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71.
两个非线性方程的准确解 总被引:3,自引:0,他引:3
借助于计算机代数系统Mathematica利用直接代数方法获得了两个有数学物理意义的非线性耗散-色散方程的准确解,这种方法也适用于高维非线性方程。 相似文献
72.
一类非经典扩散方程整体解的存在唯一性及长时间行为 总被引:5,自引:0,他引:5
本文讨论非经典扩散方程第一初边值问题整体解的存在唯一性及长时间行为,建立了一系列新的结果,较好地改进许多已有的结论. 相似文献
73.
金融时间序列分析与建模 总被引:1,自引:0,他引:1
胡锡健 《新疆大学学报(理工版)》2007,24(2):150-158
介绍了金融时间序列分析与建模的主要理论、方法,着重论述了近20多年发展起来的非平稳时间序列的建模方法及工具,指出进一步的研究方向.最后,对上证综合指数这一金融时间序列进行了实证分析. 相似文献
74.
Stochastic mechanism of relaxation, in which a dipole waits until a favourable condition for reorientation exists, is discussed. Assuming that an imposed direction of a dipole moment may be changed when a migrating defect reaches the dipole, we present a mathematically rigorous scheme relating the local random characteristics of a macroscopic system to its effective relaxation behaviour. We derive a relaxation function (the Burr survival probability) that is characterized by the stretched exponential or the power-law behaviour. 相似文献
75.
The problem treated in this paper concerns calculating the evolution of the pressure in a single-phase, slightly compressible fluid in a porous medium consisting of communicating layers. The fluid is produced through a point sink located on the side of an otherwise sealed cylindrical wellbore. This location of the sink causes the flow around the wellbore to be azimuthally asymmetric.The problem is solved through successive application of Laplace, finite Fourier and finite Hankel transforms. Although apparently straightforward, this approach leads to serious numerical difficulties. The published form of the inversion formula for the finite Hankel transform leads to inaccurate computation for the higher azimuthal modes even with 128 bit arithmetic. An alternative form is developed which enables accurate evaluation of the solution with the more practical 64 bit arithmetic. The technique for two-layer solution presented here can be directly extended to a problem with a larger number of communicating layers. This is the first instance of successful application of the finite Hankel transform to an azimuthally asymmetric diffusion problem. 相似文献
76.
Na2CO3调质钙基脱硫剂硫化机理实验研究 总被引:7,自引:0,他引:7
对经Na2CO3溶液调质石灰石煅烧产物CaO的物理结构及硫化特性进行了研究,发现同等条件下调质后石灰石煅烧产物CaO(M-CaO)比未经调质的CaO(N-CaO)具有更高的钙转化率.利用XRD技术对CaO晶体结构进行了测定,通过比较二者的晶胞参数和晶格畸变度等并结合其孔特性,证实M-CaO之所以比N-CaO具有更高的钙转化率,是由于M-CaO比N-CaO具有更高的晶体缺陷浓度,使得在硫化反应过程中通过产物层的扩散具有更高的离子扩散率. 相似文献
77.
崔霞 《高等学校计算数学学报(英文版)》2002,11(1):76-88
A new alternating direction (AD) finite element (FE) scheme for 3-dimensional nonlinear parabolic equation and parabolic integro-differential equation is studied. By using AD, the 3-dimensional problem is reduced to a family of single space variable problems, calculation work is simplified; by using FE, high accuracy is kept; by using various techniques for priori estimate for differential equations such as inductive hypothesis reasoning, the difficulty arising from the nonlinearity is treated. For both FE and ADFE schemes, the convergence properties are rigorously demonstrated, the optimal H1-and L2-norm space estimates and the 0((△t)2) estimate for time variable are obtained. 相似文献
78.
Distribution of melamine in polyester–melamine surface coatings cured under nonisothermal conditions
N. J. W. Gamage D. J. T. Hill C. A. Lukey P. J. Pomery 《Journal of polymer science. Part A, Polymer chemistry》2004,42(1):83-91
The influence of experimental cure parameters on the diffusion of reactive species in polyester–melamine thermoset coatings during curing has been investigated with X‐ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared. The diffusion of melamine plays a vital role in the curing process and, therefore, in the ultimate properties of coatings. At a low (<20%) hexamethoxymethylmelamine (HMMM) crosslinker concentration, the matrix composition is uniform, but at high HMMM concentrations, excess HMMM rapidly segregates to the air–coating interface. The rate of migration is governed by the difference in the surface free energies of polyester and HMMM and the concentration gradient of HMMM between the bulk and the surface. An increased rate of energy absorption also increases the rate of migration of HMMM to the surface. A physical model has been proposed to explain this surface segregation phenomenon in terms of cocondensation and self‐condensation reactions. It suggests that an appropriate amount of melamine can be segregated on the surface and allowed to self‐condense to form a desired thickness of a melamine topcoat through the control of the binder composition and cure conditions. This technique can be implemented to apply a melamine topcoat during cure. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 83–91, 2004 相似文献
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