• Clean Technology
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• v.20 no.4
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• pp.367-374
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• 2014

Several experiments have been done to investigate the removal of hydrogen sulfide ($H_2S$) synthetic gas from biogas streams by means of chemical absorption and chemical reaction with 0.1-1 M Fe/EDTA solution. The roles of Fe/EDTA were studied to enhance the removal efficiency of hydrogen sulfide because of oxidizing by chelate. The motivation of this investigation is first to explore the feasibility of enhancing the toxic gas treatment in the biogas facility. The biogas purification strategy affords many advantages. For instance, the process can be performed under mild environmental conditions and at low temperature, and it removes hydrogen sulfide selectively. The end product of separation is elemental sulfur, which is a stable material that can be easily disposed with minor potential for further pollution. As the Fe-EDTA concentration increased, the conversion rate of hydrogen sulfide increased because of the high stability of Fe-EDTA complex. pH as an important environmental factor was 9.0 for the stability of chemical complex in the oxidation of hydrogen sulfide.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2181-2185
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• 2008

Fuel processing systems which convert HC fuel into $H_2$ rich gas (such as stream reforming, partial oxidation, auto-thermal reforming) need high temperature environment($600-1000^{\circ}C$). Generally, anode-off gas or mixture of anode-off gas and LNG is used as input gas of fuel reformer. In order to make efficient and low emission burner system for fuel reformer, it is necessary to elucidate the combustion and emission characteristic of fuel reformer burner. The purpose of this study is to develop a porous premixed flat ceramic burner that can be used for 1-5kW fuel cell reformer. Ceramic burner experiments using natural gas, hydrogen gas, anode off gas were carried out respectively to investigate the flame characteristics by heating capacity and equivalence ratio. Results show that the stable flat flames can be established for natural gas, hydrogen gas, anode off gas and mixture of natural & anode off gas as reformer fuel. For all of fuels, their burning velocities become smaller as the equivalence ratio goes to the lean mixture ratio, and a lift-off occurs at lean limit. Flame length in hydrogen and anode off gas became longer with increasing the heat capacity.

• Journal of Ginseng Research
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• v.42 no.3
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• pp.320-326
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• 2018

Background: Explosive puffing can induce changes in the chemical, nutritional, and sensory quality of red ginseng. The antioxidant properties of ethanolic extracts of red ginseng and puffed red ginseng were determined in bulk oil and oil-in-water (O/W) emulsions. Methods: Bulk oils were heated at $60^{\circ}C$ and $100^{\circ}C$ and O/W emulsions were treated under riboflavin photosensitization. In vitro antioxidant assays, including 2,2-diphenyl-1-picrylhudrazyl, 2,2'-azinobis-3-ethyl-benzothiazoline-6-sulfonic acid, ferric reducing antioxidant power, total phenolic content, and total flavonoid content, were also performed. Results: The total ginsenoside contents of ethanolic extract from red ginseng and puffed red ginseng were 42.33 mg/g and 49.22 mg/g, respectively. All results from above in vitro antioxidant assays revealed that extracts of puffed red ginseng had significantly higher antioxidant capacities than those of red ginseng (p < 0.05). Generally, extracts of puffed red and red ginseng had high antioxidant properties in riboflavin photosensitized O/W emulsions. However, in bulk oil systems, extracts of puffed red and red ginseng inhibited or accelerated rates of lipid oxidation, depending on treatment temperature and the type of assay used. Conclusion: Although ethanolic extracts of puffed red ginseng showed stronger antioxidant capacities than those of red ginseng when in vitro assays were used, more pro-oxidant properties were observed in bulk oils and O/W emulsions.

• Clean Technology
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• v.14 no.3
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• pp.218-223
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• 2008

Decomposition of reactive organic compound dispersed in microemulsion media by hydroxide ions and proton ions generated during electrolysis was tried and the half-lifes for decomposition were compared. Absorbance of p-nitrophenoxide produced from the decomposition of p-nitrophenylacetate (PNPA) was followed to find the rate of decomposition. The applied voltage, temperature, and the amount of substrate were changed to see the effects on the decomposition rate. The advantages of electrolysis in microemulsion system were the high solubilizing capacity of substrate, easy control of decomposition rate, low operation cost, no need for any addition of chemicals, and no byproducts. The mechanism of decomposition and the application to water purification were discussed.

