• Bulletin of the Korean Mathematical Society
• /
• v.38 no.1
• /
• pp.17-27
• /
• 2001

We discuss a finite difference preconditioner for the$C^1$ Lagrance quadratic spline collocation method for a uniformly elliptic operator with homogeneous Dirichlet boundary conditions. Using the generalized field of values argument, we analyzed eigenvalues of the matrix preconditioned by the matrix corresponding to a finite difference operator with zero boundary condition.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
• /
• 2004.11a
• /
• pp.95-98
• /
• 2004

GPS double difference, carrier phase measurements are ambiguous by an unknown inter number of cycle. High precision, relative GPS positioning can be obtained from a short time span of data if the integer double difference ambiguities can be determined efficiently. In this study, we used a ambiguities resolution method indicated by Clyde Goad. And I compared with ambiguities using Lambda method. The difference of ambiguities between two method is below ${\pm}$1.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.21 no.10
• /
• pp.2724-2730
• /
• 1996

In this paper, the dispersive characteristics of the Finite-Difference Frqequency-Domain method based on the Multi-Resolution Technique(MR-FDFD) are numerically analyzed. A dispersion analysis of the MR-FDFD ority of the MR-FDFD method to the spatial discretization is shown. We expect that the multi-resoluation technique will improve the disavantage of the finite difference techqnique which needs the large comutational memory for accurate electromagnetic analysis.

• Culinary science and hospitality research
• /
• v.6 no.1
• /
• pp.103-121
• /
• 2000

All the food including Korean food is made by boiling preparing raw materials food. and to know how to cook correctly is the basis to cook delicious food. For mankind, finding out fire was the source of enormous change in the development of food culture. I have investigated the difference in cooking Korean style & Western style, by using fire, and known that there is a little difference between two methods except for cooking method by food. Preferably there is a wide difference by combinations of raw materials and cooking method.

• Journal of the Korean Mathematical Society
• /
• v.59 no.5
• /
• pp.891-909
• /
• 2022

The main objective of this paper is to develop a concrete inverse formula of the system induced by the fourth-order finite difference method for two-point boundary value problems with Robin boundary conditions. This inverse formula facilitates to make a fast algorithm for solving the problems. Our numerical results show the efficiency and accuracy of the proposed method, which is implemented by the Thomas algorithm.

• The Transactions of the Korean Institute of Electrical Engineers D
• /
• v.50 no.12
• /
• pp.590-596
• /
• 2001

The pre-emphasis is an essential process for speech signal processing. Widely used two methods are the typical method using a fixed value near unity and te optimal method using the autocorrelation ratio of the signal. This study proposes a new pre-emphasis method using the short-term energy difference of speech signal, which can effectively compensate the glottal source characteristics and lip radiation characteristics. Using the proposed pre-emphasis, speech analysis, such as spectrum estimation, formant detection, is performed and the results are compared with those of the conventional two pre-emphasis methods. The speech analysis with 5 single vowels showed that the proposed method enhanced the spectral shapes and gave nearly constant formant frequencies and could escape the overlapping of adjacent two formants. comparison with FFT spectra had verified the above results and showed the accuracy of the proposed method. The computational complexity of the proposed method reduced to about 50% of the optimal method.

• Journal of electromagnetic engineering and science
• /
• v.9 no.1
• /
• pp.12-16
• /
• 2009

This paper presents a new iterative locally one-dimensional [mite-difference time-domain(LOD-FDTD) method that has a simpler formula than the original iterative LOD-FDTD formula[l]. There are fewer arithmetic operations than in the original LOD-FDTD scheme. This leads to a reduction of CPU time compared to the original LOD-FDTD method while the new method exhibits the same numerical accuracy as the iterative ADI-FDTD scheme. The number of arithmetic operations shows that the efficiency of this method has been improved approximately 20 % over the original iterative LOD-FDTD method.

• Journal of applied mathematics & informatics
• /
• v.27 no.1_2
• /
• pp.441-452
• /
• 2009

In this paper, a fifth order numerical method is presented for solving singularly perturbed differential-difference equations with negative shift. In recent papers the term negative shift has been using for delay. Similar boundary value problems are associated with expected first exit time problem of the membrane, potential in models for neuron and in variational problems in control theory. In the numerical treatment for such type of boundary value problems, first we use Taylor approximation to tackle terms containing small shifts which converts it to a boundary value problem for singularly perturbed differential equation. The two point boundary value problem is transformed into general first order ordinary differential equation system. A discrete approximation of a fifth order compact difference scheme is presented for the first order system and is solved using the boundary conditions. Several numerical examples are solved and compared with exact solution. It is observed that present method approximates the exact solution very well.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.27 no.6
• /
• pp.782-786
• /
• 1994

Integrated finite difference method (IFDM) is used to solve one dimensional free oscillation problem in the coastal area. To evaluate the solution accuracy of IFDM in free oscillation analysis, two finite difference equations based on area discretization method and point discretization method are derived from the governing equations of free oscillation, respectively. The difference equations are transformed into a generalized eigenvalue problem, respectively. A numerical example is presented, for which the analytical solution is available, for comparing IFDM to conventional finite difference equation (CFDM), qualitatively. The eigenvalue matrices are solved by sub-space iteration method. The numerical results of the two methods are in good agreement with analytical ones, however, IFDM yields better solution than CFDM in lower modes because IFDM only includes first order differential operator in finite difference equation by Green's theorem. From these results, it is concluded that IFDM is useful for the free oscillation analysis in the coastal area.

• Atmosphere
• /
• v.26 no.3
• /
• pp.483-492
• /
• 2016

We have examined the random error of eddy covariance (EC) measurements on the basis of two-tower approach during daytime. Two EC towers were placed on the grassland with different vegetation density near Gumi-weir. We calculated the random error using three different methods. The first method (M1) is two-tower method suggested by Hollinger and Richardson (2005) where random error is based on differences between simultaneous flux measurements from two towers in very similar environmental conditions. The second one (M2) is suggested by Kessomkiat et al. (2013), which is extended procedure to estimate random error of EC data for two towers in more heterogeneous environmental conditions. They removed systematic flux difference due to the energy balance deficit and evaporative fraction difference between two sites before determining the random error of fluxes using M1 method. Here, we introduce the third method (M3) where we additionally removed systematic flux difference due to available energy difference between two sites. Compared to M1 and M2 methods, application of M3 method results in more symmetric random error distribution. The magnitude of estimated random error is smallest when using M3 method because application of M3 method results in the least systematic flux difference between two sites among three methods. An empirical formula of random error is developed as a function of flux magnitude, wind speed and measurement height for use in single tower sites near Nakdong River. This study suggests that correcting available energy difference between two sites is also required for calculating the random error of EC data from two towers at heterogeneous site where vegetation density is low.