• Advances in Computational Design
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• 제8권3호
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• pp.191-217
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• 2023

The objective of this study was to evaluate the foundation structure of a 3.6-MW wind turbine generator (WTG) installed offshore in Western Korea. The ultimate limit state (ULS) and fatigue limit state (FLS) of the multi-pile steel foundation (MSF) installed at the Saemangeum offshore wind farm were structurally investigated using the finite element (FE) software, ANSYS Workbench 19.0. According to the ULS analysis, no plastic deformation was found in any of the components constituting the substructure. At the same time, the maximal stress value reached the calculation limit of 335 MPa. According to the FLS results, the stress concentration factor (SCF) ranged from 1.00 to 1.88 in all components. The results of this study can be applied to determine the optimal design for MSFs.

• Restorative Dentistry and Endodontics
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• 제18권2호
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• pp.395-411
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• 1993

The purpose of this study was to examine the clear concept of the designs for cavity preparations. Among the several parameters in cavity designs, profound understanding of isthmus width factor would facilitate selection of the appropriate cavity preparation for a specific clinical situation. In this study, the cavities were prepared on maxillary first premolar and filled with gold inaly. A two - dimensional model was composed of 1037 - node triangle elements. In this model, isthmus was varied in width at 1/4, 1/3 and 1/2 of intercuspal width and material properties were given for four element groups, i.e., enamel, dentin, pulp and gold. The 500N occlusal load varied in direction and it was examined using three types of load : concentrated load, divided load and distributed load. The models were also examined with empty cavities using the devided load and distributed load. These models were analyzed the displacement and strees distribution by the two - dimensional Finite Element Method. The results were as follows : 1. All experimental models which filled with gold inlay after cavity preparation were similar direction of displacement with control model under same load type. But in the models with empty cavities, as isthmus width was wider, the degree of displacement was increased at same load type. 2. Among the experimental models which were filled with gold inaly after cavity preparation, the model II showed the least stress concentration under concentrated load and divided load. But in the models with empty cavities, the model III showed the largest stress concentration and tooth fracture is expected regardless isthmus width. 3. All experimental models showed similar displacement pattern beneath restorative material under a concentrated load. In the models with empty cavities, a divided load resulted in a lingual displacement of the lingual cusp, but a distributed load resulted in a buccal displacement of the lingual cusp. In regard to the above results, the restored models were stronger than empty models in respect to the bending moment and tensile stress. The empty models are expected to fracture regardless isthmus width. The safest isthmus width was 1/3 of intercuspal distance, which showed the least stress concentration in respect to the effect of stress distribution.

• 한국대기환경학회지
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• 제13권4호
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• pp.249-256
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• 1997

To identify the long-term influence of acid rain treatment on tree growth, acid rain of various composition (pH 2.0, pH 4.0 and pH 5.6 as control) was applied to several landscape trees for five months (April through August, 1991). Tree height, pH values and $Al^{3+}$ concentration in soil were investigated. Acid rain treatments seemed to promote height growth in the first year (1991), but have become an inhibiting factor over five years. All of coniferous species and most broad-leaved species, except Acer ginnala, showed opposite trends in height responses to acid rain treatments between the first (1991) and last (1996) year. In contrast, Acer ginnala showed similar trends to acid rain treatments in the height growth between 1991 and 1996. This result suggested that Acer ginnala has a characteristic adapability to acid rain stress. pH values of surface soil were lower than those of 30 cm soil depth. This fact suggested that acid rain treatments made surface soil acidic condition. In addition, physiological characteristics (photosynthesis, stomatal condition and biomass) have to be investigated to identify the relationship between long-term effects of $AL^{3+}$ concentration and growth.

• 대한조선학회지
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• 제21권1호
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• pp.13-20
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• 1984

As the first step to the dynamic stress analysis of structures, transient responses of a Timoshenko beam with variable section subject to impact load are analyzed. According to the various characteristics of impact load, time histories of the transient response of Timoshenko beam with general boundary conditions are obtained and compared with those of one degree of freedom system. Numerical solutions of the governing equations of motion are calculated by adopting the equivalent lumped-mass system and the finite difference method. It is found that the dynamic responses of Timshenko beam depend on the effect of concentration and location of impact load. As a result, increasing tendency of fluctuation in dynamic response, especially in bending moment, is found according to the increase of load concentration factor in time and space.

