中国科学院机构知识库网格系统: 检索

Structural design of primary mirror subassembly for space telescope (EI CONFERENCE) 会议论文 OAI收割
2nd International Conference on Mechatronics and Applied Mechanics, ICMAM 2012, December 8, 2012 - December 9, 2012, Taiwan
作者: Xu H.

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In order to design a large aperture primary mirror with the diameter of 1150 mm the parameters impacting on gravity deformation of the mirror were analyzed and discussed in detail including material selection diameter-thickness ratio the number of the support points location selection and lightweight structure etc. A novel space mirror structure system was put forward and its back was opened and supported by six points on back. The dynamic and static and thermal characteristics were analyzed based on the finite element method. Analysis results showed the surface figure accuracy reached to RMS 14.5nm under the action of gravity load along the optical axis direction and the first-order natural frequency was 214Hz which met to the designed indexes requirements. (2013) Trans Tech Publications Switzerland.

Immersed nanospheres super-lithography for the fabrication of sub-70nm nanoholes with period below 700nm (EI CONFERENCE) 会议论文 OAI收割
2012 12th IEEE International Conference on Nanotechnology, NANO 2012, August 20, 2012 - August 23, 2012, Birmingham, United kingdom
作者: Li S.; Du J.; Shi L.

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A maskless nano-lithography method by using polystyrene spheres (PSs) self-assembled on silver slab (NSSL) was proposed in [optics express Vol. 16 No. 19 (2008) 14397]. Following that to break the limitations in resolution and PSs period of NSSL method in this paper we present PSs immersed super-resolution lithography (NSISL) technology by embedding the PSs into appropriate material to improve the efficiency of the surface plasmon excitation. The energy modulating mechanism and the rules of the resolution affected by silver slab were studied by calculating and analysing the energy distribution. The curve of the lithography resolution versus the silver thickness was presented. In order to verify this method contrast analysis was carried out with NSSL. The results show that the lithography resolution is improved efficiently. Taking a specific configuration with PS diameter of 600nm as an example the resolution was improved to 54nm from 190nm with Ag thickness of 25nm. Based on the calculation results we carried out the experiments. Nano holes with dimension of 75nm and period of 600nm were obtained. 2012 IEEE.

Characteristic point match algorithm based on the SURF in binocular stereo vision (EI CONFERENCE) 会议论文 OAI收割
5th International Conference on Intelligent Networks and Intelligent Systems, ICINIS 2012, November 1, 2012 - November 3, 2012, Tianjin, China
作者: Wang L.; Wang L.; Wang L.; Yang L.; Yang L.

收藏 | 浏览/下载：27/0 | 提交时间：2013/03/25

One of the main components of the computer vision is 3D reconstruction. Extracts and the match based on two-dimensional picture characteristic point is the 3D reconstruction technology core. Taking binocular stereoscopic vision theory as a foundation through extracts the characteristics of SURF based on the multi-scale analysis this feature has specific scale reproducibility put the epipolar constraints and disparity constraints as conditions judgement to specific screening it is greatly reduced the search range. The experiment use the matching method for three different actual scenes the results shows that the method can enhance the image matching speed and precision and can get more precise dense parallax used for reconstruction complete scene. 2012 IEEE.

An improved hyperspectral classification algorithm based on back-propagation neural networks (EI CONFERENCE) 会议论文 OAI收割
2012 2nd International Conference on Remote Sensing, Environment and Transportation Engineering, RSETE 2012, June 1, 2012 - June 3, 2012, Nanjing, China
作者: Yu P.; Yu P.

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In this paper a new method is proposed to improve the classification performance of hyperspectral images by combining the principal component analysis (PCA) genetic algorithm (GA) and artificial neural networks (ANNs). First some characteristics of the hyperspectral remotely sensed data such as high correlation high redundancy etc. are investigated. Based on the above analysis we propose to use the principal component analysis to capture the main information existing in the hyperspectral images and reduce its dimensionality consequently. Next we use neural networks to classify the reduced hyperspectral data. Since the back-propagation neural network we used is easy to suffer from the local minimum problem we adopt a genetic algorithm to optimize the BP network's weights and the threshold. Experimental results show that the classification accuracy is improved and the time of calculation is reduced as well. 2012 IEEE.

Analysis of zenith pass problem and tracking strategy design for roll-pitch seeker (EI CONFERENCE) 会议论文 OAI收割
作者: Jiang H.

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Roll-pitch seeker is currently applied in particular missiles. There is a stubborn problem called zenith pass problem while roll-pitch seeker is used. Analysis of the zenith pass problem which always results in loss of target is presented in this paper. Based on the analysis result tracking strategy is carried out to deal with zenith pass problem. To prove the validity of tracking strategy a practical roll-pitch seeker was accomplished. Model identification and common PID controllers for the physical roll-pitch seeker are taken on after that both disadvantages derived from zenith pass problem in tracking process and meliorated phenomenons by the tracking strategy are shown. It is concluded that the tracking strategy designed for solving the zenith pass problem is efficient. 2011 Elsevier Masson SAS. All rights reserved.

Study on ultra-light secondary baffle for coaxial two-mirror telescope (EI CONFERENCE) 会议论文 OAI收割
2012 9th IEEE International Conference on Mechatronics and Automation, ICMA 2012, August 5, 2012 - August 8, 2012, Chengdu, China
作者: Zhang L.; Zhang L.

