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:A novel ZnO photoanode with high specific surface area and good light scattering ability was fabricated for dyesensitized solar cells（DSSCs）. The photoanode comprised of mesoporous ZnO microspheres which were prepared by a solvothermal process. The structures and morphologies of ZnO microspheres were measured and confirmed by means of x-ray diffraction （ XRD）, scanning electron microscopy （ SEM ）, energy dispersive spectrum （ EDS ）, and multi-point Brunauer- Emmett-Teller（BET） analysis. ZnO microspheres are in sub-micrometer scale and have BET specific surface area of - m^2·g^-1. Furthermore, a - 3μm thick photoanode made from ZnO microspheres resultes in a preliminary short-circuit current density（ Jsc ） of - 4. 5mA · cm^-2 with an open-circuit voltage （Vooc） of -602mV and a conversion efficiency of 1.28% in DSSCs. All these suggest that mesoporous ZnO microspheres can be an alternative and feasible photoanode material for DSSCs. Key words： ZnO; mesoporous microsphere; dye-sensitized solar cells （DSSCs）
Abstract:Study on the γ irradiation effects of long-wavelength HgCdTe photovoltaic detectors passivated by different structures has been carried out, one structure was a single layer of ZnS and the other was double layers of CdTe/ZnS. A real-time measurement of current-voltage (I-V) characteristic was performed during the irradiation process, and it was found that the detectors exhibited different irradiation effects. Numerical fitting of the resistance-voltage (R-V) curves of detectors was made according to the current mechanism of photovoltaic detectors. It was found that the current at larger reverse bias voltages was mainly trap-assisted-tunneling current(TAT), and was generation-recombination current (G-R) at smaller and zero reverse bias voltages. After an analysis of the R-V curves of detectors before and after irradiation, it was thought the double layers of CdTe/ZnS helped to reduce the irradiation displacement effect, and brought no obvious increase of indirect trap-assisted-tunneling current with irradiation dosage. It was also found that irradiation ionization effects were closely correlated to the initial material parameters of the detectors. A more obvious irradiation ionization effect was found for detectors with a single layer of ZnS which had a higher generation-recombination lifetime of minority carriers through fitting method, and the generation-recombination current showed a persistent increase with irradiation dosage.
Abstract:PVA/[Gd(NO3)3+Yb(NO3)3+Er(NO3)3] composite nanofibers were fabricated by the combination of sol-gel method and electrospinning. Gd2O3:Yb3+, Er3+ upconversion nanofibers were obtained by calcination of the relevant composite nanofibers. The samples were characterized using XRD, SEM, TG-DTA, FTIR and fluorescence spectroscopy techniques. The results showed that the composite nanofibers were amorphous in structure, and Gd2O3:Yb3+,Er3+ upconversion nanofibers were cubic in structure with space group Ia3. The mean diameter of the composite nanofibers was ca. 140nm, and the Gd2O3:Yb3+,Er3+ upconversion nanofibers of 60nm in average diameter were acquired at 600°C. The water, organic compounds, nitrates in the composite nanofibers were decomposed and volatilized totally, and the weight of the sample kept constant when sintering temperature was above 600°C, and the total weight loss percentage was 81%. The FTIR spectrum of the composite nanofibers was basically the same as that of the pure PVA, and Gd2O3:Yb3+, Er3+ upconversion nanofibers were formed above 600ºC. Under the excitation of a 980 nm continuous wave diode laser, the Gd2O3:Yb3+, Er3+ nanofibres emitted strong green and red upconversion emissions centered at 522nm, 560nm and 659nm, respectively. The green emissions were attributed to the transitions of 2H11/2/4S3/2→4Il5/2 energy levels of Er3+ ions, and the red emission was assigned to the transition of 4F9/2→4Il5/2 energy levels of Er3+ ions. In the course of Gd2O3:Yb3+, Er3+ upconversion nanofibers formation, PVA acted as template. When the composite nanofibers were sintered, PVA was decomposed and evaporated, and rare earth nitrates were also decomposed and oxidized into Gd2O3:Yb3+, Er3+ nanoparticles, and these nanoparticles were mutually connected to form the Gd2O3:Yb3+, Er3+ upconversion nanofibers.
