• Fisheries and Aquatic Sciences
• /
• 제22권5호
• /
• pp.9.1-9.7
• /
• 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.

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

• 산업경영시스템학회지
• /
• 제39권4호
• /
• pp.117-124
• /
• 2016

Stress is resistance to stimuli to destroy a balance of mind and body in order to maintain an original steady state : A type of response and avoidance. Mild stress, which happens in tension, has a positive effect to improve concentration, but most of stress is likely to be a main factor to damage health. This is because it causes physical ailments and psychological diseases (e.g., depression, anger, frustration, loneliness, and anxiety). The purpose of this study is to analyze the difference between two groups, daytime and night university students, on ego-state, stressors, and stress coping types to improve their academic achievement by reducing their stress. There were 266 university students, who participated in a survey from November 30, 2015 until September 30, 2016. The study employed three measuring instruments : Ego-gram, stressor scale, and stress coping type scale. All the collected data were analyzed through regression analysis and t-test. The results of the regression analysis showed no significant differences in ego-state, stressors, and stress coping types between two groups. However, the results of t-test showed significant difference between the two groups : In terms of ego-state, a CP (Critical Parent) average of the night university students was significantly higher than the daytime university students'. Also, there is a significant difference in employment, future issues, and economic issues : the daytime university students considered employment and future issues more serious, while the night university students had more mental burdens of economic issues. When it comes to coping stress types, there was no significant difference between the two groups.

• 국제물리치료학회지
• /
• 제5권2호
• /
• pp.723-729
• /
• 2014

The purpose of this study is to understand the relationship between female college students' stress level and premenstrual syndrome so that it can provide baseline data on how to cope with the syndrome. The study subjects are 250 female college students in Gyungbook area. This study chose 199 appropriate subjects and collected data. As per general menstrual phases, this study investigated the age when one had her first period, regularity and duration of period, and amount of bleeding. It used a measurement tool to measure stress level and premenstrual syndrome. Most of the subjects experienced their first period before the age of 13. The menstrual period was irregular with the duration of less than 7 days. 123 subjects had normal amount of bleeding. 121 subjects were experiencing high level of stress over 2.4. The correlation between the level of stress and premenstrual syndrome factors showed significant static correlation for each factor. Especially, the correlation between digestive system and response of autonomic nervous system was .996 and negative emotion and behavioral change was .635, and negative emotion and pain was .614 which were relatively high. The regression analysis of factors of premenstrual syndrome depending on the subjects' stress level indicated that response of autonomic nervous system had the biggest effect in the low stress group while behavioral change, negative emotion, pain, decreased concentration, water congestion, response of autonomic nervous system, and skin change had the biggest effect in the high stress group with statistical significance. Based on the result, it can be said that higher premenstrual stress is closely related to the premenstrual syndrome one experiences for some female college students.

• 대한한의학방제학회지
• /
• 제27권2호
• /
• pp.121-136
• /
• 2019

Objective : To investigate the effect of sihogayonggolmoryeotang (SY) on Single Prolonged Stress(SPS)-induced Post Traumatic Stress Disorder(PTSD). Method : To confirm the effects of SY on SPS-induced PTSD, Changes in body weight, sucrose intake open field test(OFT) and forced swimming test(FST)were observed. After behavioral tests, the plasma corticosterone(CORT) from the abdominal aorta, serotonin(5-HT) from prefrontal cortex, hippocampus, amygdala and striatum, norepinephrine(NE) and dopamine(DA) from hippocampus was measured by ELISA. mRNA expression of brain-derived neurotrophic factor(BDNF) and cAMP response element-binding protein(CREB) in hippocampus was measured by RT-PCR. Result : Weight change and sucrose intakes of rats in 14th day after the administration of SY were significantly increased in the SPS + SY450 group compared to the SPS group (p<0.05). Numbers of crossing in the central zone in the OFT were significantly increased in the SPS + SY450 group (p<0.05) compared with the SPS group. The immobility time of FST was significantly decreased in SPS + SY450 group compared with SPS group (p<0.05). The change of plasma CORT concentration was significantly decreased in SPS + SY450 group compared with that in SPS group (p<0.05). The change of 5-HT concentration was significantly increased in the SPS + SY450 group at hippocampus and amygdala compared with the SPS group (p<0.05). The concentration of DA was significantly increased in the SPS + SY450 group compared with the SPS group (p<0.05). The expression of BDNF and CREB were significantly increased in SPS + SY450 group compared with the SPS group (p<0.05). Conclusion : SY administration lowered the increase of CORT caused by PTSD and increases the 5-HT concentration and reversed the decreased expression of NE and DA and BDNF and CREB by PTSD. It is postulated that SY is effective in treating PTSD by restoring cognitive function, memory impairment, unstable emotional disturbances.

