• Korean Journal of Soil Science and Fertilizer
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• v.27 no.4
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• pp.296-302
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• 1994

To alter the paddy field to upland, mole drainages were constructed under 30cm of the surface of(Jeon buk silt loam) which is not appropriate for cultivation of upland crops. Intervals of the moles were 50cm, 100cm and 150cm and diverted to upland for soybean cultivation. By construction of the mole drainage, about 75% to 45% of the rainfall was drained and the ground water level was maintained below 40cm. After a year of drainage, the blocky surface was changed to granular or nutty structure which is common in upland fields. Oxidation was progressed to the deep layer because of soil dryness. Soybean yield were increased by 11% to 22% in the mole drained plots, but wet injury was occurred in the nontreated check plot with relatively poor growth status.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.4
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• pp.133-137
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• 2014

As a preceding process for preparing several micrometer sized Ag-coated Cu flakes, ball milling of submicrometer-sized Cu particles synthesized through a wet chemical method was performed in order to convert the particles into flakes. To suppress oxidation and aggregation of the particles during ball milling, ethylene glycol and ethyl acetate were used as a medium and a surface modifying agent, respectively. Results obtained with different rotation speeds of a jar indicated that the rotation speed changes a rotating mode, and strikingly alters the final shapes and shape uniformity of Cu particles after milling. The diameter of zirconia ball was also confirmed. Although there was aggregates in the initial submicrometer-sized Cu particles, therefore, well-dispersed Cu flakes with a size of several micrometers were successfully prepared by ball milling through optimization of rotation speed, amount of ethyl acetate, and diameter of zirconia ball.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.350-353
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• 2002

High voltage SiC Schottky barrier diodes with field plate structure have been fabricated and characterized. N-type 4H-SiC wafer with an epilayer of ∼10$\^$15/㎤ doping level was used as a starting material. Various Schottky metals such as Ni, Pt, Ta, Ti were sputtered and thermally-evaporated on the low-doped epilayer. Ohmic contact was formed at the backside of the SiC wafer by annealing at 950$^{\circ}C$ for 90 sec in argon using rapid thermal annealer. Field oxide of 550${\AA}$ in thickness was formed by a wet oxidation process at l150$^{\circ}C$ for 3h and subsequently heat-treated at l150$^{\circ}C$ for 30 min in argon for improving oxide quality. The turn-on voltages of the Ni/4H-SiC Schottky diode was 1.6V which was much higher than those of Pt(1.0V), Ta(0.7V) and Ti(0.7). The voltage drop was measured at the current density of 100A/$\textrm{cm}^2$ showing 2.1V for Ni Schottky diode, 1.45V for Pt 1.35V, for Ta, and 1.25V for Ti, respectively. The maximum reverse breakdown voltage was measured 1100V in the file plated Schottky diodes with 101an thick epilayer.

• Journal of Korean Society on Water Environment
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• v.20 no.6
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• pp.563-570
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• 2004

Phased isolation intrachannel clarifier ditch process developed in this study is an enhanced biological nutrient removal process employing two ditches with intrachannel clarifiers. Bench-scale phased isolation ditch process was used to evaluate the system performance on municipal wastewater and detailed assessment of internal behavior in a ditch and each reactions. When the system was operated at the HRTs of 6~12hours, SRTs of 9~31 days, and cycle times of 4hours, the system showed removals of BOD, TN, and TP as high as 88~97%, 73~78%, and 65~90%, respectively. The internal behavior were well matched on each reactions such as nitrification, denitrification, and phosphorus release and uptake. As the SRT became longer, TN removal increased gradually, whereas TP removal decreased contrarily. However, the system was capable of producing an effluent TP concentration 1mg/L or less even at longer SRTs except the case of solids discharge by malfunction of intra-clarifier occurred by its geometrical limit. The system performance slightly decreased by hydraulic shock loading(increasing of influent flowrate and decreasing of system HRT). However, the higher system performance could be achieved again after four cycles. Thus, the system reliability could be successfully achieved short-term hydraulic shock loading that occurred in medium- and small-sized wastewater treatment plants suffering fluctuation of influent quality and flowrate during wet season.

