• Electrical & Electronic Materials
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• v.12 no.7
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• pp.7-11
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• 1999

Fully sealed field emission display in size of 4.5 inch has been fabricated using single-wall carbon nanotubes-organic vehicle com-posite. The fabricated display were fully scalable at low temperature below 415$^{\circ}C$ and CNTs were vertically aligned using paste squeeze and surface rubbing techniques. The turn-on fields of 1V/${\mu}{\textrm}{m}$ and field emis-sion current of 1.5mA at 3V/${\mu}{\textrm}{m}$ (J=90${\mu}{\textrm}{m}$/$\textrm{cm}^2$)were observed. Brightness of 1800cd/$m^2$ at 3.7V/${\mu}{\textrm}{m}$ was observed on the entire area of 4.5-inch panel from the green phosphor-ITO glass. The fluctuation of the current was found to be about 7% over a 4.5-inch cath-ode area. This reliable result enables us to produce large area full-color flat panel dis-play in the near future. Carbon nanotubes (CNTs) have attracted much attention because of their unique elec-trical properties and their potential applica-tions [1, 2]. Large aspect ratio of CNTs together with high chemical stability. ther-mal conductivity, and high mechanical strength are advantageous for applications to the field emitter [3]. Several results have been reported on the field emissions from multi-walled nanotubes (MWNTs) and single-walled nanotubes (SWNTs) grown from arc discharge [4, 5]. De Heer et al. have reported the field emission from nan-otubes aligned by the suspension-filtering method. This approach is too difficult to be fully adopted in integration process. Recently, there have been efforts to make applications to field emission devices using nanotubes. Saito et al. demonstrated a car-bon nanotube-based lamp, which was oper-ated at high voltage (10KV) [8]. Aproto-type diode structure was tested by the size of 100mm $\times$ 10mm in vacuum chamber [9]. the difficulties arise from the arrangement of vertically aligned nanotubes after the growth. Recently vertically aligned carbon nanotubes have been synthesized using plasma-enhanced chemical vapor deposition(CVD) [6, 7]. Yet, control of a large area synthesis is still not easily accessible with such approaches. Here we report integra-tion processes of fully sealed 4.5-inch CNT-field emission displays (FEDs). Low turn-on voltage with high brightness, and stabili-ty clearly demonstrate the potential applica-bility of carbon nanotubes to full color dis-plays in near future. For flat panel display in a large area, car-bon nanotubes-based field emitters were fabricated by using nanotubes-organic vehi-cles. The purified SWNTs, which were syn-thesized by dc arc discharge, were dispersed in iso propyl alcohol, and then mixed with on organic binder. The paste of well-dis-persed carbon nanotubes was squeezed onto the metal-patterned sodalime glass throuhg the metal mesh of 20${\mu}{\textrm}{m}$ in size and subse-quently heat-treated in order to remove the organic binder. The insulating spacers in thickness of 200${\mu}{\textrm}{m}$ are inserted between the lower and upper glasses. The Y\ulcornerO\ulcornerS:Eu, ZnS:Cu, Al, and ZnS:Ag, Cl, phosphors are electrically deposited on the upper glass for red, green, and blue colors, respectively. The typical sizes of each phosphor are 2~3 micron. The assembled structure was sealed in an atmosphere of highly purified Ar gas by means of a glass frit. The display plate was evacuated down to the pressure level of 1$\times$10\ulcorner Torr. Three non-evaporable getters of Ti-Zr-V-Fe were activated during the final heat-exhausting procedure. Finally, the active area of 4.5-inch panel with fully sealed carbon nanotubes was pro-duced. Emission currents were character-ized by the DC-mode and pulse-modulating mode at the voltage up to 800 volts. The brightness of field emission was measured by the Luminance calorimeter (BM-7, Topcon).

