• Journal of Construction Engineering and Project Management
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• v.3 no.3
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• pp.23-34
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• 2013

As climate change and environmental pollution become one of the biggest global issues today, new renewable energy, especially solar photovoltaic (PV) system, is getting great attention as a sustainable energy source. However, initial investment cost of PV system is considerable, and thus, it is crucial to predict electricity generation accurately before installation of the system. This study analyzes the loss ratio of solar photovoltaic electricity generation from the actual PV system monitoring data to predict electricity generation more accurately in advance. This study is carried out with the following five steps: (i) Data collection of actual electricity generation from PV system and the related information; (ii) Calculation of simulation-based electricity generation; (iii) Comparative analysis between actual electricity generation and simulation-based electricity generation based on the seasonality; (iv) Stochastic approach by defining probability distribution of loss ratio between actual electricity generation and simulation-based electricity generation ; and (v) Case study by conducting Monte-Carlo Simulation (MCS) based on the probability distribution function of loss ratio. The results of this study could be used (i) to estimate electricity generation from PV system more accurately before installation of the system, (ii) to establish the optimal maintenance strategy for the different application fields and the different season, and (iii) to conduct feasibility study on investment at the level of life cycle.

• International conference on construction engineering and project management
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• 2013.01a
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• pp.375-385
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• 2013

As climate change and environmental pollution become one of the biggest global issues today, new renewable energy, especially solar photovoltaic (PV) system, is getting great attention as a sustainable energy source. However, initial investment cost of PV system is considerable, and thus, it is crucial to predict electricity generation accurately before installation of the system. This study analyzes the loss ratio of solar photovoltaic electricity generation from the actual PV system monitoring data to predict electricity generation more accurately in advance. This study is carried out with the following five steps: (i) Data collection of actual electricity generation from PV system and the related information; (ii) Calculation of simulation-based electricity generation; (iii) Comparative analysis between actual electricity generation and simulation-based electricity generation based on the seasonality; (iv) Stochastic approach by defining probability distribution of loss ratio between actual electricity generation and simulation-based electricity generation ; and (v) Case study by conducting Monte-Carlo Simulation (MCS) based on the probability distribution function of loss ratio. The results of this study could be used (i) to estimate electricity generation from PV system more accurately before installation of the system, (ii) to establish the optimal maintenance strategy for the different application fields and the different season, and (iii) to conduct feasibility study on investment at the level of life cycle.

• Journal of KSNVE
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• v.9 no.6
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• pp.1180-1186
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• 1999

The aim of this study is to investigate the sound insulation performance of windows according to the sound source in the field test. For this purpose, an experiment was performed by KSF 2235(method for field measurements of sound insulation of windows and doors). Based on this code, the sound insulation performance fo the windows was measured for different incident angles of the sound and the effect of incident angle was obtained and discussed. Finally, it was found that the sound insulation performance of the windows was affected by the incident angle of sound source, and the sound insulation rating scale was different for the same window. The main factor changing insulation rating scale is considered to be the sound transmission through the carck of the folding part between the two pieces of wndows. Therefore, when evaluating the sound insulation performance of the windows for the field test, first of all the place of the sound source should be identified and generalized.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.6
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• pp.697-704
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• 2008

Stormwater runoff from urban road area as non-point source has a tendency of including lots of pollutants at initial rain period. Recently, there are several cases of having installed treatment facilities for reducing pollution discharge from the impervious cover in urban area to prevent watershed environment from getting worse. The filtration type among non-point source treatment systems has been known as one of the most efficient system for treatment of non-point source pollutants. Therefore, various kinds of filter media such as expanded polypropylene(EPP), granular activated carbon, zeolite, perlite, illite, sand, gravel has been developed. This study was conducted to verify performance and hydraulic characteristics of filter media as measures for non-point source. The experiment was carried out to evaluate applicability and variation of 4 kind of most popular filter media(EPP, GAC, Zeolite, Perlite) in headloss with elapsed time and influent flow rate and to obtain data base that could be used to establish management plan for road runoff treatment. In experiment by tap water, it showed that EPP and perlite those are floatable materials showed stable operating performance and lower headloss than the others.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.96-97
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• 2000

Incoherent broadband optical sources have been applied in various areas such as a light source for optical device characterization, fiber-optic gyroscopes$^{(1)}$ , and spectrum sliced light source in wavelength division multiplexing (WDM) system$^{(2)}$ . To utilize the inherent low loss in silica optical fibers, various types of incoherent light sources are being developed. Among the light sources, the amplified spontaneous emission (ASE) from a rare earth doped fiber has benefits in temperature stability, high output power, low polarization dependence over semiconductor diodes$^{(3)}$ . Recently erbium doped fibers (EDF) have been intensively researched for ASE sources as well as optical amplifiers$^{(4)}$ . The spectrum of ASE from an EDF, however, is limited in the 1520~1560 nm range in conventional configurations. In this letter we described a new broadband ASE source which included both the conventional ASE band of Er$^{3+}$ ion, 1520nm~1560nm and ASE band from Tm$^{3+}$ ions that extends the bandwidth further. For the first time, to the best knowledge of authors, a fiber ASE source based on the energy transfer between Er$^{3+}$ and Tm$^{3+}$ ions in the range of 1460~1550 nm, has been demonstrated using a single 980nm pump laser diode. (omitted)omitted)

