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:Cu2ZnSn(S, Se)4 films were fabricated through post-selenization of Cu-Zn-Sn-S precursors co-electroplated by varied Na2S2O3·5H2O concentrations. The property of obtained films before and after selenization shows a close dependence on the concentration of Na2S2O3·5H2O. Only the film grown by 5 mM of Na2S2O3·5H2O shows a uniform surface with faceted grains, a Zn-poor composition, a single phased Cu2ZnSn(S, Se)4 structure and a 1.11 eV band gap evidencing by SEM, EDS, XRD, Raman and transmittance spectra. More than 5 mM of Na2S2O3·5H2O additive to the electrolyte yielded the films with rougher morphology and the presence of SnSex. Less than 5 mM of Na2S2O3·5H2O additive to the electrolyte resulted in the films with highly Zn-poor content and the primary formation of Cu2SnSe3.
Abstract:A millimeter wave film circulator with coplanar waveguide structure was designed and fabricated using barium ferrite films with thickness of 10 μm. The film circulator operates without external magnet and shows clear circulation at 34 GHz and 37.6 GHz. Circulation with non-reciprocal effect greater than 15 dB has been observed. The results show that circulator using very thin ferrite films can be realized with coplanar waveguide structure. The film circulator exhibits potential to integrate with MMIC.A millimeter wave film circulator with coplanar waveguide structure was designed and fabricated using barium ferrite films with thickness of 10 μm. The film circulator operates without external magnet and shows clear circulation at 34 GHz and 37.6 GHz. Circulation with non-reciprocal effect greater than 15 dB has been observed. The results show that circulator using very thin ferrite films can be realized with coplanar waveguide structure. The film circulator exhibits potential to be integrated with MMIC.
Abstract:CdS thin films are deposited on the substrate temperature of 300 ℃ by magnetron sputtering. The deposited films are annealed at temperature of 370℃, 380 ℃ and 390 ℃ respectively in two atmosphere of dry air and CdCl2 source +dry air. The morphology, structure and optical properties before and after thermal annealing are investigated. The results show that annealed in dry air, grain size, surface roughness and visible light transmittance change is not obvious, the optical band gap increases with temperature increasing. Annealed in CdCl2 source + dry air, recrystallization and grain growth are significant, surface roughness increases, visible light transmittance and optical band gap decreases with temperature increasing. Analysis revealed that the performance is the results of recrystallization temperature and the band tail states doping concentration changes at different annealing conditions.CdS thin films were deposited on the substrate at temperature of 300 ℃ by magnetron sputtering. The deposited films were annealed at temperature of 370℃, 380 ℃ and 390 ℃, respectively, in either atmosphere of dry air or a mixture of CdCl2 and dry air. The morphology, structure and optical properties before and after thermal annealing were investigated. The results show that for samples annealed in dry air, the variations of grain size, surface roughness and visible light transmittance with annealing temperature are not obvious, while the optical band gap increases with temperature increasing. Annealed in the mixture of CdCl2 and dry air, recrystallization and grain growth in the samples are significant. Surface roughness increases with temperature increasing, on the contrary, visible light transmittance and optical band gap decreases. These phenomena are the results of changes in the temperature of recrystallization and doping concentration in the band tail states at different annealing atmosphere.
Abstract:In this paper, the strained SiGe-on-Insulator (SGOI) p-MOSFET and Si-on-Insulator (SOI) p-MOSFET are respectively studied via 2-D numerical simulation by ISE TCAD software. The results indicate that compared with the conventional SOI p-MOSFET, the drain-source saturation current of SGOI p-MOSFET almost more than twice, the sub-threshold current of SGOI p-MOSFET has 1～3 orders of magnitude higher than that of SOI p-MOSFET. Because Ge alloy mole fraction is an important basic parameter to the strained SiGe channel MOSFET, the effect of Ge alloy mole fraction on the electrical characteristics of the SGOI p-MOSFET is in depth study in this paper. With the increasing of Ge alloy mole fraction, the overall electrical properties of SGOI p-MOSFET are improved.The strained SiGe-on-Insulator (SGOI) p-MOSFET and Si-on-Insulator (SOI) p-MOSFET were studied via 2-D numerical simulation by ISE TCAD software, respectively. The results indicate that the drain-source saturation current of SGOI p-MOSFET is almost more than twice that of conventional SOI p-MOSFET. The sub-threshold current of SGOI p-MOSFET is 1～3 orders of magnitude higher than that of SOI p-MOSFET. Because Ge alloy mole fraction is an important parameter for the strained SiGe channel MOSFET, its effect on the electrical characteristics of the SGOI p-MOSFET was studied in detail. With the increasing of Ge alloy mole fraction, the overall electrical properties of SGOI p-MOSFET were improved.
