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Bending of Timoshenko beam with effect of crack gap based on equivalent spring model 被引量:23
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作者 Xiao YANG Jin HUANG Yu OUYANG 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2016年第4期513-528,共16页
Considering the effect of crack gap, the bending deformation of the Timoshenko beam with switching cracks is studied. To represent a crack with gap as a nonlinear unidirectional rotational spring, the equivalent flexu... Considering the effect of crack gap, the bending deformation of the Timoshenko beam with switching cracks is studied. To represent a crack with gap as a nonlinear unidirectional rotational spring, the equivalent flexural rigidity of the cracked beam is derived with the generalized Dirac delta function. A closed-form general solution is obtained for bending of a Timoshenko beam with an arbitrary number of switching cracks. Three examples of bending of the Timoshenko beam are presented. The influence of the beam's slenderness ratio, the crack's depth, and the external load on the crack state and bending performances of the cracked beam is analyzed. It is revealed that a cusp exists on the deflection curve, and a jump on the rotation angle curve occurs at a crack location. The relation between the beam's deflection and load is bilinear, each part corresponding to an open or closed state of crack, respectively. When the crack is open, flexibility of the cracked beam decreases with the increase of the beam's slenderness ratio and the decrease of the crack depth. The results are useful in identifying non-destructive cracks on a beam. 展开更多
关键词 Timoshenko beam switching crack crack gap generalized function parameter study
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Folding beam-type piezoelectric phononic crystal with low-frequency and broad band gap 被引量:4
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作者 Shan JIANG Longxiang DAI +3 位作者 Hao CHEN Hongping HU Wei JIANG Xuedong CHEN 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2017年第3期411-422,共12页
A folding beam-type piezoelectric phononic crystal model is proposed to isolate vibration. Two piezoelectric bimorphs are joined by two masses as a folding structure to comprise each unit cell of the piezoelectric pho... A folding beam-type piezoelectric phononic crystal model is proposed to isolate vibration. Two piezoelectric bimorphs are joined by two masses as a folding structure to comprise each unit cell of the piezoelectric phononic crystal. Each bimorph is connected independently by a resistive-inductive resonant shunting circuit. The folding structure extends the propagation path of elastic waves, while its structure size remains quite small. Propagation of coupled extension-flexural elastic waves is studied by the classical laminated beam theory and transfer matrix method. The theoretical model is further verified with the finite element method(FEM). The effects of geometrical and circuit parameters on the band gaps are analyzed. With only 4 unit cells, the folding beam-type piezoelectric phononic crystal generates two Bragg band gaps of 369 Hz to1 687 Hz and 2 127 Hz to 4 000 Hz. In addition, between these two Bragg band gaps, a locally resonant band gap is induced by resonant shunting circuits. Appropriate circuit parameters are used to join these two Bragg band gaps by the locally resonant band gap.Thus, a low-frequency and broad band gap of 369 Hz to 4 000 Hz is obtained. 展开更多
