• 한국학교수학회논문집
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• 제4권1호
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• pp.103-114
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• 2001

The purpose of this study is to develop learning materials for functional concept on variable and to verify the effect of how well students could learn functional concept after they studied with those materials. To accomplish the purpose of this study, I developed learning materials and after teaching students with them. I have concluded the followings : First, there was little effect in teaching functional concept on variable between two experimental groups, whereas teaching functional concept had greater effect on forming functional concept in high level groups in those two experimental groups. Second, teaching functional concept on variable had little effect on students' understanding of functional concept and perfecting tables in Black box, graph, and mathematical problems, whereas there was much effect in students' understanding functional concept and solving relation formula, image, and range problems related to everyday life or general things. On the basis of the problems which appeared in the process of this study, the following can be suggested : First, we should develop learning materials fit for low level students so that they could understand functional concept. Second, we should continue to teach the basic problems like solving relation formula, image, and range, and understanding functional concept in graph until students are able to understand them exactly. Third, since the goals of Unit Function in a middle school textbook is to solve problems related to everyday life through functional thinking, there should be change in constructing systematic contents of Unit Function in a middle school textbook.

• Steel and Composite Structures
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• 제22권6호
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• pp.1487-1505
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• 2016

This paper presents the results of an experimental study on the behavior of a new type of composite FRP-concrete-steel member subjected to bi-axial eccentric loading. This new type of composite member is in the form of concrete-filled square steel tube slender columns with inner CFRP (carbon fiber-reinforced polymer) circular tube, composed of an inner CFRP tube and an outer steel tube with concrete filled in the two tubes. Tests on twenty-six specimens of high strength concrete-filled square steel tube columns with inner CFRP circular tube columns (HCFST-CFRP) were carried out. The parameters changed in the experiments include the slenderness ratio, eccentric ratio, concrete strength, steel ratio and CFRP ratio. The experimental results showed that the failure mode of HCFST-CFRP was similar to that of HCFST, and the specimens failed by local buckling because of the increase of lateral deflection. The steel tube and the CFRP worked together well before failure under bi-axial eccentric loading. Ductility of HCFST-CFRP was better than that of HCFST. The ultimate bearing capacity of test specimen was calculated with simplified formula, which agreed well with test results, and the simplified formula can be used to calculate the bearing capacity of HCFSTF within the parameters of this test.

• Geomechanics and Engineering
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• 제22권5호
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• pp.375-384
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• 2020

In this study, the application of conventional cubic law to a deep depth condition was experimentally evaluated. Moreover, a modified equation for estimating the rock permeability at a deep depth was suggested using precise hydraulic tests and an effect analysis according to the vertical stress, pore water pressure and fracture roughness. The experimental apparatus which enabled the generation of high pore water pressure (< 10 MPa) and vertical stress (< 20 MPa) was manufactured, and the surface roughness of a cylindrical rock sample was quantitatively analyzed by means of 3D (three-dimensional) laser scanning. Experimental data of the injected pore water pressure and outflow rate obtained through the hydraulic test were applied to the cubic law equation, which was used to estimate the permeability of rock fracture. The rock permeability was estimated under various pressure (vertical stress and pore water pressure) and geometry (roughness) conditions. Finally, an empirical formula was proposed by considering nonlinear flow behavior; the formula can be applied to evaluations of changes of rock permeability levels in deep underground facility such as nuclear waste disposal repository with high vertical stress and pore water pressure levels.

• Steel and Composite Structures
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• 제30권4호
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• pp.337-350
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• 2019

The objective of this paper is to investigate the confinement coefficient of concrete-filled square stainless steel tubular (CFSSST) stub columns under axial loading. A fine finite 3D solid element model was established, which utilized a constitutive model of stainless steel considering the strain-hardening characteristics and a triaxial plastic-damage constitutive model of concrete with features of the parameter certainty under axial compression. The finite element analysis results revealed that the increased ultimate bearing capacity of CFSSST stub columns compared with their carbon steel counterparts was mainly due to that the composite action of CFSSST stub columns is stronger than that of carbon steel counterparts. A further parametric study was carried out based on the verified model, and it was found that the stress contribution of the stainless steel tube is higher than the carbon steel tube. The stress nephogram was simplified reasonably in accordance with the limit state of core concrete and a theoretical formula was proposed to estimate the ultimate bearing capacity of square CFSSST stub columns using superposition method. The predicted results showed satisfactory agreement with both the experimental and FE results. Finally, the comparisons of the experimental and predicted results using the proposed formula and the existing codes were illustrated.

• 대한한의학방제학회지
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• 제27권2호
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• pp.151-165
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• 2019

Objectives : To analyze the latest study trend on effect of herbal medicine treatment for Colorectal Cancer in South Korea. Methods : The theses about colorectal cancer(from 1th January 2000 to 6th August 2016) were searched from National Assembly Library, KIOM OASIS, and National Digital Science Library. Results : 54 theses were analyzed from 87 studies. They were classified by the type of research; experimental theses and case report. The number of experimental theses is 48 and case report is 6. And, they were classified by the topic of research; Single herb, Herbal decoction, oriental foods and Pharmacopuncture, the number of theses about single herb is 29, herbal decoction is 14, oriental foods is 8 and Pharmacopuncture is 3. Rhus Verniciflua(乾漆), Beakduong-tang(白頭翁湯), Wild Ginseng Pharmacopuncture is the most commonly used herb in our research. Conclusion : There were many attempts to develop the way to cure colorectal cancer using korean herbs, and some meaningful results were reported. However, more clinical researches based on human body and more scientifically designed clinical studies are required to prove the effect on colorectal cancer.

