• Journal of Korea Multimedia Society
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• v.9 no.7
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• pp.827-834
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• 2006

In distributed virtual environment, system response time to users' interactions is an importance factor to determine the degree of contentment with the system. Generally, response time is affected by the efficiency of event message processing algorithm, and most of previous systems use FCFS algorithm, which processes message traffic sequentially based only on the event occurrence time. Since this method totally depends on the order of occurrence without considering the priorities of events, it has a problem that might drop the degree of system response time by causing to delay processing message traffic when a bottleneck phenomenon happens in the server side. To overcome this limitation of FCFS algorithm, this paper proposes a concurrent event scheduling algorithm, which is able to process event messages concurrently by assigning the priorities to the events. It is also able to satisfy the two goals of system together, consistency and responsiveness through the combination of occurrence time with priority concept of events.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1066-1069
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• 2004

Recently the monitoring system of tool setup in high speed precision machining tool is required for manufacturing products that have highly complex and small shape, high precision and high function. It is very important to reduce time to setup tool in order to improve the machining precision and productivity and to protect the breakage of cutting tool as the shape of product is smaller and more complex. Generally, the combination of errors that geometrical clamping error of fixing tool at the spindle of machining center and the asynchronized error of driving mechanism causes that the run-out of tool reaches to 3∼20 times of the thickness of cutting chip. And also the run-out is occurred by the misalignment between axis of tool shank and axis of spindle and spindle bearing in high speed rotation. Generally, high speed machining is considered when the rotating speed is more than 8,000 rpm. At that time, the life time of tool is reduced to about 50％ and the roughness of machining surface is worse as the run-out is increased to 10 micron. The life time of tool could be increased by making monitoring of tool-setting easy, quick and precise in high speed machining center. This means the consumption of tool is much more reduced. And also it reduces the manufacturing cost and increases the productivity by reducing the tool-setup time of operator. In this study, in order to establish the concept of tool-setting monitoring the measuring method of the geometrical error of tool system is studied when the spindle is stopped. And also the measuring method of run-out, dynamic error of tool system, is studied when the spindle is rotated in 8,000 ∼ 60,000 rpm. The dynamic phenomena of tool-setup is analyzed by implementing the monitoring system of rotating tool system and the noncontact measuring system of micro displacement in high speed.

• Journal for History of Mathematics
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• v.23 no.3
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• pp.57-73
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• 2010

Transcendental numbers are important in the history of mathematics because their study provided that circle squaring, one of the geometric problems of antiquity that had baffled mathematicians for more than 2000 years was insoluble. Liouville established in 1844 that transcendental numbers exist. In 1874, Cantor published his first proof of the existence of transcendentals in article [10]. Louville's theorem basically can be used to prove the existence of Transcendental number as well as produce a class of transcendental numbers. The number e was proved to be transcendental by Hermite in 1873, and $\pi$ by Lindemann in 1882. In 1934, Gelfond published a complete solution to the entire seventh problem of Hilbert. Within six weeks, Schneider found another independent solution. In 1966, A. Baker established the generalization of the Gelfond-Schneider theorem. He proved that any non-vanishing linear combination of logarithms of algebraic numbers with algebraic coefficients is transcendental. This study aims to examine the concept and development of transcendental numbers and to present students with its open problems promoting a research on it any further.

• Journal of Korean Elementary Science Education
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• v.37 no.3
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• pp.267-284
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• 2018

This study analyzed the types of scientific humors made by scientifically-gifted elementary school students and their perceptions of making scientific humor. For this, 77 students from $4^{th}$ to $6^{th}$ graders of gifted science education center in Seoul National University of Education were selected. Scientific humors made by the students were analyzed according to the number and types. Their perceptions of making scientific humor were also analyzed through a questionnaire and group interviews. The analysis of the results revealed that most of scientifically-gifted students made more than 2 scientific humors, and the number of scientific humor for each students varied from 0 to 11. The most types they made were the descriptive type and the pun using pronunciation type, but they made various types without any special type to be biased. And They made more the dialogue type than the narrative type, especially the riddle type. They used scientific knowledge that preceded the knowledge of science curriculum in their grade level over two or more years. The scientific knowledge of chemistry was used more than physics, biology, earth science and combination field. The name utilization type was more than the characteristic utilization type and the principle utilization type. Scientific humors in the everyday situation were more than humors in artificial situation. The students had various positive perceptions in making scientific humor such as increase of scientific knowledge, increase of various thinking abilities, deep understanding of science concept and principle, increase of interest and motivation about science and science learning, and increase on sense of humor. They had also some negative perceptions related to difficulties in the process of making scientific humor, lack of fun, and lack of time in the class.

