Strain rate effects on the compressive and tensile behavior of bundle-type polyamide fiber-reinforced cementitious composites

Kim, Hongseop,Kim, Gyuyong,Lee, Sangkyu,Son, Minjae,Choe, Gyeongcheol,Nam, Jeongsoo Elsevier 2019 Composites. Part B, Engineering Vol.160 No.-

<P><B>Abstract</B></P> <P>The compressive and tensile behavior of fiber-reinforced cementitious composites is significantly affected by the bonding and pull-out properties between matrix and reinforced fiber, as well as the fracture properties of the fibers. In addition, an increase in strain rate according to loading conditions influences the fracture behavior between the fiber and matrix. Steel fiber-reinforced cementitious composites with high flexural and tensile strength, toughness, and crack resistance are widely used in tunnels and plant structures. However, the high specific gravity and stiffness of steel fibers can cause rupture of concrete pump tubes, increase the rebound volume of shotcrete, and decrease durability by corrosion of fiber. Therefore, it is necessary to study the development and application of organic fiber which has similar mechanical properties to steel fiber and does not cause corrosion. In this study, polyamide fibers having the same aspect ratio as the hooked steel fibers, which are widely used as reinforcing fibers for concrete, have been developed. And strain rate effect on the compressive and tensile behaviors of bundle-type polyamide fiber-reinforced cementitious composite and hooked steel fiber-reinforced cementitious composite were evaluated. The results showed that the effect of strain rate over different fiber types influenced the tensile behavior more significantly than the compressive behavior. In polyamide fiber-reinforced cementitious composite (PAFRCC), a fracture behavior of fiber was observed regardless of a strain rate, and the tensile behavior of PAFRCC was influenced more by tensile strength of polyamide fiber itself than a bonding stress between fiber and matrix. In hooked steel fiber-reinforced cementitious composite (HSFRCC), a bonding stress between hooked steel fiber and matrix (frictional force at the interface between fiber and matrix, mechanical bond of the hooked part) influenced the tensile behavior significantly. Fracture properties that straightened pulled out the fiber from the matrix were observed at static tensile loading condition. However, non-straightened hooked steel fiber was observed along with the fracture of matrix due to an increase in mechanical bonding force of the hooked part and the bonding stress between the fiber and the matrix.</P>

해양강국 실천을 위한 행정조직 부활의 필요성 연구

김홍섭(Hongseop Kim) 한국항만경제학회 2011 韓國港灣經濟學會誌 Vol.27 No.4

바다를 지배한 민족이 세계를 지배한다고 로마의 키케로(Cicero)가 말했다. 세계사에서 중요역할을 한 국가는 대부분 바다의 중요성을 강조하였다. 페니키아, 그리스, 카르타고, 로마, 포르투칼, 스페인, 영국, 미국 등 세계는 바다를 지배해온 민족의 역사라 할 수 있다. 바다는 자원의 보고, 소통과 물류, 유통의 통로로 국가의 원활한 정치, 경제, 사회, 문화의 터전이며 바다는 동시에 꿈과 상상의 장이며, 가능성과 비전의 토대이다. 본 연구에서는 우리나라 해양강국의 실현이라는 비전의 실현을 위해 세계의 주요 국가와 역사를 개관하였다. 우리 주요 해양정책의 주요 이슈에 대한 실태와 전망을 살펴보았으며, 이를 토대로 우리 해양강국의 비전을 제시하였다. 2020년 세계 5대 해양강국, 세계 10위의 해양과학기술 보유 등을 비전으로 제시하고 세부추진 전략을 제안하였다. 이를 위해 해양수산부의 복원이 절실하며 그 이유와 필요성을 5가지 논리로 제시하였다. 또한 해양수산부의 복원의 향후 방향도 정책, 기능적 관점과 제도적 관점에서 제시하였다. 해양강국 대한민국은 해양수산부가 향후 정부조직 개편에서 반드시 복원되야 실현될 수 있다고 본다. The Roman thinker, Cicero said,"The Nations that rule the sea, rule the world". In the world history, the countries done critical roles, have emphasized the importance of the sea. The world history is called as the histories of the countries which governed the sea, such as Phoenicia, Greece, Carthago, Roma, Portugal, Spain, England, and USA. The sea is not only the political, economical, social and cultural basis, serving as the origin of resources and channel of communication, logistics and distribution but also the area of dreams and imaginations and ground of potentiality and visions. This paper reviewed the major countries and their histories to realize the vision of Korea, super power country of maritime and fishery. Main maritime policies and its core issues and prospects of Korea were reviewed. And on the basis of these reviews, the vision of super power country of maritime and fishery was suggested. The vision, the 5th super power country of maritime and fishery in 2020, and 10th country of maritime technology level in 2020 and their details were proposed also. For achieving the vision, the resurrection of MOMAF is necessary and its reasons and 5 necessities were suggested. And the directions of the resurrection of MOMAF were proposed in terms of two viewpoints, policy/functional and institutional basis. I think Korea, the super power country of maritime and fishery, can be realized only when MOMAF may be resurrected.

