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相速跳变优化Ka波段梯形线行波管效率研究
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作者 刘红伟 王战亮 +4 位作者 宫玉彬 魏彦玉 段兆云 巩华荣 冯进军 《微波学报》 CSCD 北大核心 2017年第S1期179-182,共4页
相速跳变技术是通过改变慢波结构的尺寸,从而改变慢波结构中微波信号的相速度,使其与互作用过后的电子注速度实现再同步,重新激励起有效的注-波互作用,实现输出功率的进一步提高。本文利用CST计算了不同周期长度的慢波结构的色散特性和... 相速跳变技术是通过改变慢波结构的尺寸,从而改变慢波结构中微波信号的相速度,使其与互作用过后的电子注速度实现再同步,重新激励起有效的注-波互作用,实现输出功率的进一步提高。本文利用CST计算了不同周期长度的慢波结构的色散特性和耦合阻抗特性,在此基础上利用粒子模拟(PIC)技术计算了注-波互作用。为进一步提高行波管的电子效率,将相速跳变技术运用到Ka波段带状注三槽梯形线慢波结构行波管中。结果证实:对于周期均匀的慢波结构构成的第一种行波管,在33GHz频点处最大输出功率为10.15kW,电子效率为10.36%;而对于由1段周期跳变的慢波结构构成的第二种行波管,在33GHz频率处输出功率为12.09kW,电子效率为12.34%;两者相比,电子效率提高了1.98%。 展开更多
关键词 Ka段带状注行 相速跳变技术 槽梯形线结构 粒子模拟 电子效率
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矩形管下气相螺旋爆轰的结构及传播方式
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作者 贾旭飞 张道平 +1 位作者 董刚 归明月 《爆炸与冲击》 EI CAS CSCD 北大核心 2024年第5期1-14,共14页
为探索极限条件下矩形管道截面长宽比对于螺旋爆轰传播的影响,采用基于五阶WENO有限差分格式和两步总包反应模型的Euler方程,对三维气相螺旋爆轰波在矩形截面管道中的结构及其传播方式进行了数值研究。通过模拟不同管道截面尺寸下爆轰... 为探索极限条件下矩形管道截面长宽比对于螺旋爆轰传播的影响,采用基于五阶WENO有限差分格式和两步总包反应模型的Euler方程,对三维气相螺旋爆轰波在矩形截面管道中的结构及其传播方式进行了数值研究。通过模拟不同管道截面尺寸下爆轰波的三波线运动轨迹、流场分布及高压印记结构,揭示了截面几何尺寸对气相临界爆轰波稳定传播的影响规律。结果表明:螺旋爆轰能在一定范围的小管道截面尺寸内通过横、竖两条三波线及其相互作用形成的斜三波线的运动来维持传播;随着管道截面尺寸长宽比的增加,螺旋爆轰在壁面上形成的高压印记逐渐由倾斜的条带结构变成局部点状分布结构,波阵面上的斜三波线的轨迹也由方管中沿着单一方向的圆周运动逐渐发展为具有转向机制的复杂运动轨迹;当长宽比进一步增加时,三维螺旋爆轰存在向二维结构的单头爆轰结构退化的趋势。 展开更多
关键词 螺旋爆轰 矩形管道 三波线 两步总包反应
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A minimum traveltime ray tracing global algorithm on a triangular net for propagating plane waves 被引量:1
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作者 于师建 刘润泽 程久龙 《Applied Geophysics》 SCIE CSCD 2010年第4期348-356,400,共10页
To address the problem of subdividing inflexible rectangular grid models and their poor definition of velocity interfaces,we propose a complex structure triangular net for a minimum traveltime ray tracing global algor... To address the problem of subdividing inflexible rectangular grid models and their poor definition of velocity interfaces,we propose a complex structure triangular net for a minimum traveltime ray tracing global algorithm.Our procedure is:(1) Subdivide a triangle grid based on the Delaunay triangular subdivision criterion and the relationships of the points,lines,and the surfaces in the subdividing area.(2) Define the topology relationships and related concepts of triangular unit ray tracing.(3) The source point and wave arrival points at any time compose the propagating plane wave and the minimum traveltime and secondary source positions are calculated during the plane wave propagation.We adopt the hyperbolic approximation global algorithm for secondary source retrieving.(4) By minimum traveltime ray tracing,collect the path from receiver to source points with the neighborhood point's traveltime and the direction of the secondary source.Numerical simulation examples are given to test the algorithm.The results show that the triangular net ray tracing method demonstrates model subdivision flexibility,precise velocity discontinuity interfaces,and accurate computations. 展开更多
关键词 triangular net ray tracing plane wave propagation secondary source
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Research on 3D marine electromagnetic interferometry with synthetic sources for suppressing the airwave interference 被引量:1
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作者 张建国 武欣 +2 位作者 齐有政 黄玲 方广有 《Applied Geophysics》 SCIE CSCD 2013年第4期373-383,510,共12页
In order to suppress the airwave noise in marine controlled-source electromagnetic (CSEM) data, we propose a 3D deconvolution (3DD) interferometry method with a synthetic aperture source and obtain the relative an... In order to suppress the airwave noise in marine controlled-source electromagnetic (CSEM) data, we propose a 3D deconvolution (3DD) interferometry method with a synthetic aperture source and obtain the relative anomaly coefficient (RAC) of the EM field reflection responses to show the degree for suppressing the airwave. We analyze the potential of the proposed method for suppressing the airwave, and compare the proposed method with traditional methods in their effectiveness. A method to select synthetic source length is derived and the effect of the water depth on RAC is examined via numerical simulations. The results suggest that 3DD interferometry method with a synthetic source can effectively suppress the airwave and enhance the potential of marine CSEM to hydrocarbon exploration. 展开更多
