• Title/Summary/Keyword: reinforcing

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Analysis of Reinforcement Effect of Steel-Concrete Composite Piles by Numerical Analysis (I) - Material Strength - (수치해석을 이용한 강관합성말뚝의 보강효과 분석 (I) - 재료 강도 -)

  • Kim, Sung-Ryul;Lee, Juhyung;Park, Jae-Hyun;Chung, Moonkyung
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.29 no.6C
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    • pp.259-266
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    • 2009
  • The steel pipe of steel-concrete composite piles increases the pile strength and induces the ductile failure by constraining the deformation of the inner concrete. In this research, the numerical models and the related input parameters were analyzed to simulate the axial load-movement relations, which were obtained from the compression loading tests for the cylindrical specimens of the steel pipe, the concrete, and the steel-concrete composite. As the results, the behavior of the steel pipe was simulated by the von-Mises model and that of the concrete by the strain-softening model, which decreases cohesion and dilation angles as the function of plastic strains. In addition, the reinforcing bars in the concrete were simulated by applying the yielding moment and decreasing the sectional area of the bars. The applied numerical models properly simulated the yielding behavior and the reinforcement effect of the steel-concrete composite piles. The parametric study for the real-size piles showed that the material strength of the steel-concrete composite pile increased about 10% for the axial loading and about 20~45% for the horizontal loading due to the reinforcement effect by the surrounding steel pipe pile.

Analysis of Plastic Hinge on Pile-Bent Structure with Varying Diameters (변단면 단일 현장타설말뚝의 소성힌지 영향분석)

  • Ahn, Sangyong;Jeong, Sangseom;Kim, Jaeyoung
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.30 no.3C
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    • pp.149-158
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    • 2010
  • In this study, the behavior of Pile-Bent structure with varying diameters subjected to lateral loads were evaluated by a load transfer approach. An analytical method based on the beam-column model and nonlinear load transfer curve method was proposed to consider material non-linearity (elastic, yielding) and P-${\Delta}$ effect. For an effective analysis of behavior Pile-Bent structure, the bending moment and fracture lateral load of material were evaluated. And special attention was given to lateral behavior of Pile-Bent structures depending on reinforcing effect of materials and ground conditions. Based on the parametric study, it is shown that the maximum bending moment is located within a depth (plastic hinge) approximately 1~3D (D: pile diameter) below ground surface when material non-linearity and P-${\Delta}$ effect are considered. And distribution of the lateral deflections and bending moments on a pile are highly influenced by the effect of yielding. It is also found that this method considering material yielding behavior and P-${\Delta}$ effect can be effectively used to perform the preliminary design of Pile-bent structures.

Structural Behavior of Fiber Reinforced Concrete Mixed with Recycled PET Fiber (재생 PET 섬유가 혼입된 섬유 보강 콘크리트의 구조거동)

  • Kim, Sung Bae;Kim, Hyun Young;Yi, Na Hyun;Kim, Jang-Ho Jay
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.29 no.5A
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    • pp.543-550
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    • 2009
  • This study was performed to prove the possibility of utilizing short plastic fibers made for recycled polyethylene terephthalate (RPET) as a structural material. In order to verify the capacity of RPET fiber, it was compared with polypropylene (PP) fiber, most widely used short synthetic fiber, for fiber volume fraction of 0%, 0.5%, 0.75%, and 1.0%. To measure material properties such as compressive strength, split tensile strength, appropriate tests were performed. Also, to measure the strength and ductility capacities of reinforced concrete (RC) member casted with RPET fiber added concrete, flexural test was performed on RC beams. The results showed that compressive strength decreased, as fiber volume fraction increased. These trends are similarly observed in the tests of PP fiber added concrete specimens. Split cylinder tensile strength of RPET fiber reinforced concrete increased slightly as fiber volume fraction increased. For structural member performance, ultimate strength, relative ductility and energy absorption of RPET added RC beam are significantly larger than OPC specimen. Also, the results showed that ultimate flexural strength and ductility both increased, as fiber volume fraction increased. These trends are similarly observed in the tests of PP fiber added concrete specimens. The study results indicate that RPET fiber can be used as an effective additional reinforcing material in concrete members.

