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1.
V. I. Aleshin 《Technical Physics》2007,52(1):7-12
Expressions for the effective conductivity and resistivity of a two-phase medium that are represented as series based on Fourier transforms are analyzed. Relationships between the Fourier coefficients for the local conductivity and resistivity of transposed systems (obtained one from the other by phase transposition without changing the geometrical structure of the material) are derived. It is shown that such relationships allow, in a number of cases, calculating an arbitrary member of the series for the effective constants. A way of renormalizing all members of the series that makes it possible to relate the effective constants of transposed systems is demonstrated with a two-dimensional problem. 相似文献
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《Journal of Electrostatics》2007,65(9):571-581
Binary mixtures of pharmaceutically relevant powders were investigated using dielectric spectroscopy over a frequency range of 10−3 to 300 kHz. Two different binary mixtures were studied as a function of concentration; pseudoephedrine hydrochloride in dicalcium phosphate dihydrate and acetaminophen in microcrystalline cellulose, respectively. Dielectric properties obtained from measurements of these systems are reported and found to follow a trend similar to the observed triboelectric behavior after low-shear tumble blending. Powder samples for charge measurement were mixed using a stainless steel blender and dispensed directly into a Faraday pail. For the two binary mixtures studied, low-frequency conductivity calculated from the imaginary part of the complex permittivity (or loss factor) was observed to be sensitive to water content. Furthermore, the unanticipated trends previously reported in the measured specific charge after blending were observed to correspond with the surface charge density calculated from the capacitance of the composite material. The implications of moisture and the physical and chemical properties of these dielectric mixtures are also discussed with supporting results. 相似文献
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《Journal of Electrostatics》2007,65(8):506-510
This paper presents research results, which confirm the possibility of influencing the electrostatic charge tendency (ECT) of selected mixtures of purely insulating liquids. Tests were performed in a spinning disk system, where the factors influencing the value of the electrification current consisted of variable composition of the toluene–cyclohexane mixture, rotational speed, and a disk diameter. Liquid hydrocarbon mixtures displayed changes in ECT as well as classic insulation parameters such as resistivity and relative permittivity for concentration changes of the admixtures. These results can be used to assist the search for inhibitors of ECT and of aging processes in insulating oils. 相似文献
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Effective dielectric function of a metal-dielectric composite with nonrandomly distributed particles
Summary The optical properties of a metal-dielectric binary composite with nonrandomly distributed particles were studied within the
framework of the effective medium theory. All the particles, as usual, were assumed to be spherical and the nonrandomness
of their distribution was achieved by forcing onto the system the correlation that prevents the metal particles from touching
each other or the one that forces them to aggregate in pairs, either oriented at random or all alike. The drawbacks of the
effective medium theory due to the assumption that the particles be very small were overcome by describing the scattering
properties of the particles through their exact Mie amplitudes. Both kinds of correlation we considered turned out to have
substantial effects on the onset of the percolation phenomena. The transition induced by the correlation of exclusion from
a behaviour typical of the Bruggeman model to one more appropriate to the Maxwell-Garnett model was followed as a function
of the exclusion radius. In the case of aggregation the onset of the percolation phenomena was found to be strongly influenced
by the further introduction of an orientational order of the pairs.
