• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1985.04a
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• pp.48-53
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• 1985

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.311-312
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• 2005

Applying a designed test coupon pattern for fabricating resistors various resistors were formed using PTF(polymer thick film) pastes. Aspect ratio from 0.25 to 4 were selected for fabricating resistors. Formed resistors were cured at $170^{\circ}C$ and $240^{\circ}C$. Electrical properties of fabricated resistors were measured and their values analyzed in relation to cure temperature and formed geometry via printing. Also effects of substrates used for fabricating resistors were observed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.212-213
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• 2006

Polymer thick film resistor paste was fabricated using various materials. Inorganic materials of carbon black and graphite were selected as fillers and epoxy resin was selected as organic material. Solvent with high boiling temperature was applied to adjust viscosity. A designed test coupon pattern was used to evaluate fabricated resistors. Aspect ratio of 1 was selected for evaluating resistor values. Electrical properties of fabricated resistors were measured and their values analyzed in relation to paste composition. PTF fabricated using carbon black as fillers achieved resistor value of $530{\Omega}/sq$.

• Korean Journal of Optics and Photonics
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• v.2 no.3
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• pp.121-126
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• 1991

The knife-edge scanning type OTF measuring equipment is improved to enhance the accuracy in off-axis OTF measurement and the accuracy of this equipment of evaluated by measuring the OTF of 50 mm plano-convex standard lens developed by SIRA group. Measured MTF values of the standard lens are in good agreement with SIRA results within $\pm$0.02 on axis and % $\pm$0.03 off-axis in 0-100 clmm frequency range except only a few spatial frequencies. Measured PTF values are good agreement with SIRA results within $\pm$$5^{\circ}$.

• Mycobiology
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• v.46 no.4
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• pp.317-327
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• 2018

While surveying undiscovered fungal taxa in Korea, three rare zygomycetous fungal strains, CNUFC-PTF2-1, CNUFC-TF3-1, and CNUFC-ESAF3-1, were isolated from soil, leaf, and freshwater samples, respectively. The strains were analyzed morphologically as well as phylogenetically based on the internal transcribed spacer region and 28S rDNA sequences. Sequence analysis of the two loci revealed that the isolates, CNUFC-PTF2-1, CNUFC-TF3-1, and CNUFC-ESAF3-1, were identified as Backusella circina, Circinella muscae, and Mucor ramosissimus, respectively. These species have not yet been previously described in Korea.

• Korean Journal of Agricultural Science
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• v.41 no.4
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• pp.391-398
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• 2014

Identifying soil water content as a major factor for evaluating irrigation and water resource is a primary module to develop a prediction model. A variety of PTFs (Pedo-Transfer Functions) are applied in the models to estimate soil water content, the analysis techniques, however, which compare the estimated from models and the measured by instruments, are not reached at the level to demonstrate the effectiveness of the PTFs in Korea. Many soil physicians such as Eom, Peterson, Rawls, Saxton, Bruand, Baties, Tomasella & Hodnett (T&H), and Minasny, have developed analytic models using PTFs. Soil data for the analysis used soil water contents on 347 soil series (10 kPa), 358 soil series (33 kPa), 356 soil series (1,500 kPa) established by NAAS (National Academy of Agricultural Science). A coefficient of determination on soil water content at 10, 33 and 1,500 kPa was the highest as 0.5932 in EM (Eom model), 0.6744 in REM (Rawls model) and 0.6108 in REM, respectively. In conclusion, it is strongly suggested that the use of EM or REM is suitable for estimating soil water content in Korea although SM (Saxton model) has been widely used.

