• Geomechanics and Engineering
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• 제37권6호
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• pp.599-614
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• 2024

To evaluate the safety status of deteriorated segments in a submarine shield tunnel during its service life, a seepage model was established based on a cross-sea shield tunnel project. This model was used to study the migration patterns of erosive ions within the shield segments. Based on these laws, the degree of deterioration of the segments was determined. Using the derived analytical solution, the internal forces within the segments were calculated. Lastly, by applying the formula for calculating safety factors, the variation trends in the safety factors of segments with different degrees of deterioration were obtained. The findings demonstrate that corrosive seawater presents the evolution characteristics of continuous seepage from the outside to the inside of the tunnel. The nearby seepage field shows locally concentrated characteristics when there is leakage at the joint, which causes the seepage field's depth and scope to significantly increase. The chlorine ion content decreases gradually with the increase of the distance from the outer surface of the tunnel. The penetration of erosion ions in the segment is facilitated by the presence of water pressure. The ion content of the entire ring segment lining structure is related in the following order: vault < haunch < springing. The difference in the segment's rate of increase in chlorine ion content decreases as service time increases. Based on the analytical solution calculation, the segment's safety factor drops more when the joint leaks than when its intact, and the change rate between the two states exhibits a general downward trend. The safety factor shows a similar change rule at different water depths and continuously decreases at the same segment position as the water depth increases. The three phases of "sudden drop-rise-stability" are represented by a "spoon-shaped" change rule on the safety factor's change curve. The issue of the poor applicability of indicators in earlier studies is resolved by the analytical solution, which only requires determining the loss degree of the segment lining's effective bearing thickness to calculate the safety factor of any cross-section of the shield tunnel. The analytical solution's computation results, however, have some safety margins and are cautious. The process of establishing the evaluation model indicates that the secondary lining made of molded concrete can also have its safety status assessed using the analytical solution. It is very important for the safe operation of the tunnel and the safety of people's property and has a wide range of applications.

• 한국정밀공학회지
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• 제16권5호통권98호
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• pp.29-39
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• 1999

Many industrial products can be assembled in various sequences of assembly operations. To save time and cost in assembly process and to increase the quality of products, it is very important to choose an optimal assembly sequence. In this paper, we propose a methodology that generates an optimal assembly sequence by using the knowledge of experts. First, a product is divided into several sub-assemblies. Next, the disassembly sequences of sub-assembly are generated using disassembly rules and special information can be extracted through the disassembly process. By combining every assembly sequence of sub-assemblies, we can generate all the possible assembly sequences of a product. Finally, the expert system evaluates all the possible assembly sequences and finds an optimal assembly sequence. It can be achieved under consideration of the parameters such as assembly operation, tool change, safety of part. basepart location, setup change, distance, and orientation. The developed system is applied to UBR(Unit Bath Room) example.

• 웰빙융합연구
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• 제7권3호
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• pp.1-11
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• 2024

Purpose: The purpose of this study is to present an efficient emission reduction ratio of plastic to reduce carbon dioxide, the main cause of greenhouse gases. Research design, data and methodology: This study calculated the absolute value of carbon dioxide by setting an equation through the emission coefficient using the US EPA's WARM model. Results: In the recycling ratio of 70%, it was found that the energy recovery ratio was 15.6%, which was the energy recovery ratio without generating carbon dioxide. When carbon dioxide is generated by changing plastic waste emissions, optimal efficiency is achieved by reducing emissions by 10% to 30% of energy recovery ratio, 20% to 50% of energy recovery ratio, and 30% to 80% or more of energy recovery ratio. Conclusions: The recycling rate should be set at a minimum of 70%, so that a carbon dioxide-free energy recovery rate could be obtained during the recycling process, supporting an eco-friendly basis for environmental policies aimed at this rate. In addition, it was possible to suggest that it is essential to reduce emissions by at least 30% for eco-friendly recycling measures that can achieve both economic and environmental feasibility in the energy recovery process through incineration during recycling in Korea.

• Journal of Information Technology Applications and Management
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• 제14권2호
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• pp.169-187
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• 2007

Most private and public organizations use, for their works, information systems that change their organizational structures. Nowadays, many organizations have team-based structures where typically a cross functional team is in charge of a business process. The effective communication among the members of a team is an important factor of team performance in that communication facilitates trust building, knowledge exchange, change acceptance, and safety improvement. This paper reviews methods for analyzing communication among team members from three aspects such as the content, the amount, and the structure of communication.

• Nuclear Engineering and Technology
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• 제54권6호
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• pp.2067-2076
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• 2022

The importance of safety culture has been emphasized to achieve a high level of safety. In this light, a systematic method to more properly deal with safety culture is necessary. Here, a decision-making tool that can apply a graded approach to the analysis of safety culture is proposed, called the F-D matrix, which determines the frequency and the difficulty of safety culture attributes recently defined by the IAEA. A hierarchical model of difficulty contributors was developed as a scoring standard, and its elements were weighted via expert evaluation using the analytic hierarchy process. The frequency of the attributes was derived by analyzing reported events from nuclear power plants in the Republic of Korea. Period-by-period comparisons with the F-D matrix can show trends in the change of the maturity level of an organization's safety culture and help to evaluate the effectiveness of previously implemented measures. In the evaluating the difficulty of the attributes in the recently developed harmonized safety culture model, the difficulties of Trending, Benchmarking, Resilience, and Documentation and Procedures were found to be relatively high, while the difficulties of Conflicts are Resolved, Ownership, Collaboration, and Respect is Evident were found to be relatively low. A case study was conducted with an analysis period of 10 years to attempt to reflect the many changes in safety culture that have been made following the Fukushima accident in March 2011. As a result of comparing two periods following the Fukushima accident, the overall frequency decreased by about 40%, providing evidence for the effects of the various improvements and measures taken following the increased emphasis on safety culture. The proposed F-D matrix provides a new analytical perspective and enables an in-depth analysis of safety culture.

