• Journal of the Korean Society for Aviation and Aeronautics
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• v.31 no.1
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• pp.43-56
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• 2023

The aviation industry has continued to grow despite the influence of external environmental factors such as SARS and MERS. However, this growth has led to a sharp decrease in air traffic and a crisis of flight suspension due to the collapse of the global value chain and the decline of the world economy as the World Health Organization (WHO) declared a COVID-19 pandemic. Due to the decrease in the number of international flights, aviation workers such as pilots and cabin crew were exposed to high psychological stress and fatigue, such as large-scale layoffs, job instability, decrease in income, and increased risk of infection during. Recently, the international community has eased immigration restrictions through quarantine activities, and airlines are taking a step further to recover existing air demand. However, during the crisis period, a significant number of professional workers have been turned off or fired, and the physical and mental fatigue of those who can perform their duties is increasing. Therefore, this paper intends to examine the direction of policy improvement and the identification of problems in aviation safety and fatigue management after the pandemic.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.1
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• pp.58-65
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• 2003

The aramid fiber reinforced metal laminates(AFRMLs) used for the wing part fair flight suffer the cyclic bending moment of variable amplitude during service. The fatigue crack propagation and delamination behavior in AFRMLs containing a saw-cut and circular hole was investigated using the average stress criterion(ASC) model. Mechanical tests were carried out using the cyclic bending moment of 4.9 N . m and delamination was observed by ultrasonic C-scan images. In case of AFRMLs containing a saw-cut fatigue crack propagated in aluminum matrix, inducing delamination. However, in case of AFRMLs containing a circular hole, delamination formed with two types under cyclic bending moment of 4.9 N . m. First, delamination formed along the fatigue crack in aluminum matrix. Second, delamination formed without any fatigue crack around the circular hole. Therefore, delamination was formed depending on the stress distribution near the circular hole.

• The Journal of Korean Physical Therapy
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• v.20 no.1
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• pp.57-65
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• 2008

Purpose: Heat shock proteins (HSPs) are a group of proteins that are activated when cells are exposed to a variety of environmental stresses, such as infection, inflammation, exposure to toxins, starvation, hypoxia, brain injury, or water deprivation. The activation of HSPs by environmental stress plays a key role in signal transduction, including cytoprotection, molecular chaperone, anti-apoptotic effect, and anti-aging effects. However, the precise mechanism for the action of small HSPs, such as HSP27 and mitogen-activated protein kinases (MAPKs: extracellular-regulated protein kinase 1/2 (ERK1/2), p38MAPK, stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK), is not completely understood, particularly in application of cell stimulators including platelet-derived growth factor (PDGF), angiotensin II (AngII), tumor necrosis factor $\alpha$ (TNF$\alpha$), and $H_2O_2$. This study examined the relationship between stimulators-induced enzymatic activity of HSP27 and MAPKs from rat smooth and skeletal muscles. Methods: 2-dimensional electrophoresis (2DE) and matrix assisted laser desorption ionizationtime-of-flight/time-of-flight (MALDI-TOF/TOF) analysis were used to identify HSP27 from the intact vascular smooth and skeletal muscles. Three isoforms of HSP27 were detected on silver-stained gels of the whole protein extracts from the rat aortic smooth and skeletal muscle strips. Results: The expression of PDGF, AngII, TNF$\alpha$, and $H_2O_2$-induced activation of HSP27, p38MAPK, ERK1/2, and SAPK/JNK was higher in the smooth muscle cells than the control. SB203580 (30${\mu}$M), a p38MAPK inhibitor, increased the level of HSP27 phosphorylation induced by stimulators in smooth muscle cells. Furthermore, the age-related and starvation-induced activation of HSP27 was higher in skeletal muscle cells (L6 myoblast cell lines) and muscle strips than the control. Conclusion: These results suggest, in part, that the activity of HSP27 and MAPKs affect stressors, such as PDGF, AngII, TNF$\alpha$, $H_2O_2$, and starvation in rat smooth and skeletal muscles. However, more systemic research will be needed into physical therapy, including thermotherapy, electrotherapy, radiotherapy and others.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.6
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• pp.699-705
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• 2011

High-maneuver missile is a projectile which demands a strong momentum at short time. To produce a necessary thrust for the flight, the gas of high temperature and pressure is generated through explosive combustion of solid propellant, and a great thrust can be obtained by expanding this high temperature and pressure gas. Although the operating time of a rocket motor is less than a few seconds, a failure of part or ablation near the throat of nozzle may take place during the expansion of high temperature and pressure gas for great thrust. In other words, for the precise control of a missile an exact stress analysis considering both, the thermal stress caused by the heat transfer between combustion gas and wall, and the mechanical stress caused by the pressure change in the flow, should be considered first. In this connection, this study investigated the safety, as a point of view of stress and melting point of the material, of the pre-designed thrust generating structure which is subjected to high temperature and pressure as a function of motor operating time.

