• 한국지반환경공학회 논문집
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• 제20권12호
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• pp.33-39
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• 2019

The upsurge of population, internal migration, economic activities and developmental works has brought significant land use and land cover (LULC) change over the period of 1990 and 2010 in the Bagmati basin of Nepal. Along with alteration on various other ecosystem services like water yield, water quality, soil loss etc. carbon sequestration is also altered. This study thus primary deals with evaluation of LULC change and its impact on the soil carbon storage for the period 1990 to 2010. For the evaluation, InVEST (Integrated Valuation of Ecosystem Services and Tradeoffs) Carbon model is used. Residential and several other infrastructural development activities were prevalent on the study period and as a result in 2010 major soil carbon reserve like forest area is decreased by 7.17% of its original coverage in 1990. This decrement has brought about a subsequent decrement of 1.39 million tons of carbon in the basin. Conversion from barren land, water bodies and built up areas to higher carbon reserve like forest and agriculture land has slightly increased soil carbon storage but still, net reduction is higher. Thus, the spatial output of the model in the form of maps is expected to help in decision making for future land use planning and for restoration policies.

• 자원ㆍ환경경제연구
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• 제24권3호
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• pp.463-488
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• 2015

본 연구에서는 2015년부터 시행된 온실가스 배출권 거래제도에 맞추어 상쇄(offset)제도의 구체적인 설계가 필요한 시점에서, 가정부문의 고효율 전자기기의 보급을 통해 확보할 수 있는 잠재 상쇄 공급량을 추정하였다. 분석대상 품목은 TV, 세탁기, 선풍기, 냉장고, 에어컨 등 다섯 가지 가전기기이며, 자기회귀시차분포모형(ARDL)을 통해 2016년부터 2022년까지의 고효율 가전기기의 보급대수를 추정하고, 효율 개선을 통한 전기 절감량과 이에 따른 탄소 환산율을 통해 최종적으로 잠재 상쇄 공급량을 도출하였다. 고효율 가전기기의 에너지 절감률을 각각 10%와 20%로 가정했을 때 2022년에 누적된 탄소 저감량은 $361,899CO_2t$과 $723,797CO_2t$으로 나타났으며, 에너지 절감량이 큰 순서로는 에어컨, 냉장고, TV, 세탁기, 선풍기 순으로 나타났다. 또한 에너지 소비효율 1등급 가전기기의 에너지 절감률이 20%라고 가정했을 때, 누적 탄소 저감량이 2015년에 비해 2022년에 약 316% 증가하는 것으로 나타났다.

• 열처리공학회지
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• 제7권1호
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• pp.44-52
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• 1994

In order to investigate the effect of tempring treatment on the mechanical properties of ausformed martensite in Fe-30%Ni-0.35%C alloy, the hardness, yield strength and elongation were examined by tensile test. 1. The strength of deformed austenite in Fe-30%Ni-0.35%C alloy was increased due to the work hardening induced from the dislocation density increased during deformation. The strength of ausformed martensite was increased because of defects inherited from deformed austenite by martensitic transformation. 2. The ductility of ausformed martensite was shown a nearly constant values independent of deformation degrees because of the interaction of multiple factors such as increased retained austenite, formation of void and decrement of twin in ausformed martensite. 3. The strength of ausformed martensite by tempering treatment was shown a little decrement up to $340^{\circ}C$, especially showed remarkable softening resistance in higher deformation degrees. 4. Virgin martensite and ausformed martensite were shown a maximum yield strength by clustering in tempering at $100^{\circ}C$ and above $100^{\circ}C$, yield strength was very small decreased due to the decrement of solute carbon by the destruction of clustering. 5. The decomposition of retained austenite was not shown up to $450^{\circ}C$ in ausformed martensite with tempering treatment, and the matrix was rapidly softening because of the decomposition of martensite and the formation of reversed austenite with tempering above $400^{\circ}C$.

