• Journal of Advanced Navigation Technology
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• v.27 no.1
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• pp.133-138
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• 2023

As a side effect of recent rapid climate change and global warming, the frequency and scale of flood disasters are increasing worldwide. In Korea, the water level of the Han River is a major management target for preventing flood disasters in Seoul, the capital of Korea. In this paper, to improve the water level prediction of the Han River based on machine learning, we perform a comprehensive assessment of the quality of related dataset and propose data preprocessing methods to improve it. Specifically, we improve the dataset in terms of completeness, validity, and accuracy through missing value processing and cross-correlation analysis. In addition, we conduct a performance evaluation using random forest and LightGBM to analyze the effect of the proposed data improvement method on the water level prediction performance of the Han River.

• Nuclear Engineering and Technology
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• v.56 no.4
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• pp.1225-1233
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• 2024

Level 3 probabilistic safety assessment (PSA) is performed to calculate radionuclide concentrations and exposure dose resulting from nuclear power plant accidents. To calculate the external exposure dose from the released radioactive materials, the radionuclide concentrations are multiplied by two factors of dose coefficient and a finite cloud dose correction factor (FCDCF), and the obtained values are summed. This indicates that a standard set of FCDCFs is required for external exposure dose calculations. To calculate a standard set of FCDCFs, the effective distance from the release point to the receptor along the wind direction should be predetermined. The TID-24190 document published in 1968 provides equations to calculate FCDCFs and the resultant standard set of FCDCFs. However, it does not provide any explanation on the effective distance required to calculate the standard set of FCDCFs. In 2021, Sandia National Laboratories (SNLs) proposed a method to predetermine finite effective distances depending on the atmospheric stability classes A to F, which results in six standard sets of FCDCFs. Meanwhile, independently of the SNLs, the authors of this paper discovered that an infinite effective distance assumption is a very reasonable approach to calculate one standard set of FCDCFs, and they implemented it into the multi-unit radiological consequence calculator (MURCC) code, which is a post-processor of the level 3 PSA codes. This paper calculates and compares short- and long-range FCDCFs calculated using the TID-24190, SNLs method, and MURCC method, and explains the strength of the MURCC method over the SNLs method. Although six standard sets of FCDCFs are required by the SNLs method, one standard sets of FCDCFs are sufficient by the MURCC method. Additionally, the use of the MURCC method and its resultant FCDCFs for level 3 PSA was strongly recommended.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.21 no.5
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• pp.1-16
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• 2018

The purpose of this study is to identify the fragmented points of mountain ranges in Daegu metropolitan city using New Sangyeongpyo (Chart of Mountain Ranges), road system map and GIS spatial analysis, and to prioritize the identified fragmented points for restoration based on quantitative assessment. Moreover, this study proposes restoration plans reflecting the assessment results and characteristics of each fragmented point. The results of this study are summarized as follows: First of all, analysis of the distribution of mountain ranges in Daegu metropolitan city showed that jimaek and semaek in Daegu account for 2% of all mountain ranges in the country, implying that the mountain ranges of Daegu do not hold significant ranking on a national level. However, it was found that numerous fragmented points are appearing due to roads. According to the analysis, 35 fragmented points were identified, of which 15 were found to be restorable. In terms of restoration potential and involved risks, assessment results of the 15 fragmented points indicated that 6 points are at Grade I, 3 points are at Grade II and 6 points are at Grade III. Therefore, a methodology of restoring fragmented mountain ranges was proposed through three suggestions of restoration plans that consider the characteristics of each fragmented points. The results of this study are expected to be highly useful as basic data for effective restoration of mountain ranges in connection with mountain range restorations and relevant projects implemented on a national level in the future.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.3
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• pp.279-287
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• 2018

This study investigated applicability of the fast running model for damage assessment of underground structures by ground shock. For this reason, the fast running model that consists of two main models such as the ground shock generation and propagation model and the underground structural damage assessment model was developed. The ground shock generation and propagation model was programed using theoretical formula and empirical formula introduced in TM5-855-1(US army manual). The single degree of freedom model of structural components was utilized to predict structural dynamic displacements which are used as index to assess damage level of components. In order to confirm the feasibility of the developed fast running model, underground structural dynamic displacements estimated from the fast running model were compared to displacements obtained from the finite element analysis.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.55 no.2
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• pp.145-151
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• 2019

The coastal composite fishery has the highest rate of around 30.0% in registered fishing vessels of Korea for the last three years. The risk analysis for the fisher's safety of coastal composite fishing vessels was conducted to serve as a basic data for improving the healthy and safe working environment of fisher using fisher's occupational accidents of the national federation of fisheries cooperatives (NFFC) from 2016 to 2018 (n = 1,105). As a result, the occupational accident occurrence rate of coastal composite fishery was 3.76% in all industries, 7.8 times the rate of that. In addition, death and missing rate was found to have a serious level management to 10.10‱. Among the accidents, 76.0% occurred at sea. The slipping, others and contact with machinery or fishing gear occurred more frequently in order in the frequency of accident occurrence pattern. In the risk assessment using frequency and severity, slipping, contact with machinery and others showed high risk during fishing. The results are expected to contribute to identification and assessment of safety hazard occurred in coastal composite fishing vessels.

