• 광물과 암석
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• 제34권4호
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• pp.277-291
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• 2021

하나의 광물상은 다양한 기원과 결정성장사를 기록하는 여러 개의 결정군집(crystal population)으로 분류될 수 있다. 울릉도 남동부에서 단사휘석 거정을 포함하면서, 유리질 급냉대(타킬라이트, tachylyte)를 가지는 반상 암맥이 발견되었다. 이 암석에 대한 암석기재학적 접근을 통해 이들이 포함하는 결정군집에 대한 연구가 수행되었다. 이번 연구는 전자 미세탐침 분석기를 사용해 이 암석을 구성하는 타킬라이트와 조암광물의 주성분원소 조성을 보고한다. 타킬라이트는 조면안산암질 조성을 가지며, 어떠한 변질의 흔적도 보이지 않는다. 이러한 특징은 타킬라이트의 조성이 이 암맥의 원래 멜트 조성을 반영할 수 있다는 점을 시사한다. 0.5mm 보다 큰 결정크기를 가지는 단사휘석과 사장석은 조면안산암질 멜트보다 초생적인 조성을 가졌던 멜트와 평형을 이루었던 재활결정(antecryst)으로 판단된다. 한편, 0.5 mm 보다 작은 결정크기를 가지는 단사휘석 및 사장석 미정(microlite)은 현재 위치에서 결정화된 초생결정(primocryst)이다. 이번 연구 결과에 따르면, 울릉도 화산단계 I 도동현무암에 대해 기존에 보고된 단사휘석의 조성변화 양상은 [Mg+Si+Fe]_basal ↔ [Al+Ti+Na]_prism를 통해 체계적으로 설명될 수 있으며, 이는 도동현무암에 포함된 모든 단사휘석이 섹터누대를 가질 수 있다는 점을 시사한다. 따라서, 단사휘석의 섹터누대에서 기인한 원소 분배가 도동현무암의 지구화학적 진화에 미친 영향이 추후 연구에 반영되어야 할 것으로 판단된다.

• 한국재료학회지
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• 제19권12호
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• pp.637-643
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• 2009

In this study, we analyzed the effect of silicon oxynitride matrix on the optical properties of Au nanoparticles dispersed on composite film and explored the effectiveness of the silicon in fine tuning the refractive index of the composite film for applications in optical waveguide devices. The atomic fraction of nitrogen in $SiO_xN_y$ films was controlled by varying the relative flow ratio of nitrogen gas in reactive sputtering and was evaluated optically using an effective medium theory with Bruggeman geometry consisting of a random mixture between $SiO_2$ and $Si_3N_4$. The Au nanoparticles were embedded in the $SiO_xN_y$ matrix by employing the alternating deposition technique and clearly showed an absorption peak due to the excitation of surface plasmon. With increasing nitrogen atomic fraction in the matrix, the surface plasmon resonance wavelength shifted to a longer wavelength (a red-shift) with an enhanced resonance absorption. These characteristics were interpreted using the Maxwell-Garnett effective medium theory. The formation of a guided mode in a slab waveguide consisting of 3 $\mu$m thick Au:$SiO_xN_y$ nanocomposite film was confirmed at the telecommunication wavelength of 1550 nm by prism coupler method and compared with the case of using $SiO_2$ matrix. The use of $SiO_xN_y$ matrix provides an effective way of controlling the mode confinement while maintaining or even enhancing the surface plasmon resonance properties.

