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本文对广义风险过程中的渐近方差作了非参数估计,得出并证明了两个定理,为广义风险过程中破产概率的区间估计作了理论准备. 相似文献
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A new method is proposed for routine determinations of oxidizable and reducible substances. A mathematical development and criticism of the method of Schierjott has led to a fundamental modification of the earlier experimental conditions (ratio of the oxidized/reduced forms of the reagent at the start and end of the redox reaction). This improvement allows a considerable increase in the sensitivity of the method and is particularly advantageous for the determination of substances of low reactivity, e.g. carbohydrates. Other advantages are a reduction in the quantity and thus cost of the necessary reagent, and a decreased risk of precipitation of the substances involved. The mathematical treatment of the proposed version allows a rigorous theoretical comparison of the two methods. An evaluation of the quality of the approximations introduced into both methods is also proposed, based on the calculation of the deviation (absolute and relative differences) of approximated values from theoretical values. The final part of the work deals with optimization of the different principal parameters, i.e. concentration of the reagent, temperature and reaction time. 相似文献
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高效液相色谱氮杂冠醚键合固定相的合成及性能研究 总被引:2,自引:0,他引:2
我们曾用γ-氯丙基键合硅胶(CPS),在氢化钠(NaH)作用下合成了3-(氮杂-18-冠-6)丙基键合固定相(BCP)[1].该固定相对碱基、核苷酸、硝基苯酚等有较好的分离选择性,但由于NaH对硅胶基质腐蚀作用较大,导致BCP柱效及渗透性较低.本文采... 相似文献
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Electrospray ionization in combination with tandem mass spectrometric techniques has been employed to study the formation of oxomanganese-salen complexes upon oxidation of [Mn(III)(salen)]+ cations as well as the properties and reactions of the oxidized species in the gas phase. Two species could be characterized as the principal oxidation products: the oxomanganese(v) complex, [Mn=O(salen)]+, which is the actual oxygen-transfer agent in epoxidation reactions, and the dinuclear, mu-oxo bridged [L(salen)Mn-O-Mn(salen)L]2+ with two terminal ligands L; the latter acts as a reservoir species. The effects of various substituents in the 5- and 5'-positions, respectively, of the salen ligand on the reactivity of the epoxidation catalyst were determined quantitatively from CID (collision-induced dissociation) experiments and B3LYP density functional calculations. Accordingly, the effect of axial donor ligands on the reactivity of the epoxidation catalyst was studied. Electron-withdrawing substitutents on the salen ligand and additional axial ligands decrease the stability and thus enhance the reactivity of the Mn=O moiety, while electron-donating salen substituents have a strong stabilizing effect. 相似文献
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Fabian Gerson William B. Martin Georges Plattner Franz Sondheimer Henry N. C. Wong 《Helvetica chimica acta》1976,59(6):2038-2048
ESR. studies are reported for the radical anions of 5,6-didehydro- and 5,6,11,12-tetradehydro-dibenzo[a,e]cyclooctene (III and IV, resp.), in addition to that of dibenzo[a,e]cyclooctene (II) itself, the spectrum of which has been reexamined. Comparison of the proton and 13C coupling constants for II·?, III·? and IV·? indicates that the three radical anions do not differ greatly in their electronic and molecular structures. This statement implies that II·? should also be substantially planar, i.e., the tub-shaped eight-membered ring in II is expected to flatten on passing from the neutral molecule to its radical anion. Support for postulating such a change in geometry, analogous to that encountered with the parent cyclooctatetraene (I), is provided by INDO calculations. 相似文献
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Focusing on the rapid prediction of acoustic field uncertainty in environment with temporal and spatial sound speed perturbation, evolvement of sound speed structure over time is predicted based on the ocean-acoustic coupled model to obtain the uncertainty distribution of the vertical structure of sound speed. Further, a method combining the arbitrary polynomial chaos expansion with the empirical orthogonal function is proposed to reduce the dimensionality of uncertain parameters and to obtain the uncertainty distribution of the acoustic field. Simulations have shown that the computational complexity can be reduced by 2 orders of magnitude compared to the conventional polynomial chaos expansion while ensures the same precision.Moreover, the computational complexity is not influenced by the complexity of the sound speed profile. The acoustic field and uncertainty predicted in uncertain environment by proposed method also have been tested with the experimental data. 相似文献