CH4/O2/N2层流火焰瞬态响应特性数值分析

用数值分析方法研究CH₄/O₂/N₂层流扩散火焰的瞬态响应特性.采用详细的GRI-Mech 3.0机理(包含53种组分,325个基元反应)描述CH₄氧化和NO_x生成.首先比较火焰面稳态结构的计算结果和实验数据,以验证数值方法的可靠性.用台阶跃变的火焰拉伸率来模拟瞬态流场对火焰面局部结构的影响,给出了火焰面结构(温度、组分浓度)的瞬态响应曲线,分析了火焰面的响应特性.着重探讨了不同拉伸率跃变幅度对响应特性的影响,发现火焰面的响应对于拉伸率正向跃变和负向跃变并不对称,而是相反,且在小的拉伸率跃变范围内火焰面响应时间和拉伸率跃变幅度近似成反比关系.另外,温度的平均响应时间远大于一个典型湍流燃烧场的流动时间尺度,说明火焰面非稳态效应对于湍流燃烧数值模拟有重要意义.     

电路暂态过程的分析

当有储能元件（L、C）的电路在换路时，就会产生过渡过程．如电路的接通、断开、短接、改接、元件参数的突然改变等，以及突然发生的短路、断线等各种故障．由于储能元件能量的储存与释放不能跃变，需要经历一定时间，因此，必然导致电路中发生过渡过程这个过程就是，电路中的u、i在过渡过程期间，     

输入受限的混沌系统同步控制

在混沌系统的同步控制中, 由于混沌系统对初始状态的敏感性, 一旦两个混沌系统的状态初值偏差大, 其状态同步往往需要高幅值的控制律来达到, 这给同步控制实现带来了困难, 并且在同步控制中, 两个混沌系统的初始值通常是未知的. 本文考虑控制输入受限情况下的混沌同步控制问题, 基于符号函数的近似表示式, 将受限的控制输入建模为连续可微的光滑函数, 在每一个采样点将同步控制误差系统近似为局部最优线性模型并设计连续型线性二次型调节器(LQR)最优控制律. 为降低混沌同步控制律的幅值和维持同步系统采样时刻之间的动态, 设计了等价的离散最优控制律, 并通过调整LQR性能加权矩阵值, 确保同步控制信号不会超出其受限的上界. 最后对统一混沌模型下的三种不同混沌系统同步控制进行了仿真研究. 仿真结果验证了方法的有效性. 关键词： 统一混沌模型 符号函数 输入受限 同步控制     

介观电路压缩态的热动力学研究

利用信息理论和密度矩阵，分析研究了频率随时间变化的介观LC电路中的相干态及压缩态。通过与密度矩阵相关算符，我们将相干态、压缩态的出现与电路的初始条件联系起来。结果显示：系统量子态的演化和初始状态密切相关。一般来说，由于环境温度的影响，初始处于某一激发态的介观LC电路系统会演化到压缩态；在低温下，让电路参数作阶跃变化，如果跃变前后电路的谐振频率不变，则能够制备出压缩最小测不准态。     

完全耦合互感电路对指数信号响应的解法研究

从时间域和变换域两个不同领域计算了完全耦合互感电路对指数信号的响应。在时间域，利用三要素法的结果，再用卷积积分可直接求出响应；在变换域，利用Ｓ域Ｏ－系统模型，直接得响应的象函数，取其拉氏逆变换可得其解。     

RC电路时间常数的电压对称法快速测量

研究发现,在因果周期方波信号激励下,一阶动态电路的稳态响应是因果周期信号.设方波信号电压的最大值u0,电容电压的最大值uCmax和最小值uCmin满足关系u0-uCmax=uCmin.电容电压波形关于时间轴有特殊的对称性.利用RC电路稳态响应的电压对称性,可导出电路时间常数r的快速测量方法和计算公式,为电容量测量提供可靠的快捷方法.     

基于分段色域颜色模型的高动态范围图像获取与合成

针对普通彩色相机采用多次曝光获取高动态范围图像的技术,提出了一种基于相机分段色域颜色模型的高动态范围图像获取及颜色合成的理论模型和实现方法.介绍了相机分段色域颜色模型的基本结构和建立方法.用NikonD70s彩色相机和修正的sRGB标准颜色转换模型对所提出的理论和方法进行了实验验证.结果表明,所提出的方法可以在普通彩色...     

