• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1951-1956
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• 2004

The transient nature and complex flow geometries of two-phase gas-liquid flows cause fundamental difficulties when measuring flow velocity using an electromagnetic flowmeter. Recently, a current-sensing flowmeter was introduced to obtain measurements with high temporal resolution (Ahn et $al.^{(1)}$). In this study, current-sensing flowmeter theory was applied to measure the fast velocity transients in slug flows. To do this, the velocity fields of axisymmetric gas-liquid slug flow in a vertical pipe were obtained using Volume-of-Fluid (VOF) method and the virtual potential distributions for the electrodes of finite size were also computed using the finite volume method for the simulated slug flow. The output signal prediction for slug flow was carried out from the velocity and virtual potential (or weight function) fields. The flowmeter was numerically calibrated to obtain the cross-sectional liquid mean velocity at an electrode plane from the predicted output signal. Two calibration parameters are required for this procedure: a flow pattern coefficient and a localization parameter. The flow pattern coefficient was defined by the ratio of the liquid resistance between the electrodes for two-phase flow with respect to that for single-phase flow, and the localization parameter was introduced to avoid errors in the flowmeter readings caused by liquid acceleration or deceleration around the electrodes. These parameters were also calculated from the computed velocity and virtual potential fields. The results can be used to obtain the liquid mean velocity from the slug flow signal measured by a current-sensing flowmeter.

• 한국음향학회지
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• 제38권2호
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• pp.145-153
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• 2019

적응빔형성 기법은 부엽을 줄이고 약한 신호에 대한 탐지 성능을 향상시킨다. MVDR(Minimum Variance Distortionless Response)과 같은 일반적인 적응빔형성 기법은 설계한 가중벡터와 실제 입사신호의 조향벡터의 불일치에 대해 매우 민감하다. 또한 센서 수가 많은 어레이를 이용하여 광대역 적응빔형성을 할 경우 공분산행렬을 산출하기 위해 긴 관측시간과 많은 연산량이 요구된다. 본 논문은 센서 수가 많은 수동 선배열 소나의 광대역 적응빔형성 성능향상 및 안정성을 위해 WBRCB(Wideband Robust Capon Beamforming)를 적용하였다. 불일치 요소에 강인한 WBRCB 구현을 위해 다양한 불일치 요소를 반영하여 최적의 불일치 파라미터를 도출하였다. 도출된 파라미터를 반영한 WBRCB 기법을 시뮬레이션 및 실험데이터에 적용하여 수동 선배열 소나의 광대역 적응빔형성 성능 향상을 검증하였다.

• 한국차세대컴퓨팅학회논문지
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• 제13권5호
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• pp.39-50
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• 2017

이동 객체에 대한 추적 기술은 최근 중요성이 강조되고 있는 동영상 이해에서 가장 핵심적인 기술의 하나라 할 수 있다. 하지만, 동영상이 가지는 조명의 불안정, 객체의 크기나 형태 변화, 카메라 움직임, 그리고 중첩 등으로 인해 동영상 내의 이동 객체 추적은 많은 어려움을 가지고 있다. 객체 추적의 가장 대표적인 종래의 방법인 칼만 필터와 파티클 필터의 문제점을 개선하는 방법으로 스웜 기반의 방법이 제안되어 있으나 동적으로 변화하는 이동 객체의 특징을 반영하는 개선된 알고리즘이 요구된다. 본 논문에서는 이러한 특징을 반영하여 파티클 스웜 최적화 방법에서 사용되는 파라미터 중 가중치 값을 동적으로 변화하는 적응적 파라미터 제어 방법을 제안한다. 각 파티클을 특성에 따라 3가지 종류로 구분하고 각각 서로 다른 가중치 값을 부여하는 방식으로 객체 추적의 성능을 개선할 수 있다. 제안된 알고리즘의 적용 결과 중첩 또는 예측하기 어려운 움직임 등과 같은 객체의 비선형적인 움직임이 있는 동영상에 대해 기존 파티클 스웜 방식에 비해 현저한 성능 개선을 보이는 것을 확인할 수 있었다.

