• 열처리공학회지
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• 제19권1호
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• pp.3-9
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• 2006

The phase changes, nitride precipitation and hardness variations of 14%Cr-6.7Ni-0.65Mo-0.26Nb-0.05V-0.03C super martensitic stainless steel were investigated after nitrogen permeation heat treatment at a temperature range between $1050^{\circ}C$ and $1150^{\circ}C$. The nitrogen-permeated surface layer was transformed into austenite. The rectangular type NbN, NbCrN precipitates and fine round type precipitate were coexisted in the surface austenite layer, while the interior region that was free from nitrogen permeation kept the martensitic phase. The hardness of surface austenite showed 280 Hv, while the interior region of martensite phase represented 340 Hv. When tempering the nitrogen-permeated steel at $450^{\circ}C$, a maximum hardness of 433 Hv was appeared, probably this is attributed to the secondary hardening effect of the precipitates. The nitrogen concentration decreased gradually with increasing depth below the surface after showing a maximum of 0.3% at the outmost surface. The strong affinity between nitrogen and Cr enabled the substitutional element Cr to move from interiors to the surface when nitrogen diffuse form surface to the interior. Corrosion resistance of nitrogen permeated steel was superior to that of solution-anneaed steel in the solution of 1N $H_2SO_4$.

• 원예과학기술지
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• 제18권1호
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• pp.14-17
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• 2000

개미취, 감국, 털머위의 양액재배시 질소원의 종류별 생육특성을 조사하기 위하여 배양액의 질소를 $NH_4-N$과 $NO_3-N$ 단용, $NH_4-N$와 $NO_3-N$을 1:1로 혼용하여 처리하였다. 털머위는 $NH_4-N$와 $NO_3-N$의 혼용처리와 $NO_3-N$ 단용처리에서 생육이 우수하고 생체중도 높았다. 개미취와 감국은 $NO_3-N$ 단용 처리에서 생육이 양호하였고, 지상부와 지하부의 생체중이 증가하였다. 질산환원효소(NR) 활성은 세 작물 모두 $NO_3-N$ 단용 처리에서 높았으며, 식물체내 엽록소와 질산염의 함량도 $NO_3-N$ 처리구에서 높았다.

• 한국환경과학회지
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• 제7권4호
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• pp.493-500
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• 1998

An experimental study was conducted to Indentify the dlrpct denitrification of ammonium nitrogen In culture water by ozone. During the experimnet period, pH was 7.8-8.8. pH was grdually lower after ammonium nitrogen was reacted with ozone under Br . In addition, it can be tmown that the culturing water was improved greatly form the inverstigation of T-N by biofilm and ozonation. As the results of a variation of recirculation rate, denitrification of ammonium nitrogen was in increased in proportion to the recirculation rate. But Nitrification of microorganism was opposite to the recirculation rate. With the increasing injected ozone in ozonation tank uner 21 clrculation/day(6.71 /min), dinitrification of ammonium nitrogen was Increased lineraly in propotion to the Increasing of injected ozone concentration.

• 산업기술연구
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• 제21권A호
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• pp.343-349
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• 2001

This study characterizes the growth of white rot fungi Phanerochaete chrysosporium IFO 31249) and lignin peroxidase(LiP) activity in different submerged culture media. P. chrysosporium was grown in the form of pellet of various sizes from a spore inoculum under shaking liquid culture condition. While the growth of mycelia was higher under the nitrogen-sufficient culture than under the nitrogen-limited culture, ligninase activity was relatively lower. The lignin peroxidase appeared in nitrogen-limited culture and was suppressed by excess nitrogen. High level(40U/l) of lignin peroxidase activity was obtained in the growth medium containing 1.5mM veratryl alcohol, a secondary metabolite of P. chrysosporium. Lignin peroxidase production was not observed under conditions of nitrogen sufficiency or in balanced media, suggesting that control parameters could increase the activity by manipulating the secondary metabolism.

• 한국물환경학회지
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• 제24권6호
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• pp.773-783
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• 2008

In this paper, data collected from 22 different rural watersheds during stormflow conditions were analyzed. Those watersheds consisted of forest and cultivated land. EMC data analysis indicates that as agricultural land use increases, EMC values of TSS, COD and TN clearly tends to increase, but TP does not show a significant increase. Pattern of the pollutographs mostly has a similarity in hydrograph shape except nitrogen which inherently shows a variability and complication. The fraction of soluble reactive-P to TP increases as cultivated land use increases while mobile-nitrogen portion was higher in the runoff from forested watersheds than agricultural areas. During stormflow, pollutograph of the nitrogen was determined mainly by change in Particle-TKN as other pollutants but its effect is thought to be masked by decrease of dissolved form of nitrogen due to the dilution.

• Journal of Biosystems Engineering
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• 제35권2호
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• pp.132-137
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• 2010

Site-specific N application for corn is one of the precision crop management. To implement the site-specific N application, various nitrogen stress sensing methods, including aerial image, tissue analysis, soil sampling analysis, and SPAD meter readings, have been used. Use of side-dressing, an efficient nitrogen application method than a uniform application in either late fall or early spring, relies mainly on the capability of nitrogen deficiency detection. This paper presents map-based variable rate nitrogen application based using a multi-spectral corn nitrogen deficiency(CND) sensor. This sensor assess the nitrogen stress by means of the estimated SPAD reading calculated from the corn leave reflectance. The estimated SPAD value from the CND sensor system and location information form DGPS of each field block was combined into the field map using a ArcView program. Then this map was converted into a raster file for a map-based variable rate application software. The relative SPAD (RSPAD = SPAD over reference SPAD) was investigated 2 weeks after the treatments. The results showed that the map-based variable rate application system was feasible.

