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Estimating the subsolar magnetopause position from soft X-ray images using a low-pass image filter

Earth and Planetary Physics 2024年第1期8卷 173-183页

作者： Hyangpyo Kim Hyunju K.Connor Jaewoong Jung Brian M.Walsh David Sibeck Kip D.Kuntz Frederick S.Porter Catriana K.Paw U Rousseau A.Nutter Ramiz Qudsi Rumi Nakamura Michael Collier Space Research Institute Austrian Academy of Sciences8042 GrazAustria Geophysical Institute University of Alaska FairbanksFairbanksAlaska 99775USA National Aeronautics and Space Administration(NASA)Goddard Space Flight Center GreenbeltMaryland 20771USA Astronomy Department University of Maryland College ParkCollege ParkMaryland 20742USA Center for Space Physics Boston UniversityBostonMassachusetts 02215USA Department of Physics and Astronomy Johns Hopkins UniversityBaltimoreMaryland 21218USA Howard University WashingtonDC 20059USA

The Lunar Environment heliospheric X-ray Imager(LEXI)and Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)missions will image the Earth’s dayside magneto pause and cusps in soft X-rays after their respective launches in the near future,to specify glo bal magnetic reconnection modes for varying solar wind conditions.To suppo rt the success of these scientific missions,it is critical to develop techniques that extract the magnetopause locations from the observed soft X-ray images.In this research,we introduce a new geometric equation that calculates the subsolar magnetopause position(RS)from a satellite position,the look direction of the instrument,and the angle at which the X-ray emission is maximized.Two assumptions are used in this method:(1)The look direction where soft X-ray emissions are maximized lies tangent to the magnetopause,and(2)the magnetopause surface near the subsolar point is almost spherical and thus RSis nea rly equal to the radius of the magneto pause curvature.We create synthetic soft X-ray images by using the Open Geospace General Circulation Model(OpenGGCM)global magnetohydrodynamic model,the galactic background,the instrument point spread function,and Poisson noise.We then apply the fast Fourier transform and Gaussian low-pass filte rs to the synthetic images to re move noise and obtain accurate look angles for the soft X-ray pea ks.From the filte red images,we calculate RS and its accuracy for different LEXI locations,look directions,and solar wind densities by using the OpenGGCM subsolar magnetopause location as ground truth.Our method estimates RS with an accuracy of10 cm-3.The accuracy improves for greater solar wind densities and during southward interplanetary magnetic fields.The method ca ptures the magnetopause motion during southwa rd interplaneta ry magnetic field turnings.Consequently,the technique will enable quantitative analysis of the magnetopause motion and help reveal the dayside reconnection modes for dynamic solar wind con

关键词： soft X-ray magnetopause reconnection low-pass filter LEXI SMILE

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Design of low-pass filter with 3-interations Koch fractal Pi-shaped DGS

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The Journal of China Universities of Posts and Telecommunications 2018年第3期25卷 92-96页

作者： Han Yunan Yuan Siyu Sun Xiaoyu Mei Chaofan College of Information Science and Technology Beijing University of Chemical Technology International School Beijing University of Posts and Telecommunications

A novel asymmetrical Pi-shaped defected ground structure （DGS） with 3-interations Koch fractal curves is proposed to design a microstrip low-pass filter （LPF） with uhra-wide stop-band （SB）. The proposed LPFs with a single resonator and two cascaded resonators are both designed, simulated, manufactured and measured. Simulation and experiment results demonstrate that the designed LPF has a very sharp transition band （TB） and an ultra-wide SB performance compared with the existed similar symmetrical and asymmetrical DGS. The proposed LPF with two cascaded resonators is with a compact size of 36. 8 mm x 24.0 mm, a very low insertion loss of less than 0.7 dB under 1.9 GHz, and a wide SB from 2.2 GHz to 8 GHz with rejection of larger than 30 dB.

关键词： low-pass filter defected ground structure Koch fractal curve broad stop-band

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UPQC Harmonic Detection Algorithm Based on Improved p-q Theory and Design of low-pass filter

UPQC Harmonic Detection Algorithm Based on Improved p-q Theo...

