• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(1)
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• pp.446-450
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• 2003

This paper makes more stronger than original model about sending station fault and saves total construction cost to replace established six-pulse bridge by each six thyristor for DC-transmission. Also, varying of controller for sending station has a robust characteristics for harmonics and unbalanced faults. This paper is verified by simulation using EMTDC program. Comparing with the results of original model, this paper is proved superiority.

• KIEE International Transactions on Power Engineering
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• 제5A권3호
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• pp.207-213
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• 2005

This paper deals with the development of benchmark systems based on the Korea Electric Power Corporation (KEPCO) system. A novel procedure for constructing a dynamic equivalent system of the KEPCO system is proposed. By using such a system, various scenarios can be simulated and compared with the original system. The results of the simulation show the benefits of the proposed equivalent system and its validity is confirmed by applying it to the KEPCO system.

• Nuclear Engineering and Technology
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• 제52권11호
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• pp.2422-2430
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• 2020

In order to improve calculational efficiency of the CAPP code in the analysis of the hexagonal reactor core, we have tried to implement a refined AFEN method with transverse gradient basis functions and interface flux moments in the hexagonal geometry. The numerical scheme for the refined AFEN method adopted here is the response matrix method that uses the interface partial currents as nodal unknowns instead of the interface fluxes used in the original AFEN method. Since the response matrix method is single-node based, it has good properties such as good calculational efficiency and parallel computing affinity. Because a refined AFEN method equivalent nonlinear FDM response matrix method tried first could not provide a numerically stable solution, a direct formulation of the refined AFEN response matrix were developed. To show the numerical performance of this response matrix method against the original AFEN method, the numerical error analyses were performed for several benchmark problems including the VVER-440 LWR benchmark problem and the MHTGR-350 HTGR benchmark problem. The results showed a more than three times speedup in computing time for the LWR and HTGR benchmark problems due to good convergence and excellent calculational efficiency of the refined AFEN response matrix method.

• International Journal of Aeronautical and Space Sciences
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• 제3권2호
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• pp.46-58
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• 2002

An inverse method is introduced to construct benchmark problems for the numerical solution of initial value problems. Benchmark problems constructed through this method have a known exact solution, even though analytical solutions are generally not obtainable. The solution is constructed such that it lies near a given approximate numerical solution, and therefore the special case solution can be generated in a versatile and physically meaningful fashion and can serve as a benchmark problem to validate approximate solution methods. A smooth interpolation of the approximate solution is forced to exactly satisfy the differential equation by analytically deriving a small forcing function to absorb all of the errors in the interpolated approximate solution. A multi-variable orthogonal function expansion method and computer symbol manipulation are successfully used for this process. Using this special case exact solution, it is possible to directly investigate the relationship between global errors of a candidate numerical solution process and the associated tuning parameters for a given code and a given problem. Under the assumption that the original differential equation is well-posed with respect to the small perturbations, we thereby obtain valuable information about the optimal choice of the tuning parameters and the achievable accuracy of the numerical solution. Illustrative examples show the utility of this method not only for the ordinary differential equations (ODEs) but for the partial differential equations (PDEs).

• Nuclear Engineering and Technology
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• 제53권3호
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• pp.752-762
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• 2021

The Smoothed Particle Hydrodynamics is one of the most widely used mesh-free numerical method for thermo-fluid dynamics. Due to its Lagrangian nature and simplicity, it is recently gaining popularity in simulating complex physics with large deformations. In this study, the 3D single/two-phase numerical simulations are performed on the Liquid Metal Reactor (LMR) centralized sloshing benchmark experiment using the SPH parallelized using a GPU. In order to capture multi-phase flows with a large density ratio more effectively, the original SPH density and continuity equations are re-formulated in terms of the normalized-density. Based upon this approach, maximum sloshing height and arrival time in various experimental cases are calculated by using both single-phase and multi-phase SPH framework and the results are compared with the benchmark results. Overall, the results of SPH simulations show excellent agreement with all the benchmark experiments both in qualitative and quantitative manners. According to the sensitivity study of the particle-size, the prediction accuracy is gradually increasing with decreasing the particle-size leading to a higher resolution. In addition, it is found that the multi-phase SPH model considering both liquid and air provides a better prediction on the experimental results and the reality.

