• Title/Summary/Keyword: Bond order

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Flexural Behavior of Reinforced Concrete Beams Strengthened by CFRP Plates (탄소섬유판으로 보강된 철근콘크리트 보의 휨거동해석)

  • Yang, Dong-Suk;Koh, Byung-Soon;Park, Sun-Kyu;You, Young-Chan;Choi, Ki-Sun
    • Proceedings of the Korea Concrete Institute Conference
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    • 2005.05a
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    • pp.243-246
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    • 2005
  • This paper focuses on the flexural behavior of RC beams externally reinforced using Carbon Fiber Reinforced Plastics plates (CFRP). A non-linear finite element (FE) analysis is proposed in order to complete the experimental analysis of the flexural behaviour of the beams. This paper is a part of a complete program aiming to set up design formulate to predict the strength of CFRP strengthened beams, particularly when premature failure through plates-end shear or concrete cover delamination occurs. An elasto-plastic behaviour is assumed for reinforced concrete and interface elements are used to model the bond and slip.

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Recent characteristics of dental esthetic restorative ceramics (임상가를 위한 특집 1 - 치과심미수복용 세라믹의 최신 특성평가)

  • Oh, Seunghan
    • The Journal of the Korean dental association
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    • v.51 no.1
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    • pp.6-11
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    • 2013
  • Dental ceramics is well known to have excellent esthetics, biocompatibility as well as high compressive strength. However, the fragility of ceramics against tensile and shear loads leading to the delayed fracture of micro crack on ceramic surface and the backwardness of ceramic fabrication technique limit the usage of ceramic materials in dentistry. Among all ceramic materials, zirconia has been introduced to overcome the drawback of conventional dental ceramics in the field of dentistry due to the nature of zirconia featuring proper opalescence and high fracture toughness. Also, novel manufacturing techniques enable ceramic materials to prepare high esthetic anterior and posterior all ceramic system. In this paper, it is introduced and discussed that novel techniques characterizing the bond strength between zirconia core and veneering ceramics and analyzing the fluorescence of dental ceramics in order to overcome the gap between the results of basic research and the feasibility of the results in the field of dental clinics.

Evaluation of Bond Strength for Self-Healing Agents Using Modified Single Lap Shear Test (접착전단시험을 적용한 자가치료제의 접착특성 평가)

  • Heo Kwang Su;Park Hee Won;Lee Jong Keun;Yoon Sung Ho
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2004.04a
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    • pp.266-269
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    • 2004
  • In this study, bond strengths for the self-healing agents were evaluated through the modified lap shear test in order to suggest the optimal healing conditions for the repair of polymeric composites. The healing agents of DCPD, ENB, and their mixtures were activated with Grubbs' catalysts. According to the results, the mixture of DCPD and ENB gave better opportunity than DCPD only due to the rapid acivation with catalyst in view of the economic and practical use.

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Shear transfer mechanisms in composite columns: an experimental study

  • De Nardin, Silvana;El Debs, Ana Lucia H.C.
    • Steel and Composite Structures
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    • v.7 no.5
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    • pp.377-390
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    • 2007
  • In the design of concrete filled composite columns, it is assumed that the load transfer between the steel tube and concrete core has to be achieved by the natural bond. However, it is important to investigate the mechanisms of shear transfer due to the possibility of steel-concrete interface separation. This paper deals with the contribution of headed stud bolt shear connectors and angles to improve the shear resistance of the steel-concrete interface using push-out tests. In order to determine the influence of the shear connectors, altogether three specimens of concrete filled composite column were tested: one without mechanical shear connectors, one with four stud bolt shear connectors and one with four angles. The experimental results showed the mechanisms of shear transfer and also the contribution of the angles and stud bolts to the shear resistance and the force transfer capacity.

Estimation of Traction return current and Impedance on Kyoungbu electrification line (경부선 전철화 구간에서의 귀선 전류 및 임피던스 예측)

  • 김용규;양도철;유창근
    • Proceedings of the IEEK Conference
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    • 2001.06e
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    • pp.123-126
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    • 2001
  • This study presents the simulation of the traction return current based on 2${\times}$25kV power supply system in order to determine the impedance bond intensity of impulse type track circuit on the Kyoungbo electrification line. The results of simulation enables us to measure the precise intensity of catenary current, returning to the substation through KTX (Korean Train Express) operated by 2${\times}$25kV power supply system with common earth network. In the wake of establishing 2${\times}$25kV and common earth network used in Korea for the first time, in particular, it is possible to determine the impedance bond intensity of impulse type track circuit, which is applicable to the Kyoungbo electrification line by specifying the relations among the traction return current, earth current, and catenary current.

