• Macromolecular Research
• /
• 제9권5호
• /
• pp.277-284
• /
• 2001

Poly(exo-3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride)s [poly(ETA)s] and poly($\alpha$-ethoxy-exo-3,6-epoxy-1,2,3,6-tetrahydrophthaloyl-5-fluorouracil)s [poly(EETFU)s ] with various average molecular weights were prepared by photopolymerizations. The number average molecular weights of the fractionated poly(ETA)s and poly(EETFU)s determined by GPC were in the range of 3,600∼21,000 and 3,600-33,400, respectively. The release rate of 5-FU from poly(EETFU) decreased with increasing average molecular weight. The in vitro cytotoxicity of poly(ETA) against a normal cell line was lower than that of 5-fluorouracil(5-FU), The in vivo antitumor activities of the synthesized samples at dosage of 0.8 mg/kg against mice bearing sarcoma 180 tumor cell line decreased in the following order: poly(EETFU) > poly(ETA) > EETFU > ETA > 5-FU. The antiangiogenic activities of the poly(ETA)s were better than those of 5-FU.

• Structural Engineering and Mechanics
• /
• 제17권5호
• /
• pp.691-706
• /
• 2004

The paper presents shear lag parameters for beam-to-column connections in steel box piers. Previous researches have analyzed beam-to-column connections in steel piers using a shear lag parameter ${\eta}_o$ obtained from a simple beam model, which is not based on a reasonable design assumption. Instead, the current paper proposes a cantilever beam model and has proved the effectiveness through theoretical and experimental studies. The paper examines the inaccuracy of the previous researches by estimating the effective width, the width-span length ratio L/b, and the sectional area ratio S of a cantilever beam. Two different shear lag parameters are defined using the cantilever model and the results are compared each other. The first type of shear lag parameter ${\eta}_c$ of a cantilever beam is derived using additional moments from various stress distribution functions while the other shear lag parameter ${\eta}_{eff}$ of a cantilever beam is defined based on the concept of the effective width. An evaluation method for shear lag stresses has been investigated by comparing analytical stresses with test results. Through the study, it could be observed that the shear lag parameter ${\eta}_{eff}$ agrees with ${\eta}_c$ obtained from the $2^{nd}$ order stress distribution function. Also, it could be observed that the shear lag parameter ${\eta}_c$ using the $4^{th}$ order stress distribution function almost converges to the upper bound of test results.

• 대한수학회논문집
• /
• 제34권1호
• /
• pp.303-319
• /
• 2019

The aim of the present paper is to study the Eisenhart problems of finding the properties of second order parallel tensors (symmetric and skew-symmetric) on a 3-dimensional LCS-manifold. We also investigate the properties of Ricci solitons, Ricci semisymmetric, locally ${\phi}$-symmetric, ${\eta}$-parallel Ricci tensor and a non-null concircular vector field on $(LCS)_3$-manifolds.

• 한국사회복지학
• /
• 제56권4호
• /
• pp.215-238
• /
• 2004

이혼가정자녀들의 부모이혼 후 적응방법을 찾기 위해 부모갈등, 부모양육태도 그리고 이혼에 대한 지각이 이혼 후 자녀들의 행동적응에 미치는 경로를 분석하였다. 이를 위해 부모가 이혼한 가정의 자녀 261명을 대상으로 설문지를 이용한 자료를 수집하였다. 수집된 자료는 구조방정식모형(SEM)을 사용해 분석되었다. 나타난 결과를 요약하면, 부모간 갈등은 부모의 양육태도와 이혼에 대한 지각에 직접적인 영향을 미치며 아동의 행동문제에는 간접적 영향을 미치는 것으로 나타났다. 부모의 양육태도는 이혼지각에 직접 영향을 주며 아동의 행동문제에 간접적인 영향을 미치나 총효과를 보면, 이혼지각에 더 강력한 영향을 미치는 것으로 나타났다. 즉, 부모의 양육태도가 부정적일수록 아동의 부모이혼에 대한 지각은 더욱 부정적으로 나타나며, 이혼에 대한 부정적 인식이 아동의 행동문제를 강력하게 예측하는 것으로 나타났다. 이는 부모의 양육태도에 따라 아동의 이혼에 대한 인식이 달라질 수 있음을 시사한다. 파악된 현상을 근거로 이혼 후 자녀들의 행동적응을 위한 예방과 전략이 모색되었다.

