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Chinese Society for Optical Engineering Conferences, CSOE 2016

作者： Wang, Hai-Yong Qin, Tian-Mu Liu, Jia-Qi Li, Zhi-Feng Li, Jian-Hua School of Aeronautics and Astronautics Beihang University Beijing100083 China Beijing Institute of Space Long March Vehicle Beijing100076 China National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical Beijing100076 China

ISBN: (纸本)9781510610118

To improve the preprocessing speed of star map and reduce the resource consumption of embedded system of star tracker, a parallel pipeline real-time preprocessing algorithm is presented. The two characteristics, the mean and the noise standard deviation of the background gray of a star map, are firstly obtained dynamically by the means that the intervene of the star image itself to the background is removed in advance. The criterion on whether or not the following noise filtering is needed is established, then the extraction threshold value is assigned according to the level of background noise, so that the centroiding accuracy is guaranteed. In the processing algorithm, as low as two lines of pixel data are buffered, and only 100 shift registers are used to record the connected domain label, by which the problems of resources wasting and connected domain overflow are solved. The simulating results show that the necessary data of the selected bright stars could be immediately accessed in a delay time as short as 10us after the pipeline processing of a 496×496 star map in 50Mb/s is finished, and the needed memory and registers resource total less than 80kb. To verify the accuracy performance of the algorithm proposed, different levels of background noise are added to the processed ideal star map, and the statistic centroiding error is smaller than 1/23 pixel under the condition that the signal to noise ratio is greater than 1. The parallel pipeline algorithm of real time star map preprocessing helps to increase the data output speed and the anti-dynamic performance of star tracker. © 2017 SPIE.

关键词： Pipelines

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Suppressing the effects of ionospheric scintillation on geosynchronous SAR by optimised orbit design

Suppressing the effects of ionospheric scintillation on geos...

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2017 International Conference on Radar Systems, Radar 2017

作者： Li, YuanHao Liu, XiangRong Hu, Cheng Dong, XiChao School of Information and Electronics Beijing Institute of Technology 100081 China National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics 100076 China Beijing Key Laboratory of Embedded Real-time information Processing Technology 100081 China

ISBN: (纸本)9781785615153

An L band geosynchronous synthetic aperture radar (GEO SAR) will be sensitive to ionosphere scintillation because of its low carrier frequency. Meanwhile, because of the high orbit, GEO SAR has a higher probability to meet ionospheric scintillation. In this paper, we propose an orbit strategy for eliminating the impacts of ionospheric scintillation. It is realized by selecting a proper orbit element (time past perigee) to avoid imaging for the sensitive region of ionospheric scintillation during the eruption time interval of ionospheric scintillation with the highest probability. Finally, the simulation based on systems tool kit (STK) software was conducted to verify the effectiveness of the method. © 2017 Institution of Engineering and technology. All rights reserved.

关键词： Synthetic aperture radar

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Influence of the Preceding Austral Summer Southern Hemisphere Annular Mode on the Amplitude of ENSO Decay

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Advances in Atmospheric sciences 2017年第11期34卷 1358-1379页

作者： Fei ZHENG Jianping LI Ruiqiang DING State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China College of Global Change and Earth System Science Beijing Normal UniversityBeijing 100875China Laboratory for Regional Oceanography and Numerical Modeling Qingdao National Laboratory for Marine Science and Technologyqingdao 266237China Plateau Atmosphere and Environment Key Laboratory of Sichuan Province Chengdu University of Information Technologychengdu 610103China

There is increasing evidence of the possible role of extratropical forcing in the evolution of ENSO. The Southern Hemi- sphere Annular Mode （SAM） is the dominant mode of atmospheric circulation in the Southern Hemisphere extratropics. This study shows that the austral summer （December-January-February; DJF） SAM may also influence the amplitude of ENSO decay during austral autumn （March-April-May; MAM）. The mechanisms associated with this SAM-ENSO relationship can be briefly summarized as follows： The SAM is positively （negatively） correlated with SST in the Southern Hemisphere middle （high） latitudes. This dipole-like SST anomaly pattern is referred to as the Southern Ocean Dipole （SOD）. The DJF SOD, caused by the DJF SAM, could persist until MAM and then influence atmospheric circulation, including trade winds, over the Nifio3.4 area. Anomalous trade winds and SST anomalies over the Nifio3.4 area related to the DJF SAM are further developed through the Bjerkness feedback, which eventually results in a cooling （warming） over the Nifio3.4 area followed by the positive （negative） DJF SAM.