• 한국강구조학회 논문집
• /
• 제10권3호통권36호
• /
• pp.497-508
• /
• 1998

본 연구에서는 평면결함의 일종인 용입부족의 크기가 맞대기 용접부의 피로 특성에 미치는 영향을 정량적으로 규명하였다. 정적실험 결과 비드를 삭제하지 않은 맞대기 용접부의 인장강도와 항복강도는 용입부족 크기에 관계없이 일정하였다. 또한 피로실험 결과 완전용입된 맞대기 용접부의 피로강도는 국내 외의 시방서에서 규정하고 있는 피로 등급을 모두 만족하며, 용입부족 크기에 따른 피로강도의 저하는 용입부족 크기가 증가함에 따라 피로강도가 급격하게 감소하였다. 파단형태에서 완전용입 시험체와 용입부족 시험체의 파단형태가 서로 다른 형식을 취하고 있음을 알 수 있었는데 이는 용접지단부와 용접루트부의 기하학적 형상에 따른 응력집중계수의 변화에 기인하는 것을 유한요소해석에서 확인하였다. 따라서 강구조물에 대한 용접제작시 발생할 수 있는 용접결함 중 평면결함의 일종인 용입부족은 반드시 피해야만 강구조물의 공용수명을 충분히 확보할 수 있을 것이다.

• Structural Engineering and Mechanics
• /
• 제53권5호
• /
• pp.881-896
• /
• 2015

In this study, a method for fatigue performance estimation of deepwater steel catenary riser (SCR) under short-term vortex-induced vibration was investigated for selected S-N curves. General tendency between S-N curve capacity and fatigue performance was analysed. SCRs are generally used to transport produced oil and gas or to export separated oil and gas, and are exposed to various environmental loads in terms of current, wave, wind and others. Current is closely related with VIV and it affects fatigue life of riser structures significantly. In this regards, the process of appropriate S-N curve selection was performed in the initial design stage based on the scale of fabrication-related initial imperfections such as welding, hot spot, crack, stress concentration factor, and others. To draw the general tendency, the effects of stress concentration factor (SCF), S-N curve type, current profile, and three different sizes of SCRs were considered, and the relationship between S-N curve capacity and short-term VIV fatigue performance of SCR was derived. In case of S-N curve selection, DNV (2012) guideline was adopted and four different current profiles of the Gulf of Mexico (normal condition and Hurricane condition) and Brazil (Amazon basin and Campos basin) were considered. The obtained results will be useful to select the S-N curve for deepwater SCRs and also to understand the relationship between S-N curve capacity and short-term VIV fatigue performance of deepwater SCRs.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
• /
• pp.327-334
• /
• 2008

This paper presents the results of investigation on the influencing factors for GESC(Geogrid-Encased Stone Column) method in soft ground. A parametric study was then conducted on the influencing factors such as replacement ratio, geogrid stiffness and thickness of soft ground using stress-porepressure coupled analysis. The results indicate that the relationship between these parameters and settlement ratio, and the relationship between these parameters and stress concentration factor can be identified.

• 한국강구조학회 논문집
• /
• 제8권3호통권28호
• /
• pp.13-20
• /
• 1996

With the adoption of welded joints rather than bolted joints, we investigate the fatigue strength and the fatigue crack initiation of U-type trough rib and welded specimen with misalignment in a steel deck plate. The stress concentration factor of welded specimens with a misalignment is also verified by a finite element method. The main conclusions obtained from this study are as follows Experimental results of full-scaled U-type trough rib models have indicated that fatigue life depends on misalignments of welded joints in steel deck plate ; The more misalignments are, the less the fatigue life is. It has also shown that fatigue crack propagates from the welded root to the bead surface. We have also obtained the same results from both the fatigue test of welded specimens with a misalignment and the stress analysis of a finite element method.

• Ocean Systems Engineering
• /
• 제3권1호
• /
• pp.1-8
• /
• 2013

This brief study aims at providing a model to predict the time of service of a cracked bar in corrosive environment, in view of both the fracture mechanics and elastic failure criteria. Dolinskii's assumption on the relationship between stress and the corrosion rate is adopted. It is superimposed with fracture mechanics consideration. A comparison between the time of service of a cracked bar and that of a uniform bar is provided.