• 한국지반공학회지:지반
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• 제6권1호
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• pp.15-24
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• 1990

This paper describes the results of study on major factors influencing time-dependent deformation behaviour of swelling shales. The study was carried out by analyzing all the swell test results available for shales from southern Ontario. Major factors studied are (1) the presence of ambient water, (2) calcite content and (3) the applied stress. The results of the study on seven shales show that the swelling of shale is associated with the formation of cracks and the absorption of water in these cracks. The magnitude of swelling potential is related linearly to the amount of absorbed water. The presence of calcite inhibits the swelling of shales studied, reducing the swelling to zero at about 30% of calcite content. All the shales studied exhibit the stress-dependent swelling behaviour, though there Is a difference in the degree of dependency.

• Interaction and multiscale mechanics
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• 제4권2호
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• pp.123-137
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• 2011

We review a series of crack problems arising in the general deformations of a linearly elastic solid (Mode-I, Mode-II and Mode-III crack) and, perhaps more significantly, when the contribution of surface effects are taken into account. The surface mechanics are incorporated using the continuum based surface/interface model of Gurtin and Murdoch. We show that the deformations of an elastic solid containing a single crack can be decoupled into in-plane (Mode-I and Mode-II crack) and anti-plane (Mode-III crack) parts, even when the surface mechanics is introduced. In particular, it is shown that, in contrast to classical fracture mechanics (where surface effects are neglected), the incorporation of surface elasticity leads to the more accurate description of a finite stress at the crack tip. In addition, the corresponding stress fields exhibit strong dependency on the size of crack.

• Structural Engineering and Mechanics
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• 제15권4호
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• pp.395-414
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• 2003

In this paper we recall briefly the constitutive equations for solids subjected to thermal strain taking in account the bounded tensile stress of the material. In view to solve the equilibrium problem via the finite element method using the Newton Raphson procedure, we show that the tangent elasticity tensor is semi-definite positive. Therefore, in order to obtain a convergent numerical method, the constitutive equation needs to be modified. Specifically, the dependency of the stress by the anelastic deformation is made explicit by means of a parameter ${\delta}$, varying from 0 to 1, that factorizes the elastic tensor. This parameterization, for ${\delta}$ near to 0, assures the positiveness of the tangent elasticity tensor and enforces the convergence of the numerical method. Some numerical examples are illustrated.

• KSBB Journal
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• 제10권5호
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• pp.547-552
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• 1995

Some functional and rheological properties of the ${\gamma}$-polyglutamic acid(${\gamma}$-PGA) produced from alkalophilic Alcaligenes sp. were investigated. Viscosity synergism with thickening agents, capacities for gelling, entrapig of heavy metals, and flocculability of ${\gamma}$-PGA were not observed, but the relatively good compatability with various polyvalent metallic ins, excellent absorption ability and spinability were observed. The ${\gamma}$-PGA solution showed non-Newtonian flow behavior and exhibited pseudoplastic property with a yield stress at above 1% concentration. The values of flow index for 1% solution were in the range of 0.41∼0.75 showing shear rate dependency and the value of yield stress was 2.28 Pa. The value of consistency index was 0.868 Pa$.$Sn and was exponentially dependent on concentration.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.274-275
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• 2005

The tensile strain dependency of critical current in YBCO coated conductors was examined at 77K and in the self magnetic field. A commercially available YBCO sample with Cu stabilizer layer was supplied. There existed a peak in the relation between the Ie and tensile strain, and the reversible variation of $I_c$ with applied tensile strain was found. In the neutral axis Ni alloy RABiTS-$Y_2O_3$/YSZ/$CeO_2$ buffered YBCO tape, the $I_c$ recovered reversibly until the applied strain reached to about 0.5%, representing that a significant residual compressive strain induced during cooling to 77 K influenced the axial strain tolerance of YBCO conductors. To investigate the strain and stress influence on the $I_c$, the stress-strain characteristics of YBCO conductors measured at 77 K were discussed.

• 대한기계학회논문집A
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• 제35권7호
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• pp.745-751
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• 2011

입자강화 알루미늄 복합재의 강도를 계산하기 위하여 압밀 후 냉각할 때 일어나는 전위 펀칭을 유한요소로 모델링 하였다. 다양한 입자의 체적비에서 입자의 크기가 강도에 미치는 영향을 고려하기 위하여 강화 입자 주위에 변형률 구배 소성과 테일러 전위 모델을 적용하였다. 변형률 구배는, 구형 단위 셀이 냉각하는 동안 입자와 기지재의 열팽창계수 차이에 의한 전위 펀칭이 일어날 때 형성되는 등가소성변형률로부터 구하였다. 펀칭된 영역에 걸쳐 평균적으로 변형률 구배를 고려함으로써 항복 응력이 증가하는 것을 관찰하였다. 유한요소 해석을 활용하여 다양한 입자 크기와 체적비에 대하여 SiC 강화 알루미늄 356-T6 복합재의 축대칭 단위 셀의 인장시 강도의 변화를 예측하였다. 예측된 강도는 실험 데이터와 잘 일치하며, 입자 크기 의존 효과를 분명히 보인다.

