• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1998년도 춘계학술대회 논문집
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• pp.298-303
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• 1998

Most of mechanical structures are combined of substructures such as beam and/or plates. There are few system with unibody structures but are not a few systems with united body structures. Generally the dynamic analysis of whole structures is perform ed under alternating load. However, the analysis of each joint area is more important than others for zero severity. This paper presents the results of analysis of concentration stress in bolt jointed structure with variable preload. At frist, a static vibration test was performed to find out a nominal stress of bolt joint ed plates from the relationship between natural frequency and nominal stress. Then a concentration stress was computed at contact point between bolt and plate in the structure. It is believed that the proposed method has promising implications for safer design with fatigue quality index of stress concentration factor and has merit for cost down and saving time at the beginning of vehicle development.

• International Journal of Korean Welding Society
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• 제2권1호
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• pp.33-39
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• 2002

The effect of out-of-plane loads on the fatigue strength of welded steel structures is examined through fatigue tests with weldment of two fillet weld joint types. The results of the fatigue tests are compared with those under axial loads, on the basis of the hot spot stress range at the weld toe. From the result of the comparison, a method on how to incorporate the effect of the out-of-plane bending stress is proposed using design S-N curves derived from fatigue tests under the axial load. The proposed method is useful for rational assessment of the fatigue strength of fillet-welded structures, where combined stresses of the in-plane axial stress and the out-of-plane bending stress are induced simultaneously due to the complexity of applied loads and structural geometry.

• 융합정보논문지
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• 제10권5호
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• pp.126-133
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• 2020

본 연구는 합창과 호흡훈련을 병합한 복합예술교육프로그램이 대학생의 호흡기능 및 스트레스와 삶의 질에 미치는 영향을 알아보기 위하여 무작위 대조군 사전 사후 연구 설계로 진행하였다. 본 연구는 대학생 25명을 대상으로 복합예술교육프로그램을 시행한 실험군 (n=13)과 일반 예술교양프로그램을 적용한 대조군 (n=12)으로 무작위 배정하였다. 그 결과 실험군에서 실험 전 후 폐활량과 호흡근력, 스트레스와 삶의 질 척도에 유의한 차이를 보였다 (p<0.05). 또한 실험군 대조군간에 비교하였을 때, 1초간 노력성 날숨량(FEV₁) 결과를 제외하고 나머지 검사결과 값은 유의한 차이를 보였다 (p<0.05). 본 연구결과를 통하여 합창과 호흡훈련을 병합한 복합예술교육프로그램은 대학생의 스트레스 감소, 호흡기능과 삶의 질을 향상 시키는 프로그램으로 유익할 것이다.

• 한국강구조학회 논문집
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• 제17권4호통권77호
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• pp.419-429
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• 2005

본 연구의 목적은 기존의 복합십자형 다이아프램을 사용한 CFT 기둥-보 인장측 접합부에 관한 연구에 이어서 접합부 각 요소의 구조적 특성을 명료하게 하는데 있다. 복합십자형 다이아프램은 기존 접합부의 하중전달 경로 및 다이아프램의 갑작스런 기하학적인 형상 변화에 대한 디테일을 개선함으로서, 보 플랜지 및 다이아프램에 응력을 고르게 분포시키고 접합부의 응력집중이 완화된 접합방식이다. 복합십자형 다이아프램을 접합부에서 중요한 요소 중 하나인 슬리브에서의 응력전달에 관하여 연구를 수행하였다. 슬리브의 두께 및 길이를 변수로 하여 해석한 결과, 슬리브의 길이 및 두께는 접합부의 내력에 큰 영향을 주지 않고 다이아프램으로부터의 하중을 콘크리트로 전달시키는 매개체의 역할을 하였다. 또한 적정 슬리브의 길이 및 두께를 각각 직경의 1배, 슬리브 직경/두께비를 20으로 제안한다. 기존의 내력식을 검토하여 메커니즘을 수정한 후 적용가능한 접합부의 극한내력식 및 항복내력식을 제안하였다.

