• 한국물환경학회지
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• 제37권6호
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• pp.510-519
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• 2021

Volatile Organic Compounds (VOCs) in sediments, which can cause human health problems, have been monitored in Korea since 2014. Measured VOC concentrations can be affected by matrix type and the volatility of target substances. In this study, (1) VOCs volatility and the influence of matrix interference were confirmed, and (2) internal standards (IS) method was applied to improve analytical method. For these purposes, method detection limit (MDL), calibration linearity, precision and accuracy of VOCs were compared in various matrices using the IS. Some of VOCs in sediments showed different peak areas and reduced rates compared to water matrix. It was suggested that adsorption properties of sediments hindered the migration to vapor during heat pretreatment in headspace method. A calibration curve was created in clean sand. Recovery rates for the calibration curve method and IS applying method were 64.1~83.1% and 99.1~119.3%, respectively. Relative standard deviations ranged from 11.1% to 21.6% for the calibration curve method and those for IS ranged 4.7% to 13.7%. In case of real sediment, calibration curve and 1,2-Dichlorobenzene-d4 (ODCB) among IS were not suitable. The average recovery rate of Fluorobenzene (FBZ) increased by 56.4% and Relative Standard Deviation (RSD) by 4.7%. However, the recovery rate was increased in the samples with large values of igniting intensity. This study confirmed that influence of the matrix of VOCs in sediment, and addition of IS materials improved precision and accuracy. Although IS corrects volatilization and adsorption, it is recommended that more than two types of IS should be added rather than single.

• 한국지반공학회지:지반
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• 제1권2호
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• pp.41-54
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• 1985

비교적 얕은 깊이에서 터널을 착굴하거나 개착을 하늘 경우, 열변지반에 침하 및 수평이동 등의 변위가 발생하게 된다. 이러한 변위는 주변 구조물의 안정에 큰 영향을 미치며, 심한 경우 주변 구조물이 파괴되는 상태에 까지 이른다. 인구가 밀집된 대도시에 지하철을 시공할 경우, 주변 문화재, 고층건물, 상하수도관, 가스관 등의 안정을 지하철 설계시 고려하여야 하므로 터널굴착에 따른 지반변위의 예측과 자세한 침하의 원인이 규명되어야 할 필요가 있다. 본 연구에서는 지반 침하량 및 침하발생 영역을 예상하거나 침하요인을 파악하기 위하여 부산지하철 NATM회간의 지표면 침하, 지표면 수평변위, 지중침하, 천단침하 들에 관한 측정 분석이 이루어졌다. 그 결과, 횡방향 지표면 침하는 Gaussian normal probability curve, 종방향 지표면 심하하는 cumulative Gaussian probability curve로서 해석이 가능하다는 것과 가인버어트의 조기폐합이 침하량 감소에 큰 영향을 미친다는 것을 알 수 있었다.

• International Journal of Internet, Broadcasting and Communication
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• 제9권2호
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• pp.70-77
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• 2017

Where there are all the flowers, the songs of all kinds of insects and birds are put in, the sunshine and shadows flicker The forest through which the water sound flows is an optimum resting space. All living creatures in these spaces will awaken the five senses of humans and perhaps turn the sensibility index (EQ). The forest meditation in the forest, which can be an optimal shelter for the people who need it, needs to feel the reverence of nature, to refine emotions, to be a self-reflection, to have a mind to respect, Have an important meaning. In this paper, we tried to consider the cause of the influence of forest sounds on human hearing from the acoustical aspect. The type of sound source of forest was divided into four seasons of spring, summer, autumn, winter. And the change in the duration of the sound during the four seasons, so that the general characteristics of the sounds of the four seasons are as follows: It can be seen that the change in the ratio of sub-band energy is almost equal to the change in dB in frequency of the equal-light curve. To compare this phenomenon, the criterion for changing the sound duration of each forest is natural The main forms of the luminance curve, such as the change in the duration of the white signal in the sound, are determined by the minimum, maximum audible frequency and the most sensitive frequency band, and the auditory characteristics of the other three inflection points Determines the overall shape of the equal-light curve.

