• Annual Conference of KIPS
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• 2008.05a
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• pp.1132-1134
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• 2008

현재 우리나라는 미래형 첨단도시, U-City구현을 현실화 하고 있다. 유비쿼터스 기반기술이 총망라되는 U-City의 건설은 우리에게 편리하고 윤택한 삶을 약속하지만 U-City속의 수많은 유 무선 단말을 통해 수집되는 개인이나 사물, 환경에 대한 정보는 전자감시에 대한 우려와 이용자 프라이버시 침해를 유발하는 원인이 될 수 있으며 그에 심각성은 작금의 정보화 사회에 비할 수 없이 클 것으로 예상된다. 이에 본 논문에서는 U-City에서 발생할 수 있는 개인정보 침해위협을 통합적으로 살펴보고 개인정보보호 향상을 위한 보안 기법을 연구하였다.

• Annual Conference of KIPS
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• 2008.05a
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• pp.1007-1010
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• 2008

최근 통신업계에서 앞으로 가장 주목받을 만한 기술로 BcN(Broadcast Convergence Network)기반 IMS(IP Multimedia Subsystem)를 꼽고 있다. 통신업계는 지금까지 빠른 기술성장과 함께 많은 이익을 창출하였다. 그러나 현재 통신사의 가입자의 수는 물론 ARPU(Average Revenue Per User)역시 정체기를 맞고 있다. 때문에 통신업계들은 BcN환경 기반 IMS구조로 사용자의 요구에 맞도록 차별화된 서비스를 제공함으로써 이익을 창출하고 앞으로도 지속 가능한 성장을 하기 위해 이에 대한 연구를 활발히 하고 있다. 하지만 현재 IMS의 구조로는 사용자들에게 차별화된 서비스를 제공하는데 어려움이 있다. 본 논문에서는 사용자들에게 차별화된 서비스를 제공하기 위해 BcN 환경에서 통합 서비스를 제공 하기 위한 전체 Enabler구조와 Enabler에서 상황에 따른 데이터처리 기법에 대해서 제시하고자 한다.

• Transactions on Electrical and Electronic Materials
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• v.13 no.1
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• pp.47-49
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• 2012

In this paper, we investigated the anomalous hump in the bottom gate staggered a-IGZO TFTs. During the positive bias stress, a positive threshold voltage shift was observed in the transfer curve and an anomalous hump occurred as the stress time increased. The hump became more serious in higher gate bias stress while it was not observed under the negative bias stress. The analysis of constant gate bias stress indicated that the anomalous hump was influenced by the migration of positively charged mobile interstitial zinc ion towards the top side of the a-IGZO channel layer.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2324-2332
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• 2017

This paper presents the electrical performances of novel AlGaSb/InGaAs heterojunction-based vertical-tunneling field-effect transistor (VTFET). The device performance was investigated in views of the on-state current ($I_{on}$), drain-induced barrier thinning (DIBT), and subthreshold swing (SS) as the gate length ($L_G$) was scaled down. The proposed TFET with a $L_G$ of 5 nm operated with an $I_{on}$ of $1.3mA/{\mu}m$, a DIBT of 40 mV/V, and an SS of 23 mV/dec at a drain voltage ($V_{DS}$) of 0.23 V. The proposed TFET provided approximately 25 times lower DIBT and 12 times smaller SS compared with the conventional $L_G$ of 5 nm TFET. The AlGaSb/InGaAs VTFET showed extremely high scalability and strong immunity against short-channel effects.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2005.11a
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• pp.440-443
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• 2005

In this paper, we introduce about a new class to analysis of partial discharge signal based on Fuzzy model. We can early diagnose life of power cable through detection of partial discharge signal. However, partial discharge signal detector is difficult because of partial discharge signal is very non-linear. Also, it is very difficult work that separate partial discharge signal from noise. We constructed partial discharge accumulation detection system that use Labview for detection of non-linear partial discharge signal. And analyzed partial discharge signal that is detected by Labview system utilizing Fuzzy model.

