• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.7
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• pp.950-957
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• 2023

For safe mooring and towing between the ship and port, the equipment must be designed in accordance with the relevant international regulations. However, some small shipyards and engineering companies often do not fully comprehend the core contents. Therefore, the international regulations regarding towing and mooring equipment are reviewed and the bollard and chock are newly developed based on the Mooring Equipment Guideline 4 (MEG4) standards. A bollard is a mooring equipment used to fix a mooring rope to the hull. It has two columns and is mostly used in a figure eight pattern knots under the mooring condition. The chock, which is used to change the mooring rope direction coming into the ship from outside, is manufactured using a casting with curvature. The two mooring equipment are widely used in the stern, bow, and mid-side. Owing to the increase in the size of container vessels and LNG ships, the mooring rope load has increased and the safe working load of the mooring equipment must be revised. This study summarizes and examines the results of the allowable stress method obtained using finite element analysis modelling. To consider the mesh size effect, a reasonable criteria was suggested by referring the existing class guidance. Additionally, the safe working load was verified through nonlinear collapse analysis, and the elastic region against load increments was confirmed. Furthermore, the proposed evaluation method can be used to develop similar equipment in the near future.

• Journal of Korean Society of Disaster and Security
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• v.16 no.2
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• pp.57-63
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• 2023

Recently, Heavy rains and super typhoons occurred by climate change cause a lot of damage in Korea. In order to reduce such damage, various types of river maintenance projects are being promoted, but it is difficult to maintain the balance of rivers in Korea with distinct flood and dry seasons. In particular, river structures installed as a river maintenance project cause various problems such as scouring of structures and their foundations during floods and river bed changes. In order to reduce such bed scour, various vanes are installed in the bend of the river, and various bed scour reduction effects appear depending on the size, arrangement, and shape of the vanes. The vane regenerates the secondary flow in the opposite direction to the secondary flow generated by the centrifugal force, thereby reducing scour around the outer bed and promoting deposition. The theory of this study uses the governing equation applying the continuity equation that satisfies the law of conservation of mass and the momentum equation that satisfies the conservation of momentum, and measures the overall average flow velocity change rate according to design factors to investigate the effect of vanes under various conditions. Both the average and cross-sectional flow velocities decreased in both the trapezoidal vane and the square vane. In addition, vanes installed perpendicularly or inclined to the direction of river flow generate a secondary flow in the opposite direction to the secondary flow generated by centrifugal force, thereby canceling the secondary flow of centrifugal force, so the effect of the vane appears.

• Journal of the Korean Society of Radiology
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• v.17 no.6
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• pp.977-983
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• 2023

Due to the development of the domestic economy and science, the people's standard of living has increased. Accordingly, we want to improve the quality of life. In other words, we guarantee human rights and pursue dignity and value as human beings. Therefore, the medical field extends human life and helps maintain a healthy life. The social medicine that protects human rights is forensic medicine. Forensic medicine identifies deaths and analyzes the cause using forensic radiology images. Forensic radiology is the acquisition and provision of medical images by the radiographer. Therefore, the radiographer must have expertise by completing forensic science-related courses. Recently, medical and nursing schools have opened and operated various subjects such as forensic medicine and forensic nursing. However, the Department of Radiology science is the only school that offers courses related to forensic science. For the future development and exploration of the radiographer and department of radiology science, forensic education should be considered. For this purpose, we investigated the necessity and demand for forensic education in the department of radiology science undergraduate and graduate schools. The department of radiology science students' awareness of forensic science was found to be 2.977 points, but the need for forensic science education for the radiographer was high at 3.759 points. In addition, current students' demand for forensic science courses was high at 84.1%, with the majority responding that it was necessary to open and operate the course. This study was able to determine the demand for forensic science-related subjects among the department of radiology science undergraduate and graduate students, and there is a need to explore diversity and expertise in education. We hope that it will be used as basic data for the development of forensic medicine and radiology science.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.6
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• pp.86-93
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• 2023

