• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.18-24
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• 2018

The policy-making and technological development of eco-friendly automobiles designed to increase their supply is ongoing, but the internal combustion engine still accounts for about 95% of the automobiles in use. Also, in order to meet the stricter emission regulations of internal combustion engines based on fossil fuels, the proportion of after-treatments for vehicles and (ocean going) vessels is gradually increasing. Natural gas is a clean fuel that emits few air pollutants and has been used mainly as a fuel for city buses. In the long term, we intend to develop a new NGOC/LNT+NGCO/SCR combined system that simultaneously reduces the toxic gases, $CH_4$ and NOx, emitted from CNG buses. The objective of this study is to investigate the characteristics of $de-CH_4/NOx$ according to the ceramic and metal substrates of the SCR (Selective Catalytic Reduction) catalysts mounted downstream of the combined system. The V and Cu-SCR catalysts did not affect the $CH_4$ oxidation reaction, the two NGOC/SCR catalysts each coated with two layers began to oxidize $CH_4$ at $400^{\circ}C$, and the amount of $CH_4$ emitted was reduced to about 20% of its initial value at about $550^{\circ}C$. The two NGOC/SCR catalysts each coated with two layers showed a negative (-) NOx conversion rate above $350^{\circ}C$. The ceramic-based combined system reached LOT50 at $500^{\circ}C$, which was about 20% higher in terms of the $CH_4$ conversion rate than the metal-based combined system, showing that the combined system of NGOC/LNT+Cu-SCR is a suitable combination.

• Applied Chemistry for Engineering
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• v.29 no.4
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• pp.461-467
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• 2018

In this study, $(n-BuCp)_2ZrCl_2$, was supported on $SiO_2/MgCl_2$ binary support. Before supporting the catalyst, the $SiO_2/MgCl_2$ binary support was surface treated with three different alkyl aluminum compound, namely trimethylaluminum, triethylaluminum, and ethylaluminum sesquichloride. The synthesized surface-treated $SiO_2/MgCl_2$ supported metallocene catalysts were used for the copolymerization of ethylene and 1-hexene. Their catalytic properties and performances were analyzed through BET, XPS analysis, ICP-AES analysis, and FE-SEM. While the resulting copolymers were analyzed through DSC analysis, GPC analysis, 13C-NMR analysis, and FE-SEM. The analysis of synthesized surface-treated $SiO_2/MgCl_2$ supported metallocene catalysts showed that the Zr content of these catalysts is relatively lower compared to that of the catalyst supported on $SiO_2$. This could be attributed to the reduction in the surface area of $SiO_2$ due to the presence of recrystallized $MgCl_2$ and alkyl aluminum. Furthermore, they exhibited a better copolymerization activity compared to that of $SiO_2$ supported catalyst, particularly the EASC-surface treated binary support, which has the highest activity of 1.9 kg PE/($mmol-Zr^*hr$) because EASC acts as a strong Lewis acid. It could also be observed that the larger the ligand of alkyl aluminum used, the rougher the particle surface of the resulting polymer.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.10a
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• pp.111-124
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• 2003