• Elastomers and Composites
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• 제51권1호
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• pp.1-9
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• 2016

Characterization of the UV oxidation for raw natural rubber (NR) was investigated in controlled conditions through image and FT-IR analysis. The UV oxidation was performed on a thin film of natural rubber coated on a KBr window at 254 nm and room temperature to exclude the thermal oxidation. Before or after exposure to UV light, image of the NR thin film was observed at a right or tilted angle. FT-IR absorption spectra were measured in transmission mode with the UV irradiation time. The UV oxidation of NR was examined by the changes of absorption peaks at 3425, 1717, 1084, 1477, 1377, and $833cm^{-1}$ which were assigned to hydroxyl group (-OH), carbonyl group (-C=O), carbon-oxygen bond (-C-O), methylene group $(-CH_2-)$, methyl group $(-CH_3)$, and cis-methine group $(cis-CCH_3=CH-)$, respectively. During the initial exposure period, the results indicated that the appearance of carbonyl group was directly related to the reduction of cis-methine group containing carbon-carbon double bond (-C=C-). Most of aldehydes or ketones from carbon-carbon double bonds were formed very fast by chain scission. A lot of long wide cracks with one orientation at regular intervals which resulted in consecutive chain scission were observed by image analysis. During all exposure periods, on the other hand, it was considered that the continuous increment of hydroxyl and carbonyl group was closely related to the decrement of methylene and methyl group in the allylic position. Therefore, two possible mechanisms for the UV oxidation of NR were suggested.

• 한국추진공학회지
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• 제19권6호
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• pp.42-53
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• 2015

고체추진제에 첨가되는 알루미늄 입자의 크기에 따른 탄소 복합재 노즐의 기계적 삭마특성 변화를 예측하는 연구를 수행하였다. 추진제에 첨가되는 알루미늄 입자의 초기 크기에 따라 연소생성물 응집체($Al(l)/Al_2O_3(l)$)의 크기와 분포를 예측할 수 있는 모델을 개발하여 사용하였으며, 모델 예측 결과로 얻어지는 응집체의 크기를 초기조건으로 하여 상용 수치해석 프로그램(STAR CCM+)을 이용한 복합재 노즐에서의 기계적 삭마특성 해석을 수행하였다. 본 연구를 통해 초기 알루미늄 첨가제의 크기가 작을수록 응집체의 크기가 작아지고, 기계적 삭마가 감소하는 특성을 확인하였으며, 특히 나노입자를 사용할 때 기계적 삭마가 확연히 개선됨을 확인하였다.

• Korean Membrane Journal
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• 제5권1호
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• pp.43-53
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• 2003

The selectivity of a gas in the carbon molecular sieve membrane (CMSM) can be expressed as the ratio of the product of the diffusivity and the solubility of two different gases. The diffusivity is also expressed as the product of the entropy and the total energy (kinetic and potential energy) in the nano-sized pore of the membrane. The present study calculates the entropic-energy and selectivity of penetrant gases such as H$_2$, O$_2$, N$_2$, and CO$_2$ from the gas-in-a box theory to physically analyze the diffusivity of penetrant gas in slit-shaped pore of CMSM focusing on the restriction of gas motion based on the size difference between penetrant gas pairs. The contribution of each energy term is converted to entropic term separately. By the conjugated calculation for each entropic-energy, the entropic effects on diffusivity-selectivity for gas pairs such as H$_2$/N$_2$, CO$_2$/N$_2$, and O$_2$/N$_2$ were analyzed within active pore of CMSM. In the activated diffusion domain, the calculated value of entropic-selectivity lies between 9.25 and 111.6 for H$_2$/N$_2$, between 3.36 and 6.0 for CO$_2$/N$_2$, and between 1.25 and 16.94 for O$_2$/N$_2$, respectively. The size decrement of active pore in CMSM had the direct effect on the reduction of translational entropic-energy and the contribution of vibrational entropic-energy for N$_2$, O$_2$, and H$_2$ was almost negligible. However, the vibrational entropic term of CO$_2$ might extravagantly affect on the entropic-selectivity.

• 공업화학
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• 제31권3호
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• pp.341-345
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• 2020

하폐수처리 및 정수처리에 사용되는 활성탄 흡착 공정에서 기존의 활성탄 열재생법 비해 활성탄 손실과 불완전 연소로 인한 오염물질 발생도 적으며, 사용 활성탄의 인발-재생-재충진에 소요되는 시간의 절약이 가능한 재생 방법으로 오존수를 이용한 in situ regeneration에 대한 기초연구를 수행하였다. 활성탄 흡착 컬럼 상에서 페놀(phenol) 및 PEG를 흡착 파과 시킨 후 오존수 접촉으로 흡착물질을 분해 제거하는 흡착-재생 싸이클을 반복하였다. 오존수 접촉에 의한 재생 횟수가 증가할수록 페놀 흡착용량은 어느 정도 감소하지만, 일정 수준으로의 감소 후에는 구조 변화가 안정화되어 추가적인 감소가 일어나지 않았다. 흡착 용량이 감소하는 이유는 오존과의 반응에 의해 활성탄의 미세공 크기가 증가하면서 비표면적이 감소하기 때문으로 나타났다. 이러한 세공 크기의 변화와 비표면적의 변화로 인하여 재생 후 in-pore adsorption이 우세한 페놀과 같은 저분자량 물질의 흡착효율은 감소하게 되나 external adsorption 비율이 큰 PEG와 같은 고분자량 물질의 흡착효율은 크게 영향을 받지 않았다. 세공 크기 및 비표면적의 변화는 오존수와의 접촉시간이 길어질수록 심화되므로 제거하려는 물질의 크기를 고려하고 접촉시간을 조절함으로써 흡착 효율의 유지를 제어하는 것이 필요하다.