• Textile Coloration and Finishing
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• v.21 no.1
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• pp.38-45
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• 2009

First of all, the properties imparted to PET fabrics are resistance to and recovery from creasing or wrinkling when wet or dry; high resistance to stretch in the filament yarns but not in the staple; high abrasion resistance; good texture and appearance; resistance to heat ageing; good chemical resistance and good resistance, behind glass, to sunlight. But, the low moisture regain of PET fabric conduces to static troubles in textile processing. Furthermore, garments made from PET may, during wear, develop electric charges which attract to the fabric particles of soil(dirt, swarf, dust) flying in the air, so that the cuffs of shirts, for example, become soiled quickly and are not easily laundered clean. The sericin constitutes 25$\sim$30％ of silk protein and surrounds the fibroin fiber with sticky layer that supports the formation of a cocoon. The useful biochemical properties of sericin protein are oxidation resistant, antibacterial, UV resistant, hydrophilic property, and good affinity with hydrophobic material. These properties can be used as an improving reagent or a coating agent for natural and synthetic fibers, fabrics, and other intermediate products. The sericin is also applied to cross-link, and can be blended with other materials. In this study, we modified the surface of PET fabric by mixture of sericin finishing agent; sericin, polyuretane binder and 1,2,3,4-butanetetracarboxylic acid (BTCA) cross-link agent. Also, we investigated the finshing effect; moisture regain, stiffness, handle, drape and electrostatic. The moisture regain of PET fabric treated with sericin finishing agent was higher than that of untreated PET fabric. As a result of evaluating influence about handle of PET fabrics treated with sericin finishing agent, it was confirmed that the sericin finishing agent could be use as a linen like finishing agent.

• Applied Chemistry for Engineering
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• v.28 no.1
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• pp.87-94
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• 2017

In this study, a catalyst based on $Pt/Al_2O_3$ supported on Mg was prepared by a wet impregnation method to investigate the $CH_4-SCR$ reaction characteristics of various alumina supports. Alumina supported on $Pt/Al_2O_3$ catalyst was converted to an $Al_2O_3$ composite, and when Mg was added, oxygen species of the active metal Pt were controlled due to electrophobic characteristics. Oxygen-controlled Pt used as a reducing agent inhibited the oxidation of $CH_4$ to $CO_2$. The addition of Mg also promoted the adsorption of NO species and the conversion of NO to $NO_2$ due to the NOx storage property on the catalyst surface.

• 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.

• Journal of Sensor Science and Technology
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• v.8 no.5
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• pp.421-426
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• 1999

In this paper, we present p-channel GaAs MOSFET having $Al_2O_3$ as gate insulator fabricated on a semi-insulating GaAs substrate, which can be operated in the depletion mode. $1\;{\mu}m$ thick undoped GaAs buffer layer, $4000\;{\AA}$ thick p-type GaAs epi-layer, undoped $500{\AA}$ thick AlAs layer, and $50\;{\AA}$ thick GaAs cap layer were subsequently grown by molecular beam epitaxy(MBE) on (100) oriented semi-insulating GaAs substrate and this wafer was oxidized. AlAs layer was fully oxidized as a $Al_2O_3$ thin film. The I-V, $g_m$, breakdown charateristics of the fabricated GaAs MOSFET showed that wet thermal oxidation of AlAs/GaAs epilayer/S I GaAs was successful in realizing depletion mode p-channel GaAs MOSFET.

• 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 Metals and Materials
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• v.56 no.12
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• pp.893-899
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• 2018

In the present study, we investigated the sulfur poisoning of the Ni anode in solid oxide fuel cells (SOFCs) as a function of operating conditions. Anode supported cells were fabricated, and sulfur poising tests were conducted as a function of current density, $H_2S$ concentration and humidity in the anode gas. The voltage drop was significant under the higher current density (${\sim}714mA/cm^2$) condition, while it was much reduced under the lower current density (${\sim}389mA/cm^2$) condition, at 100 ppm of $H_2S$. A secondary voltage drop, which occurred only at the high current density, was attributed to Ni oxidation in the anode. Thus, operation at high current density with high $H_2S$ concentration may lead to permanent deterioration in the anode. The effect of water content (10%) on the sulfur poisoning was also investigated through a constant current test (${\sim}500mA/cm^2$) at 10 ppm of $H_2S$. The cell operating with 10% wet anode gas showed a much smaller initial voltage drop, in comparison with a dry anode gas. The present study indicates that operating conditions, such as gas humidity and current density, should be carefully taken into account, especially when fuel cells are operated with $H_2S$ containing fuel.