• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.12
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• pp.1811-1820
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• 2010

Most components in the real world show nonlinear response. The nonlinearity may arise because of contact between the parts, nonlinear material, or large deformation of the components. Structural optimization considering nonlinearities is fairly expensive because sensitivity information is difficult to calculate. To overcome this difficulty, the equivalent load method was proposed for nonlinear response optimization. This method was originally developed for size and shape optimization. In this study, the equivalent load method is modified to perform topology optimization considering all kinds of nonlinearities. Equivalent load is defined as the load for linear analysis that generates the same response field as that for nonlinear analysis. A simple example demonstrates that results of the topology optimization using equivalent load are very similar to the numerical results. Nonlinear response topology optimization is performed with a practical example and the results are compared with those of conventional linear response topology optimization.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.1
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• pp.141-152
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• 2007

Considering uncertainties of random input data, it is more reasonable to use probabilistic method than the conventional deterministic method for the design of structures or for the assessment of the responses of structures, which are designed as safe even under extreme loads. Therefore, to assess the quantitative effects of the constructed cable stayed bridge by the input random variables, a sensitivity analysis is studied. Using perturbation method, an analysis program is developed for the iterative probabilistic finite element analyses and sensitivity analyses of the cable stayed bridge, except the initial shape analysis. Monte-Carlo Simulations were used for the verification of the developed program. The results of sensitivity analysis shows the governing effects of external loads. Because the results also provide the sensitive effects of the stiffness of members and the magnitudes of prestressing force of cables, the developed

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.6
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• pp.596-604
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• 2010

In order to investigate the operating conditions and major design parameters of a dual ramjet propulsion system, an theoretical analysis of ramjet and scramjet propulsion systems was performed. The performance characteristics of each engine are delivered by thermo-dynamical cycle analysis, considering loss effects in a real engine. The performance sensitivity analysis is conducted by investigating various performance parameters, such as an intake efficiency, combustor inlet Mach number, configuration of the combustor, fuel flow rate, and exhaust nozzle efficiency. Based on these analysis results, the processes of application to dual ramjet cycle engines are specified.

• Journal of KSNVE
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• v.10 no.5
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• pp.783-791
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• 2000

This describes a study on the support location optimizations of the beams using the genetic algorithm and the sensitivity analysis. The genetic algorithm is a probabilistic method searching the optimum at several points simultaneously and requiring only the values of the object and constraint functions. It has therefore more chances to find the global solution and can be applied to the various problems. Nevertheless, it has such a shortcoming that it takes too many calculations, because it is ineffective in local search. While the traditional method using sensitivity analysis is of great advantage in searching the near optimum. thus the combination of the two techniques will make use of the individual advantages, that is, the superiority in global searching form the genetic algorithm and that in local searching form the sensitivity analysis. In this thesis, for the practical applications, the analysis is conducted by FEB ; and as the shapes of structures are taken as the design variation, it requires re-meshing for every analysis. So if it is not properly controlled, the result of the analysis is affected and the optimized solution amy not be the real one. the method is efficiently applied to the problems which the traditional methods are not working properly.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.7
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• pp.637-646
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• 2010

A time-domain panel method based on the potential flow theory and the time-stepping method is developed to predict the steady/unsteady aerodynamic characteristics of FM07, which is the BWB (Blended-wing body) type MAV. In the aerodynamic analyses, we used two types of the initial model(Case I) and the improved model(Case II), which is moved the gravity center toward the rear and has larger aspect ratio. In the steady aerodynamic analyses, it is revealed that improved model has higher lift to drag ratio(L/D) and more stable pitch characteristic than those of the initial model. In the unsteady aerodynamic analyses for sudden acceleration motion similar to the launch phase of MAV, it seemed that there is a rapid increase of the lift coefficient after the launch and unsteady results are good agreed compare with steady results in just a few times. In the analysis for pitch oscillation motion, which is occurred at the cruise condition of the FM07, it shows that unsteady aerodynamic coefficients looped around steady results and the improved model has more sensitive aerodynamic characteristics.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1135-1136
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• 2011

본 논문은 LCD 원판 Glass 이송용 4,000[N]급 영구자석 여자 횡자속 선형전동기를 설계하고 해석을 통해 성능을 검토하였다. 실험계획법을 활용하여 횡자속 선형전동기의 형상을 이루는 설계변수들이 추력과 추력리플에 미치는 평균분석을 통해서 민감도분석을 수행하였다. 본 연구에서 개발된 횡자속 선형전동기 적용 추진모듈은 LCD 제조 분야의 원판 Glass 이송용으로 선형이송 시스템에 적용하고자 한다.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.351-351
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• 2016

