• Electrical & Electronic Materials
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• v.8 no.1
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• pp.21-26
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• 1995

Highly sensitive and mechanically stable gas sensors have been fabricated using the microfabrication and micromaching techniques. The sensing material used to detect the offensive trimethylarnine ((CH$_{3}$)$_{3}$N) gas is 6 wt% $Al_{2}$O$_{3}$-doped, 1000.angs.-thick ZnO deposited by r. f. magnetron sputtering. The optimum operating temperature of the sensor is 350.deg.C and the corresponding heater power is about 85mW. Excellent thermal insulation is achieved by the use of a double-layer structure of 0.2.mu.m -thick silicon nitride and 1.4.mu.m-thick phosphosilicate glass(PSG) prepared by low pressure chemical vapor deposition(LPCVD) and atmospheric pressure chemical vapor deposition(APCVD), respectively. The sensors are mechanically stable enough to endure at least 43, 200 heat cycles between room temperature and 350.deg. C.

• International Journal of Safety
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• v.2 no.1
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• pp.12-16
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• 2003

In Part 1, the flame structure of the counterflow nonpremixed flames computed by using Fire Dynamics Simulator was compared with that of OPPDIF for different concentrations of methane in the fuel stream. In this study, comparisons were made for the global strain rate that is an important parameter for diffusion flames for further evaluation of FDS. At each of the three fuel concentrations, $20% CH_4＋ 80% N_2, 50% CH_4 ＋ 50% N_2, 90% CH_4 ＋ 10% N_2$ in the fuel stream, the temperature and axial velocity profiles were investigated for the global strain rate in the range from 20 to $100s^{-1}$. Changes in flame thickness and radius were also compared with OPPDIF. There was good agreement in the temperature and axial velocity profiles between the axisymmetric simulations and the one-dimensional computations except for the regions where the flame temperature reach its peak and the axial velocity rapidly changes. The simulations of the axisymmetric flames with FDS showed that the flame thickness decreases and the flame radius increases with increasing global strain rate.

• Journal of the Korean institute of surface engineering
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• v.51 no.1
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• pp.54-61
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• 2018

Plasma Nitriding treatment was performed on STS 204Cu stainless steel samples at a temperature of $400^{\circ}C$ for 15 hours with varying $N_2$ content as 10%, 15% and 25%. Regardless of the content of $N_2$, S-Phase which is a hardened layer of Nitrogen (N) supersaturated phase, was formed in the surface of plasma treated samples. When $N_2$ content was 25%, the thickness of the hardened layer reached up to about $7{\mu}m$ and the surface hardness reached a value of $560Hv_{0.05}$, which is about 2.5 times higher than that of untreated sample (as received $220Hv_{0.05}$). From potentiodynamic polarization test, it was observed that compared to as received sample, the corrosion potential and the corrosion current density of the plasma treated samples were decreased regardless of the $N_2$ content, but the corrosion resistance was not increased much due to the precipitation of $Cr_2N$. On the other hand, pitting potential of the samples treated with 10% and 15% $N_2$ was higher than that of as received sample, however, the samples treated with 25% exhibited a lower pitting potential. Therefore, 10% $N_2$ content was selected as optimum plasma nitriding condition and to further increase both the thickness and surface hardness and the corrosion resistance of the hardened layer, different $CH_4$ content such as 1%, 3% and 5% was introduced into the plasma nitriding atmosphere. With 1% $CH_4$, the thickness of the hardened layer reached up to about $11{\mu}m$ and the surface hardness was measured as about $620Hv_{0.05}$, which is about 2.8 times that of as received sample. And the corrosion resistance of the plasma treated sample by using 1% $CH_4$ was improved significantly due to much higher pitting potential, and lower corrosion current density. When the $CH_4$ content was more than 1%, the thickness and surface hardness of the hardened layer decreased slightly and the corrosion resistance also decreased.

• Journal of Animal Science and Technology
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• v.60 no.11
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• pp.27.1-27.8
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• 2018