• 대한기계학회논문집B
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• 제29권9호
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• pp.1022-1031
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• 2005

Temporal behavior of the laser induced incandescence (LII) signal is often used for soot particle sizing, which is possible because the cooling behavior of a laser heated particle is dependent on the particle size. In present study, LII signals of soot particles are modeled using two non-linear coupled differential equations deduced from the energy- and mass-balance of the process. The objective of this study is to obtain an appropriate calibration curve for determining primary particle size by comparing the gated signal ratio and double-exponential curve fitting methods. Not only the effects of laser fluence and gas temperature on the cooling behavior but also heat transfer mechanisms of heated soot particle have been investigated. The second-order exponential curve fitting showed better agreements with the LII signals than the gated signal ratio method which was based on the lust-order exponential curve fit. And the temporal decay rate of the LII signal and primary particle size showed nearly linear relationship, which was little dependent on the laser fluence. And it also could be reconfirmed that vaporization was dominant process of heat loss during first loons after laser pulse, then heat conduction played most important role while thermal radiation had little influence all the time.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.764-771
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• 2010

The stability analysis method of an unsaturated slope considering the suction stress was performed on the infinite sand slope. During drying and wetting processes, the Soil-Water Characteristics Curve (SWCC) of the sand with the relative density of 75% was measured using the automated SWCC apparatus. Also, the Suction Stress Characteristics Curve (SSCC) was estimated. Based on these results, the stability analysis of an unsaturated infinite slope was carried out considering the slope angle, the weathering zone and the relative change in friction angle as a soil depth. According to the result of slope stability analysis, the safety factors of slope were less than 1 when the slope angles were more than $50^{\circ}$. The safety factors of slope tend to increase with increasing the depth from the ground surface. Especially, the safety factors have a tendency to increase and decrease above near the ground water level due to the suction stress. The maximum safety factor of slope in this analysis was occurred at the Air Entry Value (AEV) of drying process. The influence range of suction stress above the ground water level can be found out and can be defined as the funicular zone which means the metric suction range from the air entry point to the point of residual volumetric water content.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.1555-1558
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• 2008

Various approaches were undertaken by major PDP makers in order to improve the luminous efficacy of the plasma discharge cells. There have been many reports that state that using a high Xe content PDP is one of the most promising key technologies available to improve the luminous efficacy. In the case of the higher Xe content panel, the higher address and sustain voltage were needed to drive the panel under the same reset condition. In this study, a variety of Xe content panels were investigated in order to examine wall voltage transfer behaviors. The transferred wall voltage status after addressing discharge at the same driving condition was analyzed by comparing Vt close curve of high and low Xe content panels. Through this analysis of Vt close curve difference, the driving waveform of a high Xe panel was quantitatively adjusted Under the same address voltage condition, results showed that the amount of the transferred wall voltage and Vt close curve after addressing discharge was matched for the first sustain discharge. Taking these results into consideration, we conclude that the driving waveform for different Xe content panels could be designed for the desired addressing discharge condition and the wall voltage state of the cell could be quantitatively controlled and measured through these approaches.

• 공업화학
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• 제31권5호
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• pp.568-574
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• 2020

기체확산층은 유로에서 전극으로 반응물을 전달하고, 반응으로 생성되는 물을 배출하는 통로이며 열 배출과 전극 지지대 등의 역할을 하는 고분자전해질 연료전지의 핵심 구성요소이다. 본 연구에서는 국내외 기체확산층 상용 제품인 39BC와 JNT30-A3에 대한 연료전지의 성능 평가를 수행하였다. 25 ㎠ 단위 전지를 이용하여 유량, 상대습도 조건에 대한 분극 곡선을 측정하였고, empirical equation을 이용하여 운전 조건에 대한 성능 인자를 도출하였다. 기체확산층의 PTFE 함량이 높을수록 저항이 증가하였고, 미세다공층의 크랙은 물의 이동 통로로서 농도 손실에 영향을 미쳤다. 또한 상대습도가 낮을수록 Ohmic 저항이 증가하였지만, 전류밀도가 증가할수록 이온전도도가 증가하여 Ohmic 저항이 감소하였다. Empirical equation을 이용한 fitting curve을 통하여 기체확산층의 운전 조건에 대한 성능 인자 경향을 해석할 수 있었다.