As the hysteretic behavior of reinforced concrete members under cyclic loading progresses, the energy dissipation ability decreases due to a decrease in stiffness and strength and pinching effects. However, the guideline "Nonlinear Analysis Model for Performance-Based Seismic Design of Reinforced Concrete Building Structures, 2021" requires calculating a single energy dissipation factor for each member and all histeric step, so the decrease in energy dissipation capacity according to histeric step cannot be considered. It is judged that Therefore, in this study, the energy dissipation factor according to the histeric step was examined by comparing the existing experimental results and the nonlinear time history analysis results for a general beam under cyclic loading. The energy dissipation factor was calculated as the ratio of the energy dissipation amount of the actual specimen to the energy dissipation amount of the idealized elastoplastic behavior obtained as a result of nonlinear time history analysis. In the existing experiment results, the energy dissipation factor was derived by calculating one cycle for each histeric step, and the energy dissipation factor was derived based on the nonlinear modeling process in the guidelines. In the existing experimental study, the energy dissipation factor was calculated by setting each histeric step (Y-L-R), and the energy dissipation factor was found to be 0.36 in the Y-L step and 0.28 in the L-R step, and the energy dissipation factor in the guideline was found to be 0.31. This shows that the energy dissipation factor calculation formula in the guidelines does not indicate a decrease in the energy dissipation capacity of reinforced concrete members.

• Korean Chemical Engineering Research
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• v.61 no.4
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• pp.542-549
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• 2023

Since the growing interest in surrogate modeling, there has been continuous research aimed at simulating nonlinear chemical processes using data-driven machine learning. However, the opaque nature of machine learning models, which limits their interpretability, poses a challenge for their practical application in industry. Therefore, this study aims to analyze chemical processes using Explainable Artificial Intelligence (XAI), a concept that improves interpretability while ensuring model accuracy. While conventional sensitivity analysis of chemical processes has been limited to calculating and ranking the sensitivity indices of variables, we propose a methodology that utilizes XAI to not only perform global and local sensitivity analysis, but also examine the interactions among variables to gain physical insights from the data. For the ammonia synthesis process, which is the target process of the case study, we set the temperature of the preheater leading to the first reactor and the split ratio of the cold shot to the three reactors as process variables. By integrating Matlab and Aspen Plus, we obtained data on ammonia production and the maximum temperatures of the three reactors while systematically varying the process variables. We then trained tree-based models and performed sensitivity analysis using the SHAP technique, one of the XAI methods, on the most accurate model. The global sensitivity analysis showed that the preheater temperature had the greatest effect, and the local sensitivity analysis provided insights for defining the ranges of process variables to improve productivity and prevent overheating. By constructing alternative models for chemical processes and using XAI for sensitivity analysis, this work contributes to providing both quantitative and qualitative feedback for process optimization.

• Journal of the Institute of Convergence Signal Processing
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• v.24 no.2
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• pp.103-111
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• 2023

Consensus, that aims to converge the states of agents to the same states through information exchanges between agents, has been widely studied to control the multi-agent systems. In real systems, the measurement variables of each agent may be different, the loss of information across communication may occur, and the different networks for each state may need to be constructed for safety. Moreover, the input saturation and the disturbances in the system may cause instability. Therefore, this paper studies the PID(Proportional-Integral-Derivative)-based consensus control to achieve the swarm behavior of the multi-agent systems considering the heterogeneous state information, the input saturations, and the disturbances. Specifically, we consider the multiple follower agents and the single leader agent modeled by the second-order systems, and investigate the conditions to achieve the consensus based on the stability of the error system. It is confirmed that the proposed algorithm can achieve the consensus if only the connectivity of the position graph is guaranteed. Moreover, by extending the consensus algorithm, we study the formation control problem for the multi-agent systems. Finally, the validity of the proposed algorithm was verified through the simulations.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.17 no.2
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• pp.81-97
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• 2022

