• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.6
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• pp.1019-1026
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• 2017

The structural properties of $HfO_2$ films could be improved by calibrating the working pressure owing to the enhanced quality of a thin film. We deposited $HfO_2$ films on glass substrates by radio frequency (RF) magnetron sputtering under a base vacuum pressure lower than $4.5{\times}10^{-6}Pa$, RF power of 100 W, substrate temperature of $300^{\circ}C$. The working pressures were varied from 1 mTorr to 15 mTorr. Subsequently, their structural and optical properties were investigated. In particular, the $HfO_2$ film deposited at 1 mTorr had superior properties than the others, with a crystallite size of 10.27 nm, surface roughness of 1.173 nm, refractive index of 2.0937 at 550 nm, and 84.85 % transmittance at 550 nm. These results indicate that the $HfO_2$ film deposited at 1 mTorr is suitable for application in transparent electric devices.

• Journal of Navigation and Port Research
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• v.40 no.3
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• pp.159-164
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• 2016

The goal of this study is to implement a communication system that can monitor the status of the nacelle using the power cable itself, without the dedicated communication lines such as an UTP cable and optical fiber for the offshore wind turbine. An inductive coupling powerline communication system for a MW class offshore wind turbine was proposed and its communication performance was demonstrated. The inductive couplers was designed for operation at up to 500 A using a ferrite composite materials. Field test was carried out on the wind farms of Jeju island. Using the iperf communication test program, we have obtained more than 15 Mbps data transmission rate through the 100 m power cable that was installed between the nacelle and the bottom of the power converter. In the data transmission stability test for a week, there was no failure ever. The minimum transmission rate was 15 Mbps and the average data rate was about 20 Mbps. Next, we have installed an infrared camera inside the nacelle in order to measure the temperature distribution and variation of the nacelle. The real-time thermal image taken by the camera was successfully sent to the monitoring system without error.

• FLOWER RESEARCH JOURNAL
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• v.18 no.1
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• pp.15-22
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• 2010

These investigations were conducted to standardize several chemical and physical environments affecting in vitro propagation of gametophytes of Climacium japonicum. Propagation of this moss species was established on basal medium containing Knop macro salts and Nitsch and Nitsch trace elements. Primary cultures were initiated from apical shoots of gametophytes. Gametophyte production was accessed using chopped gametophytes, apical shoots and basal shoots. Seven ty pes of culture media and four concentrations of total nitrogen and five strengths of sucrose were tested for in vitro gametophyte production. Light and temperature factors were also evaluated. Apical shoots were the greatest among three types explants used for gametophyte propagation. Medium containing Knop macro salts and Nitsch and Nitsch trace elements was more effective than other types of media. Higher sucrose concentrations showed a positive effect on the elongation and multiplication of gametophytes. Both nitrogen deficiency and excessiveness inhibited gametophyte growth. Light intensity variation showed highly significant changes in numbers, length and fresh weight of gametophytes. Optimum light intensity for gametophyte growth seemed to be around 3000-4000 lx. Both lower and higher temperature had a negative effect on gametophyte propagation and production. This study will provide large scale and high quality propagules, and effective moss propagation system.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.281-281
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• 2016

