检索结果-内蒙古大学图书馆

arXiv 2021年

作者： Huang, Zhi-Peng Yan, Zhen Shen, Zhi-Qiang Tong, Hao Lin, Lin Yuan, Jian-Ping Liu, Jie Zhao, Ru-Shuang Ge, Ming-Yu Wang, Rui Shanghai Astronomical Observatory CAS Shanghai200030 China University of Chinese Academy of Sciences Beijing100049 China School of Physical Science and Technology ShanghaiTech University Shanghai201210 China Key Laboratory of Radio Astronomy CAS 10 Yuanhua Road JiangSu Nanjing210033 China School of Physics and Materials Science Guangzhou University Guangzhou510006 China Department of Astronomy Beijing Normal University Beijing100875 China Xinjiang Astronomical Observatory CAS Xinjiang830011 China School of Physics and Electronic Science Guizhou Normal University Guiyang550001 China Guizhou Provincial Key Laboratory of Radio Astronomy and Data Processing Guizhou Normal University Guiyang550001 China Key Laboratory of Particle Astrophysics Institute of High Energy Physics CAS 19B Yuquan Road Beijing100049 China

Swift J1818.0−1607 discovered in early 2020 is not only the fifth magnetar known with periodic radio pulsations but also the fastest rotating one. Simultaneous 2.25/8.60 GHz observations of Swift J1818.0−1607 were carried out with Shanghai Tian Ma Radio Telescope (TMRT) from MJD 58936 to 59092. The spin-frequency ν and first-order derivative ν of this magnetar were obtained with piecewise fitting method because of its instable timing properties. We found that the amplitude of short-term ν fluctuations decreased with time, and the long-term declining trend of ν discovered previously continued in our observations. The best fitted long-term ν were about −2.25 × 10−11s−2 using our observation data spanning 156 days. The derived characteristic age was about 522 yr, supporting the recent viewpoint that this magnetar may be older than initially thought shortly after its discovery. The flux density of this magnetar was increased at both 2.25 and 8.60 GHz during our observations, and its radio spectrum became flatter at the same time. We also detected bright-quiet type emission mode switching in Swift J1818.0−1607. Copyright © 2021, The Authors. All rights reserved.

关键词： Pulsars

来源：评论

学校读者我要写书评

暂无评论

The FAST Galactic Plane Pulsar Snapshot survey: IV. Discovery of five fast radio bursts

arXiv

引用

arXiv 2023年

作者： Zhou, D.J. Han, J.L. Jing, W.C. Wang, P.F. Wang, C. Wang, T. Wang, W.-Y. Luo, R. Xu, J. Xu, R.X. Wang, H.G. National Astronomical Observatories Chinese Academy of Sciences Jia-20 Datun Road ChaoYang District Beijing100101 China School of Astronomy University of Chinese Academy of Sciences Beijing100049 China CAS Key Laboratory of FAST NAOC Chinese Academy of Sciences Beijing100101 China School of Physics State Key Laboratory of Nuclear Physics and Technology Peking University Beijing100871 China Kavli Institute for Astronomy and Astrophysics Peking University Beijing100871 China CSIRO Space and Astronomy PO Box 76 EppingNSW1710 Australia Department of Astronomy School of Physics and Materials Science Guangzhou University Guangzhou510006 China Department of Astronomy Peking University Beijing100871 China National Astronomical Data Center Great Bay Area Guangzhou510006 China

We report five new fast radio bursts (FRBs) discovered from the Galactic Plane Pulsar Snapshot (GPPS) survey by the Five-hundred-meter Aperture Spherical radio Telescope (FAST): FRB 20210126, FRB 20210208, FRB 20210705, FRB 20211005 and FRB 20220306. To date, no repeating bursts from these FRB sources have been detected in the follow-up monitoring observations, leading to their classification as potential one-off events. We obtain the basic parameters for these bursts, including position, dispersion measure (DM), pulse width, spectral index, scattering time-scale, etc. The fluences and flux densities are generally lower in comparison to the values observed in one-off bursts discovered by other telescopes. Among the observed bursts, polarization data for 4 bursts were recorded during observations. Consequently, we obtain polarization profiles and Faraday rotation measures (RMs) for these bursts. Copyright © 2023, The Authors. All rights reserved.

