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:InP-based metamorphic InGaAs photodetector structures with lattice mismatch up to 2.6% were grown on InAlAs graded buffers with a relatively high mismatch grading rate of 1.1%μm-1 by gas source molecular beam epitaxy.They were compared to the samples with the same structures but smaller lattice mismatch of 1.7% and 2.1% to the InP substrate.Characteristics of the wafers were investigated by the measurements of atomic force microscopy,x-ray diffraction,photoluminescence and device performances.Results show that moderate surface morphology,large degree of relaxation and feasible optical characteristics have been obtained for the photodetector structures with lattice mismatch of 2.6%.The cut-off wavelength of the device is about 2.9μm at room temperature.The typical dark current of 2.56μA at room temperature has been achieved at reverse bias of 10 mV for the photodetector with 300 μm diameter.
Abstract:The properties of electron states in the presence of microwave irradiation play a key role in understanding the oscillations of longitudinal resistance and the zero-resistance states in a high-mobility two-dimensional electron gas (2DEG) in low magnetic field. The properties of electron states in a high-mobility low-density GaAs/Al0.35Ga0.65As 2DEG in the presence of Ka-band microwave irradiation were studied by reflectance-based optically detected cyclotron resonance (RODCR). The influence of the direction of the microwave alternating electronic field, wavelength of the laser, and temperature on RODCR results was discussed. The results show that RODCR measurements provide a convenient and powerful method for studying electron states in 2DEG.
Abstract:According the lateral collection characteristics of minority carriers in linear HgCdTe infrared focal plane array(IRFPA), an image processing method for improving the quality of images was proposed. This method was applied to the remote sensing images. which were obtained from a satellite loaded with 256-element IRFPAs developed by Shanghai Institute of Technical Physis. The results show that both the resolution and contrast of the images are improved obviously with the proposed method.
Abstract:The steady-state nonvolatile two-step, two-color holographic storage performance for both LiNbO3:Fe:Mn and LiNbO3:Fe was investigated theoretically based on the two-center model. By considering all the possible electron transfer processes between the deep-trap and the shallow-trap centers, LiNbO3:Fe was confirmed theoretically to be of bigger space-charge field and higher recording sensitivity than LiNbO3:Fe:Mn in the low intensity region.
Abstract:A Integrated readout circuit (ROIC)of focal plane arrays for uncooled infrared detector based on microcantilever was proposed. The ROIC was optimized to reduce noise based on noise modeling and analysis . A prototype of 16×16 ROIC was designed and fabricated by 0.35μm CMOS technology. The measurement results showe that the power dissipation is 16.5mW for a 5V supply voltage at 50Hz frame rate, the linearity is 99.2% at typical modes，the uniformity is larger than 97% and the equivalent noise charge (ENC) is below 150e.
Abstract:Laser dazzling is important for countermeasures of precision guided weapons and self defence. In this study, the damages of high-power CO2 laser to long-wave infrared (LWIR) HgCdTe detector were studied theoretically and experimentally. Based on the results of experiment, the relationship between he temperature-rise of detectors and the time of laser irradiation on the detector and the power of laser was calculated by using the theoretical model of temperature-rise .The theoretical results demonstrate that the interference threshold of the detector is 16.5W/cm2 and the damage threshold is 126W/cm2. The conclusions have a reference value for laser jamming satellite-based detector.
Abstract:The extended interaction klystron (EIK) consists of several reentrant multi-gap coupled cavities. The demand for high-power microwave sources in the millimeter-wave region promotes the development of a Ka-band The extended interaction klystron (EIK). In this study, The real part of the impedance of the three-gapcoupled output cavities composed by three uniform gap cavities was derived by using equivalent circuit theory and field analysis method ,respectively.The basic parameters of the broad band output circuit were obtained by using equivalent circuit theory . Filter loaded three-gap coupled output cavities with band width of 4.6% were designed by using field analysis method .It lays a solid foundation for the development of the broad band EIK.
