• Journal of Korean Society of Environmental Engineers
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• v.28 no.9
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• pp.935-939
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• 2006

The biological nutrient removal from domestic wastewater with low C/N ratio is difficult. Therefore, this study was performed to examine effect of operational parameters such as air supply, hydraulic retention time, pH on the nitrogen removal by ammonia stripping and to increase influent C/N ratio without required carbon source. The ammonia stripping system used for the bench-scale experiment in laboratory had a dimension of 15 cm diameter and 150 cm height. The ammonia stripping reactors were classified into two types, type AS I and type AS II, according to there using or not media. Results of the research showed that the T-N removal efficiency of AS I using plastic media is slightly higher than AS II without media. In experimental condition of air supply 30 L/min and pH 12.5, T-N removal efficiencies increased as HRT of ammonia stripping reactor became longer from 8 hr to 36 hr. In experimental condition of HRT 36 hr, it was also found that the T-N removal efficiencies improved through increase of air supply. On the other hand, C/N ratio of wastewater was increased from average 3.9 to 5.4 by ammonia stripping.

• Journal of the Korean Ceramic Society
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• v.35 no.12
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• pp.1316-1322
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• 1998

The amount of VC and C/N ratio in Ti(CN) was varied to investigate the effect of VC addition on the mi-crostructural change in Ti(CN)-Ni system. As the amount of VC addition increases in Ti(C0.7N0.3)-20Ni sys-tem a complete solid solution was observed in Ti(C0.7N0.3)-20Ni-25VC system. It implies that the ratio of the dissolution rates of Ti(C0.7N0.3)to that of VC is nearly 2:1 at the sintering conditions used in this study. It was found from the experiments that the system composed of the Ti(C0.7N0.3) phase exhibits a rimless structure and relatively small amount of solid solution. That is among Ti(C0.7N0.3) phase exhibits a rimless structure and relatively small amount of solid solution. This is among Ti(C1-xNx) phases the dissolution rate of Ti(C0.3N0.7) is the lowest. Also fracture toughness(KIC) of the cermet was measured by indentation method. Attentions were paid to crack propagation path to look for a dominant fracture mode and to cor-relate it with fracture toughness values. The fracture toughness was relatively high with the addition of VC content. But the addition of a large VC content reduced the overall toughness of the cermet. This result is explained with the difference in fracture mode.

• Journal of the Korean Ceramic Society
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• v.25 no.4
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• pp.415-423
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• 1988

Mixtures of carbon and silica (about 0.46${\mu}{\textrm}{m}$) which was synthesized by the hydrolysis of ethyl silicate, the molar ratio of silica/carbon was fixed as 1/10(weight ratio : 1/2), were nitrided in the temperature range 135$0^{\circ}C$~150$0^{\circ}C$. The phse of the product Si3N4 was $\alpha$ phase and the morphology was hexagnoal prism and the nitridation reaction was completed in 5 hrs at 150$0^{\circ}C$ or 7hrs at 145$0^{\circ}C$. The reaction rate above 150$0^{\circ}C$ was diffusion-controlled, following Jander equation. Activation energy Q was derived from the Arrhenius plot and the value was about 101kcal/mol. Axis ratio of Lattice constants(c/a) was 0.726 and unit volume was $\AA$3, the larger the molar ratio of carbon/Alkoxide was, the smaller the particle size of $\alpha$Si3N4 was.

• Journal of the Korean Institute of Intelligent Systems
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• v.16 no.3
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• pp.332-337
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• 2006

It has been suggested that the endoscopic color of intramucosal gastric carcinoma is correlated with mucosal vascularity within the carcinomatous tissue. The development of electronic endoscopy has made it possible to quantitatively measure the mucosal hemoglobin volume, using a hemoglobin index. The aim of this study was to make a software program to calculate the hemoglobin index (IHb) and then investigate whether the mucosal IHb determined from the electronic endoscopic data is a useful marker for evaluating the color of intramucosal gastric carcinoma, in particular with regard to its value for discriminating between the histologic types. The mean values of IHb for the carcinoma (IHb-C) and the mean values of IHb for the surrounding non-cancerous mucosa (IHb-N) were calculated in 75 intestinal-type and 34 diffuse-type gastric carcinomas. Then, we analyzed the ratio of the IHb-C to IHb-N. The mean IHb-C/IHb-N ratio in the intestinal-type carcinoma group was higher than that in the diffuse-type carcinoma group (1.28$\pm$0.19 vs. 0.81$\pm$0.18, respectively, p<0.001). When the cut-off point of the C/N ratio was set at 1.00, the accuracy rate, the sensitivity, the specificity, and the positive and negative predictive values of a C/R ratio below 1.00 for the differential diagnosis of diffuse-type carcinoma from intestinal-type carcinoma were 94.5%, 94.1%, 94.7%, 88.9% and 97.3%, respectively. IHb is useful for quantitative measurement of the endoscopic color in intramucosal gastric carcinoma and the IHb-C/IHb-N ratio would be helpful in distinguishing diffuse-type carcinoma from intestinal-type carcinoma.

