• Journal of the Korean Institute of Intelligent Systems
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• v.17 no.4
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• pp.435-442
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• 2007

To reduce damage from high concentration ozone in the air, we have researched how to predict high concentration ozone before it occurs. High concentration ozone is a rare event and its reaction mechanism has nonlinearities and complexities. In this paper, we have tried to apply and consider as many methods as we could. We clustered the data using the fuzzy c-mean method and took a rejection sampling to fill in the missing and abnormal data. Next, correlations of the input component and output ozone concentration were calculated to transform more correlated components by modified log transformation. Then, we made the prediction models using Dynamic Polynomial Neural Networks. To select the optimal model, we adopted a minimum bias criterion. Finally, to evaluate suggested models, we compared the two models. One model was trained and tested by the transformed data and the other was not. We concluded that the modified transformation effected good to ideal performance In some evaluations. In particular, the data were related to seasonal characteristics or its variation trends.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.6
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• pp.640-651
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• 2016

We propose an effective ToA-based localization method considering accuracy in indoor environments. The purpose of the localization system is to estimate the coordinates of the geographic location of target device. In indoor environments, accurately estimating the location of a target device is not easy due to various errors. The accuracy of wireless localization is influenced by NLOS errors. ToA-based localization measures the location of a target device using the distances between a mobile device and three or more base stations. However, each of the NLOS errors along a distance estimated from a target device to a base station is different because of dissimilar obstacles. To accurately estimate the target's location, an optimized localization process is needed in indoor environments. In this paper, effective ToA-based localization method process is proposed for improving accuracy in wireless sensor networks. Performance evaluations are presented, and the experimental localization system results are proved through comparisons of various localization methods with the proposed methods.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.5
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• pp.1003-1010
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• 2018

The geomagnetic sensor nodes are usually designed with wireless communication and battery for easy installation on the road without cable connection and wiring. To minimize operation cost of a system, it is important to prolong the battery lifetime of the geomagnetic sensors installed on the road. In this paper, we propose a low-power TDMA MAC protocol that reduces energy consumption while guaranteeing the real-time vehicle detection information in the vehicle detection system. The performance evaluations are conducted through a real testbed of a vehicle detection system, and it proves that the proposed low-power protocols provides 5 year lifetime by improving energy efficiency up to about 62%.

• Journal of Korea Game Society
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• v.3 no.2
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• pp.56-63
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• 2003

This research is a result of the study of 3D online game engine supported by korea science foundation in third year. The 3D engine and server engine have been upgraded from those in second year. A demonstration game has been made using our engines. Source codes of our engines have been distributed to several research centers for analysis and evaluations. The methodology of game development using our engines is described as well as the efficiency of our engines. In this paper, features and performance of the proposed engines are described as well as the methodology of utilizing the engines.

• Journal of Electrical Engineering and Technology
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• v.2 no.1
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• pp.89-97
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• 2007

This paper presents a new circuit topology of active edge resonant snubbers assisted half-bridge soft switching PWM inverter type DC-DC high power converter for DC bus feeding power plants. The proposed DC-DC power converter is composed of a typical voltage source-fed half-bridge high frequency PWM inverter with a high frequency planar transformer link in addition to input DC busline side power semiconductor switching devices for PWM control scheme and parallel capacitive lossless snubbers. The operating principle of the new DC-DC converter treated here is described by using switching mode equivalent circuits, together with its unique features. All the active power switches in the half-bridge arms and input DC buslines can achieve ZCS turn-on and ZVS turn-off commutation transitions. The total turn-off switching losses of the power switches can be significantly reduced. As a result, a high switching frequency IGBTs can be actually selected in the frequency range of 60 kHz under the principle of soft switching. The performance evaluations of the experimental setup are illustrated practically. The effectiveness of this new converter topology is proved for such low voltage and large current DC-DC power supplies as DC bus feeding from a practical point of view.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.5
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• pp.1117-1124
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• 2010

PMIPv6 is a network-based mobility support scheme, proposed and standardized by NetLMM WG of IETF. It is proposed to solve problems of conventional mobility schemes, and to improve inefficiency of those. The standard document describes network components and detailed procedures to provide mobility to MN. But it describes only a handover procedure between MAGs, not between LMAs. In order to support seamless connectivity of MN efficiently, a handover procedure between LMAs is necessary. The proposed scheme in this paper utilizes a route optimization procedure to prevent inefficiency of inter-LMA tunneling scheme. At the same time, the proposed scheme utilizes a pre-authentication scheme to reduce handover latency. According to the result of performance evaluations, the proposed scheme greatly reduces handover latency, compared to conventional mobility support schemes.

