• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.1
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• pp.1-8
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• 2015

Wind power systems have gained much attention due to the relatively high reliability, good infrastructures and cost competitiveness to the fossil fuels. Advances have been made to increase the power efficiency of wind turbines while less attention has been focused on structural integrity assessment of structural sub-systems such as towers and foundations. Among many parameters for integrity assessment, the most perceptive parameter may be the induced horizontal displacement at the hub height although it is very difficult to measure particularly in large-scale and high-rise wind turbine structures. This study proposes an indirect displacement estimation scheme based on the combined use of inclinometers and accelerometers for more convenient and cost-effective measurements. To this end, (1) the formulation for data fusion of inclination and acceleration responses was presented and (2) the proposed method was numerically validated on an NREL 5 MW wind turbine model. The numerical analysis was carried out to investigate the performance of the propose method according to the number of sensors, the resolution and the available sampling rate of the inclinometers to be used.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.4
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• pp.405-412
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• 2012

In the MCFC power generation system, the combustor supplies a high temperature mixture of gases to the cathode and heat to the reformer by using the off-gas from the anode; the off-gas includes high concentrations of $H_2O$ and $CO_2$. Since a combustor needs to be operated in a very lean condition and avoid local heating, a catalytic combustor is usually adopted. Catalytic combustion is also generally accepted as one of the environmentally preferred alternatives for generation of heat and power from fossil fuels because of its complete combustion and low emissions of pollutants such as CO, UHC, and $NO_x$. In this study, experiments were conducted on catalytic combustion behavior in the presence of Pd-based catalysts for the BOP (Balance Of Plant) of 5 kW MCFC (Molten Carbonate Fuel Cell) power generation systems. Extensive investigations were carried out on the catalyst performance with the gaseous $CH_4$ fuel by changing such various parameters as $H_2$ addition, inlet temperature, excess air ratio, space velocity, catalyst type, and start-up schedule of the pilot system adopted in the BOP.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.101-101
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• 2010

Anaerobic digestion(AD) is the most promising method for treating and recycling of different organic wastes, such as organic fraction of municipal solid waste, household wastes, animal manure, agro-industrial wastes, industrial organic wastes and sewage sludge. During AD, i.e. organic materials are decomposed by anaerobic forming bacteria and fina1ly converted to excellent fertilizer and biogas which is a mixture of carbon dioxide and methane. AD has been one of the leading technologies that can make a large contribution to produce renewable energy and to reduce $CO_2$ and other green-house gas(GHG) emission, it is becoming a key method for both waste treatment and recovery of a renewable fuel and other valuable co-products. Currently some 80% of the world's overall energy supply of about 400 EJ per year in derived from fossil fuels. Nevertheless roughly 10~15% of this demand is covered by biomass resources, making biomass by far the most important renewable energy source used to date. The representative biofuels produced from the biomass are bioethanol, biodiesel and biogas, and currently biogas plays a smaller than other biofuels but steadily growing role. Traditionally anaerobic digestion applied for different biowaste e.g. sewage sludge, manure, other organic wastes treatment and stabilization, biogas has become a well established energy resource. However, the biowaste are fairly limited in respect to the production and utilization as renewable source, but the plant biomass, the so called "energy crops" are used for more biogas production in EU countries and the investigation on the biomethane potential of different crops and plant materials have been carried out. In Korea, with steadily increasing oil prices and improved environmental regulations, since 2005 anaerobic digestion was again stimulated, especially on the biogasification of different biowastes and agro-industrial biomass including "energy crops". This study have been carried out to investigate anaerobic biodegradability by the biochemical methane potential(BMP) test of animal manures, different forage crops i.e. "energy crops", plant and industrial organic wastes in the condition of thermophilic temperature, The biodegradability of animal manure were 63.2% and 58.2% with $315m^3CH_4/tonVS$ of cattle slurry and $370m^3CH_4/tonVS$ of pig slurry in ultimate methane yields. Those of winter forage crops were the range 75% to 87% with ultimate methane yield of $378m^3CH_4/tonVS$ to $450m^3CH_4/tonVS$ and those of summer forage crops were the range 81% to 85% with ultimate methane yield of $392m^3CH_4/tonVS$ to $415m^3CH_4/tonVS$. The forge crops as "energy crops" could be used as good renewable energy source to increase methane production and to improve biodegradability in co-digestion with animal manure or only energy crop digestion.

