• 한국컴퓨터정보학회논문지
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• 제10권2호
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• pp.123-132
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• 2005

본 논문에서는 기존의 무선 PKI 에서 키 교환방식의 키 교환 설정단계가 단순히 이산대수문제에 근거하여 수행되었지만 제안한 무선 PKI 인증구조의 상호인증과정에서는 키 교환 설정단계에 타원곡선을 적용하였다. 제안한 무선 PKI 구조 안에서의 핸드오버 방법은 CRL검색시간을 단축시킬 수 있으므로 기존의 방법에 비하여 단축된 핸드오버 처리시간을 보여준다 기존 알고리즘과 제안한 인증구조를 비교하여 실험해 보았을 때 인증 대기시간이 제안한 인증 기법이 모든 란경에서 기존 알고리즘보다 우수한 성능을 보였다.

• Structural Engineering and Mechanics
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• 제20권6호
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• pp.673-693
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• 2005

A general step-by-step simulation for the time-dependent analysis of segmentally-erected prestressed concrete box-girder bridges is presented. A three dimensional finite-element model for the balanced-cantilever construction of segmental bridges, including effects of the load history, material nonlinearity, creep, shrinkage, and aging of concrete and the relaxation of prestressing steel was developed using ABAQUS software. The models included three-dimensional shell elements to model the box-girder walls and Rebar elements representing the prestressing tendons. The step-by-step procedure allows simulating the construction stages, effects of time-dependent deformations of materials and changes in the structural system of the bridges. The structural responses during construction and throughout the service life were traced. A comparison of the developed computer simulation with available experimental results was conducted and good agreement was found. Deflection of the bridge deck, changes in stresses and strains and the redistribution of internal forces were calculated for different examples of bridges, built by the balanced-cantilever method, over thirty-year duration. Significant time-dependent effects on the bridge deflections and redistribution of internal forces and stresses were observed. The ultimate load carrying capacities of the bridges and the behavior before collapse were also determined. It was observed that the ultimate load carrying capacity of such bridges decreases with time as a result of time-dependent effects.

• 한국컴퓨터정보학회논문지
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• 제8권2호
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• pp.88-96
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• 2003

마이크로스트립 라인은 마이크로웨이브와 밀리미터웨이브 집적회로에 있어서 가장 필수적인 소자 중의 하나이다. 그동안 여러 가지 주파수 영역 해석법에 의해 이러한 마이크로스트립 라인의 주파수 종속특성이 해석되었다. 하지만 본 논문에서 제시된 3차원 TLM법은 마이크로스트립 라인의 주파수 영역 해를 얻기 위한 또 다른 독립적인 해석법이다. 이러한 TLM 알고리즘을 이용하여 해석된 구조는 스텝 불연속 마이크로스트립 라인이며 대칭압축노드가 사용되었다. 수치해석 과정을 거쳐 시간 영역 데이터를 퓨리어 변환함으로써 스텝 불연속 마이크로스트립 라인의 주파수 종속 산란 파라메터가 계산되었다. 시간 영역 TLM 해석 결과로부터 이와 같은 수치해석법이 스텝 불연속 마이크로스트립 라인과 같이 복잡한 구조를 모델링하는데 있어 효율적인 방법임을 보였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.977-982
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• 2001

In this paper, we deal with the analysis and optimum design of a disc drive feeding system. Using this proposed design method, we can determine an optimal step motor and lead-screw for the shorter seek time and required seek resolution. Simulation results show that this method can be potentially implemented in the design of a feeding system.

• Kyungpook Mathematical Journal
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• 제60권4호
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• pp.753-765
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• 2020

Smoking is one of the main causes of health problems and continues to be one of the world's most significant health challenges. In this paper, we use the multi-step Adomian decomposition method (MSADM) to obtain approximate analytical solutions for a mathematical fractional model of the evolution of the smoking habit. The proposed MSADM scheme is only a simple modification of the Adomian decomposition method (ADM), in which ADM is treated algorithmically with a sequence of small intervals (i.e. time step) for finding accurate approximate solutions to the corresponding problems. A comparative study between the new algorithm and the classical Runge-Kutta method is presented in the case of integer-order derivatives. The solutions obtained are also presented graphically. The results reveal that the method is effective and convenient for solving linear and nonlinear differential equations of fractional order.