Research Trends on Hydrocarbon-Based Polymer Electrolyte Membranes for Direct Methanol Fuel Cell Applications (직접 메탄올 연료전지용 탄화수소계 고분자 전해질 막 연구개발 동향)

  • Yu-Gyeong Jeong;Dajeong Lee;Kihyun Kim
    • Membrane Journal
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    • v.33 no.6
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    • pp.325-343
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    • 2023
  • Direct methanol fuel cells (DMFCs) have been attracting attention as energy conversion devices that can directly supply methanol liquid fuel without a fuel reforming process. The commercial polymer electrolyte membranes (PEMs) currently applied to DMFC are perfluorosulfonic acid ionomer-based PEMs, which exhibit high proton conductivity and physicochemical stability during the operation. However, problems such as high methanol permeability and environmental pollutants generated during decomposition require the development of PEMs for DMFCs using novel ionomers. Recently, studies have been reported to develop PEMs using hydrocarbon-based ionomers that exhibit low fuel permeability and high physicochemical stability. This review introduces the following studies on hydrocarbon-based PEMs for DMFC applications: 1) synthesis of grafting copolymers that exhibit distinct hydrophilic/hydrophobic phase-separated structure to improve both proton conductivity and methanol selectivity, 2) introduction of cross-linked structure during PEM fabrication to reduce the methanol permeability and improve dimensional stability, and 3) incorporation of organic/inorganic composites or reinforcing substrates to develop reinforced composite membranes showing improved PEM performances and durability.

Analysis of the Reason for ROK's Foreign Strategy Adjustment: The growing threat from DPRK under the U.S.-China strategic competition and its profound influences on the security situation in Northeast Asia (韩国对外战略调整的原因分析-美中战略竞争下不断增加的北韩威胁对东北亚安全局势带来的深远影响)

  • Dongchan Kim;Jangwon Lee
    • Analyses & Alternatives
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    • v.7 no.3
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    • pp.115-144
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    • 2023
  • Under the Trump administration, the U.S. has made clear that "China is America's strategic competitor, revisionist power and a major challenge to America's prosperity and security." The Biden administration has largely inherited this perception of China. China has also responded without backing down. Therefore, the U.S.-China strategic competition has become the most important background factor in the international system and has a great impact on the security situation in Northeast Asia. Nevertheless, if you look at the recent process of establishing trilateral security cooperation among ROK, the U.S. and Japan, we can find that ROK's foreign strategy adjustment has played a key role. This is because establishing trilateral security cooperation among ROK, the U.S. and Japan depends on improving ROK-Japan relations. And the Yoon Suk Yeol government is pushing for rapid improvement in ROK-Japan relations regardless of domestic political constraints. The trilateral summit at Camp David laid the groundwork for future cooperation among ROK, the U.S. and Japan in security and other broader areas. China is strongly dissatisfied with the formation of trilateral security cooperation among ROK, the U.S. and Japan. However, this paper argues that although ROK agrees to form trilateral security cooperation with the U.S. and Japan, ROK's strategic objectives are not exactly the same as those of the U.S. and Japan. For example, looking back at the development of the U.S.-Japan alliance after the end of the Cold War, both the U.S. and Japan share similar views and perceptions of China's rise. The real goal of the strengthening of the U.S.-Japan alliance in recent years is also how to cope with China's rise. On the other hand, ROK's previous administrations have been negative about trilateral security cooperation with the U.S. and Japan. This is because ROK's main strategic goal is to reduce or eliminate threats from DPRK rather than respond to China. Faced with increasing DPRK's provocations and threats, more than half of South Koreans are in favor of reinforcing trilateral security cooperation with the U.S. and Japan to contain or mitigate threats from DPRK. As a result, if North Korea's nuclear and missile threats to ROK continue, then ROK's foreign strategy is likely to be to strengthen trilateral security cooperation between the U.S. and Japan to ensure its own safety and survival. If China wants to reduce the strategic pressure from the trilateral security cooperation among ROK, the U.S. and Japan, the best way is to reduce DPRK's provocations and threats to ROK and play a more substantive role in getting DPRK to give up its nuclear program.

