• Journal of Ocean Engineering and Technology
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• v.33 no.5
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• pp.435-446
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• 2019

Because offshore structures are affected by various environmental loads, the risk of damage is high. As a result of ever-changing ocean environmental loads, damage to offshore structures is expected to differ from year to year. However, in previous studies, it was assumed that a relatively short period of load acts repeatedly during the design life of a structure. In this study, the residual life of an offshore wind turbine support structure was evaluated in consideration of the timing uncertainty of the ocean environmental load. Sampling points for the wind velocity, wave height, and wave period were generated using a central composites design, and a transfer function was constructed from the numerical analysis results. A simulation was performed using the joint probability model of ocean environmental loads. The stress time history was calculated by entering the load samples generated by the simulation into the transfer function. The damage to the structure was calculated using the rain-flow counting method, Goodman equation, Miner's rule, and S-N curve. The results confirmed that the wind speed generated at a specific time could not represent the wind speed that could occur during the design life of the structure.

• Journal of Life Science
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• v.25 no.11
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• pp.1324-1330
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• 2015

The present study was performed to analyze and review the physical and immune responses to overtraining syndrome in humans. Overreaching refers to the initial phage of overtraining syndrome and has been known as a physical fatigue which is mainly from metabolic imbalance. It has been known that overtraining also results in a loss of adaptability which may lead to an attenuation of exercise performance, sleeping disorder, central fatigue, neurohormonal changes, difficulty recovery to physical stress, and immunological changes. Additionally, overtraining syndrome is characterized by persistent fatigue, poor performance in sport due to the prolonged and strenuous physical training. Also, previous studies reported that endurance athletes experienced a high incidence of URTI during intense training and the post training. And also, high-performance athletes reported that suppression of cell mediated and anti-body mediated immune function. NK cell numbers were also reduced in the period of overtraining syndrome. Major components of prevention and treatment for the overtraining syndrome are screening, education, and detraining. Furthermore, the combination of these prevention and treatment strategies will be much helpful. Therefore, the current review will be helpful for athletes and individuals who are at the risk of overtraining syndrome.

• International Journal of Highway Engineering
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• v.17 no.4
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• pp.77-87
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• 2015

PURPOSES: It is theoretically well known all over the world, that porous hot mixed asphalt (HMA) with hydrated Lime improves moisture and rutting resistance, and reduces pothole occurrence frequency, as well as the life cycle cost (LCC). METHODS : Addictive in the two different formations of the liquid anti-stripping Agent and powder Hydrated-Lime was applied in this investigation in order to obtain relatively clear results according to their types and conditions. Firstly, the moisture conditions were set, and applied to the porous HMA mixtures with hydrated lime (anti-stripping agent). Next, it was followed by a non-destructive test with the application of three freeze-thaw cycles, which were individually carried out thrice to compare the results of the dynamic moduli. Lastly, the hydrated lime effect related to moisture sensibility to porous HMA has been verified through the analysis of the modulus results regarding the change rate of dynamic modulus per n-cycle. RESULTS: It is clear from this investigation, that the dynamic modulus is inversely proportional to the change in temperature, as the graph representing the rigidity of the thermorheologically simple (TRS) material showed gradual decline of the dynamic modulus with the increase in temperature. CONCLUSIONS: The porous HMA mixture with the anti-stripping agent (hydrated Lime) has been found to be more moisture resistant to freezing and thawing than the normal porous HMA mixture. It is clear that the hydrated lime helps the HMA mixture to improve its fatigue resistance.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.17-17
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• 2017

In electric agricultural machine the gearhead is needed to convert the high speed low torque rotation motion generated by DC motor to lower speed high torque motion used by the vehicle. The gearhead consist of several spur gears works as reduction gears. Spur gear have straight tooth and are parallel to the axis of the wheel. Spur gears are the most easily visualized gears that transmit motion between two parallel shafts and easy to produce. The modeling and simulation of spur gears in DC motor gearhead is important to predict the actual motion behavior. A pair of spur gear tooth in action is generally subjected to two types of cyclic stress: contact stress and bending stress including bending fatigue. The stress may not attain their maximum values at the same point of contact fatigue. These types of failure can be minimized by analysis of the problem during the design stage and creating proper tooth surface profile with proper manufacturing methods. To improve its life expectation in this study modal and stress analysis of gearhead is simulated using ansys work bench software based on finite element method (FEM). The modal analysis was done to understand gearhead deformation behaviour when vibration occurs. FEM static stress analysis is also simulated on gearhead to simulate the gear teeth bending stress and contact stress behavior. This methodology serves as an approach for gearhead design evaluation, and the study of gear stress behavior in DC motor gearhead which is needed in the small workshop scale industries.

• Journal of Energy Engineering
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• v.29 no.3
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• pp.91-96
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• 2020

For the anchor bolts and brackets that fix the stone wall, which is an external finishing material, it is necessary to maintain the performance required for the mechanical structure from the initial design stage and secure high durability. For this, the design and safety evaluation in consideration of the load conditions are necessary, so the structural analysis applying the finite element analysis technique was performed as a method to verify durability. As a result of structural analysis for various shapes for optimal design, a reinforcing structure was added to alleviate the maximum stress generated at the rear part of the bracket in contact with the bolt. In addition, a reinforcing plate was additionally attached to the bracket to relieve the stress concentration of the L-shaped bracket to make the stress distribution uniform, so that the safety factor satisfies the standard conditions. In addition, the fatigue life analysis by cyclic load was performed, and the fatigue safety factor was analyzed. As a result, the durability was obtained.

