• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.12
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• pp.1061-1069
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• 2010

In this study, a simplified axisymmetric model is proposed for the problem of compressible internal flow past a microgap. Using numerical and experimental methods, the phenomena of choked flows are observed; these flows are induced by the acceleration of subsonic flows past the narrow cross-section of an annular shape made by a microgap. The relation between mass flow rate and differential pressure is obtained, and by comparing the result with experimental results, the reliability of the numerical results is discussed. The generation of a supersonic jet flow and its diffraction are visualized by performing the numerical analysis of axisymmetric compressible Navier-Stokes equations. This investigation greatly extends the physical understanding of the axisymmetric compressible flow, which has a wide range of engineering applications, e.g., in the case of valves in automotive power systems.

• Journal of the Korea Society of Computer and Information
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• v.12 no.5
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• pp.39-47
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• 2007

In this thesis, a method of generating an adaptable Region-Of-Interest(ROI) Mask for the Region-Of-Interest coding is suggested. In the method, an ROI Mask is generated using the information of the ROI designated by a user. In the existed method of ROI coding, after scanning all the pixels in order and discriminating an ROI, an ROI Mask is generated. But, in our method, after scanning a part of pixels based on the shape pattern of an ROI and discriminating a ROI by one code block unit, an ROI Mask is generated. Moreover, from the method, a pattern number, threshold of a ROI and background threshold parameter are provided. According to the result of its comparing test with the existed methods to show the usability, it is proved that our method is superior in speed to the existed ones.

• The Journal of Information Systems
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• v.23 no.1
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• pp.161-184
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• 2014

Our study measures the Digital Life Index (DLI) of baby boomers by considering the utilization of digital devices in their everyday life. The study was conducted by implementing the following three-step approach: (1) development of survey questions and data collection; (2) build Digital Life Index (DLI) model and lastly; (3) empirical analysis using the Digital Life Index (DLI). In the first stage in order to develop the survey questions to measure the digital index, two surveys were conducted. For the first preliminary survey, it was done based on the existing literatures which enabled this investigation through FGI analysis involving real professionals. The second survey was conducted by commissioning a specialized external firm. In this survey, a total of 400 data was collected to verify the validity and objectivity of the data sample. The data gathered through the survey questions was used to develop the digital index. Firstly, the appropriate factors were extracted by conducting factor analysis. This factor analysis validates and verifies the factors which are appropriate in measuring Digital Life Index (DLI). The derived factors are broadly divided into five main factors. The first factor describes the possession, purchase and use of digital device (x1). Meanwhile, the second factor describes the digital device's software (x2) and the third factor describes the participation in utilizing digital device (x3). The fourth factor describes the utilization of digital device in human personal relationship (x4) and lastly, the fifth factor describes the effect of digital device in everyday life and work environment (x5). Secondly, the digital index model was developed. The variables to represent the Digital Life Index (DLI) are ${\chi}1t,{\chi}2t,{\chi}3t,{\chi}4t$ and ${\chi}5t$. Furthermore, as experience in using the digital index grows overtime, the growth can be represented by the "S" shape. Based on the results, Digital Life Index(DLI) is distributed with the highest point at 90.3 and the lowest point at 25.9.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.6
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• pp.3-10
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• 2017

In this paper, we have designed a MIMO system using a W-OFDM modulation scheme. And then, we have evaluated and analyzed synchronization performance of the system. In this paper, we have considered Schmidl's method, Minn's method, and Park's method. As simulation results, Schmidl's method has wide plateau of timing metric and Park's method has impulse-shape timing metric. Also, we can confirm that timing metric characteristic of synchronization estimator is not changed by adjusting extension length of W-OFDM system. Because of this, we can confirm that synchronization method of OFDM can be effectively used in MIMO system using W-OFDM modulation.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.5
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• pp.199-204
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• 2015

In this study, prevention methods of radial cracks generated inside of artificial lightweight aggregate made of reject ash and dredged soil were investigated. The reject ash and dredged soil had mixed with weight ratio of 7 : 3 and formed to spheric shape of 5~20 mm diameter, then, the aggregates were manufactured using flash sintering method at $1200^{\circ}C$ for 10 min. The formation of radial cracks in the aggregates were suppressed as the size of specimen decreased. Also, the addition of silica to aggregates had prevented generation of the radial cracks. As the size and the amount of silica powder added increased, the development of radial cracks was constrained. Therefore the artificial lightweight aggregate manufactured in this study expected to be applicable to many fields such as construction and environmental usages. Also it is expected to contribute greatly to increase the recycling rate of reject ash and dredged soil.

