• Journal of the Korean Graphic Arts Communication Society
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• v.31 no.1
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• pp.1-14
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• 2013

Screen printing is a printing method with flexible plate surface characteristics. In addition, since the appearance of electronics industry the screen printing has been demanding high quality and definition. However, Screen printing is a method for taking ink through mesh opening because screen mesh tends to restrict quality of screen printing. In particular, the biggest problem compared with other printing type is halftone reproduction characteristics. Halftone reproduction characteristics for screen printing depend on screen mesh and opening. Dot losses or dot gains are observed through various types of screen mesh because thread of screen mesh interfere with the movement of the ink. Excessive dot losses or gains can affect the tonal range. Furthermore, this problem can result in other problem such as bad contrast and gray balance. Therefore, it is an important factor to use proper screen mesh for halftone screen printing. However, domestic screen printing industry relies on worker's experience in field rather than depending on objective data although standardized specifications and optimal printing conditions are required for screen printing. For this reason, it is important to stipulate standard condition for domestic screen printing industry. Therefore, it was examined to find tonal range by mesh opening in halftone prints process of screen printing used domestic paper and ink in this study. In addition, TVI(Tone Value Increase) characteristic was observed by comparing to the manuscripts and prints of the dot area ratio. Furthermore, contrast value and gray balance were confirmed for each condition of the printout. Conditions for the proper selection of screen mesh screen for the quality of the prints were also examined, compared with the international standard of screen printing, ISO 12647-5.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.3
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• pp.190-196
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• 1999

Continuation power flow has been developed to remove the ill-condition problem caused by singularity of power flow Jacobian at and near at steady-state voltage instability point in conventional power flow. Continuation power flow consists of predictor and corrector. In prddictor, the direction vector at the resent solution is caluculated and the initial guess of next solution is determined at the distance of step length. The selection of step length is a very important part, since computational speed and convergence performance are both greatly affected by the choice of the step length. This paper presents the practical step length selection algorithm using the reactive power generation sensitivith. In numulation, the proposed algorithm is compared with step length selection algorithm using TVI(tangent vector index).

• Proceedings of the Korean Society of Disaster Information Conference
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• 2015.11a
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• pp.317-318
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• 2015

이 연구에서는 아날로그 기반의 고화질 전송 시스템(HD Analog system)에 관하여 고찰하였다. 오늘날 영상감시시스템은 고해상도 적용을 위한 기술개발을 통해 고품질의 영상을 구현할 수 있는 HD-SDI나 Network camera로 전환되고 있다. 그러나 Network camera는 기존 시스템과의 현격한 구성 차이로 전체 시스템을 다시 구축해야 하고, HD-SDI는 저가형 케이블 등에서는 만족할 만한 성능이 보장되지 않았다. 이러한 배경에서 등장한 것이 HD Analog system이다. HD Analog system은 기존 동축케이블을 이용할 수 있으며 저가형 케이블에서도 최대 500m 이상 전송이 가능하고, 구축비용을 절감할 수 있는 장점이 있다. 그러나 제조사별 시스템의 호환 문제 등을 해소하기 위한 표준화는 HD Analog system의 성장을 위한 선결과제로 제기된다.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.66 no.4
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• pp.252-257
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• 2017

In this paper for developing and implementing the HD level triple streaming hybrid security camera which output the three type of video outputs(HD-SDI, EX-SDI, Analog). We design the hardware and program the firmware supporting the main and sub functions. We use MN34229PL as image sensor, EN778, EN331 as image processor, KA909A as reset, iris, day&night function part, A3901SEJTR-T as zoom/focus control part. We request the performance test of developed security camera at the broadcasting and communication fusion testing department of TTA (Telecommunication Technology Association). We can get the three outputs (HD-SDI, EX-SDI, Analog) from the developed security camera, get the world best level at the jitter and eye pattern amplitude value and exceed the world best level at the signal/noise ratio, and minium illumination, power consumption part. The HD level triple streaming hybrid security camera in this paper will be widely used at the security camera because of the better performance and function.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1517-1519
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• 1994

