• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.2 no.1
• /
• pp.33-44
• /
• 1982

In Order to study for the aeration characteristics which is one of the most important unit processes for the activated sludge process, a pitched blade type aeration model of octagonal shape with a draft tube in it was made as a pilot plant. Oxygen transfer rates, power consumptions and fluid velocities and behaviers were measured and evaluated with the various turbine shapes. And with these results, the dimensionless model analysis using the Buckingham ${\pi}$ theorem was discussed for a proper turbine shape determination.

• Journal of Korean Society of Water and Wastewater
• /
• v.22 no.4
• /
• pp.413-420
• /
• 2008

In order to utilize cinder melting slag as a filter media to control the quality of early rainwater, its environmental stability was verified by heavy metal elution experiment and improved by pre-treatment. Possibilities of improving its function as an absorbent was considered. Absorption characteristics of melting slag before and after the pre-treatment were analyzed by heavy metal equilibrium and stationary-phase column experiments, which in turn were analyzed by comparison experiment with activated carbon. As a result of heavy metal elution experiment, every metal item existed in a much lower amount than the criteria or was not detected, implying that there is no problem recycling it. Absorption equilibrium experiment showed that the time for pre-treatment melting slag to reach the equilibrium was reduced, while the absorbed amount was greatly increased. Stationary-phase column experiment assures us that the elimination rate was not changed much by influx rate, pH and the change in packing volume rate, indicating that this melting slag can be used not only as a filter media to control the quality of early rainwater but also in many areas of water-processing.

• Polymer(Korea)
• /
• v.30 no.2
• /
• pp.182-186
• /
• 2006

Due to their periodic helical structure, cholesteric liquid crystals (CLC) have a unique ability to selectively reflect light. CLC films reflecting a broad wavelength band were prepared by inducing a pitch gradient in CLC layer through a phase separation. The reflection bandwidth of the CLC cell was broaden as irradiation light intensity decreased and as the amount of the UV absorbing dye increased. Initial reflection bandwidth of 50 nm was broaden to 300 nm Various pitch distributions in the CLC cell was observed using SEM and ATR-IR technique was used to prove that the pitch distributions are induced through the phase separation.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.14 no.2
• /
• pp.367-378
• /
• 1994

The wastewater treatment characteristics of the fluidized bed filled with sand media and intermediately aerated were studied experimentally, and the obtained results were as follows; 1. The formations of biofilm on the media were greatly affected by the recirculation velocities. 2. Under the experimental condition that BOD loading rate was $4.2kg-BOD_5/m^3{\cdot}d$, the optimum media concentration was $261kg/m^3$ and the optimum recirculation velocity 1.35 cm/sec. 3. For the effluent quality of 20 mg-BOD/l and 20 mg-SS/l, the maximum allowable loading rate was about $8kg-BOD_5/m^3{\cdot}d$. 4. The dry density of biofilm was about 5.6% regardless of the filled media quantities and recirculation velocities. 5. Under the experimental conditions, the effluent solids concentration was below 20 mg/l, and the elimination of final clarifier can be expected.

• Journal of Science of Art and Design
• /
• v.6
• /
• pp.5-32
• /
• 2004

Kim Hwan-ki's New York Period works consistently present, as the central signifier, a curvilinear paradigm which has been derived from his creative consciousness. The purpose of this study is to bring to light what exists behind curvilinear paradigms; a fusion of history and society with the artist's individual consciousness as a fused aspect of history and society. To make this aspect suitably understood, this study focuses on curvilinear signifier which are analyzed and considered objectively. The results of which are as follows: It is a representative example of transforming a curved line which is the modern quotation of traditional Korean art, most directly works done in porcelain. He takes the aesthetic consciousness of Korean art as the power of his works and takes aim at the collective consciousness of all races. Looking through the background of his times, his artistic subject was to find the ethic characteristics of our excellent tradition and highlight them in his art. To him, art is not about making the most of a skill but instead about allowing one's inner spirit sing it's own song. This thought is conveyed in curvilinear signifier of his works. Therefore this study has asserted that Kim Hwan-ki's curvilinear signifier in his New York Period works has strong ties to the cultural vein of Korean history and society at it's base as well as simply in his individual level. This assertion is not to set form in a superior position as a Formalist but to show form as having the will to deal with the significance of an artist's mode by interpreting the experience of the interpreter.

