• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.389-394
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• 2006

Fully flexible cell preserves Hamiltonian in structure, so the symplectic time integrator is applied to the equations of motion. Primarily, generalized leapfrog time integration (GLF) is applicable, but the equations of motion by GLF have some of implicit formulas. The implicit formulas give rise to a complicate calculation for coding and need an iteration process. In this paper, the time integration formulas are obtained for the fully flexible cell molecular dynamics simulation by using the splitting time integration. It separates flexible cell Hamiltonian into terms corresponding to each of Hamiltonian term, so the simple and completely explicit recursion formula was obtained. The explicit formulas are easy to implementation for coding and may be reduced the integration time because they are not need iteration process. We are going to compare the resulting splitting time integration with the implicit generalized leapfrog time integration.

• 대한기계학회논문집A
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• 제31권8호
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• pp.826-832
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• 2007

Fully flexible cell preserves Hamiltonian in structure so that the symplectic time integrator is applicable to the equations of motion. In the direct formulation of fully flexible cell N-Sigma-T ensemble, a generalized leapfrog time integration (GLF) is applicable for fully flexible cell simulation, but the equations of motion by GLF has structure of implicit algorithm. In this paper, the time integration formula is derived for the fully flexible cell molecular dynamics simulation by using the splitting time integration. It separates flexible cell Hamiltonian into terms corresponding to each of Hamiltonian term. Thus the simple and completely explicit recursion formula was obtained. We compare the performance and the result of present splitting time integration with those of the implicit generalized leapfrog time integration.

• 한국측량학회지
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• 제28권6호
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• pp.573-578
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• 2010

위성항법시스템에서 정확한 위성궤도결정 기술은 측위 정확도 향상의 필수적인 조건이다. 이 연구에서는 GLONASS의 방송궤도력과 4차 Runge-Kutta 수치적분법을 이용하여 위성좌표를 결정하였으며, 적분간격과 적분시간에 따른 위성궤도의 정확도를 비교하였다. 적분간격에 따른 위성궤도 정확도분석결과, 적분간격이 l초일 때와 300초일 때의 3차원 RMS 오자의 차이가 3cm에 불과한 반면 처리시간은 100배 이상 향상되었다. 적분시간에 따른 위성좌표의 3차원 RMS 오차는 적분시간이 30분, 150분, 300분일 때 각각 8.3m, 187.3m, 661.5m로 나타났으며, 이를 통해 적분시간을 짧게 할수록 정확도가 향상되는 것을 확인하였다. 따라서 이 연구에서는 GLONASS 측위를 위한 위성좌표 결정의 정확도 향상을 위해 적분시간을 최소화할 수 있는 Forward와 Backward 적분을 적용하는 방안을 제안하였으며, 이와 같은 방법을 사용할 경우 5m이하의 위성좌표 산출 정확도를 확보할 수 있다.

• 대한원격탐사학회지
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• 제18권2호
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• pp.91-96
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• 2002

고정 검출 시간(Integration Time)을 갖고 Time Delay and Integration(TDI) Charge Coupled Device (CCD) 검출기를 사용하는 위성 영상 기기에서 위성의 고도 및 촬영각의 변화에 대한 영상 기기의 기하 성능 특성을 TDI 불일치와 관련하여 분석하였다. 본 분석을 통하여 고도 저하에 따른 기하 성능 저하를 보완할 수 있는 방법으로서 경사 촬영을 통한 TDI 불일치 제거를 제안하였고 저하된 고도에서 TDI 일치로 최적 성능을 줄 수 있는 최적 경사 촬영각을 구하였다. 본 결과는 임의의 범위의 가변 검출 시간을 갖는 TDI CCD 위성 영상 기기에도 적용 가능하다.

• Earthquakes and Structures
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• 제13권3호
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• pp.279-288
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• 2017

Having the ability to keep on yielding stable solutions in problems involving high potential of instability, composite time integration methods have become very popular among scientists. These methods try to split a time step into multiple sub-steps so that each sub-step can be solved using different time integration methods with different behaviors. This paper proposes a new composite time integration in which a time step is divided into two sub-steps; the first sub-step is solved using the well-known Newmark method and the second sub-step is solved using Simpson's Rule of integration. An unconditional stability region is determined for the constant parameters to be chosen from. Also accuracy analysis is perform on the proposed method and proved that minor period elongation as well as a reasonable amount of numerical dissipation is produced in the responses obtained by the proposed method. Finally, in order to provide a practical assessment of the method, several benchmark problems are solved using the proposed method.