关键词 folding beam-type structure phononic crystal band gap wave propagation PIEZOELECTRIC
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Acoustic beam splitting in a sonic crystal around a directional band gap
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作者 Ahmet Cicek Olgun Adem Kaya Bulent Ulug 《Chinese Physics B》 SCIE EI CAS CSCD 2013年第11期350-355,共6页
Beam splitting upon refraction in a triangular sonic crystal composed of aluminum cylinders in air is experimentally and numerically demonstrated to occur due to finite source size, which facilitates circumvention of ... Beam splitting upon refraction in a triangular sonic crystal composed of aluminum cylinders in air is experimentally and numerically demonstrated to occur due to finite source size, which facilitates circumvention of a directional band gap. Experiments reveal that two distinct beams emerge at crystal output, in agreement with the numerical results obtained through the finite-element method. Beam splitting occurs at sufficiently-small source sizes comparable to lattice periodicity determined by the spatial gap width in reciprocal space. Split beams propagate in equal amplitude, whereas beam splitting is destructed for oblique incidence above a critical incidence angle. 展开更多
关键词 sonic crystal directional band gap source size beam splitting
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Theoretical investigation of an electron beam propagating through a wide gap cavity
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作者 宋玮 林郁正 +1 位作者 刘国治 邵浩 《Chinese Physics B》 SCIE EI CAS CSCD 2008年第3期939-942,共4页
This paper presents a self-consistent nonlinear theory of the current and energy modulations when an electron beam propagates through an inductively-loaded wide gap cavity. The integro-differential equations axe obtai... This paper presents a self-consistent nonlinear theory of the current and energy modulations when an electron beam propagates through an inductively-loaded wide gap cavity. The integro-differential equations axe obtained to describe the modulation of the beam current and kinetic energy. A relativistic klystron amplifier (RKA) model is introduced, which uses an inductively-loaded wide gap cavity as an input cavity. And a numerical code is developed for the extended model based on the equations, from which some relations about the modulated current and modulated energy are numerically given. 展开更多
关键词 RKA wide gap cavity intense electron beam MODULATION
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Mode stability analysis in the beam-wave interaction process for a three-gap Hughes-type coupled cavity chain 被引量:2
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作者 罗积润 崔健 +1 位作者 朱敏 郭炜 《Chinese Physics B》 SCIE EI CAS CSCD 2013年第6期580-587,共8页