• Microbiology and Biotechnology Letters
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• v.12 no.4
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• pp.271-276
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• 1984

Effect of C/N ratios on the cell growth, cell lipid, cell protein and fatty acids of Rhodotorula sp. was examined. At low concentration of nitrogen in cultural medium the growth of the yeast was retarded, whereas its growth was favorable at high concentration but lipid yield was decreased due to a high content of cell protein. In order to increase lipid yield, the optimum C/N ratio obtained was 45-50 (5% glucose, 0.0414% nitrogen). During the cultivation cell protein synthesis occurred mainly in initia stage and the lipid was accumulated rapidly at the late phase. The highest content of total fatty acid was observed at the optimum C/N ratio. The higher C/N ratio was the more unsaturation degree of fatty acid decreased. It was attributed principally to a decreased oleic acid with palmitic acid increased. No significant changes occurred in content of other fatty acids.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.4
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• pp.355-361
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• 2006

In this study, effects of influent C/N(COD/Nitrate) ratio and dissolved oxygen(DO) concentration on biological nitrate removal from groundwater were investigated in the fixed-type biofilter. Influent nitrate of 30 mg/L was removed completely by biological denitrification at the C/N ratio of 10 and 4.0, while residual nitrate of 5 mg/L occurred at the C/N ratio of 2.0, which resulted from deficiency of organic electron donor. Furthermore, nitrite was accumulated up to about 5 mg/L as the C/N ratio decreased to 2.0. Increase in DO concentration also inhibited denitrification activity at the relatively high C/N ratio of 5.0, which decreased the nitrate removal efficiency. Although the influent DO concentration was reduced as low as 0.3 mg/L using sodium sulfite($Na_2SO_3$), effluent nitrite was up to 3.6 mg/L. On the other hand, nitrate was completely removed without detection of nitrite at the DO concentration of 0.3 mg/L using nitrogen gas($N_2$) sparging. The organic matter for denitrification in biofilter were in the range from 3.0 to $3.5gSCOD/g{NO_3}^--N$, while utilized these values increased at the high DO concentration of 5.5 mg/L. In addition to the high DO concentration and the low influent C/N ratio, DO control by chemical such as sodium sulfite affected on biological denitrification, which resulted in the reduction of nitrate removal efficiency and nitrite build-up in a biofilter.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.143-143
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• 2017

CrAlN 코팅은 높은 경도, 낮은 표면 조도 등의 상온에서의 우수한 기계적 특성 이외에 고온에서 안정한 합금상의 형성으로 인하여 우수한 내산화성 및 내열성을 보유하여 공구 코팅으로의 적용 가능성이 크다. 그러나 최근 공구사용 환경의 가혹화로 인하여 코팅의 내마모성 및 내열성 등의 물성 향상을 통한 공구의 수명 향상이 필요시 되고 있으며, 다양한 코팅 물질을 활용하여 다층 코팅을 합성함으로써 난삭재용 공구 코팅의 물성을 높이는 연구들이 진행되고 있다. 본 연구에서는 CrAlN 코팅과 WC-Co 6wt.% 모재 사이에 CrZrN, CrN, CrN/CrZrSiN 등의 중간층을 합성하여 CrAlN 코팅의 상온 및 고온 특성을 향상시키는 연구가 진행되었다. 합성된 코팅의 구조 및 물성을 분석하기 위해 field emission scanning electron microscopy(FE-SEM), nano-indentation, atomic force microscopy(AFM) 및 ball-on-disk wear tester를 사용하였다. 코팅의 고온 특성을 확인하기 위해 코팅을 furnace에 넣어 공기중에서 30분 동안 annealing 한 후에 nano-indentation을 사용하여 경도를 측정하였고, $500^{\circ}C$ annealing 코팅의 표면 조도 분석 및 $500^{\circ}C$에서 마찰마모시험을 실시하였다. CrAlN 코팅의 상온 특성을 분석한 결과, 모든 코팅의 경도(35.5-36.2 GPa)와 탄성계수(424.3-429.2 GPa)는 중간층의 종류에 상관없이 비슷한 값을 보인 것으로 확인됐다. 그러나, CrN/CrZrSiN 중간층을 증착한 CrAlN 코팅의 마찰계수는 0.33로 CrZrN 중간층을 증착한 CrAlN 코팅의 마찰계수(0.41)에 비해 향상된 값 보였으며, 코팅의 마모율 및 마모폭도 비슷한 경향을 보인 것으로 보아 코팅의 내마모성이 향상된 것으로 판단된다. 이것은 중간층의 H/E ratio가 코팅의 내마모성에 미치는 영향에 의한 결과로 사료된다. H/E ratio는 파단시의 최대 탄성 변형율로써, 모재/중간층/코팅의 H/E ratio 구배에 따라 코팅 내의 응력의 완화 정도가 변하게 된다. WC 모재 (H/E=0.040)와 CrAlN 코팅(H/E=0.089) 사이에서 CrN, CrZrSiN 중간층의 H/E ratio는 각각 0.076, 0.083 으로 모재/중간층/코팅의 H/E ratio 구배가 점차 증가함을 확인 할 수 있었고, 일정 응력이 지속적으로 가해지면서 진행되는 마모시험중에 CrN과 CrZrSiN 중간층이 WC와 CrAlN 코팅 사이에서 코팅 내부의 응력구배를 완화시키는 역할을 함으로써 CrAlN 코팅의 내마모성이 향상된 것으로 판단된다. 내열성 시험 결과, CrN/CrZrSiN 중간층을 증착한 코팅은 $1,000^{\circ}C$까지 약 28GPa의 높은 경도를 유지한 것으로 확인 되었다. $500^{\circ}C$ annealing 후 진행된 표면 조도와 마모시험 결과, 모든 코팅의 조도 값 및 마찰계수는 상온 값에 비해 증가하였으며 CrN/CrZrSiN 중간층을 증착한 CrAlN 코팅의 변화량이 가장 낮은 값을 보였다. 이는 CrZrSiN 중간층 내에 존재하는 $SiN_x$ 비정질상이 고온 annealing시에 산소 차폐막 역할을 하여, 코팅내의 잔류 산소에 의한 산화작용을 효과적으로 방지함으로써 코팅의 고온 특성이 향상된 것으로 판단된다.

