• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.10
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• pp.43-46
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• 2012

In this paper, high efficiency power amplifier is implemented with high gain amplifier. Two-stage amplifier using adaptive bias control circuit improve efficiency at low input power. Fixed bias circuit and adaptive bias circuit both have about 76 % efficiency at maximum power level. However amplifier using an adaptive bias control circuit has 70 % at 6 dBm input power level when the amplifier using fixed bias circuit has 50%. The proposed power amplifier using the adaptive bias control circuit can have high efficiency at lower power level.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2149-2151
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• 1999

This paper describes the impulse response characteristics of the grounding systems in power utility system. Several regulations regarding to electric power equipments, services and managements require that the groundings of class 1 ($E_1$) and class 2 ($E_2$) must be connected at the common point in grounding systems. In addition, the grounding for arrester ($E_{LA}$), which belongs to the grounding of class 1, should be connected at the same point. However, there is no method and position of common-connection at anywhere. In this work, when the impulse current was injected through the grounding conductor for arrester, the investigations measuring and analyzing potential rises induced at the common connection point and other grounding conductors were conducted. The experiments were carried out in the conditions of the grounding conductor of 25m long and the near or remote common connection from ground electrode. The lightning impulse current was applied so as to simulate the on-set of arrester due to lightning and/or switching surges.

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.569-575
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• 2014

A highly efficient class E power amplifier is demonstrated for application to wireless power transfer system. The amplifier is designed with an L-type matching at the output for harmonic rejection and output matching. The power loss and the effect of each component in the amplifier with the matching circuit are analyzed with the current ratio transmitted to the output load. Inductors with a quality factor of more than 120 are used in a dc feed and the matching circuit to improve transmission efficiency. The single-ended amplifier with 20 V supply voltage shows 7.7 W output power and 90.8% power added efficiency at 6.78 MHz. The wireless power transfer (WPT) system with the amplifier shows 5.4 W transmitted power and 82.3% overall efficiency. The analysis and measurements show that high-Q inductors are required for the amplifier design to realize highly efficient WPT system.

• Nuclear Engineering and Technology
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• v.54 no.1
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• pp.343-356
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• 2022

As a part of round robin analysis to develop a finite element elastic-plastic seismic analysis procedure for nuclear safety class 1 components, a series of parametric analyses was carried out on the simulated pressurizer surge line system model to investigate sensitivity of the analysis results to finite element analysis variables. The analysis on the surge line system model considered dynamic effect due to the seismic load corresponding to PGA 0.6 g and elastic-plastic material behavior based on the Chaboche combined hardening model. From the parametric analysis results, it was found that strains such as accumulated equivalent plastic strain and equivalent plastic strain are more sensitive to the analysis variables than von Mises effect stress. The parametric analysis results also identified that finite element density and ovalization option in the elbow elements have more significant effect on the analysis results than the other variables.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.76.1-76.1
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• 2014

We investigate the solar flare and CME occurrence rate and probability depending on sunspot class and its area change. These CMEs are front-side, partial and full halo CMEs associated with X-ray flares. For this we use the Solar Region Summary(SRS) from NOAA, NGDC flare catalog, and SOHO/LASCO CME catalog for 16 years (from January 1996 to December 2011). We classify each sunspot class into two sub-groups: "Large" and "Small". In addition, for each class, we classify it into three sub-groups according to sunspot class area change: "Decrease", "Steady", and "Increase". In terms of sunspot class area, the solar flare and CME occurrence probabilities noticeably increase at compact and large sunspot groups (e.g., 'Fkc'). In terms of sunspot area change, solar flare and CME occurrence probabilities for the "Increase" sub-groups are noticeably higher than those for the other sub-groups. For example, in case of the (M+X)-class flares of 'Dkc' class, the flare occurrence probability of the "Increase" sub-group is three times higher than that of the "Steady" sub-group. In case of the 'Eai' class, the CME occurrence probability of the "Increase" sub-groups is five time higher than that of the "Steady" sub-group. Our results demonstrate statistically that magnetic flux and its emergence enhance solar flare and CME occurrence, especially for compact and large sunspot groups.

