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The Society of Instrument and Control Engineers Annual Conference 2015

作者： Kezi Meng Di Zhou Runle Du Department of Control Science and Engineering Harbin Institute of Technology National Key Laboratory of Science and Technology on Test Physics&Numerical Mathematics

This paper focuses on the problem of designing a 2L, gain-scheduling state-feedback guidance law with acceleration saturation based on linear matrix inequality(LMI) approach. The planar target-missile engagement is described in a polar coordinate system and the target acceleration is viewed as unpredictable disturbance. Saturated state-feedback is placed into the convex hull of a group of linear feedbacks. Furthermore,2L gain guidance problem is formulated and solved as an optimization problem with parameter-dependent LMI constraints which are then converted into a finite number of LMIs to facilitate the computation. Finally, simulation results demonstrate that the proposed guidance law copes with acceleration saturation effectively and obtains excellent guidance performance in terms of miss distance.

关键词： L2 gain guidance law acceleration saturation LPV system linear matrix inequality(LMI)

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Study of RF structure for W band sheet beam EIK

Study of RF structure for W band sheet beam EIK

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IET International Radar Conference 2015

作者： Shuyuan Chen Zhiye Jiang Jiaqi Liu Lu Gao Jingliang Bai Hongyan Liu Gang Meng Feng Xu Hu Li Chengguo Liu Guangsheng Zhu National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing 100076 P. R. China

Microwave tubes are vacuum electron devices used for the generation and amplification of radio frequencies in the microwave frequency range. Klystron is a kind of microwave tubes which is used in radar. A sheet-beam Extended Interaction Klystron (SBEIK) is an attractive MMW amplifier because of its high gain per unit length and compact configuration. The RF structure is an important part of the whole tube, which is used for beam wave interaction. In this paper, two kinds of barbell cavity has been studied. The difference between the separating multi-gap barbell resonant cavity and the strong coupling multi-gap barbell cavity has been discussed. RF parameters have been calculated by 3D simulations.

关键词： EIK Klystron Microwave RF barbell cavity radiofrequency MICROWAVE microwave tubes Barbells Klystrons Electron devices high gain

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Research on the stability of multi-gap extended cavity for W band Sheet beam EIK

Research on the stability of multi-gap extended cavity for W...

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International Conference on Vacuum Electronics

作者： Shuyuan Chen Jiaqi Liu Zhiye Jiang Lu Gao Jingliang Bai Yong Wang National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing P. R. China National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing 100076 China Key Laboratory of High Power Microwave Sources and Technologies Chinese Academy of Sciences Beijing P. R. China

ISBN: (纸本)9781479971114

A sheet-beam Extended Interaction Klystron (SBEIK) is an attractive MMW amplifier because of its high gain per unit length and compact configuration.[1-3] However, with a large width-high ratio sheet beam, it is easier to become instable in long transmission distance. In this paper, the stability of multi-gap extended cavity for W band Sheet beam EIK has been studied. The method for judging oscillation has been proposed. The electronic conductance of multi-gap extended cavity has been calculated. The result has been demonstrated by 3D-PIC software.

关键词： Cavity resonators Software Radio frequency Oscillators

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Decadal Variability of Global Ocean Significant Wave Height

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Journal of Ocean University of China 2015年第5期14卷 778-782页

作者： ZHENG Chongwei ZHOU Lin SHI Weilai LI Xin HUANG Chaofan College of Meteorology and Oceanography People’s Liberation Army University of Science&Technology National Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG) Institute of Atmospheric Physics the Chinese Academy of Sciences Dalian Naval Academy Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science & Technology

This paper presents the long-term climate changes of significant wave height(Hs) in 1958–2001 over the entire global ocean using the 45-year European Centre for Medium-Range Weather Forecasts(ECMWF) Reanalysis(ERA-40) wave data. The linear trends in Hs and regional and seasonal differences of the linear trends for Hs were calculated. Results show that the Hs exhibits a significant increasing trend of about 4.6 cm decade-1 in the global ocean as a whole over the last 44 years. The Hs changes slowly during the periods 1958–1974 and 1980–1991, while it increases consistently during the periods 1975–1980 and 1995–1998. The Hs reaches its lowest magnitude in 1975, with annual average wave height about 2 m. In 1992, the Hs has the maximum value of nearly 2.60 m. The Hs in most ocean waters has a significant increasing trend of 2–14 cm decade-1 over the last 44 years. The linear trend exhibits great regional differences. Areas with strong increasing trend of Hs are mainly distributed in the westerlies of the southern Hemisphere and the northern Hemisphere. Only some small areas show obvious decreasing in Hs. The long-term trend of Hs in DJF(December, January, February) and MAM(March, April, May) is much more stronger than that in JJA(June, July, August) and SON(September, October, November). The linear trends of the Hs in different areas are different in different seasons; for instance, the increasing trend of Hs in the westerlies of the Pacific Ocean mainly appears in MAM and DJF.

