• 대한기계학회논문집
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• 제12권3호
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• pp.497-504
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• 1988

본 연구에서는 트랙션이 없는 커스프 균열에 적용한 방법을 확장하여 무한대 에서 균일열유동을 받는 무한체내에 하이포사이클로이드형(hypocycloid type), 대칭이 기형(symmetric airfoil type), 대칭입술형(symmetric lip type) 강체 함유물이 존재 하고 그 표면은 단열되거나 상대온도가 영으로 주어지는 경우에 대해서 열응력세기계 수(thermal stress intensity factor이하에서 TSIF로 표기함)를 유도하고자 한다.

• Structural Engineering and Mechanics
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• 제90권2호
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• pp.177-187
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• 2024

In this study, compared two distinct estimation methods (stress charts and regression equations) proposed by the Indian road congress design guideline (IRC:58-2015) to determine flexural stress in Jointed Plain Concrete Pavement (JPCP). The occurrence of critical flexural stresses in pavement slabs is due to the combined effects of wheel loads and temperature. These stresses depend on various factors such as material properties of concrete, soil-subgrade strength, loading, and geometric properties of the slab. In order to account for the practical variability of these factors, critical edge stresses are determined using both methods and compared considering tied concrete shoulder. IRC:58 (2015) suggests, the stresses calculated by both the procedures should provide the same results. However, when these stresses are compared for the same configurations and same loading conditions, large variations are observed. The effect of tied concrete shoulder on reduction in critical edge stress is observed. Based on the study, certain important conclusions and recommendations are presented.

• The Plant Pathology Journal
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• 제27권3호
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• pp.249-256
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• 2011

Tall fescue (Schedonorus phoenix Scop.) is resistant to abiotic and biotic stresses through a symbiotic relationship with Neotyphodium coenophialum. However, this endophyte has been considered detrimental since it produces toxic alkaloids to animals. It is vital to understand mutuality between these two to maximize positive impact of the endophyte on agri-ecosystem. Little research has been conducted on endophyte transmission mechanism in planta. To provide basic information related to endophyte transmission, an experiment was conducted to examine the effect of endophyte genotype and water stress on endophyte transmission by imposing soil moisture deficits at different stages of panicle development. There was water stress effect on endophyte frequency but not on concentration, whereas endophyte genotype significantly influenced endophyte concentration in pseudostem of tall fescue at boot stage. Reproductive tillers showed greater endophyte frequency and concentration. Endophyte frequency in florets or seeds depended on position within panicle. There was no drought effect on endophyte concentration, but showed the effect of endophyte genotype on endophyte concentration in florets and seeds. Overall endophyte concentration in seeds was higher. From this study, we may conclude that although water stress reduced endophyte frequency in vegetative tiller, water stress does not have effect on endophyte transmission, suggesting that drought is not an important factor controlling the endophyte transmission from plant to seed. Endophyte genotype and seed position in a panicle affected endophyte transmission, indicating that these two factors are involved in endophyte transmission and may determine seed transmission of endophyte in tall fescue.

• 한국초지조사료학회지
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• 제42권3호
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• pp.137-145
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• 2022

Aluminum (Al) is one of the major factors adversely affects crop growth and productivity in acidic soils. In this study, the effect of Al on plants in soil was investigated by comparing the protein expression profiles of alfalfa roots exposed to Al stress treatment. Two-week-old alfalfa seedlings were exposed to Al stress treatment at pH 4.0. Total protein was extracted from alfalfa root tissue and analyzed by two-dimensional gel electrophoresis combined with MALDI-TOF/TOF mass spectrometry. A total of 45 proteins differentially expressed in Al stress-treated alfalfa root tissues were identified, of which 28 were up-regulated and 17 were down-regulated. Of the differentially expressed proteins, 7 representative proteins were further confirmed for transcript accumulation by RT-PCR analysis. The identified proteins were involved in several functional categories including disease/defense (24%), energy (22%), protein destination (9%), metabolism (7%), transcription (5%), secondary metabolism (4%), and ambiguous classification (29%). The identification of key candidate genes induced by Al in alfalfa roots will be useful to elucidate the molecular mechanisms of Al stress tolerance in alfalfa plants.

• 한국직업건강간호학회지
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• 제7권1호
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• pp.55-64
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• 1998

In order to investigate and compare the health risk factors of nurses in the operating room(OR nurse) and ward (WARD nurse), the questionnaire survey for subjective symptoms was carried out on 553 nurses(132 OR nurses and 421 WARD nurses) who were employed at seven hospital. The self-administered questionnaries were composed of low back pain, subjective fatigue symptoms, musculo-skeletal symptoms, psychological stress and reproductive function. The results were as follows : 1. In the type of working posture and working environment, there were significant difference between two groups for working posture, waist form, height of working table, satisfaction of chair, lifting & carring. 2. Job satisfaction, duration of work, height of working table, satisfaction of chair, lifting & carring were significantly associated the low back pain. 3. In the complaints of subjective fatigue symptoms, the total mean score was higher in OR nurse than WARD nurse, but there was not significant. The items that the mean score of OR nurse was significantly higher than WARD nurse were 'head feels muddled', 'apt to forget', 'feel choky'. 4. In the complaints of musculo-skeletal syrrptoms, the total mean score was higher in OR nurse than WARD nurse, but there was not significant. The item that the mean score of OR nurse was significantly higher WARD nurse was 'wrist discomfort or pain'. 5. The comparison of spontatenous abortion in married nurses who had the experience of pregnancy were significantly associated the stress risk group. 6. In all of OR and Ward nurses, the job satisfaction is associated with subjective fatigue symptoms, musculo-skeletal symptoms, and stress. In conclusion, it suggested that working posture, working environment, stress, and job satisfaction were health risk factors of nurses working in the operating room. Further prospective intervention studies should be conducted to educate right working posture, improve of working environment, decrease of stress, and increase of job satisfaction.

