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1.
In this paper, we develop a leap-frog mixed finite element method for solving Maxwell’s equations resulting from metamaterials. Our scheme is similar to the popular Yee’s FDTD scheme used in electrical engineering community, and is preferable for three dimensional large scale modeling since no storage of the large coefficient matrix is needed. Our scheme is proved to obey the Gauss’s law automatically if the initial fields satisfy that. Furthermore, the conditional stability and optimal error estimate for the proposed scheme are proved. To our best knowledge, we are unaware of any other publications devoted to the convergence analysis of this leap-frog explicit scheme for Maxwell’s equations even in a simple medium, while our results for metamaterials automatically reduce to the standard Maxwell’s equations in vacuum by dropping some terms resulting from the constitutive equations. Numerical results confirming our analysis are presented.  相似文献   

2.
左手材料(LHMs)是一种介电常数ε和磁导率μ同时为负值的电磁材料,近年来在实验上取得了突破性的进展,引起了当今物理学和电磁学的关注。文章介绍了左手材料的基本原理和微波频段左手材料的实现方法,总结了左手结构在微波频段的研究进展,展望了左手材料在微波器件和天线上的应用前景。  相似文献   

3.
左手材料(LHMs)是一种介电常数ε和磁导率μ同时为负值的电磁材料,近年来在实验上取得了突破性的进展,引起了当今物理学和电磁学的关注。文章介绍了左手材料的基本原理和微波频段左手材料的实现方法。总结了左手结构在微波频段的研究进展,展望了左手材料在微波器件和天线上的应用前景。  相似文献   

4.
A new numerical framework is proposed to solve partial differential equations on curved surfaces by using the orthogonal moving frames at each grid point to compute the gradient of a scalar variable. We call this framework the method of moving frames (MMF) that is adopted and modified from the works of é. Cartan. Compared to the Eulerian method and the Lagrangian multiplier method, the MMF method uses only the surface as the domain, not additionally the ambient space enclosing it. Also different from directly solving the equations with respect to the curved axis, the MMF method is free of the metric tensors. This uniqueness is the consequence of the virtual and penalty extension of the variables in a special direction, called the exponential direction, instead of the surface normal direction that is typically taken. The exponential extension eliminates the need to extend the computational domain and the variables outside the curved surfaces, but the variables outside the curved surfaces are not extended in the direction of the surface normal, yielding an extension error. However, the overall error for the MMF scheme, caused by the extension error, is of high order in L 2 error with respect to space discretization. This high convergence rate implies that the exponential error can be made negligible compared to the error of differentiation and integration, which are also expressed with space discretization but with lower order, in adaptively-refined meshes proportional to the Gaussian curvature. As the first application of the MMF method, conservation laws are considered on curved surfaces. To display the exponential convergence and the unique features of the MMF scheme, convergence tests are demonstrated on four different types of surfaces: an open spherical shell, a closed spherical shell, an irregular closed surface, and a non-convex closed surface.  相似文献   

5.
We introduce and analyze a mixed finite element method for the numerical discretization of a stationary incompressible magnetohydrodynamics problem, in two and three dimensions. The velocity field is discretized using divergence-conforming Brezzi–Douglas–Marini (BDM) elements and the magnetic field is approximated by curl-conforming Nédélec elements. The H1-continuity of the velocity field is enforced by a DG approach. A central feature of the method is that it produces exactly divergence-free velocity approximations, and captures the strongest magnetic singularities. We prove that the energy norm error is convergent in the mesh size in general Lipschitz polyhedra under minimal regularity assumptions, and derive nearly optimal a priori error estimates for the two-dimensional case. We present a comprehensive set of numerical experiments, which indicate optimal convergence of the proposed method for two-dimensional as well as three-dimensional problems.  相似文献   

6.
The aim of this work is to develop an object-based methodology for semi-automatic geomorphological mapping. The study area is the municipality of São José dos Campos, located in the Paraíba do Sul Valley, São Paulo State, Brazil. A multilevel hierarchical semantic network driven by a set of multispectral, geomorphometric and texture variables is used. The geomorphometric and texture variables are extracted from a digital elevation model (DEM) generated from a stereo pair of advanced spaceborne thermal emission and reflection radiometer (ASTER)/Terra images. The DEM accuracy is evaluated and its root mean square error (RMSE) is found to be 9.38 m. The validation of the geomorphological map is accomplished by means of object-based statistical indices derived from an error matrix, obtained by a comparison between the classified scene and a reference map produced by visual interpretation. The object-based approach is found to be effective for geomorphological mapping.  相似文献   

