• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2010년도 춘계학술발표대회 초록집
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• pp.22-22
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• 2010

주물과 용접에서 응고 과정에서 수지상간 또는 세포상간 영역에서 최종적으로 응고하는 저융점 공정 조성의 상이 응고균열의 발생에 직접적으로 영향을 미친다. 작은 량의 공정조성의 액상 필름이 응고된 고상과 고상 사이에 존재하게 되면 이 영역에서 생성되는 불연속부는 응고균열로 남게 된다. 이러한 공정조성 액상의 유동성이 좋고 충분한 부피로 존재한다면 응력과 부피수축등으로 생성된 수지상간, 또는 세포상강 영역에서 생성된 불연속부로 용이하게 유동하여 불연속부를 충진하게 된다. 따라서 발생한 응고균열이 치유되는 효과를 얻을 수 있다. 반면에 공정조상의 상이 전혀 존재하지 않는 순금속 응고의 경우에는 최종 응고 단계에 액상 필름이 존재하지 않게 되어 고상과 고상의 인터로킹이 가능하게 되어 균열 발생 가능성이 희박하다. 따라서 응고균열 발생을 제어할 수 있는 효과적인 방법은 용탕이나 용접금속의 조성을 공정 조성에 가깝게 제어하는 것이다.

• 한국환경과학회지
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• 제28권11호
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• pp.1005-1017
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• 2019

Environmental factors and changes in phytoplankton community structure before (August 5, 2017), during (August 18 and 25) and after (August 30 and September 15) freshwater input were analyzed to investigate the effects of freshwater input from Ganwol and Bunam lakes located in the upper part of Cheonsu Bay. Due to the large amount of freshwater input in the Cheonsu Bay, the surface salinity of the bay decreased by more than 8 psu, and the thermocline existing in the bay during August weakened. In addition, hypoxic phenomena occurred temporarily in the bay as the low oxygen water mass from the freshwater lakes flowed into the bay, and chemical oxygen demand, nutrients, and N/P increased with freshwater inflow. The density of phytoplankton during the freshwater inflow increased owing to their input from the freshwater lakes. Diatom species (Eucampia zodiacus) dominated the phytoplankton community in the bay before freshwater input; nanoflagellates, chlorophyta, cyanobacteria, and diatoms (Pseudonitzschia delicatissima, Chateocceros spp.) entered during freshwater input; and after freshwater inflow ended, diatoms (Chateocceros spp.) again became predominant indicating a return to previous conditions. The amount of phytoplankton standing crops increased sharply due to the inflow of freshwater species into the bay on the second day of discharge compared to before freshwater input; pre-discharge conditions were restored at most stations except at some sites close to the Bunam Lake three days after discharge. Therefore, the large amount of freshwater flowing into the bay affects not only the geochemical circulation in the bay but also the phytoplankton community structure. In particular, the high concentration of nutrients in the freshwater lake affect the marine ecosystem of the bay during August.

• 예술인문사회 융합 멀티미디어 논문지
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• 제7권4호
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• pp.243-250
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• 2017

목재와 같은 고체에서 불이 붙는 화재현상은 고체가 외부로부터 열을 받아 재료가 열분해 과정을 통하여 생성된 가스가 연소되는 현상을 포함한다. 이러한 고체의 열분해 현상은 외부로부터 유입되는 에너지의 양, 고체재료의 열이 확산되는 정도, 고체표면과 인접하여 있는 공기와의 열전달 정도를 포함한 고체재료와 주변과의 열전달 및 고체의 표면방사율 및 주변의 공기 중 산소의 분율 등 매우 여러 인자와 복잡하게 연결되어 있다. 본 논문에서는 화재현상을 가장 간단히 모사하기 위하여 필요한 발화온도를 산출하였다. 콘칼로리미타를 이용하여 다양한 목재시편을 이용하여 목재시편에 유입되는 열유속을 다양하게 제어하여 발화시간을 측정하였으며 이를 이용하여 발화온도를 산출하였다. 이를 위하여 사용자가 쉽게 사용할 수 있는 발화온도 산출 프로그램을 개발하였다. 고려된 목재는 5종류로 저밀도 MDF, 고밀도 MDF, 합판, 방부목, PB 등이며 다양한 두께에 대하여 고려하였다. 본 논문에서 제시된 발화온도는 고체의 화재 전파현상을 해석하는데 활용될 수 있다.

