• Proceedings of the Korean Society of Organic Agriculture Conference
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• 2011.06a
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• pp.117-127
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• 2011

The paper outlines farming systems, including organic, in the UK, and provides a context for the use of biological nitrogen (N) from legumes, especially clovers, and manure in organic grassland systems. As N is dynamic within organic ruminant/grassland systems its pathway is described, including its loss and resultant environmental impact. Improvements in the predictability of response to biological N, its role in reducing the carbon footprint of ruminant products and potential to improve its efficiency are discussed.

• Korean Chemical Engineering Research
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• v.45 no.1
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• pp.73-80
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• 2007

This article aims to optimize the nitrogen removal of a sequencing batch reactor (SBR) through the use of the activated sludge model and iterative dynamic programming (IDP). Using a minimum batch time and a maximum nitrogen removal for minimum energy consumption, a performance index is developed on the basis of minimum area criteria for SBR optimization. Choosing area as the performance index makes the optimization problem simpler and a proper weighting in the performance index makes it possible to solve minimum time and energy problem of SBR simultaneously. The optimized results show that the optimal set-point of dissolved oxygen affects both the total batch time and total energy cost. For two different influent loadings, IDP-based SBR optimizations suggest each supervisory control of batch scheduling and set-point trajectory of dissolved oxygen (DO) concentration, and can save 20% of the total energy cost, while meeting the treatment requirements of COD and nitrogen. Moreover, it shows that the re-optimization of IDP within a batch can solve the modelling error problem due to the influent loading changes, or the process faults.

• Korean Journal of Agricultural Science
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• v.48 no.4
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• pp.787-796
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• 2021

Nitrogen (N) is the most important element during the process of plant growth, and the quality of crops varies depending on the amount of nitrogen present. Most of the nitrogen is used for plant growth, but approximately 10 - 20% of Nitrogen is carried away by the wind in the form of NH₃. This volatilized NH₃ reacts with various oxides in the atmosphere to generate secondary particulate matter. To address this, the present study attempts to reduce NH₃ occurring in the soil using biochar at a specific pH. Biochar was used as a treatment with 1% (w·w^-1) of the soil, and urea was applied at different levels of 160, 320, and 640 kg·N·ha^-1. NH₃ generated in the soil was collected using a dynamic column and analyzed using the indophenol blue method. NH₃ showed the maximum emission within 4 - 7 days after the fertilizer treatment, decreasing sharply afterward. NH₃ emission levels were reduced with the biochar treatment in all cases. Among them, the best reduction efficiency was found to be approximately 25% for the 320 kg·ha^-1 + pH 6.7 biochar treatment. Consequently, in order to reduce the amount of NH₃ generated in the soil, it is most effective to use pH 6.7 biochar and a standard amount (320 kg·N·ha^-1) of urea.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.7
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• pp.576-582
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• 2002

Nonvolatile semiconductor memory devices with reoxidized nitrided oxide(RONO) gate dielectrics were fabricated, and nitrogen distribution and bonding species which contribute to memory characteristics were analyzed. Also, memory characteristics of devices depending on the anneal temperatures were investigated. The devices were fabricated by retrograde twin well CMOS processes with $0.35\mu m$ design rule. The processes could be simple by in-situ process in growing dielectric. The nitrogen distribution and bonding states of gate dielectrics were investigated by Dynamic Secondary Ion Mass Spectrometry(D-SIMS), Time-of-Flight Secondary Ion Mass Spectrometry(ToF-SIMS), and X-ray Photoelectron Spectroscopy(XPS). As the nitridation temperature increased, nitrogen concentration increased linearly, and more time was required to form the same reoxidized layer thickness. ToF-SIMS results showed that SiON species were detected at the initial oxide interface which had formed after NO annealing and $Si_2NO$ species within the reoxidized layer formed after reoxidation. As the anneal temperatures increased, the device showed worse retention and degradation properties. It could be said that nitrogen concentration near initial interface is limited to a certain quantity, so the excess nitrogen is redistributed within reoxidized layer and contribute to electron trap generation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.17-20
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• 2001

Nonvolatile semiconductor memory devices with reoxidized nitrided oxide(RONO) gate dielectric were fabricated, and nitrogen distribution and bonding species which contributing memory characteristics were analyzed. Also, memory characteristics of devices according to anneal temperatures were investigated. The devices were fabricated by 0.35$\mu\textrm{m}$ retrograde twin well CMOS processes. The processes could be simple by in-situ process of nitridation anneal and reoxidation. The nitrogen distribution and bonding state of gate dielectric were investigated by Dynamic Secondary Ion Mass Spectrometry(D-SIMS), Time-of-Flight Secondary ton Mass Spectrometry(ToF-SIMS), and X-ray Photoelectron Spectroscopy(XPS). Nitrogen concentrations are proportional to nitridation anneal temperatures and the more time was required to form the same reoxidized layer thickness. ToF-SIMS results show that SiON species are detected at the initial oxide interface and Si$_2$NO species near the new Si-SiO$_2$ interface that formed after reoxidation. As the anneal temperatures increased, the device showed worse retention and degradation properties. These could be said that nitrogen concentration near initial interface is limited to a certain quantity, so excess nitrogen are redistributed near the Si-SiO$_2$ interface and contributed to electron trap generation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.139-141
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• 2007

