• 한국유체기계학회 논문집
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• 제11권2호
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• pp.38-45
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• 2008

This study presents a numerical procedure to optimize the compressor design to increase the surge margin of compressor with response surface method (RSM). The Box-Behnken design method is used to reduce the number of calculation for fitting the second-order response surface. In order to consider the increase of surge margin during numerical optimization without any calculation at the surge point, the slope of compressor characteristic curve at the design point is suggested as an objective function in the present optimization problem. Mean line performance analysis method is used to get the design and off-design characteristic curves of centrifugal compressor. The impeller exit angle, impeller exit height and impeller radius are chosen as design variables. The optimum shapes show the increase of surge margin for the surge margin optimization and increase of efficiency for the efficiency optimization in comparison with an initial shape.

• 소음진동
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• 제7권5호
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• pp.781-787
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• 1997

A new method is presented to determine two fundamental acoustic quantities of sound-absorbing materials such as characteristic impedance and propagation constant. In this study, the surface acoustic impedances of sound-absorbing materials are measured using the impedance tube and the anechoic chamber to determine the above acoustic quantities. The measured results are given for two typical sound-absorbing materials(glass wool and urethane foam) int the frequency range between 150 and 1, 600 Hz. The results are verified by other two known methods, which are Smith & Parrott method and Utsuno et al. method. The absorption coefficients calculated from the empirical models(Miki model for glass wool and Jung model for urethane foam) and two quantities by present method are in good agreement with the measured values.

• 한국광학회지
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• 제4권3호
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• pp.317-322
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• 1993

본 논문에서는 특성행렬을 사용하여 비선형 집적거울 etalon의 입출력 특성을 해석하는 방법을 제시한다. 빛의 세기에 따른 매질의 굴절률 및 흡수율의 변화 특성을 알면, 관계식과 특성행렬식을 결합하여 집적거울 etalon의 비선형 특성을 해석할 수 있다. 이 방법은 파장에 따른 각 거울의 반사율(크기와 위상)을 일일이 구하지 않고, etalon의 구조가 주어지면 바로 임의의 파장에서의 etalon의 입출력 특성을 해석할 수 있다. 또한, 특성행렬식을 이용하여 비선형 집적거울 etalon에서의 쌍안정성을 보였다.

• 한국전자파학회논문지
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• 제8권6호
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• pp.629-635
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• 1997

주기적인 축방향 슬롯이 있는 동축선로 도파관 구조에 TE 편파가 입사될 때 특성모드 이론(characteristic mode theory)을 사용하여 가중 고유방정식(weighted eigenvalue equation)을 유도하고, 일반적인 수치방볍 으로 특성값(characteristic values)과 특성전류(characteristic currents)를 구하여 미지의 등가 자기전류, 산 란패턴과 RCS(radar cross section)를 구하였다. 그리고 이 수치 결과들을 모멘트법을 이용하여 구한 결과들과 각각 비교하여 특성모드에 의한 해석방볍의 타당성을 보였다.

• 한국측량학회지
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• 제18권1호
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• pp.67-73
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• 2000

공업화, 도시화가 지속되어 내륙 수계의 수질은 날로 오염되고 있으며, 이와 함께 호수의 수질 또한 악화되어 호수 수질오염 문제는 새로운 수질관리 방안을 필요로 하게 되었다. 본 연구는 GSIS(Geo-Spatial Information System)을 이용한 호수의 수질 관리를 위한 방안의 초기단계로서 GSIS 환경에서 호수의 각종 수리학적 특성 정보를 자동 추출할 수 있는 방안에 대하여 연구하였으며 또한, 추출된 호수의 수리학적 특성정보의 활용의 일례로서 유한차분법을 이용한 호수 수체 흐름의 특성분석을 수행하였다. 수체 흐름의 특성분석에 필요한 각종 수리학적 특성 정보 추출을 GSIS를 이용하여 자동화하므로서 분석작업을 효율적으로 수행할 수 있었으며, 특히 호수단면 정보의 추출을 출력물의 형태가 아닌 다른 정보와 결합하여 분석 가능한 형태로 추출하므로서 호수의 성층현상분석과 같은 호수의 단면정보가 필수적인 각종 분석을 GSIS 환경에서 가능하도록 하였다.

• 한국통신학회논문지
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• 제26권7A호
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• pp.1257-1263
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• 2001

In the paper, the p-ranks and characteristics polynomials of cyclic difference sets are derived by expanding the trace expression of their characteristic sequences. By using this method, it is shown that the 3-ranks and characteristic polynomials of Helleseth-Kumar-Martinsen (HKM) difference set and Lin difference set can be easily obtained.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -1
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• pp.42-45
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• 2002

A novel characteristic value extraction method based on morphological spatial frequency is proposed. Morphological spatial frequency defined by morphological pattern distribution function is introduced. Superiority of the method was proved for various images by experiment. Furthermore the fact that the proposed method does not need threshold to obtain binary image provides its applicability to content-based image retrieval.

• 대한전기학회논문지
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• 제32권11호
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• pp.387-393
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• 1983

This paper descrives the computational algorithm for determination of system characteristic constants using diakoptic method. When the system charateristic contants of large scale power system are calculated by using sensitivity matrix method which requires the inversion of Jacobian matrix, the necessary computing time and memory requirements increase very largely. Diakoptic mothods is benefit to get around these problems, and it is applied to a model system compared with the integrated method to discuss the efficiency of the algorithm.

• 제어로봇시스템학회논문지
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• 제6권7호
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• pp.568-577
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• 2000

In this paper for an object grasped by a robot hand to work in stiffness control domain we first investigate the number of fingers for successful stiffness modulation in the object operational space. Next we propose a new compliance control method for robot hands which consist of two steps. RIFDS(Resolved Inter-Finger Decoupling Solver) is to decompose the desired compliance characteristic specified in the op-erational space into the compliance characteristic in the fingertip space without inter-finger coupling and RIJDS(Resolved Inter-Joint Decoupling Solver) is to decompose the fingertip space without inter-finger coupling and RIJDS(Resolved inter-Joint Decoupling Solver) is to decompose the compliance characteristic in the finger-tip space into the compliance characteristic given in the joint space without inter-joint coupling. Based on the analysis results the finger structure should be biominetic in the sense that either kniematic redundancy or force redundancy are required to implement the proposed compliance control scheme, Five-bar fingered robot hands are used as an illustrative example to implement the proposed compliance control method. To show the effectiveness of the proposed compliance control method simulations are performed for two-fingered and three-fingered robot hands.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(1)
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• pp.137-140
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• 2003

Shorted-turns can have significant effects on a generator and its performance. Shorted-turn sensor for synchronous generator's field winding have been developed. One of effective method detecting inter-turn short circuits on round rotor winding is a method using sensor detecting. But the method needs duplicate design of sensor for characteristic change according to types and forms of generator Thus sensing skill without sensor depend on change of electric property in generator. For the reason, this paper presents shorted-turns phenomenon and the characteristic analysis of shorted-turns In synchronous generator by using 2-D finite element method(FEM).