排序方式: 共有46条查询结果,搜索用时 15 毫秒
1.
Simultaneous quantitative determination of 20 active components in the traditional Chinese medicine formula Zhi‐Zi‐Da‐Huang decoction by liquid chromatography coupled with mass spectrometry: application to study the chemical composition variations in different combinations
下载免费PDF全文
![点击此处可从《Biomedical chromatography : BMC》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Zheng Tang Ran Yin Kaishun Bi Heyun Zhu Fei Han Kelin Chen Fenrong Wang 《Biomedical chromatography : BMC》2015,29(9):1406-1414
2.
应用TG-FTIR技术研究黄土庙煤催化热解特性 总被引:1,自引:0,他引:1
用浸渍法制备过渡金属氧化物担载型催化剂MOx/USY(M=Co、Mo、Co-Mo),用热重红外联用技术考察了MOx/USY催化剂对黄土庙(HTM)煤热解失重特性和热解产物生成规律的影响。热重实验结果表明,MOx/USY催化剂可使HTM煤热解的二次脱气条件更为温和,热解峰温分别提前14、23和9℃。动力学分析结果表明,MOx/USY催化剂可降低HTM煤样热解的活化能。FT-IR研究表明,MOx/USY催化剂可有效改善HTM煤热解产物的组成和分布,CoOx/USY催化剂能显著提高HTM煤热解产物中高热值气体(CO、CH4)和轻质芳烃以及脂肪烃类化合物的含量;MoOx/USY催化剂没有明显改善HTM煤热解产物组成和分布;MoOx-CoOx/USY催化剂可促进CO、CH4、轻质芳烃和脂肪烃类化合物的生成,却使热解产物的生成向高温区移动,说明USY负载的不同过渡金属氧化物对煤样热解行为和热解产物有较大影响。 相似文献
3.
The goal in this work is to investigate the effectiveness of time-frequency representations for analysing dispersive waves by comparing the performance of three different methods. In particular, the smoothed pseudo-Wigner distribution, the continuous wavelet transform and the Hilbert-Huang transform are compared and evaluated in terms of their ability to analyse dispersive elastic waves. The waves under consideration are transient flexural ones generated by an impact in a beam. In view of the results of the comparative study, the advantages and shortcomings of each method are presented and discussed. 相似文献
4.
Athina P. Bougioukou Apostolos P. Leros Vassilios Papakonstantinou 《Applied Mathematical Modelling》2008
This paper presents a new method for modeling amplitude and frequency non-stationary earthquake ground motions using a scalar first order dynamic mean reverting stochastic differential equation driven by Brownian motion with parametric time varying coefficients. It determines the proper relationship between these time varying parametric coefficients and presents the statistical and probability distribution characteristics of the response solution. It demonstrates the applicability of the method by presenting some simulations of amplitude and frequency non-stationary earthquake ground motions. The verification of the amplitude and frequency non-stationary contents of the mean reverting stochastic ground motions is demonstrated using the Hilbert–Huang transform method. Also a corresponding interpretation between the coefficients of the proposed model and the coefficients of the usual oscillatory second order differential equation driven by white Gaussian noise is presented along with some comments how it can be applied to simulate ground motions consistent with acceleration target records such as boxcar, trapezoidal, other exponential functions, or compound and target records at source, near field, and far field distances. 相似文献
5.
Cheng-Fang Wang Li Fan Mei Tian Shu-Shan Du Zhi-Wei Deng Jiang-Bin Feng 《Natural product research》2015,29(14):1380-1383
This work aimed to investigate benzophenanthridine from the roots of Zanthoxylum nitidum (Roxb.) DC. var. fastuosum How ex Huang for the first time. Thirteen benzophenanthridines were isolated, and our results of the cytotoxic activities indicated that compound 6 exhibited the best potency against A549, Hela, SMMC-7721 and EJ, with the IC50 values of 27.50, 37.50, 16.95 and 60.42 μM, respectively. Compounds 7 and 11 also showed strong cytotoxicity when tested against the four human cancer cell lines (A549, Hela, SMMC-7721 and EJ), while only compounds 12 and 13 displayed cytotoxicity in inhibiting BALL-1 proliferation among all the compounds. These results suggested that benzophenanthridines may become a valid alternative of potential basis for new anti-proliferative agents. 相似文献
6.
In a recent paper, Nguyen et al. (2018) built a distributionally robust estimator for the precision matrix of the Gaussian distribution. The distributional uncertainty size is a key ingredient in the construction of this estimator. We develop a statistical theory which shows how to optimally choose the uncertainty size to minimize the associated Stein loss. Surprisingly, rather than the expected canonical square-root scaling rate, the optimal uncertainty size scales linearly with the sample size. 相似文献
7.
Rita Khanna 《Pramana》1983,20(4):279-286
Using the continuum theory of linear elasticity, diffuse x-ray scattering has been calculated in the immediate neighbourhood
of Bragg peaks from point defects in a lattice containing more than one atom in the unit cell. General expressions are obtained
for the Debye-Waller factor, Huang diffuse scattering and the asymmetric scattering due to the defect. For lattices with one
atom per unit cell, these expressions reduce to the well-known formulae of diffuse scattering. 相似文献
8.
Investigating long-range correlation by the Hurst exponent, H, is crucial in the study of time series. Recently, empirical-mode-decomposition-based arbitrary-order Hilbert spectral analysis (EMD-HSA) has been proposed to numerically obtain without proof a scaling relationship, generated from the amplitude–frequency distribution, related to H. We propose a formalism to empirically study EMD-HSA, to deduce its scaling exponent ξ(q) from the perspective of EMD-based arbitrary-order Hilbert marginal spectrum (EMD-HMS), and to numerically compare the results with the expected H. EMD-HSA and EMD-HMS experiments show that, by incompletely removing (quasi-)periodic trends, the sunspot series should have an H value around 0.12. 相似文献
9.
黄葆同院士(1921-2005)是我国高分子化学领域的资深专家。早年留学美国,1955年回国后一直在中国科学院长春应用化学研究所工作。在乙丙橡胶合成等研究领域走在全国前列。基于对“老科学家学术成长资料采集工程”所存大量书信和日记等的解读分析,论文还原了黄葆同在美留学期间加入进步组织、争取回国的历史过程以及求学经历。并以此为缩影,探讨当时促使留美学生回国的个体与社会因素,具体而微地揭示了那一代中国留学生在困境之中的家国情怀。 相似文献
10.