• 한국지리정보학회지
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• 제18권2호
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• pp.45-58
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• 2015

본 연구는 낙동강 부유쓰레기에 대한 실태 조사와 이동 경로 추적 시험을 통해 주요 집적 구간을 파악하고자 하였다. 또한, 주요 집적 구간을 대상으로 표본 조사를 실시하여 부유쓰레기의 유입량 및 성상을 파악하였다. 그 결과 낙동강 중 하류 지역으로부터 총 5곳의 집적 구간이 선정되었으며 대량의 초목류와 생활쓰레기가 집적되어 있었다. 그리고 하류 지역에 위치한 2곳의 집적 구간에서는 부유쓰레기가 해양으로 유출될 가능성이 큰 것으로 예측되었다. 주요 집적 구간에 대한 표본 조사에서는 초목류와 생활쓰레기를 포함한 $40{\ell}$이상의 쓰레기가 수거되었다. 생활쓰레기의 성상을 분류한 결과 플라스틱류가 49%를 차지하였으며 스티로폼류가 36%로 대부분을 차지하였다. 향후 본 연구는 낙동강 부유쓰레기의 해양 유입을 줄이고 효율적인 사전 수거 활동을 계획하는데 도움을 줄 것으로 기대된다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 추계학술대회 논문집
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• pp.340-345
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• 2003

This study, as a basic study for establishing a influence forecasting/estimating model when drain the deep sea water to the ocean after using it, carried out studies as follows; 1) estimating the amount of river discharge and pollutant loads inflowing into the developing region of deep sea water in East Sea, Korea 2) a field observation of tidal current, vertical distribution of water temperature and salinity, and 3-D numerical experiment of tidal current to analysis physical oceanographic status. The amount of river discharge flowing into the study area was estimated about $462.6{times}10^{3}m^{3}/day$ of daily mean in 2002 year. annual mean pollutant load of COD, TN and TP were estimated 7.02 ton-COD/day, 4.06 ton-TN/day and 0.39 ton/day, respectively. Field observation of tidal current results usually show about $20{\sim}40cm/sec$ of current velocity at the surface layer, it indicated a tendency that the current velocity decreases under 20cm/sec as the water depth increases. We could find a stratification within approximately the depth of 30m in field observation area, and the depth increases. We could find a stratification within approximately the depth of 30m in field observation area, and the differences of water temperature and salinity between the surface layer and bottom layer were about $18^{\circ}C$ and 0.8 psu, respectively. On the other hand, we found that there was a definite as the water mass of deep sea water about 34 psu of salinity.

• 한국세라믹학회지
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• 제28권10호
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• pp.767-776
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• 1991

Effects of the additions of SiB4 as burnable poison to UO2 on the green density, densification, interdependence between density-grain growth and microstructure of sintered UO2 were studied. UO2 pellets were sintered in flowing hydrogen, at temperature 1200, 1350, 1500, and 168$0^{\circ}C$ for 3 hours and at 168$0^{\circ}C$ for 0, 1, 3, and 10 hours, respectively. Green densities were in the range of about 4.5~5.4 g/㎤, and decreased as the amount of SiB4 increased when green pellets were made by with use of a double action press at 1000 kg/$\textrm{cm}^2$. The density of sintered UO2 pellets was around 92~94% of the theoretical density and did not change significantly as the amount of SiB2 addition increased. However, the density of sintered pellets decreased with the increase in SiB4. The grain growth could be characterized in terms of two stages: Grain growth occurred with the increasing density in the first stage, whereas the second stage was characterized by the grain growth without increasing of density. A liquid phase was observed at grain boundaries and grain edges in the microstructure of sintered UO2 pellets with 5000 ppm and 10,000 ppm SiB4. This liquid, possible formed at about 168$0^{\circ}C$, did not enhance the shrinkage, but appeared to accelarate the grain growth. It seems that the second stage grain growth was due to the presence of pressurized insoluble trapped gas in isolated pores.