Based on space-charge wave theory, the formulae of the beam-wave coupling coefficient and the beam-loaded conductance are given for the beam-wave interaction in an N-gap Hughes-type coupled cavity chain. The ratio of ... Based on space-charge wave theory, the formulae of the beam-wave coupling coefficient and the beam-loaded conductance are given for the beam-wave interaction in an N-gap Hughes-type coupled cavity chain. The ratio of the nonbeam-loaded quality factor of the coupled cavity chain to the beam quality factor is used to determine the stability of the beam-wave interaction. As an example, the stabilities of the beam-wave interaction in a three-gap Hughes-type coupled cavity chain are discussed with the formulae and the CST code for the operations of the 2π, π, and π/2 modes, respectively. The results show that stable operation of the 2π, π, and π/2 modes may all be realized in an extended-interaction klystron with the three-gap Hughes-type coupled cavity chain. 展开更多
关键词 three-gap Hughes-type coupled cavity chain coupling coefficient beam-loaded conductance beam quality factor stability
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EBIC测定GaP的少子扩散长度和表面复合速度
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作者 李永良 杨锡震 +1 位作者 周艳 王亚非 《北京师范大学学报(自然科学版)》 CAS CSCD 北大核心 2001年第1期62-65,共4页
应用扫描电子显微镜 (SEM )对GaP半导体材料的 p n结进行线扫描 ,得到电子束感生电流 (EBIC)的线扫描曲线 .给出一简单模型 ,对GaP样品n区的EBIC线形进行计算 ,拟合实验曲线 。
关键词 少子扩散长度 表面合速度 电子束感生电流 半导体材料 磷化钙 P-N结 测定 EBIC线型
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GaP LPE半导体材料的扫描电子显微镜研究
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作者 李永良 杨锡震 +1 位作者 李桂英 王亚非 《现代仪器使用与维修》 1998年第3期18-20,共3页
本文论述了用扫描电子显微镜研究GaP LPE半导体材料,二次电子像用于分析样品的表面形貌,电子束感生电流像(EBIC)用于显示p-n结的位置,定量EBIC用以确定少子扩散长度和表面复合速度等重要参量。
关键词 二次电子像 电子束感生电流 磷化镓 SEM 半导体
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Effect of ion and electron beam irradiation on surface morphology and optical properties of PVA 被引量:1
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作者 H.M.Eyssa M.Osman +1 位作者 S.A.Kandil M.M.Abdelrahman 《Nuclear Science and Techniques》 SCIE CAS CSCD 2015年第6期74-79,共6页
Polyvinyl alcohol(PVA) is a well-known friendly polymer for paper-making, textiles, and a variety of coatings, biomedical applications such as artificial pancreas, synthetic vitreous body, wound dressing, artificial s... Polyvinyl alcohol(PVA) is a well-known friendly polymer for paper-making, textiles, and a variety of coatings, biomedical applications such as artificial pancreas, synthetic vitreous body, wound dressing, artificial skin,and cardiovascular device. In this paper, ion/electron beam is employed to get insight into the irradiation effect on surface morphology and optical properties of PVA polymer. UV-Vis spectra are recorded to investigate the effect of induced defects on the optical band gap and the formed carbon clusters size. Scanning electron microscopy(SEM) is used to relate and investigate surface morphology and optical properties of the target polymer with different doses(15, 30 and 60 min). Also, PVA polymer is subjected to theoretical studies by using semi-empirical PM7 quantum chemical method. 展开更多
关键词 电子束辐照 光学性质 表面形貌 聚乙烯醇 离子 扫描电子显微镜 乙烯醇聚合物 紫外-可见光谱
