• Journal of the Korean Electrochemical Society
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• v.12 no.2
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• pp.181-188
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• 2009

Pt catalyst was adsorbed on Carbon nanofiber (CNF) by modified polyol method after acid treatment of the carbon support with $HNO_3$ and $H_{2}SO_{4}$. As the time for acid treatment increases, more oxygen functional groups on carbon surface were produced which improve the loading amount and dispersion of Pt catalyst on carbon supports. In order to inspect the effect of CNF acid treatment time on electrochemical corrosion, constant potential of 1.4 V was applied to a single cell for 30 min and the amount of $CO_2$ emitted was monitored with on-line mass spectrometry. According to the results of our experiment, more $CO_2$ was produced with Pt/ oxidized-CNF catalyst in compared to that with unoxidized-CNF. Increasing acid treatment time also induces the more $CO_2$ emission. Besides, performance degradation after corrosion test expanded with severer carbon corrosion. From the observed results, it can be concluded that the acid treatment of CNF is beneficial to catalyst loading, but it also is a significant factor declining the fuel cell durability by accelerating electrochemical oxidation of carbon support.

• Korean Journal of Food Science and Technology
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• v.4 no.4
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• pp.252-258
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• 1972

Methods of separating yeast cells from oil-water-cell emulsion and subsequent purification of the recovered yeast have been studied. In addition, the results of preliminary feeding experiments in which a yeast grown on gas oil was incorporated into chick rations are reported. According to the present study, it appears that the recovery of the yeasts would be easier at pH 9, since the emulsion is relatively more unstable. A class of surface active agent at a concentration of 0.3% was found to facilitate the separation of the yeast from the emulsion. The use of electrolytes such as NaCl and KCl were found to be most effective in breaking the emulsion. Solvent treatment using iso-propyl alcohol and its azeotropic mixture with hexane at $58^{\circ}C$ are particularly suitable for purification of the yeast. In the feeding experiment it was found that 5 percent of the fishmeal in the control ration could be replaced by the yeast with no adverse effect on performance. However, when 8 percent of the fish meal in the control ration was replaced by the yeast, some effect on live-weight gain of the chicks was observed.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.11
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• pp.83-94
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• 2003

In this paper. a highly linear and low glitch CMOS current mode digital-to-analog converter (DAC) by self calibration bias circuit is proposed. The architecture of the DAC is based on a current steering 6＋4 segmented type and new switching scheme for the current cell matrix, which reduced non-linearity error and graded error. In order to achieve a high performance DAC . novel current cell with a low spurious deglitching circuit and a new inverse thermometer decoder are proposed. The prototype DAC was implemented in a 0.35${\mu}{\textrm}{m}$ n-well CMOS technology. Experimental result show that SFDR is 60 ㏈ when sampling frequency is 32MHz and DAC output frequency is 7.92MHz. The DAC dissipates 46 mW at a 3.3 Volt single power supply and occupies a chip area of 1350${\mu}{\textrm}{m}$ ${\times}$750${\mu}{\textrm}{m}$.

• Korean Chemical Engineering Research
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• v.57 no.6
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• pp.868-873
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• 2019

In this study, the evaluation of performance of AORFB using methyl viologen and TEMPOL as organic active materials in neutral supporting electrolyte (NaCl) with various membrane types was performed. Using methyl viologen and TEMPOL as active materials in neutral electrolyte solution, the cell voltage is 1.37V which is relatively high value for AORFB. Two types of membranes were examined for performance comparison. First, when using Nafion 117 membrane which is commercial cation exchange membrane, only the charge process occurred in the first cycle and the single cell couldn't work because of its high resistance. However, when using Fumasep anion exchange membrane (FAA-3-50) instead of Nafion 117 membrane, the result was obtained as the totally different charge-discharge graphs. When current density was $40mA{\cdot}cm^{-2}$ and cut off voltage range was from 0.55 V to 1.7 V, the charge efficiency (CE) was 97% and voltage efficiency (VE) was 78%. In addition, the discharge capacity was $1.44Ah{\cdot}L^{-1}$ which was 54% of theoretical capacity ($2.68Ah{\cdot}L^{-1}$) at $10^{th}$ cycle and the capacity loss rate was $0.0015Ah{\cdot}L^{-1}$ per cycle during 50 cycles. Through cyclic voltammetry test, it seems that this difference in the performance between the full cell using Nafion 117 membrane and Fumasep anion exchange membrane came from increasing resistance due to chemical reaction between membrane and active material, not the capacity loss due to cross-over of active material through membrane.

