• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.6
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• pp.26-34
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• 2010

The mutual coupling of a pair of microstrip patch antennas on a finite grounded dielectric substrate is influenced by the diffracted field of surface waves from the edges of a substrate. The effective dielectric constant of a grounded dielectric substrate determines the distance between the antenna center and the edge of a substrate to obtain the minimum mutual coupling between a pair of microstrip patch antennas. The optimum substrate size with the minimum mutual coupling is easily calculated using the image method. The optimum substrate sizes using the linage method are in good agreement with the results obtained by the full wave simulation.

• Journal of the Optical Society of Korea
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• v.16 no.3
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• pp.305-312
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• 2012

We numerically demonstrate the performance of a plasmonic lens composed of an array of nanoslits perforated on thin metallic film with slanted cuts on the output surface. Embedding Kerr nonlinear material in nanoslits is employed to modulate the output beam. A two dimensional nonlinear-dispersive finite-difference time-domain (2D N-D-FDTD) method is utilized. The performance parameters of the proposed lens such as focal length, full-width half-maximum, depth of focus and the efficiency of focusing are investigated. The structure is illuminated by a TM-polarized plane wave and a Gaussian beam. The effect of the beam waist of the Gaussian beam and the incident light intensity on the focusing effect is explored. An exact formula is proposed to derive electric field E from electric flux density D in a Kerr-Dispersive medium. Surface plasmon (SPs) modes and Fabry-Perot (F-P) resonances are used to explain the physical origin of the light focusing phenomenon. Focused ion beam milling can be implemented to fabricate the proposed lens. It can find valuable potential applications in integrated optics and for tuning purposes.

• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.1
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• pp.149-157
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• 2014

In this paper, we investigated the sensitivity of aerostatic force coefficients of multi-layer radom in the various wind speeds. The test was conducted in KOCED Wind Tunnel Center in Chonbuk National University, and wind speeds were in the range from 5 m/s to 26 m/s in order to determine the Reynolds number independence. The test results of present multi-layer radom were not affected by the Reynolds number, The maximum positive pressure coefficient was found to be 1.08 at the center of the front of the plane in angle of attack of 0 degree, the maximum negative pressure coefficient was -2.03 at the upper right corner in angle of attack of 120 degree, while maximum drag coefficient was 1.11 in angle of attack of 180 degree.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.8
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• pp.862-869
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• 2005

A study on convective cooling characteristics has been done in the channels with heat pipes and associated Plane fins Analysis with FLUENT V5.0 lies its Purpose on the possible enhancement of heat transfer capability between an existing three in-line arrayed heatpipes and an extending four in-line arrayed heatpipes with increasing channel width. Numerical analysis is limited to the laminar flow in an isolated flow channel by employing cyclic boundary conditions for calculation purposes. Friction factors for three and four in-line arrayed heatpipes are compared with experimental results. In addition, temperature behavior at the plate fin for the three in-line arrayed heatpipes is compared with experiment. Friction factors and overall channel heat transfer coefficients (and/or Nusselt numbers) are presented as a function of Reynolds number. An increase of number of heatpipes and channel width reults in a decrease of the friction factor and doesn't not result in an increase of heat transfer performance. However. considering the 25$\%$ increase of heat load accompanies with maximum 8$^{\circ}C$ rise of average temperature of heat pipes, the four in-line array with the increase of channel width of heat pipe heat sink can be considered appropriate.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.2
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• pp.186-193
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• 2008

[ $Moir{\acute{e}}$ ] interferometry is an optical method, providing whole field contour maps of in-plane displacements with high resolution. The demand for enhanced sensitivity in displacement measurements leads to the technique of microscopic $moir{\acute{e}}$ interferometry. The method is an extension of the $moir{\acute{e}}$ interferometry, and employs an optical microscope for the required spatial resolution. In this paper, the sensitivity of $moir{\acute{e}}$ interferometry is enhanced by an order of magnitude using an immersion interferometry and the optical/digital fringe multiplication(O/DFM) method. In fringe patterns, the contour interval represents the displacement of 52 nm per fringe order. In order to estimate the reliability and the applicability of the optical system implemented, the measurements of rigid body displacements of grating mold and the coefficient of thermal expansion(CTE) for an aluminium block are performed. The system developed is applied to the measurement of thermal deformation in a flip chip plastic ball grid array package.

