[Background]Traveling-wave tubes(TWTs)are widely applied in radar,imaging,and military systems owing to their excellent amplification characteristics.Miniaturization and integration are critical to the future of TWTs,...[Background]Traveling-wave tubes(TWTs)are widely applied in radar,imaging,and military systems owing to their excellent amplification characteristics.Miniaturization and integration are critical to the future of TWTs,with multi-channel slow-wave structures(SWSs)forming the foundation for their realization in high-power vacuum electronic devices.[Purpose]To provide design insights for multi-channel TWTs and simultaneously enhance their output power,a W-band folded-waveguide TWT with dual electron beams and H-plane power combining was proposed.[Methods]Three-dimensional electromagnetic simulations in CST were conducted to verify the highfrequency characteristics,electric field distribution,and amplification performance of the proposed SWS,thereby confirming the validity of the design.[Results]Results indicate that the designed TWT achieves a transmission bandwidth of 10 GHz.With an electron beam voltage of 17.9 kV and a current of 0.35 A,the output power reaches 450 W at 94 GHz,corresponding to an efficiency of 7.18%and a gain of 23.5 dB.Moreover,under fixed beam voltage and current,the TWT delivers over 200 W output power across 91–99 GHz,with a 3 dB bandwidth of 91–98.5 GHz.The particle voltage distribution after modulation further validates the mode analysis.[Conclusions]These results demonstrate the feasibility of compact dual-beam power-combining structures and provide useful guidance for the design of future multi-channel TWTs.展开更多
Wideband spectrum sensing with a high-speed analog-digital converter(ADC) presents a challenge for practical systems.The Nyquist folding receiver(NYFR) is a promising scheme for achieving cost-effective real-time spec...Wideband spectrum sensing with a high-speed analog-digital converter(ADC) presents a challenge for practical systems.The Nyquist folding receiver(NYFR) is a promising scheme for achieving cost-effective real-time spectrum sensing,which is subject to the complexity of processing the modulated outputs.In this case,a multipath NYFR architecture with a step-sampling rate for the different paths is proposed.The different numbers of digital channels for each path are designed based on the Chinese remainder theorem(CRT).Then,the detectable frequency range is divided into multiple frequency grids,and the Nyquist zone(NZ) of the input can be obtained by sensing these grids.Thus,high-precision parameter estimation is performed by utilizing the NYFR characteristics.Compared with the existing methods,the scheme proposed in this paper overcomes the challenge of NZ estimation,information damage,many computations,low accuracy,and high false alarm probability.Comparative simulation experiments verify the effectiveness of the proposed architecture in this paper.展开更多
Nyquist Folding Receiver(NYFR)is a perceptron structure that realizes a low probability of intercept(LPI)signal analog to information.Aiming at the problem of LPI radar signal receiving,the time domain,frequency domai...Nyquist Folding Receiver(NYFR)is a perceptron structure that realizes a low probability of intercept(LPI)signal analog to information.Aiming at the problem of LPI radar signal receiving,the time domain,frequency domain,and time-frequency domain problems of signals intercepted by NYFR structure are studied.Combined with the time-frequency analysis(TFA)method,a radar recognition scheme based on deep learning(DL)is introduced,which can reliably classify common LPI radar signals.First,the structure of NYFR and its characteristics in the time domain,frequency domain,and time and frequency domain are analyzed.Then,the received signal is then converted into a time-frequency image(TFI).Finally,four kinds of DL algorithms are used to classify LPI radar signals.Simulation results demonstrate the correctness of the NYFR structure,and the effectiveness of the proposed recognition method is verified by comparison experiments.展开更多
The paper discussed the limitation of ’Dominant wavelengt h theory’. The theoretical model and nonhomogeneous differential equation of fold and deformation of a monolayer sandwiched-in limited and different thickn e...The paper discussed the limitation of ’Dominant wavelengt h theory’. The theoretical model and nonhomogeneous differential equation of fold and deformation of a monolayer sandwiched-in limited and different thickn ess terranes are proposed by using mechanics of elasticity. In addition, the ′D ominant wavelength theory’ is proved by the experimental folding in elastic ma terials. The folds of a monolayer sandwiched-in limited and different thickness terranes are studied inside and are explored in the field.展开更多
