• Korean Chemical Engineering Research
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• v.48 no.3
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• pp.391-396
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• 2010

In this research the characteristics of ammonia removal from malodorous waste-air were investigated under various operating condition of biofiilter packed with equal volume of rubber media and compost for the efficient removal of ammonia, representative source of malodor frequently generated at compost manufacturing factory and publicly owned facilities. Then the optimum conditions were constructed to treat waste-air containing ammonia with biofilter. Biofilter was run for 30 days(experimental frequency of 2 times/day makes 60 experimental times.) with the ammonia loading from $2.18g-N/m^3/h$ to $70g-N/m^3/h$ at $30^{\circ}C$. The ammonia removal efficiency reached almost 100% for I through IV stage of run to degrade up to the ammonia loading of $17g-N/m^3/h$. However the removal efficiency dropped to 80% when ammonia loading increased to $35g-N/m^3/h$, which makes the elimination capacity of ammonia $28g-N/m^3/h$ for V stage of run. However, the removal efficiency remained 80% and the maximum elimination capacity reached $55g-N/m^3/h$ when ammonia loading was doubled $70g-N/m^3/h$ for VI stage of run. Thus the maximum elimination capacity exceeded $1,200g-N/m^3/day$(i.e., $50g-N/m^3/h$) of the experiment of biofilter packed with rock wool inoculated with night soil sludge by Kim et al.. However, the critical loading did not exceed $810g-N/m^3/day$ (i.e., $33.75g-N/m^3/h$) of the biofilter experiment by Kim et al.. The reason to exceed the maximum elimination capacity of Kim et al. may be attributed to that the rubber media used as biofilter packing material provide the better environment for the fixation of nitrifying and denitrification bacteria to its surface coated with coconut based-activated carbon powder and well-developed inner-pores, respectively.

• Journal of the Korean Society of Safety
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• v.7 no.4
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• pp.101-104
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• 1992

It is shown that for a characteristic equation of continuous linear system, stability can be determined by conditions srggested in this paper. And also It Is of interest to Know how much coefficients of the low-order characteristic equation(N$\leq$5) can be perturbed while simutanously preserving the stable condition of the equation. This result is analogous to result by Anderson et al. based on the Kharitonov's conditions and Hermite - Biehler theorem.

• Journal of the Korean Ceramic Society
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• v.26 no.2
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• pp.235-241
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• 1989

A study on the APCVD(atmospheric pressure chemical vapor deposition) Al2O3 was done by using the aluminum-tri-isopropoxide/N2 reaction system at 40$0^{\circ}C$. When the flow rate of the carrier gas(N2) was over 2SLPM, heterogeneous reaction was observed. However, when the flow rate of the carrier gas was below 2SLPM, a porously deposited film or powder formation was observed. The film formed by a heterogeneous reaction was optically dense. The dense film is thought to be a kind of a hydrated alumina. After a thermal treatment of the film in the range of temperature from $600^{\circ}C$ to 1, 20$0^{\circ}C$, properties of the film seems to be changed due to dehydration and densification process. In the case of the powder on heat treatment(600~1, 20$0^{\circ}C$), both a phase transformation and the change of OH peak was observed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.205-206
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• 2005

PRAM (Phase change Random Access Memory) is one of the most promising candidates for next generation Non-volatile Memories. The Phase change material has been researched in the field of optical data storage media. Among the phase change materials, $Ge_2Sb_2Te_5$(GST) is very well known for its high optical contrast in the state of amorphous and crystalline. However, the characteristics required in solid state memory are quite different from optical ones. In this study, the structural properties of GST thin films with bottom electrode were investigated for PRAM. The 100-nm thick GST films were deposited on TiN/Si and TiAlN/Si substrates by RF sputtering system. In order to characterize the crystal structure and morphology of these films, we performed x-ray diffraction (XRD) and atomic force microscopy (AFM).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.165-165
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• 2010

AZO:H films were prepared by RF magnetron sputtering system with a AZO (2wt% $Al_2O_3$) ceramic target at a temperature of $150^{\circ}C$. The annealing treatments were carried out in hydrogen ambient for 1hr at a temperature of $400^{\circ}C$. The AZO:H films were etched with 1 % HCl. The influence of the properties of AZO:H films deposited in various working pressures is investigated. As a result, the AZO:H film deposited in 4mTorr showed excellent electrical property of $\rho=5.036{\times}10^{-4}{\Omega}cm$ and strongly oriented (002) peak. The transmittance in the wavelength of 450nm was above 80%. It can be used as front electrode for increasing efficiency of GaN LED.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.7
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• pp.8-16
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• 2010

In this paper, we investigated the effects of $O_2$ fraction on the properties of Al-doped ZnO (AZO) thin films prepared by radio frequency (RF) magnetron sputtering. Hall, photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS) measurements revealed that the p-type conductivity was exhibited for AZO films with an $O_2$ fraction of 0.9 while the n-type conductivity was observed for films with $O_2$ fractions in range of 0 - 0.6. PL and XPS also showed that the acceptor-like defects, such as zinc vacancies and oxygen interstitials, increased in films prepared by an $O_2$ fraction of 0.9, resulting in the p-type conductivity in the films. Hall results indicated that AZO films prepared by $O_2$ fractions in range of 0 - 0.6 can be used for electrode layers in the applications of transparent thin film transistor. We concluded from the X-ray diffraction analysis that worse crystallinity with a smaller grain size as well as higher tensile stress was observed in the films prepared by a higher $O_2$ fraction, which is related to incorporation of more oxygen atoms into the films during deposition. The study of atomic force microscope suggested that the smoother surface morphology was observed in films prepared by using $O_2$ fraction, which causes the higher resistivity in those films, as evidenced by Hall measurements.