Abstract:This paper presents a terahertz (THz) wave reflection imaging system based on Backward Wave Oscillator (BWO). It is a new approach to non-destructive testing. The intensity information of the terahertz wave after being reflected from the sample surface or substrate is collected by a pyroelectric detector, and then imaged by computer. A number of potential imaging applications are demonstrated using the 0.7 THz radiation, including nondestructive testing for coins, badges, a model air-plane and some industrial samples that contain pre-built defects. This work reveals that THz radiation is highly transparent to many industrial materials, especially the “microwave-absorbing” material that is widely used in aero and space technologies
Abstract:The interference characteristics of colloidal gas aphrons (CGA) against IR / MMW was studied to further develop the special interference foam, which is a novel multi-band passive interfering technique. The CGA is of strong stability and good fluidity. The experiment results show that CGA has much better interference ability against IR / MMW than ordinary interference foam. The theoretical analysis shows that the CGA have more interfaces and total reflection advantage due to its structural characteristics such as the small radius of bubble and the thick liquid membrane. These advantages are the important basis of CGA’s excellent interference characteristics according to the theoretical analysis. This paper provides a more feasible and effective approach to apply the coating interference foam.
Abstract:The cause of the target fade-out in Neural Network nonuniformity correction scheme for infrared focal plane array(IRFPA)was studied. Based on analyzing the strength and limitation of edge-directed NN scheme(ED-NN-NUC) and nonuniformity correction combining one-point calibration and NN-NUC, a new combinational algorithm for nonuniformity correction was proposed. The new algorithm included three modules which are pre-correction, rough correction and accurate. The comparison experiment with real IRFPA infrared image including dim targets shows that the proposed algorithm can effectively eliminate the targets fade-out and was less time consuming than ED-NN-NUC.
Abstract:A new algorithm for mammograms enhancement and denoising based on Multiscale Geometric Analysis (MGA) is proposed. Firstly mammograms are decomposed into different scales and directional subbands using Nonsubsampled Contourlet Transform (NSCT). After modeling the coefficients of each directional subbands using Generalized Gaussian Mixture Model (GGMM) according to the statistical property, they are categorized into strong edges, weak edges and noise by Bayesian classifier. To enhance the suspicious lesion and suppress the noise, a nonlinear mapping function is designed to modify the coefficients adaptively so as to obtain a good enhancement result with significant features. Finally, the resulted mammograms are obtained by reconstructing with the modified coefficients using NSCT. Experimental results illustrate that the proposed approach is practicable and robustness.
Abstract:Partial least squares regression(PLSR) was employed to build predicting model of the content of soil carbon with on-the-go near-infrared reflectance spectroscopy(NIRS) measurements.The model based on band ratio or normalized difference of NIRS data can improve the prediction precision than the model with the original NIRS data.The reasons might be that the process of band arithmetic combination could reduce the risk of overfitting and it made the model include more useful components and information.The results showed that predicted models of soil carbon based on field NIRS measurements could be created by PLSR and the predicted accuracy might be improved by processing of NIRS with ratio or normalized difference. Therefore, it is feasible to estimate soil carbon in field by on-the-go NIRS measurements.
Abstract:Directional thermal radiation of canopy was studied and the related model was set up.According to the mechanism of radiative transfer,3D canopy scenes were established and the scenes were discretized by differential cells.According to the observed geometric parameters,the radiative transfer of scatter and emission for every internal cell and among cells was calculated.Finally,the directional thermal radiation of canopy could be retrieved from the integral calculation of all differential bodies in the hemisphere under the fixed observations geometric is performed, the polar map of total canopy directional thermal radiation can be drawn. We use the existing in-situ data to test the simulating results of 3D radiative transfer model,the correlation coefficient are 0.91 and 0.79, the RMSE are 0.4 K and0.6 K. It showed that the model is effective and able to improve the precision of temperature inversion and component temperature inversion.