Abstract:A compact, high-performance optical system with mechanical compensation was designed with a 30 times continuous zoom for a 640×512-element cooled staring focal plane array detector. The system was designed using the novel three-group zoom in the form and thrice imaging methods. The system operates in the waveband of 3.7~4.8 μm. F/#=4. The zoom ranges from 750 mm to 25 mm. First, gives the schematic drawing of the optical system was obtained with the optical design software. Then, the optical design software has the analysis of the image quality evaluation, the zoom curve analysis, the temperature environment adaptability analysis, and the Narcissus were analyzed with the same software. Finally, the paper proposed a way to improves the resolution of the system using micro-scan imaging technology. The results show that the modulation transfer function ( MTF) of the optical system is close to the diffraction limit at a spatial frequency of 30 lp/mm and the root-mean-square value of its diffusion spot diameter is less than 15 μm. Zoom curve is smooth and the maximum displacement of the move group is less than 71 mm. The focusing and the temperature compensating of the system were achieved via the axially moving of the mobile group lens. The optical system satisfies l00% cold-shield efficiency and has good image quality in the temperature range of -40~ 60 ℃. Meanwhile the optical system meets the requirements of the new generation of airborne forward looking infrared ( FLIR) system.
Abstract:By analyzing hyperspectral features of elm foliar dustfall content (FDC), a models of hyperspectral monitoring was built. Relationship between hyperspectral parameters and FDC was investigated by using regression analysis method. The results showed that FDC increased spectral reflectance in the visible band while decreased it in the near infrared band. Foliar dust didn't affect the "three edge" position but significantly affected its amplitudes and areas. FDC of elm was badly predicted with the models based on spectrum index or "three edge" parameter. Models based on multivariate linear regression, principal component regression and partial least squares regression can predict FDC primely. The model with 1st derivative value as variables was the best one for estimating FDC by the hyperspectral. Predictive correlation coefficient, predictive root mean square error, and the ratio of sample standard deviation to predictive root mean square error of this model were 0.92, 1.06, and 8.2, respectively.
Abstract:LiDAR (Light Detection and Ranging) waveform decomposition is a key issue in remote sensing data processing. Traditional waveform decomposition methods can’t detect weak sub-waveforms when sub-waveforms are overlapped in original data. Besides, these methods are time consuming and not robust to noise. To overcome the obstacle, this paper proposed a new method, which mainly includes four steps. The first is to estimate the errors by filtering the original waveform. Then, iteratively peeling off sub-waveforms from the waveforms till the value of maximum peak is less than a given threshold. The next step is to optimize the parameters of all sub-waveforms using L-BFGS method. At last, nearest sub-waveforms are combined. This new strategy can detect the weak peaks in the complex situations and is very robust to noise. Lots of experiments demonstrate the effectiveness of the proposed method.
Abstract:To correct the attenuation of radar echo at millimeter-wave band, stratus cloud, precipitating stratus cloud and convective cloud echo data were chosen as sample for the test. Method of bin-by-bin correction in the groups was used according to the empirical relationship between radar reflectivity factor Z and attenuation coefficient k. The results show that, in cases of stratus clouds with weak echo, the corrections are minor and these echoes are almost right. On the contrary, in case of rainfall, both water droplets and rich water vapor along the ray path will cause strong attenuation, and it is difficult to carry out the correction. After attenuation correction, the quality of millimeter wavelength radar data is definitely improved though difference is still existed.
