• Structural Engineering and Mechanics
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• 제76권6호
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• pp.725-736
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• 2020

In this work the mixed mode I/III fracture of sandstone has been studied experimentally and numerically. The experimental work used three-point bending specimens containing pre-existing cracks, machined at various inclination angles so as to achieve varying proportions of mode I to mode III loading. Dimensionless stress intensity factors were calculated using the extended finite element method (XFEM) for and compared with existing results from literature calculated using conventional finite element method. A total of 28 samples were used to conduct the fracture test with 4 specimens for each of 7 different inclination angles. The fracture load and the geometry of the fracture surface were obtained for different mode mixities. Prediction of the fracture loads and the geometry of the fracture surface were made using XFEM coupled with a cohesive zone model (CZM) and showed a good comparison with the experimental results.

• 자원환경지질
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• 제54권6호
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• pp.615-627
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• 2021

전라남도 고흥군 백일도에 발달하는 우수향 주향이동 단층인 백일도단층은 응회질 사암과 화산력응회암의 분포를 규제하며 복잡한 단열계를 수반한다. 본 연구에서는 백일도단층 주변의 상세 단열 지도를 기반으로 원조사법 및 위상기하 분석법을 통해 단열계의 기하 및 연결성의 공간적 변화를 파악하였다. 분석 결과 단열계의 밀도와 연결성은 화산력응회암에서보다 응회질 사암에서 더욱 높게 나타난다. 응회암질 사암 내 단층의 주향에 대한 구조적 위치에 따라 단열군의 방향 분산도, 밀도, 그리고 평균 길이가 변화한다. 또한 단층 굴곡 주변에는 단층과 고각을 이루거나 휘어진 단열이 집중되어 발달한다. 상세한 단열 관찰과 분석을 통해 본 연구에서는 다음과 같은 결론을 도출하였다. (1) 응회질 사암 내 단열계의 높은 밀도는 석영, 장석과 같은 취성 광물의 높은 비율에 의해 제어된다. (2) 단열계의 연결성은 구조적 위치에 따른 단열군 방향의 다양화 및 연장성의 증가에 의해 향상된다. (3) 불규칙한 기하를 가진 단층 굴곡은 단층 주변의 응력을 집중 및 교란시켜 단층과 고각을 이루거나 휘어진 단열을 발생시킨다. 연구 결과는 단층 주변 단열계의 발달을 제어하는 여러 지질학적, 구조적 요인에 대한 이해를 증진시키는 데에 도움이 될 것으로 기대된다.

• IMMUNE NETWORK
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• 제5권2호
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• pp.117-123
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• 2005

The immune response to any stimulus is complex, requiring coordinated action by several types of cells in a tightly regulated sequence. Thus, a physical stress such as exercise may act at any number of points in the complex sequence of events collectively termed the immune response. Although exercise causes many propound changes in parameters of immune function, the nature and magnitude of such changes rely on several factors including the immune parameters of interest; type, intensity, and duration of exercise; fitness level or exercise history of the subject; environmental factors such as ambient temperature and humidity. Although regular moderate exercise appears to be important factor for increasing immunity, Athletes are susceptible to illness, in particular upper respiratory track infection, during periods of intense training and after competition. In addition, in elite athletes, frequent illness is associated with overtraining syndrome, a neuroendocrine disorder resulting from excessive training. Through this paper, we want to investigate the effects of exercise on the immunosuppression such as exercise induced lymphopenia, asthma, anaphylaxis, URT (upper respiratory track), and TB (tuberculosis) infection. and also, we want to suggest a direct mechanism, protection and therapy of exercise induced immunosuppression.

• 대한간호학회지
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• 제39권3호
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• pp.376-385
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• 2009

Purpose: The purposes of this study were(a) to identify smoking behavior by following a cohort representative of the population of 4th grade elementary schoolers in South Korea over a four-year period(2004-2007), and(b) to explore predictors of smoking initiation among non-smokers in Wave 1. Methods: Secondary data, the Korea Youth Panel Study, was analyzed in this study. First, frequencies or percentages were calculated to identify smoking behavior(i.e., smoking initiation, smoking intensity, and smoking duration). Second, binary logistic regression analysis was performed to examine significant factors related to smoking initiation. Results: Smoking initiation and daily smoking were more pronounced when the participants entered middle school. In bivariate analysis, statistically significant predictors of smoking initiation were loneliness at school, self-control, delinquent behavior, depressive symptoms, and stress. However, after controlling for other factors, only a high level of risk-taking tendency and a greater number of delinquent behaviors remained statistically significant. Conclusion: Based on greater involvement in smoking among first-year middle schoolers, smoking prevention strategies should be provided to elementary schoolers rather than middle schoolers. A risk-taking tendency and delinquent behaviors should be considered as proxy measures to detect the high-risk group for smoking initiation.