• Membrane Journal
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• v.32 no.5
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• pp.292-303
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• 2022

An eco-friendly energy conversion device without the emission of pollutants has gained much attention due to the rapid use of fossil fuels inducing carbon dioxide emissions ever since the first industrial revolution in the 18th century. Polymer electrolyte membrane fuel cells (PEMFCs) that can produce water during the reaction without the emission of carbon dioxide are promising devices for automotive and residential applications. As a key component of PEMFCs, polymer electrolyte membranes (PEMs) need to have high proton conductivity and physicochemical stability during the operation. Currently, perfluorinated sulfonic acid-based PEMs (PFSA-PEMs) have been commercialized and utilized in PEMFC systems. Although the PFSA-PEMs are found to meet these criteria, there is an ongoing need to improve these further, to be useful in practical PEMFC operation. In addition, the well-known drawbacks of PFSA-PEMs including low glass transition temperature and high gas crossover need to be improved. Therefore, this review focused on recent trends in the development of high-performance PFSA-PEMs in three different ways. First, control of the side chain of PFSA copolymers can effectively improve the proton conductivity and thermal stability by increasing the ion exchange capacity and polymer crystallinity. Second, the development of composite-type PFSA-PEMs is an effective way to improve proton conductivity and physical stability by incorporating organic/inorganic additives. Finally, the incorporation of porous substrates is also a promising way to develop a thin pore-filling membrane showing low membrane resistance and outstanding durability.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.7
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• pp.964-970
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• 2023

As part of the International Maritime Organization ef orts to reduce greenhouse gas emissions, the maritime industry is exploring low-carbon fuels such as liquefied natural gas and methanol, as well as zero-carbon fuels such as hydrogen and ammonia, evaluating them as environmentally friendly alternatives. Particularly, ammonia has substantial operational experience as cargo on transport ships, and ammonia ship engines are expected to be available in the second half of 2024, making it relatively accessible for commercial use. However, overcoming the toxicity challenges associated with using ammonia as a fuel is imperative. Detection is possible at levels as low as 5 ppm through olfactory senses, and exposure to concentrations exceeding 300 ppm for more than 30 min can result in irreparable harm. Using the KORA program provided by the Chemical Safety Agency, an assessment of the potential risks arising from leaks during ammonia bunkering was conducted. A 1-min leak could lead to a 5 ppm impact within a radius of approximately 7.5 km, affecting key areas in Busan, a major city. Furthermore, the potentially lethal concentration of 300 ppm could have severe consequences in densely populated areas and schools near the bunkering site. Therefore, given the absence of regulations related to ammonia bunkering, the potential for widespread toxicity from even minor leaks highlights the requirement for the development of legislation. Establishing an integrated system involving local governments, fire departments, and environmental agencies is crucial for addressing the potential impacts and ensuring the safety of ammonia bunkering operations.

• Economic and Environmental Geology
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• v.50 no.5
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• pp.389-400
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• 2017

In December 2015, 195 nations agreed to cut green house gas emissions in the Paris Climate Convention, and all over the world showed their willingness to participate in greenhouse gas mitigation. Accordingly, various technologies related to greenhouse gas reduction are being considered, among which carbon dioxide capture, storage, utilization (CCUS) technologies are attracting attention as an unique technology capable of directly removing greenhouse gases. However, CCUS technologies are still costly and have low efficiency. It is still more important to analyze the level of CCUS technology before commercialization and to understand trends and to predict future direction of technology. Therefore, this study analyzes the patent trends of CCUS technology and derives implications for future directions. As a result of country analysis, the United States had the highest number of applications, and sectoral analysis shows that 64% of total patents are from capture sector. Companies such as Alstom technology, Toshiba Corp, and Mitsubishi Heavy are focusing on capturing carbon dioxide. In Korea, government research institutes have focused on storage and utilization technologies. In addition, since the late 2000s, patent applications have increased rapidly, and many countries have been interested in the development of the technology and have made efforts to reduce greenhouse gas.

