• 한국환경과학회지
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• 제13권12호
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• pp.1023-1032
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• 2004

Rapid progress in urbanization has resulted in a change of the micro climate, especially in the urban area. In order to investigate the phenomenon of the heat island in the residential micro climate, a field survey was carried out by 4 sets of the residential type in Jeonju under typical winter synoptic condition. As analytic methode, it is used the comparison on the relation of the Land-to-Coverage Rate to Heat Island and Oxygen Concentration. And as a key question it is asked how stable characteristics of the micro climate will result from the survey of the Heat Island and the Oxygen Concentration, used as indicator. To ensure the trustworthy result of research, it is calculated the critical influence of the wind velocity and the Land-to-Covearage Rate. As a result of comparative analysis, it could be confirmed that the local temperatures in all sets of the residential type were higher than the average temperature in Jeonju. But the housing type A 'exclusive use for housing zone' has relativly the most stable and best living condition. On the contrary the residential type B and D has the worst toward the oxygen concentration in the time zone 9-12 a.m., which didn't reach the minimum of the oxygen concentration $20.5{\%}.$ It means that the higer the development and population density is, the worse is the situation of the Quality of Life in the residential types in accordance with the heat island and oxygon con­centration.

• Journal of Welding and Joining
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• 제34권1호
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• pp.75-81
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• 2016

This study applied laser surface melting process using CW(Continuous wave) Yb:YAG laser and cold-work die steel SM45C and investigated microstructure and hardness. Laser beam speed, power and beam interval are fixed at 70 mm/sec, 2.8 kW and $800{\mu}m$ respectively. Depth of Hardening layer(Melting zone) was a minimum of 0.8 mm and a maximum of 1.0 mm that exceeds the limit of minimum depth 0.5 mm applying trimming die. In all weld zone, macrostructure was dendrite structure. At the dendrite boundary, Mn, Al, S and O was segregated and MnS and Al oxide existed. However, this inclusion didn't observe in the heat-affected zone (HAZ). As a result of interpreting phase transformation of binary diagram, MnS crystallizes from liquid. Also, it estimated that Al oxide forms by reacting with oxygen in the atmosphere. The hardness of the melting zone was from 650 Hv to 660 Hv regardless of the location that higher 60 Hv than the hardness of the HAZ that had maximum 600 Hv. In comparison with the size of microstructure using electron backscatter diffraction(EBSD), the size of microstructure in the melting zone was smaller than HAZ. Because it estimated that cooling rate of laser surface melting process is faster than water quenching.

• 상하수도학회지
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• 제28권2호
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• pp.161-170
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• 2014

It is essential to decrease energy consumption and excess sludge to economically operate sewage treatment plant. This becomes more important along with a ban on sea dumping and exhaustion of resource. Therefore, many researchers have been study on energy consumption reduction and strategies for minimization of excess sludge production from the activated sludge process. The aeration cost account for a high proportion of maintenance cost because sufficient air is necessary to keep nitrifying bacteria activity of which the oxygen affinity is inferior to that of heterotrophic bacteria. Also, additional costs are incurred to stabilize excess sludge and decrease the volume of sludge. There were anoxic, aerobic, membrane, deairation and concentration zone in this MBR process. Continuous aeration was provided to prevent membrane fouling in membrane zone and intermittent aeration was provided in aerobic zone through ammonia sensor. So, there was the minimum oxygen to remove $NH_4-N$ below limited quantity that could be eliminated in membrane zone. As the result of this control, energy consumption of aeration system declined by between 10.4 % and 19.1 %. Besides, we could maintain high MLSS concentration in concentration zone and this induced the microorganisms to be in starved condition. Consequentially, the amount of excess sludge decrease by about 15 %.

• Ocean and Polar Research
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• 제36권4호
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• pp.423-435
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• 2014

Verifying the similarity of environmental characteristics between an artificial impact site and a preserved or reference site is necessary to quantitatively and qualitatively evaluate the environmental impact of mining activity. Although an impact site (BIS station) and a preserved site (called KOMO station) that have been selected in the Korea manganese nodule contract area may share similar environmental characteristics, similarities in terms of the water column environment between both sites has not been investigated. In this study, we compared the chemical properties of the water columns and sinking particle fluxes between BIS and KOMO stations through two observations (August 2011 and September 2012). Additionally, we observed particle fluxes at the KOMO station for five years (July 2003~July 2008) to understand long-term natural variability. Vertical distributions of water column properties such as dissolved oxygen, inorganic nutrients (N, P, Si), total organic carbon below surface layer (within the depth range of 200 m) were not considerably different between the two sites. Especially, values of water column parameters in the abyssopelagic zone from 4000 m to bottom layer (~5000 m) were very similar between the BIS and KOMO sites. Sinking particle fluxes from the two sites also showed similar seasonality. However, natural variation of particle flux at the KOMO site varied from 3.5 to $129.9mg\;m^{-2}day^{-1}$, with a distinct temporal variation originating from ENSO events (almost forty times higher than a minimum value). These results could provide valuable information to more exactly evaluate the environmental impact of mining activity on water columns.

