• 한국정보과학회논문지:정보통신
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• 제29권2호
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• pp.156-164
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• 2002

IPSec은 공용 네트워크 상에서 암호화와 인증, 무결성을 제공하기 위해 사용되는 프로토콜이다. IPSec에서는 전송되는 패킷에 암호화와 인증, 무결성을 추가해 전달하기 위해 ESP 프로토콜을 사용한다. ESP는 패킷 암호화를 위해 DES-CBC 알고리즘을 이용하는데 이 모드에서는 ESP 데이타를 암호화하기 위한 초기 값으로 IV(Initialization Vector)가 사용된다. 이 값은 수신 측의 패킷 복호화를 위해 공개적으로 전달되므로 중간에 공격자에 의해 공격당할 위험이 많다. IV의 값이 조금이라도 변경되면 ESP 의 모든 데이타의 복호화가 이루어지지 않고 상위 레벨의 정보가 변경되는 등 심각한 문제가 발생한다. 이것은 보안을 목적으로 하는 IPSec에서는 치명적인 약점이 될 수 있다. 따라서 본 논문에서는 IV를 안전하게 전송하기 위한 새로운 알고리즘을 제시한다. 이 방법은 DES-ECB 알고리즘을 이용하여 IV 값을 암호화하여 IV 공격을 방어하고 메시지 인증 함수를 추가 적용하여 ESP 전체 데이타의 무결성 체크도 가능하게 한다. 제안된 알고리즘으로 IV와 데이타에 대한 공격을 방어하고 안전한 전송을 보장한다.

• 한국구조물진단유지관리공학회 논문집
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• 제27권4호
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• pp.1-10
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• 2023

구조물의 내진설계 시 지진력은 구조모델 수립 및 구조해석에 기반하여 산정되는데, 구조모델이 실제 구조물의 동특성치를 정확하게 반영하기 위해서는 실제 계측을 통한 보정이 요구된다. 본 연구에서는 실제 건물을 모사한 4층 골조 시험체를 대상으로 각 층별 가속도계를 부착하여 1축 진동대 실험을 수행하였다. 실험체의 주기는 실제 건축물의 주기와 유사하며, 수평부재의 무한강성을 고려하여 기둥은 이중곡률로 거동하도록 설계하였다. 입력지진파의 특성에 따른 영향을 고려하기 위해 다양한 주파수와 가속도 크기를 갖는 역사지진파와 인공지진파를 가력하였다. 동적응답신호를 통해 얻은 주파수응답함수를 이용하여 고유진동수와 감쇠비, 모드벡터를 도출하였으며, Mode assurance criterion(MAC)를 통해 입력지진파에 따른 모드벡터 간의 편차를 확인하였다. 또한 진동대 실험을 통해 도출된 감쇠비를 구조모델에 적용하였으며, 실험 결과와의 비교를 통하여 동특성 도출 방법을 검증하였다.

• Journal of the Optical Society of Korea
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• 제7권3호
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• pp.188-192
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• 2003

The modal characteristics of the photonic crystal fibers are analyzed using the reliable and efficient plane wave expansion method. The mode profile, effective index and group velocity dispersion are obtained by solving Maxwell's vector wave equations without any approximation. The zero dispersion condition of a photonic crystal fiber is derived over a wide range of wavelengths. Higher-order modes are also easily found as a by-product of the plane wave expansion method. This method can be used to quickly and accurately design various optical properties of photonic crystal fibers.

• 대한음성학회지:말소리
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• 제52호
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• pp.145-160
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• 2004

In this paper, a new noise compensation method based on the eigenvoice framework in feature space is proposed to reduce the mismatch between training and testing environments. The difference between clean and noisy environments is represented by the linear combination of K eigenvectors that represent the variation among environments. In the proposed method, the performance improvement of speech recognition systems is largely affected by how to construct the noisy models and the bias vector set. In this paper, two methods, the one based on MAP adaptation method and the other using stereo DB, are proposed to construct the noisy models. In experiments using Aurora 2 DB, we obtained 44.86% relative improvement with eigen-environment method in comparison with baseline system. Especially, in clean condition training mode, our proposed method yielded 66.74% relative improvement, which is better performance than several methods previously proposed in Aurora project.