Improving Thermal Conductivity of Neutron Absorbing B4C/Al Composites by Introducing cBN Reinforcement (cBN 입자상 강화재 첨가에 따른 중성자 흡수용 B4C/Al 복합재의 열전도도 변화 연구)

  • Minwoo Kang;Donghyun Lee;Tae Gyu Lee;Junghwan Kim;Sang-Bok Lee;Hansang Kwon;Seungchan Cho
    • Composites Research
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    • v.36 no.6
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    • pp.435-440
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    • 2023
  • This study aimed to enhance the thermal conductivity of B4C/Al composite materials, commonly used in transport/storage containers for spent nuclear fuel, by incorporating both boron carbide (B4C) and cubic boron nitride(cBN) as reinforcing agents in an aluminum (Al) matrix. The composite materials were successfully manufactured through a stir casting process and practical neutron-absorbing materials were obtained by rolling the fabricated composite ingot. The evaluation of the thermal conductivity of the fabricated composites was carried out because thermal conductivity is critical for neutron absorbing materials. The thermal conductivity measurement results indicated an approximately 3% increase in thermal conductivity under the same volume fraction when compared to composite materials using only B4C particles. Through neutron absorption cross-sectional area calculations, it was confirmed that the neutron absorption capability decreased to a negligible level. Based on the findings of this study, new design approaches for neutron absorption materials are proposed, contributing to the development of high-performance transport/storage containers.

Development and Application of a Teaching Strategy with Reinforced Teacher-Student Interactions Through Questions and Feedbacks in the Middle School Science Class (중학교 과학 수업에서 질문과 피드백을 활용한 교사-학생 상호작용 강화 수업 전략의 개발 및 적용)

  • Park, Jong-Yoon;Joung, In-Wha;Nam, Jeong-Hee;Choi, Kyung-Hee;Choi, Byung-Soon
    • Journal of The Korean Association For Science Education
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    • v.26 no.2
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    • pp.239-245
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    • 2006
  • The purposes of this study were to develop and implement a teaching strategy that reinforced teacher-student interaction for middle school first grade science and investigate the impact of the teaching strategy on student comprehension of scientific concepts, logical thinking ability, and science-related attitudes. 200 students attending a co-ed middle school located in Gyeonggi province were selected for the study and divided into an experiment and control group each consisting of 100 pupils. The teaching strategy reinforcing teacher-student interaction was applied to the experiment group, while conventional teaching, teacher-led lecturing, was carried out on the control group. To accomplish reinforced teacher-student interaction teacher asked students diversified questions and gave delayed feedbacks that deliberately focused on thought provocation. Results showed that the developed teaching strategy was effective in improving the students' logical thinking ability(p<.01). However, no significant differences were found in student comprehension of scientific concepts and science-related attitudes between the experimental and control group(p<.05). It was determined that more sound research is needed to develop and apply a lesson plan based on the teaching strategy used in this study.

Speech Reinforcement Based on G.729A Speech Codec Parameter Under Near-End Background Noise Environments (근단 배경 잡음 환경에서 G.729A 음성부호화기 파라미터에 기반한 새로운 음성 강화 기법)