• 한국컴퓨터정보학회논문지
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• 제26권1호
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• pp.11-17
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• 2021

본 논문에서는 순수 함수형 언어로 작성된 쌍방시뮬레이션 알고리듬의 성능을 멀티코어 프로세서 컴퓨터에서 병렬화로 향상시키는 방법을 연구한다. 이 병렬화에 있어 핵심 아이디어는 순수 함수형 프로그램의 참조 투명성을 십분 활용하면 병렬화가 전혀 고려되지 않고 작성된 초기 구현으로부터 최소한의 수정만으로 성능 개선 효과를 기대할 수 있다는 것이다. 초기 구현과 병렬화 구현 둘 다 순수 함수형 언어인 하스켈로 작성되었다. 초기 구현을 병렬화할 때 변화는 아주 적어서 병렬화된 구현에서도 초기 구현의 프로그램 구조가 거의 그대로 유지되었다. 벤치마크를 통해 제시된 간단한 병렬화만으로도 초기 구현과 비교해 두 배 이상의 성능 개선을 확인했다. 또한, 병렬화와는 별개의 최적화 기법인 메모이제이션이 적용된 버전의 쌍방시뮬레이션 구현에도 같은 방식의 병렬화를 적용함으로써 마찬가지로 성능을 개선할 수 있음을 확인하였다.

• Earthquakes and Structures
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• 제3권2호
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• pp.181-201
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• 2012

The benchmark on the ASCE cable-stayed bridge has gathered since its proposal the interest of many specialists in the field of the structural control and the dynamic response of long span bridges. Starting from the original benchmark statement in the MATLAB framework, a refined version of the bridge model is developed in the ANSYS commercial finite element environment. A passive structural control system is studied through non linear numerical analyses carried out in time domain for several seismic realizations in a multiple support framework. An innovative electro-inductive device is considered. Its positive performance is compared with an alternative version considering traditional metallic dampers.

• 한국측량학회지
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• 제29권4호
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• pp.393-403
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• 2011

본 연구에서는 인천만의 장기간 조위관측자료를 웨이블릿 방법을 통해 분석하여 평균해수변 결정을 위한 최적의 기간을 제시하고, 적정기간에 대한 우리나라의 수직기준을 새롭게 결정하였다. 그 후 결정된 평균해수면과 연안의 지상기준점(ICGP) 간의 정밀한 높이차를 결정하기 위하여 해수면에 대한 직접적인 레이저 관측을 수행하였으며, 결정된 높이차를 전체 조위관측자료에 대해 선형보간법으로 보정하여 ICGP의 정표고를 계산하였다. 최종적으로는 계산된 ICGP의 정표고를 정밀 GPS 관측과 중력지오이드모델을 이용한 GPS 수준측량 방법을 통해 수준원점 (ORBM)과 연결하고, 새로운 평균해수변 기준의 수준원점 정표고를 결정하였다. 그 결과, 본 연구에서 결정된 인천만의 평균해수면은 1910년대의 평균해수면에 비해 약 0.026m가 변동된 것으로분 석되었으며, 새로운 평균해수면을 기준으로 GPS 수준측량에 의해 재정의된 ORBM 성과는기존성과와 약 0.035m의 차이를 나타내었다. 새로운 ORBM 성과에서 나타난 0.009m의 연결오차는 GPS 수준측량시 GPS 타원체고 결정오차와 지오이드모델링 오차 등에 기인한 것으로 판단된다. 본 연구를 통해서 정밀한 GPS 수준측량만으로 새로운 평균해수변에 기준한 ORBM 정표고 성과를 정밀하게 결정할 수 있었으며, 향후 정표고 체계로의 효율적인 전환을 위해서는 장기간의 조위관측자료를 이용한 수직기준 결정과 함께 GPS 수준측량을 통한 수준성과의 연결을 적극적으로 고려할 필요가 있다.

• 한국멀티미디어학회논문지
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• 제21권8호
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• pp.813-820
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• 2018

This paper proposes new frame rate up-conversion algorithms. Adaptive motion estimation based on block complexity information are used to obtain more accurate motion vectors. Because the information on block complexity is extracted from the motion estimation prediction size from the original frame, additional computational complexity is not imparted. In experimental results, the proposed algorithms provide robust frame interpolation performance for whole test sequences. Also, the computational complexity of the proposed algorithm is reduced to a benchmark algorithm.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1998년도 춘계학술발표회논문집(1)
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• pp.87-92
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• 1998

A nonlinear iterative scheme developed to reduce the computing time of the AFEN method was tested and applied to two benchmark problems. The new nonlinear method for the AFEN method is based on solving two-node problems and use of two nonlinear correction factors at every interface instead of one factor in the conventional scheme. The use of two correction factors provides higher-order accurate interface noes as well as currents which are used as the boundary conditions of the two-node problem. The numerical results show that this new method gives exactly the same solution as that of the original AEFEN method and the computing time is significantly reduced in comparison with the original AFEN method.