Editor in chief：Jun-Hao CHU
International standard number：ISSN 1001-9014
Unified domestic issue：CN 31-1577
Domestic postal code：4-335
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Abstract:In0.78Ga0.22As/In0.78Al0.22As quantum wells and In0.84Ga0.16As photodetctor samples have been grown on InP-based InxAl1-xAs metamorphic graded buffers to investigate the effects of compositional overshoot on the material characteristics. Atomic force microscopy results show that the surface roughness is reduced by the compositional overshoot in the InAlAs buffer layers for both the quantum well and photodetector samples. In the case of thin quantum wells, X-ray diffraction reciprocal space mapping and photoluminescence measurements show that the use of compositional overshoot can increase the relaxation degree, reduce the residual strain and improve the optical quality. While in the case of thicker photodetectors, no obvious improvement is observed after using compositional overshoot. The different behaviours of the metamorphic quantum wells and photodetectors should be considered in the device applications.
Abstract:A tunable diode laser absorption spectroscopy system with a multi pass cell and a DFB laser diode at wavelength 1.626 μm has been developed for simultaneous measurement of ethylene and methane. A line separation method based on multi absorption peak using the least squares algorithm has been established. The characteristic peak positions and relative intensities of ethylene and methane were determined by available spectral structures from previous investigations and available databases. The accuracy of the measured concentration is within 5% comparing with the mass flow meter.
Abstract:In this study, we have created a bridge, which can connect the reference-based NUC and scene-based NUC. The right probability of the scene-based NUC parameters was calculated based on the Bayesian framework. The right probability composed of prior and observation probability was used to determine whether the calculated scene-based NUC parameters are suitable to correct the nonuniformity. The local same distribution constraint is defined in this paper, and the Infrared Focal Plane (IRFPA) gain space relativity has been discovered from the reference-based parameters by this paper firstly. The Bayesian prior probability is mainly determined by the local same distribution constraint, and the Bayesian observation probability is mainly determined by the Infrared Focal Plane (IRFPA) gain space relativity. This method can effectively balance the relationship between convergence speed and ghosting artifacts. Finally, the real and simulated infrared image sequences have been applied to demonstrate our algorithm's positive effect.In this study, we have created a bridge, which can connect the reference-based NUC and scene-based NUC. The right probability of the scene-based NUC parameters was calculated based on the Bayesian framework. The right probability composed of prior and observation probability was used to determine whether the calculated scene-based NUC parameters are suitable to correct the nonuniformity. The local same distribution constraint is defined in this paper, and the Infrared Focal Plane (IRFPA) gain space relativity has been discovered from the reference-based parameters by this paper firstly. The Bayesian prior probability is mainly determined by the local same distribution constraint, and the Bayesian observation probability is mainly determined by the IRFPA gain space relativity. This method can effectively balance the relationship between convergence speed and ghosting artifacts. Finally, the real and simulated infrared image sequences have been applied to demonstrate our algorithm’s positive effect.
Abstract:Bromine etching and bromine polishing are two different surface treatment reported. Mobility spectrum and mobility-temperature character are used to compare the influence between bromine etching and polishing. After that, the material treated with two different methods is fabricated into detector. Resistivity as a function of temperature is measured. All the experiments indicated that there is more surface electron and ionized impurity scattering counted more in the material treated by bromine etching, however, for the material polished by bromine, the surface electron concentration is much less and lattice scattering plays a major role, in result the performance of the final detector is much better.Etching and polishing with bromine are two different surface treatments for HgCdTe material. To evaluate the effectiveness of the surface treatment, both the mobility dependence of carrier concentration and temperature dependence of the mobility were investigated. Then, the material treated with the two different methods was fabricated into detectors. Resistivity as a function of temperature was measured. The experiments indicated that there are more surface electrons and ionized impurity scattering in the material treated by bromine etching than that treated by polishing, wherein lattice scattering plays a major role. Thus the performance of the final detector made of material treated by polishing is much better.
Abstract:The surfaces of soil with different moisture contents had been surveyed by the spectral polarimetry in the mid-wave infrared range. The results indicate that the thermal radiation from the water-bearing soil surface is almost unpolarized, and the polarization characteristic of the soil surface is mainly caused by the reflection of solar light. Especially in the strong sunshine spectral range, the degree of polarization increases monotonically with the increase of soil moisture. This quantitative relationship provides basis for soil moisture monitoring by the remote sensing of the polarization of light in the mid-wave infrared range.