This paper describes electrical environmental study of a 765kV double circuit test line. Corona performance on several candidate conductor bundles has been investigated in the corona cage (single phase simulation facility) since 1984. We have known that six RAIL conductor bundle is the most suitable for the 765kV transmission Line, [3] To investigate electrical environmental impact of the future commerciale line, we build a full sacle 765kV test line in 1993. The test results of Audible Noise, Radio Interference, TV Interference from August, 1993 to Jan. 1994 were measured as $48.7[dBA](L_{50})$. $57.4[dB{\mu}V/m]$(Fair weather, $L_{50})$. $14.5[dB${\mu}$V/m]$(Fair weather, $L_{50}$). We have found that the Audible Noise data were very close to the predicted(48.5 [dBA]) by BPA Corona and Field Effects Computer program, however, the RI and TVI data were much higher than predicted(42 [dBmV/m], $7.9[dB{\mu}V/m)$ by the BPA program. We have investigating the reason of the difference. In the constructing of full scale test line, we developed the tubular tower, 765kV test transformer and hardwares of 765kV transmission line insulator strings. Also we will investigate the effects of plants under the 765kV test Line.

• Journal of Electrical Engineering and Technology
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• v.9 no.3
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• pp.991-996
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• 2014

Power frequency magnetic field is still a critical problem for new construction of overhead power transmission lines in Korea because most people have been concerned about possibly carcinogenic effects of it. Although reference level of power frequency(60Hz) magnetic field has been set to 200uT in ICNIRP guidelines published in 2010, Korean government has no intention of adjusting 83.3uT specified by law in 2006 to this new reference level in consideration of people's concerns for the time being. Regardless of the current regulated magnetic field value, electric utility company has been trying to reduce magnetic field in the residential area in the vicinity of overhead power transmission lines to take into account of public concerns on the long-term effect of magnetic fields. In an effort to reduce magnetic field, engineering side has made considerable efforts to develop passive loop based, cost-effective mitigation technique of power frequency magnetic field more than ten years. In order to verify developed power frequency magnetic field mitigation technique based on passive loop, a horizontal type of passive loop was designed and installed for commercially operating 154kV overhead power transmission line for the first time in Korea. The measurement results before and after the installation of passive loop showed that magnetic field could be reduced to about 20%. The electrical environmental effects such as AN, RI and TVI were assessed before and after the installation of passive loop and these values were complied with the requirements specified by electric utility. It has been confirmed from the field test results that passive loop could be commercially and cost-effectively utilized to mitigate power frequency magnetic field.

• Korean Journal of Remote Sensing
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• v.12 no.2
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• pp.169-198
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• 1996

The objectives of this investigation are : 1. To analyze spectral signature and the associated vegetation index for geometric illumination conditions inf1uenced by low solar elevation and high slope orientations in mountainous forest. 2. To assess the accuracy of the spectral angle mapper classification for the a winter land cover in comparison with the maximum likelihood classification. 3. To produce the image of water quality and water properties that could be used to estimate the water pollution sources and the tide-included by turbid water in estuarine and coastal areas. These objectives are to characterize environmental and ecological monitoring applications of the Nak-Dong River Basin by using Fuyo-1 OPS VNIR data acquired on December 26, 1992. The results of this paper are as follows : 1. The spectral digital numbers and vegetation indexes (NDVI and TVI) of mountainous forest are higher on the slope facing the sun than on the slope hidden the sun under low sun elevation condition. 2. The spectral angle mapper algorithm produces a more accurate land cover classification of areas with steep slope, various aspects and low solar elevation than the maximum likelihood classifier. 3. The maximum likelihood classification images can be used for identifying the location and movement of both freshwater and salt water, regardless of geometric illumination conditions. 4. The color-coded density sliced image of selected water bodies by using the near-infrared band 3 can provide distribution of the water quality of the Lower Nak-Dong River. 5. The color-coded normalized difference vegetation index image of the selected mountain forest is suitable to classify winter vegetation cover types, i.e., forest canopy densities for slope orientations.