• Journal of applied mathematics & informatics
• /
• 제28권5_6호
• /
• pp.1323-1329
• /
• 2010

In this paper, a new fixed point theorem in cone is applied to obtain the existence of at least one positive pseudo-symmetric solution for the second order three-point boundary value problem {x" + f(t, x, x')=0, t $\in$ (0, 1), x(0)=0, x(1)=x($\eta$), where f is nonnegative continuous function; ${\eta}\;{\in}$ (0, 1) and f(t, u, v) = f(1+$\eta$-t, u, -v).

• Journal of applied mathematics & informatics
• /
• 제27권1_2호
• /
• pp.183-194
• /
• 2009

In this paper, we considered the following four-point boundary value problem $\{{x"(t)+h(t)f(t,x(t),x'(t))=0,\;0<t<1\atop%20x'(0)=ax(\xi),\;x'(1)=bx(\eta)}\$. where $0\;<\;{\xi}\;<\;{\eta}\;<\;1,\;{\delta}\;=\;ab{\xi}\;-\;ab{\eta}\;+\;a\;-\;b\;<\;0,\;0\;<\;a\;<\;\frac{1}{\xi},\;0\;<\;b\;<\;\frac{1}{\eta}$. After the discussion of the Green function of the corresponding homogeneous system, we establish some criteria for the existence of positive solutions by using the generalized Leggett-William's fixed point theorem. The interesting point is the expression of the Green function, which is a difficulty for multi-point BVP.

• 전산구조공학
• /
• 제11권4호
• /
• pp.351-360
• /
• 1998

본 논문에서는 실용적 체계신뢰성에 기초한 강사장교의 안전도평가를 위한 체계적인 모형을 제안하였다. 공용중인 강사장교의 시스템 안전도평가를 위하여 요소신뢰성해석을 위한 케이블, 주형 그리고 주탑의 한계 상태모형과 각 요소들간의 조합파괴를 포함하는 주파괴경로를 정의할 수 있는 체계신뢰성해석 모형을 제안하였다. 요소신뢰성해석을 위한 수치해석기법으로는 AFOSM(Advanced First Order Second Moment) 방법을 사용하였고, 체계신뢰성해석을 위해서는 부분 ETA(partial Event Tree Analysis) 모형을 사용하였다. 제안된 방법의 타당성을 고찰하기 위하여 진도대교의 안전도 평가에 적용하였다. 부분 ETA 모혀을 사용한 체계신뢰성 평가 방법은 기존의 요소신뢰성 방법에 비해 구조물의 여용성을 충분히 반영하는 상당히 합리적이며 실제적인 결과를 보여주는 실용적인 방법으로 판단된다.

• 대한수학회지
• /
• 제47권5호
• /
• pp.985-1000
• /
• 2010

Sufficient conditions for the existence of positive solutions for a coupled system of nonlinear nonlocal boundary value problems of the type -x"(t) = f(t, y(t)), t $\in$ (0, 1), -y"(t) = g(t, x(t)), t $\in$ (0, 1), x(0) = y(0) = 0, x(1) = ${\alpha}x(\eta)$, y(1) = ${\alpha}y(\eta)$, are obtained. The nonlinearities f, g : (0,1) $\times$ (0, $\infty$ ) $\rightarrow$ (0, $\infty$) are continuous and may be singular at t = 0, t = 1, x = 0, or y = 0. The parameters $\eta$, $\alpha$, satisfy ${\eta}\;{\in}\;$ (0,1), 0 < $\alpha$ < $1/{\eta}$. An example is provided to illustrate the results.

• 대한수학회지
• /
• 제57권4호
• /
• pp.1031-1052
• /
• 2020

In this paper our aim is to find various radii problems of the generalized Mittag-Leffler function for three different kinds of normalization by using their Hadamard factorization in such a way that the resulting functions are analytic. The basic tool of this study is the Mittag-Leffler function in series. Also we have shown that the obtained radii are the smallest positive roots of some functional equations.

• 한국표면공학회지
• /
• 제24권2호
• /
• pp.80-87
• /
• 1991

Investigations have been made in order to improve the toughness of TiC coated Cemented Carbide tools by CVD. The effects of coating parameters on TiC layer and eta phase and the effects of the thickness of TiC Coated layer and eta phase on TRS were studied.