Abstract:Precise determination of the relative velocity between the spacecraft and celestial body is necessary to ensure the secure landing in space exploration. An all-fiber linear frequency modulation continuous wave(LFMCW)-continuous wave(CW)Doppler laser radar was developed for landing navigation. A narrow line width laser was used as the seed laser. The laser frequency was modulated by an acousto-optic modulator. Speed vector was measured in real-time by means of balance coherent detection and digital signal processing based on FPGA. Experiments made on laser Doppler radar with a speed generator proved that 0.05cm/s or better accuracy can be achieved while the velocity direction can be discriminated.
Abstract:A laboratory SAL setup that can produce well-focused SAL images using laser illumination with one-way far-field diffraction is introduced. Using 1 550 nm fiber laser, the SAL can focus images from target distance of about 2.4 m with azimuth resolution of about 560 μm and range resolution of about 170 μm. High-resolution SAL images are generated by straightforwardly following standard SAL image formation theory, not by the aid of phase gradient autofocus (PGA) technique. Detailed results, showing both a typical two-step SAL focusing process and high resolution image, are illustrated.A laboratory SAL setup produced well-focused SAL images using laser illumination with one-way far-field diffraction. Using 1550 nm fiber laser, the SAL can focus images from target distance of about 2.4 m with azimuth resolution of about 560 μm and range resolution of about 170 μm. High-resolution SAL images are generated by straightforwardly following standard SAL image formation theory, without the aid of phase gradient autofocus (PGA) technique. Detailed results show a typical two-step SAL focusing process and a high resolution image.
Abstract:In this paper, we resolve the problem about calculation the key angle, estimate moisture interface reflection coefficient and eliminate abnormal data in situ measurement under complex conditions for the currently commercial underway water Hyperspectral Surface Acquisition Systems (SAS), and then examined the proposed method using the in situ data. The results showed that the underway-measured water-leaving radiance by SAS were quite consistent with these measured at fixed stations. Meanwhile, the variation trends of the underway-measured water-leaving radiance by SAS were similar as the underway water turbidities. These examining results indicate that the data processing method proposed is credible.The problems about calculation of the key angle, estimation of the reflection coefficient at the moisture interface, and elimination of abnormal data in situ measurement under complex conditions were solved for the currently commercial underway water Hyperspectral Surface Acquisition Systems (SAS). The proposed method was then examined using the in situ data. The results showed that the underway-measured water-leaving radiance by SAS were quite consistent with these measured data at fixed stations. Meanwhile, the variation trends of the underway-measured water-leaving radiance by SAS were similar as the underway water turbidities. These results indicate that the proposed method for the data processing is credible.
Abstract:Based on the Bloch theory of periodic structure, the Tamm states of semi-infinite one-dimensional photonic crystal with surface defect (the defect Tamm states) were studied through analytical and numerical methods. The forming condition and field properties of the defect Tamm states was obtained. The properties of the defect Tamm states and the Tamm states without defect was also compared. For TE wave, the frequency range of defect Tamm state is enlarged to both high frequency and low frequency; for TM wave, the frequency range of defect Tamm state is only enlarged to high frequency, but is narrowed in low frequency. For large refraction index of defect material, the dispersion curve of Tamm state is close to a straight line and the group velocity is close to that light velocity in the single defect layer. The frequency of the defect Tamm state can be adjusted into our needed range by changing the refraction index or thickness of the defect layer.
Abstract:he scattering matrix for the cavity with abrupt changes in radius in the gyroklystron was built with the mode-matching technique. The variations of the resonance characteristic of the cavity modes with the length and radius of the cavity have been studied. The cavities for input, bunching and output of the Ka-band TE01 mode in the gyroklystron have been designed and fabricated.The designed amplifier, as indicated by the PIC simulation, was expected to produce 390 kW peak output power, saturated gains of 42.9 dB and 50.6% efficiency at center frequency 34 GHz and 70kV, 11A annular electron beam. The full width half maximum (FWHM) bandwidth is greater than 360 MHz. The hot test shows that the fabricated gyroklystron amplifier has actually produced 301 kW peak output power, 39.1% efficiency and saturated gains of 41.8 dB at center frequency 34 GHz and 70 kV ,11 A annular electron beam . The full width half maximum (FWHM) bandwidth is greater than 285 MHz.
Abstract:The continuous spatial scaling model (CSSM) of NDVI based on fractal theory was proposed and implemented. Based on GEOEYE-1 image and taking NDVI as experimental object, the paper studied the availability of fractal methodology for high-resolution image, and discussed the selection of the best reasonable scale-level for establishing NDVI's CSSM. It was concluded that the fractal methodology is suitable for high-resolution RS image. In some definite conditions, the best reasonable scale-level for establishing NDVI's CSSM exists and can be computed. For the fractal methodology, the results in the paper extended its available range of retrievals and image's resolutions.
