• Proceedings of the Korean Fiber Society Conference
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• 1990.06b
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• pp.8-8
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• 1990

A new method for the graft polymerization of acrylonitrile onto starch is presented. Graft polymerization of acrylonitrile onto starch and the subsequent hydrolysis in sodium hydroxide solution to prepare absorbents is well known. This process has been utilized to produce the commercial product, Super Slurper. In a typical batch process, ~5% starch in water mixture is gelatinized at $95^{\circ}C$ under stirring for 1 hour then cooled to room temperature. The graft polymerization itself is carried out for approximately 2 hours at $25~30^{\circ}C$ on the gelatinized starch by eerie ion initiation. In this study, graft polymerization of acrylonitrile onto starch via a reactive extrusion process which is a continuous, efficient process is described. Initial concentration of starch in water is 35% and the reaction temperatures are between $50~80^{\circ}C$. However, the most significant difference in the reactive extrusion process is the short time in which the graft polymerization takes place. Preliminary results on the properties of graft polymerization products obtained from the reactive extrusion process are compared to those obtained from the batch process as well as the absorbency of the hydrolyzed samples. Absorbent material has also been prepared by sequential grafting and saponification in the extruder followed by a 2 hour heat treatment of the extrudate in an air circulated oven at $100^{\circ}C$.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.9
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• pp.1314-1318
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• 2012

Recently, applications of plasma display to the large public display and transparent display gain much attention. With this background, we report characteristics of opposite electrodes discharge cell with long electrode gap in comparison with conventional co-planar surface discharge. The cell size of test panel is $2950{\mu}m{\times}840{\mu}m$, which corresponds to that of the display having diagonal size of 130" with XGA resolution. Electrode gap of co-planar and opposite electrode structure are $240{\mu}m$ and $500{\mu}m$ respectively. These gap dimensions provide similar driving voltage windows. Experimental results show that opposite discharge provides approximately four fold higher luminous efficacy compared with that of the surface discharge. Resulting efficacy is found to be higher than 19 lm/W in green phosphor with 10 KHz continuous pulse operation.

• Journal of the Korean Institute of Rural Architecture
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• v.14 no.2
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• pp.59-66
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• 2012

The rate of the rural population over the age of 65 was increased from 14.7% in 2000 to 20.6% in 2010. The rate of elderly living alone in rural areas was increased from 9.2% to 13.3% for 10 years. Two million households over 40% of the elderly living alone nationwide are concentrated in rural areas. This paper investigates cases used as living space by interview and remodeling senior centers (village community center) for the elders living alone in rural areas. In Gimje two the nation's first senior centers were remodeled in 2006 (for both the village community center) and were begun to use these as group homes. Evaluation was a success. Since then, these were increased by approximately 20 centers per year by year and are currently 108 centers at the end of 2011. In Chungcheongnam-do, a pilot project has been begun for communal living by remodeling the senior center (for both the village community center) and elderly housing. Municipalities are similar in their business (is mostly). However, the interview results for each municipality are different. The success of the project depends on rules proposed by local governments and the development of programs with users to continuous financially support.

• Journal of Electrical Engineering and Technology
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• v.9 no.5
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• pp.1602-1613
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• 2014

The continuous growth of electric vehicles has caused electric power shortages in conventional utilities owing to the charging of electric-vehicle batteries. In order to increase the capacity of these utilities, photovoltaic systems may be an appropriate solution because of their benefits. However, a large amount of loss is generated in a conventional charging structure using photovoltaic sources owing to the many power conversion processes. This paper describes a simple integrated battery charger that utilizes a PV generation system. Moreover, the system control algorithm is deduced by analyzing the operation modes in order to control the proposed integrated system. The proposed system and algorithm are verified by a 3.3-kW prototype, resulting in an increase in the efficiency of approximately 7% to 15% compared with the conventional system. And, to examine the feasibility of the proposed system, the simulation for multi-charger with various conditions are progressed.

• Journal of Korea Multimedia Society
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• v.6 no.2
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• pp.332-339
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• 2003

To solve the large scale optimization problem approximately, various approaches have been introduced. Recently the Particle Swarm Optimization has been introduced. The Particle Swarm Optimization simulates the process of birds flocking or fish schooling for food, as with the information of each agent is skated by other agents. The Particle Swarm Optimization technique has been applied to various optimization problems whose variables are continuous. However, there are seldom trials for visualization of searching process. This paper proposes a new visualization tool for searching process of Particle Swarm Optimization algorithm. The proposed tool is effective for understanding the searching process of Particle Swarm Optimization method and educational for students. The computational results can be shown tiny and very helpful for education.

