Preparation of Ni-B Coating on Carbonyl Iron and Its Microwave Absorption Properties in the X Band

Ni-B coated carbonyl iron particles （CI@Ni-B） are prepared by the electroless plating technique. The structure, morphology, and antioxidant properties of the CI@Ni-B particles are analyzed. The results demonstrate that the CI particles have been coated with intact spherical-shell Ni-B coating, indicating the core-shell structure of CI@Ni-B particles, and the Ni-B coating can prevent the further oxidation of the CI particles. Compared with the raw CI particles/paraffin coatings with the same coating thickness of 2.0mm and particles content of 70%, the CI@Ni-B particles/paraffin coatings possess higher microwave absorption （the RL exceeding -10 dB is obtained in the whole X band （8.2-12.4GHz） with minimal RL of -3f.OdB at 9.2GHz）.     

A Study of Magnetic Crystallographic Anisotropy of Substituted Hexaferrites by the Method of Ferromagnetic Resonance

Russian Physics Journal -     

Dielectric-Based Electromagnetically Induced Transparency Metamaterial in the Microwave Band

An electromagnetically induced transparency metamaterial (EITM) based on dielectric resonators is presented in this paper, which consists of a cut wire (CW) and ten dielectric columns. Destructive interference between the CW, which is a branch of the microstrip line, and the dielectric resonators causes the EIT phenomenon. The simulation results show that the dielectric-based EITM designed can obtain a transmission peak of 0.938 at 2.17 GHz, and the two-oscillator model is utilized to verify the effectiveness of the structure. In addition, samples of the dielectric-based EITM are also fabricated and the effectiveness of the metamaterial is experimentally verified. The proposed metamaterial has several advantages, including high efficiency, low loss, a simple structure, and ease of manufacture, which has good prospects for application in the fields of electromagnetic switches, sensors, and nonlinear metamaterials.     

微波段左手材料光子晶体带隙特性研究

利用电磁理论和传输矩阵法仿真得到了在0.3~6.935GHz微波波段具有负折射率的左手材料,并分别对右手材料和左手材料构成的光子晶体带隙特点进行了分析.结果表明:右手材料光子晶体结构的带隙对周期数变化不敏感,而对层厚度比、入射角度变化敏感;左手材料光子晶体带隙随层厚度比的增大,带隙位置出现蓝移,随着入射角度的增大,TM波主带隙的上带边会出现红移,而TE波带隙特性对入射角度变化不敏感.研究结果对微波技术中全方位反射器等器件的设计有一定的参考意义.     

Modeling the Insertion Losses of Dielectric Resonators in Microwave Filter Designs

Modeling the insertion losses of microwave filters with dielectric resonators is based on calculating forced oscillations of polarization currents (their amplitudes and phases in the range frequencies) for different designs of microwave filters (e.g., stop-band and pass-band). Knowing the distribution of insertion losses in individual sections of a filter allows us to determine the transfer of heat by dielectric resonators in a vacuum or otherwise.     

Radiation Losses of the Relativistic Charge Moving Near a Dielectric Radiator

Russian Physics Journal - The radiation losses of a relativistic charge moving in vacuum near a dielectric radiator in which Vavilov – Cherenkov radiation is generated are estimated. For a...     

Microwave Instability in the USSR Synchrotron Radiation Source under Design

Physics of Atomic Nuclei - Investigation of instabilities that emerge in the interaction of a charged-particle beam with elements of the chamber of state-of-the-art synchrotron radiation sources...     

目标红外波段辐射亮度差通用计算方法

在采用NETD计算红外热像仪的探测距离时,需要计算目标在热像仪探测波段范围内的辐射亮度差.提出了一种红外波段目标的辐射亮度差通用计算方法,可提高利用NETD计算热像仪作用距离的准确度.     

On the Effect of Anomalous Photoabsorption in Parametric X Radiation

The parametric X radiation of relativistic electrons passing through a monocrystal is considered. It is demonstrated that, contrary to widespread opinion, conditions for the effect of anomalous photoabsorption to show up can be realized in the Laue scattering geometry. It is expected that the predicted effect will increase the spectral-angular density of the radiation several times.     

Antireflection Coating of a Dielectric Plate in the Microwave Band Using Surface Machining

Radiophysics and Quantum Electronics - We present the experimental results of measuring the reflection coefficient of a microwave output window made of radiation-modified fluoroplast...     

微波矩孔衍射仿真与实验

从基尔霍夫标量式出发,在振幅零级近似和相位一级近似条件下,由Mathematica仿真计算获得微波经不同尺寸矩孔的衍射分布,并在微波光学实验仪上进行实验验证,获得了从夫琅禾费衍射向菲涅尔衍射转化的衍射花样,实验与仿真结果较为吻合。     

Effects of Neutral and Anionic Substituents on the Carbonyl Stretching Band of Substituted Benzophenones

Satisfactory correlations were found of the frequencies of the title band (ν_CO) with 6⁺ and other substituent constants. The correlations proved valid for benzophenones with both neutral and anionic substituents (more than 100 compounds). The integrated intensities of the ν_CO bands (A^1/2 _CO) did not correlate with any type of substituent constants; the decrease in A_CO in the cases of benzophenones with strong electron-releasing substituents was ascribed to a resonance-induced intensity borrowing from ν_CO BY THE aromatic skeletal bands (8-type). This statement wa confirmed by IR data few deuterated benzophenones.     