• Journal of Practical Engineering Education
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• v.7 no.1
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• pp.25-30
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• 2015

Virtual reality is a combination of various studies, such as programming, simulation, and computer graphics. This type of new cultural paradigm requires novel concept of contents development and information exchange. This research uses 3D virtual reality technology in new equipment called I-Bench Mobile which let user to interact with the equipment for completing furniture disposition task. The simulation is manufactured in 3D with application of physics, and the ultimate goal of it is to increase customers' satisfaction by allowing them to enjoy snap shot function for arranging furniture at exact desired place. This research requires not only coding techniques but also educating process in both engineering and art, such as computer science, media art design, and visual communication; therefore, the development of software by facilitating Virtual/Augmented Reality technology in this research is a good example of fusion IT technique education.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.2 no.2
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• pp.73-79
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• 2001

In this paper, the transmitted noise reduction performance of piezoelectric smart panels is experimentally studied. The proposed piezoelectric smart panels are comprised of plate structure on which piezoelectric sensor/actuators are bonded and sound absorbing material is provided. It is a combination of passive and active approaches utilizing a passive effect at high frequencies and an active effect at low frequencies. To prove the concept of piezoelectric smart panels, an acoustic measurement experiment is performed. An acoustic tunnel is designed and its acoustic characteristics are tested. Below 800Hz, the tunnel exhibits a plane wave guide characteristics. When an absorbing material is bonded on a single plate, a remarkable transmitted noise reduction in mid frequency range is observed except the first resonance frequency. By enabling the active control of single smart panel with negative feedback control. about 10dB noise reduction is achieved at the resonance frequencies. The double smart panel got 4dB at the first resonance frequency and has more potential to reduce the transmitted noise in a wide range frequency. Piezoelectric smart panels incorporating passive absorbing material and active piezoelectric devices is a promising technology for noise reduction in a wide range frequency.

• Journal of Korean Society of Steel Construction
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• v.9 no.2 s.31
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• pp.193-204
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• 1997

In order to quantify the relationships of the important physical factors relating failure to strong earthquake loading, the plastic fatigue problems for structural components under repeated loading were reviewed first. A new concept of very low cycle fatigue failure for structural components under severe cyclic excitations as in strong earthquakes was represented. Also, an experimental study was made of the very low cycle fatigue failure of structural steel elements. It was attempted to realize the ultimate failure in the course of loading repetitions of the order of several to twenty. The test specimen had a form of rectangular plate, representing a thin-plated element in a steel member as wide-flange cross section. It was subjected to uniaxial loading repeatedly, until complete failure takes place after undergoing inelastic buckling, plastic elongation and/or their combination. It was seen as a result that the state of the ultimate failure is closely related to the maximum strain at the extreme fiber in the cross section.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.8
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• pp.654-660
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• 2014

In this paper, a conceptual design of a launch vehicles is proposed by combining Naro-1 and KSLV-II. For trans-lunar injection (TLI) to lunar orbit at 300 km LEO, the target performance is defined same as that of KSLV-II, which delivers an object of 2.6 tons into 300 km LEO. The proposal launch vehicle concept of this study is combination of 1st stage of KSLV-I and 2-3rd stage of KSLV-II. Thus, it is possible to reduce the development time and also could expand the options for national launch vehicle capabilities with proven technologies.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.1
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• pp.35-42
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• 2006

Recently, the harbor function is being reconsidered with the viewpoint of logistics, and various efforts are given to enhance the harbor performance agglomerating all procedures of stevedoring, treatment and background transportation of freight. The harbor performance largely depends on the efficient combination of the engineering part of harbor construction and the forthcoming logistics part. It may thus be anticipated in the future that the design concept of harbor construction will be transferred to a comprehensive consideration integrating both engineering and logistics parts to maximize the ultimate harbor operational performance. In the present study, various indicators for assessing a modem container terminal performance are presented far the purpose of helping harbor engineers understand the fundamental logistics through container handling operations. The indicators are compared, analyzed and compiled, by referring to the practical cases of Busan and Gwangyang ports as an illustration.

• The Journal of the Korea Contents Association
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• v.13 no.12
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• pp.551-559
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• 2013

In this paper, we proposed a tangible RealBook based on the interface of TouchFace-V which is able to recognize multi-touch and hand gesture. The TouchFace-V is applied projection technology on a flat surface such as table, without constraint of space. The system's configuration is addressed installation, calibration, and portability issues that are most existing front-projected vision-based tabletop display. It can provide hand touch and gesture applying computer vision by adopting tracking technology without sensor and traditional input device. The RealBook deals with the combination of each advantage of analog sensibility on texts and multimedia effects of e-book. Also, it provides digitally created stories that would differ in experiences and environments with interacting users' choices on the interface of the book. We proposed e-book that is new concept of electronic book; named RealBook, different from existing and TouchFace-V interface, which can provide more direct viewing, natural and intuitive interactions with hand touch and gesture.