• Structural Engineering and Mechanics
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• v.65 no.6
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• pp.679-687
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• 2018

In composite materials technology, the fiber-reinforced polymers (FRP) have opened up new horizons in infrastructural engineering field for strengthening existing structures and components of structure. The Carbon fiber reinforced polymer (CFRP) sheets are well suited for RC columns to this application because of their high strength to weight ratio, good fatigue properties and excellent resistance to corrosion. The main focus of present experimental work is to investigate effect of shapes on axial behavior of CFRP wrapped RC columns having same cross-sectional area and slenderness ratio. The CFRP volumetric ratio and percentage of steel are also adopted constant for all the test specimens. A total of 18 RC columns with slenderness ratio four were cast. Nine columns were control and the rest of nine columns were strengthened with one layer of CFRP wrap having 35 mm of corner radius. Columns confined with CFRP wrap were designed using IS: 456:2000 and ACI 440.2R.08 provisions. All the test specimens were loaded for axial compression up to failure and failure pattern for each shaped column was investigated. All the experimental results were compared with analytical values calculated as per the ACI-440.2R-08 code. The test results clearly demonstrated that the axial behavior of CFRP confined RC columns is affected with the change in shapes. The axial deformation is higher in CFRP wrapped RC circular column as compared to square and rectangular columns. Stress-strain behaviour revealed that the yield strength gained from CFRP confinement was significant for circular columns as compare to square and rectangular columns. This behaviour may be credited due to effect of shape on lateral deformation in case of CFRP wrapped circular columns at effective confinement action.

• Wind and Structures
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• v.30 no.6
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• pp.633-648
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• 2020

The objective of this work was to investigate the interference effects of two-parallel bridge decks on aerodynamic coefficients, vortex-induced vibration, flutter instability and flutter derivatives. The two bridges have significant difference in cross-sections, dynamic properties, and flutter speeds of each isolate bridge. The aerodynamic static tests and aeroelastic tests were performed in TU-AIT boundary layer wind tunnel in Thammasat University (Thailand) with sectional models in a 1:90 scale. Three configuration cases, including the new bridge stand-alone (case 1), the upstream new bridge and downstream existing bridge (case 2), and the downstream new bridge and the upstream existing bridge (case 3), were selected in this study. The covariance-driven stochastic subspace identification technique (SSI-COV) was applied to identify aerodynamic parameters (i.e., natural frequency, structural damping and state space matrix) of the decks. The results showed that, interference effects of two bridges decks on aerodynamic coefficients result in the slightly reduction of the drag coefficient of case 2 and 3 when compared with case 1. The two parallel configurations of the bridge result in vortex-induced vibrations (VIV) and significantly lower the flutter speed compared with the new bridge alone. The huge torsional motion from upstream new bridge (case 2) generated turbulent wakes flow and resulted in vertical aerodynamic damping H1^* of existing bridge becomes zero at wind speed of 72.01 m/s. In this case, the downstream existing bridge was subjected to galloping oscillation induced by the turbulent wake of upstream new bridge. The new bridge also results in significant reduction of the flutter speed of existing bridge from the 128.29 m/s flutter speed of the isolated existing bridge to the 75.35 m/s flutter speed of downstream existing bridge.

• Environmental Engineering Research
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• v.21 no.4
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• pp.333-340
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• 2016

An Artificial Neural Network including a Radial Basis Function (RBF) and a Time Delay Neural Network (TDNN) was used to predict total dissolved solid (TDS) in the river Zayanderud. Water quality parameters in the river for ten years, 2001-2010, were prepared from data monitored by the Isfahan Regional Water Authority. A factor analysis was applied to select the inputs of water quality parameters, which obtained total hardness, bicarbonate, chloride and calcium. Input data to the neural networks were pH, $Na^+$, $Mg^{2+}$, Carbonate ($CO{_3}^{-2}$), $HCO{_3}^{-1}$, $Cl^-$, $Ca^{2+}$ and Total hardness. For learning process 5-fold cross validation were applied. In the best situation, the TDNN contained 2 hidden layers of 15 neurons in each of the layers and the RBF had one hidden layer with 100 neurons. The Mean Squared Error and the Mean Bias Error for the TDNN during the training process were 0.0006 and 0.0603 and for the RBF neural network the mentioned errors were 0.0001 and 0.0006, respectively. In the RBF, the coefficient of determination ($R^2$) and the index of agreement (IA) between the observed data and predicted data were 0.997 and 0.999, respectively. In the TDNN, the $R^2$ and the IA between the actual and predicted data were 0.957 and 0.985, respectively. The results of sensitivity illustrated that $Ca^{2+}$ and $SO{_4}^{2-}$ parameters had the highest effect on the TDS prediction.