• Food Science and Biotechnology
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• v.18 no.1
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• pp.249-252
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• 2009

Two-dimensional gel electrophoresis (2-DE) was employed to assess the thermo-tolerance characteristics of Bifrdobacterium infantis ATCC 27920 to mild heat adaptation. When exposed to various heat levels, pH, and hydrogen peroxide ($H_2O_2$) stress conditions, B. infantis ATCC 27920 exhibited high level of stress resistance. Under mild-heat treatment ($46^{\circ}C$), no significant change in viability level was observed after 2 hr. Interestingly, improved viability was observed in mild-heat adapted ($46^{\circ}C$ for 1 hr) cultures exposed to $55^{\circ}C$, in comparison to control experiments. Viability was not affected by pH, bile, and $H_2O_2$ stress conditions. 2-DE analysis revealed those mild-heat adaptation up-regulated 4 proteins and down-regulated 3 proteins. Among these protein spots, isopropyhnalate dehydratase (leuD), glycosyltransferase (glgA), and ribosomal protein L5 (rp1E) were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALD1-TOF/MS).

• 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.

• Journal of Applied Biological Chemistry
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• v.64 no.2
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• pp.141-151
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• 2021

Insects affect crop harvest yield and quality, making plant response mechanisms to insect herbivores a heavily studied topic. However, analysis of plant responses to honeybees is rare. In this study, comprehensive metabolic profiling of Arabidopsis thaliana exposed to honeybees was performed to investigate which metabolites were changed by the insect. A total of 85 metabolites-including chlorophylls, carotenoids, glucosinolates, policosanols, tocopherols, phytosterols, β-amyrin, amino acids, organic acids, sugars, and starch-were identified using high performance liquid chromatography, gas chromatography-mass spectrometry, and gas chromatography-time-of-flight mass spectrometry. The metabolite profiling analysis of Arabidopsis exposed to honeybees showed higher levels of stress-related metabolites. The levels of glucosinolates (glucoraphanin, 4-methoxyglucobrassicin), policosanols (eicosanol, docosanol, tricosanol, tetracosanol), tocopherols (β-tocopherol, γ-tocopherol), putrescine, lysine, and sugars (arabinose, fructose, glucose, mannitol, mannose, raffinose) in Arabidopsis exposed to honeybees were higher than those in unexposed Arabidopsis. Glucosinolates act as defensive compounds against herbivores; policosanols are components of plant waxes; tocopherols act as an antioxidant; and putrescine, lysine, and sugars contribute to stress regulation. Our results suggest that Arabidopsis perceives honeybees as a stress and changes its metabolites to overcome the stress. This is the first step to determining how Arabidopsis reacts to exposure to honeybees.

• Journal of the Korea Institute of Military Science and Technology
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• v.26 no.1
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• pp.1-9
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• 2023

The skin structure of sensor pod mounted on the exterior of aircraft can be exposed to the acoustic dynamic load and static load such as aerodynamic pressure and inertial load during flight. Fatigue life prediction of structural model under acoustic load should be performed and also differential stiffness of model modified by static load should be considered. The acoustic noise test spectrum of MIL-STD-810G was applied to the structural model and the stress response power spectral density (PSD) was calculated. The frequency response analysis was performed with or without prestress induced by inplane static load, and the response spectrum was compared. Time series data was generated using the calculated PSD, and the time and frequency domain fatigue life were predicted and compared. The variation of stress response spectrum due to static load and predicted fatigue life according to the different structural model considering mean stress were examined and decreasing fatigue life was observed in the model with prestress of compressive static load.

• Journal of Life Science
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• v.31 no.7
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• pp.671-676
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• 2021

A cDNA encoding the protein lethal (2) essential for life [l(2)efl] was cloned from Gryllus bimaculatus and named GBl(2)efl. This protein is composed of 189 amino acids, including an N-glycosylation site and 15 phosphorylation sites. Its predicted molecular mass is 21.19 kDa, with a theoretical isoelectric point of 6.2. The secondary structure of GBl(2)efl was predicted from the identification of random coils (56.08%), alpha helices (22.22%), extended strands (17.99%), and beta turns (3.7%) through sequence analyses. A homology analysis revealed that GBl(2)efl exhibited a high similarity with other species at the amino acid level, ranging from 52% to 69%. While GBl(2)efl mRNA expression was higher in the dorsal longitudinal flight muscle following a three-day starvation and in the Malpighian tubules following a one-day starvation, no changes in expression were detected in other tissues. Furthermore, tunicamycin-induced endoplasmic reticulum (ER) stress resulted in an approximately 1.8-fold higher expression in the fat body compared with the wild type.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.12
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• pp.1281-1286
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• 2015

Fatigue cracks can be generated in aircraft as a result of the cumulative time spent during flight operations, which can extend for long periods of time and cover a variety of missions. If a crack occurs in an aircraft's main spar, it can generate many problems, including a lift time reduction. To solve this problem, it was necessary to perform an analysis of fatigue crack growth in the fatigue critical locations. Much time and expense is involved in generating the stress needed for a crack propagation analysis over a long period of time to obtain the amount of data required for an actual aircraft. In this paper, an algorithm is developed that can calculate the spectrum of stress over a long period of time for a mission by the Southwest Research Institute, which is based on the short-time load factor data produced using the peak-valley cycle counting method.