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arXiv 2020年

作者： Qin, Chen Duan, Jinming Hammernik, Kerstin Schlemper, Jo Küstner, Thomas Botnar, René Prieto, Claudia Price, Anthony N. Hajnal, Joseph V. Rueckert, Daniel Institute for Digital Communications School of Engineering University of Edinburgh Edinburgh United Kingdom Department of Computing Imperial College London London United Kingdom School of Computer Science University of Birmingham Birmingham United Kingdom Institute for AI and Informatics Klinikum Rechts der Isar Technical University of Munich Munich Germany Hyperfine Research Inc. GuilfordCT United States School of Biomedical Engineering and Imaging Sciences King's College London St. Thomas' Hospital London United Kingdom Department of Diagnostic and Interventional Radiology Medical Image and Data Analysis University Hospital of Tuebingen Tuebingen Germany

Purpose To introduce a novel deep learning based approach for fast and high-quality dynamic multi-coil MR reconstruction by learning a complementary time-frequency domain network that exploits spatio-temporal correlations simultaneously from complementary domains. Theory and Methods Dynamic parallel MR image reconstruction is formulated as a multi-variable minimisation problem, where the data is regularised in combined temporal Fourier and spatial (x-f ) domain as well as in spatio-temporal image (x-t) domain. An iterative algorithm based on variable splitting technique is derived, which alternates among signal de-aliasing steps in x-f and x-t spaces, a closed-form point-wise data consistency step and a weighted coupling step. The iterative model is embedded into a deep recurrent neural network which learns to recover the image via exploiting spatio-temporal redundancies in complementary domains. Results Experiments were performed on two datasets of highly undersampled multi-coil short-axis cardiac cine MRI scans. Results demonstrate that our proposed method outperforms the current state-of-the-art approaches both quantitatively and qualitatively. The proposed model can also generalise well to data acquired from a different scanner and data with pathologies that were not seen in the training set. Conclusion The work shows the benefit of reconstructing dynamic parallel MRI in complementary time-frequency domains with deep neural networks. The method can effectively and robustly reconstruct high-quality images from highly undersampled dynamic multi-coil data (16× and 24× yielding 15s and 10s scan times respectively) with fast reconstruction speed (2.8s). This could potentially facilitate achieving fast single-breath-hold clinical 2D cardiac cine imaging. © 2020, CC BY.

关键词： Magnetic resonance imaging

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Optical data transmission at 44Tb/s and 10 bits/s/Hz spectral density over standard fibre with a single micro-comb source chip

TechRxiv

引用

TechRxiv 2020年

作者： Moss, David J. Morandotti, Roberto Mitchell, Arnan Xu, Xingyuan Wu, Jiayang Tanmengxi tan, Mengxi Corcoran, Bill Boes, Andreas Nguyen, Thach G. Chu, Sai Tak Little, Brent E. Department of Electrical and Computer System Engineering Monash University ClaytonVIC3168 Australia Centre for Micro-Photonics Swinburne University of Technology HawthornVIC3122 Australia School of Engineering RMIT University MelbourneVIC3001 Australia Department of Physics and Material Science City University of Hong Kong Tat Chee Avenue Hong Kong Xi’an Institute of Optics and Precision Mechanics Precision Mechanics of CAS Xi’an China INRS-Énergie Matériaux et Télécommunications 1650 Boulevard Lionel-Boulet VarennesQCJ3X 1S2 Canada

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Chiral symmetry and taste symmetry from the eigenvalue spectrum of staggered Dirac operators

arXiv

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arXiv 2020年

作者： Jeong, Hwancheol Jung, Chulwoo Jwa, Seungyeob Kim, Jangho Kim, Jeehun Kim, Nam Soo Kim, Sunghee Lee, Sunkyu Lee, Weonjong Lee, Youngjo Pak, Jeonghwan Lattice Gauge Theory Research Center FPRD CTP Department of Physics and Astronomy Seoul National University Seoul08826 Korea Republic of Physics Department Brookhaven National Laboratory UptonNY11973 United States Institut für Theoretische Physik Goethe University Frankfurt am Main Max-von-Laue-Str. 1 Frankfurt am Main60438 Germany Department of Electrical and Computer Engineering The Institute of New Media and Communications Seoul National University Seoul08826 Korea Republic of Department of Statistics Seoul National University Seoul08826 Korea Republic of

