An efficient PML implementation for the ADI-FDTD method

A novel implementation of the perfectly matched layer (PML) absorber for the alternating-direction implicit finite-difference time-domain method is proposed and implemented. It is shown that, compared to the traditional PML implementation, the performance of the proposed PML is more efficient for large Courant numbers.     

Genetic algorithm in reduction of numerical dispersion of 3-D ADI-FDTD method

A new method to reduce the numerical dispersion of the three-dimensional Alternating Direction Implicit Finite-Difference Time-Domain （3-D ADI-FDTD） method is proposed. Firstly, the numerical formulations of the 3-D ADI-FDTD method are modified with the artificial anisotropy, and the new numerical dispersion relation is derived. Secondly, the relative permittivity tensor of the artificial anisotropy can be obtained by the Adaptive Genetic Algorithm （AGA）. In order to demonstrate the accuracy and efficiency of this new method, a monopole antenna is simulated as an example. And the numerical results and the computational requirements of the proposed method are compared with those of the conventional ADI-FDTD method and the measured data. In addition the reduction of the numerical dispersion is investigated as the objective function of the AGA. It is found that this new method is accurate and efficient by choosing proper objective function.     

A study of the numerical dispersion relation for the 2-D ADI-FDTD method

This letter presents a numerical dispersion relation for the two-dimensional (2-D) finite-difference time-domain method based on the alternating-direction implicit time-marching scheme (2-D ADI-FDTD). The proposed analytical relation for 2-D ADI-FDTD is compared with those relations in the previous works. Through numerical tests, the dispersion equation of this work was shown as correct one for 2-D ADI-FDTD.     

Comments on "An efficient PML implementation for the ADI-FDTD method"

For original paper see Wang and Teixeira (IEEE Microwave Wireless Comp. Lett., vol.13, p.72-4, 2003 February). In this paper, a more precise way to evaluate the actual performance of the perfectly matched layer (PML) used for the alternating direction implicit finite-difference time-domain (ADI-FDTD) method is presented. It is shown that the intrinsic numerical dispersion error of the ADI-FDTD method must be taken into account when the actual performance of the ADI-PML (as well as the ADI-FDTD method) is evaluated. Most importantly, it is demonstrated that the ADI-PMLs implemented with either the traditional manner or the way proposed in have almost the same level of accuracy when the performance of the ADI-PML is correctly evaluated.     

Improvement on the numerical dispersion of 2-D ADI-FDTD with artificial anisotropy

In this letter, by introducing artificial anisotropy into computational space, a simple and efficient approach to reduce numerical dispersion of the two-dimensional alternating direction implicit finite-difference time-domain (ADI-FDTD) method is proposed. It is shown that performance of the ADI-FDTD method can be improved significantly for both single frequency simulations and relatively wideband problems. Consequently, the usefulness and effectiveness of the ADI-FDTD method can be notably enhanced.     

On the dispersion relation of ADI-FDTD

In this letter, we analyze the alternating direction implicit finite-difference time-domain (ADI-FDTD) dispersion relation and find the numerical plane-wave relationship between the magnetic and electric fields, showing that the scheme is not divergence-free. We also show that negative-group-velocity modes with positive phase velocities may appear for high Courant numbers. A parallel comparison is made with the behavior of the classical Yee FDTD and the Crank-Nicolson schemes.     

An improved ADI-FDTD method and its application to photonicsimulations

When the alternating direction implicit-finite difference time domain method (ADI-FDTD) is applied to simulating photonic devices, full efficiency can not be achieved if reasonable accuracy is to be kept, due to numerical errors such as numerical dispersion. A simple modification to ADI-FDTD is proposed by calculating the envelope rather than the fast-varying field, so that errors are minimized. A factor of two-five in speed can usually be gained while retaining the same level of accuracy compared with conventional FDTD. The efficiency and the accuracy of this improved approach is demonstrated on several problems, from simple waveguide structures to complex photonic crystal structures     

An investigation of numerical dispersion in the vector finiteelement method using quadrilateral elements

The discretization inherent in the vector finite element method results in the numerical dispersion of a propagating wave. The numerical dispersion of a time-harmonic plane wave propagating through an infinite, two-dimensional, vector finite element mesh composed of uniform quadrilateral elements is investigated. The effects on the numerical dispersion of the propagation direction of the wave, the order of the polynomials used for the basis functions, and the electrical size of the elements are investigated. Simple formulas are presented which are excellent approximations to the exact numerical dispersion. The numerical dispersion is validated by a numerical example     

Conformal method to eliminate the ADI-FDTD staircasing errors

The alternating-direction-implicit finite-difference time-domain (ADI-FDTD) method is an unconditionally stable method and allows the time step to be increased beyond the Courant-Friedrich-Levy (CFL) stability condition. This method is potentially very useful for modeling electrically small but complex features often encountered in applications. As the regular FDTD method, however, the spatial discretization in the ADI-FDTD method is only first-order accurate for discontinuous media; several researchers have shown that the errors can be very high when the regular ADI-FDTD method is applied to such discontinuous media. On the other hand, the conformal FDTD method has recently emerged as an efficient FDTD method with higher order accuracy. In this work, a second-order accurate ADI-FDTD method using the conformal approximation of spatial derivatives is proposed. This new scheme, called the ADI-CFDTD method, retains the second-order accuracy in both temporal and spatial discretizations even for discontinuous media with metallic structures, and is unconditionally stable. 2D and 3D examples demonstrate the efficacy of this method and its application in EMC problems.     

