• Journal of Korean Society of Steel Construction
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• v.10 no.1 s.34
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• pp.85-99
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• 1998

This paper describes an experimental study to examine collapse causes of the lifting cable due to brittle failure of an fitting anchor under the lifting works. Also, in this study an collapse mechanism that was obtained from stress analysis was compared with an actual collapse procedure. Fractographical analysis as well as chemical component test, tension test and Charpy V-Notch impact test for the fractured steel members were carried out. And then, its results were compared with that of normal steel members. Circumferential surface flaws were developed at internal facets of the fitting anchor before tensile stress occurred. Hence, a higher stress than nominal stress was occurred at flaws by stress concentration at the crack tip. Also, stress intensity factor of members increased by crack size of the potential flaws. Because the stress intensity factor at the crack tip was greater than critical values(fracture toughness), brittle fracture occurred under the lifting works. It is judged that the main collapse of the lifting cable is due to brittle fracture of the fitting anchor.

• Journal of the Optical Society of Korea
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• v.16 no.2
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• pp.91-94
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• 2012

Arrayed waveguide grating (AWG) phase errors are normally assessed from the Fourier transform of the interference intensity data in the frequency domain method. However it is possible to identify the phases directly from the intensity data if one adopts a trial-and-error method. Since the functional form of the intensity profile is known, the intensities can be calculated theoretically by assuming arbitrary phase errors. Then we decide the phases that give the best fit to the experimental data. We verified this method by a simulation. We calculated the intensities for an artificial AWG which is given arbitrary phases and amplitudes. Then we extracted the phases and amplitudes from the intensity data by using our trial-and-error method. The extracted values are in good agreement with the originally given values. This approach yields better results than the analysis using Fourier transforms.

• Investigative Magnetic Resonance Imaging
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• v.9 no.1
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• pp.36-42
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• 2005

Purpose : To develop a novel approach to calculate the sensitivity profiles of the phased array coil for use in non-uniform intensity correction. Materials and Methods : The proposed intensity correction method estimates the sensitivity profile of the coil to extract intensity variations that represent the scanned image. The sensitivity profile is estimated by fitting a non-linear curve to various angles of projections through the imaged object in order to eliminate the high-frequency image content. Filtered back projection is then used to compute the estimates of the sensitivity profile of each coil. The method was applied both to phantom and brain images from 8-channel phased-array coil and 4-channel phased-array coil, respectively. Results : Intensity-corrected images from the proposed method have more uniform intensity than those from the commonly used 'sum-of-squares' approach. By using the proposed correction method, the intensity variation was reduced to $6.1\%$ from $13.1\%$, acquired from the 'sum-of-squares'. Conclusion : The proposed method is more effective at correcting the intensity non-uniformity of the phased-array surface-coil images than the conventional 'sum-of-squares' method.

• Applied Chemistry for Engineering
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• v.20 no.5
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• pp.536-541
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• 2009

Plasma-polymerized acrylic acid films were deposited on Si wafer and KBr pellet by remote plasma-enhanced chemical vapor deposition (PECVD). Effects of plasma power, reaction pressure, indirect plasma method on the growth rate, chemical structure, and chemical bonding state of the films were investigated. Chemical structure and chemical state of the films were characterized by Fourier transformed infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis and curve fitting technique. Growth rate of the film increased to a saturation value with plasma power of 100 W, but showed the maximum with reaction pressure at 300 mtorr. Whenever W/FM factor (applied energy per gas molecule) increased by increasing plasma power or lowering pressure, the fragmentation of acrylic acid molecules was promoted. From the XPS curve fitting analyses, we found that the intensity of carboxyl COO bonding peak decreased with W/FM factor, and the tendency of intensity change of carboxylic COO peak was contrary to those of ether C-O and carbonyl C=O peaks.

