Zhao F.,Key Laboratory of Precision Opto Mechatronics Technology |
Zhao F.,CAS Institute of Remote Sensing Applications |
Gu X.,CAS Institute of Remote Sensing Applications |
Verhoef W.,National Aerospace Laboratory Netherlands |
And 6 more authors.
Remote Sensing of Environment | Year: 2010
A computationally efficient reflectance model for row planted canopies is developed in this paper through separating the contributions of incident direct and diffuse radiation scattered by row canopies. The row model allows calculating the reflectance spectrum in any given direction for the optical spectral region. The performance of the model is evaluated through comparisons with field measurements of winter wheat as well as with an established 3D computer simulation model. Especially the systematic comparisons with the computer simulation model demonstrate that the model can adequately simulate the characteristic distribution of directional reflectance factors of row canopies, which is shown in the polar map of reflectance as a high or low value stripe approximately parallel to the row orientation, besides the hotspot effect. Physical mechanisms causing the dynamics were proposed and supported by comparison studies. The features of reflectance distributions of row canopies, which are distinctively different from those of homogeneous canopy, imply that it is problematic to use one-dimensional radiation transfer model to interpret radiation data and estimate the structural or spectral parameters of row canopies from reflectance measurements. Finally, further improvements needed for the current model are briefly discussed. © 2009 Elsevier Inc.
Zhanshe G.,Beihang University |
Zhanshe G.,Key Laboratory of Precision Opto mechatronics Technology |
Zhanshe G.,Key Laboratory of Inertial Science and Technology for National Defence |
Zhou F.,Beihang University |
And 8 more authors.
Microsystem Technologies | Year: 2011
This paper introduces a new theoretical model of plate capacitor for MEMS comb actuator. In this model, bulk fabrication process and edge effect are both considered using integration method and conformal transformation theory. In order to verify the correctness of the model, FEM software is used to calculate the value of the capacitance of the MEMS comb actuator. The simulated result is 1.441 pF. Relative errors to the model calculated result 1.401 pF and ideal model calculated result 1.267 pF are 2.78 and 12.07% respectively. Then, high precision capacitance measuring device is used to measure the micro-fabricated comb actuator. The tested result is 1.517 pF. Its relative error to the rectified value is 7.65%, much less than the relative error to ideal result 16.48%. This further indicates the correctness of the rectified model. © 2010 Springer-Verlag.
Li Y.,Beihang University |
Li Y.,Key Laboratory of Precision Opto mechatronics Technology |
Li Y.,Key Laboratory of Inertial Science and Technology for National Defence |
Fan S.,Beihang University |
And 11 more authors.
Journal of Sound and Vibration | Year: 2012
In this paper, frequency measurement methods of resonant vibratory gyroscopes are studied. First, the working principle and dynamic output characteristics of the resonant vibratory gyroscope are introduced, which provide a theoretical analysis base to analyze the dynamic frequency output characteristic of the resonant vibratory gyroscope. Moreover, some relevant frequency measurement methods are introduced, a frequency measurement method based on dynamic output characteristics has been proposed for the purpose of investigating the modulated output signal of resonant vibratory gyroscopes. Finally, in order to verify the feasibility of the proposed frequency measurement method, resonator oscillator and dynamic frequency measurement experiments of the resonant vibratory gyroscopes are built. It is concluded from the resonator oscillator result that the designed and observed resonant frequency of the resonator have a good match, which shows the design of resonator oscillator is feasible. It is concluded from the dynamic frequency measurement result that correlation coefficient of output fitted curve is 99.95%, and the output characteristic of the gyroscope is linear frequency output, which shows the effectiveness of the proposed frequency measurement method. © 2012 Published by Elsevier Ltd. All rightsreserved.
Guo Z.-S.,Beihang University |
Guo Z.-S.,Key Laboratory of Precision Opto mechatronics Technology |
Feng Z.,Beihang University |
Feng Z.,Key Laboratory of Precision Opto mechatronics Technology |
And 6 more authors.
Harbin Gongye Daxue Xuebao/Journal of Harbin Institute of Technology | Year: 2010
With plate capacitor theory and calculus method, the capacitance of micro electro-mechanical system (MEMS) electrostatic comb actuator is studied. Considering the affections of fabrication technology and edge effect, a calculating model is built, by which the calculations for the fabricated comb actuator are carried out under the ideal condition and the condition of considering border effect and fabricating technology. The calculated results are 1.2673 pF and 1.4403 pF respectively, of which the relative errors with the high precision LCR device measured value 1.5172 pF are 16.47% and 5.07%. This indicates that the model can be used to get higher precision, if the border effect and fabrication process are taken into account.
Fan S.-C.,Beihang University |
Fan S.-C.,Key Laboratory of Precision Opto mechatronics Technology |
Fan S.-C.,Key Laboratory of Inertial Science and Technology for National Defence |
Li Y.,Beihang University |
And 11 more authors.
Chinese Physics B | Year: 2012
Dynamic characteristics of the resonant gyroscope are studied based on the Mathieu equation approximate solution in this paper. The Mathieu equation is used to analyze the parametric resonant characteristics and the approximate output of the resonant gyroscope. The method of small parameter perturbation is used to analyze the approximate solution of the Mathieu equation. The theoretical analysis and the numerical simulations show that the approximate solution of the Mathieu equation is close to the dynamic output characteristics of the resonant gyroscope. The experimental analysis shows that the theoretical curve and the experimental data processing results coincide perfectly, which means that the approximate solution of the Mathieu equation can present the dynamic output characteristic of the resonant gyroscope. The theoretical approach and the experimental results of the Mathieu equation approximate solution are obtained, which provides a reference for the robust design of the resonant gyroscope. © 2012 Chinese Physical Society and IOP Publishing Ltd.
Wei D.,China Aerospace Geophysical Survey and Remote Sensing Center for Land and Resources |
Gan F.,China Aerospace Geophysical Survey and Remote Sensing Center for Land and Resources |
Zhang Z.,China Aerospace Geophysical Survey and Remote Sensing Center for Land and Resources |
Xiao C.,China Aerospace Geophysical Survey and Remote Sensing Center for Land and Resources |
And 6 more authors.
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2015
Infrared spectrums play an important role in the information extraction of rock and minerals. Spectrum simulation is a fundamental issue of land surface scene simulation and image simulation of remote sensing systems. Signal to Noise Ratio is regarded as an essential parameter of instrument and remote sensing image. In this study, we used MODTRAN to simulate apparent radiance and different levels of additive white Gaussian noise was added to the simulated spectrum. In the section of noise impact on object recognition, Spectral Feature Fitting was chosen to compare the fit of simulated spectra with different noise levels to reference apparent radiance spectra without noise. Relative error is also calculated for the accuracy assessment which is helpful for validation and improvement of instrument parameters. © 2015 IEEE.
Jie J.,Key Laboratory of Precision Opto mechatronics Technology |
Guangjun Z.,Key Laboratory of Precision Opto mechatronics Technology |
Zhiming W.,Key Laboratory of Precision Opto mechatronics Technology |
Qiaoyun F.,Key Laboratory of Precision Opto mechatronics Technology |
Xinguo W.,Key Laboratory of Precision Opto mechatronics Technology
Optics and Lasers in Engineering | Year: 2010
A novel attitude sensor optical system employing a microlens array (MLA) based on the Fraunhofer diffraction theory was developed. To analyze the irradiance distribution of the focal plane, a mathematic model was established by using the Fresnel-Kirchhoff formula. A numerical simulation showed that this optical system provided high accuracy and would ensure a large field of view. © 2009 Elsevier Ltd. All rights reserved.