• The Korean Journal of Nuclear Medicine
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• v.29 no.1
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• pp.118-124
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• 1995

단일광자방출전산화 단층촬영술을 이용한 영상정보를 효과적으로 얻기 위하여 고려되어야 할 사항으로는 1) 조준기(collimator)의 선택, 2) 기질(matrix)의 크기, 3) 회전각의 수 (number of angles), 4) 360도 또는 180도 획득(acquisition), 5) continuous 또는 step& shoot, 6) 원형 또는 비원형회전 등이 있다. 저자들은 비원형회전으로 검체와 검출기 사이의 거리를 단축시킴으로써 직선성, 균일성, 대조도, 해상력에 미치는 영향을 알아보기 위하여 원형회전 방법과 비교하여 다음과 같은 결과를 얻었다. (1) 비원형회전을 하여도 균일성(uniformity)과 직선성(linearlity)을 유지한다. (2) 균일성, 대조도(contrast), 해상력(resolution)들이 비원형 회전을 한 경우에 보다 더 개선되었다. (3) 영상 획득시간은 비원형회전인 경우에 더 소요되었다. (매스캔 당 10분) 따라서 검사자는 영상 화질의 개선효과와 상반되는 보정(calibration)과 설치(set-up)에 소요되는 시간(매스캔당 10분이상)을 비교하여 자료획득(data acquisition) 회전방법을 선택하여야한다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.11
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• pp.939-950
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• 2017

In this work, mathematical models are newly presented for three types of double-acting oleo-pneumatic shock absorbers as the first part of a comparative study on the several types of double-acting oleo-pneumatic shock absorbers. After a typical single-acting shock absorber model is presented for the sake of completeness, mathematical models of three types of double-acting shock absorbers are proposed. To derive the models, Bernoulli equation and orifice discharge coefficient are utilized along with the assumptions of incompressibility and poly-tropic process. The proposed models are expected to be used for investigation of the salient features of several types of double-acting oleo-pneumatic shock absorbers.

• Polymer(Korea)
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• v.37 no.3
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• pp.262-268
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• 2013

pH-sensitive P(MAA-co-PEGMA) hydrogel particles were prepared and their feasibility as smart delivery carriers for cosmetic ingredients was evaluated. P(MAA-co-PEGMA) hydrogel particles having an average size of approx. $2{\mu}m$ were synthesized via dispersion photopolymerization. There was a drastic change in the swelling ratio of P(MAA-co-PEGMA) particles at a pH of around 5 due to the ionization of MAA in the hydrogel and as the amount of MAA in the hydrogel increased, the swelling ratio increased at a pH above 5. The P(MAA-co-PEGMA) hydrogel particles showed a pH-sensitive release behavior. Thus, at pH 4 almost none of the albumin permeated through the skin while at pH 6 relatively high skin permeability was obtained. The albumin loaded in the P(MAA-co-PEGMA) hydrogel particles was hardly degraded in the presence of pepsin and its stability was maintained.

• Applied Chemistry for Engineering
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• v.7 no.1
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• pp.59-66
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• 1996

Novel chitosan beads containing a series of bisamino-terminated polyethylene glycol (Bisamino-PEG, $Jeffamine^{(R)}ED$ series) have been prepared via capillary extrusion method using an alkaline solution. The results of swelling kinetics of chitosan beads showed that as the chain length of PEG in chitosan beads increased, the swelling process of the beads proceeded slowly. In order to study the releasing kinetics quantitatively, fluorescamine was coupled to the pendant amino groups and the releasing processes were followed by UV spectra. The results revealed that the releasing process was retarded in the order of $Jeffamine^{(R)}ED$-600 < $Jeffamine^{(R)}ED$-900 < $Jeffamine^{(R)}ED$-2001 as the chain length of PEG was increased. The slow release of PEG from the beads is considered to be governed by the chain length of PEG and interpolymeric hydrogen bonding between PEG and the chitosan molecule.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.6
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• pp.1219-1226
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• 2017

In this paper, it is performed the optimal design of the UV LED bar which can be used variously. The UV LED Bar emits ultraviolet rays, so it is important to emit ultraviolet rays constantly for the purpose of use. In order to emit a certain amount of ultraviolet rays as ever, the ultraviolet ray emission should be driven by a constant current source within the operable input voltage range. And also the heat dissipation is particularly important because of the long ultraviolet emission retention time due to the UV utilization characteristics. In addition, since human body protection is essential, the algorithm is configured to operate according to human body detection using distance sensor and Bluetooth. Three 365nm UV LEDs were used in series to emit ultraviolet UVA, operating at the constant current of 500mA with an efficiency of 87.5% and a power consumption of 6.006W. The ultraviolet radiation dose was measured at $5.35mW/cm^2$ at the distance of 10 cm when measured by the Lutron ultraviolet measuring instruments.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.1
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• pp.39-45
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• 1999