We investigate general properties of the eigenvalue spectrum for improved staggered quarks. We introduce a new chirality operator [γ5⨂1] and a new shift operator [1⨂ ξ5], which respect the same recursion relation as the γ5 operator in the continuum. Then we show that matrix elements of the chirality operator sandwiched between two eigenstates of the staggered Dirac operator are related to those of the shift operator by the Ward identity of the conserved U(1)A symmetry of staggered fermion actions. We perform a numerical study in quenched QCD using HYP staggered quarks to demonstrate the Ward identity. We introduce a new concept of leakage patterns which collectively represent the matrix elements of the chirality operator and the shift operator sandwiched between two eigenstates of the staggered Dirac operator. The leakage pattern provides a new method to identify zero modes and non-zero modes in the Dirac eigenvalue spectrum. This method is as robust as the spectral flow method but requires much less computing power. Analysis using a machine learning technique confirms that the leakage pattern is universal, since the staggered Dirac eigenmodes on normal gauge configurations respect it. In addition, the leakage pattern can be used to determine a ratio of renormalization factors as a by-product. We conclude that it might be possible and realistic to measure the topological charge Q using the Atiya-Singer index theorem and the leakage pattern of the chirality operator in the staggered fermion formalism. Copyright © 2020, The Authors. All rights reserved.

关键词： Quantum theory

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Nonreciprocal Phased-Array Antennas

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Physical Review Applied 2019年第5期12卷 054008-054008页

作者： J.W. Zang A. Alvarez-Melcon J.S. Gomez-Diaz Department of Electrical and Computer Engineering University of California Davis One Shields Avenue Kemper Hall 2039 Davis California 95616 USA China Academy of Information and Communications Technology Beijing 100191 China School of Information and Electronics Beijing Institute of Technology Beijing 100081 China Universidad Politécnica de Cartagena 30202 Cartagena Spain

A phased-array antenna is a device that generates radiation patterns whose shape and direction can be electronically controlled by tailoring the amplitude and phase of the signals that feed each element of the array. These devices provide identical responses in transmission and reception due to the constraints imposed by time-reversal symmetry. We introduce the concept of nonreciprocal phased-array antennas and demonstrate that they can exhibit drastically different radiation patterns when operated in transmission or in reception. The building block of the array consists of a time-modulated resonant antenna element that provides very efficient frequency conversion between only two frequencies: one associated with waves propagating in free space and the other related to guided signals. Controlling the tunable nonreciprocal phase response of these elements with the phase of low-frequency modulation signals permits to independently tailor the transmission and reception radiation patterns of the entire array. Measured results at microwaves confirm isolation levels over 40 dB at desired directions in space with an overall loss below 4 dB. We believe that this concept can be extended across the electromagnetic spectrum provided adequate tuning elements are available, with important implications in communication, sensing, and radar systems, as well as in thermal management and energy harvesting.

关键词： Metamaterials Nanoantennas Optical & microwave phenomena Optoelectronics Radio frequency techniques Nonlinear waves T-symmetry Terahertz techniques

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Optical data transmission at 44Tb/s and 10 bits/s/Hz over the c-band with standard fibre and a single micro-comb source

arXiv

引用

arXiv 2020年

作者： Corcoran, Bill Tan, Mengxi Xu, Xingyuan Boes, Andreas Wu, Jiayang Nguyen, Thach G. Chu, Sai T. Little, Brent E. Morandotti, Roberto Mitchell, Arnan Moss, David J. Department of Electrical and Computer System Engineering Monash University ClaytonVIC3168 Australia Optical Sciences Centre Swinburne University of Technology HawthornVIC3122 Australia School of Engineering RMIT University MelbourneVIC3001 Australia Department of Physics and Material Science City University of Hong Kong Tat Chee Avenue Hong Kong Xi'an Institute of Optics and Precision Mechanics Precision Mechanics of CAS Xi'an China INRS-Énergie Matériaux et Télécommunications 1650 Boulevard Lionel-Boulet VarennesQCJ3X 1S2 Canada

