• 대한토목학회논문집
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• 제8권2호
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• pp.77-88
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• 1988

본 연구는 SBR system에서 COD/N 변화에 따른 질소제거와 탈질화에 대한 탄소원으로서 폐수 내의 유기물의 이용을 조사하였다. 실험은 실험실에서 반응조 4개를 운전방식을 세가지로 변화시켜 행하였다. 세가지 운전방식의 차이로는 Mode I은 유입기간 동안 폭기하고 Mode II는 폭기를 중단한 상태에서 유입하였으며, Mode III는 폭기를 중단한 상태에서 1 cycle 동안 두 번 유입을 하였다. COD/N비가 증가되었을 때 총 질소 제거율은 Mode I에서 8.7에서 57.7%까지 증가되었고, Mode II에서는 28.9에서 83.2%까지, Mode III에서는 42.7에서 97.8%까지 증가되었다. COD 제거율은 전 실험기간 동안에 93에서 98%까지로 비교적 높았다. 1 cycle 동안 폭기를 하지 않은 상태에서 두 번의 유입을 하는 Mode III로 운전하는 것이 질소제거에서 가장 효과적인 방법으로 판명되었으며, 유출수에 포함된 질소농도는 유입수의 COD와 질소농도를 사용하여 추정할 수 있었다.

• Journal of Welding and Joining
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• 제18권1호
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• pp.59-69
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• 2000

The purpose of the present study was to investigate weld metallurgical phenomena such as primary solidification mode, microstructural evolution and hot cracking susceptibility in nitrogen-bearing austenitic stainless steel GTA welds. Eight experimental heats varying nitrogen content from 0.007 to 0.23 wt.% were used in this study. Autogenous GTA welding was performed on weld coupons and the primary solidification mode and their microstructural characteristics were investigated from the fusion welds. Varestraint test was employed to evaluate the solidification cracking susceptibility of the heats and TCL(Total Crack Length) was used as cracking susceptibility index. The solidification mode shifted from primary ferrite to primary austenite with an increase in nitrogen content. Retained delta ferrite exhibited a variety of morphology as nitrogen content varied. The weld fusion zone exhibited duplex structure(austenite+ferrite) at nitrogen contents less than 0.10 wt.% but fully austenitic structure at nitrogen contents more than 0.20 wt.%. The weld fusion zone in alloys with about 0.15 wt.% nitrogen experienced primary austenite + primary ferrite solidification (mode AF) and contained delta ferrite less than 1% at room temperature. Regarding to solidification cracking susceptibility, the welds with fully austenitic structure exhibited high cracking susceptibility while those with duplex structure low susceptibility. The cracking susceptibility increased slowly with an increase in nitrogen content up to 0.20 wt.% but sharply as nitrogen content exceeded 0.20 wt.%, which was attributed to solidification mode shift fro primary ferrite to primary austenite single phase solidification.

• International Journal of Aeronautical and Space Sciences
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• 제18권1호
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• pp.28-37
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• 2017

Recent modeling of thermal nonequilibrium processes in simple molecules like hydrogen and nitrogen has indicated that rotational nonequilibrium becomes as important as vibrational nonequilibrium at high temperatures. In the present work, in order to analyze rovibrational nonequilibrium, the rotational mode is separated from the translational-rotational mode that is usually considered as an equilibrium mode in two- and multi-temperature models. Then, the translational, rotational, and electron-electronic-vibrational modes are considered separately in describing the thermochemical nonequilibrium of nitrogen behind a strong normal shock wave. The energy transfer for each energy mode is described by recently evaluated relaxation time parameters including the rotational-to-vibrational energy transfer. One-dimensional post-normal shock flow equations are constructed with these thermochemical models, and post-normal shock flow calculations are performed for the conditions of existing shock-tube experiments. In comparisons with the experimental measurements, it is shown that the present thermochemical model is able to describe the rotational and electron-electronic-vibrational relaxation processes of nitrogen behind a strong shock wave.

• 환경위생공학
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• 제20권2호
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• pp.12-20
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• 2005

Most of sewage treatment plants in Korea is operated for the removal of organic material. Because of low C/N ratio of domestic wastewater it is very difficult to remove nitrogen and phosphorus from wastewater. Therefore C/N ratio is key factor for the removed of nitrogen and phosphorus. PSB(photosynthetic bacteria) can remove the nutrient materials, so this study is focused on PSB characterization of nutrient removal. PSB is possible to remove nitrogen, phosphorus in anaerobic and aerobic condition. This study try to find out condition of the PSB in SBR reactor, Batch reactor. It consists of three Mode. Mode 1, 2 is to apply activated sludge process and Mode 3 is that seeded PSB in the activated sludge process. As a result of SBR process, Mode 1, 2 which was activated sludge Process showed $79\~90\%,\;66\~90\%$ of SCODcr, $94.67\~95.89\%,\;95.76\~98.56\%$ of TKN, and Mode 3 has $84\~92\%$ of SCODcr, $95.39\~99.52\%$ of TKN removal efficiency, respectively. When comparison with Mode 1, 2 and 3, most of nitrogen and phosphorus is removed at the anaerobic condition in Mode 3. but Mode 1, 2 has just revealed activated sludge process characterization. It would because of characterization of PSB.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 E
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• pp.2320-2322
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• 1999

