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1.
The theory of atomic diffraction from a classical standing wave light field in the presence of spontaneous emission in the Raman-Nath regime was developed by Tanguy et al. [6]. We describe the basis of computationally efficient methods for performing calculations in this regime and show their agreement with recent experimental results of Gould et al. [4].  相似文献   

2.
A hydrodynamic model based on lubrication theory has been developed to describe an evaporative meniscus in a complete wetting configuration, when evaporation takes place in ambient air. We focus on combined effects of evaporation and the substrate motion on the effective contact angle. Numerical simulations show two distinct regimes when varying the substrate velocity on several orders of magnitude. At a small velocity, the effective contact angle is governed by evaporation and is independent of the substrate velocity, while the substrate motion is dominant at a high velocity. In the latter case, a Landau-Levich regime is obtained for the receding contact line, and a Cox-Voinov regime for the advancing contact line. Finally, we use our numerical results to test the simplified model developed by Pham et al. [5,6].  相似文献   

3.
This paper presents numerical simulation of back discharge activity that is modelled at a pinhole in a dielectric layer on plane anode. First, for a given pinhole geometry, the transitions between back discharge regimes have been depicted as a mode diagram. Then, we have studied the influence of the dielectric layer thickness on the regime transitions. We have shown that increase in the layer thickness (within range of 0.02–0.2 mm) promotes the back discharge development. Finally, we have studied the influence of ‘crater configuration’. We have shown that ‘crater shape’ favours the back discharge ignition, whereas limits the resulting discharge development.  相似文献   

4.
5.
 运用相对论返波管非线性理论,推导出描述相对论返波管束波互作用的非线性自洽方程组;数值求解了该非线性自洽方程组,揭示了相对论返波管中由非稳态束波互作用产生的超辐射现象的基本规律:输出超辐射波峰值功率大约与参与互作用电子总电荷量的平方成正比。并将超辐射和由稳态束波互作用所产生的受激辐射作了相关比较,结果表明:超辐射是短电子束脉冲产生非稳态束波互作用的结果,而受激辐射是长电子束脉冲产生稳态束波互作用的结果;不断增加电子束脉冲宽度,辐射机制由超辐射转变为受激辐射。  相似文献   

6.
运用相对论返波管非线性理论,推导出描述相对论返波管束波互作用的非线性自洽方程组;数值求解了该非线性自洽方程组,揭示了相对论返波管中由非稳态束波互作用产生的超辐射现象的基本规律:输出超辐射波峰值功率大约与参与互作用电子总电荷量的平方成正比。并将超辐射和由稳态束波互作用所产生的受激辐射作了相关比较,结果表明:超辐射是短电子束脉冲产生非稳态束波互作用的结果,而受激辐射是长电子束脉冲产生稳态束波互作用的结果;不断增加电子束脉冲宽度,辐射机制由超辐射转变为受激辐射。  相似文献   

7.
By the joint use of the Monte Carlo and molecular dynamics techniques, we show, that a classical treatment of the Fukuyama-Lee model on ID incommensurate CDW in the weak pinning regime can well reproduce many peculiar transport properties attributed to a motion of CDW, such as the nonlinear electric conduction associated with narrow band noises. The results of the inspection of phase profiles in motion are also discussed and the importance of the CDW internal degrees of freedom is demonstrated.  相似文献   

8.
The results of simulating the Holweck pump by numerically solving the Boltzmann kinetic equation are reported. The nonlinear collision integral is calculated using the conservative projection method. The translation operator is approximated with tetrahedral grids. The ratio of pressures in pumped-in and pumpedout containers is studied as a function of the gas density (rarefaction) and the radius and rotation velocity of the rotor at Knudsen numbers close to unity.  相似文献   

