• 한국구조물진단유지관리공학회 논문집
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• 제17권4호
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• pp.9-17
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• 2013

최근, 중단열 벽체의 단열성능 향상을 위해 철과 콘크리트 코어 전단연결재를 열전도율이 낮은 유리섬유복합체 (GFRP)로 전단연결재를 대체하는 연구가 활발히 진행되고 있다. 본 연구는 단열재의 표면처리에 따른 부착력과, GFRP 전단연결재로 보강된 중단열 벽체의 전단내력을 알아보기 위하여 실시되었으며, 각 변수에 따른 영향을 분석함으로써 구조성능에 대한 검증을 실시하였다. 총 13개의 실험체에 대해 직접전단실험을 실시하였으며, 파괴양상 및 하중-상대슬립 관계에 대한 분석을 실시하였다. 실험결과, 기존의 압출법 보온판 (XPS) 단열재에 거친표면처리와 10 mm의 홈을 낸 경우 단열재와 콘크리트사이에 부착력을 향상시킬 수 있으며, 부착력의 기여는 전단연결재의 파단 상대슬립의 영향을 받는 것으로 나타났다. 파형 전단연결재의 폭이 커짐에 따라 강성이 증가하였으며, 보강단면적이 증가함에 따라 최대내력이 증가하였다. 효과적인 보강을 위해서는 파형 전단연결재의 높이와 피치의 비율을 1:2로 산정해야 할 것으로 판단되며, 안정적인 파괴를 위해서는 매립깊이에 대한 검증이 필요할 것으로 사료된다.

• Journal of Ecology and Environment
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• 제42권4호
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• pp.210-218
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• 2018

Background: Soil respiration (Rs) is a major factor of the absorption and accumulation of carbon through photosynthesis in the ecosystem carbon cycle. This directly affects the amount of net ecosystem productivity, which affects the stability and sustainability of the ecosystem. Understanding the characteristics of Rs is indispensable to scientifically understand the carbon cycle of ecosystems. It is very important to study Rs characteristics through analysis of environmental factors closely related to Rs. Rs is affected by various environmental factors, such as temperature, precipitation, soil moisture, litter supply, organic matter content, dominant plant species, and soil disturbance. This study was conducted to analyze the effects of micro-topographical differences on Rs in forest vegetation by measuring the Rs on the ridge and southern slope sites of the broadly established Quercus mongolica forest in the central Korean area. Method: Rs, Ts, and soil moisture data were collected at the southern slope and ridge of the Q. mongolica forest in the Mt. Jeombong area in order to investigate the effects of topographical differences on Rs. Rs was collected by the closed chamber method, and data collection was performed from May 2011 to October 2013, except Winter seasons from November to April or May. For collecting the raw data of Rs in the field, acrylic collars were placed at the ridge and southern slope of the forest. The accumulated surface litter and the soil organic matter content (SOMC) were measured to a 5 cm depth. Based on these data, the Rs characteristics of the slope and ridge were analyzed. Results: Rs showed a distinct seasonal variation pattern in both the ridge and southern slope sites. In addition, Rs showed a distinct seasonal variation with high and low Ts changes. The average Rs measurements for the two sites, except for the Winter periods that were not measured, were $550.1\;mg\;CO_2m^{-2}h^{-1}$ at the ridge site and $289.4\;mg\;CO_2m^{-2}h^{-1}$ at the southern slope, a difference of 52.6%. There was no significant difference in the Rs difference between slopes except for the first half of 2013, and both sites showed a tendency to increase exponentially as Ts increased. In addition, although the correlation is low, the difference in Rs between sites tended to increase as Ts increased. SMC showed a large fluctuation at the southern slope site relative to the ridge site, as while it was very low in 2013, it was high in 2011 and 2012. The accumulated litter of the soil surface and the SOMC at the depth range of 0~5 cm were $874g\;m^{-2}$ and 23.3% at the ridge site, and $396g\;m^{-2}$ and 19.9% at the southern slope site. Conclusions: In this study, Rs was measured for the ridge and southern slope sites, which have two different results where the surface litter layer is disturbed by strong winds. The southern slope site shows that the litter layer formed in autumn due to strong winds almost disappeared, and while in the ridge site, it became thick due to the transfer of litter from the southern slope site. The mean Rs was about two times higher in the ridge site compared to that in the southern slope site. The Rs difference seems to be due to the difference in the amount of litter accumulated on the soil surface. As a result, the litter layer supplied to the soil surface is disturbed due to the micro-topographical difference, as the slope and the change of the community structure due to the plant season cause heterogeneity of the litter layer development, which in turn affects SMC and Rs. Therefore, it is necessary to introduce and understand these micro-topographical features and mechanisms when quantifying and analyzing the Rs of an ecosystem.

