• Journal of Power Electronics
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• v.16 no.6
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• pp.2085-2098
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• 2016

Laminated busbars with a low stray inductance are widely used in NPC three-level inverters, even though some of them have poor performances in heat equilibrium and overvoltage suppression. Therefore, a theoretical method is in need to establish an accurate mathematical model of laminated busbars and to calculate the impedance and stray inductance of each commutation loop to improve the heat equilibrium and overvoltage suppression performance. Firstly, an equivalent circuit of a NPC three-level inverter laminated busbar was built with an analysis of the commutation processes. Secondly, on the basis of a 3D (three dimensional) cubical thermal model and mirror circulation theory, a supersymmetric mirror circulation 3D cubical thermal model was built. Based on this, the laminated busbar was decomposed in 3D space to calculate the equivalent resistance and stray inductance in each commutation loop. Finally, the model and analysis results were put into a busbar design, simulation and experiments, whose results demonstrate the accuracy and feasibility of the proposed method.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.294-298
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• 2008

Snow cover is a potential water resource for later spring and summer seasons as well as a thermal mirror with high reflectivity causing decreases of surface air temperature during cold winter seasons. In this study, current and future changes in Northern Hemisphere snow extent and their potential linkages with atmospheric circulation are examined. The NOAA AVHRR visible snow extent (1967-2006) data as well as observational (NCEP-DOE 1979-2006) and modeled (GFDL 2.1 2081-2100) pressure and surface air temperature data are used. Analyses of observational data demonstrate that the snow extent in meteorological spring (March to April) and summer (June to August) has significantly decreased since the late 1980s. The offset of snow seasons (the timing of snow melt in spring) have also significantly advanced particularly in Europe, East Asia, and northwestern North America. Analyses of pressure fields reveal that the spatial patterns of the earlier snow melt are associated with changes in atmospheric circulation such as the Arctic Oscillation (AO). In the positive winter AO years, multiple positive pressure departure cores in the upper troposphere (200hPa) are observed over the mid-latitude regions from March to mid-April, while a negative pressure departure core (70hPa) prevails over the Arctic Ocean. The reversed anomaly patterns related to later snow melt occur in negative winter AO years. The comparison between current and future thermal spring onsets suggest that snow melt patterns will intensify with larger greenhouse gas emissions, indicating earlier hydrological spring onset.

• Current Optics and Photonics
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• v.2 no.6
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• pp.595-605
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• 2018

The two-photon process of microscopy provides good spatial resolution and optical sectioning ability when observing quasi-static endogenous fluorescent tissue within an in vivo animal model skin. In order to extend the use of such systems, we developed a two-photon laser scanning microscopy system capable of also capturing $512{\times}512$ pixel images at 90 frames per second. This was made possible by incorporating a 72 facet polygon mirror which was mounted on a 55 kRPM motor to enhance the fast-scan axis speed in the horizontal direction. Using the enhanced temporal resolution of our high-speed two-photon laser scanning microscope, we show that rapid processes, such as fluorescently labeled erythrocytes moving in mouse blood flow at up to 1.2 mm/s, can be achieved.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.8
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• pp.5067-5073
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• 2015

Recently, various researches about water resources management system have been conducted in order to handle many problems, for example, climate change can provoke rapid change of water circulation, continuous population increase, population concentration phenomenon and so on. For population concentration region, many researches about water resources management system have been carried out, but many regions far away from civilization have not been handled as research topics. Especially these regions always need electricity supply infra, but significant costs will be required to construct the infra. Therefore this paper presents a methodology in order to generate the electricity from new renewable energy resources and supply the electricity into these region. For this, solar thermal generation system was experimentally studied. Moreover, this solar power generation system was considered as an important component to establish an ESS (Energy Storage System).

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.438-440
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• 2018

Cardiac arrest is a series of conditions that occur when the heart is stopped, regardless of the cause. Cardiac arrest due to heart disease is included in the cause of death in korea every year and is unpredictable. One of the only ways to save a patient's life when a cardiac arrest is cardiopulmonary resuscitation is to maintain circulation through this procedure. The visual information is transmitted to the brain through the optic nerve. Among them, the mittor can see its movement and its shape, and it can be used for correction and analysis. Therefore compared the quality of chest compressions with visual information using mirrors. There was a significant difference in the mean depth of chest compressions($48.93{\pm}6.76$, $53.86{\pm}4.56$, <0.001), and there was also a difference in compression to relaxation ratio($0.87{\pm}0.13$, $0.96{\pm}0.10$, <0.002). There was also a significant difference in attitude awareness($4.93{\pm}0.85$, $8.14{\pm}1.38$, <0.001).