• 한국응용곤충학회지
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• 제20권1호
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• pp.37-41
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• 1981

콩의 흑색뿌리썩음병을 일으키는 Cylindrocladium crotalariae은 감자한천배지와 콩의 조직을 함유한 한천 배지를 서로 다르게 Water potential를 조절하여 이 병원균을 접종한 결과 균사신장과 대형분생포자형성은 -14bars에서 좋았고 $30^{\circ}C$에서는 -100bars $25^{\circ}C$에서는 -80bars $20^{\circ}C$에서는 -64bars에서 균사신장이 중지되었으며 포자형성도 -64bars에서 중지되었다. 자낭각과 미소균핵형성은 소금을 첨가하지 않은 -1.4나 -3.0bars에서 잘 되었고 이 균에 대한 포자발아율은 -1.4bars에서 -20bars의 모든 Water potential에서 똑 같이 좋았고 -20bars에서 Water potential이 낮아지므로 발아율이 떨어지다가 -60bars에서 억제되었다.

• KCI Concrete Journal
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• 제14권2호
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• pp.86-91
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• 2002

This paper presents an experimental study to investigate the behavior of mechanical anchorage of reinforcing bars in concrete members. Three kinds of mechanical anchorage which are a kind of headed reinforcements are considered in this study. Total seven specimens were prepared to consider the effects of anchoring methods (Type A, Type B and Type C) and anchorage lengths of the reinforcing bars (14 $d_{b}$, 12 $d_{b}$, 9 $d_{b}$). Pullout tests conforming to ASTM were carried out to assess the effects of several variables on anchoring strength of bars. Based on the test results, it was concluded that the behavior of the specimen anchored by the mechanical anchorage with the anchor-age length of 12 $d_{b}$, is as good as, or better than that of the specimen anchored by 90-degree standard hook.rd hook.

• 한국균학회지
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• 제12권3호
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• pp.99-103
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• 1984

Fusarium moniliforme strain별 균사신장(菌絲伸長)은 Strain IV은 water agar나 PDA에 관계(關係)없이 -14 bars에서 좋았고 -80 bars에서도 균사(菌絲)자람이 정지되지 않았다. Strain II와 Strain IV 를 비교(比較)하여보면 Strain II가 Strain IV보다 각 water potential 에서 균사(菌絲)자람이 좋았다. 분생포자형성(分生胞子形成)은 Strain에 관계(關係)없이 소형분생포자(小型分生胞子)는 0에서 -20bars까지는 점점(漸漸) 형성(形成)이 증가(增加)하다가 -20bars에서 가장 많이 형성(形成)되었으며 -80bars에서도 아주 적은수이지만 형성(形成)이 되었다. 대형분생포자(大型分生胞子)는 -1.4bars에서 포자형성(胞子形成)이 잘 되었고 water potential 떨어짐에 따라 -32bars에서 대형분생포자(大型分生胞子)를 형성(形成)하지 않고 소형분생포자(小型分生胞子)만 형성(形成)하였다. 포자발아(胞子發芽)는 -1.4bars에서 발아율(發芽率)이 좋았고 water potential이 떨어질수록 발아율(發芽率)도 떨어졌다.

• Computers and Concrete
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• 제14권3호
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• pp.327-345
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• 2014

This paper presents the application of multi-gene genetic programming (MGP) technique for modeling the bond strength of ribbed steel bars in concrete. In this regard, the experimental data of 264 splice beam tests from different technical papers were used for training, validating and testing the model. Seven basic parameters affecting on the bond strength of steel bars were selected as input parameters. These parameters are diameter, relative rib area and yield strength of steel bar, minimum concrete cover to bar diameter ratio, splice length to bar diameter ratio, concrete compressive strength and transverse reinforcement index. The results show that the proposed MGP model can be alternative approach for predicting the bond strength of ribbed steel bars in concrete. Moreover, the performance of the developed model was compared with the building codes' empirical equations for a complete comparison. The study concludes that the proposed MGP model predicts the bond strength of ribbed steel bars better than the existing building codes' equations. Using the proposed MGP model and building codes' equations, a parametric study was also conducted to investigate the trend of the input variables on the bond strength of ribbed steel bars in concrete.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 춘계 학술논문 발표대회
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• pp.80-81
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• 2014

Generally significant reinforcement is used for nuclear power plant structures and may cause potential problems when concrete is poured. In particular pouring concrete into structural member joint area is more difficult than other areas since the joint area is very congested due to hooked bars, embedded plates, and other reinforcements. The purpose of this study is to solve the problem by applying high-strength(ASTM A615 Gr. 75/80) bars. In addition large-sized(#14 & #18) headed deformed bar could be used as alternative of standard hooked bars to relieve the congestion to some extent. In order to apply headed deformed bars to nuclear power plant structures effectively, the large-sized diameter bars and the high-strength bars shall be used as thick as clear cover thickness 1". Therefore, test results were obtained by taking bar size, yield strength, and clear cover thickness as variables.

