• Applied Chemistry for Engineering
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• v.34 no.5
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• pp.507-514
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• 2023

The selective catalytic reduction (SCR) of nitrogen oxides (NO_x) was investigated in a catalyst (Ag/γ-Al₂O₃) packed dielectric barrier discharge plasma reactor. The intermittent generation of plasma in the catalyst bed partially oxidized the hydrocarbon reductant for NO_x removal to several aldehydes. Compared to using the catalyst alone, higher NO_x conversion was observed with the intermittent generation of plasma due to the formation of highly reductive aldehydes. Under the same operating conditions (temperature: 250 ℃; C/N: 8), the NO_x reduction efficiencies were 47.5%, 92%, and 96% for n-heptane, propionaldehyde, and butyraldehyde, respectively, demonstrating the high NO_x reduction capability of aldehydes. To determine the optimal condition for intermittent plasma generation, the high voltage on/off cycle was adjusted from 0.5 to 3 min. The NO_x reduction performance was compared between continuous and intermittent plasma generation on the same energy density basis. The highest NO_x reduction efficiency was achieved at 2-min high voltage on/off intervals. The reason that the intermittent plasma discharge exhibited higher NO_x reduction efficiency even at the same energy density, compared to the continuous plasma generation case, is that the intermediate products, such as aldehydes generated from hydrocarbon, were more efficiently utilized for the reduction of nitrogen oxides.

• Bulletin of the Korean Chemical Society
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• v.34 no.6
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• pp.1693-1697
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• 2013

This study develops a novel method to remove the free cations created during the synthesis of ionic liquid. The cations are removed from the ionic liquid by size-selective adsorption onto chemically surface-modified Zeolite. The porous crystal nano-structure of Zeolite has several electron-rich Al sites to attract cations. While large cations of an ionic liquid cannot access the Zeolite nano-structure, small cations like $Na^+$ have ready access and are adsorbed. This study confirms that: $Na^+$ can be removed from ionic liquid effectively using Zeolite; and, in contrast to the conventional and extensively applied ion exchange resin method or solvent extraction methods, this can be done without changing the nature of the ionic liquid.

• Bulletin of the Korean Chemical Society
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• v.25 no.2
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• pp.185-189
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• 2004

Methanol dehydration to dimethyl ether (DME) has been investigated over ZSM-5 zeolites and compared with that of ${\gamma}-Al_2O_3$. Although the catalytic activity was decreased with an increase in silica/alumina ratio, the DME selectivity increased. H-ZSM-5 and NaH-ZSM-5 zeolites were more active for conversion of methanol to DME than ${\gamma}-Al_2O_3$. $Na^+$ ion-exchanged H-ZSM-5 (NaH-ZSM-5) shows higher DME selectivity than H-ZSM-5 due to the selective removal of strong acid sites.

• Korean Journal of Head & Neck Oncology
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• v.5 no.1
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• pp.5-13
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• 1989

Carotid body paraganglioma is uncommon, with appoximately 900 reports of it in the world literature, and with only 7 documented cases in the Korean literature. The classic carotid body paraganglioma develops in the bifurcation of common carotid artery and involves both the internal and external carotid arteries at it expands. The diagnosis may almost always be established preoperatively by selective angiography which shows a widening of the carotid bifurcation with a well defined vascular mass. Differential consideration of a single, lateral cervical mass in this location include branchial cleft cyst, neurogenic tumor, metastatic thyroid cancer, carotid body aneurysm and salivary gland tumor. Surgical therapy is the preferred method of treatment as these tumors are regarded as radioresistant. Because of their high vascularity and anatomical location, surgical removal of these tumors reguires a considerable degree of caution and a high degree of surgical expertise. With improved diagnostic and surgical technique, the morbidity and mortality has been reduced lately. This report details the management of 3 patients with carotid body paraganglioma who underwent safe resection by subadventitial dissection or using an internal vascular shunt.

• Journal of Environmental Science International
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• v.8 no.3
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• pp.393-397
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• 1999

Among various reactions which metal sulfides can undergo in the reducing environment, the lattice exchange reaction was examined in a attempt to selectively remove heavy metal ions contained in the Fe-Coagulants acid solution. We have examined Zeta potential along with pHs to investigate surface characteristics of ${FeS}_{(s)}$. As a result of this experiment, zero point charge(ZPC) of FeS is pH 7 and zeta potential which resulted from solid solution reaction between Pb(II) and ${FeS}_{(s)}$ is similar to that of ${PbS}_{(s)}$. Solubility characteristics of ${FeS}_{(s)}$ is appeared to that dissolved Fe(II) concentration increased in less than pH 4, and also increased with increasing heavy metal concentration. Various heavy metal ions(Pb(II), Cu(II), Zn(II)) contained in Fe-coagulants acid solution were removed selectively more than ninety-five percent in the rang of pH 2.5~10 by ${FeS}_{(s)}$. From the above experiments, therefore, We could know that the products of reaction between heavy metal ions and $FeS_{(S)}$ are mental sulfide such as $PbS_{(S)}$, $CuS_{(S)}$ and $ZnS_{(S)}$.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.1
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• pp.81-87
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• 2006

