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961.
Youwei Tian Dongxiao Yue Enyu Feng Mei Zhao Jing Tian Qiuyuan Zhang 《Optical and Quantum Electronics》2013,45(11):1125-1132
The spatial, temporal and spectral emission characteristics of radiation generated from electron oscillations driven by an intense circularly polarized few-cycle laser pulse have been investigated theoretically and numerically using a single electron model. For a femtosecond driving laser pulse with duration of one optical cycle, the maximal radiation emitted by the electron comprises only one electromagnetic pulse having durations much shorter than the optical cycle and belonging to the attosecond range. It is discovered that the influence of the initial phase on the process of full spatial characteristics of the radiation is apparent for intense few-cycle laser pulse. The characteristics can be used to measure the initial phase of intense circularly polarized few-cycle laser pulse in experiments. 相似文献
962.
为了减小编码光系统中的颜色耦合与颜色失衡的干扰,提高形状与颜色重建的准确度,建立了彩色编码光系统,并对其所采用的编解码方法、颜色重建的两个相关环节及颜色校正方法进行了研究。首先,给出了系统的彩色梯形相移强度比编解码法,分析了编解码过程中存在的RGB基色相互耦合现象,设计了应用Caspi模型硬件标定的颜色耦合校正方案;然后,给出了系统的逐点颜色重建法,分析了颜色重建过程中由表面曲率导致的颜色失衡现象,设计了利用表面几何信息校正颜色失衡的方案。实验结果表明:校正后单一绿色图像中的红色分量值约为校正前的1/10;单色表面色差约为0.1,趋近于人眼颜色分辨率,远低于校正前的0.4;重建的单色复杂被测表面颜色均匀、视觉效果良好,符合实际情况。提出的方法符合编码光系统抗干扰能力强的要求,有助于提高形状与颜色重建的准确度。 相似文献
963.
土壤光谱分析技术具有分析速度快、成本低、无危险、无破坏、可同时反演多种成分等特点,基于高光谱成像技术可以快速获取土壤性质及其空间分布特征。本文针对农田土壤监测的需求,设计了一种无人机载高光谱成像仪,选择Offner凸光栅光谱成像系统实现了无谱线弯曲和无色畸变的设计结果。400~1 000nm波长范围内的衍射效率为15%~30%,对地成像效果清晰,在3 km飞行高度可以获得覆盖宽度为0.6km、地面分辨率为0.6 m的地物目标高光谱图像,可提供0.4~1.0μm波长范围内120个谱段的高光谱图像,光谱数据准确、稳定。结果表明,该高光谱成像仪满足设计要求且可以快速获得高精度成像光谱信息,适合用于对农田土壤的监测。 相似文献
964.
A comparison of different entransy flow definitions and entropy generation in thermal radiation optimization 下载免费PDF全文
In thermal radiation, taking heat flow as an extensive quantity and defining the potential as temperature T or the black body emissive power U will lead to two different definitions of radiation entransy flow and the corresponding principles for thermal radiation optimization. The two definitions of radiation entransy flow and the corresponding optimization prin ciples are compared in this paper. When the total heat flow is given, the optimization objectives of the extremum entransy dissipation principles (EEDPs) developed based on potentials T and U correspond to the minimum equivalent temperature difference and the minimum equivalent blackbody emissive power difference respectively. The physical meaning of the definition based on potential U is clearer than that based on potential T, but the latter one can be used for the coupled heat transfer optimization problem while the former one cannot. The extremum entropy generation principle (EEGP) for thermal radiation is also derived, which includes the minimum entropy generation principle for thermal radiation. When the radiation heat flow is prescribed, the EEGP reveals that the minimum entropy generation leads to the minimum equivalent thermodynamic potential difference, which is not the expected objective in heat transfer. Therefore, the minimum entropy generation is not always appropriate for thermal radiation optimization. Finally, three thermal radiation optimization examples are discussed, and the results show that the difference in optimization objective between the EEDPs and the EEGP leads to the difference between the optimization results. The EEDP based on potential T is more useful in practical application since its optimization objective is usually consistent with the expected one. 相似文献
965.
在Banach空间X中利用序列的I-收敛与I*-收敛给出理想I具可加性质(AP)的等价刻画,并进一步研究弱I-收敛、弱I*-收敛、一致弱I*-收敛之间,以及弱I-收敛与收敛之间的关系,最后基于I-λ-统计收敛给出其推广:I-A-统计收敛,并以次微分映射为工具定义一族有限可加测度,用于等价刻画I-A-统计收敛,这亦是有限可加测度的一个应用体现. 相似文献
966.
One‐step boundary knot method for discontinuous coefficient elliptic equations with interface jump conditions 下载免费PDF全文
Linlin Sun Wen Chen Alexander H.‐D. Cheng 《Numerical Methods for Partial Differential Equations》2016,32(6):1509-1534
This study makes the first attempt to apply the boundary knot method (BKM), a meshless collocation method, to the solution of linear elliptic problems with discontinuous coefficients, also known as the elliptic interface problems. The additional jump conditions are usually required to be prescribed at the interface which is used to maintain the well‐posedness of the considered problem. To solve the problem efficiently, the original governing equation is first transformed into an equivalent inhomogeneous modified Helmholtz equation in the present numerical formulation. Then the computational domain is divided into several subdomains, and the solution on each subdomain is approximated using the BKM approach. Unlike the conventional two‐step BKM, this study presents a one‐step BKM formulation which possesses merely one influence matrix for inhomogeneous problems. Several benchmark examples with various discontinuous coefficients have been tested to demonstrate the accuracy and efficiency of the present BKM scheme. © 2016Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 32: 1509–1534, 2016 相似文献
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970.
利用压缩传感理论中的两步迭代收缩重建算法,开展单幅同轴全息图重建实验研究,实现单幅同轴全息图共轭重建像的消除并克服数字全息技术在轴向聚焦平面识别能力的不足。以数字图像和标准分辨率板为记录物体,比较分析了基于两步迭代收缩算法和菲涅尔近似衍射重建算法的重建质量;以两根裸光纤为实验样本,分析了两步迭代收缩重建算法对记录物体轴向不同焦平面的识别能力。实验结果表明两步迭代收缩重建算法可得到清晰度高于68.73%的重建信息,同时对直径为125 m的两根光纤在9 mm的轴向间距条件下,显示出了比全息菲涅尔近似算法更好的聚焦平面识别能力。这一轴向聚焦识别能力有助于数字全息技术应用于功能材料梯度参数或功能涂层光学器件涂层厚度检测。 相似文献