• 센서학회지
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• 제26권6호
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• pp.414-419
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• 2017

The optical characteristics of cresol red, phenol red, and neutral red immobilized in the thin film were investigated with absorbance measurement in order to find a sensing part of a fiber-optic pH sensor. Sol-Gel method with tetramethyl orthosilicate as a precursor was used to immobilize the pH indicators in the thin film. The absorbance spectra were measured when pH indicators were immobilized in the film and were dissolved in the buffer solution. Experimental results showed that the absorbance spectra could be changed when the pH indicator is immobilized in the thin film. As compared with other pH indicators, the neutral red exhibited similar absorbance spectra regardless of physical conditions and was sensitive over whole pH range between 4 and 11. In addition, the absorbance ratio of base peak to acid peak tended to increase in proportion to the increase in pH. Experimental results indicate that the neutral red is a good pH indicator for fabrication of a sensing part of the fiber-optic pH sensor.

• 한국표면공학회지
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• 제57권2호
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• pp.105-114
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• 2024

Tempering behavior and mechanical properties in AISI H13 steel, quenched and tempered from 300 ℃ to 700 ℃ for different tempering time (1, 2, 5, 10, 20 hr) were quantitatively investigated by scanning electron microscopy (SEM), x-ray diffractometer (XRD), impact test machine, rockwell apparatus, ball-on-disk tester. Under the condition that the tempering time is 2 hours, the hardness increases slightly as the tempering temperature increases, but decreases rapidly when the tempering temperature exceeds 500 ℃, while the impact energy increases in proportion to the tempering temperature. Friction tests were conducted in dry condition with a load of 30 N, and the friction coefficient and wear rate according to tempering conditions were measured to prove the correlation with hardness and microstructure. In addition, primary tempering from 300 ℃ to 700 ℃ was performed at various times to establish a kinetic model to predict hardness under specific tempering conditions.

• 한국수소및신에너지학회논문집
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• 제27권2호
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• pp.230-235
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• 2016

The purpose of this study is to evaluate the gas leakage for a 30-inch ball valve. The ball valve was designed and manufactured for a natural gas transportation through a long-distance pipeline mainly installed in the permafrost region. The gas leakage assessment is based on the pressure testing criteria of international standards. Pressure conditions of the gas leakage test was employed 70 bar, 100 bar, and 110 bar. The amount of the gas leakage at each pressure condition was small and had a value under the pressure testing criteria, ISO 5208. Gas leakage with respect to the test pressure was predicted by the polynomial curve fitting using the experimental results. It is found that the gas leakage rate according to the pressure is proportion to a second order curve.

• 대한기계학회논문집A
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• 제39권2호
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• pp.211-217
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• 2015

환경 문제 및 화석연료 고갈에 대한 관심으로 인하여 배기가스에 대한 규제는 나날이 엄격해지고 있으며 높은 연비에 대한 수요는 지속적으로 증가하고 있다. 이러한 시대적 요구를 뒷받침하기 위하여 저배기-고연비가 특징인 하이브리드 굴삭기가 현실적인 대안으로서 각광받고 있으며 지속적으로 연구되고 있다. 본 연구에서는 선회 구동 전동기, 엔진보조 전동기, 울트라 캐패시터, 전력변환장치를 중형 굴삭기에 탑재한 복합형 하이브리드 굴삭기를 개발하였으며, 일반적인 복합형 하이브리드 굴삭기의 연비개선요소(선회 구동 에너지 회생, 엔진 작동 속도 변경)외에 추가적으로 적용된 연비개선 방법론들에 대하여 다루고 있다. 본 방법론들을 적용함으로써 연비와 운전 조작성을 동시에 개선할 수 있었다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.172-172
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• 2011

Anaerobic digestion(AD) has successfully been used for many applications that have conclusively demonstrated its ability to recycle biogenic wastes. AD has been successfully applied in industrial waste water treatment, stabilsation of sewage sludge, landfill management and recycling of biowaste and agricultural wastes as manure, energy crops. During AD, i.e. organic materials are decomposed by anaerobic forming bacteria and fina1ly converted to excellent fertilizer and biogas which is primarily composed of methane(CH4) and carbon dioxide(CO2) with smaller amounts of hydrogen sulfide(H2S) and ammonia(NH3), trace gases such as hydrogen(H2), nitrogen(N2), carbon monoxide(CO), oxygen(O2) and contain dust particles and siloxanes. The production and utilisation of biogas has several environmental advantages such as i)a renewable energy source, ii)reduction the release of methane to the atomsphere, iii)use as a substitute for fossil fuels. In utilisation of biogas, most of biogas produced from small scale plant e.g. farm-scale AD plant are used to provide as energy source for cooking and lighting, in most of the industrialised countries for energy recovery, environmental and safety reasons are used in combined heat and power(CHP) engines or as a supplement to natural. In particular, biogas to use as vehicle fuel or for grid injection there different biogas treatment steps are necessary, it is important to have a high energy content in biogas with biogas purification and upgrading. The energy content of biogas is in direct proportion to the methane content and by removing trace gases and carbon dioxide in the purification and upgrading process the energy content of biogas in increased. The process of purification and upgrading biogas generates new possibilities for its use since it can then replace natural gas, which is used extensively in many countries, However, those technologies add to the costs of biogas production. It is important to have an optimized purification and upgrading process in terms of low energy consumption and high efficiency giving high methane content in the upgraded gas. A number of technologies for purification and upgrading of biogas have been developed to use as a vehicle fuel or grid injection during the passed twenty years, and several technologies exist today and they are continually being improved. The biomethane which is produced from the purification and the upgrading process of biogas has gained increased attention due to rising oil and natural gas prices and increasing targets for renewable fuel quotes in many countries. New plants are continually being built and the number of biomethane plants was around 100 in 2009.

