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IET International Radar Conference 2018, IRC 2018

作者： Chen, Jing Liu, Xiangrong Liu, Changjiang Dong, Xichao School of Information and Electronics Beijing Institute of Technology Beijing China Beijing Key Laboratory of Embedded Real-time Information Processing Technology Beijing China National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics 100076 China

In this study, modelling and characteristics analysis of forward scattering coefficients and echoes are investigated. Traditional ground-target forward scattering signal model has not considered the impact of scattering phase;thus it is not accurate enough for describing air-target echoes. To solve this problem, a novel echo model was proposed based on the analytical deduction of complex forward scattering coefficient. The novel model separately expresses the target scattering characteristics and Doppler, greatly facilitating the theoretical analyses of echo characteristics. Then, theoretical and simulation investigations on the amplitude and phase characteristics of forward scattering echoes were made based on the complex forward scattering coefficient model. Theoretical explanations for the periodical fluctuation of far-field echo amplitude, periodical saltation of far-field echo phase, shadow blocking of near-field echo amplitude, and slow variation of near-field echo phase were given, respectively. Meanwhile, the boundary between near-field forward scattering and far-field forward scattering was quantitatively defined, which laid the theoretical foundation for the corresponding signal processing algorithms. Finally, with CST simulation results the accuracy of the echo model is verified and impacts of objects' real shapes are analysed. © 2019 Institution of Engineering and technology. All rights reserved.

关键词： Forward scattering

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Design of W-band Sheet Beam EIK

Design of W-band Sheet Beam EIK

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Asia-Pacific Conference on Microwave

作者： Shuyuan Chen Jinliang Bai Ran Zhang Pei Zheng Jiaqi Liu Xin Liu Hongyan Liu Lu Gao National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China

ISBN: (数字)9781728135175

ISBN: (纸本)9781728135182

Microwave tube is a vacuum electron device which can be used for amplification in the microwave frequency range. Sheet beam Extended Interaction Klystron (EIK) is an attractive Millimeter Waves amplifier because of its compact configuration, small voltage and high gain per unit length. In this paper, RF structure and the whole tube for W-band sheet beam EIK has been designed. A new and effective method of designing and studying W-band sheet beam EIK is presented in this paper. In order to get the same output power, several kinds of W-band sheet beam EIK are designed and compared. By optimizing the position of cavities, the output power can achieve 30 kW, which is calculated by threedimensional particle in cell (3D-PIC) software. It is a powerful basis for the subsequent study of sheet beam EIK.

关键词： Power generation Klystrons Power amplifiers physics Mathematics Urban areas

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Modulation recognition of emitter signals based on SDAE-ODCNN

Modulation recognition of emitter signals based on SDAE-ODCN...

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IET International Radar Conference (IET IRC 2020)

作者： X. Wang J. Gao L. Gao F. Wang Harbin Engineering University College of Information and Communication Engineering Harbin China Beijing Institute of Space Long March Vehicle National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China

In order to improve the recognition rate of emitter signals modulation under low signal noise ratio (SNR), an end-to-end method based on the stacked denoising autoencoder (SDAE) - one dimensional convolutional neural network (ODCNN) is proposed in this paper. The SADE-ODCNN is designed in this method and trained through a two-step training. In the SDAE-ODCNN model, the encoder of the SDAE can extract the denoised and compressed features of the received emitter signals. Then the ODCNN can further extract features to realize the recognition. The simulation results show that the average recognition rate of the method can reach 0.94 under 0dB. Thus the proposed method has a good application in the field of emitter signals modulation recognition.