• Journal of Environmental Impact Assessment
• /
• v.17 no.4
• /
• pp.243-253
• /
• 2008

The purpose of this study was to simulate the reduction effect of soil loss in the Yongdam reservoir watershed using SWAT model. To evaluate accuracy for flow and sediment yield of SWAT model, calibration was performed for the period from Jan. 2002 to Dec. 2003, and the verification for Jan. 2005 to Dec. 2005. The calibration and the verification were carried out using data observed at the Cheoncheon gaging station. The $R^2$ and EI values in terms of a flow were 0.8 and 0.78 respectively for calibration, whereas they for verification were 0.88 and 0.86 respectively. In terms of a sediment yield, they were 0.7 and 0.48 respectively for calibration, whereas for verification were 0.64 and 0.54 respectively. As a results from model simulation, annual mean soil loss rates in terms of forest, paddy and upland were 0.02 ton/ha/yr, 0.15 ton/ha/yr and 7.58 ton/ha/yr, respectively. The results show that the land use type of a upland has more significant impact on a total soil loss as well as a sediment yield than other types of land use. The sediment delivery ratio was determined to be about 0.35. In this study 2 land cover change scenarios for upland area were considered. These scenarios were used an input to SWAT model in order to evaluate their impact on soil loss and sediment delivery. The results show that a reduction of the upland area would reduce the soil loss and sediment yield.

• Polymer(Korea)
• /
• v.29 no.3
• /
• pp.308-313
• /
• 2005

The effects of molecular environments on photoisomerization of an azobenzene group were investigated using In-situ UV/Vis spectroscopy and optical anisotropy measurement technique. The reversible and repeatable photoisomeritation reactions of azobenzene were observed by irradiating the film containing 4-hydroxyazobenzene and by measuring absorption intensities of the characteristic bands of trans and cis isomers simultaneously. When the self-assembled monolayer with azobenzene groups was used as an alignment layer for a liquid crystal cell, the homeotropic alignment was induced due to their compact packing structures of azobenfene groups along the vertical direction of the substrate. By irradiating UV light on this cell, the trans-azobenzene groups change to cis-isomers through the photoisonlerieation and then resulting in the planar alignment of liquid crystal molecules.

• Polymer(Korea)
• /
• v.24 no.4
• /
• pp.513-519
• /
• 2000

The effect of petroleum resin as a tackifier for polyalphaolefin (APAO) hot melt adhesive on thermal properties, crystallinity and adhesion strength was investigated. The presence of petroleum resin resulted in the melting temperature decrease in APAO/petroleum blend, especially, in APAO with low ethylene content/C$_{5}$ petroleum blend. It was also found that petroleum resin caused the decrease of crystallinity regardless of ethylene content in APAO. The maximum adhesion strength was found to be at 50/50 (APAO/petroleum) composition. $C_{5}$ resin was more effective to increase adhesion strength than $C_{9}$ for APAO with high ethylene content. In addition, it was found that the adhesion strength was improved with the decrease of crystallinity in APAO/petroleum resin hot melts.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.9 no.4
• /
• pp.135-143
• /
• 1989

The experimental study on the shape and behavior of bubbles in U-tube deep shaft of 32m has been performed. According to the results in this paper, the equivalent spherical diameter of bubbles was 0.422-0.722cm and the shape of bubbles was almost ellipsoidal for bubbles to be generated ta single-orifice of diameter 0.06cm in the downcomer of the deep shaft system. Gas hold-up and gas-liquid contact area of bubbles in the deep shaft was decreased in accordance with depth, Also downcomer velocity of bubbles was slower than circulation velocity of liquid and riser velocity of bubbles was fast than circulation velocity. The bubble-size-distribution of bubbles in the deep shaft was the logarithmic probability distribution. The number of bubbles in the deep shaft was decreased in accordance with depth and the number of bubbles in the downcomer is more than the bubbles in the riser.

• Korean Journal of Optics and Photonics
• /
• v.28 no.2
• /
• pp.53-58
• /
• 2017

This paper presents the design and fabrication of a planar nano-diffraction grating for an integrated miniature spectrometer module. The proposed planar nano-diffraction grating consists of nonuniform periods, to focus the reflected beams from the grating's surface, and an asymmetrical V-shaped groove profile, to provide uniform diffraction efficiency in the wavelength range from 400 to 650 nm. Also, to fabricate the nano-diffraction grating using low-cost UV-NIL technology, we analyzed the FT-IR spectrum of a uvcurable resin and optimized the conditions for the UV curing process. Then, we precisely fabricated the polymeric nano-diffraction grating within 5 nm in dimensional accuracy. The integrated spectrometer module using the fabricated polymeric planar nano-diffraction grating provides spectral resolution of 5 nm and spectral bandwidth of 250 nm. Our integrated spectrometer module using a polymeric planar nano-diffraction grating serves as a quick and easy solution for many spectrometric applications.