• Journal of Broadcast Engineering
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• v.13 no.1
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• pp.34-42
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• 2008

This paper proposes the mechanism which improves the qualify of video on a limited network bandwidth by applying the ROI technique to an H.264 Scalable Extension technique. The network environment assumed in this parer is the next generation network convergence environment in which the mobile device has one or more network interfaces. Therefore, we allocate the priority to video packets as the hierarchy structure of H.264 SVC-encoded video stream and ROI information, and transmit those packets over appropriate network channel for using those multiple network interfaces. This paper shows two experiments first one is extracting and allocating the video stream on an appropriate network channel, second one is unequal packet transmission by allocated priorities (e.g. ROI). Performance evaluations show that this approach delivers an improved decoded video quality when compared with conventional transmission schemes, especially on device which has multiple network interfaces.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.5
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• pp.556-560
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• 2010

In the wireless sensor networks using a multi-hop, quality variation of links occurs irregularly due to the hardware restriction and environmental factor. If an appropriate route, which is affected by the quality variation, is not selected. Traditionally, a beacon is periodically broadcasted and the link quality is estimated. However, the periodically beacon based scheme cannot efficiently estimate the quality of the link changing irregularly. In this paper, a scheme to estimate the link quality adaptively according to network state is proposed. When the link quality changes, the scheme adapts to a change agilely and packet losses are reduced. When there is no change of the link quality, the link quality is estimated in the long period and the energy consumption is reduced. Through performance evaluations, we prove that our adaptive link estimation scheme improves the energy efficiency and packet reception ratio than the periodic estimation scheme.

• Proceedings of the Korea Inteligent Information System Society Conference
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• 2005.11a
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• pp.557-567
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• 2005

The increasing complexity of the socio-economic environments makes it less and less possible for single decision-maker to consider all relevant aspects of problem. Therefore are, many organizations employ groups in decision making. In this paper, we present a multiperson decision making method using fuzzy logic with linguistic quantifier when each of group members specifies imprecise judgments possibly both on performance evaluations of alternatives with respect to the multiperson criteria and on the criteria. Inexact or vague preferences have appeared in the decision making literatures with a view to relaxing the burdens of preference specifications imposed to the decision-makers and thus taking into account the vagueness of human judgments. Allowing for the types of imprecise judgments in the model, however, makes more difficult a clear selection of alternative(s) that a group wants to make. So, further interactions with the decision-makers may proceed to the extent to compensate for the initial comforts of preference specifications. These interaction may not however guarantee the selection of the best alternative to implement. To circumvent this deadlock situation, we present a procedure for obtaining a satisfying solution by the use of linguistic quantifier guided aggregation which implies fuzzy majority. This is an approach to combine a prescriptive decision method via a mathematical programming and a well-established approximate solution method to aggregate multiple objects.

• Nuclear Engineering and Technology
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• v.52 no.1
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• pp.1-13
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• 2020

At present, the Department of Energy (DOE) in Unite State are directing the efforts of developing accident tolerant fuel (ATF) technology. As the first barrier of nuclear fuel system, the material selection of fuel rod cladding for ATFs is a basic but very significant issue for the development of this concept. The advanced cladding is attractive for providing much stronger oxidation resistance and better in-pile behavior under sever accident conditions (such as SBO, LOCA) for giving more coping time and, of course, at least an equivalent performance under normal condition. In recent years, many researches on in-plie or out-pile physical properties of some suggested cladding materials have been conducted to solve this material selection problem. Base on published literatures, this paper introduced relevant research backgrounds, objectives, research institutions and their progresses on several main potential claddings include triplex SiC, FeCrAl and MAX phase material Ti3SiC2. The physical properties of these claddings for their application in ATF area are also reviewed in thermohydraulic and mechanical view for better understanding and simulating the behaviors of these new claddings. While most of important data are available from publications, there are still many relevant properties are lacking for the evaluations.