• Carbon letters
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• 제28권
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• pp.116-120
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• 2018

Nitrogen-doped carbons have attracted much attention due to their novel application in relation to gas storage. In this study, nitrogen-doped porous carbons were synthesized using SBA-15 as a template, polypyrrole as the carbon and nitrogen precursor, and KOH as an activating agent. The effect of the activation temperature ($600-850^{\circ}C$) on the $CO_2$ adsorption capacity of the obtained porous carbons was studied. Characterization of the resulting carbons showed that they were micro-/meso-porous carbon materials with a well-developed pore structure that varied with the activation temperature. The highest surface area of $1488m^2g^{-1}$ was achieved at an activation temperature of $800^{\circ}C$ (AC-800). The nitrogen content of the activated carbon decreased from 4.74 to 1.39 wt% with an increase in the activation temperature from 600 to $850^{\circ}C$. This shows that nitrogen is oxidized and more easily removed than carbon during the activation process, which indicates that C-N bonds are more easily ruptured at higher temperatures. Furthermore, $CO_2$ adsorption isotherms showed that AC-800 exhibited the best $CO_2$ adsorption capacity of $110mg\;g^{-1}$ at 298 K and 1 bar.

• 생물환경조절학회지
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• 제15권1호
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• pp.84-90
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• 2006

This study was conducted to anticipate nitrate reduction state in tree through measurement of nitrate reductase activity (NRA) and investigate the effect of nitrogen concentrations (100, 200, 400, and 600 $mg\;L^{-1}$) on growth, the nitrogen content of various tissue, and NRA of pear (Pyrus pyrifolia cv. Niitaka) seedlings in sand culture. Nutrient solutions used in this experiment were adjusted to pH 6.5 and fixed the ratio of ammonium and nitrate to 1:3 and trickle-irrigated 3 times a day. Tree height and dry weight of various organs in seedlings were higher in low nitrogen concentration (100 and 200 $mg\;L^{-1}$) than in high nitrogen concentration (400 and 600 $mg\;L^{-1}$). The shoot growth in 600 $mg\;L^{-1}$ was extremely poor by nitrogen over supply. Increasing the nitrogen concentration, the concentration of nitrate-N in leaves and roots were insignificantly changed but that of stems increased. The accumulation of total and reduced nitrogen in all organs with increasing concentrations of nitrogen supply were increased at 30 days after treatment but those of all organs at 60 and 90 days after treatment were highest in 600 $mg\;L^{-1}$, whereas there were no significant changes among other nitrogen concentration. The in vivo (${+NO_3}^-$) NRA of all organs did not relate to nitrogen concentration but the in vivo (${-NO_3}^-$) NRA of leaves except roots increased with increasing the nitrogen concentration. Therefore, the proper nitrogen concentration to promote growth and nitrate reduction of pear tree was 200 $mg\;L^{-1}$.

• 한국가축번식학회지
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• 제21권2호
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• pp.185-189
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• 1997

The objectives of this study were to relate concentrations of plasma urea nitrogen(PUN) to conception rate in dairy cows. the relationship between PUN concentration and time postcalving was examined for 11 individual cows. Mean concentration of PUN rose for serveral weeks after calving and then was stable from 7 week. As PUN increased, the rate of conception decreased. Cows with PUN<15 and 15∼19.9mg/dl had the likelihood ratios of conception of 1.33 and 1.67. As PUN increased 20∼22.9 and 23mg/dl, the likelihood ratios decreased to 1.00 and 0.90. Thus, low PUN had a favorable association with conception, whereas high PUN had a negative association with conception.

