• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.3
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• pp.228-233
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• 2010

We studied the optical characteristics correlated with low dielectric constants of low-k SiOCH thin films through ellipsometry. The low-k SiOCH thin films were prepared by CCP-PECVD method using BTMSM(Bis-trimethylsilylmethane) precursors deposited on p-Si wafer. The Si-O-CHx, Si-O-Si, Si-CHx, CHx and Si-H bonding groups were specified by FTIR spectroscopic spectra, and the groups coupled with the nano-porous structural organic/inorganic hybrid-type of SiOCH thin films which has extremely low dielectric constant close to 2.0. The structural groups includes highly dense pore as well as ions in SiOCH thin films affecting to complex refraction characteristics of single layer on the p-Si wafer. The structural complexity originate the complex refractive constants of the films, and resulted the elliptical polarization of the incident linearly polarized light source of Xe-light source in the range from 190 nm to 2100 nm. Phase difference and amplitude ratio between s wave and p wave propagating through SiOCH thin film was studied. After annealing, the amplitude of p wave was reduced more than s wave, and phase difference between p and s wave was also reduced.

• Earthquakes and Structures
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• v.18 no.1
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• pp.129-145
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• 2020

Seismic resilience is a key feature for buildings that play a strategic role within the community. In this framework, not only the structural and non-structural elements damage but also the protracted structural dysfunction can contribute significantly to overall seismic damage and post-seismic crisis situations. Reduction of the residual and peak displacements and energy dissipation by replaceable elements are some effective aspects to pursue in order to enhance the resilience. Control systems able to adapt their response based on the nature of events, such as active or semi-active, can achieve the best results, but also require higher costs and their complexity jeopardizes their reliability; on the other hand, a passive control system is not able to adapt but its functioning is more reliable and characterized by lower costs. In this study it is proposed a strategy for the optimization of the dissipative capacity of a seismic resistant system obtained placing in parallel two different groups dissipative Re-Centering Devices, specifically designed to enhance the energy dissipation, one for the low and the other for the high intensity earthquakes. In this way the efficiency of the system in dissipating the seismic energy is kept less sensitive to the seismic intensity compared to the case of only one group of dissipative devices.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.2
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• pp.146-151
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• 2016

This study concentrates on the design of floater for 15kW-class wave energy converter that extracts the ocean energy by oscillating vertically along the wave motion. The floater connects to a arm structure that connects to a hydraulic cylinder, which drives a hydraulic generator. The study mainly focuses on the structural analysis of the floater. Previous studies have been conducted using a miniature model; however, this study focuses on the size selection of the floater for a full scale model. Static structural analysis is conducted using fine numerical grids. Due to the complexity of the whole model, it is analyzed as a separate component. There are several load cases for each floater size, and they are analyzed thoroughly for stress (von-mises, shear, and normal) and deformation. The initial design was conducted by scaling up from the miniature model of the previous study, and the final design has been redesigned by changing the thickness and internal support structure shape.

• Structural Engineering and Mechanics
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• v.21 no.3
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• pp.351-367
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• 2005

Multi-span beams carrying multiple point masses are widely used in engineering applications, but the literature for free vibration analysis of such structural systems is much less than that of single-span beams. The complexity of analytical expressions should be one of the main reasons for the last phenomenon. The purpose of this paper is to utilize the numerical assembly method (NAM) to determine the exact natural frequencies and mode shapes of a multi-span uniform beam carrying multiple point masses. First, the coefficient matrices for an intermediate pinned support, an intermediate point mass, left-end support and right-end support of a uniform beam are derived. Next, the overall coefficient matrix for the whole structural system is obtained using the numerical assembly technique of the finite element method. Finally, the natural frequencies and the associated mode shapes of the vibrating system are determined by equating the determinant of the last overall coefficient matrix to zero and substituting the corresponding values of integration constants into the related eigenfunctions respectively. The effects of in-span pinned supports and point masses on the free vibration characteristics of the beam are also studied.

• Korean Management Science Review
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• v.10 no.1
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• pp.139-156
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• 1993

Various ATM switches have been proposed since Asynchronous Transfer Mode (ATM) was recognized as appropriate for implementing broadband integrated services digital network (BISDN). An ATM switching network may be evaluated on two sides : traffic performances (maximum throughput, delay, and packet loss probability, etc.) and structural features (complexity, i.e. the number of switch elements necessary to construct the same size switching network, maintenance, modularity, and fault tolerance, etc.). ATM switching networks proposed to date tend to show the contrary characteristics between structural features and traffic performance. The Knockout Switch, which is well known as one of ATM switches, shows a good traffic performance but it needs so many switch elements and buffers. In this paper, we propose an input and output buffered Knockout Switch for the purpose of reducing the number of switch elements and buffers of the existing Knockout Switch. We analyze the traffic performance and the structural features of the proposed switching architecture through a discrete time Markov chain and compare with those of the existing Knockout Switch. It was found that the proposed architecture could reduce more than 40 percent of switch elements and more than 30 percent of buffers under a given requirement of cell loss probability of the switch.

