• Environmental Engineering Research
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• 제13권3호
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• pp.125-130
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• 2008

Free ammonia ($NH_3$-N) inhibition of nitrite-oxidizing bacteria (NOB) has been widely studied for partial nitrification (or nitrite accumulation) and denitrification via nitrite ($NO_2^-$-N) as a low-cost treatment of ammonium containing wastewater. The literature on $NH_3$-N inhibition of NOB, however, shows disagreement about the threshold $NH_3$-N concentration and its degree of inhibition. In order to clarify the confusion, a simple and cheap respirometric method was devised to investigate the effect of free ammonia inhibition of NOB. Sludge samples from an autotrophic nitrifying reactor were exposed to various $NH_3$-N concentrations to measure the maximum specific nitrite oxidation rate ($\hat{K}_{NO}$) using a respirometer. NOB biomass was estimated from the yield values in the literature. Free ammonia inhibition of nitrite oxidizing bacteria was reversible and the specific nitrite oxidation rate ($K_{NO}$) decreased from 0.141 to 0.116, 0.100, 0.097 and 0.081 mg $NO_2^-$-N/mg NOB h, respectively, as the $NH_3$-N concentration increased from 0.0 to 1.0, 4.1, 9.7 and 22.9 mg/L. A nonlinear regression based on the noncompetitive inhibition mode gave an estimate of the Inhibition concentration ($K_I$) of free ammonia to be 21.3 mg $NH_3$-N/L. Previous studies gave $\hat{K}_{NO}$ of Nitrobacter and Nitrospira as 0.120 and 0.032 mg/mg VSS h. The free ammonia concentration which inhibits Nitrobacter was $30{\sim}50\;mg$ $NH_3$-N/L and Nitrospira was inhibited at $0.04{\sim}0.08\;mg$ $NH_3$-N/L. The results support the fact that Nitrobacter is the dominant NOB in the reactor. The variations in the reported values of free ammonia inhibition may be due to the different species of nitrite oxidizers present in the reactors. The respirometric method provides rapid and reliable analysis of the behavior and community of the nitrite oxidizing bacteria.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.293.2-293.2
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• 2016

The In this paper, we have fabricated the solution processed In-Ga-ZnO thin film transistors (IGZO TFTs) by varying indium and gallium ratio. The indium ratio of IGZO TFTs was changed from 1 to 5 at fixed gallium and zinc oxide atomic percent of 1:1 and gallium ratio was varied from 1 to 5 at fixed indium and zinc oxide atomic percent of 1:1. When the indium ratio was increased at fixed gallium and zinc oxide ratio of 1:1, threshold voltage was negatively shifted from 1.03 to -6.18 V and also mobility was increased from 0.018 to $0.076cm2/V{\cdot}sec$. It means that the number of carriers in IGZO TFTs were increased due to great formation of the oxygen vacancies which generate electrons. In contrast, when the gallium ratio was increased in IGZO TFTs with indium and zinc oxide ration of 1:1, the on/off current ratio was increased from $1.88{\times}104$ to $2.22{\times}105$. It is because gallium have stronger chemical bonds with oxygen than that with the zinc and indium ions that lead to the decreased in electron concentration.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.471-474
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• 2004

We investigated field emission (FE) characteristics of multi-walled carbon nanotubes (CNTs) grown on all over patterned cathode electrode lines (CL pattern) and grown on along the central areas of the cathode lines(CL pattern). The CNTs grown on the SL pattern showed a lower threshold voltage and higher emission current than those on the CL pattern, due to the concentration of electric fields at the edges of the cathode lines. For the SL-patterned CNTs, however, the FE gradually spread out to the neighbors with time, and was instantly extinguished in some area and then slowly resumed again. Such areal- spread FE did not occur for the CL-patterned sample, leading to the stable FE together with the instant turn-on capability. It is suggested that the spread FE and instability for the SL-patterned CNTs may be related to the electrical charging on the insulator surface around the cathode line edges.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.195-196
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• 2009

This paper describes the fabrication and characteristics of polycrystalline 3C-SiC thin film diodes for extreme environment applications, in which the this thin film was deposited onto oxidized Si wafers by APCVD using HMDS In this work, the optimized growth temperature and HMDS flow rate were $1,100^{\circ}C$ and 8sccm, respectively. A Schottky diode with a Au, Al/poly 3C-SiC/$SiO_2$/Si(n-type) structure was fabricated and its threshold voltage ($V_d$), breakdown voltage, thickness of depletion layer, and doping concentration ($N_D$) values were measured as 0.84V, over 140V, 61nm, and $2.7{\times}10^{19}cm^2$, respectively. To produce good ohmic contact, Al/3C-SiC were annealed at 300, 400, and $500^{\circ}C$ for 30min under a vacuum of $5.0{\times}10^{-6}$Torr. The obtained p-n junction diode fabricated by poly 3C-SiC had similar characteristics to a single 3C-SiC p-n junction diode.

• 한국전기전자재료학회논문지
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• 제31권2호
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• pp.74-79
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• 2018

In this report, the results of a systematic study on the effects of polycrystalline silicon gate depletion on the reliability characteristics of metal-oxide semiconductor field-effect transistor (MOSFET) devices were discussed. The devices were fabricated using standard complimentary metal-oxide semiconductor (CMOS) processes, wherein phosphorus ion implantation with implant doses varying from $10^{13}$ to $5{\times}10^{15}cm^{-2}$ was performed to dope the polycrystalline silicon gate layer. For implant doses of $10^{14}/cm^2$ or less, the threshold voltage was increased with the formation of a depletion layer in the polycrystalline silicon gate layer. The gate-depletion effect was more pronounced for shorter channel lengths, like the narrow-width effect, which indicated that the gate-depletion effect could be used to solve the short-channel effect. In addition, the hot-carrier effects were significantly reduced for implant doses of $10^{14}/cm^2$ or less, which was attributed to the decreased gate current under the gate-depletion effects.

