• Journal of the Semiconductor & Display Technology
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• v.17 no.3
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• pp.70-74
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• 2018

In typical spectroscopic ellipsometry, the optical and geometrical properties of thin film and nano pattern can be obtained by measuring the polarization state of light reflected/transmitted from the object by rotating a analyzer or a compensator. We proposed a snapshot spectroscopic ellipsometric system based on a modified Michelson interferometer to overcome the time-consuring measurement principle due to rotating part. The proposed system provides spectral ellipsometric parameters (psi, delta) in real time by using a single spectral interference signal generated in the interferometric polarization module. However, it has a long-term stability problem resulting in delta(k) drift. In this paper, it is experimentally proved that the drift problem is caused by anisotropic refractive index change of the beam intersection layer in beam splitter of interferometer.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.314-318
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• 2000

For one-dimensional structures, a vibration response consists of direct and reflected waves from boundaries. Based on this concept of separable wave components, a modified travelling wave method (MTWM) is proposed in this paper: while all allowable waves are assumed and the boundary conditions are applied on by the conventional travealling wave method (TWM), in the proposed MTWM direct and reflected waves are assumed within the beam element, and the governing relations between direct and reflected waves are described in terms of the reflection or transmission coefficients. It is shown that the vibration response with considerable accuracy can be obtained compared to TWM for single and coupled beams. It is also shown that the band analysis to obtain quadratic response, or power flow response can be carried out by a slight change of the governing equations for one-dimensional structural systems. It is thought that the suggested MTWM can be used as a unified approach for predicting linear spectral response and/or quadratic band response involved in the one-dimensional structural vibration.

• Journal of The Korean Astronomical Society
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• v.45 no.4
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• pp.93-99
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• 2012

We present a 1.1mm emission map of the OMC1 region observed with AzTEC, a new large-format array composed of 144 silicon-nitride micromesh bolometers, that was in use at the James Clerk Maxwell Telescope (JCMT). These AzTEC observations reveal dozens of cloud cores and a tail of filaments in a manner that is almost identical to the submillimeter continuum emission of the entire OMC1 region at 450 and $850{\mu}m$. We perform Fourier analysis of the image with a modified periodogram and the density power spectrum, which provides the distribution of the length scale of the structures, is determined. The expected value of the periodogram converges to the resulting power spectrum in the mean squared sense. The present analysis reveals that the power spectrum steepens at relatively smaller scales. At larger scales, the spectrum flattens and the power law becomes shallower. The power spectra of the 1.1mm emission show clear deviations from a single power law. We find that at least three components of power law might be fitted to the calculated power spectrum of the 1.1mm emission. The slope of the best fit power law, ${\gamma}{\approx}-2.7$ is similar to those values found in numerical simulations. The effect of beam size and the noise spectrum on the shape and slope of the power spectrum are also included in the present analysis. The slope of the power law changes significantly at higher spatial frequency as the beam size increases.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.1639-1644
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• 2015

A study on design and structural strength analysis of a positioner in robot overlay welding system of a ball for ball-valves. Turning-unit of positioner modeled, analysis was conducted by assuming the beam. Turning-unit is applied to the stress, it was shown by 366.85MPa when weight of the ball is $9,000kg_f$. This value is higher than the yield strength of the material. Based on the results of previous, it was modeled the turning-unit by modifying. Results of analysis by a modified modeling, The value of stress was confirmed to 296.11MPa. This value is a value lower than the yield strength of the material, it was found to support the weight of the ball.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.653-660
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• 2007

Since the temperature of asphalt for deck plate of steel bridge during paying procedure is relatively high as $240^{\circ}C\;to\;260^{\circ}C$, the temperature of deck plate of bridge rises mere than $100^{\circ}C$ and excessive displacement and stress could occur. In order to avoid undesirable failure of base plate and determine the optimal pavement pattern, a thorough thermal analysis is needed. General structural model which is made of beam and plate element should be modified for transient heat transfer analysis; asphalt pavement material and convection effect on surface of structure need to be added. A new technique with the Equivalent Heat Source (EHS) for numerical thermal analysis for steel bridge under thermal load of Guss asphalt pavement is proposed. Since plate/beam elements which were generally used for structural analysis for bridge cannot explain convection effect easily on plate/beam surface, EHS which is determined based on calculated temperature with convection effect is used. To verify the EHS proposed in this study, numerical analyses with plate elements are performed and the results are compared with estimated temperatures. EHS might be used for other thermal analyses of steel bridge such as welding residual stress analysis and bridge fire analysis.

