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121.
The dependence of Mentha pulegium L. (pennyroyal) essential oil composition, obtained by supercritical carbon dioxide (SC-CO2), with the following parameters: pressure, temperature, extraction time (dynamic), and modifier (methanol) was studied. The results were also compared with those obtained by conventional hydrodistillation method in laboratory conditions. Regarding the percentages of menthone (30.3%) and pulegone (52.0%), the optimum SFE results were obtained at the following experimental conditions: pressure=100 atm, T=35 °C, dynamic time=10 min, and Vmodifier=0 μl. The results of hydrodistillation showed that the major components of M. pulegium L. were pulegone (37.8%), menthone (20.3%), and piperitenone (6.8%). The evaluation of the composition of each extract was performed by gas chromatography-mass spectrometry. 相似文献
122.
《Electroanalysis》2003,15(10):898-902
A method based on capillary electrophoresis (CE) with electrochemical detection (ED) was developed for the determination of taurine in Lycium Barbarum L., LIPOVIYAN beverage and milk powder. The effects of some important factors such as the acidity of the running buffer, separation voltage, injection time, and applied potential to working electrode were investigated. Operated in a wall‐jet configuration, a 300 μm diameter carbon‐disk electrode was used as the working electrode, which exhibits good responses at +1.05 V (vs. SCE) for taurine. Excellent linearity was obtained in the concentration range from 5.0×10?4 mol/L to 5.0×10?6 mol/L. The detection limit (S/N=3) was 1.0×10?7 mol/L. This proposed method has been successfully applied to analyze the actual samples with satisfactory assay results. 相似文献
123.
In this paper, we establish the discrete approximation of continuous-state nonlinear branching processes in Lévy random environments by using tightness and convergence sequence in infinite dimensional product space via stochastic differential equations. Taking α-stable branching as an example, the conditions which are given to discretize continuous-state nonlinear branching processes in Lévy random environments are verified. © 2022 Chinese Academy of Sciences. All rights reserved. 相似文献
124.
An augmented Lagrange algorithm for nonlinear optimizations with second-order cone constraints is proposed based on a Löwner operator associated with a potential function for the optimization problems with inequality constraints. The favorable properties of both the Löwner operator and the corresponding augmented Lagrangian are discussed. And under some mild assumptions, the rate of convergence of the augmented Lagrange algorithm is studied in detail. 相似文献
125.
Asymptotic Behavior of a Stochastic Predator-prey Model with Beddington-DeAngelis Functional Response and L\'{e}vy Jumps 下载免费PDF全文
A stochastic two-prey-one-predator model with Beddington-DeAngelis functional response and L\''{e}vy jumps is proposed and investigated in this paper. First of all, we prove the existence and uniqueness of the global positive solution, and stochastic ultimate boundedness of the solution. Next, under a simple assumption, by using It\^{o} formula and other important inequalities, some sufficient conditions are established to ensure the extinction and persistence in the mean of the system. The results show that neither strong white noise nor L\''{e}vy noise is conducive to the persistence of the population. Finally, the theoretical results are verified by numerical simulations. 相似文献
126.
Summary.
For implicit RK-methods applied to
singularly perturbed systems of ODEs it is shown
that the resulting discrete systems preserve the
geometric properties of the underlying ODE. This
invariant manifold result is used to derive sharp
bounds on the global error of RK-solutions.
Received August 26, 1993 / Revised version received May 10,
1994 相似文献
127.
It is shown that with probability 1 on , resp. ongx the irrational rotation algebra
with respect to the CAT map and the generalized Price-Powers shiftA
X
are asymptotically highly anticommutative. 相似文献
128.
A sufficient condition for the symplecticness ofq-derivative Runge-Kutta methods has been derived by F. M. Lasagni. In the present note we prove that this condition can only be satisfied for methods withq1, i.e., for standard Runge-Kutta methods. We further show that the conditions of Lasagni are also necessary for symplecticness so that no symplectic multi-derivative Runge-Kutta method can exist.This research has been supported by project PB89-0351 (Dirección General de Investigación Científica y Técnica) and by project No. 20-32354.91 of Swiss National Science Foundation. 相似文献
129.
X. -D. Cao 《Periodica Mathematica Hungarica》1994,28(1):43-54
Let
, wheref(n) is the characteristic function of square-full integers. A formula is proved that can be used to obtain better upper bound estimate for (x). We get (x)=O(x
5/33+), which improves the exponent 11/72 obtained by R. Blasubramania and K. Ramachandra. 相似文献
130.