Based on work supported in part by the U. S. Army European Research Office through Contract DAJA45-86-C-0003 and in part by
the Consiglio Nazionale delle Ricerche through the Gruppo Nazionale Struttura della Materia. 相似文献
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Strong and weak relaxation polarization in dielectric statistical mixtures of non-extended particles
A. S. Bogatin A. V. Turik E. V. Andreev Yu. A. Ignatova S. A. Kovrigina V. N. Bogatina 《Bulletin of the Russian Academy of Sciences: Physics》2013,77(3):320-323
The heterogeneous dielectric in the form of a statistical mixture of nonextended particles is considered; the existence of through conductivity in each component is examined, and an expression for the complex dielectric permeability of this system is obtained. The conditions for the development of strong relaxation polarization in such systems are found. The transition from strong to weak relaxation polarization is identified from an increase in the relationship between the contributions of the relaxation polarization and the fast polarization processes to the effective polarizability of a heterogeneous system and a change in the distribution parameter. 相似文献
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Hydrothermal synthesis and dielectric properties of chrysanthemum-like ZnO particles 总被引:1,自引:0,他引:1 下载免费PDF全文
By orthogonal design theory, technological parameters of
chrysanthemum-like ZnO particles prepared in a hydrothermal process
are optimized. This paper reports a set of technological
parameters for growing chrysanthemum-like ZnO particles on a large
scale. It investigates the morphologies and crystalline structures
of the as-synthesized three-dimensional ZnO particles with a scanning
electron microscope, x-ray diffractometer and transmission electron
microscope, and the possible growth mechanism on the three-dimensional ZnO
particles. The experimental results indicate that the values of
ε', ε ' and \tan δe gradually
increase in the X band with the improvement of the developmental level
of chrysanthemum-like ZnO particles, implying that the
electromagnetic wave absorbing property depends on the morphologies
of three-dimensional ZnO particles. 相似文献
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Giant enhancement of optical nonlinearity in mixtures of graded particles with dielectric anisotropy
To investigate the effective linear dielectric constant
and third-order nonlinear susceptibility
of composite media, in which graded inclusions with radial dielectric anisotropy are randomly embedded in a linear isotropic matrix, we develop an nonlinear anisotropic differential effective dipole approximation (NADEDA). Alternatively, based on a first-principles approach, the exact expressions for
and
are also derived for the linear dielectric profiles with small slopes. Then, excellent agreement between the two methods is numerically demonstrated. As an application, we further apply the NADEDA to a nonlinear metal-dielectric composite, in which the metal particles possess spatially varying radial dielectric anisotropy, in an attempt to study the nonlinearity enhancement and the figure of merit of the composite. To this end, it is shown that the presence of gradation in the radial dielectric constant plays a crucial role in enhancing the optical nonlinearity as well as the figure of merit.Received: 16 August 2003, Published online: 30 January 2004PACS:
77.22.Ej Polarization and depolarization - 42.65.-k Nonlinear optics - 42.79.Ry Gradient-index (GRIN) devices - 77.84.Lf Composite materials 相似文献
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在同轴圆柱单介质内外双水冷结构的DBD臭氧发生器的放电间隙内分别填充玻璃珠、高铝瓷、石英砂和熔融石英砂等颗粒,研究填充颗粒材料、粒径大小、间隙宽度等参数对臭氧生成效率的影响。结果表明:颗粒材料的介电常数是影响其臭氧制取效果的主要因素,随着介电常数的增加,间隙击穿电压降低,但由于颗粒导致电场的畸变,间隙折合场强增加,臭氧生成的最大能效降低,饱和浓度提升;高铝瓷具有最高的臭氧饱和浓度,与未填充的空床相比,饱和浓度提升136%;对于填充不同粒径熔融石英砂颗粒,随着粒径的增加,间隙击穿电压上升,间隙的折合场强提高,臭氧生成的最大能效降低,而饱和浓度提升;通过在宽间隙内填充介质颗粒可以得到窄间隙宽度的臭氧制取效果。 相似文献
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在同轴圆柱单介质内外双水冷结构的DBD臭氧发生器的放电间隙内分别填充玻璃珠、高铝瓷、石英砂和熔融石英砂等颗粒,研究填充颗粒材料、粒径大小、间隙宽度等参数对臭氧生成效率的影响.结果表明:颗粒材料的介电常数是影响其臭氧制取效果的主要因素,随着介电常数的增加,间隙击穿电压降低,但由于颗粒导致电场的畸变,间隙折合场强增加,臭氧生成的最大能效降低,饱和浓度提升;高铝瓷具有最高的臭氧饱和浓度,与未填充的空床相比,饱和浓度提升136%;对于填充不同粒径熔融石英砂颗粒,随着粒径的增加,间隙击穿电压上升,间隙的折合场强提高,臭氧生成的最大能效降低,而饱和浓度提升;通过在宽间隙内填充介质颗粒可以得到窄间隙宽度的臭氧制取效果. 相似文献
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与普通绝缘子相比,高梯度绝缘子(HGI)的金属层与绝缘介质层交替排列结构可以抑制真空沿面闪络过程,从而提高沿面闪络场强。使用不同绝缘介质材料和金属材料采用不同加工制备工艺制备的HGI样品其沿面闪络场强差别较大。对所制备的绝缘介质层分别为聚酰亚胺、交联聚苯乙烯和尼龙,金属层为不锈钢箔,形状分别为圆柱与圆环型的HGI样品进行了真空沿面耐压测试,并对相同尺寸的纯绝缘介质样品进行了对照实验,得到了不同材料不同制备工艺HGI样品的耐压性能差异。结合样品表面显微照片观察得到的样品表面状况,分析了影响样品沿面闪络场强的因素。 相似文献
13.
