• Journal of Welding and Joining
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• v.28 no.5
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• pp.64-68
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• 2010

The purpose of this study is to develop the control technology of global distortion in the deck of superstructures during manufacturing processes. The behavior of global distortion in the deck was evaluated by FEA and verified through comparing with the measured results by 3D measuring instrument. It was seen from the results that the principal factor inducing the global distortion is to be the bending moment associated with the longitudinal shrinkage force and transverse shrinkage caused by welding of stiffeners and flame heating to correct the excessive local out-of-plane distortion. Based on the results, the amount of reverse distortion in the thin deck plate was determined to control the global distortion in the deck plate. The proposed distortion control technology was verified by applying it to the actual structure.

• Journal of Welding and Joining
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• v.28 no.4
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• pp.41-48
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• 2010

The purpose of this study is to establish the control method of the global bending distortion caused by fabrication process of hatch-cover in a container ship. In order to do it, the transitional behavior of global bending distortion in the deck of hatch-cover during fabrication process was measured by 3-dimensional measuring instrument. From the results, the principal factor controlling the global bending distortion was identified as the bending moment associated with the longitudinal shrinkage force and transverse shrinkage caused by welding and flame heating and the change of the centroid axis of hatch-cover in each fabrication process. Therefore, in this study, with the predictive equations of the longitudinal shrinkage force and transverse shrinkage caused by welding and flame heating and the simplified thermo elastic method, the predictive method for the global bending distortion was established and verified by comparing with the measured result. Based on the results, the amount of reverse bending distortion of main stiffeners was determined to prevent the global bending distortion of hatch-cover.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.1
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• pp.26-37
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• 2000

The purpose of this study was to investigate the effect that three resin indexing materials had on the distortion of split cast in the procedures of solder indexing and block fabrication. The specimen had two cylinders and connecting bar Two cylinders were a reference cylinder and a test cylinder that were machined precisely and placed on metal base. The total of specimens were 30 and they were divided into 3 groups according to the resin indexing materials : Acrylic $solder^{(R)}$, G-C Pattern $resin^{(R)},\;Z-100^{(R)}$. The relative coordinates (X, Y, Z) of centroids of both cylinders were measured by using 3-D cool dinates measuring machine. The value of indexing distortion was obtained after application of indexing material, and the value of the block distortion was obtained after fabrication of soldering block, and the value of total distortion was a value sum of indexing distortion and block distortion. Intercentroidal linear distortion ${(\sqrt{X^{'2}+Y^{'2}+Z^{'2}}-{\sqrt{X^2+Y^2+Z^2)}$ and global distortion $(\sqrt{{(X^'-X)}^2+{(Y^'-Y)}^2+{(Z^'-Z)}^2}$ were calculated from data of coordinates of centroids at each measuring stages. The results of this study were as belows ; 1. The intercentroidal distance between the split casts was reduced by indexing distortion and increased by block distortion. 2. The indexing global distortion between the split casts was smaller than block global distortion. 3. The intercentroidal linear distortion and the global distortion were no significant difference between indexing materials.

• Journal of Welding and Joining
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• v.22 no.6
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• pp.25-29
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• 2004

Some industrial steel structures are composed by components linked by several welding joints to constitute an assembly. The main interest of assembly simulation is to evaluate the global distortion of welded structure. The general method, thermo-elasto-plastic analysis, leads to excessive model size and computation time. In this study, a simplified method called "Local and Global approach" was developed to break down this limit and to provide a accurate solution for distortion. Local and global approach is composed of 3 steps; 1) Local simulation of each welding joint on a dedicated mesh (usually very fine due to high thermal gradients), taking into account for the non linearity of the material properties and the moving heat source. 2) Transfer to the global model of the effects of the welding joints by projection of the plastic strain tensors. 3) Elastic simulation to determine final distortions in global model. The welding deformation test for mock-up structure was performed to verify this approach. The predicted welding distortion by this approach had a good agreement with experiment results.

