• Title, Summary, Keyword: Transition zone

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A multi-phase model for predicting the effective chloride migration coefficient of ITZ in cement-based materials

  • Yang, C.C.;Weng, S.H.
    • Advances in concrete construction
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    • v.1 no.3
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    • pp.239-252
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    • 2013
  • Mortar microstructure is considered as a three-phase composite material, which is cement paste, fine aggregate and interfacial transition zone. Interfacial transition zone is the weakest link between the cement paste and fine aggregate, so it has a significant role to determine the properties of cementitious composites. In this study, specimens (w/c = 0.35, 0.45, 0.55) with various volume fractions of fine aggregate ($V_f$ = 0, 0.1, 0.2, 0.3 and 0.4) were cast and tested. To predict the equivalent migration coefficient ($M_e$) and migration coefficient of interfacial transition zone ($M_{itz}$), double-inclusion method and Mori-Tanaka theory were used to estimate. There are two stages to estimate and calculate the thickness of interfacial transition zone (h) and migration coefficient of interfacial transition zone ($M_{itz}$). The first stage, the data of experimental chloride ion migration coefficient ($M_s$) was used to calculate the equivalent migration coefficient of fine aggregate with interfacial transition zone ($M_e$) by Mori-Tanaka theory. The second stage, the thickness of interfacial transition zone (h) and migration coefficient of interfacial transition zone ($M_{itz}$) was calculated by Hori and Nemat-Nasser's double inclusion model. Between the theoretical and experimental data a comparison was conducted to investigate the behavior of interfacial transition zone in mortar and the effect of interfacial transition zone on the chloride migration coefficient, the results indicated that the numerical simulations is derived to the $M_{itz}/M_m$ ratio is 2.11~8.28. Additionally, thickness of interfacial transition zone is predicted from $10{\mu}m$, 60 to $80{\mu}m$, 70 to $100{\mu}m$ and 90 to $130{\mu}m$ for SM30, M35, M45 and M55, respectively.

Strain Characteristics of Reinforcing materials in the transition zone of slopes (사면의 변이영역에서 보강재의 변형률 특성)

  • 김경태;장대수;장기태;한희수
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.119-127
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    • 2003
  • For the calculation of internal stability, the hypothesis in conventional design is on the basis of two distinct zones, which are‘active zone’and‘passive zone’. This means that there is an abrupt discontinuous transition from active to passive states across a potential failure line. The existence of a discontinuity of this nature appears physically unreasonable, especially from kinematic considerations. A series of pull-out model tests was undertaken from a wall being rotated about the toe to find the strain distribution mobilized from near the wall face into the deep, stable zone through the centre plane. With this finding of transition zone, the objective of study is aiming at identifying the likely effect of this zone in designing method by comparing with the prevailing design method.

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Significance of Contrast Enema in One-stage Transanal Endorectal Pull-through Operation for Hirschsprung Disease (히르슈슈프룽병의 One-stage Transanal Endorectal Pull-through 술식에서 대장조영술의 의의)

  • Shin, Man Sik;Lee, Mi Jung;Kim, Myung Joon;Hong, Young Ju;Chang, He Kyung;Han, Seok Joo;Oh, Jung-Tak
    • Advances in pediatric surgery
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    • v.18 no.2
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    • pp.75-82
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    • 2012
  • In one-stage transanal endorectal pull-through operation (TERPT) for Hirschsprung disease, preoperative evaluation by contrast enema (CE) is important tool in aspect of planning of surgical procedure as well as diagnosis. This study was to evaluate the significance of CE for identifying the extent of aganglionic bowel. A retrospective analysis was performed in 40 patients who underwent TERPT between 2003 and 2011. The authors reviewed the CE studies and their correlation with pathologic extent of aganglionosis. Total 66 contrast enemas were performed in 40 patients. Twenty patients underwent single CE, but 20 patients required multiple CEs. In single CE group, 17 had clear radiographic transition zone, but 3 had less definite transition zone. In multiple CE group, 17 patients who had equivocal finding in first or second CE had definite radiographic transition zone, but 3 patients of this group had less definite radiographic transition zones. Overall, 34 patients (85%)had clear radiographic transition zone by single or repeated CE. One (2.9%) out of 34 patients with clear radiographic transition zone had discordance between radiographic and pathologic transition zone. In contrast 4 (66.7%) out of 6 patients with equivocal radiographic transition zone had discordance between radiographic and pathologic transition zone. Observation of clear radiographic transition zone is important in preparation of TERPT, and repeated CE is helpful to reduce the discordance between radiographic and pathologic transition zone. Awareness of the possibility of discordance is also important if radiographic transitional zone is not clear.

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Evolution of Solidification Structures of Al-Si Alloys in a Vertical Centrifugal Casting (Al-Si합금의 수직원심주조시 응고조직의 형성)

  • Chang, Sung-Rak;Huh, Seung-Ho;Hong, Chun-Pyo
    • Journal of Korea Foundry Society
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    • v.20 no.3
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    • pp.197-207
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    • 2000
  • Al-Si alloys were solidified in a rotating cylindrical mold by a vertical centrifugal casting process. Under a certain casting condition, there are four distinct zones such as the chill zone, the primary fine columnar zone, the equiaxed zone, and the secondary coarse columnar zone from the mold wall. The columnar-equiaxed transition (CET) and the equiaxed-columnar transition (ECT) were measured as functions of solute content, flow rate (mold velocity), pouring temperature and mold temperature. Within the critical value of solute content, as the flow rate increases, the columnar-equiaxed transition were found, but not the equiaxed-columnar transition. The aspect ratio of the primary columnar zone was more affected by the solute content than the flow rate. However the aspect ratio of the equiaxed zone was more affected by the flow rate than the solute content. The aspect ratio of the secondary columnar zone was affected by both the flow rate and the solute content.

