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확률론적 접근방법을 이용한 복합재 샌드위치 동체의 구조설계 개선 및 최적화
이석제,조우제,김인걸,설창원 한국항공우주학회 2012 한국항공우주학회 학술발표회 논문집 Vol.2012 No.11
복합재 샌드위치 구조는 무게 대비 굽힘 강성을 획기적으로 증가시키고 단순 적층 복합재 구조에 비해 30% 정도로 중량절감이 가능하다. 그러나 복합재료는 일반 금속에 비해 더 큰 불확실성이 내재되어 있다. 그러므로 무게 경량화에 따른 구조물의 신뢰성 확보를 위해 확률론적 구조설계가 요구된다. 본 논문에서는 안전계수를 이용한 고전적 설계방법을 대체하기 위하여 PMS를 계산하였다. 또한 신뢰성 기반의 파괴확률을 구속조건으로 하는 신뢰성 기반 최적설계를 수행하였고, 효율적인 계산을 위해 RBDO-MPDF 방법을 제안하였다. 본 논문의 결과는 신뢰성 해석을 기반으로 하는 개선된 설계방법 연구에 이용될 수 있다. Composite sandwich structures can improve the specific bending stiffness considerably and save the weight nearly 30% compared with composite laminates. However, the composite material has more inherent uncertainties of the material property caused by manufacturing process than metals. Therefore, the probabilistic structural design is required to ensure the reliability of structures by lightening. In this paper, the PMS is calculated to substitute for classical design method. Furthermore, the RBDO under the probabilistic constraint is performed, and the RBDO-MPDF is proposed for an efficient computation. The examined results can be used for an advanced design method based on the reliability analysis.
정상 대조군과 알레르기 질환군에서의 혈청 IgE 측정치에 관한 연구
이석제,이현철,허갑범,이상용 대한천식알레르기학회 1983 천식 및 알레르기 Vol.2 No.2
Estimate of serum IgE levels has become apart of the diagnostic assessment of the patient with est ablished or suspected allergic diseases. The interpretation of such estim ates must, however, depend on the availability of stand ard of norm alcy for given population and serum IgE levels, because of differences of serum IgE levels with age, sexrace, community, smoking and secretor status of ABH substances, High levels ef serum IgE are associated with certain alle rgic conditions such as bronchial asthma, allergic rhi nitis, atopic dermatitis and chronic urticaria and also some parasite infestatio ns, interstitial nephritis, syphilis, drugal lergy, Wiskott Aldrich syndrome, viral infection, chronic infection, infectious mononucleosis, cryptogenic eosinophilia and some malig nancies. Serum IgE was determined by radioimmuno assay technique (PRIST) in 75 healthy Koreans and 308 patients with allergic disease (79 patients with bronchial asthma, 105 patients with allergic rhinitis, 50 patients with chronic urticaria and 74 patients with chronic cough, The results were as following. 1) Mean serum IgE value of 75 healthy Koreans was 74+ -63IU/ml. The difference of the mean serum IgE values among each age groups was not st atistically sig nificant. There was also no significant difference between male and female. 2) Serum IgE values were elevated more than 1 6 QIU /ml in 81. 0 % of bronchial asthma, 75. 2% of allergic rhinitis, 7 0. 0% of chronic urticaria and 74. 3% of chronic cough. 3) There was no significant difference ef serum IgE values between early and later age group of onset of bronchial asthma, but allergic rhinitis showed difference between age groups of onset of disease. 4) No signi 5cant difference of serum IgE values between positive and negative allergic skin test group with bronchial asthmanor allergic rhinitis was found. 5) There was no significant dif ference of serum IgE values between positive and negative dermoraphism group with chronic urticaria. 6) No significant correlation between total peripheral eosinophil counts and serum IgE values was found.
이석제,김인걸,Lee, Seok-Je,Kim, In-Gul 한국군사과학기술학회 2012 한국군사과학기술학회지 Vol.15 No.1
In this paper, the deterministic optimal design for the tail plane made of composite materials is conducted under the deterministic loading condition and compared with that of the metallic materials. Next, the reliability analysis with five random variables such as loading and material properties of unidirectional prepreg is conducted to examine the probability of failure for the deterministic optimal design results. The MATLAB programing is used for reliability analysis combined with FEA S/W(COMSOL) for structural analysis. The laminated composite is assumed to the equivalent orthotropic material using classical laminated plate theory. The response surface methodology and importance sampling technique are adopted to reduce computational cost with satisfying the accuracy in reliability analysis. As a result, structural weight of composite materials is lighter than that of metals in deterministic optimal design. However, the probability of failure for the deterministic optimal design of the tail plane structures is too high to be neglected. The sensitivity of each variable is also estimated using probabilistic sensitivity analysis to figure out which variables are sensitive to failure. The computational cost is considerably reduced when response surface methodology and importance sampling technique are used. The study of the computationally inexpensive method for reliability-based design optimization will be necessary in further work.