• Journal of Power Electronics
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• v.12 no.3
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• pp.487-494
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• 2012

A new low cost high power density photovoltaic power conditioning system (PV PCS) with an energy storage system is proposed in this paper. Its high power density and cost effectiveness can be achieved through the unification of the maximum power point tracker and the battery charger/discharger. Despite the reduced power stage, the proposed system can achieve the same performance in terms of maximum power point tracking and battery charging/discharging as the conventional system. When a utility power failure happens, the proposed system cannot perform maximum power point tracking at the UPS mode. However, the predetermined battery voltage near the maximum power point of the PV array can effectively generate a reasonable PV power even at the UPS mode. Therefore, it features a simpler structure, less mass, lower cost, and fewer devices. Finally, to confirm the operation, validity, and features of the proposed system, a theoretical analysis and experimental results from a single phase AC 220Vrms/1.5kW prototype are presented.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.164-165
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• 2000

구멍에 의한 빛의 회절은 광학의 기본적인 문제로서, 최근 근접장 광학(Near-Field Optics)의 발전과 더불어서 파장보다 작은 구멍에서 일어나는 빛의 회절에 대한 관심이 고조되고 있다.$^{(1)(2)(3)}$ 본 연구에서는 그동안 주로 이론적으로 다루어지고 있던 파장보다 작은 금속 구멍을 통한 빛의 회절에 대해 실험결과들을 보고한다. 회절된 빛의 먼장(Far-field)과, 근접장(Near-field)을 모두 측정하기 위해서 고체각 주사기(Solid angle scanner)와 근접장 주사 광학 현미경(Near-field Scanning Optical Microscopy)이 사용되었다. 고체각 주사기(Solid angle scanner)를 사용하여 반구면 위에서의 빛의 이차원 세기 분포가 다양한 편광 상태에 따라서 측정되었고$^{(4)}$ 근접장 탐침(NSOM probe)으로 작은 금속 구멍주변을 주사함으로서 근접장이 측정되었다. 작은 구멍은 최근에 개발된 고출력 근접장 광섬유 탐침(High-power near-field fiber probe)구조를 이용하여 제작되었다.$^{(5)}$

• The Korean Journal of Ecology
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• v.27 no.3
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• pp.121-126
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• 2004

The purpose of this study was to investigate the distribution of epiphytic lichens that growing near the thermoelectric power plant to obtain a basic data for air environmental evaluation around the power plant. The study areas were all 12 places including ten sites near the power plant and two sites for control. All the number of lichens appeared in this study areas were 27 species. It showed to 4∼6 species within 4㎞ from the power plant, and coverage also was low. As receding from the power plant, both the number of species and overage increased. Parmelia tinctorum sensitive to air pollution did not appear within 4㎞ from the power plant, and it was regarded as the sensitive kind to air pollution. Lepraria sp.(13.40%), Parmelia austrosinensis (13.40%), and Dirinaria applanaita (13.40%) were distributed in all sites, and it could infer that they had tolerance to air pollution. The IAP (Index of Atmosphere Purity) values in Sadungdong Apsan, Seksangeabal and the Power plant were four times as low as those in Mt, Yeonwha, and it could infer that the air in those areas was not good. It was high IAP values as being distant from the power plant.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.47-52
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• 2005

A lot of information storage devices have been introduced and developed for recently years. The trends of those devices are high capacity, compact size, low power consumption, reliability, and removability for data interchange with other device. As a satisfaction of these trends, near-field technique is in the spotlight as the next generation device. In order for a near-field recording to be successfully implemented in the storage device, a slider and suspension is introduced as actuating mechanism. The optical slider is designed considering near-filed optics. Suspension is not only supports slider performance, and tracking servo capacity but also meets the optical characteristics such as tilt aberration, and guarantee to satisfy shock performances for the mobility fir the actuator. In this study, the optical slider and the suspension for near-field probe array are designed and analyzed considering dynamic performance of head-gimbal assembly and shock simulation..