• 환경생물
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• 제31권1호
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• pp.19-36
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• 2013

남해 동부해역에서 해수는 계절에 따라 서로 다른 수질환경 특성의 수괴들에 의해 조절되는 것으로 밝혀졌다. 홍수기인 여름철 표층수는 북한한류 기원의 동해 냉수괴 특성의 수괴-A (East Sea Cold Water), 담수의 영향이 강한 연안성 수괴-B (river-dominated coastal water), 연안 염하구성 수괴-C (coastal pseudo-estuarine water)로 구분된다. 특징적으로 높은 영양염과 엽록소 농도를 갖는 저염의 염하구성 수괴-B는 홍수기인 여름철에 해안선에서 수 십 km 떨어진 해역까지 짧은 기간 일시적으로 형성되며, 집중호우 등 몬순(monsoon)기후 특성을 갖는 우리나라 연안역에서 육지-해양간 물질 순환에 상당한 역할을 할 것으로 사료된다. 여름철 저층수는 저온-고염의 냉수인 저층 냉수괴-D(bottom cold water)가 지배적이며, 표층수의 수괴들과 비교하여 전체적으로 수온, pH, 용존 산소량은 낮은 반면, 높은 영양염 농도 특성을 갖는다. 여름철 저층 냉수괴의 높은 영양염 농도는 강한 성층과 낮은 수온으로 인하여 식물플랑크톤 번식이 제한되어 보존-축적된 결과로, 갈수기인 겨울철 영양염의 주요 공급원으로 작용한다. 갈수기인 겨울철 연구해역의 해수환경은 여름철과 다르게 대마난류수 (수괴-E)가 광범위하게 분포하며, 해안선을 따라 연안역의 좁은 범위에 대마난류수가 약간 변질된 연안성 수괴-F가 분포한다. 특히 광양만, 마산만 등의 반폐쇄성 지형의 여러 만(bay)들에 위치하는 연안성 수괴-F에서는 갈수기인 겨울철에도 낮은 수심과 느린 유속 등에 의해 기초생산력이 높으며, 이로인한 겨울철 영양염 고갈(depletion) 현상이 뚜렷하게 나타난다. 또한 남해 연안성 수괴와 대마난류 수괴사이에 연안전선이 발달하며, 이러한 전선은 직간접적으로 남해의 기초생산력을 조절하는 중요 환경요소로 작용할 것으로 예상된다. 결론적으로 연구해역은 계절적으로 다른 특성의 수괴의 수괴가 복합적으로 분포하며, 여름철의 수질환경과 일차 생태계는 크게 연안 염하구성 수괴와 저층의 냉수괴 발달 정도에 따라 변화할 것으로 예상되며, 겨울철에는 외양에서 유입되는 대마난류 수괴의 특성에 따라 지배될 것으로 분석된다. 또한 용존무기인이 잠재적 제한영양염으로 작용하는 서해 연안역과 달리 남해 연안역은 대부분 용존무기질소가 잠재적 제한영양염으로 작용하는 것으로 밝혀졌다. 이러한 제한영양염의 차이는 서해와 남해 연안역이 서로 다른 환경과 다른 생태계 구조를 갖고 있음을 지시한다.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2004년도 임시총회 및 추계학술발표회
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• pp.119-120
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• 2004

