• Journal of Convergence for Information Technology
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• v.11 no.8
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• pp.84-91
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• 2021

In the 21st century, a number of storm and flood disasters caused by rapidly changing climate change is increasing, and the number of flood accidents at construction sites is also increasing. However, no specific reduction measures have been presented and thereby safety management to prevent flood accident need to be improved. Therefore, in this study, the inundation pattern by downpour at the excavation site was interpreted and the inundation risk quantification method was used to classify the risk magnitude. Finally, using the fish-bone diagram, we derived the major reasons of inundation accident at construction site systematically. The simulation results showed that the inundation depths of small-scale excavation sites and excavation sites exceeded 3 m due to the fluid flowing through the excavation surface. In addition, depending on the excavation site, a high velocity temporarily observed and decreased due to the storage effect, or high velocity surpassing 10 m/s continued. Since this type of flooding can pose a risk to most or all workers, if proper management measures are insufficient, fatal damage to life and property could occur. Consideration of the roots of these disasters is judged to be helpful in understanding the causes of inundation accidents that result in casualties and presenting accident reduction measures.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.506-513
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• 2021

The durability and safety of reinforced concrete structures significantly depend on the reinforcement conditions, concrete cover thickness, cracks, and concrete strength. There are two ways to accurately determine the information on reinforcing bars embedded in concrete - the local destructive method and the non-destructive rebar detection test. In general, the non-destructive rebar detection tests, such as the electromagnetic wave radar method, electromagnetic induction method, and radiation method, are adopted to avoid damage to the structural elements. The moisture content and temperature of concrete affect the dielectric constant, which is the electrical property of concrete, and cause interference in the non-destructive rebar detection test results. Therefore, in this study, the effects of the electromagnetic wave radar method and electromagnetic induction method have been analyzed according to the temperature and surface moisture content of concrete. Due to the technological advancement and development of equipment, the average error rate was less than 5% in the specimens at 24℃, irrespective of their operating principles. Among the tested methods, the electromagnetic induction method showed very high accuracy. The electromagnetic wave radar method indicated a relatively small error rate in the dry state than in the wet state, and exhibited a relatively high error rate at high temperatures. It was confirmed that the error could be reduced by applying the electromagnetic wave radar method when the temperature of the probe was low and in a dry state, and by using the electromagnetic induction method when the probe was in a wet state or at a high temperature.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.7
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• pp.1031-1037
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• 2021

The frequency of marine accidents of vessels in Korea is steadily increasing and it is concentrated on small vessels with less than 10 tons of gross tonnage. Therefore, preventing capsizing accidents in small vessels is important to reduce the cost in terms of human and property damage due to such accidents. However, research on the seakeeping performance of small vessels has been insufficient, and there are no domestic and international regulations on seakeeping performance. Therefore, in this study, capsizing accidents caused by poor loading conditions were investigated by examining the adjudications of the small vessels in which the capsizing accidents occurred. Hydrostatic calculations and seakeeping performance analysis were performed for a representative vessel. A vessel generally performs a six-degree-of-freedom motion during operation. In this study, the response amplitude operator and response spectrum of a representative vessel were calculated to determine the roll motion. Moreover, a short-term statistical analysis of the vessel according to the loading conditions was performed for the wave stationary status for 3 h. From the results, it was estimated that, when the loading condition of a small vessel is poor, its roll motion increases, greatly reducing its stability.

• Journal of the Society of Disaster Information
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• v.19 no.1
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• pp.117-127
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• 2023

Purpose: The number of Cold Storages at home and abroad is on the rise, fires in large Cold Storages have recently occurred. As fires continue to occur and property damage is on the rise every year, the importance of preventing fires in large Cold Storage is growing. Method: Real Cold Storages were investigated on-site and fire cases were analyzed to derive and analyze fire risk, and the ORS, which is emerging as an adaptive fire prevention technology of Cold Storage, was investigated through FDS. Result: oxygen concentration 21, 15.7% and 17.7, 16.7% were analyzed through FDS, and flashover was reached within 3~4 minutes from 21, 17.7, 16.7%, but if oxygen concentration was lowered to 15.7%, it didn't ignite for 13 minutes. Conclusion: This study understood the concept and general part of the ORS, modeled the freezer through FDS, and analyzed the oxygen concentration to analyze the fire protection adaptability of the ORS. In the future, it is expected that large-scale empirical experiments and related regulations will be prepared to provide solutions for fire prevention in Cold Storages in blind spots of fire.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.7
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• pp.1169-1178
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• 2022

This study examines an effective operational plan of a maritime safety enforcement task that is distributed in the Ministry of Oceans and Fisheries and the Korea Coast Guard for maritime safety. Considering the sinking of the MV Sewol and Seohae vessels and the MV Hebei Spirit oil spill, normally marine safety accidents tend to not only damage human life, property, and marine environment but can also expand to disasters; therefore, precautionary measures are required. However, the Korean government takes superficial efforts in case of large-scale accidents. In case of the MV Sewol ferry, the government only focused on punishing the officials involved as a follow up and never mentioned any effective plan, such as "unification of maritime safety enforcement," in contrast to an advanced country. As a result, there are endless major and minor backward accidents. The probability of large-scale maritime accidents and backwardness accidents is increasing owing to vessels becoming large sized, high speed, and aged; sailors being unqualified; port traffic increase, development of marine leisure; and inefficiency dual marine safety systems. Therefore, based on the review of previous studies related to maritime safety, major advanced country's cases, and unified case of the vessel traffic service, this study suggests effective methods such as coastal vessel safety management, port state control and aid to navigation management, which are directly connected with maritime safety.

