• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2001.04a
• /
• pp.964-967
• /
• 2001

Aspherical lens with the higher numerical aperture has been needed in the optical storage device to increase the recording density on the disk. However, high numerical aperture means the large slope angle at the clear aperture of the lens. Therefore, the measurement and manufacturing technique including the lens molding process for the slope angle should be developed. In this paper, the evaluation technique was described for the optical performance of the aspherical lens. Aspherical form error brings about the wavefront error and the side lobe of the beam intensity profile. A schematic diagram of the aspherical lens manufacturing was drawn to explain the aspherical form error compensation. Finally, form error of the aspherical lens was defined and plotted using the raw data of the Formtalysurf.

• 제어로봇시스템학회:학술대회논문집
• /
• 1991.10a
• /
• pp.264-267
• /
• 1991

In this paper, a new application method of the Kalman filter to desigin a gyro is proposed. The role of a gyro is the estimation of an input rate with minimal error covariance. The size of the error covariance depends on gyro's parameters, which makes it possible to use the parameters of gyro to minimze the estimation error covariance. Numerical analysis shows that the error covariance becomes smaller as the spin axis momentum becomes larger and the damping coefficient smaller, but production cost must be considered. Through numerical analysis the parameter set for an acceptable - performance gyro with small cost can be selected.

• Journal of Ocean Engineering and Technology
• /
• v.12 no.2 s.28
• /
• pp.97-110
• /
• 1998

The numerical damping and dispersion error characteristics associated with difference schemes and a panel shift method used for the calculation of steady free surface flows by a panel method are an analysed in this paper. First, 12 finite difference operators used for the double model flow by Letcher are applied to a two dimensional cylinder with the Kelvin free surface condition and the numerical errors with these schemes are compared with those by the panel shift method. Then, 3-D waves due to a submerged source are calculated by the difference schemes, the panel shift method and also by a higher order boundary element method(HOBEM). Finally, the waves and wave resistance for Wigley's hull are calculated with these three schemes. It is shown that the panel shift method is free of numerical damping and dispersion error and performs better than the difference schemes. However, it can be concluded that the HOBEM also free of the numerical damping and dispersion error is the most stable, accurate and efficient.

• Atmosphere
• /
• v.33 no.1
• /
• pp.33-47
• /
• 2023

In this study, for the application of observation errors to the Korean Integrated Model (KIM) to utilize the Constellation Observing System for Meteorology, Ionosphere & Climate-2 (COSMIC-2) new satellites, the observation errors were diagnosed based on the Desroziers method using the cost function in the process of variational data assimilation. We calculated observation errors for all observational species being utilized for KIM and compared with their relative values. The observation error of the calculated the Global Navigation Satellite System Radio Occultation (GNSS RO) was about six times smaller than that of other satellites. In order to balance with other satellites, we conducted two experiments in which the GNSS RO data expanded by about twice the observation error. The performance of the analysis field was significantly improved in the tropics, where the COSMIC-2 data are more available, and in the Southern Hemisphere, where the influence of GNSS RO data is significantly greater. In particular, the prediction performance of the Southern Hemisphere was improved by doubling the observation error in global region, rather than doubling the COSMIC-2 data only in areas with high density, which seems to have been balanced with other observations.

• Journal of applied mathematics & informatics
• /
• v.7 no.1
• /
• pp.175-181
• /
• 2000

The purpose of this to measure, with explicit constants as small as possible, a priori error bounds for approximation by picewise polynomials. These constants play an important role in the numerical verification method of solutions for obstacle problems by using finite element methods .

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.16 no.2
• /
• pp.21-27
• /
• 2008

An inverse method is introduced to construct the problem for the error analysis of the numerical solution of initial value problem. These problems constructed through this method have a known exact solution, even though analytical solutions are generally not obtainable. The process leading to the exact solution makes use of an initially available approximate numerical solution. A smooth interpolation of the approximate solution is forced to exactly satisfy the differential equation by analytically deriving a small forcing function to absorb all of the errors in the interpolated approximate solution. Using this special case exact solution, it is possible to investigate the relationship between global errors of a candidate numerical solution process and the associated tuning parameters for a given problem. Under the assumption that the original differential equation is well-posed with respect to the small perturbations, we thereby obtain valuable information about the optimal choice of the tuning parameters and the achievable accuracy of the numerical solution.

• Journal of Digital Convergence
• /
• v.19 no.12
• /
• pp.339-345
• /
• 2021

In this paper, estimation angle performance analysis of amplitude-comparison monopulse radar under additive noise effect is dealt with. When uncorrelated white noises are added to the squinted beams, the angle estimation performance is analyzed through the mean square error(MSE). The numerical integration-based mean square error result completely overlaps the Monte Carlo-based mean square error result, which corresponds to 99.8% of the Monte Carlo-based mean square error result. In addition, the mean square error analysis method based on numerical integration has a much faster operation time than the mean square error method based on Monte Carlo. the angle estimation performance of the amplitude comparison monopulse radar can be efficiently analyzed in various noise environments through the proposed numerical integration-based mean square error method.

• Communications of the Korean Mathematical Society
• /
• v.11 no.2
• /
• pp.503-514
• /
• 1996

We consider non-constant coefficient elliptic equations of the type -div(a \bigtriangledown u) = f$, and employ the P-version of the finite element method as a numerical method for the approximate solutions. To compute the integrals in the variational form of the discrete problem we need the numerical quadrature rule scheme. In practice the integrations are seldom computed exactly. In this paper, we give an $L_2(\Omega)$-error estimate of $\Vert u = \tilde{u}_p \Vert_{0,omega}$ in comparison with $\Vert u = \tilde{u}_p \Vert_{1,omega}$, under numerical quadrature rules which are used for calculating the integrations in each of the stiffness matrix and the load vector.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.6
• /
• pp.1431-1440
• /
• 1993

This paper presents a new NC machine performance test and calibration system. In order to measure NC machine erros in simpler, and less time-comsuming way, some indirect measuring systems such as circular disk system and double ball bar system have been developed instead of laser interferometer. But these indirect measuring systems have shown their limits in identifying each of NC machine error sources in absolute numerical value. Therefore, we developed an unique NC machine error measurement system which provides a simple measuring process like other conventional indirect methods and still can indentify each of NC machine error sources in absolute numerical value.

• Honam Mathematical Journal
• /
• v.27 no.2
• /
• pp.317-332
• /
• 2005

In this paper we consider the hp-version to solve non-constant coefficients elliptic equations on a bounded, convex polygonal domain ${\Omega}$ in $R^2$. A family $G_p=\{I_m\}$ of numerical quadrature rules satisfying certain properties can be used for calculating the integrals. When the numerical quadrature rules $I_m{\in}G_p$ are used for computing the integrals in the stiffness matrix of the variational form we will give its variational form and derive an error estimate of ${\parallel}u-{\widetilde{u}}^h_p{\parallel}_{1,{\Omega}$.