• 한국지반공학회논문집
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• 제34권12호
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• pp.43-58
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• 2018

본 연구에서는 매입말뚝 주면부의 하중전이 거동을 확인하기 위하여 14본의 강관매입말뚝에 대한 정재하시험을 수행하였다. 정재하시험을 통하여 하중-침하 곡선 및 축하중 분포를 계측하였으며, 그 결과 말뚝-지반 사이에서 발생되는 주면마찰력을 정량화 하였다. 이를 토대로 강관매입말뚝의 일반적인 하중전이곡선 형태를 도출하였다. 본 연구 결과, 말뚝의 주면하중전이 거동은 연성과 취성파괴 두 가지 형태로 나타났다. 그 결과, 강관매입말뚝의 t-z 곡선을 쌍곡선(일수현상이 없는 경우)과 톱니 형태(일수현상이 있는 경우 또는 표준관입저항치, $N{\geq}50$인 풍화암 이상)로 각각 제안하였다. 그때의 최대주면마찰력은 쌍곡선의 경우 지반의 N치 또는 암반의 일축압축강도, 톱니 형태의 경우 주입된 시멘트풀에 의해 형성된 쏘일-시멘트층의 일축압축강도의 영향을 받는 것으로 나타났다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1996년도 봄 학술발표회 논문집
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• pp.99-106
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• 1996

• 대한금속재료학회지
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• 제49권4호
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• pp.275-280
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• 2011

This paper focuses on reliability prediction of long-term creep strength for Modified 9Cr-1Mo steel (Gr. 91) which is considered as one of the structural materials of next generation reactor systems. A "Z-parameter" method was introduced to describe the magnitude of standard deviation of creep rupture data to the master curve which can be plotted by log stress vs. The larson-Miller parameter (LMP). Statistical analysis showed that the scattering of the Z-parameter for the Gr. 91 steel well followed normal distribution. Using this normal distribution of the Z-parameter, the various reliability curves for creep strength design, such as stress-time temperature parameter reliability curves (${\sigma}$-TTP-R curves), stress-rupture time-reliability curves (${\sigma}-t_{r}-R$ curves), and allowable stress-temperature- reliability curves ([${\sigma}$]-T-R curves) were reasonably drawn, and their results are discussed.

• 대한수학회보
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• 제26권2호
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• pp.169-173
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• 1989

Let V={(x,y,z):f=z$^{n}$ -npz+(n-1)q=0 for n .geq. 3} be a compled analytic subvariety of a polydisc in $C^{3}$ where p=p(x,y) and q=q(x,y) are holomorphic near (x,y)=(0,0) and f is an irreducible Weierstrass polynomial in z of multiplicity n. Suppose that V has an isolated singular point at the origin. Recall that the z-discriminant of f is D(f)=c(p$^{n}$ -q$^{n-1}$) for some number c. Suppose that D(f) is square-free. then we prove that by Theorem 2.1 .mu.(p$^{n}$ -q$^{n-1}$)=.mu.(f)-(n-1)+n(n-2)I(p,q)+1 where .mu.(f), .mu. p$^{n}$ -q$^{n-1}$are the corresponding Milnor numbers of f, p$^{n}$ -q$^{n-1}$, respectively and I(p,q) is the intersection number of p and q at the origin. By one of applications suppose that W$_{t}$ ={(x,y,z):g$_{t}$ =z$^{n}$ -np$_{t}$ $^{n-1}$z+(n-1)q$_{t}$ $^{n-1}$=0} is a smooth family of complex analytic varieties near t=0 each of which has an isolated singularity at the origin, satisfying that the z-discriminant of g$_{t}$ , that is, D(g$_{t}$ ) is square-free. If .mu.(g$_{t}$ ) are constant near t=0, then we prove that the family of plane curves, D(g$_{t}$ ) are equisingular and also D(f$_{t}$ ) are equisingular near t=0 where f$_{t}$ =z$^{n}$ -np$_{t}$ z+(n-1)q$_{t}$ =0.}$ =0.

• 한국지반공학회논문집
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• 제17권6호
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• pp.193-205
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• 2001

본 연구에서는 수직 및 수평하중을 받는 군말뚝의 배열 및 중심간격을 고려한 실내모형실험을 수행하여 군말뚝기초의 거동특성을 분석하였다. 모형말뚝은 PVC말뚝을 사용하였으며 모형지반은 주문진표준사를 이용해 조밀한 사질토 지반(Dr=73%)으로 조성하였다. 말뚝의 배열은 $2\times2,\; 3\times3$ 배열, 말뚝중심간격은 말뚝직경의 2.5, 5.0, 7.5 배인 경우를 고려하였다. 실험결과 수직하중을 받는 말뚝에서는 두부에서의 수직하중-침하량곡선, 하중전이함수인 주면마찰락력-변위곡선(t-z 곡선)과 선단지지력-변위곡선(q-z 곡선)을 구하였으며, 수평하중을 받는 말뚝에서는 두부에서의 수평하중-수평변위곡선, 하중전이함수인 지반반력-변위곡선(p-y곡선)을 구하였고 이를 토대로 말뚝의 배열 및 중심간격에 따른 군말뚝계수를 제안하였다. 또한 수평하중을 받는 군말뚝의 각 열에 대해 상호작용계수(P-multiplier)를 산정하였다.

