• Journal of the Society of Naval Architects of Korea
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• v.52 no.1
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• pp.8-18
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• 2015

Reduction of the fuel oil consumption and corresponding greenhouse gas exhausted from ships is an important issue for today's ship design and shipping. Several concepts and devices on the superstructure of a container ship were suggested and tested in the wind tunnel to estimate the air drag reduction. As a preliminary performance evaluation, air drag contributions of each part of the superstructure and containers were estimated based on RANS simulation respectively. Air drag reduction efficiency of shape modification and add-on devices on the superstructure and containers was also estimated. Gap-protectors between containers and a visor in front of upper deck were found to be most effective for drag reduction. Wind tunnel tests had been carried out to confirm the drag reduction performance between the baseline(without any modification) configuration and two modified superstructure configurations which were designed and chosen based on the computation results. The test results with the modified configurations show considerable aerodynamic drag reduction, especially the gap-protectors between containers show the largest reduction for the wide range of heading angles. RANS computations for three configurations were performed and compared with the wind tunnel tests. Computation result shows the similar drag reduction trend with experiment for small heading angles. However, the computation result becomes less accurate as heading angle is increasing where the massively separated flow is spread over the leeward side.

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.239-243
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• 1990

This paper presents a algorithm to improve accuracy and reliability in state estimation of contaminated bad data. The conventional algorithms for detection of bad data confront the problems of excessive memory requirements and long computation time. In order to overcome measurement compensation approach is proposed to reduce computation time and partitioned measurement error model has the advantage of remarkable reduction in computation time and memory requirements in estimated error computation. The proposed algorithm has been tested for IEEE sample systems, which shows its applicability to on-line power systems.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.40 no.2
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• pp.144-153
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• 1991

This paper presents an algorithm to improve accuracy and reliability in the state estimation of contaminated bad data. The conventional algorithms for detection of bad data have the problems of excessive memory requirements and long computation time. In order to overcome these problems, a measurement compensation approach is proposed to reduce computation time, and the partitioned measurement error model has the advantage of remarkable reduction in computation time and memory requirements in estimated error computation. The proposed algorithm has been tested for IEEE sample systems, which shows its applicability to on-line power systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.3C
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• pp.163-169
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• 2011

Partial transmit sequence (PTS) algorithm is known as one of the most efficient ways to reduce the peak-to-average power ratio (PAPR) in the orthogonal frequency division multiplexing (OFDM) system. The PTS algorithm, however, requires large numbers of computation to implement. Thus there has been a trade-off between performance of PAPR reduction and computational complexity. In this paper, the performance of PAPR reduction and computation complexity of PTS algorithms are analyzed and compared through computer simulations. Subsequently, a new PTS algorithm is proposed which can be a reasonable method to reduce the PAPR of OFDM when both the performance of PAPR reduction and computational complexity are considered simultaneously.

• Proceedings of the IEEK Conference
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• 2002.06d
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• pp.405-408
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• 2002

LSP(Line Spectrum Pairs) Parameter is used for speech analysis in vocoders or recognizers since it has advantages of constant spectrum sensitivity. low spectrum distortion and easy linear interpolation. However the method of transforming LPC(Linear Predictive Coding) into LSP is so complex that it takes much time to compute. Among conventional methods, the real root method is considerably simpler than others, but nevertheless, it still suffers from its jndeterministic computation time because the root searching is processed sequentially in frequency region. We suggest a method of reducing the LSP transformation time using voice characteristics The proposed method is to apply search order and interval differently according to the distribution of LSP parameters. in comparison with the conventional real root method, the proposed method results in about 46.5% reduction. And, the total computation time is reduce to about 5% in the G.723.1 vocoder.

• Structural Engineering and Mechanics
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• v.8 no.6
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• pp.579-589
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• 1999

A new way to reduce the eigenvalue computation effort in structural dynamics is presented in this paper. The degrees of freedom of a structure may be classified into groups that are termed as sub-degrees of freedom. The eigenvalue analysis is performed with each of sub-degrees of freedom so that the computing time is much shortened. Since the dynamic coupling between sub-degrees of freedom is selected to be small and it may be considered as a perturbation, the perturbation algorithm is used to obtain an accuratae result. The accuracy of perturbation depends on the coupling between sub-degrees of freedom. The weaker the coupling is, the more accurate the result is. The procedure can be used to simplify a problem of three dimensions to that of two dimensions or from two dimensions to one dimension. The application to a truss and a space frame is shown in the paper.

• ETRI Journal
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• v.32 no.4
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• pp.622-625
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• 2010

In this letter, we assess the scalability of a path computation flooding (PCF) approach to compute optimal end-to-end inter-domain paths in a path computation element-based multi-domain network. PCF yields a drastically reduced network blocking probability compared to a blind per-domain path computation but introduces significant network control overhead and path computation complexity. In view of this, we introduce and compare an alternative low overhead PCF (LoPCF) solution. From the obtained results, LoPCF leads to similar blocking probabilities to PCF while exhibiting around 50% path computation complexity and network control overhead reduction.

• Journal for History of Mathematics
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• v.15 no.2
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• pp.101-112
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• 2002

Gu-Jang-San-Sul is a book of Chinese ancient mathematics and has had an impact on Korean mathematics. The book is organized into nine chapters and each chapter is composed of problems, answers, and their computation algorithms. The contents reflect the practicality of Chinese mathematics. Especially the first chapter covers the computation of fractions for land surveying. This paper suggests how the computation methodology is used in teaching fractions for primary school students. Five strategies for fractions related to the reduction, addition, subtraction, multiplication, and division are followed by: 1) developing the ability to apply rules to problems by practicing the computation process according to the given algorithm; 2) developing the communication skill by comparing the differences of various computation algorithms; 3) setting computation problems; 4) understanding the characteristics of terminology in mathematics; and 5) being exposed to new ideas in mathematics.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.4
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• pp.1024-1034
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• 1998

Most public cryptosystem widely used in communication network are based on the exponentiation-arithmetic. But, cryptosystem has to use bigger and bigger key parameter to attain an adequate level of security. This situation increases both computation and time delay. Montgomery, yang and Kawamura presented a method by using the pre-computation, intermediately computing and table look-up on modular reduction. Coster, Brickel and Lee persented also a method by using the pre-computation on exponentiation. This paper propose to reduce computation of exponentiation with spare prime. This method is to enhance computation efficiency in cryptosystem used discrete logarithms.

• Communications for Statistical Applications and Methods
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• v.29 no.6
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• pp.721-733
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• 2022

In this paper we compare parameter estimation by Grassmann manifold optimization and sequential candidate set algorithm in a structured principal fitted component (PFC) model. The structured PFC model extends the form of the covariance matrix of a random error to relieve the limits that occur due to too simple form of the matrix. However, unlike other PFC models, structured PFC model does not have a closed form for parameter estimation in dimension reduction which signals the need of numerical computation. The numerical computation can be done through Grassmann manifold optimization and sequential candidate set algorithm. We conducted numerical studies to compare the two methods by computing the results of sequential dimension testing and trace correlation values where we can compare the performance in determining dimension and estimating the basis. We could conclude that Grassmann manifold optimization outperforms sequential candidate set algorithm in dimension determination, while sequential candidate set algorithm is better in basis estimation when conducting dimension reduction. We also applied the methods in real data which derived the same result.