• Information Systems Review
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• v.7 no.2
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• pp.23-40
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• 2005

Discovering customers' behavioral patterns from large data set and providing them with corresponding services or products are critical components in managing a current business. However, the diversity of customer needs coupled with the limited resources suggests that companies should make more efforts on understanding and managing specific groups of customers, not the whole customers. The key issue of this paper is based on the fact that the behavioral patterns extracted from the specific groups of customers shall be different from those from the whole customers. This paper proposes the idea of pre-segmentation before developing customer classification models. We collected three customers' demographic and transactional data sets from a credit card, a tele-communication, and an insurance company in Korea, and then segmented customers by major variables. Different churn prediction models were developed from each segments and the whole data set, respectively, using the decision tree induction approach, and compared in terms of the hit ratio and the simplicity of generated rules.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.1
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• pp.57-65
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• 2001

The speed control without a speed sensor is expected strongly to progress reliability, simplicity and cost performance of Induction Motor(I.M) systems. Also, it contributes to expansion of I.M systems into various industrial application fields. This paper investigates a novel speed sensorless control method of I.M considering the secondary resistance identification based on the transientless torque control technique. Especially, this paper aimed at the identification of the secondary resistance simultaneously with speed estimation superposing of sinusoidal flux wave to a constant flux value. Furthermore, the secondary flux with some frequency is controlled independently on torque control. The proposed speed estimation method is derived from a motor circuit equation theoretically and also it can be conducted easily by detecting primary motor currents and primary voltage commands at every sampling time. Some numerical simulations with the assumption of using a pulse width modulation(PWM) voltage source inverter are performed to verify the proposed method.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.49 no.6
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• pp.552-562
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• 2004

KISTI(Korea Institute of Science and Technology Information) has developed the ${\ulcorner}$KITTI­ACOMS (KISTI-Article COntribution Management System)${\lrcorner}$ as part of the national project for automating the process of processing academic information by societies, in order to convert journals published by academic societies in Korea into an electronic form and make them accessible on the Internet. This system has been developed in the year 2001 and has since been distributed to societies free of charge. The number of societies requesting the service has risen recently, which prompted us to take more recommendations of the societies that adopt this system into account in expanding and standardizing the area of service being provided by the system. This paper will investigate the functions of KISTI-ACOMS constructed for use in the Korean Society of Crop Science and list the functions and requirements for the next system to enhance the on-line paper management system.

• Journal of Korea Water Resources Association
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• v.36 no.6
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• pp.949-960
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• 2003

The resolution issue of wetness index with relaxation of the steady state assumption is explored on the platform of Digital Elevation Model (DEM). The variabilities of the quasi-dynamic wetness index and the dynamic wetness index are discussed on the base of the spatial and statistical aspects depending upon resolutions of DEM and the drainage time. The organization patterns of the wetness index can be observed upon various drainage times and pixel size. The transient behaviour of wetness patterns of the Sulmachun watershed are shown in the relatively short drainage time. The statistical analysis of the quasi-dynamic and dynamic wetness analysis provide the convergence of analysis results to the steady state characteristics later than 10,000 hours drainage time. The probability density functions of the quasi-dynamic and the dynamic wetness index shows the existence of the threshold pixel size of DEM which provide stability and consistency in the computation result of these two wetness index.

• Journal of Korea Water Resources Association
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• v.33 no.2
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• pp.195-205
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• 2000

Many types of factors were devised to calculate time of concentration. Singh(976) derived time of concentration of overland flow using kinematic wave theory for plane, converging, and diverging geometric configurations. The present paper investigated the time of concentration for particularly plane geometric configuration. A theoretical equation of time of concentration is derived based on the assumption of impervious overland flow as in the open channel flow. The study characterized the overland flow by many types of characteristic flow such as rough turbulent flow, smooth turbulent flow, laminar flow, and then suggested a theoretical equation on each flow condition. The present paper further considered the rainfall intensity as a main factor and devised an approximate composite equation reflecting the effect of rainfall intensity given at various return periods.

• Journal of Energy Engineering
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• v.12 no.1
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• pp.42-48
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• 2003

In system planing and operation, voltage and reactive power control is very important. The voltage deviation and system losses can be reduced through control of reactive power sources. In general, there are several different reactive power sources, we used switched shunt capacitor to improve the voltage profile and to reduce system losses. Since there are many switched shunt capacitors in power system, so it if necessary to coordinate these switched shunt capacitors. In this study, Genetic Algorithm (GA) is used to find optimal coordination of switched shunt capacitors in a local area of power system. In case study, the effectiveness of the proposed method is demonstrated in KEPCO's power system. The simulation is performed by PSS/E and the results of simulation are compared with sensitivity method.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.2
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• pp.189-196
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• 2009

This paper presents the subparametric finite element model formulated by partial-linear layerwise theory for the analysis of laminate composites. The proposed model is based on refined approximations of two dimensional plane for orthotropic thick laminate plate as well as thin case. Three dimensional problem can be reduced to two dimensional case by assuming piecewise linear variation of in-plane displacement and a constant value of out-of-plane displacement across the thickness. The integrals of Legendre polynomials are chosen to define displacement fields and Gauss-Lobatto numerical integration is implemented in order to directly obtain maximum values occurred at the nodal points of each layer without other extrapolation techniques. The validity and characteristics of the proposed model have been tested by using orthotropic multilayered plate problem as compared to the values available in the published references. In this study, the convergence test has been carried out to determine the optimal layer model in terms of central deflection and stresses. Also, the distribution of displacements and stresses across the thickness has been investigated as the number of layer is increased.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.1
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• pp.85-96
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• 2016

A series of tests were conducted to examine the filled tube shape with respect to the filling module type used and to investigate cone resistance properties of a dredged-soil-filled geotextile tube under water and drained conditions. Results based on the filling observation showed that the distribution of the accumulated fills inside the acrylic cell and vinyl tubes differs with respect to the type of filling modules. A crater formation around the inlet area was found during the test using I-type filling module and a horizontal sediment distribution was found during the test using inverse T-Type filling module. The dredged fill material was obtained from the Saemangeum area. The geotextile tube deformation of each filling stage was almost converged when the tube was fully drained. The cone resistance of the dredged fill in the geotextile tube under drained condition is large and is approximately 2~6 times that of the tube under water condition.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.9
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• pp.884-890
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• 2008

A new guidance law to reach circular target area with grazing angle constraint is proposed as one of midcourse guidance laws of unmanned air vehicles. The purpose of the law is to control the grazing angle between the velocity vector of the vehicle and the line of sight to the aiming point, the center of the circular target area, when the vehicle passes any point on the circle. The optimal solution is derived based on the optimal control theory minimizing a range weighted control energy subject to the nonlinear dynamic equations of the vehicle approaching to the circular target area with grazing angle constraint. The major properties including a convergence of the solution are examined and the performance of the law applied to some typical scenarios is shown by the numerical simulation.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.10 no.2
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• pp.63-70
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• 1996

In this paper, we propose the low sldelobe digital doppler filter bank design algorithm which is practically applicable to coherent radar equipment in complex air-defense system. Using the proposed algorithm, we can obtain a digital doppler filter bank of lower peak sidelobe level and higher clutter suppression capability. In this method, it is possible to achieve higher target-detectability without loss of Target SNR. The proposed algorithms are verified by simulations and experiments.