• Journal of Electrical Engineering and Technology
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• 제10권1호
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• pp.205-215
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• 2015

Common mode (CM) conducted interference are predicted and compared with experiments in a motor drive system of Electric vehicles in this study. The prediction model considers each part as an equivalent circuit model which is represented by lumped parameters and proposes the parameter extraction method. For the modeling of the inverter, a concentrated and equivalent method is used to process synthetically the CM interference source and the stray capacitance. For the parameter extraction in the power line model, a computation method that combines analytical method and finite element method is used. The modeling of the motor is based on measured date of the impedance and vector fitting technique. It is shown that the parasitic currents and interference voltage in the system can be simulated in the different parts of the prediction model in the conducted frequency range (150 kHz-30 MHz). Experiments have successfully confirmed that the approach is effective.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2000년도 봄 학술발표회논문집
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• pp.85-91
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• 2000

The smallest value of the load when the equilibrium condition becomes to be unstable is defined as the buckling load. The primary objective of this paper is to analyse stability boundaries for star dome under combined loads and is to investigate the iteration diagram under the independent loading parameter In numerical procedure of the geometrically nonlinear problems, Arc Length Method and Newton-Raphson iteration method is used to find accurate critical point(bifurcation point and limit point). In this paper independent loading vector is combined as proportional value and star dome was used as numerical analysis model to find stability boundary among load parameters and many other models as multi-star dome and arches were studied. Through this study we can find the type of buckling mode and the value of buckling load.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 봄 학술발표회 논문집
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• pp.25-32
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• 2004

In this proposed work new finite element model for multi-delaminated plates is proposed. In the current analysis procedures of multi-delaminated plates, plate element based on Mindlin plate theory is used in order to obtain accurate results of out-of-plane displacement of thick plate. And for delaminated region, plate element based on Kirchhoff plate theory is considered. To satisfy the displacement continuity conditions, displacement vector based on Kirchhoff theory is transformed to displacement of transition element. The numerical results show that the effect of delaminations on the modal parameters of delaminated composites plates is dependent not only on the size, the location and the number of the delaminations but also on the mode number and boundary conditions. Kirchhoff based model have higher natural frequency than Mindlin based model and natural frequency of the presented model is closed to Mindlin based model.

• 전기의세계
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• 제21권3호
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• pp.31-40
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• 1972

This study intends to investigate the optimal switching modes of a double-capacitive thermal system under different constraints on the state and the control variable, by the application of the Pontryagin's Minimum Principle. Throughout the development, the control effort is assumed to have two modes of state: M or zero and the terminal times being fixed. In the first part of this study, the Principle is discussed under various conditions for this particular problem, with different criterion functions and in the same time imposing a certain constraints; i) on the terminal states, ii) on functions of the terminal states. Depending upon the upper bound value of the control vector, possible driving modes of the states are studied from which particular optimal driving modes are extracted so as to meet the specified constraints and boundary conditions imposed in the problem. Numerical solutions are evaluated for an over0damped, double-capacitive thermal plant and the optimal solutions: the switching mode, the optimal switching time, and the control effort are compared with the analytical results, in the second part of this work, to confirm the development.

• 전자공학회논문지B
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• 제33B권3호
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• pp.38-46
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• 1996

In this paper, a multi-velocity log system which uses ultrasonic pulsed doppler signal is developed. The output of the system is the absoluted velcocity of the ship. By using digitral signal processing, we get the vector velocity which displays the ship's speed about fore, aft, port and starboard. And this system give us the information about depth. This multi-velocity system has a large merit that is bottom and water track velocity. In addition, this has the high accuracy and can measure the water-depth according to the deep mode. And the fish finder, echo sounder or docking system will be made by applying the speed log system.

• 한국소음진동공학회논문집
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• 제15권1호
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• pp.112-117
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• 2005

Two modified versions of subspace iteration method using accelerated starting vectors are proposed to efficiently calculate free vibration modes of structures. Proposed methods employ accelerated Lanczos vectors as starting iteration vectors in order to accelerate the convergence of the subspace iteration method. Proposed methods are divided into two forms according to the number of starting vectors. The first method composes 2p starting vectors when the number of required modes is p and the second method uses 1.5p starting vectors. To investigate the efficiency of proposed methods, two numerical examples are presented.