• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.37.1-37
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• 2001

Electric plating is used in various industry field. Specially, pulse plating is able to deposit material at high current density compared to conventional DC plating. For example, pulse plating can get more fine grain, can improve adhesion and metal distribution and current efficiency, can reduce internal stress and crack. Therefore, we developed bidirection pulse power supply(BPPS) which has high speed pulse current and high current density and improve deposition quality and increase plating speed in this paper. BPPS(Bidirection pulse power supply) needs high speed rising time, falling time and output current accuracy. BPPS consists of rectifier part, chopper part, invertor part, and control part. Rectifier part changes outprt current direction.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.42-44
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• 2004

This paper introduced and proposed the voltage unbalance of DC terminal output as new monitoring parameter for power islanding detection. This paper also presented a simple and novel detection algorithm, which effectively combines the detection results of the conventional parameter, voltage magnitude, and a newly proposed parameter. We tested the proposed method using several distribution network conditions including not only islanding operation conditions, but also non-islanding conditions of normal network load variations. The test results showed that the proposed parameters and algorithm are capable of correctly detecting the islanding operation not affected by variation of DG loading and also have a good selectivity for islanding conditions and non-islanding conditions.

• 한국자기학회지
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• 제5권5호
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• pp.745-748
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• 1995

Magnetic nanoparticles of iron and iron oxide have been prepared in a modified upward thermal diffusion cloud chamber using pulsed laser evaporation. SEM/TEM studies of these particles reveal a size distribution with a mean diameter of about $60\;{\AA}$. FTIR spectrum measurements are used to investigate the difference in oxidation level between nanoparticles prepared at different partial oxygen pressures. The complex magnetic behaviour of these particles was studied using DC- and AC-susceptibility measurements. All samples exhibit superparamagnetism with blocking temperatures ranging from 50 K to above room temperature. The coercivity fields as well as the dependence of the blocking temperature on measuring frequency have been studied. magnetic anisotropy constants are found to be one order of magnitude higher than is known for the bulk values. The mean particle size estimated from the magnetic data is found to be in perfect agreement with the TEM observations.

• Journal of Power Electronics
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• 제19권5호
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• pp.1153-1161
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• 2019

A current sharing controller is proposed in this paper for parallel-connected converters. The proposed controller is based on the calculation of the magnitudes of system current space vectors. Good current distribution between parallel converters is achieved with only one Proportional-Integral (PI) compensator. The proposed controller is analyzed and the circulating current impedance is derived for paralleled systems. The performance of the new control strategy is experimentally verified using two parallel connected converters employing Space Vector Pulse Width Modulation (SVPWM) feeding a passive RL load and a 2.2 kW three-phase induction motor load. The obtained test results show a reduction in the current imbalance ratio between the converters in the experimental setup from 53.9% to only 0.2% with the induction motor load.

• Journal of Korean Society for Atmospheric Environment
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• 제18권E2호
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• pp.85-95
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• 2002

Hydrogen peroxide and methyl hydroperoxide were measured over the northwestern Pacific Ocean during NASA's PEM (Pacific Exploratory Mission) -West. The first experiment (PEM -West A) was conducted in the fall of 1991 and PEM-West B in the early spring of 1994. Hydroperoxide data were obtained on board the NASA DC -8 aircraft through the entire depth of the troposphere. Average concentrations of both H$_2$O$_2$and CH$_3$OOH were higher during PEM -West A than B. The seasonal difference in hydroperoxide distribution was determined by the degree of photochemical activities and the strength and location of jetstream, which led to extensive and rapid continental outflow during the PEM-West B. While for H$_2$O$_2$distribution, a longitudinal gradient was more apparent than a latitudinal gradient, it was opposite for the CH$_3$OOH distribution. The longitudinal gradient indicates the proximity to the anthropogenic sources from the Asian continent, but the latitudinal gradient reflects photochemical activity. During PEM -West B, the ratio of C$_2$H$_2$/CO, a tracer for continental emission was raised and high concentrations of H$_2$O$_2$were associated with high ratios. The flux of hydroperoxide toward the North Pacific was also enhanced in the early spring. The eastward fluxes of H$_2$O$_2$ were 9% and 17% of the average photochemical production over the Pacific Basin between 140°E and 130°W during PEM-West A and B, respectively. For CH$_3$OOH, these ratios were 8% and 13%. Considering the lifetime of hydroperoxide and the rapid transport of pollutants, the export of hydroperoxide with other oxidants would have a significant influence on oxidant cycles over the North Pacific during winter/spring.

• 한국국방경영분석학회지
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• 제35권2호
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• pp.1-14
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• 2009

전시 공군은 각 지역에 거점부대를 선정하여 해당 지역에서 동원되는 품목별 물자를 인수하고, 물자가 부족한 지역의 거점부대에 잉여물자를 분배하여 전체 부대가 일정한 군수지원 수준을 유지할 수 있도록 계획하고 있다. 또한, 지역 거점부대는 해당지역에 주둔하고 있는 군소 운영부대들에 대한 DC(Distribution Center)의 역할도 담당하여 지역에서 동원되는 물자들과 타 지역 거점부대로부터 인수한 해당 지역 부족물자들을 군소운영부대에 분배한다. 하지만, 전시 동원물자 수송은 물자가 많이 동원되는 지역의 거점부대가 물자가 적게 동원되는 부대로의 분배 및 수송을 책임지기 때문에 동원물자들의 생산특성에 따라 지역 거점부대별 수송부담의 불균형과 다빈도 수송으로 인한 수송 자산(병력, 수송수단)의 낭비를 가져오게 된다. 또한, 공군본부나 군수사령부와 같은 상급부대는 전체적인 동원물자의 분배와 수송을 효율적인 방향으로 조정 통제하는데 대한 어려움이 있다. 본 연구에서는 이러한 어려움을 해소하기 위해 특정지역에 TC(Transfer Center)를 설치하여 물자를 분배하고 수송하는 방법론을 제시고자 한다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제25권2_spc호
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• pp.86-100
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• 2020

