• 소음진동
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• 제11권2호
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• pp.234-240
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• 2001

Recently, the regulations from the government and the concerns of people be raised to the interest in exhaust and intake noise of passenger car as much as other vehicles. In these demands, performance prediction software was developed in this paper. In this study, Robust design was used for improving the noise reduction capacity of intake system with the performance prediction software. On the basis of the existing design, length and radius of each component that was thought to be effective to the performance of intake system was selected. At first, factors are arranged by using Ll8 table of orthogonal array and then optimum value can be obtained by modified Ll6 table of orthogonal array.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1660-1665
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• 2003

On this study, we improved the efficiency applying algorithm that is repeatedly using orthogonal array in discrete design space and filling a defect of gradient method in continuous design space. we showed optimal ply angle that maximized 1st natural frequency of CFRP laminated composite cantilever plate by each aspect ratio. A finite element analysis on the CFRP laminated composite cantilever plate using orthogonal array is carried out, and the results are compared with those obtained by modal testing.

• 응용통계연구
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• 제4권1호
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• pp.47-63
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• 1991

다구찌 방법의 핵심인 피라미터 설계의 원리는 제품의 성능특성이 잡음에 둔감하도록 제품이나 공정을 설계하자는 것이다. 다구찌는 이 피라미터 설계를 위해 소위 직교배열이라는 실험계획의 사용을 추천하고 있다. 본 논문의 목적은 이와 같은 다구찌 직교배열의 구성원리를 밝힘으로써 앞으로 보다 적절한 활용과 개선을 위한 자료를 마련하는데 있다.

• ETRI Journal
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• 제33권6호
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• pp.831-840
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• 2011

This paper focuses on codebook-based precoding for space-division multiple access/orthogonal frequency-division multiple access (SDMA-OFDMA) systems aiming to guarantee high throughput for their users as well as to mitigate interference to fixed satellite service (FSS). A systematic design of SDMA codebook for subband-based OFDMA is proposed, which forms multiple orthogonal beams with common spatial null in the direction of a victim FSS earth station (ES). The design enables both transmitter and receiver to independently construct identical codebook by sharing only on the direction angle of an FSS ES, which takes fewer overhead bits than Gram-Schmidt process, a general method satisfying our design criterion. A system-level throughput evaluation shows that the proposed precoding provides superior performance over existing spectrum sharing method, that is, subband deactivation. The spectrum sharing analysis shows that the proposed precoding, even with an estimation error of the direction angles of an FSS ES, causes lower interference than existing precoding, knockdown precoding.

• Journal of Communications and Networks
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• 제9권2호
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• pp.150-158
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• 2007

We consider channel-coded multi-input multi-output (MIMO) orthogonal frequency-division multiplexing (OFDM) transmission and obtain a condition on its signal for it to attain the maximum diversity and coding gain. As this condition may not be realizable, we propose a suboptimal design that employs an orthogonal transform and a space-frequency interleaver between the channel coder and the multi-antenna OFDM transmitter. We propose a corresponding receiving method based on block turbo equalization. Attention is paid to some detailed design of the transmitter and the receiver to curtail the computational complexity and yet deliver good performance. Simulation results demonstrate that the proposed transmission technique can outperform the conventional coded MIMO OFDM and the MIMO block single-carrier transmission with cyclic prefixing.

• 대한기계학회논문집A
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• 제29권10호
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• pp.1369-1376
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• 2005

In structural design, the design variables are frequently selected from certain discrete values. Various optimization algorithms have been developed fDr discrete design. It is well known that many function evaluations are needed in such optimization. Recently, sequential algorithm with orthogonal arrays (SOA), which is a search algorithm for a local minimum in a discrete space, has been developed. It considerably reduces the number of function evaluations. However, it only finds a local minimum and the final solution depends on the initial values of the design variables. A new algorithm is proposed to adopt a genetic algorithm (GA) in SOA. The GA can find a solution in a global sense. The solution from the GA is used as the initial design of SOA. A sequential usage of the GA and SOA is carried out in an iterative manner until the convergence criteria are satisfied. The performance of the algorithm is evaluated by various examples.

