• Journal of Applied Biological Chemistry
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• v.42 no.4
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• pp.186-190
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• 1999

Isotope ratio ($^{15}N/^{14}N$) and nitrate-nitrogen concentration in groundwater were measured to investigate the effect of chemical fertilizer and livestock manure on temporal variations in nitrate-nitrogen concentration and to estimate the contribution of fertilizer and manure to groundwater contamination by nitrate. Four study wells from a rural area in Kyonggi province were selected. One well was located on an upper site from a livestock feedlot, and the others were situated at lower sites from the feedlot. The ${\delta}^{15}N$ values were analyzed by a stable isotope ratio mass spectrometer (Micromass, VG Optima IRMS). Reproducibility of the method and precision of the mass spectrometer were below 1.0 and 0.1‰, respectively Even though study wells were located at the same area, nitrate-nitrogen concentrations and ${\delta}^{15}N$ values differed and fluctuated during the sampling period. The ${\delta}^{15}N$ values of well located at upper site from the feedlot were extremely variable (-1.48~20.80‰). The ranges of ${\delta}^{15}N$ value of three wells situated at lower sites from the feedlot were 11.83~20.73 (ave. 16.11), 8.90~11.73 (ave.11.01), and 5.29~12.73‰ (ave. 8.21‰) with increasing distance from the feedlot. The average values of contribution proportion of nitrogen derived from livestock manure to nitrate-nitrogen in groundwater were 79% for the well closet to the feedlot, 44% for the well most distant from the feedlot, and 56% for the well in between the two wells.

• Journal of Forest and Environmental Science
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• v.29 no.2
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• pp.116-124
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• 2013

Differences in rates and patterns of nitrogen cycling have been correlated with nitrogen stable isotope measurements in forest ecosystems of tropical and temperate regions, but limited similar work has been conducted in sub-tropical forests. This study investigated patterns in stable N isotopic composition in a subtropical forest in Taiwan by sampling three soil profiles and overstory and understory foliage. Soil ${\delta}^{15}N$ in the forest floor ranged from -1.8 to -1.8‰. Mineral soils had higher ${\delta}^{15}N$ (4.1 to 6.0‰). Foliage ${\delta}^{15}N$ in overstory trees ranged from -6.6 to -2.0‰, and understory foliage ${\delta}^{15}N$ ranged from -5.0 to -1.2‰. There was a weak correlation between foliar % N and ${\delta}^{15}N$ ($r^2=0.214$). Compared to results from similar surveys in tropical and temperate forests, foliar ${\delta}^{15}N$ values were generally lower. These results help highlight the need for improved knowledge regarding the relationships between patterns in N stable isotopes and processes affecting rates of N cycling, especially as related to wider scale patterns in forest ecosystems within the east-Asia region.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.47 no.6
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• pp.486-491
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• 2002

Spikelet number and its components of rice plant are closely associated with nitrogen accumulation and biomass production during panicle formation stage. To elucidate this relationship and also compare the differences of the sink formation efficiency among cultivars, spikelet number, its components, nitrogen content, nonstructural carbohydrate content, and plant dry matter were investigated under 5 nitrogen levels with two split application methods and shading treatments by using three rice varieties. The nitrogen amount in shoot at panicle initiation stage and at 15 days after panicle initiation showed significant positive correlation with primary rachis branches per square meter, and that at 15 days after panicle initiation and at heading stage with secondary rachis branches per square meter, Primary and secondary rachis branches per square meter showed positive significant correlation with the shoot dry weight at panicle initiation stage and at 15 days after panicle initiation stage, respectively, The amount of degenerated secondary rachis branches and spikelets per square meter showed significant negative correlation with the dry weight and nonstructural carbohydrate increase of stem during 15days after panicle initiation, and the contents of nonstructural carbohydrate at 15 days after panicle initiation. Spikelets per unit area showed significant positive correlation with nitrogen amount in shoot and shoot dry weight at heading stage. The sink formation efficiency expressed as the spikelet number produced by the unit amount of nitrogen in shoot at heading stage was higher in Nampoongbyeo than Choocheongbyeo and Hwaseongbyeo. Sink formation efficiency was negatively correlated with the dry weight increase of shoot and stem during reproductive stage. but not significantly with that of leaf in all varieties. Sink formation efficiency was not significantly correlated with nonstructural carbohydrate, but was significantly negatively correlated with structural carbohydrate increase during reproductive stage.