• Journal of Electrical Engineering and Technology
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• v.8 no.4
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• pp.744-751
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• 2013

In this paper, Secant method is proposed to solve multi area economic dispatch (MAED) problem. Generator limits of all generators in each area are calculated at given area power demands plus export (or import) using secant method and the generator limits of all generators are modified as modified generator limits. Central economic dispatch (CED) problem is used to determine the output powers of all generators. Here, Secant method is applied to solve the CED problem. The proposed approach has been tested on two-area (two generators in each area) system and four-area (four generators in each area) system. It is observed from various cases that the proposed approach provides optimally best solution in terms of cost with tie line loss with less computational burden.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1768-1771
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• 2002

Automatic Transmission System(ATS) was designed to replace the human's manual operation of the gear box. So far, this system operates with the fixed shift pattern information. In this paper, new algorithm considering driver's operation tendency is proposed. Also, to get rid of the uselessly frequent shift of the ATS, the conditions and the status of the vehicle would be included for the evaluation in making a decision of shifting. A field test is done in a car equipped with the computer set connected to Transmission Control Units(TCU) to check the status of the test car, and it shows the excellency of the proposed algorithm.

• Journal of Electrical Engineering and Technology
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• v.10 no.2
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• pp.653-658
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• 2015

This paper deals with an efficient optimization design method of a compact ultra wideband (UWB) filter which can improve the characteristics of the filter. The Evolution Strategy (ES) algorithm is adopted for the optimization and modified to suppress the ripple by inserting an additional step to the ES scheme. The algorithm has the ability to control the ripple of an insertion loss in a passband as a modified approach. During the modified ES, a structure of initial shape is changed a lot, while includes the stepped impedance (SI) and the composite right/left handed transmission line (CRLH-TL). And an optimized filter satisfies the UWB specifications on the stopband and passband with an acceptable insertion loss. The filter achieves a much developed shape, the size of $15{\times}14mm$, the 3dB bandwidth from 2.7 to 10.8GHz, the flat insertion-loss less than 1dB, the wide stopband with 12~20GHz, and an acceptable return loss.

• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1468-1473
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• 2013

This paper dealt with the propagation characteristics of acoustic signals produced by partial discharges and the positioning of PD origin in insulation oil to develop insulation diagnostic techniques of oil-immerged transformers. Electrode systems such as needle to plane, plane to plane, and particle electrodes were fabricated to simulate some defects of power transformers. In addition, the frequency spectrum and propagation characteristics of acoustic signals with partial discharge (PD) in insulation oil were analyzed. Although there were differences based on the type of defect, the frequency spectra of the acoustic signals measured by wide and narrow band acoustic emission (AE) sensors were distributed in the range of 50 kHz-400 kHz. Therefore, a narrowband AE sensor is suitable for the diagnosis of oil-immersed power transformers. We could find the position of the PD source with an error margin of 10% in the experiments by calculating the position of the PD occurrence using the time difference of arrival measured by five AE sensors.

• Journal of Electrical Engineering and Technology
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• v.7 no.1
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• pp.109-114
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• 2012

In this paper, we utilize training strategy of hidden Markov model (HMM) to use in versatile issues such as classification of time-series sequential data such as electric transient disturbance problem in power system. For this, an automatic means of optimizing HMMs would be highly desirable, but it raises important issues: model interpretation and complexity control. With this in mind, we explore the possibility of using genetic algorithm (GA) and harmony search (HS) algorithm for optimizing the HMM. GA is flexible to allow incorporating other methods, such as Baum-Welch, within their cycle. Furthermore, operators that alter the structure of HMMs can be designed to simple structures. HS algorithm with parameter-setting free technique is proper for optimizing the parameters of HMM. HS algorithm is flexible so as to allow the elimination of requiring tedious parameter assigning efforts. In this paper, a sequential data analysis simulation is illustrated, and the optimized-HMMs are evaluated. The optimized HMM was capable of classifying a sequential data set for testing compared with the normal HMM.