关键词： Pulsars

来源：评论

学校读者我要写书评

暂无评论

Robust Beamforming for IRS-assisted Wireless Communications under Channel Uncertainty

Robust Beamforming for IRS-assisted Wireless Communications ...

引用

IEEE Conference on Wireless Communications and networking

作者： Yongchang Deng Yuze Zou Shimin Gong Bin Lyu Dinh Thai Hoang Dusit Niyato School of Intelligent Systems Engineering Sun Yat-sen University China School of Electronic Information and Communications Huazhong University of Science and Technology China Key Laboratory of Ministry of Education in Broadband Wireless Communication and Sensor Network Technology Nanjing University of Posts and Telecommunications China School of Electrical and Data Engineering University of Technology Sydney Australia School of Computer Science and Engineering Nanyang Technological University Singapore

In this paper, we consider IRS-assisted transmissions from a multi-antenna access point (AP) to a receiver with uncertain channel information. By adjusting the magnitude of reflecting coefficients, the IRS can sustain its operations by harvesting energy from the AP's signal beamforming. Considering channel estimation errors, we model both the AP-IRS channel and the AP-IRS-receiver as a cascaded channel by norm-based uncertainty sets. This allows us to formulate a robust optimization problem to minimize the AP's transmit power, subject to the receiver's worst-case data rate requirement and the IRS's worst-case power budget constraint. Instead of using the alternating optimization (AO) method, we firstly propose a heuristic scheme to decompose the IRS's phase shift optimization and the AP's active beamforming. Based on semidefinite relaxations of the worst-case constraints, we further devise an iterative algorithm to optimize the AP's transmit beamforming and the magnitude of the IRS's reflecting coefficients efficiently by solving a set of semidefinite programs. Simulation results reveal that the AP requires a higher transmit power to deal with the channel uncertainty. Moreover, the negative effect of channel uncertainty can be alleviated by using a larger-size IRS.

关键词： Wireless communication Uncertainty Array signal processing Simulation Transmitting antennas Channel estimation Receivers

来源：评论

学校读者我要写书评

暂无评论

Quantum Lovász local lemma: Shearer’s bound is tight 2019

Quantum Lovász local lemma: Shearer’s bound is tight

引用

51st Annual ACM SIGACT Symposium on Theory of Computing, STOC 2019

作者： He, Kun Li, Qian Sun, Xiaoming Zhang, Jiapeng CAS Key Lab of Network Data Science and Technology Institute of Computing Technology CAS Beijing China University of Chinese Academy of Sciences Beijing China Shenzhen Institute of Computing Sciences Shenzhen University China University of California San DiegoCA United States

ISBN: (纸本)9781450367059

Lovász Local Lemma (LLL) is a very powerful tool in combinatorics and probability theory to show the possibility of avoiding all "bad" events under some "weakly dependent" condition. Over the last decades, the algorithmic aspect of LLL has also attracted lots of attention in theoretical computer science. A tight criterion under which the abstract version LLL (ALLL) holds was given by Shearer. It turns out that Shearer’s bound is generally not tight for variable version LLL (VLLL). Recently, Ambainis et al. introduced a quantum version LLL (QLLL), which was then shown to be powerful for the quantum satisfiability problem. In this paper, we prove that Shearer’s bound is tight for QLLL, i.e., the relative dimension of the smallest satisfying subspace is completely characterized by the independent set polynomial, affirming a conjecture proposed by Sattath et al. Our result also shows the tightness of Gilyén and Sattath’s algorithm, and implies that the lattice gas partition function fully characterizes quantum satisfiability for almost all Hamiltonians with large enough qudits. Commuting LLL (CLLL), LLL for commuting local Hamiltonians which are widely studied in the literature, is also investigated here. We prove that the tight regions of CLLL and QLLL are different in general. This result might imply that it is possible to design an algorithm for CLLL which is still efficient beyond Shearer’s bound. In applications of LLLs, the symmetric cases are most common, i.e., the events are with the same probability and the Hamiltonians are with the same relative dimension. We give the first lower bound on the gap between the symmetric VLLL and Shearer’s bound. Our result can be viewed as a quantitative study on the separation between quantum and classical constraint satisfaction problems. Additionally, we obtain similar results for the symmetric CLLL. As an application, we give lower bounds on the critical thresholds of VLLL and CLLL for several of the most common lattices. ©