• Nuclear Engineering and Technology
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• v.55 no.11
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• pp.4246-4251
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• 2023

The optimized design of a Neutron Activation Analysis (NAA) system, including Delayed Gamma NAA (DGNAA) and Prompt Gamma NAA (PGNAA), has been proposed in this research based on Mevex Linac with 5 MeV electron energy and 50 kW power as a neutron source. Based on the MCNPX 2.6 simulation, the optimized configuration contains; tungsten as an electron-photon converter, BeO as a photoneutron target, BeD₂ and plexiglass as moderators, and graphite as a reflector and collimator, as well as lead as a gamma shield. The obtained thermal neutron flux at the beam port is equal to 2.06 × 10⁹ (# /cm².s). In addition, using the optimized neutron beam, the detection limit has been calculated for some elements such as H-1, B-10, Na-23, Al-27, and Ti-48. The HPGe Coaxial detector has been used to measure gamma rays emitted by nuclides in the sample. By the results, the proposed system can be an appropriate solution to measure the concentration and toxicity of elements in different samples such as food, soil, and plant samples.

• Korean Chemical Engineering Research
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• v.51 no.2
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• pp.272-278
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• 2013

The hybrid system composed of a photocatalytic reactor and a biofilter was operated under various operating conditions in order to treat malodorous waste air containing ammonia which is a major air pollutant emitted from composting factories and many publicly owned treatment works. Total ammonia removal efficiency of the hybrid system was maintained to be ca. 80% even though its inlet loads were increased at a higher operating stage according to an operating schedule of the hybrid system. The ammonia removal efficiency of photocatalytic reactor was decreased from 65% to 22% as ammonia inlet loads to photocatalytic reactor were increased. In spite of same inlet loads of ammonia to the photocatalytic reactor, the ammonia removal efficiency of photocatalytic reactor with lower ammonia concentration of fed-waste air was higher than that with higher ammonia concentration of fed-waste air. To the contrary, during the first half of the hybrid system operation the ammonia removal efficiency of a biofilter was quite suppressed while, despite of increased ammonia inlet loads, the ammonia removal efficiency of the biofilter was continuously increased to 78% and reached the ammonia removal efficiency similar to what Lee et al. attained. The maximum ammonia elimination capacity of the photocatalytic reactor was observed to be ca. 16 g-N/$m^3$/h. In an incipient stage of hybrid system run, the ammonia elimination capacity of the biofilter showed little sensitivity against ammonia inlet loads to the hybrid system. However, in the 2nd half of its run, the ammonia elimination capacity of the biofilter was increased abruptly in case of high ammonia inlet loads to the hybrid system. In 6th stage of hybrid system run, total ammonia inlet load attained at ca. 80 g-N/$m^3$/h corresponding to 16 g-N/$m^3$/h of ammonia elimination capacity of the photocatalytic reactor. Then, the remaining ammonia inlet load to the 2nd and main process of the biofilter and its elimination capacity was expected and shown to be ca 64 g-N/$m^3$/h and ca 48 g-N/$m^3$/h, respectively. The ammonia elimination capacity of the biofilter was close to 1,200 g-N/$m^3$/day of the maximum elimination capacity of the investigation performed by Kim et al.

• Journal of Korea Water Resources Association
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• v.36 no.3 s.134
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• pp.495-505
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• 2003

Convective weather systems such as organized mesoscale convective systems (Mesoscale Convective Complex, MCC and Convective Cloud Clusters, CCC) and much weaker Disorganized Short-lived Convection (DSC) in the region of India and Nepal were analyzed using the Meteosat-5 IR imagery. The diurnal march and propagation of patterns of convective activity in the Himalayas and Northern Indian subcontinent were examined. Results indicate that infrared satellite images of Northern India and along the southern flank of the Himalayas reveal a strong presence of convective weather systems during the 1999 and 2000 monsoons, especially in the afternoon and during the night. The typical MCCs have life-times of about 11 hours, and areal extent about $300,000km^2$. Although the core of MCC activity remains generally away from the Middle Himalayan range, the occurrence of heavy precipitation events in this region can be directly linked to MCCs that venture into the Lesser Himalayan region and remain within the region bounded by $25^{\circ}-30^{\circ}N$. One principal feature in the spatial organization of convection is the dichotomy between the Tibetan Plateau and the Northern Indian Plains: CCCs and DSCs begin in the Tibetan Plateau in the mid-afternoon into the evening; while they are most active in the mid-night and early morning in the Gangetic Plains and along the southern facing flanks of the Himalayas. Furthermore, these data are consistent with the daily cycle of rainfall documented for a network of 20 hydrometeorological stations in Central Nepal, which show strong nocturnal peaks of intense rainfall consistent with the close presence of Convective Weather Systems (CWSs) in the Gangetic Plains (Barros et al. 2000).

• Earthquakes and Structures
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• v.22 no.3
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• pp.219-230
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• 2022

Knowing that the variability of soil properties is an important source of uncertainty in geotechnical analyses, we will study in this paper the effect of this variability on the seismic response of a structure within the framework of Soil Structure Interaction (SSI). We use the proposed and developed model (N2-ISS, Mekki et al., 2014). This approach is based on an extension of the N2 method by determining the capacity curve of the fixed base system oscillating mainly in the first mode, then modified to obtain the capacity curve of the system on a flexible basis using the concept of the equivalent nonlinear oscillator. The properties of the soil that we are interested in this paper will be the shear wave velocity and the soil damping. These parameters will be modeled at first, as independent random fields, then, the two parameters will be correlated. The results obtained showed the importance of the use of random field in the study of SSI systems. The variability of soil damping and shear wave velocity introduces significant uncertainty not only in the evaluation of the damping of the soil-structure system but also in the estimation of the displacement of the structure and the base-shear force.