Nonlinear surface waves propagating along a boundary of magnetoactive plasma and vacuum

Dispersion relation is obtained for a nonlinear unpolarized surface wave propagating along a boundary between vacuum and a magnetoactive plasma in a geometry when a dc-magnetic field is parallel to both the boundary and the propagation of the surface wave. A general approach used is based on the knowledge of the corresponding first integral of Maxwell's equations.     

Analysis of propagation of ionization waves in nonuniform channels with noncircular cross sections

We investigate the propagation of ionization waves in nonuniform channels of a dc glow discharge. The dependences of the distances between adjacent strata on the cross-sectional area of the channel are measured using the method of image visualization and processing. It is found that the form of the dependences is determined to a considerable extent by the channel geometry: for a specific channel, the dependence can be increasing, decreasing, or nonmonotonic with a local peak.     

翼型绕流电磁控制的实验和数值研究

分布在弱电介质溶液中的电磁力(Lorentz力)，可以有效地控制边界层的流动.利用以转动水槽为主的实验系统和基于双时间步Roe格式的数值方法，对翼型绕流的电磁控制进行了实验和数值研究.结果表明，对于一定攻角的翼型，电磁力可以控制其绕流形态.当电磁力方向与流动方向相同时，可以抑制分离，消除涡街，其效果与减小攻角类似.当电磁力的方向与流动方向相反时，可在流场中形成大涡组成的涡街，增强流体的混合能力，其效果与增大攻角类似.     

翼型绕流电磁控制的实验和数值研究

分布在弱电介质溶液中的电磁力(Lorentz力),可以有效地控制边界层的流动.利用以转动水槽为主的实验系统和基于双时间步Roe格式的数值方法,对翼型绕流的电磁控制进行了实验和数值研究.结果表明,对于一定攻角的翼型,电磁力可以控制其绕流形态.当电磁力方向与流动方向相同时,可以抑制分离,消除涡街,其效果与减小攻角类似.当电磁力的方向与流动方向相反时,可在流场中形成大涡组成的涡街,增强流体的混合能力,其效果与增大攻角类似. 关键词： 电磁力 翼型绕流 流体控制     

Experimental study of neutral-current and charged-current neutrino cross sections

Samples of 9200 muon-neutrino and 3800 muon-antineutrino interactions on nuclei were obtained with the fine-grain calorimeter of the CHARM Collaboration at the CERN 200 GeV narrow-band neutrino beam. The interactions were classified as either neutral-current or charged-current processes on an event-by-event basis. Neutral-current and charged-current cross sections in neutrino and antineutrino interactions are presented. From these results we deduce a statistically significant contribution of right-handed coupling to the neutral hadronic current, and a value of the electroweak mixing angle corresponding to sin²θ = 0.220 ± 0.014.     

Attenuation and dispersion of Rayleigh waves propagating on a cracked surface: an effective field approach

A new effective field approach describing the attenuation and dispersion of a Rayleigh wave propagating on a surface containing a distribution of one-dimensional, surface-breaking cracks is presented. Limited by the validity of the independent scattering approximation, the model utilizes the complex transmission coefficient of a single crack to build expressions for the phase velocity and attenuation coefficient of an effective Rayleigh wave. The model is shown to be able to accommodate the effect of compressive residual stresses that tend to close the distributed cracks at their mouth, and therefore substantially reduce the attenuation and the velocity change caused by an equivalent distribution of open cracks. Wherever possible, the predictions of the new model are compared with those of other approaches and critical remarks are offered which discuss the advantages of the effective field approach over the others. Finally, an extension of this approach to distributions of two-dimensional surface-breaking cracks is outlined.     

Direct numerical reconstruction of inelastic cross sections from REELS and ISS spectra

The reconstruction of inelastic scattering cross sections faces two problems: the measured signal (energy spectrum) is a multiple scattering signal; the inelastic energy loss is nonuniform over the target depth. In this paper, we present a method for numerical reconstruction of cross sections from characteristic energy loss spectra, which efficiently solves both problems within a multilayer model. It is shown that the inverse problem of cross section extraction in the three-layer model is ill-conditioned, and the method is practically inapplicable to the three-layer model. The direct numerical reconstruction method yields a strongly “noised” result and can be applied only to obtain a priori information on the inelastic cross section form for further fitting. Using a combination of two methods, inelastic scattering cross sections were reconstructed for aluminum from characteristic energy loss spectra at probe beam energies of 5 and 40 keV. It is shown that ionization in solids should be described as a local process and as a collective one using the dispersion formula similarly to the case of excitation plasmons.     

A numerical study of the transient behaviors of solitary waves inrelativistic plasmas

The authors study the transient behaviors of solitary waves in a relativistic plasma with nonisothermal electrons. In particular, the modified Korteweg-de Vries (K-dV) equation is solved numerically with a Gaussian function as the initial condition. In addition, it is found that the time evolution of solitons from the initial profile is quite similar to that of a K-dV equation with the exception that the soliton speeds are faster. It is also found that the relativistic ions and the nonisothermal electrons tend to have a similar effect on the soliton behavior of the wave, making nonisothermal electrons more noticeable     

Experimental limits on axion production and interaction cross sections,and decay rate

Limits on axion production in proton interactions at 26 GeV are given on the basis of some results of the Gargamelle neutrino experiment at the CERN PS.     

