反射率

Improvement of MT migration tomography technology Based on the immanent relationship between tomography purpose and suitable frequency segment selection, we raise an entire frequency segment multi-parameter tomography scheme of MT finite difference migration. We establish a mathematical relationship among apparent electromagnetism reflectance, migration reflectance, background resistivity and the true resistivity distribution. After the introduction of TE/TM mode superpose rate, we carry out the associated resistivity tomography of two polarization mode to adapt the practical data interpolating situation.

大地电磁偏移成像的改进：针对频段选择和成像效果的内在关系，提出全频段、多参数有限差分偏移的解决方案；构建视反射系数、偏移反射系数、背景电阻率与实际电阻率分布的数学关系实现偏移电阻率成像；同时引入TE、TM模式加权因子以实现两个模式的联合偏移电阻率成像，更好的适应解释工作需要。

First, the effects of magnetic RAM relaxation time and the rise-time of incident pulse signal on reflection signal are discussed, the relationship between the rise-time of incident pulse and relaxation time based on the energy of reflection signal is revealed. Then, the effects of magnetic hysteric, susceptibilities and saturation upon reflection signal are analyzed, the results reveal the reflection of RAM target and UWB signal design. In the meantime, dielectric relaxation time effect about dielectric RAM target is analyzed simply, and the effects of relaxation time and the width of incident pulse upon reflection signal are probed. Finally, a few RAM targets are measured in the chamber using the impulse radar experiment system which is developed by the team of anti-stealth impulse radar on Department of Electrical Engineering, National University of Defense Technology. The experimental results show the similarity of the rule of echos with the theory. From the compared results of different tagets, we concluded, compared with 15% wideband sinusoidal signal, the impulse signal has increased 10～12dB energy from the same loaded RAM target; this, in turn, shows the nonlinear effects of RAM to the echoes, and the potentiality of the impulse signal to RAM targets.

首先分析了磁性RAM的弛豫时间及入射脉冲信号的上升时间对反射信号的影响，从反射信号能量角度出发，给出了入射脉冲上升时间与弛豫时间的关系；接着分析了磁性RAM的磁滞特性、磁化率及磁化强度对反射信号的影响，给出了RAM目标辐射和有关UWB信号设计的一般性结论；其次，对介电RAM的弛豫时间效应作了简单的分析，探讨了介电弛豫时间及入射脉冲宽度对反射信号的影响；最后利用国防科技大学电子技术系&反隐身冲激雷达技术研究组&研制的冲激雷达实验系统，在微波暗室中对几种不同的RAM目标进行了测量，结果表明：其反射波形的基本规律与上述理论分析相一致；从各种不同目标回波的能量对比结果得出，涂覆RAM目标对冲激信号的吸收比15％带宽的正弦信号要小10～12dB，证实了RAM的非线性效应对回波的影响，也证实了冲激信号反隐身的潜力。

At present, the most advanced technique for this field is to measure the total loss of a passive resonant cavity in which the mirror to be measured is consisted.

本文的目的是要在国内现有的技术水平条件下实现激光镜片的极高反射率测量。

A fiber grating is used for output of resonant cavity with 60% reflectivity. Its 3 dB-bandwidth is measured as 0.16 nm.

反射率为60%的光纤光栅用作光纤激光器谐振腔的输出，3 dB带宽为0.16 nm。

Coal ; vacuole ; mosaic structure ; refl'ectance ; anisotropy.

煤； 气孔；镶嵌结构；反射率；各向异性指数

It is shown that it is difficulty to differentiate each vegetation type among sub-tropical evergreen forest, sub-tropical coniferous forest and sub-tropical deciduous forest because of the mixture of their tree spectra. According to the reflection index in the wavelengths of 750 nm to 1 100 nm, the tree species can be divided into 4 groups with descend in reflectivity. Each tree specie can be differentiated from each other according to its slope of the spectrum curve and its reflection index in the wavelengths of 770 nm to 1 010 nm for each forest vegetation type. The unique first order derivative feature can be used to identify litsea, alder, fir, red birch, southwest birch, large schima confertiflora, taiwania flousian and small leaf schima confertiflora.

研究表明：亚热带常绿阔叶林、亚热带针叶林和亚热带落叶阔叶林等植被类型，因其树种间光谱特征混淆严重，而难以彼此区分；根据其反射率在750~1 100 nm范围上的差异，可将其归为4类；就各植被类型而言，其树种间在光谱曲线坡度，以及在770~1 010 nm范围上具有显著差异，可据此将其区分；木姜子、桤木、杉木、红桦、大叶木荷、秃杉和小叶木荷等因具有独特的光谱一阶导数特征，据此可以识别提取。

The temporal evolution in transient reflectivity change ?嵇/R is composed of two relaxing parts: a fast component with time sub picoseconds and a slow component with time constant ranging from tens of ps to hundreds of ps.

瞬时反射率的变化主要由两个部份所构成：弛缓时间在次皮秒级(sub-picosecond)的快弛缓行为，以及弛缓时间在数十到百个皮秒的慢弛缓行为。

The model considers as many factors as possible, including nonuniform distribution of photon intensity and carrier density along active region, gain spectral dispersion, spontaneous emission spectrum and facet reflectivity, and is applicable under the condition that the pulse width of injecting signal is wider than 10 picoseconds. It provides a convenient and effective theoretical platform for SOA dynamic characteristic study.

该模型考虑光子密度和载流子浓度沿有源区的非均匀分布、增益谱色散性、自发辐射噪声谱和端面反射率，适用于脉冲宽度高于10ps的信号输入的情况，为后续研究SOA动态特性提供了方便而有效的理论验证平台。

With FDDA method, the precipitation echo reflectivity field gained by observation and three dimension wind field as well as other parameters obtained by retrieval are put into the usual mesoscale or smallscale numerical model, so that the inner structure of mesoscale or smallscale weather system is better researched and precipitation is estimated more exactly.

2利用四维同化方法，将单多普勒天气雷达观测得到的降水回波的反射率场以及用反演技术得到的三维风场及其它变量，加入到通用的中小尺度数值模式中，以便更好地研究中小尺度天气系统的内部结构，预测其演变，并提供更精确的降水估计。

The sharp rising process of the reflectivity was explained quantitatively well based on the model of Auger recombination of high density plasma and Auger-recombination-induced heating to lattice, which showed the heating effect induced by Auger recombination in high density plasma should be the main mechanism of ultra-short laser pulse-induced phase change.

利用高密度等离子体的Auger复合及其感应的晶格加热模型较好地定量解释了反射率从最小到最大的快速变化过程，表明高密度等离子体的Auger复合加热导致的热效应可能是超快激光诱导相变发生的主要机制。

Breath, muscle contraction of the buttocks; arch body, as far as possible to hold his head, right leg straight towards the ceiling (peg-leg knee in order to avoid muscle tension).

呼气，收缩臀部肌肉；拱起身体，尽量抬起头来，右腿伸直朝向天花板（膝微屈，以避免肌肉紧张）。

The cost of moving grain food products was unchanged from May, but year over year are up 8%.

粮食产品的运输费用与5月份相比没有变化，但却比去年同期高8％。