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A Cosmic Microscope to Probe the Universe from Present to Cosmic Dawn:Dual-element Lowfrequency Space VLBI Observatory
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作者 AN Tao JAISWAL Sumit +2 位作者 MOHAN Prashanth ZHAO Zhen LAO Baoqiang 《空间科学学报》 CAS CSCD 北大核心 2019年第2期242-249,共8页
A space-based Very Long Baseline Interferometry (VLBI) program, named as the Cosmic Microscope, is proposed to involve dual VLBI telescopes in the space working together with giant ground-based telescopes (e.g., Squar... A space-based Very Long Baseline Interferometry (VLBI) program, named as the Cosmic Microscope, is proposed to involve dual VLBI telescopes in the space working together with giant ground-based telescopes (e.g., Square Kilometre Array, FAST, Arecibo) to image the low radio frequency Universe with the purpose of unraveling the compact structure of cosmic constituents including supermassive black holes and binaries, pulsars, astronomical masers and the underlying source, and exoplanets amongst others. The operational frequency bands are 30, 74, 330 and 1670 MHz, supporting broad science areas. The mission plans to launch two 30-m-diameter radio telescopes into 2 000 km×90 000 km elliptical orbits. The two telescopes can work in flexibly diverse modes,(i) Space-ground VLBI. The maximum space-ground baseline length is about100 000 km;it provides a high-dynamic-range imaging capacity with unprecedented high resolutions at low frequencies (0.3 mas at 1.67 GHz and 20 mas at 30 MHz) enabling studies of exoplanets and supermassive black hole binaries (which emit nanoHz gravitational waves),(ii) Space-space single-baseline VLBI. This unique baseline enables the detection of flaring hydroxyl masers, and more precise position measurement of pulsars and radio transients at mas level.(iii) Single dish mode, where each telescope can be used to monitor transient bursts and rapidly trigger follow-up VLBI observations. The large space telescope will also contribute in measuring and constraining the total angular power spectrum from the Epoch of Reionization. In short, the Cosmic Microscope offers astronomers the opportunity to conduct novel, frontier science. 展开更多
关键词 Space VLBI RADIO interferometer Low-frequency RADIO ASTRONOMY Transient EXOPLANET
Polarization multiplexing based duplex radio-over-fiber link for millimeter wave signal transmission to a ring of multiple radio access units
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作者 Tayyab MEHMOOD Hina QAYYUM Salman GHAFOOR 《信息与电子工程前沿:英文版》 SCIE EI CSCD 2019年第2期300-306,共7页
A radio-over-fiber(RoF) distributed antenna system(DAS) architecture is proposed, where millimeter wave(mm-wave) signals are transmitted to four different radio access units(RAUs) arranged in a ring topology.The propo... A radio-over-fiber(RoF) distributed antenna system(DAS) architecture is proposed, where millimeter wave(mm-wave) signals are transmitted to four different radio access units(RAUs) arranged in a ring topology.The proposed architecture transmits duplex data of 128 Mb/s to each RAU in both downlink(DL) and uplink(UL)directions. The radio frequency(RF) signals are transmitted by polarization multiplexing a multi-wavelength source.Millimeter-wave signals at a frequency of 25 GHz are generated at each RAU using remote heterodyne detection.The proposed architecture provides increased coverage while maintaining good bit error rate(BER) results. 展开更多
关键词 RADIO over FIBER MILLIMETER wave RADIO access UNITS
Commissioning progress of the FAST
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作者 Peng Jiang YouLing Yue +15 位作者 HengQian Gan Rui Yao Hui Li GaoFeng Pan JingHai Sun DongJun Yu HongFei Liu NingYu Tang Lei Qian JiGuang Lu Jun Yan Bo Peng ShuXin Zhang QiMing Wang Qi Li Di Li 《中国科学:物理学、力学、天文学英文版》 SCIE EI CAS CSCD 2019年第5期3-24,共22页
