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VARX 모형과 LSTM 알고리즘의 다변량 시계열 예측 비교
이황현(Hwanghyun Lee),홍난영(Nanyoung Hong),이태욱(Taewook Lee) 한국데이터정보과학회 2022 한국데이터정보과학회지 Vol.33 No.1
본 논문에서는 외부 요인의 효과를 반영하는 외생변수를 입력변수로 포함하는 다변량 시계열 자료에 LSTM (long short term memory network) 알고리즘을 적용하는 연구를 진행하였다. 전통적인 시계열 분야에서 외생변수를 포함하는 다변량 시계열 자료의 분석 및 예측을 위한 모형으로서 VARX (vector autoregressive with exogenous variables) 모형이 가장 일반적이다. 계열 더미변수를 포함하는 외생변수로 고려한 모의실험 결과, LSTM 알고리즘의 안정적인 예측력을 확인할 수 있었다. 실증분석을 통해서는 LSTM 알고리즘이 VARX 모형보다 예측력이 뛰어남을 확인할 수 있었다. In this paper, we studied the LSTM (long short term memory network) algorithm for prediction of multivariate time series data with exogenous variable. In the field of time series, VARX (vector autoregressive with exogenous variables) model is one of the most common models for prediction of multivariate time series data including exogenous variables. We compared the prediction performance of VARX model and LSTM algorithm through a simulation study and real data analysis. In a simulation study considering exogenous variables including seasonal dummy variables, LSTM algorithm was comparable to VARX models. In a empirical analysis, it was confirmed that LSTM algorithm outperformed VARX model in terms of prediction.
Benzyl Alcohol이 세포막의 형태 및 Calcium 이온 이동에 미치는 영향
이황현(Lee, Hwang-Hyun),하종식(Hah, Jong-Sik),김구자(Kim, Ku-Ja) 대한생리학회 1987 대한생리학회지 Vol.21 No.2
Benzyl alcohol is known to have dual effect on the red blood cell shape change. At low concentration up to 50 mM benzyl alcohol transformed the shape from discocyte to stomatocyte by preferent binding to the inner hemileaflet, however, at higher concentratransformed the shape from discocyte to stomatocyte by preferential binding to the inner monolayer, however, at higher concentration above 50 mM benzyl alcohol transformed to echinocyte by affecting both monolayers. These results suggest that the effect of benzyl alcohol on the red blood cell shape and Ca<sup>++</sup> transport across cardiac cell membranes to assess the effects of the drug on the structures and functions of the biological cell membranes. The results are as follows: 1) Benzyl alcohol up to 40 mM caused progressive stomatocytic shap change of the red blood cell but above 50 mM benzyl alcohol caused echinocytic shape change. 2) Benzyl alcohol up to 40 mM inhibited both osmotic hemolysis and osmotic volume change of the red blood cell in hypotonic and hypertonic NaCl solutions, respectively. 3) Benzyl alcohol inhibited both Bowditch Staircase and Wood-worth Staircase phenomena at rat left auricle. 4) Benzyl alcohol at concentration of 5 mM increased Ca<sup>++</sup>-ATPase activity of red blood cell ghosts slightly but above S mM benzyl alcohol inhibited the Ca<sup>++</sup>-ATPase activity. 5) Benzyl alcohol at concentrations of 5 mM and 10 mM increased Ca<sup>++</sup>-ATPase activity slightly at rat gastrocnemius muscle S.R. but above 10 mM benzyl alcohol inhibited the Ca<sup>++</sup>-ATPase activity. Above results indicate that benzyl alcohol inhibit water permeability and Ca<sup>++</sup> transport across cell membranes in part via effects on the fluidity and transition temperatures of the bulk lipid by preferential intercalation into cytoplasmic monolayer and in part via other effect on the conformational change of active sites of the Ca<sup>++</sup>-ATPase molecule extended in cytoplasmic face.
선박 외판 성형에서 목적 형상과 전개 평판의 최적 정합을 위한 ICP(Iterative Closest Point) 알고리즘 적용
이장현(Jang Hyun Lee),윤종성(Jong Sung Yoon),류철호(Cheolho Ryu),이황범(Hwang Beom Lee) (사)한국CDE학회 2009 한국CDE학회 논문집 Vol.14 No.2
Generally, curved surfaces of ship hull are deformed by flame bending (line heating), multi-press forming, and die-less forming method. The forming methods generate the required in-plane/bending strain or displacement on the flat plate to make the curved surface. Multi-press forming imposes the forced displacements on the flat plate by controlling the position of each pressing points based upon the shape difference between the unfolded flat plate and the curved object shape. The flat plate has been obtained from the unfolding system that is independent of the ship CAD. Apparently, the curved surface and the unfolded-flat surface are expressed by different coordinate systems. Therefore, one of the issues is to find a registration of the unfolded surface and the curved shape for the purpose of minimum amount of forming works by comparing the two surfaces. This paper presents an efficient algorithm to get an optimized registration of two different surfaces in the multi-press forming of ship hull plate forming. The algorithm is based upon the ICP (Iterative Closest Point) algorithm. The algorithm consists of two iterative procedures including a transformation matrix and the closest points to minimize the distance between the unfolded surface and curved surfaces. Thereby the algorithm allows the minimized forming works in ship-hull forming.
선박해양 구조물의 배관 자재 관리를 위한 Enterprise BOM 의 설계와 구현 사례
이장현(Lee, Jang Hyun),김승현(Kim, Seung Hyun),이황범(Lee, Hwang Beom),장기삼(Jang, Gi Sam) (사)한국CDE학회 2010 한국 CAD/CAM 학회 학술발표회 논문집 Vol.2010 No.1
Both enterprise information systems and CAD utilizes the BOM (Bill of Material) as the means of collaborative integration during the product design and production since the BOM has been commonly used for design, production planning, procurement, and production works. Therefore, BOM can be the referential data when it expresses not only the part lists but also product information required by product development process. Outfitting design is one of major design works in marine vessel design since marine vessels have various outfitting systems and huge number of parts. Also, the outfitting BOM has the evolutional forms that change from the initial design to the production design. In order to express the product information and part list in the enterprise BOM and the evolutional BOMs in each lifecycles, enterprise BOM of outfitting that consists of structure BOM and display BOM is suggested. Thereafter, we have developed the prototype of enterprise BOM in which some features of the outfitting BOM are implemented.