• Structural Engineering and Mechanics
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• 제19권3호
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• pp.261-279
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• 2005

The hot spot stress approach is usually adopted in the fatigue design and analysis of tubular welded joints. To apply the hot spot stress approach for fatigue evaluation of long span suspension bridges, the FEM is used to determine the hot spot stress of critical fatigue location. Using the local finite element models of the Tsing Ma Bridge, typical joints are developed and the stress concentration factors are determined. As a case for study, the calculated stress concentration factor is combined with the nominal representative stress block cycle to obtain the representative hot spot stress range cycle block under traffic loading from online health monitoring system. A comparison is made between the nominal stress approach and the hot spot stress approach for fatigue life evaluation of the Tsing Ma Bridge. The comparison result shows that the nominal stress approach cannot consider the most critical stress of the fatigue damage location and the hot spot stress approach is more appropriate for fatigue evaluation.

• 대한간호학회지
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• 제54권3호
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• pp.329-339
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• 2024

Purpose: This study investigated the moderating role of general self-efficacy (GSE) on how stress caused by pregnancy and daily hassle affect the risk of preterm birth (PTB) in women experiencing preterm labor. Methods: This cross-sectional study included 196 pregnant women experiencing preterm labor before 37 weeks of gestation. We used IBM SPSS Statistics 27 and employed Hayes process macro version 4 (model 1) and hierarchical regression to analyze the moderating effect of GSE on the relationship between pregnancy stress, daily hassle stress, and PTB risk. Results: Stress caused by pregnancy and daily hassle was positively correlated to PTB risk (r = .54, p < .001; r = .25, p < .001, respectively). While GSE did not significantly correlate with pregnancy stress, it negatively correlated with daily hassle stress (r = - .19, p = .009). GSE significantly moderated the relationship between combined stressors and PTB risk. As GSE levels increased, escalation in PTB risk in response to increasing stress levels was a more pronounced, highlighting a complex interaction between higher GSE levels and response to escalating stress levels. This model accounted for 39.5% of the variance in the PTB risk. Conclusion: Higher GSE may amplify the impact of stress on PTB risk, rather than mitigate it, which suggests a more nuanced role of GSE in the stress response of pregnant women at risk of preterm labor. GSE should be considered in care strategies, and managing its impact on stress perception and responses in pregnant women is crucial.

• 대한한의학회지
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• 제27권3호
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• pp.77-87
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• 2006

Objectives: The present study was carried out to investigate the preventive effects of Samgijiwhang-Tang(SJT) on streptozotocin(STZ)-induced diabetic nephropathy. Methods: SIT was given to rats through oral administration. The experimental animals were divided into a normal group of rats, a control group of STZ-induced diabetic rats, and a sample group with SIT administration. Rehmanniae Radix Preparat is combined in the original prescription of SIT, but in this experiment, Rehmanniae Radix was combined instead of Rehmanniae Radix Preparat to compare the effects of anti-diabetic nephropathy. Experimental diabetic nephropathy was induced by the injection of STZ(60mg/kg) in the rat via the peritoneum. The effect of SIT on STZ-induced diabetic nephropathy was observed by measuring the serum level of creatinine and BUN, in addition to urine secretion of albumin for 24 hours and the level of glucose found in the urine. Anti-oxidative stress of SIT administration in a living body was estimated by measuring lipid peroxide and GSH content in the cortex of kidneys. Results: STZ induced an increase of serum creatinine, urine glucose and renal cortical lipid peroxidation was lowered by Rehmanniae Radix Preparat combined SIT administration. Conclusions: The SIT treatment showed a protective effect on the rat diabetic nephropathy model, and action mechanism of the effect was thought to be concerned with anti-oxidative stress.