关键词 marine CSEM reflection response airwave synthetic aperture method 3D deconvolution interferometry up- and down-going field decomposition
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Nonlinear Optical Properties of Al-Doped nc-Si-SiO_2 Composite Films
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作者 郭亨群 杨琳琳 王启明 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2007年第5期640-644,共5页
The nonlinear optical properties of Al-doped nc-Si-SiO2 composite films have been investigated using the time-resolved four-wave mixing technique with a femtosecond laser. The off-resonant third-order nonlinear suscep... The nonlinear optical properties of Al-doped nc-Si-SiO2 composite films have been investigated using the time-resolved four-wave mixing technique with a femtosecond laser. The off-resonant third-order nonlinear susceptibility is observed to be 1.0 × 10-10 esu at 800nm. The relaxation time of the optical nonlinearity in the films is as short as 60fs. The optical nonlinearity is enhanced due to the quantum confinement of electrons in Si nanocrystals embedded in the SiO2 films. The enhanced optical nonlinearity does not originate from Al dopant because there are no Al clusters in the films. 展开更多
关键词 Si nanocrystals composite films third-order nonlinearity time-resolved four-wave mixing
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Big Third-order Nonlinear Optical Properties of Two Poly[(3-alkylthiophene-2, 5-diyl)-(benzylidenequinomethane-2, 5-diyl)] Derivatives
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作者 GAOChao WUHong-cai +3 位作者 YIWen-hui LIBao-ming SUNJian-ping MENGLing-jie 《Semiconductor Photonics and Technology》 CAS 2005年第2期99-102,共4页
Two novel poly[(3-alkylthiophene-2,5-diyl)-(benzylidenequinomethane-2,5-diyl)s] derivatives, poly[ (3-butylthiophene-2,5-diyl)-( p-N,N-dimethylamino) benzylidenequinomethane-2,5-diyl) ] ( PBTDMABQ) and poly [( 3-octyl... Two novel poly[(3-alkylthiophene-2,5-diyl)-(benzylidenequinomethane-2,5-diyl)s] derivatives, poly[ (3-butylthiophene-2,5-diyl)-( p-N,N-dimethylamino) benzylidenequinomethane-2,5-diyl) ] ( PBTDMABQ) and poly [( 3-octylthiophene2,5-diyl) -(p-N, N-dimethylamino ) benzylidenequinomethane-2, 5-diyl)] (POTDMABQ), were synthesized.The band gaps of the two polymers are calculated as 1. 75 eV for PBTDMABQ and 1. 69 eV for POTDMABQ,respectively. The homogenous films of the two polymers were prepared and their third-ordernonlinear optical properties were studied by the backward degenerate four-wave mixing at 532 nm. Byusing the relative measurement technique, the third-order nonlinear optical susceptibilities ofPBTDMABQ and POTDMABQ are calculated as 5. 62 X 10^(-9) and 1. 22 X 10^(-8) ESU, respectively. It isfound that substituted alky groups have strong effects on the band gap and nonlinear opticalproperties of the two polymers. The relatively big third-order nonlinear optical susceptibilitiesand small band gap of POTDMABQ resulted mainly from the longer alkyl with strong electron-donatingability can enhance the delocation degree of conjugated π electronics. 展开更多
关键词 poly [( 3-alkylthiophene)-( benzylidenequinomethane)] derivatives degeneratefour-wave mixing third-order nonlinear susceptibility band gap
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A three-dimensional matching localization algorithm based on helix triangular pyramid array
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作者 ZHAO Jiu-bin LIU Yuan-xue +1 位作者 LIU Chang-jia LING Yue 《Journal of Central South University》 SCIE EI CAS CSCD 2021年第3期816-833,共18页
