• Volume 29,Issue 3,2010 Table of Contents
    Select All
    Display Type: |
    • >Infrared Materials and Devices
    • ANOMALOUS CAPACITANCE OF GaNBASED SCHOTTKY DIODES

      2010, 29(3):161-166.

      Abstract (1829) HTML (89) PDF 742.32 K (3404) Comment (0) Favorites

      Abstract:The capacitancevoltage (CV) measurements of GaNbased Schottky diodes were carried out in the frequency range of 0.3~1.5MHz. Anomalous peaks and negative value of capacitance were observed in the CV plots of Au/iGaN Schottky diodes under forward bias, while neither of them was seen in the plots of Au/iAl0.45Ga0.55N Schottky diodes. Based on the parameters extracted from the currentvoltage (IV) and CV plots of GaN and Al0.45Ga0.55N Schottky diodes, the peak and negative capacitance are ascribed to the capture and loss of interface charges. These processes are greatly suppressed when there exists a huge series resistance in the diode.

    • OPTICAL PROPERTIES OF COLLOIDAL CdSe TETRAPOD NANOCRYSTALS

      2010, 29(3):167-171.

      Abstract (1533) HTML (122) PDF 770.74 K (1796) Comment (0) Favorites

      Abstract:Time resolved optical properties of CdSe tetrapod nanocrystals where studied. The results show that the decays of photoluminescence (PL) intensities for tetrapods in solution and on insulating silicon substrate can be well fitted by a biexponential function. Based on the emissionenergy dependence of carrier lifetimes, the fast and slow PL decays of CdSe tetrapods are attributed to the recombination of delocalized carriers and the localized carriers in the localized states, respectively. By comparing the amplitude ratio of the fastdecay component to the slowdecay component for samples in solution with those on silicon, it is concluded that the slow PL decay is associated with the recombination of localized carriers in the surface defects of CdSe tetrapods.

    • >Image Processing and Software Simulation
    • SIMULATION OF ENVIRONMENTAL FACTORS FOR PERFORMANCE RELIABILITY ESTIMATION

      2010, 29(3):172-175.

      Abstract (1568) HTML (110) PDF 747.51 K (2153) Comment (0) Favorites

      Abstract:Environmental data synthesis method is one of the effective ways to solve small sample performance reliability estimation problem for complex electronic equipments. The most important part of this method is how to estimate the environmental factors. However, the existing estimation methods have the shortage of lower estimation precision and more difficulty in modeling. In view of these situations, an evaluation method for environmental factors based on circuit simulation was proposed. Firstly, the Pspice schematic of equipment (i.e. the physics modeling of equipment) was protracted. Then, the transient analysis, MonteCarlo analysis and temperature analysis of Pspice software were used to attain the performance simulation data. Thirdly, environmental factors can be acquired for discretional environment situations by combining with the related theory of accelerated performance testing. Finally, an example of steady voltage power was provided and the validity and practicability of the proposed method were confirmed.

    • >Infrared Materials and Devices
    • MICROSTRUCTURES AND OPTICAL PROPERTIES OF PbZr0.4Ti0.6O3 MULTILAYER FILMS DEPOSITED ON FTOCOATED GLASS SUBSTRATE

      2010, 29(3):176-179.

      Abstract (1729) HTML (188) PDF 734.75 K (2010) Comment (0) Favorites

      Abstract:PbZr0.4Ti0.6O3 multilayers with 16 periods have been grown on the glass substrates coated by transparent tin oxide doped with fluorine by using chemical solution deposition, and the micro-structures and optical properties of the multilayers have been investigated. The scanning electron microscope images show that the multilayers exhibit a smooth, dense and crack-free surface morphology, and a layered structure consisting of dense and porous PbZr0.4Ti0.6O3 layers. The X-ray diffraction curves of the PbZr0.4Ti0.6O3 multilayers show a single perovskite structure. The room temperature reflectance and transmittance spectra in the wavelength range of 350-900 nm display an optical reflection-band centered at 450 nm, with a peak reflectivity of 91% and a 41 nm stop-band width, and a transmission valley at 450 nm with the same band-width as the reflection band. The minimum of the transmittance is less than 6% in the valley. This investigation is helpful to enlarge the application scale of ferroelectric multilayers.

