유동 시스템의 형상 최적 설계를 위한 성장-변형률법의 적용

한석영,이상환,김종필,맹주성,Han, Seog-Young,Lee, Sang-Hwan,Kim, Jong-Pill,Maeng, Joo-Sung 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.7

Shape optimization of a flow system is done to obtain the required effects, in the engineering fields. Most of these designs are accomplished by empirical or numerical analysis. In empirical analysis, it is difficult to obtain an optimal shape in the feasible design region. And, in numerical method, it usually needs much calculation expenses for shape optimization, because of design sensitivity analysis. In this study, we used the growth-strain method having only one distributed parameter such as a design variable. It optimizes a shape by making a distributed parameter such as dissipation energy uniform in a flow system, and then applied to two-flow systems. In order to overcome the stability occurred in numerical analysis performed by Azegami, the equation of volumic strain has been modified. Also, the shapes were compared with the known optimal shapes for the flow systems. Consequently, we confirm that the modified growth-strain method is very efficient and practical in shape optimization of the flow systems.

신경망 최적화 기법을 이용한 다익 홴/스크롤 시스템의 설부에 대한 형상 최적화

한석영,맹주성,유달현,진경욱,Han, Seog-Young,Maeng, Joo-Sung,Yoo, Dal-Hyun,Jin, Kyong-Uk 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.10

In order to improve efficiency of a system with three-dimensional flow characteristics, this paper presents a new method that overcomes three-dimensional effects by using two-dimensional CFD and neural network. The method was applied to shape optimization of cut-off in a multi-blade fan/scroll system. As the entrance conditions of two-dimensional CFD, the experimental values at the positions out of the inactive zone were used. The distributions of velocity and pressure obtained by two-dimensional CFD were compared with those of three-dimensional CFD and experimental results. It was found that the distributions of velocity and pressure have qualitative similarity. The results of two-dimensional CFD were used for teaming as target values of neural network. The optimal angle and radius of cut-off were determined as 71$^{\circ}$and 0.092 times the outer diameter of impeller, respectively. It is quantified in the previous report that the optimal angle and radius of cut-off are approximately 72$^{\circ}$and 0.08 times the outer diameter of impeller, respectively.

구조물의 피로수명 향상을 위한 형상 최적화

한석영,송시엽,Han, Seok-Yeong,Song, Si-Yeop 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.8

Most of mechanical failures are caused by repeated loadings and therefore they are strongly related to fatigue. To avoid the failures caused by fatigue, determination of an optimal shape of a structure is one of the very important factors in the initial design stage. Shape optimization fer two types of specimens, which are very typical ones in opening mode in fracture mechanics, was accomplished by the linear elastic fracture mechanics and the growth-strain method in this study. Also shape optimization for a cantilever beam in mixed mode was carried out by the same techniques. The linear elastic fracture mechanics was used to estimate stress intensity factors and fatigue lives. And the growth-strain method was used to optimize the shape of the initial shape of the specimens. From the results of the shape optimization, it was found that shapes of two types of specimens and a cantilever beam optimized by the growth-strain method prolong their fatigue lives significantly. Therefore, it was verified that the growth-strain method is an appropriate technique for shape optimization of a structure having a crack.

극압제가 윤활성 및 내소부성에 미치는 영향

한석영(Seog-Young HAN) 한국자동차공학회 1995 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1995 No.11_2

The effects on lubricity and anti-seizure properties of lubricants according to extreme pressure(EP) additives of sulfur and phophorous types in cold rolling were investigated by estimation method by use of a laboratory scale roll ing mill. where the contact conditions between work roll and strip are very close to actual cold roll ing mi 11. The experimental results were obtained as follows: (1) base oil with EP additives of sulfur or phosphorous types has better effect than base oil only. (2) the more amount of EP additives is. the better effect on lubricity is. (3) sulfur type EP additive has better effect on lubricity than phosphorous type. (4) phosphorous type EP additive has better effect on anti-seizure property than sulfur type. (5) the amount of sulfur and phosphorous type EP additives must be controlled in order to improve both lubricity and anti-seizure properties and (6) from the results of EDS analysis of worn Falex test pins. existence of EP film was verified.<br/>

일반 구조물에 대한 형상 최적화 시스템의 개발

한석영(Seog-Young Han),배현우(Hyun-Woo Bai) 한국생산제조학회 2000 한국공작기계학회 춘계학술대회논문집 Vol.2000 No.4

진화적 구조 최적화를 위한 양방향 요소 제거법의 개발

한석영(S.Y.Han),배현우(H.W.Bai) 한국자동차공학회 1998 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1998 No.11_2

The purpose of this study was to develop a new element removal method for ESO (Evolutionary Structural Optimization) which is one of topology optimization methods. In case of ESO the element removal ratio was fixed throughout topology optimization by 1 or 2%. As a result it has no flexibility for various types of structures and thus the rate of convergence might not be efficient. Also the results of topology optimization were obtained differently due to the element removal ratio. In this paper, a new element removal method was developed by adding and removing elements bi-directionally. Then it was applied to a short cantilever, a bracket and a vertical cantilever with overall stiffness constraints. From the results, it was verified that the rate of convergence was very improved and the optimal designed structures was obtained very similar to the results of ESO with the fixed element removal ratio of \%.<br/>