Extension of the ADI-FDTD method to Debye media

This paper describes an extension of the alternating direction implicit finite-difference time-domain (ADI-FDTD) method to analyze problems involving Debye media.     

An efficient numerical method for the small-signal AC analysis of MOS capacitors

A numerical method for the small-signal ac analysis of MOS capacitors is presented. The equations describing device operation, which comprise a boundary value problem, are formulated as an initial value problem and are solved by a shooting method. This results in a numerically stable and efficient algorithm for their solution. The recognized ill-conditioning of the boundary value problem, manifesting itself in numerical instabilities in the conductance-voltage characteristics of MOS capacitors is addressed. Calculated small-signal ac admittance as a function of gate bias for homogeneously doped and ion-implanted devices is shown. The high- "and low-frequency" positional dependence of convection and displacement current densities is determined.     

An efficient numerical scheme for spreading resistance calculations based on the variational method

This paper presents a simple and efficient numerical scheme for evaluating the correction factor integrals that arise in the variational method. The scheme is a modification of one recently proposed by Berkowitz and Lux for the uniform flux method. The abscissae and the weights required for the integration are given in a form which allows the numerical scheme to be readily implemented. Using this scheme, it takes, on an average, 0.8 sec to compute one value of correction factor on an Apple II Microcomputer. For a slab of varying thickness, backed by either a perfectly conducting or a high resistivity substrate, the correction factors obtained agree with those derived from the exact constant-potential method to within 1%.     

An efficient numerical spectral domain method to analyze a largeclass of nonreciprocal planar transmission lines

Presents an efficient numerical application of the Galerkin method in the spectral domain (SD) to the analysis of striplike/slotlike coplanar transmission lines embedded in a bianisotropic multilayered medium. The method is based on obtaining the spectral dyadic Green's function by the equivalent boundary method (EBM), a suitable third order extraction technique of the asymptotic behavior of the Green's dyad, an enhanced numerical integration scheme, and the use of an adequate contour integral method for searching zeros in the complex plane. This method, namely the SD-EBM, has been found to be very suitable for analyzing transmission lines with semiconductors and/or ferrites magnetized at an arbitrary direction, including the study of magnetostatic wave propagation phenomena     

一种有效减少ADI-FDTD数值色散的方法

ADI—FDTD算法的数值色散效应较为明显，本文的研究表明一种通过添加各向异性媒质来修正相速误差，从而减少FDTD数值色散的方法，同样适用于ADI-FDTD，且收效更为显著。数值运算结果证明该方法能够简单有效地去除较宽频带范围内的色散。     

An efficient approach to reduce alerts generated by multiple IDS products

Intrusion detection systems (IDSs) often trigger a huge number of unnecessary alerts. Managing the overwhelming number of alerts, especially from multiple IDS products, is a concern to every security analyst. Analyzing and evaluating these alerts is a difficult task that frustrates the effort of analysts. In fact, true alerts are usually buried under heaps of false alerts. We have identified several research gaps in the existing alert management approaches that need to be addressed, especially when handling alerts from different IDS products. In this work, we present an efficient alert management approach that reduces the unnecessary alerts produced by different IDS products using two main modules: an enhanced alert verification module that validates alerts with vulnerability assessment data; and an enhanced alert aggregator module that reduces redundant alerts and presents them in the form of meta alerts. Finally, we have carried out experiments in our test bed and recorded impressive results in terms of high accuracy and low false positive rate for multiple IDS products. Copyright © 2014 John Wiley & Sons, Ltd.     

产生安全椭圆曲线的一种有效方法

本文在寻找安全椭圆曲线的CM方法的基础上,实现了一种更具适用性的产生安全椭圆曲线的有效方法。通常,为了抵抗诸如MOV等算法可能的攻击,以域GF（q)上的椭圆曲线为基础的公钥密码系统,对该椭圆曲线必须要求满足以下条件：m阶曲线具有一个形式为2p 1的大素数因子,这是p是一个素数且q^2≠1modm。这个条件在不损害安全性的情况下对形式为2p 1的大素因子可以放宽到包括形式为2ip 1的素数（i是一个小整数）。因此,适用于公钥密码系统的安全椭圆曲线的数目显著增加。本文对这一方法进行了实现,它表明用该方法来产生适用于公钥密码系统的椭圆曲线比原来的方案快很多。     

An efficient numerical approach for modeling microstrip-typeantennas

An efficient numerical approach to model antennas that include a microstrip element radiating in the presence of material layers is developed. The class of antennas considered is fed through the ground plane by a coaxial transmission line. The reaction integral equation is formulated by treating the coaxial aperture as part of the antenna. The substrate thickness can be arbitrary, making this numerical technique suitable for high-frequency applications. The effects of the substrate are also included in the analysis. Numerical results are obtained for the current distribution and input impedance. The algorithm is validated with experimental results     

An efficient numerical model of CMOS latch-up

A one-dimensional numerical model of latch-up in bulk CMOS structures is presented. The model simulates the triggering and sustaining regimes of the parasitic SCR, yielding results nearly equivalent to those obtained using two-dimensional analysis, but with two orders of magnitude-lower computational cost. The model is used to obtain the SCR switching characteristics of typical CMOS based on two-dimensional impurity cross sections, and parameter sensitivities are examined.     

On the current source implementation for the ADI-FDTD method

The current source implementation for the alternating-direction implicit finite-difference time-domain (ADI-FDTD) method is examined in this letter. By regarding the ADI-FDTD method as an approximate factorization of the Crank-Nicolson scheme, current source is naturally coupled into simulations. As a result, field distribution is much more improved and free of asymmetry.