• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.3
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• pp.120-130
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• 2001

We present an approach to parallelizing optimal power flow that is suitable for distributed implementation and is applicable to very large interconnected power systems. This approach can be used by utilities to optimize economy interchange without disclosing details of their operating costs to competitors. Recently, it is becoming necessary to incorporate contingency constraints into the formulation, and more rapid updates of telemetered data and faster solution time are becoming important to better track changes in the system. This concern led to a research to develop an efficient algorithm for a distributed optimal power flow based on the Auxiliary Problem Principle and to study the convergence rate improvement of the distributed algorithm. The objective of this paper is to find a set of control parameters with which the Auxiliary Problem Principle (Algorithm - APP) can be best implemented in solving optimal power flow problems. We employed several IEEE Reliability Test Systems, and Korea Power System to demonstrate the alternative parameter sets.

• Journal of the Korea Convergence Society
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• v.7 no.4
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• pp.217-227
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• 2016

This paper analyzes whether social welfare services converge across the regions. We tested whether local social welfare services converge considering the congestion rate of local social welfare services during the 1985-2013 periods in Korea, using the sixteen higher level local governments panel data. The main findings are as follows. First, the absolute level of local social welfare services converge so that the -convergence exists. Second, the growth rate of local social welfare services increases as the intial level of local social welfare services is lower so that there exists -convergence. The policy implications of our findings are as follows. The local government had better consider the presence of local social welfare services in policy decision making. Also, fundamentally the social welfare policies had better be executed by the central government rather than local governments, since the national minimum welfare must be provided.

• Journal of the Korean Statistical Society
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• v.27 no.2
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• pp.153-163
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• 1998

We investigate density estimation problem in the L$^{\infty}$ norm and show that the iii optimal minimax rates are achieved for smooth classes of weakly dependent stationary sequences. Our results are then applied to give uniform convergence rates for various problems including the Gibbs sampler.

• Journal of Mechanical Science and Technology
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• v.16 no.10
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• pp.1264-1275
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• 2002

This paper is concerned with the investigation on the stability and convergence characteristics of the Crank-Nicolson-Galerkin scheme that is widely being employed for the numerical approximation of parabolic-type partial differential equations. Here, we present the theoretical analysis on its consistency and convergence, and we carry out the numerical experiments to examine the effect of the time-step size △t on the h- and P-convergence rates for various mesh sizes h and approximation orders P. We observed that the optimal convergence rates are achieved only when △t, h and P are chosen such that the total error is not affected by the oscillation behavior. In such case, △t is in linear relation with DOF, and furthermore its size depends on the singularity intensity of problems.

• Journal of Korean Institute of Industrial Engineers
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• v.42 no.3
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• pp.209-221
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• 2016

As the ICT is an industry which is the basis of the technology convergence, it is the driving force of development for new business opportunities and existing industries. But, most of the existing studies for ICT convergence have identified the trend for convergence in technological terms. So, it is difficult to identify the convergence trend in the subject innovation perspective which leads the innovation activities In the ICT industry. The newly entered companies in the ICT industry are key indicators to identify the convergence trend. They have two specific characteristics that show the wide range of the convergence technology and the application rate of the convergence. Because previous studies did not take into account these two characteristics of the newly entered companies, so it is hard to analyze the exact convergence trend. Therefore, in this paper, we classify the patents for the ICT industry depending on the subject innovation. Then, we deduct the core convergence technology in the ICT industries and application area of the non-ICT industries.

• Journal of the Korean Mathematical Society
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• v.36 no.2
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• pp.299-316
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• 1999

We consider two finite difference approxiamations to a singular boundary value problem arising in the study of a nonlinear circular membrane under normal pressure. It is shown that the rates of convergence are O(h) and O($h^2$), respectively. An iterative scheme is introduced which converges to the solution of the finite difference equations. Finally the numerical experiments are given

• Bulletin of the Korean Mathematical Society
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• v.49 no.3
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• pp.495-510
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• 2012

Let $X_1$, $X_2$,${\ldots}$, $X_n$ be a sequence of independent and identically distributed random variables with common distribution function $F$. Convergence rates for the moments of extremes are studied by virtue of second order regularly conditions. A unified treatment is also considered under second order von Mises conditions. Some examples are given to illustrate the results.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.175-177
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• 2003

The convergence characteristics of the LV scheme for the Euler equations have been investigated by using the Von Neumann stability analysis. The results indicated that the convergence rate is governed by a specific combination of CFD parameters. Based on this insight, it is shown that the convergence characteristics of the LV scheme is not deteriorated at any grid aspect-ratio as long as the local time step is defined based on the parameter combination. The numerical results demonstrated that this time step definition provide a uniform convergence for grid aspect-ratios between one to$1{\times}10^{4}$.

• Journal of the Korean Statistical Society
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• v.31 no.2
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• pp.261-276
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• 2002

Probability density or its derivatives may have a discontinuity/change point at an unknown location. We propose a method of estimating the location and the jump size of the discontinuity point based on kernel type density or density derivatives estimators with one-sided equivalent kernels. The rates of convergence of the proposed estimators are derived, and the finite-sample performances of the methods are illustrated by simulated examples.

• Journal of the Korean Mathematical Society
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• v.48 no.3
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• pp.487-497
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• 2011

In this paper we propose a simple iterative method for finding a root of a nonlinear equation. It is shown that the new method, which does not require any derivatives, has a quadratic convergence order. In addition, one can find that a hybrid method combined with the non-iterative method can further improve the convergence rate. To show the efficiency of the presented method we give some numerical examples.