• 지구물리와물리탐사
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• 제13권2호
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• pp.169-174
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• 2010

중력탐사 자료 처리 과정 중 더 정밀한 지형보정을 수행하기 위하여 삼각요소법(triangular element method)을 이용한 지형보정의 효과를 검증하였다. 삼각요소법은 임의 다면체를 삼각형 면들의 조합으로 구성하여 중력 효과를 계산하는 방법이다. 이 방법을 이용하면 기존 지형 보정에서 사용하는 사각 기둥의 조합으로 지형을 구성하는 것보다 지형을 실제에 가깝게 근사할 수 있으므로 정밀한 지형효과 계산이 가능하다. 이 연구에서는 해석해가 존재하는 원뿔모델을 이용하여 삼각요소법을 이용한 지형보정효과를 검증하였다. 또한 지금까지 많이 사용되어 왔던 사각프리즘법과의 차이를 보이기 위해 지형효과 차이가 많이 발생하는 경사모델에서 두 방법의 차이를 보였다. 이 연구에서 제안한 삼각요소법을 이용한 지형보정 프로그램을 우리나라 남해안의 중력자료에 적용하여 그 효용성을 검증하였다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2023년도 학술발표회
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• pp.519-519
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• 2023

Estuarine dams are a recent and global phenomenon. While estuarine dams can provide the benefit of improved freshwater resources, they can also alter estuarine processes. Due to the wide range of estuarine types and estuarine dam configurations, the effect of estuarine dams on estuaries is not well understood in general. To develop a systematic understanding of the effect of estuarine dam location and freshwater discharge interval on a range of estuarine types (strongly stratified, partially mixed, periodically stratified, and well-mixed), this study used a coupled hydrodynamic-sediment dynamic numerical model (COAWST) and compared flow, sediment transport, and morphological conditions in the pre- and post-dam estuaries. For each estuarine type, scenarios with dam locations at 20, 55 and 90 km from the mouth and discharge intervals of a discharge every 0.5, 3, and 7 days were investigated. The results were analyzed in terms of change in tide, river discharge, estuarine classification, and sediment flux mechanism. The estuarine dam location primarily affected the tide-dominated estuaries, and the resonance length was an important length scale affecting the tidal currents and Stokes return flow. When the location was less than the resonance length, the tidal currents and Stokes return flow were most reduced due to the loss of tidal prism, the dead-end channel, and the shift from mixed to standing tides. The discharge interval primarily affected the river-dominated estuaries, and the tidal cycle period was an important time scale. When the interval was greater than the tidal cycle period, notable seaward discharge pulses and freshwater fronts occurred. Dams located near the mouth with large discharge interval differed the most from their pre-dam condition based on the estuarine classification. Greater discharge intervals, associated with large discharge magnitudes, resulted in scour and seaward sediment flux in the river-dominated estuaries, and the dam located near the resonance length resulted in the greatest landward tidal pumping sediment flux and deposition in the tide-dominated estuaries.

• Fisheries and Aquatic Sciences
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• 제26권1호
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• pp.24-34
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• 2023

Reactive oxygen species (ROS) at high concentrations induce oxidative stress, an imbalanced redox state that is a prevalent cause of neurodegenerative disorders. This study aimed to investigate the protective effect of Capsosiphon fulvescens (CF) extract on oxidative stress-induced impairment of cognitive function in models of neurodegenerative diseases. CF was extracted with subcritical water and several solvents and H₂O₂ (0.25 mM) or aluminum chloride (AlCl₃; 25 µM) as an inducer of ROS was treated in PC12 neuronal cells and zebrafish larvae. All statistical analyses were performed using one-way analysis of variance and Dunnett's test using GraphPad Prism. H₂O₂ and AlCl₃ were found to significantly induce ROS production in PC12 neuronal cells and zebrafish larvae. In addition, they strongly affected intracellular Ca²⁺ levels, antioxidant enzyme activity, brain-derived neurotrophic factor (BDNF) and tropomyosin receptor kinase B (TrkB) signaling, acetylcholinesterase (AChE) activity, and hallmarks of Alzheimer's disease. However, treatment of H₂O₂-induced PC12 cells or AlCl₃-induced zebrafish larvae with CF subcritical water extract at 90℃ and CF water extract effectively regulated excessive ROS production, intracellular Ca²⁺ levels, and mRNA expression of superoxide dismutase, glutathione peroxide, glycogen synthase kinase-3 beta, β-amyloid, tau, AChE, BDNF, and TrkB. Our study suggested that CF extracts can be a potential source of nutraceuticals that can improve the impairment of cognitive function and synaptic plasticity by regulating ROS generation in neurodegenerative diseases.

