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应用多通道辐射高温计测量了冲击产生的氩等离子体的温度,并与理论计算结果进行了比较.测量结果与Saha方程加Debye-Huckel修正模型的计算结果符合较好. 相似文献
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基于维恩近似修正的热红外温度和发射率反演算法 总被引:1,自引:0,他引:1
温度和发射率是热红外遥感中的两个最重要的参数.提出了一种基于维恩近似修正和阿尔法获得法(ADE)的温度和发射率的反演方法.对维恩近似从基本原理上进行修正,利用ADE计算光谱大致形状以确定发射率最大最小的波段,推导出了在修正维恩近似后各个波段发射率的关系,再利用这个关系以及最大最小值差(MMD)模型计算实际的发射率.在MMD模型的选择上,比较了两种模型的精度,选择了精度较高的模型应用到算法中.从算法的计算精度以及与别的方法的比较中可见,算法的精度和稳定性都比较好,温度的反演误差在1K以内,发射率反演误差在0.015以内. 相似文献
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用BBK模型和修正后的BBK模型对入射能为27.2 eV时,共面非对称几何条件下电子离化氢原子的三重微分散射截面进行了计算,并把结果与一级玻恩近似下的计算结果以及实验数据进行了比较,对修正后的BBK模型中非一阶效应进行了分析和探讨. 相似文献
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为了克服因静脉图像照度不均造成的现有分割算法对静脉纹路分割不够精确的问题,提出了一种基于最大邻域内差(Maximal intra-neighbor difference,MIND)的静脉图像分割算法,其核心是充分利用静脉图像的邻域信息和新设计的距离函数计算出原图的MIND图像,并与经过直方图修正后的原图加权相加得到了增强图像,之后,通过计算出增强图像的均值图像并与增强图像进行加权比较得到最终的分割结果.在分割的过程中,可以根据MIND图像的直方图自适应调整算法中的分割参数提高分割效果,最后的实验结果证明了算法的有效性. 相似文献
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Image entropy and empirical mode decomposition (EMD) are effective methods for target detection. EMD algorithm is a powerful tool for adaptive multiscale analysis of nonstationary signals. A new technique based on EMD and modified local entropy is proposed in small target detection under sea-sky background. With the EMD algorithm, it is valid to estimate the background and get the target image by removing the background from the original image and segmenting the target based on the modified local entropy method. The data analysis and experiments show the validity of the proposed algorithm. 相似文献
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M. López-Aenlle R. Brincker F. Pelayo A.F. Canteli 《Journal of sound and vibration》2012,331(3):622-637
When operational modal analysis (OMA) is used to estimate modal parameters, mode shapes cannot be mass normalized. In the past few years, some equations have been proposed to scale mode shapes using the mass-change method, which consists of repeating modal testing after changing the mass at different points of the structure where the mode shapes are known. In this paper, the structural-dynamic-modification theory is used to derive a set of equations, from which all the existing formulations can be derived. It is shown that the known equations can be divided into two types, the exact and the approximated equations, where the former type does in fact fulfill the equations derived from the theory of structural modification, whereas the remaining equations do not, mainly because the change of the mode shapes of the modified structure is not properly taken into account. By simulations, the paper illustrates the large difference in accuracy between the approximate and the exact formulations. The paper provides two new exact formulations for the scaling factors, one for the non-modified structure and – for the first time in the literature – one for the modified structure. The simulations indicate the influence of errors from the measured natural frequencies and mode shapes on the estimation of the scaling factors using the two exact formulations from the literature and the new exact formulation proposed in this paper. In addition, the paper illustrates statistics of the errors on mode-shape scaling. All simulations were carried out using a plate with closely spaced modes. 相似文献
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近年来,在锂二次电池新材料的研发过程中逐渐建立了基于材料基因组思想的高通量计算理论工具与研究平台.在该平台上,通过将不同精度的计算方法组合,实现了基于离子输运性质的材料筛选;通过将信息学中数据挖掘算法引入高通量计算数据的分析,证实了材料大数据解读的可行性.上述平台实现了在锂电池固体电解质的高通量筛选、优化和设计上进行新材料研发的示范应用,通过高通量计算筛选获得了两种可用于富锂正极包覆材料的化合物Li_2SiO_3和Li2SnO_3,有效改善了富锂正极的循环稳定性;通过对掺杂策略的高通量筛选,获得了提高固体电解质β-Li_3PS_4离子电导率和稳定性的方案;通过高通量结构预测设计了全新的氧硫化物固体电解质LiAlSO;并在零应变电极材料结构与性能的构效关系研究中进行了大数据分析的尝试,分析了零应变电极材料的设计依据.上述材料基因组方法在锂电池材料研发中的应用为在其他类型材料研发中推广这种新的研发模式提供了可能. 相似文献
