• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2384-2389
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• 2007

The 2nd order response surface method (RSM) has been carried out to get optimum thermal design for enhanced heat transfer on square channel with bleed holes. The RSM was used as an optimization technique with Reynolds-averaged navier-stokes equation. Turbulence model for heat transfer analysis used RNG k-epsilon model. The wall function used enhanced wall function. Numerical local heat transfer coefficients were similar to the experimental tendency. Two design variables such as attack angle of rib (${\alpha}$), rib pitch-to-rib height ratio (p/e) were chosen. Operation condition considered bleeding ratio per bleed hole ($BR_{hole}$). A response surface were constructed by the design variables and operation condition. As a result, adjusted $R^2$ was more than 0.9. Optimization results of various objective function were similar to heat transfer in channel with and without bleed flow. But friction factor was lower than channel without bleed flow.

• 제어로봇시스템학회논문지
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• 제17권8호
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• pp.731-738
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• 2011

In this paper, we introduce an advanced architecture of K-Means clustering-based polynomial Radial Basis Function Neural Networks (p-RBFNNs) designed with the aid of SSOA (Space Search Optimization Algorithm) and develop a comprehensive design methodology supporting their construction. In order to design the optimized p-RBFNNs, a center value of each receptive field is determined by running the K-Means clustering algorithm and then the center value and the width of the corresponding receptive field are optimized through SSOA. The connections (weights) of the proposed p-RBFNNs are of functional character and are realized by considering three types of polynomials. In addition, a WLSE (Weighted Least Square Estimation) is used to estimate the coefficients of polynomials (serving as functional connections of the network) of each node from output node. Therefore, a local learning capability and an interpretability of the proposed model are improved. The proposed model is illustrated with the use of nonlinear function, NOx called Machine Learning dataset. A comparative analysis reveals that the proposed model exhibits higher accuracy and superb predictive capability in comparison to some previous models available in the literature.

• International Journal of Fluid Machinery and Systems
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• 제9권3호
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• pp.229-236
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• 2016

Exergetic analysis was introduced in optimization of a rotating equilateral triangular internal cooling channel with staggered square ribs to maximize the net exergy gain. The objective function was defined as the net exergy gain considering the exergy gain by heat transfer and exergy losses by friction and heat transfer process. The flow field and heat transfer in the channel were analysed using three-dimensional Reynolds-averaged Navier-Stokes equations under the uniform temperature condition. Shear stress transport turbulence model has been selected as a turbulence closure through the turbulence model test. Computational results for the area-averaged Nusselt number were validated compared to the experimental data. Three design variables, i.e., the angle of rib, the rib pitch-to-hydraulic diameter ratio and the rib width-to-hydraulic diameter ratio, were selected for the optimization. The optimization was performed at Reynolds number, 20,000. Twenty-two design points were selected by Latin hypercube sampling, and the values of the objective function were evaluated by the RANS analysis at these points. Through optimization, the objective function value was improved by 22.6% compared to that of the reference geometry. Effects of the Reynolds number, rotation number, and buoyancy parameter on the heat transfer performance of the optimum design were also discussed.

• 소성∙가공
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• 제20권6호
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• pp.450-455
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• 2011

This paper presents an inverse design methodology for the cross section geometry of mold spring with a rectangular cross section as the starting material for a coiling process. The cross-sections of mold springs are universally rectangular, as the parallel sides minimize the possibility of failure under high service loads. Pre-coiled wires are initially designed to have a trapezoidal cross section, which becomes a rectangle by the coiling process. This study demonstrates a numerical exercise to predict changes in the sectional geometry in spring manufacture and to obtain the initial cross section which becomes the exact rectangle desired from the manufacturing process. Finite element analysis was carried out to calculate the sectional changes for various mold springs. Geometrical parameters were the widths at inner and outer radii, the inner and the outer corner radii, and the height. A partial least square regression analysis was carried out to find the main contributing factors for deciding initial design values. The height and the width mainly affected various initial parameters. The initial width at the inner radius was mostly affected by various specification parameters.

• 한국통신학회논문지
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• 제34권11C호
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• pp.1113-1121
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• 2009

본 논문에서는 기지국간 간섭이 큰 다중기지국 환경에서 multiple-input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) 시스템을 위한 파일럿 시퀀스 설계 방법 및 채널 추정 기법을 제안한다. 제안 파일럿 시퀀스의 경우 평균 제곱 오류치 (Mean Square Error)를 최소화시키며, 설계된 파일럿에 적합한 채널 추정 방법을 제안한다. 제안된 파일럿 시퀀스 및 채널 추정 기법은 추 시퀀스의 상관관계 특성을 이용해 설계되며 모의실험을 통해 설계된 파일럿 시퀀스를 이용한 채널 추정 기법이 기지국간 간섭을 완화에 효과적임을 보여준다.

• 한국정보통신학회논문지
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• 제4권1호
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• pp.89-96
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• 2000

본 논문에서는 정방형 도파관을 이용한 커러게이트 편파기의 설계이론에 대해 제안하였다. 도파관의 불연속 경계면의 특성을 해석하고 낮은 정재파비를 얻기 위해 수정된 $TE^\chi_mn$모드 정합법과 커러게이트 지수함수를 편파기 설계에 적용하였다. 그 결과 11.7-15.8GHz 대역에서 $90^{\circ}$에 가까운 위상천이 각을 갖는 광대역 특성을 얻을 수 있었다. 특히, 11.7-12.0GHz, 14.5-14.8GHz 주파수 대역에서 위상천이 각과 최대 정재파비 및 축비가 각각 $90^{\circ},\pm1^{\circ}$, 1.03, 1.0001로 나타나 300MHz의 대역폭을 갖는 편파기를 설계할 수 있었다.