关键词： global ocean significant wave height long-term trend regional differences seasonal differences dominant season

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Systematic centroid error compensation for the simple Gaussian PSF in an electronic star map simulator

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Chinese Journal of Aeronautics 2014年第4期27卷 884-891页

作者： Wang Haiyong Wang Yonghai Li Zhifeng Song Zhenfei School of Astronautics Beihang University Beijing Institute of Space Long March Vehicle National Key Laboratory of Science and Technology on Test Physics & Numerical Mathematics

Simulated star maps serve as convenient inputs for the test of a star sensor, whose standardability mostly depends on the centroid precision of the simulated star image, so it is necessary to accomplish systematic error compensation for the simple Gaussian PSF（or SPSF, in which PSF denotes point spread function）. Firstly, the error mechanism of the SPSF is described, the reason of centroid deviations of the simulated star images based on SPSF lies in the unreasonable sampling positions（the centers of the covered pixels） of the Gaussian probability density function. Then in reference to the IPSF simulated star image spots regarded as ideal ones, and by means of normalization and numerical fitting, the pixel center offset function expressions are got, so the systematic centroid error compensation can be executed simply by substituting the pixel central position with the offset position in the SPSF. Finally, the centroid precision tests are conducted for the three big error cases of Gaussian radius r = 0.5, 0.6, 0.671 pixel, and the centroid accuracy with the compensated SPSF（when r = 0.5） is improved to 2.83 times that of the primitive SPSF, reaching a 0.008 pixel error, an equivalent level of the IPSF. Besides its simplicity, the compensated SPSF further increases both the shape similarity and the centroid precision of simulated star images, which helps to improve the image quality and the standardability of the outputs of an electronic star map simulator（ESS）.

关键词： Error compensation Image analysis Point spread function Star map simulation Star sensor

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X-band narrowband high-temperature super-conducting filter with high selectivity

X-band narrowband high-temperature super-conducting filter w...

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IET International Radar Conference 2015

作者： L. Gao Z. Y. Jiang J. Q. Liu H. Y. Liu J. L. Bai F. Xu H. Li S. Y. Chen L. Sun Y. B. Bian J. Wang Y. S. He National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics P.O. box 9200 Beijing 100076 China Chinese Academy of Sciences Beijing Beijing CN

ISBN: (纸本)9781510822023

This paper presents a development of a narrowband hightemperature superconducting filter with high selectivity. The center frequency of this filter is 8.625 GHz and the 3 dB bandwidth is 156 MHz (a fractional bandwidth of 1.81 %). In order to achieve high band edge steepness, we introduce a 10-resonator quasi-elliptic function response with two pairs of transmission zeros in the cascaded quadruplet coupling structure. The filter was manufactured on a 2-in-diameter 0.5-mm-thick MgO wafer with double-sided YBCO films. The measured results show a midband insertion loss of 0.58 dB and a return loss better than 16 dB. Band edge steepness reaches over 3.82 dB/MHz at both the high and low frequency edges. The 60 dB rectangle ratio is less than 1.19. The out-of-band rejection is over 60 dB at 17.8 MHz from the 3 dB band edge.

关键词： High-temperature superconducting (HTS) X-band microwave filter transmission zeros

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Performance test of Fourier transform infrared imaging spectrometer

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Guangxue Jingmi Gongcheng/Optics and Precision Engineering 2015年 23卷 190-196页

作者： Li, Jian-Hua Xue, Feng Xue, Lian Li, Zhi-Feng Liu, Jia-Qi National Key Laboratory of Science and Technology on Test Physics & Numerical Mathematics Beijing100076 China

The paper researches the measurement methods of key parameters of Fourier transform imaging spectrometers. Firstly, the physical meaning of the key parameter Noise Equivalent Spectral Radiance (NESR) was introduced and corresponding calculation model, test principle and data processing method were given. Then, a calibrated black body was used as radiation source, the performance parameters of Fourier transform imaging spectrometer for mid-wavelength and long-wavelength were tested experimentally, including the NESR, radiometric accuracy and spectral errors. test results show that the average NESRs of infrared imaging spectrometer for long-wavelength at 10 μm is 21.4 nW/(cm2·sr·cm-1) and that for mid-wavelength at 4.6 μm is 4.6 nW/(cm2·sr·cm-1). The radiometric accuracies of the spectrometer is less than 0.4 K and 2 K for long-wave and mid-wave, respectively. The spectral errors of the spectrometer for both mid-wavelength and long-wavelength are less than half of the spectral resolution. These parameters are all in the normal range, which verifies the feasibility of test method. It provides references for the periodically measurement of imaging spectrometers. © 2015, Chinese Academy of sciences. All right reserved.