关键词： Southern Hemisphere Annular Mode ENSO Southern Ocean Dipole

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Dual-band checkerboard plasma electromagnetic surface for radar cross section reduction

Dual-band checkerboard plasma electromagnetic surface for ra...

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IEEE Asia-Pacific Conference on Antennas and Propagation (APCAP)

作者： Qiang Xu Zhifeng Li Jinjun Mo National University of Defense Technology Changsha China National Key Laboratory of Science and Technology on Test Physics & Numerical Mathematical Beijing China

ISBN: (纸本)9781538616093

Radar cross section (RCS) can be reduced along the principal planes by applying electromagnetic band gap (EBG) structures. Checkerboard plasma electromagnetic surface (PES), combining with EBG and plasma layer, can realize a narrow band near 3 GHz and a wide band 10-dB radar cross section reduction (RCSR) covered X-band, by redirecting the scattered fields towards four quadrants. Bistatic RCS of the checkerboard PES is simulated and the results compared to the corresponding perfect electric conductor (PEC) surface show that the maxima of the bistatic RCS pattern are reduced by 5.4 dB at fixed frequency 10 GHz.

关键词： Plasmas Periodic structures Metamaterials Electromagnetics Radar cross-sections Electromagnetic scattering

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A comparison of methods for finding magnetic nulls in simulations and in situ observations of space plasmas

arXiv

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arXiv 2020年

作者： Olshevsky, Vyacheslav Pontin, David I. Williams, Benjamin Parnell, Clare E. Fu, Huishan S. Liu, Yangyang Yao, Shutao Khotyaintsev, Yuri V. KTH Royal Institute of Technology Lindstedtsvagen 5 StockholmSE-10044 Sweden Main Astronomical Observatory of NAS Akademika Zabolotnoho 27 Kyiv03680 Ukraine School of Mathematical and Physical Sciences University of Newcastle University Drive CallaghanNSW2308 Australia University of St Andrews North Haugh St Andrews United Kingdom Beihang University 37 Xueyuan Road Haidian District Beijing100191 China Institute of Space Sciences Shandong University Weihai China State Key Laboratory of Space Weather National Space Science Center Chinese Academy of Sciences Beijing China Swedish Institute of Space Physics Box 537 UppsalaSE-751 21 Sweden

Context. Magnetic nulls are ubiquitous in space plasmas, and are of interest as sites of localised energy dissipation or magnetic reconnection. As such, a number of methods have been proposed for detecting nulls in both simulation data and in situ spacecraft data from Earth’s magnetosphere. The same methods can be applied to detect stagnation points in flow fields. Aims. In this paper we describe a systematic comparison of different methods for finding magnetic nulls. The Poincaré index method, the first-order Taylor expansion (FOTE) method, and the trilinear method are considered. Methods. We define a magnetic field containing fourteen magnetic nulls whose positions and types are known to arbitrary precision. Furthermore, we applied the selected techniques in order to find and classify those nulls. Two situations are considered: one in which the magnetic field is discretised on a rectangular grid, and the second in which the magnetic field is discretised along synthetic ‘spacecraft trajectories’ within the domain. Results. At present, FOTE and trilinear are the most reliable methods for finding nulls in the spacecraft data and in numerical simulations on Cartesian grids, respectively. The Poincaré index method is suitable for simulations on both tetrahedral and hexahedral meshes. Conclusions. The proposed magnetic field configuration can be used for grading and benchmarking the new and existing tools for finding magnetic nulls and flow stagnation points. Copyright © 2020, The Authors. All rights reserved.

