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41.
Arrhenius parameters values, in non-isothermal kinetic vaporisation processes for a series of compounds with related structures, have been calculated. This was made using a method of calculation that allows to find the most probable vaporisation mechanisms. According to this method DTG curves were compared with some theoretical ones reported in literature, whose shape results to be only a function of the mechanisms. In this way the choice of the mathematical functions which can be inserted in the kinetic equations, was influenced by the shape of the DTG plots and other thermal analysis signals thus allowing to choose the most probable mechanisms. The kinetic parameters derived from these mechanisms were compared, using statistical analysis, with those obtained from another method of calculation based on ‘a priori’ vaporisation mechanism chosen for the investigated liquid–gas transition. The standard deviations of the slope and of the intercept, together with the standard deviation and the square correlation coefficient (r 2) of the linear regression equations related to the mechanisms of the two methods were calculated. Student t-test, Fisher F-test, confidence intervals (c.i.) and residuals valueswere also given. Statistical analysis shows that the mechanisms obtained with the former method (diffusive and geometrical models) and the related Arrhenius parameters result to be more significant (in terms of probability) than the corresponding quantities of the latter for which a first-order model was chosen. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
42.
激光通道传输热特性对远场光束质量的影响   总被引:3,自引:1,他引:3       下载免费PDF全文
 通过仿真计算分析了激光在光束控制系统通道内传输所产生的热效应及其对远场光束质量的影响。激光传播由近轴波方程描述,用快速傅里叶变换技术求解;激光热效应引起的流场密度变化采用完全Navier-Stokes方程计算。计算给出了不同波长、不同吸收系数条件下的远场光斑情况。计算结果表明,在典型的工作条件和状态下,较高能量激光在光束控制系统通道内产生的热效应影响不容忽视,它会明显降低远场目标处的能量集中度,增大光斑的发散。  相似文献   
43.
薛秉侃 《大学物理》2008,27(2):59-59,63
通过平面方程证明了晶面指数必无公因子.  相似文献   
44.
Starting from a discrete spectral problem, a hierarchy of integrable lattice soliton equations is derived. It is shown that the hierarchy is completely integrable in the Liouville sense and possesses discrete bi-Hamiltonian structure. A new integrable symplectic map and finite-dimensional integrable systems are given by nonlinearization method. The binary Bargmann constraint gives rise to a Bäcklund transformation for the resulting integrable lattice equations. At last, conservation laws of the hierarchy are presented.  相似文献   
45.
As an improved version of trial equation method, a new trial equation method is proposed. Using this method, abundant new exact traveling wave solutions to a high-order KdV-type equation are obtained.  相似文献   
46.
In this paper, we improve the method for deriving Jacobi elliptic function solutions of nonlinear evolution equations given in Ref. [12] and apply it to the integrable higher-order Broer-Kaup system in (2 1)-dimensional spaces.Some new elliptic function solutions are obtained.  相似文献   
47.
In this paper, we present a fully Lagrangian method based on the radial basis function (RBF) finite difference (FD) method for solving convection–diffusion partial differential equations (PDEs) on evolving surfaces. Surface differential operators are discretized by the tangent plane approach using Gaussian RBFs augmented with two-dimensional (2D) polynomials. The main advantage of our method is the simplicity of calculating differentiation weights. Additionally, we couple the method with anisotropic RBFs (ARBFs) to obtain more accurate numerical solutions for the anisotropic growth of surfaces. In the ARBF interpolation, the Euclidean distance is replaced with a suitable metric that matches the anisotropic surface geometry. Therefore, it will lead to a good result on the aspects of stability and accuracy of the RBF-FD method for this type of problem. The performance of this method is shown for various convection–diffusion equations on evolving surfaces, which include the anisotropic growth of surfaces and growth coupled with the solutions of PDEs.  相似文献   
48.
The Pauli master equation describes the statistical equilibration of a closed quantum system. Simplifying and generalizing an approach developed in two previous papers, we present a derivation of that equation using concepts developed in quantum chaos and random-matrix theory. We assume that the system consists of subsystems with strong internal mixing. We can then model the system as an ensemble of random matrices. Equilibration results from averaging over the ensemble. The direction of the arrow of time is determined by an (ever-so-small) coupling to the outside world. The master equation holds for sufficiently large times if the average level densities in all subsystems are sufficiently smooth. These conditions are quantified in the text, and leading-order correction terms are given.  相似文献   
49.
在任意温度的热库中量子位的消相干   总被引:30,自引:7,他引:30  
本文在Markov 近似下推导了在任意温度的热库中,一个量子位(qubit)的主方程,并由此讨论了由于振幅阻尼而引起的量子位消相干(decoherence). 结论表明量子位的跃迁频率与热库的特征频率及截止频率的关系对消相干有明显的影响。  相似文献   
50.
利用“神光-Ⅱ”的3路基频光输出及小透镜列阵束匀滑技术,通过优化设计和合理地选择光路组合,实现了多路叠加斜入射的驱动激光, 在靶材料中产生一个650~750μm范围内平面性良好的冲击波,有效地提高了“神光-Ⅱ”输出光束的利用率。同时,利用斜面靶进行的冲击稳定性实验表明,在靶面功率密度分别为3.26×1014及2.56×1014W/cm2时,冲击波至少在28.38~55.82和22.13~35.07μm的Al样品厚度内是稳定传播的。  相似文献   
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