• Korean Journal of Materials Research
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• v.29 no.11
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• pp.677-683
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• 2019

In this paper, nitrogen-doped reduced graphene oxide(rGO) is obtained by thermal annealing of nitrogen-containing compounds and graphene oxide (GO) manufactured by modified Hummers' method. We use melamine as a nitrogen-containing compound and treat GO thermally with melamine at over $800{\sim}1,000^{\circ}C$ and 1 ~ 3 hr under Ar atmosphere. The electrical conductivity of doped rGO is measured by 4-point probe method. As a result, nitrogen contents on rGO are found to be in the range of 2.5 to 12.5 at% depending on the doping conditions after thermal annealing. The main doping site on graphene oxide is changed from pyridinic-N and pyrrolinic N to the graphitic site as the heat treatment temperature increases. The electrical conductivity of doped rGO increases as the N doping content increases. As the thermal treatment time increases, the change of both total doping contents and doping sites is slight and the surface resistance is remarkably reduced, which is caused by healing effects of doped graphene oxide at high temperature.

• Bulletin of the Korean Chemical Society
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• v.27 no.7
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• pp.1048-1052
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• 2006

Ab initio calculations of the structure, atomic charges and natural bond orbital (NBO) have been performed at HF/6-311G** and B3LYP/6-311G** levels for the title compound of dibenzothiazyl-disulfide. The calculated results show that the two nitrogen atoms have the biggest negative charges and they are the potential sites to react with the metallic ions, which make the title compound become a di-dentate ligand. Vibrational frequencies of the title compound have been obtained and compared with the experimental value and the comparison indicates that B3LYP/6-311G** level is better than HF/6-311G** level to predict the vibrational frequencies for the system studied here. For the title compound, electronic absorption spectra calculated by time?ependent density functional theory (TD-DFT) are more accurate than Hartree-Focksingle-excitation CI (CI-Singles) method. NBO analyses show that the electronic transitions are mainly derived from the contribution of bands $\pi\rightarrow\pi^{*}$. Thermodynamic calculated results show that the formation of the title compound from 2-mercaptobenzothiazole is a spontaneous process at room temperature with the change of free Gibbs being negative value.

• Tribology and Lubricants
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• v.16 no.5
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• pp.332-340
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• 2000

The reduction of sulfur content in the diesel fuel has caused the poor lubricity of diesel fuel in the distributor type injection pumps of diesel engines that use the diesel for lubrication of their moving parts. To investigate the reason for poor lubricity of low sulfur diesel fuels, the wear scar diameters by HFRR (High Frequency Reciprocating Rig) were measured on the diesel fuels from Korean markets and the results were compared with their physical and chemical properties. Also, the lubricity change and the improvement effects on lubricity additives for the ultra low sulfur diesel fuel, were made experimentally, that will be regulated to a maximum of 0.005 wt% from about 2005 were evaluated. As a result, a good correlation was found between the wear scar diameter and the polyaromatic compound which includes heterocyclic compound in the diesel fuel. It was also found that the content of polyaromatic compound including heterocyclic compound was affected by the amount of desulfurization treatment fraction. And the lubricity additives with ester base were more effective than that with acid base on the ultra low sulfur diesel fuel. Therefore, it is suggested that the factors affecting the lubricity stated above should be taken into account to improve the lubricity property of the diesel fuel in the refining process.

• Journal of the Korean Society of Safety
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• v.11 no.4
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• pp.84-89
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• 1996

The Oxidation of aflatoxin $G_1$ ($AFG_1$) with ozone in chloroform solvent gave the stable ozonide into ozonization of the double bond in the terminal furan ring, and this reaction have been carried out for 3hr at -78. 5$^{\circ}C$. The chloroform solvent was removed in a stream of nitrogen and the residue was separated by elution chromatography(EC). The structure of this compound have been identified by using MS, $^1H-NMR$, $^l3C-NMR$ and I. R spectroscopy, respectively. This compound was formed the normal stable AFG$_1$-ozonide into spontaneous rearrangement after unstable ozonide according to sigmatropic rearrange ment dependent upon cyclo addition by ozone.

• Bulletin of the Korean Chemical Society
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• v.18 no.5
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• pp.484-488
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• 1997

The angular and planar heterocyclic compounds containing nitrogen, sulfur and oxygen were synthesized by reaction of 6,7-dichloro-5,8-quinoxalinedione with aromatic and aliphatic dinucleophiles. Nucleophilic reactivity was somewhat different between 2,3-dichloro-1,4-naphthoquinone and 6,7-dichloro-5,8-quinolinedione with dinucleophiles. The distribution of electron in heterocycle appeared to contribute to this difference. The intercalation comple of planar heterocyclic compound between GC/GC base pairs showed the optimum intercalation but the intercalation of angular heterocyclic compound was not good. Thus, the planar compound was expected to have antitumor activity.

• Environmental engineer
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• s.41
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• pp.28-32
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• 1990

본 실험은 S유가공 공장에서 생성되는 폐수의 각종 오염물질 계절별 처리효율 원유처리량에 따른 폐수량 오염물질간의 상관관계 등을 조사하기 위하여 1998.2월부터 1989.1월까지 1년간 매월 2회씩 총 24회에 걸쳐서 조사분석하였으며 그 결과를 요약하면 다음과 같다. 1. 원 폐수의 총 오염물질량(BOD, COD, SS n-Hexan, nitrogen compound $PO_4P$)은 평균 1870.9 ug/일이며 최종처리후 117.