关键词： Magnetic fields

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A seasonal grade division of the global offshore wind energy resource

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Acta Oceanologica Sinica 2017年第3期36卷 109-114页

作者： ZHENG Chongwei LI Chongyin GAO Chengzhi LIU Mingyang College of Meteorology and Oceanography People’s Liberation Army University of Science and Technology National Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG) Institute of Atmospheric PhysicsChinese Academy of Sciences Dalian Naval Academy People’s Liberation Army

Under the background of energy crisis, the development of renewable energy will significantly alleviate the energy and environmental crisis. On the basis of the European Centre for Medium-Range Weather Forecasts（ECMWF）interim reanalysis（ERA-interim） wind data, the annual and seasonal grade divisions of the global offshore wind energy are investigated. The results show that the annual mean offshore wind energy has great potential. The wind energy over the westerly oceans of the Northern and Southern Hemispheres is graded as Class 7（the highest）, whereas that over most of the mid-low latitude oceans are higher than Class 4. The wind energy over the Arctic Ocean（Class 4） is more optimistic than the traditional evaluations. Seasonally, the westerly oceans of the Northern Hemisphere with a Class 7 wind energy are found to be largest in January, followed by April and October, and smallest in July. The area of the Class 7 wind energy over the westerly oceans of the Southern Hemisphere are found to be largest in July and slightly smaller in the other months. In July, the wind energy over the Arabian Sea and the Bay of Bengal is graded as Class 7, which is obviously richer than that in other months. It is shown that in this data set in April and October, the majority of the northern Indian Ocean are regions of indigent wind energy resource.

关键词： global ocean wind energy annual grade division seasonal grade division

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Electromagnetic scattering characteristics of the plasma sheath around Re-entry hypersonic vehicles

Electromagnetic scattering characteristics of the plasma she...

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IEEE Asia-Pacific Conference on Antennas and Propagation (APCAP)

作者： Run-hui Wu Jia-qi Liu Gang Meng Xin Liu Ai-min Ren Xia Ai Song Chai Ju-yan Zhao Ya-nan Li Ming-liang Wang National Key Laboratory of Science and Technology on Test Physics & Numerical Mathematical No.1 Dahongmen South Road Fengtai District Beijing 100076 China

ISBN: (纸本)9781538616093

In order to analyze electromagnetic scattering of reentry vehicle, models of the expected electromagnetic scattering properties of the aircrafts must be developed. This paper begins with a discussion of the plasma sheath characteristics, and the interactions between electromagnetic wave and plasma sheath, and the simulation model of plasma sheath scattering is described by using physical optics and hierarchical approximation technique. Then rigorous calculations of radar cross section(RCS) for a double conical target, plasma-clad body, 30km, 40km, 50km altitude, 4km/s, 5km/s velocity are presented in context with 9.8GHz, 5.8GHz, 3.2GHz, 1.5GHz of incident wave frequency. The results are shown that plasma sheath can increase or decrease the RCS of vehicles for different altitude, velocity and wave frequency. When the aircraft has a low altitude and high-speed flight, electron density of plasma sheath will increase continuously. Influenced by it, the RCS of vehicles shows a decreasing trend.

关键词： Plasma sheaths Electromagnetic scattering Atmospheric modeling mathematical model Radar cross-sections

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Regional Meteorological Patterns for Heavy Pollution Events in Beijing

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Journal of Meteorological Research 2017年第3期31卷 597-611页

作者： ting you renguang wu gang huang guangzhou fan college of atmospheric sciences chengdu university of information technologyChengdu 610225 center for monsoon system research institute of atmospheric physicschinese academy of sciencesBeijing 100029 state key laboratory of numerical modeling for atmospheric sciences and geophysical fluid dynamics institute of atmospheric physicschinese academy of sciencesBeijing 100029 laboratory for regional oceanography and numerical modeling qingdao national laboratory for marine science and technologyQingdao 266237 joint center for global change studies Beijing100875 university of chinese academy of sciences Beijing 100049

