• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.889-901
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• 2021

The tension of cables and motion response significantly affect safety of an immersed tunnel element in the immersion process. To investigate those, a hydrodynamic scale-model test was carried out and the model experiments was conducted under wind, current and wave loads simultaneously. The immersion standby (the process that the position of the immersed tunnel element should be located before the immersion process) and immersion process conditions have been conducted and illustrated. At the immersion standby conditions, the maximum force of the cables and motion is much larger at the side of incoming wind, wave and current, the maximum force of Element-6 (6 cables directly tie on the element) is larger than for Pontoon-8 (8 cables tie on pontoon of the element), and the flexible connection can reduce the maximum force of the mooring cables and motion of element (i.e. sway is expecting to decrease approximate 40%). The maximum force of the mooring cables increases with the increase of current speed, wave height, and water depth. The motion of immersed tunnel element increases with increase of wave height and water depth, and the current speed had little effect on it. At the immersion process condition, the maximum force of the cables decrease with the increase of immersion depth, and dramatically increase with the increase of wave height (i.e. the tension of cable F4 of pontoons at wave height of 1.5 m (83.3t) is approximately four times that at wave height of 0.8 m). The current speed has no much effect on the maximum force of the cables. The weight has little effect on the maximum force of the mooring cables, and the maximum force of hoisting cables increase with the increase of weight. The maximum value of six-freedom motion amplitude of the immersed tunnel element decreases with the increase of immersion depth, increase with the increase of current speed and wave height (i.e. the roll motion at wave height of 1.5 m is two times that at wave height of 0.8 m). The weight has little effect on the maximum motion amplitude of the immersed tunnel element. The results are significant for the immersion safety of element in engineering practical construction process.

• Korean Journal of Heritage: History & Science
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• v.55 no.2
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• pp.186-197
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• 2022

The Daejanggakgibi Stele of Silleuksa Temple in Yeoju is a stone stele from the Goryeo Dynasty that is inscribed with various stories about the construction of Daejanggak, a place where Buddhist scriptures were kept. This stele has been maintained for a long time in a state in which discoloration of the body has occurred, and the inscription has been partially damaged due to dozens of cracks. Using non-destructive analysis methods for stone artifacts, material investigation, portable X-ray fluorescence analysis, and ultrasonic velocity analysis for the stele were performed. It was confirmed that the stele body was composed of light gray crystalline limestone, and the base stone, support stone, and cover stone were medium-grained biotite granite. Portable X-ray fluorescence analysis confirmed that iron(Fe) was an original coloring element of the stele surface. From the distribution pattern of the coloration, it can be inferred that iron-containing materials flew down from between the stele body and the cover stone. Thereafter, living organisms or organic contaminants attached to it so that yellow and black contaminants were formed. Ultrasonic diagnosis revealed that the physical property of both the front and back surfaces ranged from fresh rocks(FR) to completely weathered rocks(CW), and the average weathering index was grade 3(intermediate). However, the point where cracks developed intensively was judged to be the completely weathered stage(CW), and some cracks located in the upper and lower parts of the stele bear potentially very high risk. It is necessary to monitor the movement of these cracks and establish reinforcement measures for conservation in the future.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.40 no.5
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• pp.367-380
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• 2022

In this study, the periodic and simplified update and production way of the ECVAM (Environmental Conservation Value Assessment Map) was presented through the classification of environmental values using KOMPSAT-3A satellite imagery and land cover map. ECVAM is a map that evaluates the environmental value of the country in five stages based on 62 legal evaluation items and 8 environmental and ecological evaluation items, and is provided on two scales: 1:25000 and 1:5000. However, the 1:5000 scale environmental assessment map is being produced and serviced with a slow renewal cycle of one year due to various constraints such as the absence of reference materials and different production years. Therefore, in this study, one of the deep learning techniques, KOMPSAT-3A satellite image, SI (Spectral Indices), and land cover map were used to conduct this study to confirm the possibility of establishing an environmental assessment map. As a result, the accuracy was calculated to be 87.25% and 85.88%, respectively. Through the results of the study, it was possible to confirm the possibility of constructing an environmental assessment map using satellite imagery, optical index, and land cover classification.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.5
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• pp.30-42
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• 2022

