• Journal of Power System Engineering
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• v.14 no.2
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• pp.71-77
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• 2010

This paper was studied on microstructure, mechanical properties and corrosion characteristics of 316L stainless steel pipe welds was fabricated by orbital welding process. S-Ar specimen was fabricated by using Ar purge gas and S-$N_2$ specimen was fabricated by using $N_2$ purge gas. Ferrite was not detected in weld metal of S-$N_2$ specimen but the order of 0.13 Ferrite number(FN) was detected in weld metal of S-Ar specimen. Oxygen and Nitrogen concentration of S-$N_2$ specimen was higher than S-Ar specimen on HAZ and inner bead. The welds microstructural characteristics of S-Ar and S-$N_2$ specimens are similar. The microvickers hardness values of S-Ar and S-$N_2$ specimens welds were similar and average values of each regions were in the range of 174~194. The microstructures of S-Ar and S-$N_2$ weld metal were full austenite by primary austenite solidification. The Solidification structures of S-Ar and S-$N_2$ weld metal were formed directional dendrite toward bead center. The potentiodynamic polarization curve of STS 316L pipe welds exhibited typical active, passive, transpassive behaviour. Corrosion current density$(I_{corr.})$ and corrosion rate values of S-Ar specimen in 0.1M HCl solution were $0.95{\mu}A/cm^2$ and $0.31{\mu}A$/year respectively. The values of S-$N_2$ specimen were $1.4{\mu}A/cm^2$ and $0.45{\mu}m$/year.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.87-88
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• 2008

In the structure of ITO/N,N'-diphenyl-N,N' bis (3-methylphenyl)-1,1'-biphenyl-4,4'-diamine(TPD)/tris (8-hydroxyquinoline)aluminum$(Alq_3)$/Al device, we studied the efficiency improvement of organic light-emitting diodes due to variation of deposition rate of TPD materials. The thickness of TPD and $Alq_3$ was manufactured 40 nm, 60 nm, respectively under a base pressure of $5\times10^{-6}$Torr using a thermal evaporation. The $Alq_3$ used for an electron-transport and emissive layer were evaporated to be at a deposition rate of 2.5 $\AA$/s. When the deposition rate of TPD increased from 1.5 to 3.0 $\AA$/s, we found that the average roughness is rather smoother, external quantum efficiency is superior to the others when the deposition rate of TPD is 2.5 $\AA$/s. Compared to the ones from the devices made with the deposition rate of TPD 3.0 $\AA$/s, the external quantum efficiency was improved by a factor of eight.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.5
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• pp.480-486
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• 2006

On account of exchanging main process from chemical precipitation for MLE(Modified Ludzark-Ettinger), an external carbon source was required for supplementation of carbon source shortage that was needed biological denitrification in the S sewage treatment plant(S-STP). In this study, NUR(nitrate uptake rate), OUR(oxygen uptake rate) test and a field application test was conducted for the applicability assessment of Terephtalic acid(TPA) by-product contained about 4.7% acetate as alternative external carbon source. As the results, TPA by-product shows more rapid acclimation than methanol, 8.24 mg ${NO_3}^--N/g$ VSS/hr specific denitrification rate, 3.70 g $COD_{Cr}/g\;NO_3$ C/N ratio and 99.4% readily biodegradable COD contents. In the results of field application, the nutrient removal efficiency was high and effluent T-N concentration is 8.2 mg/L. It is concluded that TPA by-product is the proper alternative external carbon source.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.3
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• pp.235-238
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• 2009

This paper describes the mechanical properties of poly (Polycrystalline) 3C-SiC thin films with $N_2$ in-situ doping. In this work, the poly 3C-SiC film was deposited by APCVD (Atmospheric Pressure Chemical Vapor Deposition) method using single-precursor HMDS (Hexamethyildisilane: $Si_2(CH_3)_6)$ at $1200^{\circ}C$. The mechanical properties of doped poly 3C-SiC thin films were measured by nono-indentation according to the various $N_2$ flow rate. In the case of 0 sccm $N_2$ flow rate, Young's Modulus and hardness were obtained as 285 GPa and 35 GPa, respectively. Young's Modulus and hardness were decreased according to increase of $N_2$ flow rate. The crystallinity and surface roughness was also measured by XRD (X-Ray Diffraction) and AFM (Atomic Force Microscopy), respectively.

