• Transactions of the Korean hydrogen and new energy society
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• v.23 no.5
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• pp.503-512
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• 2012

There is a new power generation system such as direct coal fuel cell (DCFC) with a solid oxide electrolyte operated at relatively high temperature. In the system, it is of great importance to feed coal continuously into anodic electrode surface for its better contact, otherwise it would reduce electrochemical conversion of coal. For that purpose, it is required to improve the electrochemical conversion efficiency by using either rigorous mixing condition such as fluidized bed condition or just by recirculating coal particle itself successively into the reaction zone of the system. In this preliminary study, we followed the second approach to investigate how significantly particle recycle would affect the coal conversion efficiency. As a first phase, coal conversion was analyzed and evaluated from the thermochemical reaction of carbon with air under particle recirculating condition. The coal conversion efficiency was obtained from raw data measured by two different techniques. Effects of temperature and fuel properties on the coal conversion are specifically examined from the thermochemical reaction.

• Analytical Science and Technology
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• v.21 no.2
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• pp.93-101
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• 2008

The application of solid phase microextraction (SPME) is generally conducted by directly immersing the fiber into the liquid sample or by exposing the fiber in the head space (HS). The extraction temperature, the time of incubation, and application of stirring are often designated to be the most important parameters for achieving the best extraction efficiencies of HS-SPME analysis. In this study, relative importance of these three analytical parameters involved in the HS-SPME method is evaluated using a polydimethylsiloxane/carboxen (PDMS/CAR) fiber. To optimize its operation conditions the competing relationships between different parameters were investigated by comparing the extraction efficiency based on the combination of three parameters and two contracting conditions: (1) heating the sample at 30 vs. 50 C, (2) exposing samples at two durations of 10 vs. 30 min, and (3) application of stirring vs. no stirring. According to our analysis among 8 combination types of HS-SPME method, an extraction condition termed as S50-30 condition ((1) 1200 rpm stirring, (2) $50^{\circ}C$ exposure temp, and (3) 30 min exposure duration) showed maximum recovery rate of 45.5~68.5% relative to an arbitrary reference of direct GC injection. According to this study, the employment of stirring is the most crucial factor to improve extraction efficiency in the application of HS-SPME.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.393-397
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• 2001

The innovatory process, that is the direct separation and recovery of the iron and zinc metals contained in the high temperature exhaust gas generated from the electric arc furnace fer the inn scrap melting and/or the dust treatment, has been proposed. This proposed process consists of the moving coke bed filter that is directly connected to the electric furnace, and the following heavy metal condenser. The exhaust gas passes through the filter and the condenser right after exhausting from the electric furnace. The moving coke bed filter is being controlled at about 1000℃ and collects iron and slag components contained in the high temperature exhaust gas. Heavy metals such as zinc and lead pass through the filter as vapor. Based on the thermodynamic considerations, the iron oxide and the zinc oxide are reduced in the filter. The solution loss reaction rate is comparatively low at about 1000℃ in the coke bed filter by the analysis using the mathematical simulation model. The heavy metal condenser is installed in the position after the coke bed filter, and rapidly cools the gas from about 1000℃ to 450℃ by a full of the cooling medium like the solid ceramic ball in addition to the cooling from the wall. The zinc and lead vapor condense and separate f개m the gas in a liquid state. The investigation of the characteristics of the exhaust gas of the commercial electric arc furnace, the fundamental experiments of the laboratory scale and the bench scale ensured the formation of this proposed process. A small-scale pilot plant examination is carrying out at present to confirm the formation of the process. It is certain that the dust generation of the electric arc furnace is extremely decreased, and it can save the energy consumption of usual dust treatment processes by the realization of this process.

• Food Science and Biotechnology
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• v.18 no.2
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• pp.565-569
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• 2009

This study was conducted to evaluate the effects of different preparation methods on the recovery and quantification of ginsenosides in raw Korean ginseng (Panax ginseng C.A. Meyer). Eight major ginsenosides ($Rb_1$, $Rb_2$, $Rb_3$, Rc, Rd, Re, Rf, and $Rg_1$) were analyzed by high performance liquid chromatography (HPLC), after which the recovery and repeatability of the extraction of those ginsenosides using 3 different preparation methods were compared [A. direct extraction (DE) method, hot MeOH extraction/evaporation/direct dissolution; B. solid phase extraction (SPE) method, hot MeOH extraction/evaporation/dissolution/$C_{18}$ cartridge adsorption/MeOH elution; C. liquid-liquid extraction (LLE) method, hot MeOH extraction/evaporation/dissolution/n-BuOH fractionation]. Use of the DE method resulted in a significantly higher recovery of total ginsenosides than other methods and a relatively clear peak resolution. Use of the SPE and LLE methods resulted in clearer peak resolution, but lower ginsenoside recovery than the DE method. The LLE method showed the lowest ginsenoside recovery and repeatability among the 3 methods. Given that the DE method employed only extraction, evaporation, and a dissolution step (avoiding complicate and time consuming purification), this technique may be an effective method for the preparation and quantification of ginsenosides from raw Korean ginseng.

• Journal of the Korean Chemical Society
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• v.36 no.2
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• pp.273-281
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• 1992

A new sputtering chamber, as Atomsource, for atomic absorption measurements was designed and built to have maximum ground state atoms in view and minimum emission. The high velocity gas jets not only change the visual and electrical characteristics of the discharge, but also increase the amount of material atomized, as is apparent from the craters that are produced in the sample where the jets strike the surface. The use of gas jets in a sputtering cell makes this a direct sampling method practical for atomic absorption spectrometry. The factors influencing absorption sensitivity and reproducibility have been investigated for the newly developed atomizer.