• 대한임상검사과학회지
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• 제36권1호
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• pp.55-63
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• 2004

The hepatotherapeutic effect of the extract of Lycii fructus has been studied in rats against $CCl_4$ induced liver toxicity. The rats were orally treated with $CCl_4$ (corn oil/$CCl_4$ 1:1, $1m{\ell}/kg$) and then $CCl_4$ ($0.5m{\ell}/kg$) administered four times for 2 weeks. The extracts of L. fructus have been administered every day for 2 weeks after the last $CCl_4$ injection. The experimental groups consisted of negative control (G1), positive control ($CCl_4$ alone; G2), extract of L. fructus (50 mg/kg; G3, 100 mg/kg; G4, 200 mg/kg; G5), respectively. There was a significant decrement to G2 on the serum level of aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase in G5. Also, the content of thiobarbituric acid reactive substance, and phosphatidylcholine hydroperxidase, a marker of lipid peroxidation, in the liver were decreased significantly G5 and G4 compared with G2. Although, catalase or superoxide dismutase, antioxidant enzyme, in the liver were decreased significantly too, it would not be a good sign for the liver. In histopathological findings, such a hepatocellular vacuolar degeneration, lobular restructure, cellular infiltration, necrosis, and so on were shown severely in G2. However, G4 and G5 was shown a mild cytoplasmic vacuolation and inflammatory cell. In conclusion, as a protection against cell damage, lipid peroxidation and serum level, it suggested that the extract of Lycii fructus would have been a therapeutic effect of liver injury directly.

• 열처리공학회지
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• 제35권5호
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• pp.262-269
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• 2022

In order to process materials such as engineering plastics, which are difficult to mold due to their high strength compared to conventional polymer materials, it is necessary to improve the hardness and strength of parts such as screws and barrels of injection equipment in extrusion system. High-velocity oxygen fuel (HVOF) process is well known for its contribution on enhancement of surface properties. Thus in this study, using the HVOF process, WC coating layers of different thicknesses were bonded to the surface of S30C substrate by controlling the movement speed of the spray nozzle and each property was evaluated to decide the optimization condition. Through the results, the thickness of WC coating layer increased from 0 to 200 ㎛ maximum, along with the decrement of nozzle movement speed and the surface hardness get increased. Especially, the coated layer with the thickness over 180 ㎛ under the nozzle speed 500 mm/s had high hardness than thinner layer. In addition, the amount of wear consumed per unit time was also significantly reduced due to the formation of the coating layer.

• Steel and Composite Structures
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• 제49권6호
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• pp.685-699
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• 2023

In recent years, Carbon Fibre Reinforced Plastic (CFRP) strengthening is found to be one of the best methods to strengthen steel structures. The fibrous bond can also influence the vibration characteristics of the strengthened element apart from its static strength enhancement property. The main objective of this study is to understand the influence of CFRP strengthening on the dynamic Behaviour of Thin-Webbed Castellated Beams (TWCBs). A detailed experimental investigation was carried out on five sets of beams with varying parameters such as domination of shear (Shear Dominant, Moment Dominant and Moment and Shear Dominant), sectional classification (Plastic and Semi-compact) and perforation geometries (h_o/d_wratio 0.65 and e/h_o ratio 0.3). Free vibration analysis was carried out by exciting the simply supported TWCBs with an impact force generated by a ball dropped from a specific height. Logarithmic decrement method was used to obtain the damping ratio and natural frequencies of vibration were found by Fast Fourier Transform (FFT). Natural frequency showed an increase in a range of 10.5 - 55% for the different sets of castellated beams. An increase of 62.30% was noted in the damping ratio of TWCBs after strengthening which is an indication of improvement in the vibration characteristics of the beam.