The present study investigates meteorological conditions for the day-to-day changes of particulate matter （PM） concentration in Beijing city during the period 2008-2015. The local relationship of PM concentration to surface air temperature, pressure, wind speed, and relative humidity displays seasonal changes and year-to-year variations. The average correlation coefficient with PMI0 in spring, summer, fall, and winter is 0.45, 0.40, 0.38, and 0.30 for air tem- perature; -0.45, -0.05, -0.40, and -0.45 for pressure; 0.13, 0.04, 0.53, and 0.50 for relative humidity; and -0.18, -0.11, -0.45, and -0.33 for wind speed. A higher correlation with wind speed is obtained when wind speed leads by halfa day. The heavily polluted and clean days, which are defined as the top and bottom 10% of the PM values, show obvious differences in the regional distribution of air temperature, pressure, and wind. Polluted days correspond to higher air temperature in all the four seasons, lower sea level pressure and anomalous southerly winds to the south and east of Beijing in spring, fall, and winter, and a northwest-southeast contrast in the pressure anomaly and anom- alous southerly winds in summer. Higher relative humidity is observed on polluted days in fall and winter. The pol- luted days are preceded by an anomalous cyclone moving from the northwest, accompanied by lower pressure and higher air temperature, in all four seasons. This feature indicates the impacts of moving weather systems on local meteorological conditions for day-to-day air quality changes in Beijing.

关键词： PM10 Beijing local meteorology seasonal dependence weather system

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The Way from natural to artificial - the story of Periodic Electromagnetic Structures

The Way from natural to artificial - the story of Periodic E...

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International Applied Computational Electromagnetics Society Symposium in China

作者： Shengjun Zhang Mingliang Wang Xia Ai Weidong Wang Runhui Wu Xin Liu Jiaqi Liu Gang Meng Yuan Sun National Key Laboratory of Science & Technology on Test Physics and Numerical Mathematics The Institute of Effectiveness Evaluation of Flying Vehicle

In this paper, the general of artificial electromagnetic structure with analog to the natural materials were briefly reviewed. The lattice theory of artificial structure was suggested to be built.

ISBN: (纸本)9781509043118

In this paper, the general of artificial electromagnetic structure with analog to the natural materials were briefly reviewed. The lattice theory of artificial structure was suggested to be built.

关键词： Artificial structure Electromagnetic lattice Artificial structure lattice theory natural material ELECTROMAGNETIC

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Search for CP violation and observation of P violation in Λb0→pπ−π+π− decays

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Physical Review D 2020年第5期102卷 051101(R)-051101(R)页

