• Journal of the Korea Concrete Institute
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• v.19 no.3
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• pp.333-339
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• 2007

The purpose of this study was to enhance bond performance between recycled PET (polyethylene telephthalat) fiber and cement composites through hydrophilic treatment using maleic anhydride grafted polypropylene(mPP). The mPP with various concentration of 0%, 5%, 10%, 15% and 20% to determine effect on bond behavior of recycled PET fiber were applied as experimental variables. Dog bone shaped specimens according to JCI SF-8 was applied to evaluate the bond strength and pullout energy. The results showed increased bond strength and pullout energy as concentration of mPP. Concentration of 15% mPP showed the most effective results while 20% showed reduced performance results. Because 15% mPP ensures perfect coating while 20% makes thick coating area that resulted in crack propagation and consequent separation of PET fiber and coated area during pullout load occurred. Enhancement mechanism of bond performance of recycled PET fiber and cement composites with each concentration of mPP could be conformed through investigation of microstructure of fiber surface.

• Journal of the Korea Concrete Institute
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• v.25 no.1
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• pp.37-43
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• 2013

Recently, experimental and analytical researches have been performed in order to find interface failure between FRP plate and concrete in near surface-mounted (NSM) retrofit using FRP plate. As a result, it was found that the bond strength between concrete and NSM FRP plate had a close relationship with shape of FRP, concrete compressive strength and bond length. However, research need is increasing about another factors such as suitable space of FRP plate and group effect. In this study, therefore, a bond test was performed with aforementioned factors and compared with a previous equation to verify its suitability for predicting bond strength of NSM FRP plate. From the test, it was found that the bond strength increased according to the increase of space of NSM FRP plates even if its bond length was same. The splitting failure of concrete governed when space of FRPs was too narrow and it changed to FRP's tensile failure with increase of the space. From the evaluation of test specimens using previous equation, it was found that the bond strength could be predicted properly with consideration of group effect.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.4
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• pp.845-850
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• 2018

In this paper, we propose a method to estimate the number of biofouling attached to the surface of marine structures. This method estimates the number of biofouling by calculating the region maxima using images taken in underwater. To do this, we analyze the correlation between the region maxima and the number of biofouling. The analysis showed that there is a significant correlation between the number of region maxima and the number of biofouling. By using the results of this analysis, the experiments were conducted on images taken in the underwater. Experimental results show that the higher the region maxima of the image, is greater than the number of biofouling in the image. The proposed method can be used as an important technology in computer vision for underwater images.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.6
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• pp.1078-1085
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• 2022

Fouling organisms attached to a ship not only greatly increase the resistance of the ship as they grow on the hull but also cause disturbances in local marine ecosystems as they move with the ship. Accordingly, the International Maritime Organization has started discussing the removal of biofouling and evaluation of cleaning performance to prevent the migration of hull-fouling species. In this study, specimens of FRP(Fiber Reinforced Plastic), HDPE(High Density Polyethylene), and CFRP(Carbon Fiber Reinforced Plastic) materials used for small ship construction were cured in Gyeokpo Port (Jeonlakbuk-do) for about 80 days. Then, attached organism removal experiments were performed using a water jet nozzle. The results show that seaweeds, such as laver, were removed when the distance between the nozzle and the specimen was 1.8 cm and the pressure was 100 bar. Furthermore, it was confirmed that the cleaning of barnacles was possible only when the pressure was 200 bar or more.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.5
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• pp.101-108
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• 2008

The primary objective of this research is a study on the pullout bond characteristics of untensioned prestressing strand in concrete. The bond characteristics of untensioned prestressing strand in concrete differs from that of deformed reinforcing bar. In order to use and design untensioned prestressing strand as deformed reinforcing bar, a study for bond characteristics of the untensioned prestressing strand was progressed. Major test variables are embedment length ($10d_b{\sim}60d_b$), concrete cover (45mm, 70mm, 100m) and diameter of strands. (12.7mm : SWPC7, 9.3mm : SWPC7A) As a results, these showed that average bond stress was decreased as a growing the embedment length, and then showed that the bond performance of untensioned prestressing strand was improved if embedment length was above 60$60d_b$.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2001.11a
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• pp.203-203
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• 2001