Parametric X Radiation from Electrons in Mosaic Crystals

A simple model for calculating the contribution of diffraction of actual photons to the measured spectrum of parametric x radiation (PXR) from relativistic electrons in mosaic crystals is suggested. It is shown that the diffraction of real photons of bremsstrahlung and transition radiation in mosaic crystals whose thickness t is about 0.01 of the radiation length makes a significant contribution to the measurable emission spectrum. The spectra and angular distributions of PXR from electrons with energies 500 and 900 MeV have been measured in mosaic pyrolytic graphite crystals. It is demonstrated that with consideration of diffraction of actual photons in the mosaic crystal, including diffraction of PXR photons, all experimental data presently available agree well with the results of calculations for the suggested model.     

Phase Transformations in Iron Oxide under the Action of Microwave Radiation

Technical Physics - It has been shown that microwave radiation induces structural and, as a consequence, magnetic phase transformations in iron oxide α-Fe2O3 (hematite). After microwave...     

Thermal Effects of Microwave Energy in Agricultural Soil Radiation

The thermal treatment by millimeter waves for the soil disinfection can be one possible alternative to chemical treatments. This physical method is based on incrementing the soil temperature and its pathogens irradiating with high frequency electromagnetic waves. So the previous knowledge of the temperature distribution in the irradiated soil is essential for achieving an effective bad microorganism and weed seeds elimination. This report analyse the heating kinetic and spatial distribution of the maximum temperatures reached by the soil. It is presented a mathematic model about how are distributed the reached temperatures in the depth of the irradiated soil. This model concludes that when an orchard soil is irradiated superficially by microwaves, the microwaves have a big attenuation due to the soil dielectric properties and the water located in the pores of the most superficial layer. This fact causes a shield effect blocking the waves penetration in few centimetres. The heating by radiation is reduced to the superficial layer. The heating propagation in the depth is occurred by conduction following the Fourier equations.     

紫外波段大口径积分球辐射源研制

为了满足航天载荷对大口径、高亮度紫外积分球辐射源的定标需求,采用全新工艺研制了内径为2200 mm、出光口径为800 mm且采用全压制聚四氟乙烯(PTFE)涂层的大型积分球辐射源,聚四氟乙烯涂层厚度为25 mm.积分球内置10 kW卤钨灯光源并外置两台带有电动光阑的总功率为14 kW的氙灯光源,可实现4个量级的大动态范...     

Study of the Nonlinear Response of Superconductors in the Microwave Band Using a Local Technique

Using a local technique, we study the microwave radiation power P₃(T,P,H_dc) at the triple frequency of the main signal as a function of the temperature T, the input power P, and the external magnetic field H_dc perpendicular to the superconductor surface for YBa₂Cu₃O₇ (YBCO) films, monocrystals, and polycrystals and for Nb films. The most distinctive feature of the temperature dependence P₃(T) of nonlinear response of superconductors is a maximum of the nonlinearity near the critical temperature T_c. Spatial distributions of the third-harmonic power are obtained for YBCO films at various temperatures. These distributions are indicative of a nonuniform distribution of T_c over the superconductor surface. Additional nonlinearity maxima are discovered in the dependence P₃(T) for YBCO films and monocrystals at temperatures about 2T_c/3. These maxima are probably related to the existence of several superconducting phases with different critical temperatures. For Nb films, the second nonlinearity maximum in the dependence P₃(T) appears only in the presence of an external magnetic field. The experimental data are interpreted within the framework of a two-fluid model of a superconductor, which takes into account the phenomenological nonlinear relationship between the vector potential A and the supercurrent j_s(A). The origin of nonlinearity in the studied superconductors is discussed.     

Investigation of the Radiation Mechanism of Microwave Excited Cluster Lamps

Experimental and theoretical investigations towards a better understanding of the radiation mechanisms in WO₂Br₂-discharges, so-called “cluster lamps” are presented. The main purpose of the investigation is to find out whether a major part of the continuum emitted from these discharges, which in the past has been interpreted as thermal cluster radiation, could also originate from molecular band radiation, in particular from triatomic molecules in colder discharge regions. Comparing emission spectra of WO₂Br₂-discharges from different plasma regions, using lamps operated at different vapor pressures and power levels (i.e. non-LTE and LTE-discharges), we conclude that by far the major part of the strong continuum radiation emitted from WO₂Br₂ lamps is indeed thermal radiation of hot tungsten cluster particles. WO— (below 550 nm) and WO₂-molecular radiation (above 650 nm), which is superimposed on the cluster continuum, also contribute to the total radiation output, but to a lesser degree. A crude model for WO₂ molecular emission is presented. Unfortunately, the WO₂ emission component greatly impedes proper fitting of the measured cluster continuum to a thermal cluster model.