• Journal of Nutrition and Health
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• 제24권1호
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• pp.20-29
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• 1991

This study was carried out to compare the protein quality of lamb and beef meat. by feeding to growing rats. Sixty weanling rats, 30 males and 30 females, were blocked into 12 groups(6 gruops of males and 6 groups of females). They were fed casein. beef, or lamb as a protein source at two levels, 6 and 15%, for 5 weeks. The amount of food intake. food efficiency ratio, protein efficiency ratio. body weight gain. and the weights of skeletal muscles and liver were measured. Nitrogen retention, protein content in the liver and skeletal muscles, and the levels of protein and cholesterol in the serum were also assayed. Summarzing the results, there were no significant differences between lamb and beef on the growth and nitrogen utilization in the rats fed same percentage of protein diet. However. rats fed 15% protein diet showed significantly higher growth rate than those fed 6%. Therefore, it can be concluded that lamb is as good a protein food as beef in terms of protein quality.

• Journal of Microbiology and Biotechnology
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• 제15권6호
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• pp.1159-1163
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• 2005

The production of hydrogen by Chlamydomonas reinhardtii UTEX 90, a marine green alga, was performed under dark fermentation. The effects of initial nitrogen and phosphorus concentration on the cell growth and the production of hydrogen and organic substances were investigated. In the growth stage, the maximum dry cell weight (DCW) was 3 g/l when the initial ammonium concentration was 15 mM. In the dark fermentation, the maximum hydrogen production was $3.5\;{\mu}mol/\;mg$ DCW when the initial nitrogen concentration was 7.5 mM. The nitrogen concentration had a greater effect on organic compound and hydrogen production than the phosphorus concentration during the dark fermentation. An investigation of the duration of dark fermentation showed that, at least until three days, dark fermentation should be prolonged for maximum hydrogen production.

• 한국전기전자재료학회논문지
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• 제15권11호
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• pp.985-990
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• 2002

The electrical breakdown characteristics of liquid nitrogen(LN$\sub$2/) were studied under simulated quenching conditions for application of HTS apparatus. The experimental results for various quenching condition revealed that the breakdown voltage of LN$\sub$2/ with bubble flow velocity and gap spacing. In the case, breakdown voltage decreases gradually with the bubble velocity. When it is bubble velocity from 0 to 1 $\ell$ /min, breakdown voltage rapidly decreases but decreases from 2 $\ell$/min to 10 $\ell$/min slowly. The breakdown voltage for vertical electrode arrangement is higher than that for horizontal electrode arrangement. Also, it did a electric field and potential distribution interpreting at the liquid nitrogen when the bubble existed. The plots of equipotential lines for three cases are also shown.

• 한국전기전자재료학회논문지
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• 제15권2호
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• pp.147-152
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• 2002

Carbon nitride thin films were deposited by reactive sputtering for the hard coating materials on Si wafer and tool steels. When the nitrogen content of carbon nitride film on tool steel is 33.4%, the mean hardness and elastic modulus are 49.34 GPa and 307.2 GPa respectively. The nitrided or carburised surface acts as the diffusion barrier which shows better adhesion of carbon nitride thin film on the steel surface. To prevent nitrogen diffusion from the film, steel substrate can be saturated by nitrogen forming a Fe$_3$N layer. The desirable structure at the surface after carburising is martensite, but sometimes, due to high carbon content an proeutectoid Fe$_3$C structure may form at the grain boundaries, leaving the overall surface brittle and may cause defects.

• 한국전기전자재료학회논문지
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• 제15권5호
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• pp.455-459
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• 2002

I have investigated the effects of annealing on a polymeric $\alpha-C_3N_{4.2}$ at high pressure and temperature in the presence of seeds of crystalline carbon nitride films prepared by a high voltage discharge plasma. The samples were evaluated by x-ray photoelectron spectroscopy (XPS), infrared spectroscopy, Auger electron spectroscopy and x-ray diffraction(XRD). Notably, XPS studies of the film composition before and after annealing demonstrate that the nitrogen composition in $\alpha-C_3N_{4.2}$ material initially containing more than 58% nitrogen decreases during the annealing process and reaches a common, stable composition of ~43%. XPS analysis also shows that the nitrogen composition in the annealed films without polymeric $\alpha-C_3N_{4.2}$ was reduced from 35% to 17%. Furthermore the concentration of the sp$^3$bonded phase increased with the increment of the annealing temperature.

