• Transactions of Materials Processing
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• 제20권2호
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• pp.173-178
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• 2011

Environmental Stress Cracking(ESC) is one of the most common causes of unexpected brittle failure of thermoplastic polymers. The exposure of polymers to liquid chemicals tends to accelerate the crazing process, initiating crazes at stresses that are much lower than the stress causing crazing in air. In this study, ESC of acrylonitirile butadiene styrene(ABS) was investigated as a function of the molding conditions such as injection velocity, packing pressure, and melt temperature. A constant strain was applied to the injection molded specimens through a 1.26% strain jig and a mixture of toluene and isopropyl alcohol was used as the liquid chemical. In order to examine the effects of the molding conditions on ESC, an experimental design method was adopted and it was found that the injection velocity was the dominant factor. In addition, predictions from numerical analyses were compared with the experimental results. It was found that the residual stress in the injection molded part was associated with the environmental stress cracking resistance (ESCR).

• Tribology and Lubricants
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• 제16권2호
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• pp.138-143
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• 2000

The sealing performance of an elastomeric O-ring seal with a temperature gradient has been analyzed for the contact stress behaviors that develop between the O-ring seal and the housing surfaces with which it comes into contact in the dovetail groove. The leakage of an O-ring seal will occur when the pressure differential across the seal just exceeds the initial peak contact stress. The contact stress behaviors that develop in compressed O-rings, in common case of restrained geometry (grooved), are investigated using the finite element method. The FE analysis includes material hyperelasticity and axisymmetry The computed FEM results show that the contact stress behaviors are related to a compression rate and a temperature gradient between the vacuum chamber with a dovetail groove and the contacting plate with a cooling jacket.

• Journal of the Korean Society for Precision Engineering
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• 제15권11호
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• pp.227-232
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• 1998

The purpose of this study is to develop a numerical method for analyzing the transient heat transfer and evaluating the residual stress. The analysis of heat transfer and thermal stress are carried out by three-dimensional finite element method. Thermal spraying is one of the most common surface coating techniques to be used for many applications. In order to improve the mechanical properties of flame-sprayed ceramic coating layer, the accurate and effective analysis of heat transfer and thermal stress is essentially required.

• Korean Security Journal
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• 제6호
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• pp.255-272
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• 2003

The purpose of this research is to find relationships between safeguards' personality traits and stress coping behaviors. The findings then could provide data to adapt safeguards to their duties. For that, personality traits such as sociability, stability and stress coping behaviors and the effects were investigated. In addition, cognitive aspects which were known to influence stress coping behaviors were appraised. The findings of this research are as follows, First, regarding personality traits and stress coping behaviors, the unstable and unsocial group used the emotion-focused coping style more than the stable and social group. The two groups didn't show any significant differences in the problem-focused coping style. The A-type group used both the problem-focused style and the emotion-focused style more than the B-type group. The common characteristic of the unstable, the unsociable and the A-type groups was the heavy use of avoidance behaviors of the emotion-focused coping style. Second, In the correlation between the personal traits and the stress coping effects regarding adaptability, the stability influenced stress coping effects. Third, regarding the personality traits, the coping styles and the coping effects, A-type group showed high correlation with the sociability but not with the stability. The problem-focused coping style showed high correlation with the emotion-focused style. Fourth, the cognitive appraisal on the stress causes influenced the stress coping styles but not the stress coping effects. Fifth, the cognitive appraisal on the same stress causes didn't show any significant differences among the personality traits.

• The Korean Journal of Physiology and Pharmacology
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• 제22권5호
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• pp.567-575
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• 2018

Acute kidney injury (AKI), which is defined as a rapid decline of renal function, becomes common and recently recognized to be closely intertwined with chronic kidney diseases. Current treatment for AKI is largely supportive, and endoplasmic reticulum (ER) stress has emerged as a novel mediator of AKI. Since carbon monoxide attenuates ER stress, the objective of the present study aimed to determine the protective effect of carbon monoxide releasing molecule-2 (CORM2) on AKI associated with ER stress. Kidney injury was induced after LPS (15 mg/kg) treatment at 12 to 24 h in C57BL/6J mice. Pretreatment of CORM2 (30 mg/kg) effectively prevented LPS-induced oxidative stress and inflammation during AKI in mice. CORM2 treatment also effectively inhibited LPS-induced ER stress in AKI mice. In order to confirm effect of CO on the pathophysiological role of tubular epithelial cells in AKI, we used mProx24 cells. Pretreatment of CORM2 attenuated LPS-induced ER stress, oxidative stress, and inflammation in mProx24 cells. These data suggest that CO therapy may prevent ER stress-mediated AKI.