关键词： Hamiltonians

来源：评论

学校读者我要写书评

暂无评论

Space technology:A powerful tool for safeguarding world heritage

引用

The Innovation 2023年第3期4卷 27-28页

作者： Lei Luo Jie Liu Francesca Cigna Damian Evans Mario Hernandez Deodato Tapete Peter Shadie Athos Agapiou Abdelaziz Elfadaly Min Chen Lanwei Zhu Bihong Fu Ruixia Yang Shahina Tariq Mohamed Ouessar Rosa Lasaponara Xinyuan Wang Huadong Guo International Research Center of Big Data for Sustainable Development Goals(CBAS) Beijing 100094China Key Laboratory of Digital Earth Science Aerospace Information Research Institute(AIR)Chinese Academy of Sciences(CAS)Beijing 100094China International Centre on Space Technologies for Natural and Cultural Heritage(HIST)Under the Auspices of UNESCO Beijing 100094China Institute of Atmospheric Sciences and Climate(ISAC) National Research Council(CNR)00133 RomeItaly École Française d’Extreme-Orient 22 Avenue du Président Wilson75116 ParisFrance International Society for Digital Earth(ISDE) Mexico CityMexico Italian Space Agency(ASI) 00133 RomeItaly Blue Mountains World Heritage Institute 16 Dunmore LaneKatoombaNSW 2780Australia Earth Observation Cultural Heritage Research Lab Department of Civil Engineering and GeomaticsCyprus University of TechnologyPO Box 503296 Limassol 3036Cyprus National Authority for Remote Sensing and Space Sciences Cairo 1564Egypt Key Laboratory of Virtual Geographic Environment Ministry of Education of PRCNanjing Normal UniversityNanjing 210023China COMSATS University Islamabad(CUI) Islamabad 45550Pakistan Institut des Regions Arides(IRA)-Medenine Medenine 4119Tunisia Institute of Methodologies for Environmental Analysis(IMAA) CNRC.da Santa LojaTito Scalo85050 PotenzaItaly

WORLD HERITAGE AND SPACE technology The Convention Concerning the Protection of the World Cultural and Natural Heritage(WHC),adopted by United Nations Educational,Scientific and Cultural Organization(UNESCO)on November 16,1972,aims to ensure the identification,protection,conservation,presentation,and transmission to future generations of the world’s cultural and natural *** WHC works toward these goals by emphasizing the Outstanding Universal Value(OUV)of heritage sites and the unique contribution such places can make to conservation and human development agendas.1 As of the end of January 2023,theWHC has been signed by 194 state parties,covering 1,157 sites(including 900 cultural,218 natural,and 39 mixed properties),55 of which are considered to be in *** sites,totaling an area of more than 370 million hectares are designated as World Heritage(WH)sites(https://***/en/list/).WH sites have played a significant role in the sustainable development of society globally and helped effectively maintain and preserve the cultural diversity and global biodiversity of the Earth.

