• 한국해양학회지
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• v.29 no.3
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• pp.258-268
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• 1994

Nitrogenous new production and regenerated production were measured in the southern part of the Yellow Sea (Hwanghae) using a stable isotope /SUP 15/N nitrate and ammonia between April 25∼30, 1993. Nitrogen production varied between 155 and 688 mg N m/SUP -2/ d/SUP -1/, which belongs to meso to eutrophic area values. This is equivalent to 881∼3909 mg C m/SUP -2/ d/SUP -1/, assuming the Redfield ratio for C:N of 5.7:1 (by weight). the f0ratio which is the fraction of new production from primary production, varied between 0.12 and 0.26, indicating that 74 to 88% of primary production was supported by the regeneration of nutrients within the euphoric zone. This low f0ratio is the characteristics of the oligo- to mesotrophic area. Contrary to the expected, the ambient nutrient concentration was not an important factor for controlling productivity in this area during the study period. The difference in productivity among stations was mainly due to the variations in phytoplankton biomass in different water masses.

• The Korean Journal of Malacology
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• v.24 no.3
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• pp.261-267
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• 2008

The tendency of metabolism in oyster, Crassostrea gigas, was investigated in relation to the water temperature and salinity. Oxygen consumption and ammonia excretion were measured and O:N ratio were calculated according to the water temperature from February 2007 to September 2008 and body size. The relationship between oxygen consumption and body weight has been examined in C. gigas. The weight-specific oxygen consumption rate (mg $O_2$/g/h) varied inversely with size. Oxygen consumption and ammonia excretion increased with an increase in water temperature. O:N ratio measured in this study ranged from 8 to 40 under ordinary sea water and the ratio was 8 at $25^{\circ}C$ and 16 at $10^{\circ}C$. This indicates that oyster mainly use the protein as the primary catabolic substrate during gametogenesis. Lower O:N ratio in winter suggests that oysters have to meet their energy demand by metabolizing protein to survive in stressful conditions such as low temperature and lack of sufficient food supply. This studies will provide the basic data for oyster culture farm in assessing the carrying capacity and sustainable management.

• Journal of the Korean Vacuum Society
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• v.5 no.4
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• pp.377-386
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• 1996

Austenitic stainless steel type 304L has been nitrided under the low pressure of high nitrogen environment for 5 hours by the square-wave-pulse-d.c. plasma as a function of temperature 400~$600^{\circ}C$ and of pulsation. At the temperature range lower than $500^{\circ}C$ and at the relatively high ratio of pulse duration to pulse period, nonstoichiometric stainless steel nitride has been developed in the form of a thin layer which has many cracks. At the temperature range higher than $500^{\circ}C$, with the increasing temperature or with the increasing ratio of the pulse duration to pulse period up to 50s/100s, the nitrided layer was composed mainly of CrN and Fe4N phases and became thick, uniform, columnar and nearly crack-free. The nitrided layer at $500^{\circ}C$ was mixed with the low-temperature layer and the high temperature layer and was very brittle.

• ALGAE
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• v.22 no.3
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• pp.235-240
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• 2007

The red tide-causing flagellate Chattonella anticfua can cause mass fish kills by their clogging in fish gills. Thisstudy examined the nutrient requirements of C. antiqua isolated from Korea. C. anticfua displayed maximum growthat the day five, followed by a decrease in cell density. Nitrate and nitrite were the preferred nitrogen sources, alonewith adenosine diphosphate for phosphorus compounds. In medium that contained ammonium, a significantdecrease in cell density was observed. Half-saturation constants, Ks, calculated from the maximum growth ratewere 4.94 U|M for NC>3 and 0.79 flM for P04. The growth of C. antiqua was not within the function of the N:P ratio (RU= 0.29). With an N:P ratio as low as 10, the increase in cell density was apparent, with a higher division rate. At lev-els above 50 fiM of NaNOg or 8 ;uM of NaHUPCU, the growth rates were somewhat decreased. Phosphate was thelimiting factor for C. antiqua growth since the starvation of phosphate had brought about a rapid decrease in celldensity in semi-continuous culture. Studies about the temporal modification of the efficiency of nitrate or phosphateuptake may be necessary to explain the bloom dynamics of C. antiaua.

