检索结果-内蒙古大学图书馆

IEEE International Conference on Computational Electromagnetics (ICCEM)

作者： Weidong Wang Xin Liu Mingliang Wang Jiaqi Liu Gang Meng Zhiyong Gao Lei Mu Xia Ai Shengjun Zhang Jianbing Li National Key Laboratory of Science and Technology on Test Physics Beijing Institute of Space Long March Vehicle Beijing China

ISBN: (纸本)9781538612422

In this paper, a method of shielding the object behind a discrete metal wire array is proposed and verified by anechoic chamber experiments. Results show that if the metal wire array is dense enough (cell size is smaller than half of the wavelength), the object behind it can be effectually shielded by the discrete metal wire array. The principle can be applied to electromagnetic camouflage and protection.

关键词： anechoic chambers (electromagnetic) electromagnetic shielding Electromagnetic shielding half-wave ELECTRIC WIRE shielding properties Metals Cell Size Dense arrays

来源：评论

学校读者我要写书评

暂无评论

The Probability Density Function for Network Coding with Three Input Flows

The Probability Density Function for Network Coding with Thr...

引用

International Conference on Computers, Communications, and Systems (ICCCS)

作者： Xiangrong Liu Yaping Liang Qing Chang Xianxu Li National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China School of Electronic Information Engineering Beihang University Beijing China State grid information & communication branch Beijing China

ISBN: (纸本)9781538663516

Now many researches have been studying the optimization between throughput/energy consuming and delay with a couple of independent input flows in network coding (NC). However, the implementation of network coding (NC) requires a thorough investigation of its impact on relevant queueing systems which little work focuses on. In this paper, the scenario with three independent Poisson input flows based on our previous work about the pdf with two independent Poisson input flows., and one output flow is considered. The asynchronous NC-based strategy is that a new arrival evicts a head packet holding in its queue when waiting for another packet from the other flow to encode. The three flows are divided into two parts for getting the probability density function (pdf) of the output flow. The pdf for the output flow which contains both coded and uncoded packets is derived. Besides, the statistic characteristics of this strategy are analyzed. These results are verified by numerical simulations.

关键词： Probability density function Network coding Encoding Relays Merging Simulation numerical simulation

来源：评论

学校读者我要写书评

暂无评论

A Novel Gcv-Based Criterion for Parameter Selection In Image Deconvolution

A Novel Gcv-Based Criterion for Parameter Selection In Image...

引用

IEEE International Conference on Acoustics, Speech and Signal Processing

作者： Feng Xue Thierry Blu Jiaqi Liu Xia Ai National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing 100076 China Dept. of Electronic Engineering The Chinese University of Hong Kong Shatin N.T. Hong Kong

ISBN: (纸本)9781538646595

A proper selection of regularization parameter is essential for regularization-based image deconvolution. The main contribution of this paper is to propose a new form of generalized cross validation (GCV) as a criterion for this optimal selection. Incorporating a nil-trace non-linear estimate, we develop this new GCV based on Stein's unbiased risk estimate (SURE)-an unbiased estimate of mean squared error (MSE). The key advantage of this GCV over SURE is that it does not require the knowledge of noise variance. We exemplify this criterion with both Tikhonov regularization and l_1-based sparse deconvolution. In particular, we develop a recursive evaluation of GCV for the l_1-estimate based on iterative soft-thresholding (IST) algorithm. numerical experiments demonstrate the nearly optimal parameter selection and negligible loss of its resultant deconvolution quality.

关键词： Image deconvolution regularization parameter generalized cross validation (GCV) Stein's unbiased risk estimate (SURE) deconvolution Mean square error optimal selection optimal parameter Imagery (Psychotherapy) Image images

来源：评论

学校读者我要写书评

暂无评论

Recursive Evaluation of Sure for Total Variation Denoising

Recursive Evaluation of Sure for Total Variation Denoising

引用

IEEE International Conference on Acoustics, Speech and Signal Processing

ISBN: (纸本)9781538646595

Recently, total variation (TV)-based regularization has become a standard technique for signal denoising. The reconstruction quality is generally sensitive to the value of regularization parameter. In this work, based on Cham-bolle's algorithm, we develop two data-driven optimization schemes based on minimization of Stein's unbiased risk estimate (SURE)-statistically equivalent to mean squared error (MSE). First, we propose a recursive evaluation of SURE to monitor the estimation error during Chambolle's iteration;the optimal value is then identified by the minimum SURE. Second, for fast optimization, we perform alternating update between regularization parameter and solution within Chambolle's iteration. We exemplify the proposed methods with both 1-D and 2-D signal denoising. numerical experiments show that the proposed methods lead to highly accurate estimate of regularization parameter and nearly optimal denoising performance.

关键词： Signal denoising total variation (TV) Stein's unbiased risk estimate (SURE) Chambolle's algorithm

来源：评论

学校读者我要写书评

暂无评论

Meta or select?* : —history, argument and prospective about MTMs and FSS

Meta or select?* : —history, argument and prospective about...

引用

International Applied Computational Electromagnetics Society Symposium (ACES)

作者： Shengjun Zhang Mingliang Wang Xia Ai Yichun Cui Xin Liu Jiaqi Liu Gang Meng Zhaohui Qi Yuan Sun Yunhui Tang Hui Xue National Key Laboratory of Science & Technology on Test Physics and Numerical Mathematics Beijing China The Institute of Effectiveness Evaluation of Flying Vehicle Beijing China School of materials science and technology Beijing University of Technology Beijing China Beijing Institute of system engineering Beijing China

In this paper, the development history of metamaterials (MTMs) and Frequency selective surfaces (FSS) was sketched, and the two conception was discussed. Furthermore, state of the art of both terms was introduced and ... 详细信息

关键词： Frequency selective surfaces Metamaterials Lattices Crystals physics Electromagnetics Sun

来源：评论

学校读者我要写书评

暂无评论

A method for feature extraction based on SVD and machine learning

引用

IOP Conference Series: Materials science and Engineering 2019年第5期569卷

作者： Wei Mao Shuxian Huang Xin Liu Hongyan Liu Jiaqi Liu Yi Shu National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics 100076 China Beijing Institute of Precision Mechatronics and Controls 100076 China Beijing Institute of Long March Vehicle 100076 China

By studying the shortcomings of feature, which extracted from Radar-Cross Section(RCS),using mathematical and statistical method, using the idea of extracting abstract features in image recognition and speech recognition by artificial intelligence for reference[2][3]. This paper explores the possibility of extracting abstract features of target's RCS sequence, and proposes an abstract feature extraction method of RCS sequence based on singular value decomposition(SVD) feature decomposition. Because of the poor interpretability of abstract features, four different machine learning algorithms are used to classify the extracted Abstract features. The experimental results show that the machine learning algorithm can classify different types of spatial objects with high accuracy, which shows that the RCS features of different spatial objects can be characterized by abstract features.

关键词：

来源：评论

学校读者我要写书评

暂无评论

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

Suppressing the effects of ionospheric scintillation on geos...

引用

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

来源：评论

学校读者我要写书评

暂无评论

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

引用

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

来源：评论

学校读者我要写书评

暂无评论

Parallel pipeline algorithm of real time star map preprocessing

Parallel pipeline algorithm of real time star map preprocess...

引用

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

来源：评论

学校读者我要写书评

暂无评论

A seasonal grade division of the global offshore wind energy resource

引用

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

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：