ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. 相似文献
In this article, electrospinning technique has been demonstrated for the synthesis of ultra‐low dielectric constant polyimide fiber membranes. Poly(amic acid) fiber membranes have been prepared as precursor. After the treatment of thermal imidization, ultra‐low dielectric constant polyimide fibers membranes can be obtained. The morphologies and structures of precursors and products are characterized by scanning electron microscopy (SEM), Fourier transmission infrared (FTIR) spectra, and a radio frequency (RF) impedance/capacitance material analyzer. The DK of the as‐prepared polyimide membrane ranges from 1.53 to 1.56, which could be applied in the electronic packaging industry.
Optical responses in dilute composites are controlled through the
local dielectric resonance of metallic clusters. We consider two
located metallic clusters close to each other with admittances
\varepsilon1 and \varepsilon2. Through varying the
difference admittance ratio \eta [ = (\varepsilon2- \varepsilon
0) / (\varepsilon1- \varepsilon0)], we find that their
optical responses are determined by the local resonance. There is a
blueshift of absorption peaks with the increase of \eta.
Simultaneously, it is known that the absorption peaks will be
redshifted by enlarging the cluster size. By adjusting the
nano-metallic cluster geometry, size and admittances, we can control
the positions and intensities of absorption peaks effectively. We
have also deduced the effective linear optical responses of
three-component composites \varepsilone= \varepsilon0
\bigl(1 + \sumn=1^{ns} [(\gamman2+ \eta \gamman2)/({\varepsilon0(s - sn))]} \bigr), and the sum
rule of cross sections: \sumn=1^{ns} {(\gamman2+
\eta \gamman2 ) = Nh1+ Nh2, where Nh1and
Nh2 are the numbers of \varepsilon1 and \varepsilon2
bonds along the electric field, respectively. These results may be
beneficial to the study of surface plasmon resonances on a nanometre
scale. 相似文献
The stability of a unipolarly charged electrohydrodynamic boundary layer on a flat dielectric plate along which an electric current flows between electrodes located on the plate is investigated within the framework of the linear theory. The solution of the steady-state problem is obtained on the basis of methods developed earlier for conditions typical of aerodynamical experiments and various electric currents and electrode voltages. The effect of the interaction between perturbations of the electric and hydrodynamic flow parameters on the flow stability is estimated within the framework of the locally homogeneous approximation. This effect turns out to be insignificant under the conditions considered. It is shown that steady-state electrohydrodynamic action on the main flow makes it possible to obtain “accelerating” velocity profiles with increased absolute values of the second derivative in the transverse direction. This ensures a significant increase in the critical Reynolds numbers of loss of stability and a narrowing of the growing perturbation wavenumber range. 相似文献
The mechanism of explosive vaporization interaction of laser radiation with matter is studied theoretically. It is shown that,
in dielectric liquids with a free surface, periodic explosive boiling is possible if the laser radiation intensity exceeds
the rate of heat transfer from the region of laser radiation absorption. Analytical expressions are obtained to estimate the
pulsating boiling period and the thickness of the surface liquid layer dispersed by fluctuation vapor bubbles during each
boiling. The degree of absorption of laser radiation by the aerosol formed above the liquid surface is estimated.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 6, pp. 17–24, November–December, 2008. 相似文献