• Interaction and multiscale mechanics
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• 제4권4호
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• pp.321-336
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• 2011

This paper presents the results of static vertical load tests carried out on a model building frame supported by pile groups embedded in cohesionless soil (sand). The effect of soil interaction on displacements and rotation at the column base and also the shears and bending moments in the columns of the building frame were investigated. The experimental results have been compared with those obtained from the finite element analysis and conventional method of analysis. Soil nonlinearity in the lateral direction is characterized by the p-y curves and in the axial direction by nonlinear vertical springs along the length of the piles (${\tau}-z$ curves) at their tips (Q-z curves). The results reveal that the conventional method gives the shear force in the column by about 40-60%, the bending moment at the column top about 20-30% and at the column base about 75-100% more than those from the experimental results. The response of the frame from the experimental results is in good agreement with that obtained by the nonlinear finite element analysis.

• 전기학회논문지
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• 제66권2호
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• pp.363-369
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• 2017

This paper presents the experimental results related to soil ionization and electrical breakdown in a concentric hemispherical electrode system under lightning impulse voltages. Dynamic voltage-current and impedance-time characteristics of soil ionization were measured and analyzed. Also the electrical breakdowns of the soil gap were investigated. The time-lag to the peak current corresponds to the soil ionization propagation. The time of ionization propagation in wet sand is found to decrease with increasing the impulse currents. A drastic decrease in ground resistance was observed during the impulse current spreading in sand. The electrical breakdown appears at the wave tail of impulse voltage and results in a wide scatter in V-t curves. The voltage-current curves have a fan-like shape attributed to ionization processes which result in increasing current and decreasing voltage.

• 소성∙가공
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• 제4권2호
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• pp.159-168
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• 1995

The torsion tests in the range of $550~800^{\circ}C$, $5.0{\times}10^{-3}~5.0{\times}10^0/sec$ were performed to study the effects of strain rate$(\.{\varepsilon})$ and temperature(T) on the hot strength of Cu-Zn alloy. High temperature flow stresses of this alloy increased with increasing $\.{\varepsilon}$ and/or decreasing T, and than the more grain refinement could be obtained. The flow curves exhibited a peak followed by a steady steady state regime as a result of dynamic recrystallization. The hot strength dependence of $\.{\varepsilon}$ and T was described by a hyperbolic sine law, $\.{\varepsilon}=A(sinh0.017{\sigma})^4.81$exp(-216KJ/mol). Hot strength could be reduced at the arbitary condition, $\.{\varepsilon}$ and T, by constitutive parameter Z(Zenner-Hollomon parameter), $Z=A(sinh{\alpha}{\sigma})^n=\.{\varepsilon}$exp(Q/RT).

• 한국초전도ㆍ저온공학회논문지
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• 제15권2호
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• pp.16-19
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• 2013

The magneto-resistivity and electric field-current density (E-J) curves were investigated up to a magnetic field 9 T in the optimally doped $BaFe_{1.8}Co_{0.2}As_2$ single crystal with a superconducting temperature ($T_c$) of 24.6 K. The E-J Scaling behaviors below and above vortex glass transition temperature ($T_g$) were found, confirming the existence of the vortex glass phase transition. The critical exponents for the diverging spatial and time correlations at $T_g$, were obtained as v = $1.1{\pm}0.1$ and z = $4.5{\pm}0.3$, respectively. The obtained critical exponents are in good agreement with the predicted values of v ~ 1 - 2 and z > 4 within the 3D vortex glass theory.

• 천문학회보
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• 제41권2호
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• pp.40.2-40.2
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• 2016

The attenuation of starlight by dust in galactic environments is investigated through models of radiative transfer in a spherical, clumpy interstellar medium (ISM). We show that the attenuation curves are primarily determined by the wavelength dependence of absorption rather than by the underlying extinction (absorption+scattering) curve; the observationally derived attenuation curves cannot constrain a unique extinction curve unless the absorption or scattering efficiency is specified. Attenuation curves consistent with the Calzetti curve are found by assuming the silicate-carbonaceous dust model for the Milky Way (MW), but with the $2175{\AA}$ bump suppressed or absent. The discrepancy between our results and previous work that claimed the Small Magellanic Cloud dust to be the origin of the Calzetti curve is ascribed to the difference in adopted albedos; we use the theoretically calculated albedos whereas the previous ones adopted empirically derived albedos from observations of reflection nebulae. It is found that the model attenuation curves calculated with the MW dust are well represented by a modified Calzetti curve with a varying slope and UV bump strength. The strong correlation between the slope and UV bump strength, as found in star-forming galaxies at 0.5 < z < 2.0, is well reproduced if the abundance of the UV bump carriers is assumed to be 30-40% of that of the MW-dust; radiative transfer effects lead to shallower attenuation curves with weaker UV bumps as the ISM is more clumpy and dustier. We also argue that some of local starburst galaxies have a UV bump in their attenuation curves, albeit very weak.