    • >Terahertz and Millimeter Wave Technology
    • DESIGN AND FABRICATION OF KaBAND BROADBAND COMBINED POWER AMPLIFIER BASED ON FLEXIBLE SUBSTRATE INTEGRATED WAVEGUIDE TECHNOLOGY

      2010, 29(3):180-184.

      Abstract (1700) HTML (104) PDF 843.79 K (1924) Comment (0) Favorites

      Abstract:〗An eightway power amplifier at Kaband was designed, fabricated and measured. Measured results show that the maximum combined output power is 4.2W (continuous wave) at 26.5GHz. The power combining efficiency is higher than 60% over the interested frequency range (25.1~28.4GHz) and it can reach to 72.5% at 26.4GHz. The foundational cell of this amplifier is a double antipodal flexible substrate integrated waveguide (FSIW) including symmetrical dovetail taper transition structure. A number of dovetail tapers of these cells are stacked together and plugged along narrow wall into a couple of normal waveguides, a broadband power divider/combiner is then simply implemented with low insertion loss. The results demonstrate that this technique can be applied in broadband power combining amplifiers at millimeterwave frequencies.

    • >Remote Sensing Technology and Application
    • MODIFIED MONITORING METHOD OF VEGETATION WATER CONTENT BASED ON COUPLED RADIATIVE TRANSFER MODEL

      2010, 29(3):185-189.

      Abstract (1499) HTML (107) PDF 742.79 K (1776) Comment (0) Favorites

      Abstract:By coupling leaf with canopy radiation transfer model, a modified vegetation index was explored to extract the vegetation water content in order to monitor the vegetation water content from remote sensing data. Some vegetation indices for the vegetation leaf water content, such as NDVI, WI, NDWI, MSI, CSI and NDII, were analyzed and compared based on the hyperspectral data simulated by PROSAIL. The results show that the water content can not be estimated by NDVI, and CSI is not an ideal tool. The rest four indices WI, NDWI, NDII, and MSI can generate relatively good results with the correlation coefficients square between the estimation and real value being all about 0.76. Then, sensitivity factors were analyzed for NDWI extracting the water content, and the results show that NDWI and MCARI have a good linear relationship. This method can better remove the interference of LAI. The correlation coefficient square between the estimation and real value has been improved to 0.97, which is increased by 27% compared to the foregoing value. The estimated residual is reduced from 0.0156 to 0.00535, a reduction of 65% compared to NDWI method.

    • Analysis on Spectrum Data and Spectral Reflectance Characteristics for Mainly Object of the Typical Oasis in Xinjiang:A Case Study in Delta Oasis of Weigan and Kuqa Rivers

      2010, 29(3):190-195.

      Abstract (2200) HTML (155) PDF 896.60 K (2188) Comment (0) Favorites

      Abstract:The applications of remote sensing depend more and more on the particular futures in the spectrum of ground objects. To obtain the spectral characteristics of arid area, the spectrum of delta oasis of Wigan and Kuqa rivers located in the North of Tarim Basin were collected and studied. The spectral data of typical geotargets such as salinealkaline ground, silver sand ground, cotton ground, Tamarix, Alhagi, sparsifolia, Phragmites australis, Halostachys, caspica etc. as well as water body were acquired by the ASD Fieldspec HH spectrometer. These data were then analyzed. The method of moving average, which may depress partially the highfrequency components of the spectrum, was used to eliminate the noise in the spectrum. The spectrum technology of the derivative was implemented to remove the environmental noise and distinguish overlapped spectrum. Finally after continuum removal, spectral curves with highlighted absorption and reflection features were obtained. With these data, the spectral library of primary geosurface features for the delta oasis of Weigan and Kuqa rivers has been built up with the aid of ENVI software. It can provide services for the vegetation surveys, vegetation classification, and environmental monitoring in this area.

    • >Infrared Materials and Devices
    • Design of reflective zoom systems with 4 mirrors for infrared applications

      2010, 29(3):196-200.

      Abstract (1725) HTML (104) PDF 766.76 K (1978) Comment (0) Favorites

      Abstract:A relatively simple optical method based on Seidel aberration theory was presented for the design of mechanically compensated infrared reflective zoom systems with 4 mirrors. This research includes the study of image formation rules by a single mirror, the concept of the mechanical compensation method in zoom systems, and the derivation of analytical formulae for the Seidel aberration coefficients. The advantage of this method is that it allows the designer to achieve the initial structure parameters of the optical system (radii of curvature and separations between mirrors, etc.) by solving a set of Seidel aberration coefficient functions. Two design examples of 4mirror zoom systems were given. The results show that the proposed method is feasible in the design of infrared reflective zoom systems with large zoom ratios.

