• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
• /
• v.19 no.3
• /
• pp.119-123
• /
• 2013

Simplified control logic was devised to fabricate and operate the modified atmosphere (MA) container of fresh produce equipped with gas-diffusion tube whose opening/closing was controlled in response to real time $O_2$ concentration. This is a simplified ramification of the previously developed control logic using both $O_2$ and $CO_2$ concentrations ([$O_2$] & [$CO_2$]). The developed logic was applied to and tested by a container system filled with spinach at $10^{\circ}C$ having optimum MA window of [$O_2$] of 7~10% and [$CO_2$] of 5~10%. It was shown that setting the proper on-off limit (11%) for $O_2$ control based on the assumed relationship $[O_2]+[CO_2]$=21% could attain the desired $CO_2$ concentration just below the upper tolerance limit ($[CO_2]_H$, 10%). The $O_2$ control point can be the lower tolerance limit or adjusted one (21-$[CO_2]_H$) depending on the commodity's MA requirement. The developed logic using single $O_2$ sensor could attain the equilibrated [$O_2$] of 11% with [$CO_2$] of 8~9% which was desired and similar to that of its predecessor ([$O_2$] of 9~10% with [$CO_2$] of 10%) using both $O_2$ and $CO_2$ sensors. Both MA containers (one only with single $O_2$ sensor control and one with $O_2$ and $CO_2$ sensors) could also keep the spinach quality without significant difference between them, but significantly better than perforated control package of air.

• Korean Journal of Materials Research
• /
• v.4 no.6
• /
• pp.669-680
• /
• 1994

Oxidation behaviour of TiAl intermetallic compounds with the addition of Cr, V, Si, Mo, or Nb was investigated at 900~$1100^{\circ}C$ under the atmospheric environment. The reaction products were examined by XRD, SEM equipped with WDX. The weight gain by continuous oxidation increased with the addition of Cr or V, but there was less weight gain when Mo, Si or Nb was added individually. he oxidation rate of Cr- or V-added TiAl was always larger than that of TiAI. However, oxidation rate of Si-, Mo- or Nb-added TiAl was almost same or smaller than that of TiAI. Thus, it is concluded that the addition of Cr or V did not improve the oxidation resistance, whereas the addition of Si, Mo or Nb improved the oxidation resistance. Oxides formed on TiAl with Mo, Si, and Nb were found to be more protective, resulting from the decrease in diffusion rate of the alloying elements and oxygen. Nb strengthened the tendency to form $AI_{2}O_{3}$ in the early stage of oxidation, due to the continuous $AI_{2}O_{3}$ layer formation and dense $Tio_{2}+AI_{2}O_{3}$ layer. According to the Pt-marker test of TiAI- 5wt%Nb, oxygen diffused mainly inward while oxides were formed on the substrate surface. Upon thermal cyclic oxidation at $900^{\circ}C$, it is shown that the addition of Cr or Nb improved the adherence of oxide scale to the substrate.

• KSBB Journal
• /
• v.16 no.6
• /
• pp.573-578
• /
• 2001

The effects of organic supplement (acetate) and dissolved oxygen concentration on the nitrification rate of wastewater were investigated in the 27.7 L pilot-scale airlift biofilm reactor with the granular activated carbon media of 0.613 mm diameter. The ammonium oxidation rate increased stepwise up to 5 kg N/㎥$.$d at the riser air velocity of 0.063 m/s, when the air velocity and the ammonium loading rate were raised alternately. The nitrite build-up was observed during the early stage of the biofilm formation, which disappeared after the reactor operation of 128 days. As increasing the organic loading rate, the organic oxidation rate increased up to 25.0 kg COD/㎥$.$d with the removal efficiency of 94% but the oxidation rates of ammonium and nitrite decreased. The oxidation rates of ammonium and nitrite increased with the dissolved oxygen concentrations. When the pure oxygen was sparged, the ammonium oxidation rate was almost five times higher than that with air at the same velocity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07a
• /
• pp.565-568
• /
• 2003