Urban groundwater has a unique hydrologic system because of the complex surface and subsurface infrastructures such as deep foundation of many high buildings, subway systems, and sewers and public water supply systems. It generally has been considered that increased surface impermeability reduces the amount of groundwater recharge. On the other hand, leaks from sewers and public water supply systems may generate the large amounts of recharges. All of these urban facilities also may change the groundwater quality by the recharge of a myriad of contaminants. This study was performed to determine the factors controlling the recharge of deep groundwater in an urban area, based on the hydrogeochemical characteristics. The term ‘contamination’ in this study means any kind of inflow of shallow groundwater regardless of clean or contaminated. For this study, urban groundwater samples were collected from a total of 310 preexisting wells with the depth over 100 m. Random sampling method was used to select the wells for this study. Major cations together with Si, Al, Fe, Pb, Hg and Mn were analyzed by ICP-AES, and Cl, N $O_3$, N $H_4$, F, Br, S $O_4$and P $O_4$ were analyzed by IC. There are two groups of groundwater, based on hydrochemical characteristics. The first group is distributed broadly from Ca-HC $O_3$ type to Ca-C1+N $O_3$ type; the other group is the Na+K-HC $O_3$ type. The latter group is considered to represent the baseline quality of deep groundwater in the study area. Using the major ions data for the Na+K-HC $O_3$ type water, we evaluated the extent of groundwater contamination, assuming that if subtract the baseline composition from acquired data for a specific water, the remaining concentrations may indicate the degree of contamination. The remainder of each solute for each sample was simply averaged. The results showed that both Ca and HC $O_3$ represent the typical solutes which are quite enriched in urban groundwater. In particular, the P$CO_2$ values calculated using PHREEQC (version 2.8) showed a correlation with the concentrations of maior inorganic components (Na, Mg, Ca, N $O_3$, S $O_4$, etc.). The p$CO_2$ values for the first group waters widely ranged between about 10$^{-3.0}$ atm to 10$^{-1.0}$ atm and differed from those of the background water samples belonging to the Na+K-HC $O_3$ type (<10$^{-3.5}$ atm). Considering that the p$CO_2$ of soil water (near 10$^{-1.5}$ atm), this indicates that inflow of shallow water is very significant in deep groundwaters in the study area. Furthermore, the P$CO_2$ values can be used as an effective parameter to estimate the relative recharge of shallow water and thus the contamination susceptibility. The results of our present study suggest that down to considerable depth, urban groundwater in crystalline aquifer may be considerably affected by the recharge of shallow water (and pollutants) from an adjacent area. We also suggest that for such evaluation, careful examination of systematically collected hydrochemical data is requisite as an effective tool, in addition to hydrologic and hydrogeologic interpretation.ion.ion.

• 한국환경보건학회지
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• 제37권4호
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• pp.267-278
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• 2011

Objectives: A great number of hazardous agents can be emitted from various types of art-creation in a fine arts college, but little data on exposure assessment has been published. A variety of processes encompassing toxic or non-toxic materials, tools, and components are involved in a sculptor work at a fine art college. The aim of this study was to assess exposure levels to particulates and noise during sculpture classes in a college of fine arts. Methods: Students in sculpture classes participated in this study. Mass, number, and surface area concentrations of particulates, noise level, temperature and relative humidity were monitored by both personal and area sampling during the tasks of metal, wood, and stone sculpting. Results: The number and surface concentration of particulates was the highest in the task of wood sculpting, followed by metal and stone work. The mass concentration of particulates was the highest in stone sculpting (personal GM 3.0 mg/$m^3$, GSD 3.0), followed by wood (personal GM 1.5 mg/$m^3$, GSD 1.8) and metal work (personal GM 0.95 mg/$m^3$, GSD 1.51) in that order. Occupational exposure limits (OEL) for particulates depends on the type of particulate. For wood dust, 86% (six subjects) of the personal samples and all area samples exceeded the Korean OEL for wood dust (1 mg/$m^3$), while 20% (two subjects) among stone sculpting students were exposed above the Korean OEL (10 mg/$m^3$). In contrast, metal sculpting did not exceed the OEL (5 mg/$m^3$). For noise level, metal sculpting students (Leq 95.1 dB(A) in the morning, 85.3 dB(A) in the afternoon) were exposed the most, followed by stone sculpting (88.3 dB(A)), and wood sculpting (84.8 dB(A)) in that order. Compared with the 90 dB(A) of the Korean OEL and 85 dB(A) of the American Conference of Governmental Industrial Hygienists' threshold limit value (ACGIH-TLV) for noise, 100% of the subjects (five subjects) and area samples during metal sculpting in the morning session exceeded both OELs, but only three subjects (60%) exceeded the ACGIH-TLV in the afternoon session. For stone sculpting, 50% (one subject) and 100% (two subjects) exceeded the Korean OEL and ACGIH-TLV, respectively, but the area sample did not exceed either OEL. During wood sculpting, two subjects (40%) exceeded ACGIH TLV. Conclusions: This work evaluated the sculptors' exposure to particulate matter and noise in fine art college, and revealed a poor working environment for the participating students. Effective measures should be supplemented by the administration of colleges.