  • Choi, Jae-Hun;Chang, Joon-Hyuk
    • The Journal of the Acoustical Society of Korea
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    • v.28 no.4
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    • pp.392-400
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    • 2009
  • In this paper, we propose an effective speech reinforcement technique base on ITU-T G.729A CS-ACELP codec under the near-end background noise environments. In general, since the intelligibility of the far-end speech for the near-end listener is significantly reduced under near-end noise environments, we require a far-end speech reinforcement approach to avoid this phenomena. In contrast to the conventional speech reinforcement algorithm, we reinforce the excitation signal of the codec's parameters received from the far-end speech signal based on the G.729A speech codec under various background noise environments. Specifically, we first estimate the excitation signal of ambient noise at the near-end through the encoder of the G.729A speech codec, reinforcing the excitation signal of the far-end speech transmitted from the far-end. we specially propose a novel approach to directly reinforce the excitation signal of far-end speech signal based on the decoder of the G.729A. The performance of the proposed algorithm is evaluated by the CCR (Comparison Category Rating) test of the method for subjective determination of transmission quality in ITU-T P.800 under various noise environments and shows better performances compared with conventional SNR Recovery methods.

A study of Improvement of Stiffness for Plastic PET bottle with Different Geometries and Numbers of Rib (리브 형상 및 개수에 따른 사각플라스틱 페트병의 강성보강에 관한 연구)

  • Young-Hoon Lee;Bum-Jin Park;Eui-Chul Jung;Jung-Gil Oh;Seok-Guwan Hong
    • Design & Manufacturing
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    • v.17 no.4
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    • pp.33-41
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    • 2023
  • Excessive use of plastic bottles contributes to a significant environmental issue due to the high volume of plastic waste generated. To address this, efforts are needed to reduce the weight of plastic bottles. However, indiscriminate weight reduction may compromise the essential rigidity required for plastic bottles. Extensive research on rib shape for pressure vessels are exists, but there is a few research of rib shapes to enhance the stiffness of plastic bottles. The following results were obtained from the analyses conducted in this study. 1) Among the rib cross-sections of square, trapezoid, and triangle, the buckling critical load of PET bottles with square-shaped ribs is improved by about 14% compared to the buckling critical load of PET bottles without ribs. 2) The buckling critical load is improved by about 18% when a square-shaped rib with an aspect ratio of 0.2 is applied, compared to the buckling critical load of the bottle without the rib. 3) When longitudinal and transverse square ribs were applied to the axial direction of the PET bottle, the buckling critical load was improved by about 32% and 58% compared to the buckling critical load of the PET bottle without ribs, respectively, indicating that applying longitudinal ribs is effective in reinforcing the stiffness of PET bottles. 4) When 14 transverse ribs were applied, the maximum improvement was about 48% compared to the buckling critical load of the plastic bottle without ribs. 5) When 3 longitudinal ribs were applied on each side, the maximum improvement was about 76% compared to the buckling critical load of the bottle without ribs. Therefore, it was concluded that for effective stiffness reinforcement of a 500ml square bottle with a thickness of 0.5mm, 3 square-shaped ribs with an aspect ratio of 0.2 should be applied in the longitudinal direction relative to the axial direction of the bottle.

A study on the relationship between selective exposure, opinion change, and political participation in a digital news distribution environment (개인과 미디어의 선택성이 강화된 디지털 뉴스 유통 환경에서 선택적 노출과 의견변화, 정치참여의 관계 연구)

  • Jihee Shin;Seungchan Yang
    • The Journal of the Convergence on Culture Technology
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    • v.10 no.2
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    • pp.391-406
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    • 2024
  • The current distribution of digital news has the potential to produce politically biased information for users as a result of individual choices and media selection based on those choices. Consequently, this research explored the factors affecting individual news selection and the effects of opinion changes and political participation that can occur when news tailored to users' partisan preferences is recommended. The phenomenon of selective exposure has been shown to be stronger when individuals utilize more limited information processing, experience higher discussion efficacy among groups with similar political beliefs. Furthermore, When a selective exposure group was randomly provided with a one-way message news that matched their partisan leanings, it was found that opinion consolidation, opinion-reinforcing information processing, and online political participation. On the other hand, when they were randomly presented with two-way messaging news in which the media balanced two competing partisan positions, they were found to be more likely to understand the other side's views and arguments, and more willing to adjust their existing opinions. We are confirmed that the balanced use of various opinions is very important in deliberative democratic process.