재생골재 콘크리트의 수축균열 특성에 관한 연구

구봉근,라재웅,이재범,류연종,이현석 충북대학교 건설기술연구소 2003 建設技術論文集 Vol.22 No.2

As concrete is prevented from shrinking freely, tensile stresses develop which frequently result in cracking. Cracks in reinforced concrete structures reduce overall durability by allowing the penetration of water and aggressive agents, thereby accelerating the deterioration of the reinforcing steel. Highway pavement, bridge decks, and industrial floors are especially susceptible to this type of deterioration since these structures exhibit high rates of shrinkage and are frequently exposed to aggressive environmental conditions. The objectives of this investigation included the implement of experimental procedures for assessing shrinkage cracking behavior on recycled aggregate concrete, the selection of replacement rate and mix composition on recycled aggregate concrete. Specifically, the influence of a shrinkage reducing admixture(SRA) and recycled aggregate concrete was investigated. The shrinkage reducing admixture substantially reduces free, shrinkage and restrained shrinkage cracking while providing similar mechanical properties. Restrained shrinkage experiments were developed and shrinkage cracking was shown to be size dependent and recycled aggregate replacement rate. A mechanical properties experiment approach was developed to predict the behavior of a variety of recycled aggregate concrete specimens. This experimentally approach was used to successfully explain experimental results from a variety of mixture compositions and recycled aggregate concrete. This experiment was used to demonstrate the influence of material and structural properties on the potential for cracking.

모멘트 方配法에 의한 뼈대 解析

具泰槿 忠州大學校 1968 한국교통대학교 논문집 Vol.2 No.-

모멘트 분배법이란 탄성영역내에 있는 뼈대에 대한 해석방법을 말하는 것으로 Hardy cross 교수에 의하여 시작된 것이므로 간혹 Hardy cross Method라고도 불러진다. 이 모멘트 분배방법은 여러 개의 절점에 작용을 하는 모멘트가 주어진 하중으로 생기는 모멘트의 진가에 점점 가까이 접근 하게끔 순서대로 행하는 한 Serie의 간단한 단계를 포함한다. 계산 되어진 모멘트는 진모멘트에 보통은 빨리 수험하기 때문에 우리가 원하는 어떤 정도의 정확성을 얻을 수 있는 것이다.

슬래그 미분말과 석회석 미분말을 혼입한 콘크리트의 내구성에 관한 연구

구봉근,박주원 충북대학교 건설기술연구소 2003 建設技術論文集 Vol.22 No.2

This study is to investigate the durability of concrete containing slag powder and limestone powder. In order to study the effect of slag powder and limestone powder, all mixtures were prepared at a fixed water/cement ratio, slump, and entrained air quantity. The water-cement ratio was 50%, and added AE agent, water reducing agent titer as agent. When concrete containing slag powder is at a mixing rate of 40%, durability was the highest. But drying shrinkage is less than in standard concrete in general, and was the lowest at20%. When concrete containing limestone powder is at a mixing rate of 10% in all experiments, the most suitable result appeared. When cement and two admixtures are mixed together, the same result appeared. Therefore, in the case where mix slag powder is 40% and limestone powder is 10%, we can say that it gives the best concrete durability.

강섬유로 보강한 재생골재 콘코리트의 강도특성

구봉근,김창운,류택은,이재범,류연종,이현석 충북대학교 산업과학기술연구소 2002 산업과학기술연구 논문집 Vol.16 No.1

This study was performed to investigate the strength characterstics of steel fiber reinforced recycled aggregate concrete. Test specimens were prepared with compressive, split tensile, flexural specimens and tested by ultimate strength. A superplasticizer and fly-ash were added to the mix to improve performance of recycled concrete. Test-variables are substitution of recycled aggregate(0, 30, 50%), steel fiber length(0, 30, 50, 60mm), steel fiber content(0, 0.5, 1.0, 1.5%). Test-specimen were classified by test-variables. The experimental results on the various engineering properties of steel fiber reinforced recycled aggregate concrete using waste concrete are summarized as follows. It was found that the compressive and split tensile strength were proportionally affected by quantities of recycled aggregate substitutions, but flexural strength wasn't. The maximum compressive strength was 392 kgf/㎠( series 4 : R30 L30 V1.0 A20 ), the maximun split tensile strength was 40 kgf/㎠( series 7 : R30 L30 V1.5 A20) and the maximum flexural strength was 62 kgf/㎠( series 7 : R30 L30 V1.5 A20 ).

