• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.10
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• pp.1852-1857
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• 2007

The SSB modem performs the modulation process which converts the digital voltage level to the audible frequency band signal and the demodulation process which converts reversely the audible frequency signal to the digital voltage level. The modulator and the demodulator are implemented with a single DSP chip. Because of the SSB specific character, the distortion occurs when the frequency is changed. This distortion has no effect on voice communication but it has an significant effect on data communication. In other words, it is impossible to send data stream with adjacent 2 periods. Therefore, in case of using 2-tone FSK, it is needed to send at least 3 periods to transmit 1 bit. Therefore we implemented the modem using modified phase-delay shift keying to transmit 1 tone signal for high speed transmission. In the 1200[bps] mode, it generates 0, $187{\mu}s$, delay time at 1.3kHz symbol frequency, and in the 2400[bps] mode, 0, $70{\mu}s\;130{\mu}s\;200{\mu}s$, delay time at 1.5kHz symbol frequency. Finally, in the maximum 3600[bps] mode, it generates 0, $100{\mu}s\;160{\mu}s\;250{\mu}s$ 2.0kHz symbol frequency. The measured results of the implemented SSB modem shows a good transfer functional characteristic by spectrum analyzer, almost same bandwidth in pass band and 20dB higher SNR comparing the emu FACTOR and American CLOVER and in the experimental transmitting test, we verified the transmitted data is received correctly in platform.

• Journal of Practical Engineering Education
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• v.15 no.3
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• pp.671-679
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• 2023

This study aims to establish an evaluation model by quantifying the evaluation index as a follow-up study to the development of evaluation index for work-study parallel learning companies. An evaluation model was established by verifying the 2nd level components based on the quantitative factors of the learning company, the qualitative factors, the competency factors of the person in charge, and the competency factors of the learning workers, which are the highest-level components derived from previous study. For the evaluation of a learning company, an AHP survey was conducted with experts in charge of the company consulting to derive important factors that determine the quality of on-site education and training, and the evaluation model of the learning company was completed and grouped by calculating the weight between evaluation items proceeded. Work-study parallel program was promoted as a key policy to resolve the mismatch between industrial sites and school education and realize a competency-centered society, and as of December 2022, 16,664 companies participated in the training. Learning companies play a very important role as education and training supply organizations that conduct field training. It is expected that the support and consulting plan for each level of learning companies according to the evaluation model presented in this study will be used as basic data to improve the quality of work-study parallel program.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.7 no.3
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• pp.49-56
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• 1993

This paper describes design and implementation of signal transmission system using LCX as communication media, which has characteristics of high reliability easy for expansion and complex transmission of voice, data and video signal in Electric culvert. In this system, we estimated system performance as result of variable transmission characteristics test. In case of voice signal, transmission loss characteristics improved 5-10(dB] than designed Values in received signal level. In the test of speech quality estimation, we obtained satisfactory result as speech intensity = 3 (QSA value), speech atriculation = 4 (QRK value). As for data and video signal transmission, communication success rates were 981% 1 in monitoring and control functional test. As a result of transmission characteristics test in transmission line and system, transmission range by LCX communication system without repeater can reach in 6Km. This paper presents basic construction method using LCX communication system for total management in Electric culvert.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.5
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• pp.163-168
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• 2009

Most image segmentation methods are to represent observed feature vectors at each pixel, which are assumed as appropriated probability models. These models can be used by statistical estimating or likelihood clustering algorithms of feature vectors. EM algorithms have some calculation problems of maximum likelihood for unknown parameters from incomplete data and maximum value in post probability distribution. First, the performance is dependent upon starting positions and likelihood functions are converged on local maximum values. To solve these problems, we mixed the Gausian function and histogram at all the level values at the image, which are proposed most suitable image segmentation methods. This proposed algoritms are confirmed to classify most edges clearly and variously, which are implemented to MFC programs.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.4
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• pp.401-408
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• 2015

Conventional model updating methods for the structures have used global structural responses which are modal parameters obtained through vibration measurements. Although models updated by modal parameters estimate global structural responses accurately, they have difficulties to predict local responses for safety assesment of structural members. The safety of structural members in the structures has been evaluated through the stress estimation based on strain measurements. Thus, this study additionally uses measured strain responses of structural members to perform model updating besides modal parameters. In the proposed method, the objective functions are set to the differences of the global and local responses obtained from updated model and measurement and those functions are minimized by NSGA-II, one of the multi-objective optimization techniques. The strain responses predicted from updated model are used for safety assessment of the steel frame structures. The proposed method are verified by numerical and experimental studies through the impact hammer tests for a steel frame specimen.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.180-180
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• 2016

