• Korean Journal of Environment and Ecology
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• v.21 no.2
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• pp.141-148
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• 2007

To investigate the forest community structure ranging from 200 meters to 1,350 meters above sea level at Donnaeko valley of Mt. Hallasan in 2006, 15 plots were surveyed. According to the classification analysis by TWINSPAN, the plant communities were divided into five groups of Castanopsis sieboidii community, Castanopsis sieboldii - Quercus acuta community, mixed forest, Carpinus laxiflora - Quercus serrata community and deciduous broad-leaved forest. 22 species of evergreen broad-leaved trees such as Castanopsis sieboldii, Quercus acuta, Distylium racemosum, Camellia japonica, Eurya japonica, Ligustrum lucidum, Ilex crenata, Daphnipyllum macropodum, etc. were growing at Donnaeko valley. According to the attitudinal distribution of evergreen broad-leaved trees, Castanopsis sieboidii was a dominant species distributed from 200 meters to 350 meters above sea level, Castanopsis sieboldii and Quercus acuta were dominant species distributed from 400 meters to 600 meters above sea level and Quercus acuta was a dominant species distributed from 660 meters to 700 meters above sea level. Ilex crenata, Daphniphyllum macropodum, Elaeagnus glabra were distributed up to 1,350 meters above sea level in Donnaeko.

• Journal of Internet Computing and Services
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• v.24 no.1
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• pp.87-97
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• 2023

Charger infrastructure facilities are designed and installed based on a constant power supply. Initially designed charging facilities support charging of rapidly growing electric vehicles on a limited power supply basis. In addition, current commercial vehicles can only be fully charged, and are supported by the rapid equalization charging method. However, commercial vehicles operate according to a set schedule, so flexible charging is essential. In this paper, we propose a power operation method with more than 20% efficiency improvement by using a fixed schedule-based charging scheduling and power distribution technique of a commercial bus based on the same amount of power in accordance with the rapid growth and increase of electric vehicles.

• Journal of the Korean Solar Energy Society
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• v.26 no.2
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• pp.53-59
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• 2006

The number of wind generation installations are growing substantially in Jeju, Korea. Many of these installations are significant in size and directly connected to the distribution system. Utility grid interconnection standards for interconnecting non-utility distributed generation systems are essential to both power system company and generation company. These interconnection standards are important to utilities, customers, wind generation manufactures and nation. In this paper, it is investigated the voltage quality and the suitability of Jeju-Hangwon wind power generation farm by network interconnection technology standard.

• Journal of the Korean Solar Energy Society
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• v.26 no.4
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• pp.63-71
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• 2006

The installed capacity of wind turbines in KOREA are growing and enlarging by the central government's support program. Thus, the importance of power performance verification and its uncertainty analysis are recognizing rapidly. This paper described the Power testing results of a 1.5MW wind turbine and analysed an uncertainty level of measurements. The measured power curves are very closely coincide with the calculated one and the annual power production under the given Rayleigh wind speed distribution are estimated with the $4.7{\sim}22.0%$ of uncertainty but, in the dominant wind speed region as $7{\sim}8m/s$, the uncertainty are stably decreased to $7{\sim}8%$.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.56-63
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• 2015

The optimization is an important role in wide geographical distribution of electrical power market, finding the optimum solution for the operation and design of power systems has become a necessity with the increasing cost of raw materials, depleting energy resources and the ever growing demand for electrical energy. In this paper, the real coded biogeography based optimization is proposed to minimize the operating cost with optimal setting of equality and inequality constraints of thermal power system. The proposed technique aims to improve the real coded searing ability, unravel the prematurity of solution and enhance the population assortment of the biogeography based optimization algorithm by using adaptive Gaussian mutation. This algorithm is demonstrated on the standard IEEE-30 bus system and the comparative results are made with existing population based methods.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.7
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• pp.1185-1192
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• 2003

Governing parameters for determination of the location of crack initiation and direction of crack initiation were investigated by performing fretting fatigue tests and analysis on Al 2024-T351. Fatigue tests were carried out using biaxial fatigue machine. It was shown that the dominant fatigue crack tended to initiate at the outer edge of one of the four bridge pads, growing at an angle beneath a pad, before turning perpendicular to the orientation of the axial load. Distribution of stresses generated during fretting fatigue loading along the interface was calculated by elastic FE simulation. It can be known that the location of crack initiation can be predicted by using the maximum tangential stress range. Futhermore, the crack initiation direction can also be predicted by a maximum tangential stress range.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.1
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• pp.137-143
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• 2020

With the development of information and communication technology, various data have appeared and are being distributed. The use of various data has contributed to the enrichment and convenience of our lives. Data in the public areas is also growing in volume and being actively used. Public data in the field of education are also used in various ways. As the distribution and use of public data has increased, advantages and disadvantages have started to emerge. Among the various disadvantages, the privacy problem is a representative one. In this study, we deal with the privacy issues of public data in education. First, we introduce the privacy issues of public data in the education field and suggest various solutions. The various solutions include the expansion of privacy education opportunities, the need for a new privacy protection model, the provision of a training opportunity for privacy protection for teachers and administrators, and the development of a real-time privacy infringement diagnosis tool.

• 한국벤처창업학회:학술대회논문집
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• 2017.08a
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• pp.37-47
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• 2017

The digital multi-sided platform has led the growth of industries. Accelerating this growth, generativity allowed innovation based on boundary-less modularity. Online games are a rich source of research but most of the research is dedicated in examining only the online game itself. However, there is a growing need to understand online games in an ecosystem level for a new phase of evolution is starting based on generativity. With generativity, online game users now make new graphics and quest that can be added and shared to the already existing game environment. The ecosystem is moving towards finding an amicable multi-sided distribution platform for these user generated game contents. Preliminary data suggest the possibility of actual connection between generativity and users' game engagement. Interviews and surveys will be prepared to find out the details of the possible relationship and how the ecosystem will shape accordingly.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.247-250
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• 2006

This paper presents the single-stage High Power Factor TSFC(Two-Switch Forward Converter). Recently, due to growing concern about the harmonic pollution of power distribution systems and the adoption of standards such as ICE 61000-3-2 and IEEE 519, There is a need to reduce the harmonic contents of AC line currents of power supplies. This research proposed the single-stage two switch forward circuit for low voltage and high current output. The principle of operation, feature and design considerations are illustrated and verified through the experiment with a 200W(5V, 40A) 200kHz MOSFET based experimental circuit.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.1
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• pp.27-40
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• 1997

The heat in Czochralski method is transfered by all transport mechanisms such as convection, conduction and radiation and convection is caused by the temperature difference in the molden pool, the rotations of crystal or crucible and the difference of surface tension. This study delvelops the simulation model of Czochralski growth by using the finite difference method with fixed grids combined with new latent heat treatment model. The radiative heat transfer occured in the surfce of the system is treated by calculating the view factors among surface elements. The model shows that the flow is turbulent, therefore, turbulent modeling must be used to simulate the transport phenomena in the real system applied to 8" Si single crystal growth process. The effects of a cusp magnetic field imposed on the Czochralski silicon melt are studied by numerical analysis. The cusp magnetic field reduces the natural and forced convection due to the rotation of crystal and crucible very effectively. It is shown that the oxygen concentration distribution on the melt/crystal interface is sensitively controlled by the change of the magnetic field intensity. This provides an interesting way to tune the desired O concentration in the crystal during the crystal growing.