Search

Recently, the transportation means of the elderly have been insufficient due to aging and depopulation, therefore, the area volunteers have provided the demand-responsive transport (DRT) for seniors such as senior transportation service and demand bus. However, the demands collection via telephone or mobile applications has problems: the telephone call imposes a heavy burden on volunteers, and the mobile applications hinder the elderly who are not using or familiar with smartphone from using the service. In this paper, we propose a pick-up demand collection system that easily collects the demands from the elderly and makes them visible to the transportation manager. To collect demands, we designed the demand transmission device having LPWA (Low Power Wide Area) and a user interface for the elderly. As a result of asking the elderly to operate our prototype demand transmission device, it was found that the operability was better for the elderly than the existing input interface with the smartphone. In addition, we confirmed that the transmission device can transmit the demands through repeater devices with multihop communication by LPWA even if the demand request is not directly reachable to gateway due to the influence of radio shielding objects.

After a coal mine disaster, the coal mine roadway often forms an unknown nonstructural environment. Once the normal communication of the roadway is destroyed, the rescue operation of the coal mine rescue robot could be hindered. To restore the emergency wireless communication system in the unstructured environment of the coal mine thus becomes an important prerequisite for the rescue work for the coal mine rescue robot. This paper studies the characteristics of the nonstructural environment and sets up its model. Based on the Maxwell equation and the mechanism of radio electromagnetic wave propagation, this paper researches the electromagnetic characteristics of wireless communication channel in the unstructured environment, and verifies them by numerical simulation. This paper also studies the strategy of repeater's laying for the robot, thereby providing a reliably theoretical foundation to quickly start up the emergency wireless of the coal mine rescue robot.

Fast radio bursts (FRBs) are highly energetic radio pulses from cosmological origins. Despite an abundance of detections, their nature remains elusive. At least a subset of FRBs is expected to repeat, as the daily FRB rate surpasses that of any known cataclysmic event, which has been confirmed by observations. One of the proposed mechanisms to generate repeating FRBs is supergiant pulses from young and highly spinning NSs, in which case FRBs could inherit the periodicity of their parent NS. Here we examine the consequences of such a population of periodic fast radio bursts (PFRBs). We calculate the rate and lifetime of PFRB progenitors, and find that each newly born highly spinning NS has to emit a number $N_{\rm PFRB}\sim 10^2$ of bursts during its active lifetime of $\tau\sim 100$ years, after which it becomes too dim and crosses a PFRB "death line" analogous to the pulsar one. We propose several tests of this hypothesis. First, the period of PFRBs would increase over time, and their luminosity would decrease, due to the NS spin-down. Second, PFRBs may show modest amounts of rotation measure, given the lack of expelled matter from the pulsar, as opposed to the magnetar-sourced FRBs proposed to explain the first repeater FRB 121102. As an example, we study whether the second confirmed repeater (FRB 180814) is a PFRB, given the preference for an inter-pulse separation of 13 ms within its sub-bursts. We show that, if confirmed, this period would place FRB 180814 in a different category as FRB 121102. We develop tests that would identify---and characterize---the prospective population of PFRBs., Comment: 8 pages, 1 figure. Comments are welcome

Quantum communication enables various technological possibilities that are hard or impossible with classical communication. These include secure distribution of keys, transfer of quantum information and distributed quantum computation and sensing. Quantum communication relies on the ability to transmit a quantum state over some distance. Exponential photon loss from fibre inevitably limits the distance one would be able to achieve this over and therefore make use of these promising new technologies.Quantum repeaters have been proposed as a solution to this problem. Elementary repeater protocols involve dividing the channel into smaller segments with repeater nodes, distributing entanglement between these nodes and then performing swapping operations to connect entangled pairs and purification to correct operation errors. In the years since these elementary protocols, quantum repeaters have been through extensive theoretical improvements including utilising the benefits of quantum error correction to improve efficiency.However, the vast majority of these protocols are for discrete encodings of quantum information. There is significant interest in using continuous variable encodings of quantum information for quantum communication applications. This is motivated in part by the ease of generating, manipulating and detecting quantum states and additionally the increased compatibility with existing infrastructure. In this thesis we present one of the first quantum repeater protocols for continuous variable encodings of quantum information.The continuous variable quantum repeater we present in this thesis is based on concatenated error correction protocols that work to correct loss on any optical field state. We thoroughly investigate operation of this error correction protocol including the trade-offs associated with real implementations, various modifications to the error correction protocol as well as whether it can be implemented with current technology.We illustrate how these error correction protocols may be structured to form a quantum repeater that inhibits the exponential photon loss problem with a resource cost that scales polynomially with distance. We show that our continuous variable repeater is able to beat the fundamental bound on quantum communication without a repeater. Finally, we compare the performance of our first generation continuous variable repeater to existing first generation discrete variable protocols.

