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1.
This paper focuses on obtaining an asymptotic solution for coupled heat and mass transfer problem during the solidification of high water content materials. It is found that a complicated function involved in governing equations can be approached by Taylor polynomials unlimitedly, which leads to the simplification of governing equations. The unknown functions involved in governing equations can then be approximated by Chebyshev polynomials. The coefficients of Chebyshev polynomials are determined and an asymptotic solution is obtained. With the asymptotic solution, the dehydration and freezing fronts of materials are evaluated easily, and are consistent with numerical results obtained by using an explicit finite difference method. 相似文献
2.
Several technical problems of numerical method in TLM procedures arediscussed.The bandwidth of single mode in four kinds of dielectric slab loaded rect-angular waveguides is investigated,and the optimum bandwidth which is related tothe dimensions and dielectric constants is obtained.These results are useful to the de-sign of dielectric slab loaded rectangular waveguide. 相似文献
3.
Brian Tomlinson 《通化师范学院学报》2005,(8):37-40
Introduction
Materials development is both a field of study and a practical undertaking. As a field it studies the principles and procedures of the design, implementation and evaluation and adaptation of language teaching materials, by teachers for their own classrooms and by materials writers for sale or distribution. Ideally these two aspects of materials development are interactive in that the theoretical studies inform and are informed by the development and use of classroom materials （e. g. Tomlinson 1998c）. 相似文献
4.
In the present paper, a dynamic plastic damage model for concrete has been employed to estimate responses of a reinforced concrete slab subjected to blast loading. The interaction between the blast wave and the concrete slab is considered in 3D simulation. In the first stage, the initial detonation and blast wave propagation is modelled in 2D simulation before the blast wave reaches the concrete slab, then the results obtained from 2D calculation are remapped to a 3D model. The calculated blast load is compared with that obtained from TM5-1300. Numerical results of the concrete slab response are compared with the explosive test carried out- in the Weapons System Division, Defence Science and Technology Organisation, Department of Defence, Australia. 相似文献
5.
平面体波在各向异性媒质中的传播 总被引：1，自引：0，他引：1
Combining the linear transformation and the solution technique for the cubic equation,a general closed-form analyti solution for bulk waves in orthotropic anisotropic materials is obtained.This method is straightforward and general.Degenerated cases include transversely isotropic,cubic,and isotropic materials.Numerical computations are carried out on a fiber-reinforced composite plate modeled as a transversely isotropic media.The fibers are parallel to the top and bottom surfaces of the plate ,and they are rotated counterclockwise around the plate normal through different angles.The two-dimensional slowness curves corresponding to different rotations are presented graphically.The wave propagation characteristics displayed in slowness surfaces for different fiber orientation are analyzed. 相似文献
6.
Because of the different ways in which contact materials work, the basic requirements for silver metal oxide contact materials are different. They are anti-welded and anti-erosion when closed, anti-erosion when broken, and arc easily moved and have smaller contact resistance. In this paper, La2O3 is used as a stable oxide in contact material to replace CdO. A new type of Ag/SnO2-La2O3-Bi2O3 contact material is first obtained through using powder metallurgical method. Then electrical contact material parameter tester is used to test the electrical contact performance of the contact material. Through experiments, the arcing voltage and current curves, arcing energy curves, fusion power curves while broken and contact resistance while closed were obtained. Analysis of the results showed that the addition of La2O3 makes the contact material have the following advantages: smaller electrical wear, smaller arc energy, smaller contact resistance and arc is more easily extinguished. 相似文献
7.
WANG Jing-qin WANG Hai-tao WEN Ming ZHU Yan-cai 《浙江大学学报(A卷英文版)》2007,8(3):459-463
Because of the different ways in which contact materials work, the basic requirements for silver metal oxide contact materials are different. They are anti-welded and anti-erosion when closed, anti-erosion when broken, and arc easily moved and have smaller contact resistance. In this paper, La2O3 is used as a stable oxide in contact material to replace CdO. A new type of Ag/SnO2-La2O3-Bi2O3 contact material is first obtained through using powder metallurgical method. Then electrical contact material parameter tester is used to test the electrical contact performance of the contact material. Through experiments, the arcing voltage and current curves, arcing energy curves, fusion power curves while broken and contact resistance while closed were obtained. Analysis of the results showed that the addition of La2O3 makes the contact material have the following advantages： smaller electrical wear, smaller arc energy, smaller contact resistance and arc is more easily extinguished. 相似文献
8.
In this paper, we summarize some recent activities in the field of metamaterial research at the National University of Singapore （NUS）. Integral equations are applied for electromagnetic modelling of supernatural materials. Some special characteristics of the metamaterials are shown. Moreover, quasi-static Lorentz theory and numerical method （i.e., the method of moments for solving the electric field integral equation） and the transmission line theory are both presented to obtain the effective constitutive relations of metamaterials, respectively. Finally, feasibility of fabricating metamaterials based on analysis of equivalent transmission line model in the microwave spectrum and even higher is also shown and correspondingly some broad-bandwidth and low-loss metamaterial structures are designed and synthesized. 相似文献
9.