• Nutrition Research and Practice
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• 제11권3호
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• pp.206-213
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• 2017

BACKGROUN/OBJECTIVES: Although studies have revealed that black garlic is a potent antioxidant, its antioxidant mechanism remains unclear. The objective of this study was to determine black garlic's antioxidant activities and possible antioxidant mechanisms related to nuclear factor erythroid 2-like factor 2 (Nrf2)-Keap1 complex. METHODS/MATERIALS: After four weeks of feeding rats with a normal fat diet (NF), a high-fat diet (HF), a high-fat diet with 0.5% black garlic extract (HF+BGE 0.5), a high-fat diet with 1.0% black garlic extract (HF+BGE 1.0), or a high-fat diet with 1.5% black garlic extract (HF+BGE 1.5), plasma concentrations of glucose, insulin,homeostatic model assessment of insulin resistance (HOMA-IR) were determined. As oxidative stress indices, plasma concentrations of thiobarbituric acid reactive substances (TBARS) and 8-isoprostaglandin $F2{\alpha}$ (8-iso-PGF) were determined. To measure antioxidant capacities, plasma total antioxidant capacity (TAC) and activities of antioxidant enzymes in plasma and liver were determined. The mRNA expression levels of antioxidant related proteins such as Nrf2, NAD(P)H: quinone-oxidoreductase-1 (NQO1), heme oxygenase-1 (HO-1), glutathione reductase (GR), and glutathione S-transferase alpha 2 (GSTA2) were examined. RESULTS: Plasma glucose level, plasma insulin level, and HOMA-IR in black garlic supplemented groups were significantly (P < 0.05) lower than those in the HF group without dose-dependent effect. Plasma TBARS concentration and TAC in the HF+BGE 1.5 group were significantly decreased compared to those of the HF group. The activities of catalase and glutathione peroxidase were significantly (P < 0.05) increased in the HF+BGE 1.0 and HF+BGE 1.5 groups compared to those of the HF group. The mRNA expression levels of hepatic Nrf2, NQO1, HO-1, and GSTA2 were significantly (P < 0.05) increased in the HF with BGE groups compared to those in the HF group. CONCLUSIONS: The improvements of blood glucose homeostasis and antioxidant systems in rats fed with black garlic extract were related to mRNA expression levels of Nrf2 related genes.

• 한국동물생명공학회지
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• 제34권3호
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• pp.212-221
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• 2019

Sestrin-2 (SESN2) as a stress-metabolic protein is known for its anti-oxidative effects as a downstream factor of PERK pathways in mammalian cells. However, the expression patterns of SESN2 in conjunction with the UPR signaling against to ER stress on porcine oocyte maturation in vitro, have not been reported. Therefore, we confirmed the expression pattern of SESN2 protein, for which to examine the relationship between PERK signaling and SESN2 in porcine oocyte during IVM. We investigated the SESN2 expression patterns using Western blot analysis in denuded oocytes (DOs), cumulus cells (CCs), and cumulus-oocyte complexes (COCs) at 22 and 44 h of IVM. As expected, the SESN2 protein level significantly increased (p < 0.01) in porcine COCs during 44 h of IVM. We investigated the meiotic maturation after applying ER stress inhibitor in various concentration (50, 100 and 200 μM) of tauroursodeoxycholic acid (TUDCA). We confirmed significant increase (p < 0.05) of meiotic maturation rate in TUDCA 200 μM treated COCs for 44 h of IVM. Finally, we confirmed the protein level of SESN2 and meiotic maturation via regulating ER-stress by only tunicamycin (Tm), only TUDCA, and Tm + TUDCA treatment in porcine COCs. As a result, treatment of the TUDCA following Tm pre-treatment reduced SESN2 protein level in porcine COCs. In addition, SESN2 protein level significantly reduced in only TUDCA treated porcine COCs. Our results suggest that the SESN2 expression is related to the stress mediator response to ER stress through the PERK signaling pathways in porcine oocyte maturation.