关键词： radar computing modulation feature extraction neural nets image denoising learning (artificial intelligence) image classification

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The Relationship between Deterministic and Ensemble Mean Forecast Errors Revealed by Global and Local Attractor Radii

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Advances in Atmospheric sciences 2019年第3期36卷 271-278,339页

作者： Jie FENG Jianping LI Jing ZHANG Deqiang LIU Ruiqiang DING School of Meteorology University of Oklahoma College of Global Change and Earth System Science (GCESS) Beijing Normal University Laboratory for Regional Oceanography and Numerical Modeling Qingdao National Laboratory for Marine Science and Technology Cooperative Institute for Research in the Atmosphere GSD/ESRL/OAR/NOAA Fujian Meteorological Observatory Wuyishan National Park Meteorological Observatory State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Plateau Atmosphere and Environment Key Laboratory of Sichuan Province Chengdu University of Information Technology

It has been demonstrated that ensemble mean forecasts, in the context of the sample mean, have higher forecasting skill than deterministic(or single) forecasts. However, few studies have focused on quantifying the relationship between their forecast errors, especially in individual prediction cases. Clarification of the characteristics of deterministic and ensemble mean forecasts from the perspective of attractors of dynamical systems has also rarely been involved. In this paper, two attractor statistics—namely, the global and local attractor radii(GAR and LAR, respectively)—are applied to reveal the relationship between deterministic and ensemble mean forecast errors. The practical forecast experiments are implemented in a perfect model scenario with the Lorenz96 model as the numerical results for verification. The sample mean errors of deterministic and ensemble mean forecasts can be expressed by GAR and LAR, respectively, and their ratio is found to approach2^(1/2) with lead time. Meanwhile, the LAR can provide the expected ratio of the ensemble mean and deterministic forecast errors in individual cases.

关键词： attractor radius ensemble forecasting ensemble mean forecast error saturation

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Anthropogenic Influences on the Extremely Dry and Hot Summer of 2020 in Southern China and Projected Changes in the Likelihood of the Event

SSRN

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SSRN 2024年

作者： Wang, Kaixi Zheng, Zhiyuan Zhu, Xian Dong, Wenjie Tett, Simon F.B. Dong, Buwen Zhang, Wenxia Lott, Fraser C. Bu, Lulei Wang, Yumiao Li, Huixin Nanding, Nergui Freychet, Nicolas Wang, Dongqian Qiao, Shaobo Ministry of Education Sun Yat-sen University Zhuhai China Zhuhai Branch State Key Laboratory of Earth Surface Process and Resource Ecology Advanced Institute of Natural Sciences Beijing Normal University Zhuhai China School of Geosciences University of Edinburgh Edinburgh United Kingdom National Centre for Atmospheric Science Department of Meteorology University of Reading Reading United Kingdom State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China Met Office Hadley Centre ExeterEX1 3PB United Kingdom Department of Atmospheric and Oceanic Sciences Institute of Atmospheric Sciences IRDR International Center of Excellence on Risk Interconnectivity and Governance on Weather/Climate Extremes Impact and Public Health Fudan University Shanghai China School of Hydrology and Water Resources Nanjing University of Information Science and Technology Nanjing China Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Key Laboratory of Meteorological Disasters Ministry of Education Joint International Research Laboratory of Climate and Environment Change Nanjing University of Information Science and Technology Nanjing China School of Earth Sciences Yunnan University Kunming China National Climate Center China Meteorological Administration Beijing China State Key Laboratory of Earth Surface Processes and Resource Ecology Faculty of Geographical Science Beijing Normal University Beijing China Zhuhai China