The clock frequency of high-performance processors in the high-voltage turbo/burst operation mode [1] is governed primarily by the RC-dominated global interconnects in the communication fabrics and NoCs, since the interconnect RC delay does not improve proportionally with logic gate delay at higher voltages. Prior current-mode and pre-emphasis techniques for improved interconnect throughput and energy efficiency [2]–[5] do not address the critical turbo/burst mode latency requirements, and do not consider tunability across a wide voltage-frequency operating range in high-performance processors. Their transmit/receive circuits with complicated data recovery and differential signaling incur major latency and wiring resource overheads, especially for shorter bus distances typical in NoCs. Previous hybrid current/voltage-mode signaling used expensive 4-inversion repeaters without reconfigurable resistive termination strength, and required multi-cycle windows for current-mode operation with limited power savings at high data activities [6]. Other techniques address scalability to lower supply voltages, but do not focus on the critical interconnect RC delay bottlenecks at high voltages [7]. In this paper, we present reconfigurable current/voltage-mode driver/repeater/receiver circuits for on-die global interconnects/busses, fabricated in 10nm CMOS, with transient current-mode operation, achieving: i) up to 38% lower delay/mm vs. voltage-mode operation, ii) 5x lower transient current-mode power vs. always-on current-mode operation at 100% data activity, iii) similar noise immunity as voltage-mode operation, iv) tunable current-mode configuration for optimized performance vs. energy across PVT corners, and v) up to 8x increased repeater distance.

Entanglement swapping enables entanglement distribution between distant nodes in quantum networks. This paper aims at designing remote entanglement distribution (RED) protocols to schedule entanglement swapping for maximizing the entanglement distribution rate (EDR). The concept of Enodes is introduced to represent the entangled quantum bit pairs in the network. With such a concept, we can transform the design of the optimal RED protocols into solving certain linear programming problems. In addition, we study RED in the homogeneous repeater chain, which is a basic and critical quantum network. Specifically, we determine the closed-form expression for the maximum EDR in such a setting. Our results will enable the distribution of long-distance entanglement with noisy intermediate-scale quantum (NISQ) technologies.

Quantum key distribution (QKD) based on entangled photon pairs holds the potential for repeater-based quantum networks connecting clients over long distance. We demonstrate long-distance entanglement distribution by means of polarisation-entangled photon pairs through two successive deployed 96 km-long telecommunications fibres in the same submarine cable. One photon of each pair was detected directly after the source, while the other travelled the fibre cable in both directions for a total distance of 192 km and attenuation of 48 dB. The observed two-photon Bell state exhibited a fidelity 85% $\pm$ 2% and was stable over several hours. We employed neither active stabilisation of the quantum state nor chromatic dispersion compensation for the fibre., 7 pages, 3 figures

In a 3GPP-based system such as 4G-LTE and 5G-NR, a UE transmits a PRACH (Preamble Random Access Channel) signal in the initial connection with a base station. As a result, the interference canceling repeater suddenly receives a high-power narrow-band signal continuously in a no user signal state, so that the interference cancellation algorithm may malfunction and the system is likely to cause oscillation. In this paper, we propose an adaptive algorithm that can maintain the interference cancellation function without oscillation even for narrow band input with an abrupt change of the spectrum and power.

An optimised subsea system design for energy-efficient SDM operation is demonstrated using machine learning. The removal of gain-flattening filters employed in submarine optical amplifiers can result in capacity gains at no additional overall repeater cost., Comment: CLEO 2020

Inefficient parking solutions in metropolitan areas contribute to the creation of traffic jams that lead to stress for the drivers and contribute toward greenhouse emissions. Since parking issues affect most of the citizens, it is hard to imagine future smart cities with efficient parking solutions. With the introduction of the Internet of things (IoT), objects are able to connect to the Internet and may collect data in real time. The potential of these data is enormous and may allow cities to move from estimates to concrete data, which enable precise predictive models to be created and improves urban area planning and scaling. For this reason, parking solutions would benefit from the introduction of the IoT concept of connecting everything. The paper overviews the most common parking solutions, analyzing their pros and cons. Then, it introduces an IoT-oriented smart parking system that can be deployed indoor and/or outdoor. With the proposed solution, drivers can remotely monitor the vacancy status of parking spots in real time through a mobile app (or even Web). Furthermore, the solution acts as a repeater, extending the wireless signal to parking slots that are distant from the primary access point. This solution is evaluated, demonstrated, and validated through a prototype, and it is ready for use.

Secure photonic symbol masking using XPM at the optical regenerative repeater node was experimentally demonstrated for the first time. The measured BER performances of 10 GSymbol/s coherent BPSK signal show FEC limit achievement.

A wearable stripline-fed circularly polarized dual patch antenna structure that exhibits enhanced into-body gain is presented. The antenna is designed for body-surface repeater solutions and it addresses the problem of marginal into-body deep tissue communication links, where power consumption is of the utmost importance and system link efficiency is critical. Under realistic operation conditions the antenna’s circular polarization successfully mitigates implant orientation and polarization mis- match. Polarization loss for linear antennas can be up to 16 dB in anechoic environments and as much as 12.5 dB in a realistic multipath environment, as demonstrated by measured co- and cross-polar forward path gain between implanted and linearly polarized surface antennas. To overcome the body isolating effect of an antenna ground plane and to produce an effective off-body mode, a novel dual aperture stripline feed was developed which also improves the body-mounted antenna radiation efficiency. The antenna provides a 0 dBi off-body gain whilst still maintaining excellent into-body performance. The into-body link was shown to exhibit circular polarization with a maximum isolation of only 1.5 dB between co- and cross-polar measurements in the 2.36–2.4 GHz band. All measurements were carried out using an accurate, next-generation layered phantom tested representative of a wide range of the population.