The Five-hundred-meter Aperture Spherical radio Telescope(FAST) was completed with its main structure installed on September 25, 2016, after which it entered the commissioning phase. This paper aims to introduce the c... The Five-hundred-meter Aperture Spherical radio Telescope(FAST) was completed with its main structure installed on September 25, 2016, after which it entered the commissioning phase. This paper aims to introduce the commissioning progress of the FAST over the past two years. To improve its operational reliability and ensure effective observation time, FAST has been equipped with a real-time information system for the active reflector system and hierarchical commissioning scheme for the feed support system, which ultimately achieves safe operation of the two systems. For meeting the high-performance indices, a highprecision measurement system was set up based on the effective control methods that were implemented for the active reflector system and feed support system. Since the commissioning of the FAST, a low-frequency ultra-wideband receiver and 19-beam1.05-1.45 GHz receiver have been mainly used. Telescope efficiency, pointing accuracy, and system noise temperature were completely tested and ultimately achieved the acceptance indices of the telescope. The FAST has been in the process of national acceptance preparations and has begun to search for pulsars. In the future, it will still strive to improve its capabilities and expand its application prospects. 展开更多
关键词 RADIO telescopes and INSTRUMENTATION astronomical OBSERVATIONS RADIO wave RECEIVERS ALGORITHMS and implementation control systems
许魏洲:梦想全面开花
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作者 骨朵星番 蓝仁 《时代邮刊》 2019年第2期16-19,共4页
当提及当下人气最高的帅哥时,总有几个名字是你无论如何也绕不过去的。随便一条微博就有几十万次的转发,在亚洲各国都深受粉丝追捧,泰国韩国演唱会门票瞬间售罄,备受时尚品牌青睐,频频出现在各大时装周前排,出任Coach代言人、成为Tiffan... 当提及当下人气最高的帅哥时,总有几个名字是你无论如何也绕不过去的。随便一条微博就有几十万次的转发,在亚洲各国都深受粉丝追捧,泰国韩国演唱会门票瞬间售罄,备受时尚品牌青睐,频频出现在各大时装周前排,出任Coach代言人、成为Tiffany中国区品牌风格大使他是许魏洲。对于这一切,许魏洲大方地承认了自己的幸运,但这个新生代艺人非常清楚. 展开更多
关键词 拉丁舞 演唱会 周杰伦 RADIO
浅谈中国工农红军对无线电人才的培养
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作者 钟燕林 《苏区研究》 2019年第4期62-70,共9页
紧张的战争环境使红军迫切需要一种高效快捷的通讯手段,无线电作为当时的新兴技术,具有得天独厚的优势,它快捷、安全、不受空间约束,受到党和红军领导人的青睐。为了发展无线电事业,红军多措并举,千方百计网罗无线电技术人才,广泛地培... 紧张的战争环境使红军迫切需要一种高效快捷的通讯手段,无线电作为当时的新兴技术,具有得天独厚的优势,它快捷、安全、不受空间约束,受到党和红军领导人的青睐。为了发展无线电事业,红军多措并举,千方百计网罗无线电技术人才,广泛地培养无线电人才,不断壮大无线电技术人才队伍。红军无线电通信事业的发展,为粉碎敌人的"围剿"起到了积极的作用,也为日后革命根据地和新中国无线电教育的发展打下了坚实的基础。 展开更多
关键词 红军 无线电 人才培养 苏区 反“围剿”
Optimization RFID-enabled Retail Store Management with Complex Event Processing
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作者 Shang-Lian Peng Ci-Jian Liu +2 位作者 Jia He Hong-Nian Yu Fan Li 《国际自动化与计算杂志:英文版》 EI CSCD 2019年第1期52-64,共13页
Radio frequency identification(RFID)enabled retail store management needs workflow optimization to facilitate real-time decision making.In this paper,complex event processing(CEP)based RFID-enabled retail store manage... Radio frequency identification(RFID)enabled retail store management needs workflow optimization to facilitate real-time decision making.In this paper,complex event processing(CEP)based RFID-enabled retail store management is studied,particularly focusing on automated shelf replenishment decisions.We define different types of event queries to describe retailer store workflow action over the RFID data streams on multiple tagging levels(e.g.,item level and container level).Non-deterministic finite automata(NFA)based evaluation models are used to detect event patterns.To manage pattern match results in the process of event detection,optimization algorithm is applied in the event model to share event detection results.A simulated RFID-enabled retail store is used to verify the effectiveness of the method,experiment results show that the algorithm is effective and could optimize retail store management workflow. 展开更多
关键词 Complex EVENT processing(CEP) radio frequency identification(RFID) Internet of THINGS data STREAM supply chain RETAIL STORE
A Reliability Aware Protocol for Cooperative Communication in Cognitive Radio Networks
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作者 Munam Ali Shah Si-Jing Zhang Hong-Ji Yang 《国际自动化与计算杂志:英文版》 EI CSCD 2019年第1期84-92,共9页