During summer 2020, Southern China experienced an extremely dry and hot summer, which was identified as one of the top ten domestic weather and climate extreme events in 2020 by China Meteorological Administration. Summer mean precipitation, surface air temperature (TAS), and number of hot days (NHD) were about 25% dryer, 1.5℃ warmer, and 11 days larger than the 1981–2010 normal. These are the 4th largest precipitation deficit, the highest TAS, and the 2nd highest NHD in the 1961–2020 record. The large-scale circulation anomalies over the West Pacific increased the likelihood of these extremely event. Anthropogenic influences on this event were investigated using 525-member ensembles of the atmosphere-only HadGEM3-GA6 model and the multi-model ensembles from the Coupled Model Intercomparison Project Phase 6 (CMIP6). Anthropogenic forcings doubled (increased by 11%) the probability of precipitation deficits, and increased occurrence more than [[EQUATION]] times for both TAS anomaly (1.25[[EQUATION]] probability higher) and NHD anomaly (300% probability higher) in HadGEM-GA6 (CMIP6). That means that the 2020-like TAS and NHD anomalies would not occur without anthropogenic forcings, and there is weak evidence that human influences decrease rainfall over Southern China. However, the precipitation deficit increased the likelihood of exceeding the observed thresholds for both TAS and NHD by about 17 (4) and 9 (11) times in HadGEM3-GA6 (CMIP6), respectively. Under SSP2-4.5 and SSP5-8.5 scenarios in the future, 2020-like hot but wet extreme events increase in magnitude and frequency, while the frequency of dry events declines. © 2024, The Authors. All rights reserved.

关键词： Climate models

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Preliminary analysis of echolocation signals produced by fleeing Irrawaddy dolphins(Orcaella brevirostris)

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Acta Oceanologica Sinica 2019年第1期38卷 85-89页

作者： Ying Jiang Xuelei Zhang Zhiguo Yang Saifullah Arifin Jaaman Qinzeng Xu Azmi Marzuki Muda Hairul Masrini Muhamad First Institute of Oceanography Ministry of Natural Resources Laboratory for Regional Oceanography and Numerical Modeling Pilot National Laboratory for Marine Science and Technology (Qingdao) Laboratory for Marine Ecology and Environmental Science Pilot National Laboratory for Marine Science and Technology (Qingdao) China National Deep Sea Center Ministry of Natural Resources Institute of Oceanography & Environment University Malaysia Terengganu Key Laboratory of Underwater Acoustics and Marine Information Technology Department of Applied Marine Physics & Engineering College of Ocean and Earth Xiamen University

In this study, echolocation signals were recorded from a wild Irrawaddy dolphin(Orcaella brevirostris) in shallow water in the Bay of Brunei. During sound recording, a small fishing boat engine startled a nearby Irrawaddy dolphin and began chasing it on two occasions. Variations in the acoustic parameters were detected. When the Irrawaddy dolphin was startled and chased, the sound pressure level, number of click trains per minute, pulse number, and average inter-pulse interval(PI) per click train were all affected. The PI increased and exhibited a slight downward trend during the chase. The increase in PI indicated an increase in the inspection distance as the dolphin escaped. Thus, Irrawaddy dolphins may adapt their echolocation signals to stand out from ambient noise in the wild and to improve their search efforts in potentially risky situations. Appropriate management of the burst noise around the dolphins is important.

关键词： click train echolocation signal Irrawaddy dolphin signal change

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Moving target modelling and indication in MIMO GEO SAR

Moving target modelling and indication in MIMO GEO SAR

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IET International Radar Conference 2018, IRC 2018

作者： Cui, Chang Liu, Xiangrong Dong, Xichao Hu, Cheng Li, Yuanhao School of Information and Electronics Beijing Institute of Technology Beijing China National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China Beijing Key Laboratory of Embedded Real-time Information Processing Technology Beijing Institute of Technology Beijing China

Multiple-input multiple-output geosynchronous synthetic aperture radar (MIMO GEO SAR), composed by several mini-satellites in GEO orbits, has more spatial degrees of freedom, which helps to suppress clutter and improves the performance of ground moving target indication (GMTI). However, in order to ensure the satellite safety, the satellite spacing in MIMO GEO SAR is very large. It results in the failure of far-field assumption and causes the moving target defocusing because of the mismatch between the steering vector in far-field sources and the moving target echo. Here, a new signal model based on the near-field sources is first given according to the GEO SAR satellite-ground geometry relationship. Then, considering the phase difference between the different channels, the spatial steering vector is derived and the weight vector for adaptive processing is proposed to suppress clutter and indicate the moving target. Finally, computer simulations are carried out for the validation of the proposed method. © 2019 Institution of Engineering and technology. All rights reserved.