In marine air pollution control, SCR (Selective Catalytic Reduction) is reconized as the most effect method to control NOx, but on the other hand. seawater scrubber applying the basic characteristic that is naturally alkaline (pH typically around 8.1) is viewed as an economical SOx removal system at present. Especially, seawater scrubber would not be necessary to follow any of the various land based flue gas desulfurization methods. i.e. wet, dry or alkali scrubbing. However, these methods are not readily adaptable to marine conditions due to the quantifies of consumables required i.e. lime or limestone, the means of operation and the commercial availability. This research is undertaken to develop a new method as the main target of eliminating all exhaust emissions, particularly vessel, because of easy access to seawater and apt to apply a wet scrubber system. First, using the acidic seawater by seawater electrolysis, nitric monoxide(NO) is adequately oxidized to nitric dioxide $(NO_2)$by ClOx-in the acidic seawater, the electrolyzed alkaline seawater by electrolysis which contains mainly NaOH together with alkali metal ions $(i.e\;Na^{+}\;K^{+},\;Mg_{2}\;^{+},\;Ca_{2}\;^{+})$, is used as the absorption medium of NOx, the SOx are absorbed by relatively high solubility compared to other components of exhaust pollutants. The results found that the NOx and SOx removals could be achieved nearly Perfect.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.2
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• pp.152-160
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• 2016

The market demand for diesel engine tends to increase in general passenger cars as well as commercial vehicles because of its advantages. However, to meet the vehicle emissions regulation which will be more stringent in the future, it is necessary to plurally apply all after-treatment technologies such as diesel oxidation catalyst (DOC), catalyzed diesel particulate filter (CDPF), lean NOx trap (LNT) and selective catalytic reduction (SCR), and so on. Accordingly, the exhaust after-treatment system for diesel vehicle requires the technology of minimizing the numbers of catalysts by integrating every individual catalysts. The purposes of this study is to develop hybrid exhaust after-treatment device system which simultaneously uses LNT/DPF and SCR/DPF catalyst concurrently reducing NOx and particulate matter (PM). As the results, the hybrid system with $NH_3$ generated at LNT/DPF working as a reducing agent of SCR/DPF catalyst, improving NOx conversion rate, was found to be more excellent in de-NOx performance than that in LNT/DPF alone system.

• Journal of Korean Neurosurgical Society
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• v.46 no.6
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• pp.577-580
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• 2009

A 47-year-old man presented with a subarachnoid hemorrhage (SAH) and right cerebellar hematoma was referred for evaluation. Cerebral angiography revealed a distal anterior inferior cerebellar artery (AICA) aneurysm associated with an arteriovenous malformation (AVM). Successful obliteration and complete removal of the aneurysm and AVM were obtained using transcortical approach under the guidance of neuronavigation system. The association of a peripheral AICA aneurysm and a cerebellar AVM by the same artery is unique. The reported cases of conventional surgery for this disease complex are not common and their results are variable. Less invasive surgery using image-guided neuronavigation system would be helpful and feasible for a peripheral aneurysm combining an AVM of the posterior fossa in selective cases

• Resources Recycling
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• v.21 no.4
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• pp.53-59
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• 2012

In this study, behaviors of removing Sb and Pb by oxidation of molten Bi-Pb-Sb alloy which is a by-product of non-ferrous smelting process was investigated. The molten alloy was oxidized at 1173 K by bubbling $N_2+O_2$ gas through a submerged nozzle. The Sb was removed and recovered as mixed phase of $Sb_2O_3$ and metal Sb. In the case of bubbling $N_2+O_2$ gas into molten Bi-Pb alloy at 923 K, Pb was oxidized and removed to slag. But Bi could not be refined due to simultaneous oxidization of Bi with Pb.

• Journal of Korean Society for Atmospheric Environment
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• v.20 no.2
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• pp.185-193
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• 2004

A catalyst with CuO ceramic filter for simultaneous treatment of dust and HAP was prepared and characterized. Catalytic ceramic filter can not only potentially achieve the substantial savings in energy but provide with effective optimization and integration of process for simultaneous removal of SO$_2$, NO$_{x}$ and particulates from flue gases. Catalytic ceramic filters remove simultaneously particulates on exterior surface of filters and reduce NO to $N_2$ and $H_2O$ by SCR (Selective Catalytic Reduction) process. Preparation of catalyst impregnated ceramic filter with disk shape (Ψ 50) follow the processing of alumino-silicate ceramic filter, support impregnation and catalyst impregnation (copper oxide). Preparation routes of alumino-silicate catalyst carrier suitable for production of catalytic filters practically were studied and developed using the sol-gel and colloidal processing, homogeneous precipitation and impregnation method. Characterization of the catalyst, catalyst carrier catalytic filter materials have been performed the using various techniques such as BET, XRD, TGA, SEM. Combination of the sol-gel and colloidal processing and impregnation method is recommended to prepare catalyst carriers economically for catalytic filter applications.s.