In this paper,the performance characteristics of ASTM A790 S31803 and ASTM A182 F51 duplex stainless steel were introduced,and the weldabilities were analyzed. The welding repair procedures of thick wall duplex stainl...In this paper,the performance characteristics of ASTM A790 S31803 and ASTM A182 F51 duplex stainless steel were introduced,and the weldabilities were analyzed. The welding repair procedures of thick wall duplex stainless steel were developed by welding procedure qualification. Research shows that the repair welding has less effect on mechanical properties of welded joint, and great influence on phase proportions and pitting corrosion resistance. The test results meet the requirements of project specifications. The repair welding procedure can be used in project,and only one time repair shall be used.展开更多
This paper proposed a method to retrieve the land surface reflectance from the HJ-1A/B CCD data. The aerosol optical depth（AOD）, the most important factor affecting the atmospheric correction of CCD images at all ba...This paper proposed a method to retrieve the land surface reflectance from the HJ-1A/B CCD data. The aerosol optical depth（AOD）, the most important factor affecting the atmospheric correction of CCD images at all bands, is proposed to retrieve from the CCD imagery by the approach of dense dark vegetation（DDV） method. A look-up table in terms of the transmittances, the path radiances and the atmospheric spherical albedo as functions of the AOD was established for a variety of sun-sensor geometry and aerosol loadings. The atmospheric correction is then achieved with the look-up table and the MODIS surface reflectance output（MOD09） as the priori datasets. Based on the retrieved AOD and the look-up table of atmospheric correction coefficients, the land surface reflectance was retrieved for the HJ-1A/B data according to the atmospheric radiative transfer equation. Some in-situ measurement Data for Yanzhou of Shandong province in East China and MODIS land surface reflectance products MOD09 are used to preliminarily validate the proposed method. The results show that the proposed method can remove effectively the atmospheric contributions, and the overall accuracy of the retrieval land surface reflectance can be improved substantially.展开更多
For the application of the CCD camera,the most important payload on CBERS-02,the key is to provide long-term stable radiometric calibration coefficients.Although the vicarious calibration had been proved successful,it...For the application of the CCD camera,the most important payload on CBERS-02,the key is to provide long-term stable radiometric calibration coefficients.Although the vicarious calibration had been proved successful,it had its limitations such as test site requirement and unsuitable for historical data.Cross-calibration is one of the alternative methods,but it needs synchro surface spectrum to achieve spectral band matching factors.Our effort is to probe the influences on these factors.Simulations with a lot of surface spectrum showed that the factors changed with the viewing geometry,atmospheric condition and surface targets.However,simulating with the same viewing geometry and atmospheric condition,the spectral band matching factors of the same or similar surface targets’spectrum acquired from different dates and different places would like to be consistent to each other within 1%―5%.Thus,the synchro measurement data can be substituted by the same or similar target from other source.Based on this method,using the MODIS as the reference,the cross-calibration was performed for CCD camera.The research demonstrated that the traditional method with single calibration site was inappropriate for CCD camera,since the offsets for its four spectral bands were not zeros.With four calibration sites,these offsets were obtained.And the camera was detected to degrade with dates based on four times of cross-calibrations.展开更多
In this article,the approach of simulating ideal tarp scene was proposed to determine the MTF for CCD camera on CBERS-02.The MTF acquired from this technique was compared to those from some common methods.MTFs achieve...In this article,the approach of simulating ideal tarp scene was proposed to determine the MTF for CCD camera on CBERS-02.The MTF acquired from this technique was compared to those from some common methods.MTFs achieved from different approaches were employed to compensate the CCD images based on three restoration algorithms:the iterative method,the Wiener filter and the modified inverse filter(MIF).The two-dimensional MTF was established with the value at frequency 0.5 for 45°directional MTF as the value at its four corners.This article addressed the variations of the restored CCD images with different techniques of constructing two-dimensional MTF,restoring algorithms and determining the in-flight MTFs.Results showed images restored with the MTF determined from the technique of simulating ideal tarp scene represent the real scene best.And the restoration technique based on the MIF would produce better restored images than the other two techniques.This research also demonstrated that the two-dimensional MTF used for restoration should be interpolated under the control of the MTF for 45°axis,rather than by multiplying the cross-orbit MTF with along-orbit MTF.展开更多