• Journal of Nutrition and Health
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• 제42권2호
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• pp.158-170
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• 2009

This study was conducted to examine the usefulness of adding final probing step (step3) in dietary assessment by 24-hour recall method among Korean adults. One-hundred fifty five adults (37 males and 118 females) above 30 years of age who visited hospitals for health examination were recruited at three hospitals in Korea. One day dietary intake was obtained using 24-hour recall method from each subject. Dietary interview was conducted in 3 steps, (1) quick list of foods eaten during the previous day, (2) detailed information of all the foods eaten, (3) the final probing for any items forgotten. Items added at the step3 were identified and contributions of energy and nutrient intakes were calculated. The average duration of interview was 10.5 min, and time spent for each step was 4.12 minute for step 1, 5.62 minute for step 2, and 38 second for step 3. The average number of dishes reported by the subjects added at the step 3 was 2.2. (Males = 2.6, Females = 1.6) Frequently reported dishes in the step 3 were Beverage, Tea, alcohol (37.1%) and Fruits (31.8%). From mean total energy intake of 1,589 kcal (Men = 1,846 kcal, Women = 1,509 kcal), 179 kcal (11.3%) was added at the step 3. In the step 3, nutrient intakes increased significantly except retinol in total subjects and except retinol and cholesterol in males but all nutrients increased significantly in females. The final probing step can add significant information on intakes of foods and many nutrients with only about 38 seconds of interview time. Confirmation of the results with larger samples of different age groups is needed.

• 대한조선학회논문집
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• 제33권4호
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• pp.48-59
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• 1996

비정상 점성유동 수치해석단계는 연속방정식을 만족시키는 공간해석단계와 시간전진단계로 구분할 수 있다. 본 연구에서는 공간해석단계의 압력 Poisson 방정식의 해를 구하는데 스팩트럴법을 이용하였다. 압력 Poisson 방정식의 최고차미분항을 Fourier 급수로 전개하면 압력 및 압력의 1차미분항의 Fourier 급수의 적분으로 표현되므로 Gibb's 현상을 제거할 수 있어, 비주기성인 경우에도 스팩트럴법을 적용할 수 있다. 수치해법의 검증을 위하여 2차원 원주상체 및 날개주위 비정상 점성유동을 수치해석하였고, 그 결과를 비교하여 보았다.

• 한국컴퓨터정보학회논문지
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• 제9권3호
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• pp.163-169
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• 2004

본 논문에서는 기존의 무선 PKI에서 키 교환방식의 키 교환 설정단계가 단순히 이산대수문제에 근거하여 수행되었지만 제안한 무선 PID 인증구조의 상호인증과정에서는 키 교환 설정단계에 타원곡선을 적용하였다. 제안한 무선 PH 구조 안에서의 핸드오버 방법은 CRL 검색시간을 단축시킬 수 있으므로 기존의 방법에 비하여 단축된 핸드오버 처리시간을 보여준다. 기존 알고리즘과 제안한 인증구조를 비교하여 실험해 보았을 때 호 도착율, 큐의 서비스율, 큐 사이즈 변화에 관계없이 제안한 인증 기법이 모든 환경에서 기존 알고리즘보다 우수한 성능을 보였다.

• Structural Engineering and Mechanics
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• 제81권5호
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• pp.591-606
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• 2022

When the friction pendulum system and shear keys work together to resist the ground motion, which inclined inputs (non 45°) to the bridge structure, the shear keys in XY direction will be sheared asynchronously, endowed the friction pendulum system with a violent curvilinear motion on the sliding surface during earthquakes. In view of this situation, firstly, this paper abandons the equivalent linearization model of friction and constructs a Spring-Coulomb friction plane isolation system with XY shear keys, and then makes a detailed mechanical analysis of the movement process of friction pendulum system, next, this paper establishes the mathematical model of structural time history response calculation by using the step-by-step integration method, finally, it compiles the corresponding computer program to realize the numerical calculation. The results show that the calculation method in this paper takes advantage of the characteristic that the friction force is always µmg, and creatively uses the "circle making method" to express the change process of the friction force and resultant force of the friction pendulum system in any calculation time step, which can effectively solve the temporal nonlinear action of the plane friction; Compared with the response obtained by the calculation method in this paper, the peak values of acceleration response and displacement response calculated by the unidirectional calculation model, which used in the traditional research of the friction pendulum system, are smaller, so the unidirectional calculation model is not safe.

• Structural Engineering and Mechanics
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• 제45권1호
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• pp.95-110
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• 2013

In the recent decade, practical of wavelet technique is being utilized in various domain of science. Particularly, engineers are interested to the wavelet solution method in the time series analysis. Fundamentally, seismic responses of structures against time history loading such as an earthquake, illustrates optimum capability of systems. In this paper, a procedure using particularly discrete Haar wavelet basis functions is introduced, to solve dynamic equation of motion. In the proposed approach, a straightforward formulation in a fluent manner is derived from the approximation of the displacements. For this purpose, Haar operational matrix is derived and applied in the dynamic analysis. It's free-scaled matrix converts differential equation of motion to the algebraic equations. It is shown that accuracy of dynamic responses relies on, access of load in the first step, before piecewise analysis added to the technique of equation solver in the last step for large scale of wavelet. To demonstrate the effectiveness of this scheme, improved formulations are extended to the linear and nonlinear structural dynamic analysis. The validity and effectiveness of the developed method is verified with three examples. The results were compared with those from the numerical methods such as Duhamel integration, Runge-Kutta and Wilson-${\theta}$ method.