Compression tests were carried out to investigate morphologies of compressed specimen, deformation microstructure and stress-strain relation in high-nitrogen austenite stainless steel. Tests were performed under a wide range of temperature and, with true strain rates up to $\dot{\varepsilon}$ =0.05, 0.1, 0.5 and $1.0s^{-1}$. The activation energy of loading force was equal to plastic deformation energy within the temperature range of $900^{\circ}C$ to $1250^{\circ}C$. Dynamically recrystallized grain size decreased with an increasing strain rate and temperature. Flow stresses and deformation microstructures, were used to quantify the critical strain rate and recrystallized grain size. The grain size versus strain rate-temperature map obtained in the study was in good agreement with the deformation microstructures of compressed specimens.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.4
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• pp.321-326
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• 1998

Electrical breakdown characteristics of liquid nitrogen($LN_2$) taking into consideration for application of high $T_c$ superconductor is very important. Also $LN_2$ will be used as both coolant and insulator in superconducting generator. In this paper, we investigated ac breakdown characteristics of cryogenic nitrogen gas above a $LN_2$ for rod-to plane electrode configuration. As result the breakdown mechanism of $LN_2$is dependence on bubble effect. And breakdown voltage is a ratio on bubble s size but electrodes arrangement is to make no difference. The breakdown voltage decreases slightly with increasing flow velocity, it again decreases abruptly with increasing flow velocity. These results were interpreted as the within pressure of rod electrode and Maxwell force.

• Journal of Environmental Science International
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• v.17 no.11
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• pp.1265-1271
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• 2008

Aerated submerged bio-film (ASBF) pilot plant has been developed. The presented studies optimized an inexpensive method of enhanced wastewater treatment. The objectives of this research were to describe pilot scale experiments for efficient removal of dissolved organic and nitrogen compounds by using ASBF reactor in plug-flow reactor (PFR) and improve understanding of dissolved organic matter and nitrogen compounds removal rates with dynamic relationships between heterotrophs and autotrophs in the fixed-film reactor. This research explores the possibility of enhancing the performance of shallow wastewater treatment lagoons through the addition of specially designed structures. This direct gas-phase contact should increase the oxygen transfer rate into the bio-film, as well as increase the micro-climate mixing of water, nutrients, and waste products into and out of the bio-film. This research also investigated the efficiency of dissolved organic matter and ammonia nitrogen removals in the ASBF. As it was anticipated, nitrification activity was highest during periods when the flow rate was lower, but it seemed to decline during times when the flow rate was highest. And ammonia nitrogen removal rates were more sensitive than dissolved organic matter removal rates when flow rates exceeded 2.2 L/min.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.1
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• pp.23-28
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• 1999

Electrical breakdown characteristics of liquid nitrogen($LN_2$) used as both coolant and insulator for high $T_c$ superconductor system are very important. This paper presents dynamic breakdown characteristics fo $LN_2$ by quench phenomena of thermal bubble under high electric field. Experimental results revealed dynamic breakdown voltage fell down drastically compared with the static breakdown voltage without the quench. Because of increasing heat power, bubble size becomes big and breakdown voltage decreases. The breakdown voltage mechanism of $LN_2$ depends on thermal bubble effect. In the Electrode arrangement, electrical breakdown voltage of horizontal arrangement appears lower than that of vertical arrangement. Also, we observed the behavior of thermal bubbles in $LN_2$ which were generated after quench using camera.

• Progress in Superconductivity and Cryogenics
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• v.12 no.1
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• pp.61-65
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• 2010

To develop the thermal analysis method for the thermal behavior of HTS power cable system, cooled with sub-cooled liquid nitrogen, new thermo dynamic model for HTS cable system is introduced. The introduced thermal model is mainly modified from the thermal circuit following to IEC60287 for underground power cable systems such as XLPE or paper wrapped insulation cables. The thermal circuits for HTS cables are similar to the forced cooled underground cable system but the major thermal parameters and the configuration is apparently different to the normal cable systems so there has been no proposals in this field of analysing method. In this paper, 154kV HTS cable system has been introduced as an aspects of thermal models and a thermal circuit is proposed for the fundamentals on the dynamic rating systems for the HTS cable system. By using the thermal circuit developed in this paper, the optimal controls on the sub-cooling system's capacity become possible and it is expected to make the efficiency of HTS cable higher than conventional static controls.