• Journal of Korean Society of Coastal and Ocean Engineers
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• v.16 no.4
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• pp.206-212
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• 2004

The numerical analysis on the wave screening performance of the submerged breakwater with various crown widths is presented. The fluid motion is considered as linearized two dimensional potential flow and the finite element method is used to analyze the wave screening performance of the submerged breakwater. It is found that single-submerged breakwater with large crown width shows the most effective wave screening performance and single-submerged breakwater with small crown width also shows fairly good wave screening performance but its effectiveness is less than that of single-submerged breakwater with large crown width. However, double- or triple-submerged breakwater with small crown width shows more effective wave screening performance than that of single- or double-submerged breakwater with large crown width. It is expected that the submerged breakwater with small crown width is economical because it reduces the size of structure.

• Journal of Advanced Navigation Technology
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• v.11 no.4
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• pp.454-460
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• 2007

In this paper, we implemented a ray-tracing simulator with a ray-launching technique and generated the propagation path of each ray in an multiple-wall indoor environment. In this simulator, we adopted two dimension ray-tracing techniques considering the reflection and penetration were dominant propagation factor in the indoor channel. From the result, we verified that this ray-tracing simulator shows the similar pattern and delay distribution with the experiment results of the previous research.

• The Journal of Sustainable Design and Educational Environment Research
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• v.13 no.1
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• pp.58-68
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• 2014

Recently, multiple metropolitan counties and local authorities have been actively working on improving their local existence with various methods and strategies. Such change cannot be observed when local authorities were chosen by the government. Also, the public administration has recently emphasized important factors of public design which seeks better lifestyle and outward beauty from quantitative growth and policy of strongly considering outward form due to the compressive modernization. Public design intends to complete aesthetic factor and improve the quality of life as the efficiency as the value of public administration. The purpose of this study is to discuss how public school has been evolved as public space and how to create local user-centered interaction. The study retrieve the communication which the essential publicness in the school public design and the self-management which is the original value in terms of sociology. The method in which the characters of the public design of the publicness have been changed will be concentrated on in public area. In addition, the study has been focused on the efforts of the reflection of the development in public design are the challenges for the aim of the design of the publicness.

• Journal of Ocean Engineering and Technology
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• v.28 no.5
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• pp.474-483
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• 2014

The majority of existing WECs (wave energy converters) are designed to achieve maximum power at a resonance condition. In the case of a single WEC, its size must be large enough for tuning, and it has high efficiency only within a limited frequency band. Recently, wave power extraction by deploying many small buoys in a compact array has been studied under the assumption that the buoy's size and separation distance are much smaller than the water depth, wave length, and size of the array. A boundary value problem involving the macro-scale boundary condition on the mean surface covered by an infinite strip of buoys is solved using the eigenfunction expansion method. The energy extraction efficiency (${\varepsilon}=1-R^2_f-T^2_r$), where $R_f$ and $T_r$ are the reflection and transmission coefficients for a strip array of buoys, is assessed for various combinations of packing ratio, strip width, and PTO damping coefficient.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.3
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• pp.324-331
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• 2016

The present study focuses on the characteristics of a supersonic jet flowing from a rectangular nozzle exit on a flat plate. Flow visualization techniques using schlieren and kerosene-lampblack tracing are utilized to investigate shock reflection structures and boundary-layer separations over a flat plate. Wall pressure measurements are also carried out to quantitatively analyze the flow structures. All observations are repeated for multiple jet flow boundary conditions by varying the flap length and nozzle pressure ratio. The experimental results show that the jet flow structures over the flat plate are highly three-dimensional with strong bleeding flows from the plate sides, and that they are sensitive to plate length and nozzle pressure ratio. A multi-component force measurement device is also utilized to observe the characteristics of the jet flow thrust vectoring over the plate. The maximum thrust deflection angle of the jet is about $8^{\circ}$, demonstrating the applicability of thrust vector control via a flat plate installed at the nozzle exit.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.4
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• pp.295-300
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• 2013

The noise map can be applied to predict the effect of noise and establish the noise reduction measure. But the predicted value in the noise map can vary depending on the input variables. Thus, we surveyed the several prediction models and analyzed the changes corresponding to the variables for obtaining the coherency and accuracy of prediction results. As a result, we know that the Schall03 and CRN model can be applied to predict the railway noise in Korea and the correction value, such as bridges correction, multiple reflection correction, curve correction must be used for reflecting the condition of the prediction site. Also, we know that the prediction guideline is an essential prerequisite in order to obtain the unified and accurate predicted value for railway noise.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.6
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• pp.491-497
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• 2016

This study aims to develop a vision inspection system for screw threads. To inspect external defects in screw threads, the vision inspection system was developed using front light illumination from which bright images can be obtained. The front light system, however, requires multiple side images for inspection of the entire thread surface, which can be performed by omnidirectional optics. In this study, an omnidirectional optical system was designed to obtain annular images of screw threads using an image sensor and two reflection mirrors; one large concave mirror and one small convex mirror. Optical simulations using backward and forward ray tracing were performed to determine the dimensional parameters of the proposed optical system, so that an annular image of the screw threads could be obtained with high quality and resolution. Microscale surface defects on the screw threads could be successfully detected using the developed annular inspection system.

• Journal of Korea Multimedia Society
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• v.8 no.1
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• pp.88-100
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• 2005

In computer graphics, realistic skin rendering has been regarded as difficult tasks and remains as an important research subject. Translucent materials like skin have some complicated optical properties including subsurface scattering. In this paper, we proposes a skin shader based on subsurface scattering to render realistic skin and it has been implemented as a plug-in for Maya, 3D Package. The rendered image using this proposed skin shader appears more realistic than the rendered image using classical shading techniques. Furthermore, we could model sebum, epidermis, dermis using specular reflection, multiple scattering, single scattering respectively.

• Applied Science and Convergence Technology
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• v.26 no.3
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• pp.52-54
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• 2017

An InGaN/GaN multiple quantum well (MQW) structure is grown on a GaN/sapphire template using a plasma-assisted molecular beam epitaxy (PA-MBE). The fluctuation of the quantum well thickness formed from roughly-grown InGaN layer results in a disordered photoluminescence (PL) spectrum. The surface morphologies of the InGaN layers with various In compositions are investigated by reflection high energy electron diffraction (RHEED) and atomic force microscopy (AFM). A blurred InGaN/GaN hetero-interface and the non-uniform QW size is confirmed by high resolution transmission electron microscopy (HR-TEM). Inhomogeneity of the quantum confinement results in a degradation of the quantum efficiency even though the InGaN layer has a uniform In composition.

• Korean Journal of Optics and Photonics
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• v.21 no.4
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• pp.161-167
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• 2010

We suggest an effective expression of transmission coefficients between uniaxial anisotropic media. To study the transmission of oblique incident light by stratified anisotropic planar structures, we included an imaginary isotropic layer sandwiched between those anisotropic media, and then considered multiple reflection within the imaginary layer. The adequacy of this expression is confirmed by comparing the polarization analysis of light passing through the anisotropic medium and the multi.layered anisotropic media.