• Korean Journal of Clinical Laboratory Science
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• v.47 no.2
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• pp.71-77
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• 2015

Antimicrobial resistant bacteria has recently emerged and been disseminated in livestock environments because of excessive use of antimicrobial agents for the therapeutic and growth promotion purposes to food animals. In particular, there is potential for multidrug-resistant bacteria that can be transmitted from animals to mankind. In this study, we investigated the genotypes of E. coli strains isolated from humans and chickens using multi-locus sequence typing (MLST) and antimicrobial resistance patterns by disk diffusion method along with integron study involving antimicrobial resistance mechanisms. From July 2013 to July 2014, E. coli strains isolated from clinical specimens (n=44) and poultry chickens (n=34). ST131 (n=20) was most common in human-derived E. coli. ST752 (n=7) was most common in chicken-derived E. coli, with four isolates each for ST117, ST189, and ST69. Of the 44 E. coli strains isolated from humans, 25 of had a class 1 integron, as opposed to only 11 of 34 strains in the E. coli isolated from chickens. There were differences in genotypes and antimicrobial resistance patterns between the chicken-derived and the human-derived E. coli.

• Journal of Information Processing Systems
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• v.4 no.2
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• pp.61-66
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• 2008

In recent years, numerous studies have been attempted to exploit ontology in the area of ubiquitous computing. Especially, some kinds of ontologies written in OWL are proposed for major issues in ubiquitous computing such like context-awareness. OWL is recommended by W3C as a descriptive language for representing ontology with rich vocabularies. However, developers struggle to design ontology using OWL, because of the complex syntax of OWL. The research for OWL visualization aims to overcome this problem, but most of the existing approaches unfortunately do not provide efficient interface to visualize OWL ontology. Moreover, as the size of ontology grows bigger, each class and relation are difficult to represent on the editing window due to the small size limitation of screen. In this paper, we present OWL visualization scheme that supports class information in detail. This scheme is based on concept of social network, and we implement OWL visualization plug-in on $Prot{\acute{e}}g{\acute{e}}$ that is the most famous ontology editor.

• The Korean Journal of Mycology
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• v.49 no.4
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• pp.545-553
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• 2021

In 2021, seven yeast strains were isolated from earthworm (Eisenia andrei) gut samples collected from the Nanji Water Regeneration Center in Goyang City, Gyeonggi Province, Korea. A total of seven yeasts were isolated, of which three strains have not been previously reported in Korea. To identify the yeasts, pairwise sequence comparisons of large subunit (LSU) rDNA sequences were performed using the basic local alignment search tool (BLAST). Assimilation test and cell morphology analysis were performed using the API 20C AUX kit and phase contrast microscope, respectively. Five of the seven strains were assigned to the genus Candida of the order Saccharomycetales of the class Saccharomycetes, and two to the genus Apiotrichum of the order Trichosporonales of the class Tremellomycetes. The yeast strain Candida sojae E2 belongs to the family Debaryomycetaceae, and Apiotrichum laibachii E8 and A. laibachii E9 belong to the family Trichosporonaceae. All strains were cultured in yeast mold agar for three days and showed different colony forms. C. sojae E2 was round and entire shaped, while A. laibachii E8 and A. laibachii E9 was round and convex shaped. This study focuses on the description of the three yeast strains that have not been officially reported in Korea.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.129-132
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• 1999

In this Paper, new congention control schemes using the adaptive rate control for ATM LANs are presented. If is preferable for hosts in LANs to be able to send bursts at the same speed as the interface link speed in a lightly loaded condition, and as the network load increases, to reduce their traffic rate adaptively in order to avaid network congestion. We propose to apply such a rate control concept for two different traffic classed in the ATM LANs. For the first traffic class requiring no bandwidth reservation, i.e, a best effort service class, a combination of the end-to-end adaptive peak rate control with the link-by-link backpressure control is proposed. For the second traffic class, requiring the bandwidth reservation for the burst transmission, i.e. guaranteed burst service class, a combination of he adaptive peak rate control with the fast bandwidth reservation is proposed.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.6
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• pp.1071-1079
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• 2010

This paper describes the design and fabrication of a high-efficiency GaN HEMT(Gallium Nitride High-electron Mobility Transistor) Pallet power amplifier module for S-band phased array radar applications. Pallet amplifier module has a series 2-cascaded power amplifier and the final amplification-stage consists of balanced GaN HEMT transistor. In order to achieve high efficiency characteristic of pallet power amplifier module, all amplifiers are designed to the switching-mode amplifier. We performed with various PRF(Pulse Repetition Frequency) of 1, 10, 100 and 1000Hz at a fixed pulse width of $100{\mu}s$. In the experimental results, the output power, gain, and drain efficiency(${\eta}_{total}$) of the Pallet power amplifier module are 300W, 33dB, and 51% at saturated output power of 2.9GHz, respectively.