Radiation of a charge moving in a waveguide with a resonantly dispersive dielectric layer

The radiation of an ultrarelativistic point charged particle moving along the axis of a cylindrical waveguide containing a layer of resonantly dispersive dielectric medium is studied theoretically. It is shown that, in the case of a sufficiently thin waveguide, the dispersion leads to a significant contraction of the radiation, a decrease in the energy of harmonics, and an increase in the relative contribution due to the first mode as compared to the higher harmonics. These effects are less pronounced in waveguides with relatively large radii; still, they have to be taken into account, especially in determining the frequencies of harmonics. The role of the resonance dispersion is most significant in cases where the dielectric layer thickness is small compared to the waveguide radius.     

Electrostatic charge distribution in the dielectric layer of alumina electrostatic chuck

Electrostatic charge and its distribution in the dielectric layer of TiO₂- and Cr₂O₃-added alumina electrostatic chucks has been studied. The electrostatic potential was evaluated at various applied voltages by an electrostatic potential meter and it demonstrated the existence of charges with opposite polarities. Direct SEM observation and toner development of the charged ceramic surface was carried out to clarify the charge distribution. The charge contrast was not uniform on the ceramic microstructure and the charge was distributed in the form of grains. Taking into consideration these results, the relationship between electrostatic charge distribution and ceramic microstructure is discussed.     

Modeling the instability of the boundary of a dielectric liquid with a free surface charge

We have numerically modeled the development of instability of the boundary of a nonviscous dielectric liquid with a free surface charge occurring in an external electric field and compared the behavior of this system in the two limiting cases, whereby the surface charge produces complete screening of the field above and below the surface. Although the linearized equations of motion in the two cases coincide, the scenarios of instability development are substantially different, which is indicative of the determining role of nonlinearity in this process.     

Longitudinal surface curvature effects on boundary layer of a micropolar fluid

Summary The effect of longitudinal surface curvature on steady two-dimensional incompressible laminar boundary layer of a micropolar fluid has been considered. Van Dyke's first oder perturbation analysis is applied to the full equations of motion derived in curvilinear coordinate system which facilitates to carry out boundary layer approximation for flow past a curved surface. This results into two systems of partial differential equations which are called the zeroth order and the first order boundary layer equations. The zeroth order equations are the usual boundary layer equations for a micropolar fluid. The first order equations take into account the longitudinal surface curvature effect explicitly. Similar solution of the governing equations exists if (i) the inviscid flow velocity on the surface varies linearly along the surface and (ii) the longitudinal surface curvature is constant. Numerical results are presented illustrating the dependence of the important flow quantities of both zeroth order and first order boundary layers on the micropolar fluid parameters. The results have been compared with the corresponding results for a Newtonian fluid. It has been found that the skin friction decreases and the wall couple stress increases for convex side of the surface and vice versa for the concave side.

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Einfluß der longitudinalen Oberflächenkrümmung auf die Grenzschicht einer mikropolaren Flüssigkeit

Zusammenfassung Der Einfluß einer longitudinalen Oberflächenkrümmung auf die stationäre, zweidimensionale, inkompressible, laminare Grenzschicht einer mikropolaren Flüssigkeit wird untersucht. Van Dyke's Strömungsanalyse erster Ordnung wird angewendet auf die Bewegungsgleichungen in krummlinigen Koordinaten, die einfach die Grenzschichtnäherung für die Strömung hinter einer gekrümmten Oberfläche aufzeigen. Dies führt zu zwei Systemen partieller Differentialgleichungen, die die Grenzschichtgleichungen nullter und erster Ordnung genannt werden. Die Gleichungen nullter Ordnung sind die üblichen Grenzschichtgleichungen für eine mikropolare Flüssigkeit. Die Gleichungen erster Ordnung berücksichtigen den Einfluß der longitudinalen Oberflächenkrümmung explizit. Ähnliche Lösungen der Grundgleichungen existieren wenn: (i) sich die reibungsfreie Strömungsgeschwindigkeit an der Oberfläche linear entlang der Oberfläche ändert und (ii) die longitudinale Oberflächenkrümmung konstant ist. Numerische Ergebnisse werden angegeben, um die Abhängigkeit der wichtigsten Strömungsgrößen der Grenzschicht nullter und erster Ordnung von den Parametern der mikropolaren Flüssigkeit aufzuzeigen. Die Ergebnisse werden verglichen mit den entsprechenden Ergebnissen für eine Newtonsche Flüssigkeit. Es wurde festgestellt, daß für eine konvexe Fläche die Wandreibung abnimmt und die gekoppelten Spannungen an der Wand zunehmen; das Umgekehrte gilt für eine konkave Fläche.