• Journal of the Korean Electrochemical Society
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• v.17 no.2
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• pp.94-102
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• 2014

Cation exchange membrane (Nafion) was modified to reduce the vanadium ion permeation through the membrane and to increase the vanadium redox flow battery (VRB) system performance by coating the graphene oxide (GO) which has nano-plate like morphology. Modified membrane properties were studied by measuring the ion exchange capacity (I.E.C), water uptake and proton conductivity. The thickness of the coated layer on the surface of the Nafion membrane was observed as $0.93{\mu}m$ by SEM. Proton conductivity and vanadium ion permeability of the modified membrane were decreased to 27% and 25% compared to that of the commercial Nafion membrane respectively. VRB single cell performance test was performed to compare the system performance of the VRB applied with commercial Nafion membrane and modified membrane. VRB system applied with modified membrane showed higher coulombic efficiency and energy efficiency than the VRB system applied with the commercial Nafion membrane due to the reduction of the vanadium ion permeation. From these result, we could suggest that the membrane modification by coating the GO on the surface of the Nafion membrane could be one of the promising strategies to reduce the vanadium ion permeation and to increase the VRB system performance effectively.

• Tuberculosis and Respiratory Diseases
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• v.40 no.4
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• pp.367-377
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• 1993

Background: The benefits of combination chemotherapy in unresectable non-small cell lung cancer remain uncertain. But, according to the recent reports, the response rates of cisplatin-based polychemotherapy regimens are higher than those of single agent. Also, the response rates of high-dose cisplatin group are higher than those of low-dose cisplatin group. In attemp to answer the question whether treatments, combination chemotherapy (high VPP) and combination chemotherapy with radiation therapy, improve survival in advanced non-small cell lung cancer, we begin to study. Method: Thirty-five patients above stage III, diagnosed histologically as non-small cell lung cancer, were enrolled. Among them, nineteen received a combination chemotherapy consisting of VP-16 & high-dose cisplatin (100 $mg/m^2$) and/or radiation therapy. The other group (16 subjects) received no therapy. To investigate the differences of survival and response rates between two groups and the side effects related to therapy, we reviewed patients' records. Results: 1) The overall objective response rate was 47%(9/19) with one complete remission. 2) In patients who received polychemotherapy and radiation therapy, the response rate was 60%(6/10) with one complete remission and survival rates of 3 months, 6 months and 12 months were 100%, 70% and 40%. 3) In patients who received polychemotherapy, the response rate was 33% (3/9) with no complete remission and survival rates of 3 months, 6 months and 12 months were 78%, 67% and 33%. 4) Overall, treated patients survived significantly longer (p<0.05) than non-treated patients (median survival 307 days versus 95 days). 5) Analysis of the various prognostic factors disclosed that good performance status, stage III and squamous cell type showed the good response rates. 6) The toxicities were nausea and/or vomiting (100%), alopecia (90%), anemia (79%), leukopenia (69%), thrombocytopenia (2%), increased creatinine (16%) and neurotoxicity (5%). Conclusion: According to above results, there are relatively good results that high VPP combination chemotherapy in advanced non-small cell lung cancer improves survival in the treated group than in the non-treated group. Thus, it is considerd that we select the patients with proper indications and treat them with effective chemotherpy and radiation therapy. But, because improvement related to high VPP ploychemotherapy is not marked in this study, it is necessary that we should investigate follow-up studies in many cases.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.100-101
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• 2012

