• Korean Journal of Food Science and Technology
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• v.6 no.4
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• pp.231-240
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• 1974

The growth of a mixed yeast culture consisting of Canda tropicalis var. KIST 76 and Tricosporon cutaneum KIST 76-H was compared with that of pure cultures under pilot plant conditions. The mixed culture was judged stable based on the nearly constant ratio of the two organisms at the completion of fermentation. We obtained higher cell yields, protein content and productivity in the mixed culture on n-paraffin than the pure culture of C. tropicalis var. KIST 76. T. cutaneum KIST 76-H did not grow on n-paraffin medium. With the batch cultivation of mixed organisms on n-paraffin, the specific growth rates during the exponential growth phase were 0.24-0.33 $hr^{-1};$ cell yields were 96-106% and productivities were 2.9-3.6g/l. hr. The cells obtained contained 55-58% crude protein and 5.5-6.3% lipid. The critical value of dissolved oxygen concentration Ccrit. and saturation constant, km, are approximately 1.5 ppm and 0.228 ppm respectively. Also we established the optimal conditions for the mixed culture in batch fermentation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.600-608
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• 2016

This paper proposes a new high-efficient interleaved phase-shift full-bridge (PSFB) converter for low-voltage and high-current power systems. The proposed converter is composed of three switch-bridges and two transformers in the primary side and two rectifiers in the secondary side. Each transformer handles half of the total power with an interleaved operation, so that the proposed converter has high system reliability, as much as the conventional interleaved PSFB converter. The soft-switching characteristics of the proposed converter are better than those of the conventional converter due to the modulated primary side configuration. The proposed converter represents a single lagging-leg bridge, which has a poor soft switching condition in its operation, while the conventional converter has two lagging-leg bridges in its operation. Therefore, the number of switches having hard-switching conditions is reduced by half in the proposed converter. In addition, the reduced switch counts in the primary side of the proposed converter helps decrease the complexity of the proposed converter compared to that of the conventional converter. The operational principle and analysis are presented in this paper and the characteristics are verified using a PSIM simulation with 3kW server power specification.

• Resources Recycling
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• v.13 no.5
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• pp.45-50
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• 2004

To investigate the characteristics of phases formed in iron carbides, super iron carbide was synthesized from hematite fines with $CO-H_2$ gas mixture after reduction under $H_2$ gas at $600^{\circ}C$. Before carburization, the surface of iron powder reduced was pre-treated in the atmosphere of 0.05 vol% $NH_3$-Ar. The synthesized iron carbides were comprehensively explored by C/S analyzer(Low C/S determinator), M$\"{o}$ssbauer spectroscopy, X-ray diffraction patterns(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), and Raman spectroscopy at various reaction time of 5, 10, 15, 20, 25, 30, and 35 min, respectively. By adding a small amount of $NH_3$ gas, the super iron carbides containing 10 wt% carbon were synthesized, and its addition stabilized iron carbides. It was found that the $NH_3$ treatment played a major role in the formation of iron carbide without decomposition($Fe_3C{\to}$3Fe+C) of iron carbides and precipitation of free carbon. It also succeed to synthesize super iron carbide, $Fe_5C_2$, as a stable single phase without involving Fe and $Fe_3C$ phases.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.4
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• pp.36-48
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• 2008

Variable Message Signs(VMS) is one of the important subsystems of Intelligent Transportation Systems (ITS), which is useful for providing drivers with real-time information on traffic, roadway or weather conditions. In order to maximize the effectiveness of the VMS system, it is required to reflect drivers's preference on designing and operating the system. In this context, this study was conducted to develop strategies to deliver the messages in an efficient manner while many other previous studies focused primarily on the contents of the messages, from drivers's perspectives. Drivers's preference on message expression formats and message display orders were investigated through image analysis in the perspectives of a total of 40 subjects. With respect to message expression formats, drivers preferred Gulim or Dodum in font style, middle arrangement of the letters, pictogram combination as opposed to letters only, blank time less than 0.5 sec, appearing message in animation effect, messages in single phase, non-flashing message. In the matter of message display orders, drivers preferred to obtain link or traffic information in the lust place. Then, they desired to be informed of roadway condition and instructions or recommendations for drivers to cope with unexpected events among various messages for traffic condition.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.10
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• pp.1852-1857
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• 2007

The SSB modem performs the modulation process which converts the digital voltage level to the audible frequency band signal and the demodulation process which converts reversely the audible frequency signal to the digital voltage level. The modulator and the demodulator are implemented with a single DSP chip. Because of the SSB specific character, the distortion occurs when the frequency is changed. This distortion has no effect on voice communication but it has an significant effect on data communication. In other words, it is impossible to send data stream with adjacent 2 periods. Therefore, in case of using 2-tone FSK, it is needed to send at least 3 periods to transmit 1 bit. Therefore we implemented the modem using modified phase-delay shift keying to transmit 1 tone signal for high speed transmission. In the 1200[bps] mode, it generates 0, $187{\mu}s$, delay time at 1.3kHz symbol frequency, and in the 2400[bps] mode, 0, $70{\mu}s\;130{\mu}s\;200{\mu}s$, delay time at 1.5kHz symbol frequency. Finally, in the maximum 3600[bps] mode, it generates 0, $100{\mu}s\;160{\mu}s\;250{\mu}s$ 2.0kHz symbol frequency. The measured results of the implemented SSB modem shows a good transfer functional characteristic by spectrum analyzer, almost same bandwidth in pass band and 20dB higher SNR comparing the emu FACTOR and American CLOVER and in the experimental transmitting test, we verified the transmitted data is received correctly in platform.