• Current Optics and Photonics
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• v.2 no.1
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• pp.69-78
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• 2018

This paper presents a precise edge detection algorithm for the critical dimension (CD) measurement of a Thin-Film Transistor Liquid-Crystal Display (TFT-LCD) pattern. The sigmoid surface function is proposed to model the blurred step edge. This model can simultaneously find the position and geometry of the edge precisely. The nonlinear least squares fitting method (Levenberg-Marquardt method) is used to model the image intensity distribution into the proposed sigmoid blurred edge model. The suggested algorithm is verified by comparing the CD measurement repeatability from high-magnified blurry and noisy TFT-LCD images with those from the previous Laplacian of Gaussian (LoG) based sub-pixel edge detection algorithm and error function fitting method. The proposed fitting-based edge detection algorithm produces more precise results than the previous method. The suggested algorithm can be applied to in-line precision CD measurement for high-resolution display devices.

• Journal of Korea Multimedia Society
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• v.18 no.7
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• pp.827-833
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• 2015

In this paper, we have compared three level set-based active contour (LSAC) methods on inhomogeneous MR image segmentation which is known as an important role of brain diseases to diagnosis and treatment in early. MR image is often occurred a problem with similar intensities and weak boundaries which have been causing many segmentation methods. However, LSAC method could be able to segment the targets such as the level set based on the local image fitting energy, the local binary fitting energy, and local Gaussian distribution fitting energy. Our implemented and tested the subcortical image segmentations were the corpus callosum and hippocampus and finally demonstrated their effectiveness. Consequently, the level set based on local Gaussian distribution fitting energy has obtained the best model to accurate and robust for the subcortical image segmentation.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.10
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• pp.604-614
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• 2005

Color segmentation takes great attentions since a color is an effective and robust visual cue for characterizing one object from other objects. Color segmentation is, however, suffered from color variation induced from irregular illumination changes. This paper proposes a reliable color modeling approach in HSI (Hue-Saturation-Intensity) rotor space considering intensity information by adopting B-spline curve fitting to make a mathematical model for statistical characteristics of a color with respect to brightness. It is based on the fact that color distribution of a single-colored object is not invariant with respect to brightness variations even in HS (Hue-Saturation) plane. The proposed approach is applied for the segmentation of human skin areas successfully under various illumination conditions.

• Journal of the Korean Vacuum Society
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• v.2 no.2
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• pp.171-180
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• 1993

X-ray photoelectron diffraction (XPD) is used to characterize the crystallographically cleaved GaAs(110) surface. By using polar and azimuthal scans of the usual angle-resolved x-ray photoelectron spectroscopy, we get the reconstruction geometry of the clean GaAs(110) surface from the intensity ratio of Ga 3d core-level peaks. The reconstruction parameters are determined by fitting the diffraction pattern with the single scattering cluster (SSC) model, and the results show similar tendencies to those obtained by other techniques.

• Earthquakes and Structures
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• v.11 no.1
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• pp.109-127
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• 2016

This paper examines the contribution of three sources of uncertainties to probabilistic seismic behaviour of wood frame buildings, including ground motions, intensity and seismic mass. This sensitivity analysis is performed using three methods, including the traditional method based on the conditional distributions of ground motions at given intensity measures, a method using the summation of conditional distributions at given ground motion records, and the Monte Carlo simulation. FEMA P-695 ground motions and its scaling methods are used in the analysis. Two archetype buildings are used in the sensitivity analysis, including a two-storey building and a four-storey building. The results of these analyses indicate that using data-fitting techniques to obtain probability distributions may cause some errors. Linear interpolation combined with data-fitting technique may be employed to improve the accuracy of the calculated exceeding probability. The procedures can be used to quantify the risk of wood frame buildings in seismic events and to calibrate seismic design provisions towards design code improvement.

• Korean Journal of Optics and Photonics
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• v.33 no.6
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• pp.310-316
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• 2022

In this paper, the difference in modulation transfer function (MTF) results according to the change in the angle of a slant target when measuring a presampled MTF was confirmed, and the difference was reduced by fitting the edge spread function graph obtained to reduce the error by the target's rotation. Due to the feature of the presampled MTF method, the spatial frequency changed due to the sensor's projected intensity being changed by the target's rotation, and it was confirmed that the difference in the MTF value occurred depending on the rotation angle of the target. In this paper, the MTF was calculated after fitting only one column of the acquired image. It was confirmed that the rotation error is smaller compared to the case of the presampled MTF method and this fitting method can be applied to a scene that contains various target angles, such as auto-focusing using the MTF.