Abstract:This paper proposes a method for remote sensing image band simulation based on spectral features study by SVM. As taking Spectral features into account as a priori knowledge and base on study of the implicit and nolinear relationships between landmark spectrum in the different obands by support vector machine, we simulated a new band through multi-spectral remote sensing image on existing bands. Based on TM blue band simulation experiments,We confirmed that this method can precisely simulate the real spectral images due to high reliability of the simulation results. Furthermore, Simulating IRS true-color experiments verify it is a practical method to reconstruct the missing bands of multi-spectral image. This method could theoretically possible to simulate a new remote sensing image band in arbitrary spectrometer's resolution within spectral range of landmark spectrum measure put forward a new idea for establishing links between landmark spectrum and remote sensing pixel spectrum.
Abstract:Environmental influence to signal output of infrared focal plane array (IRFPA) was analyzed. A nonuniformity correction (NUC) algorithm based on environmental and target temperature was proposed. Firstly, signal was captured by UL01011 staring infrared detector, an exponential response model was established according to the principle of least square. Secondly, nonuniformity was corrected by this model. Experimental results show the proposed algorithm can give an exactly response in wider environmental temperature and improve NUC precision effectively.
Abstract:NIRS was used in rapid qualitative and quantitative detection for melamine of pure milk in this paper. Experiment was conducted by preparing two groups pure milk samples which melamine content is different for qualitative analysis and quantitative analysis. By combining NIRS technology with the cluster analysis method, A effective classification can be made on the two kinds of milk samples with and without melamine; To achieve this, spectrum pretreatment and wave length choice methods were employed before model optimization. The results showed that NIR models of predicting melamine content in pure milk has good stability and predictive ability.This paper suggested that NIR could be used as a quick, green and convenient method for predicting melamine content of dairy.
Abstract:Based on the illumination model which is widely used in computer graphics and the radiance transfer law, a simplified thermal infrared imaging model is derived by: 1) adding the surface temperature distribution and the material parameters to the geometric model, 2) introducing the self emission and the detector property into the Illumination model. Using this model, the ray tracing method is applied to construct an infrared imaging system which can get the synthetic infrared images from any angle of view of the 3D scenes. Three typical 3D scenes are made to validate the infrared imaging model, and the infrared images are calculated to compare and contrast with the real infrared images obtained by a middle infrared band imaging camera. It shows that the thermal infrared imaging model is capable of producing infrared images which are very similar to those received by thermal infrared camera. Quantitative analysis shows that the absolute brightness does not match well, and the reasons are analyzed.
Abstract:A novel infrared target extraction algorithm based on particle swarm optimization particle filter(PSOPF) was proposed. The problem of infrared target extraction was analyzed and solved in the view of state estimation. In the framework of particle filter, the threshold state space on the gray-variance weighted information entropy and the grey value of each pixel was based on extraction results evaluation function, which integrated grey, entropy, gradient and spatial distribution of pixels. Finally, the weighted average of all the particles was used as target extraction threshold. The experiment results prove that the proposed algorithm is effective and robust.
Abstract:Image segmentation is one of the difficult problems in computer vision research. Recently spectral clustering has a wide application in pattern recognition and image segmentation. Compared with traditional clustering methods, it can cluster samples in any form feature space and has a global optimal solution. Originating from the equivalence between the spectral clustering and weighted kernel K-means, the authors proposed a spectral clustering algorithm with spatial constraints based on the spatially coherent property of images, also named continuous property. The spatially coherent property means that pixels in the neighbor region should share the same label assignment with the centre one with a high probability. The algorithm adds a term of spatial constraints to the objective function of weighted kernel K-means and makes the minimization of the objective function be equivalent to the spectral clustering through approximation. Experimental results show that our proposed algorithm outperforms the traditional spectral clustering in image segmentation.
Abstract:Under the conditions of low signal-to-interference ratio, aiming at the disadvantageous influence that particles weights are evaluated by means of measurement likelihood score in the bearings-only passive tracking, a novel particle algorithm based on particle residual consistency measure is proposed. Firstly, particle residual is used to realize the mapping transformation of sampling particle from state space to measurement space. Then, confidence level distance and confidence level matrix are constructed and solved to complete the reasonable evaluation of particles weights. The new method effectively extracts and uses the latest measurement information and particles themselves redundancy and complementary information, therefore it make evaluation results of particles weights more stable and reliable. Finally, experiments demonstrate the efficiency of the proposed algorithm.
Editor in chief：Jun-Hao CHU
International standard number：ISSN 1001-9014
Unified domestic issue：CN 31-1577
Domestic postal code：4-335