• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.11a
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• pp.116-119
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• 1999

This paper presents a feeder waveguide array of slot array antennas for Direct Broadcasting from Satellite(DBS). The feed structure consists of a single waveguide placed on the same layer as radiating waveguide and is characterized by the unit divider, called a $\pi$-Junction. This K-function with an inductive wall splits part of the power into two branch waveguide through one coupling window, and can excite densely arrayed waveguide at equal phase and amplitude. The power dividing characteristics of a cascade of $\pi$ -functions are analyzed by Galerkin's method of moments. From the optimum simulation results based on the feeder waveguide using $\pi$ -Junction at 3.95GHz, we obtained the scattering matrices of the feeder divided power at 11.85CHz.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.10
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• pp.4108-4125
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• 2015

This paper presents a scalable coding method for depth images by considering the quality of synthesized images in virtual views. First, we design a new edge detection algorithm that is based on calculating the depth difference between two neighboring pixels within the depth map. By choosing different thresholds, this algorithm generates a scalable bit stream that puts larger depth differences in front, followed by smaller depth differences. A scalable scheme is also designed for coding depth pixels through a layered sampling structure. At the receiver side, the full-resolution depth image is reconstructed from the received bits by solving a partial-differential-equation (PDE). Experimental results show that the proposed method improves the rate-distortion performance of synthesized images at virtual views and achieves better visual quality.

• International Journal of Air-Conditioning and Refrigeration
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• v.12 no.1
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• pp.50-60
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• 2004

An experimental analysis using three-dimensional Laser Doppler Velocimetry(LDV) measurement and computational analysis using the Reynolds stress model in FLUENT are conducted to give a clear understanding of the effect of blade loading on the structure of tip leakage flow in a forward-swept axial-flow fan operating at the maximum efficiency condition ($\Phi$=0.25) and two off-design conditions ($\Phi$=0.21 and 0.30). As the blade loading increases, the onset position of the rolling-up of tip leakage flow moves upstream and the trajectory of tip leakage vortex center is more inclined toward the circumferential direction. Because the casing boundary layer becomes thicker and the mixing between the through-flow and the leakage jet with the different flow direction is enforced, the streamwise vorticity decays more fast with the blade loading increasing. A distinct tip leakage vortex is observed downstream of the blade trailing edge at $\Phi$=0.30, but it is not observed at $\Phi$=0.21 and 0.25.

• Journal of the Korean Institute of Landscape Architecture
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• v.19 no.3
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• pp.41-54
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• 1991

This study was executed to analyze the vegetational landscape structure and administration planning of Younguan Royal Tomb forest by the classification and DCA ordination were applied to the study are in order to classify them into several groups based on environmental variables. Also Younguan Royal Tomb forest comparison of a pair of photographs taken in 1920s and 1990. Sixteen sites were sampled with clumped sampling method in september 1990 and five quadrats were examined in each site. By classification and DCA, the plant community were divided into two groups(A. japonica community, P. densiflora, Quercus acutissima community) by the humus. Pinus densiflora community of actual vegetion covered 15.9%, Alnus japonica 6.5% and Quercus community 65.6% of the total area. And the afforested vegetation of P. koraiensis. P. rigida and Juglans mandshurica covered 13.2%. DCA ordination showed that successional trends of tree species seem to be from P. densiflora, Q. aliena to Q. acutissima in P. densiflora community and from A. japonica community of the upper layer. By the comparison of couple photographs between 1920s and 1990 we can recognize the change of historical landscape composed of P. densiflora community, A. japonaca and those community shall be conserved by the disclimax method, i.e. the broadleaf vegetation in the underlayer in the P. densiflora community should be cleared out. Otherwise the vegetational landscape sructure in Younguan Royal Tomb is successed to progress succession to Q. acutissima landscape.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.4
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• pp.294-304
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• 2003

An experimental analysis using three-dimensional laser Doppler velocimetry(LDV) measurement and computational analysis using the Reynolds stress model in FLUENT are conducted to give a clear understanding of the effect of blade loading on the structure of tip leakage flow in a forward-swept axial-flow fan operating at the maximum efficiency condition ($\Phi$=0.25) and two off-design conditions ($\Phi$=0.21 and 0.30). As the blade loading increases, the onset position of the rolling-up of tip leakage flow moves upstream and the trajectory of tip leakage vortex center is more inclined toward the circumferential direction. Because the casing boundary layer becomes thicker and the mixing between the through-flow and the leakage jet with the different flow direction is enforced, the streamwise vorticity decays more fast with the blade loading increasing. A distinct tip leakage vortex is observed downstream of the blade trailing edge at $\Phi$=0.30, but it is not observed at $\Phi$=0.21 and 0.25.