One of the challenging tasks in cognitive radio(CR)networks is to agree on a common control channel to exchange control information.This paper presents a novel medium access control(MAC)protocol for CR network which e... One of the challenging tasks in cognitive radio(CR)networks is to agree on a common control channel to exchange control information.This paper presents a novel medium access control(MAC)protocol for CR network which efficiently and intelligently establishes a common control channel between CR nodes.The proposed protocol is the first CR MAC protocol which is hybrid in nature and lies between global common control channel(GCCC)and non-GCCC family of MAC protocols.The dynamic nature of the protocol makes the CR nodes converge on a newly found control channel quicker whenever the interference from a licensed user is sensed.The analytical results show that the dynamic,hybrid and adaptive nature of proposed protocol yields higher throughputs when compared with other CR MAC protocols. 展开更多
关键词 COGNITIVE radio COMMON CONTROL CHANNEL co-operative communication MEDIUM access control(MAC)protocols DTMC
The Ways to Improve Your English Listening 预览
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作者 林璇 《疯狂英语:双语世界》 2019年第2期69-73,共5页
Many of the Chinese primary school students often ask such a question,'I can read and usually understand the English I read,but why can’t I follow the English speakers or the recording of English most of the time... Many of the Chinese primary school students often ask such a question,'I can read and usually understand the English I read,but why can’t I follow the English speakers or the recording of English most of the time?'The answer is that you are an English learner,not an English language native speaker.Since you can usually understand the English you read,you are very good at languages. 展开更多
关键词 China The WAYS to IMPROVE YOUR English LISTENING RADIO
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Cooperative Relay Based on Exploiting Hybrid ARQ 预览
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作者 Mingxuan Li Jie Lin +2 位作者 Liang Zhong Mengting Wang Wei Lv 《中国通信:英文版》 SCIE CSCD 2019年第9期187-200,共14页
In order to compensate the primary performance degradation,which is caused by the co-existing secondary communications or the heavy fading of primary link,a cooperative relay scheme is proposed in cognitive radio syst... In order to compensate the primary performance degradation,which is caused by the co-existing secondary communications or the heavy fading of primary link,a cooperative relay scheme is proposed in cognitive radio systems by taking advantage of the opportunities that are arisen by the primary ARQ(Automatic Repeat-reQuest)retransmission.With the help of this scheme,nontrivial relay assistances for the primary retransmission are achieved without initialization phase.The cooperation among secondary users provides additional spatial diversity to facilitate the primary transmission.This can be accomplished with an oblivious primary system and without assuming any non-causal information about the primary data.The scheme are further extended to the scenarios where multiple cognitive pairs exist.Performance analyses of the schemes are devised and the effectiveness is verified via simulations. 展开更多
关键词 cognitive radio cooperative relay ARQ COEXISTENCE outage probability
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带有专家信度的无人机任务分配最小风险问题
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作者 王健 郭建胜 +2 位作者 慕容政 毛声 顾涛勇 《控制与决策》 EI CSCD 北大核心 2019年第9期2036-2040,共5页
战场环境中不确定因素的存在往往导致确定条件下获得的无人机任务分配方案不可行或者非最优,而传统期望值模型通常适应于长期规划,难以考虑不确定变量波动对某次决策的影响.针对目标价值不确定的无人机任务分配问题,首先,基于不确定理... 战场环境中不确定因素的存在往往导致确定条件下获得的无人机任务分配方案不可行或者非最优,而传统期望值模型通常适应于长期规划,难以考虑不确定变量波动对某次决策的影响.针对目标价值不确定的无人机任务分配问题,首先,基于不确定理论建立以信度函数为目标的最小风险模型;然后,通过引入不确定向量的两种假设,将上述模型转化为带有分式目标函数的优化问题;最后,定义以比率为特征的辅助函数,并推导其单调性等性质,提出求解最小风险解的比率一维搜索直接算法.实验结果表明,与期望值模型相比,所提出的最小风险模型及其算法能规避不确定变量标准差较大的侦察目标点,并可通过调整预设收益获得多种不同信度水平的供选择方案. 展开更多
关键词 不确定理论 任务分配 最小风险模型 信度 比率 直接算法
我国铁路专用移动通信技术发展思路探讨 预览
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作者 姜永富 《中国铁路》 2019年第4期73-78,共6页