최근 디스플레이 시장의 주요 키워드는 flexible organic light emitting diode (OLED) 이다. OLED 소자의 수명을 결정하는 가장 큰 요인 중의 하나는 공기 중의 O2와 H2O에 의한 유기물의 열화이다. 따라서 공기 중의 O2나 H2O가 유기물에 쉽게 침투하는 것을 막는 것은 소자의 수명 향상을 위하여 필수적이라 할 수 있다[1-3]. SiNx 박막은 경질로 투과성이 우수하며, 화학적 불활성인 특성으로 이러한 Barrier 역할로 연구되어 산업분야에 다양하게 응용되고 있다[4]. SiNx 박막은 일반적으로 plasma enhanced chemical vapor deposition (PECVD) 기술을 이용하여 증착되는데 기존의 PECVD 기술을 이용한 SiNx 박막은 낮은 water vapor transmission rate (WVTR) 등의 문제점들로 인해 한계점이 들어났다. 본 연구에서는, flexible display의 thin film encapsulation (TFE) 공정에서의 적용을 알아보기 위해 $370{\times}470$ size를 증착할 수 있는 In-line 장비를 이용하였으며, 기존의 PECVD 기술의 문제점으로 지적되고 있는 낮은 WVTR을 해결하기 위하여 저온 (<$100^{\circ}C$) 선형 PECVD 기술을 이용하여 WVTR을 개선하고자 하였다. 공정가스로는 SiH4와 NH3를 사용하였으며, SiH4 Carrier 가스로 He을 추가적으로 사용하였다. 또한 공정 압력은 100mTorr를 유지하였다. 증착된 SiNx 박막의 물리적, 화학적 특성 분석을 위해 분광엘립소메타, field emission electron microscopy (FESEM), X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS) 등을 이용하여 측정하였으며, 박막에 투습되는 수분의 양은 MOCON사의 AQUATRAN 2(W)로 측정하였다. OLED 소자를 구현하기 위해서는 기본적으로 봉지층에 투습되는 양을 $10-6g/m2{\cdot}day$ 이하로 막아줘야 한다고 알려져 있으나, 기존의 PECVD 기술을 이용하여 제작된 SiNx 박막의 WVTR은 $10-2{\sim}10-3g/m2{\cdot}day$ 레벨의 WVTR 결과를 보이고 있다. 본 연구에서 사용된 저온 선형 PECVD 기술을 이용하여 제작된 SiNx 박막의 WVTR은 $5.0{\times}10-5g/m2{\cdot}day$ 이하의 개선된 결과를 확인 할 수 있었다. 또한 flexible display에 적용하기 위해 SiNx 박막의 두께를 최소화한 100nm의 두께에서도 WVTR은 $5.0{\times}10-5g/m2{\cdot}day$ 이하의 결과가 유지됨을 알 수 있었다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.5
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• pp.536-541
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• 2003

In order to avoid oxygen contamination on the diamond surface as far as possible during the device process, the A1/Ca $F_2$/diamond MISFET(metal-insulator-semiconductor field-effect transistor) was prepared by ultrahigh vacuum process and its electrical properties were investigated. The surface conductive layer of fluorinated diamond surface was employed for the conducting channel of the MISFET. The observed effective mobility(${\mu}$e$\_$ff/) of the MISFET was 300 c $m^2$/Vs, which is the highest value obtained until now in the diamond FET. Besides, the measured surface state density of the device was ∼10$\^$11//c $m^2$ eV, which is comparable with conventional Si MOSFET$\_$s/(metal-oxide-semiconductor field-effect-transistors). This work is the first report of the fluorinated diamond MISFET prepared by ultrahigh vacuum process and its application to inverter circuit.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.2B
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• pp.131-140
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• 2011

As the number of Internet users and applications is increasing, the importance of application traffic classification is growing more and more for efficient network management. While a number of methods for traffic classification have been introduced, such as signature-based and machine learning-based methods, Skype application, which uses encrypted communication on its own P2P network, is known as one of the most difficult traffic to identify. In this paper we propose a novel method to identify Skype application traffic on the fly. The main idea is to setup a list of Skype host information {IP, port} by examining the packets generated in the Skype login process and utilizes the list to identify other Skype traffic. By implementing the identification system and deploying it on our campus network, we proved the performance and feasibility of the proposed method.

• The Transactions of the Korea Information Processing Society
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• v.4 no.1
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• pp.54-66
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• 1997

Efficient retrieval of image data is an important research issue in multimedia database. This paper proposes a new approach to a content-based image retrieval which allows queries to be composed of the local texture patterns and the slope components of contour points. The texture patterns extracted from the source image using the graylevel co-occurrence matrix and the slope components of contour points extracted from the binary image are converted into a internal feature representation of reduced dimensionality which preserves the perceptual similarity and those features can be used in creating efficient indexing structures for a content-based image retrieval. Experimental results of the image retrievalare presented to illustrate the usefulness of this approach that demonstrates the precision 82%, the recall 87% and the average rang 3.3 in content-based image data retrieval.

• Journal of Practical Engineering Education
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• v.11 no.2
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• pp.251-258
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• 2019

In order to establish the NIVTPD which is only one qualification training institute for vocational training teachers in Cameroon, the research team taught such as curriculum development methods, course materials development, and lecturing methodology for master teachers of NIVTPD. Also we prepared actual operation of NIVTPD by conducting actual lecture through Pilot training. This paper also includes two different surveys (Base-line and End-line surveys) results and two different tests (pre and post-test) results to assess the impact of training gained in NIVTPD on classroom performance. The results of the survey will be used for the improvement of NIVTPD's educational program through identifying the current state of the vocational training interface and integration, modification and improvement of the curriculum. Examination results can also be used as indicators for vocational training teachers' pedagogical knowledge and for future certification.