With the realization that rocks with a schistosity parallel to bedding(S0 parallel S1)have undergone lengthy histories of deformation that predate the obvious first deformation(e.g.Bell et al.,2003; Sayab,2006;Yeh,200...With the realization that rocks with a schistosity parallel to bedding(S0 parallel S1)have undergone lengthy histories of deformation that predate the obvious first deformation(e.g.Bell et al.,2003; Sayab,2006;Yeh,2007)came recognition that large scale regional folds can form early during this process and be preserved throughout orogenesis(e.g.,Ham & Bell,2004;Bell & Newman,2006).This history is lost within the matrix because of reactivational shear展开更多
As a consequence of the collision of India with Asia, the Qilian Shan, rising 4000～5000m above the Gobi, marks the northeastern boundary of the Tibet—Qinghai Plateau. The Qilian Shan developed as a WNW—ESE fold\|an...As a consequence of the collision of India with Asia, the Qilian Shan, rising 4000～5000m above the Gobi, marks the northeastern boundary of the Tibet—Qinghai Plateau. The Qilian Shan developed as a WNW—ESE fold\|and\|thrust belt with most of the movement directed towards the NEN—NE. Its foreland margin, the Jiuxi Basin, accommodates thick sequences of Late Cenozoic alluvial sediments derived from the Qilian Shan. Thin\|skinned fold\|and\|thrust deformation in the Jiuxi basin flanking the Qilian Shan, feature Mesozoic and Cenozoic sedimentary rocks that have been detached from the underlying basal decollement and folded into a series of NW—WNW trending anticlines and synclines. Towards the south deformation in the Jiuxi basin is accommodated by a west\|north\|west fold train (Qingcaowan, Laojunmiao, and Shiyougou folds) developed during the Quaternary. These form a distinct topographic feature separating the Qilian Shan from the central Jiuxi Basin. The doubly plunging Laojunmiao anticline is 10km long and 5km wide. It is asymmetric in shape, having a steep to overturned northern limb, and a backlimb dips to the south at 20～30°. The Laojunmiao anticline is composed of two distinct stratigraphic sequences which are defined by a syntectonic unconformity.展开更多
The evolution of the Tarim southwest depression lying at the piedmont of the West Kunlun orogen differs completely from the evolution of the main part of Tarim basin after Later Palaeozoic because the former strongly ...The evolution of the Tarim southwest depression lying at the piedmont of the West Kunlun orogen differs completely from the evolution of the main part of Tarim basin after Later Palaeozoic because the former strongly subsides many times.. Subsidence is related closely to the West Kunlun fold thrust\|belt, thus the evolution of the Depression and the fold\|thrust\|belt reflects clearly the formation and evolution of the West Kunlun and even the Tibet.1 Evolution of the West Kunlun fold\|thrust\|belt\;Thrusting of the fold\|thrust\|belt can be classified into three stages:(1) Devonian thrusting:This is the oldest thrusting distinguished in the northern margin of the West Kunlun while the Silurian—Devonian thrusting was discriminated a few years ago by seismic data in the northern part of the East Kunlun. The Devonian thrusting is proved by the Upper Devonian dynamometamorphic rocks outcropping at the core of the anticline in the Sangzhu lying at the fold\|thrust\|belt. The rocks consist of slightly metamorphic clastic rock and have always been regarded as the Mid\|Proterozoic strata. But they are actually Upper Devonian strata according to the amount of perfect plant fossils that we found recently in the metamorphic rock, and they are overburdened `with an angular unconformity by another reliable Upper\|Devonian conglomerate in the core of the Aqike anticline. A possible explanation for this and its limited lined distribution parallel to the West Kunlun orogen is that they are subjected to metamorphism during the Later Devonian thrusting.展开更多
The Songpan Garzê Fold Belt records Triassic shortening of a relict Palaeo\|Tethyan basin during assembly and accretion of the Cimmerian continental chain to Laurasia’s southern margin. Enclosed by palaeo\|Laura...The Songpan Garzê Fold Belt records Triassic shortening of a relict Palaeo\|Tethyan basin during assembly and accretion of the Cimmerian continental chain to Laurasia’s southern margin. Enclosed by palaeo\|Laurasia and the Cimmerian fragments of Qiangtang (North Tibet) and Yangtze (South China), the Songpan Garzê Fold Belt was shortened by more than 50% during the Indosinian Orogeny c.200Ma. [BW(D(S,,)G2*7][BHDWG2*7,WK*2,WK5,WK15*2,WK17*2,WK*2W] 2000,7(增刊) 地 学 前 缘 [FK(K+6mm。17*2] 4\ Major Topic:Geology of the Inner Tibetan Plateau [BW(S(S,,)G2*7][BHDWG2*7,WK*2,WK17*2,WK15*2,WK5,WK*2W] [FK(K+6mm。17*2] 4\ Major Topic:Geology of the Inner Tibetan Plateau 地 学 前 缘 2000,7(增刊)South\|directed Indosinian compression decolléd onlapping basin sediments from the Yangtze Block’s passive margin—reactivating the margin’s tiered geometry and partitioning strain into margin\|normal and margin\|parallel structures on a large scale. Margin\|normal transport of the allochthonous sedimentary pile was accommodated by southeast\|directed nappe propagation in the Longmen Mountains Thrust—Nappe Belt, whilst conjugate, margin\|parallel (southwest\|directed) transport was accommodated by a flat\|lying detachment at the base of the sedimentary pile.The later is characteristic of deformation of the greater Songpan Garzê Fold Belt.展开更多
