• 분석과학
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• 제23권2호
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• pp.161-164
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• 2010

지하수 연구를 위한 추적자로 삼중수소를 이용하기 위해서는 강우중 삼중수소 양을 알아야 하므로 본 연구에서는 2007년부터 2009년까지 대전에서 매 월 강우를 채집하여 삼중수소 함량변화를 분석하였다. 분석 결과 강우중의 삼중수소 양은 최소 4.2 TU부터 최대 18.6 TU의 변화를 보였으며 여름과 겨울에 삼중수소의 양이 감소하고 봄과 가을에 그 양이 증가하는 경향을 나타내었다. 강우중의 평균 삼중수소 양을 강우량과 연관한 가중평균을 구한 결과 $7.85{\pm}0.46\;TU$를 나타내었다.

• Journal of Forest and Environmental Science
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• 제38권2호
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• pp.110-121
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• 2022

Leaf functional traits widely have been used to understand the environmental controls of resource utilization strategy of plants along the environmental gradients. By using key leaf functional traits, we quantified the relationships between leaf traits and local climate throughout the distributional range of Rhododendron caucasicum Pall. in eastern and western Georgian mountains (the South Caucasus). Our results revealed, that all traits showed high levels of intraspecific variability across study locations and confirmed a strong phenotypic differentiation of leaf functional variation along the east-west longitudinal gradient in response to the local climate; out of the explored climatic variables, the moisture factors related to precipitation and number of precipitation and dry days for winter and growth seasons were more strongly related to leaf trait variation than the elevation and air temperature. Among studied leaf traits, the leaf specific area (SLA) showed the highest level of variability indicating the different resource utilization strategies of eastern and western-central Rh. caucasicum individuals. High SLA leaves for western-central Caucasian individuals work in relatively resource-rich environments (more humid in terms of precipitation amount and the number of precipitation days in winter) and could be explained by preferential allocation to photosynthesis and growth, while eastern Caucasian samples work in resource-poor environments (less humid in terms of precipitation amount and the number of precipitation days in winter) and the retention of captured resources is a higher priority appearing in a low SLA leaves. However, more evidence from a broader study of the species throughout its distribution range by including additional environmental factors and molecular markers are needed for firmer conclusions of intraspecific variability of Rh. caucasicum.

• Journal of Radiation Protection and Research
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• 제44권3호
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• pp.118-126
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• 2019

Background: Government conducts environmental radioactivity surveillance for verification purpose around nuclear facilities based on the Nuclear Safety Law and issues a surveillance report every year. This study aims to evaluate the short and the long-term fluctuation of radionuclides detected above MDC and their origins using concentration ratios between these radionuclides. Materials and Methods: Sample media for verification surveillance are air, rainwater, groundwater, soil, and milk for terrestrial samples, and seawater, marine sediment, fish, and seaweed for marine samples. Gamma-emitting radionuclides including $^{137}Cs$, $^{90}Sr$, Pu, $^3H$, and $^{14}C$ are evaluated in these samples. Results and Discussion: According to the result of the environmental radioactivity verification surveillance in the vicinity of nuclear power facilities in 2017, the anthropogenic radionuclides were not detected in most of the environmental samples except for the detection of a trace level of $^{137}Cs$, $^{90}Sr$, Pu, and $^{131}I$ in some samples. Radioactivity concentration ratios between the anthropogenic radionuclides ($^{137}Cs/^{90}Sr$, $^{137}Cs/^{239+240}Pu$, $^{90}Sr/^{239+240}Pu$) were similar to those reported in the environmental samples, which were affected by the global fallout of the past nuclear weapon test, and Pu atomic ratios ($^{240}Pu/^{239}Pu$) in the terrestrial sample and marine sample showed significant differences due to the different input pathway and the Pu source. Radioactive iodine ($^{131}I$) was detected at the range of < $5.6-190mBq{\cdot}kg-fresh^{-1}$ in the gulfweed and sea trumpet collected from the area of Kori and Wolsong intake and discharge. A high level of $^3H$ was observed in the air (Sangbong: $0.688{\pm}0.841Bq{\cdot}m^{-3}$) and the precipitation (Meteorology Post: $199{\pm}126Bq{\cdot}L^{-1}$) samples of the Wolsong nuclear power plant (NPP). $^3H$ concentration in the precipitation and pine needle samples showed typical variation pattern with the distance and the wind direction from the stack due to the gaseous release of $^3H$ in Wolsong NPP. Conclusion: Except for the detection of a trace level of $^{137}Cs$, $^{90}Sr$, Pu, and $^{131}I$ in some samples, anthropogenic radionuclides were below MDC in most of the environmental samples. Overall, no unusual radionuclides and abnormal concentration were detected in the 2017's surveillance result for verification. This research will be available in the assessment of environment around nuclear facilities in the event of radioactive material release.

