共查询到20条相似文献,搜索用时 9 毫秒
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Jürgen M. Schmidt 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1997,124(2):298-309
High-precision heteronuclear three-bond coupling constants including3J(HN, C′),3J(HN, Cβ),3J(Hα,Cγ), and3J(Hβ, C′) are determined for the nonproline residues in uniformly13C-enrichedantamanide,cyclo-(-Val1-Pro2-Pro3-Ala4-Phe5-Phe6-Pro7-Pro8-Phe9- Phe10-), using quantitative numerical 2D NMR spectrum evaluation based on the product-operator formalism. The experimental basis comprises two-dimensional1H,13C-heteronuclear relayed E.COSY spectra [J. M. Schmidt, R. R. Ernst, S. Aimoto, and M. Kainosho,J. Biomol. NMR6,95 (1995)], the multiplet patterns of which are subjected to iterative least-squares 2D multiplet-simulation procedures. Accuracy and precision of the spectrum fit are assessed byFstatistics and analysis of variances (ANOVA) leading to confidence intervals for the optimized spin-system parameters. The long-range J coupling constants obtained and their standard deviations provide the experimental foundation for a later detailed analysis of φ and χ1dihedral-angle equilibrium conformations contributing to the flexible peptide structure. 相似文献
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Sergei Kuksin Andrey Piatniski Armen Shirikyan 《Communications in Mathematical Physics》2002,230(1):81-85
We consider a class of discrete time random dynamical systems and establish the exponential convergence of its trajectories
to a unique stationary measure. The result obtained applies, in particular, to the 2D Navier–Stokes system and multidimensional
complex Ginzburg–Landau equation with random kick-force.
Received: 7 February 2002 / Accepted: 29 April 2002 Published online: 12 August 2002 相似文献
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The E.P.R. spectra of the monovalent positive and negative ions of 1,2,3,6,7,8-hexahydropyrene reveal an alternating line broadening, caused by the non-synchronized motion of the two aliphatic bridges in the molecule. When this motion is described by the modified Bloch equations, using a four-sites jump model, spectra are obtained which agree quite well with the experimental ones. The potential barrier for the conformational interconversion can be calculated from the temperature dependence of the lifetime of each configuration and is found to be 10·0±0·4 kcal mole-1 for the radical anion and 3·5±0·4 kcal mole-1 for the radical cation. The inversion rate at 0°C equals 2·8 × 106 s-1 for the anion and 4·2 × 106s-1 for the cation. 相似文献
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通过耦合波方程的方法,考虑光折变晶体中存在基频光栅和最低阶的高频和组合光栅,本文给出了各种情形下的耦合波方程及其解,结果表明一对相干光束的耦合可以被另一束相干的总光强,相位和调制度等控制,理论上,利用这种效应,可以实现相位-振幅转换及振幅-振幅调制。 相似文献
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通过耦合波方程的方法,考虑光折变晶体中存在基频光栅和最低阶的高频和组合光栅,本文给出了各种情形下的耦合波方程及其解。结果表明一对相干光束的耦合可以被另一束相干的总光强,相位和调制度等控制。理论上,利用这种效应,可以实现相位-振幅转换及振幅-振幅调制 相似文献
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研究了偏振模色散的统计特性,在不同模式耦合条件下,应用蒙特-卡罗方法模拟偏振模色散矢量的几率分布,并对模拟结果进行了函数拟合。发现随着耦合次数增加差分群时延的几率分布从一个类似δ函数分布逐渐过渡到麦克斯韦分布;在一定的耦合下,几率分布可以呈现高斯分布。对偏振模矢量的两个方向余弦进行统计分析,发现随着耦合次数的增加,偏振模矢量两个方向余弦函数的分布从高斯分布和δ函数分布都变为均匀分布。 相似文献