본 연구는 최근 기후변화로 인해 유출량이 많이 증가하고 있으며, 또한 하도의 제내측에 많은 피해가 발생하고 있다. 우리나라의 하도는 산지위치하고 있으며, 만곡의 형상을 많이 지니고 있다. 또한 유출량의 증가로 하도 만곡부에 하상의 퇴적으로 인해 월류 및 제방이 파괴 되는 현상도 발생되고 있다. 만곡부의 흐름은 만곡도의 수공구조물을 설치하므로 유수의 흐름에 민감하게 변화하여 흐름변화를 예측하기 어렵다. 그래서 자연하고 만곡부에 하상의 변화에 따른 수리학적 문제와 제내측의 안정성을 확보하기 위해 만곡지점에 수제를 설치하여 하도의 흐름과 하상의 안정성에 필요하다고 사료되어 연구를 하였다. 본 연구는 만곡지점에 수리실험 모형을 설치하여 결과를 도출하는 방법도 있으나, 축소모형은 하도의 특성을 반영하기 결과도축에 제약이 있어 금회 연구는 수치모형은 2차원 수치모형인 RMA-2를 사용하여 하도의 특성을 파악하고자 한다. 먼저 만곡형상이 뚜렷한 지점을 파악하고 하천설계기준의 수제를 설치하여 흐름의 변화 및 유속변화를 분석하고 만곡부에서 기준수제의 길이를 여러 CASE로 변화를 주어 수리학적 특성을 분석하고자 하며, 이에 따른 수제부에서 발생하는 퇴적구간과 범위, 최대유속지점과 세굴지점에 대한 연구를 진행하여 하도 만곡부에 수제를 설치하여 합리적인 결과를 제시 할 수 있으며, 설계실무와 하천방재 관련 문제에서도 반영하여 이용 될 수 있을 것이다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.3
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• pp.173-184
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• 2013

A multi-level design optimization framework for aerodynamic design of rotary wing such as propeller and helicopter rotor blades is presented in this study. Strategy of the proposed framework is to enhance aerodynamic performance by sequentially applying the planform and sectional design optimization. In the first level of a planform design, we used a genetic algorithm and blade element momentum theory (BEMT) based on two-dimensional aerodynamic database to find optimal planform variables. After an initial planform design, local flow conditions of blade sections are analyzed using high-fidelity CFD methods. During the next level, a sectional design optimization is conducted using two dimensional Navier-Stokes analysis and a gradient based optimization algorithm. When optimal airfoil shape is determined at the several spanwise locations, a planform design is performed again. Through this iterative design process, not only an optimal flow condition but also an optimal shape of an EAV propeller blade is obtained. To validate the optimized propeller-blade design, it is tested in wind-tunnel facility with different flow conditions. An efficiency, which is slightly less than the expected improvement of 7% predicted by our proposed design framework but is still satisfactory to enhance the aerodynamic performance of EAV system.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.43 no.6 s.312
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• pp.16-26
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• 2006

In this paper, we propose a 3D shape restoration system which measures height and surface shape of transparent ITO glass and delivers errors in focal length and incident angle of laser beam to femto-second laser micromachining. The proposed system is composed of a line scan laser, a high resolution camera, a linear motion guide synchronized to image capturing, and a control station. Also, we define the sensitivity indices that represent a relation between measurement error and a position of a camera and scan laser, and utilize it for optimum design. The results of the proposed system are compared with results of SPM(Scanning Probe Microscope) and prove the usefulness of the system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.10
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• pp.1279-1289
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• 2013

In recent times, turbomolecular pumps (TMPs) have been used frequently to generate and maintain high and clean vacuum. Because of the high-speed rotation of the rotor, its structural safety should be treated as the first design concern. This paper presents the structural analysis and optimization of rotor blades of a TMP. To increase the numerical efficiency in the finite element modeling and analysis, the P-method provided in Pro/ENGINEER was used for simulation. The structural responses for several types of rotor blades were investigated, and the effects of the blade angle, blade length, and round size are thoroughly studied for each type of TMP blade. In addition, structural optimization to reduce and even the maximum stress at each stage of the TMP by changing the size of rounds between the blade and the hub was performed very successfully by using the P-method.