• Journal of Plant Biotechnology
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• 제31권3호
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• pp.249-253
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• 2004

생물반응기의 형태에 따른 인삼부정근의 생장과 ginsen-side의 생산능력에 대하여 조사한 결과, 원형의 상부와 하부에 5 cm의 bubble column을 가진 bulb type bubble bioreactor (BU)에서 건물중은 41.92 g으로 가장 많이 증가하였으며, cylindric tube bioreactor (CT)에서 건물중이 38.55g으로 가장 낮게 나타났다. 이들 두 생물반응기의 초기 kLa 값은 BU 생물반응기에서 6.98 h$^{-1}$로 가장 높게 측정되었고, 반대로 bubble column이 없는 CT 생물반응기에서 5.25 h$^{-1}$으로 가장 낮게 측정되었다. 그러나 이와 같은 초기 kLa값의 차이는 부정근내의 이차대사산물인 ginsenoside의 함량에는 영향을 주지 않는 것으로 나타났다. 또한 BU 생물반응기에서 bubble column의 길이를 기존의 5 cm에서 10 cm로 연장시켰을 때, 초기 kLa값이 6.52 h$^{-1}$에서 7.80 h$^{-1}$로 증가하면서 인삼부정근의 생장을 42.13 g에서 50.30 g으로 약 16% 증가시킨 것으로 나타났다.

• 한국해양환경ㆍ에너지학회지
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• 제18권3호
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• pp.143-156
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• 2015

서태평양에 위치한 해저산 해역($150.2^{\circ}E$, $20^{\circ}N$ 부근)에서 수층 환경의 동적 특성을 파악하고자 수괴 및 용존산소, 무기영양염(질소, 인), 엽록소-a 등과 같은 수층 환경 인자의 거동을 살펴보았다. 2014년 10월에 해저산(OSM14-2)을 중심으로 동-서 및 남-북 방향으로 총 9개의 정점에서 CTD system을 이용하여 물리 화학적 자료를 획득하였다. 수온-염분 도표로부터 연구 해역에서 파악된 수괴는 표층에서 북태평양 열대수와 수온약층수, 중층에서 북태평양 중층수 그리고 저층에서 북태평양 심층수로 구분되었다. 용존산소 농도가 낮은 최소층(평균 $73.26{\mu}M$)은 산소 결핍 환경(dysoxic<$90{\mu}M$)으로 연구 해역 전반에 걸쳐 수심 700~1,200 m 사이에 분포하였다. 아질산염+질산염과 인산염으로 대표되는 무기영양염은 표면혼합층 내에서 빈영양 환경을 보인 후 수심 증가에 따라 점차적으로 증가해 용존산소 최소층에서 최대 농도를 나타냈으며, N:P ratio(13.7) 결과로부터 연구 해역은 식물플랑크톤이 성장하기에 질소 성분이 제한된 환경으로 파악되었다. 해저산을 중심으로 동-서 및 남-북 정점 라인에서 환경 인자의 수직 분포는 서쪽과 남쪽 해역에서 저층수 유입에 의한 영향으로 수심 500 m 부근에서 그리고 수심 2,500 m 이하의 저층 내에서도 서쪽 해역과 남쪽 해역에서 반대 해역과 비교해 환경 인자의 농도가 다르게 분포하였다. Redfield ratio(N:P=16:1)을 이용하여 구해진 Excess N 값은 연구 해역 전반에 걸쳐 음의 값을 보여 질소 제거 기작이 우세한 환경임을 나타냈으며, 서쪽 해역과 남쪽 해역 저층에서 상대적으로 높은 값이 관측되었다. 이러한 결과들은 해저산의 지형적인 특성이 저층 해류 순환에 영향을 미치고 이는 수층 환경 인자들의 거동을 결정하는데 중요하게 작용함을 지시한다.

• 한국수산과학회지
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• 제23권3호
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• pp.208-214
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• 1990

한국 남해에 있어서 식물플랑크촌의 현존양은 4월이 가장 많으며 그 지리적 분포상태는 주로 연주도와 대마도간의 수온전선형성해역에 가장 풍부하고 그 전선에서 연안측이 외양측보다 더욱 풍부한 경향이므로 전선형석 위치에 따라 그 농도가 달라지게 된다. 현존양이 2월과 4월에는 최고양으로 출현한 205선의 01점에 8월에는 반대로 최소양으로 출현한 이유는 이 해역의 환경요인이 다른 연도의 것보다 뛰어나게 고온, 고염, 빈산소 및 빈영양상태이므로 이들의 특성을 지닌 Tsushima 난류수괴가 연안까지 침투한 까닭인 것으로 사료된다. 출현종류는 33속 72종 중 규조류가 27속 61종이고 경모조류가 6속 11종이며 시기별 출현종류수는 출현량이 4월에 가장 많은데 비해 8월이 가장 많은 것으로 나타났다. 우점종의 조성은 2월은 Eucampia zodiacus, 4월은 Skeletonema costatum과 Chaetoceros curvisetus 및 8월은Chaetoceros affinis 등으로서 시기별로 대차가 있었다. Eucampia zodiacus는 2월과 4월에 있어서 남해연안수역과 제주도 서방의 혼합수역을 지표하는 지표종으로서의 가치가 있다고 본다.

