• 한국산학기술학회논문지
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• 제13권4호
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• pp.1895-1899
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• 2012

유한차분법을 적용한 압밀해석을 수행하였는데 순간하중이 재하되는 경우 유한차분법에 의해 예측되는 시간별 침하량과 Terzaghi 방법에 의한 침하량 사이의 차이는 시간격자간격을 충분히 작게 하여 해결할 수 있음을 알 수 있었다. 점증하중에 대한 압밀해석을 위한 유한차분식을 유도하였는데 해석결과에 따른 과잉간극수압의 분포가 Olson의 이론해와 일치하였다. 점증하중이 작용하는 경우에 대해 예측한 시간-침하거동에 있어 유도된 유한차분식에 의한 결과와 Terzaghi 및 Olson 에 의한 결과 또한 거의 일치하였다. 다단 점증하중에 대한 해석결과 또한 신뢰성이 높은 것으로 보인다.

• 대한수학회보
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• 제48권2호
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• pp.413-426
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• 2011

Two types of new methods with variable time steps are proposed in order to valuate binary options efficiently. Type I changes adaptively the size of the time step at each time based on the magnitude of the local error, while Type II combines two uniform meshes. The new methods are hybrid finite difference methods, namely starting the computation with a fully implicit finite difference method for a few time steps for accuracy then performing a ${\theta}$-method during the rest of computation for efficiency. Numerical experiments for standard European vanilla, binary and American options show that both Type I and II variable time step methods are much more efficient than the fully implicit method or hybrid methods with uniform time steps.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 합동 추계학술대회 논문집 정보 및 제어부문
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• pp.394-397
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• 2001

There are several methods of measuring position. For example GPS, AOA, TDOA and using radio camera. In this Paper I used TDOA method in position measuring system. TDOA method uses arrival time difference. In position measuring system, three transfers which is placed in different position transfer signal to receiver in fixed time interval and receiver records arrival time of signal. Because receiver knows idle signal's arrival time, receiver can calculate the difference of the signal's arrival time between idle and real. When we obtain time difference we can know the receiver position by Newton Raphson method.

• 한국식품과학회지
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• 제33권3호
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• pp.294-300
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• 2001

저장 방법의 차이에 따른 유과의 과산화물가는 대바구니 포장이 가장 높았으며, 질소 치환 포장, 냉동 저장 순으로 나타났고, 저장 기간 증가에 따라 현저히 증가하였다. 콩물 농도가 증가함에 따라 과산화물가도 증가하였으나 incubation 시간 증가에 따른 차이는 유의적이지 않았다. 유과의 hardness는 콩물 농도, incubation 시간과 저장 기간의 증가에 따라 현저한 감소를 나타냈으나 저장 방법간에는 유의적인 차이를 나타내지 않았다. Peak number는 저장 기간 10주까지는 냉동 저장군이 다른 군보다 높게 나타났으나, 12주에는 이러한 차이가 나타나지 않았고, 저장 기간 증가에 따라서 증가하였다. 저장 3개월 후 관능 검사 결과, 유과의 색은 저장 방법과 콩물의 농도에 따라서 용적 증가율은 콩물 농도와 incubation 시간에 따라 유의적인 차이가 있었다. 산패취는 저장 방법에 따라서만 유의적인 차이가 있었으며, 부드러운 정도, 맛, 종합적 기호도는 콩물의 농도에 따라서만 유의적 차이가 있었다.

• Structural Engineering and Mechanics
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• 제17권6호
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• pp.735-749
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• 2004

This work presents a direct integration scheme, based on a fourth order finite difference approach, for elastodynamics. The proposed scheme was chosen as an alternative for attenuating the errors due to the use of the central difference method, mainly when the time-step length approaches the critical time-step. In addition to eliminating the spurious numerical oscillations, the fourth order finite difference scheme keeps the advantages of the central difference method: reduced computer storage and no requirement of factorisation of the effective stiffness matrix in the step-by-step solution. A study concerning the stability of the fourth order finite difference scheme is presented. The Finite Element Method and the Boundary Element Method are employed to solve elastodynamic problems. In order to verify the accuracy of the proposed scheme, two examples are presented and discussed at the end of this work.