기후변화로 인한 기상학적 자연재해로부터 대비하고 안정적인 용수공급을 위해 유역의 다양한 수문 요소들에 대한 분석 필요성이 증가하고 있다. 계절적 강수량의 편차가 큰 우리나라는 유역 통합 물관리가 중요하며, 효율적 수자원 관리와 물안보 확보를 위해 유역내 물순환을 이해하는 것이 중요하다. 유역의 유출을 결정하는 요소들에는 강우, 증발산량, 토양 수분 및 지하수 등이 있으며, 시간적으로는 홍수와 같이 단기에 발생하는 유출과 장기적으로 발생하는 유출이 있다. 장기 유출은 단기 유출에 비해 토양내 수분량이 무시할 수 없을 정도로 영향을 미치게 되므로, 1년 이상의 장기 유출 해석을 위해서는 강우가 발생하지 않는 기간 동안의 토양 수분량 변화와 증발산 영향을 고려할 필요가 있다. K-water에서 자체 개발된 분포형 장단기유출 모델인 K-DRUM은 유역을 격자(grid)단위로 구분하고 각 셀들에 대한 매개변수는 흐름방향도, 표고분포도, 토지이용도, 토지피복도 등을 GIS처리하여 일괄 입력할 수 있도록 함으로써 매개변수 산정과정에서 문제가 되는 경험적인 요인을 제거하였다. 흐름의 구분은 얕은면 흐름, 지표하 흐름, 지하수 흐름으로 구분하여 운동파법과 선형저류법을 적용하였다. 또한 초기 토양함수 자동보정기법으로 실제의 기저유출량을 재현하여 전체적인 유출모의 정확도를 높였으며, FAO-56 Penman-Monteith법을 적용한 증발산량 산정모듈과 Sugawara et al.(1984)이 제안한 개념적 융설 및 적설모듈을 추가하였다. K-DRUM모형을 이용한 유출분석은 용담댐 시험유역을 대상으로 2013년도 1년간의 유출모의를 수행하였다. 입력자료는 용담댐 유역의 지형, 토양 및 토지특성 정보와 시단위 강우 및 기상정보(온도, 바람, 일사 등)를 활용하였다. 분석 결과, 총 관측유출량은 7,151 ㎥/s이고 총 계산유출량 $8,257m^3/s$이며, 관측유출량 대비 계산유출량은 약 115% 정도로 나타났다. 연간 총 강우량은 1303.5 mm로 유역면적 약 $930km^2$을 적용하여 유역 총 강우량을 산정하면 $14,030m^3/s$로서 관측유출량은 유역 총 강우량 대비 51%이고 계산유출량은 59% 정도로 나타났다. 즉 유역 유출율은 약 51% 수준으로 보통의 유역과 유사한 수준이다. 관측된 토양수분량과 K-DRUM 모형의 계산된 토양수분량을 비교하기 위하여 관측 토양수분량의 비율을 이용하여 비교하였다. 모의결과 토양수분은 강우에 의해 변화하며, 관측결과와 유사한 형태로 나타남을 알 수 있었다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.1
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• pp.24-31
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• 2021

We report structural, mechanical, and thermal properties of diecast ADC12 aluminum alloys characterized using synchrotron X-ray diffraction (XRD), scanning electron microscopy, energy dispersive X-ray (EDX) analysis, thermal conductivity (λ), Vickers hardness (Hv), and stress-strain measurements. We also studied the effect of post-annealing performed in a vacuum atmosphere on the mechanical properties of diecast ADC12 alloys. EDX and XRD results revealed that Al2Cu and AlCu3 grains are formed, well dispersed in Al base and highly crystalline. Ultimate tensile strength (UTS) of 307.9 ± 9.1 MPa and elongation of 2.98 ± 0.62 % were estimated. λ was 129.3 ± 0.27 W/m·K and Hv was approximately 130. Both values were significantly higher than the reported values. At annealing temperatures ranging from 25 to 200℃, UTS and Hv values remained constant, while as the annealing temperature increased to 500℃, these values gradually decreased. This is because stabilization of the microstructure improves toughness and ductility.

• Economic and Environmental Geology
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• v.35 no.5
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• pp.379-393
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• 2002