On the eve of the occurrence of geological hazards,part of the rock and soil body begins to burst,rub,and fracture,generating infrasound signals propagating outward.3D advanced positioning of the landslide has remaine... On the eve of the occurrence of geological hazards,part of the rock and soil body begins to burst,rub,and fracture,generating infrasound signals propagating outward.3D advanced positioning of the landslide has remained unsolved,which is important for disaster prevention.Through the Fourier transform and Hankel transform of the wave equation in cylindrical coordinates,this work established a three-dimensional axisymmetric sound field model based on normal waves,and designed a 4-element helix triangular pyramid array with vertical and horizontal sampling capabilities.Based on this,the three-dimensional matching localization algorithm of infrasound for geological hazards is proposed.Applying the algorithm to the infrasound signal localization of rock and soil layers,it was found that the helix triangular pyramid array can achieve accurate estimation of depth and distance with a smaller number of array elements than the traditional array,and may overcome the azimuth symmetry ambiguity.This study shows the application prospects of this method for predicting geohazards position several hours in advance. 展开更多
关键词 geologic hazards INFRASOUND helix triangular pyramid array 3D matchinglocalization algorithm
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Third-Harmonic Generated in EH32 Mode of a Gas-Filled WavegUide by fs Laser Pulses
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作者 CHEN Bao-Zhen HUANG Zu-Qia 《Communications in Theoretical Physics》 SCIE CAS CSCD 2007年第3期567-568,共2页
In this paper it is reported for the first time that the third harmonic generated in EH32 mode of a gas-filled waveguide by fs pulses has higher generation efficiency. The new finding contrasts with the experiment in... In this paper it is reported for the first time that the third harmonic generated in EH32 mode of a gas-filled waveguide by fs pulses has higher generation efficiency. The new finding contrasts with the experiment in It. G. Durfee Ⅲ, S. Backus, M.M. Murnane, and H.C. Kapteyn, Opt. Left. 22 (1997) 1565]. Some possible factors, which produce the contradiction, are discussed briefly. 展开更多
关键词 gas-filled waveguide fs pulses third harmonic energy-pressure curves
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Nonlinear wave-wave interactions and wedge waves
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作者 Ray Q.Lin Will Perrie 《Chinese Journal of Oceanology and Limnology》 SCIE CAS CSCD 2005年第2期129-143,共15页
A tetrad mechanism for exciting long waves, for example edge waves, is described based on nonlinear resonant wave-wave interactions. In this mechanism, resonant interactions pass energy to an edge wave, from the three... A tetrad mechanism for exciting long waves, for example edge waves, is described based on nonlinear resonant wave-wave interactions. In this mechanism, resonant interactions pass energy to an edge wave, from the three participating gravity waves. The estimated action flux into the edge wave can be orders of magni- tude greater than the transfer fluxes derived from other competing mechanisms, such as triad interactions. More- over, the numerical results show that the actual transfer rates into the edge wave from the three participating gravity waves are two- to three- orders of magnitude greater than bottom friction. 展开更多
关键词 edge waves quartic interactions triad interactions gravity waves parallelwave-wave interactions
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Prediction of Core Losses of Three-Phase Distribution Transformer
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作者 Mihail Digalovski Krste Najdenkoski Goran Rafajlovski 《Journal of Energy and Power Engineering》 2013年第12期2347-2353,共7页