• Membrane and Water Treatment
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• 제7권5호
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• pp.417-431
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• 2016

Poly(vinylidene fluoride) (PVDF) powder was treated with aqueous sodium hydroxide to obtain partially defluorinated fluoropolymers with expected properties such as improving hydrophilicity and fouling resistance. Raman spectrum and FT-IR results confirmed the existence of conjugated carbon double bonds after alkaline treatment. As the concentration increased, the degree of defluorination increased. The morphology and structure of membranes were examined. The permeation performance was investigated. The results showed that membrane's hydrophilicity increased with increase of the percentage of alkaline treated PVDF powder. Moreover, in terms of the water contact angle, it decreased from $92^{\circ}$ to a minimum of $68^{\circ}$; while water up take increased from 128 to 138%. Fluxof pure water and the cleaning efficiency increased with the increase of alkaline treated PVDF powder. The fouling potential also decreased with the increase of the percentage of alkaline treated PVDF powder. The reason that makes blending PVDF show different characteristics because of partial defluorination, which led the formation of conjugated C = C bonds and the inclusion of oxygen functionalities. The polyene structure followed by hydroxide attack to yield hydroxyl and carbonyl groups. Therefore, the hydrophilicity of blending membrane was improved. The SEM and porosity measurements showed that no obvious variations of the pore dimensions and structures for blend membranes were observed. Mechanical tests suggest that the high content of the alkaline treated PVDF result in membranes with less tolerance of tensile stress and higher brittleness. TGA results exhibited that the blend of alkaline treated PVDF did not change membrane thermal stability.

• Ocean and Polar Research
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• 제30권3호
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• pp.215-224
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• 2008

A piston core (MR06-04 PC23A) collected from the northern continental slope in the central Bering Sea has recorded the high-resolution millennial-scale variation of calcium carbonate ($CaCO3$) content during the last 65 kyr. An estimation of the age of the core sediments was carried out by using the lithologic correlation of the deglacial laminated layers with a neighboring core (HLY02023JPC), complementing the last appearance datum of both Lychnocanoma nipponica sakaii (54 kyr) and Amphimelissa setosa (85 kyr). The probable age of core MR06-04 PC23A was approximately younger than 65 kyr. Two distinct events of a significant increase of $CaCO3$ in the deglacial laminated sediments clearly correspond to MWP1A and MWP1B in the Bering Sea (Gorbarenko et al. 2005) and to T1ANP and T1BNP in the North Pacific (Gorbarenko 1996). These pronounced peaks of $CaCO3$ contents result from the elevated carbonate production in the surface water and the subsequent weakened dilution due to terrestrial input, along with an enhanced oxygen minimum zone. The $CaCO3$ contents are low (${\sim}2%$) during the last glacial period mainly because of a low carbonate production caused by an expanded sea-ice cover and an increased dilution by terrigenous particles due to their closer distance to the continent during the sea-level low stand. The occurrence of seven distinct $CaCO3$ peaks in core MR06-04 PC23A is remarkable during MIS 3 and MIS 4, and they most likely correlate to the short-term millennial Dansgaard-Oeschger events.

• Korean Chemical Engineering Research
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• 제43권1호
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• pp.47-52
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• 2005

미립 금속분체에 대한 산업 수요 증가와 함께, 퇴적 금속분의 착화에 의한 화재, 폭발사고가 증가하고 있다. 본 연구에서는 퇴적 금속분체의 화재, 폭발 위험특성을 조사하기 위하여 새로운 실험장치를 개발하였다. 금속분(Mg, Zr, Ta, Ti) 및 PMMA(polymethyl methacrylate)분진을 사용하여, 연소 거동(소염거리, 화염전파속도) 및 화염전파에 미치는 $N_2$ 치환 분위기 농도의 영향 등을 실험적으로 상세히 조사하였다. 실험결과로부터, 퇴적 금속 분체의 화염전파속도는 PMMA보다 크고, 화염전파속도의 퇴적층 두께에 대한 의존성은 작으며, 질소 치환 분위기에서의 Mg의 한계 산소 농도는 3.6-3.7 vol%로 나타났다. 퇴적금속 분체층의 화염전파속도와 소염거리 역수는 높은 상관관계를 가지고 있으며, 이들 연소성 지표에 있어서 상대적인 위험성의 예측이 가능하다.