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光纤耦合对量子密钥分配系统光子探测的影响 总被引:1,自引:1,他引:0
借助量子密码术和卫星可以实现全球性的保密通信网络。但使用现有的单光子探测模块搭建星地量子密钥分配(QKD)系统,接收端就面临着空间光-多模光纤耦合的技术挑战。空间光-多模光纤耦合条件对星地量子密钥分配系统的跟瞄精度提出了严格要求。理论分析和定量计算表明,跟瞄精度ε与光束发散角θdiv的比值ε/dθiv≤0.5时,星地量子密钥分配系统的光子探测概率较高,系统可以正常工作;ε/dθiv≤0.1时,系统处于量子密钥产生速率为几kb/s的更理想状况。采用短波长更有利于满足空间光-多模光纤耦合条件,同时有利于系统获得更高的密钥产生速率。 相似文献
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对长周期光纤光栅和双锥形光纤之间的倏逝波耦合作用进行了研究。理论分析和实验研究表明,由于锥形光纤和长周期光纤光栅物理边界外倏逝波之间的交叠,长周期光纤光栅产生的包层模,可以耦合到锥形光纤的包层模并从锥形光纤的纤芯输出。要获得高的耦合效率,应满足模式匹配的条件,同时要尽量减小两光纤之间的距离。耦合特性还与长周期光栅和双锥形光纤的相对位置有关,为获得高的耦合效率,耦合区应位于长周期光栅区的后面。这种倏逝波耦合作用,为监测实际应用系统中长周期光纤光栅的特性提供了一种新方法;为利用锥形光纤和长周期光纤光栅开发新型光纤器件,提供了一种可能的方案。 相似文献
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以二维三角晶格光子晶体为研究对象,在该光子晶体中引入两行以一行耦合介质柱为间距的平行单模线缺陷波导.通过分析和研究光子晶体波导耦合结构的耦合和解耦合特性,发现在不同频率下耦合波导的耦合长度不同.利用平面波展开法和定向耦合原理计算了在不同入射光频率下,缺陷波导间耦合波导的耦合长度,设计了一种新型超微光子晶体波导耦合型三波长功分器,实现了归一化频率分别为0.369、0.394、0.435的光波的分束效果.采用时域有限差分法验证了该功分器具有很好的功率分配效果.本文结果有助于光子晶体新型滤波器、定向耦合器、波分复用器、偏振光分束器以及光开关等光子器件的研究. 相似文献
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实验研究了掺杂LiNbO3薄晶体中非直接相交的两束光之间大角光致散射的光爬行耦合现。研究了相同材料制备的厚度不同样品的二波和四波耦合的成像质量存在差异的原因。 相似文献
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Multi-source information fusion is widely used because of its similarity to practical engineering situations. With the development of science and technology, the sources of information collected under engineering projects and scientific research are more diverse. To extract helpful information from multi-source information, in this paper, we propose a multi-source information fusion method based on the Dempster-Shafer (DS) evidence theory with the negation of reconstructed basic probability assignments (nrBPA). To determine the initial basic probability assignment (BPA), the Gaussian distribution BPA functions with padding terms are used. After that, nrBPAs are determined by two processes, reassigning the high blur degree BPA and transforming them into the form of negation. In addition, evidence of preliminary fusion is obtained using the entropy weight method based on the improved belief entropy of nrBPAs. The final fusion results are calculated from the preliminary fused evidence through the Dempster’s combination rule. In the experimental section, the UCI iris data set and the wine data set are used for validating the arithmetic processes of the proposed method. In the comparative analysis, the effectiveness of the BPA determination using a padded Gaussian function is verified by discussing the classification task with the iris data set. Subsequently, the comparison with other methods using the cross-validation method proves that the proposed method is robust. Notably, the classification accuracy of the iris data set using the proposed method can reach an accuracy of 97.04%, which is higher than many other methods. 相似文献
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基于位平面分布特征的图像检索算法 总被引:2,自引:2,他引:0
针对利用颜色直方图检索时存在的问题,提出了一种基于位平面空间分布特征的图像检索算法.首先结合光照、锐化、模糊等噪声的攻击特点,将图像分解为8个位平面,然后提取对表征图像结构特征有意义的4个位平面的空间分布信息组成特征矢量来多层次地对图像特征进行描述.为了避免图像中像素灰度值的微小变化对位平面的影响,又提出了采用位平面的格林码表示方法.考虑到位平面之间的相关性,最后设计了权值矩阵,采用马氏距离进行相似性度量.实验结果表明,该算法利用位平面分解的方法来提取颜色的空间分布特征,又避免了颜色量化引起的误检问题,而且提取的特征矢量维数较低,因而具有较高的检索率. 相似文献