• International Journal of Aeronautical and Space Sciences
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• 제4권2호
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• pp.51-60
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• 2003

An experimental research program is being undertaken to develop a regeneratively-cooled experimental thrust chamber of liquid rocket engine using liquefied natural gas and liquid oxygen as propellants. Prior to firing test using a regenerative cooling with liquefied natural gas in this program, several firing tests were conducted with water as a coolant. Experimental thrust chambers with a thrust of about 10tf were developed and their firing test facility was built up. Injector used in the thrust chamber was of shear-coaxial type appropriate for propellants of gas and liquid phase and cooling channels are of milled rectangular configuration. Periodical variation of the soot deposition and discoloration was observed through an eyes' inspection on the inner wall of a combustion chamber and a nozzle after each firing test, and an intuitive concept of the periodical variation of mixture ratio near the inner wall of a combustion chamber and a nozzle at once was brought about and analyzed quantitatively. Thermal heat flux to the coolant was calculated and modified with the periodical variation model of mixture ratio, and the increment of coolant temperature at cooling channels was compared with measured one.

• 생명과학회지
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• 제23권6호
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• pp.812-824
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• 2013

Reserpine은 항고혈압제로서 알츠하이머질병의 증상을 나타내는 Caenorhabditis elegans에서 세포독성을 감소시켜 마비를 억제하고 수명을 연장시키는 것으로 알려져 있다. 본 연구에서는 이러한 reserpine의 효능을 포유동물에서 확인하기 위하여, 알츠하이머질병의 병리적 특성과 연관된 주요인자의 변화를 30일 동안 reserpine을 투여한 Tg2576 마우스에서 관찰하였다. 그 결과, 공격행동(aggressive behavior)은 vehicle 투여 그룹에 비하여 reserpine 투여 그룹에서 유의적으로 감소하였으나 사회적 접촉(social contact)은 유의적인 변화가 없었다. 뇌의 해마부분에서 알츠하이머질병의 원인 중 하나인 $A{\beta}$-42의 축적은 reserpine 투여 그룹에서 유의적으로 감소하였고, $A{\beta}$-42의 농도도 대조군에 비하여 reserpine 투여 그룹에서 감소하였다. 더불어, ${\gamma}$-secretase의 구성단백질 중에서 PS-2, Pen-2, APH-1의 발현은 대조군에 비하여 reserpine 투여군에서 유의적으로 감소하였으나 NCT 발현은 변화가 없었다. 혈청에서 NGF의 농도는 Tg2576 마우스에서 감소하였다가 reserpine 투여한 그룹에서 유의적으로 증가하였으며, high affinity receptor의 신호전달과정에 포함된 단백질 중에서 reserpine 투여 그룹은 TrkA의 인산화가 증가하고 ERK 인산화는 감소되었다. 한편 low affinity receptor의 신호전달과정에서, $p75^{NTR}$과 Bcl-2의 발현은 vehicle 그룹에 비하여 reserpine 투여 그룹에서 유의적으로 발현이 증가하였으나 RhoA의 발현은 reserpine 투여 그룹에서 감소하였다. 따라서 이러한 결과는 reserpine은 포유동물 치매모델인 Tg2576 마우스에서 행동학적 변화, $A{\beta}$-42의 축적, NGF의 농도, NGF신호전달의 변화 등을 유도하며, 향후 치매치료제로서 가능성을 제시하고 있다.

• 대한원격탐사학회지
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• 제38권6_1호
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• pp.1315-1328
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• 2022

신두리해빈 인근지역은 겨울철 북서풍의 영향으로 인하여 모래언덕을 이룬 전형적인 퇴적지형이다. 그 규모가 방대하고 잘 발달되어 있어 보존가치를 인정받아 현재 천연기념물 제431호로 지정되어 있으며 지형학적 가치 보존 측면에서 꾸준한 모니터링이 필요하다. 본 연구에서는 충청남도 태안군에 위치한 신두리 해안사구의 장기간 지형변화 관측을 위해 약 36년 동안의 항공영상, 드론영상 그리고 드론기반 LiDAR 자료를 사용하여 분석하였다. 이를 위해서 원 자료로부터 생성된 Digital Elevation Model (DEM)을 사용하여 래스터 연산기반의 DEM 차분 기법을 적용하여 각 기간별 표고 및 부피의 변화량을 산정하였다. 또한 각 자료원의 고유오차를 오차전파법칙을 이용하여 확률기반의 부피의 변화량도 산정하였다. 그 결과, 1986년부터 2022년까지 관심영역 A (면적: 17,960 m²)에서는 35,119 m³의 퇴적이 발생하였으며, 관심영역 B (면적: 17,686 m²)에서는 54,954 m³의 퇴적이 발생하였음을 알 수 있었다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2020년도 학술발표회
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• pp.327-327
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• 2020

