• Journal of the Korean Society of Industry Convergence
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• v.6 no.4
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• pp.277-289
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• 2003

This study proposes a mathematical model to characterize the removal of nitrogen oxides in a dielectric barrier discharge plasma process. As well as the reactions between nitrogen oxides, water vapor, oxygen and nitrogen, the model takes into account the effect of ethylene often used as a chemical additive to reduce the power consumption of the process on the removal of nitrogen oxides. Since the concentrations of the radicals concerned in the main reactions including O, OH, H and N should be calculated to predict the removal efficiency of nitrogen oxides, they were theoretically derived. The parameters affecting the removal of nitrogen oxides, such as initial concentration, discharge power, humidity, and ethylene concentration were experimentally evaluated, which were compared with the calculated results to verify the validity of the model proposed. The predicted concentrations of several byproducts formed in this process were also presented and discussed. The effects of several parameters mentioned above on the removal of nitrogen oxides were reasonable described by the proposed model.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.1262-1262
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• 2001

The rice plant is one of the important staple crops in Korea. The high yield with low cost in rice is required the soil fertility and the development of new precise method of fertilizer application by nutritional diagnosis. Now, in Korea, the nitrogen application system for the rice plant is composed of the basal fertilization, fertilization at tillering stage and fertilization at panicle stage, which the nitrogen fertilization at panicle stage amount to about 30 percent in the total amount. Thus, this experiment carried out to the development of the system that can measure the nitrogen content in the rice plant at panicle stage rapidly with the near infrared spectroscopy, and to predict the appropriate quantity of the nitrogen fertilization at panicle stage based on calibration model for test of nitrogen content in rice plant. The samples were collected from 48 varieties in 4 regions which are mainly cultivated in the southern part of Korea. And then, it collected by classifying into the leaf, the whole plant and the stem since 7 days before the nitrogen fertilization at panicle stage. The ranges of the nitrogen contents were 1.6∼4.0%, 1.7∼3.0% and 1.4∼2.7% in the leaf, the whole plant and the stem, respectively. In the calibration models created by each part of the plant under the Multiple Linear Regression(MLR) method, the calibration model for the leaf recorded the relatively high accuracy. The mutual crossing test on unknown samples were carried out using Partial Least Square(PLS) calibration model. That is, the nitrogen content in the stem was tested by calibration model made by the leaf model and that of stem was tested by calibration model made by whole plant sample. When unknown leaf sample was tested by calibration model made by all sample that collected from each part in rice plant such as leaf, stem and whole plant, it recorded the highest accuracy. As a result, to test the nitrogen content in the rice plant at panicle stage, the nitrogen content in the leaf shall be tested by the calibration model composed of the leaf, the stem and the whole plant. In future, to estimated the amount of nitrogen fertilization at panicle stage for rice plant , it will be calculated based on regression model between rice yield and nitrogen content of leaf measured by calibration model made by mixed sample including leaf, stem and whole plant.

• Korean Journal of Organic Agriculture
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• v.25 no.4
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• pp.805-819
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• 2017

The study was carried out to develop a mathematical model for evaluating the effect of organic fertilizers in organic rice production systems. A function to simulate the nitrogen mineralization process in the paddy soil has been developed and integrated into ORYZA2000 crop growth model. Inorganic nitrogen in the soil was estimated by single exponential models, given temperature and C:N ratio of organic amendments. Data collected from the two-year field experiment were used to evaluate the performance of the model. The revised version of ORYZA2000 provided reasonable estimates of key variables for nitrogen dynamics and crop growth in the organic rice production systems. Coefficient of determination between the measured value and simulated value were 0.6613, 0.8938, and 0.8092, respectively for soil inorganic nitrogen, total dry matter production, and rice yield. This means that the model could be used to quantify nitrogen supplying capacity of organic fertilizers relative to chemical fertilizer. Nitrogen dynamics and rice growth simulated by the model would be useful information to make decision for organic fertilization in organic rice production systems.

• Journal of Biosystems Engineering
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• v.42 no.2
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• pp.98-103
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• 2017

Purpose: Precision agriculture includes determining the right amount of nitrogen for a specific location in the field. This work focused on developing and validating a model using variable rate nitrogen application based on the estimated SPAD value from the ground-based image sensor. Methods: A variable rate N application based on the decision making system was performed using a sensor-based variable rate nitrogen application system. To validate the nitrogen application decision making system based on the SPAD values, the developed N recommendation was compared with another conventional N recommendation. Results: Sensor-based variable rate nitrogen application was performed. The nitrogen deficiency level was measured using the image sensor system. Then, a variable rate application was run using the decision model and real-ti me control. Conclusions: These results would be useful for nitrogen management of corn in the field. The developed nitrogen application decision making system worked well, when considering the SPAD value estimation.

