• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.3
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• pp.452-465
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• 2015

This paper presents the simplified welding distortion analysis method to predict the welding deformation of both plate and stiffener in fillet welds. Currently, the methods based on equivalent thermal strain like Strain as Direct Boundary (SDB) has been widely used due to effective prediction of welding deformation. Regarding the fillet welding, however, those methods cannot represent deformation of both members at once since the temperature degree of freedom is shared at the intersection nodes in both members. In this paper, we propose new approach to simulate deformation of both members. The method can simulate fillet weld deformations by employing composite shell element and using different thermal expansion coefficients according to thickness direction with fixed temperature at intersection nodes. For verification purpose, we compare of result from experiments, 3D thermo elastic plastic analysis, SDB method and proposed method. Compared of experiments results, the proposed method can effectively predict welding deformation for fillet welds.

• Journal of Broadcast Engineering
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• v.5 no.2
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• pp.260-272
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• 2000

In this paper, we propose a simple auto calibration method for a CCD camera with wide an91e lens that causes high degree of distortion. We formulate a cubic warping equation for the relationship between the cross points on the distorted calibration target and the corresponding points from the standard grid image, and calibrate distorted images using the computed parameters. The experiment has been performed with the distorted images resulted from wide angle CCD camera. The experimental results show that the proposed method, in terms of the average and maximum distorted error, has higher accuracy than the existing methods because of maintaining the calibration ratio more than 95 percent. The proposed method is applicable to wide variety of images regardless a type of lens or distortion.

• ETRI Journal
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• v.32 no.6
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• pp.972-975
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• 2010

In this letter, we consider the lossy coding of a non-uniform binary source based on GF(q)-quantized low-density generator matrix (LDGM) codes with check degree $d_c$=2. By quantizing the GF(q) LDGM codeword, a non-uniform binary codeword can be obtained, which is suitable for direct quantization of the non-uniform binary source. Encoding is performed by reinforced belief propagation, a variant of belief propagation. Simulation results show that the performance of our method is quite close to the theoretic rate-distortion bounds. For example, when the GF(16)-LDGM code with a rate of 0.4 and block-length of 1,500 is used to compress the non-uniform binary source with probability of 1 being 0.23, the distortion is 0.091, which is very close to the optimal theoretical value of 0.074.

• MALSORI
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• no.50
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• pp.99-110
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• 2004

The normal transmission characteristics of sound are hardly obtained due to the various noises and structural factors in a running car environment. It is due to the channel distortion of the original source sound recorded by microphones, and it seriously degrades the performance of the speech recognition in real driving environments. In this paper we analyze the degree of intelligibility under the various sound distortion environments by channels according to driving speed with respect to speech transmission index(STI) and compare the STI with rates of speech recognition. We examine the correlation between measures of intelligibility depending on sound pick-up patterns and performance in speech recognition. Thereby we consider the optimal location of a microphone in single channel environment. In experimentation we find that high correlation is obtained between STI and rates of speech recognition.

• Advances in aircraft and spacecraft science
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• v.8 no.1
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• pp.31-51
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• 2021

Selective laser melting (SLM), one of the most widely used powder bed fusion (PBF) additive manufacturing (AM) technology, enables the fabrication of customized metallic parts with complex geometry by layer-by-layer fashion. However, SLM inherently poses several problems such as the discontinuities in the molten track and the steep temperature gradient resulting in a high degree of residual stress. To avoid such defects, thisstudy proposes a temperature thread multiscale model of SLM for the evaluation of the process at different scales. In microscale melt pool analysis, the laser beam parameters were evaluated based on the predicted melt pool morphology to check for lack-of-fusion or keyhole defects. The analysis results at microscale were then used to build an equivalent body heat flux model to obtain the residual stress distribution and the part distortions at the macroscale (part level). To identify the source of uneven heat dissipation, a liquid lifetime contour at macroscale was investigated. The predicted distortion was also experimentally validated showing a good agreement with the experimental measurement.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1603-1606
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• 2005

Eye Glass Display (EGD) with microdisplay to realize the virtual display can make the large screen, so virtual image has been developed by using microdisplay panel. This paper shows study of low cost lens design and simulation for microdisplay system with 0.6" Liquid Crystal on Silicon (LCoS) panel. Lens design optimized consider to spherical aberration, astigmatism, distortion, and chromatic aberration. Code V is used and it designed an aspheric lens about exit pupil 6mm, eye relief 20mm and 35 degree of field of view (FOV). With the application this aspheric lens to LCOS type's microdisplay, virtual image showed 50 inch at 2m. One side of the aspheric lens was constituted from diffractive optical element (DOE) for the improvement in a performance. It had less than ${\pm}2%$ of distortion value and modulation transfer function in axial had 20% of resolution with 30 lp/mm spatial frequency. The optical system is suitable for display of 0.6"-diagonal with SVGA.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.2 no.4
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• pp.42-51
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• 2003