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Computing Eigen value equation and modal dispersion characteristics of an elliptical Bragg waveguide
Using the method of separation of variables in the elliptical coordinate system, a recursive formula for the electromagnetic fields in a new type of Bragg waveguide having elliptical core cross section with multilayered cladding is derived. The eigen equation is written in the form of Mathieu and the modified Mathieu functions and a dispersion relation is obtained for various modes supported by the proposed Bragg waveguide. The cutoff frequencies for several lower order even-odd modes have been calculated and their propagation characteristics are plotted. The results show that the dispersion curves are discontinuous and modes can exist only in particular wavelength bands. The effects of elliptical eccentricity on the mode cutoff values and mode transmission are addressed. Finally, the modal birefringence in the said waveguide is also estimated. 相似文献
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一种新的阶跃折射率光纤本征函数表达形式 总被引:4,自引:2,他引:2
为了阐明阶跃折射率光纤的模式特性,根据电磁波辐射的能量守恒定律和经过狄拉克函数奇异性修正的亥姆霍兹方程,通过数学推导和证明得出:柱面径向行波场的本征函数是经过狄拉克函数修正的整数阶汉克尔函数,阶跃折射率光纤模式场的本征函数是零、一阶贝塞尔函数经过狄拉克函数修正的零、一阶诺埃曼函数和虚参量汉克尔函数.该结论揭示了光纤芯层和包层模式场分别是径向驻波场和倏逝波场的本质,并基此推导出新的光纤模式特征方程,模式存在条件,模式数目和符合光纤实际的基模归一化截止频率的理论值. 相似文献
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This paper puts forward a novel magnetically insulated transmission line oscillator (MILO) for the first time which takes a modified HEM11 mode as its main interaction mode. The excitation of the oscillation mode is made possible by carefully adjusting the arrangements of each resonant cavity in a two-dimensional (2-D) slow wave structure. The high frequency characteristics are analyzed and a PIC simulation is carried out; the detailed results are discussed to get a better understanding of this new MILO. Employing an electron beam of about 441 kV and 39.7 kA, it finds that the modified HEM11 mode MILO generates a high power microwave output of about 1.47 GW at 1.45 GHz. The power conversion efficiency is about 8.4% and the generated microwave is in a TE11-like circularly polarized mode; its polarization direction is decided by the rotation direction of the SWS. 相似文献
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《中国物理 B》2015,(5)
We present a modified method to solve the surface plasmons(SPs) of semi-infinite metal/dielectric superlattices and predicted new SP modes in physics. We find that four dispersion-equation sets and all possible SP modes are determined by them. Our analysis and numerical calculations indicate that besides the SP mode obtained in the original theory, the other two SP modes are predicted, which have either a positive group velocity or a negative group velocity. We also point out the possible defect in the previous theoretical method in accordance to the linear algebra principle. 相似文献
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To improve the coupling effciency between fibers and conventional Ti:LiNbO3 diffused channel waveguides, it is feasible that the elliptical mode pattern of the channel waveguide can be modified by the Ti/Mg double diffusion method. By means of the three-dimensional beam propagation method, we successfully show that the mode size of the waveguide fabricated by this method is well matched to that of the fiber for TE and TM polarizations separately. 相似文献