共查询到20条相似文献，搜索用时 31 毫秒
1.
Two different bond-graph schemes for the modeling of circulating fluids are discussed and compared. The first uses a heuristic approach wherein the flow path is broken into segments. Each segment has separate hydraulic and thermal submodels which are linked with active bonds. The model is general enough to handle natural convective flows, heat storage, conduction, forced convective heat transfer and heat energy sources. The second method, applicable to pumped flows, uses a modal analysis approach to derive state equations for the modal temperatures, the time varying coefficients of the spatially varying mode shapes in a separation of variables solution for the temperature partial differential equation. Two examples are worked to illustrate the models. Numerical simulation results are presented using the first method and a simple analytic solution given to illustrate the second. 相似文献
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利用传统方法很难在计算机上实现差分方程的解析解求解,本文提出了一种获得差分方程解析解的线性算法,该算法的基础是完全线形变化法。其核心操作为降维处理,对高阶差分方程进行逐次降阶运算,直至获得其解析解表达式。本质上,该算法属于Z变换法的一种矩阵法变形。算法的线性特征使得其容易移植到计算机上实现差分方程的解析解运算,而非传统的数值迭代解。 相似文献
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This paper is devoted to the identification of analytic signals and to find a solution to the following problem. Given a realization of an analytic signal, it is necessary to find the analytic function by which the signal is described. The proposed approach to this problem is based on relatively simple relationships existing between many analytic signals and their respective derivatives. These relationships are closely related to the properties of the dynamic systems which generate the signals under investigation. Simple identification procedures are described and tested by means of computer simulation. 相似文献
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Vivian O&#x;Brien 《Journal of The Franklin Institute》1975,300(3):225-230
Solutions for pulsatile fully developed flow of Newtonian viscous fluid in a straight rectangular channel can be synthesized from analytic solutions of steady flow and oscillatory flow. A new steady solution is presented that is valid for all duct aspect ratios. Also new oscillatory solutions are given, showing dependence on a “viscous diffusion length”, the square root of the kinematic viscosity divided by frequency. 相似文献
5.
G.F. Nalesso 《Journal of The Franklin Institute》1982,313(5):247-266
The problem of the magnetic field diffusion through cylindrical structures is considered. An analytic solution is given for the problem of diffusion, through any number of resistive coaxial layers, of the three components of a quite general input vector magnetic field assigned on a boundary cylindrical surface. The limitations on the class of input functions (or more generally distributions) are the existence of the double space Fourier transform and the time Laplace transform; this makes the solution suitable for studying the transient-state behaviour in cylindrical structures of finite or infinite length. 相似文献
6.
《Journal of The Franklin Institute》1986,321(1):1-19
The solution of the optimization problem for convective pins with uniform internal heat generation is presented. Pins with constant thickness, triangular and parabolic profile are treated, and the cases considered are those of a given heat generation density, or total heat generation, when either the heat dissipation or the width of the pin is prescribed. The results are generalized, in a nondimensional form, and presented graphically. The effect of the pin's thermal conductivity upon the optimum dimensions is discussed, and limiting values of the heat generation and the heat dissipation, that may be imposed on the pin for a feasible optimization, are also obtained. 相似文献
7.
The problem of minimizing the maximum temperature of a purely conducting circular fin with heat generation is studied via a variational technique. An exact solution is obtained for an arbitrary heat source distribution and a general non-linear heat conductivity. The problem of minimum weight design of convecting circular fin is then considered. An exact solution for temperature distribution and shape of the optimum fin with constant heat generation is obtained and discussed. 相似文献
8.
以变系数径向导热问题为研究对象,由傅里叶导热定律提出了较之文献更为合理的热导计算方法.根据流的相容性原理分别推导得出极坐标、柱坐标和球坐标系下新的界面半径和界面导热系数插值格式.通过几个变系数和非线性导热问题对插值格式进行考核,并与文献中的插值格式进行对比.结果表明,推导的格式充分考虑了变截面和变物性的综合影响,对于非线性和变系数导热问题能得到更精确的结果. 相似文献
9.
Pa-Yee Tsai 《Journal of The Franklin Institute》2010,347(10):1850-1862
In this paper, a hybrid method which combines the Adomian decomposition method (ADM), the Laplace transform algorithm and the Padé approximant is introduced to solve the approximate analytic solutions of the nonlinear Riccati differential equations. This hybrid method demonstrates accurate and reliable results, and has a great improvement in the ADM truncated series solution which diverges rapidly as the applicable domain increases. Three examples herein are given to demonstrate good accuracy and fast convergence in comparison with the exact solution. 相似文献
10.