This paper was studied on the surface discharge characteristics and tracking phenomena on the solid insulator in liquid nitrogen ($LN_2$) at atmospheric pressure. In order to investigate the bubbles which have much influence on electric surface discharge in liquid nitrogen, Knife type electrode and plane electrode were arranged in different modes(Mode A, Mode B, and Mode C) and investigated for surface discharge and tracking phenomena. In Mode A, by the movement of bubbles tracking damage was formed under the electrodes. The tracking pattern in Mode B was formed along the electrode axis.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1997년도 Proceedings of the 12th KACG Technical Meeting and the 4th Korea-Japan EMGS (Electronic Materials Growth Symposium)
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• pp.275-280
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• 1997

We have investigated the deposition characteristics of (Ni0.8Fe0.2)20Ag80 thin films as a function of chamber pressure and nitrogen flow rate with scanning electron microscopy(SEM), atomic force microscopy(AFM), XRD and $\alpha$-step. The deposition rate of these film is decreased with increasing the chamber pressure and the nitrogen flow rate. With raising the chamber pressure, the growth mode of thin film is changed from island growth to columnar one, which is probably due to energy of atom. Contrary, the nitrogen flow rate is raised, growth mode is changed from columnar to island one. According to the XRD patterns, the preferred orientation is inhibited as the nitrogen flow rate is kept above 10 sccm, but that is nearly independent on the chamber pressure. When the chamber pressure decrease or the nitrogen flow rate increase, phase separation into permoally and silver is occured.

• 설비공학논문집
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• 제29권12호
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• pp.621-627
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• 2017

Nitrogen ion with various levels of dose and irradiation energy was irradiated on aluminum surfaces. Contact angle of surface was increased and surface color was changed by nitrogen ion implantation. During steam condensation experiment using nitrogen ion implanted specimen, dropwise condensation initially occurred on specimens. However, condensation mode eventually changed into filmwise condensation. The color of the surface was also changed from yellow-brown to silver-white. This change of surface color and condensation mode were results of hydrolysis reaction between condensate and nitrogen ion implanted on aluminum surfaces.

• 상하수도학회지
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• 제19권4호
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• pp.446-454
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• 2005

An economic treatment method to remove oxidized nitrogen from wastewater is biological denitrification with organic matters. Several organics can be used, however, methanol is commonly used. When methanol is provided, M:N (Methanol to Nitrogen) ratio is used to define methanol demand for denitrification. In this study, two artificial wastewaters were provided to a biological system to evaluate denitrification performance. Differences of influent total CODcr from effluent soluble CODcr were converted to methanol equivalent and oxidized nitrogen difference between influent and effluent were converted to nitrate equivalent to define M:N ratios. Modes I, II, III, I-1 and IV showed 5.1, 2.7, 3.3, 2.3 and 2.6 of M:N ratios, respectively. Since denitrifying microorganisms had to build a new metabolic system for methanol and influent organics, initial operation mode, Mode I, required more methanol and this resulted in high M:N ratios compared with later operation mode, Mode I-1. Salt in influent did not show inhibitory effects on denitrfication, although this was believed to increase effluent SS and soluble CODcr concentrations in Mode III, I-1 and IV, respectively. The concentrations of effluent soluble $COD_{Mn}$ did not changed much with influent salt.

• 조명전기설비학회논문지
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• 제17권3호
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• pp.49-55
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• 2003

본 논문에서는 고온 초전도체의 냉매로서 주목받고 있는 액체질소 중에서 고체절연물 표면의 연면 방전과 트래킹 현상에 관하여 연구하였다 액체질소중 연면 방전에 많은 영향을 주는 기포 효과를 연구하기 위해 Knife형태의 전극과 평판형태의 전극을 사용하여 A-mod, B-mode, C-mode의 전극배치형태를 각각 구성하였다. 본 실험의 결과는 향후 연구되고 개발될 초전도·극저온 전력설비의 절연설계의 기초 데이터를 제공할수 있다고 판단된다.

• Korean Journal of Hydrosciences
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• 제1권
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• pp.99-106
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• 1990

An extensive biological nutrient removal pilot plant study of anoxic/anaerobic/ aerobic treatment process was conducted to eastblish an optimum operational mode using primary dffluent. Two operational modes, (1) Qr/Q was 3.0 and maintaining EMLSS of 3100 mg/L in which the best operational results were obtained from previous bench scale study using synthetic wastewater (2) Qr/Q was 0.5 and EMLSS of 2200 mg/L which was compatible with the main plant, were Compared and evaluated for removal of nitrogen and/or phosphorous under field conditions. The nitrogen removal increased with increasing recycle ratios, but the phosphorous removal revealed more consistent results with 83percent removal efficiency in the second mode compared with 80 percent in the first mode. Above all, the two modes equally showed good BOD and nitrogen removals by nitrification-denitrification processes. It was also observed that no scum formed in the pilot plant and the sludge exhibited excellent settling characteristic all the time. The modified biological nutrient removal train can be adopted to the main plant without any major changes of their operational modes.