2세대 초전도 선재로 알려져 있는 $YBa_2Cu_3O_{7-\delta}$ coated conductor는 금속모재/완충층/초전도층/보호층의 구조를 가진다. 2개 이상의 산화물 다층 박막으로 이루어진 완충층은 금속기판의 집합조직을 초전도층까지 전달하는 역할, 금속기판의 금속이 초전도층으로 확산되어 초전도층의 전기적 특성을 열화시키는 것을 막아주는 확산장벽으로의 역할 등을 수행한다. 1차 완충층은 금속기판의 집합조직을 유지하여야하며, 금속기판의 산화를 방지하면서 증착 되어야 한다. coated conductor 제조를 위한 첫 단계로 Pulsed Laser Deposition법을 이용하여 cube texture된 Ni 기판 위에 $Y_2O_3$ 박막을 증착 하였다. 최적의 증착 조건을 찾기 위해 증착 챔버의 산소 및 $H_2/Ar$ 혼합가스 분압과 기판온도를 변화시키면서 증착 하였다. $Y_2O_3$층의 (100) 집합조직은 기판온도 $600{\sim}700^{\circ}C$와 산소 분압 $0.01{\sim}0.1mTorr$에서 증착된 Y2O3 박막에서 금속기판과 유사한 집합조직을 얻을 수 있었다. 최적의 증착 조건에서 $Y_2O_3$ (222) ${\Phi}-scan$의 full width at half maximum (fwhm)이 $11^{\circ}$이고 (400) ${\omega}-scan$ fwhm은 $6^{\circ}$이었다.

• Analytical Science and Technology
• /
• v.22 no.6
• /
• pp.464-470
• /
• 2009

For the investigation of the oxidation behavior for titanium metal at various temperatures, titanium specimens were heated for 2 hours in the range of $300{\sim}1000^{\circ}C$, individually. And then X-ray diffraction(XRD), scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS) and attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopic analyses were carried out. At $300^{\circ}C$, infrared absorption bands on the surface of the titanium specimen were shown in a spectrum by the oxygen uptake of titanium metal(hexagonal). At increased temperature, not only infrared absorption bands but also X-ray diffraction peaks for the titanium oxide were grown and shifted to low wave number ($cm^{-1}$) and angle($^{\circ}$) due to the more oxygen diffusion into titanium metal. At $700^{\circ}C$, $Ti_3O$ (hexagonal phase) was identified by X-ray diffractometer. $TiO_2$ (rutile, tetragonal phase) layer was produced on the surface of the specimen below $1{\mu}m$ in thickness at $600^{\circ}C$, and grown about $2{\mu}m$ at $700^{\circ}C$ and with $110{\mu}m$ in thickness at $1000^{\circ}C$. Above $900^{\circ}C$, (110) plane of the crystal on the surface of rutile-$TiO_2$ layer was grown.

• Applied Chemistry for Engineering
• /
• v.9 no.6
• /
• pp.798-802
• /
• 1998

Carbon granules were prepared by granulating a mixture of coconut shell powder and coal tar solution, and then by carbonizing at different temperatures. To control micropores of the carbonized granules, the deposition time of benzene vapor under nitrogen atmosphere was varied. For each prepared sample, SEM morphology and true density were investigated. The adsorption rates on the granules were measured with respect to oxygen and nitrogen by means of the Cahn D-200 system. Diffusivity, selectivity and amount of equilibrium adsorption for the gases were obtained from the measurement of adsorption rate. Based on the analysis of the adsorption characteristics, the optimum temperature and the deposition time for preparation of the molecular sieve carbon granules were found to be $800^{\circ}C$ and 10 minutes, respectively. At these optimal conditions, the selectivity coefficient, 26.4, 0f oxygen and nitrogen was obtained.

