• Korean Journal of Construction Engineering and Management
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• v.12 no.6
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• pp.110-119
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• 2011

Global warming caused by excessive greenhouse gas emission is causing climate change all over the world. In Korea, greenhouse gas emission from residential buildings accounts for about 10% of gross domestic emission. Also, the number of deteriorated multi-family housing complexes is increasing. Therefore, the goal of this research is to establish the bases to manage energy consumption continuously and methodically during MR&R period of multi-family housings. The research process and methodologies are as follows. First, research team collected the data on project characteristics and energy consumption of multi-family housing complexes in Seoul. Second, an ontology-based breakdown structure was established with some primary characteristics affecting the energy consumption, which were selected by statistical analysis. Finally, a predictive model of energy consumption was developed based on the ontology-based breakdown structure, with application of CBR, ANN, MRA and GA. In this research, PASW (Predictive Analytics SoftWare) Statistics 18, Microsoft EXCEL, Protege 4.1 were utilized for data analysis and prediction. In future research, the model will be more continuous and methodical by developing the web-base system. And it has facility manager of government or local government, or multi-family housing complex make a decision with definite references regarding moderate energy consumption.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.8
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• pp.591-597
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• 1999

The propagation characteristics of high power microwave pulse in an air-breakdown environment are examined. The maximum electron density produced by microwave air-breakdown is limited to $10^6cm^{-3}$ by the tail-erosion effect. Inorder to increase the electron density, the scheme using two pulses intersecting at a desired height is considered. Increasing the carrier frequency, it is shown that microwave pulse can be transferred without the serious erosion in the numerical simulation. This result is useful for the above scheme. Also, an experiment is conducted to show the tail-erosion effect and confirm that a rapidly generated lossy plasma can cause spectral breaking and frequency shift of a high-power microwave pulse. The experimental results are presented by comparing the frequency spectrum of an incident pulse with that of the pulse transmitted through a self-induced air-breakdown environment. The experimental results show that the amount of frequency upshift is co-related with the ionization rate, whereas that of frequency downshift is correlated with the energy losses from the pulse in the self-generated plasma.

• Journal of Electrical Engineering and Technology
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• v.5 no.2
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• pp.329-336
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• 2010

The paper describes the electrical and optical properties of underwater discharges in highly inhomogeneous electric fields caused by 1.2/50 ${\mu}s$ impulse voltages as functions of the polarity and amplitude of the applied voltage, and various water conductivities. The electric fields are formed by a point-to-plane electrode system. The formation of air bubbles is associated with a thermal process of the water located at the tip of the needle electrode, and streamer coronas can be initiated in the air bubbles and propagated through the test gap with stepped leaders. The fastest streamer channel experiences the final jump across the test gap. The negative streamer channels not only have more branches but are also more widely spread out than the positive streamer channels. The propagation velocity of the positive streamer is much faster than that of the negative one and, in fact, both these velocities are independent of the water conductivity; in addition the time-lag to breakdown is insensitive to water conductivity. The higher the water conductivity the larger the pre-breakdown energy, therefore, the ionic currents do not contribute to the initiation and propagation of the underwater discharges in the test conditions considered.

• Journal of computational fluids engineering
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• v.20 no.2
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• pp.73-80
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• 2015

Delayed Detached-Eddy Simulation was conducted to investigate surface pressure coefficient distribution and surface pressure fluctuation over an ONERA 70-degree delta wing at a high angle of attack. Time-averaged surface pressure distribution is directly affected by the primary vortices, whereas the pressure fluctuation is influenced by the unsteady fluctuating boundary layer over the surface. And pressure coefficient, velocity, pressure fluctuation, and turbulent kinetic energy were analyzed along the vortex core in order to investigate the process of vortex breakdown. Consequently, strong pressure fluctuations were found where the vortex breakdown was occurred at x~620 mm. The turbulent kinetic energy abruptly increased and followed after the vortex breakdown.