• Current Optics and Photonics
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• v.7 no.4
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• pp.408-418
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• 2023

Due to the technological limitations of infrared thermography, infrared focal plane array (IFPA) imaging exhibits stripe non-uniformity, which is typically fixed pattern noise that changes over time and temperature on top of existing non-uniformities. This paper proposes a stripe non-uniformity correction algorithm based on scene-adaptive nonlinear filtering. The algorithm first uses a nonlinear filter to remove single-column non-uniformities and calculates the actual residual with respect to the original image. Then, the current residual is obtained by using the predicted residual from the previous frame and the actual residual. Finally, we adaptively calculate the gain and bias coefficients according to global motion parameters to reduce artifacts. Experimental results show that the proposed algorithm protects image edges to a certain extent, converges fast, has high quality, and effectively removes column stripes and non-uniform random noise compared to other adaptive correction algorithms.

• Journal of information and communication convergence engineering
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• v.13 no.4
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• pp.275-279
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• 2015

There are several methods to record three dimensional (3D) information of objects such as lens array based integral imaging, synthetic aperture integral imaging (SAII), computer synthesized integral imaging (CSII), axially distributed image sensing (ADS), and axially distributed stereo image sensing (ADSS). ADSS method is capable of recording partially occluded 3D objects and reconstructing high-resolution slice plane images. In this paper, we present a computational method for depth extraction of partially occluded 3D objects using ADSS. In the proposed method, the high resolution elemental stereo image pairs are recorded by simply moving the stereo camera along the optical axis and the recorded elemental image pairs are used to reconstruct 3D slice images using the computational reconstruction algorithm. To extract depth information of partially occluded 3D object, we utilize the edge enhancement and simple block matching algorithm between two reconstructed slice image pair. To demonstrate the proposed method, we carry out the preliminary experiments and the results are presented.

• Plant Journal
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• v.12 no.3
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• pp.32-38
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• 2016

In this study, the effect of wake on the energy production of a downstream wind turbine was analyzed on the base of operation practices of wind farm in the coastal complex terrain which has 2 row array of wind turbines. And changes in the variation of wind speed and turbulence intensity was analyzed. In case wind turbines are spaced 4-rotor diameter-apart in the prevailing wind direction, reduction in energy production was confirmed due to the decrease of wind speed and the increase of turbulence intensity by wake. Especially a radical change of wind direction caused wind turbine a sudden stop and energy production significantly reduced. It is considered improvement of yaw brake can prevent the sudden stop and increase energy production.

• Structural Engineering and Mechanics
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• v.71 no.2
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• pp.197-210
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• 2019

Probabilistic buckling behavior of sandwich panel considering random system parameters using a radial basis function (RBF) approach is presented in this paper. The random system properties result in an uncertain response of the sandwich structure. The buckling load of laminated sandwich panel is obtained by employing higher-order-zigzag theory (HOZT) coupled with RBF and probabilistic finite element (FE) model. The in-plane displacement variation of core as well as facesheet is considered to be cubic while transverse displacement is considered to be quadratic within the core and constant in the facesheets. Individual and combined stochasticity in all elemental input parameters (like facesheets thickness, ply-orientation angle, core thickness and properties of material) are considered to know the effect of different degree of stochasticity, ply- orientation angle, boundary conditions, core thickness, number of laminates, and material properties on global response of the structure. In order to achieve the computational efficiency, RBF model is employed as a surrogate to the original finite element model. The stiffness matrix of global response is stored in a single array using skyline technique and simultaneous iteration technique is used to solve the stochastic buckling equations.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.3 s.147
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• pp.285-293
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• 2006

Three-dimensional and time-dependent solution for the fluid flow and heat transfer past a circular cylinder with fins is obtained using accurate and efficient spectral methods. A Fourier expansion with a corresponding uniform grid is used along the circumferential direction. A spectral multi-domain method with a corresponding Chebyshev collocation is used along r-z plane to handle fins attached to the surface of a circular cylinder. At the Reynolds number of 300 based on a cylinder diameter, results with fins are compared with those without fins in order to see the effects of the presence of fins on three-dimensional and unsteady fluid flow and heat transfer past a bluff body. The detail structures of fluid flow and temperature field are obtained as a function of time to investigate how the presence of fins changes heat transfer mechanism related to the vortical structure in the wake region.