• 경영과학
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• 제19권1호
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• pp.189-196
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• 2002

Data clustering is often one of the first steps in data mining analysis. It Identifies groups of related objects that can be used as a starling point for exploring further relationships. This technique supports the development of population segmentation models, such as demographic-based customer segmentation. This paper Purpose to present the development of two phase hierarchical clustering algorithm for group formation. Applications of the algorithm for product-customer group formation in customer relationahip management are also discussed. As a result of computer simulations, suggested algorithm outperforms single link method and k-means clustering.

• Journal of Information Processing Systems
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• 제5권4호
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• pp.237-242
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• 2009

The classical vehicle routing problem (VRP) can be extended by including customers who want to send goods to the depot. This type of VRP is called the vehicle routing problem with pickups and deliveries (VRPPD). This study proposes a novel way to solve VRPPD by introducing a two-phase heuristic routing algorithm which consists of a clustering phase and uses the geometrical center of a cluster and route establishment phase by applying a two-way search of each route after applying the TSP algorithm on each route. Experimental results show that the suggested algorithm can generate better initial solutions for more computer-intensive meta-heuristics than other existing methods such as the giant-tour-based partitioning method or the insertion-based method.

• 전기학회논문지
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• 제57권7호
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• pp.1167-1174
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• 2008

The measurement of two-dimensional magnetic properties of electrical steel sheet using single sheet tester (SST) requires to control the B-waveform as sinusoidal. The SST electric circuit, in general, has inductance, and this makes the phase lag in electric current. For this reason, the induced voltages of H- or B-coil may have phase difference from the exciting voltage. In this paper, a new algorithm is developed to compensate the phase difference and makes the B-waveform control efficient. The developed algorithm experimentally calculates the phase difference based on the measured waveform of the induced voltage for the magnetic field intensity along transverse direction. By using the proposed algorithm, the two-dimensional magnetic properties of grain-orientated electrical steel sheet (30PG110) is measured up to 2T. By comparing the measured B- and H-waveforms, the effectiveness of the proposed algorithm is proven.

• 전자공학회논문지A
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• 제29A권11호
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• pp.62-69
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• 1992

In this paper, a measurement system of surface flatness test using 2-Bucket algorithm phase-shifting interferometry is designed and constructed. In the conventional surface flatness test system using phase shifting interferometry, it is needed more than 3 fringe datas but we propose 2-Bucket algorithm phase-shifting interferometry which only uses two fringe datas. 2-Bucket algorithm uses the relative phase differences of the neighbour pixels. If we watch the result of phase-shift error test simulation, 2-Bucket algorithm has the same calculating values that 3-Bucket, 4-Bucket and 5-Bucket algorithm have them. Experiments have been carried out on the silicon wafer. The measurement of silicon wafer's surface flatness shows that the flatness topography using 2-Bucket algorithm is similar to that of other algorithms.

• 천문학회지
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• 제34권4호
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• pp.237-241
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• 2001

Our goal is to present a simple volume-of-fluid type interface-tracking algorithm to compressible two-phase flow in two space dimensions. The algorithm uses a uniform underlying Cartesian grid with some cells cut by the tracked interfaces into two subcells. A volume-moving procedure that consists of two basic steps: (1) the update of volume fractions in each grid cell at the end of the time step, and (2) the reconstruction of interfaces from discrete set of volume fractions, is employed to follow the dynamical behavior of the interface motion. As in the previous work with a surface-tracking procedure for general front tracking (LeVeque & Shyue 1995, 1996), a high resolution finite volume method is then applied on the resulting slightly nonuniform grid to update all the cell values, while the stability of the method is maintained by using a large time step wave propagation approach even in the presence of small cells and the use of a time step with respect to the uniform grid cells. A sample preliminary numerical result for an underwater explosion problem is shown to demonstrate the feasibility of the algorithm for practical problems.

• 전력전자학회논문지
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• 제26권4호
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• pp.256-262
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• 2021

Six-phase motors can be used in industrial applications, such as an electric vehicle, due to their high reliability and low current magnitude per phase. An asymmetrical PMSM with two sets of three-phase windings is a commonly used structure for six-phase motors, with each winding set demonstrating a phase difference of 30°. Although the asymmetrical PMSM presents low torque ripples, its dynamic torque response deteriorates due to coupled components in the two three-phase windings. The decoupled VSD control is applied to eliminate the coupling effect. Load ratio control of two inverters for the six-phase PMSM is proposed in this study. DQ currents are controlled on the basis of two synchronous reference frames, and the six-phase drive system can be changed to a three-phase drive system when one inverter presents fault conditions. The operation and effectiveness of the proposed algorithm is verified through simulation and experiments. The six-phase drive system is transferred to a three-phase drive system by changing the current reference of the second DQ reference frame. Moreover, control of both torque and speed exhibits satisfactory performance before and after the mode change.