• 한국초지조사료학회지
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• 제25권2호
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• pp.119-124
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• 2005

본 시험은 제주지역에서 한지형 잔디의 적정 질소 분시 횟수를 구명하기 위하여 2004년 3월 26일부터 7월 8일까지 질소시비량을 20kg/10a로 고정하고, 15일 간격으로 1회에서 5회까지 분시하여 잔디의 식생변화를 조사하였다. 초장은 4~5회 분시에서 각각 21.8cm, 21.9cm로 가장 길었으나, 시비횟수가 적어짐에 따라 초장은 참아졌다. 근장과 엽록소는 초장반응과 비슷한 경향이었다. 질소 시비횟수가 1회에서 5회로 증가함에 따라 엽중은 1,091kg에서 1,485kg/10a로, 근중은 2,236kg에서 2,808kg/110a로 증가되었다. 질소분시 횟수가 1회에서 5회로증가함에 따라 잔디의 피도는 $96.0\%$에서 $98.4\%$로 증가되었으나, 잡초는 $4.0\%$에서 $1.6\%$로 감소되었다. 잔디의 밀도는 $97.4\%$에서 $98.9\%$로 증가되고 있는 반면, 잡초의 밀도는 $2.6\%$에서 $1.1\%$로 감소되는 경향이었다. 질소분시 횟수가 전량 시비구에서 5회로 증가됨에 따라 침입잡초는 15.7종에서 11.8종으로 감소되었다. 잡초의 우점순위는 전량 시비구에서 쇠비름, 여뀌, 별꽃 순위였으며, 2회 분시에서 쇠비름, 여뀌, 바랭이 순위로, 3회 분시에서 바랭이, 쇠비름, 여뀌 순위로, 4회와 5회 분시에서 쇠비름, 새포아풀, 여뀌 순위였다. 이상의 결과를 종합해 볼 때, 제주지역에서 질소비료를 4회 분시하는 것이 효과적일 것으로 판단된다.

• 한국토양비료학회지
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• 제16권1호
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• pp.50-55
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• 1983

화본과(禾本科) 및 두과사료작물(豆科飼料作物)의 단파(単播)와 혼파(混播)에서 중질소(重窒素)를 시용(施用)하여 시비질소(施肥窒素)의 작물별(作物別) 건물수량(乾物收量), 질소흡수량(窒素吸收量), 질소고정량(窒素固定量)에 대(対)한 질소(窒素)의 효과(効果)를 조사(調査)하였다. 1. 두과작물(豆科作物)에서 질소고정량(窒素固定量)은 alfalfa > red clover > birdsfoot trefoil의 순(順)이었으며 토양질소의존도(土壌窒素依存度)는 red clover가 가장 컸다. 2. 건물수량(乾物收量)에 대(対)한 질소시용효과(窒素施用効果)는 orchardgrass에서만 높이 인정(認定)되었고 alfalfa와 birdsfoot trefoil는 혼파(混播)의 경우 초기(初期)에만 인정(認定)되었다. 3. 건물수량(乾物收量)은 단파(単播)에서는 alfalfa > red clover > orchardgrass > birdsfoot trefoil의 순(順)이고 혼파(混播)에서는 orchardgrass + alfalfa > orchardgrass + red clover > orchardgrass + birdsfoot trefoil순(順)으로 나타났다. 4. 질소흡수량(窒素吸收量)은 전구(全区) 공(共)히 시비구(施肥区)가 무비구(無肥区)보다 증가(増加)하였고 단파시(単播時) alfalfa > red clover > orchardgrass > birdsfoot trefoil순(順)으로 작물별(作物別)로 흡수량(吸收量)의 차이를 보였다. 5. Orchardgrass의 질소흡수량(窒素吸收量)은 3:7의 red clover 혼파(混播) 시비구(施肥区)만 제외(除外)하고 시비(施肥)에 관계없이 파구(播区)가 단파구(単播區)보다 높았다.