In order to make quantitative watercolor sensing with China-Brazil Earth Resources Satellite(CBERS-02)CCD camera,the MODIS data with higher accuracy is used to cross-calibrate the CCD camera over water targets.In homo...In order to make quantitative watercolor sensing with China-Brazil Earth Resources Satellite(CBERS-02)CCD camera,the MODIS data with higher accuracy is used to cross-calibrate the CCD camera over water targets.In homogeneous clear water area,two pairs of images obtained over the same area on the same day by the two sensors are selected.The top-of-atmosphere(TOA)radiances of the multispectral bands of CCD are calculated with the water and aerosol parameters from MODIS based on a water-atmosphere radiative transfer algorithm.The stripes in CCD image that caused by unequal response of the CCD array detectors are firstly removed before making the cross-calibration.The same part of CCD detectors is selected for the calibrations in the two images to eliminate the residual error of destriping and uniformity correction for the focus plane irradiance.It is shown that the calibration results from two different images are consistent.The error of this method is about 5%.展开更多
CCD and WFI are payloads in the visible light and near infrared bands on CBERS satellites and they have not been applied widely,especially WFI.This article mainly probes into the potential of these two sensors’applic...CCD and WFI are payloads in the visible light and near infrared bands on CBERS satellites and they have not been applied widely,especially WFI.This article mainly probes into the potential of these two sensors’application in the vegetation monitoring and analyses the influences of radiometric calibration,atmosphere conditions and sun-observing geometry,etc.on NDVI obtained from these two sensors respectively.In addition it analyses the effect of the spectral response difference of red and near infrared spectral bands in CCD and WFI sensors on NDVI.Results indicate that radiometric calibration is the most important factor on NDVI,which cannot be applied to vegetation monitoring without radiometric calibration.Results also demonstrate that near surface NDVI is different greatly from that of TOA which change with atmosphere conditions.The study shows that NDVI is also affected by the non-lambertian character of surface and the change of the atmospheric path with the observing geometry.And NDVI of WFI is higher than that of CCD.They are very different because of their spectral difference,but they have a good linear relevant relationship.展开更多
文摘In this paper,the performance characteristics of ASTM A790 S31803 and ASTM A182 F51 duplex stainless steel were introduced,and the weldabilities were analyzed. The welding repair procedures of thick wall duplex stainless steel were developed by welding procedure qualification. Research shows that the repair welding has less effect on mechanical properties of welded joint, and great influence on phase proportions and pitting corrosion resistance. The test results meet the requirements of project specifications. The repair welding procedure can be used in project,and only one time repair shall be used.
基金National High Technology Research and Development Program of China,No.2012AA12A302
文摘This paper proposed a method to retrieve the land surface reflectance from the HJ-1A/B CCD data. The aerosol optical depth（AOD）, the most important factor affecting the atmospheric correction of CCD images at all bands, is proposed to retrieve from the CCD imagery by the approach of dense dark vegetation（DDV） method. A look-up table in terms of the transmittances, the path radiances and the atmospheric spherical albedo as functions of the AOD was established for a variety of sun-sensor geometry and aerosol loadings. The atmospheric correction is then achieved with the look-up table and the MODIS surface reflectance output（MOD09） as the priori datasets. Based on the retrieved AOD and the look-up table of atmospheric correction coefficients, the land surface reflectance was retrieved for the HJ-1A/B data according to the atmospheric radiative transfer equation. Some in-situ measurement Data for Yanzhou of Shandong province in East China and MODIS land surface reflectance products MOD09 are used to preliminarily validate the proposed method. The results show that the proposed method can remove effectively the atmospheric contributions, and the overall accuracy of the retrieval land surface reflectance can be improved substantially.
基金supported by the Hundred Talents Program of CAS(Grant No.KZCX0415)the Scientific Research Foundation for the Returned Overseas Chinese Scholars+1 种基金the Ministry of Education(Grant No.HX040013)the fund from Commission of Science Technology and Industry for National Defense(KJSX0401).