• Journal of Chest Surgery
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• v.26 no.9
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• pp.667-676
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• 1993

Boprosthetic cardiac valves fail from biological and metabolic as well as mechanical reasons, and the limited durability is the main factor of marked withdrawal in their clinical use. Starting the use of bioprosthetic valves in 1976, up to the end of 1992, the consecutive 178 patients have undergone re-replacement of glutaraldehyde-treated xenograft valves for primary tissue failure [PTF]among the patients who had initial valve replacement at Seoul national University Hospital. The explanted valves were 69 porcine aortic [51 Hancock, 12 Angell-Shiley and 6 Carentier-Edwards] and 141 bovine pericardial [129 standard-profile and 12 low-profile ionescu-Shiley] valwes, with an overall incidence of PTF of 15.2%. The operative mortality rate of re-replacement was 5.1%. Calcific degeneration and tissue damage in relation to calcification were the most frequent modes of PTF on gross examinatin of the explanted valves resulting hemodynamically in valvular regurgitation. The number of Hancocg porcine and the standard-profile Ionescu-Shiley valves in valves in mitral position failed more often from tissue damage [tears, holes, and loss or destruction of cuspal tissue] than calcification [68.3% vs. 39.0%, p<0.01] with resultant regurgitation in 61%, the Ionescu-Shiley valves in the same position in 53%. The tendency of more calcification than tissue damage[71.3% vs. 33.3%, p<0.001]with stenosis in 53%. The tendency of more calcification and immobility of cusps in the latter group was partly explainable by the inclusion of patients of pediatric age. Observation made in this study suggest : many of bioprosthetic valves would fail from calcification and tissue damage : some fail prematurely because of mechanical stress probably owing to the valve design in construction ; andeven those valves escaped early damage would be subject to calcify in the prolonged follow-up period. In conclusion, at the present time, the clinical use of bioprostheticxenograft valves seems to be quite limited until further improvement in biocompatibility and refinement in valve design in manufacture are achieved.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.116-121
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• 2006

The pressurization system in a liquid rocket propulsion system provides a controlled gas pressure in the ullage space of the vehicle propellant tanks. It is advantage to employ a hot gas heat exchanger in the pressurization system to increase the specific volume of the pressurant and thereby reduce over-all system weight. Therefore a significant improvement in pressurization system performance can be achieved, particularly in a cryogenic system. For this study air and $CN_2$ are employed as external fluid and pressurant respectively Numerical analysis on the pressurant discharging characteristics have been compared with the experimental results performed at the PTF(Propellant-feeding Test Facility). It is shown that the discrepancy of analytic and experimental results is within about ${\pm}15%$. It is estimated that the temperature drop rate of cryogenic pressurant immersed liquid oxygen can be predicted using this analytic approach method.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.322-325
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• 2007

This paper shows the development procedure of the low pressure LOX feed system which is used in the liquid rocket with a turbopump. Korean Air has cooperated with KARI in developing the LOX feed system to turbopump. The LOX feed system is characterized with cryogenic temperature and the thin-thickness tube for weight saving. The system in this project is composed with a main feed line and a recirculation line for the LOX temperature conditioning. Each piping system has many components, namely, bellows, filter, orifice, valves, flange and support. In this paper, system design & manufacturing, structural & thermal analyses, and component tests are explained. Finally, the system was assembled to the KARI's PTF test facility and functioned well to meet its required performance.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.85.1-85.1
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• 2014

The progenitors of Type Ibc supernovae (SNe Ibc) have been believed to be massive Wolf-Rayet (WR) stars, formed either through stellar wind mass loss or Roche-lobe outflow in a binary system. But observations indicate that ordinary SNe Ibc have relatively low ejecta masses (~2 Msun), which is not compatible with the WR star scenario for SN Ibc progenitors. On the other hand, helium stars in binary systems which can be produced via mass transfer are also suggested as a possible candidate for SN Ibc progenitors. Binary star evolution models predict that SN Ibc progenitors having final masses of 3-7 Msun can be produced, but their observational properties are not well understood. In this study, we present the parameter study on the observational constraints of helium stars of 3-5 Msun in binary systems using evolutionary models and the atmospheric radiative transfer code CMFGEN. We present the predicted magnitudes and spectra of helium stars in optical bands for different wind velocity profiles and mass loss rates. We also present those observables of the progenitor binary system considering O-type companion stars. Based on the results, we discuss the expected observational properties of SN Ibc progenitors in binary systems. In particular, we discuss the constraints on the progenitor of the SN Ib iPTF13bvn of which progenitor candidate has been identified for the first time in pre-explosion images among SNe Ibc.