• Atmosphere
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• v.25 no.2
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• pp.271-281
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• 2015

The objectives of this study are to develop a hydrological drought outlook system using GloSea5 (Global Seasonal forecasting system 5) which has recently been used by KMA (Korea Meteorological Association) and to evaluate the forecasting capability. For drought analysis, the bilinear interpolation method was applied to spatially downscale the low-resolution outputs of GloSea5 and PR (Predicted Runoff) was produced for different lead times (i.e., 1-, 2-, 3-month) running LSM (Land Surface Model). The behavior of PR anomaly was similar to that of HR (Historical Runoff) and the estimated values were negative up to lead times of 1- and 2-month. For the evaluation of drought outlook, SRI (Standardized Runoff Index) was selected and PR_SRI estimated using PR. ROC score was 0.83, 0.71, 0.60 for 1-, 2- and 3-month lead times, respectively. It also showed the hit rate is high and false alarm rate is low as shorter lead time. The temporal Correlation Coefficient (CC) was 0.82, 0.60, 0.31 and Root Mean Square Error (RMSE) was 0.52, 0.86, 1.20 for 1-, 2-, 3-month lead time, respectively. The accuracy of PR_SRI was high up to 1- and 2-month lead time on local regions except the Gyeonggi and Gangwon province. It can be concluded that GloSea5 has high applicability for hydrological drought outlook.

• Structural Engineering and Mechanics
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• v.47 no.6
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• pp.881-898
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• 2013

This paper describes analytical investigation into a new dual function system including a couple of shear links which are connected in series using chevron bracing capable to correlate its performance with magnitude of earthquakes. In this proposed system, called Chevron Knee-Vertical Link Beam braced system (CK-VLB), the inherent hysteretic damping of vertical link beam placed above chevron bracing is exclusively utilized to dissipate the energy of moderate earthquakes through web plastic shear distortion while the rest of the structural elements are in elastic range. Under strong earthquakes, plastic deformation of VLB will be halted via restraining it by Stopper Device (SD) and further imposed displacement subsequently causes yielding of the knee elements located at the bottom of chevron bracing to significantly increase the energy dissipation capacity level. In this paper first by studying the knee yielding mode, a suitable shape and angle for diagonal-knee bracing is proposed. Then finite elements models are developed. Monotonic and cyclic analyses have been conducted to compare dissipation capacities on three individual models of passive systems (CK-VLB, knee braced system and SPS system) by General-purpose finite element program ABAQUS in which a bilinear kinematic hardening model is incorporated to trace the material nonlinearity. Also quasi-static cyclic loading based on the guidelines presented in ATC-24 has been imposed to different models of CK-VLB with changing of vertical link beam section in order to find prime effectiveness on structural frames. Results show that CK-VLB system exhibits stable behavior and is capable of dissipating a significant amount of energy in two separate levels of lateral forces due to different probable earthquakes.

• Journal of Broadcast Engineering
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• v.13 no.3
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• pp.339-349
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• 2008

We present a novel method to estimate the light source direction and relight a face texture image of a single 3D model under arbitrary unknown illumination conditions. We create a virtual irradiance sphere to detect the light source direction from a given illuminated texture image using both normal vector mapping and weighted bilinear interpolation. We then induce a relighting equation with estimated ambient and diffuse coefficients. We provide the result of a series of experiments on light source estimation, relighting and face recognition to show the efficiency and accuracy of the proposed method in restoring the shading and shadows areas of a face texture image. Our approach for face relighting can be used for not only illuminant invariant face recognition applications but also reducing visual load and Improving visual performance in tasks using 3D displays.

• Geotechnical Engineering
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• v.8 no.4
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• pp.5-16
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• 1992

The main purpose of this the sutdy is to develop the reinforced earth structure design method considering induced stresses and deflections resulting from placement and compaction of soil. In this paper, the new reinforcement Geolog developed by the author is also introduced which is being used as one of the effective earth reinforcing structure against compaction induced stresses. This study adopted the Seed's bilinear model in the estimation of the com paction induced stresses and compute the peak lateral stresses during compaction by doubled Boussinessq's elastic solution of mirror image theory, thereafter, calculate the residual compaction induced lateral stresses from the above peak lateral stress by the residual fraction. It is considered to be reasonable that the compaction induced stresses be added to the lateral earth pressures estimated from conventional gravity analysis considering the actual stresses during service life of the structures. "GEOLOG", a composite of steel bar and attached concrete stopper is found to be effective against tension and pull - out failure. In this paper, the design method considering the compaction induced stresses and the effect of Geolog reinforcement is suggested for the remforced earth structures where backkfill settlement on displacements are not allowed as in the cases of the bridge abutments or double faced reinforcement earth structures.tructures.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.2
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• pp.69-77
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• 1987

A finite element method has been developed to study the material nonlinear analysis of reinforced concrte structures. Concrete behavior under the biaxial state of stress is represented by a nonlinear constitutive relationship which incorporates tensile cracking, tensile stiffening effect between cracks and the strain-softening phenomenon beyond the maximum compressive strength. The concrete model used is based upon nonlinear elasticity by assuming concrete to be an orthotropic material and modeled as equivalent uniaxial stress-strain constitutive relationship using equivalent uniaxial strain. The streel reinforcement is assumed to be in a uniaxial stress state and is modeled as a bilinear, elasto-plastic material with strain hardening approximating the Bauschinger effect. In plane stress state, R.C. beams is modeled as a quadratic element that has two degrees of freedom in each node. And this results of finite element analysis are compared with the experimential results of midspan deflection, stresses and strains.

