• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제3B권2호
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• pp.79-83
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• 2003

The topology optimization for the magnet design is studied. The magnet design in the C-core actuator is investigated by using the derived topology optimization algorithm and finite element method. The design sensitivity equation for the topology optimization is derived using the adjoint variable method and the continuum approach.

• Nuclear Engineering and Technology
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• 제30권4호
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• pp.353-363
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• 1998

The H$_{\infty}$ algorithms of the mixed weight sensitivity is used for the robust design of the reactor power control system. The mixed weight sensitivity method requires the selection of the proper weighting functions for the loop shaping in frequency domain. The complexity of the system equation and the non-convexity of the problem make it very difficult to determine the weighting functions. The genetic algorithm which is improved and hybridized with the simulated annealing is applied to determine the weighting functions. This approach permits an automatic calculation and the resultant system shows good robustness and performance.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.288-293
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• 2008

The standard prestressed concrete I-girder bridge (PSC I-girder bridge) is one of the most prevalent types for small and medium bridges in Korea. When determining the member forces in a section to assess the safety of girder in this type of bridge, the general practice is to use the simplified practical equations or the live load distribution factors proposed in design standards rather than the precise analysis through the finite element method or so. Meanwhile, the live load distribution factors currently used in Korean design practice are just a reflection of overseas research results or design standards without alterations. Therefore, it is necessary to develop an equation of the live load distribution factors fit for the design conditions of Korea, considering the standardized section of standard PSC I-girder bridges and the design strength of concrete. In this study, to develop an equation of the live load distribution factors, a parametric analysis and sensitivity analysis were carried out on the parameters such as width of bridge, span length, girder spacing, width of traffic lane, etc. Then, an equation of live load distribution factors was developed through the multiple linear regression analysis on the results of parametric analysis. When the actual practice engineers design a bridge with the equation of live load distribution factors developed here, they will determine the design of member forces ensuring the appropriate safety rate more easily. Moreover, in the preliminary design, this model is expected to save much time for the repetitive design to improve the structural efficiency of PSC I-girder bridges.

• 대한기계학회논문집A
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• 제25권2호
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• pp.182-191
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• 2001

The paper describes the improvement on concurrent subspace optimization(CSSO) via automatic differentiation. CSSO is an efficient strategy to coupled multidisciplinary design optimization(MDO), wherein the original design problem is non-hierarchically decomposed into a set of smaller, more tractable subspaces. Key elements in CSSO are consisted of global sensitivity equation, subspace optimization, optimum sensitivity analysis, and coordination optimization problem that require frequent use of 1st order derivatives to obtain design sensitivity information. The current version of CSSO adopts automatic differentiation scheme to provide a robust sensitivity solution. Automatic differentiation has numerical effectiveness over finite difference schemes tat require the perturbed finite step size in design variable. ADIFOR(Automatic Differentiation In FORtran) is employed to evaluate sensitivities in the present work. The use of exact function derivatives facilitates to enhance the numerical accuracy during the iterative design process. The paper discusses how much the automatic differentiation based approach contributes design performance, compared with traditional all-in-one(non-decomposed) and finite difference based approaches.

• 한국기계가공학회지
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• 제20권8호
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• pp.11-17
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• 2021

This paper describes the time rate of change of dynamic response of a cantilever beam inserted with a damping element, such as bonding, which is excited under a general force at various locations. A sensitivity analysis was performed in a finite element model to show that two types of second-order algebraic governing equations were used to predict the rate of change of dynamic displacement: one is related to the modal coordinate linked to a physical coordinate, and the other to the design parameter of the time rate of change of displacement. The sensitivity differential equation formulation includes more complicated terms compared with that of the undamped cantilever beam. The sensitivities of the dynamic response were observed by changing the location of the excitation force, displacement extraction, and cross-sectional area of the beam. The analytical results obtained by this suggested theory showed a relatively good agreement when compared with those obtained using the commercial finite element program. The suggested analysis procedure enables the prediction of the response sensitivity for any finite element model of the dynamic system.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.22-25
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• 2005

In the paper, algorithms for disturbance observers are newly presented in the time-domain. Attention is paid to observing a ramp disturbance by introducing an integral term to the output equation of a constant disturbance observer. In order to reduce the sensitivity to the measurement noise, the disturbance observer is combined with the state observer. It will be shown that the estimation dynamics can be arbitrarily chosen by assigning the eigenvalues of a characteristic equation. Also, we provide the analysis of observer behaviors subject to non-ramp-style disturbances. Finally, we propose the generalized disturbance observer that accurately estimates disturbances of higher order in time series expansion.

