• Journal of the Korean Institute of Telematics and Electronics B
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• v.30B no.5
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• pp.73-81
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• 1993

We have developed a system which can analyze the status of signal sent from/received to a signalling service equipment within the fully electronic switching system such as TDX-10. The system has such functions that acquire PCM signal of the preferred channel from the subhighway of the thirth-two channel by which a Universal Signal Tr ansceiver Unit(USTU) is connected with Time Switch Unit (TSU), and then classify the type of signal such as R2MFC/DTMF/CCT/VOICE, and determine the digit. Up to now, we have analyzed the frequency spec trum using the FFT. This paper describes the developement of PCM acquirer which can analyze the signal characteristics by acquiring the PCM signal in SHW(subhighway), and proposes the CZT(Chirp Z-Transform) algorithm. An algorithm which analyzes the acquired signal and determines the signal frequency and the corresponding power spectrum using the CZT is also discussed here.

• Proceedings of the KIEE Conference
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• 2004.04a
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• pp.208-211
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• 2004

Photovoltaic(PV) array, which is generally installed outside, has the possibility to be damaged by high voltage due to lightning. Because the electrical characteristics of PV array have not been fully identified by lightning yet, there is a very important issue whether PV array should be connected with ground or not. In this paper, a basic model of PV array is provided considering the PV cell's barrier capacitance and ground capacitance for analysis of electrical characteristics by lightning using PSCAD/EMTDC.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.291-292
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• 2010

The main purpose of this study is to design and develop the grid connected 4kW photovoltatic PCS(Power Conditioning System) targeting for Japanese market. To make this task, the development of DC to DC converter, one phase inverter and EMI filters, and the research on connection between inverter and utility line are made. The developed 4kW PCS has fully carried out performance verifications and evaluation works and acquired the JET(Japan Electrical Safety & Environment Technology Laboratories) certification for safety and performance.

• Journal of the Korean Operations Research and Management Science Society
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• v.30 no.1
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• pp.55-74
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• 2005

Bankruptcy prediction has drawn a lot of research interests in previous literature, and recent studies have shown that machine learning techniques achieved better performance than traditional statistical ones. This paper employs a relatively new machine learning technique, support vector machines (SVMs). to bankruptcy prediction problem in an attempt to suggest a new model with better explanatory power and stability. To serve this purpose, we use grid search technique using 5-fold cross-validation to find out the optimal values of the parameters of kernel function of SVM. In addition, to evaluate the prediction accuracy of SVM. we compare its performance with multiple discriminant analysis (MDA), logistic regression analysis (Logit), and three-layer fully connected back-propagation neural networks (BPNs). The experiment results show that SVM outperforms the other methods.

• Journal of Korean Society of Steel Construction
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• v.8 no.4 s.29
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• pp.121-131
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• 1996

Semi-rigid frames are frames for whcih the connections joining the beam and column are neither fully rigid nor perfectly pinned. In reality, all steel frames are semi-rigid in nature as all connections exhibit a certain degree of flexibility under loads. For semi-rigid frmaed structures, it is tended to reduce more rigidity of the member for the nonlinear behavior of connections and the P-delta effects of framed structure. To predict the actual behavior of semi-rigid steel frames, a more realistic analysis methods which explicitly takes into account the effect of connection flexibility should be used. In this research, the effect of connection flexibility in the semi-rigid structure has been investigated. To predict the response of flexibility connected frames, the algorithm of semi-rigid steel frame is developed using connection model having nonlinear spring on end of beam.

• Proceedings of the Acoustical Society of Korea Conference
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• 1994.06a
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• pp.1070-1075
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• 1994

This paper describes the method for designing loudness ratings as transmission quality for ISDN telephone connected to fully digital network. To design the desirable loudness ratings for ISDN telephone, the model system of digital speech communication for subjective test is developed and opinion tests for establishing the optimal CODEC input level, the range of overall loudness rating, and sidetone masking rating are performed. As the results, the desirable ranges of loudness ratings are proposed as 6 to 8dB for sending, 0 to 2dB for receiving, and 10 to 14dB for sidetone masking rating.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.82-84
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• 2004

Java's performance is sometimes not acceptable due to interpretation overhead by the Java Virtual Machine (JVM). In this paper, we present a compiler structure of Java-to-C translator for high performance on resource limited environment like mobile devices. Our compiler framework translates Java into C codes to preserve Java's programming semantics such as inheritance, method overloading, virtual method invocation, and so on. Also our compiler fully supports Connected Limited Device Configuration (CLDC) 1.0 API's. We show that our compiler improves the speedup by up to eleven times more than JVM-only execution in measured benchmarks.

• Proceedings of the KSR Conference
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• 1998.05a
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• pp.548-555
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• 1998

The influences of high speed train on the dynamic responses of steel composite railway bridges are investigated. The bridge system which has two Ⅰ-girder and several cross beams is modeled with plate and frame elements. With assumption of concrete slabs ate fully connected with steel girders, the offset between slabs and girders is modeled using rigid link. The track system is modeled using beams on elastic foundation theory. And, the TGV train is modeled in 2-dimension considering bouncing and pitching motion. And, braking action of vehicle is considered using speed dependent braking function. To investigate the behavior of bridges due to moving trains, parametric studies are performed.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.3
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• pp.218-223
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• 2012

Maintenance and improvement of the graph connectivity is very important for decentralized multi-agent systems. Although the CBBA (Consensus-Based Bundle Algorithm) guarantees suboptimal performance and bounded convergence time, it is only valid for connected graphs. In this study, we apply a decentralized estimation procedure that allows each agent to track the algebraic connectivity of a time-varying graph. Based on this estimation, we design a decentralized gradient controller to maintain the graph connectivity while agents are traveling to perform assigned tasks. Simulation result for fully-actuated first-order agents that move in a 2-D plane are presented.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.6
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• pp.170-176
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• 2005

The hydraulic cylinder is used for actuating the sluice gate which controls the volume of water in the reservoir. The locating points of hydraulic cylinder are restricted to limited space and determined to minimize the cylinder force necessary for actuating the sluice gate. Generally, the head end point of cylinder is fixed at underground and the rod end point of cylinder is connected to the gate plate when it is fully opened. Therefore there exist three parameters to be determined to minimize the cylinder force in the operation range of sluice gate. The optimal locating points of hydraulic cylinder are obtained using the complex method that is one kind of constrained direct search m method.