Increase in Earth's surface temperature, higher rainfall intensity rate, and rapid changes in land cover are just some of the most evident effects of climate change. Flooding, and river sedimentation are two inevitable natural processes in our environment, and both issues poses great risks in the dam industry when not addressed properly. River sedimentation is a significant issue that causes reservoir deposition, and thus causes the dam to gradually lose its ability to store water. In this study, the long-term effects of climate change on the sediment discharge in Yongdam Dam watershed is analyzed through the utilization of SWAT, a semi-distributed watershed model. Based from the results of this study, an abrupt increase on the annual sediment inflow trend in Yongdam Dam watershed was observed; which may suggests that due to the effects of climate change, higher rainfall intensity, land use and land cover changes, the sedimentation rate also increased. An efficient sedimentation management should consider the increasing trend in sedimentation rate due to the effects of climate change.

• 통합자연과학논문집
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• 제11권1호
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• pp.30-38
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• 2018

CALPUFF is one of the recommended air pollution models by EPA with AERMOD. It has been used to simulate the ambient concentration of critical air pollutants as well as non-critical pollutants such as persistent organic matters and the organic materials causing odor. In this model, the air pollutants go through dispersion, transportation, chemical reaction, and deposition process. These mechanisms are significantly influenced by meteorological condition. This study produces the meteorological field in three different methods for the simulation of $SO_2$ using CALPUFF: 1) CALMET model by using both ground-level and aerological observation, 2) CALMET model by using MM5 results with NCEP/NCAR reanalyzed data, 3) CALMET model by using MM5 results in which FDDA is applied with NCEP/NCAR reanalyzed data as well as the meteorological data of Korea Meteorological Administration. As a result of CALPUFF model, the resolved concentration of $SO_2$ showed different behaviors in three cases. For the first case, the fluctuation of SO2 concentration was frequently observed while the fluctuation is reduced in the second and third cases. In addition, the maximum concentration of $SO_2$ in the first case was about 2~3 times higher than the second case, and about 4~6 times higher than the third case. These results can be caused by the accuracy of the resolved meteorological field. It is inferred that the meteorological field of the first case could be less accurate than other two cases. These results show that the use of correct meteorological data can improve the result of dispersion model. Moreover, the contribution of various sources such as point, line, and area sources on the ambient concentration of air pollutant can be roughly estimated from the sensitivity analysis.

• Journal of Microbiology and Biotechnology
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• 제17권10호
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• pp.1622-1628
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• 2007

We characterized the efficacy of an electrostatic precipitator (ESP) air-cleaner in reducing the concentration of Serratia marcescens in an enclosed space. We used an experimental room ($4.5{\times}3{\times}2.9\;m$) in which electrostatic air-cleaners were located. Two air-cleaners enhanced the equivalent ventilation rates in the chamber by about 3.3 air changes per hour (ACH) over the 2 ACH provided by the mechanical ventilation system. Natural die-off of the organisms provided an additional equivalent of 3 ACH, so that the total ventilation rate with the ESP air-ccleaners was 8.3 ACH. We also examined whether the ESP air-cleaners altered the deposition of Serratia marcescens aerosols on the experimental room surfaces. We did not find any significant differences in the number of colony forming units recovered from surfaces with and without the air-cleaners. We installed UV lights inside the ESPs and determined if UV light, in addition to electrical fields, increased the efficacy of the ESPs. The presence of UV light inside the ESP reduced S. marcescens aerosols by approximately 2 ACH. Finally, a box model indicates that the efficiency of the air-cleaner increases for both biological and nonbiological particles at ventilation rates of 0.2-1, which are typical for residential settings.

• The Korean Journal of Physiology and Pharmacology
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• 제21권1호
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• pp.55-64
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• 2017

Progressive memory impairment such as that associated with depression, stroke, and Alzheimer's disease (AD) can interfere with daily life. In particular, AD, which is a progressive neurodegenerative disorder, prominently features a memory and learning impairment that is related to changes in acetylcholine and abnormal ${\beta}$-amyloid ($A{\beta}$) deposition in the brain. In the present study, we investigated the effects of dehydroevodiamine HCl (DHED) on cognitive improvement and the related mechanism in memory-impaired rat models, namely, a scopolamine-induced amnesia model and a $A{\beta}_{1-42}$-infused model. The cognitive effects of DHED were measured using a water maze test and a passive avoidance test in the memory-impaired rat models. The results demonstrate that DHED (10 mg/kg, p.o.) and Donepezil (1 mg/kg, p.o.) ameliorated the spatial memory impairment in the scopolamine-induced amnestic rats. Moreover, DHED significantly improved learning and memory in the $A{\beta}_{1-42}$-infused rat model. Furthermore, the mechanism of these behavioral effects of DHED was investigated using a cell viability assay, reactive oxygen species (ROS) measurement, and intracellular calcium measurement in primary cortical neurons. DHED reduced neurotoxicity and the production of $A{\beta}$-induced ROS in primary cortical neurons. In addition, similar to the effect of MK801, DHED decreased intracellular calcium levels in primary cortical neurons. Our results suggest that DHED has strong protective effects against cognitive impairments through its antioxidant activity and inhibition of neurotoxicity and intracellular calcium. Thus, DHED may be an important therapeutic agent for memory-impaired symptoms.

