• International Journal of Fluid Machinery and Systems
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• v.4 no.1
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• pp.33-46
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• 2011

Concave surface boundary-layer flows are subjected to centrifugal instability which results in the formation of streamwise counter-rotating vortices. Such boundary layer flows have been experimentally investigated on concave surfaces of 1 m and 2 m radius of curvature. In the experiments, to obtain uniform vortex wavelengths, thin perturbation wires placed upstream and perpendicular to the concave surface leading edge, were used to pre-set the wavelengths. Velocity contours were obtained from hot-wire anemometer velocity measurements. The most amplified vortex wavelengths can be pre-set by the spanwise spacing of the thin wires and the free-stream velocity. The velocity contours on the cross-sectional planes at several streamwise locations show the growth and breakdown of the vortices. Three different vortex growth regions can be identified. The occurrence of a secondary instability mode is also shown as mushroom-like structures as a consequence of the non-linear growth of the streamwise vortices. Wall shear stress measurements on concave surface of 1 m radius of curvature reveal that the spanwise-averaged wall shear stress increases well beyond the flat plate boundary layer values. By pre-setting much larger or much smaller vortex wavelength than the most amplified one, the splitting or merging of the streamwise vortices will respectively occur.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.3
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• pp.220-226
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• 2000

The piezoelectric material for piezoelectric transformer needs the high electromechanical coupling factor( $k_{p}$) the piezoelectric constant( $d_{33}$) and the mechanical quality factor( $Q_{m}$)in order to obtain high voltage step-up ratio and low temperature rising. In this study the piezoelectric transformers were fabricated using Pb［$Zr_{0.45}$/ $Ti_{0}$48//L $u_{0.02}$(M $n_{1}$3//S $b_{2}$3/)$_{0.05}$］ $O_3$(PMS-PZT) and Pb［Z $r_{0.25}$/ $Ti_{0.375}$(M $g_{1}$3//N $b_{2}$3/)$_{0.375}$］ $O_3$+0.5wt%Mn $O_2$(PMN-PZT) ceramics. The piezoelectric properties of PMS-PZT and PMN-PZT were measured. The voltage set-up ratios of the piezoelectric transformers using PMS-PZT and PMN-PZT were the value of 15, 20 respectively under 100$_{KΩ}$ in Rosen type transformer.r.ormer.r.r.r.r.r.r.

• 한국생물공학회:학술대회논문집
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• 2003.10a
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• pp.351-355
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• 2003

Response surface methodology was employed to study the interactive effect of sucrose, nitrogen, temperature and to optimize their levels to enhance the production of human granulocyte-macrophage colony-stimulation factor from Nicotiana tabacum cell suspension cultures. A 15-runs Box-Behnken design including three center points was the response surface method selected for the initial set of experiments. The analysis of the data from the Box-Behnken experiments showed interactive effects of sucrose:nitrogen, sucrose:temperature and nitrogen:temperature. The optimal combinations of sucrose, nitrogen and temperature for hGM-CSF production from surface plot were sucrose 90 g/L, nitrogen 41 mM and 22$^{\circ}C$, respectively. The optimization of there factors enhanced the hGM-CSF production by 2 times because high sucrose concentration stimulated the secretion of hGM-CSF and low temperature prevented hGM-CSF degradation in media by pretenses.

• Journal of Korean Society on Water Environment
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• v.25 no.6
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• pp.964-971
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• 2009

In this paper, activated sludge settling was characterized based on field trip and zone settling tests. Plants used for this study include 5 conventional activated sludge processes and 3 A2O type treatment processes. The treatment capacities are in the range from 12,000 to $250,000m^3$/day. Total number of zone settling tests were 188 set and SVI values representing settling characteristics were from 100 to 300 mL/g. It was found out that zone settling velocity of these examined plant sludges can be approximated by mean values calculated by Keinath and Daigger/Roper models. Based on these three models, solid flux analysis were carried out in order to compare design criteria ($3.96{\sim}6.04kg/m^2-hr$) recommended by Korea Sewage Facility Design Guideline with two models used in USA. The results show that design criteria are only applicable for normal condition in settling characteristics (below SVI 100 mL/g). Solid flux analysis of surveyed plants indicates that most of the plants are operated underload conditions except several plants experiencing poor sludge settling problem. Most of the plants are operated under high sludge blanket depths (SBD).