• Korean Journal of Materials Research
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• v.15 no.5
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• pp.313-317
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• 2005

The relation between bulk microdefect (BMD) and mechanical strength of $P/P^-$ epitaxial silicon wafers (Epitaxial wafer) as a function of nitrogen concentrations was studied. After 2 step anneal$(800^{\circ}C/4hrs+1000^{\circ}C/16hrs)$, BMD was not observed in nitrogen undoped epitaxial silicon wafer while BMD existed and increased up to $3.83\times10^5\;ea/cm^2$ by addition of $1.04\times10^{14}\;atoms/cm^3$ nitrogen doping. The slip occurred for nitrogen undoped and low level nitrogen doped epitaxial wafers. However, there was no slip occurrence above $7.37\times10^{13}\;atoms/cm^3$ nitrogen doped epitaxial wafer. Mechanical strength was improved from 40 to 57 MPa as nitrogen concentrations were increased. Therefore, the nitrogen doping in silicon wafer plays an important role to improve BMD density, slip occurrence and mechanical strength of the epitaxial silicon wafers.

• Korean Journal of Agricultural Science
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• v.46 no.3
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• pp.629-636
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• 2019

This study was conducted to investigate the growth characteristics and yield of whole green rice grains during the ripening period. These were investigated using Hopumbyeo and Unkwangbyeo at two transplanting times and with two kinds of nitrogen fertilization. The transplanting times were May 30 and June 20, respectively, using 30-day seedling culture and transplanting conducted with 3 - 4 plants per hill in planting space of $15cm{\times}30cm$. During nitrogen fertilization, 9 kg and 18 kg was used, respectively. The harvest of the green whole rice grains was carried out on the 15th, 20th, 25th, 30th, and 40th day after the heading date. The clum length was greater with later planting and with application of more nitrogen. The rice yield was higher with nitrogen fertilization of 18 kg/10 a when transplanted on May 30 for Hupumbyeo, and for Unkwangbyeo, was higher at 9 kg/10 a nitrogen fertilization when transplanted on May 30. The protein content of Hopumbyeo was higher when the nitrogen fertilizer was 18 kg/10 a, and that of Unkwangbyeo was lower than that when transplanting on June 20. The greenness was not related to the nitrogen fertilization level when transplanted on May 20 but for later transplanting, the greenness was higher when the nitrogen application was increased, and the greenness was the greatest about 30 days after the heading date.

• Applied Biological Chemistry
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• v.25 no.4
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• pp.232-238
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• 1982

From ^{15}N$ labelled nitrogen experiments on 13 fields use efficiency by difference method was higher than that by labelling method in 80% of fields tested indicating augmentation of soil nitrogen uptake by fertilizer nitrogen. Both methods showed very similar trend among fields. Sulfur coated urea(SCU) and point application increased fertilization efficiency(yield increment per fertilizer nitrogen applied, Fe) to 23 from 15 of split application through the increase of fertilizer use efficiency from 29(Eu) to 50 but tended to decrease efficiency of absorbed fertilizer nitrogen(yield increment per nitrogen derived from fertilizer, Ef) from 50. to 46 High yielding capacity of Tongil line appears to be attributed to the higher Ef, translocation efficiency and soil nitrogen preference index(soil nitrogen increment in plant per the increment of fertilizer nitrogen in plant, PI). This studies confirmed that yield under fertilizer application system depends on Fe which is the multiplication of Eu and Ef and that the improvement of fertilizer management(form, application method and time) increases principally Eu, the limit of which is controlled by Ef that is attributed mainly to varietal characteristics.

