효율적 구조최적화를 위한 유전자 알고리즘의 방향벡터

이홍우,Lee, Hong-Woo 한국공간구조학회 2008 한국공간구조학회지 Vol.8 No.3

본 연구에서는 방향벡터(direction vector)를 이용한 지역 탐색법과 유전자 알고리즘을 결합한 새로운 알고리즘인 D-GA를 제안한다. 새로운 개체(individual)를 찾기 위한 방향벡터로는 진화과정 중에 습득되는 정보를 활용하기 위한 학습방향벡터(Loaming direction vector)와 진화와는 무관하게 한 개체의 주변을 탐색하는 랜덤방향벡터(random direction vector) 등 두 가지를 구성하였다. 그리고, 10 부재 트러스 설계 문제에 단순 유전자 알고리즘과 D-GA를 적용하여 최적화를 수행하였고, 그 결과를 비교 검토함으로써 단순 GA에 비하여 D-GA의 정확성 및 효율성이 향상되었음을 확인하였다. In this study, the modified genetic algorithm, D-GA, is proposed. D-GA is a hybrid genetic algorithm combined a simple genetic algorithm and the local search algorithm using direction vectors. Also, two types of direction vectors, learning direction vector and random direction vector, are defined without the sensitivity analysis. The accuracy of D-GA is compared with that of simple genetic algorithm. It is demonstrated that the proposed approach can be an effective optimization technique through a minimum weight structural optimization of ten bar truss.

한국설화의 분류에 관한 제언: 형식담(形式譚)에서 유희담(遊戱譚)으로

이홍우 ( Hong Woo Lee ),김경희 ( Kyung Hee Kim ),정숙영 ( Sook Young Chung ),조선영 ( Sun Young Cho ),심우장 ( Woo Jang Sim ) 겨레어문학회 2014 겨레어문학 Vol.52 No.-

본 논문은 스티스 톰슨(Stith Thompson)에 의해 처음으로 제시되었고, 그간 학계에서 통용되었던 ‘형식담(形式譚)’이라는 용어가 과연 적합 한지에 대한 의문에서 시작되었다. 톰슨은 중심사건(central situation)은 단순하지만 그것을 다루는 형식은 어떤 복잡성을 띠는 이야기를 형식담 (formula tales)이라고 명명했다. 하지만 톰슨이 분류한 형식담의 하위 항목들이 그가 규정한 형식담의 개념에 부합되는지 검토한 결과 많은 문 제점을 발견할수 있었다. 한국설화의 유형 분류에서도 형식담은 톰슨의 형식담 분류가 지니고 있는 근본적인 문제점을 고스란히 안고 있으면서 몇 가지 문제가 추가되 었다. 소화와의 구분이 모호하고, 민요와 교섭하는 양상을 보이며, 모방 담이 형식담에 포함될 수 없는 이유가 불명확하다는 점이다. 이에 ‘형식 담’이라는 용어와 그것이 포괄하는 유형 범주가 설화의 분류항으로 적절 하지 않다고 판단되어 새로운 용어를 제시할 필요가 있었다. 형식담이라는 용어와 그것이 포괄하는 유형 범주가 분류항으로서 부적절하다는 것과는 별개로 기존에 형식담이라고 일컬었던 일군의 작품들은 군집성과 독립성을 보여주고 있었다. 특히 이 설화들은 구연 현장의 목 소리에 주목할 필요가 있었는데, 여기에서 이 설화들의 주요한 특징으로 ‘놀이적 성격’을 추출할 수 있었다. 이 설화들은 화자가 이야기를 매개로 청자를 놀리거나 당황하게 만드는 놀이의 양상으로 펼쳐지는데, 이에 형 식담이 아닌 유희담(遊戱譚)이라는 용어를 제안했다. ‘형식’이 아닌 ‘유희’ 라는 점에 주목하면 이 유형의 설화들이 가지고 있었던 범주적 혼란을 많은 부분 해소할 수 있었다. 마지막 장에서는 유희담의 분류를 시도했는데, 이는 유희담으로의 실 제적인 분류가 가능한지를 가늠해보려는 시안적인 성격이 짙다. 이에 유 희담은 크게 ‘이야기유희담’과 ‘노래유희담’으로 나누고, 이야기유희담은 다시 ‘형식유희담’과 ‘상황유희담’으로 분류했다. This paper began with doubts as to whether the term “formula tale,” first proposed by Stith Thompson and since widely adopted in academia, is actually appropriate. Thompson referred to tales in which “the central situation is simple, but the formal handling of it assumes a certain complexity” as formula tales. However, an examination of whether the subcategories of formula tales as classified by Thompson correspond to the concept of formula tales as he defined them led to the discovery of a number of problems. The classification of Korean folktale types suffers from the same problems found in Thompson’s classification of formula tales, and to these are added a few more problems: the distinction between tales and jokes is vague, aspects of interaction with folk songs are evident, and the reason why imitation tales cannot be included in formula tales is unclear. As a result, it was judged that the term “formula tales” and the type categories that this term includes are not suited as classifications of tales, and there was the need to propose a new term. Setting aside the issue of the inadequateness as classifications of the term “formula tales” and the type categories that it includes, the corpus of works that have been referred to asformula tales exhibited both grouping and independence. In particular, there was a need to pay attention to the voice of the teller at the time and place of the telling, and it was possible to isolate “playful character” as a primary characteristic of these tales. These tales exhibited a playful aspect, in which the teller through the medium of the story teased or bewildered the listener(s), and as a result the term “play-oriented tales” (yuhuidam) was proposed instead of “formula tales.” When the orientation toward play, rather than the formula, became the focus, it was possible to resolve much of the categorical confusion surrounding this type of tale. The final section attempted a classification of play-oriented tales as a tentative attempt to determine the feasibility of such a classification. Play-oriented tales were first divided into “story play-oriented tales” and “song play-oriented tales,” and then “story play-oriented tales” were further classified as either “formula play-oriented tales” and “situation play-oriented tales.”