• Clean Technology
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• v.25 no.4
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• pp.289-295
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• 2019

Though the usage of vinyls and plastics produced from fossil fuels has been increasing in the world, the eco-friendly domestic disposal or recycling of waste vinyls has to be executed because the migration or importation of waste vinyls or waste plastics are globally prohibited. Even though the eco-friendly domestic disposal or recycling of waste vinyls and waste plastics should be developed, promising eco-friendly recycling methods are few because there are extraneous substances in waste vinyls and waste plastics. Also, conventional incineration and landfill methods result in secondary contamination and then increase disposal costs. Therefore, the selective elimination of extraneous substances or other materials included in waste vinyls and waste plastics could make valuable recycling or reuse possible. In particular, the novel hybrid process in which crushing and screening are simultaneously conducted in a rotary kiln type reactor can domestically maximize the material recycling or reuse. In this study, the feasibility study for a crushing/screening hybrid process developed in Korea was performed and evaluated in case of thermal recycling (TR) and material recycling (MR). The effect of various subsidies on economic efficiency was especially evaluated by means of domestic recycling plans. The incentive revenues from waste vinyl recycling and the incineration share of waste vinyls affected the net present values and internal rate of returns of the hybrid process.

• Journal of Environmental Science International
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• v.29 no.1
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• pp.109-117
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• 2020

Asthmatics are more susceptible to fine particulate matters (PM_2.5), compared to the general population. It has been reported that indoor PM_2.5 is mainly generated by combustion of fossil fuels, meat or fish In particular, asthmatics are known to be more susceptible to indoor PM_2.5 because 65~95% of child or adult asthmatics stay inside the house. Thus, understanding the association between indoor activity patterns and variations in indoor PM_2.5 levels is important. The purpose of this study is to determine the distribution of hourly indoor PM_2.5 concentrations in asthmatics' homes, and to evaluate its association with pan-frying cooking activity patterns, the most common PM_2.5 emission related activity. From November 2017 to February 2018, real-time PM_2.5 concentrations were measured in the living room of each asthmatic's house (n = 35) for three weeks at 1 minute intervals. At the same time, self-reported daily activity patterns, hourly proportion (%) of cooking activities, were also recorded every hour over three weeks for each patient. In this study, we provided quantitative evidence that the distribution patterns of indoor hourly PM_2.5 concentrations were associated with indoor cooking activities, especially in the homes of adult asthmatics. In addition, we observed that PM_2.5 emitted by pan-frying could maintain even over up to 2 hour lagtime.

• Membrane Journal
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• v.28 no.2
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• pp.136-141
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• 2018

Carbon dioxide ($CO_2$) exists not only as a component of natural gas, biogas, and landfill gas, but also as a major combustion product of fossil fuels which leads to a major contributor to greenhouse gases. Hence it is essential to reduce or eliminate carbon dioxide ($CO_2$) in order to obtain high fuel efficiency of internal combustion engine, to prevent corrosion of gas transportation system, and to cope with climate change preemptively. In recent years, there has been a growing interest in not only conventional membrane-based separation but also new adsorbent-based separation technology. Particularly, in the case of metal-organic frameworks (MOFs), it has been received tremendous attentions due to its unique properties (eg : flexibility, gate effect or strong binding site such as open metal sites) which are different from those of typical porous adsorbents. Therefore, in this study, stereotype of two MOFs have been selected as its flexible MOFs (MIL-53) representative and numerous open metal sites MOFs (MOF-74) representative, and compared each other for $CO_2/CH_4$ separation performance. Furthermore, varying and changeable separation performance conditions depending on the temperature, pressure or samples' unique properties are discussed.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.417-417
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• 2016

