• Bulletin of the Korean Space Science Society
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• 2004.04a
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• pp.35-35
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• 2004

Inhomogeneity Is important in wave coupling and mode conversion. We numerically examine the conversion of extraordinary(X) waves into upper hybrid(UH) waves in inhomogeneous plasmas by using a three-dimensional multi-fluid numerical model. A one-dimensional Inhomogeneous density profile is assumed in a cold and collisionless plasma. The density gradient is taken to be perpendicular to the magnetic field. An impulsive input is assumed to excite the X waves in the inhomogeneous box model. (omitted)

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2014.06a
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• pp.241-243
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• 2014

Recently, as the coastal erosion impacts greats to both social and economical aspects, each local government is trying to setup its countermeasures. However, it is necessary to survey the change of sediment movement characteristics and investigate the continuous environment change by long-term monitoring after building prevention constructions. In this study, predictions on wave deformation and sediment movement deduced through the numerical modeling are made, based on the ordinary and extraordinary wave through seasonal superiority wave direction, height, period and long-term wave characteristics on the eroded beach of central West sea.

• Nuclear Engineering and Technology
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• v.50 no.7
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• pp.1106-1111
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• 2018

Electromagnetic waves potentially have been used to heat overdense nuclear fusion plasmas through a double mode conversion from ordinary to slow extraordinary and finally to Electron Bernstein Wave (EBW) modes, OSXB. This scheme is efficient and has not any plasma density limit of electron cyclotron resonance heating due to cut-off layer. The efficiency of conversion depends on the isotropic launching angles of the microwaves with the plasma parameters. In this article, a two-step mode conversions of OSXB power transmission efficiency affected by the fast extraordinary (FX) loses at upper hybrid frequency are studied. In addition, the kinetic (hot) dispersion relation of a overdense plasma in a full wave analysis of a OSXB in Wendelstein 7X (W7-X) stellarator plasma has been numerically simulated. The influence of plasma dependent parameters such as finite Larmor radius, electron thermal velocity and electron cyclotron frequency are represented.

• Proceedings of the Optical Society of Korea Conference
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• 1990.02a
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• pp.157-161
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• 1990

Self-pumped phase conjugation(SPPC) in BaTiO3 single crystal is experimentally investigated at a wavelength of 514.5nm from an Ar+ laser. The incident Gaussian beam enters the crystal as an extraordinary ray. The maximum SPPC reflectivity of 48% is obtained at incident angle 80 degree. the SPPC wave demonstrates good image reconstruction. The response time (r) of SPPC wave as a function of incident intensity is measured to be r=36$\times$I-0.79sec.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.35 no.12
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• pp.541-554
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• 1986

This paper presents the results of driving performance analysis of permanent magnet synchronous motor using a microprocessor based control system. The system consists of three phase power transistor inverters, three phase controlled rectifier, three central processing units, and sensors. The three CPUs are, respectively, used to generate PWM control signals for the inverter generating three phase sine wave, to generate the gate control signals for firing the converter, and to supervise other two CPUs. The supervisor is used to compute PI control algtorithm to three phase reference sine wave for the inverter. It is also used to maintain a constant voltage frequency ratio for the converter operating as a constant torque controller. The inverter CPU retrieves precomputed PWM patterns from look up tables because of computation speed limitations found in almost available microprocessors. The converter CPU also retrieves precomputed gate control patterns from another look-up tables. For protecting the control ststem from any damage by extraordinary over currents, the supervisor receives the data from current sensor, CT, and break down the CB to isolate the circuits from source. A resolver has a good performance characteristics of overall speed range, especially on low speed range. Therefor the speed control accuracy is impoved. The microprocessor based PM synchronous motor control system, thus, has many advantages such as constant torque characteristics, improvement of wave, limitation on extraordinary over currents, improvement of speed control accuracy, and fast response speed control using multi-CPU and look-up tables.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2014.10a
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• pp.9-11
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• 2014