Abstract:In the uncooled optical readout infrared imaging technology based on knife edge filter, the reflection of the optical elements bring in stray light spots in the CCD target surface. It makes the proportion of FPA image in the detected light intensity signal reduced, thus the sensitivity of optical detection is reduced. A polarized optical readout system was proposed. Polarizers and a quarter wave plate are added to the system. The polarizing beam splitter is used to replace the original beam splitter. The reflected stray light of the optical components in the optical path is thus eliminated. The proportion of the FPA image received in the CCD target surface substantially increased, so the optical detection sensitivity is enhanced. The polarized optical readout infrared imaging experiment result showed that the detection sensitivity increased by about 47% than the non-polarized system, which is close to the theoretical value.
Abstract:FY-2 Visible and Infrared Spin Scan Radiometer had obviously nonlinear characteristics at low signal. It brought significant biases when using linear calibration in low temperature targets monitoring especially for typhoon targets, which seriously influences FY-2 quantitative application. Nonlinearity of FY-2D infrared detector in window channels was investigated using laboratory calibration measurements and collocation samples based on high-spectral sensor IASI. It was found that nonlinear performance existed both at high and low signal, but impacts at low signal were the most significant. Comparing with laboratory measurements, linear calibration could cause more than 10 K deviations at low temperature. In order to guarantee the quality of calibration results and its stability, nonlinear calibration scheme was applied only in low temperature area. Nonlinear calibration scheme was investigated from its consistency, and also typhoon application. The results indicated nonlinear calibration was stable, and significantly improved calibration accuracy at low temperature, especially in typhoon monitoring which was advanced at least by 7K.
Abstract:The oscillation characteristics of 980 nm electrically-pumped vertical-external-cavity surface-emitting laser (EP-VECSEL) with periodic gain structure active region of InGaAs/GaAsP quantum well was analyzed theoretically and experimentally. The relationship between the DBR & external cavity mirror reflectivity and the oscillating characteristic characteristics of the EP-VECSEL with coupled cavity was simulated. Furthermore, based on the results of simulation, the device structure was optimized. EP-VECSEL devices with different external cavity reflectivity were fabricated and the continuous-wave (CW) oscillation output characteristics were studied. The results of experiment indicated that the threshold current of the 300 μm-device with 90% external mirror reflectivity was 1.2 A and its output power was 270 mW while under injected current of 4A; the output power of the 300 μm-device with 95% external mirror reflectivity was 150 mW at 4 A of injected current and the threshold current was 0.9 A. The experimental results were in good agreement with theoretical analysis, indicating that the model using in this article is suitable for the optimization of EP-VECSEL’s oscillation characteristics.The oscillation characteristics of 980 nm electrically-pumped vertical-external-cavity surface-emitting laser (EP-VECSEL) with periodic gain structure active region of InGaAs/GaAsP quantum well was analyzed theoretically and experimentally. The relationship between the DBR & external cavity mirror reflectivity and the oscillating characteristic characteristics of the EP-VECSEL with coupled cavity was simulated. Furthermore, based on the results of simulation, the device structure was optimized. EP-VECSEL devices with different external cavity reflectivity were fabricated and the continuous-wave (CW) oscillation output characteristics were studied. The results of experiment indicated that the threshold current of the 300 μm-device with 90% external mirror reflectivity was 1.2 A and its output power was 270 mW while under injected current of 4A; the output power of the 300 μm-device with 95% external mirror reflectivity was 150 mW at 4 A of injected current and the threshold current was 0.9 A. The experimental results were in good agreement with theoretical analysis, indicating that the model using in this article is suitable for the optimization of EP-VECSEL's oscillation characteristics.