• Journal of the Korean Applied Science and Technology
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• v.22 no.1
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• pp.62-70
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• 2005

Step-feed process for biological nitrogen removal were analyzed numerically for the each unit and final total nitrogen(TN) effluent by water quality management(WQM) model and the results were compared data from these wastewater treatment plants. No bugs and logic error were occurred during simulation work. All of the simulation results tried to two times were obtained and both results were almost same as this model has become good reappearance. It was concluded that most of nitrogen removal occurred in the first oxic tank. Thus the controlling of the first anoxic tank may be more important in term of nitrogen removal. Also each unit of simulation result was kept good relationship with that of measured data. Accordingly this WQM model has good reliance. Finally, WQM model can predict final TN effluent within ${\pm}6.0mg/{\ell}$.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.4
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• pp.1-15
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• 2017

Eutrophication of surface waters is of concern worldwide, because it can result in many undesirable water-quality and ecological problems, such as hypoxic 'dead' zones and harmful algal blooms, both associated with considerable economic costs. In this study, we used LSM (Land Surface Model) to simulate nitrogen in five major rivers in the Southern Korean Peninsula. The main objective of this research was to enhance nitrogen data for input of LM3V model in South Korea. Input data for nitrogen fluxes were categorized into three sections including agriculture fertilizer, livestock manure, atmosphere deposition, biological fixation, and sewage pollutants were used as the nitrogen input. For using LM3V model, the nitrogen input data were regenerated by considering states of agriculture and industry in South Korea at a $1/8^{\circ}$ resolution. Then, we simulated stream/river flows and N loads throughout the entire drainage networks in South Korea at a $1/8^{\circ}$ resolution. By using the same parameters for the entire country ($100,210km^2$), composed of 5 river basins with varying climate and land use, the model simulates spatial (11 sites) and temporal (1999~2010) patterns of flows and nitrate-N loads are resonable by comparing observed flow and nitrate-N loads. The r (Pearson's linear correlation) for water temperature, flow and nitrate-N at river were 080~0.93, 0.62~0.92 and 0.5~0.9 respectively. Based on enhanced N input data and model results, we find that LM3V model as land surface model can be applied in South Korea with interaction of atmosphere and land conditions.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.04a
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• pp.195-198
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• 2002

Nitrogen pollution in urban and rural groundwater is a common problem and poses a major threat to drinking water supplies based on groundwater. In this work, the kinetics of nitrification-denitrification coupled reactions are modeled and new reaction modules for the RT3D code (Clement, 1997) describing the fate and transport nitrogen species, dissolved oxygen, dissolved organic carbon, and biomass are developed. The proposed nitrogen transformations and transport model showed very good match with results of a conceptual model. However, the model simulation results for the major reactive species should be tested for validation using experimental and field data.

• Journal of Welding and Joining
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• v.33 no.3
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• pp.68-74
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• 2015

Superduplex stainless steels are important materials to the oil and gas industry, especially for off-shore production. TIG welding of super duplex stainless steels to obtain the optimal phase balance between austenite and ferrite is mainly achieved by controlling the cooling rate and the weld chemistry. The latter depends on the filler wire chosen and the shielding gas used. If TIG welding of superduplex stainless steels is performed with argon shielding gas only, then nitrogen gets lost from the weld pool, which can result in a ferrite-rich weld metal, with an inferior corrosion resistance than parent metal. In the present study, nitrogen permeation model from the shield gas which gets into the weld metal in DCEN-TIG welding has suggested. This plasma stream model shows characteristics of permeation of nitrogen ions into the molten metal due to the strong physical effect of plasma stream which formed by the arc pressure rather than the permeation of nitrogen ions caused by electric effect.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.430-433
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• 2003

Nitrogen pollution in urban and rural groundwater is a common problem and poses a major threat to drinking water supplies based on groundwater. In this work, the kinetics of nitrification-denitrification coupled reactions are modeled and new reaction modules for the RT3D code describing the fate and transport of nitrogen species, dissolved oxygen, dissolved organic carbon, and biomass are developed and tested. The proposed nitrogen transformations and transport model showed very good match with the results of other public codes.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.320-329
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• 2008

The influence of thermodynamic transition associated with transcritical nitrogen injection upon the flow structure was investigated to explore numerical simulation of the injectant dynamics of oxygen/hydrogen coaxial jet in liquid rocket engines. Single and coaxial nitrogen jets were treated by comparing the transcritical and perfect-gaseous conditions, wherein the numerical model was accommodative to the real-fluid thermodynamics and transport properties at supercritical pressures. The model was in the first place validated by comparing the results of transcritical nitrogen injection between calculations and available experiments. For a single jet under the transcritical condition, the nitrogen kept a relatively high density up to its pseudo-critical temperature inside the mixing layer, since it remains less expanding until heated up to its pseudo-critical temperature. Numerical analysis revealed that cryogenic jets exhibit strong dependence of specific enthalpy profile upon the associated density profile that are both dominated by turbulent thermal diffusion. In the numerical model, therefore, exact evaluation of turbulent heat fluxes becomes very important for simulating turbulent cryogenic jets under supercritical pressures. Concerning the coaxial jets due to transcritical/gaseous nitrogen injections, the density profile inside the mixing layer was again affected by the thermodynamic transition of nitrogen. However, hydrodynamic instability modes of the inner jet did not show significant differences by this thermodynamic transition, so that further study is needed for the mixing process downstream of the near injection position.