• 한국항공우주학회지
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• 제38권5호
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• pp.414-420
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• 2010

본 연구에서는 천음속 날개/동체 모텔에 대한 축소모델 (Reduced Order Model; ROM)의 정확성을 검증하고, Proper Orthogonal Decomposition(POD)을 이용한 최적설계를 통해 그 효율성을 검토하였다. full order 공력해석을 통한 Snapshot을 추출하기 위해 삼차원 오일러 방정식을 이용하였으며, 이들 Snapshot들을 통해 날개/동체 모델 주위 유동장의 거동을 모사하는 POD의 기저벡터를 계산 하였다. 이러한 과정을 거쳐 구축된 축소모텔은 6개의 Case들로 검증하였으며, 그 결과 ROM을 이용해 관심영역에 대한 유동장의 예측을 할 수 있다는 것을 확인하였다. 그리고 ROM을 통한 날개/동체 모델의 최적설계를 수행 하였으며, 그 결과는 반응면모델 (Response Surface Model; RSM)을 이용한 최적설계 결과와 비교 하였다. 이를 통해 ROM을 바탕으로한 최적설계가 RSM을 이용한 것보다 효율적임을 확인하였다.

• Journal of Microbiology and Biotechnology
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• 제16권12호
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• pp.1940-1946
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• 2006

The influence of environmental conditions on the ganoderic acid (GA) content in the fungus Ganoderma lucidum was investigated using a one-factor-at-a-time design and orthogonal design. Among the various medium components examined, sucrose, soybean powder or peptone, ferrous sulfate, and pH 6.0 were the most suitable carbon source (factor A), nitrogen source (factor B), mineral source (factor C), and initial pH (factor D), respectively, for the GA content in the one-factor-at-a-time design. According to the orthogonal design, the order of effect for the four factors on the GA content was A>C>D>B. The best level of factor A was $A_2$ (sucrose) with a value of +0.34 mg/100 mg DW. The optimal treatment combination was $A_2B_1C_3D_1$ with which the GA content reached up to 2.63$\pm$0.011 mg/100 mg DW. The interactions between the mineral ion and the nitrogen source, and the mineral ion and the pH were both highly significant (P<0.01). The highest interaction effect was ($B_2{\times}D_2$) with a value of +0.19 mg/100 mg DW, which was higher than the level effect value for $B_2$ (peptone) and D$_2$ (pH 5.0). Therefore, the results proved that interactions between factors cannot be ignored. The results also indicated the importance of the interactions between the factors, which may help to understand the metabolic pathway leading to triterpene biosynthesis and the expression and regulation of the key enzymes involved.

• 대한기계학회논문집A
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• 제35권10호
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• pp.1273-1279
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• 2011

자동차 압축기는 연비 개선효과를 위해 가변 사판형 압축기를 사용한다. 가변 사판의 회전 토크와 피스톤에 작용하는 압력은 사판의 형상과 변형에 중요한 영향을 미친다. 본 논문은 Chebyshev 직교다항식과 최적화 기법을 이용하여 가변 사판의 최적 형상을 결정하였다. 사판의 설계 요구사항은 정상 운전상태에서 최대 응력과 변형을 최소화하면서 체적을 감소시키는 것이다. 직교배열표, 분산분석과 반응표면최적화 방법은 최적 설계변수를 결정하고 주효과를 찾는데 사용하였다. 최적설계 결과로부터, 사판의 유의한 설계변수를 확인하고 이의 최적해와 설계요구조건 만족에 대한 유용성을 설명하였다.

• 대한기계학회논문집A
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• 제31권1호
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• pp.97-104
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• 2007

Vibration analysis of a rigid body supported by in-parallel linear springs can be greatly simplified by utilizing the conditions for a plane of symmetry. The vibration modes of an oscillatory system having plane of symmetry are classified into the in-plane and out-of-plane modes. From the viewpoint of screw theory, they represent respectively the vibration axes perpendicular to the plane of symmetry and lying in the plane of symmetry. In this paper, the sets of orthogonal and mutually intersecting three springs are used as resilient support of a rigid body. The geometrical conditions for the system to have a plane of symmetry and diagonalized stiffness matrix are presented. From the orthogonality of the vibration modes with respect to the inertia matrix, the geometrical relation between the reaction wrenches and the vibration modes are derived. This geometrical relation is then used to get the cubic design equation for the design of out-of-plane modes. The numerical design example of engine mounts is presented in order to explain the suggested design technique.