• 한국해양공학회지
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• 제19권1호
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• pp.14-19
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• 2005

As a basic study for establishing the input conditions of a forecasting/estimating model, used for deep-sea water drainage to the ocean, this study was carried out as follows: 1) estimating the amount of river discharge and pollutant loads into the developing region of deep sea water in the East Sea, Korea, 2) a field observation of tidal current, vertical water temperature, and salinity distribution, 3) 3-D numerical experiment of tidal current to analyze the physical oceanographic status. The amount of river discharge flowing into this study area was estimated at about $462.7{\times}103 m\^3/day$ of daily mean in 2002. Annual mean pollutant load of COD, TN, and TP were estimated at 7.02 ton-COD/day, 4.06 ton-TN/day, and 0.39 ton/day, respectively. Field observation of tidal current normally shows 20-40cm/sec of current velocity at the surface layer, and it decreases under 20cm/sec as the water depth increases. We also found a stratification condition at around 30m water depth in the observation area. The differences in water temperature and salinity, between the surface layer and the bottom layer, were about 18 C and 0.8 psu, respectively. On the other hand, we found a definite trend of 34 psu salinity water mass in the deep sea region.

• 한국인터넷방송통신학회논문지
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• 제19권4호
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• pp.139-149
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• 2019

2018년 현재, 중국에서는 편서풍을 타고 다량의 미세먼지가 한국으로 유입되고 있다. 하지만 국내에서 발생되는 미세먼지양도 무시할 수 없다. 심지어 미세먼지 발생원인의 52%가 국내요인이다. 특히 인구가 밀집된 서울에서는 다른 지역과 비교할 수 없을 만큼 미세먼지 수치가 높다. 서울시에서도 구별로 미세먼지 수치는 다르게 나타난다. 구별로 미세먼지의 발생 차이를 이해하기 위해 서울시 미세먼지 발생원인 중 가장 높은 교통량을 기준으로 판단한다. 2017년의 교통량과 미세먼지의 농도를 비교해 실제로 교통량이 영향을 미치는지, 얼마나 영향을 미치는지, 만약 영향을 주지 않는다면 그 원인은 무엇인지 R을 이용해 비교해보고 서울시 미세먼지 발생의 원인을 확실히 인식한다.

• 한국물환경학회지
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• 제37권3호
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• pp.175-189
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• 2021

In this study, 48 streams in the Sapgyo Watershed were selected, and the Load Duration Curves (LDC) were drawn up for each stream using water quality and flow monitoring over the last three years (2018-2020), and it was evaluated whether the target water quality was achieved for each flow section. As a result of evaluating whether or not the target water quality exceeded according to the LDC, it was found that 22 rivers exceeded the target water quality. Five rivers exceeded the target water quality due to point pollutant sources, 13 rivers exceeded the target water quality due to non-point pollutant sources, and 4 rivers exceeded the target water quality due to both point and non-point pollutant sources. Among the rivers that exceeded the target water quality due to point pollutant sources, which included domestic sewage of the untreated population, there is a need to reduce the influx of polluted loads by the untreated population. The use of eco-friendly fertilizers is recommended for rivers with a relatively high farmland ratio among rivers exceeding the target water quality due to non-point pollutant sources, and installation of boiling point reduction facilities that can reduce the amount of polluted load introduced during rainfall or manage water shores. In rivers with a large number of livestock breeding heads, the livestock houses located in these rivers need to be preferentially transferred to livestock manure treatment plants. Due to the high ratio of land area because of urbanization, initial rainwater treatment facilities are required to reduce the amount of pollutant load flowing into the river through the impermeable layer during rainfall.

• 한국환경과학회지
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• 제17권6호
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• pp.601-609
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• 2008

In this study for the development of area due to the increasing of industry, population and spreading of urbanization is rapidly increasing but about seventy percent of our nation's areas consists of the mountainous districts. In such case, when those areas have the heavy rains break, they are washed away by a fast-flowing stream of a valley and overflowed. Thus it could result on human life and property damage and also the widespread of flood damage in the downstream area. To decrease those damage, the construction of flood control reservoir is necessary. This research was aim to construct the flood runoff models of a mountainous small district and to determine the probability rainfall by analyzing precipitation. The study also examined the effects of location and size of flood control reservoir on flood reduction. The result showed that the construction of detention basin was an effective way to ensure the safety of flood control and multiple detention basin had superior result for reducing amount of runoff in the down stream area than the single detention basin.