• Laser Solutions
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• v.14 no.4
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• pp.1-8
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• 2011

This study is about laser welded joints in order to replace the traditional screw connection of a differential gear and its case in the differential gear assembly. Screws are usually used to join these parts. But the screws take up weight and space. So we needed to improve the joining method. In the welding of a differential gear and its case, the quality is much harder to control, because the high carbon contents of the two components results in cold cracks. But a new method that adds wire allows these materials to be joined. Additionally, more distortions generally occurs in the welded joints than in screws. We tried to prove that laser welding is an available method for joining these parts through the measurement and various tests.

• Journal of the Semiconductor & Display Technology
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• v.17 no.4
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• pp.11-15
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• 2018

The parts of equipment for semiconductor are protected by anodic aluminum oxide film to prevent corrosion. This study investigated contamination particle and cracking behavior of anodic oxidation in sulfuric acid containing cerium salt. The insulating properties of the sample were evaluated by measuring the breakdown voltage. It was confirmed that the breakdown voltage was about 50% higher when the cerium salt was added, and that the breakdown voltage after the heat treatment was 55% and 35% higher at $300^{\circ}C$ and $400^{\circ}C$, respectively. After heating at $300^{\circ}C$ and $400^{\circ}C$, cracks were observed in non cerium and cerium 3mM, and more cracks occur at $400^{\circ}C$ than at $30^{\circ}C$. The amount of contamination particles generated in the plasma is about 45% less than that of non-cerium specimens.

• Progress in Superconductivity and Cryogenics
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• v.9 no.1
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• pp.1-4
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• 2007

The total Fluorine content in the precursor solution for MOD processing of YBCO coated conductors can be significantly reduced by synthesizing precursor solution with F-free Y & Cu precursor and Barium trifluoroacetate(TFA). It was shown that crack-free and uniform precursor films were formed after calcinations in humidified oxygen atmosphere. Less than 2 hours are required to finish the calcinations process and XRD measurement shows that $BaF_2,\;CuO,\;Y_2O_3$ are major constituent of calcined precursor films. Film thickness after calcinations was improved to be 2.8um by applying slot-die coating method. In particular, addition of Samarium shows critical current of $I_c=273A/cm-w(J_c=3.8MA/cm^2)$. It is shown that uniform and fast processing route to YBCO coated conductor with high Ic can be provided by employing F-free Y & Cu precursor solution in MOD process.

• International conference on construction engineering and project management
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• 2013.01a
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• pp.616-623
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• 2013

One of the oldest, most common engineering problems is measuring the dimensions of different objects and the distances between locations. In AEC/FM, related uses vary from large-scale applications such as measuring distances between cities to small-scale applications such as measuring the depth of a crack or the width of a welded joint. Within the last few years, advances in applying new technologies have prompted the development of new measuring devices such as ultrasound and laser-based measurers. Because of wide varieties in type, associated costs, and levels of accuracy, the selection of an optimal measuring technology is challenging for construction engineers and facility managers. To tackle this issue, we present an overview of various measuring technologies adopted by experts in the area of AEC/FM. As the next step, to evaluate the performance of these technologies, we select one indoor and one outdoor case and measure several dimensions using six categories of technologies: tapes, total stations, laser measurers, ultrasound devices, laser scanners, and image-based technologies. Then we evaluate the results according to various metrics such as accuracy, ease of use, operation time, associated costs, compare these results, and recommend optimal technologies for specific applications. The results also revealed that in most applications, computer vision-based technologies outperform traditional devices in terms of ease of use, associated costs, and accuracy.

