대공간 구조물의 UHPC 적용을 위한 기계학습 기반 강도예측기법

이승혜,이재홍,Lee, Seunghye,Lee, Jaehong 한국공간구조학회 2020 한국공간구조학회지 Vol.20 No.4

There has been increasing interest in UHPC (Ultra-High Performance Concrete) materials in recent years. Owing to the superior mechanical properties and durability, the UHPC has been widely used for the design of various types of structures. In this paper, machine learning based compressive strength prediction methods of the UHPC are proposed. Various regression-based machine learning models were built to train dataset. For train and validation, 110 data samples collected from the literatures were used. Because the proportion between the compressive strength and its composition is a highly nonlinear, more advanced regression models are demanded to obtain better results. The complex relationship between mixture proportion and concrete compressive strength can be predicted by using the selected regression method.

트러스 구조물 사이즈 최적화를 위한 무응력 부재의 선택

이승혜,이종현,이기학,이재홍,Lee, Seunghye,Lee, Jonghyun,Lee, Kihak,Lee, Jaehong 한국공간구조학회 2021 한국공간구조학회지 Vol.21 No.1

This paper describes a novel zero-stress member selecting method for sizing optimization of truss structures. When a sizing optimization method with static constraints is implemented, the member stresses are affected sensitively with changing the variables. However, because some truss members are unaffected by specific loading cases, zero-stress states are experienced by the elements. The zero-stress members could affect the computational cost and time of sizing optimization processes. Feature selection approaches can be then used to eliminate the zero-stress member from the whole variables prior to the process of optimization. Several numerical truss examples are tested using the proposed methods.

위상 최적화를 위한 생산적 적대 신경망 기반 데이터 증강 기법

이승혜,이유진,이기학,이재홍,Lee, Seunghye,Lee, Yujin,Lee, Kihak,Lee, Jaehong 한국공간구조학회 2021 한국공간구조학회지 Vol.21 No.4

In this paper, a GAN-based data augmentation method is proposed for topology optimization. In machine learning techniques, a total amount of dataset determines the accuracy and robustness of the trained neural network architectures, especially, supervised learning networks. Because the insufficient data tends to lead to overfitting or underfitting of the architectures, a data augmentation method is need to increase the amount of data for reducing overfitting when training a machine learning model. In this study, the Ganerative Adversarial Network (GAN) is used to augment the topology optimization dataset. The produced dataset has been compared with the original dataset.

텐세그리티 구조물의 형상탐색 기법 비교

이승혜,이재홍,Lee, Seunghye,Lee, Jaehong 한국전산구조공학회 2014 한국전산구조공학회논문집 Vol.27 No.4

텐세그리티 구조물은 인장력을 받는 연속된 케이블 안에 압축력을 받는 스트럿이 결합된 형태로 구성된다. 텐세그리티 구조물은 자기 응력 상태를 갖는 프리스트레스 핀 접합 구조물에 속한다. 텐세그리티 구조물 설계의 핵심은 평형 배열상태를 구하는 일명 형상탐색 과정이다. 본 논문에서는 세 가지의 효과적인 텐세그리티 구조물의 형상탐색 기법을 제안하였다. 형상탐색과정을 수행하면 평형상태의 내력 밀도와 그에 대응하는 위상을 얻을 수 있다. 이 때 평형상태를 형성하는 적절한 내력밀도 값을 얻기 위해 유전자 알고리즘을 결합한 내력밀도법이 사용되었다. 수치해석 예제를 통해 제안 알고리즘의 효율성을 입증하였다. A tensegrity structure consists of a set of continuous cables in tension and a set of discontinuous struts in compression. The tensegrity structure can be classified into self-stressed and pre-stressed pin-jointed structure. A key step in the design of tensegrity structures is the determination of their equilibrium configuration, known as form-finding. In this paper, three effective methods are presented for form-finding of tensegrity structures. After performing form-finding process, a set of force density and corresponding topology results can be obtained. Then the force density method combined with a genetic algorithm is adopted to uniquely define a single integral feasible set of force densities. Numerical examples are presented that demonstrate the excellent performance of the algorithms.

하이브리드 메타휴리스틱 기법을 사용한 트러스 위상 최적화

이승혜,이재홍,Lee, Seunghye,Lee, Jaehong 한국공간구조학회 2021 한국공간구조학회지 Vol.21 No.2

This paper describes an adaptive hybrid evolutionary firefly algorithm for a topology optimization of truss structures. The truss topology optimization problems begins with a ground structure which is composed of all possible nodes and members. The optimization process aims to find the optimum layout of the truss members. The hybrid metaheuristics are then used to minimize the objective functions subjected to static or dynamic constraints. Several numerical examples are examined for the validity of the present method. The performance results are compared with those of other metaheuristic algorithms.