• Mycobiology
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• v.43 no.3
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• pp.280-287
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• 2015

In this study, transcriptome analysis of twelve laccase genes in Pleurotus ostreatus revealed that their expression was differentially regulated at different developmental stages. Lacc5 and Lacc12 were specifically expressed in fruiting bodies and primordia, respectively, whereas Lacc6 was expressed at all developmental stages. Lacc1 and Lacc3 were specific to the mycelial stage in solid medium. In order to investigate their biochemical characteristics, these laccases were heterologously expressed in Pichia pastoris using the pPICHOLI-2 expression vector. Expression of the laccases was facilitated by intermittent addition of methanol as an inducer and sole carbon source, in order to reduce the toxic effects associated with high methanol concentration. The highest expression was observed when the recombinant yeast cells were grown for 5 days at $15^{\circ}C$ with intermittent addition of 1% methanol at a 12-hr interval. Investigation of enzyme kinetics using 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) as a substrate revealed that the primordium-specific laccase Lacc12 was 5.4-fold less active than Lacc6 at low substrate concentration with respect to ABTS oxidation activity. The optimal pH and temperature of Lacc12 were 0.5 pH units and $5^{\circ}C$higher than those of Lacc6. Lacc12 showed maximal activity at pH 3.5 and $50^{\circ}C$, which may reflect the physiological conditions at the primordiation stage.

• Korean Journal of Materials Research
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• v.26 no.3
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• pp.109-116
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• 2016

To achieve the fabrication of high-quality Ag-coated Cu particles through a wet chemical process, we reported herein pretreatment conditions using an ammonium-based mixed solvent for the removal of a $Cu_2O$ layer on Cu particles that were oxidized in air for 1 hr at $200^{\circ}C$ or for 3 days at room temperature. Furthermore, we discussed the results of post-Ag plating with respect to removal level of the oxide layer. X-ray diffraction results revealed that the removal rate of the oxide layer is directly proportional to the concentration of the pretreatment solvent. With the results of Auger electron spectroscopy using oxidized Cu plates, the concentrations required to completely remove 50-nm-thick and 2-nm-thick oxides within 5 min were determined to be X2.5 and X0.13. However, the optimal concentrations in an actual Ag plating process using Cu powder increased to X0.4 and X0.5, respectively, because the oxidation in powder may be accelerated and the complete removal of oxide should be tuned to the thickest oxide layer among all the particles. Back-scattered electron images showed the formation of pure fine Ag particles instead of a uniform and smooth Ag coating in the Ag plating performed after incomplete removal of the oxide layer, indicating that the remaining oxide layer obstructs heterogeneous nucleation and plating by reduced Ag atoms.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.1
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• pp.16-19
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• 2006

The characteristic of negative differential resistance(NDR) is decreased current when the applied voltage is increased. The NDR is potentially very useful in molecular electronics device schemes. Here, we investigated the NDR characteristic of self-assembled 4,4'-di(ethynylphenyl)-2'-nitro-1-benzenethiolate, which has been well known as a conducting molecule. Self-assembly monolayers(SAMs) were prepared on Au(111), which had been thermally deposited onto $pre-treatment(H_2SO_4:H_2O_2=3:1)$ Si. The Au substrate was exposed to a 1 mM/1 solution of 1-dodecanethiol in ethanol for 24 hours to form a monolayer. After thorough rinsing the sample, it was exposed to a 0.1 ${\mu}M/l$ solution of 4.4'-di(ethynylphenyl)-2'-nitro-1-(thioacetyl)benzene in dimethylformamide(DMF) for 30 min and kept in the dark during immersion to avoid photo-oxidation. After the assembly, the samples were removed from the solutions, rinsed thoroughly with methanol, acetone, and $CH_2Cl_2,$ and finally blown dry with N_2. Under these conditions, we measured electrical properties of self-assembly monolayers(SAMs) using ultra high vacuum scanning tunneling microscopy(UHV-STM). The applied voltages were from -2 V to +2 V with 298 K temperature. The vacuum condition was $6{\time}10^{-8}$ Torr. As a result, we found the NDR voltage of the 4,4'-di(ethynylphenyl)-2'-nitro-1-benzenethiolate were $-1.61{\pm}0.26$ V(negative region) and $1.84{\pm}0.33$ V(positive region). respectively.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.1844-1846
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• 2005