• Journal of Korean Society of Disaster and Security
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• v.16 no.1
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• pp.1-11
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• 2023

The comprehensive natural disaster reduction plan, the highest plan in the disaster prevention field, was implemented by local governments. second plan is currently being formulated. In order to minimize human and property damage, structural and non-structural measures for each of the nine disaster types are established and implemented for 10 years. Structural measures are based on engineering and quantitative analysis, and the criteria for setting reduction measures are clear. Non-structural measures, however, currently lack the set criteria. the basic disaster and safety management law included the safety vulnerable class in 2018. Currently, the safety vulnerable class of the detailed establishment criteria of the comprehensive natural disaster reduction plan is being established, including children, the elderly, and the disabled. However, due to the lack of data securing and database construction by local governments, it is difficult to prepare a location map for establishing reduction measures for the safety vulnerable. Therefore, in this study, OPEN API data of the safety vulnerable class were collected and statistical information and GIS of SGIS information services were used. The distribution diagram of the safety vulnerable class in Samcheok, Gangwon-do, which is a sample area, and the distribution diagram of the safety vulnerable class in units of the output area (OA) in Geundeok-myeon were prepared.

• Journal of Aerospace System Engineering
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• v.17 no.4
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• pp.67-74
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• 2023

Recently, Urban Aircraft Mobility (UAM) has been attracting attention as a transportation system of the future, and small drones also play a role in various industries. The failure of various types of aviation systems can lead to crashes, which can result in significant property damage or loss of life. In the defense industry, where aviation systems are widely used, the failure of aviation systems can lead to mission failure. Therefore, this study proposes an anomaly detection model using deep learning technology to detect anomalies in aviation systems to improve the reliability of development and production, and prevent accidents during operation. As training and evaluating data sets, current data from aviation systems in an extremely low-temperature environment was utilized, and a deep learning network was implemented using the convolutional neural network, which is a deep learning technique that is commonly used for image recognition. In an extremely low-temperature environment, various types of failure occurred in the system's internal sensors and components, and singular points in current data were observed. As a result of training and evaluating the model using current data in the case of system failure and normal, it was confirmed that the abnormality was detected with a recall of 98 % or more.

• Journal of Korean Society of Forest Science
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• v.112 no.3
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• pp.340-351
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• 2023

Landslides are major natural geological hazards that cause enormous property damage and human casualties annually. The vulnerability of mountainous areas to landslides is further exacerbated by the impacts of climate change. Soil depth is a crucial parameter in landslide and debris flow analysis, and plays an important role in the evaluation of watershed hydrological processes that affect slope stability. An accurate method of estimating soil depth is to directly investigate the soil strata in the field. However, this requires significant amounts of time and money; thus, numerous models for predicting soil depth have been proposed. However, they still have limitations in terms of practicality and accuracy. In this study, 71 seismic survey results were collected from domestic mountainous areas to estimate soil depth on hill slopes. Soil depth was estimated on the basis of a shear wave velocity of 700 m/s, and a database was established for slope angle, elevation, and soil depth. Consequently, the statistical characteristics of soil depth were analyzed, and the correlations between slope angle and soil depth, and between elevation and soil depth were investigated. Moreover, various soil depth prediction models based on slope angle were investigated, and corrected linear and exponential soil depth prediction models were proposed.

• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.2773-2784
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• 2023

It is essential to evaluate the blasting-enhanced permeability (BEP) feasibility of a low-permeability sandstone-type uranium deposit. In this work, the mineral composition, reservoir physical properties and rock mechanical properties of samples from sandstone-type uranium deposits were first measured. Then, the reformability evaluation method was established by the analytic hierarchy process-entropy weight method (AHP-EWM) and the fuzzy mathematics method. Finally, evaluation results were verified by the split Hopkinson Pressure Bar (SHPB) experiment and permeability test. Results show that medium sandstone, argillaceous sandstone and siltstone exhibit excellent reformability, followed by coarse sandstone and fine sandstone, while the reformability of sandy mudstone is poor and is not able to accept BEP reservoir stimulation. The permeability improvement and the distribution of damage fractures before and after the SHPB experiment confirm the correctness of evaluation results. This research provides a reformability evaluation method for the BEP of the low-permeability sandstone-type uranium deposit, which contributes to the selection of the appropriate regional and stratigraphic horizon of the BEP and the enhanced ISL of the low-permeability sandstone-type uranium deposit.

• Journal of the Korean GEO-environmental Society
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• v.24 no.4
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• pp.23-29
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• 2023

Ground subsidence shows a mechanism in which the upper ground collapses due to the formation of a cavity due to the movement of soil particles in the ground due to the formation of a waterway because of damage to the water supply/sewer pipes. As a result, cavity is created in the ground and the upper ground is collapsing. Therefore, ground subsidence frequently occurs mainly in downtown areas where a large amount of underground facilities are buried. Accordingly, research to predict the risk of ground subsidence is continuously being conducted. This study tried to present a ground subsidence risk prediction model for two districts of ○○ city. After constructing a data set and performing preprocessing, using the property data of underground facilities in the target area (year of service, pipe diameter), density of underground facilities, and ground subsidence history data. By applying the dataset to the machine learning model, it is evaluated the reliability of the selected model and the importance of the influencing factors used in predicting the ground subsidence risk derived from the model is presented.