• 한국대기환경학회지
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• 제34권2호
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• pp.244-258
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• 2018

We performed this study to investigate the spatial, seasonal, and daily variations of the concentrations of volatile organic compounds (VOCs) in Pohang, where large steel industrial complexes are located. Ambient air sampling was undertaken at 4 sites during 4 seasons. Each sample was taken for 4 hours continuously for 8 consecutive days per season at each site. Three sites were located within the Pohang city, but one as a control site in Gyeongju. A total of 72 individual VOCs were determined by thermal desorption coupled with GC/MS, including aliphatics, aromatics, carbonyls and halides. The most abundant VOC was toluene, being followed by ethylbenzene and xylenes. Benzene concentrations(c.a. 0.7 ppb) were found to be much lower than the national ambient standard of 1.5 ppb. Overall, the VOCs levels in Pohang appeared to be lower than other national industrial complexes in Korea such as Shiwha-Banwol, Yeosu-Gwangyang, Gumi, and Ulsan. This implies that steel industry may not give significant impacts on the atmospheric levels of VOCs as much as petrochemical, electronic, and/or textile industries, where large amounts of organic solvents are used.

• 한국환경보건학회지
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• 제13권2호
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• pp.9-24
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• 1987

This study was conducted to measure the diurnal variation and behaviour of atmospheric mercury in an urban area by gold amalgamation and cold vapour atomic absorption spectrophotometry. The results were as follows: 1. The Hg concentration in ambient air averaged. 21.13ng/m$^3$ for 111 determinations (C.V. 78.5) in urban area and 5.91ng/m$^3$ for 140 determinations (C.V. 21.3) in suburban area. The urban area concentration was significantly higher and fluctuated more than its rural counterpart. 2. Regression analysis of the interaction between mercury concentration and other components showed a significant correlation between mercury concentration and sulfur dioxide also, TSP were found. Mercury concentration was shown to have a similar behaviour, on the whole, with other air pollutants. 3. It demonstrated a positive correlation with sunlight (UV-ray), while it had a negative response to wind speed and humidity. Its concentration showed a tendensy to increase during calm weather specifically. 4. The Hg concentration at the Mt. Dok You inland clean area ranged from 1.33ng/m$^3$ to 2.0ng/m$^3$, with a mean value of 1.63ng/m$^3$.

• 한국대기환경학회지
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• 제15권2호
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• pp.159-173
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• 1999

Based on air quality monitoring data('89~'97) operated by the Department of Environment, we provide various fundamental statistics for ground ozone. The purpose of this paper are to review the national ambient ozone standard, to study spatial distribution of ozone. Since we, in Korea, calculate average ozone level, to examine the occurrences of ozone level 3 times a day (1~8, 9~16, 17~24 hours), the method does not seem to be scientifically sound comparing to a running average method adapted by the USEPA. When we counted the number of cases with 8-h average O3 level exceeding 60ppb(8-h average standard in Korea)and 80 ppb (that in the U.S.A) and also when we calculated 8-hour average ozone level based on th US method, some regions were classified as non-attainment areas. Especially in Seoul, results of spatial distribution analysis showed that high level ozone over 80 ppb was observed at Kuui-Dong and Pangi-Dong in the eastern part and at Ssangmun-Dong in the northeastern part. Also, occurrences of ozone episode defined as number of days then ozone level exceeding 80 ppb for 3 consecutive hours were extensively reviewed in this paper.

