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光纤中喇曼散射理论的研究是分布式光纤温度传感重要的理论基础。文中首先介绍了喇曼散射,然后对传感光纤中的喇曼散射进行了全面的理论分析,这些分析为分布式光纤传感器的设计提供了有益参考。 相似文献
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为了消除掺铒光纤放大器的放大自发辐射噪声对分布式光纤温度传感器测温精度的影响,采用精确的修正公式进行温度解调是一种有效手段。通过分析掺铒光纤放大器的放大自发辐射噪声对系统产生的影响,并将计算的中间结果代入理论公式获得了修正后的温度解调公式。实验中分别采用理论公式和修正公式对温度进行分布式测量并获得了实验数据。结果表明,修正后的温度解调公式有效补偿了掺铒光纤放大器噪声引起的误差,并显著提高了系统的信噪比和测温精度;修正公式可将系统的整体测温精度提高到1℃~2℃;此外,实验中观察到多模光纤中喇曼背向自发散射同样会出现放大现象,这与单模光纤中的情形类似,且放大喇曼自发散射依然具有理想的温度效应。 相似文献
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本文使用染料测Q红宝石激光激励液氮的受激喇曼散射,观察到一级斯托克斯、一级反斯托克斯和二级反斯托克斯线,测得散射光的喇曼频移、线宽、能量转换率和退偏振度等参数.并对所得结果进行了讨论。 相似文献
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对流层散射通信是一种典型的随参信道,多径衰落十分突出,所以要实现高速大容量散射通信是非常困难的。为了抵抗由于多径衰落所带来的散射通信性能恶化,提出了基于MIMO-OFDM结构的的新一代对流层散射通信系统框架。通过分析散射信道中的MIMO-OFDM结构,讨论MIMO-OFDM技术应用的主要问题,发现运用该技术可以有效提高散射通信的可靠度,克服高速数据在散射信道下的多径衰落,实现散射的大容量、远距离通信。 相似文献
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With method of Van Derberg,this paper gives the electron mobilities at different temperature in In0.53Ga0 .47As on InP by LPE, and analyses them from scatters of polaried optical phonons, ioned impurities and alloy. The results of the experiment and theory show that the scatter of ioned impurities and alloy scatter play an importment role at low temperature and the scatter of polaried optical phonon is superior at high temperature. It is also indicated that the alloy scatter is very, active for the ternary alloy density of about 1×1018cm-3. At last, we choose the optimal alloy potential △U= 0.83eV and give the limitation of Matthiessen rule. 相似文献
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薄膜电致发光器件中硫空位的散射作用 总被引:1,自引:1,他引:0
利用分波法计算了薄膜电致发光器件中硫空位对电子的散射速率,并将其与其它散射机制进行了比较。研究了散射速率与电子能量及温度的关系,并比较了硫空位俘获电子前后的散射速率。提出硫空位的存在是阻碍获得高亮度蓝色薄膜电致发光器件的关键。 相似文献
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The use of cellular or foamed plastics in various microwave applications, such as supports at radar ranges, makes it desirable to know the back scattering properties of such materials. Since the cell structure is of a random nature with some predictable average properties such as cell size and density, it is modeled by an aggregate of randomly distributed spherical shells. Assemblies of scatterers will in general have a coherent and an incoherent scatter. Coherent scattering comes primarily from sudden particle density changes such as that at the boundaries of a particle system. Since coherent scattering comes only from the boundaries of a constant density material, it can sometimes be reduced by appropriate shaping. Incoherent scattering is the result of the contribution of all the particles in the system, i.e, a volume or an interior effect. It represents the irreducible scattering contribution to the total back scatter. As such it can be looked upon as the minimum cross section that can be obtained from a foam structure provided all coherent scatter has been removed. The magnitude of the incoherent scattering is illustrated by calculating radar cross sections for a cylinder made of styrofoam. Since the compressive strength of styrofoam is known, the maximum load that a styrofoam structure can support and the minimum achievable cross section from it can be easily calculated. 相似文献
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基于平衡态非相干散射理论的GUISDAP程序包在拟合含有纯增长模式线的非相干散射功率谱及反演加热扰动电离层参量中存在严重误差,该文提出一种以未加热时刻的电离层参量为先验信息,利用最小二乘法搜寻最佳高斯峰描述纯增长模式线来修正实测非相干散射谱,并使用电子超高斯分布的非相干散射理论拟合修正后非相干散射谱来反演获取加热扰动电子温度的方法。通过将该方法用于分析2010年秋季我国在挪威开展的电离层加热实验数据表明:利用该方法对含纯增长模式线的实测谱修正拟合后获得的电子温度比未加热时刻提高约800 K左右,增幅比例约13%~50%,该结果与现有文献报道的电离层加热引起的电子温度增幅范围吻合较好。结论表明该方法适用于基于含纯增长模式线的非相干散射谱反演扰动电离层参量。 相似文献
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基于微运动的旋转散射中心空域散射特征提取 总被引:1,自引:0,他引:1
本文研究了旋转运动对雷达目标回波的幅度调制作用,进而提出了一种基于微运动的旋转散射中心空域散射特征提取方法。首先对含旋转部件目标的雷达回波进行时频分析得到回波的谱图,然后基于目标上各旋转散射中心的微多普勒频率差异,利用谱图的边缘特性估计各散射中心的回波能量随时间的起伏变化关系。结合微运动的参数估计,提取旋转部件的空域散射特征。通过仿真试验和外场实验对本文所提出的方法进行了验证。旋转部件的空域散射特征可以揭示旋转部件的结构属性信息,为目标识别提供重要依据。 相似文献
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Characterizing the scatter point-spread-function (PSF) yields a model for predicting the behavior of the scatter and a PSF for deconvolution techniques that correct for scatter. Assuming the X-ray scatter is isotropic, the authors present a model for the scatter point-spread-function parameterized only by air gap. This model suggests that small increases in air gap significantly attenuate the higher-frequency structure of the scatter distribution. To evaluate this model, the authors examined the behavior of the spatial frequency distributions of experimental scatter images as a function of air gap. Using film as the detector, they imaged a 20-cm uniformly thick water phantom with aperture diameters of 8, 12, 16, 20, and 24 mm at air gaps of 0-24 cm. 相似文献
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An approach of three-dimensional vector radiative transfer (3-D-VRT) equation for inhomogeneous scatter media 总被引:3,自引:0,他引:3
To solve a three-dimensional vector radiative transfer (3-D-VRT) equation for the model of spatially inhomogeneous scatter media, the finite enclosure of the scatter media is geometrically divided, in both the vertical z and horizontal (x,y) directions, to form very thin multiboxes. The zeroth-order emission, first-order Mueller matrix of each thin box, and an iterative approach of high-order radiative transfer are applied to deriving high-order scattering and emission of whole inhomogeneous scatter media. Numerical results of polarized brightness temperature at microwave frequency from an inhomogeneous scatter model such as vegetation canopy are calculated and discussed. 相似文献