• The Journal of Korea Robotics Society
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• v.16 no.2
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• pp.94-102
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• 2021

This study addresses a method for 3D reconstruction using acoustic data with heterogeneous sonar devices: Forward-Looking Multibeam Sonar (FLMS) and Profiling Sonar (PS). The challenges in sonar image processing are perceptual ambiguity, the loss of elevation information, and low signal to noise ratio, which are caused by the ranging and intensity-based image generation mechanism of sonars. The conventional approaches utilize additional constraints such as Lambertian reflection and redundant data at various positions, but they are vulnerable to environmental conditions. Our approach is to use two sonars that have a complementary data type. Typically, the sonars provide reliable information in the horizontal but, the loss of elevation information degrades the quality of data in the vertical. To overcome the characteristic of sonar devices, we adopt the crossed installation in such a way that the PS is laid down on its side and mounted on the top of FLMS. From the installation, FLMS scans horizontal information and PS obtains a vertical profile of the front area of AUV. For the fusion of the two sonar data, we propose the probabilistic approach. A likelihood map using geometric constraints between two sonar devices is built and a monte-carlo experiment using a derived model is conducted to extract 3D points. To verify the proposed method, we conducted a simulation and field test. As a result, a consistent seabed map was obtained. This method can be utilized for 3D seabed mapping with an AUV.

• Korean Journal of Materials Research
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• v.29 no.9
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• pp.532-541
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• 2019

Information and communication technologies are developing rapidly as IC chip size becomes smaller and information processing becomes faster. With this development, digital circuit technology is being widely applied to mobile phones, wireless LANs, mobile terminals, and digital communications, in which high frequency range of GHz is used. In high-density electronic circuits, issues of noise and EMC(Electro-Magnetic Compatibility) arising from cross talk between interconnects or devices should be solved. In this study, sheet-type electromagnetic wave absorbers that cause electromagnetic wave attenuation are fabricated using composites based on soft magnetic metal powder and silicon rubber to solve the problem of electromagnetic waves generated in wireless communication products operating at the frequency range of 2.4 GHz. Sendust(Fe-Si-Al) and carbonyl iron(Fe-C) were used as soft magnetic metals, and their concentrations and sheet thicknesses were varied. Using soft magnetic metal powder, a sheet is fabricated to exhibit maximum electromagnetic attenuation in the target frequency band, and a value of 34.2dB(99.9 % absorption) is achieved at the target frequency.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.2
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• pp.32-40
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• 1994

In this study by using EMAT(electro magnetic acoustic transducer)the artificial slit is installed on 12B-SUS pipe test piece. By making 4 cycle SH-burst (EMA) incidence to 45 .deg. angle, the signal data of pulse, received from EMAT are translated into digital-signal-processing- method SSP(Split Spectrum Processing) and Deconvolution method. The main conclusions obtained are as follows; (1) the signal data received from EMAT are translated with digital signal proc- essing of SSP-method and Deconvolution-method and this method shows exellent results more than Ultrasonic testing method does; (2) noise can well be removed by SSP with signal data, and resolution and S/N ratio are advanced; (3) when used with Ultrasonic wave general stainless steel has proporties of multiscattering and reflection phenomena, but resolution is progressed by using Deconvolution method;and (4) as addition-averaging-processing mumber is increasing, the resolution and S/N ratio are improved and the satisfactory signal is obtained.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.29-30
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• 2023

Wood is a construction material that has the advantages of carbon dioxide storage ability, noise reflection, and eco-friendliness. In order to use wood for a long time, you must use wood-specific paint, which is called oil stain. Oil stain improves water resistance and moisture resistance, but has the disadvantage of being weak against fire. This is because the oil contained in the oil stain causes a chemical reaction, and this chemical reaction causes the oil stain to spontaneously ignite, igniting nearby combustible materials and causing frequent fires. To improve this, in this study, different flame retardants were mixed and added to oil stain to produce functional oil stain. In addition, we would like to apply it to wood to check glow time and carbonization area. As a result of the experiment, it shows the best performance when mixed at 30(15 + 15)(%) and added to oil stain. The remaining burn time is satisfied from 10% for all samples, and the carbonized area is satisfied when it is 30%.