鐵筋 콘크리트 보의 塑性變形

具奉槿 忠州大學校 1967 한국교통대학교 논문집 Vol.1 No.-

법랑질 변연으로 이루어진 복합레진 수복물의 체적과 C-factor가 미세누출에 미치는 영향

구봉주,신동훈 대한치과보존학회 2006 Restorative Dentistry & Endodontics Vol.31 No.6

와동벽과 복합레진 수복물이 접착될 때, 복합레진의 치질에 대한 접착력과 레진 자체의 중합 시 발생하는 수축응력이 상충하게 된다. 이러한 수축응력의 크기는 와동의 형태요소 (C-factor)와 수복물의 체적에 영향을 받는다. 이에 본 실험에서는 단일 병 접착제를 사용한 복합레진 수복 시 법랑질 변연만으로 이루어진 와동의 C-factor와 체적이 미세누출에 미치는 영향을 미세 전류 측정법을 이용하여 정량적으로 분석하고 평가하였다. 연마기를 이용하여 40개의 건전한 우치 협면에 편평한 법랑질 표면을 형성하였다. 각각 10개 치아에 원통형 와동을 형성하였으며, 와동의 깊이와 직경에 따라 4개 군으로 분류하였다 ( 군: 1.5 mm × 2.0 mm, Ⅱ군: 1.5 mm× 6.0 mm, Ⅲ군: 2.0 mm × 1.72 mm, Ⅳ군: 2.0 mm × 5.23 mm). 각기 와동의 C-facto는 4, 5.62, 2, 2.54를 보였다. 산 부식 후 단일 병 접착제인 BC Pus^(™) (Vericom, Korea)를 제조사의 지시에 따라 적용하, 미세혼합형 복합레진인 Denfil^(™)(Vericom)을 충전하였다. 40초씩 광중합 후 치아를 실온에서 증류수에 24시간 동안 보관한 다음, Sof-Lex system을 이용하여 연마하였고, 5℃와 55℃ 범위에서 500회 열순환을 시행하였다. 이후 미세전류 측정을 위해 치수강 내에 증류수를 채우고 치근단공을 통해 0.018 stainless wire를 삽입한 후sticky wax로 근첨부를 봉하였으며, nail varnish를 수복물의 변연에서1mm 를 외한 전체 치면에 2회 도포하였다. 미세누출의 측정은 전기 화학적 방법을 이용하여 측정하였으며, 통계적 유의성은 95% 유의 수의 Two-way ANOVA로 검증하여, 다음과 같은 결과를 얻었다. 1.복합레진 수복물의 체적이 적은 것이 큰 것에 비해 미세누출도가 적었으나, 통계학적으로 유의한 차이는 없었다. 2.와동 형태와 연관된 C-factor는 복합레진 수복물의 미세누출도에 영을 주지 않았다. 법랑질 변연을 갖는 와동에 단일 병 접착제를 사용한 본 실험에서는 복합레진의 중합 시 발생하는 수축응력에 영을 미치는 것으로 알려진 수복물의 체적과 C-factor가 미세누출도에 영향을 주지 못하였다. 이는 법랑질과 접착시스템과의 강력한 접착력에 기인한 것으 보이며, 앞으로 이에 대한 더 많은 연구가 필요할 것으로 사료된다. Competition will usually develop between the opposing walls as the restorative resin shrinks during polymerization. Magnitude of this phenomenon may be depended upon cavity configuration and volume. The purpose of this sturdy was to evaluate the effect of cavity configuration and volume on microleakage of composite resin restoration that has margins on the enamel site only. The labial enamel of forty bovine teeth was ground using a model trimmer to expose a flat enamel surface. Four groups with cylindrical cavities were defined, according to volume and configuration factor (Depth × Diameter / C-factor) - Group Ⅰ : 1.5 mm × 2.0 mm / 4.0, Group Ⅱ :1.5 mm × 6.0 mm / 2.0, Group Ⅲ : 2.0 mm × 1.72 mm / 5.62, GroupⅣ : 2.0 mm × 5.23 mm / 2.54. After treating with fifth-generation one-bottle adhesive- BC Plus^(™) (Vericom, AnYang, Korea), cavities were bulk filled with microhybrid composite resin-Denfill^(™) (Vericom). Teeth were stored in distilled water for one day at room temperature and were finished and polished with Sof-Lex system. Specimens were thermocycled 500 times between 5℃ and 55℃ for 30 second at each temperature. Teeth were isolated with two layers of nail varnish except the restoration surface and 1mm surrounding margins. Electrical conductivity (㎂) was recorded in distilled water by electrochemical method. Microleakage scores were compared and analyzed using two-way ANOVA at 95% level. The results were as follows : 1. Small cavity volume showed lower microleakage score than large one, however, there was no statistically significant difference. 2. There was no relationship between cavity configuration and microleakage. Factors of cavity configuration and volume did not affect on microleakage of resin restorations with enamel margins only.

Evidence for Harmony in Karok Consonant

구봉림 서울産業大學校 1993 논문집 Vol.38 No.1

본 논문의 주된 목적은 Karok의 음운현상을 조사 분석함으로써 자음조화에 대한 증거를 포착하고 그것의 과정과 체제를 어떻게 설명할 수 있는지를 밝혀 보려는 것이다. 자음조화의 증거는 여러 자료를 통하여 분명해지며 그것의 과정과 체제는 규칙의 설정과 자립분절이론의 틀에 입각하여 규명될 수 있다.

유럽 농촌지역의 지속가능 개발정책과 환경정책수단의 평가기준

김봉구,이상엽 고려대학교 자연자원연구소 2000 自然資源科學硏究 Vol.8 No.-

Gramsci의 이데올로기론

강봉구 경상대학교 1988 民族統一論集 Vol.1988 No.4

Gramsci was opposed to economism. He denied epiphenominalism that ideology was no more than the reflection of base, and stressed the autonomy of ideology from base. He criticized the reductionist interpretation of historical materialism which took ideology to be reduced to class. He stressed the material-institutional characters of ideology. Ideology is more than a specific system of ideas in him. He distinguishes between historically organic ideologies, those, that is, which are necessary to a given structure, and ideologies that are arbitrary, rationalistic, or willed. Ideology, when it acquires the force of popular belifes, often has the same energy as a material force. He expanded the concept of ideology into the field of the common sense which was the most widespread form of ideology. Common sense, in the ideological struggle, is the terrain on which hegemony is formed and also challenges are made. Ideology is core foundation in the war of position which is new strategy of revolution. In the formation of national-popular collective will, ideology is the arms for intellectual-moral reform, and operates as cement for the formation of historical bloc which unites organically various social forces.

농업여건변화와 환경보전형 농업정책방향

金鳳九 高麗大學校 自然資源科學硏究所 1996 自然資源科學硏究 Vol.4 No.-