• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.10
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• pp.4844-4864
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• 2017

Interference-aware routing protocol design for underwater wireless sensor networks (UWSNs) is one of the key strategies in reducing packet loss in the highly hostile underwater environment. The reduced interference causes efficient utilization of the limited battery power of the sensor nodes that, in consequence, prolongs the entire network lifetime. In this paper, we propose an energy-efficient interference-aware routing (EEIAR) protocol for UWSNs. A sender node selects the best relay node in its neighborhood with the lowest depth and the least number of neighbors. Combination of the two routing metrics ensures that data packets are forwarded along the least interference paths to reach the final destination. The proposed work is unique in that it does not require the full dimensional localization information of sensor nodes and the network total depth is segmented to identify source, relay and neighbor nodes. Simulation results reveal better performance of the scheme than the counterparts DBR and EEDBR techniques in terms of energy efficiency, packet delivery ratio and end-to-end delay.

• Journal of Broadcast Engineering
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• v.15 no.2
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• pp.236-247
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• 2010

Recently, mean shift tracking algorithms have been proposed which use the information of color histogram together with some spatial information provided by the kernel. In spite of their fast speed, the algorithms are suffer from an inherent instability problem which is due to the use of an isotropic kernel for spatiality and the use of the Bhattacharyya coefficient as a similarity function. In this paper, we analyze how the kernel and the Bhattacharyya coefficient can arouse the instability problem. Based on the analysis, we propose a novel tracking scheme that uses a new representation of the location of the target which is constrained by the color, the area, and the spatiality information of the target in a more stable way than the mean shift algorithm. With this representation, the target localization in the next frame can be achieved by one step computation, which makes the tracking stable, even in difficult situations such as low-rate-frame environment, and partial occlusion.

• Journal of Digital Contents Society
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• v.19 no.7
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• pp.1263-1270
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• 2018

We investigated the e-learning platforms for higher education in developing countries. First, we introduced e-learning environmental factors such as ICT technology as well as ASEAN Cyber University (ACU) project for developing countries. And then, we presented Cambodian case as an example of e-learning platform for developing countries. We analyzed the national education policy and ICT environment as well as the demands and obstacles of e-learning in Cambodia. We derived e-learning strategies and plans based on the analysis results, and finally proposed e-learning platform C-MOOC Net. In order to verify the proposed scheme, we developed prototype of C-MOOC Net system which is implemented based on open software. As a result, we have met the requirement of networking the C-MOOC hub, supporting localization of local language and personalization of favorite courses respectively.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.1
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• pp.24-30
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• 2016

The accuracy of small and low-cost CCD cameras is insufficient to provide data for precisely tracking unmanned aerial vehicles (UAVs). This study shows how a quad rotor UAV can hover on a human targeted tracking object by using data from a CCD camera rather than imprecise GPS data. To realize this, quadcopter UAVs need to recognize their position and posture in known environments as well as unknown environments. Moreover, it is necessary for their localization to occur naturally. It is desirable for UAVs to estimate their position by solving uncertainty for quadcopter UAV hovering, as this is one of the most important problems. In this paper, we describe a method for determining the altitude of a quadcopter UAV using image information of a moving object like a walking human. This method combines the observed position from GPS sensors and the estimated position from images captured by a fixed camera to localize a UAV. Using the a priori known path of a quadcopter UAV in the world coordinates and a perspective camera model, we derive the geometric constraint equations that represent the relation between image frame coordinates for a moving object and the estimated quadcopter UAV's altitude. Since the equations are based on the geometric constraint equation, measurement error may exist all the time. The proposed method utilizes the error between the observed and estimated image coordinates to localize the quadcopter UAV. The Kalman filter scheme is applied for this method. Its performance is verified by a computer simulation and experiments.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1037-1040
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• 2008

In order to predict the remaining life of marine concrete structures under climatic loads, it is necessary to develop an analytical approach to predict the time and space dependent deterioration of concrete structures due to mainly chloride attack up to corrosion initiation and additional deterioration like cracking of cover concrete. This study aims to introduce FEM model for life-time simulation of concrete structures subjected to chloride attack. In order to consider uncertainties in materials as well as environmental parameters for the prediction, Monte Carlo Simulation is integrated in that FEM modeling for reliability-based remaining service life prediction. The paper is organized as follows: firstly general scheme for reliability-based remaining service life of concrete structures is introduced, then the FEM models for chloride penetration, corrosion product expansion and cover cracking are briefly explained, finally an example is demonstrated and the effects of localization of chloride concentration and corrosion product expansion on service life using above model are discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.2
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• pp.149-156
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• 2014