• Journal of Power Electronics
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• 제16권6호
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• pp.2258-2271
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• 2016

In this paper, some crucial performance characteristics related to the operational reliability of the post-fault Pulse Width Modulated (PWM) rectifiers, such as line current harmonic distortion, Common Mode Voltage (CMV), and current stress on the capacitors, are fully investigated. The aforementioned performance characteristics of post-fault rectifiers are highly dependent on the utilized space vector modulation (SVM) schemes, which are also examined. Detailed analyses of the three most commonly used SVM schemes for post-fault PWM rectifiers are provided, revealing the major differences in terms of the zero vector synthesis approaches. To compare the performances of the three SVM schemes, the operating principles of a post-fault rectifier are presented with various SVM schemes. Using analytical and numerical methods in the time domain, the performances of the line current distortion, common mode voltage and capacitor current are evaluated and compared for each SVM scheme. The proposed analysis demonstrates that the zero vector synthesis approaches of the considered methods have significant impacts on the performance characteristics of rectifiers. In addition, the advantages and disadvantages of the proposed SVM schemes are discussed. The experimental results verify the effectiveness and validity of the proposed analysis.

• Safety and Health at Work
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• 제6권4호
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• pp.263-267
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• 2015

Significant changes in the past year have taken place in the world of work that are bringing new challenges with regard to employee safety and health. These changes have led to emerging psychosocial risks (PSRs) at work. The risks are primarily linked to how work is designed, organized, and managed, and to the economic and social frame of work. These factors have increased the level of work-related stress and can lead to serious deterioration in mental and physical health. In tackling PSRs, the European labor inspectorates can have an important role by enforcing preventive and/or corrective interventions in the content and context of work. However, to improve working conditions, unilateral interventions in the context and content of work are insufficient and require adopting a common strategy to tackle PSRs, based on a holistic approach. The implementation of a common strategy by the European Labor Inspectorate for tackling PSRs is restricted by the lack of a common legislative frame with regard to PSR evaluation and management, the different levels of labor inspectors' training, and the different levels of employees' and employers' health and safety culture.

• Journal of the Korean Home Economics Association
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• 제39권9호
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• pp.27-48
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• 2001

The objective of this study was to develop the stress coping program for pregnant adolescent to alleviate the stress levels and symptoms, and to cope with the stress adequately. The program of this study was based on the cognitive-behavioral theory and the stress management. The program was done twice a week totally 8 times and preview meeting was done 1 week before the program and follow-up was formed 4 weeks after finishing the program. one-group pretest-posttest design was held and the group was 13. In case of qualitative research, the content of discussion in the course of group process, investigation, and the materials which were made from the group members were classified and analysed to the objects of program. first, the common change of members was reduction of stress levels by attending stress management program. Second, the coping skills for stress were verified and improved. More than one new coping skills were acquired such as positive re-evaluation, persuasion, self-talk, I-message communication method, assertive self-expression, and problem settlement. Third, the group members admitted their irrational beliefs and partially had a change of it. The implications for the future practice are discussed.

• Journal of Haehwa Medicine
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• 제15권1호
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• pp.111-115
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• 2006

Tension headache is one of the most common form of headache. It may occur at any age, but is most common in adult and adolescents. One cause of this muscle contraction is a response to stress that induces changes and imbalance on autonomic nerve system. To cure tension headache, getting rid of psychological stress and anxiety have to do first. In this case, we described a 42 years old woman who diagnosed as tension headache. She complained headache with scruff pain, dyspepsia, nausea and coldness of toes. through oriental medical treatment(for example, acupuncture, herbal medicine ect.), her condition was improved.

• Journal of Power System Engineering
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• 제10권4호
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• pp.90-98
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• 2006

본 연구에서는 체철공장에서 래이들 카의 매우 높은 열에 주기적으로 빈번히 노출되는 공동가대의 열적 피해에 대한 체계적인 평가를 수행하였다 먼저 실험과 함께 유한요소법을 사용한 열해석이 수행되었다. 기존 공동가대와 향후 설치될 신 공동가대 모두에 대한 적합한 기준을 검증하기위하여 가장 심각한 상태에 대한 열평가가 포함되었다. 또한 공동가대에 적합한 방열판의 설계를 위하여 실험결과에 근거한 수치해석이 사용되었다. 마지막으로 새로 설치될 공동가대의 안전성과 내구성을 평가하기위한 피로해석을 수행하였다. 6m 신형공동가대의 열응력해석 및 피로해석 결과 기존 공동가대보다는 취약하나 설치 및 사용에는 문제가 없음을 확인하였다.