Abstract:The principle of Vlasov mode converter for whispering-gallery mode gyrotron was studied in detail by using a geometric optics model. The radiation field passing through the mode converter was analyzed by using the equivalent image source model and the vector diffraction theory. After considering some particular parameters of W-band whispering-gallery mode gyrotron, the field distribution of radiated beam passing through Vlasov mode converter was discussed by numerical calculation. The results indicate that the high-order whispering-gallery mode inside the gyrotron is converted into Gaussian beams in free space by the Vlasov mode converter, and the Gaussian distribution in the far zone is superior to that in the near zone.
Abstract:FTIR spectra were used to measure the spectra information of isoprene. The infrared spectra were calculated by using Gaussian 03 program under density functional (DFT) theory level. The experimental results agree with the theoretical values. The OH-iniated photooxidation of isoprene was conducted by using a smog chamber system made by ourselves. The photooxidation products were detected using FTIR method to study the functional groups and qualitatively analyze the chemical components.The results shown that the photooxidation products contained carbonyl group, C-O bond compounds, aldehyde, ketone, carboxyl acid, and nitric acid compounds.
Abstract:In recent years, wireless sensor networks（WSN） are widely applied to three-dimensional monitoring, distributed monitoring, target tracking, space exploration, random distribution of measurement and other fields. Information transmission security of WSN is attracting more attention of researchers because of the wide applications of WSN for military purpose during the last decade,such as enemy reconnaissance,strength monitoring , etc. In this study, time reversal technique as a new technology was utilized to reduce probability that the signal were illegally detected in space and time domains. TR technique allows signals to be detected only at a specific time and specific space, while in the other time and space the signal will be very difficult to be detected . Thus, TR technology enhance the information security of WSN.
Abstract:In order to apply spatial spectrum estimation to millimeter-wave radiation array system for detecting targets with supper resolution, it is needed to solve two key-problems which are weakness of thermal signals’energy emitted from targets and the decline of performance caused by array errors. To solve this problems, an array error model with low signal noise ratio (SNR) were presented. In this model, the influence of amplitude and phase errors on signal source and channel noise were considered, and the perturbation range of the eigenvalues and the error distance of the signal eigenvector space of the autocorrelation matrix received by array were derived. Then the calibration algorithm for amplitude and phase errors based on the model was proposed, which can make spatial spectrum estimation with high resolution be used in millimeter-wave radiation array system effectively. The effectiveness and correctness of the model are verified by the experiments.
Abstract:A new chemometric method for determining the contents of fat and protein in milk powder was established by using near infrared (NIR) spectroscopy combined with chemometric methods . The calibration and prediction sets were partitioned by Kernard-Stone algorithm. Wavelet transform (WT) was used for de-noising and compressing signals. The radical basis function neural networks (RBFNN) model for the contents of fat and protein was built by combining with the reconstruction spectral signal . Three parameters,i.e., the spread value of RBF network, the wavelet functions and decomposition levels were discussed in detail. The results show that the precision of the prediction model is the best when wavelet function, compression level and spread value are db2, 4, and 3.5 for fat. In some way, the precision is the best when wavelet function, compression level and spread value are db8, 4, and 6 for protein. Correlation coefficient (Rp) of prediction set for the correction model of fat and protein are 0.990 and 0.994, and root mean square error prediction(RMSEP) is 0.007 or 0.004, respectively. The results also showe that the model is easy and robust, and prediction acduracy is improved by using RBFNN combined with WT for building NIR models. This method is suitable for determining the content of fat and protein in milk powder rapidly and nondestructively.
Abstract:Dynamic spectrum (DS) method was used to measure non-invasively human erythrocyte content for the first time. In vivo measurements were carried out to 28 healthy volunteers, and parital least-squares(PLS) regression was used to establish the calibration model of subjects’ erythrocyte content values against DS data. The correlation coefficients were 0.9193 and 0.9058 for calibration set and validation set, respectively. The biggest relative error of validation is 7.96%, and the average relative error is 6.21%. Measurement results show that the influences of individual differences on spectra can be decreased effectively by DS method, and this method can measure accurately human erythrocyte content and it is a promising method for non-invasive blood analysis.