• Corrosion Science and Technology
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• v.4 no.4
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• pp.155-163
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• 2005

Heavy duty coating are required to have minimum durable period of 15 years under average usage environment because these paints are coated with purpose of anti-corrosion, antifouling, plastering etc. Onto steel structures constructed upon land and sea and other ferrous structures of electric power generation plants, electricity transmission towers, large structures of various plants, etc. Therefore we tried to estimate heavy duty coating longevity through reliability evaluation method and used combined cyclic anti-conrrosion test method composed of drying, moisturizing and salt spray as for accelerated life test to estimate longevity. Accelerated life test hours to heavy duty coating of first grade (with longevity not less than 15 years) specification may be obtained from troubleless test hours $t_n=\frac{B_p}{n^{1/\beta}}\left[\frac{1n(1-CL)}{1n(1-p)} \right]^{1/\beta}=19.671$ (yr) where shape parameter $\beta=1.1$, confidence level CL=80 %, warranty life $B_{10}=15$ yr and sampling size n=10 (2 sets). Because acceleration factor {AF} found by accelerated test is 41.7, accelerated life test hours required may be represented about 4,132 hr so that if this amount of hours is converted to number of cycles(6 hr/cycle) of complex cycle corrosion resistance test then the amount is tantamount about 690 cycles. That means if there does not occur trouble failure (with defect factor sum not more than 20) during when there is performed 690 cycles of combined cyclic anti-corrosion test to heavy duty coating specimen then it signifies that there can be warranted longevity $B_{10}$ of 15 yr under condition of confidence level CL=80 %.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.3
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• pp.335-342
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• 2015

Laboratory facilities for biology are designed as biosafety level 1, biosafety level 2, biosafety level 3, and biosafety level 4. Biosafety level designations are based on a composite of the design features, construction, containment facilities, equipment, practice and operation procedures required for working with agents from the various risk groups. Generally, biosafety level 3 means the facility that is appropriate for the experiments using pathogens which can cause serious diseases by aerosol transmission. The biosafety level assigned for the specific work to be done is driven by professional judgement based on a risk assessment, rather than by automatic assignment according to the particular risk group designation of the pathogenic agents to be used. In this paper, we introduced the biosafety level 3 facility operated in ADD(Agency for defense development). It contains the overview of facility, microbiological experiment, animal experiment, decontamination and waste disposal. Biosafety level 3 laboratory in ADD has served the vital role in the research of biological agents and antidote development.

• International Journal of Computer Science & Network Security
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• v.23 no.6
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• pp.77-83
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• 2023

This research is conducted to minimize the potential security risks of conducting online exams to an acceptable level as vulnerabilities and threats to this type of exam are presented. This paper provides a general structure for the risk management process and some recommendations for increasing the level of security.

• Asia pacific journal of information systems
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• v.16 no.4
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• pp.27-47
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• 2006

Software companies try to upgrade the level of technology and quality of their products by adopting Software Process Improvement (SPI). First of all, the companies must understand affecting factors based on various environmental view points in order to acquire competitive advantage. In this study, a research model gets started on the basis of literature reviews, and identifies SPI factors that affect the maturity levels of organizations. Organizational members and assessment types are chosen as moderating factors. An empirical research has been made for analyzing the causal relationships among affecting factors and CMM levels. The results of this study will suggest several implications to decision makers who handle SPI issues.

• Nuclear Engineering and Technology
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• v.38 no.6
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• pp.489-504
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• 2006

A review has been made for the previous studies on safety of a geologic repository for high-level radioactive wastes (HLW) related to autocatalytic criticality phenomena with positive reactivity feedback. Neutronic studies on geometric and materials configuration consisting of rock, water and thermally fissile materials and the radionuclide migration and accumulation studies were performed previously for the Yucca Mountain Repository and a hypothetical water-saturated repository for vitrified HLW. In either case, it was concluded that it would be highly unlikely for an autocatalytic criticality event to happen at a geologic repository. Remaining scenarios can be avoided by careful selection of a repository site, engineered-barrier design and conditioning of solidified HLW. Thus, criticality safety should be properly addressed in regulations and site selection criteria. The models developed for radiological safety assessment to obtain conservatively overestimated exposure dose rates to the public may not be used directly for the criticality safety assessment, where accumulated fissile materials mass needs to be conservatively overestimated. The models for criticality safety also require more careful treatment of geometry and heterogeneity in transport paths because a minimum critical mass is sensitive to geometry of fissile materials accumulation.