• Computers and Concrete
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• 제2권2호
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• pp.125-146
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• 2005

The objective of this paper is setting out, for a cable-stayed bridge with a curtain suspension, a method to determine the modes of vibration of the structure. The system of differential equations governing the vibrations of the bridge, derived by means of a variational formulation in a nonlinear field, is reported in Appendix C. The whole analysis results from the application of Hamilton's principle, using the expressions of potential and kinetic energies and of the virtual work made by viscous damping forces of the various parts of the bridge (Monaco and Fiore 2003). This paper focuses on the equation concerning the transversal motion of the girder of the cable-stayed bridge and in particular on its final form obtained, restrictedly to the linear case, neglecting some quantities affecting the solution in a non-remarkable way. In the hypotheses of normal mode of vibration and of steady-state, we propose the resolution of this equation by a particular method based on a numerical approach. Respecting the boundary conditions, we derive, for each mode of vibration, the corresponding frequency, both natural and damped, the shape-function of the girder axis and the exponential function governing the variability of motion amplitude in time. Finally the results so obtained are compared with those deriving from the dynamic analysis performed by a finite elements calculation program.

• Steel and Composite Structures
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• 제17권3호
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• pp.271-285
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• 2014

This paper aims to examine the behavior of slender reinforced concrete columns confined with external glass fiber reinforced polymers (GFRP) sheets under eccentric loads. The experimental work conducted in this paper is an extension to previous work by the author concerning the behavior of eccentrically loaded short columns strengthened with GFRP wrapping. In this study, nine reinforced concrete columns divided into three groups were casted and tested. Three eccentricity ratios corresponding to e/t = 0, 0.10, and 0.50 in one direction of the column were tested in each group. The first group was the control one without confinement with slenderness ratio equal 20. The second group was the same as the first group but fully wrapped with one layer of GFRP laminates. The third group was also fully wrapped with one layer of GFRP laminates but having slenderness ratio equal 15. The experimental results of another two groups from the previous work were used in this study to investigate the difference between short and slender columns. The first was control one with slenderness ratio equal 10 and the second was fully wrapped and having the same slenderness ratio. All specimens were loaded until failure. The ultimate load, axial deformation, strain in steel bars, and failure mechanisms of each specimen were generated and analyzed. The results show that GFRP laminates confining system is less effective with slender columns compared with short one, but this solution is still applied and it can be efficiently utilized especially for slender columns with low eccentric ratio.

• 디지털콘텐츠학회 논문지
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• 제10권4호
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• pp.521-527
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• 2009

본 논문에서는 마커 기반의 가상 객체나 opengl 을 이용하여 구현된 가상 객체, 웹 카메라 영상 프레임을 통해 입력된 실물 객체의 충돌처리를 유효화시켜 사용자에게 보다 높은 현실성을 제공하는 증강현실 충돌기법을 제안한다. 증강현실 시스템은 현실의 환경에 가상의 객체를 추가하여 사용자에게 시각적 정보를 제공하는 시스템으로 객체간의 상호작용, 사용자와의 상호작용에 대하여 관심이 높아가고 있다. 그러나 본 논문에서 제안한 충돌처리는 상호작용에 있어서 가장 기본적인 문제가 되기 때문에 선결해야 할 문제이다. 따라서 제안된 시스템에서는 이 문제를 해결하여 마커를 기반으로 구현된 객체와 Opengl을 기반으로 구현된 가상 객체, 웹 카메라 영상 프레임으로부터 입렵된 실물 객체 사이에서 객체간의 충돌을 유효화 시킴으로써 현실성과 몰입도를 증대시킨다.

• 한국수학사학회지
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• 제28권2호
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• pp.85-102
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• 2015

Elliptic curves are a common theme among various fields of mathematics, such as number theory, algebraic geometry, complex analysis, cryptography, and mathematical physics. In the history of elliptic curves, we can find number theoretic problems on the one hand, and complex function theoretic ones on the other. The elliptic curve theory is a synthesis of those two indeed. As an overview of the history of elliptic curves, we survey the Diophantine equations of 3rd degree and the congruent number problem as some of number theoretic trails of elliptic curves. We discuss elliptic integrals and elliptic functions, from which we get a glimpse of idea where the name 'elliptic curve' came from. We explain how the solution of Diophantine equations of 3rd degree and elliptic functions are related. Finally we outline the BSD conjecture, one of the 7 millennium problems proposed by the Clay Math Institute, as an important problem concerning elliptic curves.

• 한국과학교육학회지
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• 제16권3호
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• pp.278-285
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• 1996

High school students' achievements in algorithmic problems, and figure-formatted and textual-formatted conceptual problems concerning stoichiometry, gaseous state, and solution, were measured by the Chemistry Problem Solving Ability Test. The relationships among the achievement scores in the three types of problems and cognitive variables such as logical thinking ability, mental capacity, and field dependence/field independence were examined. The portion of variance of explanation for each achievement score was also studied by a multiple regression analysis. The results showed that logical thinking ability was significantly correlated with the achievement score in the algorithmic problems, and accounted for the significant portion of the variance of the score. Mental capacity accounted for the significant portion of the variance of the score in the figure-formatted conceptual problems. Although field dependence/field independence was significantly correlated with all the achievement scores, it did not significantly account for any scores in multiple regression analyses. However, the magnitudes of correlation coefficients among the achievement scores were higher than those between the achievement scores and cognitive variables. The best predictor for each score was also found to be one of the other achievement scores. Educational implications are discussed.

