• Journal of the Institute of Convergence Signal Processing
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• v.8 no.3
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• pp.185-191
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• 2007

Remote sensing images are multispectral image data collected from several band divided by wavelength ranges. The classification of remote sensing images is the method of classifying what has similar spectral characteristics together among each pixel composing an image as the important algorithm in this field. This paper presents a pattern classification method of remote sensing images by applying a possibilistic fuzzy c-means (PFCM) algorithm. The PFCM algorithm is a hybridization of a FCM algorithm, which adopts membership degree depending on the distance between data and the center of a certain cluster, combined with a PCM algorithm, which considers class typicality of the pattern sets. In this proposed method, we select the training data for each class and perform supervised classification using the PFCM algorithm with spectral signatures of the training data. The application of the PFCM algorithm is tested and verified by using Landsat TM and IKONOS remote sensing satellite images. As a result, the overall accuracy showed a better results than the FCM, PCM algorithm or conventional maximum likelihood classification(MLC) algorithm.

• Journal of the Korea Society of Computer and Information
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• v.13 no.4
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• pp.133-140
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• 2008

The cable TV network has delivered downward broadcasting signals from distribution centers to subscribers. Since the traditional coaxial cable has been upgraded by the Hybrid Fiber Coaxial(HFC) cable, the upward channels has expanded broadband services such as Internet. This upward channel is vulnerable to ingress noises. When the noises from the children nodes accumulated in an amplifier exceeds a certain level, that node has to be cut off to prevent the noise propagation. The node selection problem(NSP) is defined to select nodes so that the noise in each node does not exceed the given threshold value and the sum of Profits of selected nodes can be maximized. The NSP has shown to be NP-hard. In this paper, we have proposed heuristics to find the near-optimal solution for NSP. The experimental results show that interval partitioning is better than greedy approach. Our heuristics can be used by the HFC network management system to provide privileged services to the premium subscribers on HFC networks.

• Journal of Power System Engineering
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• v.22 no.1
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• pp.41-47
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• 2018

This paper analyzes the output characteristics of a self excited induction generator with isolated mode according to change of its speeds and loads for building a hybrid electric propulsion system in special purpose ships by using power take off. The induction generators are being considered as an alternative choice to the well-developed generators because of their lower unit cost, inherent ruggedness, operational and maintenance simplicity. However, the generator working by stand alone has a few problems that the reactive power is required to establish the air gap magnetic flux, and the induced voltage and magnetizing current fluctuate when the load is varied. In spite of its advantages, basic design data of the capacitor bank and behaviors of the output characteristics of the generator are not sufficient for the system. Based on the operating condition(speed range of main engine) of the target boat, a reduced experimental equipment system was constructed to analyze the output characteristics of the SEIG. And a suitable capacitor bank of a stand-alone generator and its output characteristics under various loads was investigated in detail through these experiments. According to the experimental result, it was confirmed that the capacitor bank should be $70{\mu}F{\sim}100{\mu}F$, and the proper SEIG induced voltage should be DC 80 V ~ 250 V in order to storage electrical energy into a battery.

• Journal of Digital Convergence
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• v.18 no.3
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• pp.35-42
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• 2020

Digital transformation is about revolutionizing the interaction between virtual and reality. The complex problems that arise in this process must be solved, and one of the methods is computing thinking. Therefore, this study aims to observe whether software education that uses unplugged as liberal education is effective in enhancing computing thinking. For this, 5 elements of computing thinking were extracted and unplugged was applied to liberal software classes, and classes were conducted. During one semester, 16 sessions of classes were conducted and computing thinking enhancement was measured through surveys. As a result, the computing thinking of the students increased overall after classes. Observation surveys showed that, among computing thinking elements, students of all academic fields felt difficulties conceptualizing abstraction elements, those of arts and physical education felt more difficulties with algorithm elements, and those of the humanities felt more difficulties with pattern recognition elements. In the future, various contents for each element should be developed by academic field to aid learner understanding.