• Journal of IKEEE
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• v.22 no.2
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• pp.339-343
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• 2018

Power semiconductors are semiconductors capable of controlling power over 1W and are mainly used as switches. This power semiconductor device has been developed with the goal of reducing power consumption and high breakdown voltage. This research was analyzed electrical characteristics of IGBT(Insulated Gate Biopolar Transistor) according to diffusion length of JFET region. The Diffusion length of JFET region was controlled by temperature and time using T-CAD simulator. As a result of experiments, we could obtain 1.14V low on state voltage drop by fixing 1440V breakdown voltage.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.44 no.1
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• pp.64-69
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• 1999

Gelatinization characteristics of 111 glutinous rice varieties were evaluated by Rapid Visco Analyzer. Gelatinization viscosity of glutinous rice tested varied with ecotypes or varietal groups: indica, japonica, and Tongil type. Indica rice showed the highest average value of initial pasting temperature. The average values for peak, hot, and cool viscosities were highest in Tongil-type rice, and lowest in japonica rice. Japonica showed the lowest breakdown and consistency, but the highest setback value. Indica was lower in alkali digestion value (ADV), and shorter in gel length after gelatinization thanjaponica and Tongil-type. Glutinous rices tested could be divided into six groups by cluster analysis based on their gelatinization characteristics. Group I-A was mostly early maturing japonica varieties while I-B was mostly indica and Tongil-type rices. Groups II-A and II-B were consisted of very early maturingjaponica, and III-A and III-B included medium or medium late maturingjaponica varieties. Group III-A showed the lowest average values of peak, hot, cool, and consistency viscosities, and also in breakdown and setback ratios. Group I-B revealed the highest values in peak, hot, cool, breakdown, and consistency viscosities. ADV was low in groups I-A, I-B, and II-B, and gel consistency was not different among the six varietal groups. Principal component analysis using seven traits related with gelatinization produced four effective components, and the first and second components were highly correlated with all the gelatinization characters evaluated.

• 전기의세계
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• v.16 no.4
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• pp.11-16
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• 1967

A physical analysis is applied to the measured phenomena of aromatic organic compounds under the uniform electric field of 0.1MV/cm through 1.5MV/cm, when they are irradiated or non-irradiated respectively. Upon the observations about irradiation effects, space charge effects and their temperature dependance, the conditions of lattice defects act conspicuously on electric conductrivity, photo conductivity and dielectric breakdown. Although the qualitative agreement with Frohlich's high energy criterion theory for the above mechanisms is poor, it is concluded that the phenomena of aromatic compounds may possibly be due to the effect of lattice defects or impurity centers generated by .gamma.-ray irradiations.

• Korean Journal of Materials Research
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• v.29 no.3
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• pp.175-182
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• 2019

This study examines paraelectric $Bi_{1.5}Zn_{1.0}Nb_{1.5}O_7$ (BZN), which has no hysteresis and high dielectric strength, for energy density capacitor applications. To increase the breakdown dielectric strength of the BZN film further, poly(vinylidene fluoride) BZN-PVDF composite film is fabricated by aerosol deposition. The volume ratio of each composition is calculated using dielectric constant of each composition, and we find that it was 12:88 vol% (BZN:PVDF). To modulate the structure and dielectric properties of the ferroelectric polymer PVDF, the composite film is heat-treated at $200^{\circ}C$ for 5 and 30 minutes following quenching. The amount of ${\alpha}-phase$ in the PVDF increases with an increasing annealing time, which in turn decreases the dielectric constant and dielectric loss. The breakdown dielectric strength of the BZN film increases by mixing PVDF. However, the breakdown field decreases with an increasing annealing time. The BZN-PVDF composite film has the energy density of $4.9J/cm^3$, which is larger than that of the pure BZN film of $3.6J/cm^3$.

• Journal of IKEEE
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• v.25 no.2
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• pp.350-355
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• 2021

IGBT is a power semiconductor device that contains both MOSFET and BJT structures, and it has fast switching speed of MOSFET, high breakdown voltage and high current of BJT characteristics. IGBT is a device that targets the requirements of an ideal power semiconductor device with high breakdown voltage, low V_CE-SAT, fast switching speed and high reliability. In this paper, we analyzed Gate oxide thickness, Trench Gate Width, and P+Emitter width, which are the top process parameters of 1,200V Trench Gate Field Stop IGBT, and suggested the optimized top process parameters. Using the Synopsys T-CAD Simulator, we designed IGBT devices with electrical characteristics that has breakdown voltage of 1,470 V, V_CE-SAT 2.17 V, Eon 0.361 mJ and Eoff 1.152 mJ.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.05a
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• pp.275-276
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• 2005