• 한국유체기계학회 논문집
• /
• 제10권2호
• /
• pp.7-15
• /
• 2007

A numerical procedure for optimizing the shape of three-dimensional channel with V-shaped ribs extruded on both walls has been carried out to enhance the turbulent heat transfer. The response surface based optimization is used as an optimization technique with Reynolds-averaged Wavier-stoked analysis. Shear stress transport (SST) turbulence model is used as a turbulence closure. Computational results for average heat transfer rate show good agreements with experimental data. The objective function is defined as a linear combination of heat transfer and friction loss-related terms with a weighting factor. Three dimensionless variables such as, rib pitch-to-rib height ratio, rib height-to-channel height ratio, and the attack angle of the rib are chosen as design variables. Nineteen training points obtained by D-optimal designs for three design variables construct a reliable response surface. In the sensitivity analysis, it is found that the objective function is most sensitive to the ratio of rib height-to-channel height ratio. And, optimal values of design variables have been obtained in a range of the weighting factor.

• International Journal of Automotive Technology
• /
• 제8권3호
• /
• pp.337-342
• /
• 2007

A multi-objective optimization technique was implemented to obtain optimal topologies of the inner reinforcement for a vehicle's hood simultaneously considering the static stiffness of bending and torsion and natural frequency. In addition, a smoothing scheme was used to suppress the checkerboard patterns in the ESO method. Two models with different curvature were chosen in order to investigate the effect of curvature on the static stiffness and natural frequency of the inner reinforcement. A scale factor was employed to properly reflect the effect of each objective function. From several combinations of weighting factors, a Pareto-optimal topology solution was obtained. As the weighting factor for the elastic strain efficiency went from 1 to 0, the optimal topologies transmitted from the optimal topology of a static stiffness problem to that of a natural frequency problem. It was also found that the higher curvature model had a larger static stiffness and natural frequency than the lower curvature model. From the results, it is concluded that the ESO method with a smoothing scheme was effectively applied to topology optimization of the inner reinforcement of a vehicle's hood.

• 대한기계학회논문집B
• /
• 제28권9호
• /
• pp.1051-1057
• /
• 2004

A numerical optimization procedure for the shape of three-dimensional channel with angled ribs mounted on one of the walls to enhance turbulent heat transfer is presented. The response surface method is used as an optimization technique with Reynolds-averaged Wavier-Stokes analyses of flow and heat transfer. SST turbulence model is used as a turbulence closure. Computational results for local heat transfer rate show reasonable agreements with experimental data. The pitch-to-height ratio of the rib and rib height-to-channel height ratio are set to be 9.0 and 0.1, respectively, and width-to-rib height ratio and attack angle of the rib are chosen as design variables. The objective function is defined as a linear combination of heat-transfer and friction-loss related terms with weighting factor. Full-factorial experimental design method is used to determine the data points. Optimum shapes of the channel have been obtained in the range from 0.0 to 0.1 of weighting factor.

• 전력전자학회논문지
• /
• 제18권1호
• /
• pp.103-109
• /
• 2013

The conventional LCL filter design method of the utility interactive inverter considers only harmonics attenuation of the current injected to the grid. However, in case of utility-interactive inverter with critical load the voltage quality of the critical load should also be considered for LCL filter design. Also, considering cost and volume of LCL filters. it is important to have minimum values of inductance and capacitance as far as the harmonic standards are satisfied. In this paper a LCL filter design method is proposed to satisfy not only the harmonic standards of the grid current during the grid-connected mode but the voltage quality of the critical load during grid-connected mode and stand-alone mode. With the proposed method optimized values of LCL filters could be obtained by applying weighting factor to voltage ripple across the critical load, inductor volume, amount of reactive current and system bandwidth.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 B
• /
• pp.657-659
• /
• 1998

In order to optimize fuzzy modeling of nonlinear system, we proposed a optimal fuzzy model according to the characteristic of I/O relationship, HCM method, the genetic algorithm, and the objective function with weighting factor. A conventional fuzzy model has difficulty in definition of membership function. In order to solve its problem, the premise structure of the proposed fuzzy model is selected by both the partition of input space and the analysis of input-output relationship using the clustering algorithm. The premise parameters of the fuzzy model are optimized respectively by the genetic algorithm and the consequence parameters of the fuzzy model are identified by the standard least square method. Also, the objective function with weighting factor is proposed to achieve a balance between the performance results for the training and testing data.

