최적제어를 통한 복합적층판의 형상최적화

한석영,백춘호,박재용 한국공작기계학회 2003 한국공작기계학회 추계학술대회논문집 Vol.2003 No.-

The growth-strain method was applied to cutout optimization in laminated composite plates. Since the growth-strain method optimizes a shape by generating the bulk strain to make the distributed parameter uniform, the distributed parameter was chosen as Tsai-Hill value. In this study, of particular interest is to see whether the growth-strain method developed for shape optimization in isotropic media would work for laminated composite plates. In volume control of the growth-strain method, it makes Tsai-Hill value at each element uniform in laminated composite plates under the predetermined volume. The shapes optimized by Tsai-Hill fracture index were compared with those of the initial shapes for the various load conditions and predetermined volumes of laminated composite plates. As a result, it was verified that volume control of the growth-strain method worked very well for cutout optimization in laminated composite plates.

마이크로 유전자 알고리즘을 이용한 구조 최적설계

한석영,최성만 한국공작기계학회 2003 한국공작기계학회 춘계학술대회논문집 Vol.2003 No.-

SGA (Single Genetic Algorithm) is a heuristic global optimization method based on the natural characteristics and uses many populations and stochastic rules. Therefore SGA needs many function evaluations and takes much time for convergence. In order to solve the demerits of SGA, μGA(Micro-Genetic Algorithm) has recently been developed. In this study, μGA which have small populations and fast convergence rate, was applied to structural optimization with discrete or integer variables such as 3, 10 and 25 bar trusses. The optimized results of μGA were compared with those of SGA. Solutions of μGA for structural optimization were very similar or superior to those of SGA, and faster convergence rate was obtained. From the results of examples, it is found that μGA is a suitable and very efficient optimization algorithm for structural design.

좌굴 하중을 고려한 프레임 구조물의 최적 설계

한석영,진경욱 韓國工作機械學會 2000 한국생산제조학회지 Vol.9 No.2

In this paper, the comparison of the first order approximation schemes such as SLP (sequential linear programming), CONLIN (convex linearization), MMA(method of moving asymptotes) and the second order approximation scheme, SQP(sequential quadratic programming) was accomplished for optimization of nonlinear structures. It was found that MMA and SQP are the most efficient methods for optimization. But the number of function call of SQP is much more than that of MMA. Therefore, when it is considered with the expense of computation, MMA is more efficient than SQP. In order to examine the efficiency of MMA for complex optimization problem, it was applied to the helicopter tail boom con-sidering column buckling and local wall buckling constraints. It is concluded that MMA can be a very efficient approxima-tion scheme from simple problems to complex problems.

황산스트렙토마이신 근육주사시 혼합용매가 조직손상과 동통에 미치는 영향

한석영,오상은 전남대학교 간호과학연구소 2000 Nursing and Health Issues(NHI) Vol.5 No.1

Streptomycin sulfate is an anti-tuberculous agent, which can be injected intra muscularly. With the increased frequency of its injection, the complication such as pain, discomfort, and damage in nerves, vessels, and iocal tissues is on the rise. In particular, local tissue damage of injection site gives a discomfort continuously to patients by fibrosis, necrosis, delayed healing of the tissue, and decreased absorption of the drug. Eventually the recovery and healing process is delayed. The purpose of this study is to compare tissue damage and pain between when streptomycin is injected in normal saline and when injected in distilled water. Also, correlations between damage and pain in terms of gender, age, walking amount, and total body fat after injection have been explored. The subjects of this study were 13 patients who had been diagnosed of pulmonary tuberculosis and hospitalized at K hospital in K wangju from Jan. 3 to Mar. 3, 1999. Streptomycin was injected once a day on each gluteal area of the subjects alternately. After 12 injections tissue damage and pain on the injected area with streptomycin dissolved in saline were compared to those in distilled water as control. The degree of tissue damage and pain after streptomycin injection were measured by needle EMG and self-reported graphic rating scale. The collected data were analysed by SPSS program. The differences of tissue damage and pain between experimental group and control group were analysed by non-parametric Wilcoxon signed rank test. And pain intensities were shown using Box-Plot. Also, correlations between tissue damage and pain in terms of age, total body fat, and walking amount after injection were analysed by Spearman‘s rho correlation coefficient. The difference of tissue damage and pain according to gender was analysed by non-parametric Wilcoxon rank sum test The results of this study were summarized as follows; 1. Needle EMG showed that the muscle tissue of experimental group with normal saline less damaged than that of control group with distilled water(Z=-3.464, p= .001). 2. No significant difference was noted in the degree of pain between experimental group and control group(Z=-.312, p=.755). 3. In the variables of age, total body fat, and walking amount after injection, the tissue damage was correlated with age positively( γ =.516, p=.000). 4. In the variables of age, total body fat, and walking amount after injection, the pain was correlated with walking amount in both groups(normal saline: r =-.328 , p=.003 ; distilled water : r =-.271 , p=.016). 5. No significant difference were noted in the degree of tissue damage (Z=-1.684, p=.092) and pain (Z=- .416, p=.678) according to gender. In conclusion, it is highly recommended that the use of normal saline as a solvent for streptomycin injection to decrease damage of tissue and to promote healing of tissue.

마이크로 믹서의 형상 최적화

한석영,김성훈 한국공작기계학회 2004 한국공작기계학회 춘계학술대회논문집 Vol.2004 No.-

In this study, shape optimization of micro-static mixer with a cantilever beam was accomplished for maximizing the mixing efficiency by using successive response surface approximations. Variables were chosen as the length of cantilever beam and the angle between horizontal and the cantilever beam. Sequential approximate optimization method was used to deal with both highly nonlinear and non-smooth characteristics of flow field in a micro-static mixer. Shape optimization problem of a micro-static mixer can be divided into a series of simple subproblems. Approximation to solve the subproblems was performed by response surface approximation, which does not require the sensitivity analysis. To verify the reliability of approximated objective function and the accuracy of it, ANOVA analysis and variables selection method were implemented, respectively. It was verified that successive response surface approximation worked very well and the mixing efficiency was improved very much comparing with the initial shape of a micro-static mixer.

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.

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.

경험적 최적화 기법을 이용한 자동차 공력저항 예측 프로그램 개발

한석영,맹주성,박재용 한국공작기계학회 2002 한국공작기계학회 춘계학술대회논문집 Vol.2002 No.-

At present, wind tunnel test or CFD is used for predicting aerodynamic drag coefficient in motor company. But, wind tunnel test requires much cost and time, and CFD has about 30% error. In this study a predicting program of the aerodynamic drag coefficient based on empirical techniques was developed. Also a mathematical optimization method using GRG method was added to the program. The program was applied to six cars. Aerodynamic drag coefficient values of six cars were predicted with 4.857% average error. The optimization method was also applied to six cars. Three parameters selected from sensitivity analysis were determined to reduce the afterbody drag coefficient to the value established by a designer and when some parameters were changed for a developing automotive, optimal modifiable parameters were determined to preserve the same drag coefficient as the original automotive. It was verified that this program could predict the aerodynamic drag coefficient effectively and accurately, and this program with GRG method could determine optimal values of parameters.

다중재료 구조물의 위상 최적화를 위한 재료혼합법의 개발

한석영,이수경 대한기계학회 2004 大韓機械學會論文集A Vol.28 No.6

체적제어에 의한 적층 복합재 구멍의 형상 최적화

한석영,마영준 대한기계학회 2004 大韓機械學會論文集A Vol.28 No.9