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861.
Bixia Yao Fengping Zhan Guangyan Yu Zhifen Chen Wenjing Fan Xiongping Zeng Qingle Zeng Wen Weng 《Journal of chromatography. A》2009,1216(28):5429-5435
In this work, the enantioseparations of 1,1′-bi-2-naphthol (BINOL) and its three derivatives were performed on an immobilized polysaccharide-based chiral stationary phase, Chiralpak IA, under normal-phase mode. The effects of the content of polar modifier in the mobile phase and the column temperature on the retention and enantioseparation were investigated in detail. Temperature-induced inversion of elution order for BINOL was observed directly when n-hexane/2-propanol (92/8, v/v) was used as mobile phase. The isoenantioselective temperature (Tiso) was calculated to be 31.4 °C. When n-hexane/2-propanol/THF (93/2/5, v/v/v) was used as mobile phase, the Tiso value decreased to −8.2 °C. Entropically driven enantioseparation which had practical application was obtained successfully (separation factor being 1.189 and 1.332 at 25 °C and 50 °C, respectively). The corresponding thermodynamic parameters for other three binaphthyl compounds were compared with that for BINOL. Some inferences about chiral recognition mechanism were stressed. 相似文献
862.
The decomposition in HTPB bonded HMX was characterized with two highly sensitive methods: heat flow microcalorimetry (HFMC)
and Chemiluminescence (CL). The material is stabilized with a phenolic antioxidant. The heat generation (HFMC) rate was determined
from 120 to 150 °C using a TAM™ microcalorimeter and the oxidation of the substance was followed by the CL emission between
100 and 140 °C directly from the solid state sample. The end of antioxidant activity results in both measurements sets in
characteristic changes in the curves. Kinetic parameters were calculated applying Arrhenius parameterization for the times
to the end of antioxidant activity and by applying modelling with an autocatalytic model extended by a side reaction, which
is assigned to the antioxidant consumption. The evaluation with the characteristic times gives good agreement between the
two methods; the modelling represents the different but supplementing probing of the two measurement methods.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
863.
When applied to the classical dynamical equations, generally, conventional time-stepping methods cannot conserve the total energy exactly, but up to their algebraic order. To obtain an energy-conserving method, we add an energy calibrated parameter to some conventional ones. The periodic stability and phase-lag property of this type of energy-conserving methods are investigated in this note. Some numerical results are reported to illustrate our conclusions. 相似文献
864.
The parameterized Uzawa preconditioners for saddle point problems are studied in this paper. The eigenvalues of the preconditioned matrix are located in (0, 2) by choosing the suitable parameters. Furthermore, we give two strategies to optimize the rate of convergence by finding the suitable values of parameters. Numerical computations show that the parameterized Uzawa preconditioners can lead to practical and effective preconditioned GMRES methods for solving the saddle point problems. 相似文献
865.
Alewyn P. Burger 《Discrete Mathematics》2009,309(8):2473-2036
The relationship ρL(G)≤ρ(G)≤γ(G) between the lower packing number ρL(G), the packing number ρ(G) and the domination number γ(G) of a graph G is well known. In this paper we establish best possible bounds on the ratios of the packing numbers of any (connected) graph to its six domination-related parameters (the lower and upper irredundance numbers ir and IR, the lower and upper independence numbers i and β, and the lower and upper domination numbers γ and Γ). In particular, best possible constants aθ, bθ, cθ and dθ are found for which the inequalities and hold for any connected graph G and all θ∈{ir,γ,i,β,Γ,IR}. From our work it follows, for example, that and for any connected graph G, and that these inequalities are best possible. 相似文献
866.
This paper presents the dual bases for Wang-Bézier curves with a position parameter L, which include Bézier curve, Wang-Ball curve and some intermediate curves. The Marsden identity and the transformation formulas from Bézier curve to Wang-Bézier curve are also given. These results are useful for the application of Wang-Bézier curve and their popularization in Computer Aided Geometric Design. 相似文献
867.
含估计参数的加权经验过程 总被引:1,自引:0,他引:1
在讨论(广义)非参数似然比拟合优度检验时,加权经验过程理论是一个非常重要的基础.但对含估计参数的加权经验过程理论,目前文献中很少讨论.对含估计参数的加权经验过程的上界型和积分型两种统计量的近似分布进行了讨论,给出了较一般的结果.所得结论叮以为进一步讨论复合零假设下(广义)非参似然比拟合优度检验提供理论基础. 相似文献
868.
In this paper, we propose a discrepancy rule-based method to automatically choose the regularization parameters for total variation image restoration problems. The regularization parameters are adjusted dynamically in each iteration. Numerical results are shown to illustrate the performance of the proposed method. 相似文献
869.
In this paper, we consider the problem of testing for the parameter change in discretely observed diffusion processes. For
a test, we perform the cusum test based on the estimator proposed by Kessler (J Stat 24:211–229, 1997). It is shown that the
test statistic weakly converges to the sup of the square of a Browian bridge. Simulation results are illustrated for the Ornstein-Uhlenbeck
and Cox-Ingersoll-Ross processes. 相似文献
870.
递归关系不仅在数学中有广泛应用,而且在计算机算法设计与分析中也有广泛应用.本文对Josephus问题进行了推广,得到一类更广泛的递归关系模型.讨论了这类模型的求解方法,采用d-进制记数法,给出了这类递归关系模型的解. 相似文献