Transformers are normally designed and built for use at rated frequency and sinusoidal load current. A non-linear load on a transformer leads to harmonic power losses which cause increased operational costs and additi... Transformers are normally designed and built for use at rated frequency and sinusoidal load current. A non-linear load on a transformer leads to harmonic power losses which cause increased operational costs and additional heating in transformer parts. It leads to higher losses, early fatigue of insulation, premature failure and reduction of the useful life of the transformer. To prevent these problems, the rated capacity of transformer which supplies harmonic loads must be reduced. In this work, a typical 50 kVA three-phase distribution transformer with real practical parameters is taken under non-linear loads generated due to domestic loads. The core losses is evaluated using the three dimensional model of the transformer developed in FEM (finite element method) program based on valid model of transformer under high harmonic conditions. And finally a relation associated with core losses and amplitude of high harmonic order are reviewed & analyzed and then a comparison is being carried out on the results obtained by different excitation current in transformer windings. 展开更多
关键词 Core losses three-phase transformer HARMONIC 3D model finite element method magnetic flux distribution.
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On the universal third order Stokes wave solution 被引量:2
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作者 SONG ZhiYao ZHAO HongJun +1 位作者 LI Ling Lü GuoNian 《Science China Earth Sciences》 SCIE EI CAS 2013年第1期102-114,共13页
This paper presents a universal third-order Stokes solution with uniform current. This solution is derived on the basis of potential theory by expanding the free surface and potential function in Fourier series and de... This paper presents a universal third-order Stokes solution with uniform current. This solution is derived on the basis of potential theory by expanding the free surface and potential function in Fourier series and determining the Fourier coefficients by solving a set of nonlinear algebraic equations through the Taylor expansion and perturbation method. The universal solution is expressed upon the still water depth with the still water level as datum and retains a global perturbation parameter. The wave set-up term generated by the self-interaction of oscillatory waves is explicitly included in the free surface function. With the use of different definitions for the wave celerity, different water levels as the datum, different non-dimensional variables as the perturbation parameter, and different treatments for the total head, the universal solution can be reduced to the existing various Stokes solutions, thus explaining the reasons and the physical significance of different non-periodic terms in them, such as the positive or negative constant term in the free surface expression and the time-or space-proportional term in the potential function. 展开更多
关键词 universal Stokes wave solution uniform current global perturbation parameter SET-UP non-periodic terms
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Terahertz generation based on four-wave mixing difference frequency by resonance-enhanced third-order nonlinear of media 被引量:1
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作者 张少华 姚建铨 +3 位作者 周睿 温午麒 徐德刚 王鹏 《Optoelectronics Letters》 EI 2011年第6期415-418,共4页
Using nanosecond pulse near-infrared and mid-infrared laser pulses as the pump source, we obtain terahertz wave sources via four-wave difference frequency mixing. From the coupled wave theory, we analyze the four-wave... Using nanosecond pulse near-infrared and mid-infrared laser pulses as the pump source, we obtain terahertz wave sources via four-wave difference frequency mixing. From the coupled wave theory, we analyze the four-wave mixing process of GaSe crystal and alkali metal vapor in detail, get the analytical expression of terahertz wave output power, and discuss the conditions for achieving phase matching. By adjusting the pump frequency, the third-order nonlinear polarization of alkali metal vapor is resonance-enhanced. This program offers a new type of high-power terahertz radiation source. 展开更多
关键词 Alkali metals Four wave mixing Infrared devices Optical parametric oscillators Optical pumping VAPORS
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On Exact Controllability of Networks of Nonlinear Elastic Strings in 3-Dimensional Space 被引量:1
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作者 Gnter R.LEUGERING E.J.P.Georg SCHMIDT 《Chinese Annals of Mathematics,Series B》 SCIE CSCD 2012年第1期33-60,共28页