• Bulletin of the Korean Chemical Society
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• v.19 no.8
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• pp.847-851
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• 1998

13C, 15N, and 29Si NMR chemical shifts have been computed for selected X-substituted silatranes (X=Cl, F, H, CH3) using Gauge-Including Atomic Orbitals (GIAO) and Continuous Set of Gauge Transformations (CSGT) at the Hartree-Fock level of theory. The isotropic 13C chemical shifts are largely insensitive to substituent-induced structural changes. In this study, the isotropic 13C chemical shifts GIAO and CSGT calculations at the HF/6-31G and HF/6-31G* levels are sufficiently accurate to aid in experimental peak assignments. The isotropic 13C chemical shifts X-substituted silatranes at HF/6-31G* level are approximately 4 ppm different from the experimental values. In contrast, the isotropic 15N and 29Si chemical shifts and the chemical shielding tensors are quite sensitive to substituent-induced structural changes. These trends are consistent with those of the experiment. The 15N chemical shift parameters demonstrate a very clear correlation with Si-N distance, especially when we use the polarization function. Changes in anisotropy, 3a as well as in the 15N isotropic chemical shifts are due primarily to changes in the value of a.. But in case of "Si the correlations are not as clean as for the 15N chemical shift.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.30 no.2
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• pp.66-73
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• 2019

Objectives: This study aimed to investigate the trajectory of change of diverse attention and working memory in Koreans from 4 to 40 years of age. Methods: The data of 912 subjects from 4 to 15 years of age obtained from a previous standardization study of the computerized comprehensive attention test were merged with the newly obtained data of 150 subjects aged 16 to 40 years from this study. We evaluated the various kinds of attention, in which each subtest had five indicators. Working memory, with parameters such as number of correct responses and span, was also measured. Results: Our findings indicated that attention developed as age increased, and it decreased or was maintained after a certain age. Selective and sustained attention developed rapidly in children and adolescents, until mid-teens or 20 s when it ceased development. Divided attention, however, developed up to approximately age 20. In addition, working memory developed until mid-teens or 20 s. Conclusion: We presented the standardized data on diverse kinds of attention and working memory in children, adolescents, and adults in Korea. We could recognize any patterns of change in attention and working memory with increasing age.

• Journal of The Korean Society of Clinical Toxicology
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• v.16 no.2
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• pp.176-180
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• 2018

Drug abuse and its related problems are increasing continuously in Korea. One of the most frequently abused drugs is methamphetamine, but there are few medical report in Korea. This is the first report of the identification of methamphetamine in the blood of a patient who had a return of spontaneous circulation after cardiac arrest and survived discharge. A 33-year-old male arrived at the emergency department presenting with chest pain and dyspnea. He had ingested methamphetamine and alcohol approximately 7 hours before arrival. One hour after arrival, he had seizure followed by cardiac arrest. Spontaneous circulation was recovered after 4 minutes of CPR. An analysis of the National Forensic Service identified plasma methamphetamine with an estimated average concentration of plasma methamphetamine at the time of arrival of 0.6 mg/L, a lethal dose. He had rhabdomyolysis and acute kidney injury but survived after continuous renal replacement therapy. Since then, he has suffered chronic kidney disease, and he is being followed up at the out-patient department. In Korea, although drug abuse is still uncommon, it is on the increase. Therefore, emergency physicians should be aware of the clinical characteristics of methamphetamine poisoning.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.83.4-83.4
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• 2019

We present multi-color, high-cadence photometric study of a distant SU UMa-type dwarf nova KSP-OT-201611a discovered by the Korea Microlensing Telescope Network (KMTNet) Supernova Program (KSP). From October 2016 to May 2017, two outbursts with an interval of approximately 90 days were detected in the BV I-bands. The shapes and amplitudes of the outbursts reveal the nature of KSP-OT-201611a to be a SU UMa-type dwarf nova of outside-in origin with a superhump and an inferred orbital period of 1.69 h. The two observed bursts show a distinctively different color evolutions during the bursts due most likely to the viscosity different in accretion disk between them. The observed quiescent magnitudes and properties of the source during the outbursts indicate that it is at a large distance (~7.3 kpc) and height (~1.7 kpc) from the Galactic disk, possibly belonging to the group of poorly-studied Population II dwarf novae. The continuous monitoring of this source may offer a rare opportunity to study a PopII dwarf nova.

• ETRI Journal
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• v.42 no.6
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• pp.943-950
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• 2020

We propose 8.2-GHz band radar RFICs for an 8 × 8 phased-array frequency-modulated continuous-wave receiver developed using 65-nm CMOS technology. This receiver panel is constructed using a multichip solution comprising fabricated 2 × 2 low-noise amplifier phase-shifter (LNA-PS) chips and a 4ch RX front-end chip. The LNA-PS chip has a novel phase-shifter circuit for low-voltage operation, novel active single-to-differential/differential-to-single circuits, and a current-mode combiner to utilize a small area. The LNA-PS chip shows a power gain range of 5 dB to 20 dB per channel with gain control and a single-channel NF of 6.4 dB at maximum gain. The measured result of the chip shows 6-bit phase states with a 0.35° RMS phase error. The input P1 dB of the chip is approximately -27.5 dBm at high gain and is enough to cover the highest input power from the TX-to-RX leakage in the radar system. The gain range of the 4ch RX front-end chip is 9 dB to 30 dB per channel. The LNA-PS chip consumes 82 mA, and the 4ch RX front-end chip consumes 97 mA from a 1.2 V supply voltage. The chip sizes of the 2 × 2 LNA-PS and the 4ch RX front end are 2.39 mm × 1.3 mm and 2.42 mm × 1.62 mm, respectively.