• Journal of Information Technology Applications and Management
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• v.26 no.1
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• pp.77-93
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• 2019

Recently, office workers are increasingly aware of the right to disconnect because of the pressure from strong connections with Internet messengers. In this study, we examined the reason why the perception of the right to disconnect increases and how to deal with it. This research model is that smart working and psychological attachment from work affect right to disconnect, and that open communication and gender moderate the intensity of these effects. To verify this research model, survey questionnaires were distributed to workers in smart working environments, and 400 data were collected and analyzed using Smart-PLS. As results of data analysis, it was verified that smart working and psychological attachment from work had a significant influence on right to disconnect, that open communication group had a lesser effect of psychological attachment from work on right to disconnect than closed communication group, and that women had a lesser effect of psychological attachment from work on right to disconnect than men. Organizations need to maintain a desirable level of right to disconnect in order to improve the quality of working life. But, if it is impossible, They need to change the way of communication more openly so as to absorb the burden of strong connection by Internet. And they need to perform task assignment or stress relief policy reflecting gender characteristics.

• Structural Engineering and Mechanics
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• v.77 no.5
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• pp.571-586
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• 2021

The present paper studies the influence of the inhomogeneous initial stresses in the bi-layered hollow cylinder and it is assumed that these stresses are caused by the hydrostatic pressures acting on the interior and outer free surfaces of the cylinder. The study is made by utilizing the version of the three-dimensional linearized theory of elastic waves in bodies with initial stresses for which the initial stress-strain state in bodies is determined within the scope of the classical linear theory of elasticity. For the solution to the corresponding eigenvalue problem, the discrete-analytical method is employed. Numerical results are presented and analyzed for concrete selected pairs of materials. According to these results and their analyses, it is established that, unlike homogeneous initial stresses, the influence of the inhomogeneous initial stresses on the torsional wave dispersion has not only quantitative but also qualitative character. For instance, in particular, it is established that as a result of the initial stresses caused by the hydrostatic pressure acting in the interior free surface of the cylinder, the cut-off frequency appears for the fundamental dispersive mode and the values of this frequency increase with the intensity of this pressure.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.7
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• pp.8-14
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• 2021

Even welds that have passed non-destructive testing in the case of brittle crack arrest steel materials will actually have very fine weld defects. Based on studies showing that these defects adversely affect the structure if subjected to a certain period of load, the following conclusions were obtained by conducting CTOD tests on welding joints of high-strength BCA materials, structures comprising the upper decks of a large container vessel. First of all, the fatigue pre-cracking in the weld metal and heat affected areas was tested and the behavior was identified. Both parts of the welding joint are allowable range for the class regulations. In addition, CTOD results showed that the CTOD value in the heat affected area was more than 0.5 times higher than in the weld metal area.

• Journal of East-West Nursing Research
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• v.28 no.2
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• pp.122-131
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• 2022

Purpose: This study aimed to identify the factors related to fear of falling (FOF) in different age groups from community-dwelling mid to late-adults. Methods: To identify the factors related to FOF, data of 162,684 adults over 45 years of age from 2019 Community Health Survey was analyzed using logistic regression with complex samples. Results: Factors related to FOF found in all age groups were sex, previous experience of falls, physical activity levels over moderate intensity, subjective health status, number of chronic diseases, stress, depression, and cognitive decline. In the 45-64 age group, the FOF was significantly higher in the groups of low education level and low monthly household income. In the 65-74 and over 75 age groups, the FOF was significantly higher in the groups of not living with spouse and walking not practiced. Conclusion: We suggests that understanding of risk factors and early detection of fall risk patients in each age group are necessary to establish and apply tailored fall prevention programs for prevention and management of the FOF in community-dwelling mid to late-adults.