简要回顾我国铁路无线通信技术发展和主要业务应用,从铁路无线通信业务应用场景、应用业务、频率选择、网络运用、技术体制分析入手,阐述铁路专用移动通信技术发展趋势,以及专用移动通信在智能铁路发挥的关键作用。从技术发展路线、无... 简要回顾我国铁路无线通信技术发展和主要业务应用,从铁路无线通信业务应用场景、应用业务、频率选择、网络运用、技术体制分析入手,阐述铁路专用移动通信技术发展趋势,以及专用移动通信在智能铁路发挥的关键作用。从技术发展路线、无线电频谱规划、标准体系建设、关键技术研发、适应技术发展需要等多角度探讨我国铁路专用移动通信技术发展思路,提出以LTE-R为基础构建铁路综合无线信息接入与应用平台的新观点、新方法。 展开更多
关键词 铁路 移动通信 无线电 5G LTE-R
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A Dynamic Distributed Spectrum Allocation Mechanism Based on Game Model in Fog Radio Access Networks 预览
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作者 Yao Yu Shumei Liu +1 位作者 Zhongshi Tian Siyu Wang 《中国通信:英文版》 SCIE CSCD 2019年第3期12-21,共10页
With the explosive growth of highspeed wireless data demand and the number of mobile devices,fog radio access networks(F-RAN)with multi-layer network structure becomes a hot topic in recent research.Meanwhile,due to t... With the explosive growth of highspeed wireless data demand and the number of mobile devices,fog radio access networks(F-RAN)with multi-layer network structure becomes a hot topic in recent research.Meanwhile,due to the rapid growth of mobile communication traffic,high cost and the scarcity of wireless resources,it is especially important to develop an efficient radio resource management mechanism.In this paper,we focus on the shortcomings of resource waste,and we consider the actual situation of base station dynamic coverage and user requirements.We propose a spectrum pricing and allocation scheme based on Stackelberg game model under F-RAN framework,realizing the allocation of resource on demand.This scheme studies the double game between the users and the operators,as well as between the traditional operators and the virtual operators,maximizing the profits of the operators.At the same time,spectrum reuse technology is adopted to improve the utilization of network resource.By analyzing the simulation results,it is verified that our proposed scheme can not only avoid resource waste,but also effectively improve the operator’s revenue efficiency and overall network resource utilization. 展开更多
关键词 FOG radio access networks(F-RAN) game theory SPECTRUM REUSE technology base station DYNAMIC COVERAGE SPECTRUM PRICING and allocation
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ALMA observations of the circumstellar envelope around EP Aqr
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作者 Pham Thi Tuyet Nhung Do Thi Hoai +6 位作者 Pham Tuan-Anh Thibaut Le Bertre Piene Darriulat Pham Ngoc Diep Nguyen Thi Phuong Nguyen Thi Thao Jan Martin Winters 《天文和天体物理学研究:英文版》 SCIE CAS CSCD 2019年第3期97-110,共14页
Atacama Large Millimetre/sub-millimetre Array(ALMA)observations of CO(1–0)and CO(2–1)emissions from the circumstellar envelope of the asymptotic giant branch(AGB)star EP Aqr have been made with four times better spa... Atacama Large Millimetre/sub-millimetre Array(ALMA)observations of CO(1–0)and CO(2–1)emissions from the circumstellar envelope of the asymptotic giant branch(AGB)star EP Aqr have been made with four times better spatial resolution than previously available.They are analysed with emphasis on the de-projection in space of the effective emissivity and flux of matter using as input a prescribed configuration of the velocity field,assumed to be radial.The data are found to display an intrinsic axisymmetry with respect to an axis making a small angle with respect to the line of sight.A broad range of wind configurations,from prolate(bipolar)to oblate(equatorial)has been studied and found to be accompanied by significant equatorial emission.Qualitatively,the effective emissivity is enhanced near the equator to produce the central narrow component observed in the Doppler velocity spectra and its dependence on star latitude generally follows that of the wind velocity with the exception of an omni-present depression near the poles.In particular,large equatorial expansion velocities produce a flared disc or a ring of effective emissivity and mass loss.The effect on the determination of the orientation of the star axis of radial velocity gradients,and possibly competing rotation and expansion in the equatorial disc,is discussed.In general,the flux of matter is found to reach a broad maximum at distances of the order of 500 AU from the star.Arguments are given that may be used to favour one wind velocity distribution over another.As a result of the improved quality of the data,a deeper understanding of the constraints imposed on morphology and kinematics has been obtained. 展开更多