• 한국세라믹학회지
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• 제38권10호
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• pp.936-941
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• 2001

5.31 mol% ${Y_2}{O_3}$-4.45 mo1% ${Nb_2}{O_5}$-90.31 mo1% $ZrO_2$에 ${Al_2}{O_3}$를 첨가한 복합체를 제조하여 알루미나 입도가 복합체의 균열 전파 저항성에 미치는 영향을 조사하였다. $ZrO_2/{Al_2}{O_3}$ 복합체에서는 R-cuve 거동이 관찰되었으며 0.2, $2.8{\mu}m$ ${Al_2}{O_3}$가 20 vol%가 첨가된 복합체의 인성값은 각각 7.9, $8.8MPam^{1/2}$이었다. 파괴인성값의 차이는 ${Al_2}{O_3}$ 입도 크기에 의존하는 $ZrO_2/{Al_2}{O_3}$ 복합체 내의 정방정 $ZrO_2$의 결정립 크기 차이에 의한 것으로 추정된다.

• 한국방재학회 논문집
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• 제3권2호
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• pp.119-125
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• 2003

불포화토에서 물의 흐름은 함수비 특성곡선과 투수계수 특성곡선(permeability-suction relation ship)이라 불리우는 두 방정식에 의해서 영향 받는다. 함수비 특성곡선은 체적함수비와 석션(suction)간의 관계를 나타내는 방정식이다. 많은 연구자들은 특성곡선식들을 제시해 왔다. 이 논문은 불포화토에서 물의 흐름을 분석할 때 특성곡선식들을 정확하게 결정하는 것이 중요하다는 것을 보여준다. 비교목적을 위해서 두 방법 즉, Gardner (1958)에 의해서 제시된 특성곡선식들과 Fredlund (1994) 의해서 제시된 특성곡선식들이 사용된다. 이 두 방법을 사용하여 유한요소법에 의한 물 흐름의 수치해석이 수행된다. 수치해석 결과들은 미 Ohio주 Delaware County에 있는 TDR (Time-domain reflectometry) 계측기로부터 얻어진 현장 데이터와 비교된다. 이 데이터는 전략적 고속도로 연구 프로그램(Strategic Highway Research Program)의 한 부분으로 포함된 계절 계측 프로그램(Seasonal Instrumentation Program)에 의해 얻어졌다.

• 환경정책연구
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• 제10권4호
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• pp.3-37
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• 2011

한국과 중국, 일본 세 국가의 1971년부터 2006년까지의 시계열 자료를 바탕으로 이산화탄소 배출량과 경제성장 그리고 경제개방도의 인과관계를 파악하고, 환경 쿠즈네츠 곡선(Envirionmental Kuznets Curve, EKC)의 존재여부에 대해 분석하였다. 경제개방도나 경제성장에 따른 이산화탄소 배출량은 국가별로 상이한 형태를 보였다. 추정된 EKC는 국가별로 다른 패턴을 보이는데, 경제성장과 $CO_2$ 배출량의 경우 한국은 U자 곡선, 중국은 상승추세, 일본은 역 N자 형태를 보였다. 일본은 약 30,000달러의 경제성장을 달성하면서 이산화탄소 배출 감소구간을 보이고 있다. 이와 같은 결과를 통해, EKC의 최고점에 이르지 않고도 선진국의 경험과 기술을 이용하여 터널을 거쳐 환경이 개선될 수 있다는 가능성을 확인할 수 있었다. 경제개방도와 $CO_2$ 배출량의 관계를 보면 한국은 역 U자 곡선, 중국의 경우 U자곡선, 일본은 증가추세를 보였다. 또한 벡터자기회귀모형(vector auto regression, VAR)과 벡터오차수정모형(vector error correction model, VECM)을 사용하여 변수들 간의 동태적 관계를 분석하였다. 각 국가의 경제성장, 개방화 정도에 따른 이산화탄소 배출과의 관계를 보다 가시적으로 접근했다는 데 의의가 있다.