• 융합신호처리학회논문지
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• 제4권3호
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• pp.15-20
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• 2003

핸즈프리 마이크를 이용한 원격회의나 원격 통신 시스템과 같은 몇 가지의 응용분야에서, 음성 신호는 주위 잡음뿐만 아니라 마이크와 스피커사이의 결합에 의해 발생하는 에코에 의해서 왜곡되기 쉽다. 게다가 채널 왜곡이나 부가적인 잡음을 포함한 환경 잡음들은 원래의 입력 음성신호에 영향을 미치리라 고려된다. 본 논문에서는, 이러한 핸즈프리 음성에 있어서의 음성 인식률을 향상시키기 위해 에코 제거기와 최대 사후 추정(MAP)을 이용한 새로운 접근방식을 소개한다. 이 접근방식에서, 제안된 시스템이 에코를 포함한 주위 잡음 환경에서의 핸즈프리 음성인식에 효과적이라는 것을 보여준다 또한, 실험 결과는 에코 제거기와 MAP 환경적응 기술의 결합 시스템이 에코와 잡음 환경에 잘 적응하는 것을 보여준다.

• 한국환경보건학회지
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• 제41권3호
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• pp.163-170
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• 2015

Objectives: This study evaluated the effect of construction on ambient PM-10 in the surrounding area. Methods: Four study sites were selected from total AAQMN 11 points in Daegu city. All the four study sites were located near under or completed construction. Mean monthly PM-10 in 2007 to 2013 were analyzed. Results: Impact of residential construction on PM-10 was more obvious than industrial area. PM-10 was positively associated with number of construction near the study site. When there were 2 or 3 construction sites, PM-10 level was higher. Wind direction and the surrounding terrain affected PM-10. Conclusions: Construction has a strong influence on PM-10 in the surrounding Area. Reduce PM-10 there is the need for special construction site management. Proper management is required to minimize fugitive dust in construction sites.

• 한국환경보건학회지
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• 제41권4호
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• pp.259-267
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• 2015

Objectives: This study evaluated the regional and seasonal concentrations of ambient hazardous heavy metals in an industrial complex area in Daegu City. Methods: A total of 64 SPM (Suspended Particulate Matter) samples were collected in non-industrial and industrial areas during 2014 and were analyzed for hazardous heavy metals elements (As, Cd, Mn, Ni, Pb) with ICP after acid extraction. Results: SPM and hazardous heavy metals concentrations showed regional (industrial complex area>non-industrial complex area) and seasonal (spring, winter>fall, summer) variations. All of the hazardous heavy metals were influenced by anthropogenic sources. The pollution index of hazardous heavy metals was very low, showing roughly one-quarter of the level of the air quality guidelines of WHO. The correlation analysis among SPM and hazardous heavy metals indicated that components of non-industrial complex areas were more related to each other than those of industrial complex areas, and the correlation in the winter was higher than in other seasons. Conclusion: It is necessary to control air pollution sources and establish related policy because hazardous heavy metals from industrial areas can influence residential areas.

• 대한환경공학회지
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• 제31권11호
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• pp.1041-1050
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• 2009

광주지역 기상자료를 이용하여 기온변화를 예측하고, 광주지역의 이산화탄소, 일산화탄소, 상대습도의 상관성연구를 실시하였다. 2008년까지 48년간 광주지역 전체 평균기온은 $13.5^{\circ}C$이며, 2108년까지 100년간 $2.7^{\circ}C$정도 증가할 것으로 예측되었다. 안면도지역에서 이산화탄소 연평균 농도는 1999년과 2008년에 각각 370.7 ppm과 391.4 ppm으로서 기온의 증가에 영향을 주었다. 1997년부터 2008년까지 광주의 평균기온은 $14.2^{\circ}C$로 나주, 담양, 화순, 장성지역 보다 훨씬 높았다. 2108년경 광주의 봄 시작일은 1월 중순 이전, 여름의 시작일은 5월 중순, 가을의 시작일은 10월 중순, 겨울의 시작일은 12월 말경으로 전망되었다. 48년간 평균상대습도는 71.3%로 7월이 가장 높았으며, 해가 지날수록 감소하여 연도와는 반대현상을 보여주었다. $CO_2$와 CO는 양의 상관도(0.87)를 보여주었고, 조사기간 중 $CO_2$ 평균 농도는 457 ppm으로 우리나라 배경농도인 안면도의 397.3 ppm(2008)에서 보다 65.6 ppm이나 높았다. $CO_2$는 CO(0.87)와 상대습도 (0.48) 모두에 대하여 양의 상관성을 보여주었다.