• Progress in Medical Physics
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• v.18 no.2
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• pp.98-106
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• 2007

In June 2005, Yonsei University Medical Center, Severance Hospital upgraded a full-PACS system by adding twenty (5 mega pixels) Totoku ME511L flat panel LCD display devices for diagnostic interpretation purposes. Here we report upon the quantitative (or visual) acceptance testing of the twenty Totoku ME511L display devices for reflection, luminance response, luminance spatial dependency, resolution, noise, veiling glare, and display chromaticity based on AAPM TG 18 report. The tools used in the tests included a telescopic photometer, which was used as a colorimeter, illuminance meter, light sources for reflection assessment, light-blocking devices, and digital TG18 test patterns. For selected 8 flat panel displays, mean diffuse reflection coefficient ($R_d$) was $0.019{\pm}0.02sr^{-1}$. In the luminance response test, luminance ratio (LR), maximum luminance difference ($L_{max}$), and deviation of contrast response were $550{\pm}100,\;2.0{\pm}1.9%\;and\;5.8{\pm}1.8%$, respectively. In the luminance uniformity test, maximum luminance deviation was $14.3{\pm}5.5%$ for the 10% luminance of the TG18-UNL10 test pattern. In the resolution test with luminance measurement method, percent luminance (${\Dalta}L$) at the center was $0.94{\pm}0.64%$. In all cases of noise testing, rectangular target In every square in the three quadrants was visible and all 15 targets except the smallest one in the every corner pattern and the center pattern. The glare ratio (GR) was $12,346{\pm}1,995$. The color uniformity, (u',v'), was $0.0025{\pm}0.0008$. Also, the research results of qualify control guideline of primary disply devices suitable for domestic circumstance are presented All test results are in-line with the criteria recommended by AAPM TG18 report and are thus fully acceptable for diagnostic image interpretation. As a result, the acceptance testing schedule described provides not only an acceptance standard but also guidelines for quality control, optimized viewing conditions, and a means for determining the upgrading time of LCD display devices for diagnostic interpretation.

• The Journal of Engineering Geology
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• v.22 no.4
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• pp.459-466
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• 2012

A difficulty encountered in engineering seismic mapping is that reflection events from shallow discontinuities are commonly overlapped with coherent noise such as air wave, direct waves, head waves, and high-amplitude surface waves. Here, the radial trace transform, a simple geometric re-mapping of a trace gather (x-t domain) to another trace gather (v-t domain), is applied to investigate the rejection effect of coherent linear noises. Two different types of data sets were selected as a representative database: good-quality data for intermediate sounding (hundreds of meters) in a sedimentary basin and very noisy data for shallow (${\leq}50m$) mapping of the weathered zone and bedrock surface. Results obtained with cascaded application of the radial transform and low-cut filtering proved to be as good as, or better than, those produced using f-k filtering, and were especially effective for air wave and direct wave. This simple transform enables better understanding of the characteristics of various types of noise in the RT domain, and can be generally applied to overcoming diffractions and back-scatterings caused by joints, fractures, and faults commonly that are encountered in geotechnical problems.

• Geophysics and Geophysical Exploration
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• v.11 no.3
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• pp.242-249
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• 2008

Recently, AVO analysis has been widely used in oil exploration with seismic subsurface section as a direct indicator of the existence of the gas. In the case of the deep reservoirs like the gas reservoirs in the East-sea, it is often difficult to observe AVO responses in CMP gathers even though the bright spots are shown in the stacked section. Because the reservoir becomes more consolidated as its depth deepens, P-wave velocity does not decrease significantly when the pore fluid is replaced by the gas. Thus the difference in Poisson's ratio, which is a key factor for AVO response, between the reservoir and the layer above it does not increase significantly. In this study, we analyzed the effects of Poisson's ratio difference on AVO response with a variety of Poisson's ratios for the upper and lower layers. The results show that, as the difference in Poisson's ratio between the upper and lower layers decreases, the change in the reflection amplitude with incidence angle decreases and AVO responses become insignificant. To consider the limitation of AVO responses shown in the gas reservoir in East-sea, the velocity model was made by simulation Gorae V structure with seismic data and well logs. The results of comparing AVO responses observed from the synthetic data with theoretical AVO responses calculated by using material properties show that the amount of the change in reflection amplitude with increasing incident angle is very small when the difference in Poisson's ratio between the upper and lower layers is small. In addition, the characteristics of AVO responses were concealed by noise or amplitude distortion arisen during preprocessing. To overcome such limitations of AVO analysis of the data from deep reservoirs, we need to acquire precisely reflection amplltudes In data acquisition stage and use processing tools which preserve reflection amplitude in data processing stage.