We studied the problem of bifurcation and chaos in a 4-side fixed rectangular thin plate in electromagnetic and mechanical fields. Based on the basic nonlinear electro-magneto-elastic motion equations for a rectangular thin plate and the expressions of electromagnetic forces, the vibration equations are derived for the mechanical loading in a steady transverse magnetic field. Using the Melnikov function method, the criteria are obtained for chaos motion to exist as demonstrated by the Smale horseshoe mapping. The vibration equations are solved numerically by a fourth-order Runge-Kutta method. Its bifurcation diagram, Lyapunov exponent diagram, displacement wave diagram, phase diagram and Poincare section diagram are obtained. 相似文献
10.
Numerical Derivation of Strain Rate Effects on Material Properties of Masonry with Solid Clay Bricks
WEI Xueying HAO Hong 《天津大学学报(英文版)》2006,12(B09):147-151
In this paper, numerical method is used als. A typical unit of masonry is selected to serve merical model of RVE is established with detailed to study the strain rate effect on masonry materias a representative volume element （RVE）. Nudistinctive modeling of brick and mortar with their respective dynamic material properties obtained from laboratory tests. The behavior of brick and mortar are characterized by a dynamic damage model that accounts for rate-sensitive and pressuredependent properties of masonry materials. Dynamic loads of different loading rates are applied to RVE. The equivalent homogenized uniaxial compressive strength, threshold strain and elastic modulus in three directions of the masonry are derived from the simulated responses of the RVE. The strain rate effect on the masonry material with clay brick and mortar, such as the dynamic increase factor （DIF） of the ultimate strength and elastic modulus as a function of strain rate are derived from the numerical results. 相似文献
11.
Transmission properties of fractal Cantor distribution with left-handed materials (LHM) are investigated. The transmittance
and reflectance spectra can be calculated by using the optical transmission matrix method. Comparing with the conventional
Cantor multilayers, these structures with LHM have double functions of stopbands and defects. Through adjusting the thickness
of dielectric layers, the properties of stopbands and defects can be obtained, respectively. For stopbands, a broad stopband
filter is studied. For defect modes, multi-frequencies narrow passband filters are proposed. 相似文献
12.
基于三层平板波导TE模的色散关系,分析覆盖层为左手介质而其他层为右手介质的非对称三层平板波导的模式特性.结果表明,只有满足一定条件TE0才存在,而高次模的截止频率随着非对称因子a增大而减小. 相似文献
13.
INTRODUCTION Left-handed materials (LHMs), first investigated theoretically by Veselago (1968), have received sub- stantial attention in the scientific and engineering communities. The unique properties of these meta- materials are promising for a diversity of microwave applications, such as new types of beam steerers, modulators, filters, superlens (Pendry, 2000), cou- plers and antenna radoms (Smith et al., 2004). Re- cently, a transmission line (TL) approach has been successfully in… 相似文献
14.
本文对光轴任意取向各向异性超常介质涂层平板镜像波导的横电波（TE模）的特性进行了细致分析与推导,得到了特征方程及其色散关系式,以及时间平均坡印亭矢量式,并进行了相应的数值模拟,描绘出它们各自的特性曲线,得出光轴任意取向各向异性超常介质涂层平板镜像波导的模式,既不同于各向同性左手介质涂层中的,也不同于各向同性常规介质层的导波特性。 相似文献
15.
针对广泛关注的左手材料(负折射率媒质),对电磁波穿过左手材料(Left-handedm aterial)构成的平行板时的传播特性做了理论分析;采用FDTD方法对正弦电磁波穿过了LHM的平行板的传播过程进行了数值建模,数值模拟的结果证明了正弦电磁波在穿过平板状的左手材料,会有类似一般凸透镜的聚光效果,以及负折射特性,为LHM的广泛应用提供了理论基础. 相似文献
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17.
lintroductionCalculationofthepropagationconstantsofplanardielectricwaveguidescuirentlyusedinintegratedopticsisnecessarytbraccuratelydesigningcomponentssuchasdirectionalcouplersandmodulatol.slll.Solutionforathreelayerslabwaveguideissimpleandwellknownasthel… 相似文献
18.
INTRODUCTION Veselago (1968) showed that if both the permit- tivity ε and the magnetic permeability μ of a material are negative, the propagation direction of an elec- tromagnetic (EM) wave will be opposite to its energy flow direction. Such media are called left-handed materials (LHMs) since the electric field E, magnetic field H, and wave vector k in these media form a left-hand triplet of vectors, instead of a right-hand triplet observed in conventional materials. For a long time, … 相似文献
19.
近年来的研究表明,左手材料的实现已成为可能.人工复合的左手材料已成为固体物理、材料科学、光学以及应用电磁学领域的重要研究课题之一.回顾左手材料的研究进展,对其独特性质、理论原理及实验制备进行详细梳理. 相似文献
20.
Analytical solution for electromagnetic scattering from a sphere of uniaxial left-handed material 总被引：2，自引：0，他引：2
INTRODUCTION The concept of left-handed materials (LHM for short, also called negative index materials) was in- troduced by Veselago (1968). An LHM has both negative permittivity and negative permeability, which makes the wave vector, the electric-field vector, and the magnetic-field vector in the LHM obey the left-hand rule. Experimental verifications for the existence of an LHM were made and its use as a perfect lens was suggested (Pendry, 2000; Shelby et al., 2001a; 2001b; Smith … 相似文献