The plasma damage free and room temperature processedthin film deposition technology is essential for realization of various next generation organic microelectronic devices such as flexible AMOLED display, flexible OLED lighting, and organic photovoltaic cells because characteristics of fragile organic materials in the plasma process and low glass transition temperatures (Tg) of polymer substrate. In case of directly deposition of metal oxide thin films (including transparent conductive oxide (TCO) and amorphous oxide semiconductor (AOS)) on the organic layers, plasma damages against to the organic materials is fatal. This damage is believed to be originated mainly from high energy energetic particles during the sputtering process such as negative oxygen ions, reflected neutrals by reflection of plasma background gas at the target surface, sputtered atoms, bulk plasma ions, and secondary electrons. To solve this problem, we developed the NBAS (Neutral Beam Assisted Sputtering) process as a plasma damage free and room temperature processed sputtering technology. As a result, electro-optical properties of NBAS processed ITO thin film showed resistivity of $4.0{\times}10^{-4}{\Omega}{\cdot}m$ and high transmittance (>90% at 550 nm) with nano- crystalline structure at room temperature process. Furthermore, in the experiment result of directly deposition of TCO top anode on the inverted structure OLED cell, it is verified that NBAS TCO deposition process does not damages to the underlying organic layers. In case of deposition of transparent conductive oxide (TCO) thin film on the plastic polymer substrate, the room temperature processed sputtering coating of high quality TCO thin film is required. During the sputtering process with higher density plasma, the energetic particles contribute self supplying of activation & crystallization energy without any additional heating and post-annealing and forminga high quality TCO thin film. However, negative oxygen ions which generated from sputteringtarget surface by electron attachment are accelerated to high energy by induced cathode self-bias. Thus the high energy negative oxygen ions can lead to critical physical bombardment damages to forming oxide thin film and this effect does not recover in room temperature process without post thermal annealing. To salve the inherent limitation of plasma sputtering, we have been developed the Magnetic Field Shielded Sputtering (MFSS) process as the high quality oxide thin film deposition process at room temperature. The MFSS process is effectively eliminate or suppress the negative oxygen ions bombardment damage by the plasma limiter which composed permanent magnet array. As a result, electro-optical properties of MFSS processed ITO thin film (resistivity $3.9{\times}10^{-4}{\Omega}{\cdot}cm$, transmittance 95% at 550 nm) have approachedthose of a high temperature DC magnetron sputtering (DMS) ITO thin film were. Also, AOS (a-IGZO) TFTs fabricated by MFSS process without higher temperature post annealing showed very comparable electrical performance with those by DMS process with $400^{\circ}C$ post annealing. They are important to note that the bombardment of a negative oxygen ion which is accelerated by dc self-bias during rf sputtering could degrade the electrical performance of ITO electrodes and a-IGZO TFTs. Finally, we found that reduction of damage from the high energy negative oxygen ions bombardment drives improvement of crystalline structure in the ITO thin film and suppression of the sub-gab states in a-IGZO semiconductor thin film. For realization of organic flexible electronic devices based on plastic substrates, gas barrier coatings are required to prevent the permeation of water and oxygen because organic materials are highly susceptible to water and oxygen. In particular, high efficiency flexible AMOLEDs needs an extremely low water vapor transition rate (WVTR) of $1{\times}10^{-6}gm^{-2}day^{-1}$. The key factor in high quality inorganic gas barrier formation for achieving the very low WVTR required (under ${\sim}10^{-6}gm^{-2}day^{-1}$) is the suppression of nano-sized defect sites and gas diffusion pathways among the grain boundaries. For formation of high quality single inorganic gas barrier layer, we developed high density nano-structured Al2O3 single gas barrier layer usinga NBAS process. The NBAS process can continuously change crystalline structures from an amorphous phase to a nano- crystalline phase with various grain sizes in a single inorganic thin film. As a result, the water vapor transmission rates (WVTR) of the NBAS processed $Al_2O_3$ gas barrier film have improved order of magnitude compared with that of conventional $Al_2O_3$ layers made by the RF magnetron sputteringprocess under the same sputtering conditions; the WVTR of the NBAS processed $Al_2O_3$ gas barrier film was about $5{\times}10^{-6}g/m^2/day$ by just single layer.

• Radiation Oncology Journal
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• v.27 no.4
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• pp.173-180
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• 2009

Purpose: To investigate the role of radiotherapy for squamous cell carcinomas of the external auditory canal and middle ear. Materials and Methods: A series of 35 patients who were treated at a single institution from 1981 through 2007 were retrospectively analyzed. Thirteen patients were treated by radiotherapy alone; four by surgery only and 18 by a combination of surgery and radiotherapy. The total radiation dose ranged from 39~70 Gy (median, 66 Gy) in 13~35 fractions for radiotherapy alone and 44~70 Gy (median, 61.2 Gy) in 22~37 fractions for the combined therapy. Clinical end-points were the cause of specific survival (CSS) and local relapse-free survival (LRFS). The median follow-up time was 2.8 years (range, 0.2~14.6 years). Results: The 3-year CSS and LRFS rate was 80% and 63%, respectively. Based on a univariate analysis, performance status and residual disease after treatment had a significant impact on CSS; performance status and histologic grade for LRFS. Patients treated by radiotherapy alone had more residual disease following the course of treatment compared to patients treated with the combined therapy; 69% vs. 28%, respectively. Conclusion: Our results suggest that radiation alone was not an inferior treatment modality for CSS compared to the combined therapy for squamous cell carcinoma of the external auditory canal and middle ear. However, local failure after radiotherapy is the main issue that will require further improvement to gain optimal local control.