• Journal of Astronomy and Space Sciences
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• v.35 no.4
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• pp.227-233
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• 2018

This study presents the generation and accuracy assessment of predicted orbital ephemeris based on satellite laser ranging (SLR) for geostationary Earth orbit (GEO) satellites. Two GEO satellites are considered: GEO-Korea Multi-Purpose Satellite (KOMPSAT)-2B (GK-2B) for simulational validation and Compass-G1 for real-world quality assessment. SLR-based orbit determination (OD) is proactively performed to generate orbital ephemeris. The length and the gap of the predicted orbital ephemeris were set by considering the consolidated prediction format (CPF). The resultant predicted ephemeris of GK-2B is directly compared with a pre-specified true orbit to show 17.461 m and 23.978 m, in 3D root-mean-square (RMS) position error and maximum position error for one day, respectively. The predicted ephemeris of Compass-G1 is overlapped with the Global Navigation Satellite System (GNSS) final orbit from the GeoForschungsZentrum (GFZ) analysis center (AC) to yield 36.760 m in 3D RMS position differences. It is also compared with the CPF orbit from the International Laser Ranging Service (ILRS) to present 109.888 m in 3D RMS position differences. These results imply that SLR-based orbital ephemeris can be an alternative candidate for improving the accuracy of commonly used radar-based orbital ephemeris for GEO satellites.

• Korean Chemical Engineering Research
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• v.62 no.1
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• pp.87-98
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• 2024

This study was conducted to investigate the efficiency of the filtering sets composed of fiberboards, which were fabricated with lignocellulosic fiber and cork oak bark-based activated carbon (COA), as well as traditional Korean paper handmade from mulberry trees (KP) for the filtration of PM, TVOC and HCHO. Three-layers fiberboards (WRF) were fabricated with wood fiber in its surface layers and recycled fiber/COA in its core layer using a protein-based adhesive with the resin content of 8%. Filtering sets were composed of three WRF and one sheet of KP. Concentrations of PM, TVOC and HCHO generated with the combustion of a incense in a sealed laboratory hood were reduced efficiently with the operation of air-purifier installed the filtering sets. Except for the WRF fabricated with 4%/4% resin contents, other WRF were prepared with 5%/3% and 6%/2% resin contents in surface/core layers, and then the WRF were used with KP for the fabrication of filtering sets. Filtration efficiency of the filtering sets was improved as the core-layer resin content applied in the fabrication of WRF decreased. In addition, filtration efficiency of the WRF-based filtering set fabricated with KP of 25 g/m² basis weight was higher than that with KP of 45 g/m² basis weight. Filtering sets composed of three-layers fiberboards (RWF) that recycled fiber and wood fiber/COA were used in its surface and core layers, respectively, and KP-25g showed higher filtration efficiency than those of WRF-based filtering sets. Air-inhalation equipment installed the RWF-based, WRF-based filtering sets and without filtering set were operated in small indoor and large outdoor spaces. Efficiency for filtering PM and TVOC of the RWF-based filtering sets was higher than that of other filtering sets. It is concluded that fiberboard-based filtering sets composed of RWF and KP-25g can be used as a filter for reducing the concentrations of PM and TVOC existed in indoor and outdoor spaces.

• Journal of Korean Society for Atmospheric Environment
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• v.27 no.1
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• pp.16-29
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• 2011

The cyclone/annular denuder system/filter pack sampling system (ADS) was used to collect data set of the acidic air pollutants in the vicinity of industrial complexes in Gwangyang. The data set was collected during sixty different days with 24 hour sampling period from January 8, 2008 through November 12, 2008. The annual mean concentrations of $HNO_3$, $HNO_2$, $SO_2$ and $NH_3$ in the gas phase were 1.12, 1.40, 10.2 and 1.28 ${\mu}g/m^3$, respectively. The annual mean concentrations of $PM_{2.5}$ ($d_p$<2.5 ${\mu}m$), $SO_4^{2-}$, $NO_3^-$, and $NH_4^+$ in the particulate phase were 29.2, 8.25, 3.30 and 3.42${\mu}g/m^3$, respectively. $HNO_3$ and $NH_3$ exhibited higher concentrations during the summer, while $HNO_2$, $PM_{2.5}$, $NO_3^-$ and $NH_4^+$ were higher during the winter. The highest level of $SO_2$ was, unlikely, observed in the summer and $SO_4^{2-}$ was not showed seasonal variation. $SO_4^{2-}$, $NO_3^-$, and $NH_4^+$ accounted for 49~57% of the $PM_{2.5}$ mass. $SO_4^{2-}$ was the most abundant component, which constituted 23~40% of $PM_{2.5}$. High correlations were found among $PM_{2.5}$, $SO_4^{2-}$, $NO_3^-$, and $NH_4^+$.

