共查询到18条相似文献,搜索用时 50 毫秒
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糖酵解模型差速流动引起的不稳定性和时空结构 总被引:1,自引:0,他引:1
建立了糠酵解模型(Selkov模型)差速流动型反应扩散方程,理论研究 了均匀定态的稳定性,结果表明,当自催化物B的流速φ大于临界值φc时,系统存在运流不稳定性(Convective instability);数值模拟分别得到了B在不同时刻和不同流速φ下的时空结构,显示了一些特殊,性质同时也证实了运流不稳定性的存在。 相似文献
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利用麦克斯韦方程组和场的轴对称性,分别对含不稳定电荷源和不稳定电流源的轴对称非静态空间电磁场进行了研究.首先,导出了3个基本表达式,然后,以对称轴的已知不稳定场量作为初始值,通过不断迭代并总结其规律,给出由对称轴上的已知不稳定场量来表示轴外任意一点电磁场的无穷级数表达式,最后,对结果进行了验证,对其敛散性进行了分析. 相似文献
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采用稳态的和非稳态的火焰面模型同时对一个湍流甲烷射流扩散火焰进行了数值模拟,比较了两者对湍流平均火焰结构、活性自由基和污染物(氮氧化物)排放的模拟效果。速度场采用κ-ε模型计算,守恒标量混合物分数的分布通过其概率密度函数(PDF)输运方程的求解得到。稳态的火焰面结构由查询火焰面数据库得到,而非稳态的火焰面结构由火焰面方程和流场方程耦合求解来计算。采用详细的GRI—Mech 3.0机理描述甲烷的氧化和氮氧化物的形成。数值模拟结果和实验数据作了广泛的对比,验证了火焰面模型对湍流扩散燃烧的定量模拟能力。 相似文献
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研究El-Nabulsi动力学模型下非Chetaev型非完整系统精确不变量与绝热不变量问题. 首先, 导出El-Nabulsi-d'Alembert-Lagrange原理并建立系统的运动微分方程. 其次, 建立El-Nabulsi模型下未受扰动的非Chetaev 型非完整系统的Noether对称性与Noether对称性导致的精确不变量之间的关系; 再次, 引入力学系统的绝热不变量概念, 研究受小扰动作用下非Chetaev型非完整系统Noether对称性的摄动导致绝热不变量问题, 给出了绝热不变量存在的条件及其形式. 作为特例, 本文讨论了El-Nabulsi模型下Chetaev型非完整系统的精确不变量与绝热不变量问题. 最后分别给出非Chetaev型和Chetaev型两种约束下的算例以说明结果的应用. 相似文献
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中高能区的破碎和敲出反应,由于机制相对简单、对核的表面敏感、理论处理比较成熟等原因,在非稳定核的晕结构、壳移动等奇特性质研究中发挥了独到作用。针对次级束流强度较弱、能散较大等特点,实验上发展和应用了逆运动学有效立体角完全测量、轻重靶结合、高精度消色差磁谱仪、前向中子谱仪、在束γ测量等技术手段,大大提升了实验的探测能力和选择性。从物理问题探索和实验路线演变的角度,回顾了非稳定核破碎和敲出反应的发展过程与启示,并探讨未来的走向。 相似文献
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A. Bret 《等离子体物理论文集》2007,47(3):133-138
The Weibel instability is prompted by a temperature anisotropy within a plasma. We investigate its growth rate for wave vectors making an arbitrary angle with the high temperature axis. We use a two temperatures waterbags model and derive stability conditions depending on both temperatures and wave vector orientation. It is found that the growth rate is maximum for wave vectors normal to the high temperature axis. Also, a critical angle is evidenced in the k space in which direction modes are unstable at high k although the growth rate decreases quickly in this direction. Exact results are derived in most cases. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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采用双层线性耦合Lengyel-Epstein模型,在二维空间对简单正四边和超点阵四边形进行了数值分析.结果表明:当两子系统波数比N1时,随耦合强度的增大,基模的波矢空间共振形式发生改变,系统由简单六边形自发演化为结构复杂的新型斑图,除已报道的超六边形外,还获得了简单正四边和多种超点阵四边形,包括大小点、点线、白眼和环状超四边等斑图.当耦合系数α和β在一定范围内同步增大时,两子系统形成相同波长的Ⅰ型简单正四边;当α和β不同步增大时,由于两图灵模在短波子系统形成共振,系统斑图经相变发生Ⅰ型正四边→Ⅱ型正四边→超点阵四边形的转变;当系统失去耦合作用时,短波子系统波长为λ的Ⅰ型正四边斑图迅速失稳并形成波长为λ/N的Ⅰ型正四边,随模拟时间的延长,两子系统中不同波长的正四边均会经相变发生Ⅰ型正四边→Ⅱ型正四边→六边形的转变. 相似文献