Experimental and numerical investigations of the texture evolution in copper wire drawing

Polycrystalline copper wires are drawn in a single and multiple step for the equivalent area reduction (RA) of ∼33% The single step and multiple step drawing process was simulated using a rate independent crystal plasticity with finite strain, which is implemented as a user routine in commercial finite element package ABAQUS. The texture of the copper wires were characterized by X-ray diffraction (XRD) and compared with the texture based finite element (FE) simulation predictions. Initial 〈10 0〉 fiber decreases during the drawing process and is replaced by 〈1 1 1〉 fiber. The 〈1 1 1〉 oriented grains are predominant in a single step drawing compared to a multiple step of the equivalent area reduction. The finite element analysis takes into account active crystallographic slip and orientation effects during the drawing process. Regions at the interface of die–wire exhibited complex textures, which was widely seen in the multiple step drawing pattern.     

Experimental and numerical investigations of axisymmetric wave propagation in cylindrical pipe filled with fluid

Acoustic wave propagation in fluid-filled cylindrical pipe with arbitrary thickness is investigated numerically and experimentally. The vibrational properties of the coupled fluid-pipe system are evaluated by a layerwise approach, which is similar to the finite-strip method. In this approach, the thick cylindrical wall is divided into a number of thin cylindrical layers in the thickness direction. The displacements in the thickness direction for each layer are approximated by linear-shape functions. The governing equation is obtained by using an energy minimization principle. The dispersion curves, distribution of vibrational energy between pipe wall and contained fluid, and displacement fields are examined. The dependence of the dispersion curves on wall thickness is discussed. Two PZT ring transducers adhered to the outer surface of pipe are used as source and receiver, respectively. The propagating waves generated by burst signals are measured. To localize transient signal both in time and frequency domains, the discrete wavelet transform is applied to decomposing the receiving signal into several components. Each component is limited to a narrower bandwidth. Therefore the frequency-dependent group velocity is estimated. The experimental and numerical results are compared.     

The structure of a shock electromagnetic wave synchronous with several waves propagating in coupled transmission lines with different types of dispersion

A shock electromagnetic wave is studied numerically in the case when its structure is equally defined by two or more synchronous waves. The analysis relies on the previously suggested electrodynamic system of two coupled transmission lines one of which is normally dispersive (coaxial line) and the other is anomalously dispersive (ladder-type bar slow-wave structure).     

内孤立波沿缓坡地形传播特性的实验研究

以南中国海东北部海域底部缓坡地形为背景, 在大型重力式分层流水槽中模拟了下凹型内孤立波沿缓坡地形传播过程中的浅化、破碎、分裂等现象, 利用分层染色标识方法和多点组合探头阵列技术对内孤立波沿缓坡地形演化特征进行了定性分析和定量测量. 实验表明: 浅化效应使内孤立波传播速度减小, 对大振幅内孤立波具有抑制作用, 对小振幅波具有放大效应; 浅化效应可导致内孤立波的剪切失稳及破碎, 还可导致大振幅内孤立波的分裂. 利用Miles稳定性理论可定性描述内孤立波沿缓坡地形传播时发生不稳定状态的位置, 实验结果与理论分析相符合. 关键词： 分层流 缓坡地形 内孤立波 不稳定性     

Direct numerical experiment on the measurement of the dispersion relation for gravity waves in the presence of the condensate

During previous numerical experiments on isotropic turbulence of surface gravity waves we observed formation of the long wave background (condensate). It was shown (Korotkevich, Phys. Rev. Lett. 101, 074504 (2008)) that the presence of the condensate changes a spectrum of direct cascade, corresponding to the flux of energy to the small scales from pumping region (large scales). Recent experiments show that the inverse cascade spectrum is also affected by the condensate. In this case mechanism proposed as a cause for the change of direct cascade spectrum cannot work. But inverse cascade is directly influenced by the linear dispersion relation for waves, as a result direct measurement of the dispersion relation in the presence of condensate is necessary. We performed the measurement of this dispersion relation from the direct numerical experiment. The results demonstrate that in the region of inverse cascade influence of the condensate cannot be neglected.     

兰姆波锂电池极化电压优化实验*

为了降低极化对电池的影响,应用兰姆波技术对锂电池进行优化极化电压的实验。结合二阶电路模型,计算锂电池的极化电压,分析极化电压随各影响因素的变化关系。实验结果表明：当兰姆波的激发频率一定时,极化电压优化幅值随加在压电陶瓷两端的激发电压的增大而增大,呈线性变化;当兰姆波的激发电压保持不变时,极化电压优化幅值与加在压电陶瓷两端的激发频率不成线性关系,而是在某一共振激发频率内达到最优。