• 한국환경과학회지
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• 제12권12호
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• pp.1285-1292
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• 2003

당진 지역과 안면도 지역의 강수특성을 비교해 보기 위하여 수용성 이온성분 및 pH, 전기전도도 등을 2002년 4월 1일부터 2002년 11월 30일까지 당진 지역 총 47개의 시료와 안면도 지역 총 59개의 시료를 측정 분석해 본 결과 다음과 같은 결론을 얻었다. 1) 강수의 신뢰성 검토에는 WMO에서 사용하고 있는 이온수지법과 전기전도도법에 의한 방법 두 가지를 사용하였는데, 당진 지역의 강수는 이온수지법($r^2$ : 0.9429), 전기전도도법($r^2$ : 0.9916)의 값을 나타냈으며, 안면도 지역의 강수는 이온수지법($r^2$ : 0.9620), 전기전도도법($r^2$ : 0.9955)의 값을 보임으로써 WMO에서 권고하는 분석 자료에 대한 신뢰성을 확인 할 수 있었다. 2) 당진과 안면도 지역의 pH 분포는 당진 지역이 년 평균 pH 4.6, 안면도 지역이 년평균 pH 4.8로 산성비 기준인 5.6보다 산성을 나타내었다. 산성비 기준인 pH 5.6이하의 총 발생빈도는 당진이 약 76.8%, 안면도 지역이 81.4%로 나타났는데 이것은 두 지역에서 산성비가 그만큼 내렸다는 것과 같고, 또한 pH의 저하요인인 음이온이 상대적으로 많이 포함되어 있음을 추측할 수 있다. 3) 강수량과 pH와의 관계를 살펴보면 당진 지역과 안면도 지역 모두 여름철인 7, 8월에 강수량이 집중되었고 pH 또한 4.1-5.5 사이로 봄철이나 가을철에 비해 pH가 높게 나타났다. 이는 여름철의 장마로 인한 대기 중의 세정효과로 볼 수 있다.

• 공업화학
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• 제20권2호
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• pp.234-240
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• 2009

마그네슘염과 알칼리를 출발물질로 하는 수산화마그네슘 제조에서 공정 변수가 생성되는 입자의 크기, 형상 및 응집도에 미치는 영향에 대해 완전 요인배치(full factorial) 실험계획법(Design of experiment)으로 연구하였다. 수열합성에서는 알칼리/$MgCl_2$ 몰 비가 낮을수록, $MgCl_2$ 농도와 수열처리 온도가 높을수록 평균입경은 커지고 1차 입자 크기와 2차 입자 크기가 유사하지만, 침전법으로 제조한 수산화마그네슘은 1차 입자의 응집현상으로 2차 입경은 커지며, 응집성은 알칼리원의 종류와 $MgCl_2$의 농도에 따라 달라졌다. 알칼리원의 종류에 따른 차이는 $NH_4OH$를 사용한 경우 NaOH를 사용한 것보다 입자의 크기가 커지고 분산성이 우수하였다. 크기 및 표면 상태가 다른 샘플을 선정하여 LDPE와 EVA 혼합수지에 혼합하여 난연 특성을 비교하였을 때, 50, 55% 함량에서는 일반적으로 2차 입경 크기가 감소함에 따라 LOI값은 상승하지만, UL-94에서는 1차 입자가 작은 경우에 더 우수한 등급을 받는 경우가 있었다. 60%의 높은 함량에서 입자의 제조경로와 무관하게 UL-94는 V0 등급이지만, 미립이더라도 응집성있는 경우 한계산소지수가 상대적으로 낮다는 것을 알 수 있었다.

• 대한금속재료학회지
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• 제49권3호
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• pp.203-210
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• 2011

Bake hardening steels have to resist strain aging to prevent the yield strength increment and stretcher strain during press process and to enhance the bake hardenability during baking process after painting. The bake hardening steels need to control the solute carbon and the solute nitrogen to improve the bake hardenability. Ti and/or Nb alloying for nitride and carbide precipitation and low carbon content below 0.003% are used to solve strain aging and formability problem for automotive materials. However, in the present study, the effect of micro-precipitation of copper sulfide on the bake hardenability and fatigue properties of extremely low carbon steel has been investigated. The bake hardenability of Cu-alloyed bake hardening (Cu-BH) steel was slightly higher (5 MPa) than that of Nb-alloyed bake hardening (Nb-BH) steel, but the fatigue limit of Cu-BH steel was far higher (45 MPa) than that of Nb-BH steel. All samples showed the ductile fracture behavior and some samples revealed distinct fatigue stages, such as crack initiation, stable crack growth and unstable crack growth.

