• 대한기계학회논문집A
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• 제29권3호
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• pp.369-386
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• 2005

Various aspects of structural optimization techniques under transient loads are extensively reviewed. The main themes of the paper are treatment of time dependent constraints, calculation of design sensitivity, and approximation. Each subject is reviewed with the corresponding papers that have been published since 1970s. The treatment of time dependent constraints in both the direct method and the transformation method is discussed. Two ways of calculating design sensitivity of a structure under transient loads are discussed - direct differentiation method and adjoint variable method. The approximation concept mainly focuses on re- sponse surface method in crashworthiness and local approximation with the intermediate variable Especially, as an approximated optimization technique, Equivalent Static Load method which takes advantage of the well-established static response optimization technique is introduced. And as an application area of dynamic response optimization technique, the structural optimization in flexible multibody dynamic systems is re- viewed in the viewpoint of the above three themes

• 한국지반공학회논문집
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• 제25권9호
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• pp.93-100
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• 2009

본 연구에서 역해석에 이용한 직접법은 실제 변위와 목적함수의 차이를 최소화하고 미지변수를 보정하는 최적화가 핵심 과정이다. 연구과정이 복수의 지층을 단계별로 역해석하여 각 지반의 미지변수를 역해석하기 때문에 지층 간 미지변수의 간섭 효과를 최소화 할 수 있는 추가적인 최적화가 필요하다. 따라서 효율적이고 정확한 최적화를 위해서 목적함수의 편미분 계산과정이 없이 최적해를 구할 수 있는 직접탐색법(direct search method)을 사용하였다. 본 연구의 목적은 지하구조체가 포함된 지층을 상부와 하부의 지층으로 모형화하고, 다중 미지변수를 역해석하는 기법을 개발하는 데에 목적을 둔다. 또한 단계별 역해석된 미지변수의 상호 간섭 오차를 최소화하기 위해서 반복 역해석을 실시하고, 실제 존재하는 터널에 대하여 적용성에 대해 검토하였다. 그 결과, 단층 모형화보다 다층 모형화 결과가 실제 지하구조물거동을 정확히 나타냈으며 다층 경계부에 위치한 지하구조물의 다층지반 모형화를 통한 역해석이 유효함을 확인하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.602-606
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• 2000

A general procedure for the design sensitivity analysis of structural dynamic problems has been presented in frame of the FRF-based substructuring formulation. In the procedure, the direct differentiation method is used for the sensitivity formula. For a system response function, the proposed method gives a parametric design sensitivity formula in terms of the partial derivatives of the connection element properties and the transfer matrix of the subsystems. The derived design sensitivity formula is applied to a numerical example. The comparison of sensitivities derived by the proposed method and the finite difference method shows that the proposed method is efficient and accurate.

• 전산구조공학
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• 제8권1호
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• pp.85-94
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• 1995

수압을 받는 원통형 쉘의 몸체설계는 구조물에 외압이 작용할 때 발생하는 최대 응력과 변형 및 좌굴을 해석하여, 주어진 한계를 견딜 수 있는 쉘의 두께를 구해야 한다. 중앙 평형부 몸체의 두께를 설계변수로 선정하여 형상 최적화법으로서 원통형 쉘의 치수를 설계하는 방법을 제안하였다. 민감도 해석은 직접 미분법을 사용하여 유도하였으며, 비선형 계획법으로 최대 응력과 변형 및 좌굴 제한식 등을 만족하는 최적설계를 수행하였다.

• Journal of Electrical Engineering and Technology
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• 제8권4호
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• pp.780-786
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• 2013

In the reliability-based design optimization of electromagnetic devices, the accurate and efficient reliability assessment method is very essential. The first-order sensitivity-assisted Monte Carlo Simulation is proposed in the former research. In order to improve its accuracy for wide application, in this paper, the second-order sensitivity analysis is presented by using the hybrid direct differentiation-adjoint variable method incorporated with the finite element method. By combining the second-order sensitivity with the Monte Carlo Simulation method, the second-order sensitivity-assisted Monte Carlo Simulation algorithm is proposed to implement reliability calculation. Through application to one superconductor magnetic energy storage system, its accuracy is validated by comparing calculation results with other methods.