• 환경생물
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• 제28권2호
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• pp.101-107
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• 2010

Metal ions are essential to life. However, some metals such as mercury are harmful, even when present at trace amounts. Toxicity of mercury arises mainly from its oxidizing properties. Ionizing radiation (IR) is an active tool for destruction of cancer cells and diagnosis of diseases, etc. IR induces DNA double strand breaks in the nucleus, In addition, it causes lipid peroxidation, ceramide generation, and protein oxidation in the membrane, cytoplasm and nucleus. Yeasts have been a commonly used material in biological research. In yeasts, the physiological response to changing environmental conditions is controlled by the cell types. Growth rate, mutation and environmental conditions affect cell size and shape distributions. In this work, the effect of IR and mercury chloride (II) on the morphology of yeast cells were investigated. Saccharomyces cerevisiae cells were treated with IR, mercury chloride (II) and IR combined with mercury chloride (II). Non-treated cells were used as a control group. Morphological changes were observed by a scanning electron microscope (SEM). The half-lethal condition from the previous experimental results was used to the IR combined with mercury. Yeast cells were exposed to 400 and 800 Gy at dose rates of 400Gy $hr^{-1}$ or 800 Gy $hr^{-1}$, respectively. Yeast cells were treated with 0.05 to 0.15 mM mercury chloride (II). Oxidative stress can damage cellular membranes through a lipidic peroxidation. This effect was detected in this work, after treatment of IR and mercury chloride (II). The cell morphology was modified more at high doses of IR and high concentrations of mercury chloride(II). IR and mercury chloride (II) were of the oxidative stress. Cell morphology was modified differently according to the way of oxidative stress treatment. Moreover, morphological changes in the cell membrane were more observable in the frequently stress treated cells than the temporarily stress treated cells.

• 한국농공학회지
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• 제30권2호
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• pp.67-81
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• 1988

The purpose of the present study is to set up an efficient optimum design method for the large-scale reinforced concrete cylindrical shell structures like intake tower of reservoir and to establish a solid foundation for the automatic optimum structural design combined with finite element analysis. The major design variables are the dimensions and steel areas of each member of the structures. The construction cost which is composed of the concrete, steel, and form work costs, respectively, is taken as the objective function. The constraint equations for the design of intake-tower are derived on the basis of the working stress design method. The corresponding design guides including the standard specification for concrete structures have been also employed in deraving the constraint conditions. The present nonlinear optimization problem is solved by SUMT method. The reinforced concrete intake-tower is decomposed into three major substructures. The optimization is then conducted for both the whole structure and the substructures. The following conclusions can be drawn from the present study. 1. The basis of automatic optimum design of reinforced concrete cylindrical shell structures which is combined with finite element analysis was established. 2. The efficient optimization algorithms which can execute the automatic optimum desigh of reinforced concrete intake-tower based on the working stress design method were developed. 3. Since the objective function and design variables were converged to their optimum values within the first or second iteration, the optImization algorithms developed in this study seem to be efficient and stable. 4. The difference in construction cost between the optimum designs with the substructures and with the entire structure was found to be small and thus the optimum design with the substructures,rnay conveniently be used in practical design. 5. The major active constraints of each structural member were found to be the tensile stress insteel for salb, the minimum lonitudinal steel ratio constraints for tower body and the shearing stress in concrete, tensile stress in steel and maximum eccentricityconstraints for footing, respectively. 6. The computer program develope in the present study can be effectively used even by an unexperienced designer for the optimum design of reinforced concrete intake-tower.

• 소성∙가공
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• 제14권4호
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• pp.327-337
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• 2005

In the present work, the two back stress kinematic hardening models are proposed by combining Armstrong-Frederick, Phillips and Ziegler's hardening rules. Simple combination of hardening rules using simple rule of mixtures results in various evolutions of the kinematic hardening parameter. Using the combined hardening models the ultimate back stress fur the present models is also derived. The stress rate is co-rotated with respect to the spin of substructure due to the assumption of kinematic hardening rule in finite deformation regime. The work piece under consideration is assumed to consist of the elastic and the rigid plastic deformation zone. Then, the J2 deformation theory is facilitated to characterize the plastic deformation behavior under various loading conditions. The plastic deformation localization behaviors strongly depend on the constitutive description namely back stress evolution and its hardening parameters. Then, the analysis for Swift's effects under the fixed boundaries in axial directions is carried out using simple shear deformation.