• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.21-26
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• 2016

This paper presents a step-down DC-DC buck converter with a CCM/DCM dual-mode function for the internal power stage of portable electronic device. The proposed converter that is operated with a high frequency of 1 MHz consists of a power stage and a control block. The power stage has a power MOS transistor, inductor, capacitor, and feedback resistors for the control loop. The control part has a pulse width modulation (PWM) block, error amplifier, ramp generator, and oscillator. In this paper, an external capacitor for compensation has been replaced with a multiplier equivalent CMOS circuit for area reduction of integrated circuits. In addition, the circuit includes protection block, such as over voltage protection (OVP), under voltage lock out (UVLO), and thermal shutdown (TSD) block. The proposed circuit was designed and verified using a $0.18{\mu}m$ CMOS process parameter by Cadence Spectra circuit design program. The SPICE simulation results showed a peak efficiency of 94.8 %, a ripple voltage of 3.29 mV ripple, and a 1.8 V output voltage with supply voltages ranging from 2.7 to 3.3 V.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12B
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• pp.1452-1458
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• 2009

In this paper, Our proposed Multipurpose Complex Card UHF band RFID small-size Tag antenna. Multi purpose Complex Card UHF band RFID small-size Tag antenna that is to minimize the low efficiency of RFID Tag Read Range that generates space limitation and a conductor surrounded by inducing fingerpring system with dual(HF, UHF) Card is presented. Our proposed UHF band RFID small-size Tag antenna is for the Multipurpose Complex Card that is mounted on the fingerpring system as well as the HF Tag. It also enables to minimize and facilitates Tag chip matching by adjusting Tapered, Meander line and Loop structure. Given the card substance properties and periphery circuit, the proposed small-size Tag antenna, in this report, is designed with PET film with size of $50{\times}15mm^2$. The RFID small-size Tag method for measurements is used by EPCglobal Static Test instrument in Anechoic Chamber, which is tested with dual Card, within the car and in wallet. It is found that Read Range is 3.8m from the EPCglobal Static Test, Maximum Read Range within the car from the field test results in 7.6m. Proposed Tag antenna is will be used in the parking control security system.

• Journal of The Geomorphological Association of Korea
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• v.19 no.2
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• pp.31-49
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• 2012

Satae cheon, a tributary of the Suip cheon in Yanggu, Gangwon province, is an international river extended to North Korea. Most of drainage basin area of the river was the fierce battle field during the Korean War(1950-1953) and hard to access as it located between the MDL(Military Demarcation Line) and the CCZ(Civilian Control Zone: about 10km south from MDL). By the restriction of access to the sites, most of natural landscape have been well conserved except limited use for military activities. Even the landfoms in that area were not studied, except the government's heritage reports. Satae Cheon's channel follows the Imdang fault line(N-S) to Satae-ri and flow to west to the Dutayeon area. The river meanders along geological structure or weak line at the Dutayeon area. The meandering channel was shorten by the meander cut which linked the thalweg line of meander loop ant the meander neck. As a result of this cut, the river cliff formed by the Satae cheon became the part of newly formed channel bed and the S-forms are formed. After the channel route stabilized, channel incised the rock with large potholes and undulating walls were formed. The channel width changes from 1m to 10m with restriction of the undulating walls, so this part can be regarded as inner channel or inner gorge. From the point of planar forms it also can be slot-type canyon.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.96-97
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• 2019