• 대한본초학회지
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• 제28권4호
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• pp.57-62
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• 2013

Objectives : Lonicerae Japonicae Flos (LJF) has been shown anti-oxidant, anti-inflammatory, anti-viral, anti-rheumatoid properties. However, it is still largely unknown whether LJF inhibits skin injury against oxidative stress in human keratinocyte, HaCaT cells. The purpose of this study was to evaluate the protective effects of LJF against hydrogen peroxide($H_2O_2$)-induced oxidative stress in human keratinocytes, HaCaT cells. Methods : To evaluate out the protective effects of LJF on oxidative injury in HaCaT cells, an oxidative stress model of HaCaT cells was established under a suitable concentration (500 ${\mu}M$) hydrogen peroxide. HaCaT keratinocyte cells were pre-treated with LJF (0.1, 0.25 or 0.5 mg/ml), and then stimulated with $H_2O_2$. Then, the cells were harvested to measure the cell viability, DNA damage, and release of reactive oxygen species (ROS). Results : LJF (0.1, 0.25 or 0.5 mg/ml) itself did not show any significant toxicity in HaCaT cells. The treatment of $H_2O_2$ caused the oxidative stress, leading to the cell death, and DNA injury. However, pretreatment with LJF reduced cell death, and DNA injury. The stimulation of $H_2O_2$ on HaCaT cells resulted in excessive release of ROS, which is the main factor of oxidative stress. The excessive release of ROS was inhibited by LJF treatment significantly. Conclusions : These results could suggest that LJF exhibited the protective effects of HaCaT cells against $H_2O_2$-induced oxidative stress by inhibiting ROS release. It could be explained that LJF inhibit skin damages against oxidative stress. Thus, LJF would be useful for the development of drug or cosmetics treating skin troubles.

• 한국산업융합학회 논문집
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• 제14권2호
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• pp.67-72
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• 2011

Recently, it is possible for small sized and high speed diesel engines by development of commonrail system. And in order to increase the engine performance, the cylinder firing pressure is a tendency which increases. On the other side, the weight of engine becomes lightly in spit of high performance diesel engine. Therefore, the weight optimization for engine components is very important point on the design process. Also, the weight optimization must necessarily be considered the robust design against a fatigue failure. This paper focuses on the weight optimization of crankshaft according to web shape at the light duty diesel engine, and torsion characteristics of crankshaft is considered with 1D and 3D analysis tools.

• 동력기계공학회지
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• 제9권4호
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• pp.77-82
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• 2005

Bellows is a familiar component in piping systems as it provides a relatively simple means of absorbing thermal expansion and providing system flexibility. In routine piping flexibility analysis by finite element methods, bellows is usually considered to be straight pipe runs modified by an appropriate flexibility factor; maximum stresses are evaluated using a corresponding stress concentration factor. In this paper, the dynamic characteristics of bellows were investigated by Finite element methods. Using Anany program, the natural frequencies and evaluation of the reliability of bellows were also investigated.

• 한국추진공학회지
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• 제22권6호
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• pp.94-103
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• 2018

발사체 및 유도무기 기체에 사용되는 복합재 격자구조물은 구조물에 작용하는 하중을 고려하여 최소한의 두께와 무게로 설계되는 구조물이다. 이를 위하여 실리콘 몰드에 탄소섬유를 와인딩하는 공정으로 격자구조물을 만들며, 이때 발사체 및 유도무기 기체 내부의 장비 등을 점검하기 위하여 점검창을 설치하는 것이 일반적으로 요구된다. 본 논문에서는 필라멘트 와인딩 공정으로 제작된 실린더형 격자구조물에 대하여 압축시험을 수행하고, 이 구조물에 대한 유한요소해석을 수행하여 얻은 해석 결과를 설치된 격자구조물에 대하여 유한요소해석을 수행하였다. 또한 구조물의 리브(Rib)와 노트(Knot)의 파손강도를 통해 육각형 점검창의 두께 및 위치를 변수로 선정하여 수행한 유한요소해석 결과는 다음과 같다; (1) 육각형 점검창의 안전계수가 사각형 점검창 보다 높게 계산되었으며, (2) 수직 점검창이 상단 헬리컬 리브의 중간에 위치할 때 안전계수가 높게 계산되었고, (3) 구조안전성 확보를 위하여 점검창의 두께를 증가시킬 경우 구조물의 불연속 부분에 응력집중이 발생하므로 유한요소 해석을 통해 안전계수가 가장 높은 점검창 형상을 선정해야 한다.