Due to the increase in construction of tunnels, the burdens of maintenance works for tunnel structures have been increasing in Korea. In addition, the increase of traffic volume and aging of materials also threatens the safety of tunnel facilities, therefore, maintenance costs are expected to increase significantly in the future. Accordingly, automated condition assessment technologies like image-based tunnel scanning system for inspection and diagnosis of tunnel facilities have been proposed. For image-based tunnel scanning system, it is key to create a planar image through stitching of multiple images captured by tunnel scanning system. In this study, performance of feature-based stitching algorithms suitable for stitching tunnel scanning images was evaluated. In order to find a suitable algorithm SIFT, ORB, and BRISK are compared. The performance of the proposed algorithm was determined by the number of feature extraction, calculation speed, accuracy of feature matching, and image stitching result. As for stitching performance, SIFT algorithm was the best in all parts of tunnel image. ORB and BRISK also showed satisfactory performance and short calculation time. SIFT can be used to generate precise planar images. ORB and BRISK also showed satisfactory stitching results, confirming the possibility of being used when real-time stitching is required.

• Journal of Appropriate Technology
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• v.6 no.2
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• pp.94-102
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• 2020

Renewable energy (RE) is essential to comprise sustainable societies, especially, in rural villages of developing countries. Furthermore, application of off-grid RE systems to health care can improve the quality of life. In this research, a RE-based vaccination supply management system was constructed to enlarge the cold-chain in developing countries for the safe storage and delivery of vaccines. The system was comprised of the construction of RE plants and development of vaccine carriers. RE plants were constructed and connected to health posts in local villages. The cooling mechanism of vaccine carriers was improved and monitoring devices were installed. The effect of the system on vaccine cold-chain was evaluated from the field test and topographical analysis in the southern village of Nepal. RE plants were normally operated for the vaccine refrigerator in the health post. The modified vaccine carriers had a longer operation time and better temperature control via monitoring and RE-based recharging functionality. The topographical analysis estimated that the system can cover larger region. The system prototype showed great potential regarding the possibility of a sustainable and enlarged cold-chain. Thus, RE-based vaccine supply management is expected to facilitate vaccine availability while minimizing waste in the supply chain.

• Journal of Christian Education in Korea
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• v.66
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• pp.309-341
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• 2021

The purpose of this study is to develop an intelligent learning platform model for faith education in preparation for the post-corona era. This study reviewed artificial intelligence algorithms, research on learning platform development, and prior research related to faith education. The draft of the intelligent learning platform design model was developed by synthesizing previous studies. The developed draft model was validated by a Delphi survey targeting 5 experts. The content validity of the developed draft model was all 1. This is the validation of the draft model. Three revised opinions of experts were presented on the model. And the model was revised to reflect the opinions of experts. The modified final model consisted of three areas: learning materials, learning activities, learning data, and artificial intelligence. Each area is composed of 9 elements of curriculum, learning content additional learning resources, learner type, learning behavior, evaluation behavior, learner characteristic data, learning activity data, artificial intelligence data, and learning analysis. Each component has 29 sub-elements. In addition, 14 learning floors were formed. The biggest implication of this study is the first development of a basic model of an intelligent learning platform for faith education.