The characteristic of negative differential resistance(NDR) is decreased current when the applied voltage is increased. The NDR is potentially very useful in molecular electronics device schemes. Here, we investigated the NDR property of self-assembled 4,4- Di(ethynylphenyl)-2'-nitro-1-(thioacetyl)benzene, which has been well known as a conducting molecule. Self-assembly monolayers(SAMs) were prepared on Au(111), which had been thermally deposited onto pre-treatment$(H_2SO_4:H_2O_2=3:1)$ Si. The Au substrate was exposed to a 1mM/l solution of 1-dodecanethiol in ethanol for 24 hours to form a monolayer. After thorough rinsing the sample, it was exposed to a $0.1{\mu}M/l$ solution of 4,4-Di(ethynylphenyl)-2'-nitro-1-(thioacetyl)benzene in dimethylformamide(DMF) for 30 min and kept in the dark during immersion to avoid photo-oxidation. After the assembly, the samples were removed from the solutions, rinsed thoroughly with methanol, acetone, and $CH_2Cl_2$, and finally blown dry with $N_2$. Under these conditions, we measured electrical properties of self-assembly monolayers(SAMs) using ultra high vacuum scanning tunneling microscopy(UHV-STM). The applied voltages were from -2V to +2V with 299K temperature. The vacuum condition is $6{\times}10^{-8}$ Torr. As a result, we found the NDR voltage of the nitro-benzene is $-1.61{\pm}0.26$ V(negative region) and $1.84{\pm}0.33$ (positive region), respectively.

• Journal of the Korean Society of Safety
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• v.24 no.1
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• pp.31-36
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• 2009

This paper focuses on techniques of improving refinery reliability, availability, and profitability. Our team developed a corrosion control document(CCD) for processing of the crude distillation unit(CDU). Recent study shows the loss due to corrosion in US is around $276 billion. It's a big concern for both managers and engineers of refinery industry. The CCD consists of numerous parts namely damage mechanism(DM), design data, critical reliability variable(CRV), guidelines, etc. The first step in the development of CCD is to build material selection diagram(MSD). Damage mechanisms affecting equipments and process need to be chosen carefully based on API 571. The selected nine DM from API 571 are (1) creep/stress rupture, (2) fuel ash corrosion, (3) oxidation, (4) high temperature sulfidation, (5) naphthenic acid corrosion, (6) hydrochloric acid(HCL) corrosion, (7) ammonium chloride(salt) corrosion, (8) wet $H_2S$ corrosion, and (9) ammonia stress corrosion cracking. Each DM related to corrosion of CDU process was selected by design data, P&ID, PFD, corrosion loop, flow of process, equipment's history, and experience. Operating variables affecting severity of DM are selected in initial stage of CRV. We propose the guidelines for reliability of equipments based on CRV. The CCD has been developed on the basis of the corrosion control in refinery industry. It also improves the safety of refinery process and reduces the cost of corrosion greatly.

• Korean Journal of Materials Research
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• v.22 no.10
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• pp.545-551
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• 2012

In semiconductor manufacturing, the circuit integrity of packaged BGA devices is tested by measuring electrical resistance using test sockets. Test sockets have been reported to often fail earlier than the expected life-time due to high contact resistance. This has been attributed to the formation of Sn oxide films on the Au coating layer of the probe pins loaded on the socket. Similar to contact failure, and known as "fretting", this process widely occurs between two conductive surfaces due to the continual rupture and accumulation of oxide films. However, the failure mechanism at the probe pin differs from fretting. In this study, the microstructural processes and formation mechanisms of Sn oxide films developed on the probe pin surface were investigated. Failure analysis was conducted mainly by FIB-FESEM observations, along with EDX, AES, and XRD analyses. Soft and fresh Sn was found to be transferred repeatedly from the solder bump to the Au surface of the probe pins; it was then instantly oxidized to SnO. The $SnO_2$ phase is a more stable natural oxide, but SnO has been proved to grow on Sn thin film at low temperature (< $150^{\circ}C$). Further oxidation to $SnO_2$ is thought to be limited to 30%. The SnO film grew layer by layer up to 571 nm after testing of 50,500 cycles (1 nm/100 cycle). This resulted in the increase of contact resistance and thus of signal delay between the probe pin and the solder bump.