• Membrane and Water Treatment
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• 제4권2호
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• pp.127-142
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• 2013

In order to investigate the significance of "salting-out" and "pore swelling" effects on the nanofiltration of neutral solutes, rejection properties of two NF ceramic and polymeric membranes were studied with single polyethyleneglycol (PEG) solution and mixed PEG/inorganic electrolyte solutions. For both membranes, the rejection rate of PEG was found to decrease significantly in the presence of ions. In the case of the ceramic membrane (rigid pores), this phenomenon was imputed to the sole partial dehydration of PEG molecules induced by the surrounding ions. This assumption was confirmed by the lowering of the PEG rejection rates which followed the Hofmeister series. Experimental data were used to compute the resulting decrease in the Stokes radius of PEG molecules in the presence of the various salts. Concerning the polymeric membrane, the decrease in the rejection rate was found to be systematically higher than for the ceramic membrane. The additional decrease was then ascribed to the swelling of the pores. The experimental data of rejection rates were then used to compute the variation in the mean pore radius in the presence of the various salts. The pore swelling phenomenon due to accumulation of counterions inside pores was supported by electrokinetic charge density measurements.

• 한국측량학회지
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• 제17권4호
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• pp.383-391
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• 1999

본 논문은 GIS를 사용하여 1998년도 전국의 벼 병해충을 분석하고, 처리된 자료를 인터넷을 통해 정보를 공유 및 분석하는 인터넷 GIS 시스템의 개발에 관한 것이다. 인터넷 GIS는 컴퓨터 네트워크의 광범위한 활용성에 의해 인터넷 환경에서 GIS의 기능을 구현하는 시스템으로서, 본 연구에서는 대화식 인터페이스로 구성된 인터넷 GIS를 개발함으로써 클라이언트들이 기존의 정적인 지도와 양적인 통계 값의 벼 병해충 자료대신에 인터넷상에서 시각적이고 동적인 정보를 제공받을 수 있는 효율적인 방안을 제시하였다.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2001년도 학술대회지
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• pp.11-16
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• 2001

본 연구는 하도급법 제14조에 규정된 하도급대금의 직접지급에 따른 계약관리방안을 제시하는 것을 목적으로 한다. 이를 위하여 문헌조사 및 연역적 논증의 방법을 이용하였다. 본 연구의 결과를 요약하면 다음과 같다. (1) 하도급대금직접지급의 요건과 효과를 고찰하여 그 의미와 내용을 명확히 하였다. (2) 하도급대금직접지급과 관련한 실무상·이론상 쟁점에 대한 검토와 논증을 통하여 타당한 해석을 제시하였다. (3) 하도급대금의 직접지급에 따른 발주자·원수급인·하수급인의 계약관리방안을 제시하였다.

• Fibers and Polymers
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• 제6권1호
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• pp.35-41
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• 2005

Research and development of nano fiber products is very active over the world. Physical characteristics and dyeing properties of nylon 66 nano fiber were investigated in this study. X-ray diffraction, DSC, analysis of amino end group, and water absorption were performed to get information concerning physical properties of nano fiber. Nylon 66 nano fiber was dyed with high molecular mass acid dyes. Effects of dyeing temperature, pH of dyeing solution, and concentration of acid dyes on dyeing properties such as rate of dyeing and the extent of exhaustion, were examined and compared to those of regu­lar fiber. It was found that nano fiber adsorbed acid dyes at lower temperature, got rapidly dyed, and its extents of exhaustion at specific dyeing temperature were higher than regular fiber. It was also observed that nano fiber could adsorb a large amount of acid dye without a significant loss in the extent of exhaustion. Washing fastness of the dyed nano fiber was lower by $1/2\~1$ grade, light fastness by 1 grade than the dyed regular fiber.

• Computers and Concrete
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• 제4권5호
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• pp.403-424
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• 2007

The investigation of corrosion effects on the tensile behavior of reinforced concrete (RC) members is very important in region prone to high corrosion conditions. In this article, an experimental study concerning corrosion effects on tensile behavior of RC members is presented. For this purpose, a comprehensive experimental program including 58 cylindrical reinforced concrete specimens under various levels of corrosion is conducted. Some of the specimens (44) are located in large tub containing water and salt (5% salt solution); an electrical supplier has been utilized for the accelerated corrosion program. Afterwards, the tensile behavior of the specimens was studied by means of the direct tension tests. For each specimen, the tension stiffening curve is plotted, and their behavior at various load levels is investigated. Average crack spacing, loss of cross-section area due to corrosion, the concrete contribution to the tensile response for different strain levels, and maximum bond stress developed at each corrosion level are studied, and their appropriate relationships are proposed. The main parameters considered in this investigation are: degree of corrosion ($C_w$), reinforcement diameter (d), reinforcement ratio (${\rho}$), clear concrete cover (c), ratio of clear concrete cover to rebar diameter (c/d), and ratio of rebar diameter to reinforcement percentage ($d/{\rho}$).