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Linear thermoacoustic theory is currently well accepted for simulating thermoacoustic systems, and correction is used to reduce the discrepancy between calculations and experimental results for turbulent flow. In order to calculate passive tube systems and make linear thermoacoustic theory coincide closely with experiments, a passive network model based on fluid network theory is derived. An amendment method is proposed to further correct for turbulence by amending thermal and viscous penetration depths when the ratio of the tube radius to the viscous penetration depth R/δv is large. The experiments have been done to verify the model in the acoustic amplifier, Helmholtz resonator, and inertance tube. In addition, the mechanisms of such tubes are further analyzed based on the model. 相似文献
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阐述齐次边界条件Et=0和Hn=0在求解波导管和谐振腔中电磁波的重要作用;说明附加边界条件ЭEn/Эn=0和ЭH1/Эn=0在何种情况下有用。 相似文献
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准周期加载微波腔的基本结构是周期结构,在强引导磁场作用下,强流电子束同微波强作用产生高功率微波;作用过程分为三个阶段:电子俘获、群聚和换能;而周期结构的作用主要在于电子俘获。适当设计的结构,不仅束波转换效率高,而且对电子束质量(如能散)的要求也不高。从微波场对电子运动的影响,研究了电子束在微波腔中的俘获、群聚和换能的束波互作用过程。基于760kV,7kA的环形电子束,采用准周期加载微波腔结构,在模拟上获得了X波段(9.3GHz)峰值功率为1.3GW的微波输出,效率接近24%。 相似文献
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利用荧光灯等离子体管覆盖金属腔体内壁,测量了筒状等离子体覆盖的金属腔体对电磁波的回波衰减。测试结果表明:金属圆筒内壁的等离子体能够有效吸收0.80~1.75 GHz波段的入射波,入射电磁波的回波衰减值为5~25 dB;当入射电磁波频率接近1.75 GHz时,回波衰减最为强烈,在入射角度为10°时,吸收峰值可达26.71 dB,因此选择合适的电磁波入射角度,能够使等离子体对微波的吸收达到峰值。理论分析了影响等离子体对电磁波衰减的主要因素。结果表明:等离子体可有效缩减腔体结构的雷达散射截面面积,因此在进气道等腔体结构的隐身方面具有一定的应用前景。 相似文献
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利用荧光灯等离子体管覆盖金属腔体内壁,测量了筒状等离子体覆盖的金属腔体对电磁波的回波衰减。测试结果表明:金属圆筒内壁的等离子体能够有效吸收0.80~1.75 GHz波段的入射波,入射电磁波的回波衰减值为5~25 dB;当入射电磁波频率接近1.75 GHz时,回波衰减最为强烈,在入射角度为10°时,吸收峰值可达26.71 dB,因此选择合适的电磁波入射角度,能够使等离子体对微波的吸收达到峰值。理论分析了影响等离子体对电磁波衰减的主要因素。结果表明:等离子体可有效缩减腔体结构的雷达散射截面面积,因此在进气道等腔体结构的隐身方面具有一定的应用前景。 相似文献
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Quantum manipulation of macroscopic mechanical systems is of great interest in both fundamental physics and ap- plications ranging from high-precision metrology to quantum information processing. For these purposes, a crucial step is to cool the mechanical system to its quantum ground state. In this review, we focus on the cavity optomechanical cooling, which exploits the cavity enhanced interaction between optical field and mechanical motion to reduce the thermal noise. Recent remarkable theoretical and experimental efforts in this field have taken a major step forward in preparing the mo- tional quantum ground state of mesoscopic mechanical systems. This review first describes the quantum theory of cavity optomechanical cooling, including quantum noise approach and covariance approach; then, the up-to-date experimental progresses are introduced. Finally, new cooling approaches are discussed along the directions of cooling in the strong coupling regime and cooling beyond the resolved sideband limit. 相似文献
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The increasing level of experimental control over atomic and optical systems gained in recent years has paved the way for the exploration of new physical regimes in quantum optics and atomic physics, characterised by the appearance of quantum many‐body phenomena, originally encountered only in condensed‐matter physics, and the possibility of experimentally accessing them in a more controlled manner. In this review article we survey recent theoretical studies concerning the use of cavity quantum electrodynamics to create quantum many‐body systems. Based on recent experimental progress in the fabrication of arrays of interacting micro‐cavities and on their coupling to atomic‐like structures in several different physical architectures, we review proposals on the realisation of paradigmatic many‐body models in such systems, such as the Bose‐Hubbard and the anisotropic Heisenberg models. Such arrays of coupled cavities offer interesting properties as simulators of quantum many‐body physics, including the full addressability of individual sites and the accessibility of inhomogeneous models. 相似文献