• 한국지역지리학회지
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• 제18권1호
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• pp.17-26
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• 2012

한반도 서부의 황토현에 분포하는 적색의 풍화층은 온대몬순기후의 한반도 기후환경과 어울리지 않는 토색을 띤다. 이 적색토(풍화층)는 화학적 풍화를 반영한 것으로서, 화학적 풍화지수(CIA)와 A-CN-K 도식을 활용하면 그 특색을 규명할 수 있다. CaO와 $Na_2O$의 손실은 대부분 이루어진 상태이며, $K_2O$의 손실이 단면 하부에서 상부로 가면서 점차 진행되고 있는 상태이다. 풍화단계에 따른 풍화 진전 방향을 유형화 하면, A-CN-K 도식에서 일반 구릉대 풍화층에서 나타나는 풍화 초 중기 단계에는 A-CN 선을 따라 풍화가 진전되며, 황토현 일대와 같이 강한 화학적 풍화가 진전된 풍화 후기에는 A-K 선을 따라 $K_2O$의 손실이 이루어지면서 풍화가 진전된다.

• 청정기술
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• 제7권1호
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• pp.65-74
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• 2001

본 연구는 디젤엔진에서 배출되는 NOx환원용 촉매로서 산화반응에서 우수한 활성을 나타내고 있는 페롭스카이트상의 $LaCoO_3$을 sol-gel 공정을 이용하여 촉매코팅용액을 제조한 후, 이를 기존의 dip-coating방법보다 코팅시간, 코팅량, NO-CO 산화 환원 반응에 있어서 경제적이고 효율적인 modified dip-coating방법을 이용하여 촉매코팅필터를 제조하고 이를 후처리장치에 부착함으로써 디젤엔진에서 배출되는 배가스를 효과적으로 제거시키고자 한다. 실험결과, modified dip-coating방법이 기존의 dip-coating방법에 비해서 코팅에 소요되는 용액량이 8.3배 코팅시간 83.3배 단축되었으며, 코팅량은 2~3배정도 커지고, NO-CO 산화 환원 반응성도 1.1~1.8배 가량 증가하였다. 그리고 코팅점도는 $0.006202kg{\cdot}m/sec$을 이용하여 코팅횟수 2회, 코팅량은 88.56mg/g에서 우수한 반응을 보였다. 또한 세라믹 필터의 셀수에 있어서는 200 CPSI가 적절함을 확인할 수 있다.