최근 홍수파 또는 댐 및 보 등의 하천구조물과, 본류와 지류의 합류로 인해 발생하는 배수영향 등으로 하천에 고리형 수위-유량관계가 나타나 수위-유량관계식의 신뢰도가 저하된다고 판단되는 대하천 본류와 합류부 인근 지류에서 초음파유속계 측정결과를 지표로 활용하는 자동유량장치가 현재 58개소에 도입되어 운용되고 있다. 그러나, 최근 4대강 사업으로 다기능보 설치 등 하천의 수리적 특성이 변동하였고, 지류에서 주로 운용되는 수위-유량관계 기반 유량관측소에 본류-지류합류로 인한 배수영향으로 고리형 수위-유량관계가 형성될 경우, 지류 수위관측소를 자동유량관측소로 대체할 필요성이 제기되고 있다. 또한, 기존 자동유량관측소의 경우 홍수량이 기준이하로 나타날 경우 수위-유량 관계식으로 대체하는 경우도 있는데 적용기준이 명확하지 않다. 본 연구에서는 신규 자동유량장치 설치, 기존 수위관측소의 자동유량관측소대체, 자동유량관측소에서 수위-유량관계곡선의 활용 기준 마련 등을 명확하게 판단하기 위해 고리형 수위-유량관계 패턴을 분석하고 배수영향구간을 산정하여 제시하고 지류 수위관측소의 존속여부, 유량자료의 적절성을 판단할 수 있는 방법론을 제시 하고자한다. 이를 위해, 다기능보 설치 및 지류-본류로 인한 지류하천의 배수영향과 홍수파에 의한 고리형 수위-유량관계의 양상을 다양한 수문사상에 대해 분석하였다. 분석방법으로는 대상유역을 선정하고, 대상유역에 대한 부정류 모형을 구축하기 위해 HEC-RAS 모형을 사용하고, 대상유역에 대한 HEC-RAS 지형자료와 유량입력자료를 구축한다. HEC-RAS 부정류 모형 구축 후 다양한 본류와 지류의 유량을 가정하여 고리형 수위-유량 발생 패턴을 분석한다. 지류-본류 합류 영향의 경우, 본류영향의 유무를 고려하여 상승된 수위의 비율로부터 일정 유의수준을 두어 배수영향구간을 산정한다. 다기능보의 영향은 다기능보 설치 전후를 가정하여 영향을 분석한다. 본 연구에서는 시범구역으로 하류에 창녕함안보가 위치한 낙동강과 합류하는 남강과 하류에 달성보가 위치한 낙동강과 합류하는 금호강을 대상하천으로 하여 위 분석방법을 적용하였다. 분석결과 남강의 경우 지류 유량이 작은 경우에도 본류 유량이 상대적으로 큰 경우 배수영향에 의한 고리형이 나타났고, 다기능보에 의한 배수영향은 매우 적은 것으로 나타났다. 또한, 지류의 유량이 큰 경우 홍수파에 의한 고리형 관계도 발생함을 알 수 있었다. 금호강의 경우 또한 마찬가지로 본류의 유량에 의해 발생하는 고려형 관계가 지배적임을 알 수 있었다. 따라서 이러한 결과를 바탕으로 95%의 유의 수준을 기반으로 고리형 발생 여부를 확일할 수 있는 모노그래프를 남강, 금호강에 대해 작성하여 수위-유량관계 기반 유량 산정의 적절성을 판단하는 기준으로 제안하였다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.6
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• pp.739-745
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• 2017

Many studies have been conducted to reduce environmental pollution by ships and reduce fuel consumption. As part of this effort, research on power conversion systems through DC distribution systems that link renewable energy with conventional power grids has been pursued as well. The diode rectifiers currently used include many lower harmonics in the input current of the load and distort supply voltage to lower the power quality of the whole system. This distortion of voltage waveforms causes the malfunctions of generators, load devices and inverter pole switching elements, resulting in a large number of switching losses. In this paper, a controller is presented to improve DC output waveforms, the input Power Factor and the THD of an AFE type PWM rectifier used for PLL. DC output voltage waveforms have been improved, and the input Power Factor can now be matched to the unit power factor. In addition, the THD of the input power supply has been proven by simulation to comply with the requirements of IEEE Std514-2014.

• Journal of the Korean Magnetics Society
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• v.18 no.4
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• pp.142-146
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• 2008

The angular dependence of the exchange bias($H_{ex}$) and coercivity($H_c$) in multilayer $[Pt/Co]_N-IrMn$ with applied measuring field rotated toward in-plane at angle $\theta$ from perpendicular-to-plane, has been measured. Multilayer films consisting of $Si/SiO_2/Ta(50)/Pt(4)/[Pt(15)/Co(t_{Co})]_N/IrMn(50)/Ta(50)(in\;{\AA})$ were prepared by magnetron sputtering under typical base pressure below $2{\times}10^{-8}$ Torr at room temperature. Magnetization measurements were performed on a vibrating sample magnetometer and extraordinary Hall voltage measurement systems after cooling from 550 K under a field of 2 kOe applied along the perpendicular to film direction. The hysteresis loop shifts from the origin not only along the field axis but also along the magnetization axis. $H_{ex}$ and $H_c$ show a $1/cos{\theta}$ and $1/|cos{\theta}|$ dependence on the angle($\theta$) between the applied measuring field and the perpendicular-film direction, respectively. This $1/cos{\theta}$ dependence can be accounted for by considering the angular dependence of strong out-of-plane magnetic anisotropy introduced during the field cooling.