Abstract:A suitable chromosome encoding method, which could correspond with the network one by ,was proposed. The species invasion genetic algorithm was used to train artificial neural networks. In the invading process, the genetic algorithm adjusts adaptive crossing operation and mutation operation. A method based on the average fitness values was proposed to determine the scale of invasion species,and a detailed description of the algorithm steps was given, Finally, the validity and superiority of the algorithm are proved by the experimental results.
Abstract:Several classic image fusion methods were analyzed by using the extended model of general component substitution(GCOS) framework.The relations between the injection models of these fusion methods were investigated. On this basis, a novel spatial variable detail injection method, which took the correlations of panchromatic and multispectral bands into consideration, was established.By combining with different spatial detail extracton methods, three novel high-pass modulation(HPM) image fusion schemes were proposed. The fusion results of Ikonos and Quickbird data were analyzed quantitatively by using the proposed methods, and the result was compared with those by the traditional HPM. Fusion result of visible bands show that fusion performance is improved by the proposed modification of modulation coefficients and detail extraction methods compared to HPM, and the contribution of the improved modulation coefficients is more significant. However, experiment result of near infrared (NIR) bands indicate that the study of the filter design should be paid more attentions for the fusion in NIR and panchromatic bands.
Abstract:Since the segmentation results of SAR images by traditional transform domain hidden Markov Tree (HMT) Model were unsatisfactory in homogenous regions and exact edges， a new segmentation method based on second generation bandelet-domain HMT-3S model was proposed . The method was called BHMT-3Sseg shortly. HMT-3S is a special kind of HMT which combines the correlation of different subbands. It is more reasonable to characterize texture regions than HMT model. BHMT-3Sseg models the second generation Bandelet coefficients of an image by using HMT-3S, and the SAR image segmentation results were obtained by training the parameters of HMT-3S and computing the likelihood of each scale and multiscale fusion based on a context model. The segmentation results by BHMT-3Sseg not only have more exact and more continuous edges, but also retain better region information. The experiments show that BHMT-3Sseg is efficient and effective for SAR image segmentation.
Abstract:In order to overcome the serious background interferences for small target detection of hyperspectral imagery, a nonlinear anomaly detection algorithm based on the background residual error data was proposed. After the background endmembers were extracted, spectral unmixing technique was applied to all mixed spectral pixels to separate target information from complicated background clutter.Then, the unmixing residual error data that included abundant target information was mapped into a high-dimensional feature space by a nonlinear mapping function. Nonlinear information between the spectral bands of hyperspectral imagery was exploited and the anomaly targets could be detected by using RX operator in the feature space. Thus, the ninlinear statistical characteristics between the hyperspectral bands were used effectively on the basis of suppressing the large probability background information. Numerical experiments were conducted on real AVIRIS data to validate the effectiveness of the proposed algorithm. The detection results were compared with those detected by the classical RX algorithm and KRS which did not suppress the backguound information. The results show that the proposed algorithm has better detection performance, lower false alarm probability and lower computational complexity than other detection algorithms.
Abstract:To obtain ultra-high spatial resolution image, a kind of non-conventional fiber bundle, whose input was line array while output was plane array, was designed. The coordinate table of each fiber in input and output terminal must be ascertained when synthesizing object images by using the scanning-imaging system of fiber bundle. However, limited by manufacture technology, the fiber bundle output structure was not strictly aligned. An algorithm based on Kalman Filter，aiming at the coordinates errors, was proposed in this paper.Different initial searching step was given to inner layer and intra layer respectively,by searching fiber center's position one by one in the output terminal, under the principle of minimum mean square error.The coordinate table of the output was established ,and the position mapping relationship between output and input was built.Comparing the termination margin and marking the searche fiber were the two ways to improve the robustness of the algorithm.Z-shaped path improve the efficiency of the algorithm.The results show that the coordinates obtained by the proposed algorithm can demarcate the position of the fiber and the object image was testored by extracting the information of the scanning imaging system coupled by the bundle.
Editor in chief：Jun-Hao CHU
International standard number：ISSN 1001-9014
Unified domestic issue：CN 31-1577
Domestic postal code：4-335