• Journal of the Semiconductor & Display Technology
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• v.5 no.1 s.14
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• pp.13-16
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• 2006

AIN thin films were prepared on amorphous glass and $SiO_2(1{\mu}m)/Si(100)$ substrate by the facing targets sputtering (FTS) apparatus, which can provide high density plasma, a high deposition rate at a low working gas pressure. The AIN thin films were deposited at a different nitrogen gas flow rate ($1.0{\sim}0.3$) and other sputtering parameters were fixed such as sputtering power of 200w, working pressures of 1mTorr and AIN thin film thickness of 800 nm, respectively. The thickness and crystallographic characteristics of AIN thin films as a function of $N_2$ gas flow rate $[N_2/(N_2+Ar)]$ were measured by $\alpha$-step and an X-ray diffraction (XRD) instrument. And the c-axis preferred orientations were evaluated by rocking curve. In the results, we could prepared the AIN thin film with c-axis preferred orientation of about $5^{\circ}$ on substrate temperature R.T. at nitrogen gas flow rate 0.7.

• 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 Society of Environmental Restoration Technology
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• v.6 no.6
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• pp.41-48
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• 2003

Nitrogen removal rate and emergent plant growth were investigated of a free-water-surface constructed treatment wetland system, whose dimensions were 31m in length and 12m in width. The system was constructed on floodplain in the Kwangju Stream from May to June 2001. Cattails(Typha angustifolia) were transplanted from natural wetlands and their stems were cut at about 40cm height from their bottom ends. Water of the Kwangju Stream were funneled into the system by gravity flow and its treated effluent was discharged back into the stream. The average height of the cattail stems was 45.2cm in July 2001 and 186cm in October 2001. The number of stems averaged 22 stems/$m^2$ in July 2001 and 52 stems/$m^2$ in September 2001. Volume and water quality of inflow and outflow were analyzed from July 2001 through December 2001. Inflow and outflow averaged 40.01 and 39.55 $m^3$/day, respectively. Hydraulic detention time was about 1.5 days. Average nitrogen uptake by cattails was 69.31 $N\;mg\;m^{-2}\;day^{-1}$. Removal rate of $NO_3-N$, $NH_3-N$ and T-N averaged 195.58, 53.65 and 628.44 $mg\;m^{-2}\;day^{-1}$, respectively. The average removal rate of T-N was about 39%.

• Journal of environmental and Sanitary engineering
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• v.13 no.1
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• pp.26-31
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• 1998

Removal of nitrogen and phosphate in wastewater is concerned to important for the prevention of eutrophication in receiving water and lake. Conventional activated sludge system designed for organics removal can be retrofitted only by modification of aeration basin to maintain anaerobic and aerobic state. Biological nutrient removal processes(BNR) such as Bardenpho, A$^{2}$/O, UCT, VIP were generally used for the treatment of wastewater. However these BNR processes used in large scale WWTP were not suitable in small scale WWTP(i.e., package type WWTP) due to relatively large fluctuation of flow rate and concentration of pollutants. The purpose of this research was to develop the compact, effective and economical package type WWTP for the removals of carbon and nitrogen in small scale wastewater. Intermittently aerated activated sludge system (IADFAS) were investigated for removal of nitrogen in both domestic wastewater, Bardenpho process was also evaluated. Nitrogen removal of IAAS, IADFAS, Bardenpho were 75, 77 and 67%, respectively.

• Journal of Korean Society on Water Environment
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• v.22 no.2
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• pp.203-208
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• 2006

A continuous feed and cyclic draw SBR process was developed to overcome flow rate fluctuation and to maximize organic matters utilization efficiency for nitrogen and phosphorus removal. The developed SBR process was operated with two parallel reactors. Influent was supplied to one reactor which was not obligately aerated. At the same time, the other reactor was just aerated without supplying influent. In addition this mode was changed periodically. Cycle time was 6hr and aeration time ratio($t_{aer}/t_{total}$) was 0.33, respectively. $COD_{cr}$ and SS removal efficiencies of 95% or higher were achieved. Nitrogen removal was so greatly influenced by influent $COD_{cr}/T-N$ ratio. At influent $COD_{cr}/T-N$ ratio of 5.7, removal efficiencies of ammonia-N, T-N and T-P were 96%, 78% and 55%, respectively. Influent $COD_{cr}/T-N$ of 4 or higher ratio was necessary to achieve 60% or higher nitrogen removal. Organic matters of influent was efficiently utilized in denitrification reaction and consumed COD has a good correlation with removed T-N(about 6.5 mgCOD/mgTN). Continuous feed and cyclic draw SBR process could be one of alternative processes for the removal of nutrients in rural area where $COD_{cr}/T-N$ ratio was low and fluctuation of flow rate was severe.