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Effects of Tool Rotation and Transition Speed during Friction Stir Welding of Al 7075-T651 Alloy (Al 7075-T651의 마찰교반 용접에 대한 회전속도와 이송속도의 영향)

  • Han, Min-Su;Jeon, Jeong-Il;Jang, Seok-Gi
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.31 no.4
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    • pp.532-539
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    • 2007
  • The 7075-T651 Al alloy was welded by friction stir welding. Microstructure, macro behaviors and fracture type in the nugget, thermo-mechanically affected zone(TMAZ) and heat affected zone(HAZ) of the welded part were compared to base metal. The microsturctures of nugget zone were compared with tool rotation speeds and various tool transition speed. When the rotation speeds were decreased and transition speeds were increased, the hardness of nugget zone were decreased. Also, the optimal microstructure was observed at the low rotation speed of 800rpm and the high transition speed of 124mm/min. The transgranular dimple and quasi-cleavage at fractured part of nugget zone were investigated.

Analysis on the Reinforcement Effect for Large Type Sleeper on Transition zone between Earthwork and Tunnel (터널/토공 접속부에 대한 대형침목 보강효과 분석)

  • Lee, Jin-Wook;Choi, Chan-Yong;Lee, Il-Wha
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.1279-1286
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    • 2006
  • It is very important to pay careful attention to construction of earthwork/tunnel transition zone for railway. The transition zone of the railway is the section which roadbed stiffness is suddenly varied. Differences in stiffness have dynamic effects and these increase the forces in the track and the extent of deformation. In this study, performance of transition zone was investigated through the field tests. The wheel loads and sleeper settlement were measured after installing field testing sections.

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Strain Distribution of transition zone in a nailed wall (네일로 보강된 구조물에서의 변이영역과 변형률 분포)

  • 장기태;남궁한;유병선;김경태;권병근;이선경
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.235-239
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    • 2000
  • For the calculation of internal stability, the hypothesis in conventional design is on the basis of two distinct zones, which are 'active zone' and 'passive zone'. This means that there is an abrupt discontinuous transition from active to passive states across a potential failure line. The existence of a discontinuity of this nature appears physically unreasonable, especially from kinematic considerations. A series of pull-out model tests was undertaken from a wall being rotated about the toe to find the strain distribution mobilized from near the wall face into the deep, stable zone through the centre plane. With this finding of transition zone, the objective of study is aiming at identifying the likely effect of this zone in designing method by comparing with the prevailing design method.

  • PDF

Strain Distribution of Transition Zone in a Nail Wall (네일로 보강된 구조물에서의 변이영역과 변형률 분포)

  • Chang, Ki-Tae;NamGung, Han;Yoo, Byung-Sun
    • Journal of the Korean Geophysical Society
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    • v.8 no.1
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    • pp.39-43
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    • 2005
  • For the calculation of internal stability, the hypothesis in conventional design is on the basis of two distinct zones, which are 'active zone' and 'passive zone'. This means that there is an abrupt discontinuous transition from active to passive states across a potential failure line. The existence of a discontinuity of this nature appears physically unreasonable, especially from kinematic considerations. A series of pull-out model tests was undertaken from a wall being rotated about the toe to find the strain istribution mobilized from near the wall face into the deep, stable zone through the centre plane. With this finding of transition zone, the objective of study is aiming at identifying the likely effect of this zone in designing method by comparing with the prevailing design method.

  • PDF

Experimental study on the Variation of Stiffness Transition Zone between Earthwork and Tunnel (열차운행시 터널-토공접합부에서의 강성천이구간에 대한 실험적 연구)

  • Lee Jin-Wook;Choi Chan-Yong;Lee Il-Hwa
    • Proceedings of the KSR Conference
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    • pp.726-733
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    • 2005
  • It is very important to pay careful attention to construction of earthwork/tunnel transition zone for railway. The transition zone of the railway is the section which roadbed stiffness is suddenly varied. Differences in stiffness have dynamic effects and these increase the forces in the track and the extent of deformation. In this study, performance of transition zone was investigated through the field tests. The wheel loads and sleeper settlement were measured after installing field testing sections.

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Trophic State Index (TSI), Spatial Gradient Characteristics and the Empirical Models for Eutrophication Evaluations in Daecheong Reservoir (대청호 수질오염 평가를 위한 부영양도 지수산정, 공간적 구배 특성 및 경험적 모델)

  • Kwon, Hyuk-Hyun;An, Kwang-Guk
    • Journal of Environmental Science International
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    • v.23 no.9
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    • pp.1537-1549
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    • 2014
  • The objectives of this study were to analyze reservoir trophic state, based on Trophic State Index (TSI), spatial variation patterns of three zones (riverine, transition, and lacustrine zone), and empirical models through 20-years long-term data analysis. Trophic variables of TP and CHL-a were highest during the summer monsoon, and decreased along the main axis from the riverine to lacustrine zone. In the mean time, TN did not show the trend. Ratios of N:P and Secchi disc transparency (SD) increased from the riverine to lacustrine zone. The analysis of trophic state index (TSI) showed that mean TSI (TP) and TSI (CHL-a) were 62 and 57, respectively, and these values were highest in the transition zone during the summer. This zone should be managed well due to highest lake water pollution. The analysis of Trophic State Index Deviation (TSID) showed that algal growth was primarily limited by light penetration, and this was most pronounced in the monsoon season. The analysis of empirical models showed that the value of $R^2$, based on CHL-SD model, was 0.30 (p < 0.0001) in the transition zone and the $R^2$, based on TP-SD model, was 0.41 (p < 0.0001) in the transition zone.