关键词： Temperature measurement

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A novel GCV-based criterion for parametric PSF estimation 12

A novel GCV-based criterion for parametric PSF estimation

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2014 12th IEEE International Conference on Signal Processing, ICSP 2014

作者： Xue, Feng Liu, Jiaqi Li, Zhifeng Meng, Gang National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing100076 China

ISBN: (纸本)9781479921881

We propose a generalized cross validation (GCV) as a novel criterion for estimating a point spread function (PSF) from the degraded image only. The PSF is obtained by minimizing this new objective functional over a family of Wiener processings. Based on this estimated PSF, we then perform deconvolution using our recently developed SURE-LET algorithm. The GCV-based criterion is exemplified with a number of parametric PSF, involving a scaling factor that controls the blur size. A typical example of such parametrization is the Gaussian kernel. The experimental results demonstrate that the GCV minimization yields highly accurate estimates of the PSF parameters, which also result in a negligible loss of visual quality, compared to that obtained with the exact PSF. The highly competitive results outline the great potential of developing more powerful blind deconvolution algorithms based on this criterion. © 2014 IEEE.

关键词： Optical transfer function

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Pulse Phase Modulation for On-Off Thruster Pair

Pulse Phase Modulation for On-Off Thruster Pair

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IEEE Aerospace Conference

作者： Runle Du Jiaqi Liu Li Zhang Lu Gao National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics

ISBN: (纸本)9781479916191

On-Off thrusters have limitation both at minimum on-time and minimum off-time, so the output is nonlinear pulses. Use on-off thrusters to provide linear or near linear control force is a fundamental and important research topic. Existing previous works do not overcome the limitation of on-time and off-time constraints, so the output is only an approximation of demanded force output. In this paper, Pulse Phase modulation (PP) is proposed to generate linear output through on-off thruster pair. PP modulation exploited the dynamic output curve of thrusters. By adjusting phase difference of thruster pair that installed in the opposite direction, thrust output can be linear proportional to demanded force output. PP modulation breaks the limitation caused by minimum on-time and off-time, and thus achieves high continuity of thrust output. For practical engineering implementation, two approximate methods are proposed as double frequency phase modulation and quadruple frequency phase modulation. Theoretical analysis and experimental results are provided to prove that PP modulation can yield much better precision in stabilizing space vehicles.

关键词： THRUSTER phase modulation on-off Punctuality phase difference Output off time Time constraints Polypropylenes Space vehicles Pairing

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Detecting Changes in Precipitation and Temperature Extremes over China Using a Regional Climate Model with Water Table Dynamics Considered

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Atmospheric and Oceanic science Letters 2014年第2期7卷 103-109页

作者： QIN Pei-Hua XIE Zheng-Hui WANG Ai-Wen The National Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG) Institute of Atmospheric Physics Chinese Academy of Sciences School of Applied Science Beijing Information and Science Technology University

Simulations were conducted with the regional climate model RegCM incorporating water table dynamics from 1 September 1982 to 28 August 2002 to detect precipitation and temperature extremes. Compared with observed r10(number of days with precipitation ≥ 10 mm d–1), RegCM3_Hydro(the regional climate model with water table dynamics considered) simulated rain belts, including those in southern China and the middle and lower reaches of the Yangtze River, and provided data for arid to semi-arid areas such as the Heihe River Basin in northwestern China. RegCM3_Hydro indicated a significant increasing trend of r95p(days with daily precipitation greater than the 95th percentile of daily amounts) for the Yangtze, Yellow, and Pearl River basins, consistent with r95p observations. The Haihe River Basin was also chosen as a specific case to detect the effect of groundwater on extreme precipitation using peaks over threshold(POT)-based generalized Pareto distribution(GPD) with parameters estimated by the L-moment method. Quantile plots showed that all but a few of the plotted points were distributed near diagonal lines and the modeled data fitted well with the samples. Finally, the effects of water table dynamics on temperature extremes were also evaluated. In the Yellow River Basin and Songhuajiang River Basin, the trends of the number of warm days(TX95n) from RegCM3_Hydro matched observed values more closely when water table dynamics were considered, and clearly increasing numbers of warm days from 1983 to 2001 were detected.

关键词： climatic extreme groundwater runoff river basin regional climate

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