• Steel and Composite Structures
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• 제38권3호
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• pp.271-280
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• 2021

In this study, the fatigue property of U rib-to-crossbeam connections in orthotropic steel bridge (OSB) crossbeams under heavy traffic vehicle load was investigated considering the effects of in-plane shear stress. The applicability of an improved structural stress (ISS) method was validated for the fatigue behavior analysis of nonwelded arc-shaped cutout regions in multiaxial stress states. Various types of fatigue testing specimens were compared for investigating the equivalent structural stress, fatigue crack initiation positions, and failure modes with the unified standards. Furthermore, the implications of OSB crossbeams and specified loading cases are discussed with respect to the improved method. The ISS method is proven to be applicable for analyzing the fatigue property of nonwelded arc-shaped cutout regions in OSB crossbeams. The used method is essential for gaining a reliable prediction of the most likely failure modes under a specific heavy traffic vehicle load. The evaluated results using the used method are proven to be accurate with a slighter standard deviation. We obtained the trend of equivalent structural stress in arc-shaped cutout regions and validated the crack initiation positions and propagation directions by comparing them with the fatigue testing results. The implications of crossbeam spans on fatigue property are less significant than the effects of crossbeams.

• 화약ㆍ발파
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• 제30권1호
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• pp.1-8
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• 2012

본 연구에서는 충격 하중을 받은 콘크리트 재료의 내부 주응력 변화를 확인하기 위하여 Visual FEA 유한요소 프로그램으로 콘크리트 재료의 단면을 모델링하여 절점에서의 최대주응력을 분석하였다. 결과적으로, 콘크리트 재료의 탄성계수가 작을수록 최대주응력은 증가하는 것으로 나타났고, 콘크리트 재료의 물성 변화에 따라 최대주응력 편차는 2~3배 차이를 나타냈다.

• Journal of Welding and Joining
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• 제22권3호
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• pp.45-49
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• 2004

Generally, it is used the compensation spring to compensate the inaccuracy of screen image induced by thermal deformation in CRT monitor. Its mechanism is hi-metallic system made of heterogeneous metals and these springs are bonded by laser welding. But laser welding induces a non-uniform temperature distribution, and residual stress is yielded locally by these temperature deviation. Therefore, this study measures the curvature constant to assess functions of the compensation spring of shadow mask with respect to increment temperature and estimates the effect of residual stress on the performance of tri-metal used to compensation spring.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.229-230
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• 2023

In this study, the hydration heat differential method was applied to mass concrete structures, and the hydration heat analysis was compared and analyzed with on-site measurement results. The results showed that the temperature history measurements of mass concrete were managed at a difference of 8.4 ℃, and although there was some deviation in thermal stress, a similar trend was observed. Consequently, it was determined that the thermal stress on the surface of mass concrete is less than its tensile strength, which would prevent the occurrence of thermal cracks.

• 설비공학논문집
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• 제27권11호
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• pp.596-602
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• 2015

In this study, experiments using bioelectronic signals and questionnaire surveys were carried out in learning conditions when temperatures changed from low- and high-uncomfortable to comfortable. As a result, the stress factor Photoplethysmography (PPG) decreased, while the Root Mean Square of Standard Deviation (RMSSD) of PPG increased when the indoor temperature was changed from low- or high-uncomfortable to comfortable. Additionally, the absolute power of the ${\alpha}$-wave in the brain increased. According to the analysis of the association between the questionnaire and bioelectronic signals, the standard deviation of the stress factor as measured by pulse was closely related to the result of the thermal sensation questionnaire. In addition, it was found that the concentration on studying improved under comfortable temperatures when compared to uncomfortable temperatures.

• 한국안전학회지
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• 제19권4호
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• pp.123-128
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• 2004

This study investigated effect of arm posture, repetition of wrist motion and external load on perceived discomfort. The arm postures were controlled by shoulder flexion, elbow flexion, and ist motions such as flexion, extension, radial deviation and ulnar deviation. An experiment was conducted to measure discomfort scores for experimental treatments using the magnitude estimation, in which the L16 orthogonal array was adopted for reducing the size of experiment. The results showed that while the effect of the shoulder flexion, repetition of wrist motion and external load was statistically significant at $\alpha=0.05$or 0.10, that of the elbow and wrist motions was not. Discomfor ratings increased linearly as levels of wrist repetition and external load increased. This implies that the existing posture classification schemes such as OWAS, RULA, which do not properly consider effect of motion repetition and external load, may underestimate postural load. Based on the regression equation for wrist repetition and external load, isocomfort region indicating the region within which discomfort scores were expected to be the same was proposed. It is recommended that when assessing risk of postures or developing new posture classification schemes, motion repetition and external load as well as posture itself be fully taken into consideration for precisely evaluating postural stress.