关键词 stars: AGB and post-AGB (stars:) CIRCUMSTELLAR matter stars: individual: EP Aqr stars:mass-loss radio lines: STARS
Verification of Fengyun-3D MWTS and MWHS Calibration Accuracy Using GPS Radio Occultation Data
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作者 Xueyan HOU Yang HAN +1 位作者 Xiuqing HU Fuzhong WENG 《气象学报:英文版》 SCIE CSCD 2019年第4期695-704,共10页
The newly launched Fengyun-3D(FY-3D)satellite carries microwave temperature sounder(MWTS)and microwave humidity sounder(MWHS),providing the global atmospheric temperature and humidity measurements.It is important to a... The newly launched Fengyun-3D(FY-3D)satellite carries microwave temperature sounder(MWTS)and microwave humidity sounder(MWHS),providing the global atmospheric temperature and humidity measurements.It is important to assess the in orbit performance of MWTS and MWHS and understand their calibration accuracy before using them in numerical weather prediction and many other applications such as hurricane monitoring.This study aims at quantifying the biases of MWTS and MWHS observations relative to the simulations from the collocated Global Positioning System(GPS)radio occultation(RO)data.Using the collocated FY-3C Global Navigation Satellite System Occultation Sounder(GNOS)RO data under clear-sky conditions as inputs to Community Radiative Transfer Model(CRTM),brightness temperatures and viewing angles are simulated for the upper level sounding channels of MWTS and MWHS.In order to obtain O–B statistics under clear sky conditions,a cloud detection algorithm is developed by using the two MWTS channels with frequencies at 50.3 and 51.76 GHz and the two MWHS channels with frequencies centered at 89 and 150 GHz.The analysis shows that for the upper air sounding channels,the mean biases of the MWTS observations relative to the GPS RO simulations are negative for channels 5–9,with absolute values<1 K,and positive for channels 4 and 10,with values<0.5 K.For the MWHS observations,the mean biases in brightness temperature are negative for channels 2–6,with absolute values<2.6 K and relatively small standard deviations.The mean biases are also negative for channels 11–13,with absolute values<1.3 K,but with relatively large standard deviations.The biases of both MWTS and MWHS show scan-angle dependence and are asymmetrical across the scan line.The biases for the upper air MWTS and MWHS sounding channels are larger than those previously derived for the Advanced Technology Microwave Sounder. 展开更多
关键词 SATELLITES Fengyun satellites microwave sounding CROSS-CALIBRATION radio occultation
A Hybrid Offline-Online Approach to Adaptive Downlink Resource Allocation Over LTE 预览
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作者 Satish Kumar Rajesh Devaraj Arnab Sarkar 《自动化学报:英文版》 CSCD 2019年第3期766-777,共12页
Radio resource management mechanisms in current and future wireless networks is expected to face an enormous challenge due to the ever increasing demand for bandwidth and latency sensitive applications on mobile devic... Radio resource management mechanisms in current and future wireless networks is expected to face an enormous challenge due to the ever increasing demand for bandwidth and latency sensitive applications on mobile devices. This is because an optimal resource allocation scheme which attempts to multiplex the available bandwidth in order to maximize Quality of service (QoS), will pose an exponential computational burden at eNodeB. In order to minimize such computational overhead, this work proposes a hybrid offline-online resource allocation strategy which effectively allocates all the available resources among flows such that their QoS requirements are satisfied. The flows