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Delayed feedbacks are quite common in many physical and biological systems and in particular many physiological systems. Delay can cause a stable system to become unstable and vice versa. One of the well-studied non-biological chemical oscillators is the Belousov-Zhabotinsky(BZ) reaction. This paper presents an investigation of stability and Hopf bifurcation of the Oregonator model with delay. We analyze the stability of the equilibrium by using linear stability method. When the eigenvalues of the characteristic equation associated with the linear part are pure imaginary, we obtain the corresponding delay value. We find that stability of the steady state changes when the delay passes through the critical value. Then, we calculate the explicit formulae for determining the direction of the Hopf bifurcation and the stability of these periodic solutions bifurcating from the steady states, by using the normal form theory and the center manifold theorem. Finally, numerical simulations results are given to support the theoretical predictions by using Matlab and DDE-Biftool. 相似文献
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It is shown that non-rotating black holes in three or four dimensions possess a canonical entropy. Recently study indicated
that there were logarithmic corrections to Bekenstein–Hawking entropy in area with a uncertain coefficient which depends on
specific models. In this paper, the thermal fluctuations on Bekenstein–Hawking entropy in five-dimensional topological AdS
(TAds)-black holes and topological de Sitter (Tds) spaces will be considered based on a uniformly spaced area spectrum approach. 相似文献
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高效液相色谱法测定大豆中13种三嗪类除草剂多残留量 总被引:17,自引:4,他引:17
建立了同时检测大豆中13种三嗪类除草剂多残留量的反相高效液相色谱(RP-HPLC)方法。样品经乙腈提取,凝胶渗透色谱和中性氧化铝SPE柱净化,然后采用RP-HPLC-二极管阵列检测法测定,外标法定量。对样品前处理和色谱分离条件进行了研究和优化。13种三嗪类除草剂在0.06~5.0 mg/L范围内线性良好,相关系数为0.9998~0.9999。在0.02~1.0μg/g浓度范围内,平均加标回收率在71.9%~101.9%之间,相对标准偏差为2.3%~10.7%。方法简便、快速,净化效果较好,可同时满足进、出口大豆中多种除草剂残留量的检验工作需要。 相似文献
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高效液相色谱法同时测定大豆中10种磺酰脲类除草剂的残留量 总被引:13,自引:0,他引:13
首次建立了同时检测大豆中10种磺酰脲类除草剂(环氧嘧磺隆、噻吩磺隆、甲磺隆、醚苯磺隆、氯磺隆、苄嘧磺隆、氟磺隆、吡嘧磺隆、氯嘧磺隆和氟嘧磺隆)多残留量的反相高效液相色谱(RP-HPLC)方法。样品经乙腈提取、正己烷液-液分配、Florisil填充柱净化后,采用RP-HPLC-二极管阵列检测器检测(DAD)法测定,外标法定量。对样品前处理和色谱分离条件进行了详细的研究和优化。10种磺酰脲类除草剂的质量浓度在0.1~10.0 mg/L范围内其浓度与峰面积的线性关系良好,相关系数为0.9996~0.9997;在 相似文献
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气相色谱分析柑橘类水果中残留的苯丁锡 总被引:3,自引:0,他引:3
建立了气相色谱-火焰光度检测器测定柑橘类水果中苯丁锡残留量的检测方法。样品在酸性条件下经丙酮及正己烷萃取并浓缩,用正己烷溶解残渣,经乙基溴化镁衍生后,采用硅胶固相萃取柱净化,正己烷-二氯甲烷(体积比为4:1)混合液洗脱,用毛细管气相色谱-火焰光度检测器(锡滤光片: 610 nm)测定,外标法定量。结果表明: 该方法的线性范围为0.2~2.0 mg/L,相关系数r≥0.9995;当阴性脐橙样品中加标水平为0.1~0.4 mg/kg时,苯丁锡的回收率为79.6%~109.6%,相对标准偏差为3.60%~9.05%,方法的检出限为0.1 mg/kg。该方法重复性好,灵敏度高,完全满足国内外柑橘类水果中苯丁锡残留分析的要求。 相似文献
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Normal forms theory is one of the most powerful tools for the study of nonlinear differential equations, in particular, for stability and bifurcation analysis. Many works paid attention to normal forms associated with nilpotent Jacobian where the critical eigenvalues have algebraic multiplicity k ($k>1$) and geometric multiplicity one, and in particular, the case $k>2$ is more complicated for determining unfolding. Despite a lot of theoretical results on nilpotent normal forms have been obtained, computation developing can not satisfy practical applications. To our knowledge, no results have been reported on the computation of explicit formulas of the nilpotent normal forms for $k>3$ with perturbation parameters. The main difficulty is how to determine the complementary spaces of the Lie transformation. In this paper, we achieve the following results. (1) A simple dimension formula for the complementary space of the Lie transform; (2) a simple direct method to determine a basis of the complementary spaces; (3) a simple direct method to determine the projection of any vector to the complementary spaces. Using this method, the second-order normal forms for any n-dimensional nilpotent systems can be given easily. As an illustrative application, the normal forms for the vector field with triple-zero or four-fold zero singularity and functional differential equation with a triple-zero singularity are presented, and explicit formulas for the normal form coefficients with three or four unfolding parameters are obtained. 相似文献
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Sequential 1,4‐/1,2‐Addition of Lithium(trimethylsilyl)diazomethane onto Cyclic Enones to Induce C−C Fragmentation and N−Li Insertion
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Matthew J. O'Connor Chunrui Sun Xinyu Guan Venkata R. Sabbasani Prof. Daesung Lee 《Angewandte Chemie (International ed. in English)》2016,55(6):2222-2225
α,β‐Unsaturated ketones generally undergo addition reactions with nucleophiles with a preference for either 1,2‐ or 1,4‐addition, but rarely both. However, the right combination of reagents allows for consecutive 1,4‐ and 1,2‐additions to occur: Cyclic α,β‐unsaturated ketones undergo double additions with lithium(trimethylsilyl)diazomethane, effectively generating various molecular frameworks with complexity and diversity. Owing to the sequential generation of several intermediates of multifaceted reactivity, including diazoalkane derivatives and alkylidene carbenes, it is possible to induce novel Grob‐type C?C fragmentations, alkylidene carbene mediated Li?N insertions, and dipolar cycloadditions by controlling the reaction parameters. 相似文献