• Journal of Information Processing Systems
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• v.17 no.2
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• pp.213-226
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• 2021

Given that most of the link prediction algorithms for signed social networks can only complete sign prediction, a novel algorithm is proposed aiming to achieve both link prediction and sign prediction in signed networks. Based on the structural balance theory, the local link tightness and global link tightness are defined respectively by using the structural information of paths with the step size of 2 and 3 between the two nodes. Then the total similarity of the node pair can be obtained by combining them. Its absolute value measures the possibility of the two nodes to establish a link, and its sign is the sign prediction result of the predicted link. The effectiveness and correctness of the proposed algorithm are verified on six typical datasets. Comparison and analysis are also carried out with the classical prediction algorithms in signed networks such as CN-Predict, ICN-Predict, and PSNBS (prediction in signed networks based on balance and similarity) using the evaluation indexes like area under the curve (AUC), Precision, improved AUC', improved Accuracy', and so on. Results show that the proposed algorithm achieves good performance in both link prediction and sign prediction, and its accuracy is higher than other algorithms. Moreover, it can achieve a good balance between prediction accuracy and computational complexity.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.2
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• pp.1080-1099
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• 2019

A better tradeoff between robustness and invisibility will be realized by using the just noticeable (JND) model into the quantization-based watermarking scheme. The JND model is usually used to describe the perception characteristics of human visual systems (HVS). According to the research of cognitive science, HVS can adaptively extract the structure features of an image. However, the existing JND models in the watermarking scheme do not consider the structure features. Therefore, a novel JND model is proposed, which includes three aspects: contrast sensitivity function, luminance adaptation, and contrast masking (CM). In this model, the CM effect is modeled by analyzing the direction features and texture complexity, which meets the human visual perception characteristics and matches well with the spread transform dither modulation (STDM) watermarking framework by employing a new method to measure edge intensity. Compared with the other existing JND models, the proposed JND model based on structural regularity is more efficient and applicable in the STDM watermarking scheme. In terms of the experimental results, the proposed scheme performs better than the other watermarking scheme based on the existing JND models.

• Structural Engineering and Mechanics
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• v.77 no.4
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• pp.495-508
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• 2021

This study devises a novel approach, namely quadruple 1D convolutional neural network, for detecting connection stiffness reduction in steel truss bridge structure using experimental and numerical modal data. The method is developed based on expertise in two domains: firstly, in Structural Health Monitoring, the mode shapes and its high-order derivatives, including second, third, and fourth derivatives, are accurate indicators in assessing damages. Secondly, in the Machine Learning literature, the deep convolutional neural networks are able to extract relevant features from input data, then perform classification tasks with high accuracy and reduced time complexity. The efficacy and effectiveness of the present method are supported through an extensive case study with the railway Nam O bridge. It delivers highly accurate results in assessing damage localization and damage severity for single as well as multiple damage scenarios. In addition, the robustness of this method is tested with the presence of white noise reflecting unavoidable uncertainties in signal processing and modeling in reality. The proposed approach is able to provide stable results with data corrupted by noise up to 10%.

• Structural Engineering and Mechanics
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• v.82 no.3
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• pp.355-367
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• 2022

The effect of hydrodynamic damping on intake tower is twofold: one is fluid damping and another is structural damping. Fluid damping can be derived analytically from the governing equation of the fluid-structure-interaction (FSI) problem which yields a very complicated solution. To avoid the complexity of the FSI problem water-tower system can be simplified by considering water as added mass. However, in such a system a reconsideration of structural damping is required. This study investigates the effects of this damping on the dynamic response of the intake tower, where, apart from the "no water (NW)" condition, six other cases have been adopted depending on water height. Two different cross-sections of the tower are considered and also two different damping properties have been used for each case as well. Dynamic analysis has been carried out using horizontal ground motion as input. Finally, the result shows how hydrodynamic damping affects the dynamic behavior of an intake tower with the change of water height and cross-section. This research will help a designer to consider more conservative damping properties of intake tower which might vary depending on the shape of the tower and height of water.

• Wind and Structures
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• v.39 no.1
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• pp.47-69
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• 2024

Pounding of structures may result in considerable damages, to the extent of total failure during severe lateral loading events (e.g., earthquakes and wind). With the new generation of tall buildings in densely occupied locations, wind-induced pounding becomes of higher risk due to such structures' large deflections. This paper aims to develop mathematical formulations to determine the maximum pounding force when two adjacent structures come into contact. The study will first investigate wind-induced pounding forces of two equal-height structures with similar dynamic properties. The wind loads will be extracted from the Large Eddy Simulation models and applied to a Finite Element Method model to determine deflections and pounding forces. A Genetic Algorithm is lastly utilized to optimize fitting parameters used to correlate the maximum pounding force to the governing structural parameters. The results of the wind-induced pounding show that structures with a higher natural frequency will produce lower maximum pounding forces than those of the same structure with a lower natural frequency. In addition, taller structures are more susceptible to stronger pounding forces at closer separation distances. It was also found that the complexity of the mathematical formula from optimization depends on achieving a more accurate mapping for the trained database.