• Korean Journal of Food Science and Technology
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• v.26 no.6
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• pp.665-669
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• 1994

A rapid gas chromatographic (GC) profiling method was applied to dairy products (milk and cheeses) for the simultaneous analysis of volatile and nonvolatile organic acids. Cheese samples were first made into aqueous samples by dissolving in water. The aqueous samples were then extracted with organic solvents after the acidification and NaCI saturation. The organic layers (diethyl ether : hexane= 1 : 1) were extracted with $NaHCO_3$ saturated solution with subsequent solid-phase extraction of the aqueous phases using Chromosorb P column/diethyl ether followed by triethylamine treatment. The resulting triethylammonium salts of acids were directly converted into volatile tert.-butyldimethylsilyl derivatives, which were analyzed by dual-capillary column GC, and GC-mass spectrometry. From milk and four cheese samples studied, 31 organic acids including 21 fatty acids and other hydroxy and dioic acids were tentatively identified. The amounts of the fatty acids were different among the kinds of cheese and thus the simplified retention index (RI) spectra of organic acids were useful for the visual pattern recognition of each sample, when the Direct Comparision method between cheese and a blind sample were attempted, it was quickly recognized to be a gouda cheese with the 999 ppt match quality value.

• Food Engineering Progress
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• v.14 no.3
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• pp.249-255
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• 2010

Ten commercial activated carbons (ACs) prepared from four different sources (bamboo, wood, peat, and coal) were evaluated for their adsorptive efficiency of six volatile compounds (isoamyl alcohol, hexanal, furfural, ethyl lactate, ethyl octanoate, 2-phenyl ethanol) which were dissolved in a 30% alcoholic model solution. These six volatile compounds are frequently found in alcoholic beverages and possibly contribute to physiological hangover due to their high concentrations. They are also generally regarded as off-flavor compounds at certain levels in alcoholic beverages such as whisky and vodka. Two hundred mL of 30% alcoholic solutions containing these six volatile compounds were treated with 0.2 g of ACs while stirring for 16 hr; the treated solutions were then measured for their adsorptive efficiencies (or removal efficiencies) by gas chromatographic analysis using two different sampling methods (direct liquid injection and headspace-solid phase microextraction). The adsorptive efficiencies of the ACs varied depending on the identity of the volatile compounds and the source material used for making the ACs. Ethyl octanoate, 2-phenyl ethanol, and hexanal were removed at high efficiencies (34-100%), whereas isoamyl alcohol, ethyl lactate, and furfural were removed at low efficiencies (5-13%). AC prepared from bamboo showed a high removal efficiency for isoamyl alcohol, aldehydes (hexanal and furfural), and 2-phenyl ethanol; these major fusel oils have been implicated as congeners responsible for alcohol hangover.

• Journal of the Korean Chemical Society
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• v.38 no.3
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• pp.214-220
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• 1994

A glow discharge atomic absorption system for the direct analysis of conducting solid samples has been designed and constructed. An arrestor made of machinable ceramic which is a main component for confining the discharge between cathode and anode is modified to have a better stability in discharge. Discharge voltage or current, shape of arrestor, pressure, and gas flow rate can be controlled by an ADC/DAC board with a personal computer. The effect of discharge parameters such as discharge voltage, pressure, and gas flow rate on the sample loss rate, absorbance, and the surface morphology of sample by SEM has been studied to find optimum discharge conditions.

• Safety and Health at Work
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• v.9 no.4
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• pp.479-485
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• 2018

The aim of this study is to validate an integrated air monitoring approach for assessing airborne formaldehyde (FA) in the workplace. An active sampling by silica gel impregnated with 2,4-dinitrophenylhydrazine, a passive solid phase microextraction technique using O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine as on-fiber derivatization reagent, an electrochemical direct-reading monitor, and an enzyme-based badge were evaluated and tested over a range of 0.020-5.12 ppm, using dynamically generated FA air concentrations. Simple linear regression analysis showed the four methods were suitable for evaluating airborne FA. Personal and area samplings in 12 anatomy pathology departments showed that the international occupational exposure limits in the GESTIS database were frequently exceeded. This monitoring approach would allow a fast, easy-to-use, and economical evaluation of both current work practices and eventual changes made to reduce FA vapor concentrations.

• Journal of Microbiology and Biotechnology
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• v.31 no.11
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• pp.1519-1525
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• 2021

Hexavalent chromium (Cr(VI)) is recognized to be carcinogenic and toxic and registered as a contaminant in many drinking water regulations. It occurs naturally and is also produced by industrial processes. The reduction of Cr(VI) to Cr(III) has been a central topic for chromium remediation since Cr(III) is less toxic and less mobile. In this study, fermentative Fe(III)-reducing bacterial strains (Cellu-2a, Cellu-5a, and Cellu-5b) were isolated from a groundwater sample and were phylogenetically related to species of Cellulomonas by 16S rRNA gene analysis. One selected strain, Cellu-2a showed its capacity of reduction of both soluble iron (ferric citrate) and solid iron (hydrous ferric oxide, HFO), as well as aqueous Cr(VI). The strain Cellu-2a was able to reduce 15 μM Cr(VI) directly with glucose or sucrose as a sole carbon source under the anaerobic condition and indirectly with one of the substrates and HFO in the same incubations. The heterogeneous reduction of Cr(VI) by the surface-associated reduced iron from HFO by Cellu-2a likely assisted the Cr(VI) reduction. Fermentative features such as large-scale cell growth may impose advantages on the application of bacterial Cr(VI) reduction over anaerobic respiratory reduction.