• Journal of Digital Convergence
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• v.18 no.1
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• pp.23-33
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• 2020

This study discussed 'inclusive growth', which recently has gained attention as the 4th Industrial Revolution spreads, and considered innovative growth as a requirement for inclusive growth. Combining inclusiveness and innovativeness, a new concept of 'Digital New Deal' is suggested. Specifically, the new market creation strategy through digital transformation of existing industries and public sectors, and solving social problems were presented. It also analyzed problems of the past government-led top-down innovation drive and suggested the "Hybrid" approach as a new way of promoting digital New Deal. Finally, we looked at the 'job creation' effect, discussed the meaning of it in terms of inclusiveness and innovativeness, and proposed a policy alternatives to create lasting effects.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.5
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• pp.298-311
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• 2003

Iterative Fourier transform algorithm, (IFTA) is tile iterative numerical algorithm for the design of the diffractive optical elements (DOE), by which the phase distribution of a DOE converges on a local optimal solution. The convergence of IFTA depends on several factors 3s initial phase distribution, the structure of the degree of freedom on the observation plane, and the values of internal parameters. In this paper, we analyze tile dependence of the convergence of IFTA on an internal parameter of IFTA, the relaxation parameter, and propose a new hybrid scheme of genetic algorithm and IFTA to obtain more accurate solution.

• Journal of the Korean Institute of Intelligent Systems
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• v.21 no.1
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• pp.29-35
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• 2011

In this paper, an integrated simulation model for designing multi-agent system based DEMS (distributed energy management system) in stand-alone micro-grid system is proposed. In the design of the EMS(energy management system), the multi-agent based DEMS are more effective than conventional centralized EMS, but it is difficult to design the DEMS by general design tools for power system because of various states of a microgrid system during operation of stand-alone mode. Also, since performance test of the DEMS using a real system is inefficient, an integrated simulation model is required for designing an effective multi-agent system based DEMS. The proposed model consists of Matlab/SimPowerSystems based simulation model of the microgrid system and the Multi-agnet based DEMS designed by Matlab/StateFlow tool. In order to show the effect of the proposed model, the model outputs are analyzed for specified operation conditions.

• Korean Chemical Engineering Research
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• v.46 no.5
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• pp.915-921
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• 2008

In most PEM fuel cell research, effects of cell geometry, physical properties of component such as membrane, carbon cloth, catalyst, etc. and water transport phenomena are key issues. The scope of these research was limited to single cell and stack except BOP(Balance of plant) of fuel cell. The research fouced on the fuel cell system usually neglect to consider detailed transport phenomena in the cell. The research of the fuel cell system was interested in a system performance and system dynamics. In this paper, the effect of the anode recirculation is calculated using the 2D steady-state model. For this work, 2D steady-state modeling and experiments are performed. For convenience of modifying of model equation, not commercial pakage but the in-house algorithm was used in simulation. For an vehicle industry, the analysis of the anode recirculation system helps the optimization of operating condition of the fuel cell.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.5
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• pp.484-492
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• 2013

With the industrial acceleration in a lot of countries of the world, the demand for anti-corrosion and anti-abrasion material increases continuously. Particularly, stainless steel with the fine surface and excellent corrosion resistance is widely used in various industrial fields including ship, offshore structures tidal power plant, and etc. In marine environment, however, it is easy to generate by the corrosion damage by $Cl^-$ ion and cavitation damage due to high rotation speed on stainless steel. Therefore, in this research, the cavitation erosion-corrosion test (Hybrid test) was performed for 304 stainless steel specimen used in the high flow rate seawater environment. And the cavitation damage behavior in the corrosive environment was analyzed overall. The high hardness was shown due to the formation of compressive residual stress by the water cavitation peening effect in cavitation condition. However, high current density in the potentiodynamic polarization experiment presented with the breakdown of the passive film caused by physical impact. Therefore, both electrochemical characteristics and mechanical properties must be taken into account to improve the cavitation resistance in seawater.

• Journal of Digital Contents Society
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• v.19 no.2
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• pp.371-376
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• 2018

In the system security technology, the information hiding field is developed as technologies for embedding information, which are generally used as contents media. The proposed technique is a technical steganography technique which uses a technique of concealing certain information through physical / statistical change of signal values of contents. Recently, there have been various studies based on histogram shifting in reversible data concealment. In multi - peak histogram shifting, the capacity of data concealment gradually increased by applying multiple peak histogram method. In this paper, we analyze the effect of concealment in terms of adopting the histogram shift method including skipping. In addition, we propose multi - branch data concealment as a general method to improve concealment capacity. The above proposal has proved to be an example using mathematical expressions, and further improvement measures could be derived.