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The coaxial two-mirror telescope consists of two mirrors facing each other. Classical two-mirror arrangements are Gregorian and Cassegrain. These systems are usually applied to space telescopes and often have optical baffles to prevent stray light from entering the focal plane. The optical baffles consist of concentric rings suspended between the secondary and the primary mirror. The secondary baffle for a large two-mirror optical system is designed and analyzed in this paper. According to mission of a telescope the structure should have high stiffness and high reliability and light weight. Compared with invar aluminum alloy and titanium alloy carbon fiber composite is currently the best material in terms of weight-to-strength ratio. It also has advantages of high temperature tolerance and low thermal expansion. So carbon fiber composite is chosen as material to meet requirements of the coaxial telescope. In this paper optimization method based on finite element analysis (FEA) is used for design the secondary baffle. Minimum weight of the baffle is chosen as an objective function. Thicknesses of former tube and vanes are chosen as variables. Analysis results show that the designed secondary baffle has maximum diameter of 180mm total length of 120mm and weighs 142g. And its fundamental frequency reaches 651Hz. Therefore the baffle has many advantages such as ultra-light weight high stiffness and dimensional stability etc. The optimization method and the baffle design can be helpful to other coaxial telescopes such as Cassegrain Gregorian and their subdivisions. 2012 IEEE.

The research of digltal CR medicine image adapitive enhancement method (EI CONFERENCE) 会议论文 OAI收割
4th International Conference on Mechanical and Electrical Technology, ICMET 2012, July 24, 2012 - July 26, 2012, Kuala Lumpur, Malaysia
Ming-Hui Z.; Yao-Yu Z.

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Digital CR medicine radiation image is in doctor's favor and has became medicine imaging technology new hot spot because of its high gray contrast powerful computer disposal function little radiation dosage non-film diagnosis different area consultation. But degradation of digital X-ray medical image such as low contrast and blurring during radiographic imaging caused by complexity of body tissue and effects of X-ray scattering and electrical noise etc. can worsen the results of analysis and diagnosis. So it is usually needed that CR medicine image is enhanced to improve its vision quality and easy to doctor's more accurate diagnosis. The general enhancement algorithms over enhancing the contrast and lose image details aiming at the defects an enhancement algorithm for CR image is proposed based on the ratio of deviation to mean of domain. The arithmetic enhance CR image edge details by adjusting factor K based on the ratio of deviation to mean of domain of CR image. Experiment results demonstrate that the algorithm enhances CR image detail and CR image enhanced has good visual effect the adaptive enhancement method is fit for CR medicine image. (2012) Trans Tech Publications Switzerland.

Comparison and simulation of subpixel imaging modes for linear CCD (EI CONFERENCE) 会议论文 OAI收割
2012 3rd International Conference on Information Technology for Manufacturing Systems, ITMS 2012, September 8, 2012 - September 9, 2012, Qingdao, China
作者: Li Y.; He B.; Li Y.; Li Y.; Li Y.

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Subpixel technique of linear CCD is effective to enhance the spatial resolution without increasing the focal length of optics and reducing the pixel size. To compare image quality of two main subpixel imaging modes quincunx sampling and four-point sampling a method to quantitatively evaluate image quality of subpixel based on MTF was proposed. The MTF of quincunx and four-point sampling modes were derived. Analytical results shows that theoretical limiting resolution of quincunx sampling and four-point sampling is improved to 1.4 and 1.86 times respectively and MTF values at Nyquist frequency of two modes are increased by 0.1106 and 0.1679 respectively. MTFA in (0 0.5) of two subpixel imaging modes were calculated and results illustrates that four-point sampling offers much more improvement with image quality than quincunx sampling at the cost of double amount of data. A model for simulating subpixel imaging using Matlab was established and simulation results of spoke target verify the theoretical analysis. (2012) Trans Tech Publications Switzerland.

Application of trend extrapolation method to spectrum analysis of microtremor signal (EI CONFERENCE) 会议论文 OAI收割
2nd World Congress on Computer Science and Information Engineering, CSIE 2011, June 17, 2011 - June 19, 2011, Changchun, China
Zhou X.; Guo T.; Jiao J.

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The trend extrapolation method is applied to spectrum analysis of microtremor signal in order to increase the spectral estimation accuracy. First establish an appropriate extrapolation model based on the existing data series and then fit correlation functions other than existing data by derivative least squares method finally perform spectrum analysis using extrapolated correlation functions. Numerical simulations and the experimental results show that good results are achieved no matter correlation functions change slow or rapid and the extrapolation error is not more than 2.3%. 2012 Springer-Verlag Berlin Heidelberg.

Trajectory tracking control for mobile robot based on the fuzzy sliding mode (EI CONFERENCE) 会议论文 OAI收割
10th World Congress on Intelligent Control and Automation, WCICA 2012, July 6, 2012 - July 8, 2012, Beijing, China
Xie M.-J.; Li L.-T.; Wang Z.-Q.

收藏 | 浏览/下载：26/0 | 提交时间：2013/03/25

The trajectory tracking control problem of the uncertain mobile robot with nonholonomic constraints is analyzed. Sliding mode control is presented based on the kinematics models analysis. Switching function of sliding model control is designed according to back-stepping method. Trending law control is selected to improve the system dynamic performance. In order to solve the constant speed problem caused by conventional trending law control fuzzy control is used to adjust trending speed in the real time. The simulation results demonstrate that the fuzzy sliding mode controller improves the rapidity of trajectory tracking and reduces the tracking error and the chattering of the control output. 2012 IEEE.