    • >Remote Sensing Technology and Application
    • INVERSING THE BEST BANDS OF BRINY DENSITY BY USING HYPERSPECTRAL MULTIANGLE AND POLARIZATION INFORMATION

      2010, 29(3):201-204.

      Abstract (1937) HTML (115) PDF 662.35 K (2596) Comment (0) Favorites

      Abstract:The relation between the polarization index and the liquid density can be established in term of refractive index. USB2000 spectroscopy was used to obtain the hyperspectral polarization information of brine with different concentrations, and the briny density was calculated. It is found that the optimum wavelength bands of light incident at different angles are different for brine with different concentrations. The precision of the briny density calculated in the best bands is the highest. The best bands become wider when incident angle approaches the Brewster angle, which can satisfy the demand of the present remote sensing technology. The results provide a new scientific basis for monitoring the density of water by using remote sensing technology.

    • >Image Processing and Software Simulation
    • HYPERSPECTRAL MULTIBAND IMAGE FUSION ALGORITHM BY USING PULSE COUPLED NEURAL NETWORKS

      2010, 29(3):205-210.

      Abstract (1968) HTML (113) PDF 956.19 K (1605) Comment (0) Favorites

      Abstract:Considering hyperspectral images with multiband and large data amount, a novel fusion algorithm of hyperpsectral multiband images based on pulse coupled neural networks (PCNN) was proposed. Firstly, the original PCNN model was expanded according to the multiinput characteristics of the hyperspectral images, and a multichannel PCNN model was applied to fuse the multiple input images in a nonlinear manner. Then, the modified variable threshold exponent increasing attenuation model was proposed to improve fusion effect and reduce time complexity by analyzing the characteristics and shortage of the traditional variable threshold attenuation model. Finally, the fusion image with a certain degree of enhancement effect was obtained by the time matrix which recorded the ignition time. The experiment results show that the proposed algorithm outperforms the traditional fusion algorithms based on principle component analysis (PCA) and wavelet transform.

    • UNMIXING ALGORITHM OF HYPERSPECTRAL IMAGES

      2010, 29(3):210-215.

      Abstract (2659) HTML (113) PDF 1.10 M (2314) Comment (0) Favorites

      Abstract:The traditional hyperspectral image unmixing algorithm involves the extraction of endmember and the estimation of abundance values for each endmember. Although many models usually provide acceptable unmixing results, the bias may be great in those pixels where an unknown endmember exists. Therefore, a hyperspectral image unmixing algorithm based on support vector data description (SVDD) was proposed. First, hyperspectral image datas were classified into two parts,i.e., innerclass and outerclass. The datas in the innerclass were considered as the pixels mixed by known endmember datas entirely, and the datas in outerclass included unknown endmembers. The boundary between the two classes was considered as points mixed by known and unknown endmember datas. Then, unmixing operation was carried out. Experimental results on synthetic and real hyperspectral data demonstrate that this method reduces effectively the influence of the existing unknown endmembers on unmixing results, and unmixing component with unknown endmember can be given. The results unmixed by the proposed algorithm are hardly affected by unknown endmembers and are superior to that of direct unmixing.

    • STORAGE PERIOD DETERMINATION OF BEE POLLEN BY VISIBLENEAR INFRARED SPECTROSCOPY WITH LEAST SQUARESSUPPORT VECTOR MACHINES

      2010, 29(3):216-219.

      Abstract (1770) HTML (102) PDF 648.53 K (1674) Comment (0) Favorites

      Abstract:In order to investigate a fast and efficient method determining the freshness of bee pollen, visible and nearinfrared (VisNIR) reflectance spectroscopy with least squaressupport vector machines (LSSVM) was applied to determine storage period of bee pollen. The Camellia bee pollens stored for 4~50(47) days at room temperature were investigated. Spectra were collected by an ASD Fieldspec spectrometer as the input variables to build the LSSVM model. Results show that the prediction performance of LSSVM model is better than partial least square (PLS) and principal component regression (PCR). Its correlation coefficient of prediction set (rp) is 0.996, standard error of prediction (SEP) is 1.310, and root mean square error of prediction (RMSEP) is 1.308. It is concluded that VisNIR spectroscopy with LSSVM is a feasible method to determine the storage period of bee pollen. Moreover, the results for different storage periods were compared. It is shown that the storage periods between 11~50 can be well determined by LSSVM.