• Journal of Conservation Science
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• v.35 no.5
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• pp.403-415
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• 2019

According to oral tradition, the King Sejo's palanquin is indeed the palanquin of King Sejo, the 7^th monarch of the Joseon dynasty who reigned from 1455 to 1468, which was left behind after visiting the Magoksa temple. The palanquin is painted in five colors, mainly black, white, yellow, red and green. The chromaticity measurement of the yellow pigment showed that orpiment and gold are a noticeable distinction between the lightness and b^⁎ values. In the case of the red pigment, a^⁎ values of areas painted with cinnabar tend to measure at high values. As a result of the optical microscopy, scanning electron microscopy and energy dispersive spectroscopy analyses, it was determined that Chinese ink was used for the black pigment, lead white and white clay were used for the white, and orpiment and gold for the yellow. The red pigment was found to be the result of minium, cinnabar and red ocher, atacamite was used as green pigment. Though the analysis results of the cross sections on very small exfoliation fragments of pigments, it was confirmed that white clay and lead white were used for the preparation layer. In addition, several coloration techniques were considered based on these analyses.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.12
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• pp.1013-1020
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• 2017

In this study, the failure prediction of composite laminates under flexural loading is investigated. A FEA(finite element analysis) using 2D strain-based interactive failure theory. A pregressive failure analysis was applied to FEA for stiffness degradation with failure mode each layer. A three-point bending test based on the ASTM D790 are performed for cross-ply $[0/90]_8$ and quasi-isotropic $[0/{\pm}45/90]_{2s}$ laminated composites. The accuracy of the applied failure theory is verified with the experimental results and other failure criteria such as maximum strain, maximum stress and Tsai-Wu theories.

• Journal of KIISE:Information Networking
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• v.37 no.4
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• pp.284-293
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• 2010

For the successful deployment of Mobile Internet, fast handover technologies are essential. For the past few years several handover mechanisms are suggested, and Fast Handover for Proxy Mobile IPv6 (PFMIPv6) is one of the promising schemes for this purpose. In this paper, we propose a novel L2/L3 cross layer handover scheme based on ARIMA prediction model to apply PFMIPv6 to Mobile Internet environment effectively. Performance gains are evaluated in terms of probabilities of predictive-mode operation, handover latencies, packet loss probabilities, and signaling costs. Three mobilities models are used for our simulation: Manhattan Model, Open Area Model, and Freeway Model. Simulation results show that the proposed scheme can increase probabilities of predictive-mode operation and reduce handover latency, packet loss probabilities, and signaling cost.

• Proceedings of the KSRS Conference
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• v.1
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• pp.11-14
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• 2006

We present an overview on the observation and research for the China seas using both field experiments and multi-sensor satellite data at ORSI/OUC, covering two topics: (1) Spatial and temporal distribution of internal waves in the China Seas and retrieval of internal wave parameters; (2) Retrieval, validation, and cross-comparison of multi-sensor ocean color data as well as ocean optics in situ experiments in the East China Sea. We also present an incoherent Doppler wind lidar, developed by ORSI, and its observation for marine-atmospheric boundary layer.

• Polymer(Korea)
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• v.34 no.1
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• pp.8-13
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• 2010

The physical properties of polymeric foams depend on the density of foams, physical properties of base polymers, the content of open cells, and cell structures including the size and its distribution, the shape of cell, and the thickness of skin layer. The foam density is affected by the chemistry of raw materials, the concentration of crosslinking agent and the blowing agent as well as the operating parameters during production process. In this study, the basic formulations of foams are composed of polyester polyol, MDI, amine catalyst, tin catalyst, silicone surfactant, and water. Cross-linking density of polyurethane was increased by using chain extenders. Also, the mechanical properties of polyurethane foam were improved by using the inorganic fillers (silica 1,2 and talc 1,2) having different $SiO_2$ contents and particle sizes. We investigated the properties of modulus, tensile strength, compressive strength and hardness of foams obtained by changing kind of inorganic filler and chain extender, and observed the distribution of inorganic filler as well as variation of cell size within the foams by electron microscopy.

• Membrane Journal
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• v.15 no.2
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• pp.105-113
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• 2005

Silica membranes were prepared on a porous metal sheet by ultrasonic spray pyrolysis method for gas separation at high temperatures. In order to improve the permselectivity, silica was deposited in the sol-gel derived $silica/\gamma-alumina$ intermediate layer by pyrolysis of tetraethyl orthosilicate (TEOS) at 873 K. The pyrolysis with forced cross flow through the porous wall of the support was very effective in plugging mesopores, Knudsen diffusion regime, that were left unplugged in the membranes. At permeation temperature of 523 K, the silica/alumina composite membrane showed $H_2/N_2$ and water/methanol selectivity as high as 17 and 16, respectively, by molecular sieve effect.

• Journal of the Korea Society of Computer and Information
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• v.19 no.7
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• pp.59-70
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• 2014

This paper propose a new wireless multi-hop routing protocol that takes the hierarchical mesh of the hybrid WMN into account. WMN that is possible to provide various applications of wireless networks still has many open issues that should be solved despite the studies carried out over a decade. Especially, in routing protocol area, a problem degrading the routing efficiency by applying one of the routing protocols, which are designed for the MANET, to the hybrid WMN be solved above all. For the improvement of the routing performance, both good routing protocol and metric are essential. However, the recent studies are only concentrated in routing metric by use of the cross-layer design. Therefore, this paper is dedicated to the routing protocol that is essential for the performance of the routing but needed more studies. The proposed protocol in this paper is reactive, and designed to reorganize the hybrid WMN with several pseudo domains, and carry out domain-based route decision. By the simulation result for the performance analysis of the proposed protocol, the average delay for the route decision was decreased by 43% compared to AODV that is the typical reactive protocol.