作者： R. Aaij C. Abellán Beteta T. Ackernley B. Adeva M. Adinolfi H. Afsharnia C. A. Aidala S. Aiola Z. Ajaltouni S. Akar P. Albicocco J. Albrecht F. Alessio M. Alexander A. Alfonso Albero G. Alkhazov P. Alvarez Cartelle A. A. Alves, Jr. S. Amato Y. Amhis L. An L. Anderlini G. Andreassi M. Andreotti F. Archilli J. Arnau Romeu A. Artamonov M. Artuso K. Arzymatov E. Aslanides M. Atzeni B. Audurier S. Bachmann J. J. Back S. Baker V. Balagura W. Baldini A. Baranov R. J. Barlow S. Barsuk W. Barter M. Bartolini F. Baryshnikov G. Bassi V. Batozskaya B. Batsukh A. Battig V. Battista A. Bay M. Becker F. Bedeschi I. Bediaga A. Beiter L. J. Bel V. Belavin S. Belin N. Beliy V. Bellee K. Belous I. Belyaev G. Bencivenni E. Ben-Haim S. Benson S. Beranek A. Berezhnoy R. Bernet D. Berninghoff H. C. Bernstein E. Bertholet A. Bertolin C. Betancourt F. Betti M. O. Bettler Ia. Bezshyiko S. Bhasin J. Bhom M. S. Bieker S. Bifani P. Billoir A. Birnkraut A. Bizzeti M. Bjørn M. P. Blago T. Blake F. Blanc S. Blusk D. Bobulska V. Bocci O. Boente Garcia T. Boettcher A. Boldyrev A. Bondar N. Bondar S. Borghi M. Borisyak M. Borsato J. T. Borsuk T. J. V. Bowcock C. Bozzi S. Braun A. Brea Rodriguez M. Brodski J. Brodzicka A. Brossa Gonzalo D. Brundu E. Buchanan A. Büchler-Germann A. Buonaura C. Burr A. Bursche J. S. Butter J. Buytaert W. Byczynski S. Cadeddu H. Cai R. Calabrese S. Cali R. Calladine M. Calvi M. Calvo Gomez A. Camboni P. Campana D. H. Campora Perez L. Capriotti A. Carbone G. Carboni R. Cardinale A. Cardini P. Carniti K. Carvalho Akiba A. Casais Vidal G. Casse M. Cattaneo G. Cavallero R. Cenci J. Cerasoli M. G. Chapman M. Charles Ph. Charpentier G. Chatzikonstantinidis M. Chefdeville V. Chekalina C. Chen S. Chen A. Chernov S.-G. Chitic V. Chobanova M. Chrzaszcz A. Chubykin P. Ciambrone M. F. Cicala X. Cid Vidal G. Ciezarek F. Cindolo P. E. L. Clarke M. Clemencic H. V. Cliff J. Closier J. L. Cobbledick V. Coco J. A. B. Coelho J. Cogan E. Cogneras L. Cojocariu P. Collins T. Colombo A. Comerma-Montells A. Contu N. Cooke G. Coombs S. Coquere Nikhef National Institute for Subatomic Physics Amsterdam Netherlands Physik-Institut Universität Zürich Zürich Switzerland Oliver Lodge Laboratory University of Liverpool Liverpool United Kingdom Instituto Galego de Física de Altas Enerxías (IGFAE) Universidade de Santiago de Compostela Santiago de Compostela Spain H.H. Wills Physics Laboratory University of Bristol Bristol United Kingdom Université Clermont Auvergne CNRS/IN2P3 LPC Clermont-Ferrand France University of Michigan Ann Arbor USA (associated with Syracuse University Syracuse New York USA) INFN Sezione di Milano Milano Italy University of Cincinnati Cincinnati Ohio USA INFN Laboratori Nazionali di Frascati Frascati Italy Fakultät Physik Technische Universität Dortmund Dortmund Germany European Organization for Nuclear Research (CERN) Geneva Switzerland School of Physics and Astronomy University of Glasgow Glasgow United Kingdom ICCUB Universitat de Barcelona Barcelona Spain Petersburg Nuclear Physics Institute NRC Kurchatov Institute (PNPI NRC KI) Gatchina Russia Imperial College London London United Kingdom Universidade Federal do Rio de Janeiro (UFRJ) Rio de Janeiro Brazil Université Paris-Saclay CNRS/IN2P3 IJCLab Orsay France INFN Sezione di Firenze Firenze Italy Institute of Physics Ecole Polytechnique Fédérale de Lausanne (EPFL) Lausanne Switzerland INFN Sezione di Ferrara Ferrara Italy Physikalisches Institut Ruprecht-Karls-Universität Heidelberg Heidelberg Germany Aix Marseille Univ CNRS/IN2P3 CPPM Marseille France Institute for High Energy Physics NRC Kurchatov Institute (IHEP NRC KI) Protvino Russia Protvino Russia Syracuse University Syracuse New York USA Yandex School of Data Analysis Moscow Russia INFN Sezione di Cagliari Monserrato Italy Department of Physics University of Warwick Coventry United Kingdom Department of Physics and Astronomy University of Manchester Manchester United Kingdom INFN Sezione di Genova Genova Italy National University of Science

A search for CP violation in the Λb0→pπ−π+π− decay is performed using LHCb data corresponding to an integrated luminosity of 6.6 fb−1 collected in pp collisions at center-of-mass energies of 7, 8 and 13 TeV. The analysis uses both triple product asymmetries and the unbinned energy test method. The highest significances of CP asymmetry are 2.9 standard deviations from triple product asymmetries and 3.0 standard deviations for the energy test method. Once the global p-value is considered, all results are consistent with no CP violation. Parity violation is observed at a significance of 5.5 standard deviations for the triple product asymmetry method and 5.3 standard deviations for the energy test method. The reported deviations are given in regions of phase space.

关键词： Particle decays Bottom baryons Bottom quark Hadron colliders Heavy baryons CP symmetry CP violation P-symmetry

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