Absorption of electromagnetic radiation by an inhomogeneous cylindrical particle

The cross section for the electromagnetic radiation absorption by an inhomogeneous cylindrical particle has been calculated for an arbitrary ratio of the dielectric core radius to the particle radius. The boundary conditions correspond to the diffuse reflection of electrons from the internal and external surfaces of the metal layer. Limiting cases are considered, and the results of analysis are discussed.     

Generation of electromagnetic waves by a rotating cylindrical electron layer

Generation of electromagnetic waves by electrons orbiting in crossed radial electrostatic and axial magnetic fields was studied. Frequencies and increments of the generated waves were calculated. The wave increments increase with the frequency for sufficiently large values of the radial electrostatic field strength. Strong radial electrostatic fields may considerably magnify the frequencies of waves generated in the systems.     

Scattering of electromagnetic radiation by a metal nanoparticle

The scattering cross section of electromagnetic radiation by a small spherical metal particle has been calculated in the framework of the standard kinetic theory in a dipole approximation. The calculation has been performed for relatively small (～10 nm) particles, which allows the skin effect to be ignored. A mechanism of mixed specular-diffuse reflection of conduction electrons from the particle surface is considered. It is established that, at certain angles of scattering, the mechanism of magnetic-dipole scattering becomes dominating. The influence of kinetic effects on the differential scattering cross section is analyzed.     

Nonlinear effects in media heated by electromagnetic radiation

The features of thermal processes in dielectric absorbing media heated by high-frequency electromagnetic radiation are investigated. It is shown that the temperature dependence of the absorption coefficient of the electromagnetic radiation can result in the development of nonlinear effects: progressive heating in a regime with peaking and localization of the heating region, heating in a regime of lightening of the medium, and formation of quasistationary temperature waves. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 4, pp. 832–838, July–August, 2000.     

Focusing of electromagnetic radiation by hyperboloidal and ellipsoidal lenses

A solution to the problem of plane electromagnetic waves focused by an ellipsoidal or a hyperboloidal lens is derived from the Stratton-Chu integral by solving a boundary-value problem. The current method is more rigorous than those hitherto published in the literature. Results show that for linearly polarized incident illumination and in the vicinity of the focus, the distribution of the time-averaged electric energy density is almost fully transverse electric.     

Size-controlled synthesis of dendrimer-protected gold nanoparticles by microwave radiation

Well-stable dendrimer-protected gold nanoparticles were synthesized by microwave radiation of a third-generation poly(propyleneimine) dendrimer (PPI G3)–HAuCl₄ aqueous solution without the additional step of introducing other reducing agents and protective agents. The size of these gold nanoparticles thus formed can be controlled by molar ratio of dendrimer to gold.     

Removal of ammonia nitrogen in wastewater by microwave radiation

Ammonia nitrogen contaminated wastewater has posed great threat on the safety of water resources. In this study, a novel process, microwave (MW) radiation, was developed for the removal of ammonia nitrogen from wastewater. The effects of pH, radiation time, aeration and initial ammonia concentration on the removal were investigated. pH and radiation time showed significant influence on the removal of ammonia nitrogen. The largest removal was obtained at pH 11 in 3 min. Initial ammonia concentration and aeration had minute influence. The mechanism of ammonia removal was proposed as the formation of molecular ammonia (NH(3)) and the subsequent evaporation of NH(3) by MW radiation. Compared with conventional heating (CH) mode, MW radiation led to higher ammonia removal. Both thermal and non-thermal effects were responsible for the removal, but the contribution of thermal effect was more significant. In the end, coke-plant wastewater containing high concentration of ammonia nitrogen was treated by MW radiation. With the initial ammonia concentration of 5000 mg/L at pH 11, ammonia was reduced to 350 mg/L at 750 W by 10 min MW radiation. It could be proposed that MW radiation was an effective method for the removal of ammonia nitrogen from wastewater.     

Measurement method of the refractive index of biotissue by total internal reflection

A simple method based on total internal reflection is presented for measuring the refractive index of biological tissue. Anarrow laser beam and a semicylindrical lens in contact with a tissue specimen are used in the experimental apparatus. The dependence of the internal reflectivity on the angle of incidence is measured to determine the critical angle and therefore the refractive index of tissue. The experimental results for several tissue samples show that the method is reliable and useful for studying tissue optics. The principal advantages of the method are its elimination of scattering effects, suitability to a small in vitro sample, and excellent accuracy.     

Solid-state chemical reactions initiated by optical and microwave radiation

It is experimentally demonstrated that the simultaneous exposure of dielectric powders and mixtures to optical and microwave radiation pulses can lead to the development of chemical reactions. This phenomenon is explained by the light-induced absorption of microwave radiation in the dielectric powder, which leads to heating of the mixture and the initiation of a chemical reaction that can subsequently proceed at the expense of the intrinsic heat evolution.     

