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排序方式: 共有233条查询结果,搜索用时 31 毫秒
61.
62.
Gary E. Martin Kirill A. Blinov Mikhail Reibarkh R. Thomas Williamson 《Magnetic resonance in chemistry : MRC》2012,50(11):722-728
Establishing the carbon skeleton of a molecule greatly facilitates the process of structure elucidation, leaving only heteroatoms to be inserted, heterocyclic rings to be closed, and stereochemical features to be defined. INADEQUATE, and more recently PANACEA, have been the only means of coming close to the goal of totally defining the carbon skeleton of a molecule. Unfortunately, the extremely low sensitivity and prodigious sample requirements of these experiments and the multiple receiver requirement for the latter experiment have severely restricted the usage of these experiments. Proton‐detected ADEQUATE experiments, in contrast, have considerably higher sensitivity and more modest sample requirements. By combining experiments such as 1,1‐ADEQUATE and 1,n‐ADEQUATE with higher sensitivity experiments such as GHSQC through covariance processing, sample requirements can be further reduced with a commensurate improvement in the s/n ratio and F1 resolution of the covariance processed spectrum. We now wish to report the covariance processing of an inverted 1JCC 1,n‐ADEQUATE experiment with a non‐edited GHSQC spectrum to afford a spectrum that can trace the carbon skeleton of a molecule with the exception of correlations between quaternary carbons. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
63.
V. L. Lobas 《International Applied Mechanics》2005,41(2):197-202
A generalized mathematical model of an inverted double pendulum with asymmetric follower force is developed. The model accounts for all possible types of springs: hard, soft, and linear. The influence of equitype springs on the equilibrium states is examined__________Translated from Prikladnaya Mekhanika, Vol. 41, No. 2, pp. 103–109, February 2005. 相似文献
64.
An antimagic labeling of a graph withq edges is a bijection from the set of edges to the set of positive integers{1,2,...,q}such that all vertex weights are pairwise distinct,where the vertex weight of a vertex is the sum of the labels of all edges incident with that vertex.A graph is antimagic if it has an antimagic labeling.In this paper,we provide antimagic labelings for a family of generalized pyramid graphs. 相似文献
65.
真彩色传递双波段图像融合 总被引:1,自引:0,他引:1
针对基于颜色传递的双波段(中波红外、可见光)图像融合时,由于参考图像选择不当,造成的彩色融合图像对比度差、图像边缘细节下降等问题,提出了基于拉普拉斯金字塔分解及对比度可调的色彩传递图像融合算法。对待融合的两幅图像进行拉普拉斯金字塔三级分解,每一级按照不同的融合规则进行融合,以重构后的灰度融合图像作为融合结构的亮度分量Y,将可见光与红外图像的差值图像作为U分量,以红外图像为V分量。在颜色传递公式中,加入可调的比例系数,通过适当调节比例系数可调节融合图像的对比度。实验结果表明,获得的融合图像较好地保留了可见光图像的细节,既突出了红外目标同时又具有参考图像的颜色特征。图像评价结果表明,融合图像的均值、方差、熵等评价指标均得到较大提高。 相似文献
66.
67.
刘华 《数学的实践与认识》2021,(5):138-146
先给出了广义逆指数分布在双边定时截尾样本下形状参数的最大似然估计,并不能得到估计的显式表达式,但证明了参数在(0,+∞)上最大似然估计是唯一存在的.其次提出用EM算法求出形状参数的估计且该估计具有良好的收敛性,还给出了形状参数的EM估计的渐近方差和近似置信区间;最后通过数值模拟,对形状参数的最大似然估计和EM估计的效果进行了比较,说明了用EM算法求形状参数的估计是可行的,并且模拟效果相对比较好. 相似文献
68.
This paper studies the stabilization to an inverted pendulum under a delayed proportional-derivative-acceleration (PDA) feedback, which can be used to understand human balance in quiet standing. The closed-loop system is described by a neutral delay differential equation (NDDE). The optimal feedback gains (OFGs) that make the exponential decaying rate maximized are determined when the characteristic equation of the closed-loop has a repeated real root with multiplicity 4. Such a property is called multiplicity-induced dominancy of time-delay systems, and has been discussed intensively by many authors for retarded delay differential equations (RDDEs). This paper shows that multiplicity-induced dominancy can be achieved in NDDEs. In addition, the OFGs are delay-dependent, and decrease sharply to small numbers correspondingly as the delay increases from zero and varies slowly with respect to moderate delays. Thus, the inverted pendulum can be well-stabilized with moderate delays and relatively small feedback gains. The result might be understandable that the elderly with obvious response delays can be well-stabilized with a delayed PDA feedback controller. 相似文献
69.
An extended growth curve model is considered which, among other things, is useful when linear restrictions exist on the mean in the ordinary growth curve model. The maximum likelihood estimators consist of complicated stochastic expressions. It is shown how, by the aid of fairly elementary calculations, the dispersion matrix for the estimator of the mean and the expectation of the estimated dispersion matrix are obtained. Results for Wishart, inverted Wishart, and inverse beta variables are utilized. Additionally, some asymptotic results are presented. 相似文献
70.
针对一类一维热传导反演问题,导出了一种稳定的定层逐点反演方法,推证了该方法的热传导系数离散解具有整体二阶精度。 相似文献