• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.11B no.3
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• pp.112-118
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• 2001

In the near future, the voltage of power system for passenger vehicle will be changed to 42V from existing 14V./ Because of increasing power and voltage ratings used in the vehicle the motor drive system has high switching dv/dt and it generates electromagnetic interference (EMI) To solve these problems multi-level inverter system may be used The feature of multi-level inverter is the output voltage to be synthesized from several levels of voltage Because of this feature high switching dv/dt and EMI can be reduced in the multi-level inverter system But as the number of level is increased manufacturing cost is getting expensive and system size is getting large. Because of these disadvantages the application of multi-level inverter has been restricted only to high power drives. The method to reduce manufacturing cost and system size is to integrate circuit of multi-level inverter into a few chips But isolated power supply and signal isolation circuit using transformer or opto-coupler for drive circuit are obstacles to implement the integrated circuit (IC) In this paper a drive circuit of 4-level inverter suitable for integration to hybrid or one chip is proposed In the proposed drive circuit DC link voltage is used directly as the power source of each gate drive circuit NPN transistors and PNP transistors are used to isolate to transfer the control signals. So the proposed drive circuit needs no transformers and opto-couplers for electrical isolation of drive circuit and is constructed only using components to be implemented on a silicon wafer With th e proposed drive circuit 4- level inverter system will be possible to be implemented through integrated circuit technology Using the proposed drive circuit 4- level inverter system is constructed and the validity and characteristics of the proposed drive circuit are proved through the experiments.

• Journal of Korea Society of Industrial Information Systems
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• v.17 no.7
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• pp.139-148
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• 2012

An ensemble of classifiers is to employ a set of individually trained classifiers and combine their predictions. It has been found that in most cases the ensembles produce more accurate predictions than the base classifiers. Combining outputs from multiple classifiers, known as ensemble learning, is one of the standard and most important techniques for improving classification accuracy in machine learning. An ensemble of classifiers is efficient only if the individual classifiers make decisions as diverse as possible. Bagging is the most popular method of ensemble learning to generate a diverse set of classifiers. Diversity in bagging is obtained by using different training sets. The different training data subsets are randomly drawn with replacement from the entire training dataset. The random subspace method is an ensemble construction technique using different attribute subsets. In the random subspace, the training dataset is also modified as in bagging. However, this modification is performed in the feature space. Bagging and random subspace are quite well known and popular ensemble algorithms. However, few studies have dealt with the integration of bagging and random subspace using SVM Classifiers, though there is a great potential for useful applications in this area. The focus of this paper is to propose methods for improving SVM performance using hybrid ensemble strategy for bankruptcy prediction. This paper applies the proposed ensemble model to the bankruptcy prediction problem using a real data set from Korean companies.

• Smart Structures and Systems
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• v.14 no.5
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• pp.847-867
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• 2014

There are continuous efforts to mitigate structural losses from earthquakes and manage risk through seismic risk assessment; seismic fragility curves are widely accepted as an essential tool of such efforts. Seismic fragility curves can be classified into four groups based on how they are derived: empirical, judgmental, analytical, and hybrid. Analytical fragility curves are the most widely used and can be further categorized into two subgroups, depending on whether an analytical function or simulation method is used. Although both methods have shown decent performances for many seismic fragility problems, they often oversimplify the given problems in reliability or structural analyses owing to their built-in assumptions. In this paper, a new method is proposed for the development of seismic fragility curves. Integration with sophisticated software packages for reliability analysis (FERUM) and structural analysis (ZEUS-NL) allows the new method to obtain more accurate seismic fragility curves for less computational cost. Because the proposed method performs reliability analysis using the first-order reliability method, it provides component probabilities as well as useful byproducts and allows further fragility analysis at the system level. The new method was applied to a numerical example of a 2D frame structure, and the results were compared with those by Monte Carlo simulation. The method was found to generate seismic fragility curves more accurately and efficiently. Also, the effect of system reliability analysis on the development of seismic fragility curves was investigated using the given numerical example and its necessity was discussed.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.4
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• pp.94-101
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• 2015

Each of power systems of solar cell and fuel cell were configured and validated for long endurance UAV, as the preliminary research for the integration of power systems. Solar power system consisted of solar modules fabricated by solar cells of Sunpower's C60, commercial solar MPPT controller and Li-po battery, and then was validated. The re-start characteristics of hydrogen production from $NaBH_4$ hydrolysis was validated for operating the commercial fuel cell. The average voltage drop of Li-po battery in solar power system was -2.9 V/hour. The performance of re-start characteristics of $NaBH_4$ hydrolysis was stable in sequence mode of mission profile. Each of single systems were satisfied for the proposed mission profile.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.11
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• pp.2267-2272
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• 2009

The six-port direct conversion receiver front-end that is comprised of a carrier recovery and a phase shifter, which gets the same structure with six-port phase correlator using the multi-layer coupled line, was designed and fabricated in this paper. The six-port element that is comprised of the power divider and the hybrid coupler is designed by multi-layer coupled line structure. The multi-coupled structure is utilized as the basic structure in receiver phase correlator, carrier recovery circuit and phase shifter. The receiver front-end with the same multi-layer coupled line structure for the receiver elements shows the simple structure and no difficulty in integration. The fabricated multi-layer coupled six-port receiver front-end re-generates the carrier signal with a constant phase and demodulates the PSK transmission signal.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.7
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• pp.646-652
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• 2013