关键词： Synthetic aperture radar

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Automatic MHT Method Based on Target Characteristics Applied in the Small Space Targets 3

Automatic MHT Method Based on Target Characteristics Applied...

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3rd International Conference on Design, Mechanical and Material Engineering, D2ME 2018

作者： Zhao, Qian Niu, Zhenhong Xue, Lian Liu, Xin Li, Jianhua Li, Zhifeng National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics China

The Multi-Hypothesis Tracking (MHT) method is one of the most promising approaches to realize automatic tracking of small and dim targets in complex space scene. However, the number of hypotheses generated by this algorithm has an exponentially increasing relationship with the number of trajectories, measurement data, and the number of image frames. In the paper, the automatic detection and tracking method of judging the confidence coefficient of the trajectory obtained by the MHT which is based on the characteristics of dim targets, has been realized in the IRST system. The performance of this method is greatly improved. © 2018 The Authors, published by EDP sciences.

关键词： Target tracking

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The Design of Large Arc-shape High-precision Walking Device in TV (thermal-vacuum) Conditions 3

The Design of Large Arc-shape High-precision Walking Device ...

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3rd International Conference on Design, Mechanical and Material Engineering, D2ME 2018

作者： Lian, Xue Hua, Nan Jiaqi, Liu Xin, Liu Gang, Meng National Key Laboratory of Science Technology on Test Physics and Numerical Mathematics China

The large-sized space environmental simulation test facility is mainly used for providing thermal radiation environment in high-vacuum, cold and dark space for satellites, spacecraft, lunar spacecraft to carry out whole satellite thermal vacuum test and for large equipment like antenna to carry out tests in TV conditions. Monitoring the spacecraft's surface optical image or temperature is a main task in space environment simulation test. In previous tests, optical image test mainly took place in a fixed position, so the measuring location and angle are limited. This paper focuses on large spherical space environmental simulation test facility, and designs a large arc-shape high-precision walking device in a space environment simulation test device. It introduces key technology in detail like structure design, thermal design, processes and manufacturing, etc. The test results show that this device can work steadily and reliably under simulation space environments, and the precision exceeds 0.5°. © 2018 The Authors, published by EDP sciences.

关键词： Design

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Pathways of Influence of the Northern Hemisphere Mid–high Latitudes on East Asian Climate: A Review

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Advances in Atmospheric sciences 2019年第9期36卷 902-921页

作者： Jianping LI Fei ZHENG Cheng SUN Juan FENG Jing WANG Key Laboratory of Physical Oceanography–Institute for Advanced Ocean Studies Ocean University of China and Qingdao National Laboratory for Marine Science and TechnologyQingdao 266003China College of Global Change and Earth System Science Beijing Normal UniversityBeijing 100875China State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China

This paper reviews recent progress made by Chinese scientists on the pathways of influence of the Northern Hemisphere mid-high latitudes on East Asian climate within the framework of a“coupled oceanic-atmospheric(land-atmospheric or seaice-atmospheric)bridge”and“chain coupled bridge”.Four major categories of pathways are concentrated upon,as follows:Pathway A—from North Atlantic to East Asia;Pathway B—from the North Pacific to East Asia;Pathway C—from the Arctic to East Asia;and Pathway D—the synergistic effects of the mid-high latitudes and *** addition,definitions of the terms“combined effect”,“synergistic effect”and“antagonistic effect”of two or more factors of influence or processes and their criteria are introduced,so as to objectively investigate those effects in future research.

关键词： East Asian climate Northern Hemisphere mid-high latitudes coupled oceanic-land-sea-ice-atmospheric bridge chain coupled bridge pathway synergistic effect

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