• Journal of the Korean Society of Radiology
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• v.15 no.6
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• pp.781-788
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• 2021

Due to the high sensitivity to radiation, excessive exposure needs to be prevented by accurately measuring the dose irradiated to the skin during radiation therapy. Although clinical trials use dosimeters such as film, OSLD, TLD, glass dosimeter, etc. to measure skin dose, these dosimeters have difficulty in accurate dosimetry on skin curves. In this study, to solve these problems, we developed a skin dosimeter that can be attached according to human flexion and evaluated its response characteristics. For the manufacture of the dosimeter, lead oxide (PbO) with high atomic number (Z_Pb: 82, Z_O: 8) and density (9.53 g/cm³) and silicon binders that can bend according to human flexion were used. In the case of a dosimeter made of PbO material, the performance degradation has been prevented by using parylene and others due to the presence of degradation due to oxidation, but the previously used parylene is affected by bending, so a new form of passive layer was produced and applied to the skin dosimeter. The characteristic evaluation of the skin dosimeter was evaluated by analyzing SEM, reproducibility, and linearity. Through SEM analysis, bending was evaluated, reproducibility and linearity at 6 MeV energy were evaluated, and applicability was assessed with a skin dosimeter. As a result of observing the dosimeter surface through SEM analysis, the parylene passive layer PbO dosimeter with the positive layer raised to the parylene produced cracks on the surface when bent. On the other hand, no crack was observed in the silicon passive layer PbO dosimeter, which was raised to silicon passive layer. In the reproducibility measurement results, the RSD of the silicon passive layer PbO dosimeter was 1.47% which satisfied the evaluation criteria RSD 1.5% and the linearity evaluation results showed the R² value of 0.9990, which satisfied the evaluation criteria R² 9990. The silicon passive layer PbO dosimeter was evaluated to be applicable to skin dosimeters by demonstrating high signal stability, precision, and accuracy in reproducibility and linearity, without cracking due to bending.

• International Journal of Highway Engineering
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• v.15 no.2
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• pp.11-18
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• 2013

PURPOSES : This study presents the noise level and frequency characteristics investigated in the national highways with the consideration of various measuring conditions and/or methods. METHODS : The noise levels on the asphalt concrete pavement(ACP) and the jointed plain concrete pavement(JPCP) of the national highway were measured and analysed with respect to three variables, i.e., pavement type, surface condition, and measurement distance. The PASS-By method is utilized for the noise measurement and then using CPB spectrum analysis method with 1/3 octave bandwidth, the noise levels and frequency characteristics were calculated for two-second periods before and after the peak noise. RESULTS : Depending on the pavement type, the noise level was changed as the average noise levels are 73.3dB(A) and 78.3dB(A) for ACP and JPCP, respectively. With respect to the effect of surface condition, the average noise levels for crack H(high), M(medium), and L (low) sections are 77.4dB(A), 77.4dB(A), and 78.1dB(A), respectively. Regarding the measurement distance, 1.2meter difference in measuring location reduces 1.6dB(A) of noise level; the average noise levels at 5.3m and 7.5m from the centerline of outer lane are 72.8dB(A) and 71.2dB(A), respectively. It should be noted that the noise levels are slightly different as a function of vehicle speed and type. However, the overall trends for each case was similar. It was found that the domain frequency bands for ACP and JPCP were 400Hz~2000Hz and 500Hz~2000Hz, respectively. CONCLUSIONS : Based on the analysis with the measured noise date from national highway, it was concluded that the noise level and frequency band vary depending on the various conditions. It was also found that some variables significantly affect the noise level while others do not. With further systematic investigation, the comprehensive noise characteristics on the national highway can be achieved. Using such database, it is possible to develop the fundamental noise reduction technology.

• Journal of Korean Tunnelling and Underground Space Association
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• v.26 no.2
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• pp.113-128
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• 2024