The study claims that Folding Beijing can not only be read as science fiction but also as Gothic hterature,in which perspective,Gothic Elements such as Gothic Setting,Gothic Wanderer and Transgressions,and Gothic Terr...The study claims that Folding Beijing can not only be read as science fiction but also as Gothic hterature,in which perspective,Gothic Elements such as Gothic Setting,Gothic Wanderer and Transgressions,and Gothic Terror are discussed respectively.展开更多
基金National Key Research and Development Program of China(2022YFF0707602)National Natural Science Foundation of China(62471097,62471115,62471101)National Natural Science Foundation of Sichuan(2025ZNSFSC0537)。
文摘[Background]Traveling-wave tubes(TWTs)are widely applied in radar,imaging,and military systems owing to their excellent amplification characteristics.Miniaturization and integration are critical to the future of TWTs,with multi-channel slow-wave structures(SWSs)forming the foundation for their realization in high-power vacuum electronic devices.[Purpose]To provide design insights for multi-channel TWTs and simultaneously enhance their output power,a W-band folded-waveguide TWT with dual electron beams and H-plane power combining was proposed.[Methods]Three-dimensional electromagnetic simulations in CST were conducted to verify the highfrequency characteristics,electric field distribution,and amplification performance of the proposed SWS,thereby confirming the validity of the design.[Results]Results indicate that the designed TWT achieves a transmission bandwidth of 10 GHz.With an electron beam voltage of 17.9 kV and a current of 0.35 A,the output power reaches 450 W at 94 GHz,corresponding to an efficiency of 7.18%and a gain of 23.5 dB.Moreover,under fixed beam voltage and current,the TWT delivers over 200 W output power across 91–99 GHz,with a 3 dB bandwidth of 91–98.5 GHz.The particle voltage distribution after modulation further validates the mode analysis.[Conclusions]These results demonstrate the feasibility of compact dual-beam power-combining structures and provide useful guidance for the design of future multi-channel TWTs.
基金supported by the Key Projects of the 2022 National Defense Science and Technology Foundation Strengthening Plan 173 (Grant No.2022-173ZD-010)the Equipment PreResearch Foundation of The State Key Laboratory (Grant No.6142101200204)。
文摘Wideband spectrum sensing with a high-speed analog-digital converter(ADC) presents a challenge for practical systems.The Nyquist folding receiver(NYFR) is a promising scheme for achieving cost-effective real-time spectrum sensing,which is subject to the complexity of processing the modulated outputs.In this case,a multipath NYFR architecture with a step-sampling rate for the different paths is proposed.The different numbers of digital channels for each path are designed based on the Chinese remainder theorem(CRT).Then,the detectable frequency range is divided into multiple frequency grids,and the Nyquist zone(NZ) of the input can be obtained by sensing these grids.Thus,high-precision parameter estimation is performed by utilizing the NYFR characteristics.Compared with the existing methods,the scheme proposed in this paper overcomes the challenge of NZ estimation,information damage,many computations,low accuracy,and high false alarm probability.Comparative simulation experiments verify the effectiveness of the proposed architecture in this paper.
基金supported by the National Defence Pre-research Foundation of China。
文摘Nyquist Folding Receiver(NYFR)is a perceptron structure that realizes a low probability of intercept(LPI)signal analog to information.Aiming at the problem of LPI radar signal receiving,the time domain,frequency domain,and time-frequency domain problems of signals intercepted by NYFR structure are studied.Combined with the time-frequency analysis(TFA)method,a radar recognition scheme based on deep learning(DL)is introduced,which can reliably classify common LPI radar signals.First,the structure of NYFR and its characteristics in the time domain,frequency domain,and time and frequency domain are analyzed.Then,the received signal is then converted into a time-frequency image(TFI).Finally,four kinds of DL algorithms are used to classify LPI radar signals.Simulation results demonstrate the correctness of the NYFR structure,and the effectiveness of the proposed recognition method is verified by comparison experiments.
文摘The paper discussed the limitation of ’Dominant wavelengt h theory’. The theoretical model and nonhomogeneous differential equation of fold and deformation of a monolayer sandwiched-in limited and different thickn ess terranes are proposed by using mechanics of elasticity. In addition, the ′D ominant wavelength theory’ is proved by the experimental folding in elastic ma terials. The folds of a monolayer sandwiched-in limited and different thickness terranes are studied inside and are explored in the field.