• Journal of the Korea Institute of Building Construction
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• v.14 no.3
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• pp.207-215
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• 2014

As a reinforcement material for RC members, the modified epoxy mortar has been reported one of the superior materials since the material can improve the load capacity and the seismic performance of the RC members. However, there were few experimental studies and analytical research for improving seismic performance with the material. This study is to propose an effective reinforcement plan for RC Ordinary Moment Resisting Frame (OMRF) with the evaluation of seismic performance and economic analysis. For the objective, first, the load-deflection curve of a simple beam specimen was compared with the analytical results. Second, a 5-story RC OMRF structure was designed only for gravity load and the alternatives for seismic reinforcement were suggested. Third, pushover analysis was executed for evaluation of design coefficients and seismic performance of the structures. Finally, an effective reinforcement plan was suggested based on the results of quantity take-off and economic analysis. The findings of this study can be utilized as the basic data when the modified epoxy mortar is applied to practice for improving the seismic performance of RC members.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.2
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• pp.65-75
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• 1984

A comparative study between several methods for the marine drilling riser analysis is carried out. One static analysis method and four dynamic methods are studied. The dynamic analysis methods used are two time domain methods using regular and random waves, and two frequency domain methods using the conventional and an improved linearization techniques. Two different sizes of risers are investigated. The analysis model of the structure is based on the beam-column element with lateral wave/current loads in a vertical plane. The forces on the riser are calculated using a modified farm of the Morison's equation. The finite element method is used to solve the equation for several wave/current conditions.

• Smart Structures and Systems
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• v.25 no.5
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• pp.605-617
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• 2020

The existence of damages in structures causes changes in the physical properties by reducing the modal parameters. In this paper, we develop a two-stages approach based on normalized Modal Strain Energy Damage Indicator (nMSEDI) for quick applications to predict the location of damage. A two-dimensional IsoGeometric Analysis (2D-IGA), Machine Learning Algorithm (MLA) and optimization techniques are combined to create a new tool. In the first stage, we introduce a modified damage identification technique based on frequencies using nMSEDI to locate the potential of damaged elements. In the second stage, after eliminating the healthy elements, the damage index values from nMSEDI are considered as input in the damage quantification algorithm. The hybrid of Teaching-Learning-Based Optimization (TLBO) with Artificial Neural Network (ANN) and Particle Swarm Optimization (PSO) are used along with nMSEDI. The objective of TLBO is to estimate the parameters of PSO-ANN to find a good training based on actual damage and estimated damage. The IGA model is updated using experimental results based on stiffness and mass matrix using the difference between calculated and measured frequencies as objective function. The feasibility and efficiency of nMSEDI-PSO-ANN after finding the best parameters by TLBO are demonstrated through the comparison with nMSEDI-IGA for different scenarios. The result of the analyses indicates that the proposed approach can be used to determine correctly the severity of damage in beam structures.

• Steel and Composite Structures
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• v.25 no.1
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• pp.117-126
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• 2017

The component method is an analytical approach for investigating the moment-rotation relationship of steel connections. In this study, the component method was improved from two aspects: (i) load analysis of mechanical model; and (ii) combination of spring elements. An optimized component method with more reasonable component models, spring arrangement position, and boundary conditions was developed using finite element analysis. An experimental testing program in two major-axis and two minor-axis connections under symmetrically loading was carried out to verify this method. The initial rotational stiffness obtained from the optimized component method was consistent with the experimental results. It can be concluded that (i) The coupling stiffness between column and beam flanges significantly affects the effective height of the tensile-column web. (ii) The mechanical properties of the bending components were obtained using an equivalent t-stub model considering the bending capacity of bolts. (iii) Using the optimized mechanical components, the initial rotational stiffness was accurately calculated using the spring system. (iv) The characteristics of moment-rotation relationship for beam to column connections were effectively expressed by the SPRING element analysis model using ABAQUS. The calculations are simpler, and the results are accurate.

• Polymer(Korea)
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• v.36 no.3
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• pp.268-274
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• 2012

The silane coupling agent, 3-(trimethoxysilyl)propyl methacrylate (${\gamma}$-MPTS), was grafted on the surface of alumina nanoparticles. We used the surface modified nanoparticles in the hard coating layer for in-mold decoration (IMD) foils and evaluated the coating properties such as hardness and anti-abrasion property. The effects of electron beam (EB) irradiation on color layer and anchor layer of IMD foils were observed through the difference in color and the cross-cut tape test, respectively. Also, cure kinetics as studied quantitatively under various reaction temperatures by analysis of surface properties and Fourier transform infrared (FTIR) spectroscopy. From these results, we constructed database for the commercial exploitation of EB curing system.