9.
In this paper, the importance of molecular diffusion versus turbulent transport in the moderate or intense low-oxygen dilution (Mild) combustion mode has been numerically studied. The experimental conditions of Dally et al. [Proc. Combust. Inst. 29 (2002) 1147–1154] were used for modelling. The EDC model was used to describe the turbulence–chemistry interaction. The DRM-22 reduced mechanism and the GRI 2.11 full mechanism were used to represent the chemical reactions of an H2/methane jet flame. The importance of molecular diffusion for various O2 levels, jet Reynolds numbers and H2 fuel contents was investigated. Results show that the molecular diffusion in Mild combustion cannot be ignored in comparison with the turbulent transport. Also, the method of inclusion of molecular diffusion in combustion modelling has a considerable effect on the accuracy of numerical modelling of Mild combustion. By decreasing the jet Reynolds number, decreasing the oxygen concentration in the airflow or increasing H2 in the fuel mixture, the influence of molecular diffusion on Mild combustion increases.  相似文献   

10.
Li  Wenqiang  Hu  Huizhu  Su  Heming  Zhu  Qi  Li  Nan 《Optical Review》2021,28(1):1-7
Optical Review - The radiation force calculated in the Rayleigh regime is investigated by comparison with the generalized Lorenz Mie Theory (GLMT). The basic concepts behind the Rayleigh regime and...  相似文献   

11.
用二维全电磁数值模拟方法研究了轴向加速管,虽然没有实现理想群聚,但通过加一个中间腔, 大大提高了前两阶谐波电流分量,其中一阶谐波电流调制系数达到了140%,二阶谐波电流调制系数达到了68%。通过对提取腔的设计,可以选择地输出不同的频率,其中一次谐波频率为2.2GHz,输出功率1.25GW,效率9.33%;二次谐波频率为4.4GHz,输出功率0.48GW,效率3.6%。  相似文献   

12.
 用二维全电磁数值模拟方法研究了轴向加速管,虽然没有实现理想群聚,但通过加一个中间腔, 大大提高了前两阶谐波电流分量,其中一阶谐波电流调制系数达到了140%,二阶谐波电流调制系数达到了68%。通过对提取腔的设计,可以选择地输出不同的频率,其中一次谐波频率为2.2GHz,输出功率1.25GW,效率9.33%;二次谐波频率为4.4GHz,输出功率0.48GW,效率3.6%。  相似文献   

13.
J. Chen  X. Cui  S. Zhuo  B. Huang  X. Jiang 《Laser Physics》2006,16(12):1672-1680
The motion equation for ? between the molecular axis and laser polarization direction in a high-frequency off-resonance femtosecond laser field is deduced while simultaneously examining the effects of a permanent dipole moment and field-induced polarizability and hyperpolarizability to molecular rotation. Femtosecond-laser-induced dynamic alignment of CO, N2, and Br2 molecules are investigated by numerically solving the obtained rotation equation for the angle ?. The effects of the molecular permanent dipole moment and the field-induced polarizability and hyperpolarizability on the degree of alignment are presented at different intensities. Our computational results show that the dynamic alignment of molecules is primarily determined by field-induced polarizability and the second hyperpolarizability for the laser intensity range from 5 × 1014 to 5 × 1016 W/cm2. The contributions of higher order correction terms to molecular alignment can usually be neglected. The polarizability-field interaction makes the angular distributions of a molecule have a maximum along the polarization axis and a minimum perpendicular to it. The role of the second hyperpolarizability keeps the molecular counts maximum along the laser polarization direction but minimum at an angle of 45° between the molecular axis and the polarization direction. There is also a second maximum of molecular counts perpendicular to the polarization axis. For CO, N2, and Br2 molecules, the dependences of laser-induced dynamic alignment on laser intensity exhibit completely different characteristics.  相似文献   