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With 2 Figures     

Interplay of surface effects in a thin nematic liquid crystal layer

Manifestations of the competition of surface effects in a thin nematic liquid crystal (LC) layer are considered. It is shown that the LC director field lines remain straight irrespective of the preferred anchoring angles at the LC boundary surfaces. The angle between the director field lines and the plane of the LC layer depends on these preferred anchoring angles and on the Rapini-Papoular energy ratio at the boundary surfaces. There are two possible director orientations differing by 90°. Switching between these states can be induced by chemical factors or by external fields. In contrast to the well-known Fréedericksz transition, the work required for such switching is partly performed by the competing surfaces. Hence, the LC layer switching only requires overcoming the difference between the Rapini-Papoular energies, which can be rendered small by properly selecting LC-substrate pairs.     

加载高介电薄层的宽带频率选择表面吸波材料设计与制备研究

设计仿真并实验验证了一种加载高介电薄层的宽带频率选择表面吸波材料,该吸波材料由FR4介质板、电阻损耗型频率选择表面、聚氨酯泡沫和金属背板组成。仿真结果表明,该吸波材料对入射电磁波在3.6~24GHz频段范围内具有90%以上的吸收效果,且具有极化无关和宽入射角的吸收特性。加载高介电薄层的频率选择表面吸波材料的相对带宽能够达到带宽极限的58.0%,较未加载高介电薄层的优化带宽增加了11.0%,证明了加载高介电薄层有利于从结构上改善材料的吸收带宽。同时,通过Smith圆图从阻抗匹配的角度进一步分析论证了加载高介电薄层有利于在更宽的频段范围内提升吸波材料与空气的阻抗匹配程度,从而实现宽带强吸收。该吸波材料电磁结构与夹层复合材料的力学结构非常类似,便于实现吸波与力学性能的兼容,具有一定的工程应用价值。     

Effect of the dielectric layer with photo-controllable surface relief on liquid crystal devices

We present experimental results for the dielectric layer effect on the electro-optical properties of liquid crystal (LC) devices together with numerical simulations. The photo-controllable polymer is used as a dielectric material on which the alignment agent of the LC is prepared. The surface relief structure can be induced on the dielectric polymer layer by photo-irradiation for fabricating LC microlens arrays or wide-viewing LC displays. It is found that the operation voltage of the LC device decreases with increasing the dielectric constant or with decreasing the layer thickness of the polymer. The experimental data agree well with theoretical results predicted from a simple dielectric model in the continuum theory.     

Behaviour of an edge dislocation in a semi-infinite solid with surface energy effects

The method of continuously distributed dislocations and the method of discrete distribution of dislocations have been used to determine the effect of surface energy on the surface boundary conditions of a semi-infinite solid containing an edge dislocation. The surface dislocation model which incorporates two surface dislocation arrays, the primary and the secondary, in order of importance, is used to study the effect of surface energy. The surface dislocation model in conjunction with the method of continuously distributed dislocations enables the exact determination of the dislocation distribution function of the primary and secondary dislocation arrays and the effect of surface energy tends to lower both the total Burgers vector associated with the surface arrays and dislocations in evaluating the effect of surface energy is illustrated and is compared with the method of continuously distributed dislocations. It has been found that the surface energy tends to lower both the total Burgers vector associated with the surface arrays and the length of the region within which they are spread on the surface. Although the effect on the primary surface arrays is not very large, the secondary surface arrays are completely eliminated with normal values of surface energy encountered in real solids. Thus, the effect of surface energy is to bring non-vanishing stress components to the surface. The surface is also non-uniformly stressed. The superiority of the surface dislocation model over the other methods hitherto used in the literature is illustrated.     