• Korean Journal of Pharmacognosy
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• v.44 no.4
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• pp.362-367
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• 2013

Ojeok-san has been commonly used to treat low back pain disease. We performed the experiments on simultaneous analysis of 11 compounds and antioxidant effects of Ojeok-san. A HPLC method was established for simultaneous analysis of 11 compounds. The detection wavelengths were set at 230, 254, 280, 320, and 330 nm. The detected 11 compounds from Ojeok-san water extract showed good linearity($r^2{\geq}0.9997$). Limit of detection(LOD) and limit of quantification(LOQ) were 0.04-0.87 ${\mu}g/mL$ and 0.13-2.63 ${\mu}g/mL$, respectively. The antioxidant effects of Ojeok-san water extract were investigated by DPPH and ABTS assays. Ojeok-san water extract significantly increased the DPPH and ABTS radical scavenging effects in a dose-dependent manner. The $RC_{50}$ value of Ojeok-san on DPPH radical was 284.71 ${\mu}g/mL$ and that of ABTS radical was 96.16 ${\mu}g/mL$.

• Journal of Environmental Science International
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• v.24 no.10
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• pp.1273-1283
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• 2015

In present study, the temporal characteristics of nine selected volatile organic compounds (VOCs), including four alcohol, 2 aldehyde, and 3 ketone compounds, in high-stories urban apartments over a 2-y period were investigated. The indoor VOC concentrations had generally a decreasing trend over the 2-y follow-up period. For examples, the 2E1H indoor concentration decreased from $10.8{\mu}g/m^3$ for the first two months to $5.1{\mu}g/m^3$ for the last two months. In addition, the DCA and ACT indoor concentrations decreased from 5.0 and $14{\mu}g/m^3$ for the first two months to 2.2 and $6.4{\mu}g/m^3$, respectively, for the last two months. The indoor-to outdoor concentration ratios over the 2-y period were much greater than 1, indicating that indoor VOC concentrations were higher than the outdoor VOC concentrations. Similar to those of the individual VOCs, the indoor-to-outdoor concentration ratios of all three VOC groups were higher than 1 over the 2-y follow-up period, suggesting higher indoor concentrations of the three VOC groups than outdoor concentrations. In consistence with the results of VOC indoor concentrations, the VOC emission rates decreased gradually as time passed, due to the decreased VOC emission strengths of indoor sources. Finally, there was an initial sharp decrease in the indoor VOC concentrations followed by a slower decrease, indicating a multi-exponential decay model for the target VOCs, which was demonstrated by comparison of the residuals and the adjusted coefficient of determination associated with the one and two-exponential fits of each data set.

• Genomics & Informatics
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• v.15 no.2
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• pp.56-64
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• 2017

We have previously reported that NS-398, a cyclooxygenase-2 (COX-2)-selective inhibitor, inhibited replicative cellular senescence in human dermal fibroblasts and skin aging in hairless mice. In contrast, celecoxib, another COX-2-selective inhibitor, and aspirin, a non-selective COX inhibitor, accelerated the senescence and aging. To figure out causal factors for the senescence-modulating effect of the inhibitors, we here performed cDNA microarray experiment and subsequent Gene Set Enrichment Analysis. The data showed that several senescence-related gene sets were regulated by the inhibitor treatment. NS-398 up-regulated gene sets involved in the tumor necrosis factor ${\beta}$ receptor pathway and the fructose and mannose metabolism, whereas it down-regulated a gene set involved in protein secretion. Celecoxib up-regulated gene sets involved in G2M checkpoint and E2F targets. Aspirin up-regulated the gene set involved in protein secretion, and down-regulated gene sets involved in RNA transcription. These results suggest that COX inhibitors modulate cellular senescence by different mechanisms and will provide useful information to understand senescence-modulating mechanisms of COX inhibitors.