7.
在行人惯性导航领域,地磁修正算法作为一种有效的修正航向漂移误差的方法,应用在磁干扰环境中时,存在航向失真的问题,而航向精度往往决定了整个导航系统的优劣.为此,在Afzal提出的准静止磁场检测算法的基础上,提出了行人导航算法框架iIEZ+,即以Jiménez A R提出的IEZ+框架为基础,融入了改进后的准静止磁场检测算法,对地磁修正算法和启发式航向漂移消除算法的使用做出选择,实现了两种算法间的优势互补.实验表明,本文提出的算法框架可以有效抵御磁干扰的影响,提供可靠的航向和位置信息.经过多次室内外行走实验,定位误差约为路程的0.6%~1.6%,优于文中提到的其他基于IEZ框架的算法.  相似文献   

8.
变频系统测控软件抗干扰研究   总被引:1,自引:0,他引:1  
介绍了变频系统中强电条件下设计运行测控软件抗干扰技术,论述了抗干扰、防系统“死机”程序的设计思路,讨论了软件抗干扰的数据的置处方式、容错设计以及软件设计应注意的问题及方法。  相似文献   

9.
We present a PDE observer that estimates the velocity, pressure, electric potential and current fields in a magnetohydrodynamic (MHD) channel flow, also known as Hartmann flow. This flow is characterized by an electrically conducting fluid moving between parallel plates in the presence of an externally imposed transverse magnetic field. The system is described by the inductionless MHD equations, a combination of the Navier-Stokes equations and a Poisson equation for the electric potential under the so-called inductionless MHD approximation in a low magnetic Reynolds number regime. We identify physical quantities (measurable on the wall of the channel) that are sufficient to generate convergent estimates of the velocity, pressure, and electric potential field away from the walls. Our observer consists of a copy of the linearized MHD equations, combined with linear injection of output estimation error, with observer gains designed using backstepping. Pressure, skin friction and current measurements from one of the walls are used for output injection. For zero magnetic field or nonconducting fluid, the design reduces to an observer for the Navier-Stokes Poiseuille flow, a benchmark for flow control and turbulence estimation. We show that for the linearized MHD model the estimation error converges to zero in the L2 norm. Despite being a subject of practical interest, the problem of observer design for nondiscretized 3-D MHD or Navier-Stokes channel flow has so far been an open problem.  相似文献   

10.
磁通门技术及其应用   总被引:6,自引:0,他引:6  
磁通门是测量环境磁场的系统 ,它利用高磁导率、低矫顽力的软磁材料铁芯在激磁作用下 ,感应线圈出现随环境磁场强度而变的偶次谐波分量电势的特征 ,通过高性能的滤波器测量偶次谐波分量。磁通门的典型应用是载体姿势方位的测量 ,实际应用中结构参数校正是十分重要的。  相似文献   

11.
Magnetic-interference-free dual-electric compass   总被引:1,自引:0,他引:1  
The purpose of this research is to improve the reliability of automobile navigation system that utilizes the electric compass for localization. On account of its sensitivity to external interferences of the magnetic field, the electric compass itself is not accurate enough to be used for localization compared with the rate gyroscope. To overcome this shortcoming, in this research, a robust electric compass was designed by using two electric compasses to efficiently cancel out the low-frequency interferences. That is, in this paper, a dual-compass predictive calibration algorithm, which corrects irregular and long-lasting magnetic-field interferences, is newly proposed and implemented. When the external interferences are eliminated from the dual-electric compass, it becomes much more accurate than the gyroscope-based system that suffers from accumulative drift error. The reliability and performance of the designed system were verified through real navigation experiments.  相似文献   

12.
The error of Padé approximations to the logarithm of a matrix and related hypergeometric functions is analysed. By obtaining an exact error expansion with positive coefficients, it is shown that the error in the matrix approximation at X is always less than the scalar approximation error at x, when ∥X∥ < x. A more detailed analysis, involving the interlacing properties of the zeros of the Padé denominator polynomials, shows that for a given order of approximation, the diagonal Padé approximants are the most accurate. Similarly, knowing that the denominator zeros must lie in the interval (1,∞) leads to a simple upper bound on the condition number of the matrix denominator polynomial, which is a crucial indicator of how accurately the matrix Padé approximants can be evaluated numerically. In this respect the Padé approximants to the logarithm are very well conditioned for ∥X∥ < 0·25. This latter condition can be ensured by using the ‘inverse scaling and squaring’ procedure for evaluating the logarithm.  相似文献   

