一种基于负折射电路的宽带圆极化微带天线

 文章基于负折射电路原理,提出利用集总电容、电感加载构造得到宽带90度功分移相器,并提出了利用该功分移相器结合翻转容性馈电结构来拓展宽微带天线的阻抗带宽和轴比带宽的方法.设计并制作了工作频率为1.375GHz、轴比小于3dB的相对带宽为52.37%、在此频带内驻波比小于2的天线.     

双光楔可控扫描一维轨迹分析

根据几何光学和光的标量衍射理论,对双光楔的折射特性进行了数学分析.研究发现,以相反旋向相同转速旋转的双光楔对光的折射作用等效于一个折射角随2个光楔转角变化的单光楔.在此基础上,对通过双光楔的光束在像面上的衍射光场分布作了理论分析,得到了在夫琅禾费衍射下,光束经转动双光楔在像平面上的衍射光斑随时间变化的规律,从而为一维扫描的可控操作提供了理论指导.     

光学雷达大气折射误差修正方法研究

光学雷达是靶场试验外弹道测量系统中的主要设备之一.由于大气对光波传播引起的折射效应,使得光学雷达测量中产生折射误差.针对靶场常用的光学雷达系统,根据光波射线在大气中的运行轨迹,利用逐次逼近法得到了实用的光学雷达大气折射误差修正方法.通过对某靶场的实际测量数据检验,证实了该方法的适用性和有效性.目前,该方法已成功地应用于试验靶场,满足了靶场试验的精度要求.     

大气折射引起的雷达定位误差模型

大气折射引起的雷达定位误差是限制雷达精度进一步提高的关键因素之一.针对目前只给出雷达测量参数的折射误差,不能明显给出实际应用中所需要的目标位置偏移误差现状.通过采用我国大气折射率的统计模型和目前公认的高精度的电波折射误差修正方法一射线描迹法,对大气折射引起的雷达定位误差进行了目标位置偏离的计算和拟合,建立了大气折射引起雷达测量目标的位置偏移误差模型,从而为雷达实际使用和精度评估奠定基础.     

光影舞曲

光是构成宇宙的基本要素之一。从古典主义至文艺复兴,再到现代建筑,光影变幻与夸张的效果给建筑空间带来了令人叹为观止的精神力量,建筑师们不断采用不同的手法让光更随意地参与到建筑空间中,成为构筑空间与实体的特殊“材质”。本文从理论和实践两方面,对光影进行重新解读。     

海上搜救雷达应答器天线架设高度的研究

研究了多径和海面大气折射这两种环境因素对雷达搜索应答器最远距离的影响,使用PE方程计算了不同蒸发波导高度条件下导航雷达和应答器发射信号的传播衰减,通过对计算结果分析和解释,结合东海试验的实测数据,得出应答器天线高度的最佳选择。     

凝胶色谱法测定负载化硅胶的相对分子质量

目的建立测定负载化硅胶的相对分子质量的凝胶色谱法。方法使用凝胶色谱法测定负载化硅胶的相对分子质量,选取已知不同分子量的聚乙二醇高聚物作为标准品,对检测结果进行标准曲线拟合,得到最佳拟合标曲,采用Shoedex SB-802 HQ凝胶色谱柱分离,示差折光检测器检测,测得准确负载化硅胶的相对分子质量。结果使用本方法测得未知负载化硅胶样品相对分子量为6.326×103,相对标准偏差(relative standard deviation, RSD)为1.45%。结论该方法简单、可靠,可用于测定负载化硅胶的相对分子质量。     

Reflection and refraction of incident p-, T-, and SV-waves at interface between magnetized two solid-liquid media with heat sources and initial stress with and without thermal relaxation times

We investigate the problem of reflection and refraction of thermoelastic waves at a magnetized solid-liquid interface in presence of initial stress. In the context of Green-Lindsay and coupled thermoelastic theories of thermoelasticity, the problem has been solved and the effect of magnetic field, external heat sources, and initial stress on p-, T-, and SV-waves propagation have been discussed. The boundary conditions at the interface for displacement continuity, vanishing the tangential displacement, continuity of normal force, tangential force, and continuity of temperature are applied. The amplitudes ratios for the incident p-, T-, and SV-waves have been obtained. The effect of the initial stress, heat sources, and magnetic field on the reflection and transmitted coefficients for the incident waves have been discussed.     

The correlation between porosity characteristics and the crystallographic texture in extruded stabilized aluminium titanate for diesel particulate filter applications

Porous ceramic diesel particulate filters (DPFs) are extruded products that possess macroscopic anisotropic mechanical and thermal properties. This anisotropy is caused by both morphological features (mostly the orientation of porosity) and crystallographic texture. We systematically studied those two aspects in two aluminum titanate ceramic materials of different porosity using mercury porosimetry, gas adsorption, electron microscopy, X-ray diffraction, and X-ray refraction radiography. We found that a lower porosity content implies a larger isotropy of both the crystal texture and the porosity orientation. We also found that, analogous to cordierite, crystallites do align with their axis of negative thermal expansion along the extrusion direction. However, unlike what found for cordierite, the aluminium titanate crystallite form is such that a more pronounced (0 0 2) texture along the extrusion direction implies porosity aligned perpendicular to it.     

Analytical study of surface wave multiple refraction in boundary of a scalar impedance surface with a tensor impedance surface

In this paper, the multiple refraction phenomenon is investigated on the boundary of a scalar impedance surface (SIS) and a tensor impedance surface (TIS). When a surface wave (SW) propagates on the SIS and radiates to the boundary of the TIS, the propagation direction of it is changed and the refraction phenomenon is accrued. The method that is proposed in this paper can predict the multiple refraction for the SW. Moreover, another analytical method is introduced for designing the proposed structure which the double refraction (DR) occurs at arbitrary angles on it. Using it, a sample of the structure is designed by printed circuits in 15.2GHz and the results are verified by the full‐wave simulation and measurement. The results are shown that in the structure, DR is occurred in 2° and 22° as predicted. The proposed method can provide many applications such as design of SW power dividers based on the TISs, impedance surface based waveguides, holographic antennas, and feeding of array antennas.