Micro-combs [1-4] - optical frequency combs generated by integrated micro-cavity resonators - offer the full potential of their bulk counterparts [5,6], but in an integrated footprint. The discovery of temporal soliton states (DKS - dissipative Kerr solitons) [4,7-11] as a means of mode-locking microcombs has enabled breakthroughs in many fields including spectroscopy [12,13], microwave photonics [14], frequency synthesis [15], optical ranging [16,17], quantum sources [18,19], metrology [20,21] and more. One of their most promising applications has been optical fibre communications where they have enabled massively parallel ultrahigh capacity multiplexed data transmission [22,23]. Here, by using a new and powerful class of micro-comb called "soliton crystals" [11], we achieve unprecedented data transmission over standard optical fibre using a single integrated chip source. We demonstrate a line rate of 44.2 Terabits per second (Tb/s) using the telecommunications C-band at 1550nm with a spectral efficiency - a critically important performance metric - of 10.4 bits/s/Hz. Soliton crystals exhibit robust and stable generation and operation as well as a high intrinsic efficiency that, together with a low soliton micro-comb spacing of 48.9 GHz enable the use of a very high coherent data modulation format of 64 QAM (quadrature amplitude modulated). We demonstrate error free transmission over 75 km of standard optical fibre in the laboratory as well as in a field trial over an installed metropolitan optical fibre network. These experiments were greatly aided by the ability of the soliton crystals to operate without stabilization or feedback control. This work demonstrates the capability of optical soliton crystal micro-combs to perform in demanding and practical optical communications networks. Copyright © 2020, The Authors. All rights reserved.

关键词： Solitons

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A Bit-To-Symbol Mapping Scheme for Spatial Modulation with Partial Channel State Information

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IEEE communications Letters 2017年第5期21卷 995-998页

作者： Althunibat, Saud Mesleh, Raed Communications Engineering Department Faculty of Engineering Al-Hussein Bin Talal University Ma'an Jordan Communications Engineering Department School of Computer Engineering and Information Technology German Jordanian University Amman11180 Jordan

This letter presents a bit to symbol mapping scheme for spatial modulation multiple input single output systems. The proposed scheme relies on the transmitter knowledge of partial information about the channel's magnitude and the phase for each transmit antenna. The aim of the proposed mapping is to minimize the hamming distance between adjacent symbols, which consequently, reduces the average bit error rate at the receiver. Monte Carlo simulation results corroborate the effectiveness of the proposed scheme as compared with the conventional and hybrid mapping schemes in the literature. As well, the proposed scheme is shown to be less complex as compared with the transmit antenna selection algorithms. © 1997-2012 IEEE.

关键词： Hamming distance

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First field-trial of a high capacity micro-comb based optical communications system 45

First field-trial of a high capacity micro-comb based optica...

引用

45th European Conference on Optical Communication, ECOC 2019

作者： Corcoran, Bill Tan, Mengxi Xu, Xingyuan Wu, Jiayang Nguyen, Thach G. Chu, Sai T. Little, Brent E. Morandotti, Roberto Boes, Andreas Mitchell, Arnan Moss, David J. Department of Electrical and Computer System Engineering Monash University Clayton Australia Centre for Micro-Photonics Swinburne University of Technology Hawthorn Australia School of Engineering RMIT University Melbourne Australia Department of Physics and Material Science City University of Hong Kong Hong Kong Xi'an Institute of Optics and Precision Mechanics Precision Mechanics of CAS Xi'an China INRS-Énergie Matériaux et Télécommunications Varennes Canada ITMO University St. Petersburg Russia Inst. of Fundamental and Frontier Sciences U. of Electronic Science and Tech. of China Chengdu China

ISBN: (纸本)9781839531859

We present the first demonstration of micro-comb based communications system in installed optical fibre. Robust soliton-crystal states enable open-loop control, and achieve 32.5 Tb/s (8.2 b/s/Hz spectral efficiency) over 72.8 km, providing a path to compact, high capacity transceivers for legacy fibre, metro-area systems. © 2019 Institution of engineering and Technology. All rights reserved.