As Daecheon beach, which is the study area, has problem of erosion and loss of most beach under the extraordinary wave during the typhoon event, it is necessary to apply erosion control measures for short term impact. Therefore, we analyzed the status and reason of the erosion by field survey, collection of hydraulic model test, and numerical model experiment. For the erosion control measure, we adopted beach feeding and submerged reef method available at that site among various counter measures. Numerical analyses were made for both beach feeding only and beach feeding with submerged reefs and these were compared with the present status to find out the optimum design and to contribute for preparing a long term plan of beach loss protection.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.12
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• pp.22-27
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• 2015

Conoscopic holography, which consists of two linear polarizers and two wave plates, and an uniaxial crystal, is incoherent holographic technology for three-dimensional display. In the uniaxial crystal, the wave from object divides into extraordinary and ordinary waves and phase difference between two waves is caused by the different refractive index of two waves. Four intensity patterns, which are made by phase difference, are obtained using LCLV(liquid crystal light valve) and conoscopic holography system. By combining four intensity patterns, the complex hologram without bias and conjugate image. In this paper, we propose the optimized system, which consists of a wave plate and a linear polarizer, and uniaxial crystal. In the proposed system, it doesn't need LCLV. By adjusting the azimuth angle of a linear polarizer and a wave plate, we derive four intensity patterns in recording plane. We demonstrate theoretically that the complex hologram with bias and a conjugate image is obtained using the proposed system.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.105-112
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• 2006

Freak waves in the ocean are recently drawing much attention as a natural disaster to ocean structures and navigating ships as well. Several observation data, among them the Draupner New Year Wave, show the very impressive feature of Freak waves whose wave height is up to three times as high as the significant wave height of surrounding waves, In addition, Freak wave appears as an isolated very high crest in somewhat stationary random waves of same order in their wavelengths. Bearing such characteristics in mind, one notices its extraordinary steepness. This strongly suggests that Freak wave is not long lived but transient nature on the whole. A great number of studies to explain these natures were published from both theoretical and numerical point of view. However it is not sure if they are applicable to actual ocean environment. In this paper, we deal with the results concerning abnormal and/or Freak waves from in-situ ocean wave data and point out several remarks to the problems lain behind the contributions in this context. A physical experiment is described to reinforce the subject discussed from the observation data.

• Atmosphere
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• v.17 no.4
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• pp.463-470
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• 2007

This study aims to assess the impact of the hot summer weather on daily mortality in Busan. Daily total all-caused mortality in the entire population in Busan has been examined during 1991-2005. The daily deaths were standardized to account for the long-term trend in mortality and their seasonal and weekly cycles. We found the net increase (about 8.2%) of excess deaths during the extraordinary heat wave period in July of 1994. It corresponds to the excess deaths of 109.5 during the month. The abnormality of temperature extremes in July of 1994 and their impacts on human health were also investigated. Unusual heat wave appeared in the first ten days in July of 1994. The excess deaths are likely to be attributable to the record-breaking heat waves. The result suggests that unusual early heat waves would be dangerous, even for inhabitants who live in an acclimated region to the heat waves such as Busan.

• KDI Journal of Economic Policy
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• v.39 no.2
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• pp.53-74
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• 2017

This paper focuses on the recent extraordinary growth of Chinese cross-border online shopping and draws implications for firm strategies and government policies in Korea to utilize the phenomenon as an opportunity to expand into a broader market via e-commerce exports. I conduct a survey of Chinese cross-border online consumers to identify constraining and determining factors during the stages of their purchase decisions of Korean products. Given the fact that Chinese cross-border online shopping is at the incipient stage and consumers have expressed a strong intent to repurchase, future strategies should focus on attracting new consumers. Accordingly, Korean firms should build a powerful brand image, improve product quality and post-purchase services, and take full advantage of the popularity of the Korean Wave. Meanwhile, the government must step up policy efforts by, for instance, improving e-commerce export statistics, simplifying logistics and clearance procedures, and building trust in Chinese consumers.