인천항의 브랜드파워 제고 전략에 관한 연구

김병일(Byungil Kim),김홍섭(Hongseop Kim) 한국항만경제학회 2011 韓國港灣經濟學會誌 Vol.27 No.2

본 연구는 항만당국 및 마케터들로 하여금 실제로 통제하고 관리하기에 쉽도록 항만브랜드자산을 구성하는 요소들이 브랜드파워 및 성과에 어떻게 영향을 미치는지에 대한 상대적인 영향력을 보여주고자 하였다. 또한 인천항과 경쟁관계에 있는 국내항만과의 브랜드경쟁력 수준을 비교하여 인천항의 브랜드파워 증진을 위한 유용한 전략적시사점을 제시하고자 하였다. 연구결과 항만브랜드 자산의 구성요인이 인지도, 이미지, 서비스품질, 관계만족으로 구분됨을 확인하였고, 이들 4차원과 충성도간 영향관계에서 인천항은 인지도 및 관계만족이 매우 유의한 것으로 나타났다. 특히 항만간 비교평가를 통해 인천항과 평택항은 관계만족만이, 부산항은 이미지와 서비스품질에서 경영성과가 높게 나타나는 고객군에 있어 유의하게 영향을 미치는 것으로 나타남을 확인하였다. This article aims to reveal the relative influences to the Brand Power and Performance of Factors that comprise the port brand assets in order to control and manage the ports. And also this Paper want to suggest the useful strategies and implications for the improvement of Brand Power by comparing the level of brand competitiveness of Incheon Port with those of other Korean ports that are in competitive relation. In this research we can find out that the components of port brand asset are awareness level, image, service quality, and satisfaction of relation. And among those 4 factors, recognition level and satisfaction of relation are very significant relation factors for the loyalty in Incheon Port. In comparison study between Incheon and Pyungtack Ports, satisfaction of relation is revealed as especially significant factor for the customers that show highly effective management performances and we can find that, in Busan Port, image and service quality are significant as well.

크루즈관광에서 기존 - 잠재 고객간 행동의도 결정요인 차이에 관한 연구

김병일(ByungIl Kim),김홍섭(HongSeop Kim) 한국항만경제학회 2012 韓國港灣經濟學會誌 Vol.28 No.4

본 연구는 국내 크루즈 수요층을 대상으로 크루즈관광에 있어 고객 행동의도와 그것의 결정요인이라 할 수 있는 서비스품질, 고객만족과 같은 마케팅 변수들과의 관계를 파악하고자 하였다. 그를 통해서 잠재고객의 유치를 위해서는 어떤 서비스 요인을 더 강조해야 하고, 기존고객들의 행동의도를 높이기 위해서는 어떤 서비스 요인에 대해 더 집중해야 할 지 전략적 방안을 모색하였다. 연구결과 기존고객의 경우 서비스품질 세차원의 구성요인 중 물리적환경만이 행동의도에 유의하게 영향을 미치는 것으로 나타났다. 즉 전용부두건설 등 편의시설 구축에 우선적인 마케팅 노력이 필요할 것으로 보인다. 잠재고객의 경우 서비스전달이 행동의도에 가장 크게 영향을 미치는 것으로 나타났다. 따라서 크루즈 기항빈도, 쇼핑 및 먹거리 시설, 크루즈상품 등에 대한 이슈 발굴 및 개발 그리고 홍보 등의 촉진활동이 요구된다. This study aims to find out the relationship of customer behavioral intention and marketing variables such as service quality and customer satisfaction which are regarded as its determinants. And then this study has suggested what service factors shall be emphasized to induce the latent customers. And it has grouped strategic Schemes on which service variables shall be focused to enhance the existing customer behavioral intentions. This study has found, to the existing customers, only physical environments among 3 dimension components of Service quality significantly affects to the Behavioral intentions. Priorly, marketing efforts, namely, expansion of convenient facilities such as special berth construction is necessary. To the latent customer, service delivery is the most powerful factor to the behavioral intentions. Consequently, frequency of cruise calling, Facilities of shopping and eating, issues and their development of cruise goods and publicity and promotions are needed.

