• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.1
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• pp.97-103
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• 2000

In this paper band-stop filters that reject the undesired 3th and/or 5th harmonics generated from high frequency generator are analyzed using equivalent circuit concept, and optimized using iterative optimization algorithm. The length of the band-stop filter is setup initially a quarter of a wavelength of the harmonic, but initial filter structure is exactly unable to cutoff the harmonics because of the fringing effect at the discontinuous boundary. To reduce the mismatch between the cutoff frequency and the harmonics, iterative LMA(Levenberg-Marquardt Algorithm) is introduced and band-stop filters in coaxial line are optimized.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.7C
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• pp.658-666
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• 2007

In general, the earlier linear-phase MAXFLAT(maximally flat) lowpass FIR filters have the main disadvantage of a gain response in the half frequency band $(0{\leq}w{\leq}{\pi}/2)$ by the closed form transfer functions used in design techniques for realizing them. Moreover, most of them has existent problems as follows : ripple error in the stopband, gentle-cutoff attenuation, phase and group delay and inexact cutoff frequency response. It is due to the approximation algorithms such as Chebyshev norm and Remez exchange which are used to approach MAXFLAT and linear-phase characteristics in frequency domain. In this paper, a new mathematically closed-form transfer function is introduced for the design of MAXFLAT lowpass FIR filters which have the zero-phase and wideband-gain response. In addition, we verify that the closed-form transfer function is easily realized due to our generalized formulas derived newly by using MAXFLAT conditions including an arbitrary cutoff point. This method is, therefore, useful for "simple and quick designs". Conclusively, we propose a technique for the design of new zero-phase wideband MAXFLAT lowpass FIR filters which can achieve sharp-cutoff attenuation exceeding 250 dB almost everywhere.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.11a
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• pp.636-639
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• 2002

This article is focused on the research for the system design that isolate noxious data from internet for juveniles Normally, by motivating this software which was designed to isolate noxious data, harmful data was deleted or graded But these normal process contains a lot of complexity, for example, essential continual upgrade, grading mistake, etc. So, to solve these fallacy, word-weighting process, where several harmful words which can be optained in internet site are discriminance and weighted, is utilized by using AC machine. At the result, the isolation rate of harmful site rose up to 90%, which means this process is greatly efficient.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.11B
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• pp.730-735
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• 2005

While the E-mail is a important way of fast communication in these days. it is real that the E-mail is often misused as a commercial advertisement method and creates many social problems. Even though various filtering techniques for blocking spam mails have been developed, reliability of mail systems is decreased by misreading normal mails as spam mails, i.e. false-positive errors. In this paper, the SMBC(Spam Mail Blocking Center) platform employing spam mail recovery method based on privacy information is proposed and designed. The SMBC is designed in frame layer based on spam blocking system of proxy sewer and can be physically implemented in various topology so that flexible development with layered module is possible. Using privacy information makes the proposed SMBC platform minimize processing load and false-positive error rates so that it can improve mail system reliabilities.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.133-134
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• 2015

최근 전자기술이 발달함에 따라, 전자기기의 집적도가 높아지고 있으며, 그에 따라 전자기적 간섭(Electromagnetic Interference)이 큰 문제로 대두되고 있다. 특히, 집적도가 높은 스마트 기기(Smart Device)의 AP(Applicaton Processor)의 경우, 여러 기능을 수행하는 부품이 집적된 SOC(System On Chip)이기 때문에, 전자기적 간섭에 더 민감할 수 있다. 더불어 LTE(Long Term Evolution)을 무선통신으로 이용하는 다양한 주파수대에서 전자기적 간섭은 어플리케이션 및 전자기기의 오작동을 초래할 수 있다. 이를 해결하기 위하여 본 논문에서는 칩패캐지 레벨의 Meander 구조의 기존 필터(Filter)가 가진 문제점을 해결한 구조를 설계하여 3차원 상의 전자장 시뮬레이션을 수행하였다. 또한, 칩의 내성(Immunity)이 취약한 여러 주파수 범위를 차단할 수 있는 이 중 대역차단 필터(Dual Band Stop Filter)를 Meader Line구조를 단순하게 만들어 설계하고 그에 따른 결과를 분석하였다.