• Journal of the Korea Society of Computer and Information
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• v.17 no.12
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• pp.49-60
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• 2012

In this paper, we propose a hardware design for correction of barrel distortion using the nearest coordinates in the corrected image. Because it applies the nearest distance on corrected image rather than adjacent distance on distorted image, the picture quality is improved by the image whole area, solve the staircase phenomenon in the exterior area. But, because of additional arithmetic operation using design of bilinear interpolation, required arithmetic operation is increased. Look up table(LUT) structure is proposed in order to solve this, coordinate rotation digital computer(CORDIC) algorithm is applied. The results of the synthesis using Design compiler, the design of implementing all processes of the interpolation method with the hardware is higher than the previous design about the throughput, In case of the rear camera, the design of using LUT and hardware together can reduce the size than the design of implementing all processes with the hardware.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.1197-1199
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• 2003

ROCSAT-2 mission is to daily image over Taiwan and the surrounding area for disaster monitoring, land use, and ocean surveillance during the 5-year mission lifetime. The satellite will be launched in December 2003 into its mission orbit, which is selected as a 14 rev/day repetitive Sun-synchronous orbit descending over (120 deg E, 24 deg N) and 9:45 a.m. over the equator with the minimum eccentricity. National Space Program Office (NSPO) is developing a ROCSAT-2 Image Processing System (IPS), which aims to provide real-time high quality image data for ROCSAT-2 mission. A simulated ROCSAT-2 image, based on Level 1B QuickBird Data, is generated for IPS verification. The test image is comprised of one panchromatic data and four multispectral data. The qualification process consists of four procedures: (a) QuickBird image processing, (b) generation of simulated ROCSAT-2 image in Generic Raw Level Data (GERALD) format, (c) ROCSAT-2 image processing, and (d) geometric error analysis. QuickBird standard photogrammetric parameters of a camera that models the imaging and optical system is used to calculate the latitude and longitude of each line and sample. The backward (inverse model) approach is applied to find the relationship between geodetic coordinate system (latitude, longitude) and image coordinate system (line, sample). The bilinear resampling method is used to generate the test image. Ground control points are used to evaluate the error for data processing. The data processing contains various coordinate system transformations using attitude quaternion and orbit elements. Through the qualification test process, it is verified that the IPS is capable of handling high-resolution image data with the accuracy of Level 2 processing within 500 m.

• Atmosphere
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• v.31 no.2
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• pp.185-198
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• 2021

In this study, we examined a spatial downscaling method based on Gradient and Inverse Distance Squared (GIDS) weighting to produce high-resolution grid data from a numerical weather prediction model over Korean Peninsula with complex terrain. The GIDS is a simple and effective geostatistical downscaling method using horizontal distance gradients and an elevation. The predicted meteorological variables (e.g., temperature and 3-hr accumulated rainfall amount) from the Limited-area ENsemble prediction System (LENS; horizontal grid spacing of 3 km) are used for the GIDS to produce a higher horizontal resolution (1.5 km) data set. The obtained results were compared to those from the bilinear interpolation. The GIDS effectively produced high-resolution gridded data for temperature with the continuous spatial distribution and high dependence on topography. The results showed a better agreement with the observation by increasing a searching radius from 10 to 30 km. However, the GIDS showed relatively lower performance for the precipitation variable. Although the GIDS has a significant efficiency in producing a higher resolution gridded temperature data, it requires further study to be applied for rainfall events.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.2
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• pp.181-186
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• 2022

Poisson-Boltzmann equation (PBE) is used to model problems arising from various disciplinary including bio-pysics and colloid chemistry. Therefore, to predict a numerical solution of PBE is an important issue. The authors proposed deep learning based methods to solve PBE while the computational time to generate finite element method (FEM) solutions were bottlenecks of the algorithms. In this work, we shorten the generation time of FEM solutions in two directions. First, we experimentally find certain penalty parameter in a bilinear form. Second, we applied algebraic multigrids methods to the algebraic system so that condition number is bounded regardless of the meshsize. In conclusion, we have reduced computation times to solve algebraic systems for PBE. We expect that algebraic multigrids methods can be further employed in various disciplinary to generate deep learning samples.

• Journal of the Korean Geotechnical Society
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• v.27 no.10
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• pp.81-92
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• 2011

The rheological properties of Wyoming bentonites are strongly influenced by the size of particles, cation exchangeable capacity, arrangement and morphology of clay mineral. This paper presents the results of rheological investigations on the Wyoming bentonites aqueous dispersions: two types of particle flocculation were considered. For the Wyoming bentonite, 0g/L and 30g/L NaCl equivalent salinity were added in fresh and salt water to examine the rheological behavior. This paper examined the general rheological characteristics, compatibility of rheological models and correlation between soil structure and change in rheological properties of Wyoming bentonite caused by increasing salinity. From flow curves of bentonites hydrated with fresh water and salt water, the observed general flow behavior is very close to shear thinning with yield stress (or ideal Bingham fluid with yield stress and plastic viscosity). However, the change of shear stress at the same shear rate is clear, particularly for lower shear rate. Well-known rheological models are used to fit the data. There is a good agreement between rheological model and data: Carreau, Herschel-Bulkley and power-law for S=0g/L and bilinear, Herschel-Bulkley and power-law for S=30g/L. It may be due to the fact that the internal structural bonding (strong modification of particle-particle interactions from edge-to-edge and/or edge-to-face to face-to-face) in soil matrix is affected from the evolution of rheological properties with different salinities.