Abstract:The paper proposed a method to monitor LNC in crop with hyperspectral remote sensing. Taking the LNC monitoring of barley that is more demanding for nitrogen fertilization as a case, this study employs new spectral features such as slopes and angles extracted from the normalized reflectance curves in Visible-Near Infrared region to evaluate LNC, At the same time, the optimal combination principle that was widely used in the combinated forecasting domains was presented to estimate LNC. The analysis resluts proved that most of the new spectral features propsoed in the study exhibited significant correlations with LNC. Among the new spectral features, the key features of slopes (Kre/Kpb and Kpb) and angles (Aδ/Aα and Aδ/Aθ) could well describe the dynamic pattern of LNC changes in crop. The optimal combination algorithm determined the optimal combination with Kre/Kpb and Knir1, which could increase the spectral responding to LNC, strengthen the stability of models monitoring LNC and improve the accuracy of LNC estimates.
Abstract:A SAM weighted KEST algorithm based on kernel eigenspace separation transform (KEST) was proposed for anomaly detection in hyperspectral imaging. Weights are introduced for each sample in the difference correlation matrix (DCOR), and the input pixel neighbor surroundings. All samples were weighted according to the angle between the sample spectral vector and the centered vector in detection window to minimize the influence of anomalous data and outstand the contribution of principle component. In this way, DCOR represented the difference between target and background distribution much better. Experimental results indicate that the proposed method shows superior performance over the conventional anomaly detection algorithms and KEST.
Abstract:To minimize the uncertainties related to the FTIR spectrometer, three improved methods were proposed to measure the spectral emissivity. For method 1 (M1) and method 2 (M2), an invented device was used to change the environment radiation which makes the ill conditioned equation solvable. Method 3 (M3) is based on the gray body assumption, and an iterative procedure was applied to derive the temperature of samples, then the spectral emissivity can be retrieved based on this temperature and the FTIR measurements. In order to validate these methods, the emissivity derived from the measured temperature was used as a reference. The results indicate that for the samples with high emissivity, such as quartz plates and cardboard, three improved methods have comparable accuracy; while for the samples with low emissivity, such as rusty iron plate and aluminum plate, the M3 is more reliable than the other two methods. M1 and M2 need to go through more procedures than M3, and this may lead to some deviation from the reality. Overall, three improved methods greatly improved the spectral emissivity measurements with FTIR spectrometer.
Abstract:Based on four filed cruises from 2004 to 2010 in Tai Lake, four models were investigated in the present study, including two-ration-model (TRM), three-band-model (TBM), enhanced three-band-model (ETM) and four-band model (FBM) using in situ measurements and MERIS image data. The validation was performed using samples from Taihu (n=13) and Chaohu Lake (n=21). The results demonstrated that the ETM was the most appropriate to estimate chlorophyll a concentration in highly turbid waters with higher R2(0.34~0.94) and lower RMSE (3.17~8.70 μg/L). Furthermore, the lookup table of the molding input parameters was determined for the four seasons in Taihu Lake. The resultant model was applied to MERIS images (8, 9 and 10 waveband) to detect the temporal and spatial variations of chlorophyll a concentration in Tai Lake.
Abstract:To promote the evaluation precision of millimeter wave transmission attenuation in the complex precipitation condition, representative size distribution parameters for five kinds of precipitations (stratiform rain, mixed stratiform and cumulonimbus rain, cumulonimbus rain, dry snow and wet snow) were obtained by analysis of precipitation characteristics in many areas. Combined with the shape, phase and dielectric model of the precipitation particles, the scattering characteristics of precipitation particle clusters at the millimeter waveband were calculated. The numerical simulation results show that the precipitation intensity is not the only factor that influence the millimeter wave propagation characteristics; the phase of particle, drop size distribution, incidence wave frequency and temperature have different effects on the millimeter wave propagation, The size distribution and number density are the main factors influencing the millimeter wave propagation attenuated by rain. The composition of ice and water are the main factors influencing the millimeter wave propagation attenuated by snow. The phase of precipitation particles also have strong effect on the millimeter wave propagation. There are distinct differences between the snow and rain. The temperature is the least factors. At precipitation attenuation model was established based on the drop size distribution and temperature is established.
Editor in chief：Jun-Hao CHU
International standard number：ISSN 1001-9014
Unified domestic issue：CN 31-1577
Domestic postal code：4-335