• 대한화학회지
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• 제67권1호
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• pp.33-41
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• 2023

Nanocrystallne WO₃ and MoO₃ with several different sizes and crystal structures were prepared by simple acid precipitation and subsequent heat treatment. The photochromic (PC) properties of these samples were comparatively investigated in powder state by monitoring diffuse reflectance spectral changes after bandgap irradiation. The PC effect of hexagonal WO₃ and monoclinic WO₃ strongly depended upon crystallite size rather than crystal structure. The smaller the crystallite size, the better the PC effect. However, orthorhombic WO·H₂O and MoO₃ having hexagonal and orthorhombic structures did not follow this trend. One consistent result for all WO₃ and MoO₃ samples is that the heat treatment in air, which changes crystallinity, whether it changes the crystal structure or only the crystallite size, reduces the PC effect. Since the thermal treatment reduces the surface oxygen defect sites, we believe that the PC effect of WO₃ and MoO₃ depends critically on the surface oxygen defect sites that serve as deep trap sites for photogenerated electrons and oxygen radical holes. We also found that the proton insertion claimed by double charge injection model is not critical for the PC effect.

• 한국대기환경학회지
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• 제10권2호
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• pp.98-104
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• 1994

Precipitation samples were collected at Kosan, Cheju Island over a period of 6 months An automatic rain sampler was manufactured domestically and installed at Kosan station. All samples were collected on a weekly basis. Samples were analyzed for S $O_4$$^{=}$, N $O_3$$^{[-10]}$ , C $l^{[-10]}$ , N $H_4$$^{+}$, N $a^{+}$, $K^{+}$, $Ca^{++}$, $Mg^{++}$, and pH and specific conductivity. The quality analysis of rain sample data were performed based on ion balance and specific conductivity. The pH of rain samples ranged between 4.6 to 6.6. Bicarbonate ion concentration were included in ion balance and specific conductivity calculations. The sum of cation concentrations were slightly greater than the sum of anion concentrations. Calculated specific conductivity was greater than measured specific conductivity. The most probable explanations for this discrepancy is "an anion too low or anion missing." Two criteria were used to identify outliners. They are 1) the difference between the sum of anion concentrations and cation concentration is more than 50 $\mu$eq./1 and 2) the difference between calculated and measured specific conductivity is more than 25%. Chemical analysis from several samples did not satisfy these quality control criteria. Volume weighted average concentrations were calculated. Dominant free acids in rain samples were N $a^{+}$, C $l^{[-10]}$ , S $O_4$$^{=}$, N $O_3$$^{[-10]}$ ions in order of abundance. Non-seasalt sulfate comprises 76% of total sulfate.sulfate.e.ate.e.

• 미생물학회지
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• 제35권1호
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• pp.41-46
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• 1999

수계에 분포하는 장바이러스를 검출하기 위해 민감도가 높고 검출시간이 빠른 PCR법을 이용하였다. 바이러스입자를 보다 순수하게 농축하기 위해 몇 가지 바이러스농축법을 비교조사하고 그것의 변형을 통하여 개선된 방법을 확립하였다. 비교한 농축방법중 흡탈착/Polyethyleneglycol(PEG) 침전법과 플록화/촉속원심분리법을 통해 10 PFU $ml^{-1}$ 까지 검출이 가능하여 다른 방법에 비해 효과적임이 판명되어Te. Sephadex resin을 이용한 부가적인 시료정제 과정을 통해 시료의 순도를 높일 수 있어검출한계를 10배정도 낮추었다. 서정된 검출법을 통해 한강수계에서 장바이러스의 분포를 조사한 결과 조사한 시료중 한강의 지천에서는 75%, 본류에서는 20%의 시료에서 바이러스가 검출되었다. 본 조사결과 흡탈착/PEG 침전법-PCR 검출기법이 수계의 바이러스 오염도를 간편하고 신속하게 검출하는데 매우 유용하였으며 국내 수계에도 바이러스 오염이 광범위함을 확인하였다.

• Biomaterials and Biomechanics in Bioengineering
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• 제4권1호
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• pp.21-32
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• 2019

Eggshell is a waste material after the usage of egg. In this work, biowaste chicken eggshells were used for preparing carbonated hydroxyapatite (HA) nanoparticles of high purity through aqueous precipitation method at room temperature. The eggshell-derived HA will be a cost-effective bioceramics for biomedical applications and an effective material-recycling technology. Additionally, mulberry leaf extract was used as a template to regulate the morphology, size and crystallinity of HA, and the effects of pH value were also examined. Characterization of the samples was performed by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. Scanning electron microscopy (SEM) was used to determine the size, shape and morphology of HA. The results indicate that only one phase of HA were synthesized in the both absence and presence of mulberry leaf extract at pH of 7 and above, while DCPD or DCPA/DCPD phase was observed at pH 4 condition. The crystallite sizes of the HA samples obviously decreased when adding mulberry leaf extract as a template, while they decreased gradually as the solution pH levels increased. With increasing pH level from 7 to 14, the rod-like HA nanoparticles gradually changed to spherical shape at pH 14. Note that, the obtained product is Mg and Sr containing A- and B-type carbonate HA at alkaline pH and it can be a potential material for biomedical applications.