Effective electromagnetic properties of honeycomb substrate coated with dielectric or magnetic layer
L. Liu C. Z. Fan N. B. Zhu Z. Y. Zhao R. P. Liu 《Applied Physics A: Materials Science & Processing》2014,116(3):901-905
Effective electromagnetic properties of aramid honeycomb board coated with a layer of multi-wall carbon nanotube or iron flakes composites were measured with waveguide method from 4 to 12 GHz. It was proved that homogenization theory could predict the effective permittivity or permeability of the honeycomb composites with good accuracy. The coated honeycomb composites of relatively high permittivity and permeability could potentially be used to develop dielectric or magnetic substrate for shielding layer or absorbing structures working at microwave frequencies. 相似文献
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Pure and rare earth oxides (Sm2O3, La2O3) coated LiCoO2 nanoparticles were prepared by acrylamide-assisted polymeric citrate and resin-coating processes, respectively. The prepared powders were characterized by X-ray diffraction, X-ray fluorescence, scanning electron microscopy, and impedance spectroscopy. Powder X-ray diffraction patterns confirmed the formation of phase pure LiCoO2 with nanocrystallite size. X-ray fluorescence spectra confirm the presence of Sm2O3 and La2O3 in coated samples. The conductivity, dielectric and electric modulus studies of the samples were carried out at room temperature. Dielectric spectra of the samples show the decrease in dielectric constant with an increase in frequency of the applied field. The modulus studies indicate the non-Debye behavior of the samples, which is due to long-time slow polarization and relaxation of hopping charges. 相似文献
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New effective fields are defined in QCD by averaging the phase factor P exp∫x0x0+?iAμdxμ in small four-dimensional boxes. Their effective lagrangian is constructed explicitly for G=SU(2). It is a version of the dielectric theory proposed by 't Hooft, Kogut and Susskind. The classical electric flux-tube solution is analyzed quantitatively. 相似文献
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Temperature-dependent dielectric properties of Au/Si_3N_4/n-Si (metal insulator semiconductor) structures 下载免费PDF全文
The dielectric properties of Au/Si3N4/n-Si(MIS)structures are studied using the admittance measurements(C–V and G/ω–V)each as a function of temperature in a range from 80 K to 400 K for two frequencies(100 kHz and 1 MHz).Experimental results show that both the dielectric constant(ε)and the dielectric loss(ε)increase with temperature increasing and decrease with frequency increasing.The measurements also show that the ac conductivity(σac)increases with temperature and frequency increasing.The lnσacversus 1000/T plot shows two linear regions with different slopes which correspond to low(120 K–240 K)and high(280 K–400 K)temperature ranges for the two frequencies.It is found that activation energy increases with frequency and temperature increasing. 相似文献
19.
A.Y. PerelmanN.V. Voshchinnikov 《Journal of Quantitative Spectroscopy & Radiative Transfer》2002,72(5):607-621
The range of the applicability of the soft particles approximation (S-approximation) has been extended by means of the procedure which may be considered as a specific form of the analytic continuation. The initial element is represented by the standard version of the approximation while the branch of the continuation should be chosen in correspondence with the short wavelength asymptotic of the optical characteristic under consideration. As for the extinction efficiency of dielectric spherical particles, the improved version of the S-approximation fairly well describes the behaviour of Mie curves for particles with the refractive indices up to 2.0 or more and may be useful in order to get in the analytical form the “smoothed” Mie curves when the ripple-type fluctuations were averaged. The leading role of the van de Hulst approximation both for the electric and magnetic components of the extinction efficiency has been shown. 相似文献
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Broadband dielectric measurements for 60, 70, and 80 wt% ethyleneglycol-water mixtures were performed in the frequency range of 0.1 mHz–30 GHz and in the temperature range of 140.5 K–298.0 K. In the lower temperature range for mixtures of 60 and 70 wt%, separation of the β-process from -process occurred. The glass transition temperature depended on the water content for the -process but fragility did not. The peak frequency of the β-process depended on the water content. The β-process exhibiting larger activation energy at the lower frequency was caused by the large cooperative rearranging region constructed by strongly interacting molecules through hydrogen-bond. 相似文献