• 대한간호학회지
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• 제26권4호
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• pp.963-975
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• 1996

The purpose of this study was to call attention to the mental, physical and occupational hazards of the anticancer-drug-handling nurses by examining the possible urinary mutagenicity and measuring physical symptoms and stress level of the nurses exposed to anticancer drugs. The experimental group of the urinary mutagenicity assay was 14 nurses handling anticancer drugs at the medical wards of a hospital located in J city ; the control group was 12 psychiatric nurses of the same hospital. The test material was the nurses' 24hrs urine, which was concentrated by XAD-2 column chromatography. Tester strains were TA98(±S9 mix), TA100(±S9 mix), TA1535(±S9 mix) and TA1537(±S9 mix) ; Salmonella mammalian-microsomal test(Ames test) was employed for the urinary mutagenicity assay. The physical symptoms of which the nurses experienced were investigated through self-reports on open-questionnaires. The stress levels of the experimental group were measured by a stress measuring instrument developed by this author. Reliability of this instrument was found to be adequate (Cronbach's Alpha=0.9079). To ascertain the urinary mutagenicity of the experimental group, the mean and the standard deviation of the colonies of Tester strains appearing on the minimal plates were taken and compared differences between two groups. T-test was employed for the significance test of two groups. The physical symptoms were compared between the two groups through the analysis of the nurse' self-reports. The mean and standard deviation of the stress levels of the experimental group were also calculated and were examined through t-test. The results were summarized as follows : 1. The experimental group revealed significantly higher urinary mutagenicity both in the activation method test and the non-activation method test of the tester strains TA98, TA100 and TA1535. In the case of TA1537, two groups showed no difference in the non-activation method test, but the activation method revealed difference. 2. The physical symptoms were also much more frequently reported in the experimental group. 79.3% of the experimental group reported more than 1 kind of physical symptoms. On the other hand, 33.2% of the control group complained of 1 kind of physical symptom. The items with high symptom frequency were 'headache', 'itching sensation', 'corneal congestion', 'skin allergy' 3. The mean score of stress in the experimental group was 2.41(range 1-4). The experimental group showed the stress level above 2.0 in the 14 of 15 items in all. The highest stress level were recorded in the following items in the order quoted, 'I fear that anticancer drug may touch any part of body while handling it.', 'I feel concerned there is no protective countermeasure against anticancer drug handling.', 'I am afraid the anticancer drug handling may produce a fetal loss in the future'.

• Child Health Nursing Research
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• 제12권4호
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• pp.470-477
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• 2006

Purpose: The purpose of this study was to identify the relationship among stress, physical symptoms and coping styles of high school students. Methods: In this study, 356 second grade high school students (male 181, female 175) from two schools, which were located in Dae-gu city, participated in the study. Mean scores with standard deviation, T-test, ANOVA, Pearson's Correlation Coefficient were used to analyze the data. Analysis was done using the SPSS/PC program. Results: The stress level of high school students averaged 2.59 out of a possible score range between 1 and 5, and physical symptoms, 2.38. The average level for coping styles was 1.36 of a possible range between 0 and 3. The correlations between stress and physical symptoms (r=.506), between physical symptoms and coping styles (r=.304) and between stress and coping styles (r=.363) were all significant. Conclusions: To guide the high school health program, we must try to understand the traits of the students and make efforts to identify personal and concrete difficulties in coping. Therefore it is necessary to use a stress care program to systematically improve their health.

• 대한기계학회논문집A
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• 제33권1호
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• pp.72-81
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• 2009

This paper provides simulational round robin test results for welding residual stress prediction of safety/relief nozzle. To quantify the welding variables and define the recommendation for prediction and determination of welding residual stress, 6 partners in 5 institutes participated in round robin test. It is concluded that compressive axial and hoop residual stress occurs in dissimilar metal weld and pre-existing residual stress distribution in dissimilar metal weld was affected by similar metal weld due to short length of safe end. Although the reason for the deviation among the results was not pursued further, the effect of several key elements of FE analyses on welding residual stress was investigated in this paper.

• 한국직업건강간호학회지
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• 제26권1호
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• pp.47-54
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• 2017

Purpose: The purpose of the study is to examine the impact of job stress on the patient safety nursing activities among nurses. Methods: The subjects of the study are 258 nurses working at 15 small-medium sized hospitals in D city. Data analysis was done using frequency, percentage, average and standard deviation, t-test, one-way ANOVA, $Scheff{\acute{e}}test$, Pearson's correlation coefficient, stepwise multiple regression. Results: The job stress scored average 3.67 and patient safety nursing activity scored average 4.35. Job stress was positively associated with patient safety nursing activity. It explains 9.49% of the variance. Conclusion: Universal and inevitable job stress among nurses should not exceed optimum level to assure patient safety. So, personal and organizational efforts to manage job stress are needed.