• 한국정보과학회논문지:데이타베이스
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• 제36권2호
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• pp.123-138
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• 2009

최근 웹 서비스 관련 기술들이 많은 관심을 받고 있다. 그 중 하나인 웹 서비스 컴포지션에 대한 연구도 활발히 진행되고 있다. 웹 서비스 컴포지션은 기존에 존재하던 웹 서비스들을 조합하여 마치 하나의 서비스처럼 보여 주는 것이다. 웹 서비스 컴포지션을 사용하면 기존에 존재하지 않던 웹 서비스의 기능도 제공할 수 있으며 사용자에게 더 많은 질의 결과를 줄 수도 있다. 기존의 많은 웹 서비스 컴포지션 관련 연구들은 전향 혹은 후향 체인 방식을 사용하였다. 그러나 전향 체인 방식이나 후향 체인 방식은 질의와 상관없는 방향을 탐색하는 경우가 많기 때문에 많은 시간이 걸린다는 단점이 있다. 전향과 후향을 모두 사용하여 2단계로 컴포지션을 찾는 방식도 있으나, 이 방식은 컴포지션에 포함되지 않아도 되는 웹 서비스를 포함한 결과를 낸다는 문제점이 있다. 본 논문에서는 전향 단계와 후향 단계를 거쳐 웹 서비스 컴포지션을 찾는 2단계 웹 서비스 컴포지션 탐색 방법을 제안하였다. 전향 단계에서는 미리 구축한 연결 인덱스를 사용하여 좀 더 빠르게 후보 컴포지션을 찾는다. 후향 단계에서는 토큰을 사용하여 후보 컴포지션을 잉여 웹 서비스가 포함되지 않은 컴포지션으로 분해한다. 실험을 통해 2단계 웹 서비스 컴포지션이 기존의 한 방향으로 진행하는 방식보다 더 효율적이라는 것을 보였다. 또한 기존의 2단계 방식보다 더 많은 컴포지션 결과를 사용자에게 돌려주면서도 실행 시간 면에서 기존의 2단계 방식에 필적한다는 것을 보였다.

• 전자공학회논문지SC
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• 제41권3호
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• pp.25-32
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• 2004

본 논문에서는 두 개의 사인파 신호의 위상 차이를 계산해 내기위한 개선된 위상 측정 알고리즘을 제안하였다. 이 알고리즘은 두 개의 입력신호의 양자화된 샘플링 데이터를 사용하여 위상과 크기를 구해낸다. 측정 알고리즘의 중요 파라메타들은 몇개의 해석식으로 표현되기 때문에 위상을 계산하기 위해 필요한 연산량이 상당히 줄어들고 따라서 더 빠른 속도로 위상을 계산해 낼 수 있게 되었다. 또한 본 논문에서 제시한 알고리즘을 사용하여 입력신호의 한주기 전체를 샘플링할 경우에는 입력신호에 harmonic distortion이 발생하더라도 위상 측정 오차가 전혀 발생하지 않음을 수식으로 증명하였으며 컴퓨터 시뮬레이션을 통하여 이를 확인하였다. 그리고 입력신호에 가우시안 백색 잡음(white gaussian noise)이 발생할 경우에 위상 측정 오차가 얼마나 발생하는 지에 대하여 여러 가지 관점에서 컴퓨터 시뮬레이션을 수행하고 그 결과를 분석하였다.

• The Journal of the Acoustical Society of Korea
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• 제19권2E호
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• pp.8-13
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• 2000

In this paper, we present an adaptive formant tracking algorithm for speech using closed phase WRLS-VFF-VT method. The pitch synchronous closed phase methods is known to give more accurate estimates of the vocal tract parameters than the pitch asynchronous method. However the use of a pitch-synchronous closed phase analysis method has been limited due to difficulties associated with the task of accurately isolating the closed phase region in successive periods of speech. Therefore we have implemented the pitch synchronous closed phase WRLS-VFF-VT algorithm for speech analysis, especially for formant tracking. The proposed algorithm with the variable threshold(VT) can provide a superior performance in the boundary of phone and voiced/unvoiced sound. The proposed method is experimentally compared with the other method such as two channel CPC method by using synthetic waveform and real speech data. From the experimental results, we found that the block data processing techniques, such as the two-channel CPC, gave reasonable estimates of the formant/antiformant. However, the data windows used by these methods included the effects of the periodic excitation pulses, which affected the accuracy of the estimated formants. On the other hand the proposed WRLS-VFF-VT method, which eliminated the influence of the pulse excitation by using an input estimation as part of the algorithm, gave very accurate formant/bandwidth estimates and good spectral matching.

• 한국해양공학회지
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• 제29권3호
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• pp.263-269
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• 2015

This paper proposes a new approach for solving the weather routing problem by dividing it into two phases with the goal of fuel saving. The problem is to decide two optimal variables: the heading angle and speed of the ship under several constraints. In the first phase, the optimal route is obtained using the Real-Time Adaptive A* algorithm with a fixed ship speed. In other words, only the heading angle is decided. The second phase is the speed scheduling phase. In this phase, the original problem, which is a nonlinear optimization problem, is converted into a geometric programming problem. By solving this geometric programming problem, which is a convex optimization problem, we can obtain an optimal speed scheduling solution very efficiently. A simple case of numerical simulation is conducted in order to validate the proposed method, and the results show that the proposed method can save fuel compared to a constant engine output voyage and constant speed voyage.