In this paper, we are going to analyze on relation of an output spectrum along phase distortion of power amplifier in wireless LAN system, and then considered an ACPR characteristic of power amplifier and consideration of an OFDM method for this. Also, we did implementation for OFDM modulation and transmission section of an IEEE 802.11a standard to have transmission speed of the maximum 54Mbps in order to know an OFDM modulation method and relation of non-linear characteristic of power amplifier. The non-linear characteristic of power amplifier did modeling with AM-to-AM and AM-to-PM, and we analyzed an output spectrum characteristic along phase distortion composed input signal supply for power amplifier. When output spectrum analysis results phase distortion increased, and an AM-to-PM characteristic of power amplifier in 5 degrees, the output spectrum was satisfied with a demand spectrum in P1 dB, but 10-20 degrees were able to confirm what cannot be satisfied with a demand spectrum in phase distortion. Also, an output spectrum of power amplifier by frequency re-growth generated by a non-linear characteristic of power amplifier did not satisfied in P1dE. therefore, a back-off value was requested according to an AM-to-PM distortion degree, and smaller back-off value were able to know what demand became in case of modulation section that used OFDM.

• Journal of the Korea Safety Management & Science
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• v.15 no.4
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• pp.427-433
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• 2013

Recently, 18F-FDG PET based CT scan was a critical examination that the after, before plan diagnosis and treatment of tumors. But, due to the distortion of SUV that should be proportional to the metabolic rate of glucose in the tumor, the other measurement methods are being on study. In this study, compared the degree of distortion of SUV that according to the volume of the tumor analysis ROI and VOI using the NEMA IEC Phantom. The results, the SUVmax, mean value are rapidly decreased with threshold value 500 mm2 interval of the ROI analysis, 1500 mm3 interval of the VOI analysis. When compared SUVmax value SUVmean, ROI and VOI analysis VOI measurements was 1.077 times higher SUVmax was 0.981 times highe compared to the value of the ROI measurement. Compare MTV, SUV 2.0 as measured by the volume of the VOI to Volume showed a slightly higher results(Volume / MTV = $93.4 %{\pm}14.8 %$). Considering the above results, Tumor evaluation by 18F-FDG PET / CT scan Consider each threshold value should be analyzed due to larger SUV's Distortion depending on the size of the tumor. VOI analysis is recommended. because it showed the VOI analysis is higher than the ROI analysis SUVmax and lower SUVmean due to VOI analysis than once as a measure of the wider area as measured ROI analysis. MTV (R2 = 0.999), a result close to the actual size of the tumor. but, more research is needed in this regard, because SUV according to the standards of value are affected.

• Journal of the Korea Computer Graphics Society
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• v.26 no.3
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• pp.133-142
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• 2020

In this research, we describe the method of implementing a 360-degree panorama using one projector, in terms of hardware and in the production of projected pre-distortion images. We propose a method of installing a projector and a reflector on the central ceiling of the space to minimize the shadows generated based on the position of the spectators. We used a virtual camera and virtual space where the projector and hemisphere positions were set to the same as in the exhibition space in Unity. After the image projected on the screen was mapped on the wall of the virtual space, the pre-distortion image was created by the method of capturing from the virtual camera using the ray tracing technique. When the produced pre-distortion image is hemispherical reflected and projected by the projector installed at the same position as the virtual camera, the image is reflected and projected 360 degrees on the panoramic screen.

• Journal of the Korea Society of Computer and Information
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• v.24 no.1
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• pp.93-100
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• 2019

One of critical issues in dealing with 360-degree realistic contents is the performance degradation in searching and recognition process since they support up to 4K UHD quality and have all image angles including the front, back, left, right, top, and bottom parts of a screen. To solve this problem, in this paper, we propose an efficient search and comparison method for 360-degree realistic contents. The proposed method first corrects the distortion at the less distorted regions such as front, left and right parts of the image excluding severely distorted regions such as upper and lower parts, and then it extracts feature points at the corrected region and selects the representative images through sequence classification. When the query image is inputted, the search results are provided through feature points comparison. The experimental results of the proposed method shows that it can solve the problem of performance deterioration when 360-degree realistic contents are recognized comparing with traditional 2D contents.