• Journal of the Institute of Electronics Engineers of Korea SC
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• v.47 no.1
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• pp.62-66
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• 2010

A new soft recovery pulse width modulation quasi resonant converter composed only passive devices snubber network is proposed. This passive devices snubber network is revised form of folding snubber network that suppressed the reverse recovery current of main rectify diode in PWM converter. It also makes the MOSFET switching devices operate in soft state. The efficient of the proposed converter is almost same level to that of the converter of active snubber type. The overall circuit is simple and easy to realized. Therefore, it is suitable to apply to middle range output power source.

• Journal of the Korea Society of Computer and Information
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• v.24 no.7
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• pp.87-91
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• 2019

In the IoT(Internet of Things) environment, various devices are utilized and applied for different sites. But attackers can access easy to IoT systems, and try to operate DDoS(Distributed Denial-of-Service) attacks. In this paper, Sensor nodes, Cluster heads, and Gateways operates lightweight mutual authentication each others. Since authenticated sensor nodes and cluster heads only send transactions to Gateways, proposed techniques prevent DDoS attacks. In addition, the blockchain system contains secure keys to decrypt data from sensor nodes. Therefore, attackers can not decrypt the data even if the data is eavesdropped.

• Journal of Engineering Education Research
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• v.21 no.3
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• pp.12-19
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• 2018

In this study, a new experimental device was developed for measurement of the coefficient of kinetic friction using a photo gate timer system which have advantages of easy and accurate detection of motion. This device, consisting of a side air-guide track and a side friction-free glider, forces a friction sample to move in a straight line without producing unnecessary friction. The new device is compared to two conventional measuring methods of friction for four different friction samples: one is using a camera system and the other is using a force sensor. It is demonstrated that the developed friction device in this study is easier to operate and produces the most accurate and the least deviating results among them. On the basis of these results, we propose that friction experiment using the new friction device is included in general physics experiment, so that engineering students should have a chance to get correct understanding of classical mechanics including friction phenomenon.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1642-1646
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• 2011

One of the rolling stocks, low floor tram is recognized as the important alternative to improve traffic and environmental problems. There are many advantages of tram transportation system. It has, especially, low construction costs and easy accessibility. Trams operate with vehicles on roadways. The bogie configuration including traction motor of tramcar is different from that of conventional electric trains because tram has lower floor than train. In these reasons, the traction motors of tramcar are exposed to dusts, water and so on. Therefore, motors are designed by totally enclosed type. In this paper, we explain the design and test of totally enclosed traction motor for tramcar. Characteristic tests and temperature-rising tests were carried out in order to predict the performance of motor and the maximum temperature of coil.

• Management & Information Systems Review
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• v.1
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• pp.309-331
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• 1997

When the international insurance market is expected to change rapidly, the insurance barriers of some key countries in OECD have been studied. Many foreign insurers within the U.S. can enjoy national treatment in their market access, establishement and operations. but it can be viewed as an easy country to access and operate when we understand socio-cultural surroundings more deeply than their laws and regulations Japan, our neighbourhood is seeking the liberalization in the provision of international insurance services by the new insurance law in 1996. However, its main barriers are the official gazette and rules of the administrative authorities. EU, after the intergation, is running after the supervision of home country, to say nothing of the liberalization and the deregulation. The particular protectionist measure might be justified by the corresponding rationale.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.65 no.4
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• pp.321-325
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• 2016

The purpose of this study was to develop a system capable of operating a digital signage system at a low cost by utilizing existing equipment (TV, monitors, tablet PC, etc.). In particular, by developing an easy way to install the store's small business owners it can operate their small business installing digital signage in the store in addition to a public place. This easily exposed by a targeted advertising and local advertising and information of each store customers can maximize the advertising effect.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.744-746
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• 2015

EDMS(Enterprise Document Management System) is generally as an office business management solutions in the form of an application running in a Web browser environment, has been utilized as an Electronic Document Management System. This system, users access the browser has led to inconvenience not easy. For for ease of use this, how to implement a system that can be used to operate the EDMS on the screen of the Windows Explorer, in this study, are presented.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.2
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• pp.181-185
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• 2008

In this paper, we investigates accident actual conditions of electric outlet for low voltage that is used into interior and clear hazardous factor. Electric outlet for general can know that melting of socket-outlet and carbonization of support occur if a contaminant becomes burnout because is flowed in. Existent outlet consists of structure that special quality is good but inflow of a contaminant is easy when is dry. But, waterproof outlet passes silicon layer and have connected structure plug. As developed outlet covers whole surface and back side, interval was shut. Safety pin of developed outlet was established to operate to vertical direction. Therefore, we estimate that contribute on prevention of electrical disaster if use developed outlet to a restaurant, a laundry, a laboratory etc.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.688-692
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• 2007

Solar thermal power generation allows additional benefits of cheap thermal storage and easy hybridization with other fossil fuel-driven power generation. KIER has been performing the project for solar thermal chemical reaction hybrid power generation. The project is to build and operate the first solar thermal chemical reaction hybrid power generation system in Korea. For concentrating solar thermal energy $m^2$ dish type concentrator was adapted and a heliostat is installed for reflecting horizontal insolation to the dish concentrator. At the moment building the dish concentrator including mirror and heliostat with sun tracking system was completed and it's performance are being closely evaluated. This paper will introduce some detailed designs and construction procedures which we have experienced so far.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.739-742
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• 2002

This article proposes a Four-Quadrant Analog Multiplier (4-QAM) applying switched-capacitor and pulse-width amplitude modulation (PWAM) principles. The features of the presented circuit are that it can function as analog multiplier with a wide dynamic range of input signal and no disturbing from deviation of carrier frequency of PWM signal. In addition, the circuit detail is simpler than that of the previously proposed circuits. It is then easy and applicable for employing it into Integrated Circuit (IC) realization to especially operate in low-frequency and low-power applications. The experimental results granted are in correspondence to the theoretical analysis.