• 대한영양사협회학술지
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• 제26권4호
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• pp.278-288
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• 2020

This study examined the effects of response-facilitating factors(Food-related Knowledge, Response-Efficacy, and Self-Efficacy) and response-inhibiting factors(Severity, Vulnerability, and Consumer Stress) on the consumer' behavior intention based on protection motivation theory, which explains the behavioral change to protect oneself. This study was conducted to reduce the customers' concerns regarding food safety accidents and introduce ways to make them more interested in food safety. A sample of 225 adults over 19 years of age was collected in February 2018 through a self-administered questionnaire. The results of the cognitive mediation process of protective motivation theory showed that the consumers' knowledge and self-efficacy which are response-facilitating factors, positively influence the behavioral intention. Severity and consumer stress were response-inhibiting factors. On the other hand, response-efficacy, which is a response-facilitating factor, and vulnerability, which is a response-inhibiting factor, did not influence the behavioral intention. Therefore, severity and consumer stress are response-inhibiting factors. The results were analyzed as a result of a behavioral change to protect oneself from food safety accidents. The applicability of the theory of protection motivation on the topic of food safety was also confirmed.

• Nuclear Engineering and Technology
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• 제55권8호
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• pp.2905-2918
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• 2023

The valve assembly used in nuclear power plants is important safety-related equipment. In the new standard, the physical attributes are measured using a valve diagnosis test, which is used in the expansion to other non-tested valves using a quantitative test-basis methodology. With a motor-operated actuator, the state of stem's lubrication is related to physical attributes such as the stem factor and the friction coefficient. This study analyzed the numerical transient of fluid and solid lubrication with a squeeze film effect due to the loading rate on the stem and the stem nut using the experimental data. The differential equation that governs the motion mechanism of the stem and stem nut is established and analyzed. The flow rate, the fluid and the solid contact forces are calculated with the friction coefficient. Finally, we found that a change in the friction coefficient results from a change of the shear force in the solid contact mode during the interchange process between the solid contact mode and the fluid contact mode. The qualitative understanding of the squeeze film effect is expanded quantitatively for forces, thread surface distance, velocity, and acceleration, with consideration of the metal solid contact and fluid contact.

• 한국가시화정보학회지
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• 제21권2호
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• pp.34-45
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• 2023

When lithium-ion batteries operate out of the proper temperature range, their performance can be significantly degraded and safety issues such as thermal runaway can occur. Therefore, battery thermal management systems are widely researched to maintain the temperature of Li-ion battery cells within the proper temperature range during the charging and discharging process. This study investigates the cooling performance and isothermal maintenance of cooling materials by measuring the surface temperature of a battery cell with or without cooling materials, such as silicone oil, thermal adhesive, and phase change materials during discharge process of battery by the experimental and numerical analysis. As a result of the experiment, the battery pack filled with phase change material showed a temperature reduction of 47.4 ℃ compared to the case of natural convection. It proves the advanced utility of the cooling unit using phase change material that is suitable for use in battery thermal management systems.

• 한국안전학회지
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• 제8권4호
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• pp.207-212
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• 1993

상변화 에너지 저장장치는 변동하는 액체-고체 상접합면과 자연대류의 존재에 기인한 비선형성 때문에 해석적으로 분석하기가 어렵다. 핀(fin) 형태의 상변화 에너지 저장장치를 준선형화 시켜 열전달을 수치적으로 해석하여 실험 데이타와 비교 검증하였다. 대칭형 수평 핀에 대하여 준선형, 비정상의 얇은 2차원적 모델을 세우고 유한체적방법(FVM)에 의해 시간의 함수로 융해된 상변화물질의 비율과 액체-고체 상접합면의 형상을 예측하였다. 유한체적방법(FVM)에 의한 결과는 실험결과와 비교적 잘 일치하였다. 벽과 융해점 사이의 온도차가 클수록 융해된 상변화물질의 비율은 증가하였으며 대류항을 포함하는 경우가 없는 경우보다 실험결과에 더 가까운 해를 얻을 수 있었다.

• 대한안전경영과학회지
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• 제13권4호
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• pp.71-79
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• 2011

The work environment of locomotive cabs has long been an important issue in the design of railload systems since it is quite critical in terms of system's operational safety. It is getting more attention as the running speed of the trains goes up these days. To this end, this paper describes how to systematically construct a DB for the requirements set in the course of the improvement process for the aforementioned cab work environment. As a solution approach, we have adopted the requirement architecture concept to cover the whole activities required to do such as in requirements generation, DB construction, change management, and traceability management. Specifically, based on the requirement architecture framework a requirement process to collect requirements for improvement is discussed, and the guide lines are suggested for verification and validation of the developed requirements. In addition, a base schema and requirements templates are developed, which will be used in generating requirements and constructing a DB. Finally, it is demonstrated how the requirements DB for locomotive cabs can be constructed using a computer-aided tool in an integrated fashion.