• Structural Engineering and Mechanics
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• v.75 no.6
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• pp.713-722
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• 2020

This article aims to illustrate the damped dynamic responses of layered functionally graded (FG) thick 2D beam under dynamic pulse sinusoidal load by using finite element method, for the first time. To investigate the response of thick beam accurately, two-dimensional plane stress problem is assumed to describe the constitutive behavior of thick beam structure. The material is distributed gradually through the thickness of each layer by generalized power law function. The Kelvin-Voigt viscoelastic constitutive model is exploited to include the material internal damping effect. The governing equations are obtained by using Lagrange's equations and solved by using finite element method with twelve -node 2D plane element. The dynamic equation of motion is solved numerically by Newmark implicit time integration procedure. Numerical studies are presented to illustrate stacking sequence and material gradation index on the displacement-time response of cantilever beam structure. It is found that, the number of waves increases by increasing the graduation distribution parameter. The presented mathematical model is useful in analysis and design of nuclear, marine, vehicle and aerospace structures those manufactured from functionally graded materials (FGM).

• Current Optics and Photonics
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• v.8 no.1
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• pp.30-37
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• 2024

Implemented at the Geochang Observatory in South Korea, our slope detection and ranging (SLO-DAR) system features a 508 mm Cassegrain telescope (f /7.8), incorporating two Shack-Hartmann wave-front sensors (WFS) for precise measurements of atmospheric phase distortions, particularly from nearby binary or double stars, utilizing an 8 × 8 grid of sampling points. With an ability to reconstruct eight-layer vertical atmospheric profiles, the system quantifies the refractive index structure function (C_n²) through the crossed-beam method. Adaptable in vertical profiling altitude, ranging from a few hundred meters to several kilometers, contingent on the separation angle of binary stars, the system operates in both wide (2.5 to 12.5 arcminute separation angle) and narrow modes (11 to 15 arcsecond separation angle), covering altitudes from 122.3 to 611.5 meters and 6.1 to 8.3 kilometers, respectively. Initial measurements at the Geochang Observatory indicated C_n² values up to 181.7 meters with a Fried parameter (r₀) of 8.4 centimeters in wide mode and up to 7.8 kilometers with an r₀ of 8.0 centimeters in narrow mode, suggesting similar seeing conditions to the Bohyun Observatory and aligning with a comparable 2014-2015 seeing profiling campaign in South Korea.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.3
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• pp.291-300
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• 2017

Quantum-dot cellular automata(QCA) is a computing model designed to be similar to cellular automata, and an alternative technology for next generation using high performance and low power consumption. QCA is undergoing various studies with recent experimental results, and it is one of the paradigms of transistors that can solve device density and interconnection problems as nano-unit materials. An XOR gate is a gate that operates so that the result is true when either one of the logic is true. The proposed XOR gate consists of five layers. The first layer consists of OR gates, the third and fifth layers consist of AND gates, and the second and fourth layers are designed as passages in the middle. The half adder consists of an XOR gate and an AND gate. The proposed half adder is designed by adding two cells to the proposed XOR gate. The proposed half adder consists of fewer cells, total area, and clock than the conventional half adder.

• Journal of Korean Society of Transportation
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• v.20 no.1
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• pp.131-139
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• 2002

This study introduces a developed artificial neural networks(ANN) model as a more efficient and reliable prediction model in operating speed Prediction with the 85th percentile horizontal curve of two-way rural highway in the aspect of evaluating highway design consistency. On the assumption that the speed is decided by highway geometry features, total 30 survey sites were selected. Data include currie radius, curve length, intersection angle, sight distance, lane width, and lane of those sites and were used as input layer data of the ANN. The optimized model structure was drawn by number of unit of hidden layer, learning coefficient, momentum coefficient, and change in learning frequency in multi-layer a ANN model. To verify learning Performance of ANN, 30 survey sites were selected while data in obtained from the 20 cites were used as learning data and those from the remaining 10 sites were used as predictive data. As a result of statistical verification, the model D of 4 types of ANN was evaluated as the most similar model to the actual operating speed value: R2 was 85% and %RMSE was 0.0204.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.2
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• pp.257-267
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• 2001

This paper presents a design for a single-layer feeder waveguide array using $\pi$-junctions with the inductive wall. The feed structure consists of a single waveguide placed on the same layer as radiating waveguide and is characterized by the unit divider, called a $\pi$-junction. This $\pi$-junction with an inductive wall splits part of the power into two branchs waveguide through one coupling window, and can excite densely arrayed waveguide at equal phase and amplitude. The power dividing characteristics of the cascade of $\pi$ -junctions are analyzed by Galerkin's method of moments. The numerical results show reasonable agreement with the experimental results. From the optimum simulation results based on the feeder waveguide using $\pi$-junction, we obtained the scattering matrices of the feeder divided power at 3.95 GHz.