• 대한토목학회논문집
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• 제38권4호
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• pp.555-565
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• 2018

최근 임시 지보, 보강 및 지하수 차수와 같은 다양한 지질공학분야에서 차수 및 지반보강 공법으로 인공동결공법(artificial ground freezing method)이 적용되고 있다. 인공동결공법은 지중에 매설된 동결관 내로 냉매를 순환시켜 대상 지반에 차수벽 및 지지체의 역할을 할 수 있는 동결벽체(frozen wall)를 형성한다. 본 연구에서는 해성 점토지반(marine clay)에 대한 인공동결공법 현장실증시험을 수행함으로서 인공동결공법에 따른 해성 점토지반에서의 동결속도(freezing rate)를 평가하였다. 현장실증시험은 지중에 3.2m 깊이로 매설된 동결관 내로 초저온 냉매인 액화질소를 순환시키는 방법으로 단일공 시험과 동결벽체 형성 시험을 수행하였다. 자동밸브를 통해 유출되는 액화질소의 온도를 일정하게 유지시켰으며, 동결과정에서 동결관 외벽 및 지중의 온도변화를 측정하였다. 시험결과, 단일공 시험은 부피가 약 $2.12m^3$인 원기둥 모양의 동결체를 형성하는데 총 3.5일 동안 약 11.9ton의 액화질소가 소요되었고, 동결벽체 형성 시험은 부피 약 $7.04m^3$의 동결벽체를 형성하는데 총 4.1일 동안 약 18ton의 액화질소가 소요된 것으로 산정되었다. 임의의 깊이에서 동결면적이 동결반경의 제곱에 비례하기 때문에 동결반경이 증가할수록 방사방향 1차원 동결속도가 감소하였고, 이를 바탕으로 방사방향 1차원 동결속도 예측식을 제시하였다.

• 한국연초학회지
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• 제4권1호
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• pp.51-59
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• 1982

This experiment was conducted to investigate the effects of fertilization level, additional dressing time and form of nitrogen on the growth and formation of Alkaloid in flue-cured tobacco. The results are abstracted as follows. Length and width of harvested leaves, area of a leaf, leaf area per plant, number of harvested leaves, weight of a leaf, and leaf weight of a plant were larger in the $NO_3$-N plot than $NH_4$-N plot. Length, width and area of the middle leaves increased by additional dressing on 7 days before topping, but the dry weight Per unit leaf area of those was decreased. Leaf shape was broaden in additional dressing plots in comparison with 100% of basal dressing plot, but there is no difference among the additional dressing plots. And the smallest leaf shape index was shown at upper leaves in 100% of basal dressing Plot. Leaf weight of a Plaint was the highest in 12kg/10a Plot among $NO_3$-N form and in 12kg/10a plot among $NH_4$-N form. Total Alkaloid content was higher in $NH_4$-N plot between fertilization forms, and highest in 15kg/10a plot among fertilization levels and at the position of middle and upper leaves in the plot of 7 days before topping among additional dressing times.

• 한국환경보건학회지
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• 제16권2호
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• pp.31-39
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• 1990

An analytical method for particulate carbon and other elements by using elemental analyzer was investigated. Carbon, hydrogen, and nitrogen was determined as CO$_{2}$, H$_{2}$, and N$_{2}$, respectively. Organic was determined after scparation from elemental carbon(Cae) by volatilization and thermal decomposition in a heated helium flow. With organic materials examined in this reprot, more than 90% of carbon was detected as above 600$^{\circ}$C. But it is considered that a few percents of some compounds were charred above 550$^{\circ}$C. A small amount of Cae was oxidized in the inert atmosphere above 850$^{\circ}$C, but the reason was not explained clearly. Based on the thermal chracteristics of Cao it was found that the optimum temperature of heating in the helium flow of an elemental analyzer for Cao analysis is 630$^{\circ}$C. Carbon in a sample after removing Cao was assumed as Cae and the gramatom ratio of hydrogen to carbon in the sample was 0.4 and less. Rescovery of nitrogen derived from some ammonium salts and nitrates was 100% by two-step measurement with elemental analyzer. By the analytical method investigated in this report, carbon and other elements in suspended particulates(S.P) collected at an urban area in Seoul were measured. There was a good correlation between total nitrogen in SP measured by elemental analyzer and nitrogen estimated form ammonium ions and nitrate ions in SP. The nitrogen from these ions accounts for 80% of the total nitrogen. It is further suggested that the residue(20%) of the total nitrogen is attributed to the other nitrogeneous compounds.

• 열처리공학회지
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• 제13권5호
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• pp.337-345
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• 2000

As a case hardening process for stainless steels, nitriding is more preferred and widely used than carburizing which deterioates corrosion resistance severely. In order to add the nitrogen into the stainless steels, passive film on the surface must be removed effectively before nitriding. Conventional gas nitriding process is performed in the temperature range of 500 to $600^{\circ}C$ with $NH_3$ gas, which often leads to sensitization of stainless steels. In this study, we tried to activate passive film of austenitic stainless steels by heating at low pressure. ($900^{\circ}C$, $5{\times}10^{-2}$ Torr.) Nitriding was performed at the solution treatment temperature of $1100^{\circ}C$ with nitrogen molecules instead of $NH_3$ gas. An attainable nitrogen content in a case depends on the nitrogen gas pressure at constant nitriding temperature. A case depth is proportional to the square root of solution time, which suggests that inward diffusion of nitrogen follows the Fick's 2nd law. Surface nitrogen atoms are dissolved as interstitial solutes, or precipitated in the form of MN, $M_2N$ nitrides, which increase the case hardeness. Dissolved nitrogen in the case enhances the cavitation resistance of austenitic stainless steels dramatically.