• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.5
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• pp.86-96
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• 1998

A numerical study has been carried out of three-dimensional turbulent flows around a MIRA reference vehicle model both with and without wheels in computation. Two convective difference schemes with two k-$\varepsilon$ turbulence models are evaluated for the performance such as drag coefficient, velocity and pressure fields. Pressure coefficients along the surfaces of the model are compared with experimental data. The drag coefficient, the velocity and pressure fields are found to change considerably with the adopted finite difference schemes. Drag forces computed in the various regions of the model indicate that design change decisions should not rely just on the total drag and that local flow structures are important. The results also indicate that the RNG model with the QUICK scheme predicts fairly well the tendency of velocity and pressure fields and gives more reliable drag coefficient rather than the other cases.

• Journal of computational fluids engineering
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• v.4 no.1
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• pp.34-40
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• 1999

Drag reduction on vehicles are the main concern for the body shape designers in order to lower the fuel consumption rate and to aid the driving stability. The drag of bluff bodies like transportation vehicles is mostly pressure drag due to the flow separation, which can be minimized by controlling the location and size of the separation bubble. In the present study, the TURBO-3D code is incorporated with optimal algorithm based on analytical approximation method to obtain an optimal afterbody shape of the MIRA Model corresponding to the lowest drag coefficient. For this purpose three mutually independent afterbody angles are chosen as design variables, while the drag coefficient is chosen as an objective function. It is demonstrated in the present study that an optimal body shape having the lowest drag coefficient which is about 6% lower than that of the original shape has been successfully obtained within number of iterations of tile optimal design loop.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.565-568
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• 2002

In the flow analysis around a bluffbody such as road vehicles, drag reduction has been of the primary concern mainly due to the effect on fuel economy. To reduce the drag, which is mostly due to the pressure difference caused by the flow separation, the location of the separation and eddy sizes are controlled. However, less attention has been given to the effect of the lift. The effect of lift may cause the driving stability problem of the vehicle at high speed white heavy downward effect of lift together with the vehicle weight may require more power to drive the vehicle forward. It is considered worthwhile to pursue the optimal design of the low drag tail shape of the MIRA model while taking the lift effect into account, even though it is considered as a reference. To this end, a commercial multi-objective optimization code, FRONTIER, Is used together with the CFD code, STAR-CD. It is hoped that the results will provide more insight into the flow field around the bluffbody as transportation means.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.386-391
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• 2001

A finite element code based on P2P1 tetra element has been developed for the large eddy simulation (LES) of turbulent flows around a complex geometry. Fractional 4-step algorithm is employed to obtain time accurate solution since it is less expensive than the integrated formulation, in which the velocity and pressure fields are solved at the same time. Crank-Nicolson method is used for second order temporal discretization and Galerkin method is adopted for spatial discretization. For very high Reynolds number flows, which would require a formidable number of nodes to resolve the flow field, SUPG (Streamline Upwind Petrov-Galerkin) method is applied to the quadratic interpolation function for velocity variables, Noting that the calculation of intrinsic time scale is very complicated when using SUPG for quadratic tetra element of velocity variables, the present study uses a unique intrinsic time scale proposed by Codina et al. since it makes the present three-dimensional unstructured code much simpler in terms of implementing SUPG. In order to see the effect of numerical diffusion caused by using an upwind scheme (SUPG), those obtained from P2P1 Galerkin method and P2P1 Petrov-Galerkin approach are compared for the flow around a sphere at some Reynolds number. Smagorinsky model is adopted as subgrid scale models in the context of P2P1 finite element method. As a benchmark problem for code validation, turbulent flows around a sphere and a MIRA model have been studied at various Reynolds numbers.

• Proceedings of the Korea Information Processing Society Conference
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• 2021.11a
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• pp.626-628
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• 2021

사건 관계 추출 태스크는 구조화되지 않은 텍스트 데이터에서 사건의 구조화된 표현을 얻는 것이다. 하나의 문장에서도 많은 정보를 얻을 수 있는 중요한 태스크임에도 불구하고, 다양한 사전 학습 모델을 적용한 연구는 아직 활발하게 연구되지 않고 있다. 따라서 본 연구에서 사전 학습된 모델의 임베딩 기법 중 BERT, RoBERTa, SpanBERT에 각각 base, large 아키텍처를 적용하여 실험하였다. 사건을 식별하기 위한 trigger와 해당 trigger의 세부 argument를 식별하기 위한 분류기를 상위레이어로 각각 설계하였고, 다양한 배치 크기를 적용하여 실험하였다. 성능평가는 trigger/argument 각각 F1 score를 적용하였고, 결과는 RoBERTa large 모델에서 좋은 성능을 보인 것을 확인하였다.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.69.1-69.1
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• 2010

