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241.
XIONG YUE-SHAN 《高校应用数学学报(英文版)》1994,9(2):153-167
THE ERRORS ESTIMATION OF THE CHEBYSHEV SPECTRAL-DIFFERENCE METHOD FOR TWO-DIMENSIONAL VORTICITY EQUATIONTHEERRORSESTIMATIONOF... 相似文献
242.
针对传统的ElGamal加密机制不能抵抗自主选择密文攻击的问题,通过引入安全Hash函数和伪随机数发生函数给出了一种新的增强ElGamal加密机制.结果表明,该机制不仅能够抵抗自主选择密文攻击,且由于伪随机数发生函数的引入,解决了加密过程中随机数的暴露问题.该机制加密过程需要两次模幂运算,解密过程仅需一次模幂运算.完全适合于对安全性要求较高但是对系统资源要求消耗低的应用环境. 相似文献
243.
给出一种基于进程系统调用的实时IDS方案.该方案选择网络服务进程(特权进程)作为系统的代表进行监测,使用隐马尔可夫模型(HMM)对系统行为进行模拟和测试,使用实时P(O|λ)值和近期对“某些重要文件”的读、写频率这两个条件作为判断系统是否遭受入侵的标准.实验和分析表明,该方案有较高的预报准确率和较小的时间开销. 相似文献
244.
本文讨论奇异摄动椭圆抛物型偏微分方程的周期边界问题.构造一个差分格式,利用分离解的奇性项的方法,结合问题的渐近展开,证明所构造的差分格式具有O(τ h~2)一致收敛阶. 相似文献
245.
E. B. Tereshin V. A. Trofimov M. V. Fedotov 《Computational Mathematics and Mathematical Physics》2006,46(1):154-164
Conservative finite-difference schemes are constructed for the problems of self-action of a femtosecond laser pulse and of second-harmonic generation in a one-dimensional nonlinear photonic crystal with nonreflecting boundary conditions. The invariants of the governing equations are found taking into account these conditions. Nonreflecting conditions substantially improve the efficiency of conservative finite-difference schemes used in the modeling of complex nonlinear effects in photonic crystals, which require much smaller steps in space and time than those used in the case of linear propagation. The numerical experiments performed show that the boundary reflects no more than 0.01% of the transmitted energy, which corresponds to the truncation error in the boundary conditions. The amplitude of the reflected pulse is less than that of the pulse transmitted through the boundary by two (and more) orders of magnitude. The simulation is based on the approach proposed by the authors for the given class of problems. 相似文献
246.
在一般的近代物理实验教材中,关于电子衍射实验采用的是晶体表面反射衍射或金属箔透射衍射。本文提出一套基于双缝衍射的、用于研究微观粒子波粒二象性的电子衍射实验方案,并且鉴于在一般的实验中不具备进行电子双缝衍射实验的条件,本实验方案是在电子双缝衍射计算机模拟的仿真环境下进行的。 相似文献
247.
Shidu Dong Xiaofan Yang Bo He Guojin Liu 《International Journal of Infrared and Millimeter Waves》2006,27(11):1517-1528
Radiance coming from the interior of an uncooled infrared camera has a significant effect on the measured value of the temperature
of the object. This paper presents a three-phase compensation scheme for coping with this effect. The first phase acquires
the calibration data and forms the calibration function by least square fitting. Likewise, the second phase obtains the compensation
data and builds the compensation function by fitting. With the aid of these functions, the third phase determines the temperature
of the object in concern from any given ambient temperature.
It is known that acquiring the compensation data of a camera is very time-consuming. For the purpose of getting the compensation
data at a reasonable time cost, we propose a transplantable scheme. The idea of this scheme is to calculate the ratio between
the central pixel’s responsivity of the child camera to the radiance from the interior and that of the mother camera, followed
by determining the compensation data of the child camera using this ratio and the compensation data of the mother camera
Experimental results show that either of the child camera and the mother camera can measure the temperature of the object
with an error of no more than 2°C. 相似文献
248.
In this paper, we present a unified finite volume method preserving discrete maximum principle (DMP) for the conjugate heat transfer problems with general interface conditions. We prove the existence of the numerical solution and the DMP-preserving property. Numerical experiments show that the nonlinear iteration numbers of the scheme in [24] increase rapidly when the interfacial coefficients decrease to zero. In contrast, the nonlinear iteration numbers of the unified scheme do not increase when the interfacial coefficients decrease to zero, which reveals that the unified scheme is more robust than the scheme in [24]. The accuracy and DMP-preserving property of the scheme are also veried in the numerical experiments. 相似文献
249.
Aastha Gupta Aditya Kaushik Manju Sharma 《Numerical Methods for Partial Differential Equations》2023,39(2):1220-1250
We propose a hybrid numerical scheme to discretize a class of singularly perturbed parabolic reaction–diffusion problems with robin-boundary conditions on an equidistributed grid. The hybrid difference scheme is developed by using a modified backward difference scheme in time, a combination of the cubic spline and exponential spline difference scheme in space. The proposed scheme uses a cubic spline difference scheme for the discretization of robin-boundary conditions. For the time discretization of the problem, we use the standard uniform mesh while a layer adapted equidistributed grid is generated for the spatial discretization. By equidistributing a curvature-based monitor function, the spatial adaptive grid is able to capture the presence of parabolic boundary layers without using any prior information about the solution. Parameter uniform error estimates are derived to illustrate an optimal convergence of first-order in time and second-order in space for the proposed discretization. The accuracy of the proposed scheme is confirmed by the numerical experiments that underpin the theoretical analysis. 相似文献
250.
Some new sixth-order compact finite difference schemes for Poisson/Helmholtz equations on rectangular domains in both two- and three-dimensions are
developed and analyzed. Different from a few sixth-order compact finite difference
schemes in the literature, the finite difference and weight coefficients of the new
methods have analytic simple expressions. One of the new ideas is to use a weighted
combination of the source term at staggered grid points which is important for grid
points near the boundary and avoids partial derivatives of the source term. Furthermore, the new compact schemes are exact for 2D and 3D Poisson equations if the
solution is a polynomial less than or equal to 6. The coefficient matrices of the new
schemes are $M$-matrices for Helmholtz equations with wave number $K≤0,$ which
guarantee the discrete maximum principle and lead to the convergence of the new
sixth-order compact schemes. Numerical examples in both 2D and 3D are presented
to verify the effectiveness of the proposed schemes. 相似文献