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Theoretical investigation of band-gap and mode characteristics of anti-resonance guiding photonic crystal fibres 被引量:1
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作者 苑金辉 桑新柱 +5 位作者 余重秀 忻向军 张锦龙 周桂耀 李曙光 侯蓝田 《Chinese Physics B》 SCIE EI CAS CSCD 2011年第2期302-310,共9页
With the full-vector plane-wave method (FVPWM) and the full-vector beam propagation method (FVBPM), the dependences of the band-gap and mode characteristics on material index and cladding structure parameter in an... With the full-vector plane-wave method (FVPWM) and the full-vector beam propagation method (FVBPM), the dependences of the band-gap and mode characteristics on material index and cladding structure parameter in anti- resonance guiding photonic crystal fibres (ARGPCFs) are sufficiently analysed. An ARGPCF operating in the near- infrared wavelength is shown. The influences of the high index cylinders, glass interstitial apexes and silica structure on the characteristics of band-gaps and modes are deeply investigated. The equivalent planar waveguide theory is used for analysing such an ARGPCF filled by the isotropic materials, and the resonance and the anti-resonance characteristics r:~n h~ w~|] r^r~dlrtpd 展开更多
关键词 anti-resonance guiding photonic crystal fibres full-vector plane-wave method full-vector beam propagation method band-gap and mode characteristics
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Modeling and analysis of piezoelectric beam with periodically variable cross-sections for vibration energy harvesting 被引量:7
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作者 M.HAJHOSSEINI M.RAFEEYAN 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2016年第8期1053-1066,共14页
A bimorph piezoelectric beam with periodically variable cross-sections is used for the vibration energy harvesting. The effects of two geometrical parameters on the first band gap of this periodic beam are investigate... A bimorph piezoelectric beam with periodically variable cross-sections is used for the vibration energy harvesting. The effects of two geometrical parameters on the first band gap of this periodic beam are investigated by the generalized differential quadrature rule (GDQR) method. The GDQR method is also used to calculate the forced vibration response of the beam and voltage of each piezoelectric layer when the beam is subject to a sinusoidal base excitation. Results obtained from the analytical method are compared with those obtained from the finite element simulation with ANSYS, and good agreement is found. The voltage output of this periodic beam over its first band gap is calculated and compared with the voltage output of the uniform piezoelectric beam. It is concluded that this periodic beam has three advantages over the uniform piezoelectric beam, i.e., generating more voltage outputs over a wide frequency range, absorbing vibration, and being less weight. 展开更多
关键词 vibration energy harvesting piezoelectric cantilever beam periodically variable cross-section vibration band gap forced vibration analysis generalized differential quadrature rule (GDQR)
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A Family of Inertial Manifolds for a Class of Generalized Kirchhoff-Beam Equations
