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141.
A series of hyperbranched aromatic polyamide copolymers has been prepared and characterized from direct polycondensation of AB2 and AB monomers. Structure of the monomers and the molar ratio of AB2/AB showed strong influence on the properties of resulting copolymers. A small amount of AB2 branching unit improved markedly the solubility of the resulting copolymer. Mark-Houwink parameters of the copolymers were essentially independent of the mole ratio of the monomers. The physical and mechanical properties of resulting copolymers were influenced not only by the mole ratio of monomers, but also by the structure of the monomers employed. 相似文献
142.
G. Mairle Liu Ken Pao G. J. Wagner K. T. Knöpfle H. Riedesel 《Zeitschrift für Physik A Hadrons and Nuclei》1981,301(2):157-163
The reactions22Ne(d, t)21Ne and22Ne(d, τ)21F have been investigated in a parallel experiment atE d=52MeV. Energy spectra of tritons andτ particles have been measured up to excitation energies of 18MeV in both21Ne and21F nuclei. Thel values could be determined, and spectroscopic factors have been obtained by a DWBA analysis of the measured angular distributions. Together with the results from a preceding \({}^{22}Ne(\vec d, \tau ){}^{21}F\) experiment, several spins could be determined in21F. From a comparison of the triton andτ particle spectra,T=3/2 states in21Ne could be identified and on this basis the new information on spins of21F states could be transferred to their analog states in21Ne. The completeT < andT > parts of the (2s, 1d) strengths could be observed. The 1p strength is highly fragmented. Of theT < part only 60% of the 1p1/2 and 40% of the lp3/2 strength could be found, but the totalT > part of the 1p strength could be localized. The spectroscopic results for positive parity states are in qualitatively good agreement with shell model predictions. 相似文献
143.
The computation ofL
1 smoothing splines on large data sets is often desirable, but computationally infeasible. A locally weighted, LAD smoothing spline based smoother is suggested, and preliminary results will be discussed. Specifically, one can seek smoothing splines in the spacesW
m
(D), with [0, 1]
n
D. We assume data of the formy
i
=f(t
i
)+
i
,i=1,..., N with {t
i
}
i=1
N
D, the
i
are errors withE(
i
)=0, andf is assumed to be inW
m
. An LAD smoothing spline is the solution,s
, of the following optimization problem
相似文献
144.
Guan-Yeow Yeap Michi Nakata Yoichi Takanishi Ken Ishikawa Hideo Takezoe 《Liquid crystals》2013,40(11):1437-1443
In order to study the difference in microscopic orientation of ferro- and antiferroelectric liquid crystalline molecules, we synthesized the partially deuteriated chiral compounds, (S)-(-)-2-methylbutyl 4-(4-(d13)-hexyloxy- and (S)-(-)-2-methylbutyl 4-(4-(d17)-octyloxy-phenyl)benzoates. Fundamental physical properties such as phase transition temperatures, spontaneous polarization and tilt angle were determined. Polarized FTIR measurements were also made to provide information on molecular structure and orientation. 相似文献
145.
In order to suppress sidelobes of holographic filter’s spectral response we propose to use weighting of grating intensity distribution along light propagation. This can be realized in photorefractive material (for example in LiNbO3:Fe) by using spatial selective decaying of conventional uniform grating by illumination of light through some transparent mask. Experimental results show that it is able to obtain 8 dB improvement of sidelobe level compared to uniform grating. But it is accompanied by 1.7 times expansion of main lobe and two times decrease of diffraction efficiency. 相似文献
146.
基于任意形状颗粒集合的二值图像,提出了估计其体积(或质量)的方法.首先利用发光背景台面获取的颗粒灰度图像变换为相应的二值图像,得到颗粒的边界轮廓.然后再基于其边界信息,定义与颗粒形状特征相关的描述量,并将其无量纲化.将由此定义的无量纲参变量作为回归变量建立一个多元线性回归(multiple linear regression)模型用以估计颗粒集合的扁平度,进而估算颗粒体积.回归变量的系数由随机采样的501个样本颗粒(尺寸范围为4.75~25 mm)用误差最小平方和求得.将模型应用于由具有相似统计分布特征的其他颗粒集合,并将得到的体积估计值与其体积真实值相比较,实验结果显示模型的相对误差在±2%以内. 相似文献
147.
The geometrical constraints of the fluoride-initiated and Lewis acid-catalyzed intramolecular addition of allylsilanes to enone systems were shown to be governed by kinetic-ring-size preferences. Molecules containing adjacent quaternary carbon atoms can be prepared using this method. 相似文献
148.
Komeyama K Sasayama D Kawabata T Takehira K Takaki K 《Chemical communications (Cambridge, England)》2005,(5):634-636
Rare-earth silylamide complexes, Ln[N(SiMe3)2]3 (Ln = Y, La, Sm, Yb), effectively catalyzed the coupling reaction of isocyanides with both aliphatic and aromatic terminal alkynes under mild conditions. 相似文献
149.
150.
Fruit juice authentication by <Superscript>1</Superscript>H NMR spectroscopy in combination with different chemometrics tools 总被引:1,自引:0,他引:1
Cuny M Vigneau E Le Gall G Colquhoun I Lees M Rutledge DN 《Analytical and bioanalytical chemistry》2008,390(1):419-427
To discriminate orange juice from grapefruit juice in a context of fraud prevention, 1H NMR data were submitted to different treatments to extract informative variables which were then analysed using multivariate
techniques. Averaging contiguous data points of the spectrum followed by logarithmic transformation improved the results of
the data analysis. Moreover, supervised variable selection methods gave better rates of classification of the juices into
the correct groups. Last, independent-component analysis gave better classification results than principal-component analysis.
Hence, ICA may be an efficient chemometric tool to detect differences in the 1H NMR spectra of similar samples, and so may be useful for authentication of foods. 相似文献
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