• Journal of Korean Society for Atmospheric Environment
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• v.17 no.E3
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• pp.109-115
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• 2001

Acidic air pollutants were collected to characterize indoor air quality at a private house in Seoul during the spring period. All indoor and outdoor samples were measured simultaneously using an annular denuder system. The data set was collected on twelve different days with a 24-hr sampling period in April and May 1997. The chemical species measured were HN $O_3$, HN $O_2$, S $O_2$ and N $H_3$in the gas phase and P $M_{2.5}$ (dp 2.5 ${\mu}{\textrm}{m}$), S $O_4$$^{2-}$, N $O_3$$^{[-10]}$ and N $H_4$$^{+}$ in the particulate phase. Indoor concentrations of HN $O_2$, N $H_3$, and P $M_{2.5}$ were greater than outdoor levels. However, indoor concentrations of HN $O_3$, S $O_2$, N $O_3$$^{[-10]}$ and N $H_4$$^{+}$ were less than those found from outdoors. In the case of S $O_4$$^{2-}$, the indoor and outdoor concentrations were similar. Indoor concentrations of P $M_{2.5}$ , S $O_4$$^{2-}$ and N $O_3$$^{[-10]}$ were dependent upon the outdoor concentrations. A tracer-gas decay technique with sulfur hexafluoride (S $F_{6}$ ) as the tracer gas was used to estimate the air exchange rate of a private home in the spring. The average air exchange rate was computed to be 2.87 h $r^{-1}$ .X> .

• Journal of Environmental Health Sciences
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• v.27 no.1
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• pp.93-99
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• 2001

This study aims at finding out pertinent reaction conditions for treating high concentration ammonia contained in N-chemical factory wastewater with decompressed ammonia stripping method that was designed. And it also tries to investigate adsorption capability of removed ammonia to soil. The results from experiments are as follows ; 1. The removal rate of N $H_3$-N of synthetic wastewater was under 85% at pH 10 with decompressed ammonia stripping method. The reaction time in pressure 360 mmHg at pH 11 and 12 was shorter than in 460 mmHg, and the removal rate of N $H_3$-N with decompressed ammonia stripping method at 9$0^{\circ}C$ was 11~15% higher than air stripping 2. The optimum conditions for decompressed ammonia stripping with synthetic sample were shown as pH 12, temperature 9$0^{\circ}C$, internal reaction pressure 460 mmHg and reaction time 50 minutes. These conditions were applied to treat the wastewater containing organic-N 290.5mg/$\ell$, N $H_3$-N 168.9mg/$\ell$, N $O_2$-N 23.2mg/$\ell$, N $O_3$-N 252.4mg/$\ell$, T-N 735mg/$\ell$. Organic-N turned out to be removed 60%, the removal rate of N $H_3$-N IS 94%, T-N is 50%. But N $O_2$-N and N $O_3$-N were increased with 7.8% and 14.9% respectively. 3. The CO $D_{Sr}$ removal rate in decompressed ammonia stripping reaction was 42% and S $O_4$$^{2-}$ was removed 8.2%. It was turned out caused with higher pH and thermolysis. 4. In soil adsorption of ammonia desorbed from the decompressed stripping process of wastewater, the recovery rate was 76% in wet soil.