• Geophysics and Geophysical Exploration
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• v.11 no.1
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• pp.26-33
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• 2008

The analysis of wide-angle seismic reflection and refraction data plays an important role in lithospheric-scale crustal structure study. However, it is extremely difficult to develop an appropriate velocity structure model directly from the observed data, and we have to improve the structure model step by step, because the crustal structure analysis is an intrinsically non-linear problem. There are several subjective processes in wide-angle crustal structure modelling, such as phase identification and trial-and-error forward modelling. Because these subjective processes in wide-angle data analysis reduce the uniqueness and credibility of the resultant models, it is important to reduce subjectivity in the analysis procedure. From this point of view, we describe two software tools, PASTEUP and MODELING, to be used for developing crustal structure models. PASTEUP is an interactive application that facilitates the plotting of record sections, analysis of wide-angle seismic data, and picking of phases. PASTEUP is equipped with various filters and analysis functions to enhance signal-to-noise ratio and to help phase identification. MODELING is an interactive application for editing velocity models, and ray-tracing. Synthetic traveltimes computed by the MODELING application can be directly compared with the observed waveforms in the PASTEUP application. This reduces subjectivity in crustal structure modelling because traveltime picking, which is one of the most subjective process in the crustal structure analysis, is not required. MODELING can convert an editable layered structure model into two-way traveltimes which can be compared with time-sections of Multi Channel Seismic (MCS) reflection data. Direct comparison between the structure model of wide-angle data with the reflection data will give the model more credibility. In addition, both PASTEUP and MODELING are efficient tools for handling a large dataset. These software tools help us develop more plausible lithospheric-scale structure models using wide-angle seismic data.

• 한국지구물리탐사학회:학술대회논문집
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• 2002.09a
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• pp.101-125
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• 2002

A lake seismic survey was carried out to investigate possible geohazards for construction of the underground LPG storage at Namyang Lake. The proposed survey site has a land-lake combined geography and furthermore water depth of the lake is shallow. Therefore, various seismic methods such as marine single channel high resolution seismic reflection survey, sonobuoy refraction survey, land refraction survey and land-lake combined refraction survey were applied. Total survey amounts are 34 line-km of high resolution lake seismic survey, 14 lines of sonobuoy refraction survey, 890 m of land refraction survey and 8 lines of land-lake combined refraction survey. During the reflection survey, there were severe water reverberations from the lake bottom obscured subsurface profiling. These strong multiple events appeared in most of the survey area except the northern and southern area near the embankment where seems to be accumulated mainly mud dominated depositions. The sonobuoy refraction profiles also showed the same Phenomena as those of reflection survey. Meanwhile the results of the land-lake combined refraction survey showed relatively better qualities. However, the land refraction survey did not so due to low velocity soil layer and electrical noise. Summarized results from the lake seismic survey are that acoustic basement with relatively flat pattern appeared 30m below water level and showed three types of bedrock such as fresh, moderately weathered and weathered type. According to the results of the combined refraction survey, a velocity distribution pattern of the lake bottom shows three types of seismic velocity zone such as >4.5 km/s, 4.5-4.0km/s and <4.0km/s. The major fault lineament in the area showed NW-SE trend which was different from the Landsat image interpretation. A drilling was confirmed estimated faults by seismic survey.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.44 no.1
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• pp.94-104
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• 2007

Iris recognition is biometric technology which uses a unique iris pattern of user in order to identify person. In the captured iris image by conventional iris recognition camera, it is often the case with eyelid occlusion, which covers iris information. The eyelids are unnecessary information that causes bad recognition performance, so this paper proposes robust algorithm in order to detect eyelid. This research has following three advantages compared to previous works. First, we remove the detected eyelash and specular reflection by linear interpolation method because they act as noise factors when locating eyelid. Second, we detect the candidate points of eyelid by using mask in limited eyelid searching area, which is determined by searching the cross position of eyelid and the outer boundary of iris. And our proposed algorithm detects eyelid by using parabolic hough transform based on the detected candidate points. Third, there have been many researches to detect eyelid, but they did not consider the rotation of eyelid in an iris image. Whereas, we consider the rotation factor in parabolic hough transform to overcome such problem. We tested our algorithm with CASIA Database. As the experimental results, the detection accuracy were 90.82% and 96.47% in case of detecting upper and lower eyelid, respectively.