• Restorative Dentistry and Endodontics
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• 제34권2호
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• pp.145-153
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• 2009

본 연구에서는 측정장치의 compliance유무가 복합레진의 중합수축응력 측정에 미치는 영향을 알아보았다. 변위센서, cantilever load cell과 부궤환 (negative feedback) 시스템을 적용하여 compliance를 허용하는 것과 허용하지 않는 두 가지 모드로 중합수축응력의 측정이 가능한 stress-strain analyzer를 제작하였다. 한 종의 flowable (Filtek Flow: FF) 복합레진과 두 종의 universal hybrid (Z100: Z1 and Z250: Z2) 복합레진이 사용되었다. Load cell의 끝과 base plate에 고정된 직경 3.0 mm의 금속 막대에 silane을 처리하였다. 1.0 mm의 거리로 고정한 두 개의 금속 막대 사이 에 복합레진을 적용한 후 광중합을 하였다. 복합레진의 수직 중합수축률과 중합수축응력을 10 분 동안 기록하였고 인장탄성계수도 구하였다. 통계처리는 일원분산분석과 paired t-test를 시행하였고 95% 유의수준에서 Tukey's test로 사후 검정하였다. 측정된 중합수축 응력은 재료와 compliance의 유무에 따라 큰 차이를 보였다. Compliance를 허용한 모드에서 중합수축응력은 FF: 3.11 (0.13)이 가장 컸으며 Z1: 2.91 (0.10), Z2: 1.94 (0.09) Mpa의 순서였다. 측정장치의 compliance를 허용하지 않은 경우에는 Z1 17.08 (0.89)이 가장 컸고 FF: 10.11 (0.29), Z2: 9.46 (1.63) MPa의 순이었다. 또한 Z1, Z2, FF의 인장탄성계수는 각각 2.31 (0.18), 2.05 (0.20), 1.41 (0.11) GPa 이었다. 중합수축응력은 compliance mode에서는 복합레진의 수직 중합수축률이 주요 영향 요인이었으며, compliance를 배제한 모드에서는 탄성계수의 효과가 지배적이었다.

• 동력기계공학회지
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• 제13권6호
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• pp.35-42
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• 2009

The piping systems in the steam-driven power engines lie under the cyclic condition of thermal expansion and contraction by superheated steam. These phenomena might cause some severe damages on the pipes and the accessory devices. To avoid these damages, the calculation of the proper strength and the consideration of the reduced resultant forces on the materials are needed. In the present study, numerical investigations on the effects of the thermal deformation of the industrial piping system were performed with comparison of the design data. Commercial software, ABAQUS with the thermal-fluidic loadings based on the design conditions was used for the thermal stress analysis of the piping system. From the analysis of the initially-designed pipe supporters, the rearrangement was suggested to improve the piping design.

• 설비공학논문집
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• 제14권12호
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• pp.1056-1062
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• 2002

This paper reports the characteristics of the three dimensional turbulent flow in the 180 degree bends with decreasing cross-sectional area by numerical method. Calculated pressure and velocity, Reynolds stress distributions are compared to the experimental data. Turbulence model employed are low Reynolds number k-epsilon model and algebraic stress model. The results show that the main vortex generated from the inlet part of the bend maintained to outlet of the bend because of the contraction of cross-sectional area. The rate of increase of turbulent kinetic energy through the bend are lower than that of mean flow. Secondary flow strength of the flow is lower about 60% than that of square duct flow.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.108-113
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• 2004

Korea Gas Corp. has developed the design technology of the LNG storage tank. The membrane to be applied inside of the LNG storage tank is provided with corrugations to absorb thermal contraction and expansion caused by LNG temperature changes. It is very important to measure their thermal strains under LNG temperatures by analytical and experimental stress analysis of the membrane. We have developed a stress measurement system using strain gages and measured the strain during cooldown and storing the LNG. We also analyzed the measured data by comparison with the FEM data. On the basis of these results, we could design and assure the application of the Kogas Membrane to large scale LNG storage.

• 한국지반공학회논문집
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• 제27권2호
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• pp.35-42
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• 2011

현장타설말뚝의 하중전이분석 시, 말뚝에 작용하는 잔류응력은 종종 무시되어 왔다. 그러나 말뚝에 작용하는 초기 하중를 무시함에 따라서 분석된 하중전이거동이 실제 하중전이거동과 상이하게 나타나는 결과를 초래하기도 한다. 이러한 현장타설말뚝에 작용하는 잔류응력은 콘크리트의 수축/팽창 또는 지반의 특성에 영향을 받는 것으로 몇몇의 연구결과에 의하여 나타났다. 본 연구에서는 암반에 근입된 현장타설말뚝을 시험시공하여 잔류응력을 측정하고 분석 하였으며, 이에 따른 잔류응력에 미치는 요소들에 대하여 검토 분석하였다.