文摘For the application of the CCD camera,the most important payload on CBERS-02,the key is to provide long-term stable radiometric calibration coefficients.Although the vicarious calibration had been proved successful,it had its limitations such as test site requirement and unsuitable for historical data.Cross-calibration is one of the alternative methods,but it needs synchro surface spectrum to achieve spectral band matching factors.Our effort is to probe the influences on these factors.Simulations with a lot of surface spectrum showed that the factors changed with the viewing geometry,atmospheric condition and surface targets.However,simulating with the same viewing geometry and atmospheric condition,the spectral band matching factors of the same or similar surface targets’spectrum acquired from different dates and different places would like to be consistent to each other within 1%―5%.Thus,the synchro measurement data can be substituted by the same or similar target from other source.Based on this method,using the MODIS as the reference,the cross-calibration was performed for CCD camera.The research demonstrated that the traditional method with single calibration site was inappropriate for CCD camera,since the offsets for its four spectral bands were not zeros.With four calibration sites,these offsets were obtained.And the camera was detected to degrade with dates based on four times of cross-calibrations.
基金supported by the Hundred Talents Program of the Chinese Academy of Sciences(Grant No.KZCX0415)the Scientific Research Foundation for the Returned Overseas Chinese Scholars+1 种基金the Ministry of Education(Grant No.HX040013)the fund from Commission of Science Technology and Industry for National Defense(KJSX0401).
文摘In this article,the approach of simulating ideal tarp scene was proposed to determine the MTF for CCD camera on CBERS-02.The MTF acquired from this technique was compared to those from some common methods.MTFs achieved from different approaches were employed to compensate the CCD images based on three restoration algorithms:the iterative method,the Wiener filter and the modified inverse filter(MIF).The two-dimensional MTF was established with the value at frequency 0.5 for 45°directional MTF as the value at its four corners.This article addressed the variations of the restored CCD images with different techniques of constructing two-dimensional MTF,restoring algorithms and determining the in-flight MTFs.Results showed images restored with the MTF determined from the technique of simulating ideal tarp scene represent the real scene best.And the restoration technique based on the MIF would produce better restored images than the other two techniques.This research also demonstrated that the two-dimensional MTF used for restoration should be interpolated under the control of the MTF for 45°axis,rather than by multiplying the cross-orbit MTF with along-orbit MTF.
基金supported by the HY-1Ground Application System,the National Hi-Tech Program(Grant Nos.2001AA636010/7010/7030,2002AA639160)and National Administration of Space Technology Project“HY-1 Calibration and Navigation Algorithm”+2 种基金The hundred talents program of CAS(KZCX0415)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry(HX040013)the fund from Commission of Science Technology and Industry for National Defense(KJSX0401).
文摘In order to make quantitative watercolor sensing with China-Brazil Earth Resources Satellite(CBERS-02)CCD camera,the MODIS data with higher accuracy is used to cross-calibrate the CCD camera over water targets.In homogeneous clear water area,two pairs of images obtained over the same area on the same day by the two sensors are selected.The top-of-atmosphere(TOA)radiances of the multispectral bands of CCD are calculated with the water and aerosol parameters from MODIS based on a water-atmosphere radiative transfer algorithm.The stripes in CCD image that caused by unequal response of the CCD array detectors are firstly removed before making the cross-calibration.The same part of CCD detectors is selected for the calibrations in the two images to eliminate the residual error of destriping and uniformity correction for the focus plane irradiance.It is shown that the calibration results from two different images are consistent.The error of this method is about 5%.
基金supported by the hundred talents program of CAS(KZCX0415)the project sponsored by the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State EducationMinistry(HX040013)the fund from Commission of Science Technology and Industry for National Defense(KJSX0401).
文摘CCD and WFI are payloads in the visible light and near infrared bands on CBERS satellites and they have not been applied widely,especially WFI.This article mainly probes into the potential of these two sensors’application in the vegetation monitoring and analyses the influences of radiometric calibration,atmosphere conditions and sun-observing geometry,etc.on NDVI obtained from these two sensors respectively.In addition it analyses the effect of the spectral response difference of red and near infrared spectral bands in CCD and WFI sensors on NDVI.Results indicate that radiometric calibration is the most important factor on NDVI,which cannot be applied to vegetation monitoring without radiometric calibration.Results also demonstrate that near surface NDVI is different greatly from that of TOA which change with atmosphere conditions.The study shows that NDVI is also affected by the non-lambertian character of surface and the change of the atmospheric path with the observing geometry.And NDVI of WFI is higher than that of CCD.They are very different because of their spectral difference,but they have a good linear relevant relationship.