• Journal of the Korean Society of Tobacco Science
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• v.4 no.1
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• pp.29-35
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• 1982

Potassium deficiency symptoms were studied with flue-cured tobacco which was applied with different levels of compound fertilizer (10-15-20) ; 75kg, 100hg, and 125kg/10a. Ratio of N/$K_2O$ in leaves was increased from bottom to top stalk position due to the increase of nitrogen content in leaves. Nitrogen content in leaves was increased from stalk to tip as wall as from midrib to laminae, but vice versa in potassium content. Consequently, resulting in potassium deficiency symptoms in tip of leaves. Rate of reabsorption by rainfall during the latter part of growth was highest at top stalk position in case of nitrogen, but lowest in potassium. This observation was more evident with higher application rate of fertilizer. Nitrogen content of about 4 % in leaves of top stalk position applied with 125kg/10a was maintained up to 85days after trans planting. No increase in potassium in upper leaves was observed over the level of 100kg/10a fertilizer application. As the result, N/$K_2O$ ratio in leaves of top stalk position applied with 125kg/10a was kept at more than 1.0 up to 85days after transplanting, but it was less than 0.9 at 65days after tracts planting with less than 100kg/10a fertilizer application.

• Korean Journal of Soil Science and Fertilizer
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• v.48 no.5
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• pp.421-427
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• 2015

Angelica gigas Nakai is one of the most widely used herbal medicines and is known to have many pharmaceutical effects including an anti-oxidant, anti-cancer etc. This study was carried out to investigate an effect of fertilization on leaf yield, production of dry-matter and accumulation of pyranocurmarine compounds such as decursin (DE) and decursinol angelate (DA) in Angelica gigas Nakai. Effect of fertilization was determined from response surface regression equation composing of 2 by 3 factorial arrangement of urea, sodium dihydrogen phosphate and potassium chloride. Yield of leaf in Angelica gigas Nakai significantly increased until 100 days after transplanting. Production of leaf also tended to increase with increasing nitrogen fertilization. Model of regression equation showed that leaf production depended upon nitrogen ($Pr>{\mid}t{\mid}$ : 0.087, 0.256 and 0.079). Also, statistical results between nitrogen application level and production of dry-matter showed significant relationship (p<0.05) and contents of dry-matter was highest in 10 kg 10a-1 treatment on 24 Sep. Active compound isolated and purified from leaf and root of Angelica gigas Nakai was identified as DE and DA by gas chromatograph-mass spectrophotometry (GC-MS). Concentration of DA as prevalent compound in leaf was highest on 20 Aug. but decreased on 24 Sep. Amount of DE and DA accumulated in Angelica gigas Nakai significantly increased with growth stages and nitrogen level. The result of our investigation imply that nitrogen fertilization is important factor for production of leaf and accumulation of pyranocurmarine in Angelica gigas Nakai as a medicinal/food materials.

• Journal of environmental and Sanitary engineering
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• v.10 no.1
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• pp.66-75
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• 1995

This survey is executed about the water quality and improvement measure of Imjin- river. The results are summarized as follows; 1 ) Ammonia nitrogen concentration in tap water was two times higher than drinking water standard. 2) The concentration of BOD in textile wastewater was 235ppm which is higher than wastewater distribution standard and leather wastewater showed high nitrogen concentration. 3) Water quality of the Imjin- river upstream was not in problem but that of Shin- stream showed somewhat high concentration in BOD, COD, and ammonia nitrogen. Especially the detected Cynide compound on the lower of Shin- stream implied seriously polluted condition. 4) The heavy metal in soil of the river bed was not detected but iron, zinc was detected to high concentration. 5) It Is urgently suggested to build more municipal sewage and sanitary treatment plants, and run dredging and river bed rearrangement project. 6) The Construction of the wastewater treatment complexes of relevant industries shall be propelled as soon as possible.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.3
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• pp.43-51
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• 2000

The effect of time, temperature and gas composition on the case hardened thickness, hardness and nitride formation in the surface of ductile cast iron(GCD400) have been studied by micro-pulse plasma technique. Typically, external compound layer and internal diffusion layer which is much thicker than compound layer was observed in the nitride hardening of ductile cast iron. The relative amount kind of phases formed in the nitrided hardening changed with the change of nitriding conditions. Generally, only nitride phases such as $\gamma^'$($Fe_4N$), or $\varepsilon$($Fe_{2-3}N$) phases were detected in compound layer by XRD analysis. The thickness of compound layer increased with the increase of nitrogen content in the gas composition. The optimum nitriding temperature was obtained at $520^{\circ}C$. The nitrided hardening thickness parabolically with nitriding time(t) and thus, the case hardened layer(d) fits well with the typical parabolic equation ; d=kt. The material constant k for GCD400 nitrided at $520^{\circ}C$ was $0.04919\times10^3{\mu}m.hr^{-1/2}$.