Photon loss in optical fibers prevents long-distance distribution of quantum information on the ground. Quantum repeater is proposed to overcome this problem, but the communication distance is still limited so far because of the system complexity of the quantum repeater scheme. Alternative solutions include transportable quantum memory and quantum-memory-equipped satellites, where long-lived optical quantum memories are the key components to realize global quantum communication. However, the longest storage time of the optical memories demonstrated so far is approximately 1 minute. Here, by employing a zero-first-order-Zeeman magnetic field and dynamical decoupling to protect the spin coherence in a solid, we demonstrate coherent storage of light in an atomic frequency comb memory over 1 hour, leading to a promising future for large-scale quantum communication based on long-lived solid-state quantum memories., Quantum memories are key components for quantum communication, but current storage times are still too short. Here, the authors use the atomic frequency comb protocol in a zero-first-order-Zeeman field to coherently store an optical pulse for an hour in a cryogenically cooled rare-earth doped crystal.

arXiv:2003.12748v2, et al., We report on the lowest-frequency detection to date of three bursts from the fast radio burst FRB 180916.J0158+65, observed at 328 MHz with the Sardinia Radio Telescope (SRT). The SRT observed the periodic repeater FRB 180916.J0158+65 for five days from 2020 February 20 to 24 during a time interval of active radio bursting, and detected the three bursts during the first hour of observations; no more bursts were detected during the remaining ~30 hr. Simultaneous SRT observations at 1548 MHz did not detect any bursts. Burst fluences are in the range 37 to 13 Jy ms. No relevant scattering is observed for these bursts. We also present the results of the multi-wavelength campaign we performed on FRB 180916.J0158+65, during the five days of the active window. Simultaneously with the SRT observations, others with different time spans were performed with the Northern Cross at 408 MHz, with XMM-Newton, NICER, INTEGRAL, AGILE, and with the TNG and two optical telescopes in Asiago, which are equipped with fast photometers. XMM-Newton obtained data simultaneously with the three bursts detected by the SRT, and determined a luminosity upper limit in the 0.3–10 keV energy range of ~1045 erg s−1 for the burst emission. AGILE obtained data simultaneously with the first burst and determined a fluence upper limit in the MeV range for millisecond timescales of ${10}^{-8}\,\mathrm{erg}\,{\mathrm{cm}}^{-2}$. Our results show that absorption from the circumburst medium does not significantly affect the emission from FRB 180916.J0158+65, thus limiting the possible presence of a superluminous supernova around the source, and indicate that a cutoff for the bursting mechanism, if present, must be at lower frequencies. Our multi-wavelength campaign sensitively constrains the broadband emission from FRB 180916.J0158+65, and provides the best limits so far for the electromagnetic response to the radio bursting of this remarkable source of fast radio bursts., A.Po., M.B. and A.R. gratefully acknowledge financial support from the research grant “iPeska” (P.I. Andrea Possenti) funded under the INAF national call PRIN-SKA/CTA with Presidential Decree 70/2016. V.G. is supported by Breakthrough Listen, which is managed by the Breakthrough Initiatives and sponsored by the Breakthrough Prize Foundation (http://www.breakthroughinitiatives.org). F.P. acknowledges financial support from ASI/INAF agreement n.2019-35-HH.0 and PRIN-INAF SKA-CTA 2016. A.Pa. and L.Z. acknowledge financial support from the Italian Space Agency (ASI) and National Institute for Astrophysics (INAF) under agreements ASI-INAF I/037/12/0 and ASI-INAF n.2017-14-H.0 and from INAF Sostegno alla ricerca scientifica main streams dellINAF, Presidential Decree 43/2018. N.R. is supported by the ERC Consolidator Grant “MAGNESIA” under grant agreement Nr. 817661, Catalan grant SGR2017-1383, Spanish grant PGC2018-095512-BI00, and acknowledge support from the PHAROS COST Action (CA16214). The Sardinia Radio Telescope is funded by the Department of Universities and Research (MIUR), the Italian Space Agency (ASI), and the Autonomous Region of Sardinia (RAS), and is operated as a National Facility by the National Institute for Astrophysics (INAF).

This chapter introduces clock network reconfiguration for wide adaptation from nominal voltage down to deep sub-threshold voltages. Reconfiguration resolves the conflicting repeater insertion requirements at different voltages, in conventional static clock networks. In reconfigurable clock networks, the number of repeater levels is dynamically adapted to the supply voltage to ultimately mitigate the clock skew degradation across a wide voltage range. At nominal voltage, the number of repeater levels is adjusted to the highest value to mitigate the important clock skew contribution of wire delays. At lower voltages, the number of repeaters is progressively lowered to mitigate the increasingly dominant clock skew contribution of repeaters.

Fast radio bursts are mysterious millisecond-duration transients prevalent in the radio sky. Rapid accumulation of data in recent years has facilitated an understanding of the underlying physical mechanisms of these events. Knowledge gained from the neighboring fields of gamma-ray bursts and radio pulsars also offered insight. Here I review developments in this fast-moving field.Two generic categories of radiation model invoking either magnetospheres of compact objects (neutron stars or black holes) or relativistic shocks launched from such objects have been much debated. The recent detection of a Galactic fast radio burst in association with a soft gamma-ray repeater suggests that magnetar engines can produce at least some, and probably all, fast radio bursts. Other engines that could produce fast radio bursts are not required, but are also not impossible., Comment: Review article published in Nature

We present a detailed description of the diagrammatic technique for a semianalytical description of large-scale quantum repeater networks devised recently by V. V. Kuzmin et al. [npj Quantum Inf. 5, 115 (2019)]. The technique takes into account all essential experimental imperfections, including continuous dissipative Liouville dynamics of the network quantum memories and the classical communication delays. The results obtained with the semianalytic method match the exact Monte Carlo simulations while the required computational resources scale only linearly with the network size, thus allowing for precise comparison and optimization of large-scale quantum networks subjected to relevant realistic imperfections. We illustrate the potential of the method by optimizing the secret key rate in one- and two-dimensional quantum networks for a range of network sizes and memory coherence times. The presented approach opens new possibilities for the development and efficient optimization of future quantum networks.