• Korean Journal of Soil Science and Fertilizer
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• v.6 no.2
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• pp.107-113
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• 1973

A pot experiment on paddy rice was carried out to investigate the effect of temperature after heading with application of phosphate, potash and silica on the yield and nutrient uptake. The results obtained are as follows: 1. The Grain yield was greatly affected by temperature during ripening. The yield at $20^{\circ}C$ and at $15^{\circ}C$ decreased to 62.3% and to 37.2% of that at $25^{\circ}C$ respectively. However, the application of phosphate, potash and silica at transplanting increased the grain yield even at low temperature of $15^{\circ}C$. 2. Percentage of ripened grain and weight of 1,000 grains decreased with decreasing temperature but they were increased by the application of phosphate, potash and silica at the low temperature of $15^{\circ}C$. 3. The grain filling rate was fast in the early stage of ripening at high temperature while it was fast in the later stage at low temperature. Low temperature damage was severe in the early stage of ripening. 4. Accumulation of carbohydrate in the grain was small at low temperature of $15^{\circ}C$ and the application of phosphate, potash and silica was effective to increase carbohydrate content in the grain at low temperature. 5. The content of T-N and $P_2O_5$ in straw grown at low temperature were high whereaas those of $K_2O$ and $SiO_2$ were low which were increased by the application of potash and silica. 6. There was a positive correlation between the grain yield and rate of ripening, 1,000 grain weight, contents of $K_2O$ and $SiO_2$, $K_2O/N$ and $SiO_2/N$ ratio, but a negative correlation between grain yield and contents of T-N and $P_2O_5$ in the straw at harvesting stage. 7. Ripening rate and weight of 1,000 grains showed a significant positive correlation with $K_2O$, $SiO_2$, $K_2O/N$ and $SiO_2/N$ ratio in the straw. Further, there was a negative correlation between ripening rate and the contents of T-N and $P_2O_5$ but a positive correlation between weight of 1,000 grains and these elements.

• Membrane Journal
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• v.24 no.1
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• pp.20-30
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• 2014

A membrane-coupled sequencing batch reactor (MSBR) was used for the advanced treatment of rural village sewage which is very low C/N ratio. The effect of powdered activated carbon, aeration rate, and external organic material loadings on the treatment efficiency and filtration performance were investigated in sequencing batch reactor, in which a flat-sheet type microfiltration membrane with a pore size of $0.4{\mu}m$ was submerged. At the initial operation (within 54 days) MLSS concentration, and the removal efficiencies of COD, T-N, and T-P were increased with the increase of C/N ratio. After 89 days the removal efficiencies of COD, T-N, and T-P were 97.1%, 75.0%, and 48.3%, respectively. Suspended solid-free effluent was obtained by membrane filtration. The T-P removal was relatively low because of depending on the amount of excess sludge wasting. During the operation of MSBR with powdered activated carbon, the particle size of the sludge reduced by the increase of collision frequency and mixing intensity. In comparison with MSBR without powdered activated carbon, TMP of MSBR with that was significantly elevated.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.58.2-58.2
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• 2020

We present a method for determining the abundance ratio of nitrogen to iron ([N/Fe]) from low-resolution (R~2000) stellar spectra from large spectroscopic surveys such as Sloan Digital Sky Survey (SDSS) and Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). The basic idea of the method is to match a grid of synthetic spectra with an observed spectrum in the CN band region around 3883 Å. To calibrate our estimate of [N/Fe], we make use of the giants observed in Apache Point Observatory Galaxy Evolution Experiment (APOGEE), which are also observed in the SDSS. This method will be applied to the Galactic halo stars to determine [N/Fe], and the measured nitrogen abundance ratios will be used to investigate the C-N anti-correlation, which is observed in globular clusters, to trace their origin with their kinematic properties.

• Journal of the Korean Ceramic Society
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• v.38 no.11
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• pp.1037-1041
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• 2001

Silicon diosixde thick film using silica optical waveguide cladding was fabricated by Plasma Enhanced Chemical Vapor Deposition (PECVD) method, at a low temperature (32$0^{\circ}C$) and from (SiH$_4$+$N_2$O) gas mixtures. The effects of deposition parameters on properties of SiO$_2$thick films were investigated by variation of $N_2$O/SiH$_4$flow ratio and RF power. As the $N_2$O/SiH$_4$flow ratio decreased, deposition rate increased from 2.9${\mu}{\textrm}{m}$/h to maximum 10.1${\mu}{\textrm}{m}$/h. As the RF power increased from 60 W to 120 W, deposition rate increased (5.2~6.7 ${\mu}{\textrm}{m}$/h) and refractive index approached at thermally grown silicon dioxide (n=1.46).

• Journal of Industrial Technology
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• v.13
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• pp.3-17
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• 1993

The composting process is a suitable to dispose the livestock manure in terms of resources recovery. However the performence of composting process is greatly affected by the environmental conditions such as characteristics of manure, type of the bulking agent, initial moisture contents, temperature, recycle and so on. The purpose of this study is to evaluate the optimum environmental conditions of composting process for livestock manures. The analytical results indicated that no bulking agent was necessary for the cow manure because of the proper C/N ratio. However the pig manure required a bulking agent since the pig manure had not only low in C/N ration but poor ventilation characteristics. In addtion, the initial miosture content for optimum composting appeared to be about 60%. The temperature control was also an essential factor to enhance the activity of thermophilic microorganisms in the laboratory composting unit. It was further found that the recycle of composts may contributed the completion of composting precess as well as C/N ratio reduction and moisture control.

• 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.