Within the Boseong-Jangheung area of Korea, five hydrothermal gold (-silver) quartz vein deposits occur. They have the characteristic features as follows: the relatively gold-rich nature of e1ectrurns; the absence of Ag-Sb( -As) sulfosalt mineral; the massive and simple mineralogy of veins. They suggest that gold mineralization in this area is correlated with late Jurassic to Early Cretaceous, mesothermal-type gold deposits in Korea. Fluid inclusion data show that fluid inclusions in stage I quartz of the mine area homogenize over a wide temperature range of 200$^{\circ}$ to 460$^{\circ}$C with salinities of 0.0 to 13.8 equiv. wt. % NaCI. The homogenization temperature of fluid inclusions in stage II calcite of the mine area ranges from 150$^{\circ}$ to 254$^{\circ}$C with salinities of 1.2 to 7.9 equiv. wt. % NaCI. This indicates a cooling of the hydrothermal fluid with time towards the waning of hydrothermal activity. Evidence of fluid boiling including CO2 effervescence indicates that pressures during entrapment of auriferous fluids in this area range up to 770 bars. Calculated sulfur isotope composition of auriferous fluids in this mine area (${\delta}^34S$_{{\Sigma}S}$$\textperthousand$) indicates an igneous source of sulfur in auriferous hydrothermal fluids. Within the Sobaegsan Massif, two representative mesothermal-type gold mine areas (Youngdong and Boseong-Jangheung areas) occur. The ${\delta}^34S values of sulfide minerals from Youngdong area range from -6.6 to 2.3$\textperthousand$ (average=-1.4$\textperthousand$, N=66), and those from BoseongJangheung area range from -0.7 to 3.6$\textperthousand$ (average=1.6$\textperthousand$, N=39). These i)34S values of both areas are comparatively lower than those of most Korean metallic ore deposits (3 to 7TEX>$\textperthousand$). And, within the Sobaegsan Massif, the ${\delta}^34S values of Youngdong area are lower than those of Boseong-Jangheung area. It is inferred that the difference of ${\delta}^34S values within the Sobaegsan Massif can be caused by either of the following mechanisms: (1) the presence of at least two distinct reservoirs (both igneous, with ${\delta}^34S values of < -6 $\textperthousand$ and 2$\pm$2 %0) for Jurassic mesothermal-type gold deposits in both areas; (2) different degrees of the mixing (assimilation) of 32S-enriched sulfur (possibly sulfur in Precambrian pelitic basement rocks) during the generation and/or subsequent ascent of magma; and/or (3) different degrees of the oxidation of an H2S-rich, magmatically derived sulfur source ${\delta}^34S = 2$\pm$2$\textperthousand$) during the ascent to mineralization sites. According to the observed differences in ore mineralogy (especially, iron-bearing ore minerals) and fluid inclusions of quartz from the mesothermal-type deposits in both areas, we conclude that pyrrhotite-rich, mesothermal-type deposits in the Youngdong area formed from higher temperatures and more reducing fluids than did pyrite(-arsenopyrite)-rich mesothermal-type deposits in the Boseong-Jangheung area. Therefore, we prefer the third mechanism than others because the ${\delta}^34S values of the Precambrian gneisses and Paleozoic sedimentary rocks occurring in both areas were not known to the present. In future, in order to elucidate the provenance of ore sulfur more systematically, we need to determine ${\delta}^34S values of the Precambrian metamorphic rocks and Paleozoic sedimentary rocks consisting the basement of the Korean Peninsula including the Sobaegsan Massif.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.9
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• pp.58-67
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• 2009

This paper presents a fully digital gain control system with a new high bandwidth and wide dynamic range power detector for DVB-S2 application. Because the peak-to-average power ratio (PAPR) of DVB-S2 system is so high and the settling time requirement is so stringent, the conventional closed-loop analog gain control scheme cannot be used. The digital gain control is necessary for the robust gain control and the direct digital interface with the baseband modem. Also, it has several advantages over the analog gain control in terms of the settling time and insensitivity to the process, voltage and temperature variation. In order to have a wide gain range with fine step resolution, a new AGC system is proposed. The system is composed of high-bandwidth digital VGAs, wide dynamic range power detectors with RMS detector, low power SAR type ADC, and a digital gain controller. To reduce the power consumption and chip area, only one SAR type ADC is used, and its input is time-interleaved based on four power detectors. Simulation and measurement results show that the new AGC system converges with gain error less than 0.25 dB to the desired level within $10{\mu}s$. It is implemented in a $0.18{\mu}m$ CMOS process. The measurement results of the proposed IF AGC system exhibit 80-dB gain range with 0.25-dB resolution, 8 nV/$\sqrt{Hz}$ input referred noise, and 5-dBm $IIP_3$ at 60-mW power consumption. The power detector shows the 35dB dynamic range for 100 MHz input.