• Nuclear Engineering and Technology
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• v.35 no.5
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• pp.387-398
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• 2003

For reference human intrusion scenarios constructed in previous study, a probabilistic safety assessment to derive the radionuclide concentration limits for the low- and intermediate- level radioactive waste disposal facility is conducted. Statistical approach by the Latin Hypercube Sampling method is introduced and new assumptions about the disposal facility system are examined and discussed. In our previous study of deterministic approach, the post construction scenarios appeared as most limiting scenario to derive the radionuclide concentration limits. Whereas, in this statistical approach, the post drilling and the post construction scenarios are mutually competing for the scenario selection according to which radionuclides are more important in safety assessment context. Introduction of new assumption shows that the post drilling scenario can play an important role as the limiting scenario instead of the post-construction scenario. When we compare the concentration limits between the previous and this study, concentrations of radionuclides such as Nb-94, Cs-137 and alpha-emitting radionuclides show elevated values than the case of the previous study. Remaining radionuclides such as Sr-90, Tc-99 I-129, Ni-59 and Ni-63 show lower values than the case of the previous study.

• Economic and Environmental Geology
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• v.31 no.6
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• pp.509-518
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• 1998

Fly ashes have been deposited around Youngwol power plant until electrostatic precipitator was installed in 1981. Fresh fly ash samples from electrostatic precipitator and weathered fly ash from ash disposal site were collected from Youngwol power plant, along with 65 soil samples of nearby area to look into the influence of PFA deposit on the soils in surrounding area. In chemistry, EPA does not contain high level of toxic elements and there is no notable concentration of toxic elements in soil near power plant. Total concentrations of Co, Cr, Cu, V, and Zn are 13 ppm, 89 ppm, 73 ppm, 157 ppm and 57 ppm in PFA. Concentrations of theses elements in ash-rich soils are 15 ppm, 78 ppm, 60 ppm, 133 ppm and 68 ppm, and those in ash-poor soils are 19 ppm, 70 ppm, 38 ppm, 91 ppm and 97 ppm. But these metal elements are highly concentrated in magnetic fractions of EPA (Co, 129 ppm; Cr, 217 ppm; Cu, 210 ppm; V, 197 ppm; Zn 90 ppm). Considering the process of long-term weathering of PFA, potentially toxic substances from the ash could be leached into soils and groundwater.

• New & Renewable Energy
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• v.5 no.2
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• pp.3-8
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• 2009

Tidal current power system is one of ocean renewable energies that can minimize the environmental impact with many advantages compared to other energy sources. Not like others, the produced energy can be precisely predicted without weather conditions and also the operation rate is very high. To convert the current into power, the first device encountered to the incoming flow is the rotor that can transform into rotational energy. The performance of rotor can be determined by various design parameters including numbers of blade, sectional shape, diameter, and etc. The stream lines near the rotating rotor is very complex and the interference effects around the system is also difficult to predict. The paper introduces the experiment of rotor performance and also the fundamental study on the characteristics of three different rotors and flow near the rotor by CFD.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.978-980
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• 2013

In this paper, we have presented a basic idea of a power shut-off client based on NFC (near field communication). For the first step of the system design, we have shown the conceptual diagrams of the hardware configuration and the software logic flow. This system can be applied to the integrated power control in home, office, school, factory, and apartment. The standby power shut-off system will bring saving in electrical energy and cost.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1608-1610
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• 2000

In this work, the effect of annealing on physical and electrical properties of XLPE cable insulation was investigated. One sample was non-annealed and the other two samples were treated under air circulated oven at 80$^{\circ}C$ for five and ten days. In the DSC patterns of annealed specimen, new peaks appeared at near 80$^{\circ}C$ as a proof of thermal history. The degree of crystallinity increased by annealing effect. In the FT-IR spectrums, the change of absorbances to acetophenone and cumyl alcohol were observated according to the radial direction of cable insulation. They slowly diffused into both semi-conductive layer of the cable in proportion to annealing time and lastly led to near equilibrium state through cable insulation. The AC breakdown strength did not increased but the values were stabilized by effects of crystallinity and diffusion of by-products.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.87.1-87.1
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• 2011

We analyze the I-GALFA HI 21-cm line survey data in order to study the characteristics of interstellar turbulence in the neutral hydrogen medium in the Galaxy. We select several regions of 4.3 deg x 4.3 deg area near or far from the galactic plane both in the inner and outer Galaxy, transform the power of those regions into Fourier planes and derive one- and two-dimensional power spectra of HI emission. Our Fourier-analysis shows that the iso-power contours generally elongate along the latitude direction more in the outermost spiral arm, which indicates that the HI structure is "filamentary" and mainly aligned along the longitude. At high latitudes or in the interarm region, on the other hand, the iso-power contours are close to circles implying that the HI structures are randomly distributed or "clumpy". In the inner Galaxy, we derive two-dimensional spectra both far from and near the arm and explore the nature of the turbulence.