• 충청수학회지
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• 제28권3호
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• pp.491-497
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• 2015

In this paper, we have suggested an extended double Newton's method with sixth-order convergence by considering a control parameter ${\gamma}$ and a weight function H(s, u). We have determined forms of ${\gamma}$ and H(s, u) in order to induce the greatest order of convergence and established the main theorem utilizing related properties. The developed theory is ensured by numerical experiments with high-precision computation for a number of test functions.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.135-138
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• 1999

The objective of this study is to investigate the compressive strength property of antiwashout underwater concrete with curing water through experimental researches. Type of casting and curing water(fresh water, sea water) are used as main experimental parameter, additionally a few variables affecting compressive strength property are used ; water-cement ratio (45%, 48%, 50%, 52%, 55%), and unit weight of admixtures (antiwashout underwater agent ; 0.6%, 0.8%, 1.0%, 1.2%, 1.4% of unit weight of water, superplasticizer ; 0.5%, 1.0%, 1.5%, 2.0%, 2.5% of unit weight of cement)) Compressive strength level of antiwashout underwater concrete which was cast and cured in fresh water is higher than other one. Consequently, incremental modulus has to increase when the antiwashout underwater concrete is made use of underwater work from ocean.

• Industrial Engineering and Management Systems
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• 제8권4호
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• pp.247-256
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• 2009

In mass production industries such as steel making that have large equipment, sudden stops of production process due to machine failure can cause severe problems. To prevent such situations, machine diagnosis techniques play important roles. Many methods have been developed focusing on this subject. In this paper, we propose a method for the early detection of the failure on rotating machine, which is the most common theme in the machine failure detection field. A simplified method of calculating autocorrelation function is introduced and is utilized for ARMA model identification. Furthermore, an absolute deterioration factor such as Bicoherence is introduced. Machine diagnosis can be executed by this simplified calculation method of system parameter distance with weight. Proposed method proved to be a practical index for machine diagnosis by numerical examples.

• 한국수산과학회지
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• 제53권5호
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• pp.790-793
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• 2020

Length-weight relationships (LWR) for 27 fish species inhabit Southern sea in Korea were investigated to describe several biological characters. Total 7,399 individuals were collected by R/V Tamgu-20 using bottom trawl between 2018 to 2019 and were identified as 19 families and 27 species. Parameter b ranged from 2.414 to 3.472. Thirteen species among 27 species showed isometric growth (b=3), six species showed negative allometry (b<3) and eight species showed positive allometry (b>3). The results of this study provide useful basic biological information about 27 fishes and are highly reliable due to use of data measured directly.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 1993년도 Fifth International Fuzzy Systems Association World Congress 93
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• pp.1218-1221
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• 1993

The elevator group control systems are the control systems that manage systematically three or more elevators in order to efficiently transport the passingers. In the elevator group control system, the area-weight which determines the load biases of elevators is a control parameter closely related to the system performance. This paper proposes a fuzzy model based method to determine the are-weight. The proposed method uses a two-stage fuzzy inference model which is built by the study of area-weight properties and expert knowledge. The proposed method shows the more desirable results than the conventional method in the simulations that use real traffic data.

• 정보학연구
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• 제9권4호
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• pp.65-74
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• 2006

The back propagation of neural networks has the problems of falling into local minimum and delay of the speed by the iterative learning. An algorithm to solve the problem and improve the speed of the learning was already proposed in[8], which updates the learning parameter related with the connection weight. In this paper, we propose the algorithm generating initial weight to improve the efficiency of the algorithm by offering the difference between the input vector and the target signal to the generating function of initial weight. The algorithm proposed here can classify more than 98.75% of the handwritten digits and this rate shows 30% more effective than the other previous methods.

• Bulletin of the Korean Chemical Society
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• 제20권11호
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• pp.1323-1328
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• 1999

Interdiffusion between two partially miscible polymers of similar chemical structures with different molecular weights is characterized theoretically by using the reptation model for the interdiffusion. This model provides more reliable results than the early Rouse model for same molecular weights, compared with the experiments. Furthermore, by introducing the molecular weight ratio R into the reptation model, we can see the dynamic effect of molecular weight on the diffusion behaviors of the asymmetric system. Near the critical point the diffusion behaviors of asymmetric binary polymer mixtures are well characterized by the interfacial width W(t), the mass transport M(t) for the different values of the Flory Χ parameter and different molecular weight ratios ofpolymers of the diffusion couple. These two quantities and composition profiles by this model give betteragreement with experiments.