• Nuclear Engineering and Technology
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• v.54 no.5
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• pp.1726-1746
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• 2022

This paper presents fracture mechanics analysis results for various cracks located at pressurized water reactor pressure vessel nozzle crotch corners taking into consideration constraint effect. Technical documents such as the ASME B&PV Code, Sec.XI were reviewed and then a fracture mechanics analysis procedure was proposed for structural integrity assessment of various nozzle crotch corner cracks under normal operation conditions considering the constraint effect. Linear elastic fracture mechanics analysis was performed by conducting finite element analysis with the proposed analysis procedure. Based on the evaluation results, elastic-plastic fracture mechanics analysis taking into account the constraint effect was performed only for the axial surface crack of the reactor pressure vessel outlet nozzle with cladding. The fracture mechanics analysis result shows that only the axial surface crack in the reactor pressure vessel outlet nozzle has the stress intensity factor exceeding the low bound of upper-shelf fracture toughness irrespectively of considering the constraint effect. It is confirmed that the J-integral for the axial crack of the outlet nozzle does not exceed the ductile crack initiation toughness. Hence, it can be ensured that the structural integrity of all the cracks is maintained during the normal operation.

• Transactions of Materials Processing
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• v.31 no.3
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• pp.117-123
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• 2022

In this study, a commercial AZ61 magnesium alloy is extruded at 300 ℃ and 400 ℃ and the microstructures, mechanical properties, and high-cycle fatigue properties of the extruded materials are investigated. Both extruded materials have a fully recrystallized microstructure with no Mg₁₇Al₁₂ precipitates. The average grain size and maximum basal texture intensity of the extruded material increase with increasing extrusion temperature. The material extruded at 400 ℃ (AZ61-400) has higher tensile yield strength and lower compressive yield strength than the material extruded at 300 ℃ (AZ61-300) because of the stronger basal texture of the former. Because of coarser grain size, the tensile elongation of AZ61-400 is lower than that of AZ61-300. Despite the differences in microstructures and tensile/compressive properties, the two extruded materials have the same fatigue strength of 110 MPa. This is because the finer grain size of AZ61-300 causes an increase in fatigue strength, but its weaker texture causes a decrease in fatigue strength. In both extruded materials, fatigue cracks initiate at the surface of fatigue specimens at all stress amplitudes tested.

• Korean Journal of Exercise Nutrition
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• v.23 no.2
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• pp.1-6
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• 2019

[Purpose] Strenuous exercise often induces skeletal muscle damage, which results in impaired performance. Sphingolipid metabolism contributes to various cellular processes, including apoptosis, stress response, and inflammation. However, the relationship between exercise-induced muscle damage and ceramide (a key component of sphingolipid metabolism), is rarely studied. The present study aimed to explore the regulatory role of sphingolipid metabolism in exercise-induced muscle damage. [Methods] Mice were subjected to strenuous exercise by treadmill running with gradual increase in intensity. The blood and gastrocnemius muscles (white and red portion) were collected immediately after and 24 h post exercise. For 3 days, imipramine was intraperitoneally injected 1 h prior to treadmill running. [Results] Interleukin 6 (IL-6) and serum creatine kinase (CK) levels were enhanced immediately after and 24 h post exercise (relative to those of resting), respectively. Acidic sphingomyelinase (A-SMase) protein expression in gastrocnemius muscles was significantly augmented by exercise, unlike, serine palmitoyltransferase-1 (SPT-1) and neutral sphingomyelinase (N-SMase) expressions. Furthermore, imipramine (a selective A-SMase inhibitor) treatment reduced the exercise-induced CK and IL-6 elevations, along with a decrease in cleaved caspase-3 (Cas-3) of gastrocnemius muscles. [Conclusion] We found the crucial role of A-SMase in exercise-induced muscle damage.

