• Proceedings of the KSR Conference
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• 2008.06a
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• pp.39-45
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• 2008

A levitation rail is placed on the top of track structure to operate Maglev vehicles and a part of track that link up with a sleeper is applied repeated load in Maglev vehicles operation. This paper aimed to verify validity of design for levitation rail, through the fatigue analysis about load which is applied to levitation rail in Maglev vehicles operation and impact load occurring in an emergency landing. Load conditions applied design load(23kN/m) in normal operation and skid drop load(24kN/m) in vehicle drop. And boundary conditions are consider bolt fixing and welding. Through static analysis, weak point and maximum stress of levitation rail could be obtained. S-N(stress-life) method was used in oder to predict fatigue life, and Goodman relationship was applied to consider a effect of mean stress. Also damage was calculated by using Miner's. As a result of fatigue analysis, levitation rail had a fatigue life which was more than requirement ($10^6$cycle) in all analysis conditions. Assumption that $10^8{\sim}10^9$cycles is infinite life, all analysis conditions had infinite life except a case under drop load and bolt fixing($1.21{\times}10^6$).

• 한국기계연구소 소보
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• v.4 no.1
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• pp.19-26
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• 1981

Fatigue, the birth and growth of cracks in metal parts subjected to repeated loading, has been a problem plaguing engineers since the Industrial Revolution and the advent of rotating or reciprocating machinery. Designing against metal fatigue was studied briefly in several aspects. Examples of fatigue failures were shown. Fatigue was classified by loading: uniaxial Fatigue, multiaxial fatigue, cumulative fatigue da¬mage. Fatigue design criteria were discussed: Infinite-Life Design, Safe-Life Design, Fail-Safe Design, and Damage Tolerant Design. Mitigation of notch effects by design, improvement of fatigue strength of metal parts by residual stress and surface finishing were discussed. Relative fatigue beha¬vior was studied under various environmantal conditions. Especially the effects of corrosion, temperature, fretting, and irradiation were covered.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.4
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• pp.168-172
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• 2012

Control arm is the structural component that pivots on two places. One end of the control arm is attached to the body frame and the other end is attached to the steering knuckle. The former research proposed the structural design by applying optimization technique with aluminum alloy. This study suggests a durability test method on the developed upper control arm to validate the analysis results. The durability analysis results of the developed control arm by using MSC Fatigue is confirmed to be close to infinite life. The weak model of developed control arm which occurs to finite life is made to perform the durability test and the zig design is developed in this process.

• Reproductive and Developmental Biology
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• v.31 no.4
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• pp.221-226
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• 2007

Embryonic stem (ES) cells are known to have an infinite proliferation and pluripotency that are associated with complex processes. The objective of this study was to examine expression of genes differentially regulated during differentiation of human ES cells by suppression subtractive hybridization (SSH). Human ES cells were induced to differentiate into neural precursor cells via embryoid body. Neural precursor cells were isolated physically based on morphological criteria. Immunocytochemical analysis showed expression of pax6 in neural precursor cells, confirming that the isolated cells were neural precursor cells. Undifferentiated human ES cells and neural precursor cells were subject to the SSH. TPX2 (Targeting Protein for Xklp2 (Xenopus centrosomal kinesin-like protein 2)) was identified, cloned and analyzed during differentiation of human ES cells into neural lineages. Expression of TPX2 was gradually down-regulated in embryoid bodies and neural precursor cells relative to undifferentiated ES cells. Targeting Protein for Xklp2 has been shown to be involved in cell division by interaction with microtubule development in cancer cells. Taken together, result of this study suggests that TPX2 may be involved in proliferation and differentiation of human ES cells.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.2
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• pp.81-88
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• 2020

The damping hinge of a built-in refrigerator was examined in terms of its stress and fatigue life. Analysis of the initial design showed that stress concentration occurred at the concave surface of the hinge lever, which was broken during the door opening-and-closing endurance test of the prototype. The maximum von Mises stress at this location exceeded the yield strength. In addition, Goodman fatigue analysis of the initial design showed that the fatigue life at this location was consistent with the failure observed during the endurance test. Based on these results, an improved design for the damping hinge was derived. Analysis of this improved design showed that the stress concentration in the hinge lever of the initial design was eliminated. In this case, the maximum stress occurred at the position where the hinge lever was in contact with the door stopping pin, and the maximum von Mises stress was smaller than the yield strength. Goodman fatigue analysis of the improved design indicated that the fatigue life of the entire damping hinge was infinite. It was therefore concluded that the improved design does not suffer from fatigue damage during the endurance test.