EU's Galileo project is a market-based GNSS (Global Navigation Satellite System) that is under development. It is expected that Galileo will provide the positioning services based on new technologies in 2020s. Because Galileo E1 signal for OS (Open Service) shares the same center frequency with GPS L1 C/A signal, CBOC (Composite Binary Offset Carrier) modulation scheme is used in the E1 signal to guarantee interoperability between two systems. With E1 signal consisting of a data channel and a pilot channel at the same frequency band, there exist several options in designing signal acquisition for Assisted-Galileo receivers. Furthermore, compared to SNR worksheet of Assisted-GPS, some factors should be examined in Assisted-Galileo due to different correlation profile and code length of E1 signal. This paper presents SNR worksheets of Galileo E1 signals in E1-B and E1-C channel. Three implementation losses that are quite different from GPS are mainly analyzed in establishing SNR worksheets. In the worksheet, hybrid long integration of 1.5s is considered to acquire weak signal less than -150dBm. Simulation results show that the final SNR of E1-B signal with -150dBm is 19.4dB and that of E1-C signal is 25.2dB. Comparison of relative computation shows that E1-B channel is more profitable to acquire the strongest signal in weak signal environment. With information from the first satellite signal acquisition, fast acquisition of the weak signal around -155dBm can be performed with E1-C signal in the subsequent satellites.

• Convergence Security Journal
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• v.12 no.4
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• pp.3-8
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• 2012

Smartphones have all the recent technology integration and NFC (Near Field Communication) Technology is one of them and become an essential these days. Despite using smartphones with NFC technology widely, not many security vulnerabilities have been discovered. This paper attempts to identify characteristics and various services in NFC technology, and to present a wide range of security vulnerabilities, prevention, and policies especially in NFC Contactless technology. We describe a security vulnerability and an possible threat based on human vulnerability and traditional malware distribution technic using Peer-to-Peer network on NFC-Enabled smartphones. The vulnerability is as follows: An attacker creates a NFC tag for distributing his or her malicious code to unspecified individuals and apply to hidden spot near by NFC reader in public transport like subway system. The tag will direct smartphone users to a certain website and automatically downloads malicious codes into their smartphones. The infected devices actually help to spread malicious code using P2P mode and finally as traditional DDoS attack, a certain target will be attacked by them at scheduled time.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.28-31
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• 2002

Filmless full-PACS in korea has rapidly been growing, since government had supported collaborative PACS project between industry and university hospital in late of 1995. At the same time, a small company had started PACS business, while the Korea PACS society was being formed. In the beginning, PACS societies had focused on developing peripheral solutions such as DICOM gateway for image acquisition, x-ray film digitizer, and viewing software for research or management of personal image data, while Samsung Medical Center had started installing an imported partial PACS system which had recently upgraded with a new system. In similar time frame, a few hospitals had started developing and installing domestic large scale full-PACS system. Several years later, many hospitals have installed full-PACS system with national policy of reimbursement for PACS exams in November 1999. It is believed that Korea is the first country that adopted PACS reimbursement for filmless full-PACS as a national policy. Both experiences of full-PACS installation and national policy generated tremendous intellectual and technological expertise about PACS at all levels, clinical, hospital management, education, and industrial sectors. There are currently three types of PACS system which includes domestic, imported, and hybrid PACS system with imported solution for core system and domestic solution for peripheral system. There are more than 20 domestic PACS companies and they have now enough experiences so that they are capable of installing a truly full-PACS system for large-scale teaching hospitals. PACS societies in Korea understand how to design, implement, install, manage, sustain, and provide good services for large-scale full-PACS. PACS society has also strength for the highest integration technology of the Hospital Information. However, further understanding and timely implementation of continuously evolving international standard and integrated healthcare enterprise concepts may be necessary for international leading of PACS technologies for the future.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10b
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• pp.74-78
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• 1992

This paper describes an intelligent system to automatic evaluation of eddy current(EC) signal for Inspection of steam generator(SG) tubes in nuclear power plant. Some features of the intelligent system design in the proposed system are : (1) separation of representation scheme ,or event capturing knowledge in EC signal and for structural inspection knowledge in SG tubes inspection; (2) each representation scheme is implemented in different methods, one is syntactic pattern grammar and the other is rule based production. This intelligent system also includes an data base system and an user interface system to support integration of the hybrid knowledge processing methods. The intelligent system based on the proposed concept is useful in simplifying the knowledge elicitation process of the rule based production system, and in increasing the performance in real time signal inspection application.

• Archives of design research
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• v.11
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• pp.84-93
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• 1995

The paper aims to identify major research issues and basic framework of computer supported collaborative work in design through reviewing recent changes in product development which is getting more integrated, collaborative and computerized. At first the importance of collaborative work in design is discussed throughout the development of design process: from blackbox approach in vernacular design to recent Nigel Cross' es Hybrid model. Then Concurrent Engineering and Quality Function Depolyment are reviewed for showing recent phenomena of integration and collaboration in the process of product development. Computer-aided product development is demonstrated with the case of Blackboard system and Computergenerated form development. In order to outline the fundamental approach for computer-supported collaborative work in design, structures and processes of some related projects are introduced. Finally, based on the findings, some research issues for further rJevelopment are proposed.