• 한국수산과학회지
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• 제45권2호
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• pp.114-121
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• 2012

A novel neuropeptide was isolated from the skin of the snakehead Channa argus using the dorsal retractor muscle (DRM) of a starfish Asterina pectinifera as a bioassay system. The amino acid sequence of the purified peptide was analyzed using automated sequencing and MALDI-TOF mass spectrophotometry. The primary structure of the purified peptide was determined to be Pro-Ala-Leu-Ala-Leu. To investigate the complete primary structure of this peptide, Pro- Ala-Leu-Ala-Leu-OH and Pro-Ala-Leu-Ala-Leu-NH2 were synthesized. The chemical and pharmacological properties of the synthetic peptides were compared with those of the native peptide. Both the native peptide and synthetic Pro-Ala- Leu-Ala-Leu-OH had identical behaviors on the reverse-phase and cation-exchange HPLC chromatograms. Synthetic Pro-Ala-Leu-Ala-Leu-OH showed contractile activity on the DRM, and the threshold concentration of this peptide was approximately $10^{-8}$ M. The maximal contractile effect ($E_{max}$) of this peptide was $294{\pm}45.4$% at $10^{-5}$ M.

• Macromolecular Research
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• 제15권4호
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• pp.343-347
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• 2007

Novel composite membranes, which delivered high separation performance for propylene/propane mixtures, were developed by coating inert poly(ethylene-co-propylene) rubber (EPR) onto a porous polyester substrate, followed by the physical distribution of $AgBF_4$. Scanning electron microscopy-wavelength dispersive spectrometer (SEM-WDS) revealed that silver salts were uniformly distributed in the EPR layer. The physical dispersion of the silver salts in the inert polymer matrix, without specific interaction, was characterized by FT-IR and FT-Raman spectroscopy. The high separation performance was presumed to stem from the in-situ dissolution of crystalline silver ionic aggregates into free silver ions, which acted as an active propylene carrier within a propylene environment, leading to facilitated propylene transport through the membranes. The membranes were functional at all silver loading levels, exhibiting an unusually low threshold carrier concentration (less than 0.06 of silver weight fraction). The separation properties of these membranes, i.e. the mixed gas selectivity of propylene/propane ${\sim}55$ and mixed gas permeance ${\sim}7$ GPU, were stable for several days.

• 한국토양비료학회지
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• 제49권6호
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• pp.768-775
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• 2016

Heavy metal pollution in arable field is an critical problem due to crop safety. For this reason, national survey of heavy metal pollution in the arable field near at the industrial area has been conducted from 1999 in Korea. The main purpose of this research was to monitor heavy metal pollution in Chungnam/chungbuk province and to evaluate pollution index (PI) in soil. Total of 15 sampling locations were examined and average concentration of each heavy metals were following: As - $2.99{\pm}2.63$, Cd - $0.23{\pm}0.07$, Cu - $9.35{\pm}6.48$, Ni - $9.26{\pm}8.03$, Pb - $10.18{\pm}3.32$, Zn - $52.9{\pm}17.18$. No sampling site was exceeded threshold level of each heavy metals. Calculated PI in soil was ranged between 0.03 - 0.27 indicating that also no heavy metal pollution is occurred in examined sampling locations. Although, no heavy metal pollution was observed in the examined sites but monitoring of heavy metal pollution should be continued for possible accidental pollution in arable field near at the industrial area.

• 한국정보통신학회논문지
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• 제10권9호
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• pp.1648-1653
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• 2006

이 연구에서는 해석학적 전류-전압 모델을 이용하여 DGMOSFET(Double Gate MOSFET)의 전송특성을 분석하였다. MOSFET의 게이트길이가 100nm이하로 작아지면 산화막두께가 1.5m이하로 작아져야만하고 채널의 도핑이 매우 증가하기 때문에 소자의 문턱전압변화, 누설전류의 증가 등 다양한 문제가 발생하게 된다 이러한 문제를 조사하기 위하여 해석학적 전류-전압 모델을 이용하여 소자의 크기를 변화시키면서 전류-전압특성을 조사하였다 소자의 크기를 변화시키면서 해석학적 전류-전압 모델의 타당성을 조사하였으며 온도 변화에 대한 특성도 비교 분석하였다. 게이트 전압이 2V에서 77K의 전류-전압 특성이 실온에서 보다 우수하다는 것을 알 수 있었다.

• Journal of information and communication convergence engineering
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• 제10권2호
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• pp.200-204
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• 2012

This study has presented the analysis of breakdown voltage for a double-gate metal-oxide semiconductor field-effect transistor (MOSFET) based on the doping distribution of the Gaussian function. The double-gate MOSFET is a next generation transistor that shrinks the short channel effects of the nano-scaled CMOSFET. The degradation of breakdown voltage is a highly important short channel effect with threshold voltage roll-off and an increase in subthreshold swings. The analytical potential distribution derived from Poisson's equation and the Fulop's avalanche breakdown condition have been used to calculate the breakdown voltage of a double-gate MOSFET for the shape of the Gaussian doping distribution. This analytical potential model is in good agreement with the numerical model. Using this model, the breakdown voltage has been analyzed for channel length and doping concentration with parameters such as projected range and standard projected deviation of Gaussian function. As a result, since the breakdown voltage is greatly changed for the shape of the Gaussian function, the channel doping distribution of a double-gate MOSFET has to be carefully designed.