• 대한기계학회논문집B
• /
• 제28권7호
• /
• pp.879-886
• /
• 2004

A numerical optimization has been carried out to determine the shape of the three-dimensional channel with oblique ribs attached on both walls to enhance turbulent heat transfer. The response surface based optimization is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis of fluid flow and heat transfer. Shear stress transport (SST) turbulence model is used as a turbulence closure. Numerical results fur heat transfer rate show good agreements with experimental data. four dimensionless variables such as, rib pitch-to-rib height ratio, rib height-to-channel height ratio, streamwise rib distance on opposite wall to rib pitch ratio, and the attack angle of the rib are chosen as design variables. The objective function is defined as a linear combination of heat-transfer and friction-loss related coefficients with a weighting factor. D-optimal method is used to determine the training points as a means of design of experiment. Sensitivity of the objective parameters to each design variable has been analyzed. And, optimal values of the design variables have been obtained in a range of the weighting factor.

• 대한전자공학회논문지
• /
• 제22권6호
• /
• pp.58-62
• /
• 1985

이온 주입된 소형 MOSFET소자에 대한 해석적 문턱 전압 모델이 유도되었다. 일정한 도우핑 농도를 갖는 MOSFET에 적용되는 Yau 모델을 implanted channel구조와 bird's beat구조의 MOSFET에 대하여 적합한 형태로 수정하여 short channel 현상과 narrow width 현상을 정량적으로 설명하였다. Channel영역의 불순물 분포를 SUPREM 결과에서 2-step profile로 근사시켜 문턱 전압의 short channel model을 제안하였다. Weighting factor를 사용하여 bird's beat 영역의 불순물 분포를 고려함으로써 narrow width 현상을 성공적으로 설명하였다.

• Journal of Electrical Engineering and Technology
• /
• 제4권1호
• /
• pp.43-48
• /
• 2009

The purpose of the this paper is to make decision of the maintenance priority of power distribution system using Time-Varying Failure Rate(TVFR) with interruption cost. This paper emphasizes the practical use of the reliability indices and interruption cost. To make a decision of maintenance priority on power distribution system equipment, the quantification of the reliability level should be represented as a cost. In this paper, the TVFR of power distribution system equipment applied in this paper utilizes analytic method to use the historical data of KEPCO. From this result, the sensitivity analysis on TVFR of equipment was done for the priority, which represents that high priority of the equipment has more effect on system reliability, such as SAIDI or SAIFI, than other equipment. By this priority, the investment plan is established. In this result, customer interruption cost(CIC) could be extracted, and CIC is used as weighting factor to consider a importance of customer. After that, the result calculated the proposal method in this paper is compared with other priority method, such as lifetime, failure rate or only sensitivity.

• 한국산학기술학회논문지
• /
• 제12권7호
• /
• pp.2913-2918
• /
• 2011

본 논문은 기계시스템의 마찰 현상 중 히스테리시스 현상을 실험적으로 규명하고 뉴럴 네트워크 알고리즘을 이용한 프라이자흐(Preisach) 모델을 제안하였다. 제안된 모델은 실험을 통해 구한 마찰 특성을 오류역전파(back propagation) 알고리즘을 이용하여 뉴럴 네트워크의 가중 행렬(weighting factor)를 갱신할 수 있도록 하였다. 학습된 가중행렬은 프라이자흐 모델의 파라미터로 활용하였다. 마찰 거동을 규명하기 위한 실험 및 제안된 프라이자흐 모델은 LabView소프트웨어를 이용하여 구현하고 마찰이 있는 기계 및 로봇 시스템의 정밀 제어 시스템 구축을 위한 알고리즘으로 활용할 수 있도록 제안하였다. 제안된 모델의 성능은 실험을 통해 규명하였다.

• 한국방재학회 논문집
• /
• 제8권5호
• /
• pp.15-21
• /
• 2008

본 연구의 목적은 현재 지방자치단체에서 수행하는 상수관로 개량 및 교체 사업시 상수관로의 노후도 평가를 위한 항목별 가중치를 산정하는 것이다. 상수도시스템에 상수관로의 노후도 항목은 지역 및 위치, 토지이용 등의 특성에 영향을 받을 수 있다. 본 연구에서는 국내외 자료를 바탕으로 국내 실정에 맞는 노후도 항목 16개를 선정하였다. 또한, 노후도 항목별 세분화된 가중치 산정을 위해 실무업체를 선정하여 해당 전문가들을 대상으로 노후도 항목별 중요도에 대한 설문을 실시하였다. 설문 조사 방법으로는 델피법을 이용하여 이 결과를 바탕으로 계층적분석과정(AHP)을 적용하여 노후항목별 가중치를 산정하였다. 분석결과 국내 실무에 적합한 16개 결함항목별 점수배점표를 작성하여 명확한 판단기준을 마련하였으며 관거 개량사업에 있어서 복잡한 의사결정 문제들에 대한 활용 가능성을 제시하였다.