• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.4
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• pp.55-61
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• 2024

Recently, the number of aging concrete structures is steadily increasing. This is because many of these structures are reaching their expected lifespan. Such structures require accurate inspections and persistent maintenance. Otherwise, their original functions and performance may degrade, potentially leading to safety accidents. Therefore, research on objective inspection technologies using deep learning and computer vision is actively being conducted. High-resolution images can accurately observe not only micro cracks but also spalling and exposed rebar, and deep learning enables automated detection. High detection performance in deep learning is only guaranteed with diverse and numerous training datasets. However, surface damage to concrete is not commonly captured in images, resulting in a lack of training data. To overcome this limitation, this study proposed a method for generating concrete surface damage images, including cracks, spalling, and exposed rebar, using stable diffusion. This method synthesizes new damage images by paired text and image data. For this purpose, a training dataset of 678 images was secured, and fine-tuning was performed through low-rank adaptation. The quality of the generated images was compared according to three base models of stable diffusion. As a result, a method to synthesize the most diverse and high-quality concrete damage images was developed. This research is expected to address the issue of data scarcity and contribute to improving the accuracy of deep learning-based damage detection algorithms in the future.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.4
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• pp.1289-1298
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• 2014

Pavement crack sealing method, which is one of the methods to maintain and repair the road, prevents the extending of cracks by repairing cracks in its early occurrence and has already been applied to many roadworks in advanced foreign country for a long time. But in the conventional crack sealing method, traffic accidents occur frequently during the repair because it's commonly performed on the heavy traffic road or highway. It also has some difficulties in securing the safety of workers from the risk of burns caused by heated sealant. In an effort to solve these problems, automated pavement crack sealing machines such as ARMM, OCCSM, TTLS have been developed in advanced foreign country since early 1990s. Also APCS in 2004 and ACSTM in 2013 were already developed domestically. However, since these automated crack sealers developed from a number of research institutions have different test-bed conditions and productivity measurement models, it's difficult to compare and evaluate them objectively. In this study, the image processing time of the respective machines and the movement time of each motion on the work process were estimated by using fully autonomous mapping and semi-automatic mapping in order to measure the productivity in the same environmental conditions. In addition, the productivity measurement test-bed reflected domestic road characteristics was designed to estimate and compare the productivity of the automated crack sealing machines.

• Journal of the Korea Concrete Institute
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• v.23 no.6
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• pp.773-780
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• 2011

In this study, thermal stress analysis are carried out considering material properties, curing condition, ambient temperature, and casting date of the mass concrete placed in bottom slab and side wall of the in-ground type LNG tank as a super massive structure. Also, based on the numerical results, cracking possibility is predicted and counter measures to prevent the cracking are proposed. For the tasks, two optimum mix proportions were selected. From the results of the thermal stress analysis, the through crack index of 1.2 was satisfied for separately caste concrete lots except for the bottom slab caste in 2 separate sequences. For the double caste bottom slab, it is necessary introduce counter measures such as pre-cooling prior to the site construction. Also, another crack preventive measure is to lower the initial casting temperature by $25^{\circ}C$ or less to satisfy 1.2 through crack index criterion. In the $1^{st}$ and $2^{nd}$ caste bottom slab, the surface crack index was over 1.2. Therefore, the surface cracks can be controlled by implementing the curing conditions proposed in this study. Since the side wall's surface crack index was over 1.0, it is safe to assume that the counter preventive measures can control width and number of cracks.

• Journal of the Semiconductor & Display Technology
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• v.21 no.3
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• pp.74-79
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• 2022