How to design network coding beyond the butterfly network is desired to be resolved. Quantum repeaters are potential candidates to create nonlocal entanglement between distant particles and realize long-distance quantum communication.

GNSS (Global Navigation Satellite System) spoofing has a great impact on the receiver getting trusted position, navigation and timing information, letting the receiver output erroneous information without any notice and causing an incalculable loss to the user. Since the spatial location of the spoofing interference source, the relative position between the repeater and the user, the parameter characteristics of the deceptive signal are different from the authentication signal, the research on the all above difference are getting great improvements. In the complex electromagnetic interference environment, the carrier-to-noise ratio (CN0) estimation will decrease with the increase of the jamming power. However, the CN0 will not follow this rule under the repeater spoofing scene, which may give rise to false missing probability of the spoofing detection method based on CN0 estimation. In addition, the spoofing detection method based on absolute total power measurements will get higher false alarm probability under the jamming interference scene. This paper proposes a constant false-alarm rate (CFAR) repeater spoofing detection method based on In-Phase correlation values under common signal power scenarios and power-enhanced signal scenarios. This method is realized and verified by simulation under various scenes.

A repeating coil (repeater) is a coil inserted into the air gap formed between a transmitting coil and a receiving coil that operates at the same resonance frequency as both coils. The purpose of a repeating coil is to further extend this air gap such that the power transmission may exceed the limitations of the gap.

Currently, non-destructive testing is an interdisciplinary field of science and technology that serves to ensure the safe functioning of complex technical systems in the face of multifactorial risks. In this regard, there is a need to consider new information technologies based on intellectual perception, recognition technology, and general network integration. The purpose of this work was to develop an ultrasonic flaw detector, which uses a smartphone to process the test results, as well as transfer them directly to an powerful information processing center, or to a cloud storage to share operational information with specialists from anywhere in the world. The proposed flaw detector consists of a sensor unit and a smartphone. The exchange of information between the sensor and the smartphone takes place using wireless networks that use "bluetooth" technology. To ensure the operation of the smartphone in the ultrasonic flaw detector mode, the smartphone has software installed that runs in the Android operating system and implements the proposed algorithm of the device, and can serve as a repeater for processing data over a considerable distance (up to hundreds and thousands of kilometers) if it necessary. The experimental data comparative analysis of the developed device with the Einstein-II flaw detector from Modsonic (India) and the TS-2028H+ flaw detector from Tru-Test (New Zealand) showed that the proposed device is not inferior to them in terms of such characteristics as the range of measured thicknesses, the relative error in determining the depth defect and the object thickness. When measuring small thicknesses from 5 to 10 mm, the proposed device even surpasses them, providing a relative measurement error of the order of 1 %, while analogues give this error within 2–3 %. В настоящее время неразрушающий контроль является междисциплинарной областью науки и техники, служащей обеспечению безопасного функционирования сложных технических систем в условиях многофакторных рисков. В связи с этим возникает необходимость рассмотреть в этой области новые информационные технологии, основанные на интеллектуальном восприятии, технологии распознавания, повсеместной сетевой интеграции. Целью данной работы являлась разработка ультразвукового дефектоскопа, который использует смартфон для обработки результатов контроля, а также передачи их непосредственно в центр обработки информации, обладающий мощным оборудованием, или в облачное хранилище, что позволит получать доступ к оперативной информации для её изучения и обработки любому специалисту из любой точки мира. Предложенный дефектоскоп состоит из сенсорного блока и смартфона. Обмен информацией между сенсором и смартфоном происходит с помощью беспроводных сетей, которые используют технологию «bluetooth». Для обеспечения работы смартфона в режиме ультразвукового дефектоскопа в смартфон инсталлировано программное обеспечение, которое работает в среде операционной системы Android и реализует предложенный алгоритм работы прибора, а при необходимости автоматически может выполнять роль ретранслятора для обработки данных на значительном расстоянии (до сотен и тысяч километров). Сравнительный анализ экспериментальных данных разработанного устройства с дефектоскопом Einstein-II компании Modsonic (India) и дефектоскопом TS-2028H+ компании Tru-Test (New Zealand) показал, что предложенное устройство не уступает им по таким характеристикам, как диапазон измеряемых толщин, относительная погрешность определения глубины залегания дефекта и толщины объекта. При измерении малых толщин от 5 до 10 мм, предложенное устройство даже превосходит их, обеспечивая относительную погрешность измерения порядка 1 %, в то время как аналоги дают эту погрешность в пределах 2–3 %.