• Parasites, Hosts and Diseases
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• 제54권1호
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• pp.9-14
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• 2016

Tamoxifen is an antagonist of the estrogen receptor and currently used for the treatment of breast cancer. The current treatment of cutaneous leishmaniasis with pentavalent antimony compounds is not satisfactory. Therefore, in this study, due to its antileishmanial activity, effects of tamoxifen on the growth of promastigotes and amastigotes of Leishmania major Iranian strain were evaluated in vitro. Promastigotes and amastigotes were treated with different concentrations (1, 5, 10, 20, and $50{\mu}g/ml$) and time periods (24, 48, and 72 hr) of tamoxifen. After tamoxifen treatment, MTT assay (3-[4,5-dimethylthiazol-2-yl]-2,5 biphenyl tetrazolium bromide assay) was used to determine the percentage of live parasites and Graph Pad Prism software to calculate $IC_{50}$. Flow cytometry was applied to investigate the induction of tamoxifen-induced apoptosis in promastigotes. The half maximal inhibitory concentration ($IC_{50}$) of tamoxifen on promastigotes was $2.6{\mu}g/ml$ after 24 hr treatment. Flow cytometry analysis showed that tamoxifen induced early and late apoptosis in Leishmania promastigotes. While after 48 hr in control group the apoptosis was 2.0%, the $50{\mu}g/L$ concentration of tamoxifen increased it to 59.7%. Based on the in vitro antileishmanial effect, tamoxifen might be used for leishmaniasis treatment; however, further researches on in vivo effects of tamoxifen in animal models are needed.

• Advances in concrete construction
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• 제2권3호
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• pp.177-192
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• 2014

One of the main applications of FRP composites is confining concrete columns. Hence identifying the cyclic and monotonic stress-strain behavior of confined concrete columns and the parameters influencing this behavior is inevitable. Two significant parameters affecting the stress-strain behavior are aspect ratio and corner radius. The present study aims to scrutinize the effects of corner radius and aspect ratio on different aspects of stress-strain behavior of FRP confined concrete specimens (rectangular, square and circular). Hence 44 FRP confined concrete specimens were tested and the results of the tests were investigated. The findings indicated that for specimens with different aspect ratios, the relationship between the ultimate stress and the corner radius is linear and the variations of the ultimate stress versus the corner radius decreases as a result of an increase in aspect ratio. It was also observed that increase of the corner radius results in increase of the compressive strength and ultimate axial strain and increase of the aspect ratio causes an increase of the ultimate axial strain but a decrease of the compressive strength. Investigation of the ultimate condition showed that the FRP hoop rupture strain is smaller in comparison with the one obtained from the tensile coupon test and also the ultimate axial strain and confined concrete strength are smaller when a prism is under monotonic loading. Other important results of this study were, an increase in the axial strain during the early stage of unloading paths and increase of the confining effect of FRP jacket with the increase and decrease of the corner radius and aspect ratio respectively, a decrease in the slope of reloading branches with cycle repetitions and the independence of this trend from the variations of the aspect ratio and corner radius and also quadric relationship between the number of each cycle and the plastic strain of the same cycle as well as the independence of this relationship from the aspect ratio and corner radius.