Floor number determination has attracted considerable attention because many applications require accurate floor number information for providing better localization services in multistory buildings. This paper describes a Wi-Fi-based, low-complexity floor number determination method for multistory buildings. In our scheme, with the exception of floor ID and received signal strength of each WAP, detailed information on the wireless access point (WAP) coordinates is not needed. The multi-wall-floor model is used for the simulation and analysis. The simulation results show that the floor determination accuracy is nearly 100 given an adequate deployment density of WAPs on each floor. The results also show that the proposed method provides a good estimate of floor number even when only a few WAPs are implemented on each floor. Specifically, the proposed method can work under extreme conditions, i.e., where there are no WAPs on a floor.

• Smart Structures and Systems
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• v.31 no.1
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• pp.13-27
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• 2023

Fatigue crack is a fatal problem for steel structures. Early detection and maintenance can help extend the service life and prevent hazards. This paper presents the ultrasonic guided waves-based (UGWs-based) fatigue crack detection of a steel I-beam. The semi-analytical finite element model has been built to obtain the wave propagation characteristics. Damage indices in both time and frequency domains were analyzed by considering the characteristic variations of UGWs including the amplitude, phase angle, and wave packet energy. The pulse-echo and pitch-catch methods were combined in the detection scheme. Lab-scale experiments were conducted on welded steel I-beams to verify the proposed method. Results show that the damage indices based on the characteristic variations in the time domain can identify and localize the fatigue crack before it enters the rapid growth stage. The damage severity can be reasonably evaluated by analyzing the time-domain damage indices. Two nonlinear damage indices in the frequency domain give earlier warnings of the fatigue crack than the time-domain damage indices do. The identification results based on the above two nonlinear indices are found to be less consistent under various excitation frequencies. More robust nonlinear techniques needed to be searched and tested for early crack detection in steel I-beams in further study.

• Journal of the Korean Geographical Society
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• v.30 no.2
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• pp.132-145
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• 1995

The Purpose of this study is to integrate two opposite paradigms, (development from above) and (development from below), by means of A. Giddenss (structuration theory) and to provide practical development strategies on the basis of integrated paradigm. The integration of these two opposite paradigms is in fact the internalization of epistemological overcoming of 'dependency', which means the structural transformation of dualistic thinking into monistic thinking that the enlargement of capitalist world-system can be 'development' and it may also be 'dependency'. Therefore the practical main issue of this integrated paradigm results in how peripheral countries should achieve self-reliant and continuous development under the circumstances of dependency. To achieve such development while resisting the growing arrogance of transnational capital, development strategies should be prepared to maker revitalized political community designed to fit a human scale and for the economy to be subordinated to the political will of the community. And at the same time the 'empowerment' of people should be strengthened.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.10
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• pp.1057-1068
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• 2014

This paper proposes elastic-plastic constitutive relations for a composite material with two phases-inclusion and matrix phases-using a homogenization scheme. A thermodynamic framework is employed to develop non-local plasticity constitutive relations, which are specifically represented in terms of the second-order gradient terms of the internal state variables. A combined two back-stress evolution equation is also established and the degradation of the state and internal variables is expressed by continuum damage mechanics in terms of the damage factor. Then, deformation localization is analyzed; the analysis results show that the proposed model yields a wide range of shear band formation behaviors depending on the evolution of the specific internal state variables. The analysis results also show good agreement with the results of simplified Rice instability analyses.

• Journal of the Korean Society for information Management
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• v.30 no.4
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• pp.215-239
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• 2013

Even though the overall scholarly community has recognized a dramatic growth and changes in the Information Science research in Korea over the last few decades, there are still only few studies that have identified the changes in terms of long-term and dynamic point of view. We have analyzed 1,007 IS-research articles from leading Korean journals in KCI (Korea Citation Index), published between 2000 and 2011. To discern the trendline of changes in research interests over time, we conducted a time-series analysis by developing grounded subject scheme from the article set and checking the growth rate of the number of published articles and title keywords. A comparative analysis was also conducted by constructing and comparing co-word maps over time to discover visible changes in research topics over this 12-year period of the IS-research in Korea. As a result, we identified some developments and transformations in major subject areas and knowledge structure of the IS-research in Korea over time. The major trend we discovered is that IS-studies over the 12-year period evolved from system-oriented research to library-application research. The changes are especially observed in knowledge management, Web-based system evaluation, and information retrieval areas. When compared to the results of other studies, the result of our study may serve as an evidence of the localization of Korean IS-studies in the first decade of the $21^{st}$ century.