跃变参数混沌同步及其应用

建立了跃变参数混沌同步的数学模型，提出并证明了其同步的充分条件，在理论上分析了充分条件的可实现性.提出了跃变参数混沌同步和跃变周期同步的有效算法，借助Chua混沌系统仿真实现了参数跃变混沌同步保密通信.最后，分析了跃变参数混沌保密通信对抗现有混沌窃听方法的性能.仿真结果表明跃变参数混沌同步及其保密通信具有易实现和强保密性等优点.     

耦合互感电路初始值的确定

利用ｓ域０－系统,直接得出完全响应的象函数,取其拉普拉斯逆变换得到解析解,依据 语互感电路的初始值。     

感性神经元模型及其动力学特性研究

神经元的大小属于介观尺度范围,本文考虑神经元的电感特性,建立了由细胞膜电感、膜电容、钾离子忆阻器和氯离子电阻构成的神经元经典电路模型和介观电路模型.利用经典电路理论和介观电路的量子理论,推导了在外部冲击激励下神经元细胞膜电压响应的表达式.将枪乌贼神经元的电生理参数代入膜电压表达式并计算可知,两种模型下的膜电压均先增大后减小,最后达到零值的静息状态,且其能量主要集中在0—30 Hz的脑电频率范围内.进一步比较发现,介观电路模型下膜电压的峰值及达到峰值所需的时间(达峰时间)均低于经典电路模型下的值,并与枪乌贼轴突受到刺激后的实验结果更接近,说明介观电路模型更能反应神经元受到刺激后的生理特征.基于介观电路模型,随着外部激励强度的增加,膜电压的峰值增加且达峰时间变短.膜电压峰值及达峰时间等参数更易受神经元膜电容的影响.神经元的介观电路模型对于理解神经元受到刺激后的兴奋性,推动受大脑功能启发的量子神经网络的发展等具有重要意义.     

用可调可读电阻探究非线性混沌电路实验

将FD-NCE-II非线性混沌电路实验仪接入可调可读电阻,使实验者在观察相图变化的同时读出电阻R的变化情况,得出电路出现平衡态、分岔以及涡旋状态时的电阻值及其范围。另外通过对比电路初始状态的电阻值,还可以探究非线性电路对初始参数的敏感性。     

A dynamic approach to the sudden jump model in single molecule spectroscopy

Various theories that use the sudden jump model to explain the time dependence of the optical band of a single molecule in a fluctuating environment are analyzed. It is shown that the dynamic theory of the optical band, based on the Hamiltonian of the system, should necessarily include the initial conditions for the quantum system. We show how these initial conditions should be chosen for the dynamic theory to properly describe the quantum jumps of the optical band of a single molecule. Unlike stochastic theories based on the sudden jump model, the dynamic theory predicts several absorptances of a single molecule and directly connects the absorptance fluctuations with this fact. The theory is used to account for the time dependence of the broadening of experimentally measured lines of individual molecules.     

A two-dimensional multispecies fluid model of the plasma in an ACplasma display panel

A time dependent, two-dimensional model for simulating the plasma evolution in an AC plasma display panel (AC-PDP) is described. Reaction-convection (mobility)-diffusion equations for charged particles and excited heavy neutral species are solved along with Poisson's equation, a radiation transport equation, a surface charge buildup equation, and an external L-R-C circuit equation using a fully implicit numerical method. Electron-driven rate coefficients are computed with a 0-D Boltzmann solver in the local field approximation. For studying the particle dynamics in pure helium, we consider a reduced model in which radiation transport is ignored and the excited species manifold is collapsed to composite metastable and excited states. The model predictions of breakdown voltage are quite sensitive to the value of the secondary electron emission coefficient assumed and the uncertainties in the electron-driven reaction rates. An initial comparison between the model predictions and I-V measurements from a specially constructed helium-filled panel is made with qualitatively similar behavior. The lack of quantitative agreement can be explained by a combination of uncertainties in the model input data and uncertainty in the initial surface charge state in the experiments     