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传统的电动式换能器设计理论中,未考虑压力补偿系统等声腔结构对声学性能的影响,声源级理论设计结果与实测结果存在较大差别。研究中将电动式换能器内部的三段气腔视为突变截面声腔结构,给出了声腔的四端网络等效电路,将其作为辐射面的负载添加到电动式换能器的传统等效电路中,获得了电动式换能器改进的等效电路。基于改进的等效电路求解了带有声腔结构的电动式换能器声源级曲线,该曲线与有限元仿真分析结果基本一致,验证了该改进的等效电路在预报电动式换能器声源级方面的正确性。基于该等效电路研究了声腔的结构尺寸、末端声学边界及腔内气体声学参数对声源级起伏特征的影响。结果显示,在声腔末端敷设吸声材料或在声腔内充入特性阻抗较小的气体对于抑制或消除声源级起伏具有明显作用。 相似文献
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In this paper, a fully coupled vibro-acoustic model is developed to characterize the structural and acoustic coupling of a flexible panel backed by a rectangular-like cavity with a slight geometrical distortion, which is introduced through a tilted wall. The combined integro-modal approach is used to handle the acoustic pressure inside the irregular-shaped cavity. Based on the model proposed, the distortion effect on the vibro-acoustic behavior of the coupled system is investigated using the averaged sound pressure level inside the enclosure and the averaged quadratic velocity of the vibrating plate. Simulations are conducted to examine the distortion effect on acoustic natural frequencies, acoustic pressures and structural responses. Effects of the wall inclination on coupling coefficients are also assessed, and an index is proposed to quantify the degree of variation of coupling strength. 相似文献
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多腔回旋速调管中的调制腔采用内外腔同轴结构,对回旋电子注角向群聚起着关键作用。用场匹配理论及HFSS软件对调制腔冷腔特性进行了研究,对多种输入结构、耦合缝尺寸和方位、腔体长度、半径进行了模拟。分析表明,耦合狭缝中心线与输入波导轴线成45°,耦合缝长度达到0.72时,内外腔储能比值达到41.65;耦合缝尺寸对腔体Q值影响较大,但并非呈简单线性关系,并且Q值对缝长的变化比缝宽的变化要敏感得多;而狭缝尺寸变化对谐振频率的影响不大;计算了内外腔储能,得到了模式转换效率高、内外腔储能比高、性能优良的调制腔。 相似文献
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讨论了理想和非理想情况下耦合腔阵列中两个最邻近的腔与Λ-型三能级原子非局域耦合系统中单光子的传输特性.运用准玻色子方法,精确地解出了开放系统中单光子的透射率.Λ-型三能级原子与耦合腔阵列非局域耦合系统具有更多的优点,如:该系统比其他系统调控光子传输特性的可调控参数更多;单光子在该系统中传输的透射谱有三个透射峰.此外,该系统还具有自身的特点,当拉比频率?取值给定之后,改变原子与其中一个腔的耦合强度时,光子的透射谱有一个透射率始终为1的定点,该点对应的光子频率为ω_c-?.在非理想情况下,系统耗散对光子的透射谱有着很大的影响.当只考虑原子耗散时,耗散使得光子透射谱的谷值增大,而峰值不变;当只考虑腔场耗散时,光子透射谱的峰值减小,而谷值不变.另外,随着腔场耗散率和腔的个数的增多,光子透射谱的峰值逐渐减小,但谷值始终不变.对比原子耗散和腔场耗散的情况可以发现,原子耗散使得光子不能被完全反射,而腔场耗散使得光子不能被完全透射.当同时考虑原子和腔场耗散时,光子透射谱谷值的大小不但会受原子耗散率大小的影响,也受腔场耗散率大小的影响,随着腔场耗散率的增大,谷值反而减小;而光子透射谱的峰值始终只受腔场耗散率大小和腔的个数的影响,与原子耗散率取值的大小无关. 相似文献
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Using numerical simulations, we investigated the transmission properties for coupled cavity waveguides form in two-dimensional photonic dielectric rods in air with square lattice. The dispersion for the coupled cavity waveguides with different radius of the defects is given. The optimum design waveguide should be perfect transmission for pulse though with a quasi-flat dispersion band. Based on the coupled cavity waveguides, a 3 dB power splitter is designed. Our results may have an important role in the design of efficient power splitters in a photonic circuit. 相似文献
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To solve out of operation induced by the disarrangement of cavity mirrors in half intra-cavity He–Ne lasers, a new structure of alignment-free He–Ne laser with folded cavity is invented. A corner cube prism (CCP) is used to structure a folded cavity. This novel laser can work conveniently without any adjustment. Both intensity curves of solid and hollow CCPs are studied, which indicate that it is a finely robust and stabile, and has a large changeable range (approximately, 60 mm) of cavity length. Bright prospect in applications improving the nanometer laser ruler invented by our group before is also shown. 相似文献
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