• Korean Chemical Engineering Research
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• v.57 no.3
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• pp.400-407
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• 2019

Oxy-combustion with a circulating fluidized bed (Oxy-CFBC) technology has been paid attention to cope with the climate change and fuel supply problem. In addition, Oxy-CFBC technology as one of the methods for carbon dioxide capture is an eco-friendly that can reduce air pollutants, such as $SO_2$, NO and CO through a flue gas recirculation process. The newly developed $100kW_{th}$ pilot-scale Oxy-CFBC system used for this research has been continuously utilizing to investigate oxy-combustion characteristics for various fuels, coals and biomasses to verify the possibility of fuel diversification. The anthracite is known as a low reactivity fuel due to a lot of fixed carbon and ash. Therefore, this study aims not only to improve combustion efficiency of an anthracite, but also to capture carbon dioxide. As a result, compared to air-combustion of sub-bituminous coal, oxy-combustion of anthracite could improve 2% combustion efficiency and emissions of $SO_2$, CO and NO were reduced 15%, 60% and 99%, respectively. In addition, stable operating of Oxy-CFBC could capture above 94 vol.% $CO_2$.

• Journal of the Korea Institute of Building Construction
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• v.22 no.3
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• pp.251-258
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• 2022

In the cement industry, in order to reduce CO₂ emissions, technology for raw materials substitution and conversion, technology for improving process efficiency of utilizing low-carbon new heat sources, and technology for collecting and recycling process-generated CO₂ are being developed. In this study, we conducted a basic experiment to contribute to the development of CSC that can store CO₂ as carbonate minerals among process-generated CO₂ capture and recycling technologies. Three types of CSC clinker with different SiO₂/(CaO+SiO₂) molar ratios were prepared with the clinker raw material formulation, and the characteristics of the clinker were analyzed. As a result of analysis and observation of CSC clinker, wollastonite and rankinite were formed. In addition, as a result of the carbonation test of the CSC paste, it was confirmed that calcite was produced as a carbonation product. The lower the SiO₂/(CaO+SiO₂) molar ratio in the CSC clinker chemical composition, the lower the wollastonite production amount, and the higher the rankinite production amount. And the amount of calcite production increased with the progress of carbonation of the CSC paste specimen. It is judged that rankinite is more reactive in mineralizing CO₂ than wollastonite.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.26 no.3
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• pp.19-28
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• 2023

The purpose of this study is to estimate carbon dioxide emissions from soil microbial respiration by forest type of Sobaeksan National Park. As a result of estimating the annual soil microbiological respiration volume by forest type in Sobaeksan National Park, broad-leaved forests, coniferous forest, artificial forests were similar to around 19.5 CO₂-ton/ha/yr. In the case of coniferous forests in sub-alpine and grassland near Birobong Peak, 12.2 CO₂-ton/ha/yr and 8.1 CO₂-ton/ha/yr, respectively, were lower than general forest areas. And as a result of analyzing the changes in soil microbiological respiration rate according to forest type in Sobaeksan National Park, the soil microbiological respiration rate in coniferous forests, broad-leaved forests, artificial forests, and sub-alpine areas was the highest in the July survey in summer and the lowest in November in late autumn. The change in soil microbial respiratory volume according to the measurement time in Sobaeksan National Park was the highest between 12:00 and 16:00, when the soil temperature was generally the highest among the days. It is known that the soil temperature is relatively low and the amount of soil microbial respiration decreases during winter, and the change in respiratory volume over the measurement time during the day was the smallest in November, when the amount of soil microbial respiration was relatively smaller than the May-September survey. However, this study has limitations in revealing the causal relationship of various environmental factors that affect the soil microbial respiration. Therefore, it is suggested that long-term research and investigation of various factors affecting soil respiration are needed to understand the carbon cycle of forest ecosystems.