are firstly classified into priority buckets based on real-time criticality factors. During the offline phase, the scheduler attempts to maintain the system load within a pre-specified safe threshold value by selecting an appropriate number of buckets. This offline selection procedure makes use of supervisory control theory of discrete event systems to synthesize an offline scheduler. Next, we have devised an online resource allocation strategy which runs on top of the offline policy and attempts to minimize the impact of the inherent variability in wireless networks. Simulation results show that the proposed scheduling framework is able to provide satisfactory QoS to all end users in most practical scenarios. 展开更多
关键词 Discrete event systems (DES) HYBRID scheduling long TERM evolution (LTE) quality of service (QoS) radio resource management supervisory control
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Preface:Planning the scientific applications of the Five-hundred-meter Aperture Spherical radio Telescope
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作者 Di Li John M.Dickey Shu Liu 《天文和天体物理学研究:英文版》 SCIE CAS CSCD 2019年第2期3-4,共2页
The Five-hundred-meter Aperture Spherical radio Telescope(FAST) is by far the largest telescope of any kind ever built. FAST produced its first light in September 2016 and it is now under commissioning, with normal op... The Five-hundred-meter Aperture Spherical radio Telescope(FAST) is by far the largest telescope of any kind ever built. FAST produced its first light in September 2016 and it is now under commissioning, with normal operation to commence in late 2019. During testing and early science operation, FAST has started making astronomical discoveries, particularly pulsars of various kinds, including millisecond pulsars, binaries, gamma-ray pulsars, etc. The papers in this mini-volume propose ambitious observational projects to advance our knowledge of astronomy, astrophysics and fundamental physics in many ways.Although it may take FAST many years to achieve all the goals explained in these papers, taken together they define a powerful strategic vision for the next decade. 展开更多
关键词 radio telescopes:FAST
地震射电现象与气象 地震预测 预览
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作者 粟淘 粟鹏元 《办公自动化》 2019年第8期15-19,共5页
发现空间监测到的磁暴为地震震源射电所致,无形震源射电通过大气时使大气中水分发生极化聚合形成雨、冰雹、雪、云、霾或沙尘暴等气象现象,从而将不可见的地震电磁场轨迹通过气象显示出,通过天气观测和监测空间指数变化量而实现地震预测。
关键词 空间天气 地磁暴 射电现象 地震云 空气相对湿度 强极性 积分
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Dynamic Matching-Based Spectrum Detection in Cognitive Radio Networks 预览
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作者 Yu Gu Qingqi Pei Hongning Li 《中国通信:英文版》 SCIE CSCD 2019年第4期47-58,共12页
Cognitive Radio Network provides an opportunity to reduce the spectrum resource crisis by allowing secondary users to access the idle spectrum allocated to primary users.The precondition of spectrum sharing is to obta... Cognitive Radio Network provides an opportunity to reduce the spectrum resource crisis by allowing secondary users to access the idle spectrum allocated to primary users.The precondition of spectrum sharing is to obtain the Spectrum Availability Information(SAI).Energy detection is a typical technology to get SAI.With the mobility of primary users,the energy received by secondary users varies greatly with the distance from the target primary users.Most of the existing energy detection algorithms that use fixed thresholds are not suitable.We propose a Dynamic Matching-Based Spectrum Detection(DMBSD)scheme which can detect sensing data,reduce the impact of malicious data and make final sensing results more accurate with dynamic threshold setting and data matching.Simulation results show that the proposed scheme can detect tempered data,and increase detection probability by decreasing false alarm probability and missed detection probability. 展开更多
关键词 COGNITIVE radio SPECTRUM SENSING degradation DOMAIN dynamic MATCHING
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Astrophysical constraints on the proton-to-electron mass ratio with FAST
