• International Journal of Air-Conditioning and Refrigeration
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• 제16권1호
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• pp.1-8
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• 2008

Numerical optimization for design of a blade stacking line of a low speed axial flow fan with a fast and elitist Non-Dominated Sorting of Genetic Algorithm(NSGA-II) of multi-objective optimization using three-dimensional Navier-Stokes analysis is presented in this work. Reynolds-averaged Navier-Stokes(RANS) equations with ${\kappa}-{\varepsilon}$ turbulence model are discretized with finite volume approximations and solved on unstructured grids. Regression analysis is performed to get second order polynomial response which is used to generate Pareto optimal front with help of NSGA-II and local search strategy with weighted sum approach to refine the result obtained by NSGA-II to get better Pareto optimal front. Four geometric variables related to spanwise distributions of sweep and lean of blade stacking line are chosen as design variables to find higher performed fan blade. The performance is measured in terms of the objectives; total efficiency, total pressure and torque. Hence the motive of the optimization is to enhance total efficiency and total pressure and to reduce torque.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.19-21
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• 2008

The purpose of this paper is the optimal design of a single-phase LSPM(Line-Start Permanent Magnet Motor). A single-phase LSPM has a permanent magnet in the rotor that is same as induction motor. For that reason, magnet is operated by breaking torque in starting region and alignment torque in driving region. Therefore, we need the design process considering the trade-off relationship. In this paper, we propose the design process of a single-phase LSPM for a high starting torque and efficiency with equivalent circuit and FEM. And we use Taguchi Method for considering tolerance in manufacture. Finally, we compared the LSPM that is designed in this paper and conventional induction motor.

• Journal of Mechanical Science and Technology
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• 제14권9호
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• pp.1005-1012
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• 2000

Numerical optimization techniques combined with a three-dimensional thin-layer Navier-Stokes solver are presented to find an optimum shape of a stator blade in an axial compressor through calculations of single stage rotor-stator flow. Governing differential equations are discretized using an explicit finite difference method and solved by a multi-stage Runge-Kutta scheme. Baldwin-Lomax model is chosen to describe turbulence. A spatially-varying time-step and an implicit residual smoothing are used to accelerate convergence. A steady mixing approach is used to pass information between stator and rotor blades. For numerical optimization, searching direction is found by the steepest decent and conjugate direction methods, and the golden section method is used to determine optimum moving distance along the searching direction. The object of present optimization is to maximize efficiency. An optimum stacking line is found to design a custom-tailored 3-dimensional blade for maximum efficiency with the other parameters fixed.

• Bulletin of the Korean Chemical Society
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• 제32권6호
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• pp.2039-2044
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• 2011

A semi-continuous and automated method for quantifying atmospheric ammonia at the parts per billion level has been developed. The instrument consists of a high efficiency diffusion scrubber, an electrolytic on-line anion exchange device, and a conductivity detector. Water soluble gases in sampled air diffuse through the porous membrane and are absorbed in an absorbing solution. Interferences are eliminated by using an anion exchange devises. The electrical conductivity of the solution is measured without chromatographic separation. The collection efficiency was over 99%. Over the 0-200 ppbv concentration range, the calibration was linear with $r^2$ = 0.99. The lower limit of detection was 0.09 ppbv. A parallel analysis of Seoul air over several days using this method and a diffusion scrubber coupled to an ion chromatography system showed acceptable agreement, $r^2$ = 0.940 (n = 686). This method can be applied for ambient air monitoring of ammonia.

• 한국산학기술학회논문지
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• 제9권1호
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• pp.87-92
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• 2008

본 논문은 초고속 통신 사업자가 적은 비용으로 고효율의 광 통신망 구축을 할 수 있는 설계 방안에 대해 제시한다. 하나의 광 코어를 사용하여 다중의 광 신호를 전송할 수 있는 기술인 CWDM과 DWDM기술에 대하여 비교 분석하고, 고속의 데이터의 장거리 전송을 안전하게 할 수 있는 OPTICAL 재생기 기술에 대한 고찰을 통해 장거리 전송에서 나타나는 광 신호의 품질 저하를 TX/RX단의 안정화를 통한 보정에 대해 기술한다. CWDM기반 선로공유장치는 4:1 집선 용 가입자 망을 제공하여 집선 효율이 8배 증가된다.