패선/구부림 가공은 후가공의 일부분으로서. 박스가공 시 종이에 패션치기와 구부림 공정이 들어가게 되며 이때 종이표면이 약할 경우 금이가는 현상이 발생한다. 본 연구 는 이러한 가공과 다층판지의 물성이 패선/구부림 적성에 영향을 미치는가에 대한 연 구로서 2000년도 추계논문발표시 종이 물성 중 패션/구부림 가공에 영향을 주는 것으 로 표면층의 층간결합력과 내절도 그리고 인장강도가 중요한 변수로 작용하는 결과를 얻었으며 이후 이들 영향인자 중 핵심영향인자의 도출을 위하여 침엽수를 배합하지 않 은 상태에서 상질고지 재생펄프를 고해 처리하여 특성을 향상시켜 실제 공정에서 실험 하였다. 1차 실험은 공정실험 전 예비 실험으로서 재생펄프를 공장 refiner를 사용하여 고해 처리하여 강도향상 효과를 분석하였다. 분석결과 인장강도는 증가하나 내절도 향상은 기대에 미치지 못하는 것으로 나타났다. 이에 따라 1차 공정실험 조건을 부착량을 향상 시켜 인장강도를 침엽수 펄프 배합수준으로 끌어올리는 방법을 선택하였으며 그 결과 패선/구부림 적성이 기존대비 양호한 결과를 얻었다. 즉 인장강도 향상으로 침엽수 펄 프를 대체할 수 있다는 결론을 얻었다. 2차 실험은 부착량 대선 refiner를 사용하여 상 질고지 재생펄프를 고해 처리하여 인장강도를 향상시켜 생산하였다. 실험결과 인장강도 가 침엽수펄프 배합 시 대비 동등이상 수준에 있을 경우 패션/구부린 가공 시 금이가 는 터짐문제는 발생하지 않는 것으로 나타났다. 3차 실험은 두 차례 동안 실시된 공정 실험을 기준으로 refining 처리와 부착량 기준을 설정하고 장시간 생산하여 그 특성을 측정하였다. 실험결과 표면층의 인장강도가 낮아질 때 패선/구부림 적성이 약해지는 경 향을 보였으며 인장강도가 기존 침엽수펄프 배합대비 동등이상일 경우 패선/구부림 가 공적성이 양호하게 나타났으며 실제 가공업체에서도 터짐 문제가 발견되지 않았다. 결론적으로 표면층의 인장강도가 패션/구부림에 가장 중요한 변수로 작용하며 어떠 한 형태로 표면층의 인장강도를 향상시킬 경우 침엽수 펄프는 재생펄프로 대체가 가능 할 것으로 판단된다.

• Journal of the Korea Institute of Building Construction
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• v.16 no.3
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• pp.237-245
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• 2016

Structural performance and durability of ultra high performance concrete could demonstrate optimal performance when unity was kept. Accordingly, it is necessary to involve the characteristics and quantitative surface treatment at the same time in order to retain oneness of Ultra-High-Performance Concrete(UHPC) according to construction joint occurrence. Therefore, this study derives a reasonable surface treatment method in a material's point of view through the shear adhesion performance evaluation according to the construction joints surface processing method as a part for securing the adhesion performance of the construction joints when casting UHPC. 180 MPa of required average strength was used for mix of UHPC and surface treatment method was set to totally 7 level that MN, GR-10-0, GR-20-0, GR-30-0, SH-30-5, SH-30-10. After the specimen were manufactured to a size of $150{\times}150{\times}150mm$, Direct shear test was performed to evaluate the shear adhesion strength. As a result, it was confirmed that the adhesion performance was improved when executing a surface treatment for the construction joint interface and standard of failure mode of specimen was over Type C. Also, It was considered that interface of cross section and depth of concavo-convex should be concerned.