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.250.1-250.1
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• 2014

A multicusp ion source has been used widely in negative hydrogen cyclotrons mainly for radioisotope productions. The ion source is designed to have cusp geometries of magnetic field inside plasma chamber, where ions are confining and their mean lifetimes increase. The magnetic confinement produced a number of permanent magnetic poles helps to increase beam currents and reduce the emittance. Therefore optimizing the number of magnets confining more ions and increasing their mean lifetime in plasma has to be investigated in order to improve the performance of the ion source. In this work a numerical simulation of the magnetic flux density from a number of permanent magnets is carried to optimize the cusp geometries producing the highest plasma density, which is clearly indicated along the full-line cusp geometry. The effect of magnetic fields and a number of poles on the plasma structure are investigated by a computing tool. The electron confinement effect becomes stronger and the density increases with increasing the number of poles. On the contrary, the escape of electrons from the loss cone becomes more frequent as the pole number increases [1]. To understand above observation the electron and ion's trajectories along with different cusp geometries are simulated. The simulation has been shown that the optimized numbers of magnets can improve the ion density and uniformity.

• Journal of Radiation Protection and Research
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• v.42 no.2
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• pp.106-113
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• 2017

Background: Interfacing-system loss-of-coolant-accident (ISLOCA) has been identified as the most hazardous accident scenario in the typical PWR plants. The present study as an effort to improve the knowledge of the source term to the environment during ISLOCA focuses on an improvement of the estimation method. Materials and Methods: The improvement was performed to take into account an effect of broken pipeline and auxiliary building structures relevant to ISLOCA. An estimation of the source term to the environment was for the OPR-1000 plants by MELOCR code version 1.8.6. Results and Discussion: The key features of the source term showed that the massive amount of fission products departed from the beginning of core degradation to the vessel breach. Conclusion: The release amount of fission products may be affected by the broken pipeline and the auxiliary building structure associated with release pathway.

• Journal of Power Electronics
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• v.3 no.4
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• pp.239-248
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• 2003

This paper presents a novel prototype of three-phase voltage source type zero voltage soft-switching inverter with the auxiliary resonant snubbers suitable for high-power applications with IGBT power module packages in order to reduce their switching power losses as well as electromagnetic conductive and radiative noises. A proposed single inductor-assisted resonant AC link snubber circuit topology as one of some auxiliary resonant commutation snubbers developed previously to achieve the zero voltage soft-switching (ZVS) for the three-phase voltage source type sinewave PWM inverter operating under the instantaneous space voltage vector modulation is originally demonstrated as compared with the other types of resonant AC link snubber circuit topologies. In addition to this, its operation principle and unique features are described in this paper. Furthermore, the practical basic operating performances of the new conceptual instantaneous space voltage vector modulation resonant AC link snubber-assisted three-phase voltage source type soft-switching PWM inverter using IGBT power module packages are evaluated and discussed on the basis of switching voltage and current waveforms, output line to line voltage quality, power loss analysis, actual power conversion efficiency and electromagnetic conductive and radiative noises from an experimental point of view, comparing with those of conventional three-phase voltage source hard-switching PWM inverter using IGBT power modules.

• Nuclear Engineering and Technology
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• v.37 no.4
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• pp.327-362
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• 2005

The design, construction, and operation of a light water reactor (LWR) are subject to compliance with safety criteria specified for accident situations, such as loss-of-coolant accident (LOCA) and reactivity-initiated accident (RIA). Because reactor fuel is the primary source of radioactivity and heat generation, such a criterion is established on the basis of the characteristics and performance of fuel under the specific accident condition. As such, fuel behavior under accident situations impact many aspects of fuel design and power generation, and in an indirect manner, even spent fuel storage and management. This paper provides a comprehensive review of: the history of the current LOCA criteria, results of LOCA-related investigations on conventional and new classes of fuel, and status of on-going studies on high-burnup fuel under LOCA situations. The objective of the paper is to provide a better understanding of important issues and an insight helpful to establish new LOCA criteria for modem LWR fuels.

• Journal of the Korean Institute of Telematics and Electronics
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• v.23 no.2
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• pp.264-268
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• 1986

A thchnique has been studied for the measurement of the spectral loss and the cut-off wave length, at which the first high-order mode disappears. The near-field patterns of a fiber which is excited by a variable wavelength source are used for the measurement of cut-off wavelength. Because of the absorptive phenomenon of OH- molecular vibration, spectral loss of a single mode optical fiber sample is 5.6dB/km at 1380 nm wavelength and 1dB/km at 1240 nm wavelength. From the near field intensity patterns and the mode field diameter graph for the half power width, the cut-off wavelength of the fiber is measured to be 1120 nm.