• Steel and Composite Structures
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• 제46권2호
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• pp.211-220
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• 2023

Welded hollow spherical joints are commonly used joints in space grid structures. An internal stiffener is generally adopted to strengthen the joints when large hollow spheres are used. To further strengthen it, external stiffeners can be used at the same time. In this study, axial compression tests are conducted on four full-scale 550 mm spherical joints. The failure modes and strengths of the tested joints are investigated. It shows that the external stiffeners are able to increase the strength of the joint up to 25%. A numerical model for large spherical joints with stiffeners is established and verified against the experimental results. Parametric studies are executed considering six main design factors using the verified model. It is found that the strength of the spherical joint increases as the thickness, height and number of the external stiffeners increase, and the hollow sphere's diameter has a neglectable effect on the enhancement caused by the external stiffeners. Based on the experimental and numerical results, a practical formula for the compressive bearing capacity of large welded hollow spherical joints with both internal and external stiffeners is proposed. The proposed formula gives a conservative prediction on the compressive capacity of large welded hollow spherical joints with both internal and external stiffeners.

• 한국강구조학회 논문집
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• 제11권2호통권39호
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• pp.109-116
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• 1999

본 논문은 관통형 고력볼트를 사용한 엔드플레이트형식 콘크리트 충전 각형 강관 기둥 H형강 보 접합부에 대한 단조가력하에서의 실험적 연구이다. 본 실험의 목적은 전회(前回)에서는 파악되지 않았던 엔드플레이트의 두께와 볼트의 배열에 대한 영향을 정확하게 평가하는데 있다. 실험의 주요변수는 엔드플레이트의 두께(12mm, 16mm)와 볼트의 배열 (EP1, EP2, EP3)이다. 변수에 따른 실험결과를 비교, 분석하였다. 1)실험체는 Bjorhovde와 EC3의 분류법에 의해 분류하였다. 2)T-stub모델에 근거한 접합부의 최대 모멘트 예측식에 의해 계산된 이론치$(_tM_u)$는 실험치$(_eM_u)$에 잘 대응하였다.

• Clinical and Experimental Pediatrics
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• 제48권10호
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• pp.1055-1060
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• 2005

목 적 : 모유수유아와 분유수유아의 생후 첫 일년간의 성장 패턴을 비교하기 위함이다. 방 법 : 의무 기록지를 통해 출생시, 1, 3, 6, 9 그리고 12개월의 신체 계측치(체중, 신장, 두위)가 수집되었고, 설문 조사를 통해 대상의 특징들이 모아졌다. 358명의 소아들 중 모유수유아는 161명(남아 84명, 여아 77명)이었고, 분유수유아는 90명(남아 42명, 여아 48명)이었다. 두 군 모두에서 4개월 이전에는 이유식을 공급하지 않았다. 각 연령별 체중, 신장, 두위가 계산되었다. 모유수유군은 다시 두 군(4-11개월간 모유수유를 한 군과 12개월 이상 모유수유를 한 군)으로 세분되었다. 결 과 : 엄마의 연령을 제외하면 대상의 특징들은 두 군에서 유사하였다. 모유수유군의 평균 체중은 12개월에만 분유수유군 보다 낮게 측정되었다(male : P=0.004, female : P=0.004). 하지만, 12개월 이상 모유수유만 한 군의 평균 체중은 9개월과 12개월에 분유수유군 보다 낮았다(P<0.05). 평균 신장과 두위는 두 군에서 유사하였다. 결 론 : 모유수유아와 분유수유아의 성장 지표들은 출생시에는 유사하나 생후 첫 일년간 두 군의 체중 곡선이 다르게 나타난다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 봄 학술발표회 논문집
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• pp.455-462
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• 2003

The current practice of estimating bearing capacity usually employs the conventional bearing capacity formula originally developed for strip footings under vertical central loading, In order account for the effect of footing shape and eccentricity and inclination of loads, correction factors are introduced in the formula, which are derived based on a number of small-scale model test observations. In this paper, comparison of several formulations of bearing capacity factors, as well as values of these factors, are presented. And the conventional bearing capacity equations are compared with some of other failure loci proposed for cohesive soil. Also, the bearing capacity of shallow foundation estimated by the conventional bearing capacity equations are compared with the experimental load test results.

• Structural Engineering and Mechanics
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• 제9권4호
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• pp.365-374
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• 2000

The structural behavior of connections between concrete-filled rectangular tubular column (CFRT column) and steel beam has been studied in this paper through sub-assemblage loading tests. It is found that the sub-assemblages exhibit ductile restoring force characteristics under seismic loading. A formula for the prediction of the yield strength of each member in the connection is proposed by using the yield line theory under the assumption of a simple stress transfer mechanism. It is shown that the proposed formula can produce a reasonable prediction while providing a basis for further investigation.