• Journal of the Korean housing association
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• v.21 no.3
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• pp.115-124
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• 2010

The environment which has been destroyed for the national growth since 1960's would seem to offer infinite resources to human, but now, the existence of human being is threatened by the development thoughtless for the environment. The World Powers have concentrated on green growth with eco-friendly resource since the end of 20th century. Korea suggested that the vision was the low carbon for green growth in 2008. It is necessary to supply Long-Life Housing in the green technology in terms of the sustainable housing development based on various life style, life cycle of the residences, the restrain remodeling and redevelopment in construction. This study is aim to establish the development of maintenance process to make continuous inhabitation of Long-Life Housing that has the separated SI for maintenance, durability, variability and remodeling. The maintenance for Long-Life Housing is very important to have more than 50~70 years the long term of life cycle in comparison with Housing. Also, the roles of manager and user are important parts in Long-Life Housing. The present maintenance for Housing is shift and repair works by the routine maintenance and demage. However, The maintenance for Long-Life Housing should consider movement and flexibility. In addition, Long-Life Housing requires the proper process of maintenance because it is different from Housing in housing concept, design and constructions stage. Therefore this study shows the efficient maintenance process for Long-Life Housing.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.9 no.3
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• pp.278-284
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• 2016

Software reliability in the software development process is an important issue. In infinite failure NHPP software reliability models, the fault occurrence rates may have constant, monotonic increasing or monotonic decreasing pattern. In this paper, infinite failures NHPP models that the situation was reflected for the fault occurs in the repair time, were presented about comparing property. Commonly, the software model of the infinite failures using the linear hazard rate distribution software reliability based on intercept parameter was used in business economics and actuarial modeling, was presented for comparison problem. The result is that a relatively large intercept parameter was appeared effectively form. The parameters estimation using maximum likelihood estimation was conducted and model selection was performed using the mean square error and the coefficient of determination. The linear hazard rate distribution model is also efficient in terms of reliability because it (the coefficient of determination is 90% or more) in the field of the conventional model can be used as an alternative model could be confirmed. From this paper, the software developers have to consider intercept parameter of life distribution by prior knowledge of the software to identify failure modes which can be able to help.

• Korean Journal of Agricultural Science
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• v.43 no.3
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• pp.441-449
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• 2016

Agricultural tractors are designed using the empirical method due to the difficulty of measuring precise load cycles under various working conditions and soil types. Especially, directly drives various tractor implements, the power take off (PTO) gear. Therefore, alternative design methods using gear design software are needed for the optimal design of tractors. The objective of this study is to simulate fatigue life of the PTO gear according to the operating point of the tractor engine. The PTO gear was made with SCr415 alloy steel with carburizing and quenching treatments. The fatigue life of the PTO gear was simulated by using bending and contact stress according to the torque of the load levels. The PTO gear simulation was conducted by the KISSsoft commercial software for gear analysis. Bending and contact stress were calculated by the ISO 6336:2006 Method A and B. The simulation of fatigue life was calculated by the Miner's cumulative damage law. The total fatigue life of tractors can be estimated to 3,420 hours; thus, 3,420 hours of fatigue life were used in the simulation of the PTO gear of tractors. The main simulation results showed that the maximum fatigue life of the PTO gear was infinite fatigue life at maximum engine power. Minimum fatigue life of the PTO gear was 19.61 hours at 70% of the maximum engine power. Fatigue life of the PTO gear changed according to load of tractor. Therefore, tractor work data is needed for optimal design of the PTO gear.

• Journal of The Korean Society of Integrative Medicine
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• v.8 no.4
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• pp.203-212
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• 2020

Purpose : Middle school students in the early stages of adolescents need balanced growth and development, and they are in the process of forming healthy lifestyles and are in an important period when they need to lay the foundation for a healthy life through active health management and guidance. Through systematic health-related policies and education, I intend to lay the groundwork for them to form healthy lifestyles in their high schools and adulthood. Methods : For this study, a survey was conducted from September 1 to October 30, 2019, and 300 middle school students based in Busan Metropolitan City were surveyed. Based on the analysis and results of preceding studies, a research model was set up to find out the effect of family support, health control activities and self-efficacy on health promoting behaviors and how health promoting behaviors affect the quality of life. Results : First, if family support is high, health promotion behavior and quality of life are analyzed to be high, so family support is affecting health promotion behavior and quality of life. Second, health control behavior had a significant effect on health promotion behavior, but did not affect the quality of life. Third, self-efficacy was having a significant effect on health promotion behavior and quality of life. Fourth, health promotion behavior was affecting the quality of life. Conclusion : In order to improve the quality of life, middle school students should first increase their health promotion behavior, and it is important to be supported by their family members and strengthen their self-efficacy as variables that increase their health promotion behavior. First of all, they should be given the infinite trust of the family and the strong belief that the family always supports them, and based on this, the student himself will be able to strengthen his or her self-efficacy. In addition, the process of physical and mental change of students comes to everyone, but during this process, members of society, such as families and schools, should send them support and trust so that they can grow up to be the decent members of society.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1667-1674
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• 2010

The fatigue life is estimated while determining the reliability of aircraft structures. In this study, the estimation of fatigue life was carried out on the basis of a cumulative damage theory; the working S-N curve and the equivalent stress on the engine support structure significantly affect the safety of the aircraft. The maximum stress observed was 1,080 MPa in the case of scissors link under crash load condition, and there was a 5% margin for the allowable stress corresponding to the temperature reduction factor. The maximum stress was 876 MPa, and the stress equation coefficient had a maximum value of 0.019 MPa/N in the case of scissors link under fatigue loads. In the results of the fatigue life analysis, the safety life in a fretting area of scissors link upper part was 416,667 flight hour, and other parts showed to infinite life. Therefore, it was demonstrated that the fatigue life requirement of aircraft engine support structure (scissors link, straight link) could be satisfied.