基于毫米波辐射特性的水面植被检测方法

针对采用3mm波段辐射计对水面植被辐射特性进行检测的问题,在研究分析了水面的亮度温度和水面植被的介电特性的基础上,采用相干法建立了水面植被辐射特性的多层介质模型,与3层介质模型相比,仿真结果与实验数据更加吻合,表明多层介质模型能更精确地模拟水面植被的辐射特性。通过实验得出,在不同的入射角下,水面植被亮温相比水面亮温均有上升,说明水面相比植被具有亮温低、冷目标的毫米波辐射特征,可利用毫米波辐射特性监测区域内水面植被。     

周期性梯度折射率多层膜的软X射线反射率

由于界面互扩散的存在，实际的超薄多层膜很难具有清晰的界面结构.假设超薄多层膜为具有周期性梯度折射率的多层膜结构，用直线模型和余弦模型模拟了周期性梯度折射率多层膜的软X射线反射率.结果证明，折射率余弦渐变的多层膜虽然不具有清晰的界面，但它同样具有很高的反射率.     

多层绝热材料规模化干燥处理时温度场的测试与分析

对大批量处理多层绝热材料的大型专用干燥箱满负荷运行时工作区域的温度场进行测试,通过温度分布和温度场均匀性的分析,得出了最高温度发生点的位置与成因以及影响温度场均匀性的主要因素,并对温度的控制方法、多层材料的布置方案和干燥设备的改进提出了建议。     

Confinement in a planar waveguide with porous silicon omnidirectional mirrors as confining walls

We present the design and study of waveguide structures based on porous silicon where the light confinement is not due to the usual total reflection effect but to the use of photonic crystals (PCs) as confining walls. These PC are omnidirectional mirrors (OMs), consisting of the periodic repetition of two porous silicon layers with different refractive indices and thicknesses. They reflect the radiation for all angles of incidence within a frequency range called the omnidirectional band gap (OBG). We have followed the PC formalism to investigate the properties of the OM as a multimode waveguide: the number of modes within the band gap, their field spatial distribution and their confinement as a function of the frequency and the core thickness.     

UV protection filters by dielectric multilayer thin films on Glass BK-7 and Infrasil 301

The increasing use of Ultraviolet (UV) light in medicine, industrial environments, for cosmetic use, and even in consumer products necessitates that greater attention be paid to the potential hazards of this type of electromagnetic radiation. To avoid any adverse effects of exposure to this type of radiation, four suitable protection filters were produced to block three UV bands (UVA, UVB, and UVC). The design structure of the required dielectric multilayer filters was done by optical thin film technology using the absorbing property of UV radiation for the substrates and dielectric materials. The computer analyses of the multilayer filter formulas were prepared using Macleod Software for the production processes. The deposition technique was achieved on optical substrates (Glass BK-7 and Infrasil 301) by dielectric material combinations including Titanium dioxide (Ti₂O₃), Hafnium dioxide (HfO₂), and Lima (mixture of oxides SiO₂/Al₂O₃); deposition being achieved using an electron beam gun. The output results of the theoretical and experimental transmittance values for spectral band from 200 nm to 800 nm were discussed in four processes. To analyze the suitability for use in ‘real world’ applications, the test pieces were subjected to the durability tests (adhesion, abrasion resistance, and humidity) according to Military Standard MIL-C-675C and MIL-C-48497A.     

Nonlinear convective flows in multilayer fluid system

The nonlinear thermocapillary and buoyant-thermocapillary flows in a three-layer system, filling a closed cavity and subjected to a temperature gradient directed along the interfaces, are investigated. The nonlinear simulations of convective regimes are performed by the finite-difference method. The process of transition of unicell structures into multicell structures is studied.     

Rheological study of multilayer functionalized polymers: characterization of interdiffusion and reaction at polymer/polymer interface

Rheological behavior in molten state of multilayered polymers was investigated by dynamic mechanical measurements. The competition between polymer/polymer interdiffusion and interfacial reaction of functionalized polymers in a sandwich structure was followed by oscillatory mode under small amplitudes of deformation. The systems chosen for study were polyethylene (PE) grafted with glycidyl methacrylate/polyamide (PA) 6 as a reactive system and PE/PA6 as nonreactive one. Moreover, the interphase thickness was estimated by using thermodynamical models. Experimental results of bilayer systems were compared to existing models of multiphase systems. An expression of storage modulus as a function of welding time was also suggested. Thus, the fit between this one and the experimental data was satisfactory with the different appearing phenomena.     

Network analysis of eigenvalue problem for multilayer dielectric waveguide consisting of arbitrary number of layers

In this paper, the eigenvalue problem of a multilayer dielectric waveguide consisting of arbitrary number of layers is solved by the microwave network method. A general program with the function of computer graphics has been developed for analyzing the dispersion characteristics and the electromagnetic field distributions of an N layer dielectric waveguide. As examples of practical applications of the program, first, the dispersions and field patterns for the planar waveguides with refractive index of parabolic and exponential profiles are analyzed. Secondly, the procedure of mode conversion and mode separation in dielectric branching waveguides is vividly demonstrated through analyzing the field distributions of asymmetric multilayer dielectric structures and the general rules of mode conversion are discussed. The examples show that the present method possesses the advantages of versatility, rapidity, simplicity and accuracy.     

Photoacoustic measurement of thermal properties and thickness of buried layers in a multilayer film

The photoacoustic model of multilayer with a strong-absorbing surface layer is developed. The phase of ph0toacoustie signal is measured as a function of modulated frequency using apparatus totally controlled by a computer system. The thermal diffusivity, effusivity as well as thickness of several buried layers are obtained independently through the best fit of experimental data according to the theoretical model. The multilayers of thin metal and alloy film are investigated. This method is proved to be valuable particularly in nondestructive examination of subsurface physical properties.     

Radiative emission properties of a-SiN : H based nanometric multilayers for light emitting devices

Optical and photoluminescence characterizations were performed on nanometric multilayer structures based on amorphous silicon nitrogen alloys. Evidences are shown that the radiative efficiency of multilayers increases with respect to single-layer structures. This is ascribed to a strong electron–hole pair localization and a low heterointerfaces defect density. Time-resolved photoluminescence measurements yield fast recombination with an energy-dependent lifetime due to hopping processes. Finally, the performance of an electroluminescent device based on multilayers is presented.