This paper establishes a clear procedure for the variational problem solution via the Walsh functions.technique. First the Walsh functions are introduced and their properties briefly summarized. Then an operational matrix is derived for integration use. The variational problems are solved by means of the direct method using the Walsh series. An illustrative example and a practical application to a heat conduction problem are included. 相似文献
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Mayo Dyer Hersey 《Journal of The Franklin Institute》1935,220(3):305-331
The modern understanding of lubrication is based on the equations of the hydrodynamic theory. These equations, as has been seen, describe the performance of a bearing in terms of the actual film viscosity but, of course, this depends on the temperature of the film, which in general is unknown. We have next to consider whether there is any way of calculating or predicting the steady running temperature of a bearing.It is not commonly realized that there is a rational solution for this problem.The solution depends both on the rate of generating heat by friction, and on the rate of heat transfer from the bearing to its surroundings. 相似文献
13.
Stephen B. Margolis 《Journal of The Franklin Institute》1979,307(1):39-58
A multidimensional, time-dependent model of the thermocline degradation in a packed bed thermal storage tank is presented. The formulation includes the effects of finite tank length, multidimensional thermal conduction, heat transfer between the fluid and solid portions of the bed, and heat losses across all tank surfaces. The technique used to solve the coupled pair of parabolic partial differential equations describing the degradation of the thermocline is based on a vectorized separation of variables approach. Assuming cylindrical geometry, the analysis leads to separate eigenvalue problems for the radial, angular, and axial spatial dependencies of the fluid and solid temperatures in the bed. The eigenvalues are readily calculated and the corresponding eigenfunctions are shown to form a complete set of spatial basis functions for the solution space. The method and results are illustrated by several examples. 相似文献
14.
A new approach to the input-output uniform decoupling problem of linear time-varying analytic systems via proportional state feedback is presented. A major feature of the proposed approach is that it reduces the solution of the uniform decoupling problem to that of solving a linear algebraic system of equations. This system of equations greatly facilitates the solution of the three major aspects of the decoupling problem: the necessary and sufficient conditions, the general analytical expressions for the controller matrices, and the structure of the uniformly decoupled closed-loop system. 相似文献
15.
本文建立了基于层次分析法和熵值法的综合评价模型,该模型利用组合赋权法就是对不同方法求得的权重进行组合,使得到的新权重既不会偏向主观判断,又不会偏重客观判断。本文通过层次分析法和熵值法求图书馆期刊选定中各指标的权重,利用组合赋权法求出各指标的最终有效权重,并结合实例求出图书馆最优期刊种类选定方案。 相似文献
16.
广义创新网络的演化结构及其现实意义 总被引：1，自引：0，他引：1
李金华 《科学学与科学技术管理》2008,29(2):101-107
针对创新网络由于复杂而难以定量分析的困难,提出了一个具有普遍意义的概念--广义创新网络,应用复杂网络理论建立了它的结构演化模型,并作了解析求解,演化模型显示了不同结构形态创新网络的演化机制;然后基于网络的演化机制与特征进一步提出了创新网络的演化谱系;最后结合几种现实的典型创新网络作了分析. 相似文献
17.
建立了单个液滴在高频感应热等离子体中内部传热传质的数学模型,考虑了希尔球形涡的影响,模拟了液滴在不同入射尺寸下的内部传热传质变化过程。结果表明,随着液滴入射尺寸的增大,液滴表面溶质质量分数到达饱和状态所需时间缩短,且其内部环流的对流作用占主导因素,使得溶质在液滴表面集中,易形成浓度集中的表面薄层。 相似文献
18.
对流换热边界条件下球体内固液相变过程移动热源法求解 总被引：1，自引：0，他引：1
应用移动热源法求解了对流换热条件下球体内具有明显相变界面的固液相变问题,分析了球体半径、相变材料潜热、外界对流换热条件对相变过程的影响,并进一步考虑实际相变过程存在的变对流边界条件,构造了一实用解法.为求解相变问题的数值方法提供了一校核其可靠性的新途径,还为实验结果提供了相互比较的数据.该方法及其结果对相变材料的分析与设计具有重要的实用价值 相似文献
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Pontryagin's maximum principles are applied to obtain the solution of minimum mass convective fins with variable heat transfer coefficients. It is shown that the volume and the width of the fin are uniquely related to the specified heat transfer rate and the properties of the material. For a power law spatial variation of the heat transfer coefficient, the results are set forth in a dimensionless form and they are given in tables or graphs, in order to aid design procedures. Several properties relating to the optimum volume, base thickness and the width of the fins with the properties of the material are also discussed. The method can also be used to solve problems of minimum mass fins having restricted width, often encountered in practice. 相似文献