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作者 Xi Chen Simon P.Ellingsen Ying Mei 《天文和天体物理学研究:英文版》 SCIE CAS CSCD 2019年第2期15-24,共10页
That the laws of physics are the same at all times and places throughout the Universe is one of the basic assumptions of physics. Astronomical observations provide the only means to test this basic assumption on cosmo... That the laws of physics are the same at all times and places throughout the Universe is one of the basic assumptions of physics. Astronomical observations provide the only means to test this basic assumption on cosmological time and distance scales. The possibility of variations in the dimensionless physical constant μ-the proton-to-electron mass ratio, can be tested by comparing astronomical measurements of the rest frequency of certain spectral lines at radio wavelengths with laboratory determinations. Different types of molecular transitions have different dependencies on μ and so observations of two or more spectral lines towards the same astronomical source can be used to test whether there is any evidence for either temporal or spatial changes in the physical fundamental constants. μ will change if the relative strength of the strong nuclear force compared to the electromagnetic force varies. Theoretical studies have shown that the rotational transitions of some molecules which have transitions in the frequency range that will be covered by FAST(e.g., CH3 OH, OH and CH) are sensitive to changes in μ. A number of studies looking for possible variations in μ have been undertaken with existing telescopes, however, the greater sensitivity of FAST means it will open new opportunities to significantly improve upon measurements made to date.In this paper, we discuss which molecular transitions and sources(both in the Galaxy and external galaxies)are likely targets for providing improved constraints on μ with FAST. 展开更多
关键词 ISM:molecules radio lines:ISM techniques:radial VELOCITIES ELEMENTARY particles
How can FAST improve study of the pulsar emission mechanism and magnetospheric dynamics?
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作者 Hong-Guang Wang Guo-Jun Qiao +4 位作者 Yuan-Jie Du Ji-Guang Lu Ren-Xin Xu Ke-Jia Lee Xiong-Wei Liu 《天文和天体物理学研究:英文版》 SCIE CAS CSCD 2019年第2期55-64,共10页
The Five-hundred-meter Aperture Spherical radio Telescope(FAST) has the potential to discover many new pulsars and new phenomena. In this paper we mainly concentrate on how FAST can impact study of the pulsar emission... The Five-hundred-meter Aperture Spherical radio Telescope(FAST) has the potential to discover many new pulsars and new phenomena. In this paper we mainly concentrate on how FAST can impact study of the pulsar emission mechanism and magnetospheric dynamics. Several observational programs heading to this direction are reviewed. To make full use of the superior performance of FAST and maximize the scientific outcome, these programs can be arranged in different phases of FAST according to their demands for observational conditions. We suggest that programs can be performed following the test phase, which are observations of multifrequency mean pulse profiles, anomalous X-ray pulsars(AXPs)/soft gamma-ray repeaters(SGRs), mode changing, drifting subpulse and nulling. The long-term monitoring can be carried out for mode changing, AXPs/SGRs and precessional pulsars. Others programs, including polarization observations of radio and γ-ray pulsars, searching for weak pulse components, and multifrequency observations of subpulse drifting, microstructure and giant pulses, can be conducted in all the normal operating phases(the first and second phases). These programs will push forward the frontier in this field in different respects. The search for sub-millisecond pulsars and follow-up observations of their emission properties are very important projects for FAST, but they may be covered by other papers in this mini-volume;therefore,they are not discussed here. 展开更多
关键词 pulsars:general pulsars: radio EMISSION RADIATION mechanisms:non-thermal
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