    • >Infrared Spectroscopy and Spectral Analysis
    • SIMULTANEOUS AND RAPID DETERMINATION OF PHYSICAL AND CHEMICAL INDICES OF FLAVOR AND FRAGRANCE BY FOURIER TRANSFORM NEARINFRARED SPECTROSCOPY

      2010, 29(3):220-224.

      Abstract (1419) HTML (102) PDF 700.76 K (1806) Comment (0) Favorites

      Abstract:〗A method to determine some physical and chemical indices of tobacco flavor and fragrance simultaneously and rapidly was established. Prediction models of four indices including refraction index, pH, relative density, and total volatile constituents were founded by using Fourier transform nearinfrared (FTNIR) spectroscopy. The effect of spectra pretreatment on models was studied. At the same time, reliability and repeatability of the predicted results of these models were evaluated. Results show that these models are applicable to different flavors and fragrances, and can predict simultaneously four indexes including refraction index, pH, relative density, and total volatile constituents. The values of RMSEP are 0.00182, 0.374, 0.00393 and 3.04, respectively. Therefore, the qualities of tobacco flavor and fragrance can be controlled rapidly without any damage by FTNIR.

    • >Image Processing and Software Simulation
    • IMPROVING THE CORRECTION ACCURACY OF FARADAY ROTATION BY USING TEC DATA RELEASED BY IGS

      2010, 29(3):225-229.

      Abstract (1451) HTML (111) PDF 660.70 K (1659) Comment (0) Favorites

      Abstract:Faraday rotation induced when electromagnetic wave penetrates through ionosphere is the major source for the cross polarization in observed Stokes brightness temperature with a polarimetric microwave radiometer. Faraday rotation correction employing TEC (total electron content) data generated by IRI (international reference ionosphere) model can not meet polarization rotation correction accuracy in some low latitude regions. To improve the correction accuracy, the following two methods were used: 1.integrating Faraday rotation angle along observation path and 2.correcting Faraday rotation by using TEC data released by IGS. Analysis results show that the first method is hardly helpful to improve the correction accuracy, while the second one can improve Faraday rotation correction accuracy considerably. By using TEC data, the correction method can satisfy the correction accuracy of polarization rotation angles which a polarimetric microwave radiometer demands.

    • The Research Maneuvering Tracking Algorithm for MMW/IR Multi-sensor Fusion

      2010, 29(3):230-235.

      Abstract (1956) HTML (114) PDF 698.80 K (1964) Comment (0) Favorites

      Abstract:Millimeter wave(MMW)/infrared (IR) sensor is a key technology for composite guidance system of missiles. Aimming to solve the problems that there were linear errors in the algorithm of squareroot unscented Kalman filter (SRUKF) and it was difficult to obtain the importance density function for the algorithm of particle filter(PF), a squareroot unscented Kalman particle filter (SRUKPF) algorithm with the sequential fusion was presented by combining SRUKF with PF. The main idea of this algorithm was to calculate the state transition matrix and the error covariance matrix by SRUKF, and to construct the importance density function by the sequential fusion of particle filter. Thus, the importance density function could integrate the latest observation into system state transition density, and the proposal distribution could be more in line with the distribution of real states. To demonstrate the effectiveness of this model, simulations were carried out based on tracking algorithm for the surfacetoair missile with MMW/IR sensor.The results show that this technique can overcome the flaw that it is hard to get the optimization importance density function in the particle filter, and it can significantly improve the accuracy of state estimation for the system with multisensors.

    • RADIOMETER ARRAY CALIBRATION WITH PARTIAL SPATIAL INFORMATION MISSING

      2010, 29(3):236-240.

      Abstract (1608) HTML (101) PDF 845.64 K (1525) Comment (0) Favorites

      Abstract:The spatial response matrix in all directions needs to be measured for the traditional radiometer array calibration algorithm, and the reversed image can be blurred by missing partial spatial information. To solve this problem, an improved calibration algorithm with partial spatial information missing was proposed. Experimental results for the real scene show that the image blur can be restrained effectively by the improved calibration algorithm

Editor in chief:Jun-Hao CHU

International standard number:ISSN 1001-9014

Unified domestic issue:CN 31-1577

Domestic postal code:4-335

  • Most Read
  • Most Cited
  • Most Downloaded
Press search
Search term
From To