• Toxicological Research
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• v.14 no.2
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• pp.177-181
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• 1998

Dithiocarbamate and mixed disulfide containing allyl functions were designed and synthesized as putative chemopreventive agents, i.e. N,N-diallyldithiocarbamate (DATC) and S-(N,N-diallyldithiocarbamoyl)-N-acetylcysteine (AC-DATC). DATC and AC-DATC were administered and the activities of cytosolic glutathione S-transferase (GST), glutathione reductase (GR) and microsomal N-nitrosodiethylamine (NDEA) deethylase were assayed in order to test the effects of these organosulfur com-pounds on the detoxification and metabolic activation system of NDEA. The amounts of hepatic glutathione (GSH and GSSG) was also determined. The administration of DATC to rats led to an increase in the activity of GR and to an inhibition of CYP2E1-mediated NDEA deethylation. AC-DATC induced the activity of GR and GST, increased the hepatic GSH content and inhibited the rate of NDEA deethylation. The level of GSSG was decreased as a consequence of the increased activity of GR. These effects may contribute to possible antimutagenic and anticarcinogenic action of the dithiocarbamates investigated.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1997.10a
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• pp.149-154
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• 1997

광소자 및 새로운 개념의 전력소자 응용을 위하여 Wide Bandgap 반도체에 대한 관심이 급증되고 있다. 특히 직접천이형인 GaN는 청색 발광소자 응용 및 고출력, 고주파용 전력소자 응용에 이상적인 전자물성을 갖고 있다. 따라서 본 연구에서는 GaCl$_3$와 NH$_3$를 source gas로 하는 CVPE법을 사용하여 (0001) sapphire와 비교하였다. 기판의 증착온도 104$0^{\circ}C$에서 source gas의 III/V flow rate를 2로 분석하여 45분간 성장시킨 경우 그 증착속도는 약 40 $\mu\textrm{m}$/hr 정도였으며, 이 때 XRD을 향상시키기 위하여 증착이전에 기판의 표면에 증착온도에서 NH$_3$를 이용한 nitridation 처리를 하였으며, 그 처리시간이 3분일 때 XRD의 FWHM 특성이 가하여 조사한 결과 363 nm에서 peak가 검출되었다. 본 연구에서는 양질의 GaN 박막성장을 위한 증착조건 인자중 source gas의 flow rate가 가장 중요한 변수임을 적정 온도 범위가 75$0^{\circ}C$ 근처로 조사되었다. 실험과 모사결과의 박막 증착 최적온도의 차이는 GaN 증착시의 반응 Kinetics가 느리기 때문인 것으로 해석된다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.04a
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• pp.54-55
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• 2006

Organic light-emitting diodes(OLEOs) are attractive because of possible application in display with low operating voltage, low power consumption, self-emission and capability of multicolor emission by the selection of emissive material. We investigated the effects of deposition rate on the electrical characteristics, physical characteristics and optical characteristics of OLEOs in the ITO(indium-tin-oxide)/N.N'-diphenyl-N,N'-bis(3-methyphenyl)-1,1'-biphenyl-4,4'-diamine(TPD)/tris(8-hydroxyquinoline)aluminum($Alq_3$)/Al device. We measured current density, luminous flux and luminance characteristics of devices with varying deposition rates of TPD and $Alq_3$. It has been found that optimal deposition rate of TPD and $Alq_3$ were respectively $1.5{\AA}/s$ from the device structure. An AFM measurement results, surface roughness of the deposited film was the lowest when deposition rate was $1.5{\AA}/s$.

• Proceedings of the Korean Statistical Society Conference
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• 2002.05a
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• pp.61-66
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• 2002

We consider a generalized N-policy for an M/M/1 queueing system. The idle server starts to work with ordinary service rate when a customer arrives. If the number of customers in the system reaches N, the service rate gets faster and continues until the system becomes empty. Otherwise, the server finishes the busy period with ordinary service rate. We obtain the limiting distribution of the number of customers in the system. After assigning various operating costs to the system, we show that there exists a unique fast service rate minimizing the long-run average cost per unit time.