• 전기학회논문지
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• 제65권11호
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• pp.1813-1819
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• 2016

In this paper, LS-SynRM (Line Start-Synchronous Reluctance Motor) has been attracting attention in replace of induction motor which hardly provides high efficiency. Compared to induction motor, LS-SynRM has better efficiency per unit area. This study demonstrated the electromagnetic design methods of LS-SynRM while maintaining the frame of existing IE3 induction motor for blower. We documented the design procedures for generating high saliency which is the most essential and mechanical stress analysis is also treated. In conclusion, we proved the validity of our design by manufacturing and testing our LS-SynRM models.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(2)
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• pp.704-708
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• 2004

Recently, many nation have released standard such as IEC 61000-3-2 and IEEE 59, which impose a limit on the harmonic current drawn by equipment connected to AC line in order to prevent the distortion of an AC Line. Therefore, Plasma Display Panel (PDP) which is highlightened in digital display device also has the Power Factor Correction (PFC) circuit to meet the harmonic requirements. In PDP power module, the conventional boost converter is usually used for the PFC circuit. However, it comes serious thermal problem on it's bridge diode due to heat of PDP, and therefore the system stability is not guaranteed. In this paper, the bridgeless boost converter, which is used for PFC circuit of the PDP power module, is designed and verified the possibility of the application in a practical product in a view of efficiency, component count, temperature and etc.

• 한국통신학회논문지
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• 제32권1B호
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• pp.17-21
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• 2007

본 논문에서는 멀티미디어 네트워크상에서 우선순위가 높은 서비스의 QoS를 보장하며 동시에 프로세서의 에너지 효율을 최대화하는 적응적 온라인 프로세서 관리기법을 제안하였다. 이 기법은 현재 네트워크의 트래픽 상황을 기반으로 하여 실시간으로 프로세서를 관리한다. 제안된 방법의 가장 큰 특징은 상호 상충하는 다양한 성능 메트릭들 사이에 적정한 균형을 이루어 안정적으로 시스템을 운영하는데 있다. 컴퓨터 시뮬레이션을 통하여 기존에 제안된 프로세서 관리기법에 비해 본 논문에서 제안된 방법이 다양한 트래픽 상황에서 우수한 성능을 가지는 것을 확인할 수 있었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1993년도 추계학술대회 논문집
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• pp.60-63
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• 1993

We have prepared n-CdS/p-InP hetero- junction solar cells by thermal evaporation. The efficiency under the optium conditions without the grid line contact was 7.3%, and the solar cell having glid line contact with SiO AR coating was the open circuit voltage of 0.71V, the short circuit voltage current density of 15mA/cm$^2$, the fill factor of 0.73, and the efficiency of 11.5%. As result of photoresponse in 400-1000nm wavelength the cutoff of n-CdS/p-InP solar at 500nm results from absorption by the CdS \"window\" and the cutoff at 930 nm result from absorption by the InP.

• 한국통신학회논문지
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• 제18권1호
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• pp.39-46
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• 1993

본 논문에서는 Ku 밴드 VSAT 안테나로서 효율 60% 이상, 사이드로블 포락선 29-25 $log\theta$를 만족하는 저 사이드로브 오프셋 파라볼라 반사경 안테나를 설계하고 시작했다. 안테나의 해석을 위해서는 Zernike 다항식을 이용한 새로운 급수전개법을 적용하였다. 시작안테나의 복사패턴 측정치는 이론적 계산치에 근접하는 것으로 타나탔으며, 첫번째 사이드로브 레벨을 제외하고 이득, 효율 및 사이드로브 포락선 등은 설계사양을 충분히 만족하는 것으로 나타났다.