• Advances in concrete construction
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• 제14권5호
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• pp.331-339
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• 2022

Geopolymer concrete (GPC) is one of the best substitute materials for conventional concrete in construction. The conventional concrete provided by Portland cement has a detrimental influence on the environment during its production. In this study, the bond strength, which is an important structural property, of deformed steel bars with slag-based GPC was measured. In accordance with the ASTM C234 procedure, bond strength was measured on 18 specimens of slag-based GPC with three sizes of steel bars and different embedded lengths. Two groups of GPC specimens with different compressive strengths, which were cured under ambient conditions, were tested. The results indicated that the bar diameter has a great effect on the bond strength, and the bond strength behavior of the slag-based GPC is comparable with that of conventional concrete. The ACI-318 Code for the bond strength of ordinary Portland cement concrete can be used conservatively to determine the bond strength of the GPC reinforced with deformed steel bars.

• Computers and Concrete
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• 제14권2호
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• pp.109-125
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• 2014

The force transfer mechanism in positive moment continuity details for prestressed concrete girder bridges is investigated in this paper using a three-dimensional detailed finite element model. Positive moment reinforcement in the form of hairpin bars as recommended by the National Cooperative Highway Research Program Report No 519 is incorporated in the model. The cold construction joint that develops at the interface between girder ends and continuity diaphragms is also simulated via contact elements. The model is then subjected to the positive moment and corresponding shear forces that would develop over the service life of the bridge. The stress distribution in the continuity diaphragm and the axial force distribution in the hairpin bars are presented. It was found that due to the asymmetric configuration of the hairpin bars, asymmetric stress distribution develops at the continuity diaphragm, which can be exacerbated by other asymmetric factors such as skewed bridge configurations. It was also observed that when the joint is subjected to a positive moment, the tensile force is transferred from the girder end to the continuity diaphragm only through the hairpin bars due to the lack of contact between the both members at the construction joint. As a result, the stress distribution at girder ends was found to be concentrated around the hairpin bars influence area, rather than be resisted by the entire girder composite section. Finally, the results are used to develop an approach for estimating the cracking moment capacity at girder ends based on a proposed effective moment of inertia.

• Ecology and Resilient Infrastructure
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• 제3권1호
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• pp.14-21
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• 2016

본 연구에서는 2차원 수치모형을 이용하여 복단면 하도에서 낙차공을 고려하여 하도 변화와 사주의 거동 특성을 분석하였다. 교호사주에 의하여 흐름이 분리되며, 사주의 선단부에서 흐름이 집중되고 수충부가 형성되었다. 낙차공에 의하여 흐름은 하도 전체에 균등하게 분산되었으며, 낙차공 하류에서는 흐름이 집중되고 하상고가 낮아졌다. 그러나 사주의 형상은 낙차공 상류의 영향을 받아 교호사주의 형상을 유지되었다. 하폭 대 수심이 증가하면서 교호사주, 중앙사주, 복렬사주가 형성되었으며, 사주의 수가 증가하였다. 낙차공에 의하여 흐름이 집중되어 낙차공 상류에서 사주길이보다 낙차공 하류에서 사주길이가 더 짧게 나타났다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2019년도 추계 학술논문 발표대회
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• pp.110-111
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• 2019

In ACI 318-19 published recently, the conditions and development length equation to use the headed deformed bars were changed considerably. Although the use of the larger-diameter(No.14 and 18) headed deformed bars isn't yet permitted, the use of the high strength(80,000psi) headed deformed bars is permitted and the effect of bar-diameter($d_b$) on the development length is increased considerably. Therefore, structures using larger-diameter headed deformed bars will be expected to be affected by this code change. We will study the effect of the code change on the development design and find out the design optimization method to minimize the effect of the changed conditions and development length equation.

• 천문학회보
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• 제10권
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• pp.14.3-14.3
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• 1985