In this study, the plasma corrosion resistance and the change in the number of contamination particles generated using the plasma etching process and cleaning process of coating parts for semiconductor plasma etching equipment were investigated. As the coating method, atmospheric plasma spray (APS) was used, and the powder materials were Y₂O₃ and Y₃Al₅O₁₂ (YAG). There was a clear difference in the densities of the coatings due to the difference in solubility due to the melting point of the powdered material. As a plasma environment, a mixed gas of CF₄, O₂, and Ar was used, and the etching process was performed at 200 W for 60 min. After the plasma etching process, a fluorinated film was formed on the surface, and it was confirmed that the plasma resistance was lowered and contaminant particles were generated. We performed a surface cleaning process using piranha solution(H₂SO₄(3):H₂O₂(1)) to remove the defect-causing surface fluorinated film. APS-Y₂O₃ and APS-YAG coatings commonly increased the number of defects (pores, cracks) on the coating surface by plasma etching and cleaning processes. As a result, it was confirmed that the generation of contamination particles increased and the breakdown voltage decreased. In particular, in the case of APS-YAG under the same cleaning process conditions, some of the fluorinated film remained and surface defects increased, which accelerated the increase in the number of contamination particles after cleaning. These results suggest that contaminating particles and the breakdown voltage that causes defects in semiconductor devices can be controlled through the optimization of the APS coating process and cleaning process.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.44 no.1
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• pp.1-9
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• 2024

Bridges, which are construction structures, have increased from 584 to 38,405 since the 1970s. However, as the number of bridges increases, the number of bridges with a service life of more than 30 years increases to 21,737 (71%) by 2030, resulting in fatal accidents due to basic human resource maintenance of facilities. Accordingly, the importance of bridge safety inspection and maintenance measures is increasing, and the need for decision-making support for supervisors who manage multiple bridges is also required. Currently, the safety inspection and maintenance method of bridges is to write down damage, condition, location, and specifications on the exterior survey map by hand or to record them by taking pictures with a camera. However, errors in notation of damage or defects or mistakes by supervisors are possible, typos, etc. may reduce the reliability of the overall safety inspection and diagnosis. To improve this, this study visualizes damage data recorded in the BIM model in an AR environment and proposes a maintenance plan for bridges with a small number of people through maintenance decision-making support for supervisors.

• The Journal of Engineering Geology
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• v.3 no.2
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• pp.167-176
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• 1993

The high resolution studies for shallow seismic reflection are carried out using 24-channel seismograph and the high sensitivity geophone(50-500Hz). In order to study the underground structures such as small faults, fractures, cracks and cavities, it is of great importance to enhance high resolution of the seisrnic records for the targets vertically and laterally. In analysis of high resolution seismic reflection, Nyquist frequency($F_N$) should be lager than the highest frequency in the records and the highest wave number should not be exceed the Nyquist wave number($1/2{\Delta}x$). The highest frequency above the Nyquist will be removed using low pass filter or antialias filter. The trace interval Ax should be taken into account so that the highest wave number(f/v) can be less than $1/2{\Delta}x$. The Fraunhofer diffraction of a hyperbola seismic section above the tunnel appeares on the common offset method, and little first arrivals of direct wave on the single-end shooting, delayed strong impulsive reflections are also shown above the tunnel. Ray Method(Cherveney and Psencik, 1983) also represents the same results that the reflected waves from the tunnel are delayed and single impulsive with little first arrivals, while transrnitted waves through the tunnel are delayed with low frequency.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.5
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• pp.46-52
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• 2022

Although pipe performs various functions in industrial sites and residential spaces, if it is damaged due to corrosion caused by the external environment, it may cause equipment failure or a major accident. For this reason, various studies for safety management are being conducted, but studies on detecting corrosion or cracks on the pipe surface using a laser displacement sensor have hardly been conducted. Therefore, in this study, the corrosion degree of the pipe surface was compared and classified into 4 corrosion conditions, and inspection equipment using a laser scanner was manufactured. The corrosion height was calculated from the four surface data obtained from the measuring equipment and applied to various CNN algorithms, and 91% accuracy was obtained during training using the Modified VGGNet16 code with reduced number of parameters.