• 한국해양공학회지
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• 제11권1호
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• pp.3-9
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• 1997

In this paper, design sensivity of plate natural frequency is computed for thickness design variables. Once the variational equation is derived from Lagrange quation using the virtual displacement, governing energy bilinear form is obtained and sensivity equation is formulated through the first variation. Natural frequency is obtained using the commercial FEM code and the accuracy of sensivity is verified by finite difference. The accuracy of natural frequency and sensivity improves for the fine mesh model.

• 대한토목학회논문집
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• 제42권1호
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• pp.11-21
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• 2022

가뭄은 장기간에 걸쳐 광범위하게 발생하며, 사회·경제적으로도 큰 피해를 발생시킨다. 가뭄 위험도는 기상학적 및 수문학적 요소와 더불어 사회적, 환경적, 물리적 및 경제적 요소로 이루어져 있기 때문에, 가뭄 위험도에 대한 영향을 정량적으로 파악하는 것이 중요하다. 본 연구에서는 충청북도를 대상으로 구조방정식모형을 이용하여 가뭄 노출성, 취약성, 대응능력 및 위험도 사이의 영향 관계를 파악하고, 베이지안 네트워크를 적용하여 가뭄 위험도에 대한 영향을 평가하였다. 또한, 가뭄 위험도 평가 인자별 민감도 분석을 통해 가뭄 위험도의 변화 정도를 분석하였다. 그 결과 과거 가뭄 위험도가 가장 큰 지역은 충주시로, 노출성 및 대응능력을 변화시켰을 때에도 가장 크게 산정되었다. 다만, 취약성을 변화시켰을 때에는 음성군이 위험도가 가장 큰 것으로 나타났다. 위험도에 대한 영향인자들의 민감도 분석을 실시한 결과 증평군이 민감도가 가장 컸으며, 노출성, 취약성 및 대응능력에서 제천시, 음성군, 옥천군이 민감도가 크게 나타났다. 이러한 결과를 통해 가뭄 위험도 및 가뭄 위험도에 대한 영향인자를 확인하였으며, 영향인자별 지역의 특성을 고려한 가뭄 대책 마련이 가능하다.

• 아동학회지
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• 제37권4호
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• pp.31-46
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• 2016

Objective: This study examined the influences of maternal and paternal psychological control and children's rejection sensitivity on relational aggression in elementary school students, and investigated whether children's rejection sensitivity mediated the relation of parental psychological control and relational aggression. Methods: The participants of this study were 596 fifth to sixth graders from seven elementary schools located in Seoul, Incheon, and Gyeonggi province. To measure the research variables, the Peer Conflict Scale (Marsee, Kimonis, & Frick, 2004), the Psychological Control Scale (Barber, 1996) and the Children's Rejection Sensitivity Questionnaire (Downey, Lebolt, $Rinc\acute{o}n$, & Freitas, 1998) were used. The data were analyzed by means of descriptive statistics and t -tests. Also, structure equation model (SEM) were used to examine the mediating role of rejection sensitivity. Results: The results of this study were as follows. First, the level of paternal psychological control increased the level of children's relational aggression whereas the level of maternal psychological control had no significant effect on it. In addition, the level of rejection sensitivity had a significant positive influence on the level of relational aggression. These tendencies were observed on both boys and girls. Second, only for boys, rejection sensitivity in upper elementary school students partially mediated the relation between paternal psychological control and relational aggression. Also, for both boys and girls, rejection sensitivity completely mediated the relation between maternal psychological control and relational aggression. Conclusion: In conclusion, the higher the level of paternal psychological control, the higher the level of children's rejection sensitivity, and subsequently the higher the level of their relational aggression.

• 한국항공우주학회지
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• 제43권4호
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• pp.368-376
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• 2015

본 논문은 헬리콥터 초기 설계를 위해 수정된 추정식을 적용한 헬리콥터 초기 설계 모델 정립 연구의 응용에 대한 내용으로 헬리콥터 초기 설계의 효율성을 제고하고 개선하고자 하였다. 헬리콥터 설계 시 중량계수 영향성을 확인하고 적정한 중량계수 적용방법을 제시하였으며, 중량계수 및 회전면 하중, 블레이드 개수, 블레이드 종횡비와 같은 주요 매개변수에 대한 민감도 분석과 연관관계에 대해 고찰하였다. 연구 결과, 설계 시 변수에 대한 연관관계 및 민감도의 양을 고려하여 설계 할 헬기 특성을 최적화해야하며, 주요 매개변수들 사이에는 복합적인 연관관계가 존재하므로 설계 시 설계자는 설계 인자들에 대한 신중한 고려가 필요한 것으로 분석되었다.