Two-layer nonreflective absorber of electromagnetic radiation

Conditions for reflectionless quenching of electromagnetic radiation in the layer of absorbing dielectric applied to a nonabsorptive quarter-wave substrate have been found. These conditions as functions of the layer thickness and the dielectric properties of the coating and the substrate are investigated.     

Scattering of electromagnetic radiation by multilayered spheroidal particles: recursive procedure

A formalism is developed for the calculation of the electromagnetic field scattered by a multilayered spheroidal particle. The suggested formalism utilizes the recursive approach with respect to passing from one layer to the next; thus it does not require an increase in the size of the equation matrices involved as the number of layers increases. The equations operate with matrices of the same size as for a homogeneous spheroid. The special cases of extremely prolate and weakly prolate spheroids are considered in more detail. It is shown that in such cases one can avoid the matrix calculations by instead using the iterative scalar calculations.     

Optical emission patterns and microwave field distributions in a cylindrical microwave plasma source

A cylindrical high density (10¹² cm⁻³) large volume (32 cm in diameter and 50 cm in length) homogeneous argon plasma has been produced by a microwave with a frequency of 2.45 GHz and a power of 900 W without a magnetic field. The plasma source is based on a ring shaped rectangular waveguide with eight equally spaced slots in its inside wall. Several optical emission patterns are observed on different conditions and the microwave field is measured by a movable antenna, which showed a clear relationship between the optical emission patterns and the electron field distributions. A mode transition, from a TE_8j mode to a TE_16j mode, occurs when the gas pressure increases from 660 to 1000 Pa. And there is an optical emission pattern when the microwave power decreases from 900 to 300 W. All these phenomena are described in detail and analyzed according to the interactional theory of electrons in plasma with microwave.     

Spectroscopy and microscopy of spin-sensitive rectification current induced by microwave radiation

Amplitude-modulated microwave radiation was applied to the junction of a scanning tunneling microscope (STM). Rectification in the tunneling current was induced by the microwave because of the nonlinearity of the junction. It is shown that this rectification current is proportional to the d(2)I/dV(2) signal and exhibits spin-sensitivity. The magnetic domain at the apex of an iron-coated tip was manipulated by applying an external magnetic field. The moment of spin flip and the magnetic hysteresis were measured by changes in the spin-dependent current through the Cr(001) surface.     

纳米银/PAMPS复合材料的微波合成及表征

在不加还原剂的条件下,采用微波辐射双原位聚合方法合成了纳米银/2-丙烯酰胺基-2-甲基丙磺酸均聚物(PAMPS)复合材料,并通过UV-Vis、XRD、FTIR、TEM、XPS和TG分析方法对其进行分析和表征。结果表明:纳米银粒子具有面心立方结构,且均匀地分散在聚合物基体中;微波辐射时间不影响纳米银粒子的形态;纳米银与基体PAMPS中的氮原子和羰基氧原子存在相互作用,降低了基体PAMPS的热稳定性。     

圆波导界面电磁场的传播特性

从麦克斯韦方程及边界条件出发对含有两种不同介质的金属波导管进行了研究 ,得到特征方程 (γ1ε2 -γ2 ε1) 2 (μ1γ2 -μ2 γ1) 2 =0 ,指出当γ1ε2 =γ2 ε1,μ1γ2 ≠μ2 γ1时两区域波导模为横磁模 ,γ1ε2 ≠γ1ε2 ,μ1γ2 =μ2 γ1为横电模 ,γ1ε2 =γ2 ε1,μ1γ2 =μ2 γ1为杂交模 .并讨论了截止条件和传播特性 .     

Low-loss electromagnetic composites for RF and microwave applications

Low-loss electromagnetic composites with high permittivity and permeability will benefit the miniaturization and multifunctional of RF devices. A kind of low-loss dielectric-magnetic ceramic-ceramic composite was developed by hybrid processing technology with the goal of integrating the dielectric properties and magnetic properties. The hybrid processing technology exhibits the advantage of lowered sintering temperatures for the composites while retaining good microstructure and high performance. By introducing elastomer as matrix, a kind of flexible low-loss dielectric-magnetic ceramic-polymer composite was prepared and studied. The obtained flexible dielectric-magnetic ceramic-polymer composite exhibited low loss and good mechanical properties. The results show good effects on lowering the dielectric loss and extending the cut-off magnetic frequency of the electromagnetic composite. Methods for tailoring the properties of the multifunctional composites were proposed and discussed.     

钢筋混凝土圆柱壳声辐射特性的有限元研究

空气中两端简支支撑的钢筋混凝土加肋壳体的声辐射问题,由于加强钢筋及环肋的作用增加了系统共振频谱的复杂性,用解析的方法解决此类问题存在困难。利用有限元软件ANSYS,分析了内部空气及环肋数量对壳体声辐射特性的影响。计算结果表明,在低频情况下,内部空气对壳体的声辐射特性影响不大,采取合理的加肋措施可降低结构的辐射声压级。