• 한국환경복원기술학회지
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• 제26권4호
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• pp.51-59
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• 2023

Despite countries' efforts to reduce carbon emissions, carbon emissions have increased in recent decades along with energy use, of which building energy uses account for a large proportion. Energy savings are essential as a strategy to reduce carbon emissions in existing buildings. The field experiment on the roof of a building located in Seoul was designed to measure the temperature reduction effect of green roof with rainwater storage tank to reduce cooling energy consumption in summer. The results showed that the mean mean surface temperature under the green roof was 14.77 degrees lower than that of the non-green roof from 13:00 P.M. to 15:00 P.M., which would have a great effect on reducing cooling energy. From 01:00 A.M. to 03:00 A.M., the effect was 3.36 degrees, showing that tropical nights could be improved. The temperature reduction effect due to the rainwater storage system increased by 1.45 degrees during the day and decreased by 0.63 degrees at night. The storage system can be strategically utilized to reduce carbon emissions during the week when cooling energy increases significantly.

• 자원ㆍ환경경제연구
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• 제30권4호
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• pp.557-579
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• 2021

집단에너지는 에너지전환의 중간단계이자, 분산전원으로서 전력구조에 미치는 영향이 크다. 하지만 최근 일부 집단에너지사업자의 수익성 악화로 인해 집단에너지사업의 문제가 대두되고 있다. 본 연구는 우리나라 집단에너지사업자의 기술적 생산효율성 추정을 통해, 주요 사업자의 기술적 생산효율성을 측정하였으며 이를 바탕으로 사업자의 수익구조 개선방안을 살펴보았다. 16개 집단에너지사업자의 2016~19년 세부 재무 및 생산 자료를 수집한 후, 패널 확률 프론티어모형을 이용하여 사업자들의 기술적 생산효율성을 추정하였다. 추정 결과, 증기공급병행, 대형 전기중심, 소규모 구역전기, 역송CHP 사업자 순으로 생산효율성이 높음을 확인하였다. 더 나아가 수익성 영향요인에 대해 살펴본 결과, 기술적 생산효율성은 전반적으로 수익성과 양(+)의 영향 관계를 가지나, 소규모 구역전기사업자와 같이 열 생산 비중이 높은 사업자는 수익성이 악화됨을 확인하였다. 이는 현재 열 판매 시장의 구조적 한계로 인한 현상이며, 수익성 개선을 위해서는 열 판매단가에 대한 조정이 필요함을 확인하였다.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2002년도 추계학술발표회
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• pp.9-12
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• 2002

The purpose of this study is to understand the high saline water phenomenon of Handong-ri area in the eastern coast of Jeju Island, were investigate the tidal effect of groundwater level, variation of electric conductivity and temperature, geological logging on the monitoring wells, chemical water quality, and ratios of oxygen istope of groundwater and seawater Results in investigating variation of interface zone of freshwater and saline water represented that the hyaloclastites formed at below groundwater table is developing toward the coast; this area consisted of stratum of good permeability. Hyaloclastites is presumed the main path of the high salinity water There are a lot of movement by the tide at upper layer. Salinity of lower layer spreads to upper up step in proportion to tidal energy. Because of hydrogeological characteristics, Interface zone of freshwater and saline water is made, High salinity of groundwater occur in east coastal area of Jeju Island. Therefore, I think that high saline groundwater phenomenon is natural condition by simple mixing.

• International Journal of Naval Architecture and Ocean Engineering
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• 제5권2호
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• pp.246-262
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• 2013

With increases in international oil prices, the proportion of fuel cost to the operational costs of a ship is currently increasing. To reduce fuel cost, a method for determining an economical route for a ship based on the acquisition of the sea state and the estimation of fuel consumption is proposed. The proposed method consists of three items. The first item is to acquire the sea state information in real time. The second item is to estimate the fuel consumption of a ship according to the sea state. The last item is to find an economical route for minimal fuel consumption based on the previous two items. To evaluate the applicability of the proposed method, it was applied to routing problems in various ocean areas. The result shows that the proposed method can yield economical ship routes that minimize fuel consumption. The results of this study can contribute to energy savings for environmentally friendly ships.

• International Journal of Concrete Structures and Materials
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• 제4권2호
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• pp.119-125
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• 2010

In this study, the effects of the fineness modulus of reactive aggregate on ASR expansion and ASR products have been investigated. The reactive aggregate used was metamorphic aggregate originated from Korea. ASR tests were conducted according to accelerated mortar bar test. The morphology and chemical composition of products formed in mortar bars, 5 years after the mortar bar test had been performed, were studied by scanning electron microscopy equipped with energy dispersive spectroscopy. Test results indicated that ASR expansion of mortar bars decrease in linear proportion to the fineness modulus of reactive aggregate. SEM images indicated that mortar bars showed reactive products formed in cement paste, within air voids and within cracks through particles except for the mortar bar with the fineness modulus of 3.25. The EDS analysis of the reactive products showed presence of silica, calcium and sodium, typical of ASR product composition.