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991.
在刚体转动定律研究的实验理论中,常做某种简化,本文将对这种简化产生的系统误差做以估计;本文还将论及如何进行最小二乘法数据处理的教学。 相似文献
992.
993.
本文系统研究了二元分子TTP—O—Pc和TTP—O—(CH2)5—O—Pc的吸收光谱,发射光谱和激发光谱,区分了两组发光谱带的来源, 证实了由TTP到Pc的能量转移,利用激光频域技术获得了电荷弛豫时闻分别是18.5和82ps。 相似文献
994.
Parina Hassanaly Gaston Vernin Henri J. M. Dou Jacques Metzger 《Journal of heterocyclic chemistry》1975,12(4):703-704
Free radicals obtained from 3- and 8-aminoquinolines were studied in various aromatic substrates. Isomer percent, reaction yields, and overall reactivities towards benzene are recorded. 相似文献
995.
The remarkable differences between the infrared spectra of oxygen adsorption and nitrogen desorption in coal have been experimentally and theoretically investigated. Density functional theory calculations were performed to better explain the mechanism of oxygen adsorption using six different molecular models of coal. In addition, the remarkable differences of infrared spectra between oxygen adsorption and nitrogen desorption was defined as the index V, which was used to classify the spontaneous combustion tendency of coal. The experimental data indicated that the spectra in the 4000–2000 cm?1 and 1250–1050 cm?1 regions exhibited significant changes. These results suggest that the mechanism of oxygen adsorption is the alteration and transfer of charge density around the activated sites, which leads to the observed changes of the infrared spectra. The V, which is related to the alteration of spectral intensity, is found to decrease with the increase of adiabatic oxidation time and the relative spontaneous combustion period of coal. This observation solidifies the connection between sample spectral intensity and oxygen chemisorption. These data suggest that the hydroxy in hydroxy and carboxyl groups on the surface of coal particles is the site of oxygen chemisorption, and the V can be used to rapidly and accurately categorize the spontaneous combustion tendency of coal. 相似文献
996.
By using Fourier Optics, the general analytical expression of intensity distribution for the coherently combined beams positioned on the X-Y plane, which is applicable to both Gaussian and non-Gaussian beams, can be derived. Considering the fact that in many cases the array configuration can be regarded as composed of several regular polygons with a common center, an explicit analytical expression of the far-field intensity distribution for these cases has been derived. As an example, the above expression has been applied to study a 19 emitter array. Studies have also been done on the dark fringes of the far-field pattern for the specific emitters, whose numbers are 2 and 4, respectively. 相似文献
997.
Shi Sun Jingchun Liu Xiuxiu Sun Wenjun Zhu Fei Yang Lisa Felczak Q. Ping Dou Kequan Zhou 《Tetrahedron letters》2017,58(19):1895-1899
Five bioactive Annonaceous acetogenins, including three new compounds, annonamuricins A (1), B (2), and C (3), one registered but no spectral data reported compounds, annonamuricin D (4), and one known compound annonacin (5) were isolated from Graviola fruit (Annona muricata) and further determined through bioassay-guided fractionation. All five compounds are C35 Anonnonaceous acetogenins with a mono-tetrahydrofuran ring and four hydroxyls. Their structures were elucidated using spectral methods as well as chemical modification after isolation via chromatographic techniques and HPLC purification. These acetogenins demonstrated potent anti-proliferative activities against human prostate cancer PC-3 cells. 相似文献
998.
999.
The paper studies the 1-D piston problem of the relativistic Euler equations when the speed of the piston is a perturbation
of a constant. A sequence of approximate solutions constructed by a modified Glimm scheme is proved to be convergent to the
weak solution (which includes a strong leading shock) to the piston problem. In particular, we give the precise estimates
on the reflection of the perturbed waves on the piston and the leading shock.
The paper is supported by the National Natural Science Foundation of China (Grant 10626034) and the Special Research Fund
for Selecting Excellent Young Teachers of the Universities in Shanghai. 相似文献
1000.