• Computers and Concrete
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• 제16권1호
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• pp.67-97
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• 2015

This article presents a computing procedure developed to predict the torsional strength of axially restrained reinforced concrete beams. This computing procedure is based on a modification of the Variable Angle Truss Model to account for the influence of the longitudinal compressive stress state due to the axial restraint conditions provided by the connections of the beams to other structural elements. Theoretical predictions from the proposed model are compared with some experimental results available in the literature and also with some numerical results from a three-dimensional nonlinear finite element analysis. It is shown that the proposed computing procedure gives reliable predictions for the ultimate behaviour, namely the torsional strength, of axially restrained reinforced concrete beams under torsion.

• 대한약침학회지
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• 제20권4호
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• pp.257-264
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• 2017

Introduction: Pharmacopuncture, which combines acupuncture with herbal medicine, is one of the newly developed acupuncture techniques that has recently been put into use. The possible mechanisms of scolopendra pharmacopuncture, as well as its potential effects on depressive symptoms, were investigated in this study by using a mouse model of chronic immobilization stress (CIS). Methods: C57BL/6 male mice were randomly assigned into three groups: mice not stressed with restraint and injected with distilled water, mice stressed with restraint and injected with distilled water, and mice stressed with restraint injected with scolopendra pharmacopuncture at a cervical site. Behavioral tests (an open field test, tail suspension test, and forced swimming test) were carried out after two weeks of CIS and injection treatments. The expression levels of glial fibrillary acidic protein (GFAP) in the hippocampus were determined by using western blot and immunohistochemistry analyses. Results: Mice exposed to CIS showed decreased behavioral activity, while scolopendra pharmacopuncture treatment significantly protected against the depressive-like behaviors induced by CIS. Moreover, scolopendra pharmacopuncture treatment increased GFAP protein levels in the hippocampi of the mice stressed by chronic immobilization. Conclusion: Scolopendra pharmacopuncture has an ameliorating effect on depressive behavior, which is partially mediated through protection against glial loss in the hippocampus.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.391-396
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• 2002

The so called setting is defined as the onset of rigidity in fresh concrete. In the analysis of the early-age concrete behavior, we consider fresh concrete as a structural element immediately after mixing. But for the activation of real structural behavior of fresh concrete, it takes some time after the beginning of hydration reaction. So, the very early age deformations due to hydration heat and shrinkage which occur before the setting do not produce restraint stresses. In this paper, we propose a setting characteristic model based on the so called percolation theory. From the analysis using the model, the influence of curing temperature is investigated and analytical results are compared with experimental results. From the comparison, the validity of proposed model is verified. This model is also applied to evaluate stress development in a temperature-stress test machine (TSTM) specimen and then the effect of setting time on the stress development is discussed.

• 한국식품위생안전성학회지
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• 제5권4호
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• pp.187-196
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• 1990

랫드에서 스트레스에 의한 위궤양 모델 개발과 이에 영향을 미치는 몇가지 요인을 알아보기 위하여 본 실험을 실시하였다. 랫드를 적당한 크기의 속박틀에 넣어 속박만 시킨 것, 속박과 함께 침수시킨 것, 수온을 달리한 것 ($20^{\circ}C와\;30^{\circ}C$), 주령을 달리한 것 (5주령과 10주령), 성(sex)을 달리한 것, 절식시킨 것과 절식시키지 않은 것, Strain(Wistar 랫드와 Sprague-Dawley 랫드)을 달리한 것 등의 조건을 두어 8시간 있게 하였고, 발생한 궤양의 길이를 합하여 궤양지수 (ulcer index)를 구하였다. 본 연구의 결과는 속박과 함께 물에 침수시킨 것이 속박만 시킨 것에 비해 궤양지수가 유의성있게 (p<0.001) 높았으며, 궤양은 선위(glandular stomach) \에 국한되어서 발생했다. 또한 수온이 낮은 것이 높은 것보다 궤양지수가 높았고(p<0.001), 절식시킨 것이 절식시키지 않은 것보다 궤양지수가 높았으며(p<0.001), 연령이 낮은것(5주령)이 높은 것 (10주령)보다 궤양지수가 높았다.(p<0.001) 그러나, 성별(sex)에 의한 감수성 차이나 품종간(strain)에 의한 감수성의 차이는 없었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.591-594
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• 2005

Concrete structure that has been constructed in real field is on multi-axial stress state condition. After placing of concrete, hydration heat and shrinkage of concrete can cause various stress conditions with respect to the restraint level and condition. So, to predict the early age behavior of concrete structure, multi-axial material model is required and microplane model is acceptable. Recently, many studies have been performed on the microplane model, but the model developed up to now has been related to hardened concrete that material property is constant with concrete age. So, it is inappropriate to apply this model immediately to analyze the early age behavior of concrete. In this study, microplane model that can predict early age behavior of concrete was developed and cracking analysis using that was performed to describe cracking behavior for massive concrete sturucture.