文摘With the realization that rocks with a schistosity parallel to bedding(S0 parallel S1)have undergone lengthy histories of deformation that predate the obvious first deformation(e.g.Bell et al.,2003; Sayab,2006;Yeh,2007)came recognition that large scale regional folds can form early during this process and be preserved throughout orogenesis(e.g.,Ham & Bell,2004;Bell & Newman,2006).This history is lost within the matrix because of reactivational shear
文摘As a consequence of the collision of India with Asia, the Qilian Shan, rising 4000～5000m above the Gobi, marks the northeastern boundary of the Tibet—Qinghai Plateau. The Qilian Shan developed as a WNW—ESE fold\|and\|thrust belt with most of the movement directed towards the NEN—NE. Its foreland margin, the Jiuxi Basin, accommodates thick sequences of Late Cenozoic alluvial sediments derived from the Qilian Shan. Thin\|skinned fold\|and\|thrust deformation in the Jiuxi basin flanking the Qilian Shan, feature Mesozoic and Cenozoic sedimentary rocks that have been detached from the underlying basal decollement and folded into a series of NW—WNW trending anticlines and synclines. Towards the south deformation in the Jiuxi basin is accommodated by a west\|north\|west fold train (Qingcaowan, Laojunmiao, and Shiyougou folds) developed during the Quaternary. These form a distinct topographic feature separating the Qilian Shan from the central Jiuxi Basin. The doubly plunging Laojunmiao anticline is 10km long and 5km wide. It is asymmetric in shape, having a steep to overturned northern limb, and a backlimb dips to the south at 20～30°. The Laojunmiao anticline is composed of two distinct stratigraphic sequences which are defined by a syntectonic unconformity.
文摘The evolution of the Tarim southwest depression lying at the piedmont of the West Kunlun orogen differs completely from the evolution of the main part of Tarim basin after Later Palaeozoic because the former strongly subsides many times.. Subsidence is related closely to the West Kunlun fold thrust\|belt, thus the evolution of the Depression and the fold\|thrust\|belt reflects clearly the formation and evolution of the West Kunlun and even the Tibet.1 Evolution of the West Kunlun fold\|thrust\|belt\;Thrusting of the fold\|thrust\|belt can be classified into three stages:(1) Devonian thrusting:This is the oldest thrusting distinguished in the northern margin of the West Kunlun while the Silurian—Devonian thrusting was discriminated a few years ago by seismic data in the northern part of the East Kunlun. The Devonian thrusting is proved by the Upper Devonian dynamometamorphic rocks outcropping at the core of the anticline in the Sangzhu lying at the fold\|thrust\|belt. The rocks consist of slightly metamorphic clastic rock and have always been regarded as the Mid\|Proterozoic strata. But they are actually Upper Devonian strata according to the amount of perfect plant fossils that we found recently in the metamorphic rock, and they are overburdened `with an angular unconformity by another reliable Upper\|Devonian conglomerate in the core of the Aqike anticline. A possible explanation for this and its limited lined distribution parallel to the West Kunlun orogen is that they are subjected to metamorphism during the Later Devonian thrusting.
文摘The Songpan Garzê Fold Belt records Triassic shortening of a relict Palaeo\|Tethyan basin during assembly and accretion of the Cimmerian continental chain to Laurasia’s southern margin. Enclosed by palaeo\|Laurasia and the Cimmerian fragments of Qiangtang (North Tibet) and Yangtze (South China), the Songpan Garzê Fold Belt was shortened by more than 50% during the Indosinian Orogeny c.200Ma. [BW(D(S,,)G2*7][BHDWG2*7,WK*2,WK5,WK15*2,WK17*2,WK*2W] 2000,7(增刊) 地 学 前 缘 [FK(K+6mm。17*2] 4\ Major Topic:Geology of the Inner Tibetan Plateau [BW(S(S,,)G2*7][BHDWG2*7,WK*2,WK17*2,WK15*2,WK5,WK*2W] [FK(K+6mm。17*2] 4\ Major Topic:Geology of the Inner Tibetan Plateau 地 学 前 缘 2000,7(增刊)South\|directed Indosinian compression decolléd onlapping basin sediments from the Yangtze Block’s passive margin—reactivating the margin’s tiered geometry and partitioning strain into margin\|normal and margin\|parallel structures on a large scale. Margin\|normal transport of the allochthonous sedimentary pile was accommodated by southeast\|directed nappe propagation in the Longmen Mountains Thrust—Nappe Belt, whilst conjugate, margin\|parallel (southwest\|directed) transport was accommodated by a flat\|lying detachment at the base of the sedimentary pile.The later is characteristic of deformation of the greater Songpan Garzê Fold Belt.
文摘The study claims that Folding Beijing can not only be read as science fiction but also as Gothic hterature,in which perspective,Gothic Elements such as Gothic Setting,Gothic Wanderer and Transgressions,and Gothic Terror are discussed respectively.
