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31.
For structural parameters with uncertainties, interval mathematics can, in the case where the probabilistic distribution density
of uncertain variables is unavailable, deal with the influence of uncertainties in structural parameters on the response of
structures. In order to evaluate the region containing natural frequencies of structures with interval parameters, the interval
parameter perturbation method is presented in this paper. The advantage of the present method is its computational efficiency
in evaluating the region containing natural frequencies. A numerical example is used to illustrate the efficiency of the method
proposed.
The project is supported by National Youth Natural Science Foundation of China and National Outstanding Youth Science Foundation
of China. 相似文献
32.
秦俊法 《广东微量元素科学》2007,14(10):11-19
根据全国人口普查资料,用指数函数拟合法计算了中国百岁老人的死亡率和生存率,得出中国人口的最高自然寿限为120岁,并预测到2010年中国百岁老人绝对数将达4万多人,届时每百万人口中将有30位百岁老人,比2000年增加1倍以上。 相似文献
33.
34.
The natural products cis-p-menthane-1,7-diol (cis-IV), cis-p-menth-8-ene-1,7-diol (cis-I) and cis-p-menthane-1,7,8-triol (cis-II) are obtained starting from the corresponding cis-cyanohydrins, cis-2 and cis-7, respectively, by chemical transformation of the cyano into the hydroxymethyl group. The key step of the synthesis is the very high cis-selectivity (> or = 96 %) of the MeHNL-catalyzed HCN addition to 4-alkylcyclohexanones. From 4-isopropylcyclohexanone (1) the cyanohydrin cis-2 and from 4-(1-methylvinyl)cyclohexanone (6) the cyanohydrin cis-7 result almost quantitatively. Regioselective hydroxylation of cis-I affords the triol cis-II. X-ray crystal structure determinations of the final products confirm their cis-configuration. 相似文献
35.
36.
苯并咪唑及其衍生物具有良好的生物活性和荧光性质[1,2],在DNA拓扑酶抑制剂、HIV逆转录酶的抑制剂、分子探针等领域已有广泛应用,一直以来都是广大学者研究的热点[3]。苯并咪唑类化合物是一类活性很强的内吸型杀菌剂,它的主要作用方式是植物病原的R-微管蛋白结合,破坏R-微管蛋白的功能,抑制真菌的有丝分裂和形态建构。然而,随着使用时间的增加,病菌的抗生越来越强,导致在部分地区失效,给农业生产带来巨大损失。所以迫切需要寻找高效、新型的杀菌剂。近些年来,二茂铁衍生物因其广泛的生物活性,如抗癌、杀菌、杀虫、抗炎及调节植物生长等… 相似文献
37.
Atomic populations and localization [lambda(A)] and delocalization [delta(A,B)] indices (LIs and DIs) are calculated for a large set of molecules at the Hartree-Fock (HF), MP2, MP4(SDQ), CISD, and QCISD levels with the 6-311++G(2d,2p) basis set. The HF method and the conventional correlation methods [MP2, MP4(SDQ), CISD, and QCISD] yield distinct sets of LIs and DIs. Yet, within the four conventional correlation methods the differences in atomic populations and LIs and DIs are small. Relative to HF, the conventional correlation methods [MP2, MP4(SDQ), CISD, QCISD] yield virtually the same LIs and DIs for molecules with large charge separations while LIs and DIs that differ significantly from the HF values--the LIs are increased and DIs decreased--are obtained for bonds with no or small charge separations. Such is the case in the archetypal homopolar molecules HC(triple bond)CH, H2C=CH2, CH3-CH3, and "protonated cyclopropane" C(3)H(7) (+), in which case the bonding may be atypical. Relative to HF, the typical effect of the conventional correlation methods is to decrease the DI between atoms. 相似文献
38.
Simultaneous isolation and determination of esculin and rutin in natural materials using SPE and HPLC 总被引:1,自引:0,他引:1
Summary Esculin (ESC) and rutin (RUT) have been simultaneously isolated from pharmaceutical natural materials by solid phase extraction (SPE). Determination of both substances was performed by reversed phase high performance liquid chromatography (RPHPLC) with UV detection. Optimization of the separation conditions showed that simultaneous isolation and determination of rutin and esculin from pharmaceutical material was possible. The recovery obtained was not lower than 95±2%. 相似文献
39.
Bernards T.N.M. Huls B.G. van Bommel M.J. 《Journal of Sol-Gel Science and Technology》1997,10(2):193-202
This article describes the SmartKom Companion, one of three demonstrators developed within the SmartKom project whose goal
has been to provide an intuitive and intelligent interface for non-expert users to everyday computer-based applications in
different scenarios of use. Conceived for the SmartKom Mobile scenario, the Companion allows intuitive multimodal interaction
for drivers and pedestrians. The development of the SmartKom prototypes was constantly accompanied by Wizard-of-Oz experiments
as well as system evaluations at different stages of the project. Some usability evaluation results relative to the SmartKom
Companion will also be presented. 相似文献
40.
Björn O. Roos Valera Veryazov Per-Olof Widmark 《Theoretical chemistry accounts》2004,111(2-6):345-351
New basis sets of the atomic natural orbital (ANO) type have been developed for the atoms Li–Fr and Be–Ra. The ANOs have been obtained from the average density matrix of the ground states and the lowest excited states of the atom, the positive ion, and the dimer at its equilibirium geometry. Scalar realtivisitc effects are included through the use of a Douglas–Kroll Hamiltonian. Multiconfigurational wave functions have been used with dynamic correlation included using second-order perturbation theory (CASSCF/CASPT2). The basis sets are applied in calculations of the ground-state potentials for the dimers. Computed bond energies are accurate to within 0.05 eV for the alkaline dimers and 0.02 eV for the alkaline-earth dimers (except for Be2).Acknowledgments.ensp;B.O.R. would like to express his gratitude to Prof. Jacopo Tomasi for all the inspiration that his scientific work has given him through the years and continues to do in particular through the work on solvent effects on molecular properties. This work has been supported by a grant from the Swedish Science Research Council, VR.Contribution to the Jacopo Tomasi Honorary Issue 相似文献