We report the experimental realization of heralded distribution of single-photon path entanglement at telecommunication wavelengths in a repeater-like architecture. The entanglement is established upon detection of a single photon, originating from one of two spontaneous parametric down conversion photon pair sources, after erasing the photon's which-path information. In order to certify the entanglement, we use an entanglement witness which does not rely on post-selection. We herald entanglement between two locations, separated by a total distance of 2 km of optical fiber, at a rate of 1.6 kHz. This work paves the way towards high-rate and practical quantum repeater architectures., Comment: 5+9 pages, 7 figures

Automatic sectionalizing and redundancy of power transmission lines is one of the conditions for network intellectualization and can significantly reduce the power supply interruption time for rural consumers. However, both sectionalizing and redundancy of power transmission lines in 0.4 kV electric networks are used extremely limitedly since there are no sufficiently effective methods and technical means for their implementation. This article presents a method to automatically deactivate the automatic load transfer switch when restoring the normal network operation mode. The paper considers the implementation of the method on the example of damage occurring in the network where power is supplied to consumers from two power sources using an automatic load transfer switch and two sectionalizing units. A device is developed which allows implementing the developed method of automatic load transfer switch deactivation. The device consists of sectionalizing unit, automatic load transfer switch, voltage presence sensor, power direction sensor, memory element, repeater element, element AND and 3 elements NOT. The work of the device is described. The proposed method for automatically disconnecting the automatic load transfer switch in order to return the consumers’ power supply circuit to its initial state solves the problem of eliminating unreasonable power supply interruptions for consumers.

The design of large-scale quantum networks and any future quantum internet will rely on quantum repeaters and how quantum information flows through it. Tasks performed on such networks will go well beyond quantum key distribution and are likely to include quantum remote sensing and distributed quantum computation. In this presentation we will explore the various ways that such networks could be designed to support those advanced tasks. Critical to this will be quantum routing which we should is highly dependent on the repeater architecture. We introduce a quantum quality of service to help characterize the systems performance and shows how it leads interesting network and routing behavior.

Full list of authors: Lin, L.; Zhang, C. F.; Wang, P.; Gao, H.; Guan, X.; Han, J. L.; Jiang, J. C.; Jiang, P.; Lee, K. J.; Li, D.; Men, Y. P.; Miao, C. C.; Niu, C. H.; Niu, J. R.; Sun, C.; Wang, B. J.; Wang, Z. L.; Xu, H.; Xu, J. L.; Xu, J. W.; Yang, Y. H.; Yang, Y. P.; Yu, W.; Zhang, B.; Zhang, B. -B.; Zhou, D. J.; Zhu, W. W.; Castro-Tirado, A. J.; Dai, Z. G.; Ge, M. Y.; Hu, Y. D.; Li, C. K.; Li, Y.; Li, Z.; Liang, E. W.; Jia, S. M.; Querel, R.; Shao, L.; Wang, F. Y.; Wang, X. G.; Wu, X. F.; Xiong, S. L.; Xu, R. X.; Yang, Y. -S.; Zhang, G. Q.; Zhang, S. N.; Zheng, T. C.; Zou, J. -H., Fast radio bursts (FRBs) are millisecond-duration radio transients of unknown physical origin observed at extragalactic distances1–3. It has long been speculated that magnetars are the engine powering repeating bursts from FRB sources4–13, but no convincing evidence has been collected so far14. Recently, the Galactic magnetar SRG 1935+2154 entered an active phase by emitting intense soft γ-ray bursts15. One FRB-like event with two peaks (FRB 200428) and a luminosity slightly lower than the faintest extragalactic FRBs was detected from the source, in association with a soft γ-ray/hard-X-ray flare18–21. Here we report an eight-hour targeted radio observational campaign comprising four sessions and assisted by multi-wavelength (optical and hard-X-ray) data. During the third session, 29 soft-γ-ray repeater (SGR) bursts were detected in γ-ray energies. Throughout the observing period, we detected no single dispersed pulsed emission coincident with the arrivals of SGR bursts, but unfortunately we were not observing when the FRB was detected. The non-detection places a fluence upper limit that is eight orders of magnitude lower than the fluence of FRB 200428. Our results suggest that FRB–SGR burst associations are rare. FRBs may be highly relativistic and geometrically beamed, or FRB-like events associated with SGR bursts may have narrow spectra and characteristic frequencies outside the observed band. It is also possible that the physical conditions required to achieve coherent radiation in SGR bursts are difficult to satisfy, and that only under extreme conditions could an FRB be associated with an SGR burst. © 2020, The Author(s), under exclusive licence to Springer Nature Limited., This work is supported by the Natural Science Foundation of China (grants 11988101, 11673002, 11703002, 11543004, 11722324, 11690024, 11633001, 11920101003, 11833003, 11722324, 11633001, 11690024, 11573014, 11725314, 11690024, 11743002, 11873067, 11533003, 11673006, U1938201, 11725313, 11721303, 1172130, U15311243, U1831207, U1838201, U1838202, U1838113, U1938109), National Key Research and Development Programs of China (grants 2018YFA0404204, 2017YFA0402600), the Program for Innovative Talents and Entrepreneur in Jiangsu, the KIAA-CAS Fellowship, the China Postdoctoral Science Foundation (grants 2018M631242, 2016YFA0400800, 2018YFA0400802, E01S11BQ10, XDB23010200,XDB2304040, QYZDY-SSW-SLH008), the International Partnership Program of Chinese Academy of Sciences (grant number 114A11KYSB20160008), the Cultivation Project for FAST Scientific Payoff and Research Achievement of CAMS-CAS, the Max-Planck Partner Group, the Spanish Science Ministry “Centro de Excelencia Severo Ochoa” Program (grant SEV-2017-0709), the Junta de Andalucía (Project P07-TIC-03094) and the Spanish Ministry Projects AYA2012-39727-C03-01, AYA2015-71718R and PID2019-109974RB-I00. We thank E. Fernández-García (IAA-CSIC), I. M. Carrasco-García and C. Pérez del Pulgar (UMA) and the rest of the BOOTES Team for making the reported BOOTES Network observations possible. This work made use of data from FAST—a Chinese national mega-science facility, built and operated by the National Astronomical Observatories, Chinese Academy of Sciences. We also acknowledge the use of public data from the Fermi Science Support Center (FSSC).