• 방송공학회논문지
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• 제27권6호
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• pp.872-884
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• 2022

IoT 산업 발전으로 다양한 산업군에서 서로 다른 형태의 시계열 데이터를 생성하고 있으며 이를 다시 통합하여 재생산 및 활용하는 연구로 진화하고 있다. 더불어, 실제 산업에서 데이터 처리 속도 및 활용 시스템의 이슈 등으로 인해 시계열 데이터 활용 시 데이터의 크기를 압축하여 통합 활용하는 경향이 증가하고 있다. 그러나 시계열 데이터의 통합 가이드라인이 명확하지 않고 데이터 기술 시간 간격, 시간 구간 등 각각의 특성이 달라 일괄 통합하여 활용하기 어렵다. 본 논문에서는 통합 기준 설정 방법과 시계열 데이터의 통합시 발생하는 문제점을 기반으로 두 가지의 통합 방법을 제시하였다. 이를 기반으로 시계열 데이터의 특성을 고려한 이질적 시계열 데이터 통합 프레임워크를 구성하였으며 압축된 서로 다른 이질적 시계열 데이터의 통합과 다양한 기계 학습에 활용할 수 있음을 확인하였다.

• Smart Structures and Systems
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• 제14권6호
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• pp.1269-1289
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• 2014

With the sub-stepping technique, the numerical analysis in real-time dynamic hybrid testing is split into the response analysis and signal generation tasks. Two target computers that operate in real-time may be assigned to implement these two tasks, respectively, for fully extending the simulation scale of the numerical substructure. In this case, the integration time-step of solving the dynamic response of the numerical substructure can be dozens of times bigger than the sampling time-step of the controller. The time delay between the real and desired feedback forces becomes more striking, which challenges the well-developed delay compensation methods in real-time dynamic hybrid testing. This paper focuses on displacement prediction and force correction for delay compensation in the real-time dynamic hybrid testing with a large integration time-step. A new displacement prediction scheme is proposed based on recently-developed explicit integration algorithms and compared with several commonly-used prediction procedures. The evaluation of its prediction accuracy is carried out theoretically, numerically and experimentally. Results indicate that the accuracy and effectiveness of the proposed prediction method are of significance.

• 한국자동차공학회논문집
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• 제2권1호
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• pp.106-115
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• 1994

A parallel integration approach is proposed for real-time simulation of controlled mechanical systems. The proposed approach, which employs the dual-rate integration method in a parallel computing environment, is developed to deal with stiffness and high frequency characteristics of the controlled mechanical systems effectively. Numerical experiments are performed to demonstrate the effectiveness of the approach in shared memory multiprocessors, Alliant FX/8 and Alliant FX/80.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
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• pp.216-221
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• 2002

A spherical Earth surface is used fur realistic analysis of the geometrical performance characteristics about the variation of satellite altitude and 2-dimensional line-of-sight(LOS) tilt angle in a satellite imager using Time Delay and Integration(TDI) technique with fixed integration time. In the spherical Earth surface model TDI synchronization using LOS tilt is investigated as a solution to compensate geometric performance degradation due to altitude decrease. This result can be used fur a TDI CCD imager with variable integration time in a certain as well.

• Structural Engineering and Mechanics
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• 제13권5호
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• pp.569-589
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• 2002

In performing the dynamic analysis, the step size used in a step-by-step integration method might be much smaller than that required by the accuracy consideration in order to capture the rapid chances of dynamic loading or to eliminate the linearization errors. It was first found by Chen and Robinson that these difficulties might be overcome by integrating the equations of motion with respect to time once. A further study of this technique is conducted herein. This include the theoretical evaluation and comparison of the capability to capture the rapid changes of dynamic loading if using the constant average acceleration method and its integral form and the exploration of the superiority of the time integration to reduce the linearization error. In addition, its advantage in the solution of the impact problems or the wave propagation problems is also numerically demonstrated. It seems that this time integration technique can be applicable to all the currently available direct integration methods.