中国科学院机构知识库网格系统: 检索

GIS-based landslide susceptibility mapping in the Longmen Mountain area (China) using three different machine learning algorithms and their comparison 期刊论文 OAI收割
ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH, 2023, 页码: 15
作者: Huang, Ziyan; Peng, Li; Li, Sainan; Liu, Ying; Zhou, Shuang

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收藏 | 浏览/下载：22/0 | 提交时间：2023/10/09

Landslide susceptibility assessment Random forest model Frequency ratio method Support vector machine model Longmen Mountain area

Study on MTEM frequency-domain ratio method and apparent resistivity calculation 期刊论文 OAI收割
CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION, 2018, 卷号: 61, 期号: 10, 页码: 4171-4181
作者: Zhang WenWei; Zhen QiHui; Di QingYun

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收藏 | 浏览/下载：34/0 | 提交时间：2018/12/11

MTEM Frequency-domain ratio method Earth impulse response Peak time Apparent resistivity

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.

收藏 | 浏览/下载：63/0 | 提交时间：2013/03/25

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.

The application of adaptive enhancement algorithm based on gray entropy in mammary gland CR image (EI CONFERENCE) 会议论文 OAI收割
2012 2nd International Conference on Consumer Electronics, Communications and Networks, CECNet 2012, April 21, 2012 - April 23, 2012, Three Gorges, China
Zhang M.-H.; Zhang Y.-Y.

收藏 | 浏览/下载：34/0 | 提交时间：2013/03/25

Mammary gland is composed entirely of soft tissue with approximate density therefore mammary gland CR medicine radiation image presents a low contrast and slight difference changes may be a manifestation of tumor so it is necessary to enhance mammary gland CR image to improve its visual quality in order to meet the demands of doctor's clinical diagnosis. However the general enhancement algorithms over enhance the contrast and noise due to image details lost aiming at the defects a mammary gland CR medicine image adaptive enhancement arithmetic based on image gray entropy is put forward. The arithmetic adapts dizzy image to magnify selected spatial frequency response in order to enhance the edge details of mammary gland CR images. It can adjust weighted factor K according to image gray characteristics namely pixel gray entropy. Experiments results demonstrate that mammary gland CR image enhanced by the algorithm has abundant details and high signal-to-noise ratio moreover CR image enhanced has good visual effect. So the method is effective and fit for enhancing CR medical radiation image edge details. 2012 IEEE.

Improved TOPS about direction of arrival estimation for wideband signals (EI CONFERENCE) 会议论文 OAI收割
2011 International Conference on Vibration, Structural Engineering and Measurement, ICVSEM2011, October 21, 2011 - October 23, 2011, Shanghai, China
作者: He B.

收藏 | 浏览/下载：17/0 | 提交时间：2013/03/25

The study about the direction-of-arrival (DOA) estimation for wideband signals is a basic topic of Signal Processing. The method called test of orthogonality of projected subspaces (TOPS) does not require initial values to form focusing matrix compared with the coherent signal subspace method (CSSM) but it has poor performance for coherent wideband signals at low signal-to-noise ratio (SNR). Based on the lack of the conventional TOPS this paper reconstructs a set of new matrices with the narrowband correlated matrices coming from the DFT decomposition of the array output and modifies the method frame of the conventional TOPS. So we get a set of reconstructed matrices with full rank corresponding to each frequency bin and which have no array aperture loss. The improved TOPS can estimate the DOA for coherent wideband sources at low SNR and enhances the performance of the conventional TOPS. Simulation results show that the improved TOPS is effective and the total performance of which is similar to the rotational signal-subspace (RSS) method. (2012) Trans Tech Publications.

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.

收藏 | 浏览/下载：62/0 | 提交时间：2013/03/25

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.

Three-loop autopilot design and simulation (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 Y.

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In order to realize missile real-time change flight trajectory three-loop autopilot is setting up. The structure characteristics autopilot model and control parameters design method were researched. Firstly this paper introduced the 11th order three-loop autopilot model. With the principle of systems reduce model order the 5th order model was deduced. On that basis open-loop frequency characteristic and closed-loop frequency characteristic were analyzed. The variables of velocity ratio dynamic pressure ratio and elevator efficiency ratio were leading to correct system nonlinear. And then autopilot gains design method were induced. System flight simulations were done and result shows that autopilot gains played a good job in the flight trajectory autopilot satisfied the flight index. 2012 IEEE.

