• Journal of Mechanical Science and Technology
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• v.18 no.10
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• pp.1700-1711
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• 2004

Piston friction is one of the important but complicated sources of energy loss of a hydraulic axial piston machine. In this paper, two formulas are derived for estimating instantaneous piston friction force and average piston friction moment loss. The derived formula can be applicable for piston guides with or without bushing as well as for axial piston machines of motoring and pumping operations. Through the formula derivation, a typical curve shape of friction force found from several experimental measurements during one revolution of a machine is clearly explained in this paper that it is mainly due to the equivalent friction coefficient dependent on its angular position. Stribeck curve effect can easily be incorporated into the formula by replacing outer and inner friction coefficients at both edges of a piston with the coefficient given by Manring (1999) considering mixed/boundary lubrication effects. Novel feature of the derived formula is that it is represented only by physical dimensions of a machine, hence it allows to estimate the piston friction force and loss moment of a machine without hardworking experimental test.

• Proceedings of the Korea Contents Association Conference
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• 2005.05a
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• pp.263-267
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• 2005

Presentation is the most important factor in the usability of a web site. A poor layout makes a bad influence on the searching ability of the user by reducing search speed and causing mistakes. Recently many web sites visualize 3D information and there is plenty of research on it. Such a layout improves the usability of web pages and information awareness both in quantity and quality. This paper proposes design guides on 3D information browsing and has experiments on searching speed of the users for 2D and 3D displays of the same data and were analyzed.

• Education of Primary School Mathematics
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• v.8 no.2 s.16
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• pp.97-113
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• 2004

The purpose of this study is to develop instructional methods for the formalized algorithm through informal knowledge in teaching division of fractions. The following results have been drawn from this study: First, before students learn formal knowledge about division of fractions, they knowledge or strategies to solve problems such as direct modeling strategies, languages to reason mathematically, and using operational expressions. Second, students could solve problems using informal knowledge which is based on partitioning. But they could not solve problems as the numbers involved in problems became complex. In the beginning, they could not reinvent invert-and-multiply rule only by concrete models. However, with the researcher's guidance, they can understand the meaning of a reciprocal number by using concrete models. Moreover, they had an ability to apply the pattern of solving problems when dividend is 1 into division problems of fractions when dividend is fraction. Third, instructional activities were developed by using the results of the teaching experiment performed in the second research step. They consist of student's worksheets and teachers' guides. In conclusion, formalizing students' informal knowledge can make students understand formal knowledge meaningfully and it has a potential that promote mathematical thinking. The teaching-learning activities developed in this study can be an example to help teachers formalize students' informal knowledge.

• Journal of Educational Research in Mathematics
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• v.23 no.4
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• pp.449-466
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• 2013

Mathematical discussion has been highlighted so that what students do actually guides their learning of mathematics and mathematical practice. However, the work of leading mathematical discussions has not yet been specified in such a way that it can be adequately studied and taught to teachers. This study analyzes a teacher's lessons that show full engagement in leading discussions, and examines the work of leading mathematical discussions in elementary classrooms. It identifies and illustrates the central tasks of leading mathematical discussions with single case questions with five steps. This article argues several key issues in leading mathematical discussions: helping students engage in struggling with important mathematical ideas, treating mathematical connections in an explicit and public way to have coherent and structured discussions, and parsing the work of teaching at a grain size that is usable in educating teachers.

• Journal of the Korea Safety Management & Science
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• v.10 no.4
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• pp.165-171
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• 2008

In the policy management system of the safety&health(same as the environment and the quality), the documentation of the management system is required in various international standards & guides. In case of 3 level classification of the system documents, it generally will be identified such name as the manual, the procedure(or the process) and the job instruction. Each level of the document has the unique role and usage though, the job instructions, especially, would be developed to support the practical job worker. Considering such document level, the job instructions should be reflect the latest know-how of the job-handling methods. And that, it should be used at any times by the related job worker. This paper is prepared for surveying the actual usage status of the job instructions of the domestic enterprises holding ISO certificate and trying to suggest the better way of application of the system documents.

• Journal of Korea Game Society
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• v.15 no.4
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• pp.59-68
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• 2015

The progress in Information & Communication Technology enables data scientists to analyze big data for identifying peoples' daily lives and tacit preferences. A variety of industries already aware the potential usefulness of analyzing big data. However limited use of big data has been performed in game industry. In this research, we adopt data mining technique to analyze data gathered from a strategic simulation game. Decision Tree, Random Forest, Multi-class SVM, and Linear Regression techniques are used to find the most important variables to users' game levels. We provide practical guides for game design and usability based on the analyzed results.

• Journal of Digital Convergence
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• v.9 no.4
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• pp.213-222
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• 2011

The purpose of this paper is to propose a smart work implementation strategy of Korean companies. Recently in Korea, the interest in smart work is growing and actively promoting but the introduction of private enterprise strategy is absent. However the smart work has been highlighted several issues. In this paper, among the issues, we studied the strategy for introducing smart work system with respect to the related research and literature on strategies and guidelines that may be introduced to the system. With reference to the actual introduction of the basic directions for the procedure proposed by the Korea Communications Commission, we try to review the operating guides and to propose smart work 2.0 implementation strategy, framework and some procedure.

• Nuclear Engineering and Technology
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• v.50 no.6
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• pp.950-956
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• 2018

For complete assessment of inhalation doses of radon and its progeny inside the three main ancient Egyptian tombs in Saqqara, seasonal radon concentrations have been measured by using a new electronic device that allows for measurement of real-time-resolved radon concentrations. Measurements were complemented by very fast measurements of thoron concentrations, which turned out to be low. Based on these measurements, annual residence time inside these tombs and the newest International Commission on Radiological Protection-recommended radon dose conversion coefficients or seasonal effective doses were calculated. The results indicate that workers receive highest annual effective doses of up to 140 mSv, which exceeds the annual limit of 20 mSv, whereas lower values up to 15 mSv are received by guides. In contrast, much lower doses were obtained for one-time visitors of the investigated tombs. The obtained results are somewhat different but still consistent with those previously obtained by means of fixed passive dose meters at some of the investigated places. This indicates that reasonable estimates of the effective dose of radon can be also obtained from short-term radon measurements carried out only twice a year (summer and winter season). Increasing the ventilation, minimizing the working times, etc., are highly recommended to reduce the annual effective dose.

• Journal of the Korea Society of Computer and Information
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• v.13 no.5
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• pp.237-246
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• 2008

When a fire occurs in a large-scale or complicated facility there is a possibility of large-scale loss of life if there is no information on the location of fire and the location of emergency exits for people to take shelter. Consequently, the fire or disaster prevention system and the shelter course guidance system that optimally guides the shelter course are necessary to reduce the loss of life. This paper proposes a shelter course guidance system using a sensor network to reduce the loss of life in a building where a fire occurs. The experimental result of this research shows that the shelter course guidance system provides the optimum shelter course to people in infrastructure when a fire occurs.

• Journal of Korea Society of Industrial Information Systems
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• v.24 no.4
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• pp.29-36
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• 2019

We propose a smart parking space guiding system based on user preferences in a parking lot. This system guides each vehicle to the most suitable parking space in a parking lot to meet the user preferences such as the available parking spaces in the parking zones and the proximity to the destination by exploiting the traffic to each parking zone gathered at the sensors near each guiding display. For this purpose, this paper proposes the cost function for the optimal route guide based on the various user preferences. In addition, the paper reports the design and implementation results of an event based simulator to show the feasibility of the smart parking guidance system.