• Archives of Plastic Surgery
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• 제43권6호
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• pp.551-558
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• 2016

Background Fascial free flaps have been widely used for reconstruction of the hand because they are thin. However, studies reporting objective data regarding the advantages of this approach are lacking. Thus, we report our experience with such flaps. Methods Forty-five cases of fascial free flaps between November 2006 and March 2014 were reviewed. Nine cases involving reconstructed dorsal or lateral defects were included. Four anterolateral thigh fascial free flaps and 5 lateral arm fascial free flaps were examined. Maximal flap contour was assessed by measuring reconstructed tissue thickness at the central area from the surface of the skin to below the bone in a vertical manner using ultrasonography and X-ray data. Contralateral regions were examined in the same manner and a comparative analysis was performed. A questionnaire survey regarding aesthetic satisfaction was also administered. Results All reconstructed parts had a thicker contour than the contralateral side. The average relative percentage of reconstructed tissue thickness was found to be 152% using ultrasonography and 143% using X-ray imaging. According to the aesthetic satisfaction survey, the average rate of satisfaction for patients was 62%, and satisfaction with the flap contour was 72%. Conclusions Using a fascial free flap, the reconstructed tissue was approximately $1.5{\times}$ as thick as the contour of the normal side, which led to positive responses regarding aesthetic satisfaction.

• 한국환경과학회지
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• 제8권2호
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• pp.189-195
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• 1999

Determining factors and temporal & spatial characteristics of COD(Chemical Oxygen Demand) at the sea surface in Jinhae bay have been examined by using seasonal data, taken at twenty six stations over the whole bay during 1989~1994 by NERDA. The data have been analyzed in terms of long term means, anomalously large values. Jinhae bay is divided into three regions based on the time mean : mouth of Jinhae bay, inner sea of Masan bay, western sea of Jinhae bay called region 1,2 and 3, respectively. The horizontal distribution of the long term mean of COD at each station is similar to those of nitrogen and phosphorus. Characteristics of whole mean variation in the year shows high range of variation in region 2. It was appear to decreases every year in whole trend. Factors determining seasonal variation in whole COD mean are relative to salinity and nutrient, affected by precipitation in summer. Spatial variation shows high range of fluctuation in region 2 compare to other region. Factors determining of spatial variation of COD was appear to nutrient, affected by pollutant load of land area and bottom sediment. The long term mean of COD at each station is closely related with thats of nutrients. The correlation coefficient between COD and nitrogen, phosphate phosphorus was found to be high as 0.75, 0.78, respectively. Anomalously large COD was observed 14 times at 6 stations. These stations are located in inner sea of Masan bay(Region 2) and Songjeong bay(Region 1). The seasonal frequency of the observed anomalous COD is large in April, and other seasons are much the same.

• 한국재료학회지
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• 제21권3호
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• pp.180-185
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• 2011

This study is aimed to increase the activity of cathodic catalysts for PEMFCs(Polymer Electrolyte Membrane Fuel Cells). we investigated the temperature effect of 20wt% Pt/C catalysts at five different temperatures. The catalysts were synthesized by using chemical reduction method. Before adding the formaldehyde as reducing agent, process was undergone for 2 hours at the room temperature (RT), $40^{\circ}C$, $60^{\circ}C$, $80^{\circ}C$ and $100^{\circ}C$, respectively. The performances of synthesize catalysts are compared. The electrochemical oxygen reduction reaction (ORR) was studied on 20wt% Pt/C catalysts by using a glassy carbon electrode through cyclic voltammetric curves (CV) in a 1M H2SO4 solution. The ORR specific activities of 20wt% Pt/C catalysts increased to give a relative ORR catalytic activity ordering of $80^{\circ}C$ > $100^{\circ}C$ > $60^{\circ}C$ > $40^{\circ}C$ > RT. Electrochemical active surface area (EAS) was calculated with cyclic voltammetry analysis. Prepared Pt/C (at $80^{\circ}C$, $100^{\circ}C$) catalysts has higher ESA than other catalysts. Physical characterization was made by using X-ray diffraction (XRD) and transmission electron microscope (TEM). The TEM images of the carbon supported platinum electrocatalysts ($80^{\circ}C$, $100^{\circ}C$) showed homogenous particle distribution with particle size of about 2~3.5 nm. We found that a higher reaction temperature resulted in more uniform particle distribution than lower reaction temperature and then the XRD results showed that the crystalline structure of the synthesized catalysts are seen FCC structure.