Evaluation of the operating range for ground-based infrared imaging tracking system (EI CONFERENCE) 会议论文 OAI收割
International Symposium on Photoelectronic Detection and Imaging 2011: Advances in Infrared Imaging and Applications, May 24, 2011 - May 24, 2011, Beijing, China
作者: Zhang Z.-D.

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Ground-based infrared imaging tracking system (GIITS) is of great importance for aerial target warning and guard. The operating range is one of the key performance specifications on the other which should be calculated calculate the radiation power received on the detector in order to analysis whether the output signal meets the detection requirements or not analyzed and studied during the whole GIITS design process. The operating range is mostly influenced by a few factors without considering the effect of the background radiation. By improving of the traditional method including atmospheric attenuation a new operating range calculation model of the GIITS was established based on two requirements. One is that the image size of observed target should meet the requirement of the processor signal extraction. The number of the pixel occupied by target image should be more than 9. The other is that the signal noise ratio (SNR) of the GIITS should not be less than 5 to meet the requirements of the target detection probability and spatial frequency. The SNR calculation equation in form of energy is deduced and the radiation characteristic of the observed target and background are analyzed. When evaluate the operating range of the GIITS using the new method the performance of GIITS and feature of target and background. This paper firstly makes analysis and summarization on the definite localizations of the traditional operating range equation of the GIITS. The localizations are mainly in two aspects. On one hand we should successively calculate two operating range values according to two requirements mentioned above and choose the minimum value as the analytic result. In the end the dispersion of the image and the effect of image dispersion are not considered in the traditional method an evaluation of operating range for fighter aircraft is accomplished as an example. The influence factors in every aspect on operating range were explored by the calculated result. The new operating range calculation model provides the theoretical basis for the design and applications as well as the comprehensive evaluation of a GIITS. 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).

Correction method for detection of the frequencies of railway fsk signals (EI CONFERENCE) 会议论文 OAI收割
2008 9th International Conference on Signal Processing, ICSP 2008, October 26, 2008 - October 29, 2008, Beijing, China
作者: Yu J.

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In order to acquire the information of railway binary frequency-shift keying signals which include upper/down side frequencies and base low-frequency with high-accuracy a novel frequency detection algorithm for France UM-71 system is proposed. Combining fast Fourier transform with the ratio correction method the carrier frequency and the base frequency are obtained. Furthermore the hardware consumption has been decreased. And it possesses the advantage of simple algorithm and fast operation speed. Comparing with the detection of the base frequency the upper/down side frequency of railway signal is more difficult. Based on spectrum analysis and the spectrum correction a new method which adopts the sliding window is put forward in this paper. The absolute differences between the upper side frequencies and the down side frequencies obtained are regarded as the criterion for judgment. Then the set of data in which the maximum absolute value is is to be the result of the upper/down side frequency. Because the sliding window will go through every stage when the upper/down side frequency changes therefore it is not sensitive enough to the position of data which need to be transformed. Using the method mentioned above the experiment results show that the accuracy requirement of the side frequency is satisfied well. 2008 IEEE.

Wavelet-based contourlet coding using SPECK algorithm (EI CONFERENCE) 会议论文 OAI收割
2008 9th International Conference on Signal Processing, ICSP 2008, October 26, 2008 - October 29, 2008, Beijing, China
Xiu-Wei T.; Xi-Feng Z.; Tie-Fu D.

收藏 | 浏览/下载：55/0 | 提交时间：2013/03/25

We proposed a new still image compression algorithm called CSPECK witch was constructed by the wavelet-based contourlet transform (WBCT) and set partitioning embedded block coding (SPECK). In the WBCT the high frequency sub-band decomposed by the wavelet transform was further decomposed into multiple directional sub-bands by directional filter bank so as to explain the edge and texture of the image more sparsely. The SPECK algorithm exhibits lower complexity and more efficient compression ratio than SPIHT based on WBCT. Experimental results demonstrate that the proposed method is efficient in coding images that possess mostly textures and contours. The simulation results also show that this new coding algorithm increases the PSNR over CSPIHT. 2008 IEEE.