• Solar Energy
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• v.15 no.2
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• pp.65-75
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• 1995

We have summarised some important aspects of our recent basic and applied studies in the area of photocatalytic detoxifcation with Degussa P25 titanium dioxide($TiO_2$) being the photocatalyst. Heterogeneousphotocatalytic decompositions of two components such as TCE-chloroform, TCE-phenol and TCE-benzene as well as single component organic, TCE, chloroform and $CCl_4$ were carried out to investigate the effect of additional compound on the TCE decomposition rate. In laboratory experiments, the optimum flow rate of TCE solution was $200cm^3/min$ with annular photoreactor in the presence of 0.1 wt% $TiO_2$ powder under illumination. It was observed that the second compound such as $CHCl_3$, phenol and benzene has a negative effect on the TCE decomposition rate. Result presented that TCE decomposition ratio was increased at low pH in the TCE-phenol two component solution. It could be shown that the photocatalytic reactor exhibits technical feasibility of detoxifying the multicomponent under proper experimental conditions.

• Journal of the Korean Magnetics Society
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• v.25 no.5
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• pp.156-161
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• 2015

The electronic structures of the potential candidate semiconductor nanoparticles for dye-sensitized solar cell (DSSC), such as $ZnSnO_3$ and $Zn_2SnO_4$, have been investigated by employing X-ray photoemission spectroscopy (XPS). The measured X-ray diffraction patterns show that $ZnSnO_3$ and $Zn_2SnO_4$ samples have the single-phase ilmenite-type structure and the inverse spinel structure, respectively. The measured Zn 2p and Sn 3d core-level XPS spectra reveal that the valence states of Zn and Sn ions are divalent (Zn 2+) and tetravalent (Sn 4+), respectively, in both $ZnSnO_3$ and $Zn_2SnO_4$. On the other hand, the shallow core-level measurements show that the binding energies of Sn 4d and Zn 3d core levels in $ZnSnO_3$ are lower than those in $Zn_2SnO_4$. This work provides the information on the valence states of Zn and Sn ions and their chemical bonding in $ZnSnO_3$ and $Zn_2SnO_4$.

• Journal of the Korean Magnetics Society
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• v.21 no.5
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• pp.157-162
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• 2011

The effect of ferrous/ferric molar ratio and precipitants on the formation of nano size magnetite particle was investigated by coprecipitation method. Ferrous sulfate and ferric sulfate were used as iron sources and sodium hydroxide and ammonium hydroxide was used as a precipitant. Single phase magnetite was synthesized with all of experiment conditions (ferrous/ferric molar ratios and precipitants). Particle size was smaller, and particle size distribution was narrower when NaOH was used than $NH_4OH$ was used. The crystallinity and particle size was increased and narrower particle size distribution with increasing molar ratio ferrous/ferric sulfate with the same precipitant. Super paramagnetism could be obtained at all of experiment conditions. The highest saturation magnetization (72 emu/g) was obtained when the ferrous/ferric molar ratio was 2.5 and precipitant was used $NH_4OH$.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• v.31 no.1
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• pp.22-31
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• 2018

Objectives : In this study, we investigated whether Astragali Radix Pharmacocupuncture (ARP) has an effective on the full thickness defect wound healing process of mouse. Methods : A total of 50 mice (ICR mouse, 7 week-old male) were divided into control group and ARP group. A single full thickness skin defect was made on the dorsal side of the each mouse using an 8mm diameter biopsy punch. Control group were treated with 0.2㎖ saline and ARP group were treat with 0.2ml ARP at 8 points around the wound every three days total 4 times during the experimental period. The change in wound size, contraction rate, healing rate, and epithelization rate was measured by digital images taken on days 3, 6, 9, and 13, and evaluated using a digital image analysis program. Tissues were collected for histological analysis, RT-PCR, and Western blot on days 3, 6, 9, and 15. Results : The results are as follows. ARP group accelerated the rate of wound contraction, wound healing and epithelization compared to the control group. ARP group showed the decrease of inflammatory cells in early inflammatory phase compared to the control group. ARP group upregulated PECAM-1 mRNA and protein expression compared to the control group. ARP group inhibited the scar width and area compared to the control group. Conclusions: ARP showed positive effects on wound healing through the inhibition of inflammatory reaction and increase of PECAM-1 expression related to the wound healing process.

• Korean Journal of Optics and Photonics
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• v.17 no.5
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• pp.469-474
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• 2006

A $1{\times}16$ thermo-optic switch with small excess loss using multimode interference(MMI) couplers is designed, fabricated, and measured. This paper introduces the proposed $1{\times}16$ thermo-optic switch, and discusses the measurement results. The $1{\times}16$ thermo-optic switch is farmed as 4-stage which consists of 15 unit devices. The unit devices are the $2{\times}2$ thermo-optic switches with Mach-Zehnder interferometer(MZI) structure. The characteristics of the $1{\times}16$ thermo-optic switch depends strongly on each unit device. The unit deviceconsists of two 3-dB general interference MMI couplers and two single mode waveguide arms as a phase shifter. First of all, the 3-dB optical splitter and $2{\times}2$ MZI thermo-optic switch have been tested to confirm the characteristics of the unit devices of the $1{\times}16$ MZI thermo-optic switch. Using the measurement results of the unit devices, the $1{\times}16$ MZI thermo-optic switch can be produced with better characteristics. The resultant structure of the MMI coupler with the optical light source of wavelength of 1550nm for the $1{\times}16$ thermo-optic switch is that the width and the optimized length are $25{\mu}m\;and\;1580{\mu}m$, respectively. The smallest excess loss fur the unit device is -0.5dB and the average excess loss is -0.7dB.