Abstract:A 300 mm offset-feed reflector antenna is designed for a W-band radiometer in this paper, its parameter are 94.5 GHz operating frequency, sidelobe level of less than-25 dB, cross polarization level of less -30 dB and half-power beamwidth of better than 1 °. A smaller offset angle is adopted to improve the antenna cross polarization characteristics, and this matching feed is designed with the focal plane field matching method and the modulus ratio method and is optimized to get good VSWR and lobe equalizing level. Measurement results show that this antenna meets the requirements of the radiometer and its measured and theoretical values are coincided.
Abstract:Various types of surface emissivities for dust source regions in northwest China were measured by 102F. The comparison between field measured spectra and the ASTER JHU spectral library data showed the reliability and necessity of the field measurement. The analysis results showed that emissivity had significant differences for different types of land surface. The regular differences in emissivity for the same type surface were related to the different physical characteristics. The emissivity was relatively stable on the time scale. The measurement and analysis of the emissivity data for the sand dust source regions provide important information for sandstorm related researches.
Abstract:Because the landing security of Chang'E-3 is the most critical requirements during the second stage of Chang'E project, the high-resolution landing image is necessary. The super-resolution reconstruction problem for the single Lunar Rover landing image was solved using compressed sensing theory. A super-resolution reconstruction algorithm for sparse representation by using over-complete dictionary was presented. The goal was to reconstruct an original image from its blurred and down-scaled noisy version. The algorithm assumed a local Sparse-Land model on image patches, serving as regularization. The images from Apollo project, CE-1, CE-2 and tests of the second stage of Chang'E project were applied to extract patches for building two dictionaries. The K-SVD algorithm was adopted for training the dictionaries. Through solving optimization problem via Orthogonal Matching Pursuit algorithm, the sparse representation for each low-resolution landing image patch with respect to Al was obtained. The representation coefficients were applied to Ah in order to generate the corresponding high-resolution landing image patch. At the end of the experiment the high-resolution image which satisfied the reconstruction constraint was obtained by using least squares algorithm. Numerical experiments for Lunar Rover landing images from the tests of the second stage of Chang'E project demonstrated the effectiveness of the proposed algorithm. Moreover, the proposed algorithm outperforms bicubic interpolation based method and the algorithm via Yang in terms of visual quality, the Peak Signal to Noise Ratio (PSNR) and Root Mean Square Error (RMSE).
Abstract:As one of the high-power radiating sources in terahertz region, the output power of gyrotrons is up to several tens of kilowatts. The traditional terahertz gyrotrons are difficult to meet the needs of nuclear magnetic resonance using the dynamic nuclear polarization technique, for working in a fixed frequency. In this paper the continuous frequency tunable 0.42 THz coaxial gyrotron with 2 GHz bandwidth by mechanical tuning has been studied. The results show that the output power can keep over 8 kW level in the tuning bandwidth with unchanged operating magnetic field.
Abstract:The spectra of mineral powder and mineral rock were compared and analyzed. A quantitative inversion based on DRS was performed on powder mixtures of plaster and allochite to extract the strong linear bands of each component separately. Combining with the absorption characteristics of endmember minerals, the distribution characteristics of strong linear bands on the reflectance spectra, the ratio spectra and the derivative of ratio spectra were discussed.
Abstract:Sub-tensor based lower rank tensor analysis used for dimensionality reduction and classification in hyperspectral imagery is proposed in this paper. The method aims at raising classification accuracy by representing the hyperspectral image as a tensor, divides it into sub-tensors and performs dimensionality reduction and pixel classification in each sub-tensor. Owing to the idea of creating sub-tensors, the method capitalizes on local spatial correlation, exploits interaction between spatial and spectral dimensions, and maintains hyperspectral data structure with 3D tensor. Compared with existing theories based on tensor analysis, the proposed method eliminates the negative impacts of poor subspace dimension estimation and low global spatial correlation, which might seriously degrade performances of dimensionality reduction. Moreover, as long as subspace dimensions are smaller than sub-tensor dimensions, the method with sub-tensors achieves much higher classification accuracy than the method without sub-tensors. Therefore, for the proposed method, it is not necessary to estimate the subspace dimension. Finally, experimental results of both simulated and real hyperspectral data demonstrate that Sub-Tensor based Lower Rank Tensor Analysis gives better performance in dimensionality reduction and brings higher classification accuracy than existing methods do.
Editor in chief：Jun-Hao CHU
International standard number：ISSN 1001-9014
Unified domestic issue：CN 31-1577
Domestic postal code：4-335