• Asian-Australasian Journal of Animal Sciences
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• v.26 no.10
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• pp.1446-1458
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• 2013

The study assessed the effect of dietary supplementation of leaf meal mixture (LMM) containing condensed tannins (CT) on feed intake, nutrient utilization and performance of sheep infected with Haemonchus contortus. Eighteen adult sheep of similar age and body weight ($25.03{\pm}1.52$) were included in this study and out of these, 12 sheep were infected with single dose of infective third stage larvae of H. contortus at 2,000 larvae per sheep. The experimental sheep were allocated in three different groups' i.e. negative control (NC; no infection), control (C; H. contortus infected) and treatment (T; H. contortus infected+CT at 1.5% of the DM through LMM) and the experiment was conducted for a period of 90 d. The intake of dry matter (DM), organic matter (OM) and digestibility of DM, OM, neutral detergent fibre (NDF) and acid detergent fibre (ADF) were comparable among three animal groups. However, digestibility of crude protein (CP) and ether extract (EE) were significantly (p<0.05) higher in NC group as compared to both C and T groups. Nitrogen (N) retention (g/d or % of N intake) was significantly (p = 0.038) lower in C group as compared to T and NC groups. Daily intake (g/kg $W^{0.75}$) of digestible crude protein (DCP), digestible organic matter (DOM) and total digestible nutrient (TDN) did not differ significantly (p<0.05) in the three groups. Haemoglobin (Hb) and packed cell volume (PCV) were significantly (p<0.001) higher in treatment group as compared to control. The level of Hb and PCV reduced (p<0.001) after 30 days of experimental feeding. CT significantly (p<0.001) reduced serum urea in T group as compared to NC and C groups. Serum proteins differed significantly (p<0.01) among the three groups. The activity of serum enzymes AST, ALT, ALP and LDH were also statistically non significant (p<0.05) among treatments. The weight of abomasal lymph nodes (ALN) in T group was higher (p<0.05) than in C group. Treatment group had lower (p<0.05) total worms and fecal egg count compared to control group. It may be concluded that dietary supplementation of CT through LMM significantly improved the N retention, and inhibited the different developmental stages of Haemonchus contortus in experimental sheep.

• Journal of Electrical Engineering and Technology
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• v.1 no.2
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• pp.216-225
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• 2006

This paper presents a new circuit topology of DC busline switch and snubbing capacitor-assisted full-bridge soft-switching PWM inverter type DC-DC power converter with a high frequency link for low voltage large current applications as DC feeding systems, telecommunication power plants, automotive DC bus converters, plasma generator, electro plating plants, fuel cell interfaced power conditioner and arc welding power supplies. The proposed power converter circuit is based upon a voltage source-fed H type full-bridge high frequency PWM inverter with a high frequency transformer link. The conventional type high frequency inverter circuit is modified by adding a single power semiconductor switching device in series with DC rail and snubbing lossless capacitor in parallel with the inverter bridge legs. All the active power switches in the full-bridge inverter arms and DC busline can achieve ZVS/ZVT turn-off and ZCS turn-on commutation operation. Therefore, the total switching losses at turn-off and turn-on switching transitions of these power semiconductor devices can be reduced even in the high switching frequency bands ranging from 20 kHz to 100 kHz. The switching frequency of this DC-DC power converter using IGBT power modules is selected to be 60 kHz. It is proved experimentally by the power loss analysis that the more the switching frequency increases, the more the proposed DC-DC converter can achieve high performance, lighter in weight, lower power losses and miniaturization in size as compared to the conventional hard switching one. The principle of operation, operation modes, practical and inherent effectiveness of this novel DC-DC power converter topology is proved for a low voltage and large current DC-DC power supplies of arc welder applications in industry.