• Journal of Welding and Joining
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• 제22권4호
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• pp.73-81
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• 2004

Failure mechanisms of welded joints under fatigue loads are interpreted that multiple collinear surface cracks initiating randomly along the weld toes propagate under the mutual interaction and coalescence of adjacent two cracks. To estimate fatigue crack propagation life for three types of the representative welded joints, i.e. non-load carrying cruciform, cover plate and longitudinal stiffener joint, the stress intensity factors at the front of the surface cracks have to be calculated, which are influenced strongly by the geometry of attachments, weld toes and the crack shapes. For the effective calculation of the stress intensity factors the Mk-factor was introduced which can be derived by a parametric study performed by FEM considering influence of the geometrical effects. The fatigue life of the cruciform joint was estimated by using the Mk-factors and the method considering the propagation mechanisms of the multiple surface cracks. Analysis results for the fatigue life had a good agreement with that of experiment.

• 상하수도학회지
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• 제19권2호
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• pp.181-192
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• 2005

This study evaluated the effect of factors influencing the initial biofilm formation in drinking water distribution pipe by running experiments using a $2^{4-1}$ fractional factorial experimental design with a replicate. Important variables used for assessing biofilm formation included BDOC(biodegradable dissolved organic carbon), viable heterotrophic bacteria present in drinking water, water temperature, and shear stress at two levels each. Based on the statistical analysis of biofilm levels measured as attached HPC(heterotrophic plate count) and community-level assay, the main factors that have significant effects on biofilm formation were found to be viable heterotrophic bacteria and BDOC. Water temperature only exhibited significant effect on the levels of attached HPC, while shear stress was not a significant factor under given conditions. Moreover, the statistical analysis revealed that interactions between the important variables were not statistically significant at a 0.05 significance level.

• 대한간호학회지
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• 제35권4호
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• pp.672-679
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• 2005

Introduction. Cardiovascular disease has the potential to lead to sudden in-flight incapacitation and permanent grounding. The aims of this study are to examine the relationships between lifestyle, job stress and blood lipid levels of male aircrew personnel of a Korean airline and to identify which factors influence their hyper-lipidemia. Methods. Two hundred sixteen male aircrew personnel completed a questionnaire by self-report and consented to participate in the study. The questionnaire collected data related to job stress, life style, serum cholesterol levels and general characteristics of the aircrew. The cholesterol levels of the subjects were collected from their most recent health check-up records. Subjects were divided into two groups (the desirable group and the risk group) based on their serum cholesterol level, 200 mg/dl. Results. Mean age and marital status were significantly different between the two groups. More subjects in the risk group had habits of eating high lipid foods, while more subjects in the desirable group exercised more frequently than the risk group. In logistic regression analysis, after controlling age and marital status, types of working situation (domestic duty or international duty, odds ratio=.390, p=.018), diet (odds ratio=.429, p=.037), and exercise (odds ratio=.320, p=.055) were influencing factors on aircrew's serum cholesterol lev-els. Conclusions. The cholesterol level of aircrew personnel is closely related to their lifestyle, such as lipid diet and exercise. The type of work situations, e.g. staying in an airplane for long periods of time or staying abroad, may influence these diet patterns and exercise habits.

• 대한가정학회지
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• 제38권9호
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• pp.93-106
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• 2000

The Purpose of this study was to examine the adolescents'stress and social supports and the relationships of there two factors. Specifically, this study investigated the adolescents'stress and social supports depending on their sex, family status, socio-economic status. The subjects of this study were 467 middle school students in Pusan. Questionnaires were used consisting of adolescents'perceived stress and social supports for data analysis, Cronbach's $\alpha$-coefficient, frequency distribution, percentage, Oneway-ANOVA, t-test and Pearson's γ-coefficient were used. Major findings were as follows: Adolescents'stress were significantly different depending on their sex, father's educational level, family income and family intimacy The source of the adolescents'social support sources were different depending on their sex, family status, father's educational level, mother's educational level, family income and family intimacy. Adolescents'social support types were different depending on family status, lather educational level, mother educational level, father\`s job, family income and family intimacy. There were negative correlation between stress and social supports.

• 대한기계학회논문집A
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• 제24권9호
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• pp.2252-2258
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• 2000

In order to investigate the effect of nozzle on stress concentration in pressure vessels, three dimensional finite element analyses were performed. The results were compared with those for corresponding two dimensional axisymmetric finite element analyses. A three dimensional finite element model with a surface crack was also designed to evaluate the effect of internal pressure and heat transfer on crack face, and the resulting stress intensity factors from the finite element analyses were compared with those for ASME Sec. XI and Raju-Newman's stress intensity factor solution. As a result, the validity of currently available stress intensity factor solutions for a surface crack was reviewed in the presence of geometrical complexity, heat transfer and internal pressure.