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Low Temperature Bonding Process of Silicon and Glass using Spin-on Glass (Spin-on Glass를 이용한 실리콘과 유리의 저온 접합 공정)

  • Lee Jae-Hak;Yoo Choong-Don
    • Journal of Welding and Joining
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    • v.23 no.6
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    • pp.77-86
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    • 2005
  • Low temperature bonding of the silicon and glass using the Spin-on Glass (SOG) has been conducted experimentally to figure out the effects of the SOG solution composition and process variables on bond strength using the Design of Experiment method. In order to achieve the high quality bond interface without rack, sufficient reaction time of the optimal SOG solution composition is needed along with proper pressure and annealing temperature. The shear strength under the optimal SOG solution composition and process condition was higher than that of conventional anodic bonding and similar to that of wafer direct bonding.

Theoretical Studies on the Photo-Skinsensitizing Psoralens (II)

  • Kim, Ja-Hong;Shim, Sang-Chul
    • Bulletin of the Korean Chemical Society
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    • v.2 no.3
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    • pp.112-114
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    • 1981
  • The photocycloaddition reaction of 8-methoxypsoralen with purine and/or pyrimidine bases is studied as a model for the charge transfer interactions of psoralens with DNA bases by the FMO method. The results indicate that, in the case of the molecular complex formation between psoralens and purine and/or pyrimidine bases, the most probable photocycloaddition should occur in the following order: Thy (5,6)<>(3,4) 8-MOP, Cyt(5,6)<>(3,4)8-MOP, Ade (7,8)<>(3,4)8-MOP, Gua(7,8)<>(3,4)8-MOP. The theoretical results for the photocycloaddition reaction are also correlated with the experimental results. The photoadducts between 8-methoxypsoralen and adenine are likely to be C4-cycloadducts through the cycloaddition of 3,4-pyrone double bond of 8-methoxypsoralen to 7,8-double bond of adenine.

Theoretical Study of the Cobalt Substituting Site in the Framework of $AlPO_{4}-5$ Molecular Sieves

  • Sang Joon Choe;Dong Ho Park;Do Sung Huh
    • Bulletin of the Korean Chemical Society
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    • v.14 no.1
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    • pp.55-58
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    • 1993
  • In order to determine the cobalt substituting site in $AlPO_4-5$ framework, ASED-MO theory has been used. The substitution of cobalt for aluminum is energetically more favorable than that for phasphorous. The stabilized energy of the former is 51 eV lower than that of the latter. The calculated net charge was +1.27 for Al, +0.85 for P, and +1.56 for Co, respectively. The valence electron population (VEP), reduced overlap population (ROP) and net charge for the charged cluster models were compared for $AlPO_4-5$ and $CoAlPO_4-5$ systems. Then, twe find that the covalency of P-O bond was greater than that of Al-O bond.

Infrared Absorption Spectroscopic Studies of ${\alpha},{\omega}$-Diphenylpolyenyl Anions with Odd Numbered Polyene Molecules

  • Kim, Jin Yeol;Kim, Eung Ryeol;Son, Dae Won
    • Bulletin of the Korean Chemical Society
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    • v.22 no.8
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    • pp.833-836
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    • 2001
  • Infrared absorption spectra of $\alpha\omega-diphenylpolyenyl$, anions Ph(CH)nPh- (DPn-, n=7, 9, and 13) in the tetrahydrofuran-d6 solutions was measured in the range of 1700 and 1200 cm-1 . The infrared spectra obtained from anions (DPn) showed considerable difference from their neutral species (DPn); their intensities were enhanced at least two orders of magnitude stronger than their neutral species. The in-plane CH bending modes at 1464 and 1375 cm-1 are correspondingly strengthened with the chain length increased, but the C=C stretching at 1541 cm-1 is weakened and frequencies are not changed. We provide an IR evidence for the first time that the bond order or bond alternations of the anions (soliton) are different from those of radical anions (polaron) as well as neutral species.

Ab initio Studies on the Hetero Diels-Alder Cycloaddition

  • 이본수;김찬경;최정욱;이익준
    • Bulletin of the Korean Chemical Society
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    • v.17 no.9
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    • pp.849-853
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    • 1996
  • Hetero Dieis-Alder reactions containing phosphorus atom at various positions of diene and dienophile as well as standard Dieis-Alder reaction between ethylene and cis-l,3-butadiene have been studied using ab initio method. Activation energy showed a good linear relationship with the FMO energy gap between diene and dienophile, which can be normally used to explain Dieis-Alder reactivity. Since π-bond cleavage and σ-bonds formation occur concertedly at the TS, geometrical distortion of diene and dienophile from the reactant to the transition state is the source of barrier. Based on the linear correlations between activation barrier and deformation energy, and between deformation energy and π-bond order change, it was concluded that the activation barrier arises mainly from the breakage of π-bonds in diene and dienophile. Stabilization due to favorable orbital interaction is relatively small. The geometrical distortions raise MO levels of the TS, which is the origin of the activation energy. The lower barrier for the reactions of phosphorus containing dienophile (reactions C, D, and E) can be explained by the electronegativity effect of the phosphorus atom.