• International Journal of Highway Engineering
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• v.13 no.4
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• pp.41-50
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• 2011

It is well-known that pavement is easily damaged by several factors including permanent deformation and fatigue crack, causing service life of the pavement to be shorter than expected. It is very important to predict amount of permanent deformation for designing pavement and developing design method of pavement. A new model of permanent deformation of pavement materials based on concept of shear stress ratio has been proposed because the lower pavement materials are highly affected by shear strength of the material. In this study a large repetitive triaxial load test has been adapted for performing test of permanent deformation of crushed subbase materials. The test procedure which includes concept of shear stress ratio has been newly developed. Several important model parameters can be obtained from the test that can be used for making correct permanent deformation model of the material.

• International Journal of Highway Engineering
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• v.14 no.1
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• pp.17-24
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• 2012

This study evaluated the performance of Korean epoxy asphalt mixtures using several laboratory tests. Four types of epoxy asphalt mixtures were manufactured based on 13mm dense graded asphalt mixtures: three Korean and one Japanese epoxy asphalt mixtures where 20% or 40% of asphalt binder was replaced by epoxy resins. Curing time was determined as 3 and 6 hours for the mixtures containing 40% and 20% of epoxy resins, respectively. From the laboratory tests including wheel tracking, indirect tension fatigue, bending beam, and moisture susceptibility tests, it was concluded that the epoxy asphalt mixtures had superior performance than conventional asphalt mixtures except moisture susceptibility. Also, the performance of the Korean epoxy asphalt mixtures was comparable to the Japanese mixtures. Thermal coefficient, bond strength, and indirect tension tests were conducted to examine the applicability of the Korean epoxy asphalt mixtures to concrete repair. Its adhesion was strong enough to be bonded to surrounding concrete materials and its tensile strength was comparable to the concrete, but thermal expansion coefficient was 5 times greater than the surrounding concrete.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.3
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• pp.121-129
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• 2022

Recently the growth of the renewable energy production has caused the flexible operation in LNG combined cycle power plant. Due to the rapid start and stop operations, large CrMoV castings used for turbine casings and valve bodies could be distorted and lead to replacement or welding repair. This study was performed to find out the characteristics of the repair welding for a damaged CrMoV casting steel. A typical field repair method (arc & TIG welding) was applied to making specimens. The degraded N2 packing head sample from the steam turbine was used. The evaluations of weldments were carried out in terms of microstructural characterization, microhardness measurements, tensile, creep-rupture and fatigue tests. Color etching was also applied for better understanding of welding microstructures. As the boundary between HAZ and base material was deteriorated by welding, it caused microstructural changes formed during PWHT and the shortening of the remaining residual life. By comparing the properties according to repair welding method, it was possible to derive what important welding factors were. As a result, arc welding method is more suitable for repair welding on CrMoV castings.

• Journal of Hospice and Palliative Care
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• v.25 no.2
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• pp.55-65
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• 2022

Caring for patients with cancer is highly stimulating and rewarding, attracting health professionals to the field who enjoy the challenge of managing a complex illness. Health professionals often form close bonds with their patients as they confront ongoing disease or treatment impacts, which may be associated with multiple losses involving function and/or eventual loss of life. Ongoing exposure to patient loss, along with a challenging work setting, may pose significant stress and impact health professionals' well-being. The prevalence rates of burnout and compassion fatigue (CF) are significant, yet health professionals have little knowledge on these topics. A 6-week continuing education program consisting of weekly small-group video-conferencing sessions, case-based learning, and an online community of practice was delivered to health care providers providing oncology care. Program content included personal, organization and team-related risk and protective factors associated with CF, grief models, and strategies to mitigate against CF. Content analysis was completed as part of the program evaluation. In total, 189 participants (93% nurses) completed the program, which was associated with significant improvements in confidence and knowledge of CF and strategies to support self and team resilience. Qualitative themes and vignettes from experiences with the program are presented. Key themes included knowledge gaps, a lack of support related to CF and strategies to support resilience, organization-and team-based factors that can inhibit expression about the impacts of clinical work, the health professional as a "person" in caregiving, and the role of personal variables, self-skill practices, and recommendations for education and support for self and teams.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1D
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• pp.73-79
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• 2006

A major purpose of this study is to develop high modulus asphalt mixtures for perpetual asphalt pavements which can save maintenance cost by increasing the design and performance periods of the pavements. Various physical and mechanical laboratory tests are performed for the high modulus asphalt binder developed in this study. The test results show that the properties of the high modulus binder are similar to those of the French high modulus binders. In addition to the binder tests, various performance tests are conducted for the high modulus and conventional mixtures. The dynamic modulus test results indicate that the dynamic modulus values of the high modulus mixtures are higher than those of the conventional mixtures by 10~15% at $5^{\circ}C$, 20~25% at $15^{\circ}C$ and 100% at $30^{\circ}C$. It is observed from the performance tests that the high modulus mixtures yield better fatigue, rutting and moisture damage performance than the conventional mixtures.