• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.12
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• pp.1917-1923
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• 2010

This study focuses on model identification and a 2-DOF PID control algorithm for cooling processes; a pneumatic butterfly-type control valve is used for this purpose. The mathematical model is a transfer function composed of a time delay and a second-order delay system. The control valve is identified as a first-order delay system with a time delay and included in the controlled plant. From the experimental data sets for a demo plant, the model parameters are identified, and the 2-DOF PID control gains are analytically derived by Kitamori's method. We show via a computer simulation and an experimental test that the performance of the proposed 2-DOF PID control system is better than that of a conventional 1-DOF PID control system.

• Journal of Educational Research in Mathematics
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• v.14 no.3
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• pp.305-325
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• 2004

This study is on the teaching-learning of parameter concept in secondary school mathematics. In our school mathematics curriculum, parameter concept is explicitly presented at high school mathematics textbook. But student have difficulty in understanding parameter concept because this concept is implicitly used in the textbook from 7-grade mathematics. Moreover, it is true that mathematics teacher give a little attention to student's understanding of parameter con- cept. In this study, we analyzed concept definition of parameter and the extension of parameter on the basis of preceding research, our mathematical curriculum, mathematical dictionaries. After that, we concluded that parameter is explicitly called in t where x= f(t), y= g(t) and parameter is implicitly treated in the learning of relation between quantities in our mathematical curriculum. We pointed to the importance of parameter concept in the successful learning of school algebra. Specially, when the level of algebra is in the learning of relation between quantities, parameter is the key concept for understanding and representing of families of equations or functions. In mathematics class, students have opportunity to reflect that what the role of each variable(parameter, dependent variable, independent variable etc.) is, and where the information which determines it comes from. It is for mathematical communications as well as learning school algebra. Therefore, mathematics teacher's didactical attention is more needed to student have a good concept image of parameter before they learn explicitly its concept definition.

• Proceedings of the Korea Contents Association Conference
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• 2007.11a
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• pp.951-953
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• 2007

Generation of Corporate risk Contents using Financial Data The purpose of this paper is to capture risk profiles of smaller-sized Korean firms vis-$\grave{a}$-vis larger-sized firms during the Asian financial crisis. For this purpose, risk profiles are provided by estimating expected default risks and by tracking how these have changed during this period with respect to their magnitude, volatility, and sensitivity measures. Methodology used in this study employs the Black-Scholes-Merton model for producing estimates of default risks. And the conventional trans-log function is utilized for obtaining sensitivity measures of the estimated default risks. According to empirical evidence obtained here, it is revealed that contractions of corporate loans associated with IMF austerity policy was the main factor responsible for the drastic change in the default risk profile of Korean firms after occurrence of the Asian financial crisis.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.2
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• pp.151-164
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• 2003

In this paper, induction motor drives with low switching acoustic noise based on the 2 phase modulated RLL(Random Lead-Lag) PWM is proposed and implemented. The proposed switching method is much bettor than 3 phase modulated RLL-PWM from the standpoint of the broadening effect of the acoustic noise spectrum. Along with the randomization of PWM Pulses, SVM(Space Vector Modulation) is executed in the TMS320C31 DSP(Digital Signal Processor). To verify the validity of the proposed RPWM(Random PWM), the experimental study was tried. The experimental results show that the performance of the proposed method and the 3 phase center-aligned SVM / conventional RLL-PWM are nearly the same from the viewpoint of the constant v/f centrel. But, in case of the proposed 2 phase modulated RLL-PWM, the spectrum characteristics of the voltage and the switching acoustic noise are shown to have better broadening effect than 3 phase modulated one.

• The KIPS Transactions:PartD
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• v.14D no.3 s.113
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• pp.293-302
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• 2007

The study of the web graph yields valuable insight into web algorithms for crawling, searching and community discovery, and the sociological phenomena which characterize its evolution, also it is useful for understanding the evolution process of web graph and predicting the scale of the Web. In this paper, we report experimental results on properties of the Korea web graph with over 116 million pages and 2.7 billion links. We indicate to study the Korea web properties such as the power law phenomenon and then to analyze the similarity and difference between the global and Korea web graph. Our analysis reveals the Korea web graph have different properties compared with the global web graph from the structure to the evolution of the Web. Finally, a number of measurements of the evolution of the Korea web graph ill be represented.