• Journal of the Optical Society of Korea
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• v.20 no.1
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• pp.140-149
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• 2016

For visual measurement under dynamic scenarios, a zoom lens camera is more flexible than a fixed one. However, the challenges of distortion prediction within the whole focal range limit the widespread application of zoom lens cameras greatly. Thus, a novel sequential distortion correction method for a zoom lens camera is proposed in this study. In this paper, a distortion assessment method without coupling effect is depicted by an elaborated chessboard pattern. Then, the appropriate distortion correction model for a zoom lens camera is derived from the comparisons of some existing models and methods. To gain a rectified image at any zoom settings, a global distortion correction modeling method is developed with bundle adjustment. Based on some selected zoom settings, the optimized quadratic functions of distortion parameters are obtained from the global perspective. Using the proposed method, we can rectify all images from the calibrated zoom lens camera. Experimental results of different zoom lens cameras validate the feasibility and effectiveness of the proposed method.

• Journal of the Korean Physical Society
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• v.73 no.11
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• pp.1637-1643
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• 2018

To reduce the laser pulse shape distortion accompanying the amplification process and achieve an intended output pulse shape in the Nd:YAG amplifier chain, we propose a frequency-modulated pulse-amplification method. Assuming carrier-frequency-modulated seed pulses, we numerically simulate the pulse amplification in an Nd:YAG amplifier chain where severe distortion occurs. For the calculation, we develop a modified Frantz-Nodvik equation, which enables two inputs with different carrier frequencies. The simulation results indicate that the temporal contrast of the seed pulse needed to obtain a flat output pulse shape is reduced by 16 - 25 dB when frequency modulation is applied.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.12
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• pp.1613-1618
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• 2012

The wheel bearing is one of the important parts in a vehicle for translating power and bearing weight. When it is mounted on the knuckle by using bolts, the distortion of the outer ring including the seal mounting point and raceway occurs. In this study, a numerical analysis was performed to analyze the distortion of the outer ring by using a finite element method. The commercial software MSC.MARC was used for this purpose. Elastoplastic and contact analysis were carried out to compute the clamping behavior of the outer ring, bolts, and knuckle. Because the concavity on the flange of the outer ring affects the deformation, its effect was considered. To verify the reliability of this study, the roundness of the outer ring was measured. The experimental results were comparatively in agreement with the computational results.

• IEIE Transactions on Smart Processing and Computing
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• v.3 no.4
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• pp.205-211
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• 2014

This paper reports an efficient algorithm for accurate rolling shutter distortion removal. A hierarchical global motion estimation approach for a group of blocks reduces the level of computation by three orders of magnitude. In addition, the motion of each scanline is determined accurately by averaging two candidates obtained through cubic spline interpolation. The experimental results show that the proposed method produces accurate motion information with significant computation reduction and corrects the rolling shutter distortion effectively.

• Journal of computational fluids engineering
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• v.17 no.4
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• pp.32-40
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• 2012

Efficient Global Optimization (EGO) method is a global optimization technique which can select the next sample point automatically by infill sampling criteria (ISC) and search for the global minimum with less samples than what the conventional global optimization method needs. ISC function consists of the predictor and mean square error (MSE) provided from the kriging model which is a stochastic metamodel. Also the constrained EGO method can minimize the objective function dealing with the constraints under EGO concept. In this study the constrained EGO method applied to the RAE2822 airfoil shape design formulated with the constraint. But the noisy CFD data caused the kriging model to fail to depict the true function. The distorted kriging model would make the EGO deviate from the correct search. This distortion of kriging model can be handled with the interpolation(p=free) kriging model. With the interpolation(p=free) kriging model, however, the search of EGO solution was stalled in the narrow feasible region without the chance to update the objective and constraint functions. Then the accuracy of EGO solution was not good enough. So the three-step search method was proposed to obtain the accurate global minimum as well as prevent from the distortion of kriging model for the noisy constrained CFD problem.

• Journal of Digital Contents Society
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• v.15 no.6
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• pp.751-761
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• 2014

Color deficient people do not have sufficient discernment for the colors with low saturation and brightness and at the same time express their negative emotions regarding emotion distortion. The purpose of recovering the distortion of the vision which is the basis for emotion is to increase positive emotions rather than negative ones that those with color vision deficiency feel when they experience digital culture contents. Contrast increases saturation and brightness by differing the direction of their conversion and by doing so, delivers emotion distortion such as dynamic vs. static and vivid vs. somber that the original images intend to convey to those with color vision deficiency by reducing such a contrast. In this respect, this study proposes a contrast-based color conversion method to convert saturation and brightness in the zone of color conversion and identifies if this method can reduce emotion distortion by using color conversion simulation and user test.