Supporting electrolyte and solvent effects on single-electron double layer capacitance charging of hexanethiolate-coated Au140 nanoparticles

Sequential injections of single electrons (or holes) into the cores of Au(140) hexanethiolate monolayer-protected clusters (MPCs) occur at measurably different electrochemical potentials owing to the extremely small (subattofarad) values of the single MPC capacitance (C(MPC)) of the nanoparticle. The potential increment for each sequential injection is DeltaV = e/C(MPC). The dependence of DeltaV on the concentration of supporting electrolyte (from 1 to 100 mM), measured using square wave voltammetry, is shown to be caused, primarily, by changes in the diffuse double layer component (C(DIFFUSE)) of C(MPC). The dependence of C(DIFFUSE) on r(core), the radius of the nanoparticle, is considered. Additionally, significant changes in the magnitude of the compact double layer component (C(COMPACT), equivalent to the Stern layer) of C(MPC) were induced by adding hydrophobic solvent components such as hexane or dodecane or by introducing hydrophobic electrolyte ions (tetrabutyl-, tetrahexyl-, and tetraoctylammonium, perchlorate, and tetraphenylborate). These changes are interpreted as specific solvation and ion penetration of the hexanethiolate monolayer. For brevity we will refer to these phenomena as solvation/penetration phenomena.     

A high-frequency discharge on a dielectric surface

Plasma generation from a high-frequency (HF) oscillator, operating in the frequency range from hundreds of kilohertz to hundreds of megahertz, is one of the most interesting and promising ways of plasma creation in gas flows. A feature of an HF oscillator is that it utilizes only a single electrode, which can be placed inside the body and have no direct contact with the medium. The surrounding medium including the elements of the setup acts as the second electrode.     

Influence of charge flow along a semiconductor surface on the nature of the multiplication coefficient in a silicon-wide-gap layer structure

It has been shown that the flow of mobile minority carriers along the semiconductor-wide-gap layer interface substantially influences the uniformity of the multiplication coefficient in an avalanche photodetector. Around inhomogeneities in the semiconductor substrate, a “dead zone” of fairly large area is formed, where the multiplication coefficient is several orders of magnitude lower than that on the remaining area of the device. Specific methods are proposed to improve the uniformity of the avalanche process in a semiconductor-wide-gap layer structure. Pis’ma Zh. Tekh. Fiz. 23, 72–76 (April 26, 1997)     

Effect of deformation on electrochemical properties of the double layer and surface charge of metals

Electrochemical measurements on plastically deformed metals revealed the previously predicted [1] deformation-induced shifts toward positive surface charge values and clarified the character of the intensification of the electrochemical heterogeneity of deformed metal surfaces (localization of activated anodes as a result of mechanochemical phenomena). The deformation-induced increase in the differential capacitance of the double layer is attributable to an increase in the intensity of physical (electrostatic) adsorption of SO ₄ ^2– and HSO ₄ ^– HSO ₄ ^– anions on a positively charged surface in sulfuric acid solutions. A necessary (but not always sufficient) condition of the effectiveness of cation-active inhibitors of corrosion of plastically deformed metals is their stable chemisorption at potentials in the range of deformation-induced changes in the surface charge (of the order of tenths of a volt on the -scale).     