• Korean Journal of Construction Engineering and Management
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• v.24 no.6
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• pp.81-90
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• 2023

Climate change has resulted in increased frequency and intensity of heat waves, which poses a significant threat to the health and safety of construction workers, particularly those engaged in labor-intensive and heat-stress vulnerable working environments. To address this challenge, this study aimed to propose an interpretable machine learning approach for forecasting personal heat strain by considering the cumulative effect of heat exposure as a situational variable, which has not been taken into account in the existing approach. As a result, the proposed model, which incorporated the cumulative working time along with environmental and personal variables, was found to have superior forecast performance and explanatory power. Specifically, the proposed Multi-Layer Perceptron (MLP) model achieved a Mean Absolute Error (MAE) of 0.034 (℃) and an R-squared of 99.3% (0.933). Feature importance analysis revealed that the cumulative working time, as a situational variable, had the most significant impact on personal heat strain. These findings highlight the importance of systematic management of personal heat strain at construction sites by comprehensively considering the cumulative working time as a situational variable as well as environmental and personal variables. This study provided a valuable contribution to the construction industry by offering a reliable and accurate heat strain forecasting model, enhancing the health and safety of construction workers.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2022.09a
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• pp.31-31
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• 2022

Plant-derived antioxidants are used as a healthy diet and are known to inhibit various human diseases. In this study, we investigated free radical scavenging and antioxidant activity of extracts from three plants (Ammannia multiflora, Ammannia coccinea and Salix gracilistyla) with the most DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity from 196 plant extracts inhabiting along Nakdong River in Republic of Korea. The three extracts also have strong total antioxidant activity. Moreover, the extracts inhibited hydrogen peroxide (H₂O₂)-induced reactive oxygen species production and depolarized mitochondrial membrane potential in RAW264.7 macrophages. In zebrafish larvae, 2',7'-dichlorodihydrofluorescein diacetate (DCFDA) fluorescent intensity, induced by H₂O₂, was markedly reduced by the extracts of A. multiflora, A. coccinea and S. gracilistyla. Meanwhile, the extracts were upregulated Nrf2 and HO-1 expression, and an HO-1 inhibitor reversed the extract-induced oxidative responses both in vivo and in vitro. The data suggest that the extracts of A. multiflora, A. coccinea, and S. gracilistyla exert potential free radical scavenging and antioxidant capacities both in vivo and in vitro by activating the Nrf2/HO-1 signaling pathway.

• Journal of Oral Medicine and Pain
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• v.33 no.1
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• pp.41-48
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• 2008

The focus of this study is to analyze the effect of stress on the health of bruxism patients using the MBTI system. The most common personality type will be identified among the bruxism patients and by understanding their personality & their handling of stress, more comprehesive and effective treatment plan can be constructed. The study will also conclude that the type of personality has big effect on the cause of bruxism, and that this will be considered in the treatment plan in this hospital. The result of the study is as follow. First, more bruxism patients were type I than type E. It can be suggested that this result is due to the introversive people maintaining their energy how within themselves, and private are less to likely to release there stress than the expressive people. Second, among the bruxism patients significantly more type T were found compared to type F. This implies the bruxism tend to follow principals, scientific and analysing during decision making rather than basing their decision an meanings, emotions and influences. Thirdly, more bruxism patients clarified into ST in comparison to non-bruxism patients. This is thought to be due to probable increased stress and anxiety following ST people's tendency to more strict and realistic thinking according to effectiveness, evidence-based and productivity. Fourth, the type IJ was the most of the bruxism patients. We can come to the conclusion that decision-oriented introversion people who have hard to change, a thoroughgoing preparation characters are likely to grind their teeth by their detailed characters. Fifth, the type IT was the most of the bruxism patients. Bruxism patients are usually influenced by spirit, easily hearted, awed of relationship and attention. So, their intensity of stress is much bigger because of their personality. The last, Type IS was the most of the bruxism patients. It means that introvert sensitive types who have characters of calm, passive but defence to other's emotion, also neutral, keep moderation, and have cold-heartedness are likely to grind their teeth frequently. In conclusion it is evident that bruxism patients have particular personality types. Precisive, analysing and introversive bruxism patients are expected to have higher sensitivities to stress.