• Steel and Composite Structures
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• v.21 no.5
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• pp.1157-1182
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• 2016

A newly puzzle shape of crestbond rib shear connector is a type of ductile perfobond rib shear connector. This shear connector has some advantages, including relatively easy rebar installation and cutting, as well as the higher shear resistance strength. Thus, this study proposed a newly puzzle shape of crestbond rib with a "${\mho}$" shape, and its shear resistance behaviors and shear strengths were examined using push-out tests. Five main parameters were considered in the push-out specimens to evaluate the effects of shear resistance parameters such as the dimensions of the crestbond rib, transverse rebars in the crestbond dowel, concrete strength, rebar strength, and dowel action on the shear strength. The shear loading test results were used to compare the changes in the shear behaviors, failure modes, and shear strengths. It was found that the concrete strength and number of transverse rebars in the crestbond rib were significantly related to its shear resistance. After the initial bearing resistance behavior of the concrete dowel, a relative slip occurred in all the specimens. However, its rigid behavior to shear loading decreased the ductility of the shear connection. The cross-sectional area of the crestbond rib was also shown to have a minor effect on the shear resistance of the crestbond rib shear connector. The failure mechanism of the crestbond rib shear connector was complex, and included compression, shear, and tension. As a failure mode, a crack was initiated in the middle of the concrete slab in a vertical direction, and propagated with increasing shear load. Then, horizontal cracks occurred and propagated to the front and rear faces of the specimens. Based on the results of this study, a design shear strength equation was proposed and compared with previously suggested equations.

• Korean Journal Plant Pathology
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• v.14 no.4
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• pp.325-330
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• 1998

On the basis of the fact that the pycnidiospore of Botryosphaeria dothidea, the causal fungus of apple white rot is a typical water borne spore, a method for quantitative analysis of pycnidiospore dispersal from the warts produced on the diseased apple tree stem was developed. The warts on which cracks developed either on or around them were cut off at the base, and shaked in the water for 4hours at 2$0^{\circ}C$, in which condition the maximum number of spores were released. The volume of shaking solution was calculated as 1 ml per one wart. At the end of shaking, Trio, a household detergent was added to the shaking solution to the concentration of 0.1%, and shaked for additional 10 minutes at 35$^{\circ}C$ to take off the spores attached on the glass ware. One milliliter of the spore suspension thus prepared were passed through transparent membrane filter (pore size : 3.0 ${\mu}{\textrm}{m}$), and the spores attached on the filter were counted under a microscope ($\times$200) after staining them with lactophenol supplemented with aniline blue. The results thus obtained were statistically consistent when at least 30 warts were used simultaneously in single shaking. This method can be applicable in the elucidation of ecology of sporulation and spore dispersal, and also in the screening of the sporulation inhibitor which can be used in the control of the disease by reducing the inoculum density.

• Journal of the Earthquake Engineering Society of Korea
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• v.22 no.3
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• pp.169-174
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• 2018

A total of 594 reservoirs (17%), which are managed by KRC, equipped with earthquake-resistant facilities whereas remaining ones did not. In addition, reservoirs were placed without the effect of geological structures (i.e., fault and lineament). Therefore, development on technique for alleviating the potential hazards by natural disasters along faults and lineaments has required. In addition, an effective reinforcement guideline related to the geological vulnerabilities around reservoirs has required. The final goal of this study is to suggest the effective maintenance for the safety of earth fill dams. A radius 2 km, based on the center of the reservoir in the study area was set as the range of vulnerability impacts of each reservoir. Seismic design, precise safety diagnosis, seismic influence and geological structure were analyzed for the influence range of each reservoir. To classify the vulnerability of geological disasters according to the fault distribution around the reservoir, evaluation index of seismic performance, precise safety diagnosis, seismic influence and geological structure were also developed for each reservoir, which were a component of the vulnerability assessment of geological disasters. As a result, the reservoir with the highest vulnerability to geological disasters in the pilot district was analyzed as Kidong reservoir with an evaluation index of 0.364. Within the radius of 100km from the epicenter of the Pohang earthquake, the number of agricultural infrastructure facilities subject to urgent inspections were 1,180 including reservoirs, pumping stations and intakes. Four reservoirs were directly damaged by earthquake among 724 agricultural reservoirs. As a result of the precise inspection and electrical resistivity survey of the reservoir after the earthquake, it was reported that cracks on the crest of reservoirs were not a cause of concern. However, we are constantly monitoring the safety of agricultural facilities by Pohang aftershocks.