그린카용 인버터 전력모듈의 열전달 해석 및 평가에 대한 연구

김철수(Chulsoo Kim),이준호(Junho Lee),이기수(Geesoo Lee),이홍섭(Hongseop Lee),김찬중(Chanjung Kim),이봉현(Bonghyun Lee) 한국자동차공학회 2013 한국자동차공학회 부문종합 학술대회 Vol.2013 No.5

Since the high-powered power modules for use in motor inverter and DC-DC converter of green cars such as xEVs require the power chips of higher current and thermal density, it is very important to design the power chips considering to its effective thermal dissipation path. Thermal resistance is a key factor in the power module package design for the effective thermal dissipation path from its junction to base plate. Generally the more the thermal resistance decreases, the more the allowable dissipation power and current increase. The thermal resistance of the power module largely depends on the thermal properties of a direct bond copper material. In this paper temperature rise characteristic and thermal resistance are evaluated through the heat transfer analysis on the 2-pack power module for use in inverter of the green car. The experimental measuring method of the thermal resistance referred to the international testing standard is introduced. The heat transfer analysis is conducted about the various direct bond copper materials of the power module package with the commercial code.

Experimental Investigation on the Blast Resistance of Fiber-Reinforced Cementitious Composite Panels Subjected to Contact Explosions

Nam, Jeongsoo,Kim, Hongseop,Kim, Gyuyong Korea Concrete Institute 2017 International Journal of Concrete Structures and M Vol.11 No.1

This study investigates the blast resistance of fiber-reinforced cementitious composite (FRCC) panels, with fiber volume fractions of 2%, subjected to contact explosions using an emulsion explosive. A number of FRCC panels with five different fiber mixtures (i.e., micro polyvinyl alcohol fiber, micro polyethylene fiber, macro hooked-end steel fiber, micro polyvinyl alcohol fiber with macro hooked-end steel fiber, and micro polyethylene fiber with macro hooked-end steel fiber) were fabricated and tested. In addition, the blast resistance of plain panels (i.e., non-fiber-reinforced high strength concrete, and non-fiber-reinforced cementitious composites) were examined for comparison with those of the FRCC panels. The resistance of the panels to spall failure improved with the addition of micro synthetic fibers and/or macro hooked-end steel fibers as compared to those of the plain panels. The fracture energy of the FRCC panels was significantly higher than that of the plain panels, which reduced the local damage experienced by the FRCCs. The cracks on the back side of the micro synthetic fiber-reinforced panel due to contact explosions were greatly controlled compared to the macro hooked-end steel fiber-reinforced panel. However, the blast resistance of the macro hooked-end steel fiber-reinforced panel was improved by hybrid with micro synthetic fibers.

Experimental Investigation on the Blast Resistance of Fiber-Reinforced Cementitious Composite Panels Subjected to Contact Explosions

Jeongsoo Nam,Hongseop Kim,Gyuyong Kim 한국콘크리트학회 2017 International Journal of Concrete Structures and M Vol.11 No.1

This study investigates the blast resistance of fiber-reinforced cementitious composite (FRCC) panels, with fiber volume fractions of 2%, subjected to contact explosions using an emulsion explosive. A number of FRCC panels with five different fiber mixtures (i.e., micro polyvinyl alcohol fiber, micro polyethylene fiber, macro hooked-end steel fiber, micro polyvinyl alcohol fiber with macro hooked-end steel fiber, and micro polyethylene fiber with macro hooked-end steel fiber) were fabricated and tested. In addition, the blast resistance of plain panels (i.e., non-fiber-reinforced high strength concrete, and non-fiberreinforced cementitious composites) were examined for comparison with those of the FRCC panels. The resistance of the panels to spall failure improved with the addition of micro synthetic fibers and/or macro hooked-end steel fibers as compared to those of the plain panels. The fracture energy of the FRCC panels was significantly higher than that of the plain panels, which reduced the local damage experienced by the FRCCs. The cracks on the back side of the micro synthetic fiber-reinforced panel due to contact explosions were greatly controlled compared to the macro hooked-end steel fiber-reinforced panel. However, the blast resistance of the macro hooked-end steel fiber-reinforced panel was improved by hybrid with micro synthetic fibers.

