共查询到19条相似文献,搜索用时 203 毫秒
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在共振情况下,且原子-场耦合系数随时间线形变化时,研究了V-型三能级原子与单模场相互作用系统中熵的演化特性,分析了耦合系数变化的快慢和不同的初始光场对场(原子)熵的影响.结果表明:初始光场的统计性质的不同将导致系统的场(原子)熵演化发生很大的变化.当原子-场耦合系数变化缓慢时,原子进入统计混合态的速度被减缓;而当原子-场耦合系数变化较快时,则使场熵演化曲线的振荡频率加快. 相似文献
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该文在单晶硅基底上设计了AlN/PZT复合压电薄膜层声表面波(SAW)器件,采用有限元法(FEM)研究了复合压电材料厚度(PZT厚度hPZT和AlN厚度hAlN)对AlN/IDT/PZT/Si结构中零阶、一阶SAW的相速度、机电耦合系数和电极反射系数的影响,根据色散特性得到最优化薄膜厚度。结果表明,AlN/IDT/PZT/Si结构中,当hPZT =0.025λ,hAlN=λ时,零阶、一阶SAW都能取得最高相速度(分别为5 582 m/s和5 711 m/s),适用于高频器件设计;在hPZT=0.2λ,hAlN=0.1λ时,零阶SAW波的机电耦合系数最大(为21.55%),但此时相速度最小(仅为2 890 m/s),适用于移动通信领域宽带低损耗SAW滤波器和延迟线结构信号处理器件的设计。 相似文献
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该文从理论上计算得到了ZnO(a面)/蓝宝石(r面)结构的声表面波相速度和机电耦合系数色散曲线。依据该色散曲线设计了ZnO(a面)/蓝宝石(r面)结构声表面波滤波器。采用在蓝宝石衬底上先制备ZnO薄膜然后再制作芯片结构的方案研制出了声表面波器件样品。研制过程中生长出了a面结构的ZnO薄膜,其中厚膜样品测试得到了3种声波模式,即模式0、1及2,模式0、1和2的频率分别为1 073.79 MHz,1 290.63 MHz和1 572.3 MHz,因此,间接测得了模式0、1和2的相速度分别为3 865.67m/s,4 646.25m/s和5 660.27m/s。 相似文献
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该文从理论上计算得到了ZnO(a面)/蓝宝石(r面)结构的声表面波相速度和机电耦合系数色散曲线。依据该色散曲线设计了ZnO(a面)/蓝宝石(r面)结构声表面波滤波器。采用在蓝宝石衬底上先制备ZnO薄膜然后再制作芯片结构的方案研制出了声表面波器件样品。研制过程中生长出了a面结构的ZnO薄膜,其中厚膜样品测试得到了3种声波模式,即模式0、1及2,模式0、1和2的频率分别为1 073.79 MHz,1 290.63 MHz和1 572.3 MHz, 因此,间接测得了模式0、1和2的相速度分别为3 865.67 m/s, 4 646.25 m/s和5 660.27 m/s。 相似文献
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S. N. SAMADDAR 《International Journal of Electronics》2013,100(2):93-107
This paper considers the possibility of excitation of lateral waves in a compressible plasma in contact with conducting boundaries. The present investigation demonstrates the existence of a peculiar type of lateral wave which travels a certain distance along the conducting surface with the phase velocity of light in a cold plasma and is then reflected back at the critical angle into the compressible plasma in which the wave propagates with the phase velocity of acoustic waves. These electro-acoustic lateral waves ore the contribution to the pressure field integral from the integration around the branch cut which depends on both the velocity of light and the adiabatic sound velocity in plasma-electrons. 相似文献
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Jianxiang Xie Yanyu Wei Yubing Gong Jin Xu Wenxiang Wang 《Journal of Infrared, Millimeter and Terahertz Waves》2005,26(10):1473-1489
This paper gives the investigations of the fundamental wave of a free elliptical helix slow-wave structure (SWS) with arbitrary eccentricity. The wave properties including the phase velocity characteristics, interaction impedance and the longitudinal electric field distribution of this mode has been fully studied. It is found that, when the eccentricity increases, the interaction impedance and the operating frequency of such SWS will be improved, which allows to have a higher gain and operating in a higher frequency band. Furthermore, the field configuration is different from that of a round helix; the azimuthal distribution of the E-field follows with the angular Mathieu function of the first kind, even with mode of zero. In radial, E-field is elliptical surface wave. When the eccentricity tends to zero, all the characteristics will be smoothly degenerates to the case of round helix correspondingly. 相似文献
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《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1968,56(9):1449-1458
A traveling-wave, MHD induction generator with varying fluid velocity between inlet and exit can have the same internal electrical efficiency as a rotating induction generator. The fraction of electric retarding work converted to electric output at each station in the flow channel is (1 + s)-1, where s is the local slip (U - Us )/Us , between the velocity of the fluid U and the velocity of the zero crossing of the magnetic field wave Us . To produce the rotating-machine efficiency, the product of magnetic field amplitude, wave velocity, and flow channel width is held constant from inlet to exit. The local slip can be freely chosen for maximum electric output from the fluid in the presence of friction, and the inlet magnetic field can be selected for maximum output after winding and end losses. An efficiency of 0.63 is found possible with a 325-kW lithium generator. 相似文献
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该文使用SiO2和金属材料钨(W)构造布喇格反射叠层,将其应用于由横向电场激励体声波谐振器(XBAR),并分析了金属层对谐振器性能的影响。所设计的谐振器以128°YX-切铌酸锂为压电层,Al为电极,SiO2和W为周期层叠结构,单晶硅作为衬底的固态装配型谐振器(SMR),利用叉指电极换能器(IDT)激发出A1模式。首先计算声阻抗层厚度对SiO2/W叠层传输系数的影响,得到中心频率为3.7 GHz的布喇格阻带。横波(主模)在经过叠层时被反射,纵波(杂模)则部分地泄露到衬底。由于钨具有电导性,致使IDT与钨之间形成并联分布电容,改变了原有的电场分布,导致谐振器的耦合系数下降。通过实验测试谐振器的实际性能,获得耦合系数为12%。虽然W具有高声阻抗,但分布电容的影响恶化了电气参数。 相似文献
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Internal higher-order mode coupling between adjacent longitudinal radiating slots cut in a broad wall of a rectangular waveguide is examined rigorously. Method-of-moments solutions to pertinent coupled integral equations are investigated. Higher-order mode coupling effects on the amplitude and phase of the aperture electric field are studied as a function of waveguide and slot parameters. It is shown that higher-order mode coupling effects are accounted for, to a substantial extent in standard-height waveguides and almost completely in reduced-height waveguides, by including the TE20 mode coupling in the analysis 相似文献
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An electrically variable phase shifter employing surface acoustic waves is described that uses electrical depolarisation of a poled PZT ceramic. Phase shifting occurs in a depoling region in which an electric field of variable strength opposes the remanent ferroelectric moment, causing a change in the piezoelectric coupling and surface-wave velocity. 相似文献
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