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第30届中国控制与决策会议

作者： Silun Shen Hong Zheng Yong Lin Wei Zhao School of Electrical and Information Engineering Jiangsu University Jiangsu Key Laboratory of Drive and Intelligent Control for Electric Vehicle

With the development of smart grid, the power quality problems are getting more and more serious, such as voltage sag/swell, voltage and current harmonic distortion and so on. The unified power quality conditioner（UPQC） has been used to improve multiple power quality problems which is an important developmental trend of current power system. In this paper, a harmonic comprehensive detection algorithm based on improve p-q theory is proposed to be applied to the UPQC. It can quickly and accurately detect a variety of power quality problems such as harmonic currents, voltage sag/swell, unbalanced three-phase voltage. Furthermore, an enhanced low-pass filter is designed to improved accuracy of low-pass filter in this harmonic detection algorithm. Simulation results are presented to verify the rationality of this detection method and the performance of the enhanced low-pass filter.

关键词： UPQC Harmonic detection p-q theory low-pass filter

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Research on low pass filter based on Memristor and Memcapacitor

Research on Low Pass Filter based on Memristor and Memcapaci...

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第36届中国控制会议

作者： Yifan Li Chenyu Yang Yongbin Yu Francisco Fernández Díez School of Information and Software Engineering University of Electronic Science and Technology of China

The paper highlights a way to introduce memristive components into the filter circuit.In light of memristor and memcapacitor,a novel low pass filter circuit（LPF） is presented.First,inspired by the typical RC-LPF and the Memristor-C-LPF,a novel Memristor-Memcapacitor-LPF is designed.Then transfer function of the LPF is obtained,and the amplitude-frequency response,phase-frequency response are presented.Finally,Simulation results demonstrates our analysis,and the memristive elements can be extended to the other filter circuits.

关键词： memristor memcapacitor low-pass filter

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Comparative Study of low-pass filter and Phase-Locked Loop Type Speed filters for Sensorless Control of AC Drives

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CES Transactions on Electrical Machines and Systems 2017年第2期1卷 207-215页

作者： Dong Wang Kaiyuan Lu Peter Omand Rasmussen Zhenyu Yang Department of Energy Technology Aalborg UniversityAalborgDK-9220Denmark IEEE

High quality speed information is one of the key issues in machine sensorless drives,which often requires proper filtering of the estimated speed.This paper comparatively studies typical low-pass filters(LPF)and phase-locked loop(PLL)type filters with respect to ramp speed reference tracking and steady-state performances,as well as the achievement of adaptive cutoff frequency control.An improved LPF-based filter structure with no ramping and steady-state errors caused by filter parameter quantization effects is proposed,which is suitable for applying LPF for sensorless drives of AC machines,especially when fixed-point digital signal processor is selected e.***.in mass production.Furthermore,the potential of adopting PLL for speed filtering is explored.It is demonstrated that PLL type filters can well maintain the advantages offered by the improved LPF.Moreover,it is found that the PLL type filters exhibit almost linear relationship between the cutoff frequency of the PLL filter and its proportional-integral(PI)gains,which can ease the realization of speed filters with adaptive cutoff frequency for improving the speed transient performance.The proposed filters are verified experimentally.The PLL type filter with adaptive cutoff frequency can provide satisfactory performances under various operating conditions and is therefore recommended.

关键词： Adaptive cutoff frequency low-pass filter machine sensorless drive phase-locked loop speed filter static error

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Design of low-pass filter based on a novel defected ground structure

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Journal of Shanghai University(English Edition) 2007年第4期11卷 396-399页

作者：钟小明李国辉 School of Communication and Information Engineering Shanghai University Shanghai 200072 P. R. China

A novel defected ground structure （DGS） for the microstrip line is proposed in this paper. The DGS lattice has more defect parameters so that it can provide better performance than the conventional dumbbell-shaped DGS. Selectivity is improved by 97.2% with a sharpness factor of 24.6%. The method is applied to the design of a low-pass filter to confirm validity of the proposed DGS.