关键词： Integrated optics

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Using Metamaterial Complementary Split-Ring Resonators for Measuring Dielectric Constants and Loss Tangents at 22 GHz 3

Using Metamaterial Complementary Split-Ring Resonators for M...

引用

3rd International Symposium on Instrumentation Systems, Circuits and Transducers: Chip in the Pampa, INSCIT 2018

作者： Chuma, E.L. Iano, Y. Bravo Roger, L.L. Fontgalland, G. Department of Communications School of Electrical and Computer Engineering University of Campinas - UNICAMP Campinas Brazil School of Technology University of Campinas - UNICAMP Campinas Brazil Applied Electromagnetics and Microwave Lab University of Campina Grande Campina Grande Brazil

ISBN: (纸本)9781538672983

This paper presents a method using a metamaterial complementary split-ring resonator (CSRR) to measure the dielectric constant (Dk) and loss tangent (Df) of materials at a frequency of 22 GHz. The method involves calculating the permittivity of an unknown material based on the oscillation frequency changes of a CSRR, which is caused by the material under test. This method with a CSSR sensor uses only the resonance frequency and the $S{{21}}$ magnitude response at the resonance frequency to calculate Dk and Df. The measurement accuracy was assessed by comparing the results with the declared values specified in the datasheets of material manufacturers. The results show good agreement with the declared values in the datasheets. Thus, with this method, the dielectric properties of materials at high frequencies of millimeter waves (mm-waves) can be characterized and a non-destructive sensor can be built. © 2018 IEEE.

关键词： Metamaterials

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One-Shot Hybrid State Redistribution

arXiv

引用

arXiv 2020年

作者： Wakakuwa, Eyuri Nakata, Yoshifumi Hsieh, Min-Hsiu Department of Communication Engineering and Informatics Graduate School of Informatics and Engineering The University of Electro-Communications Tokyo182-8585 Japan Department of Computer Science Graduate School of Information Science and Technology The University of Tokyo Bunkyo-ku Tokyo113-8656 Japan Yukawa Institute for Theoretical Physics Kyoto university Kitashirakawa Oiwakecho Sakyo-ku Kyoto606-8502 Japan Photon Science Center Graduate School of Engineering The University of Tokyo Bunkyo-ku Tokyo113-8656 Japan JST PRESTO 4-1-8 Honcho Saitama Kawaguchi332-0012 Japan University of Technology Sydney SydneyNSW Australia Research Institute Taipei Taiwan

We consider state redistribution of a "hybrid" information source that has both classical and quantum components. The sender transmits classical and quantum information at the same time to the receiver, in the presence of classical and quantum side information both at the sender and at the decoder. The available resources are shared entanglement, and noiseless classical and quantum communication channels. We derive one-shot direct and converse bounds for these three resources, represented in terms of the smooth conditional entropies of the source state. Various coding theorems for two-party source coding problems are systematically obtained by reduction from our results, including the ones that have not been addressed in previous literatures. © 2020, CC BY.

关键词： Quantum entanglement

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A reliable broadcast approach for VANET's safety messages 29

A reliable broadcast approach for VANET's safety messages

引用

29th International Conference on Microelectronics, ICM 2017

作者： Ahmad, Abdel Mehsen Bazzal, Zouhair Kalakesh, Ali Wardani, Laura Al Department of Computer and Communications Engineering Lebanese International University Lebanon

ISBN: (纸本)9781538640494

Vehicular ad-hoc networks (VANETs) technology has been introduced mainly to provide safety across the roads in addition to other interactive applications between vehicles. VANETs adopt IEEE 802.11p and IEEE 1609.4 for MAC layer which is responsible for giving access to nodes across the network. Till now, these protocols suffer from high rate of collisions between safety packets that are characterized by their strict conditions and thus results in the failure of safety message delivery. For this reason, we proposed an enhanced mechanism that overcomes the different problems and limitations presented in the standard mechanism by which it decreases the failure rate of safety message delivery and guarantees the successful arrival of safety packets as much as possible. © 2017 IEEE.

关键词： Vehicular ad hoc networks

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