• 생약학회지
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• 제43권1호
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• pp.72-78
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• 2012

Alnus japonica Steud (A. japonica) have long been used in the traditional medicine for gastric disorder, hepatitis and fatty liver in Korea. Antiulcer effects of A. japonica hot water extract (AJ ext) were evaluated by in vitro antibacterial activity against H. pylori, by the inhibitory action against the in vitro gastric $H^+/K^+$-ATPase and using rat models of gastric mucosal damage and gastric ulcer induced by HCl-ethanol, indomethacin, and restraint and water-immersion stress. For the determination of antibacterial activity of AJ ext against H. pylori, the activity of urease which released from H. pylori was measured in culture. AJ ext showed weak antibacterial activity against H. pylori with the growth inhibitions of 37% and 61% by adding final concentrations of 500 and $1000{\mu}g/ml$ culture, respectively at 24 h. To observe the inhibitory activity of AJ ext against the $H^+/K^+$-ATPase in hog gastric membrane vesicle, $IC_{50}$ value of AJ ext was $806.3{\mu}g/ml$. Pretreatment of AJ ext (200, 500 mg/kg, p.o.) prevented in a dose-dependent manner the acute gastritis in HCl-ethanol model and the formation of gastric ulcer in indomethacin model and restraint and water-immersion stress model. These results suggest that the AJ ext can be used for prevention and treatment of gastric mucosal damage and ulcers induced by various stress.

• Journal of Welding and Joining
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• 제28권2호
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• pp.60-65
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• 2010

Although two dimensional axi-symmetric modeling is useful for calculating the residual stresses of a cylindrical weldment such as a core barrel, this conventional axi-symmetric modeling can not express the behavior of shrinkage well in the locally heated weld zone. New technique of two dimensional axi-symmetric modeling using a virtual fixture is suggested to simulate the behavior of dimensional changes in the weld zone during the heating period of the welding. The virtual fixture in the model has a role to restrain the expansion of the high temperature heated region, which simulates equivalent intrinsic restraint effect of the weldment. In the restraint condition of the virtual fixture above the critical yield strength, the calculated shrinkages by using the suggested axi-symmetric model agreed well with those measured in a welded mock-up. The calculated residual stresses by using the suggested axi-symmetric model also agreed well with those calculated by using conventional axi-symmetric model which has beenused for calculating residual stresses in the weldment.

• International Journal of Naval Architecture and Ocean Engineering
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• 제7권5호
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• pp.805-816
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• 2015

In the present study, external restraints imposed normal to the plate during the cooling stage were determined to be effective for reduction of the angular distortion of butt-welded or fillet-welded plate. A welding analysis model under external force during the cooling stage was idealized as a prismatic member subjected to pure bending. The external restraint was represented by vertical force on both sides of the work piece and bending stress forms in the transverse direction. The additional bending stress distribution across the plate thickness was reflected in the improved inherent strain model, and a set of inherent strain charts with different levels of bending stress were newly calculated. From an elastic linear FE analysis using the inherent strain values taken from the chart and comparing them with those from a 3D thermal elasto-plastic FE analysis, welding deformation can be calculated.

• Structural Engineering and Mechanics
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• 제67권5호
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• pp.465-479
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• 2018

In a previous study, design charts where proposed to help the torsional design of axially restricted reinforced concrete (RC) beams with squared cross section. In this article, new design charts are proposed to cover RC beams with rectangular cross section. The influence of the height to width ratio of the cross section on the behavior of RC beams under torsion is firstly shown by using theoretical and experimental results. Next, the effective torsional strength of a reference RC beam is computed for several values and combinations of the study variables, namely: height to width ratio of the cross section, concrete compressive strength, torsional reinforcement ratio and level of the axial restraint. To compute the torsional strength, the modified Variable Angle Truss Model for axially restricted RC beams is used. Then, an extensive parametric analysis based on multivariable and nonlinear correlation analysis is performed to obtain nonlinear regression equations which allow to build the new design charts. These charts allow to correct the torsional strength in order to consider the favourable influence of the compressive axial stress that arises from the axial restraint.

• Steel and Composite Structures
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• 제9권2호
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• pp.89-101
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• 2009

This paper presents a simplified model to study post-buckling behaviours of the axially restrained steel column at elevated temperatures in fire. The contribution of axial deformation to the curvature of column section is included in theoretical equations. The possible unloading at the convex side of the column when buckling occurs is considered in the stress-strain relationship of steel at elevated temperatures. Parameters that affect structural behaviours of the axial restrained column in fire are studied. The axial restraint cause an increase in the axial force before the column buckles; the buckling temperature of restrained columns will be lower than non-restrained steel columns. However, the axial force of a restrained column decreases after the column buckles with the elevation of temperatures, so make use of the post-buckling behaviour can increase the critical temperature of restrained columns. Columns with temperature gradient across the section will produce lower axial force at elevated temperatures.