Focusing on the problem of vulnerable anti-deception and weak anti-jamming ability in classical pseudorandom code correlation ranging, we present a navigation ranging scheme with true random entangled microwave signals. One path of the entangled microwave signals uses for transmitting signal and another path of the signals preserves at locality. Firstly, the target that possesses the function of quantum repeater receives transmitting signal and forwards it to the locality. Then, correlation detection is implemented between the forwarded signal and the local delayed signal. Finally, the target distance can be calculated by delay measurement. We analyze the ranging precision and anti-deception ability. Results indicate that the scheme not only is superior to classical code correlation ranging precision, but also has very strong anti-multipath ability and anti-multipath interference ability, which will enhance the security of the navigation ranging system. Our investigation has significant application prospects.

The article presents the differential ranging method of locating modern earth stations with narrow radiation patterns. Earth station position data is proposed to be calculated using maximum-likelihood procedure system solution from three differential equations using one of numerical methods. In this case supplementary assessment parameter of location, calculated by measuring a mutual signal delay of an earth station, relayed through a spacecraft on geostationary orbit and a mobile repeater on the unmanned aerial vehicle, can improve the accuracy of coordinate estimation earth station. For the developed method the analytical expressions of potential accuracy of calculation of coordinates of the earth station on the basis of the Cramer–Rao lower bound are developed. To measure the positioning accuracy of located emitters it is suggested to use the errors ellipsoid corresponding to the provision of a source of a radio emission in space. The analysis of standard routes of the movement of a repeater on the unmanned aerial vehicle is carried out and the conclusion is drawn that the best accuracy and the shortest route simultaneously are achieved, if the unmanned aerial vehicle follows a circular trajectory along the control area. Calculation of potential accuracy of positioning of the terrestrial station for the area of 50 by 50 km is executed.It is shown that the error of the estimates, received as a result of statistical tests, doesn’t surpass the size of a big half shaft of the error ellipsoid calculated with application of analytical expressions. The application of the developed method is possible in the implementation of the software of electronic control systems to counteract illegitimate use of frequency resource of space vehicles-satellite repeaters communication system.

This paper presents a high-performance microstrip diplexer based on the coupled triangular microstrip cells. The proposed diplexer has a compact size of 0.018 λg2. It is designed to work at 1 GHz for aeronautical military systems and aeronautical navigation and 1.3 GHz for active sensors, GNSS repeaters, radiolocation, and satellite systems. The low insertion and return losses better than 0.21 dB and 25 dB respectively, are obtained at both channels. Another advantage of this diplexer is high isolation of 40 dB between its channels. Moreover, the 1st, 2nd and 3rd harmonics are suppressed with a maximum level of − 30 dB. The designing process is based on proposing an LC model of a novel microstrip cell. Then, the effective parameter on the resonance frequency is found. To verify the designing method, the introduced diplexer is simulated, fabricated and measured. The simulation results are in a good agreement with the measurements.

This paper reports on the proposed design of a low profile broadband array antenna for home repeater applications. The proposed antenna consists of 1 × 4 patch elements and two ground planes, one of which is slitted. By using the gap feeding method, the impedance matching of the antenna is improved by a multi-resonance phenomenon. The proposed antenna provides a wide −10 dB reflection coefficient bandwidth simultaneously covering the Global System for Mobile communications (GSM-1800), Personal Communications Service (PCS), and the Universal Mobile Telecommunication System (UMTS) bands (1.67–2.32 GHz). In order to reduce the mutual coupling between adjacent patch elements, slits are embedded in the ground plane. An isolation level of −20 dB is realized over the entire operating frequency band.

A temperature-dependent delay optimization model for a multilayered graphene nanoribbon (MLGNR) with top contact (TC-GNR), side contact (SC-GNR), and Cu-based nano-interconnects using a wire sizing method was applied to determine the delay for different interconnects widths (11 nm, 16 nm, and 22 nm) and lengths (10 μm, 50 μm, and 100 μm), being the first such model for TC-GNR, SC-GNR, and Cu interconnects applied at three different chip operating temperatures (233 K, 300 K, and 378 K). The results reveal that the SC-GNR requires ~ 3–6× and ~ 2–3× fewer repeaters w.r.t. the TC-GNR or Cu interconnect, and that the SC-GNR and Cu interconnects can achieve ~ 4–5× and ~ 2–2.5× reduction in repeater dimension compared with the TC-GNR interconnect. Meanwhile, the SC-GNR interconnect can achieve 73× less propagation delay w.r.t. the TC-GNR interconnect for interconnect width of 22 nm, interconnect length of 10 μm, and two different chip operating temperatures of 233 K and 300 K. Similarly, the Cu interconnect can achieve 6× less propagation delay w.r.t. the TC-GNR interconnect at interconnect width of 22 nm and 16 nm, interconnect length of 10 μm, and 300 K.

Power repeaters are used to extend the power transfer range or enhance the power transfer capability of Inductive Power Transfer (IPT) systems, but how to tune the power repeaters to improve the system power transfer performance remains an unsolved problem. In this paper, studies of the effect of the tuning capacitance of the power repeater of an IPT system on the power transfer capability are presented. A theoretical model is established to analyze the output power of the system with the primary coil and secondary coil tuned at a nominal resonant frequency, and a passive power repeater placed in between. By analyzing the relationship between the tuning capacitance of the power repeater and the output power, a critical tuning capacitance which sets up the boundary between enhancing and reducing the output power is determined, and the optimal tuning capacitances corresponding to the maximum and minimum output power are also obtained. A practical IPT system with a passive power repeater placed at 40, 80, and 104 mm from the primary coil is built. It has shown that the practically measured critical capacitance and the optimal tuning capacitance for maximum power transfer are in good agreement with the analytical results.