위상 구조 최적화를 위한 개선된 요소 제거법의 개발

한석영(Seog Young Han),최강석(Kang Suk Choi) 한국자동차공학회 1998 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1998 No.5_2

The purpose of this study was to develop a new improved element reduction method for ESO(Evolutionary Structural Optimization) method which is one of topology optimization methods. In case of ESO method the element reduction ratio was fixed throughout topology optimization by 1 or 2 %. As a result it has no flexibility for various types of structures and thus the rate of convergence might not be efficient. In this paper, the developed method was explained by an example with overall stiffness constraints and then applied to some examples. From the results, it was verified that the rate of convegence was very improved and the optimal designed structures was obtained compared with ESO method.<br/>

간호대학생의 스마트폰 중독, 학습몰입 및 학업성취도의 관계연구

한석영(Han Seok Young) 학습자중심교과교육학회 2015 학습자중심교과교육연구 Vol.15 No.12

본 연구는 간호대학생의 스마트폰 사용양상과 중독 정도를 파악하고, 스마트폰 중독정도에 따른 학습몰입 및 학업성취도의 관계를 파악하는데 있다. K시 일 간호 대학교의 스마트폰을 사용하고 있는 간호대학생 345명을 편의표집하였다. 자료분석 은 SPSS/WIN 19.0을 사용하여 대상자의 일반적 특성, 스마트폰 사용양상, 스마트 폰 중독정도, 학습몰입, 학업성취도는 서술통계로 제시하였고, 일반적 특성에 따른 스마트폰 중독정도는 χ²-test, ANOVA를 사용하였다. 그리고 스마트폰 중독, 학습 몰입, 학업성취도 간의 상관관계는 Pearson s correlation coefficients로 분석하였다. 스마트폰 사용시간은 주로 하루 평균 3시간 이상(62.6%)이었고, 전공과목보다 교양 과목 강의시간에 2배 정도 더 많이 사용하였다. 스마트폰 중독 정도는 일반 사용군 (89.6%), 과다 사용군(5.8%), 중독군(4.6%)으로 대부분이 일반 사용군이었다. 스마트 폰 중독과 학습몰입은 역상관관계가 있었고(r=-.24, p=.008), 학습몰입과 학업성취도 는 순상관관계를 보였다(r=.25, p= .007). 따라서 스마트폰 중독 예방지침의 교육과 스마트폰 중독의 개선 프로그램의 개발 및 적용이 요구되고, 학습몰입을 증진시킬 수 있는 방안들을 다양하게 적용함으로써 학업성취도를 높여 대학생활의 적응, 진 로, 취업을 증진시킬 수 있을 것이다. The purpose of this study was to investigate the smart phone using pattern, smart phone addiction, learning-flow, and learning achievement of nursing students. The study subjects consisted of 345 nursing students who completed a informed consent. Data were collected through self-reported questionnaires, and analyzed using the SPSS/WIN 19.0 IBM program. The smart phone using pattern consisted of using time and purpose of use. The smart phone using time was over 3 hours(62.6%) in daily average, below 10 minutes(52.5%) per 1hour during lecture, and below 10 minutes (26.4%) per 1hour during practice hours. The purpose of smart phone using was messenger(30.2%), internet surfing(22.4%), SNS(19.0%) etc. The smart phone addiction level was average users(89.6%), heavy users(5.8%), and smart phone addicted(4.6%). A statistically significant correlation was found between smart phone addiction and learning-flow(r=-.24, p=.008). No correlation was found between smart phone addiction and learning achievement(r=.18, p=.016). Therefore more positive and effective smart phone addiction management for nursing students is to considers, and developing programs of learning flow should be studied.

간호대학생의 문화적 역량 측정도구 개발

한석영(Han, Seok-Young),정향인(Cho Chung, Hyang-In) 한국간호과학회 2015 Journal of Korean Academy of Nursing Vol.45 No.5

Purpose: This methodological study was conducted to develop and test a cultural competence scale for nursing students. Methods: Based on the five constructs of cultural competency identified in the conceptual analysis of Suh, 76 items for the tool were derived initially. These items were reduced to 58 items after content validity tests (two times) by 6 multicultural experts. Data collected from 526 nursing students were utilized to test the validity and reliability of the preliminary tool. Item analysis, factor analysis, Pearson correlation coefficients, and Cronbach’s alpha were used for the analysis. Results: Twenty-seven items were selected for the final scale, and categorized into 5 factors explaining 62.1% of the total variance. Cronbach’s alpha was .91 and the reliability of the subscales ranged from .76 to .91. Criterion validity between the developed tool and empathy (r=.26, p <.001) was significant. Conclusion: The results show that this scale can provide scientific and empirical data when evaluating the effectiveness of school curriculums or multicultural empowerment programs regarding cultural competence of nursing students.

위상 최적화를 위한 효율적인 요소 제거법

한석영(Seog-Young Han),이동진(Dong-Jin Lee) 한국생산제조학회 2000 한국공작기계학회 춘계학술대회논문집 Vol.2000 No.4