Background: Enteric methane ($CH_4$) accounts for about 70% of total $CH_4$ emissions from the ruminant animals. Researchers are exploring ways to mitigate enteric $CH_4$ emissions from ruminants. Recently, nano zinc oxide (nZnO) has shown potential in reducing $CH_4$ and hydrogen sulfide ($H_2S$) production from the liquid manure under anaerobic storage conditions. Four different levels of nZnO and two types of feed were mixed with rumen fluid to investigate the efficacy of nZnO in mitigating gaseous production. Methods: All experiments with four replicates were conducted in batches in 250 mL glass bottles paired with the ANKOM$^{RF}$ wireless gas production monitoring system. Gas production was monitored continuously for 72 h at a constant temperature of $39{\pm}1^{\circ}C$ in a water bath. Headspace gas samples were collected using gas-tight syringes from the Tedlar bags connected to the glass bottles and analyzed for greenhouse gases ($CH_4$ and carbon dioxide-$CO_2$) and $H_2S$ concentrations. $CH_4$ and $CO_2$ gas concentrations were analyzed using an SRI-8610 Gas Chromatograph and $H_2S$ concentrations were measured using a Jerome 631X meter. At the same time, substrate (i.e. mixed rumen fluid+ NP treatment+ feed composite) samples were collected from the glass bottles at the beginning and at the end of an experiment for bacterial counts, and volatile fatty acids (VFAs) analysis. Results: Compared to the control treatment the $H_2S$ and GHGs concentration reduction after 72 h of the tested nZnO levels varied between 4.89 to 53.65%. Additionally, 0.47 to 22.21% microbial population reduction was observed from the applied nZnO treatments. Application of nZnO at a rate of $1000{\mu}g\;g^{-1}$ have exhibited the highest amount of concentration reductions for all three gases and microbial population. Conclusion: Results suggest that both 500 and $1000{\mu}g\;g^{-1}$ nZnO application levels have the potential to reduce GHG and $H_2S$ concentrations.

• Korean Journal of Materials Research
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• v.21 no.10
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• pp.546-549
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• 2011

Nano-sized $SnO_2$ thick films were prepared by a screen-printing method onto $Al_2O_3$ substrates. The sensing characteristics were investigated by measuring the electrical resistance of each sensor in a test box as a function of the detection gas. The nano-sized $SnO_2$ thick film sensors were treated in a $N_2$ atmosphere. The structural properties of the nano $SnO_2$with a rutile structure according to XRD showed a (110) dominant $SnO_2$ peak. The particle size of $SnO_2$:Ni nano powders at Ni 8 wt% was about 45 nm, and the $SnO_2$ particles were found to contain many pores according to the SEM analysis. The sensitivity of the nano $SnO_2$-based sensors was measured for 5 ppm $CH_4$ gas and $CH_3CH_2CH_3$ gas at room temperature by comparing the resistance in air with that in the target gases. The results showed that the best sensitivity of $SnO_2$:Ni and $SnO_2$:Co sensors for $CH_4$ gas and $CH_3CH_2CH_3$ gas at room temperature was observed in $SnO_2$:Ni sensors doped with 8 wt% Ni. The response time of the $SnO_2$:Ni gas sensors was 10 seconds and recovery time was 15 seconds for the $CH_4$ and $CH_3CH_2CH_3$ gases.

• Asian Journal of Atmospheric Environment
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• v.9 no.3
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• pp.187-193
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• 2015

Livestock is one of the major contributors of greenhouse gases (GHGs). It accounts for 14.5% of the global GHGs emissions like methane ($CH_4$) from enteric fermentation and manure, nitrous oxide ($N_2O$) from manure and fertilizer. Since enteric emissions are a major contributor of $CH_4$ than that of manure emissions hence primary efforts were made on reducing enteric emissions, with minor attention to dung emissions. Many researches were conducted by dietary manipulation to mitigate enteric $CH_4$ emission. However dietary manipulation also had significant effects on manure GHGs emissions too. Several works proved that manure $CH_4$ emissions were increased with high level of concentrate supplementation despite reduction in enteric $CH_4$. Fat and CP content of the diet has shown inconsistent results on manure $CH_4$ emissions. Amount of concentrate in the diet has shown little effect whereas dietary CP content exhibited conflicting effects on manure $N_2O$ emissions.

• Bulletin of the Korean Chemical Society
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• v.6 no.3
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• pp.141-144
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• 1985

N-Arylation reaction of nitrogen-containing heterocycles such as pyridine, nicotinamide and 4,4'-bipyridine was studied. We prepared N-2,4-dinitrophenyl derivatives initially by reacting the above heterocycles with 2,4-dinitrochlorobenzene in ethanol, and then treated the N-2,4-dinitrophenylated heterocycles with various aniline derivatives, $XC_6H_4NH_2$(X = -H, p-$CH_3$, p-$C_2H_5$, p-Cl, p-CN, p-OH, p-$OCH_3$, o-Cl, m-$CH_3$) to yield the corresponding N-arylated compounds in fairly good yields. $H^1$-nmr patterns and peak assignments of the N-arylated products were described.