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作者 Yuhuai Liao Guoguang Lin Jie Liu 《Journal of Applied Mathematics and Physics》 2022年第7期2153-2163,共11页
In this paper, we deal with a class of generalized Kirchhoff-Beam equations. At first, we take advantage of Hadamard’s graph to get the equivalent form of the original equations. Then, the inertial manifolds are prov... In this paper, we deal with a class of generalized Kirchhoff-Beam equations. At first, we take advantage of Hadamard’s graph to get the equivalent form of the original equations. Then, the inertial manifolds are proved by using spectral gap condition. We gain main result is that the family of inertial manifolds are established under the proper assumptions of nonlinear terms M(s) and N(s). 展开更多
关键词 Kirchhoff-beam Equations Inertial Manifold Hadamard’s Graph Spectral gap Condition
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局域共振夹芯超结构梁带隙特性及实验研究
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作者 付强 姚飞 张红艳 《人工晶体学报》 北大核心 2024年第1期65-72,共8页
本文提出了一种新型局域共振夹芯超结构梁,该结构由夹芯梁基体和由软材料包裹质量块组成的局域共振单元构成。分别采用传递矩阵法和有限元法计算了该结构的带隙分布和振动传输特性,搭建了局域共振夹芯超结构梁的振动传输测试实验平台,... 本文提出了一种新型局域共振夹芯超结构梁,该结构由夹芯梁基体和由软材料包裹质量块组成的局域共振单元构成。分别采用传递矩阵法和有限元法计算了该结构的带隙分布和振动传输特性,搭建了局域共振夹芯超结构梁的振动传输测试实验平台,并与数值计算结果进行对比验证,最后分析了结构参数对结构带隙分布特性的调控规律。研究结果表明,该结构在低频范围内共出现两条弯曲波带隙,带隙频率分别为196.1~339.0 Hz和377.2~655.6 Hz。而完全带隙位于弯曲波带隙内,频率范围为380.0~423.6 Hz。且在这两条弯曲波带隙范围内,弯曲振动传输会发生明显的减弱现象。另外,局域共振夹芯超结构梁的结构参数会对带隙分布特性产生较大影响,通过合理选择结构参数,可以实现局域共振夹芯超结构梁低频率和高带宽的减振要求。 展开更多
关键词 夹芯结构 夹芯超结构梁 局域共振 传递矩阵 振动衰减 振动带隙
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周期结构细直梁弯曲振动中的振动带隙 被引量:26
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作者 温激鸿 郁殿龙 +2 位作者 王刚 赵宏刚 刘耀宗 《机械工程学报》 EI CAS CSCD 北大核心 2005年第4期1-6,共6页
通过将声子晶体中的周期结构思想引入到细直梁的结构设计中,构造了一种二组元变截面周期结构细直梁。采用平面波展开法计算了无限周期条件下该细直梁弯曲振动中的弹性波能带结构。计算结果表明,在该细直梁中存在振动带隙。晶格尺寸、材... 通过将声子晶体中的周期结构思想引入到细直梁的结构设计中,构造了一种二组元变截面周期结构细直梁。采用平面波展开法计算了无限周期条件下该细直梁弯曲振动中的弹性波能带结构。计算结果表明,在该细直梁中存在振动带隙。晶格尺寸、材料组分比、截面尺寸对振动带隙的影响也进行了讨论。采用有限元法计算了有限周期的细直梁的振动传输特性,计算得到的振动传输特性曲线上的频率衰减范围与平面波计算得到的带隙位置基本吻合。最后以有机玻璃及铝构成的细直梁为例,采用振动试验对其振动传输特性进行了测试。试验结果同理论计算及仿真结果基本吻合。梁类结构是噪声及振动控制领域研究的主要对象之一,周期结构细直梁中存在弯曲振动带隙为梁类结构的减振提供了一种新的思路。 展开更多
关键词 声子晶体 振动带隙 减振
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采动铁路桥移动变形规律实测研究 被引量:10
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作者 谭志祥 杨怀勇 邓喀中 《采矿与安全工程学报》 EI 北大核心 2007年第2期243-247,共5页
为推广铁路桥下安全开采经验,根据地表及桥梁移动变形观测资料,总结了地表和铁路桥移动变形规律,获得了地表移动参数和概率积分法预计参数,并首次研究了铁路桥变形与地表变形之间的对应关系,得出了地表下沉、倾斜、水平变形与桥梁对应... 为推广铁路桥下安全开采经验,根据地表及桥梁移动变形观测资料,总结了地表和铁路桥移动变形规律,获得了地表移动参数和概率积分法预计参数,并首次研究了铁路桥变形与地表变形之间的对应关系,得出了地表下沉、倾斜、水平变形与桥梁对应变形之间的系列经验公式,给出了桥梁缝隙变化量与桥梁水平变形之间的关系式.石台煤矿在龙河铁路桥下采取井下开采措施和地面保护措施相结合的方法,安全开采了铁路桥正下方的煤炭. 展开更多
关键词 铁路桥下采煤 移动变形 移动参数 预计参数 桥梁缝隙
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细直梁弯曲振动中的局域共振带隙 被引量:9
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作者 王刚 温激鸿 +2 位作者 温熙森 郁殿龙 刘耀宗 《机械工程学报》 EI CAS CSCD 北大核心 2005年第10期107-110,共4页
通过将声子晶体中的局域共振思想引入到细直梁的结构设计中,构造了一种具有低频局域共振带隙的周期结构细直梁。采用传递矩阵法计算了周期边界条件下该细直梁弯曲振动中的弹性波能带结构,计算结果表明该结构中存在低频弯曲振动带隙。采... 通过将声子晶体中的局域共振思想引入到细直梁的结构设计中,构造了一种具有低频局域共振带隙的周期结构细直梁。采用传递矩阵法计算了周期边界条件下该细直梁弯曲振动中的弹性波能带结构,计算结果表明该结构中存在低频弯曲振动带隙。采用有限元法计算了有限周期该细直梁的振动传输特性。以有机玻璃、橡胶/铜块振子构成的该局域共振细直梁为例,采用振动试验方法对其振动传输特性进行了测试。试验结果同理论及仿真结果相吻合。结果表明,局域共振结构可大大降低带隙频率,并增大带隙衰减。梁类结构是噪声及振动控制领域研究的主要对象之一,局域共振结构的应用为其提供了一种新的思路。 展开更多