关键词： defected ground structure （DGS） low-pass filter bandgap sharpness factor selectivity

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Smoothness Prior Approach for Spectral Smoothing and Baseline Correction

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Journal of Beijing Institute of Technology 2017年第1期26卷 121-128页

作者： Lu Li He Chen Siying Chen Yinchao Zhang Long Gao School of Optoelectronics Beijing Institute of Technology Beijing 100081 China Beijing Institute of Space Mechanics & Electricity Beijing 100094 China

Smoothness prior approach for spectral smoothing is investigated using Fourier frequency filter analysis.We show that the regularization parameter in penalized least squares could continuously control the bandwidth of low-pass filter.Besides,due to its property of interpolating the missing values automatically and smoothly,a spectral baseline correction algorithm based on the approach is proposed.This algorithm generally comprises spectral peak detection and baseline estimation.First,the spectral peak regions are detected and identified according to the second derivatives.Then,generalized smoothness prior approach combining identification information could estimate the baseline in peak regions.Results with both the simulated and real spectra show accurate baseline-corrected signals with this method.

关键词： smoothness priors low-pass filter second derivative spectral smoothing baselinecorrection

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On the characteristics of ADRC: a PID interpretation

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Science China(Information Sciences) 2020年第10期63卷 258-260页

作者： Huiyu JIN Jingchao SONG Weiyao LAN Zhiqiang GAO School of Aerospace Engineering Xiamen University Center for Advanced Control Technologies Cleveland State University

Dear editor,This study reports the discovery of active disturbance rejection control (ADRC).Second-order linear ADRC (LADRC),the basic and most popular ADRC,can be interpreted as a modified proportional-integral-derivative (PID) control.LADRC filters the PID feedback compensator with a second-order low-pass filter;it also adds a pre-filter.Simultaneously,each given PID con-

关键词： Active disturbance rejection control PID Feedback compensator Bode plot low-pass filter

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A COMBINED DATA PROCESSING METHOD ON WATER IMPACT FORCE MEASUREMENT

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Journal of Hydrodynamics 2012年第5期24卷 692-701页

作者： ZHAO Meng-hua CHEN Xiao-peng School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi'an 710072China

A combined method is proposed to determine the water entry acceleration at a low impact velocity through image processing. The procedure includes：（1） a sequence of images for water impact are recorded by a high speed camera, （2） the sub-pixel image processing method is employed to calculate the displacement with an accuracy on the ＂sub-pixel＂ level, （3） the acceleration of the object is acquired by differentiating the displacement twice and with results being further filtered by a carefully designed low-pass Butterworth filter. A theoretically based analysis is conducted for designing the parameters of the low-pass filters. It is shown that the water entry can be regarded as a procedure with a slowly changing velocity. The method is validated with the standard sinusoidal motion and the water entry of a sphere. This approach could be considered as an auxiliary method during the early-stage study of the water entry, and it could be further applied to some complicated circumstances, like the water entry of spinning spheres.

关键词： water impact force measurement image processing low-pass filter sub-pixel edge detection

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An improved method of unfolding neutron TOF spectrum for low ion temperature inertial confinement fusion

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Chinese Physics C 2014年第6期38卷 50-54页

作者：宋仔峰唐琦刘中杰詹夏宇陈家斌 Research Center of Laser Fusion China Academy of Engineering Physics

The fuel ion temperature in inertial confinement fusion can be determined from the neutron energy spectrum. For the implosion experiment with low neutron yield, and thus low signal-to-noise ratio, a new technique to unfold the neutron energy spectrum from the observed neutron time-of-flight signal is presented in this paper. This method uses a low-pass filter to remove noise from the signal with a threshold value determined by power spectrum analysis. This technique has been applied to the analysis of the observed neutron time-of-flight signals in the indirect drive implosion experiment conducted on Shenguang III prototype laser facility, and fuel ion temperatures of about 1.0 keV are obtained.

关键词： time-of-flight detector deconvolution low-pass filter power spectrum

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