• Computers and Concrete
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• 제21권6호
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• pp.661-667
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• 2018

The purpose of this study was to model and design a concrete catenary shell using a modern computer program without performing experiments. The modeling idea stems from the study by Pendergrast, but he listed supplementary items that should be improved in his paper. This study aims to resolve those issues and overcome the drawbacks of the study by Pendergrast. The process of experiment for the design of a catenary shell was reproduced by Grasshopper script. In order to ensure credibility, two models designed from the Grasshopper script were analyzed using a finite element program, SAP2000; one is a square-based catenary shell and the other is a special catenary shell called as the Naturtheater $Gr{\ddot{o}}tzingen$ shell, which was completed in 1977. First, the developed modeling approach was proved to be reasonable from the analysis of the square-based shell. The reliability was further confirmed by a comparison between the current and previous analysis results for the Naturtheater $Gr{\ddot{o}}tzingen$ shell.

• Steel and Composite Structures
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• 제46권4호
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• pp.577-589
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• 2023

In this study, on-site testing was carried out to investigate the vibration performance of a cold-formed thin-walled steel floor system. Ambient vibration, walking excitation (single and double persons), and impulsive excitation (heel-drop and jumping) were considered to capture the primary vibration parameters (natural frequencies, damping ratios, and mode shapes) and vertical acceleration response. Meanwhile, to discuss the influence of cement fiberboard on structural vibration, the primary vibration parameters were compared between the systems with and without the installation of cement fiberboard. Based on the experimental analysis, the cold-formed thin-walled steel floor possesses high frequency (> 10 Hz) and damping (> 2%); the installed cement fiberboard mainly increases the mass of floor system without effectively increasing the floor stiffness and may reduce the effects of primary vibration parameters on acceleration response; and the human-structure interaction should be considered when analyzing the vibration serviceability. The comparison of the experimental results with those in the AISC Design Guide indicates that the cold-formed thin-walled steel floor exhibits acceptable vibration serviceability. A crest factor 𝛽_rp (ratio of peak to root-mean-square accelerations) is proposed to determine the root-mean-square acceleration for convenience.

• 정보처리학회논문지B
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• 제12B권4호
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• pp.379-386
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• 2005

본 논문은 다차원 서브밴드 필터 뱅크에서 양자화 효과에 대한 분석과 그에 따른 최적의 필터 설계 방법에 대한 이론을 제안한다. 기존의 서브밴드 필터뱅크에 대한 연구에서 양자화 과정에 대한 고려는 매우 미미하였다. 본 연구에서는 확률 밀도에 최적화된 양자화기가 이득에 무상관성 잡음이 더하여진 비선형 형태로 모델링 되어 서브밴드 구조에 결합된다. 분석/합성 필터 뱅크에 다위상 분리 방법을 적용하여 양자화 과정에 의한 출력에서의 MSE가 유도되며 이 에러의 최소화 과정을 통하여 최적의 필터 설계 방법이 개발된다. 또한 5점형 구조의 표본화 격자를 이용한 최적의 비분리 파라유니터리와 이중직교 필터의 설계와 이를 이용한 영상 데이터의 압축 및 복원 과정을 통하여 성능 분석을 한다. 시뮬레이션 결과 제안한 설계방법에 따른 필터가 기존의 단순한 PR 서브밴드 필터보다 영상의 압축 및 복원에서 10에서 20퍼센트 정도의 MSE 감소를 보여주었고 낮은 비트율에서 특히 우수한 성능을 나타내었다.

• 한국터널지하공간학회 논문집
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• 제14권5호
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• pp.485-501
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• 2012

본 연구에서는 비개착 공법에서 상부구조물의 하중을 지지하는데 유용한 사각형 강관의 관입이 지반에 미치는 영향을 파악하고자, 모형토조에 강사장치를 이용하여 상대밀도가 일정한 모래지반을 조성하고, 조성된 모래지반에 모형 오거에 의한 굴착과 동시에 사각형 강관이 관입되는 모형 토조실험을 실시하였다. 실험 결과, 토피고가 낮을 경우에는 사각형 강관 주변의 모든 방향으로 대체로 균등하게 영향범위가 나타난 반면, 토피고가 높아질수록 사각형 강관 관입에 의한 영향범위는 주로 강관 상부에서 넓게 나타나고, 특히 상부 영역의 수평 변형률에 크게 영향을 미치는 것으로 나타났다. 특히, 사각형 강관 상부의 모래 표면의 변위는 무차원 관입속도가 약 0.2일 경우에 최소로 나타났다. 또한 사각형 강관의 관입속도가 일정할 경우, 오거의 회전속도에 따라 모래 표면의 변위량이 달라지는 것으로 나타나, 안전시공을 위해서는 시공조건에 적합한 무차원 관입속도의 선정이 중요하다는 것을 알 수 있다.