유한요소법을 이용한 이강도 부품 제조공정 해석

이홍우(Hong Woo Lee) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.4

강재 열처리 공정의 FEM 해석 정도 평가

이홍우(Hong Woo Lee) 한국자동차공학회 2010 한국자동차공학회 학술대회 및 전시회 Vol.2010 No.11

Recently, improvement in fuel efficiency and safety has become the biggest issue in worldwide automotive industry. In order to reduce weight and to improve the safety of vehicles, car makers need very high resistance flat product with very good formability and toughness for structural and impact resistant parts. As a new approach unlike conventional stamping process, to obtain good formability and very high strength, hot press forming (named as hot forming or press hardening in other literatures) has been developed and applied to impact resistant parts. The phenomena during hot press forming can be divided into heat transfer between hot sheet and cold dies, plastic deformation of sheet, and phase transformation of sheet due to cooling in the dies. Thus, finite element simulation is becoming an increasingly important tool in the development process for structural automotive components to analyze hot press forming process accurately. This paper will discuss the accuracy of FEM analysis for heat transfer with phase transformation in the hot press forming process.

지오데식 돔의 구조최적화에서 패턴서치 알고리즘과 유전자 알고리즘의 비교

이홍우(Lee Hong-Woo) 대한건축학회 2010 大韓建築學會論文集 : 構造系 Vol.26 No.7

Structural design can significantly improve if numerical optimization is used, especially for large space structures like geodesic dome. However, the optimization problems for structural optimization consist of ill-behaved discontinuous and non-differentiable functions, are difficult to solve by traditional optimization techniques using sensitivity analysis. Therefore the intuitive and heuristic techniques like genetic algorithm and generalized pattern search algorithm which allow the flexible formulation can be the most powerful tools for structural design. For structural design problems it is unclear how the genetic algorithm and generalized pattern search algorithm perform. I am interested in how these algorithms perform if used in conjunction with the functions for the design of geodesic dome. In this paper I will show what can be expected from the two algorithms and compare their performance in minimizing the weight of the geodesic dome structure. From the optimum structural design point of view the objective of dome design is to determine the appropriate steel sections for each member group of a dome from the available steel sections set such that with these set of sections the response of the dome structure is within the limitations imposed by the design code and it has the minimum weight. The optimization algorithms determine the sectional designations for the members of a geodesic dome under the external loads. The steel pipe sections list of the reference [5] which were used commonly in Korea are adopted for the cross sections of dome members. The algorithms select appropriate sections from this list such that the weight of dome becomes the minimum. The numerical results show that the generalized pattern search algorithm is more efficient than the genetic algorithm in the optimization of the geodesic dome.

Kirchhoff 평판의 면적평균 자연요소 근사화

이홍우(Lee Hong Woo) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11

A robust and efficient numerical analysis of thin elastic shells and plates has been a great challenging subject in the computational mechanics community, so that intensive research efforts have focused on the development of numerical formulation and finite element for several decades to achieve this goal. Nevertheless, several numerical difficulties such as numerical locking still leave this goal unsatisfactory and require further refinement. A representative refinement is a rotation-free plate and shell element introduced more recently, in which each node contains only the degrees-of-freedom of in-plane displacement part and the rotation part is interpolated indirectly. The main purpose of this study is to explore the applicability of the natural element method for the efficient and robust analysis of thin elastic plates. The complicated plate domain is discretized efficiently by Delaunay triangulation and the deflection field is more accurately approximated with Laplace interpolation functions. Only one deflection becomes DOF of each node, while the curvature is interpolated by area-averaging the high-order derivatives of the deflection. Meanwhile, the stabilized conforming nodal integration incorporated with Voronoi diagram is employed to have the deflection field satisfy the integration constraint. The validity of the proposed method is examined through the numerical experiments.

IPC거더 연속교의 장기거동 모니터링

이홍우(Lee, Hong Woo),안정생(Ahn, Jeong Saeng),김경원(Kim, Kyoung Won),유상희(Yu, Sang Hui) 한국콘크리트학회 2008 한국콘크리트학회 학술대회 논문집 Vol.2008 No.5

SegBeam이란?

이홍우(Hong-woo Lee) 대한토목학회 2010 대한토목학회지 Vol.58 No.2

활동중심원가계산을 이용한 품질관리활동의 성과평가

이홍우(Hong-Woo Lee),이진춘(Jin-Choon Lee) 한국산업정보학회 2002 한국산업정보학회논문지 Vol.7 No.1

차체 레이아웃 설계를 위한 위상최적설계의 적용

이홍우(Hong Woo Lee),강연식(Yeon Sik Kang),김재현(Jaehyun Kim) 한국자동차공학회 2011 한국자동차공학회 학술대회 및 전시회 Vol.2011 No.11

This paper presents topology optimization as a tool for structural lay-out design of auto body, especially underbody. BESO(bi-directional evolutionary structural optimization) based on finite element method is applied to create optimal lightweight underbody under various external load conditions. In order to treat multi-load condition, weighted average objection function was introduced. According to the numerical formulae, a PC-based test program is coded in Fortran. To verify the proposed test program, the numerical results on several benchmark problems are compared with those obtained by references. The validity of the topology optimization is examined through the numerical examples on EV(electric vehicle) underbody concept design.