• Tribology and Lubricants
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• v.23 no.4
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• pp.149-155
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• 2007

The CAD model of a elliptical gear for wire cutting has been developed. The rolling contact of pitch ellipses whose rotation axes coincide with their focus has been analyzed, and the perimeter of the pitch ellipse has been divided into equal-length segments by the number of teeth. A master tooth profile, which is a composite curve of circular arcs that represents involute, has been introduced. The elliptical gear has been designed by imposing the master tooth on the divided points of the pitch ellipse, and a full fillet has been achieved between neighbour teeth. Thus, the whole profile of an elliptical gear is a composite curve of arcs only, and consequently NC codes for wire cutting can be easily generated. Furthermore, a computer simulation program is developed to verify the mesh of the elliptical gear.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.255.2-255.2
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• 2014

Electrode erosion is indispensable for atmospheric plasma systems, as well as for switching devices, due to the high heat flux transferred from arc plasmas to contacts, but experimental and theoretical works have not identified the characteristic phenomena because of the complex physical processes. Our investigation is concerned with argon free-burning arcs with anode erosion at atmospheric pressure by computational fluid dynamics (CFD) analysis. We are also interested in the energy flux and temperature transferring to the anode with a simplified unified model of arcs and their electrodes. In order to determine two thermodynamic quantities such as temperature and pressure and flow characteristics we have modified Navier-Stokes equations to take into account radiation transport, electrical power input and the electromagnetic driving forces with the relevant Maxwell equations. From the simplified self-consistent solution the energy flux to the anode can be derived.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2004.10a
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• pp.51-67
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• 2004

World Wide Web is nearly ubiquitous and the tremendous growing number of Web information strongly requires a structuring framework by which an overview visualization of Web sites has provided as a visual surrogate for the users. We have a viewpoint that the Web site is a directed graph with nodes and arcs where the nodes correspond to Web pages and the arcs correspond to hypertext links between the Web pages. In dealing with the WWW, the goal in this paper is not to derive a naive shortest path or a fast access method, but to generate an optimal structure based on the context centric weight. We modeled a Web site formally so that a integer programming model can be formulated. Even if changes such as modification of the query terms, the optimized Web site structure can be maintained in terms of sensitivity.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.627-630
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• 1993

The arc characteristics have influences on the current interruption phenomena in the regimes of low current as well as high current. It is very important to understand the arc characteristics for the initial design of a circuit breaker. This article describes the theoretical analysis of the arc characteristics by means of arc energy integral method when convection dominated low current arcs are produced in the dual-nozzle air and $SF_6$ gas flows of a model interrupter. The arc radius, average electric field strength and arc voltage have been investigated at the current range of 60 to 230 A and at the upstream pressure of 0.6 MPa in both air and SF6 gas. The results have been compared to show the difference of both gases and the trends similar to those of other investigations.

• Journal of Engineering Education Research
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• v.17 no.4
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• pp.58-61
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• 2014

This paper introduces a tool for effective teaching of introductory computer programming. In order for the class to be effective, we try to attain attention, relevance, confidence, and satisfaction based on Keller's ARCS model. A web-based tool is developed to help both the students and the instructors.

• International Journal of Contents
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• v.15 no.4
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• pp.89-96
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• 2019

This study examines the impact of online collaborative English language learning to enhance learner motivation and classroom engagement in university English instruction. The role of learner motivation and classroom engagement has gained much attention under the premises of current constructivist framework of English as a foreign language education. To promote learner motivation and classroom interaction in English instruction, participants in this study engaged in integrative English learning activities through online group collaboration and peer-tutoring. They exchanged productive peer response and shared their learning experiences throughout the integrative English learning activities. Digital technology played an integral role in motivating the learning process of the participants. Data for this study were gathered through an online questionnaire survey and semi-structured interviews. The data were analyzed based on the ARCS motivational model of instructional design to identify the motivational aspects of integrative English learning activities. This study reveals that participants of this study regarded online collaborative English learning activities as the positive and motivating learning experience. The online collaborative English reading instruction had positive effect on improving EFL university students' learning performance. Participants of this study also identified affective and metacognitive benefits of online collaborative EFL learning activities for learner motivation and classroom engagement. This study reveals that the social networking platform in online group collaboration played a crucial role for the participants in understanding the integration of online group collaboration as the positive and effective language learning strategy. This study may have implications in suggesting the effective instructional design for promoting learner motivation and classroom interaction in EFL education.

• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.220-223
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• 1988

A the dependent model for wail-stabilized local thermodynamic equilibrium (LTE) arcs has been used to examine the high-pressure sodium vapor arc. Arc properties including temperature, electrical conductivity, and optically thick and optically thin radiation fluxes were calculated as functions of radius and time.

• Journal of Korea Water Resources Association
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• v.36 no.4
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• pp.547-559
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• 2003

In this study, a mathematical model is developed for sewer rehabilitation planning by considering cost and inflow/infiltration. A sewer rehabilitation planning model is required to decide the economic life of the sewer by considering trade-off between cost and inflow/infiltration. And it is required to find the optimal rehabilitation timing, according to the cost effectiveness of each sewer rehabilitation within the budget. To solve the problem, we formulated a multiple objective mixed integer programming(MOMIP) model based on network flow optimization. The network is composed of state nodes and arcs. The state nodes represent the remaining life and the arcs represent the change of the state. The model considers multiple objectives which are cost minimization and minimization of inflow/infiltration. Using the multiple objective optimization, the trade-off between the cost and inflow/infiltration is presented to the planner so that a proper sewer rehabilitation plan can be selected.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.26 no.1
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• pp.217-231
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• 2015

This study aims to infer the gene-protein 'brings_about' chains of pancreatic cancer which were referred to in the pancreatic cancer related researches by constructing the gene-protein interaction network of pancreatic cancer. The chains can help us uncover publicly unknown knowledge that would develop as empirical studies for investigating the cause of pancreatic cancer. In this study, we applied a novel approach that grafts text mining and the main path analysis into Swanson's ABC model for expanding intermediate concepts to multi-levels and extracting the most significant path. We carried out text mining analysis on the full texts of the pancreatic cancer research papers published during the last ten-year period and extracted the gene-protein entities and relations. The 'brings_about' network was established with bio relations represented by bio verbs. We also applied main path analysis to the network. We found the main direct 'brings_about' path of pancreatic cancer which includes 14 nodes and 13 arcs. 9 arcs were confirmed as the actual relations emerged on the related researches while the other 4 arcs were arisen in the network transformation process for main path analysis. We believe that our approach to combining text mining analysis with main path analysis can be a useful tool for inferring undiscovered knowledge in the situation where either a starting or an ending point is unknown.

• International Journal of Aeronautical and Space Sciences
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• v.13 no.3
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• pp.317-322
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• 2012

The low speed aerodynamic characteristics for a modified sonic arc airfoil which is designed by using the nose shape function of sonic arc, the shape function of NACA four-digit wing sections, and Maple are experimentally investigated. The small rotor blades of a modified sonic arc and NACA0012 airfoil are precisely fabricated with a commercially available light aluminum(Al 6061-T6) and are spin tested over a low speed range (3000rpm-5000rpm). In a consuming power comparison, the consuming powers of NACA0012 are higher than that of modified sonic arcs at each pitch angle. The measured rotor thrust for each pitch angle is used to estimate the rotor thrust coefficient according to momentum theory in the hover state. The value of thrust coefficients for both two airfoils at each pitch angle show almost constant values over the low Mach number range. However, the rotor thrust coefficient of NACA0012 is higher than that of the modified sonic arc at each pitch angle. In conclusion, the aerodynamic performance of NACA0012 is better than that of modified sonic arcs in the low speed regime. This test model will provide a convenient platform for improving the aerodynamic performance of small scale airfoils and for performing design optimization studies.