• Asian Journal of Turfgrass Science
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• v.9 no.4
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• pp.265-273
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• 1995

This investigation is carried out to clarify the cycles of nitrogen in the grassland ecosystems of Zoysia japonica and a Miscanthus sinensis on Mt. Kwanak. The hasic differential equation for the rate of change of nitrogen storage is illustrated hy huild-up and turnover of organic nitrogen, particularly in the ecosystems. The turnover velocity fractions of nitrogen for the Z. japonica and M .sinensis grasslands were k= 0. 181 and k=0. 166, respectively. The times required to reach 50, 95 and 99 percent of the steady state levels and turnover values of nitrogen on the grassland floors were 3.85, 16.67 and 27.78 years in the Z japonica grassland and 4.08, 17.65 and 29.41 years in the M sinensis grassland. The amount of annual cycles of nitrogen are 560.2 g /$m^2$ in the Z.japonica grassland and 654.1 g /$m^2$ in the M. sinensis grassland. Key words : Zsysia japonica Alisca nthus sinensis, Mt. Kivanak, Nitrogen cycle.

• Journal of Korean Society on Water Environment
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• v.20 no.1
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• pp.86-92
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• 2004

Lab-scale experiments have been carried out to investigate ammonia stripping with a modified spray tower for removing ammonia nitrogen from swine wastewater. The operating conditions such as initial pH, temperature, air flow, hole size of distributor determining the diameter of water drops, and influent solids concentration were closely examined focusing on removal efficiency of ammonia. As a result of the experiment, in order to achieve high rate of ammonia removal by the air stripping system, the air flow rate must be supplied at high rate with sufficiently high initial pH, temperature. The optimum operating condition to meet the residual ammonia concentration of 300 mg/L was the initial pH of 11.0 at $35^{\circ}C$ with the air flow rate of 20 L/min. It also showed that the smaller hole size is, the higher removal rate of ammonia is expected. However, when used a small sized distributor (2 mm), the flooding problem at the upper column occurred due to clogging of the hole. With regard to the influent solids concentration, it was showed that the lower concentration of solids, the higher removal rate of ammonia. The removal of particulate materials in influent led to improve the removal efficiency of ammonia, rather than to control the operating condition including initial pH, temperature, and air flow. The empirical correlation between KLa and operating parameters would be driven as, $K_{La}=(0.0003T-0.0047){\cdot}G^{0.3926}{\cdot}L^{-0.5169}{\cdot}C^{-0. 1849}$. The calculated $K_{La}$ from proposed formula can be used effectively to estimate the optimum reaction time and to calculate the volume of modified spray tower system.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.236-236
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• 2011

Silicon oxynitride (SiON) was deposited for gas barrier film on polyethylene terephthalate (PET) using octamethylycyclodisiloxane (Si4O4C8H24, OMCTS) precursor by plasma enhanced chemical vapor deposition (PECVD) at low temperature. The ion flux and substrate temperature were measured by oscilloscope and thermometer. The chemical bonding structure and barrier property of films were characterized by Fourier transform infrared (FT-IR) spectroscopy and the water vapor transmission rate (WVTR), respectively. The deposition rate of films increases with RF bias and nitrogen dilution due to increase of dissociated precursor and nitrogen ion incident to the substrate. In addition, we confirmed that the increase of nitrogen dilution and RF bias reduced WVTR of films. Because, on the basis of FT-IR analysis, the increase of the nitrogen gas flow rate and RF bias caused the increase of the C=N stretching vibration resulting in the decrease of macro and nano defects.

• Transactions of the Korean hydrogen and new energy society
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• v.9 no.3
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• pp.93-100
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• 1998

The ortho-para $H_2$ catalytic conversion equipment has been developed to reduce the evaporation loss from stored liquid hydrogen. The ortho-para $H_2$ conversion heat is evaluated at liquid nitrogen temperature. This problem is of particular interest in the design of the ortho-para $H_2$ converter in a hydrogen liquefaction system. The ortho-para $H_2$ conversion equipment consists of a catalytic converter, a precooler, and a liquid nitrogen bath. 30-90 cc of $Fe(OH)_3$ are employed as a catalyst in the present converter. The conversion heat and conversion effectiveness are evaluated when mass flow rate of hydrogen is in the range of 0.05-l.6 g/min. It is found that the ortho-para conversion heat is increased while conversion effectiveness is decreased as the mass flow rate of hydrogen is increased. Both the ortho-para conversion heat and conversion effectiveness are increased with an increase in the amount of the catalyst.

• Journal of Energy Engineering
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• v.25 no.4
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• pp.152-158
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• 2016

Nitrogen oxide is generated by the chemical reaction of oxygen and nitrogen in higher temperature environment of combustion facilities. The NOx reduction equipment is generally used in the power plant or incineration plant and it causes enormous cost for the construction and maintenance. The flue gas recirculation method is commonly adopted for the reduction of NOx formation in the combustion facilities. In the present study, the computational fluid dynamic analysis was accomplished to elucidated the cold flow characteristics in the flue gas recirculation burner with coanda nozzles in the flue gas recirculation pipe. The inlet and outlet of flue gas recirculation pipes are directed toward the tangential direction of circular burner not toward the center of burner. The swirling flow is formed in the burner and it causes the reverse flow in the burner. The ratio of flue gas recirculation flow rate with the air flow rate was about 2.5 for the case with the coanda nozzle gap, 0.5mm and it was 1.5 for the case with the gap, 1.0mm. With the same coanda nozzle gap, the flue gas recirculation flow rate ratio had a little increase when the air flow rate changes from 1.1 to 2.2 times of ideal air flow rate.