This paper concerns a system of nonlinear wave equations describing the vibra- tions of a 3-dimensional network of elastic strings. The authors derive the equations and appropriate nodal conditions, determine equilibr... This paper concerns a system of nonlinear wave equations describing the vibra- tions of a 3-dimensional network of elastic strings. The authors derive the equations and appropriate nodal conditions, determine equilibrium solutions, and, by using the methods of quasilinear hyperbolic systems, prove that for tree networks the natural initial, boundary value problem has classical solutions existing in neighborhoods of the "stretched" equilibrium solutions. Then the local controllability of such networks near such equilib- rium configurations in a certain specified time interval is proved. Finally, it is proved that, given two different equilibrium states satisfying certain conditions, it is possible to control the network from states in a small enough neighborhood of one equilibrium to any state in a suitable neighborhood of the second equilibrium over a sufficiently large time interval. 展开更多
关键词 Nonlinear strings NETWORK Quasilinear system of hyperbolic equations CONTROLLABILITY
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Localization and shock waves in curved manifolds
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作者 Claudio Conti 《Science Bulletin》 SCIE EI CAS CSCD 2016年第7期570-575,共6页
The investigation of the interplay between geometry and nonlinearity may open the road to the control of extreme waves. We study three-dimensional localization and dispersive shocks in a bent cigar shaped potential by... The investigation of the interplay between geometry and nonlinearity may open the road to the control of extreme waves. We study three-dimensional localization and dispersive shocks in a bent cigar shaped potential by the nonlinear Schro¨ dinger equation. At high bending and high nonlinearity, topological trapping is frustrated by the generation of curved wave-breaking. Four-dimensional parallel simulations confirm the theoretical model. This work may contribute to novel devices based on geometrically constrained highly nonlinear dynamics and tests and analogs of fundamental physical theories in curved space. 展开更多
关键词 Nonlinear waves Shock wavesNonlinear optics CURVATURE BOSE-EINSTEINCONDENSATION
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Triad mode resonant interactions in suspended cables
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作者 Tie Ding Guo Hou Jun Kang +1 位作者 Lian Hua Wang Yue Yu Zhao 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS CSCD 2016年第3期75-88,共14页
A triad mode resonance, or three-wave resonance, is typical of dynamical systems with quadratic nonlinearities. Suspended cables are found to be rich in triad mode resonant dynamics. In this paper, modulation equation... A triad mode resonance, or three-wave resonance, is typical of dynamical systems with quadratic nonlinearities. Suspended cables are found to be rich in triad mode resonant dynamics. In this paper, modulation equations for cable's triad resonance are formulated by the multiple scale method. Dynamic conservative quantities, i.e., mode energy and Manley-Rowe relations, are then constructed. Equilibrium/dynamic solutions of the modulation equations are obtained, and full investigations into their stability and bifurcation characteristics are presented. Various bifurcation behaviors are detected in cable's triad resonant responses, such as saddle-node, Hopf, pitchfork and period-doubling bifurcations. Nonlinear behaviors, like jump and saturation phenomena, are also found in cable's responses. Based upon the bifurcation analysis, two interesting properties associated with activation of cable's triad resonance are also proposed, i.e., energy barrier and directional dependence. The first gives the critical amplitude of high-frequency mode to activate cable's triad resonance, and the second characterizes the degree of difficulty for activating cable's triad resonance in two opposite directions, i.e., with positive or negative internal detuning parameter. 展开更多
关键词 suspended cables triad mode interaction multiple scale method
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