• Nuclear Engineering and Technology
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• v.16 no.3
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• pp.141-154
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• 1984

An analysis is presented of key phenomena and scenario which imply some general trends for beyond design-basis-accident in Kori-1 PWR dry containment. The study covers a wide range of severe accident sequences initiated by small break LOCA. The MARCH computer code, with KAERI modifications was used in this analysis. The major emphasis of the paper are two folds, 1) the phenomenologic understanding of severe accident and 2) a study of H2 combustion and debris/ water interactions in a specific small break LOCA for Kori-1 plant. The sensitivity studies for the specific plant data and thermal interaction modelings used in the SASA were performed. The results show that if hydrogen burning does occur at low concentration, the resulting peak pressure does not exceed the design value, while the lower concentration assumption results in repeated burning due to the continuing H$_2$ generation. For debris/water interaction, the particle size has no effect on the magnitude of peak pressure for the amount of water assumed to be in the reactor cavity. But, the occurrence of peak pressure is considerably delayed in case of using the dryout correlation. The peak containment pressure predicted from the hydrogen combustion and steam pressure spite during full core meltdown scenario does not present a severe threat to the containment integrity.

• Journal of Sericultural and Entomological Science
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• v.50 no.2
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• pp.161-165
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• 2012

Antimicrobial peptides of insects are found and reported as immune defence system against infectious agents. The peptides are produced by fat body cells and thrombocytoids, a blood cell type. Defensin is 38-45 amino acids long and consists of an ${\alpha}$-helix linked by a loop to an antiparallel ${\beta}$-sheet. Defensin from a bumblebee, Bombus ignitus, is known to comprise 52 amino acid residues. This peptide consists of two ${\alpha}$-helixes; ACAANCLSM and KTNFKDLWDKRF and one ${\beta}$-sheet; GGRCENGVCLCR. We carried out antibacterial activity test by radial diffusion assay against Staphylococcus aureus (Gram positive), Escherichia coli (Gram negative), Pseudomonas syringae (Gram negative), Candida albicans (fungi), MDRPA, MRSA, and VRE (antimicrobial resistant microbes) with synthetic oligopeptides from Peptron (Daejeon, Korea). The predicted curtailment fragment (GGRCEVCLCR-$NH_2$) for ${\beta}$-sheet had strong antibacterial activity when internal amino acids were removed. But, curtailment fragments (ACAANCLSM-$NH_2$ and TNFKDLWDKR-$NH_2$) of ${\alpha}$-helix were not showed antibacterial activity. These synthetic oligopeptides were showed the great activity against Gram positive and negative bacteria.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.6
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• pp.744-753
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• 2021

This study suggests ways to improve the standard test method and judgment criterion for the "Eco-toxicity Test" based on the rules and regulations provided in 'performance and qualifying test standards for marine pollution prevention materials and chemicals' in the Republic of Korea. Compared with the relevant references of other countries, this study attempted to find the limitations in the existing standards. As for the growth inhibition test of algae using Skeletonema costatum as an indicator, applying comparative analysis to measure specific growth rates, together with statistical analysis, instead of applying current methods, judged by the appearance of colors from the culture medium was suggested. Considering the exponential growth phase of the test species, the test duration was suggested to be reduced to less than four days. For the test with fish as an indicator, resetting the appropriate body size was suggested to, show consistent sensitivity against chenicals applied during testing. Furthermore, it is necessary to consider the criteria needs, which should be established in reasonable and objective ways. For the testing species, marine rotifer, Brachionus plicatilis could be a replacement for Artemia sp., and a bivalve for fish in the test. To improve the performance effectiveness of the "Eco-toxicity test", it is worth considering the designation of accredited testing institutes, by placing it in the same loop. Thus it is also expected to have a reliable management system in place, having the capacity of cost calculation properly and adjusting testing items if required.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.6
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• pp.442-448
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• 2021

In this work, the (K_1-xAg_x)(Ta_0.8Nb_0.2)O₃ (x=0.1-0.4) ceramics were fabricated using mixed-oxide method, and their structural and electrical properties were measured. All specimens represented a pseudo cubic structure with the lattice constant of 0.3989 nm. When 0.4 mol of Ag was added, second phases induced from metallic Ag and K₂(Ta,Nb)₆O₁₆ phase were observed. Dielectric constant and dielectric loss of K(Ta_0.8Nb_0.2)O₃ specimen doped with 0.3 mol of Ag were 2,737 and 0.446, respectively. The curie temperature was about -5℃, which does not change with Ag addition. The remanent polarization began to decrease sharply around 12~15℃, and the temperature at which the remanent polarization began to decrease as the applied voltage increased shifted to the high temperature side. The electrocaloric effect (ΔT) and electrocaloric efficiency (ΔT/ΔE) of the (K_0.7Ag_0.3)(Ta_0.8Nb_0.2)O₃ ceramics were 0.01024℃ and 0.01825 KmV^-1, respectively.