• Applied Biological Chemistry
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• 제29권4호
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• pp.339-345
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• 1986

발아 옥수수로 부터 분리한 전분의 리올로지 특성을 생옥수수 전분과 비교검토하면서 조사하였다. 발아전분의 유동형태는 생전분과 마찬가지로 빙햄 의가소성 거동을 보였으나 발아전분 호화액의 점조도지수 및 항복응력은 생전분보다 낮은 값을 보였고, 유동거동지수는 비슷한 값을 보였다. 정조도지수의 온도 의존성은 발아전분이 생전분보다 낮았으나 농도 의존성은 변화가 없었다. 발아전분의 시간 의존특성은 생전분과 마찬가지로 틱소트로픽 거동을 보였으나 발아로 인하여 생전분에 비하여 전단하의 구조붕괴가 컸으며 탄성적 성질은 약한 특성을 나타내었다.

• Steel and Composite Structures
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• 제22권1호
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• pp.91-112
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• 2016

In this paper, post-buckling behavior of sandwich plates with functionally graded (FG) face sheets under uniform temperature rise loading is examined based on both sinusoidal shear deformation theory and stress function. It is supposed that the sandwich plate is in contact with an elastic foundation during deformation, which acts in both compression and tension. Thermo-elastic non-homogeneous properties of FG layers change smoothly by the variation of power law within the thickness, and temperature dependency of material constituents is considered in the formulation. In the present development, Von Karman nonlinearity and initial geometrical imperfection of sandwich plate are also taken into account. By employing Galerkin method, analytical solutions of thermal buckling and post-buckling equilibrium paths for simply supported plates are determined. Numerical examples presented in the present study discuss the effects of gradient index, sandwich plate geometry, geometrical imperfection, temperature dependency, and the elastic foundation parameters.

• Journal of Forest and Environmental Science
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• 제39권4호
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• pp.225-234
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• 2023

This study verified the effect of a combined forest/thermal therapy (FT/TT) program on participants with depressive symptoms and smoking or alcohol dependence. The participants included 20 people in the experimental group and 18 people in the control group. The experimental group participated in the FT/TT program for 2 nights and 3 days at the National Center for Forest Healing, in Hoengseong (National Hoengseong Supchewon), and a charcoal kiln operated by the Gangwon Charcoal Farming Association. The control group carried out their daily life for the same period. Psychological, physiological, and biochemical tests were conducted to determine the effect of the program. The results showed that there were significant improvements in stress, anxiety, depression, sleep quality, sleep satisfaction, and IL-6 levels. However, no significant difference was found in the cortisol, serotonin and melatonin levels between the experimental and control groups. Thus, the FT/TT therapy had psychological and biochemical effects on individuals with depression and nicotine or alcohol dependency. Further studies should be conducted to verify the effect of forest healing in various conditions.

• Structural Engineering and Mechanics
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• 제28권2호
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• pp.207-220
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• 2008

The shear lag has been studied for many years. Nevertheless, existing research gives a variety of stress concentration factors. Unlike the elementary beam theory, the application of load is not unique in reality. For example, concentrated load can be applied as point load or distributed load along the height of the web. This non-uniqueness may be a reason for the discrepancy of the stress concentration factors in the existing studies. The finite element method has been often employed for studying the effect of the shear lag. However, not many researches have taken into account the influence of the finite element mesh on the shear lag phenomenon, although stress concentration can be quite sensitive to the mesh employed in the finite element analysis. This may be another source for the discrepancy of the stress concentration factors. It also needs to be noted that much less studies seem to have been conducted for the shear lag effect on deflection while some design codes have formulas. The present study investigates the shear lag effect in a simply supported box girder by the three-dimensional finite element method using shell elements. The whole girder is modeled by shell elements, and extensive parametric study with respect to the geometry of a box girder is carried out. Not only stress concentration but also deflection is computed. The effect of the way load is applied and the dependency of finite element mesh on the shear lag are carefully treated. Based on the numerical results thus obtained, empirical formulas are proposed to compute stress concentration and deflection that includes the shear lag effect.