• 대한치과보철학회지
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• 제31권1호
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• pp.39-50
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• 1993

The purpose of this study was to investigate the association between characteristics of temporomandibular joint sound and possible contributing factors of temporomandibular joint sound. 1487 high school students (798 men and 689 women) aged from 16 to 18 were asked by questionnaires which was made for this study by T.M.J. clinic, dental infirmary, School of Dentistry, Chosun University, and data obtained from questionnaires were analyzed by chi-square test. The following results were obtained: 1. The prevalence of temporomandibular joint sound were found in 35.7% of all the subjects. 2. Temporomandibular joint sound could be unchanged, reduced and increased frequencey over time dependent on the individual. 3. The intensity of temporomandibular joint sound could be unchanged and increased during the chewing of hard food dependent on the individual. 4. The unilateral chewing and bruxism were not considered as possible contributing factors upon the occurring of temporomandibular joint sound. 5. Statistical significant association was found between clenching, stiffness, stress and tempore-mandibular joint sound, respectiely.(P<0.001, P<.01, P<0.05).

• 대한기계학회논문집A
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• 제26권8호
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• pp.1512-1519
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• 2002

Most of mechanical failures are caused by repeated loadings and therefore they are strongly related to fatigue. To avoid the failures caused by fatigue, determination of an optimal shape of a structure is one of the very important factors in the initial design stage. Shape optimization fer two types of specimens, which are very typical ones in opening mode in fracture mechanics, was accomplished by the linear elastic fracture mechanics and the growth-strain method in this study. Also shape optimization for a cantilever beam in mixed mode was carried out by the same techniques. The linear elastic fracture mechanics was used to estimate stress intensity factors and fatigue lives. And the growth-strain method was used to optimize the shape of the initial shape of the specimens. From the results of the shape optimization, it was found that shapes of two types of specimens and a cantilever beam optimized by the growth-strain method prolong their fatigue lives significantly. Therefore, it was verified that the growth-strain method is an appropriate technique for shape optimization of a structure having a crack.

• 환경생물
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• 제19권1호
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• pp.1-6
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• 2001

Many researchers have been studied with guard cell protoplasts and detached epidermis as they think that properly stabilized protoplasts and detached epidermis retain many of the properties of intact guard cells. However, some studies have shown that stomata in detached epidermis behave differently, both quantitatively and qualitatively, from those in the intact leaf. Stomata in the intact leaf are very sensitive to environmental factors such as light, $CO_2$ and osmotic stress, but stomata in detached epidermis are less sensitive to these factors than those in the intact leaf. The clearest evidence to suggest the different response between detached epidermis and intact leaf obtained from the experiments with heavy metal, cadmium. 3-weeks old Commelina. communis was transferred to and grown in Hoagland solution in the presence or absence of 5 mM $Cd^{2+}$ for 4 days. The application of $Cd^{2+}$ showed about 70% inhibition of stomatal conductance when measured at various light intensity (100-1,000 $\mu$mole $m^{-2}s^{-1}). However, stomata in detached epidermis floated on an incubation medium containing 100 $\mu$M $Cd^{2+}$ opened to a degree of about 8.38 fm, but the stomata treated with no cadmium opened to 3.74 ${\mu}{\textrm}{m}$. These results were unexpected as the intact leaf grown in a Hoagland solution containing cadmium showed very negative physiological responses. These results showed that stomata in detached epidermis and in the intact leaf could respond reversely. Therefore, it is possible that we now misunderstand how stomata open in real natural condition.