EDLC电容和电极活性炭孔型及其表面积之间的关系

研究了商用活性炭作为电极的双电层电容器在水系和有机系电解液中的电容和活性炭孔结构的关系.水系电解液采用1 mol/L的H2SO4溶液、有机系电解液采用1 mol/L的TEMA/PC溶液.结果表明:水系和有机系电解液中的电容存在线性关系.电容由活性炭微孔表面和其他大孔构成的表面两部分提供(分别称为Cmicro和Cext).其中Cmicro较小并对电流有依赖性、而Cext近似为一个常数、不随电流改变.     

Absorption of electromagnetic radiation in a polar dielectric layer

Conditions are investigated for initiation of nonreflecting absorption of electromagnetic radiation in a polar dielectric layer applied to a reflecting metal substrate.     

Influence of surface effects in vapor condensation on a nanodimensional aerosol particle having an electric charge

The influence of surface phenomena and size effects on vapor condensation on a charged aerosol particle is considered. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 1, pp. 54–59, January–February, 2007.     

Near-field optical properties and surface plasmon effects generated by a dielectric hole in a silver-shell nanocylinder pair

Near-field optical properties and surface plasmon effects in a silver-shell nanocylinder pair with five different dielectric holes (DHs) that interact with a transverse magnetic mode incident plane wave are simulated by use of the finite-element method, which includes the investigation of particle-particle interaction. The proposed structure exhibits a redshifted localized surface plasmon that can be tuned over an extended wavelength range by varying the dielectric constant in DHs and the thickness of the nanocylinder silver shell. The increase in the near-field intensity is attributed to a larger effective size of DH that is filled with a higher refractive medium.     

基于镜像法提取多层介质中3D电容参数的研究

提出了一种适用于任意多层电介质分层结构中的3D互连电容参数提取的新方法--反射镜像法.该方法无需对格林函数进行推导,而是根据自由电荷反射原理计算反射镜像的位置和镜像电荷系数从而获得各级镜像分布,继而计算任意多层电介质环境下的3D电容,包括底层或顶层介质接地情况下的3D电容.该方法可克服级数形式的格林函数因受限于电介质分层数目而难以适应大规模集成电路中复杂多变电介质环境下的3D电容参数提取问题.通过对导体面元建立层次式数据结构,这一方法可以利用层次式算法(hierarchical method)实现计算加速.实验证明,该方法能在保证可靠精度的情况下达到迅速收敛,与层次式加速算法结合后,计算效率可达到FastCap法的数倍.     

Edge dislocation in a surface layer

The paper treats an edge dislocation in a layer that adheres to a substrate. The elastic fields are constructed using a Fourier exponential transform, and the behavior of the dislocation is discussed on basis of the Peach-Kochler force.     

Light propagation in a planar dielectric waveguide with a gyrotropic layer

The nature of the magneto-optic Kerr effect in a planar dielectric waveguide geometry has been investigated by calculation of the Jones matrix for a planar waveguide structure with a gyrotropic magnetic material as one wall. The intensity of the component of the field that is in the polarization state orthogonal to the input was calculated as a function of length of the gyrotropic material and input polarization state. The degree of polarization rotation depends on the relative orientation of the magnetization in the magnetic material and the direction of propagation. It is found that there exists an optimal waveguide length and input polarization at which the output signal is maximized and that a significant enhancement in polarization rotation is available with respect to free-space reflection. These results indicate that a magnetic-film-bounded planar waveguide can be used for device applications such as magnetic field sensors or magneto-optic modulators.     

Evidence of surface charge effects in T-branch nanojunctions using microsecond-pulse testing

The understanding of the influence of surface charge effects on the electrical properties of nanostructures is a key aspect for the forthcoming generations of electronic devices. In this paper, by using an ultrafast electrical pulse characterization technique, we report on the room-temperature time response of a T-branch nanojunction which allows us to identify the signature of surface states. Different pulse widths from 500 ns to 100 μs were applied to the device. For a given pulse width, the stem voltage is measured and compared with the DC result. The output value in the stem is found to depend on the pulse width and to be related to the characteristic charging time of the interface states. As expected, the results show that the well-known nonlinear response of T-branch junctions is more pronounced for long pulses, beyond such a characteristic time.