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By considering the fluctuation of grand potential Ω around equilibrium with respect to small one-particle density fluctuations δρα\vec{r}, the phase instability of restricted primitive model (RPM) of ionic systems is investigated. We use the integral equation theory to calculate the direct correlation functions in the reference hypernetted chainapproximation and obtain the spinodal line of RPM. Our analysis explicitly indicates that the gas-fluid phase instability is induced by k=0 fluctuation mode, while the fluid-solid phase instability is related to k≠0 fluctuation modes. The spinodal line isqualitatively consistent with the result of computer simulations by others. 相似文献
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By considering the fluctuation of grand potential f~ around equilibrium with respect to small one-particle density fluctuations δpα(r→), the phase instability of restricted primitive model (RPM) of ionic systems is investigated. We use the integral equation theory to calculate the direct correlation functions in the reference hypernetted chain approximation and obtain the spinodai line of RPM. Our anaiysis explicitly indicates that the gas-fluid phase instability is induced by k = 0 fluctuation mode, while the fluid-solid phase instability is related to k ≠ 0 fluctuation modes. The spinodai line is qualitatively consistent with the result of computer simulations by others. 相似文献
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We consider the static Holstein model, describing a chain of fermions interacting with a classical phonon field, when the interaction is weak and the density is a rational number p = P/Q, with P, Q relative prime integers. We show that the energy of the system, as a function of the phonon field, has one (if Q is even) or two (if Q is odd) stationary points, defined up to a lattice translation, which are local minima in the space of fields periodic with period equal to the inverse of the density. 相似文献
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Cross-diffusion is a ubiquitous phenomenon in complex networks, but it is often neglected in the study of reaction–diffusion networks. In fact, network connections are often random. In this paper, we investigate pattern dynamics of random networks with cross-diffusion by using the method of network analysis and obtain a condition under which the network loses stability and Turing bifurcation occurs. In addition, we also derive the amplitude equation for the network and prove the stability of the amplitude equation which is also an effective tool to investigate pattern dynamics of the random network with cross diffusion. In the meantime, the pattern formation consistently matches the stability of the system and the amplitude equation is verified by simulations. A novel approach to the investigation of specific real systems was presented in this paper. Finally, the example and simulation used in this paper validate our theoretical results. 相似文献
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研究了光子晶体光纤中调制不稳定性效应.从非线性薛定谔方程出发,计算和分析了光子晶体光纤中反常色散区以及正常色散区内的调制不稳定性现象,详细讨论了超短脉冲的脉宽、峰值功率、高阶色散和高阶非线性效应(如脉冲内喇曼散射、自陡峭效应)对调制不稳定性产生的影响.结果表明:二阶色散对调制不稳定性的影响要远大于三阶色散,同时也发现随着初始脉冲宽度的减小,调制不稳定性旁瓣增大但是强度有所降低.另外还发现高阶非线效应如自陡峭和喇曼效应会在不同程度上抑制调制不稳定性. 相似文献