• IMMUNE NETWORK
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• 제5권4호
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• pp.232-236
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• 2005

Background: A physically active lifestyle and regular exercise training incurs many health benefits. One recently recognized benefit of regular moderate exercise is stress reduction and immune enhancement. Thus, a physical stress such as exercise may act at any number of points in the complex sequence of events collectively termed the immune response. Although exercise causes many propound changes in parameters of immune function, the nature and magnitude of such changes rely on several factors including the immune parameters of interest; type, intensity, and duration of exercise; fitness level or exercise history of the subject; environmental factors such as ambient temperature and humidity. Methods: This study was undertaken to investigate the effect of different type of exercise on superoxide dismutase (SOD), neutrophils, and T lymphocytes of Sprague-Dawley rats. Sprague-Dawley rats were randomly divided into three groups; a non-Trained group (NTG, n=6), a swim-Trained group (STG), and a treadmill-Trained group (TTG). The exercise regimen was designed in a treadmill (5 times/5 days/week) during 8-weeks for TTG, and swim training (5 times/5 days/week) during 8-weeks for STG, and the volume of exercise training was the same in both groups. Results: 8 weeks of regular swim and treadmill training significantly increased liver SOD concentration however, muscle SOD concentration was not statistically significant. In the level of neutrophils, TTG and STG showed significant difference, compared to NTG. TTG was the highest level of neutrophils. In the level of immune cell counts, there was significant difference among TTG, STG, and NTG both in the spleen and thymus. Conculsion: In conclusion, it can be stated that eight weeks swim and treadmill exercise training has beneficial effect in improving immune response and antioxidant defence capacity by augmenting immune cells and SOD activities of SD rats.

• 한국건설관리학회논문집
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• 제13권4호
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• pp.120-131
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• 2012

오늘날의 기업들은 무한 경쟁과 불확실한 경영환경 속에 있으며, 이로 인해 실무자들은 다양한 직무요구들과 스트레스에 노출되어 있다. 특히 설계사무소 직원들은 타 산업현장과 달리 작업에 대한 강도가 커서 육체적으로 힘들고, 타 산업의 주 5일제 근무와 달리 공정이 상호 관련되어 있기 때문에 정기적인 공휴일과 휴가가 보장되기 어렵다. 또한 최근 건설 산업에서는 BIM이 도입되면서 업무환경 및 범위 그리고 역할 등과 같은 개인적 역할뿐만 아니라 조직차원에서의 다양한 변화가 요구되기 때문에 이로 인한 직무스트레스의 범주 및 요인 또한 변하고 있는 상황이다. 이에 본 연구에서는 BIM을 도입 한 이후 설계사무소 실무자들의 직무스트레스 수준 및 유발요인을 확인하여 경력, 직급, 성별, BIM 교육 및 BIM 템플릿 유/무 등과 같은 특성에 따른 직무스트레스를 파악하였다. 이는 추후 활용도가 높을 것으로 예상되는 BIM기반 프로젝트의 주 참여자인 설계사무소의 업무환경을 구축하는데 의의가 있다.

• Safety and Health at Work
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• 제9권2호
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• pp.216-223
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• 2018

Background: Many studies have reported negative psychological or physical effects of emotional labor. Relationship between work-related musculoskeletal disorder and psychosocial factors has been reported. To manage organizational and psychosocial factors of musculoskeletal disorder with work place intervention among emotional laborers, the factors contributing to musculoskeletal pain must be identified and clarified. Methods: Data from the fourth Korean Working Conditions Survey was analyzed. Based on the questionnaire, we selected emotional laborers and included 3,979 participants, excluding participants whose variables were of interest to the researcher. Weight variable was applied. The association with musculoskeletal pain and psychosocial factors, such as workload, monotonous work, job control, social support, and job satisfaction, was investigated. Results: Univariate analysis demonstrated that there was a statistically significant relationship between social support, job satisfaction, and musculoskeletal pain. In multivariate analysis, job satisfaction showed a strong correlation with musculoskeletal pain at all sites. Social support was significantly associated with backache. Monotonous work seemed to reduce the pain in the neck and/or upper limbs. Job control and work intensity were not significantly associated with musculoskeletal pain. Conclusion: In this study, job satisfaction was significantly associated with musculoskeletal pain, and social support among the social psychological stressors could reduce musculoskeletal pain. However, unlike previously known, the presence of monotonous work resulted in reduced musculoskeletal pain. The results of this study will help to establish the direction of improvement of atmosphere in the workplace to prevent the musculoskeletal pain of emotional laborers.