• The Research Journal of the Costume Culture
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• v.18 no.4
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• pp.612-625
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• 2010

People have more expectations for arts and design and accordingly, various artworks were combined with fashion to meet the consumer needs. As people live a decent life, the development of leisure activities and industry has a much effect on apparel. With this phenomenon, a free and active casual look is making progress centering around the practical apparel, pursuing diversified efficiency irrespective of a season and considering sensibility not formality. In this study, paintings of Henri Matisse were analyzed in every respect and were applied in apparel design with diverse color arrangement and a motif originating in the phenomenon of modern fashion design which leads to the integration of arts and design. Painting image and color of Henri Matisse were used. Sportive casual and cultural casual was used in design as well. Originality of its color in the paintings which were used an a motif is coming from Gauguin and Gogh. Henri had influenced to the next generation with pursuit of violent color. The following conclusions were drawn from this study. First, the color of Henri Matisse's paintings has a strong contrast effect. It combines notable violent color with a simple yet decorative motif. Therefore color from Matisse's paintings suit for apparel of marked individuality with its free color arrangement. Second, free and active image in Henri Matisse's paintings is easy to express efficiency and popularity. It accords with the feature of casual wear. Third, through adding a flowing curved line in Henri Matisse's paintings to materials and applying various colors putting into a curved line image to a rib section, a decorative effect which goes with the whole shape is obtained. This study presents possibility of emergence of unique design using free color arrangement and motif from the image of paintings and aims development of modern fashion design in accordance with modern fashion giving importance to the difference and sensibility by integration of modern garments and artworks.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.34.1-34.1
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• 2009

A great deal of attention has been focused on ZnO nanowires for various electronics and optoelectronics applications. in the pursuit of next generation nanodevices, it would be highly preferred if well-ordered ZnO nanowires of lower dimension could be fabricated on silicon. Before the growth of nanowires, silicon substrates were selectively etched using silicon nitride as masking layer. Vertical aligned ZnO nanowires were grown by metal organic chemical vapor deposition on patterned silicon substrate. The shape of nanostructures was greatly influenced by the micropatterned surface of the substrate. The aspect ratio, packing fraction and the number density of nanowires on top surface are around 10, 0.8 and $10^7\;per\;mm^2$, respectively, whereas the values are 20, 0.3 and $5\times10^7\;per\;mm^2$, respectively, towards the bottom of the cavity. XRD patterns suggest that the nanostructures have good crystallinity. High-resolution transmission electron microscopy confirmed the single crystalline growth of the ZnO nanowires along [0001] direction.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.4
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• pp.750-769
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• 2015

The geometry of engineering systems affects their performances. For this reason, the shape of engineering systems needs to be optimized in the initial design stage. However, engineering system design problems consist of multi-objective optimization and the performance analysis using commercial code or numerical analysis is generally time-consuming. To solve these problems, many engineers perform the optimization using the approximation model (response surface). The Response Surface Method (RSM) is generally used to predict the system performance in engineering research field, but RSM presents some prediction errors for highly nonlinear systems. The major objective of this research is to establish an optimal design method for multi-objective problems and confirm its applicability. The proposed process is composed of three parts: definition of geometry, generation of response surface, and optimization process. To reduce the time for performance analysis and minimize the prediction errors, the approximation model is generated using the Backpropagation Artificial Neural Network (BPANN) which is considered as Neuro-Response Surface Method (NRSM). The optimization is done for the generated response surface by non-dominated sorting genetic algorithm-II (NSGA-II). Through case studies of marine system and ship structure (substructure of floating offshore wind turbine considering hydrodynamics performances and bulk carrier bottom stiffened panels considering structure performance), we have confirmed the applicability of the proposed method for multi-objective side constraint optimization problems.

• Convergence Security Journal
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• v.2 no.1
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• pp.77-86
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• 2002

In this paper, we propose a segmentation algorithm that can reliably separate moving objects from noisy background in the image sequence received from a camera at the fixed position. Image segmentation is one of the most difficult process in image processing and an adoption in the change of environment must be considered for the increase in the accuracy of the image. The proposed algorithm consists of four process : generation of the difference image between the input image and the reference image, removes the background noise using the background nois modeling to a difference image histogram, then selects the candidate initial region using local maxima to the difference image, and gradually expanding the connected regions, region by region, using the shape information. The test results show that the proposed algorithm can detect moving objects like intruders very effectively in the noisy environment.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.7 no.1
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• pp.33-45
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• 1995

This paper as a sequel to Kang et al. (1994) describes the development of a three-dimensional nonlinear Galerkin-FEM model. Nonlinear advective terms have been incorporated in a manner used by Lardner and Song (1992), that is, using velocities at given nodes computed with linear Galerkin FEM model. The Proposed model is computationally more efficient than previous nonlinear Galerkin models developed by Owen (1980) and Davies (1980) because the model uses a linear shape function as a basis and, furthermore, the similarity transform technique developed by Kang (1994). Two experiments have been carried out to examine effects of nonlinear terms. One is an experiment of wind-driven current in a rectangular basin (Heaps' basin) and the other is an experiment concerning eddy generation behind a jetty with specified downstream and upstream open boundary conditions. The computed Pattern was found to be in good agreement qualitatively with previous model experiments by Stelling (1984).