Processes that cause immobilization of contaminants in soil are of great environmental importance because they may lead to a considerable reduction in the bioavailability of contaminants and they may restrict their leaching into groundwater. Previous investigations demonstrated that pollutants can be bound to soil constituents by either chemical or physical interactions. From an environmental point of view, chemical interactions are preferred, because they frequently lead to the formation of strong covalent bonds that are difficult to disrupt by microbial activity or chemical treatments. Humic substances resulting from lignin decomposition appear to be the major binding ligands involved in the incorporation of contaminants into the soil matrix through stable chemical linkages. Chemical bonds may be formed through oxidative coupling reactions catalyzed either biologically by polyphenol oxidases and peroxidases, or abiotically by certain clays and metal oxides. These naturally occurring processes are believed to result in the detoxification of contaminants. While indigenous enzymes are usually not likely to provide satisfactory decontamination of polluted sites, amending soil with enzymes derived from specific microbial cultures or plant materials may enhance incorporation processes. The catalytic effect of enzymes was evaluated by determining the extent of contaminants binding to humic material, and - whenever possible - by structural analyses of the resulting complexes. Previous research on xenobiotic immobilization was mostly based on the application of $^{14}$ C-labeled contaminants and radiocounting. Several recent studies demonstrated, however, that the evaluation of binding can be better achieved by applying $^{13}$ C-, $^{15}$ N- or $^{19}$ F-labeled xenobiotics in combination with $^{13}$ C-, $^{15}$ N- or $^{19}$ F-NMR spectroscopy. The rationale behind the NMR approach was that any binding-related modification in the initial arrangement of the labeled atoms automatically induced changes in the position of the corresponding signals in the NMR spectra. The delocalization of the signals exhibited a high degree of specificity, indicating whether or not covalent binding had occurred and, if so, what type of covalent bond had been formed. The results obtained confirmed the view that binding of contaminants to soil organic matter has important environmental consequences. In particular, now it is more evident than ever that as a result of binding, (a) the amount of contaminants available to interact with the biota is reduced; (b) the complexed products are less toxic than their parent compounds; and (c) groundwater pollution is reduced because of restricted contaminant mobility.

• Resources Recycling
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• v.29 no.2
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• pp.55-61
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• 2020

Selective catalytic reduction (SCR) has been a promising technology to reduce the air pollution caused by nitrogen oxides (NOx) in several industries. The consumption of SCR catalysts increases every year as technology evolves, however those have a limited lifespan and usually end up in landfills after they deactivate. Currently, the most widely used catalyst for and stationary applications is V₂O₅-WO₃/TiO₂ which can contain around 50% wt V₂O₅ and 7-10% wt of WO₃. The vast uses for both vanadium and tungsten and the worldwide interest in recycling methods that allow for the extraction of metals from secondary sources represent the major motivation for this research. The extraction time, pH dependency, extraction concentration studies were carried out using Aliquat 336 in exxol D80 as the extractant. It was determined that to optimize the extraction of both metals 30min of contact time with an organic phase containing 0.5mol/L of Aliquat 336 are needed at a slightly acidic pH (~5.0). In addition, counter McCabe-Thiele studies allowed us to determine that one stage is necessary for the removal of 99% of vanadium while 2 stages are necessary for the extraction of tungsten and counter current simulations proved that the theoretical approach was correct.

• Journal of the Microelectronics and Packaging Society
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• v.31 no.2
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• pp.54-62
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• 2024

SICM (Scanning Ion Conductivity Microscopy) is a technique for measuring surface topography in an environment where electrochemical reactions occur, by detecting changes in ion conductivity as a nanopipette tip approaches the sample. This study includes an investigation of the current response curve, known as the approach curve, according to the distance between the tip and the sample. First, a simulation analysis was conducted on the approach curves. Based on the simulation results, then, several measuring experiments were conducted concurrently to analyze the difference between the simulated and measured approach curves. The simulation analysis confirms that the current squeezing effect occurs as the distance between the tip and the sample approaches half the inner radius of the tip. However, through the calculations, the decrease in current density due to the simple reduction in ion channels was found to be much smaller compared to the current squeezing effect measured through actual experiments. This suggests that ion conductivity in nano-scale narrow channels does not simply follow the Nernst-Einstein relationship based on the diffusion coefficients, but also takes into account the fluidic hydrodynamic resistance at the interface created by the tip and the sample. It is expected that SICM can be combined with SECM (Scanning Electrochemical Microscopy) to overcome the limitations of SECM through consecutive measurement of the two techniques, thereby to strengthen the analysis of electrochemical surface reactivity. This could potentially provide groundbreaking help in understanding the local catalytic reactions in electroless plating and the behaviors of organic additives in electroplating for various kinds of patterns used in semiconductor damascene processes and packaging processes.