• 한국인터넷방송통신학회논문지
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• 제17권5호
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• pp.9-16
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• 2017

향상된 의료 기술과 건강관리 기술의 최근 발전으로 인해 지난 수십 년 동안 기대 수명이 꾸준히 늘게 되었다. 그 결과 세계 인구는 빠르게 고령화되고 있다. 고령자의 복지를 향상시키고 일상생활에서 독립성을 제공하는 해결책을 기반으로 하는 정보통신기술 지원에 대한 다양한 연구가 진행되고 있다. 전천후 보조 생활은 개인의 일상생활 및 근무 환경에서 정보 통신 기술을 사용하여 더 오래 활동성을 유지하고 사회활동을 할 수 있도록 하여 노년기에 독립적으로 살아갈 수 있도록 하는 것으로 정의된다. 전천후 생활 보조 시스템에서 전송되는 정보는 매우 민감한 정보이므로, 이러한 데이터의 보안 및 개인 정보는 중요한 문제로 대두되고 있다. 본 논문에서는 전천후 보조 생활 시스템을 위한 새로운 경량 인증 프로토콜을 제안한다. 제안된 인증 프로토콜은 전천후 생활 지원 시스템에 필요한 몇 가지 중요한 보안 요구 사항을 지원할 뿐만 아니라 다양한 유형의 공격으로부터 안전하다. 또한 보안 분석 결과를 통해 제안된 인증 프로토콜이 기존 프로토콜보다 더 효율적이고 안전하다는 것을 보여준다.

• 한국전기전자재료학회논문지
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• 제18권6호
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• pp.554-559
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• 2005

Ni/Cr thin film is very interesting material as thin film resistors, filaments, and humidity sensors because their relatively large resistivity, more resistant to oxidation and a low temperature coefficient of resistance (TCR). These interesting properties of Ni/Cr thin films are dependent upon the preparation conditions including the deposition environment and subsequent annealing treatments. Ni/Cr thin films of 250 nm were deposited by DC magnetron sputtering on $Al_2O_3/Si$ substrate with 2-inch Ni/Cr (80/20) alloy target at room temperature for 45 minutes. Annealing treatments were performed at $400^{\circ}C,\;500^{\circ}C,\;and\;600^{\circ}C$ for 6 hours in air or $H_2$ ambient, respectively. The clear crystal boundaries without crystal growth and the densification were accomplished when the pores were disappeared in air ambient. Most of surface was oxidic including NiO, $Ni_2O_3$ and $Cr_xO_y$(x=1,2, y=2,3) after annealing in air ambient. The crystal growth in $H_2$ ambient was formed and stabilized by combination with each other due to the suppression of oxidized substance on film surface. Most oxidic Ni was restored when the oxidic Cr was present due to its stability in high-temperature $H_2$ ambient.

• 한국재료학회지
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• 제25권7호
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• pp.336-340
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• 2015

For rear metallization with Al paste, Al back contacts require good passivation, high reflectance, and a processing temperature window compatible with the front metal. In this paper, the effect of the firing ambient during the metallization process on the formation of Al rear metal was investigated. We chose three different gases as ambient gases during the firing process. Using SEM, we observed the formation of a back surface field in $N_2$, $O_2$, and Air ambients. To determine the effect of the ambient on Voc, the suns-Voc tool was used. In this study, we described the mechanism of burn-out of organic materials in Al paste during the firing process. The oxygen ambient plays an important role in the burn-out process. We calculated the efficiency with obtained the back surface recombination velocities using PC1D simulation. It was found that the presence of oxygen during the firing process influenced the uniform back surface field because the organic materials in the Al paste were efficiently burned out during heating. The optimized temperature with oxygen flow shows an absolute efficiency of 19.1% at PC1D simulation.