• Journal of applied mathematics & informatics
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• v.33 no.1_2
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• pp.185-191
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• 2015

This paper considers a discrete-time buffer system with session-based arrivals, an infinite storage capacity and one unreliable output line. There are multiple different types of sessions and the output line is governed by a finite state Markov chain. Based on a generating functions approach, we obtain an exact expression for the mean buffer content.

• Proceedings of the Safety Management and Science Conference
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• 2011.04a
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• pp.719-730
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• 2011

The live-line works are very dangerous works on direct contacts or neighboring contacts with the distribution line. But most of domestic electrical construction companies that have performed live-line works are small-scale companies. Accordingly, safety management system and manuals to insure worker's safety haven't sufficiently had. In this paper, risk and status of accidents for the live-line works were analyzed and the necessity of introducting risk assessment for live-line works was identified by a questionnaire survey of electrical construction companies and education institutions.

• Proceedings of the KAIS Fall Conference
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• 2012.05b
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• pp.512-516
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• 2012

Recently the Korean government's green energy growth policy has been taken at the national level due to the sufficient supply of renewable energy. Some specific technique should be taken in consideration for the operation of the grid voltage and power quality management. In this case, there may have some chance of operational problems. Typical problems arise when grid-connected solar power produced by Pacific sunshine. The power flow in the reverse direction can create overvoltage on the distribution line and gives value of malfunction on the system. Line voltage and overvoltage adjustment practice can stop these symptoms occurred. Under these circumstances, this paper presents an interconnection test devices for photovoltaic(PV) systems composed of distribution system simulator, PV system simulator and control and monitoring systems using the LabVIEW S/W, and simulates the customer voltage characteristics considering the 3 parameters on the introduction capacity for PV systems, system configuration and Power factor. This paper also proposes a new calculation algorithm for voltage profile to make comparison between calculation values and test device values. The results show that the simulation results for the normal operation characteristics of PV systems which are very practical and effective.

• East Asian mathematical journal
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• v.31 no.3
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• pp.321-335
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• 2015

The existence of at least one solution to a system of multipoint boundary value problems on an infinite interval is investigated by using the Alternative of Leray-Schauder.

• Journal of Power Electronics
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• v.17 no.1
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• pp.294-304
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• 2017

This paper proposes a point of common coupling (PCC) voltage compensation method for islanding microgrids using an improved power sharing control scheme among distributed generators (DGs) without communication. The PCC voltage compensation algorithm is implemented in the droop control scheme to reduce the PCC voltage deviation produced by the droop controller itself and the voltage drop on the line impedance. The control scheme of each individual DG unit is designed to use only locally measured feedback variables and an obtained line impedance to calculate the PCC voltage. Therefore, traditional voltage measurement devices installed at the PCC as well as communication between the PCC and the DGs are not required. The proposed control scheme can maintain the PCC voltage amplitude within an allowed range even to some extent assuming inaccurate line impedance parameters. In addition, it can achieve proper power sharing in islanding microgrids. Experimental results obtained under accurate and inaccurate line impedances are presented to show the performance of the proposed control scheme in islanding microgrids.

• Journal of the Korea Institute of Building Construction
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• v.12 no.4
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• pp.426-432
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• 2012

For students majoring in Architecture or Architectural Engineering, describing a building with pictures and signs is equal to expressing his/her opinion with sentences and presentations. CAD (computer aided design) is a method of describing buildings, and is used practically in architecture-related companies. Many universities prescribe CAD instruction as a compulsory subject, and ABEEK (Accreditation Board for Engineering Education of Korea) requires an introduction to CAD as a basic subject for visual expression. The Architectural Drawing and CAD class in the department of Architectural Engineering of J University is a 2-credit course, with 4 hours of lectures per week. Relative to other subjects, this is insufficient for practical study. Thus, to make up for this insufficient time, the class has adopted a Blended learning system that mixes off-line and on-line classes. The objective of this research is to introduce Blended learning, and to give a case study of the CAD class using Blended learning.

• The Journal of Korean Association of Computer Education
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• v.16 no.1
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• pp.33-42
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• 2013

In this paper, through conducting a survey from 547 male and female high school students in Busan, we found their favorite computer games are about five and the highest linguistic problem in on-line computer games was vulgar languages. Most of respondents thought that the vulgar languages on the on-line games were serious and said that we have experienced the vulgar languages before high school. Therefore, in this paper, we suggest it is necessary to prepare a countermeasure system about adolescents' vulgar languages on the on-line games and for adolescents to take etiquette lessons on the on-line games from either the primary school or before then.

• Journal of The Korean Association of Information Education
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• v.8 no.1
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• pp.15-23
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• 2004

In this study, we analyzed the login frequencies and the learner's results of an examination related in the teacher's information distance learning. The results of analysis are as follows. First, most of learners connected to the learning system in school at office hours. And the login frequencies on Sunday are high remarkably in test pole. Seconds, the on-line assessment and the ratio of completion is high the learner who participation with a fellow worker than the learner who not so. But because of the low allotment of marks about on-line estimation, it hardly influence in the last results. Third, the ratio allotment of marks about on-line estimation is suitable $20{\sim}30%$. Forth, learners of low grade are higher the login frequencies, the last results is high. Therefore the operator of the learning system estimates ability of learners by pre-test and must have continues and encouragement about leaners of law grade.

• Journal of The Korean Association of Information Education
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• v.6 no.3
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• pp.288-297
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• 2002

The paradigm of education has changed with the progress of the information and communication technology. In school, there has been developing and animately discussing many data and ways of using web-practicality for teaching and learning. On the other hand, relatively, there are negligent faces about web-practicality for extension of emotion and will of our children. The common points of pre-studies about the increase of self-concept show that it is difficult to join all of the information because the work is off-line, therefore limiting it's advance so that the program is improved. This study has designed and embodied the system of web based self-expression training program. The result of application of this system has showed the positive effect on formation of self-concept of Cheongju elementary school students.

• Journal of Digital Contents Society
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• v.2 no.1
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• pp.1-7
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• 2001

The authoring systems for digital contents using multimedia technologies ate requested in many fields such as education, medical science, entertainment market e-commerce and etc. Especially, the emergence of cyber universities and the rapid expansion of on-line education market require the effective contents authoring systems, which have various functions to generate the qualified contents. Therefore, many systems arc developed and currently used. However, since the developed systems considered only the developer's convenience, the generated digital contents by using these systems are failed to draw tile users'(or learners') active interaction with contents. That is, since the users just watch the contents like watching a drama or a film, it causes many problems in delivering the contents effectively or in evaluating the users. This paper presents, develops, and implements the new contents authoring system by using programing languages and/or software tools. The presented, developed, and implemented system mimics the face-to-face education in off-line system, induces the users' active interaction with contents, and continuous evaluation to the users.