• Journal of the Korea Concrete Institute
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• v.25 no.1
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• pp.53-61
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• 2013

A new deformation of reinforcing bar in coils was proposed to improve a machinability of straightening process, which has crescent-shaped transverse ribs with an inclination angle of 50 degrees, a crest width of $0.15d_b$, and a flank inclination of 55 degrees. The proposed deformation can increase contact area between a surface of re-bar and a groove of a roller during a straightening process and, therefore, it might reduce a damage of ribs, improve a final straightness, and enhance an efficiency of the straightening process. Splice tests were conducted to evaluate bond strengths of three types of re-bar in coils including the proposed re-bar, of which the inclination angles of transverse ribs were 50, 60, and 90 degrees, respectively. Test results show that the re-bars in coils have higher bond strengths than predicted strengths by equations of Orangun et al., ACI 408, and KCI by at least 10%. Correlation coefficients of bond strengths between a straight bar and re-bars in coils are 0.94 and more. Consequently, equations of the KCI code for determining development and splice lengths can be applied to the tested re-bars in coils.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.3
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• pp.311-322
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• 2022

This study performed 4-point flexural tests of reinforced concrete to which was attached a distributed optical fiber sheet and carbon fiber reinforced polymer (CFRP) sheets in order to assess the effect of the CFRP sheets and the applicability of a BOTDR sensor simultaneously. To evaluate the reinforcing effect, various degrees of CFRP sheet attachment were manufactured, and to evaluate the sensing ability, strains obtained from a BOTDR sensor were compared with strains measured from electric resistance strain gauges that were attached to the concrete surface. From the results, the reinforcing effects were evidently different according to the attachment type of the CFRP sheets, and it was confirmed that the main influencing factor on the reinforcing effect was the type of attachment rather than the attachment area. The reinforced concrete structural behavior was visualized with strains measured from the BOTDR sensor as load increased, and it was identified that load was concentrated in the CFRP reinforced area. Strains from the BOTDR sensor were similar to those from the electric resistance strain gauge; thereby a BOTDR sensor can be effective in the analysis of structural behaviorsof massive infrastructure. Finally, the strain from a BOTDR sensor was high where CFRP sheet fall-off occurs, and it would therefore be efficient to track local damage locations of CFRP sheets by utilizing a BOTDR sensor.

• Proceedings of the Korean Aquaculture Society Conference
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• 2003.10a
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• pp.92-92
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• 2003

본 연구는 부착규조류에 따른 부착성 요각류 Tigriopus japonicus의 nauplius 생산력을 알아보기 위하여 실시하였다. 실험에 사용된 T. japonicus는 부산 동백섬 부경대학교 수산과학연구소 부근에 있는 tidal pool에서 동물성부유생물망으로 채집하였다. 먹이생물로는 부경대학교 한국해양 미세조류 은행에서 보관중인 부착규조류 중 중형종인 Caloneis schroder를 대표종으로 이와 크기가(14.8~27.5$\mu\textrm{m}$) 유사한 종들을 대상으로 형태를 현미경 하에서 관찰하고, 지역과 분리일자 등을 고려하여 유사종을 선별한 후 최종적으로 종의 유전적 유사성을 밝히기 위하여 RAPD-PCR (random amplified polymorphic DNA polymerase chain reaction)을 실시하였다. 이 중 Caloneis schroder와 유전적으로 유사성이 낮은 Navicula spp. (KMCC B-245, 393, 394, 581) 4종을 선별하여 T. japonicus의 먹이로 사용하여 포란한 암컷의 nauplius 생산력을 3반복 조사하였다. Genomic DNA는 대부분의 종에서 성공적으로 검출되었으며, 종에 따라 PCR 증폭산물이 나타나지 않은 경우도 있었으므로, PCR 산물이 나타난 종에 대해서만 분석하였고, 증폭된 DNA band는 대부분 크기 0.5~2.0kb 범위에서 나타났다. 실험에 사용된 부착규조류 간의 유사성을 알아보기 위하여 similarity matrix를 분석한 결과 F값의 범위는 0.00에서 1.00까지 였으며, Caloneis schroder와 유사성이 낮은 종들에 비하여 유사성이 높은 종들이 더 많이 나타났다. 이들을 먹이로 하여 포란한 T. japonicus의 실험구별 nauplius 평균 개체수를 살펴보면, KMCC B-394가 255.7마리로 가장 높았던 반면 KMCC B-581가 29.7마리로 가장 낮았다. 그 외 KMCC B-245가 120.0마리, KMCC B-393가 76.0마리, Caloneis schroder가 32.3마리 각각 나타났다. 이와같은 결과를 볼 때 T. japonicus의 nauplius 생산력은 규조 종에 따라 큰 차이가 있는 것으로 판단된다.