In this paper, we propose an evolutionary multiobjective regenerator placement strategy for elastic optical networks (eMORP). The proposed optimization strategy uses the genetic algorithm NSGA-II to determine non-dominated solutions when the call request blocking probability and the total amount of regenerators used in the network are taken into account. In our simulations, we considered the amplified spontaneous emission noise generated by optical amplifiers (in-line, booster, and pre-amplifier) as physical impairment. Two recently proposed heuristics for regenerator assignment have been used, together with the regenerator placement strategies proposed and analyzed in this paper, for comparison purpose. The results obtained for two different network physical topologies state the efficiency of eMORP. Our regenerator placement strategy reduced considerably the call request blocking probability for the same number of regenerators in the network, as well as it acquired efficient solutions with just a fraction of the nodes with regeneration capability in comparison to other heuristics presented in the literature.

The faithful storage and coherent manipulation of quantum states with matter-systems would enable the realization of large-scale quantum networks based on quantum repeaters. To achieve useful communication rates, highly multimode quantum memories are required to construct a multiplexed quantum repeater. Here, we present a demonstration of on-demand storage of orbital-angular-momentum states with weak coherent pulses at the single-photon-level in a rare-earth-ion-doped crystal. Through the combination of this spatial degree-of-freedom (DOF) with temporal and spectral degrees of freedom, we create a multiple-DOF memory with high multimode capacity. This device can serve as a quantum mode converter with high fidelity, which is a fundamental requirement for the construction of a multiplexed quantum repeater. This device further enables essentially arbitrary spectral and temporal manipulations of spatial-qutrit-encoded photonic pulses in real time. Therefore, the developed quantum memory can serve as a building block for scalable photonic quantum information processing architectures., Multiplexing of quantum memories would enable higher communication rate for repeater based quantum networks. Here, the authors demonstrate multiplexed storage of single-photon-level pulses using multiple degree-of-freedom, with the additional function of arbitrary manipulation of photonic pulses in real time.

In this letter, we present a comprehensive performance analysis of ferroelectric (FE)-based logic gates and repeaters. In addition, we highlight the key aspects of negative capacitance FET (NCFET) characteristics, including the proper circuit initialization, the negative capacitance (NC) effect on leakage currents, and the impacts of the FE viscosity coefficient. The threshold voltage adjustment is proposed to optimize the NCFET-based devices according to the activity factor. Furthermore, we study the interconnect repeater insertions and optimize the numbers and sizes of repeaters to minimize the overall energy-delay product. The NCFET is implemented in SPICE, with FE dynamics described by the Landau-Khalatnikov equation. Our analyses with the SPICE circuit model can provide useful insights into future studies of low-power devices.

Quantum key distribution (QKD) allows two distant parties to share encryption keys with security based on physical laws. Experimentally, it has been implemented with optical means, achieving key rates of 1.26 Megabit/s over 50 kilometres (km) of standard optical fibre and 1.16 bit/hour over 404 km of ultralow-loss fibre in a measurement-device-independent configuration. Increasing the bit rate and range of QKD is a formidable, but important, challenge. A related target, currently considered unfeasible without quantum repeaters, is overcoming the fundamental rate-distance limit of point-to-point QKD. Here we introduce a conceptually new scheme where pairs of phase-randomised optical fields are first generated at two distant locations and then combined at a central measuring station. The fields imparted with the same random phase are "twins" and can be employed to distil a quantum key, as we prove under an explicit security assumption. The key rate of this Twin-Field QKD (TF-QKD) shows the same dependence on distance as a quantum repeater, scaling with the square-root of the channel transmittance, irrespective of whom is in control of the measuring station. Differently from a quantum repeater, however, the new scheme is feasible with current technology and presents manageable levels of noise even on 550 km of standard optical fibre. This is promising to overcome the QKD rate-distance barrier and to greatly extend the range of secure quantum communications.

This paper analyzes and evaluates the statistical properties of the rms delay spread (delay spread) in a two-path simulcast environment and same frequency in cell repeater. Each path is subjected to multipath fading characterized by wideband Weibull distribution. A novel, unified, and accurate analytical expressions for the probability density function, the cumulative distribution function, the mean, the mean square, and the standard deviation for the delay spread have been derived. The derived expressions are then used to study the implication of the fading and scale parameters on the statistical characteristics of the delay spread. To validate the accuracy of the derived formulas, the analytical results are compared with Monte-Carlo simulation results. Full agreement has been noticed between the simulated and the analytical results over a wide range of received signals levels ratio and different values of the fading parameters.