Analyzing and monitoring environmental contaminants based on geophysical exploration techniques have become important and it is now widely applied to delineate spatial distribution geophysical characteristics in wide area. Among the techniques, induced polarization (IP) method, which measures polarization effects on electrical potential distribution, has drawn much attention as an effective tool for environmental monitoring since IP is sensitive to changes in biochemical reactions. However, various reactions stemming from the presence of multiple contaminants have greatly enhanced heterogeneity of polluted sites to result in highly variable electrical characteristics of the site. Those contaminants influence chemical and physical state of soil and groundwater to alter electrical double layer, which in turn influences polarization of the media. Since biochemical reactions between microbes and contaminants result in various IP effects, IP laboratory experiments were conducted to investigate IP responses of the contaminated soil samples under various conditions. Field IP surveys can delineate the spatial distribution of contamination, while providing additional information about electrical properties of a target medium, together with DC resistivity. Reviewing IP effects of contaminants as well as IP surveys can serve as a good starting point for the application of IP survey in site assessment for environmental remediation.

• Applied Microscopy
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• 제47권1호
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• pp.29-35
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• 2017

Transverse magnetic field annealing (TFA) was carried out on $Fe_{73.5}Cu_1Nb_3Si_{15.5}B_7$ nano-crystalline magnetic core with the aim at decreasing coercivity ($H_c$) while keeping high inductance ($L_s$). The magnetic field generated by direct current (DC) was applied on the magnetic core during different selected annealing stages and it was proved that the nanocrystalline magnetic core achieved lowest $H_c$ when applying transverse field during the whole annealing process (TFA1). Although the microstructure and crystallization degree of the nanocrystalline magnetic core exhibited no obvious difference after TFA1 compared to no field annealing, the TFA1 sample showed a more uniform nanostructure with a smaller mean square deviation of grain size distribution. $H_c$ of the nanocrystalline magnetic core annealed under TFA1 decreased along with the increasing magnetic field. As a result, the certain size nanocrystalline magnetic core with low $H_c$ of 0.6 A/m, low core loss (W at 20 kHz) of 1.6 W/kg under flux density of 0.2 T and high $L_s$ of $13.8{\mu}H$ were obtained after TFA1 with the DC intensity of 140 A. The combination of high $L_s$ with excellent magnetic properties promised this nanocrystalline alloy an outstanding economical application in high frequency transformers.

• 한국진공학회지
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• 제22권3호
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• pp.126-130
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• 2013

PSG/$SiO_2$ 보호막 처리된 Al-1%Si 박막배선 내 sodium (Na)과 수분($H_2O$) 게터링(gettering) 현상을 측정, 분석하였다. PSG/$SiO_2$ 보호막과 Al-1%Si 박막을 상압CVD (APCVD: atmosphere pressure chemical vapor deposition)법과 DC 마그네트론 스퍼터로 각각 증착하였고, 이차이온 질량분석기(SIMS: secondary ion mass spectrometry)를 이용한 깊이분포측정(depth profiling) 분석을 통해 PSG/$SiO_2$ 보호막으로부터 Al-1%Si 박막배선 층까지의 sodium과 수분 등 성분들의 분포를 확인하였다. Sodium과 수분 피크 모두 Al-1%Si 박막배선 내부보다는 막 간 계면에서 강하게 나타났다. PSG와 $SiO_2$ 보호막 계면에서는 sodium 피크는 관찰되었지만 수분 피크는 관찰되지 않았다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.790-799
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• 2010

The Upper Devonian Grossmont Formation in Alberta, Canada reserves an estimated 50 billion cubic meters of bitumen and possess about 1/6 of the total bitumen resources in northern Alberta. However, unlike the overlying Athabasca oil sands, non conventional bitumen resources has not been developed as yet. The carbonate rocks of Grosmont Formation have been subject to various stages of diagenesis, including dolomatization and karstification with a strong effect on the distribution of porosity and permeability, which resulted in highly heterogeneous reservoirs. An extensive fracture logging and mapping was performed on total of six boreholes located in the study area to explore the characteristics of fracture geometry system and the subsurface structures of carbonates reservoir that holds bitumen. Fractal dimension was used as a measure of the statistical homogeneity of the fractured rock masses. The applicability of random Cantor dust, Dc, as a fractal parameter was examined systematically. The statistical homogeneity of fractured carbonates rock masses was investigated in the study area. The structural domains of the rock masses were delineated depthwise according to estimated Dc. The major fracture orientation was dominated by horizontal beddings having dip of $0-20^{\circ}$. Also, fractures having high dip angles existed with relatively low frequency. Three dimensional fracture network modeling for each structural domain has been performed based on fracture orientation and intensity, and some representative conceptual models for carbonates reservoir in the study area has been proposed. The developed subsurface conceptual models will be used to capture the geomechanical characteristics of the carbonates reservoir.