• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.3
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• pp.178-185
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• 2005

Crack tip displacement is originated by tensile stress component, s and shear stress component, t on pure Mode I and pure Mode II. The crack tip displacement(CTD) depends on combined types of different two stress components under mixed-mode loading conditions (MMLC). Thus, the analysis of crack tip displacement must be CTD vector, dv which is composition of ds and dt under MMLC. In this paper, various effects of MMLC on the crack closure are studied experimentally. The crack closure magnitude is calculated from the information of crack tip displacement under MMLC. This information has been obtained from the high resolution optical microscope in direct observations of crack displacement behavior at the crack tip. Observed crack tip displacement is analyzed by using CTD vector to determine crack opening load. The various effects of MMLC on the crack closure are explained using crack opening ratio with crack length and mode mixture. The effective stress intensity factor considering crack closure is also discussed.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.2
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• pp.80-89
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• 1996

Fatigue life of a notched shaft was evaluated in order to estimate the durability and integrity of the notched shaft in design stage. Cumulative fatigue dama- ge analysis was performed using local strain approach based on the assumption that the fatigue life of a notched component is approximately same as that of a smooth specimen is subjected to the same strain at the notched component. In this paper, shafts with different notch root radius of 1, 2㎜ resulting in different values of stress concentration factors were tested under||rotating bending fatigue loading condition. Theoretical stress concentration factor for each notch type was calculated using finite element method. Fatigue life prediction program, FALIPS, written in C language was developed using the strain-life curve, and the local strain approach integrating Neuber's rule, cyclic stress-strain, and hysteresis loop equations. The fatigue life evaluated using the fatigue notch factor obtained from the experimentally determined fatigue strength showed very large scattering with nonconservatism, but the fatigue notch factors derived from the stress concentration factors and Peterson's equation reduced the considerablely accurate fatigue life evaluation within a factor of three.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.5
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• pp.51-59
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• 2016

STS 321 stainless steel is generally used for a material of high-temperature and high-pressure system including liquid rocket engine. The constitutive equation for flow stress has been suggested using thermal stress component and athermal stress component based on Kocks dislocation barrier model to predict 321 stainless steel's deformation behavior at elevated temperature. The suggested model predicted well the material deformation behaviors of 321 stainless steel at the wide temperature range from room temperature to $500^{\circ}C$.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.2
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• pp.304-309
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• 2015

Applicable range of Photoplethysmography (PPG) becomes wider as a non-invasive physiological measurement technique. However, PPG waveform is easy to be distorted by ambient light or vascular variation from temperature changes. Especially, irregular variation of PPG waveform caused by ambient temperature not only severely distorts the PPG, but also leads miss interpretation in clinical applications. Therefore, the investigation of between temperature and PPG waveform is quite important in using PPG. The purpose of this research is to quantify the PPG waveform characteristic and to investigate the waveform variation following the temperature change on measuring site. To quantify the fluctuation of PPG waveform, we use two techniques; detrended fluctuation analysis (DFA) and AC/DC analysis of PPG. We record PPG under temperature stress, which applied by medical use heat pack ($40^{\circ}C$) and ice pack ($0^{\circ}C$). Ten participants were applied to the experiment, and the result was evaluated to approve the temperature effect with statistical method, Wilcoxon signed rank test. The result shows that the AC component (p<0.05) and perfusion index DFS scale exponent (p<0.01) of PPG have the significance to temperature stress except for a DC component of PPG.

• Fisheries and Aquatic Sciences
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• v.22 no.5
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• pp.9.1-9.7
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• 2019

The study investigated the changes in growth performance, hematological parameters, plasma components, and stress indicators of juvenile starry flounder, Platichthys stellatus, depending on varying exposure to hexavalent chromium. P. stellatus was exposed to waterborne chromium at 0, 50, 100, 200, and 400 ppb for 4 weeks. The result showed that Cr exposure resulted in decreased daily length gain (DLG), daily weight gain (DWG), condition factor (CF), and hepatosomatic index (HIS) in P. stellatus. In terms of hematological parameters, red blood cell (RBC) count, hematocrit (Ht), and hemoglobin (Hb) significantly decreased at 400 ppb after 2 weeks. In terms of plasma components, inorganic analysis was unchanged and cholesterol, an organic component, considerably increased at 400 ppb after 4 weeks. Plasma enzyme components including glutamic oxalate transaminase (GOT) and glutamic pyruvate transaminase (GPT) were significantly increased. Stress indicators such as cortisol and glucose were notably increased over 100 ppb after 4 weeks with increasing chromium concentration. The results indicate that exposure to waterborne Cr induced toxic effects on growth, hematological parameters, plasma components, and stress indicators.

