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浏览/检索结果: 共10条，第1-10条 帮助

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Characteristics of coal re-oxidation based on microstructural and spectral observation 期刊论文  OAI收割
International Journal of Mining Science and Technology, 2015, 卷号: 25, 期号: 5, 页码: 749-754
作者:  Liang Yuntao;  Tian Fuchao;  Luo Haizhu;  Tang Hui
  |  收藏  |  浏览/下载：37/0  |  提交时间：2021/02/03
Studies on Preparation of Meso-Hangjin2(#) Clay and Its Characteristic of Spectrum 期刊论文  OAI收割
SPECTROSCOPY AND SPECTRAL ANALYSIS, 2013, 卷号: 33, 期号: 4, 页码: 1087-1091
作者:  Erihemu;  Sagala;  Zhang Yu;  Zhaorigetu
  |  收藏  |  浏览/下载：24/0  |  提交时间：2019/04/09
Response spectrum 0.9-2.65 m of In0.82Ga0.18As detectors by two-step growth technique (EI CONFERENCE) 会议论文  OAI收割
2012 International Conference on Material Sciences and Manufacturing Technology, ICMSMT 2012, October 5, 2012 - October 6, 2012, Dalian, China
作者:  Zhang T.
收藏  |  浏览/下载：46/0  |  提交时间：2013/03/25
InP/In0.82Ga0.18As/InP heterostructure used for infrared detector were grown on (100) S-doped InP substrates using two-step growth technique by low temperature metal-organic chemical vapor deposition. The growth was performed using TMIn  TMGa  AsH3  and PH3 as growth precursors in a horizontal reactor. The substrates on a graphite susceptor were heated by inductively coupling RF power  their temperatures were detected by a thermocouple  and the reactor pressure was kept at 10000 Pa. The growth structure of detector included In0.82Ga0.18As buffer with the thickness of 100 nm  In0.82Ga0.18As absorption layer with the thickness of 2.8 m  and the InP cap with the thickness of 0.8 m. The planar type of p-i-n detector was fabricated by Zn diffusion. The properties of In0.82Ga0.18As detector were studied  the curves of the I-V characteristics  the range of response spectrum  and the detectivity (D*) were obtained. (2013) Trans Tech Publications  Switzerland.  
The angular velocity estimation principal of -- filter based on high sampling rate (EI CONFERENCE) 会议论文  OAI收割
2011 2nd International Conference on Mechanic Automation and Control Engineering, MACE 2011, July 15, 2011 - July 17, 2011, Inner Mongolia, China
作者:  Zhang Y.
收藏  |  浏览/下载：36/0  |  提交时间：2013/03/25
In order to get angular velocity of stabilization servo mechanism from angular position sensors  -- filter and its angular velocity transfer function were predigested. Combing with optimum parameters  -- filter based on high sampling rate was established  the effect of and sample rate on filter nature frequency were evaluated. According to the requirements of stabilization platform  the principle of steady and transient tracking filter differential were proved. With the hypothesis of constant acceleration  the frequency characteristics of angular velocity transfer function were analyzed  three-dimensional Kalman filter was simplified  and the filter parameters were designed. The results show that when the spectrum of input signal was lower than 6rad/s  parameters was 0.02  and sampling period were 0.08ms and 0.1ms respectively  the filter can realize differential exactly  when the spectrum was 9rad/s  the precision was no less than 1.1%  the phase leading of angular position was no less than 70  the natural frequency should be higher than the cut-off frequency of stabilization platform was two or three times. In the engineering of electro-optical stabilization servo mechanism  -- filter has properties of tracking differential  and reached the requirement of platform angular velocity estimation. Also it is one of the effective methods to get angular velocity from angular position sensors. 2011 IEEE.  
Comparison of valence-band structures of NiAl alloy containing Cr and Ti: Photoelectron spectrum and first-principles calculations 期刊论文  OAI收割
Intermetallics, 2010, 卷号: 18, 期号: 5, 页码: 1062-1066
H. Wei; J. J. Liang; B. Z. Sun; P. Peng; Q. Zheng; X. F. Sun; M. S. Dargusch; X. Yao
收藏  |  浏览/下载：25/0  |  提交时间：2012/04/13
Temperature characteristics of high power vertical cavity surface emitting lasers (EI CONFERENCE) 会议论文  OAI收割
Semiconductor Lasers and Applications III, November 12, 2007 - November 13, 2007, Beijing, China
作者:  Qin L.
收藏  |  浏览/下载：34/0  |  提交时间：2013/03/25
By using oxidation confinement technology high power vertical-cavity surface-emitting lasers are fabricated in experiment. The electrical and optical performance characteristics such as threshold current  efficiency  emission wavelength  and output power are measured under continuous wave (CW) condition at room temperature. The maximum output power is up to watt regime at wavelength of about 980nm. The temperature characteristics of the device are investigated experimentally in detail. The variation in lasing threshold current with temperature is studied. The characteristic temperature T0 of the device is derived  and the value is about 211K. Such a high characteristic temperature T0 of threshold current can lead to good temperature sensitivity of the device. At the same time  the lasing spectrum characteristics with temperature are also measured. The wavelength shift with temperature is just about 0.06nm/K. From the measured results  it is shown that the device can still operate at high temperature condition.  