We present a 35-mm diameter skin-adhesive antenna intended to operate as a gateway to relay the low power signals from a sensor implanted in the body to an external base station (BS). Such a device would be useful in the context of body area networks (BANs) for continuous body-signal monitoring. The proposed adhesive repeater is of very low profile, and it is designed for dual-band operation at the ISM band (2.4 GHz) and in the ultrawideband (UWB) spectrum (4–10.6 GHz) using a single excitation port. The ISM band is used for in-body communication with the implants and the UWB band for off-body burst communication with the BS. The antenna consists of three layers that grant it compactness and performance robustness. We assess the in-body link between the repeater and a custom-designed miniaturized implantable probe antenna. The study is performed in the frequency domain with results showing adequate input impedance matching ( s 11 ≤ −10 dB) and robustness to different body parts. We extend the analysis to time domain by transmitting a synthetized medical signal between the two antennas. In addition, we evaluate the feasibility of an off-body link for burst communication. Again, the results indicate very good performance by the repeater antenna both in terms of impedance matching ( s 11 ≤ −10 dB) and preservation of time signals (fidelity ≥ 75%), which is relevant in impulse radio systems. To the authors’ best knowledge, this is the first time this kind of dual-band adhesive antenna is being proposed for BANs, complete with performance tests using frequency- and time-domain figures-of-merit.

Inductor-capacitor (LC) passive wireless sensors allow for a continuous, real-time monitoring for various parameters of interest in situations, where wired connections are difficult or even impossible. However, geometrical constraints reduce the magnetic coupling between the sensor and the readout coil, resulting in a limited interrogation distance. Here, we propose a left-handed metamaterial as a repeater to enhance the readout of the LC passive wireless sensors. The left-handed metamaterial consists of double-side square spirals and possesses negative relative permeability. The operating frequency of the left-metamaterial is designed adjustable to cover the frequency spectrum of the sensor. By monitoring the relative humidity as an example, we have demonstrated that the readout distance with the left-handed metamaterial can achieve nearly 1.8 times as long as that without metamaterial, while keeping their signal strength and sensitivity the same. Overall, this strategy through the metamaterials-based repeaters represents an effective approach for enhancing the readout.

Methods for active protection of computer-processed data using low-energy electromagnetic noise are considered. Information and ecology–ergonomic safety of workstations equipped with active protection systems is analyzed. An intermodulation repeater for active protection of workstations is proposed and experimentally tested.

This paper presents an active cancellation method based on repeater jamming to weaken the incident wave rather than to weaken the scattered wave in conventional method. The method works well on chirp-subpulse stepped frequency (CSSF) signal. The incident plane wave is interfered by a spherical wave which is generated by a horizontal electric dipole. The analysis and simulation show that the plane wave can be reduced obviously via this method. By incorporating frequency and phase modulation, the backscattering of the target is reduced significantly. Numerical experiments also show that with greater wavelength, the cancellation performance gets better.

In recent years, there has been an increase in the number of studies on biological effects of Electromagnetic (EM) fields emitted from Base Transceiver Stations (BTSs). The biological effects of generated and real telecommunication signals produced by different types of exposure systems are discussed. However, the proper exposure methods for such experiments are very limited. We successfully developed a simple and cost-effective exposure unit with real GSM/DCS/UMTS signal from BTS containing proper modulations or intermittence (continuous, interrupted). Signal processing and conditioning unit is based on a Radiofrequency (RF) repeater. The downlink signal is filtered by integrated high selectivity passband filters and amplified to a required level. The main part of exposure unit is a Faraday cage with the specimen (exposure) area measuring 150 x 250 mm with E-field percent deviation less than 18%. This exposure system can be helpful in experiments with living organisms in in vivo studies and in vitro studies with normal or pathological cells and other micro scale structures being exposed to RF EM fields from BTS.

Dual-band coil modules facilitate efficient access to distinct-band, high-power, or rapid-charging wireless power transfer (WPT) systems. However, they do not function efficiently when the frequency ratio between two operating frequencies is large. To overcome this problem, we propose enhanced dual-band coil modules that adopt repeaters in the WPT system. We present a circuit-based analysis of repeaters in various dual-band coil modules compared with those in a single-band WPT system. The analytical results provide a design methodology applicable to diverse types of dual-band coil modules with a repeater in the WPT system. Our experimental results are consistent with the circuit-based analysis: coil power transfer efficiencies of 55% at 200 kHz and 74% at 6.78 MHz were obtained concurrently in the dual-band WPT system with a dual-band repeater. This paper reduced the application constraint of dual-band coil modules and facilitated the realization and application of multiband WPT systems.

This paper recommends a practical way to insert buffer and flop repeaters onto global signals of a complex system-on-chip (SoC). With the advent of deep sub-micrometer technology and new business environment, the market prefers a highly integrated SoC with fast design productivity and low development cost. We observed that many algorithms proposed in the prior arts, which used exact algorithms to optimize design solely for performance, power, and/or area, are no longer practical. With that, we introduced a hybrid meta-heuristic based flow, which combines meta-heuristic algorithm with different artificial intelligent algorithms such as exact and heuristic algorithms, to search for a near optimum buffer repeater insertion recipe, optimize the floor-plan pin placement, and then correctly insert flop repeater into the design. Our experiments on 10- and 14-nm SoC products showed that the flow managed to produce a “good enough" quality of repeater designs with past turn-around-time and less design effort.

By partial interception and multiple forwarding of a radar transmitting signal, digital radio frequency memory-based interrupted sampling repeater jamming can yield a partial processing gain and form multiple false target groups in the range direction, achieving jamming effects of both suppression and deception. Various improved jamming strategies have been proposed, while jamming suppression problems have not been fully addressed. In this study, a jamming suppression method based on the idea of `reconstruction and cancellation' is proposed by analysing the jamming principle. The method firstly analyses the pulse compression results with time-frequency analysis to obtain the intercepted slice number and forwarding times; then, the slice width is estimated by deconvolution processing; finally, iterative cancellation is used to suppress the jamming. Performance of the method was verified by Monte Carlo simulation. The results show that the normalised error of the slice width estimation is 16 dB.