李王家博物館 佛像 컬렉션의 형성과 의미

이승혜(Lee Seunghye) 한국미술사학회 2021 美術史學硏究 Vol.309 No.309

강구조물의 건전성 모니터링을 위한 딥러닝 기법

이승혜(Seunghye Lee),이재홍(Jaehong Lee) 한국강구조학회 2023 韓國鋼構造學會誌 Vol.35 No.4

CEO Duality and Corporate Social Performance : The Moderating Role of CEO Regulatory Focus

Seunghye Lee(이승혜),Yangmin Kim(김양민) 한국전략경영학회 2020 전략경영연구 Vol.23 No.1

CEO가 이사회 의장직을 겸임하는 리더십 구조에 대한 선행 연구들은 그것이 기업의 재무성과에 미치는 영향에 주로 주목해 왔고, 엇갈린 실증 연구 결과들을 보고해 왔다. CEO의 이사회의장 겸직은 기업지배구조 측면에서 CEO의 이사회에 대한 상대적 권력을 나타내는 변수로, 본 연구는 이러한 리더십 구조가 기업의 사회적 책임성과(corporate social performance)에 어떠한 영향을 미치는지 살펴보았다. 기업의 사회적 책임성과는 기업의 지속가능경영을 나타낼 수 있는 지표로서 재무적 성과 못지않게 최근 전략경영연구에서 주목받는 변수이다. 본 연구는 CEO의 이사회의장 겸직이 갖는 기업지배구조상의 약점 때문에 그것과 기업의 사회적 책임성과 간에 부(-)의 관계가 있을 것으로 예측하였다. 또한 최고경영자가 성취지향형인지 또는 안정지향형인지에 따라서 CEO의 이사회의장 겸직 구조와 기업의 사회적 책임성과 간의 관계가 달라질 것으로 예측하였다. 즉, 최고경영자가 성취지향형인 경우 CEO의 이사회의장 겸직과 기업의 사회적 책임성과 간 부정적 관계가 약화될 것으로, 반면에 안정지향형인 경우에는 CEO의 이사회의장 겸직과 기업의 사회적 책임성과 간 부정적인 관계가 오히려 강화될 것이라 예측하였다. 이러한 가설을 검증하기 위해, 본 연구는 2006년부터 2011년까지 미국 167개 대기업을 대상으로 분석을 진행하였다. 그 결과, 최고경영자와 이사회의장직을 분리하는 기업이 그렇지 않은 기업에 비해 기업의 사회적 책임성과가 높은 것을 발견하였다. 즉, CEO의 이사회의장 겸직과 기업의 사회적 책임성과 간에는 부정적 관계가 있는 것으로 나타났다. 한편, 성취지향적 성향이 강한 최고경영자/이사회 의장인 경우 CEO의 이사회의장 겸직과 기업 사회적 책임성과 간 부정적 관계를 약화시키는 것으로, 즉 기업의 사회적 활동에 보다 적극적으로 임하는 것으로 해석되는 결과가 나왔다. 이러한 결과를 바탕으로 그 시사점과 한계점에 대해서 논의하였다. Empirical evidence regarding the impacts of CEO duality on organizational outcomes is very limited. An extensive body of research that examined CEO duality and firm financial performance relationship produced only mixed results. We extend this area of inquiry by examining CEO duality-corporate social performance (CSP) relationship while focusing on CEO regulatory focus as the moderators. CSP is an important indicator of sustainable management and regarded as a vital part of sustainable development of corporations. Drawing from agency theory, dual leadership theory, and regulatory focus theory, we hypothesize that firms with CEO duality demonstrate lower levels of CSP, while the negative impacts of CEO duality on CSP will be moderated by CEO’s regulatory focus. Specifically, the level of promotion focus of CEO-chairperson attenuates the negative relationship between CEO duality and CSP while such relationship will be strengthened by the level of CEO-chairperson’s prevention focus. Using a sample of large 167 U.S. firms from 2006 to 2011 with their KLD ratings, we found strong support for two of our three hypotheses. Our findings suggest that firms interested in enhanced corporate social performance might consider splitting the titles of the CEO and the chairperson of the board. Also, we find that promotion focused CEOs are more willing to engage in CSR practices even when they hold both CEO and chairperson titles. Based on the results, theoretical and practical implications of the study are discussed.

10~11세기 중국(中國)과 한국(韓國)의 불탑(佛塔) 내 봉안 『보협인경(寶篋印經)』 재고

이승혜 ( Lee Seunghye ) 이화여자대학교 이화사학연구소 2021 梨花史學硏究 Vol.- No.62

Buddhism was a vehicle, which connected many states that thrived on the Chinese continent and the Korean peninsula in the tenth and eleventh centuries. A short text, entitled Sūtra of the Dhāraṇī of the Precious Casket Seal of the Concealed Complete-body Relics of the Essence of All Tathāgatas, provides us a window to look into the material and devotional culture of Buddhism developed into diverse forms across East Asian continent. It was transmitted from South Asia to China and translated into Chinese by the Indian monk Amoghavajra in the early eighth century. It was circulated and put into practice in Chang’an and in the region of Mount Wutai where Amoghvajra was active but it seems not to have been known in the Jiangnan region until the beginning of the tenth century. It gained wide popularity in the Jiangnan region only after the last king of Wuyue Kingdom reproduced it three times on a massive scale in the late tenth century. The printing project and dissemination of the xylograph copies spurred a widespread circulation of the text and renewed interest in the cult of textual relics across the Chinese continent and Korean peninsula beyond political borders in the tenth and eleventh centuries. This study re-examines historical implications of the Wuyue “re-discovery” of this text, while closely looking at material forms of this text from Wuyue, Northern Song, Koryŏ, and Khitan that constituted a multi-centered yet closely connected Buddhist cultural sphere in this time. For example, although the patron of the earliest Koryŏ edition of the sūtra dated it by using the Khitan reign name, the overall composition of the xylograph including the frontispiece points to the first Wuyue edition of the text as its prototype. This alone is enough to show the multivalence of cultural exchanges apart from the tributary system or official envoys.

구조설계 및 성능평가를 위한 기계학습모델

이승혜(Seunghye Lee),이재홍(Jaehong Lee) 한국강구조학회 2022 韓國鋼構造學會誌 Vol.34 No.2