13.
Xiao  Wan-shen  Gao  Yang  Zhu  Haiping 《Microsystem Technologies》2019,25(6):2451-2470

The problem of the nonlinear thermal buckling and post-buckling of magneto-electro-thermo-elastic functionally graded porous nanobeams is analyzed based on Eringen’s nonlocal elasticity theory and by using a refined beam model. The beams with immovable clamped ends are exposed to the external electric voltages, magnetic potentials, a uniform transverse load and uniform temperature change. For the first time, the four types of porosity distribution in the nanobeam are considered and compared in complex electric–magnetic fields. Besides, the new formula of the effective material properties is proposed in this paper to simultaneously estimate the material distribution and porosity distribution in the thickness direction. The generalized variation principle is used to induce the governing equations, then the approximate analytical solution of the METE-FG nanobeams based on physical neutral surface is obtained by using a two-step perturbation technique. Finally, detailed parametric analyses are performed to get an insight into the effects of different physical parameters, including the slenderness ratio, small-scale parameter, volume fraction index, external electric voltages, magnetic potentials, porosity coefficient and different porosity distributions, for providing an effective way to improve post-buckling strength of porous beams.

  相似文献   

14.
给出了封闭的2m次Bèzier曲线的降次逼近公式,并讨论了相应的逼近误差。文章工作除了具有传统的端点约束、C1—约束外,还具有以下特点:首先,基于欧几里德范数讨论逼近误差,更加符合人们的认识;其次,对于分段降阶逼近的情形,首先考虑并采用了选择拐点的策略;第三,考虑并采用了选择极大值点的策略。大量数值试验表明:第二、三两条策略的采用可以在很大程度上减少了2m-1次Bèzier曲线段达到逼近2m次Bèzier平面曲线的容差要求。  相似文献   

15.
We show that Maxwell's fish-eye lens can make a semi-circular perfect electric conductor look like a circular one. Such an effect can also be achieved (not perfectly) by using negative index metamaterials, but only within a single frequency. Maxwell's fish-eye lens, however, can work for a set of eigenfrequencies. Numerical simulations are performed to verify the effect.  相似文献   

16.
An ultra‐wideband magnetic near‐field probe based on a conventional low‐cost four layers of FR‐4 printed circuit board is proposed in this article. It can be used to measure the magnetic near‐field strength from RF magnetic sources or electronic devices for EMI conformance test. The operating frequency of the probe is from 1 GHz up to 20 GHz. The probe is constructed based on a coplanar waveguide and stripline with a short‐end loop. The probe dimension is 10 mm × 25 mm × 0.6 mm. The prototype probe is electric field‐shield structure and has a very high unwanted electric field suppression ratio about 17.7 dB. The probe calibration factor from the simulation agrees well with the calibration factor computed from the measurement. The average probe factor is 38.8 dBS/m and probe sensitivity is 47.4 dB μ A/m.  相似文献   

17.
Magnetic sensor arrays are proposed to measure electric current in a non-contact way. In order to achieve higher accuracy, signal processing techniques for magnetic sensor arrays are utilized. Simulation techniques are necessary to study the factors influencing the accuracy of current measurement. This paper presents a simulation method to estimate the impact of sensing area and position of sensors on the accuracy of current measurement. Several error models are built up to support computer-aided design of magnetic sensor arrays.  相似文献   

18.
The Lamé functions are of considerable interest for boundary-value problems in electromagnetics and mechanics that involve ellipsoid geometry. Up to now efficient algorithms for the verified computation of these functions do not exist. In this article we provide a new effective scheme for the numerical treatment of Lamé functions of the first and second kind. It involves computing the Lamé functions with high accuracy combined with safe error estimates.  相似文献   

19.
电涡流传感器特性曲线拟合的新方法   总被引:3,自引:0,他引:3  
为了减小电涡流传感器的非线性误差,在最小二乘法的基础上,结合0.618优选法,使拟合方程式中的常数更合理。用这种方法可以求得最佳拟合直线方程和最小的非线性误差。此法适用于各种类型的线性传感器或可以通过适当的变量代换把变量之间的非线性关系化为线性关系的传感器或测量系统。  相似文献   

20.
梁志国 《测控技术》2022,41(5):75-86
为了定量评估量化采样序列对四参数正弦拟合结果影响的误差规律,针对16 bit量化对四参数正弦拟合带来的影响,分别在有效位数、幅度、频率、初始相位和直流分量五项参数上进行了拟合误差界的搜索。选取的条件变量分别是幅度、序列所含波形的周波数、初始相位、直流分量以及序列数据点数。以两两联动的双条件组合方式进行误差界搜索,获得了各项参数的误差界随不同条件变化而变化的曲线规律,筛分出了显著影响量和不显著影响量,以及明确的误差上界和下界。以往的研究仅使用正态随机噪声方式表征其谐波失真以外的误差要素,本文揭示了量化误差影响的周期性特征,并以曲线包络方式给出了量化误差影响的误差界。量化误差对四参数拟合影响的误差界,可用于不确定度估计,以及测量条件选择。  相似文献   

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