• Journal of the Korea Society of Computer and Information
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• v.12 no.6
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• pp.177-185
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• 2007

Lately, it is a trend that diffusion of Mobile Information Appliance that do various function by development of IT technology. There is function that do more convenient and efficient exchange information and business using mobile phone that is Mobile Information Appliance, but disfunction that is utilized by pointed end engineering data leakage, individual's privacy infringement, threat, etc. relationship means to use mobile phone is appeared and problems were appeared much. However, legal research of statute unpreparedness and so on need research and effort to prove delete, copy, integrity of digital evidence that transfer secures special quality of easy digital evidence to objective evidence in investigation vantage point is lacking about crime who use this portable phone. It is known that this Digital Forensic field is Mobile Forensic. In this paper. We are verify about acquisition way of digital evidence that can happen in this treatise through mobile phone that is Mobile Forensic's representative standing and present way to prove integrity of digital evidence using Hash Function.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.4
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• pp.621-628
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• 2017

The efficiency of implementation of the arithmetic operations in finite fields depends on the choice representation of elements of the field. It seems that from this point of view normal bases are the most appropriate, since raising to the power 2 in $GF(2^n)$ of characteristic 2 is reduced in these bases to a cyclic shift of the coordinates. We, in this paper, introduce our algorithm to transform fastly the conventional bases to normal bases and present the result of H/W implementation using the algorithm. We also propose our algorithm to calculate the multiplication and inverse of elements with respect to normal bases in $GF(2^n)$ and present the programs and the results of H/W implementations using the algorithm.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.423-423
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• 2009

미진동 제어라는 분야에 대한 연구는 반도체 산업이 초고도화 및 초정밀화가 진전되고 있는 최근에 들어와 학계보다는 전문 반도체와 TFT-LCD의 미진동제어 관련 엔지니어 그룹과 정밀 장비 제작사를 중심으로 이루어져왔다. 고집적 생산 제품을 가공 및 검사하기 위해서는 가공 선폭 이상의 분해 성능을 가진 고정밀도의 생산 및 검사 장비가 필요하다. 이런 고정밀도 생산 및 검사장비는 내외부로부터 입력되는 진동에 민감한 영향을 받는다. 초기 반도체 산업을 주도한 미국을 중심으로 일부 학자와 반도체 진동 제어를 수행하는 전문연구소에서 작성한 BBN-Criteria는 정밀장비의 용도나 분해능 별로 정리된 진동허용규제치를 지침서로 사용하여 왔다. 그러나 장비의 엄밀한 주파수 특성 및 정밀도 측면에서 불확실한 영역부분을 가지고 있기 때문에 미소한 진동을 제어하는 구조 설계자 관점에서는 불충분한 자료이다. 그리고 주파수 분해능을 가진 진동허용규제치를 제시하는 것이 바람직하지만 대부분의 제작사에서는 그렇지 못하고 있다. 그런 이유에는 장비 개개의 진동허용규제치가 다른 고가의 장비 전량에 대하여 시험을 수행해야 하는 점, 가진(加振)특성, 중량, 크기 등의 진동실험 자체에 어려움 때문이다. 또한 진동실험시 가진주파수의 분해능의 결려에 따른 장비의 동적 특성이 고려되지 않은 불확실한 영역 부분을 포함한 진동허용규제치를 제시함으로서 불확실한 영역부분의 진동 하한치를 진동허용규제치의 상한치로 결정하는 문제로 인하여 진동허용규제치가 더욱 가혹하게 제시되어 건물 구조 설계와 방진의 어려움을 가중시킬 여지가 있다. 본 논문에서는 이런 어려움 등을 회피하는 방법으로 주파수응답함수(Frequency Response Function, FRF)를 이용하여 정밀장비의 진동허용규제치를 결정하는 간편하면서도 더욱 정밀한 새로운 방법을 모색하였다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.29 no.1
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• pp.47-53
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• 2005

This paper presents the method for developing an optimum hull form with minimum wave resistance using SQP(sequential quadratic programming) as an optimization technique. The wave resistance is evaluated by a Rankine source panel method with non-linear free surface conditions and the ITTC 1957 friction line is used to predict the frictional resistance coefficient. The geometry of the hull surface is represented and modified using NURBS(Non-Uniform Rational B-Spline) surface patches. To verity the validity of the developed program the numerical calculations for Wigley hull and Series 60(C${_B}$=0.6) hull had been performed and the results obtained after the numerical calculations had been compared with the original hulls.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.11
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• pp.92-100
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• 2009

In this paper, we analyze the hardware architecture of Low Density Parity Check (LDPC) decoder using Log Likelihood Ration-Belief Propagation (LLR-BP) decoding algorithm. Various design issues that affect the decoding performance and the hardware complexity are discussed and the tradeoffs between the hardware complexity and the performance are analyzed. The message data for passing error probability is quantized to 7 bits and among them the fractional part is 4 bits. To maintain the decoding performance, the integer and fractional parts for the intrinsic information is 2 bits and 4 bits respectively. We discuss the alternate implementation of $\Psi$(x) function using piecewise linear approximation. Also, we improve the hardware complexity and the decoding time by applying overlapped scheduling.