• Membrane and Water Treatment
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• 제11권1호
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• pp.1-10
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• 2020

An understanding of particle-particle interactions in filtration requires studying the detachment as well as the attachment of nanoparticles. Nanoparticles captured in a granular media filter can be released by changing the physicochemical factors. In this study, the detachment of captured silver nanoparticles (AgNPs) in granular media filtration was examined under different ionic strengths, ion type, and the presence or absence of natural organic matter (NOM). Filtration velocity and ionic strength were chosen as the physical and chemical factors to cause the detachment. Increasing filtration velocity caused a negligible amount of AgNP detachment. On the other hand, lowering ionic strength showed different release amounts depending on the background ions, implying a population of loosely captured particles inside the filter bed. Overall detachment was affected by ionic strength and ion type, and to a lesser degree by NOM coating which resulted in slightly more detachment (in otherwise identical conditions) than in the absence of that coating, possibly by steric effects. The secondary energy minimum with Na ions was deeper and wider than with Ca ions, probably due to the lack of complexation with citrate and charge neutralization that would be caused by Ca ions. This result implies that the change in chemical force by reducing ionic strength of Na ions could significantly enhance the detachment compared to that caused by a change in physical force, due to a weak electrostatic deposition between nanoparticles and filter media. A modification of the 1-D filtration model to incorporate a detachment term showed good agreement with experimental data; estimating the detachment coefficients for that model suggested that the detachment rate could be similar regardless of the amount of previously captured AgNPs.

• 분석과학
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• 제29권6호
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• pp.269-276
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• 2016

고산리 유적은 우리나라 최초 토기로 알려진 고산리식 토기가 출토된 초기 신석기시대 유적이다. 이 연구에서는 고산리 유적의 형성 및 점유에 대한 절대연대 편년을 위하여 유적 내 표준 퇴적층에서 채취된 시료를 대상으로 OSL 연대측정을 수행하였다. 각 퇴적층의 고고선량은 $220^{\circ}C$ 열전처리 온도의 단일시료재현법을 적용하여 산출되었으며, 최종적으로 유적의 퇴적환경을 고려하여 maximum age model을 적용하여 결정하였다. 산출된 고고선량을 연간선량율로 나누어 고산리 유적 퇴적층의 OSL 연대를 결정하였다. 각 퇴적층의 OSL 연대와 14C 연대를 종합한 결과, 고산리 유적은 신석기인들에 의해 기원전 9천년 이후에 형성된 이후 고산리식 토기를 포함하는 신석기시대 초기 유적에서부터 다양한 시기의 다양한 유구가 존재해 오다가 기원전 4천년 중반에 폐기되어 현재에 이르렀다고 추론된다.

• Journal of Ginseng Research
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• 제46권6호
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• pp.771-779
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• 2022

Background: As a kind of common complication of the surgery of perianal diseases, perianal ulcer is known as a nuisance. This study aims to develop a kind of 20(S)-ginsenoside Rg3 (Rg3)-loaded hydrogel to treat perianal ulcers in a rat model. Methods: The copolymers PLGA₁₆₀₀-PEG₁₀₀₀-PLGA₁₆₀₀ were synthesized by ring-opening polymerization process and Rg3-loaded hydrogel was then developed. The perianal ulcer rat model was established to analyze the treatment efficacy of Rg3-loaded hydrogel for ulceration healing for 15 days. The animals were divided into control group, hydrogel group, free Rg3 group, Rg3-loaded hydrogel group, and Lidocaine Gel® group. The residual wound area rate was calculated and the blood concentrations of interleukin-1 (IL-1), interleukin-6 (IL-6), and vascular endothelial growth factor (VEGF) were recorded. Hematoxylin and eosin (H&E) staining, Masson's Trichrome (MT) staining, and tumor necrosis factor α (TNF-α), Ki-67, CD31, ERK1/2, and NF-κB immunohistochemical staining were performed. Results: The biodegradable and biocompatible hydrogel carries a homogenous interactive porous structure with 10 ㎛ pore size and five weeks in vivo degradation time. The loaded Rg3 can be released sustainably. The in vitro cytotoxicity study showed that the hydrogel had no effect on survival rate of murine skin fibroblasts L929. The Rg3-loaded hydrogel can facilitate perianal ulcer healing by inhibiting local and systematic inflammatory responses, swelling the proliferation of nuclear cells, collagen deposition, and vascularization, and activating ERK signal pathway. Conclusion: The Rg3-loaded hydrogel shows the best treatment efficacy of perianal ulcer and may be a candidate for perianal ulcer treatment.