• Bulletin of the Korean Chemical Society
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• v.29 no.10
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• pp.1905-1910
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• 2008

The reaction of 3,14-dimethyl-2,6,13,17-tetraazatetracyclo[16.4.0$0^{1.18}.0^{7.12}$]docosane ($L^1$) with formaldehyde in warm methanol yielded 3,14-dimethyl-2,6,13,17-tetraazatetracyclo[16.4.$1^{2.6}.0^{1.18}.0^{7.12}$]tricosane ($L^7$) containing one 1,3-diazacyclohexane subunit. In methanol, $L^7$ readily reacts with $Cu^{2+}$ ion to form [$CuL^7(H_2O)$]$^{2+}$ which is extremely inert against methanolysis. In the solution containing $Ni^{2+}$ ion, however, $L^7$ reacts with methanol to yield [$NiL^3$]$^{2+}$ ($L^3$ = 2-(methoxymethyl)-5,16-dimethyl-2,6,13,17-tetraazatricyclo[16.4.$0^{1.18}.0^{7.12}$]- docosane), in which one N-$CH_2OCH_3$ pendant arm is appended. The copper(II) complex [$CuL^7(H_2O)$]- $(ClO_4)_2{\cdot}3H_2O\;(I{\cdot}3H_2O)$ has a severely distorted trigonal bipyramidal coordination geometry with a 4-5- 6-5 chelate ring sequence. The crystal structure of [$NiL^3$]$(PF_6)_2{\cdot}2H_2O$ (IIb) shows that the N-$CH_2OCH_3$ pendant arm is not coordinated to the metal ion in the solid state. In various solvents (S), however, the nickel(II) complex exists as a mixture of [$NiL^3$(S)]$^{2+}$, in which the N-$CH_2OCH_3$ group as well as S is coordinated to the metal ion, and [$NiL^3$]^{2+}.

• Bulletin of the Korean Chemical Society
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• v.15 no.11
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• pp.990-996
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• 1994

New ferrocene-based chelate amines, $Fe[C_5H_4CH(Me)NMe_2]_2\;(3), \;Fe[C_5H-3(CH(Me)NMe_2)(PPh_2)-1,2]_2\;(4),\;(C_5H_5)Fe(C_5H_3(CH_2NMe_2)(CH(CN)NMe_2-1,2)\;(6),\;and\;(C_5H_5)Fe(C_5H_3(CH_2NMe_2)(CH(Me)NMe_2-1,2)$ (7) have been prepared. The reaction and the coordination chemistry of 4 and other related compounds (S,R)-(1-N,N-dimethylaminoethyl)-2-dicyclohexylphosphino)ferrocene (CPFA) and 1,1'-bis-(diphenylphosphino)ferrocene (BPPF) with $Rh_2(OAc)_4(MeOH)_2$ were investigated. The reaction of the chiral ligand (S,R)-CPFA forms a complex of the type (${\eta}^1$-(S,R)-CPFA-P)$_2Rh_2(OAc)_4$ (8) in which the ligand is coordinated to both rhodium centers in a monodentate fashion through phosphorus. In contrast, the bisphosphine analogues such as BPPF and 4 afford chelate complexes of the type (${\eta}^2-PP)Rh_2(OAc)_4$ (9 & 10) where both ligands act as a chelate bidentate to a single rhodium atom. All these complexes were characterized by microanalytical and spectroscopic techniques. In one case, the structure of 8 was determined by X-ray crystallography. Crystals are monoclinic, space group C2 (No. 5), with a=26.389 (3), b=12.942 (1), c=11.825 (1) A, ${\beta}$=111.22(1)$^{\circ}$, V=3964.7 (8) $A^3$, Z=4, and $D_{calc}$=1.58 g $cm^{-3}$. Two Rh(II) centers are bridged by four $AcO^-$ groups in the ${\eta}^1$ : ${\eta}^1$ mode across a Rh-Rh single bond, and octahedral coordination at Rh(1) and Rh(1') is completed by axially coordinating (S,R)-CPFA and a briding $AcO^-$, respectively.

• Journal of Astronomy and Space Sciences
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• v.28 no.1
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• pp.13-16
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• 2011

The $CH_3OH$ $4_2-5_1$ E transition was observed toward the Sgr B2 region, including the Principal Cloud and its surroundings. This methanol transition shows an extended emission along the 2'N cloud, which is believed to be colliding with the Principal Cloud and may trigger the massive star formation in this cloud. This extended methanol emission may also suggest that the 2'N cloud is under shocks. We derive total methanol column density $N(CH_3OH)\;=\;2.9{\pm}0.3{\times}10^{14}\;cm^{-2}$ toward the peak position of the extended emission. The fractional abundance of methanol is about 10.9, relative to the estimated total $H_2$ abundance, which is similar to the methanol abundances in quiet gas phase.