• Korean Journal of Ecology and Environment
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• v.48 no.3
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• pp.147-152
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• 2015

Nitrogen (N) loading from domestic, agricultural and industrial sources can lead to excessive growth of macrophytes or phytoplankton in aquatic environment. Many studies have used nitrogen stable isotope ratios to identify anthropogenic nitrogen in aquatic systems as a useful method for studying nitrogen cycle. In this study to evaluate the precision and accuracy of Kjeldahl processes, two reference materials (IAEA-NO-3, N-1) were analyzed repeatedly. Measured the ${\delta}^{15}N-NO_3$ and ${\delta}^{15}N-NH_4$ values of IAEA-NO-3 and IAEA-N-1 were $4.7{\pm}0.2$‰ and $0.4{\pm}0.3$‰, respectively, which are within recommended values of analytical uncertainties. Also, we investigated spatial patterns of ${\delta}^{15}N-NO_3$ and ${\delta}^{15}N-NH_4$ in effluent plumes from a waste water treatment plant in Han River, Korea. ${\delta}^{15}N-NO_3$ and ${\delta}^{15}N-NH_4$ values are enriched at downstream areas of water treatment plant suggesting that dissolved nitrogen in effluent plumes should be one of the main N sources in those areas. The current study clarifies the reliability of Kjeldahl analytical method and the usefulness of stable isotopic techniques to trace the contamination source of dissolved nitrogen such as nitrate and ammonia.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.6
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• pp.551-557
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• 2002

Carbon nitride films have been deposited on Si(100) substrate by a high voltage discharge plasma combined with laser ablation in a nitrogen atmosphere. The films were grown both with the without the presence of an assisting focused Nd:YAG laser ablation. The laser ablation of the graphite target leads to vapor plume plasma expending into th ambient nitrogen arc discharge area. X-ray photoelectron spectroscopy and Auger electron spectroscopy were used to identify the binding structure and the content of the nitrogen species in the deposited films. The nitrogen content of the films was found to increase drastically with an increase of nitrogen pressure. The surface morphology of the films was studied using a scanning electron microscopy. Data of infrared spectroscopy and x-ray photoelectron spectroscopy indicate the existence of carbon-nitrogen bonds in the films. The x-ray diffraction measurements have also been taken to characterize the crystal properties of the obtained films.

• Journal of Korean Society on Water Environment
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• v.31 no.2
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• pp.159-165
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• 2015

The organic matter sources of phytoplankton and related environmental factors influencing algal bloom in Paldang reservoir were studied using nitrogen and carbon isotope ratio(${\delta}^{15}N$, ${\delta}^{13}C$). Phytoplankton samples for stable isotope analysis were collected from four points in reservoir using a plankton net. Physicochemical water quality, algal taxa and hydrological data were collected from published monitoring material. Phytoplankton samples were analyzed by IRMS. CN ratio of each sample was very similar to that of phytoplankton from literature cited. ${\delta}^{15}N$ of each sample was decreased during July. Mixing and dilution of nitrogen sources due to increment of influx by concentrated rainfall were considered as the main reason for the decline of ${\delta}^{15}N$. Based on analyzed ${\delta}^{15}N$ value of each sample, nitrogen source of Bughan river sample was presumed to come from soil. The nitrogen sources of Namhan river and Kyeongan stream samples seemed to be sewage or animal waste. Low ${\delta}^{15}N$ value in August (2012) seemed to be influenced by isotope fractionation due to the blooming of nitrogen-fixation blue-green algae (Anabaena spp.). Variation in ${\delta}^{15}N$ values particularly by blue-green algal bloom was considered the important factor for estimating the organic matter sources of phytoplankton.

• Journal of The Korean Society of Grassland and Forage Science
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• v.23 no.2
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• pp.107-114
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• 2003

Growth characteristics and seed productivities of orchardgrass "Hwabsung 2 Ho" cultivated for seed production were examined in the NLRI from 2000 to 2002. The experimental design was a split-plot arrangement with three replications. The main-plots were three drill widths of 15, 30 and 45cm, and subplots were four nitrogen application levels of 45, 90, 135 and 180kg/ha in early spring. Lodging was less in 45cm of drill width than in 15 and 30cm and was not severe by 90kg per ha of nitrogen including 45cm of drill width. Number of panicles per $1\m^2$ was tended to be more in 15cm of drill width than in 30 or 45cm. Among 45cm of drill widths. 45kg per ha of nitrogen had most numerous panicles. Panicle length, number of 1st branch, weight of 1,000 grain, and germination of 30 or 45cm of drill width showed better characters than that of 15cm. Seed yield was not statistical different among the treatments but was some more in 30cm of drill width, and was tended not to be different among nitrogen levels. Therefore, considering lodging tolerances, seed yield components, and mechanizations, treatment with 45cm of drill width including 45kg per ha of nitrogen in early spring was better than other treatments for orchardgrass seed production.