• KSBB Journal
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• v.7 no.2
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• pp.102-106
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• 1992

Effects of nitrogen souses and C/N ratio were investigated on the production of extracellular microbial surfaclant, sophorolipid, from C. bombiocola. Organic nitrogen sources, such as urea, peptone and yeast extract was found to be more effective for sophorolipid production, than inorganic nitrogen sources. Depending on the nitrogen sources, sophorolipid production pattern varied by increasing C/N ratio. Increased production of sophrolipid could be obtained up to 90g/L by feeding carbon source again 2 days after cultivation.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.1
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• pp.7-14
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• 2006

In this study, nitrogen removal characteristics of SBR3 process, which is two-sludge system of sequencing batch reactor(SBR) type, were investigated, with comparison of those of SBR1 process, which is conventional SBR process, and SBR2 process, which was designed to enhance denitrification efficiency through step-feeding of wastewater, using domestic wastewater. SBR3 process of two-sludge type can perform external nitrification, on which nitrification occurs in separated reactor, and enhanced denitrification using biosorbed organics. In the results with domestic wastewater, T-N removal efficiency of SBR3 process was better than those of SBR1 and SBR2 processes. It was observed that bigger difference of T-N removal efficiency between SBR3 process and SBR1 & SBR2 processes was showed at low C/N ratio than that at high C/N ratio resulting from more efficient use of organics by biosorption mechanism in denitrification of SBR3 process than those of SBR1 and SBR2 processes. In addition, T-N removal efficiency of SBR3 process according to influent T-N loading rate was better than those of SBR1 and SBR2, even though influent T-N loading rate of SBR3 process was higher than that of SBR1 and SBR2 process resulting from operation of SBR3 process in short hydraulic retention time(HRT) by external nitrification.

• Magazine of the Korean Society of Agricultural Engineers
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• v.44 no.6
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• pp.106-114
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• 2002

In this study, the results of a series of consolidation test for undisturbed Ariake clay in Japan were analyzed by three methods, e-log p (e: void ratio, p: consolidation pressure), log e-log p and n-log p (n: porosity). Moreover, the characteristics of each analysis method were studied. For undisturbed Ariake clay, the log o-Log p and the n-log p relationships can be found as two groups of straight lines of different gradients, but both the elastic consolidation and plastic consolidation regions of e-log p relationship are expressed as a curve. In this paper, the porosity of consolidation yield n$\_$y/, consolidation yield stress p$\_$y/, and the gradient of the plastic consolidation region C$\_$p/ were represented by the log e-log p method, and n$\_$c/, P$\_$cn/ and C$\_$cn/ were represented by the n-log p method. The meaning and the relationships of each value were studied, and the interrelationships among compression indices i.e. C$\_$cn/, C$\_$p/ and C$\_$c/ are obtained from each analysis method as a function of initial porosity n$\_$0/.