monitors. The weight factors （coefficients） determined from marine gravity data by the factory are obviously not optimal for airborne application. These coefficients are recalibrated by minimizing the difference between airborne data and upward continued surface data （external calibration） and by minimizing the errors at line crossings （internal calibration） respectively. An integrating method to recalibrate the above-mentioned coefficients and the beam scale factor simultaneously is also presented. Experimental results show that the systemic errors in the airborne gravity anomalies can be greatly reduced by using any of the recalibrated coefficients. For example, the systemic error is reduced from 4.8 mGal to 1.8 mGal in Datong test.
基金financially supported by National Nonprofit institute Research Grant of IGGE(Nos.AS2017J06,AS2017Y04,and AS2016J10)Survey on coastal area for airborne magnetic method of UNV in Jiangsu(No.DD20160151-03)+3 种基金Key National Research Project of China(No.2017YFC0601900)Key Program of National Natural Science Foundation of China(No.41530320)Natural Science Foundation(No.41274121)China Natural Science Foundation for Young Scientists(No.41404093)
文摘Electrically anisotropic strata are abundant in nature, so their study can help our data interpretation and our understanding of the processes of geodynamics. However, current data processing generally assumes isotropic conditions when surveying anisotropic structures, which may cause discrepancies between reality and electromagnetic data interpretation. Moreover, the anisotropic interpretation of the time-domain airborne electromagnetic （TDAEM） method is still confined to one dimensional （1D） cases, and the corresponding three-dimensional （3D） numerical simulations are still in development. In this study, we expanded the 3D TDAEM modeling of arbitrarily anisotropic media. First, through coordinate rotation of isotropic conductivity, we obtained the conductivity tensor of an arbitrary anisotropic rock. Next, we incorporated this into Maxwell＇s equations, using a regular hexahedral grid of vector finite elements to subdivide the solution area. A direct solver software package provided the solution for the sparse linear equations that resulted. Analytical solutions were used to verify the accuracy and feasibility of the algorithm. The proven model was then applied to analyze the effects of arbitrary anisotropy in 3D TDAEM via the distribution of responses and amplitude changes, which revealed that different anisotropy situations strongly affected the responses of TDAEM.
基金supported by the Doctoral Fund Project of the Ministry of Education(No.20130061110060 class tutors)the National Natural Science Foundation of China(No.41504083)National Basic Research Program of China(973Program)(No.2013CB429805)
文摘Frequency-domain airborne electromagnetics is a proven geophysical exploration method.Presently,the interpretation is mainly based on resistivity-depth imaging and onedimensional layered inversion;nevertheless,it is difficult to obtain satisfactory results for two- or three-dimensional complex earth structures using 1D methods.3D forward modeling and inversion can be used but are hampered by computational limitations because of the large number of data.Thus,we developed a 2.5D frequency-domain airborne electromagnetic forward modeling and inversion algorithm.To eliminate the source singularities in the numerical simulations,we split the fields into primary and secondary fields.The primary fields are calculated using homogeneous or layered models with analytical solutions,and the secondary（scattered） fields are solved by the finite-element method.The linear system of equations is solved by using the large-scale sparse matrix parallel direct solver,which greatly improves the computational efficiency.The inversion algorithm was based on damping leastsquares and singular value decomposition and combined the pseudo forward modeling and reciprocity principle to compute the Jacobian matrix.Synthetic and field data were used to test the effectiveness of the proposed method.
文摘In order to study the influence of parameters on airborne transmitted diseases in a hospital ward,a pollutant decay equation and a Wells-Riley model are adopted to study the relationship between the airborne infection risk and the parameters such as the ventilation rate,the number of susceptible persons and the volume of the ward.The results show that the airborne infection risk can be reduced by increasing the ventilation rate.For two wards with the same air change per hour（ACH）but different volumes,the ventilation rate in a large room is higher than that in a small one.The number of the infected persons in the ward increases with the increase in the susceptible persons when the ACH is a constant.Therefore,the ventilation rate in the ward is not only estimated by the ACH but also related to the volume of the ward and the number of the susceptible persons.
基金The research was supported by the National Innovation Research Group Science Fund(No.41521002)the National Key Research and Development Program of China(No.2018YFC1505202)。
文摘Geohazard recognition and inventory mapping are absolutely the keys to the establishment of reliable susceptibility and hazard maps. However, it has been challenging to implement geohazards recognition and inventory mapping in mountainous areas with complex topography and vegetation cover. Progress in the light detection and ranging(Li DAR) technology provides a new possibility for geohazard recognition in such areas. Specifically, this study aims to evaluate the performances of the Li DAR technology in recognizing geohazard in the mountainous areas of Southwest China through visually analyzing airborne Li DAR DEM derivatives. Quasi-3 D relief image maps are generated based on the sky-view factor(SVF), which makes it feasible to interpret precisely the features of geohazard. A total of 146 geohazards are remotely mapped in the entire 135 km^(2) study area in Danba County, Southwest China, and classified as landslide, rock fall, debris flow based on morphologic characteristics interpreted from SVF visualization maps. Field validation indicate the success rate of Li DAR-derived DEM in recognition and mapping geohazard with higher precision and accuracy. These mapped geohazards lie along both sides of the river, and their spatial distributions are related highly to human engineering activities, such as road excavation and slope cutting. The minimum geohazard that can be recognized in the 0.5 m resolution DEM is about 900 m^(2). Meanwhile, the SVF visualization method is demonstrated to be a great alternative to the classical hillshaded DEM method when it comes to the determination of geomorphological properties of geohazard. Results of this study highlight the importance of Li DAR data for creating complete and accurate geohazard inventories, which can then be used for the production of reliable susceptibility and hazard maps and thus contribute to a better understanding of the movement processes and reducing related losses.