• Annual Conference of KIPS
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• 2014.11a
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• pp.933-935
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• 2014

휴대전화 사용의 대중화로 인하여 개개인의 휴대전화로 수신되는 스팸메시지의 양도 덩달아 증가하게 되었다. 이것은 휴대전화 사용자가 불법광고 노출의 원인이 되고 있다. 이에 많은 스팸메시지 차단기법이 제시되었지만 이는 텍스트기반의 문자메시지에 특화되어있어 문자가 포함되어있는 이미지스팸에는 차단이 어렵다는 문제점이 존재 한다. 이에 본 논문에서는 휴대전화로 오는 이미지메시지 중 스팸이미지를 검출해 내는 모바일 스팸이미지 필터링 시스템을 제시하고자 한다. 제시하고자 하는 시스템은 스팸이미지를 분석하여 이미지의 패턴을 검사하여 특정 패턴이 포함된 이미지에 대해서 스팸이미지로 분류하여 필터링하게 됨으로써, 실제 휴대전화로 수신되는 스팸이미지를 이용한 실험을 진행하였다. 그 결과 기존 텍스트기반 스팸필터링시스템에서 할 수 없었던 스팸이미지 필터링을 할 수 있음을 확인 하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.11a
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• pp.413-417
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• 2002

E-mail was very particular way of communication in the past, but it becomes one of daily communication methods now. Due to E-mail has a property which is not complete for security, sometimes it is used for purpose of commercial or badthings, therefore it becomes the latest problem to keep off a Spam-mail and commercial advertising E-mail, many ways to keep off were perposed for it. In this paper, I explained how to sort and keep off these Spam-mail and commercial advertising E-mail with three way, prevention by server level, prevention by construction of network level, prevention by client level. we designed a prevention system for Spam-mail and implemented it by Visual Basic.

• Journal of IKEEE
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• v.9 no.2 s.17
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• pp.108-114
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• 2005

While E-mail has become an important way of communications in IT societies, it creates various social problems due to increase of spam mails. Even though many organizations and corperations have been doing researches to develop spam mail blocking technologies, more cost and system complexities are required because of varieties of blocking technologies. In case of adopting spam blocking technologies, system reliability largely relies on the False-positive error rate with the order of employing spam blocking filters. In this paper, a False-positive mail recovery technique based on privacy information is proposed and implemented in order to improve the reliability of spam locking filters. Through the implemented prototype, recovery procedure for False-positive mails is verified and the results are summarized and analyzed.

• Journal of Navigation and Port Research
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• v.30 no.5 s.111
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• pp.331-334
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• 2006

In this paper, we designed and fabricated the lowpass filter with the wide stopband characteristics using microp- strip line. Adding the $\lambda_g/4$ open stub at the input and output ports, we developed the L-C ladder type lowpass filter using the open stub which has wide stopband characteristics. In order to reduce the entire size qf this filter, the high impedance microstrip lines were made with the meander structure. The lowpass filter was fabricated with the cutoff frequency 2.3 GHz and its measured frequency responses agree well with the simulation results.

• Korean Chemical Engineering Research
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• v.61 no.3
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• pp.401-406
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• 2023

With the development of industry, fine dust is causing difficulties in various fields such as environment, health, and life, and a large amount of pollutants generated from human social activities are emerging as a serious environmental problem due to air pollution. Therefore, in this study, activated carbon was added to remove fine dust and volatile organic compounds by spinning cellulose acetate polymer fibers on a silicon support using the electrospinning method. By varying the activated carbon ratio and electrospinning time, the fine dust blocking effect and toluene adsorption performance were confirmed according to the activated carbon ratio and filter thickness. As a result, it was shown that the particles were effectively blocked with the increase in the electrospinning time due to the filter thickness increase. Adsorbed amount of toluene was increased with increase in activated carbon amount. Light transmittance was decrease with increase in electrospinning time, showing that there were light transmittance in filters electrospun for 20~30 minutes.