Comparison of the effects of muscle stretching exercises and cupping therapy on pain thresholds, cervical range of motion and angle: a cross-over study

Yim, Jongeun,Park, Junhyuck,Kim, Hongseop,Woo, Juyeon,Joo, Soyeong,Lee, Sumin,Song, Jewon korean Academy of Physical Therapy Rehabilitation 2017 Physical therapy rehabilitation science Vol.1 No.1

Objective: Computers and smartphones have become a necessity for modern people, and the use of these things in an inappropriate position has increased the number of people who complain about neck problems. The purpose of this study was to compare the changes of cervical angle, range of motion (ROM) and pain threshold according to the McKenzie stretching and dry cupping therapy. Design: Cross-over design. Methods: We included 12 male and 6 female college students in their twenties, and conducted a pre- and post-test to evaluate the changes of each variable after the application of the McKenzie stretching and dry cupping therapy. Results: Neither the cervical spine angle nor the turtle neck angle showed any change in both the McKenzie stretching and the dry cupping treatment. In the McKenzie stretching, the pain threshold decreased, and the ROM of the cervical spine increased in all directions but there was no significant difference. The pain threshold was increased in the dry cupping treatment, and the ROM of the cervical spine was significantly increased in all directions (p<0.05). Comparisons of the McKenzie stretching and cupping treatment showed that the cupping treatment produced significantly greater pain thresholds and improvements in ROM of the cervical spine than the McKenzie stretching technique (p<0.05). Conclusions: Cupping treatment is more effective in improving ROM of the cervical spine and pain thresholds than the McKenzie stretching technique. In the future, cupping treatment will be one of the treatment options for pain and ROM impairments of the cervical spine.

Study on heat storage and transportation system for recovering non-using low-temperature heat

Changyong Oh(오창용),Hongseop Im(임홍섭),Insu Kim(김인수) 한국신재생에너지학회 2014 한국신재생에너지학회 학술대회논문집 Vol.2014 No.11

Comparison of the effects of muscle stretching exercises and cupping therapy on pain thresholds, cervical range of motion and angle: a cross-over study

( Jongeun Yim ),( Junhyuck Park ),( Hongseop Kim ),( Juyeon Woo ),( Soyeong Joo ),( Sumin Lee ),( Jewon Song ) 물리치료재활과학회 2017 Physical therapy rehabilitation science Vol.6 No.2

Objective: Computers and smartphones have become a necessity for modern people, and the use of these things in an inappropriate position has increased the number of people who complain about neck problems. The purpose of this study was to compare the changes of cervical angle, range of motion (ROM) and pain threshold according to the McKenzie stretching and dry cupping therapy. Design: Cross-over design. Methods: We included 12 male and 6 female college students in their twenties, and conducted a pre- and post-test to evaluate the changes of each variable after the application of the McKenzie stretching and dry cupping therapy. Results: Neither the cervical spine angle nor the turtle neck angle showed any change in both the McKenzie stretching and the dry cupping treatment. In the McKenzie stretching, the pain threshold decreased, and the ROM of the cervical spine increased in all directions but there was no significant difference. The pain threshold was increased in the dry cupping treatment, and the ROM of the cervical spine was significantly increased in all directions (p<0.05). Comparisons of the McKenzie stretching and cupping treatment showed that the cupping treatment produced significantly greater pain thresholds and improvements in ROM of the cervical spine than the McKenzie stretching technique (p<0.05). Conclusions: Cupping treatment is more effective in improving ROM of the cervical spine and pain thresholds than the McKenzie stretching technique. In the future, cupping treatment will be one of the treatment options for pain and ROM impairments of the cervical spine.