• 대한원격탐사학회지
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• 제32권4호
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• pp.383-401
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• 2016

In this paper, we described the statistical modeling of crop yields using satellite images, climatic datasets, soil property maps, and fertilizer data for the Midwestern United States during 2001-2012. Satellite images were obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS), and climatic datasets were provided by the Parameter-elevation Regressions on Independent Slopes Model (PRISM) Climate Group. Soil property maps were derived from the Harmonized World Soil Database (HWSD). Our multivariate regression models produced quite good prediction accuracies, with differences of approximately 8-15% from the governmental statistics of corn and soybean yields. The unfavorable conditions of climate and vegetation in 2012 could have resulted in a decrease in yields according to the regression models, but the actual yields were greater than predicted. It can be interpreted that factors other than climate, vegetation, soil, and fertilizer may be involved in the negative biases. Also, we found that soybean yield was more affected by minimum temperature conditions while corn yield was more associated with photosynthetic activities. These two crops can have different potential impacts regarding climate change, and it is important to quantify the degree of the crop sensitivities to climatic variations to help adaptation by humans. Considering the yield decreases during the drought event, we can assume that climatic effect may be stronger than human adaptive capacity. Thus, further studies are demanded particularly by enhancing the data regarding human activities such as tillage, fertilization, irrigation, and comprehensive agricultural technologies.

• 한국광학회지
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• 제13권1호
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• pp.9-14
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• 2002

감쇠 전반사(attenuated total reflection)를 이용하여 액체의 농도 변화를 측정할 수 있는 표면 플라즈몬 공명 센서를 제작하였다. 센서의 구조는 프리즘 밑면에 금속 박막을 코팅하고 그 밑에 유전체론 접촉시킨 Kretschmann-Raether타입으로 하였고, 금속 박막으로는 센서 물질로 적합한 은(Ag) 박막을 사용하였다. 본 센서의 특성은 일반적으로 금속 박막의 두께에 영향을 받는데, 이론적 분석을 통하여 은 박막의 경우 54 nm의 두께에서 매우 좋은 특성을 나타냄을 알 수 있었다. 물과 에탄올을 혼합한 용액에서 에탄올의 농도를 변화시켜 가며 이에 따른 보면 플라즈몬 공명 각을 측정하였고, 표면 플라즈몬 공명 각의 변화로부터 혼합 용액의 농도 변화를 구하였다. 에탄올의 농도가 증가하여 50% 질량비 가지 변하는 구간에서 SPR센서가 매우 좋은 특성을 보였으며, 에탄올의 농도 변화를 3$\times$$10^{-2}$ % 질량비 가지 측정할 수 있었다. 또한 물과 에탄올을 혼합한 용액의 굴절률이 용액의 농도 변화에 따라 비선형적으로 변함을 관측하였으며, 물과 에탄을 혼합 용액의 농도에 따른 밀도 변화를 이용해 굴절률 변화의 비선형적 경향을 설명할 수 있었다.

• 한국지리정보학회지
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• 제19권3호
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• pp.127-143
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• 2016

본 연구는 상이한 셀 크기에 따라 밀도구분적 인구추정의 정확성이 어떻게 변화하는지를 탐색하였다. 미국 조지아주 풀턴 카운티를 사례로 한 밀도구분적 인구 지도가 지능적인 밀도구분적 지도제작기법, 인구자료, 원본 및 모의된 토지이용 및 피복 자료를 이용하여 30m에서 420m의 해상도까지 매 30m 간격으로 생성되었다. 밀도구분적 인구 지도의 정확성은 RMSE 및 수정 RMSE 통계치를 이용하여 평가되었다. 프랙털 차원 값은 TPSA 방법을 사용하면서 30m에서 420m의 해상도까지 생성된 밀도구분적 인구 지도에 대해 각각 계산되었다. 연구결과에 따르면, 속성의 정확성 측면에서 인구를 보다 정확하게 추정하기 위해서 210m 이하의 격자 셀 크기가 적절하였나, 사례지역에서 밀도구분적 인구추정의 허용가능한 공간적 정확성을 충족시키기 위해 30m의 격자 셀 크기가 적절하였다. 또한, 프랙털 분석은 120m의 격자 셀 크기가 사례지역에서 밀도구분적 인구추정을 위한 최적의 해상도 이다는 것을 보여준다.