• 대한금속재료학회지
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• 제49권6호
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• pp.462-467
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• 2011

In order to understand why annealing at $480^{\circ}C$ for several hour prevents the initiation of PWSCC, the residual stress variation with isothermal annealing at $480^{\circ}C$ and isochronal annealing between 480 and $800^{\circ}C$ in cold rolled Alloy 600 was investigated by the XRD method. The isothermal annealing decreased residual stress slightly in the rolling direction but not in the transverse direction, whereas the isochronal annealing for two hours increased residual stress. It seemed that the decrease in residual stress by isothermal annealing was due to lattice contraction by an ordering reaction because the isothermal annealing increased hardness. The effects of the isochronal annealing could be interpreted as the influence of thermal expansion and a disordering reaction.

• 대한물리치료과학회지
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• 제13권2호
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• pp.129-135
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• 2006

Vascular smooth muscle contraction is mediated by activation of extracellular signal-regulated kinase (ERK) 1/2, an isoform of mitogen-activated protein kinase (MAPK). However, the role of stress-activated protein kinase/c-Jun N-terminal kinase (JNK) in vascular smooth muscle contraction has not been defined. We investigated the role of JNK in the contractile response to norepinephrine (NE) in rat aortic smooth muscle. NE evoked contraction in a dose-dependent manner, and this effect was inhibited by the JNK inhibitor SP600125. NE increased the phosphorylation of JNK, which was greater in aortic smooth muscle from hypertensive rats than from normotensive rats. NE-induced JNK phosphorylation was significantly inhibited by SP600125 and the conventional-type PKC (cPKC) inhibitor Go6976, but not by the Rho kinase inhibitor Y27632 or the phosphatidylinositol 3-kinase inhibitor LY294002. Thymeleatoxin, a selective activator of cPKC, increased JNK phosphorylation, which was inhibited by $G{\ddot{o}}6976$. SP600125 attenuated the phosphorylation of caldesmon, an actin-binding protein whose phosphorylation is increased by NE. These results show that JNK contributes to NE-mediated contraction through phosphorylation of caldesmon in rat aortic smooth muscle, and that this effect is regulated by the PKC pathway, especially cPKC.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.348-352
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• 2004

In finite element analysis of mechanical behavior of weld, typical process is first to obtain a finite element model containing residual stress by conducting welding analysis and then to examine the computational specimen for various external loading. The numerical specimen with residual stress has irregular boundary lines since one usually begins the welding analysis from a body having regular straight boundary lines and large thermal contraction takes place during cooling of weld metal. We notice that these numerical weld specimens are different from the real weld specimens as the real specimens are usually cut from a bigger weld part and consequently have straight boundaries neglecting elastic relaxation associated with the cutting. In this paper, an iterative finite element method is described to obtain a weld specimen which is bounded by straight lines. The stress distributions of two types of weld specimen, one with regular and the other with irregular boundaries, are compared to check the effect of the boundary shape. Results show that the stress distribution can be different when large plastic deformation is induced by the application of external loading. In case of elastic small deformation, the difference turns out almost negligible.

• 지역사회간호학회지
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• 제19권1호
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• pp.46-56
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• 2008

Purpose: The purpose of this study was to identify the effects of pelvic floor muscle exercise on reducing the symptoms of stress urinary incontinence and improving attitude toward exercise and quality of life. Method: The research adopted was a nonequivalent control group pretest posttest design. The subjects were 55 persons who were surveyed using a structured questionnaire, and 23 persons in the experimental group among the total sample were measured for the peak pressure and the duration of PMC and trained correct pelvic floor muscle contraction using peritron in the first week. Then, pelvic floor muscle exercise was implemented for 6 weeks. The data was analyzed by $\chi^2$-test and t-test with the SPSS 10.0 program. Results: 1) The degree of stress urinary incontinence, frequency of urination, nocturia, urgency, noctural incontinence, the frequency and quantity of incontinence, outer clothing change and incomplete emptying decreased significantly more in the experimental group than in the control group. 2) Attitude toward pelvic floor muscle exercise and the qualify of life were improved significantly more in the experimental group than in the control group. 3) The peak pressure and duration of PMC increased significantly more in the posttest. Conclusion: Based on the results above, it is judged that pelvic floor muscle exercise is an effective nursing intervention in order to care for stress urinary incontinence.

• 한국주조공학회지
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• 제25권5호
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• pp.209-215
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• 2005

The design of the Metal mold casting should consider several variables such as the material properties and shape of the mold. In particular, the thermal stress generated by the thermal expansion and contraction depending on the thermal gradient of the mold causes partial plastic deformation on the mold, which causes damage or fracture of the cast. Consequently, the thermal deformation along with thermal stress leads to thermal deformation of the cast itself. In this study, the temperature analysis of the cast and mold is simulated by FDM to control the thermal deformation and stress as a result of the thermal gradient of mold. Using the results from FDM simulation, the thermal deformation and stress are analyzed by FEM and, the optimal mold design with minimum thermal deformation of the cast is suggested.