Because of internal voids in insulators give rise to partial discharge(PD), which cause local breakdown and even entire insulation breakdown. Treeing due to PD is one of the main causes of breakdown of the insulating materials and nrluction of the insulation life. 1berefore the necessity for establishing a rrethod to diagnose the aging of insulation materials and to predict the breakdown of insulation has becorne irrportant. From this viewpoint, our studies diagnose insulation degradation using the rrethod of computer sensing system, which has PD and acoustic emission(AE) sensing system. To use advantages of these two methods can be used effectiveiy to search for treeing location and PD in sorre materials. In analysis rrethod of degradation, we analyzed the PD and AE pulses by regression analysis, corrpared to these obtained the correlation coefficient and retermination coefficient by T-distribution and saw that PD and AE pulses show a similar pattern on the whole. This has a similar teIlrency to the results of the research by Yoshimura and Fujita.Fujita.

• Korean Chemical Engineering Research
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• v.56 no.3
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• pp.388-403
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• 2018

We investigated design requirements of vent lines for Sodium-Water Reaction Pressure Relief System of Prototype Generation-IV Sodium-Cooled Fast Reactor. We developed design requirements of areas of the rupture disks of the steam generator, a diameter of the gas vent line of the sodium dump tank, a diameter of the gas vent line of the water dump tank, a diameter of the water dump line of the steam generator. With the design requirements, we calculated the time to vent fluid inside the steam generator and analyzed the transient pressure behavior, also evaluated the close pressure value of the isolation valve of the water dump line. Our results are expected to be used as basis information to design Sodium-Water Reaction Pressure Relief System of Prototype Generation IV Sodium-Cooled Fast Reactor.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.1
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• pp.46-53
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• 2001

The purpose of this paper is to develop a new feature selection method for AE signal classification. The neural network of back propagation algorithm is used. The proposed feature selection method uses the difference between feature coordinates in feature space. This method is compared with the existing methods such as Fisher's criterion, class mean scatter criterion and eigenvector analysis in terms of the recognition rate and the convergence speed, using the signals from the defects in welding zone of austenitic stainless steel and in the metal contact of the rotary compressor. The proposed feature selection methods such as 2-D and 3-D criteria showed better results in the recognition rate than the existing ones.

• Journal of the Korean Society of Radiology
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• v.16 no.3
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• pp.249-255
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• 2022

Positron emission tomography for small animals has very high spatial resolution for imaging very small organs. To achieve good spatial resolution, the system must be constructed using very small scintillation pixels. When a detector is constructed using very small scintillation pixels, the size of the applicable array varies depending on the photosensor pixel. In a previous study, a study was conducted to find the maximum scintillation pixel arrangement according to the size of the photosensor. In this study, a detector with a light guide was designed to configure the detector using a more extended array of scintillation pixels, and try to find the maximum arrangement in which all scintillation pixels are imaged. The detector was designed using DETECT2000, which can simulate a detector made of a scintillator. Simulations were performed by configuring the detectors from an 11 × 11 scintillation pixel array to a 16 × 16 array. After obtaining a flood image by collecting the light generated from the scintillation pixel with a photosensor, the largest arrangement without overlap was found through image analysis. As a result, the largest arrangement in which all scintillation pixels could be distinguished without overlapping was a 15 × 15 arrangement.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.2 no.2
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• pp.97-104
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• 2004

Neutron induced prompt gamma-ray spectroscopy(NIPS) system measures the prompt gamma-ray emitting by the interaction of a neutron with various materials. This system will be of great benefit to scientists worldwide, since it provides the non-destructive measurement of many element in either solid or liquid wastes. In this study, the full-energy-peak (FEP) efficiency calibration for a HPGe detector was constructed in the ${\gamma}$-ray energy range from 80 keV to 8 MeV, using $^{l33}$Ba and >TEX>$^{152}Eu$ RI sources and $ ^{35}Cl(n, ${\gamma}$)^{36}Cl$ thermal neutron captured reaction. The FEP efficiency curve for the higher energies using the $^{35}Cl(n, ${\gamma}$)^{36}Cl$ reaction was normalized with the curve obtained from the RI sources, since the accurate activity of its prompt ${\gamma}$-ray is unknown. The average thermal neutron flux was theoretically calculated using the FEP efficiency curve for the KCl standard solutions. The NIPS system equipped with a ${\gamma}$-${\gamma}$ coincidence setup with two n-type coaxial HPGe detectors was considered in order to reduce the interfering ${\gamma}$-ray background. The FEP efficiency curve for the ${\gamma}$-${\gamma}$ coincidence system was also obtained for full energy range. The performance of the normal and coincidence NIPS system was tested by comparing signal-to-noise ratio in each mode using the reference sample.e.