• Korean Journal of Clinical Laboratory Science
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• v.53 no.2
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• pp.143-150
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• 2021

The recent spread of novel and highly variant pathogenic viruses, including the coronavirus (SARS-CoV-2), has increased the demand for diagnostic testing for rapid confirmation. This has resulted in investigating the functional capability of each space, and preparing facility guidelines to secure the safety of medical technologists. During viral evaluations, there is a requirement of negative pressure facilities along with thread separation, during pre-treatment of samples and before nucleic acid amplification. Space composition therefore needs to be planned by considering unidirectional air flow. This classification of safety management facilities is designated as biosafety level 2, and personal protective equipment is placed accordingly. In case of handling dangerous materials, they need to be carried out of the biosafety cabinet, and sterilizers are required for suitable disposal of infectious agents. A common feature of domestic laboratories is maintenance of the sample pre-treatment space at a negative pressure of -2.5 Pa or less, and arranging separate pre-treatment and reagent preparation spaces during the test process. We believe that the data generated in this study is meaningful, and offers an efficient direction and detailed flow for separation of the inspection process and space functions. Moreover, this study introduces construction of the laboratory by applying the safety management standards.

• The Journal of Engineering Geology
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• v.31 no.4
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• pp.579-588
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• 2021

Reinforced earth retaining walls have been widely used in recent years, as they are superior from the landscape perspective than normal concrete retaining walls. However, as reinforced earth retaining walls are made of various materials depending on site, existing design methods cannot secure stability, and a variety of problems have occurred. Studies on the design and stability analysis methods, which are different from existing methods, have been conducted to address these problems. This study conducted a stability investigation using numerical analysis, and blocks of reinforced earth retaining walls were individually applied, which is different from pre-existing numerical analyses. To verify the input values of the numerical analysis when applying individual blocks, real-scale experiments of the friction characteristics between the blocks and the connection properties between the blocks and stiffener were conducted. The applicability of the block conditions, which were the same as those of real sites, was verified through numerical analysis, and will be used for the stability review and design of various combinations of blocks and stiffeners.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.3
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• pp.263-278
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• 2022

This paper contains experimental study for the development and performance of TBM backfill material with thixotropic properties. The LW backfill material is widely applied to fill the cavity on the back side of the shield TBM excavation, but has disadvantages such as settlement caused by strength reduction, material separation by groundwater, and reduced plasticity. In this paper, laboratory tests and a model test were conducted to assess the performance of inorganic thixotropic backfill material proposed to improve these problems. The results of laboratory tests show that 1 hr-uniaxial compressive strength of ITB was 12 times higher than LW, and the rate of bleeding of 20 hr was 8.3 times lower, and the result of flow table test was more than 27 times higher. This result indicated that the inorganic thixotropic backfill material has superior properties to LW backfill in terms of strength reduction, material separation, and thixotropy. In the model experiment, a model injection device tester was manufactured and the injection performance and filling rate were verified. When material was injected in the water, it was visually checked whether material separation occurred, and it was confirmed that the filling rate was 96% or more. Comparison results with the test of LW and ITB materials was concluded that ITB can reduce the material separation by groundwater and the occurrence of tunnel cavity.

• Journal of the Korean Geotechnical Society
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• v.38 no.12
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• pp.7-17
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• 2022

The ratios of water and controlled low-strength materials (CLSM) were selected as 1:0.4, 1:0.6, 1:0.8, 1:1.0, and 1:1.2 to minimize the construction and long-term decrease in uniaxial compressive strength due to dry shrinkage through the combination of water, CLSM, and expansion agent. Approximately 2% and 5% of the expansion agent were added for each blending condition. As a result, it was found that the compressive strength decreased and the expandability increased as the specific gravity of the water increased. In addition, it was confirmed that the compressive strength increased rapidly up to 15 days of age compared to the CLSM used in the field. However, the compressive strength decreased compared to the 15 days of the age as of the 28 days of the age. It showed engineering characteristics similar to CLSM generally used in the field. Therefore, the water and the CLSM were mixed at a ratio of 1:0.8, and the field test was performed by adding 5% of an expansion agent. As a result, 28 days after age, the cavity waveform was observed using the handy GPR exploration system, and it was found that cavity waveform was relaxed or disappeared.