• Journal of the Korean Ceramic Society
• /
• v.41 no.12 s.271
• /
• pp.900-906
• /
• 2004

Solid oxide fuel cells have a limitation in their low-temperature application due to the low ionic conductivity of electrolyte materials and difficulties in thin film formation on porous gas diffusion layer. These problems can be solved by improvement of ionic conductivity through controlled nanostructure of electrolyte and adopting nanoporous electrodes as substrates which have homogeneous submicron pore size and highly flattened surface. In this study, ultra-thin oxide films having submicron thickness without gas leakage are deposited on nanoporous substrates. By oxidation of metal thin films deposited onto nanoporous anodic alumina substrates with pore size of $20nm{\sim}200nm$ using dc-magnetron sputtering at room temperature, ultra-thin and dense ionic conducting oxide films with submicron thickness are realized. The specific material properties of the thin films including gas permeation, grain/gran boundaries formation, change of crystalline structure/microstructure by phase transition are investigated for optimization of ultra thin film deposition process.

• Journal of the Korean Vacuum Society
• /
• v.13 no.2
• /
• pp.65-71
• /
• 2004

ESR spectrum change has been investigated for the PECVD deposited a-C : H films exposed in the atmosphere. Though depending on the deposition conditions, it was observed that generally ESR signal height decreased and linewidth increased as the exposure time increased. The spin density decreased down to 40-80% depending on samples. The decrease of spin density of the a-C : H films in the air was attributed to permeation of moisture into the films and subsequent migration and redistribution of hydrogens. And the ESR signal height increased again and the linewidth decreased when the a-C : H samples were placed again in the vacuum, which was attributed to oxygens extracted from the samples. Consequently, the ESR spectrum change for the a-C : H films exposed in the air was regarded to be associated with the decrease of spin density as well as the permeation of oxygens into films.

• Polymer(Korea)
• /
• v.24 no.2
• /
• pp.237-244
• /
• 2000

Phenolic resin used as a precursor of carbonized matrix for carbon-carbon composites was modified by addition of molybdenum disilicide (MoSi$_2$) in various concentrations of 0, 4, 12 and 20% by weight to improve the anti-oxidation properties of the composites. The green body was manufactured by a prepreg method and was submitted to carbonization up to 110$0^{\circ}C$. In this work, the oxidation behavior of carbon-carbon composites with MoSi$_2$ as an oxidation inhibitor was investigated at the temperature range of 600-100$0^{\circ}C$ in an air environment. The carbon-carbon composites with MoSi$_2$ showed a significantly improved oxidation resistance due to both the reduction of the porosity formation and the formation of mobile diffusion barrier for oxygen when compared to those without MoSi$_2$. Carbon active sites should be blocked, decreasing the oxidation rate of carbon. This is probably due to the effect of the inherent MoSi$_2$ properties, resulted from a formation of the protective layer against oxygen attack in the composites studied.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.26 no.5
• /
• pp.742-749
• /
• 2002

Numerical Study with detailed chemistry has been conducted to investigate the flame structure and NOx formation characteristics in oxygen -enhanced(CH$_4$/O$_2$-$N_2$) and oxygen-enhanced-EGR(CH$_4$/O$_2$-$CO_2$) counter diffusion flame with various strain rates. A small amount of $N_2$is included in oxygen-enhanced-EGR combustion, in order to consider the inevitable $N_2$contamination by $O_2$production process or air infiltration. The results are as follows : In CH$_4$/O$_2$-$CO_2$flame it is very important to adopt a radiation effect precisely because the effect of radiation changes flame structure significantly. In CH$_4$/O$_2$-$N_2$flame special strategy to minimize NO emission is needed because it is very sensitive to a small amount of $N_2$. Special attention is needed on CO emission by flame quenching, because of increased CO concentration. Spatial NO production rate of oxygen-enhanced combustion is different from that of air and oxygen-enhanced-EGR combustion in that thermal mechanism plays a role of destruction as well as production. In case CH$_4$/O$_2$-$CO_2$flame contains more than 40% $CO_2$it is possible to maintain the same EINO as that of CH$_4$/Air flame with accomplishing higher temperature than that of CH$_4$/Air flame. EINO decreases with increasing strain rate, and those effects are augmented in CH$_4$/O$_2$flame.