This paper's purpose is to get hold of the recent research trend by analyzing the variables uesd in startups related papers. The startups related papers in this paper are the papers which include 'startups' in the title of the registered papers from the year 2013 to the year 2020. This study's analysis methods are text-mining of all variables and text-network analysis of affected variables. Visualizing tool for network analysis is Gephi. The result of variables' analysis is as follows. First, independent variables consist mainly of variables about startups' internal factors and outside environment, but due to startups' features like early stage company's features, innovative features, most of variables are about enterprise internal competitiveness, marketing 4P strategy, entrepreneurship, coopreation method, transformational leadership, enterprise features, lean startup strategy, enterprise internal communication, value orientation, task conflict, relationship conflict, knowledge sharing, etc. Second, dependent variables are mainly about outcome, and are classified into financial performance and non-financial performance by overall concept. In other words, startups related papers have higher interest in non-financial performance, like management performance, team performance, SCM performance as well as financial performance like sales quantity owing to startups' immaturity in getting good financial performance. Through this study we can find out as follows. Although there are not many officially registered papers dealing with startups, those papers include various themes about stratups. For example, there are trendy themes like lean startups strategy, crowdfunding, influencer and accelerator, etc.

• Journal of Korean Elementary Science Education
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• v.43 no.1
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• pp.35-47
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• 2024

Thirty-five elementary schools in Gwangju and Jeollanam-do were surveyed on the installation status of plant labels. As a result of a comprehensive evaluation of the installation and condition of the plant labels, 12 out of 35 elementary schools were evaluated as "excellent," 13 as "good," and 8 as "insufficient." In some cases, various types of plant labels were installed on various types of plants and were updated continuously, indicating that the school members recognize the plant labels as an important educational tool. Meanwhile, some schools did not have a single plant label. Although plant labels were installed, instances occurred where they were neglected without continuous maintenance and management. Some plant labels were produced and installed by specialized companies, leading to errors in content or inadequate post-installation management, thereby compromising the school landscape. Therefore, we propose an alternative-allowing schools to independently produce and install plant labels. This approach preserves the school's uniqueness, and the process of producing and installing sustainable plant labels becomes an active educational tool.

• Journal of the Korean Geotechnical Society
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• v.40 no.3
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• pp.93-100
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• 2024

Pore water freezes in low-temperature compaction, which leads to different compaction characteristics compared to room temperature conditions. In regions like Alberta, Canada, where organic soils are prevalent, compaction performance is influenced by the high water retention and compressibility of organic soils, as well as their sensitivity to freezing and thawing. Alberta's strict environmental regulations demand the reuse of excavated soil for backfill, and the long winter season creates challenging conditions for civil engineering projects. In this study, a laboratory compaction test was conducted to evaluate the low-temperature compaction characteristics of organic soils with varying organic content. The results indicate that the optimum moisture content increases as the organic content increases, and the maximum dry unit weight decreases by up to 21.9%. In addition, under temperature conditions below -4℃, no optimum moisture content was observed, and the dry unit weight decreased as the moisture content increased.

• Korean Journal of Environment and Ecology
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• v.37 no.6
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• pp.473-483
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• 2023

This study was conducted to find out the psychological or physiological healing effects of real natural forests and virtual forest experiences using virtual reality (VR) in an artificially-controlled digital environment. To find out this, 81 healthy undergraduate students from C University were experimented on visual forest stimulation effects in the digital environment from September 5 to December 9 in 2022. The experiment evaluated the psychological and physiological healing effects of visual forest stimulation in the digital forest environment (2D, 3D). The SRI (stress response inventory) experiment for analyzing psychological effect showed statistically significant differences among groups. As for the SRI experiment for measuring psychological stress, except Control group, 2D group in the digital environment showed little difference before and after the experiment. But 3D group showed less stress than before. As a result, it was proved that visual forest stimulation in a forest-based digital environment (2D, 3D) reduces psychological stress significantly. And when analyzing how visual forest stimulation changes EEG (electroencephalogram) in the digital environment, alpha waves (RA), which are activated during relaxation or stabilization, were more active than beta waves (RB), which are activated during tension or awakening. This study is expected to be used to create a psychological and physiological healing environment for those who cannot go to a natural forest due to mobility difficulties by providing them visual forest stimulation experiences in a digital environment. It is also expected that the results will be the basis for forest healing in the digital environment and virtual reality programs will help forest healing activities.