• Journal of Energy Engineering
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• v.11 no.2
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• pp.81-89
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• 2002

IGCC (Integrated Coal Gasification Combined Cycle) is a technology that generates electric power using coal gasification and gasified fuel. Carbon conversion value of IGCC is higher and the influence on the environment is lower than the pulverized coal power plant. Especially, in the nations where the weight of fossil fuel for power generation is remarkably high like in Korea, IGCC stands out as an alternative plan to cope with sudden limitation for the emissions. In this paper, system design study for the commercial IGCC system which the introduction is imminent to Korea was performed. Two cases of entrained gasification process are adapted, one is FHR(full heat recovery) type IGCC system for high efficiency and the other is Quench type IGCC system for low cost. System simulations using common codes like AspenPlus were performed for each system. In the case of Quench system, system option study and sensitivity analysis of the air extraction rate was performed. Thermal performance result for the FHR system is 42.6% (HHV, Net) and for the quench system is 40% (HHV, net) when 75% air is extracted.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.3
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• pp.178-185
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• 2006

This paper investigates the steady-state combustion characteristics of the Homogeneous charge compression ignition(HCCI) engine with variable valve timing(VVT) and dimethyl ether(DME) direct injection, to find out its benefits in exhaust gas emissions. HCCI combustion is an attractive way to lower carbon dioxide($CO_2$), nitrogen oxides(NOx) emission and to allow higher fuel conversion efficiency. However, HCCI engine has inherent problem of narrow operating range at high load due to high in-cylinder peak pressure and consequent noise. To overcome this problem, the control of combustion start and heat release rate is required. It is difficult to control the start of combustion because HCCI combustion phase is closely linked to chemical reaction during a compression stroke. The combination of VVT and DME direct injection was chosen as the most promising strategy to control the HCCI combustion phase in this study. Regular gasoline was injected at intake port as main fuel, while small amount of DME was also injected directly into the cylinder as an ignition promoter for the control of ignition timing. Different intake valve timings were tested for combustion phase control. Regular gasoline was tested for HCCI operation and emission characteristics with various engine conditions. With HCCI operation, ignition delay and rapid burning angle were successfully controlled by the amount of internal EGR that was determined with VVT. For best IMEP and low HC emission, DME should be injected during early compression stroke. IMEP was mainly affected by the DME injection timing, and quantities of fuel DME and gasoline. HC emission was mainly affected by both the amount of gasoline and the DME injection timing. NOx emission was lower than conventional SI engine at gasoline lean region. However, NOx emission was similar to that in the conventional SI engine at gasoline rich region. CO emission was affected by the amount of gasoline and DME.

• Asian Journal of Atmospheric Environment
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• v.12 no.2
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• pp.153-164
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• 2018

We measured $^1H$ and $^{13}C$ nuclear magnetic resonance (NMR) spectra of Humic-like substances (HULIS) in urban atmospheric aerosols isolated by diethylaminoethyl (DEAE) and hydrophilic-lipophilic balance (HLB) resin to characterize their chemical structure. HULIS isolated by DEAE resin were characterized by relatively high contents of aromatic protons and relatively low contents of aliphatic protons in comparison with HULIS isolated by HLB resin, while the contents of protons bound to oxygenated aliphatic carbon atoms were similar. These results were consistent with the results of the $^{13}C$ NMR analysis and indicate that hydrophobic components were more selectively adsorbed onto HLB, while DEAE resins selectively retained aromatic carboxylic acids. Furthermore, we demonstrated that the chemical structural features of HULIS were significantly different between spring and summer samples and that these disparities were reflective of their different sources. The estimated concentrations of HULIS in spring were found to be regulated by vehicle emissions and pollen dispersion, while the behavior of HULIS in summer was similar to photochemical oxidant and nitrogen dioxide concentrations. The proportion of aliphatic protons for summer samples was higher than that for spring samples, while the proportion of aromatic protons for summer samples was lower than that for spring samples. These seasonal changes of the chemical structure may also involve in their functional expression in the atmosphere.