Elastic properties of composites: periodical homogenisation technique and experimental comparison using acoustic microscopy and resonant ultrasonic spectroscopy

The macroscopic elastic properties of two composites (Duralumin/air and Duralumin/tungsten carbide (WC)) have been calculated using periodical homogenisation methods and the elastic properties of each phase (measured by high frequency acoustic microscopy). In order to check the validity of such an approach, acoustical resonant spectroscopy has also been applied. Thanks to the comparison between the resonant frequencies predicted and measured, two major conclusions have been obtained: the homogenisation method is very accurate for the composite Duralumin/air, but not for the Duralumin/WC sample: the experimental results are not in very good agreement with the simulation. This result can be then explained by the major role of interfacial state between Duralumin and tungsten carbide.     

Resonantly laser induced plasmas in gases: The role of energy pooling and exothermic collisions in plasma breakdown and heating

The present work is a systematic experimental study of the plasma formation in cesium vapor induced by a continuous laser tuned to the resonance transition 6S_1/2–6P_3/2. Taking into account the measured absolute population densities of Cs ground and excited state atoms as well as the electron densities derived from Stark broadening of the Cs lines, complete local thermodynamic equilibrium in the laser-produced plasma was found for laser power densities ≈ 10 Wcm^− 2 at cesium ground state number densities of about 10¹⁷ cm^− 3. Direct conversion of the excitation energy or parts of the excitation energy in exothermic collisions of laser-excited atoms is concluded to be the major process for atomic vapor heating and subsequent formation of LTE plasmas.     

Multiple solutions of two-point nonlinear boundary value problems

A quasi-linear boundary value problem has a solution with properties induced by oscillatory properties of the linear part of an equation. This result is proved for two dimensional systems. Consequences for Φ-Laplacian equations and problems with resonant linear parts are discussed.     

Resonant Raman spectroscopy and spectroelectrochemistry characterization of carbon nanotubes/polyaniline thin film obtained through interfacial polymerization

Thin, transparent, and self‐assembled films of neat polyaniline and polyaniline/carbon nanotube nanocomposites were deposited over glass substrates by interfacial polymerization. The effect of the carbon nanotubes on the structure and conformation of the polyaniline, and the type of interaction between the polymer and the nanotubes, have been studied by resonant Raman spectroscopy and UV–Vis and Raman spectroelectrochemistry. The results indicate clearly that the carbon nanotubes induce important changes in the electronic structure of the polymer, resulting in a more polaronic organization. Additionally, an effective interaction between the polymer and the nanotube, based on a polyaniline‐to‐nanotube charge transfer, is proposed in this work. Copyright © 2012 John Wiley & Sons, Ltd.     

一维掺杂光子晶体缺陷模的共振理论

为了得到一维掺杂光子晶体的共振理论,建立了一维掺杂光子晶体的谐振腔模型,利用谐振腔的共振条件推导出缺陷模频率满足的解析公式,从理论上解释了产生一维掺杂光子晶体缺陷模的物理机理.利用频率的解析公式对缺陷模的频率随入射角、杂质光学厚度以及杂质折射率的变化规律进行了研究,解释了一维掺杂光子晶体缺陷模的变化规律.与特征矩阵法的计算结果相比,其结果完全吻合,从而证明了共振理论的正确性,弥补了一维光子晶体研究中数值计算方法的不足.     

一个山路引理的应用

本文主要考虑如下形式的Dirichlet问题-△u(x)=f(x,u),x∈Ω,∈H01(Ω),其中f(x,t)∈C(Ω×R),f(x,t)/t关于t单调不减,并且当t∈R时关于x∈Ω一致趋向于某个L∞函数q(x)(此时,称f(x,t)关于t在无穷远处是渐近线性的).显然,在该条件下常用的Ambrosetti-Rabinowitz型条件,即关于所有的|s|>M和x∈Ω,0<θF(x,s)2,M>0为常数, F(x,s)=∫0s f(x,t)dt. 众所周知,条件(AR)在山路引理的应用中起着非常重要的作用.本文通过应用一种改进了的山路引理在没有条件(AR)的情况下来证明上面Dirichlet问题(P)也有正解存在。此方法也适用于f(x,t)关于t在无穷远处是超线性,即q(x)≡+∞的情形.     

近红外波段CO2分子弛豫动力学效应对光声信号的影响

介绍了一种基于低功率的分布反馈式(DFB)半导体激光器和自行设计的一阶纵向共振光声池构成的共振光声光谱测量系统.该系统具有结构简单、操作方便、价格低廉等优点.通过对光声池的性能进行的研究,实验研究和理论分析具有很好的一致性;系统地研究了近红外1.573μm附近分子弛豫效应对光声探测CO2信号的影响,并给出了相应的理论分析,表明利用分子弛豫效应可有效地提高系统探测灵敏度.     

Tunnelling Dynamics of Kicked Systems: A Route to Tunnelling Control

The effects of discontinuously time-varying perturbations on the dynamics of a particle moving in harmonic, symmetric double well and symmetric triple well potentials, are investigated both classically and quantum mechanically. The quantum dynamics is followed using the time-dependent Fourier grid Hamiltonian (TDFGH) method while the classical dynamics is analyzed within the framework of classical Hamiltonian mechanics. Depending on the spatial symmetry of the perturbation and the characteristic features of the reversal time , different types of ‘phase space’ structures are observed in each of the potentials. For symmetric double and triple well potentials, quantum dynamics reveals that complete destruction of tunnelling (CDT) can be achieved in the presence of a time-dependent spatially asymmetric perturbing field that is continuous in time. Any discontinuity in time-variation of the perturbation may induce over the barrier transition. The relevance of these results in the context of (i) tunnelling control and (ii) quantum computing with 3-state or 2-state quantum registers is briefly discussed.     

Photodissociation of sodium iodide and resonant ionization of sodium atom produced

Resonant ionization spectroscopy (RIS) and resonant ionization mass spectroscopy (RIMS) are employed to detect the photodissociation product of sodium iodide molecules in a molecular beam in an intense laser field in the absence of the buffer gases. Time of flight mass spectra is recorded. In particular, the appearances of multiphoton ionization are discussed.