Global environmental deterioration has become more serious year by year and thus scientific interests in the renewable energy as environmental technology and replacement of fossil fuels have grown exponentially. Photoelectrochemical (PEC) cell consisting of semiconductor photoelectrodes that can harvest light and use this energy directly to split water, also known as photoelectrolysis or solar water splitting, is a promising renewable energy technology to produce hydrogen for uses in the future hydrogen economy. A major advantage of PEC systems is that they involve relatively simple processes steps as compared to many other H2 production systems. Until now, a number of materials including TiO2, WO3, Fe2O3, and BiVO4 were exploited as the photoelectrode. However, the PEC performance of these single absorber materials is limited due to their large charge recombinations in bulk, interface and surface, leading low charge separation/transport efficiencies. Recently, coupling of two materials, e.g., BiVO4/WO3, Fe2O3/WO3 and CuWO4/WO3, to form a type II heterojunction has been demonstrated to be a viable means to improve the PEC performance by enhancing the charge separation and transport efficiencies. In this study, we have prepared a triple-layer heterojunction BiVO4/WO3/SnO2 photoelectrode that shows a comparable PEC performance with previously reported best-performing nanostructured BiVO4/WO3 heterojunction photoelectrode via a facile solution method. Interestingly, we found that the incorporation of SnO2 nanoparticles layer in between WO3 and FTO largely promotes electron transport and thus minimizes interfacial recombination. The impact of the SnO2 interfacial layer was investigated in detail by TEM, hall measurement and electrochemical impedance spectroscopy (EIS) techniques. In addition, our planar-structured triple-layer photoelectrode shows a relatively high transmittance due to its low thickness (~300 nm), which benefits to couple with a solar cell to form a tandem PEC device. The overall PEC performance, especially the photocurrent onset potential (Vonset), were further improved by a reactive-ion etching (RIE) surface etching and electrocatalyst (CoOx) deposition.

• Journal of Environmental Impact Assessment
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• v.26 no.4
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• pp.217-226
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• 2017

Although the effects of climate change are universal, Small Island Developing States (SIDS) are considered to be most vulnerable. SIDS heavily rely on imported oil and fossil fuels for electricity generation and transportation, which makes them economically vulnerable and exposed to fluctuating oil price. Among the reasons SIDS highly depend on diesel fuel is due to the dispersed population living in remote islands which means, providing electricity through on on-grid system is difficult. Fiji as one of the SIDS, has actively promoted renewable sourced energy through a national plan to mitigate the impacts of climate change. In order to determine how feasible implementing a renewable energy (RE) system will be in Fiji, this study chose a remote island called Mavuva Island to test application of a hybrid RE system using HOMER. A combination of energy storage system (ESS), solar photovoltaic (PV) and diesel generator turns out to be the most cost effective and optimal configuration, resulting in effective greenhouse gas reduction for the given region.

• KDI Journal of Economic Policy
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• v.14 no.1
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• pp.61-87
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• 1992

Reducing the level of greenhouse gas emissions is necessary to mitigate global warming. One of the most feasible methods to reduce emissions would be to conserve energy and substitute fossil fuels. Yet reducing emissions entails huge financial costs, so it is advisable to employ cost-effective economic instruments such as a carbon tax or tradeable emissions permits. Assuming that the proper economic tools will be used in the future, we calculated the optimal level of emissions reduction for Korea. We applied to our cost-benefit analysis Nordhaus' scenario regarding the economic damage from a $3^{\circ}C$ rise in global temperatures, which is the calculated result when the greenhouse gas level doubles. The result of our analysis based on the 1990 data indicates that the optimal level of emissions reduction ranges from 2% to 15 % of current emissions depending on the value of damage parameters. We also found that the amount of emissions must be reduced will increase if action is postponed, when the development of climate engineering technology or more efficient use of energy is expected. In addition, we discussed the advantages and disadvantages of the economic instruments available to implement emissions reduction. Tradeable permits and carbon tax are equivalent in their cost-effectiveness, but have different implications in practice.

• Journal of Life Science
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• v.8 no.3
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• pp.257-262
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• 1998

Benzo(a)pyrene(B(a)P), an extensively studied polycyclic aromatic hydrocarbon(PAH), is a common contaminant produced through the burning of fossil fuels, particularly coal, and from the exhaust products of internal combustion engines. It produces a wide range of toxicities, including carcinogenicity in experimental animals. B(a)P has been shown to suppress systemic immunity in experimental animals, which may contribute to the growth of the chemical-induced tumors. Using colorimetric MTT assay natural killer(NK) cell-mediated growth inhibition of tomor cell was measured in normal and B(a)P-exposed C57BL/6 mice. Non-adherent splenocytes of normal or B(a)P-exposed mice were cultured with Yac-1 cells at four different effector/target(E/T) cell ratios ranging from 200/1, 100/1, 50/1, and 25/1 in an assay volume of 0.1 ml. After the optical density of culture wells containing MTT solution was measured at a wavelength of 540 nm, the percentage of dead cells relative to the control target cell number was calculated. The NK activity of B(a)P-exposed mice was markedly lower than that of non-exposed mice group at all E/T ratios. These results indicated that suppression of NK cell activity may play a role in allowing for the growth of tumors.