14.
李俊成  郭立新  刘松华 《物理学报》2012,61(12):124102-124102
本文运用等效参数提取方法验证了双线螺旋结构在不同频率处不仅能够实现负的磁导率, 而且可以实现负的介电常数. 在电磁波平行和垂直入射到双线螺旋结构表面两种情况下, 发现其负介电常数的形成机理相同. 以往的单面左手材料的研究仅仅局限于微波波段, 通过改进双线螺旋结构, 在THz频段设计出一种新型单面左手材料, 同时利用LC等效电路解释了其设计原理. 一般的左手材料是由刻蚀在基板两侧的电谐振器和磁谐振器组合而成的复合结构, 与这些复合结构相比, 这种新型单面左手材料具有低损耗, 结构简单, 易于加工等优点.  相似文献   

15.
Monte Carlo simulations based on the Trotter-Suzuki transformation were carried out using 6×6 and 12×12 lattices and the single-band Hubbard model with intermediaterange repulsive interaction. The absence of the minus-sign problem for sufficiently low temperatures and appropriate doping indicates bosonic behavior reminiscent of superconductivity. It was found that holes prefer to pair on next-nearest-neighbor sites while nearest neighbors are suppressed.  相似文献   

16.
利用11/2-D平衡演化程序对EAST的首轮纯欧姆放电进行了数值模拟,获得的模拟结果与实验结果吻合得很好。同时,对放电全过程中的伏秒消耗进行了分析。  相似文献   

17.
微通道热沉是制作在硅芯片基底背面的微细通道,其水力直径范围为10~1 000 μm.微通道具有高表面积-体积比、低热阻、低流量等特点,是一种高效散热的解决方案.一个典型应用是激光二极管列阵的致冷.然而,微通道里流体的状态和传热与宏观状态相比有很大不同,有必要开展进一步研究.论文采用商业软件CoventorWareTM建立一个平板式微通道的有限元模型,据此对微通道中流体状态及传热进行了数值计算,获得了单个微通道中流场和温度的分布.结果表明,对于2 000 μm×50 μm×500 μm的微通道,能够对500 W/cm2的热通量快速散热,热阻仅有0.042 3 K/(W·cm-2).  相似文献   

18.
We have developed the Peresvet program for numerical simulation of energy accumulation above active regions. This program solves 3D MHD equations for the compressible plasma with allowance for the dissipative terms. It is shown that the energy can be stored in a layer of current by focusing the photospheric disturbances.  相似文献   

19.
In the framework of C. Wilson’s hypothesis substantiating a possibility of electric discharge development in the Earth’s atmosphere at high altitudes above thunderclouds, numerical simulations were executed of the discharge exciting the sprite halo with realistic variations of thundercloud dipole moment transferred to the ground by positive lightning discharge. For various values of time and altitude, at which the avalanche-to-streamer transition occurs, optical radiation was calculated in the 1P, 2P, and 1N bands of the nitrogen molecule and Meinel’s band of the N 2 + ion. The calculated brightness and space-time evolution of the luminescence are consistent with the data of the field observations of the halo luminescence.  相似文献   

20.
In this paper, the importance of fluctuations in flow field parameters is studied under MILD combustion conditions. In this way, a turbulent non-premixed CH4+H2 jet flame issuing into a hot and deficient co-flow air is modeled using the RANS Axisymmetric equations. The modeling is carried out using the EDC model to describe the turbulence-chemistry interaction. The DRM-22 reduced mechanism and the GRI2.11 full mechanism are used to represent the chemical reactions of H2/methane jet flame. Results illustrate that although the fluctuations in temperature field are small and the reaction zone volume are large in the MILD regime, the fluctuations in temperature and species concentrations are still effective on the flow field. Also, inappropriate dealing with the turbulence effect on chemistry leads to errors in prediction of temperature up to 15% in the present flame. By decreasing of O2 concentration of hot co-flow air, the effect of fluctuations in flow field parameters on flame characteristics are still significant and its effect on species reaction rates does not decrease. On the other hand, although decreasing of jet inlet Reynolds number at constant inlet turbulence intensity addresses to smaller fluctuations in flow filed, it does not lead to lower the effect of turbulence on species distribution and temperature field under MILD combustion conditions.  相似文献   

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