交流源作用下介观RLC电路系统量子态随时间的演化

根据量子不变量理论，同时考虑介观电容器极板间电子波函数的耦合作用和电路的耗散,研究介观RLC电路系统在交流电流源作用下动力学的演化过程，并且得到描述系统量子态随时间的演化算符.进一步的分析结果表明，介观RLC电路系统的波函数将由任意的初态演化到一般的压缩态. 关键词： 介观RLC电路 交变电源 不变量理论 时间演化算符     

某些傅里葉级数的求和法

一.引言 在许多工程问题中,如整流,接焊,电视等等,周期性的非正弦函数如电流或电压时时出现,如果这些电压和电流是由傅里叶级数的形式表出,则因为这类问题中的电压或电流中的谐波丰富而各谐波的递减又相当慢,所以如果要对这些     

求解结构动力响应的卷积型DQ半解析法

通过卷积将原始控制方程构造成包含初始条件的新的具有完整初值问题特征的控制方程.该方程既与Gurtin变分原理一样有合理的数学内涵,又避免了卷积型Gurtin变分原理泛函和计算的繁复.对新的控制方程在时间域取解析函数,在空间域采用离散的DQ法,经对梁的动力响应问题的计算表明,该方法是一种精度好效率高的求解动力响应问题的计算方法.     

Relaxation dynamics of the Kuramoto model with uniformly distributed natural frequencies

The Kuramoto model describes a system of globally coupled phase-only oscillators with distributed natural frequencies. The model in the steady state exhibits a phase transition as a function of the coupling strength, between a low-coupling incoherent phase in which the oscillators oscillate independently and a high-coupling synchronized phase. Here, we consider a uniform distribution for the natural frequencies, for which the phase transition is known to be of first order. We study how the system close to the phase transition in the supercritical regime relaxes in time to the steady state while starting from an initial incoherent state. In this case, numerical simulations of finite systems have demonstrated that the relaxation occurs as a step-like jump in the order parameter from the initial to the final steady state value, hinting at the existence of metastable states. We provide numerical evidence to suggest that the observed metastability is a finite-size effect, becoming an increasingly rare event with increasing system size.     

Exact Solutions to the Quantum Rabi-Stark Model Within Tunable Coherent States

The quantum Rabi-Stark model, where the linear dipole coupling and the nonlinear Stark-like coupling is present on an equal footing, is studied within the tunable extended coherent states. The eigenvalues and eigenstates are therefore obtained exactly. Surprisingly, the entanglement entropy in the ground-state is found to jump suddenly with the coupling strength. The first-order quantum phase transition can be detected by level crossing of the ground state and the first excited state, which is however lacking in the original linear quantum Rabi model. Performing the first-order approximation in the present theory, we can derive closed-form analytical results for the ground-state. Interestingly, it agrees well with the exact solutions up to the ultra-strong coupling regime in a wide range of model parameters. The spectral collapses when the absolute value of the nonlinear coupling strength approaches to twice the cavity frequency is observed with the help of new solutions in the limits.     

Bulk conductivity and polarization of ionic crystals exhibiting defect exchange between inequivalent sites

The bulk conductivity of ionically conducting crystals in which Schottky or Frenkel defects jump between inequivalent sites can be appreciably more complex than that of simpler materials. An equivalent electrical circuit is derived to describe the bulk ac response of crystals of the tysonite type. The circuit has the form of a two-component Maxwell-Wagner capacitor and includes a capacitative element which represents a frequency-dependent bulk polarization not associated with dipolar complexes. The application of the model to LaF₃ is discussed.     

Dynamical behavior of a mesoscopic circuit in phonons bath derived by virtue of the IWOP technique

Taking into account the interactions between electrons and phonons, we study the dynamic behavior of a dissipative mesoscopic circuit for pure initial coherent state of phonon bath modes by virtue of the IWOP technique. It shows that if the bath modes are initially in coherent states, some phenomena like Brownian behavior will appear in mean charge and current of the mesoscopic circuit. The quantum fluctuations of charge and current are constant and irrelevant to the coupled coefficients between electrons and phonons.