关键词 声子晶体 局域共振 振动带隙
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曲梁周期结构隔振器特性研究 被引量:4
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作者 黄修长 徐时吟 +2 位作者 蒋爱华 张志谊 华宏星 《振动与冲击》 EI CSCD 北大核心 2012年第5期171-175,共5页
利用曲梁具有径向刚度和切向刚度耦合以及波形转换的特性,设计了具有低频宽频带隙的曲梁周期结构隔振器。该隔振器由多层面板-支撑曲梁结构构成。针对曲梁对边支撑的结构,推导了分析含有内部自由度的周期结构的能带结构以及利用子结构... 利用曲梁具有径向刚度和切向刚度耦合以及波形转换的特性,设计了具有低频宽频带隙的曲梁周期结构隔振器。该隔振器由多层面板-支撑曲梁结构构成。针对曲梁对边支撑的结构,推导了分析含有内部自由度的周期结构的能带结构以及利用子结构迭代法进行响应求解的一般公式,并进行了验证,该子结构迭代法特别适合于周期数较多的复杂周期结构的响应求解。对带隙起始频率和终止频率所对应的结构模态进行了分析。讨论了曲梁和面板结构参数变化对周期结构隔振器带隙结构的影响。并且对一对边支撑的曲梁周期结构隔振器进行试验研究,测得其原点导纳和传递导纳,验证了这种周期结构低频宽频带隙的存在和建模方法的正确性。 展开更多
关键词 周期结构 曲梁 带隙结构 子结构迭代法
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一类局域共振型声子晶体梁的带隙分析 被引量:3
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作者 舒海生 张法 +1 位作者 余豪华 刘少刚 《哈尔滨工程大学学报》 EI CAS CSCD 北大核心 2011年第9期1249-1253,共5页
针对局域共振带隙生成机理问题,给出一类由树脂基体、硫化橡胶套和铅套所构成的一维局域共振型声子晶体梁结构,并对其弯曲振动传输特性进行有限元分析,研究带隙起止频率的形成机理,给出相应的简化计算模型.结果表明:该声子晶体梁能够产... 针对局域共振带隙生成机理问题,给出一类由树脂基体、硫化橡胶套和铅套所构成的一维局域共振型声子晶体梁结构,并对其弯曲振动传输特性进行有限元分析,研究带隙起止频率的形成机理,给出相应的简化计算模型.结果表明:该声子晶体梁能够产生低频带隙;带隙的起始频率由局域振子的摆动模式决定,相邻振子间相位排列关系不具有明显的规律性;带隙截止频率由振子和基体的反相位横向弯曲振动模式决定,相邻元胞间呈现出反相关系. 展开更多
关键词 局域共振 声子晶体梁 带隙 有限元 起始频率 截止频率 弯曲振动
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周期结构空腹梁的动态特性研究 被引量:5
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作者 陈荣 吴天行 《振动与冲击》 EI CSCD 北大核心 2013年第14期122-126,共5页
设计了一种内部周期性挖空的梁,它在中高频具有良好的带通和带阻特性,带阻频率范围内的弹性波不能传播。空腹梁由周期单元串联而成,把周期单元分解成薄梁和刚性联接杆等子结构,推导了Timoshenko梁纵向、弯曲振动导纳,给出了刚性联接杆... 设计了一种内部周期性挖空的梁,它在中高频具有良好的带通和带阻特性,带阻频率范围内的弹性波不能传播。空腹梁由周期单元串联而成,把周期单元分解成薄梁和刚性联接杆等子结构,推导了Timoshenko梁纵向、弯曲振动导纳,给出了刚性联接杆振动导纳,利用传递矩阵法计算得到了周期结构空腹梁的力传递率和带隙位置。数值模拟计算表明,当激励频率在周期结构的阻带之内时,周期结构空腹梁上的位移响应和传递到基础的力响应将大大衰减。 展开更多
关键词 周期结构 空腹梁 导纳 TIMOSHENKO梁 带隙
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多注双间隙耦合腔电子电导计算与模拟 被引量:3
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作者 全亚民 丁耀根 +1 位作者 王树忠 高冬平 《电子与信息学报》 EI CSCD 北大核心 2009年第5期1214-1217,共4页
该文基于空间电荷波理论模型,推导出多注双间隙耦合腔电子电导的单模理论和多模理论计算公式。比较结果显示对于双间隙耦合腔,单模理论计算结果足够准确。由粒子模拟结果与计算结果的一致证明了计算结果的正确性。最后使用粒子模拟研究... 该文基于空间电荷波理论模型,推导出多注双间隙耦合腔电子电导的单模理论和多模理论计算公式。比较结果显示对于双间隙耦合腔,单模理论计算结果足够准确。由粒子模拟结果与计算结果的一致证明了计算结果的正确性。最后使用粒子模拟研究了电压调制系数和聚焦磁场对电子电导的影响。结果显示当电压调制系数小于0.1并且聚焦磁场大于1.5倍布里渊磁场时,小信号理论计算的电子电导是准确的。 展开更多
关键词 多注速调管 双间隙耦合腔 电子电导
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双周期声子晶体梁弯曲振动带隙特性分析 被引量:4
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作者 冯青松 杨舟 +2 位作者 梁玉雄 陆建飞 雷晓燕 《噪声与振动控制》 CSCD 2020年第3期1-7,32,共8页
提出一种双周期五组元声子晶体梁结构,用以研究弯曲波的带隙特性。在无限结构条件下,将其等效为铁木辛柯梁,利用传递矩阵法推导、计算其能带结构,并与简单二组元声子晶体梁结构的带隙进行对比分析,结果表明内部周期的存在主要影响带隙... 提出一种双周期五组元声子晶体梁结构,用以研究弯曲波的带隙特性。在无限结构条件下,将其等效为铁木辛柯梁,利用传递矩阵法推导、计算其能带结构,并与简单二组元声子晶体梁结构的带隙进行对比分析,结果表明内部周期的存在主要影响带隙的宽度。在有限结构条件下,利用有限元法研究双周期五组元声子晶体梁的振动传递特性,证明理论推导的正确性,并得到双周期五组元声子晶体梁的弯曲波衰减特性。结果表明,双周期五组元声子晶体梁可以看作是一种滤波器,弯曲波沿波传播方向在禁带中逐渐衰减,而在通带中传播不衰减。最后讨论参数对带隙的影响,研究发现内部周期的存在能够解决低频与宽频相悖的问题,通过改变内部周期数,能够成功产生低频、宽频带隙,可为低频减振降噪设计提供新的思路。 展开更多
关键词 振动与波 双周期声子晶体梁 弯曲波带隙 铁木辛柯梁 传递矩阵法 振动传递特性
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