• 한국산학기술학회논문지
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• 제20권9호
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• pp.156-166
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• 2019

본 연구는 일반적인 중기업과 소기업을 통하여 경영전략과 혁신활동을 통해 궁극적으로 경영성과에 미치는 영향에 관한 통합적인 인과관계를 실증적으로 분석하는데 그 목적을 두었다. 본 연구 대상은 서울 경기지역 소재의 중소기업에 재직중인 종사자를 대상으로 이루어졌으며, 최종적으로 총 328부가 분석에 사용 되었다. 연구가설을 위한 자료 분석을 위해 SPSS Statistics 22.0과 AMOS 22.0 통계프로그램을 사용하였으며, 가설검증을 위한 분석방법으로 구조방정식 모형을 사용하였다. 본 연구의 주요 결과는 첫째, 경영전략 요인과 혁신활동, 경영성과의 상관관계 분석 결과 혁신활동과 상관이 높은 요인으로는 기술차별화 전략, 마케팅차별화 전략, 원가주도 전략으로 나타났으며, 경영성과와 상관이 높은 요인으로는 마케팅차별화 전략, 기술차별화 전략, 원가주도 전략으로 나타났다. 둘째, 혁신활동에 영향을 미치는 경영전략 요인으로 마케팅 차별화 전략, 기술차별화 전략, 원가주도 전략의 순으로 나타났으며, 경영성과에 영향을 미치는 요인으로는 마케팅차별화 전략과 원가주도 전략만 유의한 영향을 미치는 것으로 나타났다. 셋째, 경영성과에 기술차별화 전략이 직접적으로 영향을 미치지 못하는 것으로 분석되었으나, 기술차별화 전략과 경영성과의 관계에서 혁신활동이 완전매개하는 효과가 있음을 밝혀내었다. 본 연구에서 이러한 결과들을 종합하면 기업의 혁신활동이 마케팅차별화와 기술차별화 전략으로 연계되어야만 경영성과에 기여할 수 있다는 것을 의미한다고 볼 수 있다. 최근 중소기업들은 경영환경의 악화로 스스로의 핵심역량으로는 기술혁신, 생산혁신, 경영전반의 혁신을 꾀하기 어렵다는 사실을 알 수 있었다. 그러나 중소기업의 경영전략은 혁신 활동을 통해 경영성과를 창출할 수 있다는 것이 확인되었다.

• Structural Engineering and Mechanics
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• 제4권4호
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• pp.425-436
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• 1996

An application of the perturbation method to optimum structural design with random parameters is presented. It is formulated on the basis of the first-order stochastic finite element perturbation method. It also takes into full account the stress, displacement and eigenvalue constraints, together with the rates of change of the random variables. A method for calculating the sensitivity coefficients in regard to the governing equation and the first-order perturbed equation has been derived, by using a direct differentiation approach. A gradient-based nonlinear programming technique is used to solve the problem. The numerical results are specifically noted, where the stiffness parameter and external load are treated as random variables.

• 대한기계학회논문집
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• 제19권8호
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• pp.1822-1831
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• 1995

A general formulation of the design optimization problem with the random parameters is presented here. The formulation is based on the stochastic finite element second-order perturbation method ; it takes into full account of the stress and displacement constraints together with the rates of change of the random variables. A method of direct differentiation for calculating the sensitivity coefficients in regard to the governing equation and the second-order perturbed equation is derived. A gradient-based nonlinear programming technique is used to solve the problem. The numerical results are specifically noted, where the stiffness parameter and external load are treated as random variables.

• 한국축산식품학회지
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• 제40권3호
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• pp.350-361
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• 2020

Quality control of meat products is one of the main concerns of consumers, governmental control authorities, and retailers. The purpose of this study was to employ ribose-induced Maillard reaction in detection of meat adulteration and differentiation of fresh-chilled from frozen-thawed minced veal. The browning intensity was assessed through measuring the absorbance at 420 nm with a spectrophotometer as well as the direct analysis of the color and pH. The results showed that CIE b*, CIE a*, and A_420* values in the extract of fresh-chilled veal were significantly (p<0.05) higher than frozen-thawed samples. The extract of frozen meat samples stored at -18℃ became significantly darker and more yellowish compared to -4℃. The results showed that the A_420* value in the frozen-thawed veal stored at -4℃ and -18℃ was reduced by approximately 17.22±3.53% and 11.68±2.49%, respectively, compared with fresh-chilled veal. The findings also showed that the storage temperature of minced veal and the heating time in this reaction had a significant effect on all tested variables (p<0.0001). The proposed method can be considered as an easy, quick, and inexpensive test for differentiating between the fresh-chilled and frozen-thawed minced veal.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.746-752
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• 2001

Design sensitivity analysis for nonlinear structural problems has been emerged in the last decade as a glowing area of engineering research. As a result, theoretical formulations and computational algorithms have already developed for design sensitivity of nonlinear structural problems. There is not enough research for practical nonlinear problems using multi-element, due to difficulties of implementation into FEA. Therefore, nonlinear response analysis for stiffened shell which consists of Mindlin plate and Timoshenko beam, was considered. Specially, it presents the backward-Euler method which is adopted to describe an exact yield state in the stress computation procedure. Then, design sensitivity analysis of nonlinear structures, particularly elasto-perfectly-plastic structure, is developed using direct differentiation method. The accuracy of the developed sensitivity analysis was compared with the central finite difference method. Finally, on the basis of above results, design improvement for stiffened shell is suggested.