• Korean Journal of Occupational Health Nursing
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• v.28 no.2
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• pp.94-103
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• 2019

Purpose: This study aimed to investigate variables affecting health-related quality of life of manufacturing industry workers. Methods: We used data from 200 survey questionnaires collected from a vehicle manufacture factory located in Ulsan metropolitan area. The participants were manufacturing workers. The data were analyzed using t-test, one-way analysis of variance, and $Scheff{\acute{e}}^{\prime}s$ test to identify differences among variables. Pearson's correlation coefficient and stepwise multiple regression were used to identify variables that affected health-related quality of life. Results: The findings revealed that occupational stress and quality of sleep were statistically significant variables of the physical component score with an explanatory power of 42.2%. Occupational stress, depression, and religion were statistically significant variables of the mental component score with an explanatory power of 43.3%. Conclusion: Continuous monitoring and appropriate intervention for occupational stress, quality of sleep, and depression are needed to improve manufacturing workers' health-related quality of life.

• Nuclear Engineering and Technology
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• v.56 no.5
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• pp.1863-1873
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• 2024

In the Korean domestic nuclear industry, to analyze the reliability of instrumentation and control (I&C) systems, the failure rates of the electronic components constituting the I&C systems are predicted based on the MIL-HDBK-217F standard titled 'Reliability Prediction of Electronic Equipment'. Based on these predicted failure rates, the mean time to failure of the I&C systems is calculated to determine the replacement period of the I&C systems. However, this conventional approach to the prediction of electronic component failure rates assumes that factors affecting the failure rates such as ambient temperature and operating voltage are static constants. In this regard, the objective of this study is to propose a prediction method for the remaining useful life (RUL) of electronic components considering mean time to failure calculations reflecting dynamic environments, such as changes in ambient temperature and operating voltage. Results of this study show that the RUL of electronic components can be estimated depending on time-varying temperature and electrical stress, implying that the RUL of electronic components can be predicted under dynamic stress conditions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.3
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• pp.341-346
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• 2010

The effect of specimen geometry on the bending and tensile strengths of dissimilar joints ($\beta-Si_3N_4/S45C$) with copper interlayers was evaluated. The average bending strength of specimens with circular cross sections was higher than that of specimens with rectangular cross sections. The crack initiation stress ($\sigma_i$) was successfully determined by the acoustic emission (AE) method and was approximately 60~80% of the bending strength. The residual stresses near the interfaces on the ceramic side were measured by X-ray diffraction before conducting the bending test. The bending strength and the crack initiation stress decreased with an increase in the residual stresses. The effect of the bending strain component was evaluated by the tensile testing; the tensile strength decreased with an increase in the bending strain component and was approximately 80% of the bending strength.

• The Journal of Advanced Prosthodontics
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• v.6 no.5
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• pp.361-371
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• 2014

PURPOSE. In case of large horizontal discrepancy of alveolar ridge due to severe resorption, cantilevered crown is usually an unavoidable treatment modality. The purpose of this study was to evaluate the clinical criteria for the placement of the aforementioned implant crown. MATERIALS AND METHODS. The mandible model with 2 mm thick cortical bone and cancellous bone was fabricated from CT cross-section image. An external connection type implant was installed and cantilevered crowns with increasing offset of 3, 4, 5, 6, and 7 mm were connected. Vertical load and $30^{\circ}$ oblique load of 300 N was applied and stress around bone and implant component was analyzed. A total of 14 cases were modeled and finite element analysis was performed using COSMOS Works (Solid works Inc, USA). RESULTS. As for the location of the vertical load, the maximum stress generated on the lingual side of the implant became larger according to the increase of offset distance. When the oblique load was applied at $30^{\circ}$, the maximum stress was generated on the buccal side and its magnitude gradually decreased as the distance of the offset load increased to 5 mm. After that point, the magnitude of implant component's stress increased gradually. CONCLUSION. The results of this study suggest that for the patient with atrophied alveolar ridge following the loss of molar teeth, von-Mises stress on implant components was the lowest under the $30^{\circ}$ oblique load at the 5 mm offset point. Further studies for the various crown height and numbers of occusal points are needed to generalize the conclusion of present study.

• International Journal of Fluid Machinery and Systems
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• v.4 no.4
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• pp.387-395
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• 2011

Single-blade centrifugal pumps are widely used as sewage pumps. However, the impeller of a single-blade pump is subjected to strong radial thrust during pump operation because of the geometrical axial asymmetry of the impeller. Therefore, to improve pump reliability, it is necessary to quantitatively understand radial thrust and elucidate the behavior and mechanism of thrust generating. This study investigates the radial thrust acting up on a single-blade centrifugal impeller by conducting experiments and CFD analysis. The results show that the fluctuating component of radial thrust increases as the flow rate deviates from the design flow rate to low or high value. Radial thrust was modeled by a combination of three components, inertia, momentum, and pressure by applying an unsteady conservation of momentum to the impeller. The sum of these components agrees with the radial thrust calculated by integrating the pressure and the shearing stress on the impeller surface. The behavior of each component was shown, and the effects of each component on radial thrust were clarified. The pressure component has the greatest effect on the time-averaged value and the fluctuating component of radial thrust. The time-averaged value of the inertia component is nearly 0, irrespective of the change in the flow rate. However, its fluctuating component has a magnitude nearly comparable with the pressure component at a low flow rate and slightly decreased with the increase in flow rate.