关键词： heritage maintain SPACE

来源：评论

学校读者我要写书评

暂无评论

Experimental side-channel-free quantum key distribution

arXiv

引用

arXiv 2021年

作者： Zhang, Chi Hu, Xiao-Long Chen, Jiu-Peng Liu, Yang Zhang, Weijun Yu, Zong-Wen Li, Hao You, Lixing Wang, Zhen Wang, Xiang-Bin Zhang, Qiang Pan, Jian-Wei Hefei National Laboratory for Physical Sciences at Microscale Department of Modern Physics University of Science and Technology of China Hefei230026 China Shanghai Branch CAS Center for Excellence Synergetic Innovation Center in Quantum Information and Quantum Physics University of Science and Technology of China Shanghai201315 China Jinan Institute of Quantum Technology JinanShandong250101 China State Key Laboratory of Low Dimensional Quantum Physics Department of Physics Tsinghua University Beijing100084 China State Key Laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information Technology Chinese Academy of Sciences Shanghai200050 China Data Communication Science and Technology Research Institute Beijing100191 China

Quantum key distribution can provide unconditionally secure key exchange for remote users in theory. In practice, however, in most quantum key distribution systems, quantum hackers might steal the secure keys by listening to the side channels in the source, such as the photon frequency spectrum, emission time, propagation direction, spatial angular momentum, and so on. It is hard to prevent such kinds of attacks because side channels may exist in any of the encoding space whether the designers take care of or not. Here we report an experimental realization of a side-channel-free quantum key distribution protocol which is not only measurement-device-independent, but also immune to all side-channel attacks in the source. We achieve a secure key rate of 4.80 × 10−7 per pulse through 50 km fiber spools. © 2021, CC BY.

关键词： Quantum cryptography

来源：评论

学校读者我要写书评

暂无评论

A Novel Distributed Anomaly Detection Algorithm for Low-density data

A Novel Distributed Anomaly Detection Algorithm for Low-dens...

引用

Advances in Electrical Engineering and Computer Applications( AEECA), 2020 IEEE International Conference on

作者： Lin Mei Fengli Zhang University of Electronic Science and Technology of China Chengdu China Southwest Minzu University Chengdu China Network and Data Security Key Laboratory of Sichuan Province University of Electronic Science and Technology of China Chengdu China

ISBN: (数字)9781728165219

ISBN: (纸本)9781728165226

Anomaly detection becomes an interesting and significant problem in data mining area. It, in turn, generates many promising applications such as Intrusion Detection, Fraud Detection, Mobile cellular network fraud, and etc. Most of the existing anomaly detection methods are specifically modeled on certain tasks or datasets. And the density-based model has widely applied in anomaly detection. However, for many real-world applications, domain experts usually confront with large scale low-density data. This paper aims to solve the anomaly detection problem of large-scale low-density data. The Relative Local Density-based Outlier Factor (RLDOF) is a highly efficient and promising method for low-density data. While it is not easy to achieve considerable results concerning large-scale data. In this paper, we propose a distributed RLDOF model for low-density data on a large scale. The experimental results indicate that, compared with the existing methods, the model can effectively improve the anomaly detection performance of large-scale low-density data.

关键词： Anomaly detection Computational modeling Resource management Distributed databases Task analysis Processor scheduling

来源：评论

学校读者我要写书评

暂无评论

How to coadd images: II. Anti-aliasing and PSF deconvolution

arXiv

引用

arXiv 2024年

作者： Wang, Lei Shan, Huanyuan Nie, Lin Liu, Dezi Yan, Zhaojun Li, Guoliang Cheng, Cheng Xie, Yushan Qu, Han Zheng, Wenwen Kang, Xi Purple Mountain Observatory Chinese Academy of Sciences No. 10 Yuan Hua Road Nanjing210023 China Department of Information Engineering Wuhan Institute of City Hubei Wuhan430083 China Shanghai Astronomical Observatory Nandan Road 80 Shanghai200030 China National Basic Science Data Center Building No.2 4 Zhongguancun South 4th Street Haidian District Beijing190 China Zhejiang University Purple Mountain Observatory Joint Research Center for Astronomy Zhejiang University Hangzhou327 China South-Western Institute for Astronomy Research Yunnan University Kunming650500 China The Shanghai Key Lab for Astrophysics Shanghai Normal University Shanghai200234 China Chinese Academy of Sciences South America Center for Astronomy National Astronomical Observatories CAS Beijing100101 China CAS Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China Key Laboratory of Radio Astronomy and Technology Chinese Academy of Sciences A20 Datun Road Chaoyang District Beijing100101 China University of Chinese Academy of Sciences Beijing100049 China