A high-accuracy parameter estimation algorithm for jointless Frequency-shift track circuit (EI CONFERENCE) 会议论文  OAI收割
ISECS International Colloquium on Computing, Communication, Control, and Management, CCCM 2008, August 3, 2008 - August 4, 2008, Guangzhou, China
作者:  Zheng X.
收藏  |  浏览/下载：31/0  |  提交时间：2013/03/25
FSK (Frequency Shift keying) signal  which has advantages of narrow-bandwidth  strong anti-interference ability  long transmission distance and so on  is used in jointless Frequency-shift track circuit to send different kinds of control signals. However  as FSK is non-linearly modulated  parameter estimation with high accuracy is hard to realize. Based on the spectrum analysis complement with time-frequency distribution  a highaccuracy FSK signal parameter estimation algorithm is put forward in this paper. According to the signal characteristics  under-sampling and ZFFT are used to improve the accuracy of spectrum analysis  and the base frequency resolution meets system requirement of 0.02Hz. Wigner-Ville distribution has an excellent time-frequency concentration while serious cross-term interference at the same time. Through the design of kernel function  the cross-terms are almost suppressed and the upper/down side frequency resolution meets the system requirement of 0.2Hz. The effectivities of all the methods mentioned above have been proved by MATLAB simulation  which pave a solid way for the development of high-accuracy FSK signal parameter estimation devices. 2008 IEEE.  
CR image filter methods research based on wavelet-domain hidden markov models (EI CONFERENCE) 会议论文  OAI收割
ICO20: Optical Information Processing, August 21, 2005 - August 26, 2005, Changchun, China
作者:  Wang J.-L.;  Wang J.-L.;  Li D.-Y.;  Wang Y.-P.
收藏  |  浏览/下载：24/0  |  提交时间：2013/03/25
In the procedure of computed radiography imaging  we should firstly get across the characters of kinds of noises and the relationship between the image signals and noises. Based on the specialties of computed radiography (CR) images and medical image processing  we have study the filtering methods for computed radiography images noises. On the base of analyzing computed radiography imaging system in detail  the author think that the major two noises are Gaussian white noise and Poisson noise. Then  the different relationship of between two kinds of noises and signal were studied completely. By considering both the characteristics of computed radiography images and the statistical features of wavelet transformed images  a multiscale image filtering algorithm  which based on two-state hidden markov model (HMM) and mixture Gaussian statistical model  has been used to decrease the Gaussian white noise in computed images. By using EM (Expectation Maximization) algorithm to estimate noise coefficients in each scale and obtain power spectrum matrix  then this carried through the syncretized two Filter that are IIR(infinite impulse response) Wiener Filter and HMM  according to scale size  and achieve the experiments as well as the comparison with other denoising methods were presented at last.  
Displacement estimation by the phase-shiftings of fourier transform in present white noise (EI CONFERENCE) 会议论文  OAI收割
ICO20: Optical Information Processing, August 21, 2005 - August 26, 2005, Changchun, China
作者:  Wu Y.-H.
收藏  |  浏览/下载：33/0  |  提交时间：2013/03/25
Displacement estimation is a fundamental problem in Real-time video image processing. It can be typically approached by theories based on features in spatial domain. This paper presents an algorithm which improves the theory for estimating the moving object's displacement in spatial domain by its Fourier transform frequency spectrum. Because of the characters of Fourier transform  the result is based on all the features in the image. Utilizing shift theorem of Fourier transform and auto-registration  the algorithm employs the phase spectrum difference in polar coordinate of two frame images sequence with the moving target1  2. The method needn't transform frequency spectrum to spatial domain after calculation comparing with the traditional algorithm which has to search Direc peak  and it reduces processing time. Since the technique proposed uses all the image information  including all the white noise in the image especially  and it's hard to overcome the aliasing from noises  but the technique can be an effective way to analyze the result in little white noise by the different characters between high and low frequency bands. It can give the displacement of moving target within 1 pixel of accuracy. Experimental evidence of this performance is presented  and the mathematical reasons behind these characteristics are explained in depth. It is proved that the algorithm is fast and simple and can be used in image tracking and video image processing.  
Ejection of energetic photoelectrons in laser-induced autoionisation: effects of high-order ionisation processes 期刊论文  OAI收割
j. phys. b-at. mol. opt. phys., 1989, 卷号: 22, 期号: 2, 页码: 211, 221
姚关华; 徐至展
收藏  |  浏览/下载：1058/88  |  提交时间：2009/09/18