Items of road tunnel PISD (Precise Inspection for Safety and Diagnosis) were reviewed and analyzed using newly enhanced MMS (Mobile Mapping System) technology. Possible items with MMS can be visual inspection, survey and non-destructive test, structural analysis, and maintenance plan. The resolution of 3D point cloud decreased when the vehicle speed of MMS is too fast while the calibration error increased when it is too slow. The speed measurement of 50 km/h is determined to be effective in this study. Although image resolution by MMS has a limit to evaluating the width of crack with high precision, it can be used as data to identify the status of facilities in the tunnel and determine whether they meet disaster prevention management code of tunnel. 3D point cloud with MMS can be applicable for matching of cross-section and also possible for the variation of longitudinal survey, which can intuitively check vehicle clearance throughout the road tunnel. Compared with the measurement of current PISD, number of test and location of survey is randomly sampled, the continuous measurement with MMS for environment condition can be effective and meaningful for precise estimation in various analysis.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.4
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• pp.276-284
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• 2000

The acoustic emission (AE) behavior of reinforced concrete beams tested under flexural loading was investigated to characterize and identify the source of damage. This research was aimed at identifying the characteristic AE response associated with micro-crack development, localized crack propagation, corrosion, and debonding of the reinforcing steel. Concrete beams were prepared to isolate the damage mechanisms by using plain, notched-plain, reinforced, and corroded-reinforced specimens. The beams were tested using four-point cyclic step-loading. The AE response was analyzed to obtain key parameters such as the time history of AE events, the total number and rate of AE events, and the characteristic features of the waveform. Initial analysis of the AE signal has shown that a clear difference in the AE response is observed depending on the source of the damage. The Felicity ratio exhibited a correlation with the overall damage level, while the number of AE events during unloading can be an effective criterion to estimate the level of corrosion distress in reinforced concrete structures. Consequently, AE measurement characterization appears to provide a promising approach for estimating the level of deterioration in reinforced concrete structure.

• Journal of the Korean Ceramic Society
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• v.52 no.6
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• pp.410-416
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• 2015

Recently, a new $Y_2O_3$ coating deposited using the EB-PVD method has been developed for erosion resistant applications in fluorocarbon plasma environments. In this study, surface crack formation in the $Y_2O_3$ coating has been analyzed in terms of residual stress and elastic modulus. The coating, deposited on silicon substrate at temperatures higher than $600^{\circ}C$, showed itself to be sound, without surface cracks. When the residual stress of the coating was measured using the Stoney formula, it was found to be considerably lower than the value calculated using the elastic modulus and thermal expansion coefficient of bulk $Y_2O_3$. In addition, amorphous $SiO_2$ and crystalline $Al_2O_3$ coatings were similarly prepared and their residual stresses were compared to the calculated values. From nano-indentation measurement, the elastic modulus of the $Y_2O_3$ coating in the direction parallel to the coating surface was found to be lower than that in the normal direction. The lower modulus in the parallel direction was confirmed independently using the load-deflection curves of a micro-cantilever made of $Y_2O_3$ coating and from the average residual stress-temperature curve of the coated sample. The elastic modulus in these experiments was around 33 ~ 35 GPa, which is much lower than that of a sintered bulk sample. Thus, this low elastic modulus, which may come from the columnar feather-like structure of the coating, contributed to decreasing the average residual tensile stress. Finally, in terms of toughness and thermal cycling stability, the implications of the lowered elastic modulus are discussed.

• Journal of the Korean Magnetics Society
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• v.22 no.2
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• pp.49-57
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• 2012

From among the NDT (Non-Destructive Testing) methods, the MFL (Magnetic Flux Leakage) PIG (Pipeline Inspection Gauge) is especially suitable for testing pipelines because the pipeline has high magnetic permeability. MFL PIG showed high performance in detecting the metal loss and corrosions. However, MFL PIG is difficult to detect the crack which occured by exterior-interior pressure difference in pipelines and the shape of crack is very long and narrow. Therefore, the new PIG is needed to be researched and developed for detecting the cracks. The CMFL (Circumferential MF) PIG performs magnetic fields circumferentially and can maximize the magnetic flux leakage at the cracks. In this paper, CMFL PIG is designed and the distribution of the magnetic fields is analyzed by using 3 dimensional nonlinear finite element method (FEM). By Simulating and Measuring the magnetic leakage field, it is possible to detect of axial cracks in the pipeline.