장주기 Mira 변광성의 외피층에서 발생하는 SiO 메이저에 대해 non-local한 1차원 수치계산 결과를 처음으로 제시한다. 별의 유체역학적인 맥동모델에서 얻은 시간에 따른 별 주위 가스의 속도, 온도, 밀도 분포를 사용하여 계산하였다. 임의의 속도장을 갖는 구형 분자운에서의 복사전달문제를 풀었던 이전 연구에서 개발한 수치계산코드를 이용하였고, 특정 구간에서 급격한 변화를 겪는 물리량을 잘 반영할 수 있도록 수정하였다. 또한 계산에 사용되는 거대희소행렬을 압축희소행렬로 변환하여 메모리를 절약하였고 비선형방정식의 자코비안을 해석적으로 구하여 계산속도를 향상시켰다. v=1, J=1-0, J=2-1과 v=2, J=1-0 SiO 메이저의 공간분포, 상대세기 등에 대해 이전의 LVG 모델을 이용한 연구결과와 정성적으로 비교 논의한다.

• Journal of Korean Society of Archives and Records Management
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• v.19 no.1
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• pp.23-67
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• 2019

Records in Contexts (RiC) is an international archival description standard developed by integrating and normalizing four archival description standards of the International Council of Archives (ICA). RiC has the advantage of diversifying archival description, exposing the context of records, and ensuring data interoperability between disparate systems. In this study, RiC is set up as a key tool in the design of archive systems, and logical data modeling is performed to implement the database. Because of RiC's conceptual model, RiC-CM can be used as a data reference model, and which makes it possible to develop a data model that meets user requirements. Therefore, this study intends to implement these two data models: relational data model, which is widely used as the database on legacy systems, and graphical data model, which can flexibly extend objects around the relationship between information entities.

• Proceedings of the Korea Information Processing Society Conference
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• 2023.11a
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• pp.601-604
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• 2023

기술이 발전함에 따라 복합적인 모달리티 정보를 포함하는 멀티미디어 데이터의 수집이 용이해지면서, 사람의 성격 특성을 이해하고 이를 개인화된 에이전트에 적용하고자 하는 연구가 활발히 진행되고 있다. 본 논문에서는 비디오 스트림 구조를 활용하여 사용자 특성을 예측하기 위한 동적 키프레임 추출 방법을 제안한다. 비디오 데이터를 효과적으로 활용하기 위해서는 무작위로 선택한 프레임에서 특징을 추출하던 기존의 방법을 개선하여 영상 내 시간에 따른 정보와 변화량을 기반으로 중요한 프레임을 선택하는 방법이 필요하다. 본 논문에서는 제 3자가 평가한 Big-five 지표 값이 레이블링된 대표적인 데이터셋인 First Impressions V2 데이터셋을 사용하여 외면에서 발현되는 특징들을 기반으로 영상에서 등장하는 인물들의 성격 특성을 예측했다. 결론에서는 선택된 키프레임에서 멀티 모달리티 정보를 조합하여 성격 특성을 예측한 결과와 베이스라인 모델과의 성능을 비교한다.

• Journal of Digital Convergence
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• v.18 no.10
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• pp.397-402
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• 2020

Hologram can be categorized into analog and digital hologram but there's a clear limitation in expensive equipment and content realization for ordinary people to realize. In addition, it's required to conduct study on hologram contents with interaction added, escaping out of exiting stable format like endlessly repetitive contents or passive view through specific video. Therefore, this article aims to suggest fusion image system, especially focusing on floating hologram among similar holograms. Eight elements of hologram interaction are as follows: height of camera in a three-dimensional space, interval between 3D model, overlapped model, scale, animation, position, color and 3D model change. For the floating hologram, the audience can control by themselves in real time, the popular, active hologram contents-making methodology is suggested by making the best use of fusion image system and making floating hologram easily without using expensive hologram equipment. The image system developed in actual exhibition and feedback should be complemented to develop better hologram image system.

• Publications of The Korean Astronomical Society
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• v.25 no.1
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• pp.15-21
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• 2010

We report results of image simulations of the KVN and VLBI experiments of the KVN with several other East Asia VLBI facilities. To investigate their imaging capability a model-generated image of 7 mm SiO maser emission in Mira variables is used. The resulting simulations show that the joint VLBI experiments of the KVN with East Asia VLBI facilities can produce reasonably good images at 7 mm spectral line experiments. However, there are no apparent differences in peak flux densities and images themselves in the simulations among different combinations of these facilities. In addition, the simulated images of observations which include bigger antennas do not show any expected improvement to the image sensitivity. The small variations in the peak flux density and similar image sensitivity, irrespective of different antenna sizes or numbers of baselines used in the simulations, turn out due to a specific characteristic of the adopted model image. Test simulations using another SiO maser image from R Cas observations prove that the participation of bigger antennas in the VLBI experiments does improve image sensitivity. We confirm the need of additional longer baselines in the experiments of the East Asia VLBI facilities to study very compact maser clumps on sub-milliarcsecond scales.