Courants caractéristiques et analyse de SEREigen currents and RCS analysis

In this Note, we return to the theory of characteristic modes which was introduced 30 years ago for electromagnetic scattering problems. A simple mathematical framework is proposed and complete definitions are given. The potential interest of this theory in terms of Radar Cross Section (RCS) analysis is then discussed, especially in the low frequency case. Finally, a 3-D example is presented to illustrate the efficiency of this decomposition. To cite this article: Y. Morel et al., C. R. Mecanique 332 (2004).     

Analysis and modeling for time-dependent behavior of polymers exhibited in nanoindentation tests

Through the arrangement of the applied load, experimental nanoindentation results of polymethylmethacrylate (PMMA) and polyurethane (PU) employed to establish a mechanical model. The proposed model consists of irreversible delayed plastic (viscoplastic) deformation, irreversible viscous deformation, and reversible delayed elastic (viscoelastic) deformations. The phase lag exhibited between the responding depth and the oscillating load is found to be linear proportional to frequency in the range of 1-50 Hz. The residual cavity profile of the PMMA scanned by an atomic force microscope gives a validity of accommodation assumption applied in the present model. The effects of overshooting, which occurred in the dwelling process, are also discussed.     

A novel capacitive pressure sensor structure with high sensitivity and quasi-linear responseUne nouvelle structure de capteur de pression capacitif avec haute sensibilitée et réponse quasi-linéaire

This paper describes a new capacitive structure of pressure sensor to increase simultaneously the sensitivity and the linearity of the transducer. This structure contains two capacitors which change in response to pressure, but in opposite senses. To increase even more the sensitivity of each capacitor, the pressure sensitive diaphragm carries a central boss. The optimal position and the length of the boss are also calculated. To cite this article: A. Ettouhami et al., C. R. Mecanique 332 (2004).     

Une méthode de calcul des coefficients de réflexion et de transmission d'une houle bidimensionnelle en milieu confinéA new method for the calculation of transmission and reflection coefficients for water waves in a small basin

This paper presents a method to estimate reflected and transmitted wave amplitude spectra in a bounded domain such as a wave tank, when available data signals must be shortened due to interferences and wall effects. This paper extends the well known Goda and Suzuki two-probe method to three probes. The paper also suggests solutions to compute reliable transmission and reflection coefficients in spite of problems linked to higher harmonics and to the interference between different wave trains propagating in the tank. To cite this article: G. Duclos, A.H. Clément, C. R. Mecanique 331 (2003).     

De Sitter空间中具有常均曲率的类空超曲面（Ⅱ）

设Ｍ＾ｎ是Ｄｅ Ｓｉｔｔｅｒ空间Ｓ１＾ｎ＋１中具有常数平均曲率且第二基本形式长度的平方为常数的完备类空超曲面，若Ｓ≤２（ｎ－１）＾１／２，则Ｍ＾ｎ是等参超曲面。     

Constructive and Destructive Two-Pulse Excitation Investigated with a White-Light Michelson Interferometer

Linear propagation of two pulses through methanol solution of aluminum phthalocyanine chloride is investigated using a modified white-light Michelson interferometer. The observed coherence time of the white light is 6 fs, and the separation between the two-excitation pulses is set to about 10 fs. The excitation is dependent on the phase-relation between the two pulses. We have observed an enhancement of the excitation when the two pulses are in-phase and strong suppression of the excitation when the two pulses are out of phase by π.     

Carleson测度与Bloch的刻画

在文中，对于C^n中有界强拟凸域。我们得到Carleson测度，消没Carleson测度的刻画。利用Carleson测度，我们还得到Bloch，小Bloch的刻画。     

One-pot synthesis of an ionic half-sandwich complex of neodymium. Application to isoprene polymerisation catalysis

The reaction of one equivalent of Nd(BH₄)₃(THF)₃ with an half equivalent of dialkylmagnesium in the presence of a stoichiometric amount of pentamethylcyclopentadiene cleanly affords a new kind of half-sandwich of neodymium that is stable toward comproportionation. This strategy can be advantageously applied to generate in situ catalysts allowing the controlled polymerisation of isoprene.     

频率受随机过程调制的体系中的光谱扩散

通过在Bloch方程中增加描述对频率微扰的随机过程项{ω(t)},我们讨论了系统在窄谱带的光激发后的光谱扩散。特别是以下两种情况:1)如果ω以相同的概率变化为系综中的任一ω’,光谱是一个指数式衰减的定域峰和指数式增长的动态非均匀背底的叠加。2)如果ω'到ω的概率仅与|ω’-ω|有关,非定域峰随时间变宽。作为一个例子,我们讨论了频率受多个独立随机电报过程调制的系统中的光谱扩散。