• Journal of electromagnetic engineering and science
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• 제9권1호
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• pp.12-16
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• 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.

• 한국항해학회지
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• 제18권4호
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• pp.137-146
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• 1994

In this paper, a new algorithm to measure the ultrasonic travel time is proposed, which is fundamental to estimate distance depth and volume in several media. Pulse wave has been used to measure travel time of transmitted signal. However, due to the characteristic of transducer and propagation, the received signal is so distorted that it is difficult to measure travel time, which is propagation, the received signal is so distorted that it is difficult to measure travel time, which is to be time difference between transmitted and received signals. In this proposed method, transmitted and received signal are transformed respectively into norm phase newly designed by this paper and displayed on phase-time curve. And travel time is simply determined by the arithmetic numerical mean of time difference at the identical norm phase on the phase-time curves of transmitted and received signals. This method has several features; firstly, travel time is calculated analytically with high accuracy by least square error method, secondly, it is useful to compare the difference of signal magnitude for time information, thirdly, noise and discrete errors are relatively small, finally, the measurement accuracy is not influenced by D.C. bias. In particular, this method is useful and applicable to measuring very short distance and sound speed with high accuracy.

• Journal of Magnetics
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• 제22권1호
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• pp.104-108
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• 2017

Induction motors have wide applicability in many fields, both in industrial sectors and households, for their advantages of a high efficiency and robust structure. The introduction of power-source-containing harmonics into the induction motor winding lowers its efficiency and increases its temperature, greatly affecting its operation characteristics. In this study, we performed an electromagnetic field analysis using the time-difference finite-element method with the purpose of analyzing the steady-state current characteristics of an induction motor. Additionally, we calculated the steady-state current with a method combining an electromagnetic field equation and a circuit equation. In the electromagnetic field analysis, the nonlinearity was taken into account using the Newton-Raphson method, and a backward time-difference method was employed for the time derivative term. Then, we compared the steady-state current of the induction motor obtained by calculation with the experimentally measured values, thus validating the proposed algorithm. Furthermore, we analyzed the impacts of the shape and material of the rotor conductor bar of the induction motor on the steady-state current of the main winding.

• Smart Structures and Systems
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• 제14권6호
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• pp.1081-1103
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• 2014

Real-time hybrid simulation (RTHS) has emerged as an important tool for testing large and complex structures with a focus on rate-dependent specimen behavior. Due to the real-time constraints, accurate dynamic control of servo-hydraulic actuators is required. These actuators are necessary to realize the desired displacements of the specimen, however they introduce unwanted dynamics into the RTHS loop. Model-based actuator control strategies are based on linearized models of the servo-hydraulic system, where the controller is taken as the model inverse to effectively cancel out the servo-hydraulic dynamics (i.e., model-based feedforward control). An accurate model of a servo-hydraulic system generally contains more poles than zeros, leading to an improper inverse (i.e., more zeros than poles). Rather than introduce additional poles to create a proper inverse controller, the higher order derivatives necessary for implementing the improper inverse can be calculated from available information. The backward-difference method is proposed as an alternative to discretize an improper continuous time model for use as a feedforward controller in RTHS. This method is flexible in that derivatives of any order can be explicitly calculated such that controllers can be developed for models of any order. Using model-based feedforward control with the backward-difference method, accurate actuator control and stable RTHS are demonstrated using a nine-story steel building model implemented with an MR damper.

• 한국정보통신학회논문지
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• 제2권4호
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• pp.653-660
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• 1998

본 연구는 시간영역 유한 차분법(finite difference-time domain method:FDTD)을 이용하여 마이크로스트립 배열 안테나의 전자계 특성들을 해석한다. 직각좌표계에서 맥스웰 방정식의 유한차분 방정식을 정의하였으며, 자유공간과 같은 무한영역해석을 위해서 Mur의 흡수경계조건을 이용하였다 마이크로스트립 배열 안테나를 단위격자 구조로 모델링한 후 시간영역에서 필드분포를 도시하였다.