Passive Fourier transform infrared （FTIR） remote sensing measurement of chemical gas cloud is a vital technology. It takes an important part in many fields for the detection of released gases. The principle of conce...Passive Fourier transform infrared （FTIR） remote sensing measurement of chemical gas cloud is a vital technology. It takes an important part in many fields for the detection of released gases. The principle of concentration measurement is based on the Beer-Lambert law. Unlike the active measurement, for the passive remote sensing, in most cases, the difference between the temperature of the gas cloud and the brightness temperature of the background is usually a few kelvins. The gas cloud emission is almost equal to the background emission, thereby the emission of the gas cloud cannot be ignored. The concentration retrieval algorithm is quite different from the active measurement. In this paper, the concentration retrieval algorithm for the passive FTIR remote measurement of gas cloud is presented in detail, which involves radiative transfer model, radiometric calibration, absorption coefficient calculation, et al. The background spectrum has a broad feature, which is a slowly varying function of frequency. In this paper, the background spectrum is fitted with a polynomial by using the Levenberg-Marquardt method which is a kind of nonlinear least squares fitting algorithm. No background spectra are required. Thus, this method allows mobile, real-time and fast measurements of gas clouds.展开更多
Measurement of vegetation coverage on a small scale is the foundation for the monitoring of changes in vegetation coverage and of the inversion model of monitoring vegetation coverage on a large scale by remote sensin...Measurement of vegetation coverage on a small scale is the foundation for the monitoring of changes in vegetation coverage and of the inversion model of monitoring vegetation coverage on a large scale by remote sensing. Using the object-oriented analytical software, Definiens Professional 5, a new method for calculating vegetation coverage based on high-resolution images （aerial photographs or near-surface photography） is proposed. Our research supplies references to remote sensing measurements of vegetation coverage on a small scale and accurate fundamental data for the inversion model of vegetation coverage on a large and intermediate scale to improve the accuracy of remote sensing monitoring of changes in vegetation coverage.展开更多
Recently, with the rapid development of precision machining, microvibration measurement is required for the manufacturing and installation of parts and components. In this paper, a self-mixing microvibration measureme...Recently, with the rapid development of precision machining, microvibration measurement is required for the manufacturing and installation of parts and components. In this paper, a self-mixing microvibration measurement system of a π-phase shifted Distributed feedback (DFB) fiber laser is introduced. An all-fiberized configuration Er<sup>3+</sup>-Yb<sup>3+</sup> co-doped DFB fiber laser was used as light source, in which an active π-phase shifted fiber Bragg grating (FBG) was wrote on Er<sup>3+</sup>-Yb<sup>3+</sup> co-doped fiber. Using this, it can easily get a single-mode lasing with narrow linewidth. Experimental results demonstrate that the amplitude of vibration can be achieved down to λ/5 without any modulation parts while utilizing the reflecting mirror. It is in good agreement with the theoretical analysis and very helpful in proving sensitivity and stability of the measurement system. In addition, remote vibration measurement with a distance of 20 km is also realized with this system.展开更多
The ability of the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) for flooding and soil wetness detection has been demonstrated in this study.On the basis of TMI measurements,four methods,the classi...The ability of the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) for flooding and soil wetness detection has been demonstrated in this study.On the basis of TMI measurements,four methods,the classification method,the soil wetness index (SWI) method. the polarization difference index (PDI) method,and the polarization ratio index (PRI) method, were brought out to monitor flooding and study soil wetness in the Changjiang and Huaihe River Basins during the summer 1998.Compared with the images provided by L-band Synthetic Aperture Radar (L-SAR) and Radar Satellite (Radarsat) and the figures derived from daily rainfall data based on the Z-index method,the detection of flooding and soil wetness by TMI was proved to be feasible.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No 083H311501)the National High Technology Research and Development Program of China (Grant No 073H3f1514)
文摘Passive Fourier transform infrared （FTIR） remote sensing measurement of chemical gas cloud is a vital technology. It takes an important part in many fields for the detection of released gases. The principle of concentration measurement is based on the Beer-Lambert law. Unlike the active measurement, for the passive remote sensing, in most cases, the difference between the temperature of the gas cloud and the brightness temperature of the background is usually a few kelvins. The gas cloud emission is almost equal to the background emission, thereby the emission of the gas cloud cannot be ignored. The concentration retrieval algorithm is quite different from the active measurement. In this paper, the concentration retrieval algorithm for the passive FTIR remote measurement of gas cloud is presented in detail, which involves radiative transfer model, radiometric calibration, absorption coefficient calculation, et al. The background spectrum has a broad feature, which is a slowly varying function of frequency. In this paper, the background spectrum is fitted with a polynomial by using the Levenberg-Marquardt method which is a kind of nonlinear least squares fitting algorithm. No background spectra are required. Thus, this method allows mobile, real-time and fast measurements of gas clouds.
基金funded by the National Natural Science Foundation of China(Grant No.40571029).
文摘Measurement of vegetation coverage on a small scale is the foundation for the monitoring of changes in vegetation coverage and of the inversion model of monitoring vegetation coverage on a large scale by remote sensing. Using the object-oriented analytical software, Definiens Professional 5, a new method for calculating vegetation coverage based on high-resolution images （aerial photographs or near-surface photography） is proposed. Our research supplies references to remote sensing measurements of vegetation coverage on a small scale and accurate fundamental data for the inversion model of vegetation coverage on a large and intermediate scale to improve the accuracy of remote sensing monitoring of changes in vegetation coverage.
文摘Recently, with the rapid development of precision machining, microvibration measurement is required for the manufacturing and installation of parts and components. In this paper, a self-mixing microvibration measurement system of a π-phase shifted Distributed feedback (DFB) fiber laser is introduced. An all-fiberized configuration Er<sup>3+</sup>-Yb<sup>3+</sup> co-doped DFB fiber laser was used as light source, in which an active π-phase shifted fiber Bragg grating (FBG) was wrote on Er<sup>3+</sup>-Yb<sup>3+</sup> co-doped fiber. Using this, it can easily get a single-mode lasing with narrow linewidth. Experimental results demonstrate that the amplitude of vibration can be achieved down to λ/5 without any modulation parts while utilizing the reflecting mirror. It is in good agreement with the theoretical analysis and very helpful in proving sensitivity and stability of the measurement system. In addition, remote vibration measurement with a distance of 20 km is also realized with this system.
基金the National Key Program of Science and Technology of China (2001BA610A-06-05)the National Natural Science Foundation of China (40375001)the Science Foundation of China Meteorological Administration and Jilin Provincial Government Joint Laboratory for Weather Modification
文摘The ability of the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) for flooding and soil wetness detection has been demonstrated in this study.On the basis of TMI measurements,four methods,the classification method,the soil wetness index (SWI) method. the polarization difference index (PDI) method,and the polarization ratio index (PRI) method, were brought out to monitor flooding and study soil wetness in the Changjiang and Huaihe River Basins during the summer 1998.Compared with the images provided by L-band Synthetic Aperture Radar (L-SAR) and Radar Satellite (Radarsat) and the figures derived from daily rainfall data based on the Z-index method,the detection of flooding and soil wetness by TMI was proved to be feasible.