We have developed a novel method for co-adding multiple under-sampled images that combines the iteratively reweighted least squares and divide-and-conquer algorithms. Our approach not only allows for the anti-aliasing of the images but also enables PSF deconvolution, resulting in enhanced restoration of extended sources, the highest PSNR, and reduced ringing artefacts. To test our method, we conducted numerical simulations that replicated observation runs of the CSST/VST telescope and compared our results to those obtained using previous algorithms. The simulation showed that our method outperforms previous approaches in several ways, such as restoring the profile of extended sources and minimizing ringing artefacts. Additionally, because our method relies on the inherent advantages of least squares fitting, it is more versatile and does not depend on the local uniformity hypothesis for the PSF. However, the new method consumes much more computation than the other approaches. © 2024, CC BY.

关键词： Anti-aliasing

来源：评论

学校读者我要写书评

暂无评论

Privacy-preserving data outsourcing with integrity auditing for lightweight devices in cloud computing 14th

Privacy-preserving data outsourcing with integrity auditing ...

引用

14th International Conference on Information Security and Cryptology, Inscrypt 2018

作者： Liu, Dengzhi Shen, Jian Chen, Yuling Wang, Chen Zhou, Tianqi Wang, Anxi Jiangsu Engineering Center of Network Monitoring Nanjing University of Information Science and Technology Nanjing China Guizhou Provincial Key Laboratory of Public Big Data Guiyang China

ISBN: (纸本)9783030142339

The cloud can provide unlimited storage space to users via the Internet. Unlike locally data storing, users will lose the direct control of the data after outsourcing it to the cloud. Moreover, the cloud is an untrusted entity. It is possible that the cloud may try to extract, discard and destroy users’ data due to benefits. Hence, the data security in cloud computing needs to be well guaranteed. In this paper, we propose a privacy-preserving data outsourcing scheme with integrity auditing for lightweight devices in cloud computing. On the one hand, the blind signature is used in the proposed scheme to delegate the generation of users’ data signatures to the TPA. On the other hand, based on the property of the BLS signature, the blinded signatures received from the TPA can be verified by the user and the data integrity stored in the cloud can be audited by the TPA. In addition, the proposed scheme supports batch operation. Security analysis shows that the proposed scheme achieves the properties of correctness, privacy-preserving and non-forgeability. Performance analysis indicates that the proposed scheme can be performed with high efficiency. © 2019, Springer Nature Switzerland AG.

关键词： Outsourcing

来源：评论

学校读者我要写书评

暂无评论

Repeated-root constacyclic codes with optimal locality

arXiv

引用

arXiv 2021年

作者： Zhao, Wei Shum, Kenneth W. Yang, Shenghao The School of Science and Engineering The Chinese University of Hong Kong Shenzhen China University of Science and Technology of China China The School of Science and Engineering The Chinese University of Hong Kong Guangdong Shenzhen518172 China The Shenzhen Key Laboratory of IoT Intelligent Systems and Wireless Network Technology The Chinese University of Hong Kong Guangdong Shenzhen518172 China The Shenzhen Research Institute of Big Data Guangdong Shenzhen518172 China

A code is called a locally repairable code (LRC) if any code symbol is a function of a small fraction of other code symbols. When a locally repairable code is employed in a distributed storage systems, an erased symbol can be recovered by accessing only a small number of other symbols, and hence alleviating the network resources required during the repair process. In this paper we consider repeated-root constacyclic codes, which is a generalization of cyclic codes, that are optimal with respect to a Singleton-like bound on minimum distance. An LRC with the structure of a constacyclic code can be encoded efficiently using any encoding algorithm for constacyclic codes in general. In this paper we obtain optimal LRCs among these repeated-root constacyclic codes. Several infinite classes of optimal LRCs over a fixed alphabet are found. Under a further assumption that the ambient space of the repeated-root constacyclic codes is a chain ring, we show that there is no other optimal LRC. © 2021, CC BY.

关键词： Multiprocessing systems

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：