• Title/Summary/Keyword: 대교& #40;對校& #41;

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A Study on the Physcial and Mechanical Properties of Hot - Compressed Wood (열압처리(熱壓處理) 목재(木材)의 이학적(理學的) 성질(性質)에 관(關)한 연구(硏究))

  • Park, Young-Kyu;Chung, Dae-Kyo
    • Journal of the Korean Wood Science and Technology
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    • v.15 no.4
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    • pp.45-58
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    • 1987
  • This study was carried out to improve the physical and mechanical properties of Pupulus alba $\times$ glandulosa treated by the heat and compression. The results obtained were as follows. 1. The specific gravity of the wood was conspicuously increased by the lincreasing of pressing level. 2. The shrinkage of the wood was increased. by the increasing of pressing level. The radial shrinkage was 6.41-8.81%, the tangential shrinkage was 8.98-19.81 %, and the longitudinal shrinkage was 1.46-1.91 %. Comparing to the untreated stock, the rate of increase was 48.7-104.4% in radial direction. 1.7-124.4% in tangential direction and 60.4-109.9% in longitudinal direction, respectively. 3. The rate absorption of 30% compressed stock was Similar to that of untreated stock. but the rate of absorption of 40 % or more compressed stock was increased highly. 4. The thickness swelling of the wood was not changed in radial direction at pressing level, but was conspicuously increased in tangential direction under the pressing level of 40% and 50%. 5. The heat and compression treatment affected on the mechanical properties of the wood. The longitudinal compressive strength was increased under the pressing level of up to 40%, but was decreased under the pressing level of 50%. The bending strength was not changed under the compression percentage of up to 30%, but was decreased under the pressing level of 30% or more. And, the absorbed energy in impact bending was increased to 128% under the pressing level of up to 30%, but was decreased under the pressing level of 30% or more. Conclusionly, the mechanical properties of the wood was improved by the heat and compression treatment, but the strength of the wood was decreased under the pressing level of a certain level or more(in this study, pressing level of 30% or more). This was because of the wood deterioration due to the deformation(shrinkage, crack, failure) of wood tissues induced by the heat and compression treatment, the heat analysis of wood components induced by the heating, and the drop of the degree of polymerization.

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Characteristics of Mass Transport Depending on the Feature of Tidal Creek at Han River Estuary, Gyeong-gi Bay, South Korea (경기만 염하수로에서의 비정규 격자 수치모델링을 통한 조간대 조수로의 고려에 따른 Mass Transport 특성)

  • Kim, Minha;Woo, Seung-Buhm
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.25 no.2
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    • pp.41-51
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    • 2013
  • The tidal creek dependent mass transport characteristic in Gyeong-Gi Bay (west coast of Korea) was studied using field measured data and numerical model. Gyeong-Gi Bay consists of 3 main tidal channels and contains a well-developed vast tidal flat. This region is famous for its large tidal difference and strong current. We aim to study the effect of tidal creek in the tidal flat on the mass exchange between the estuary and the ocean. For numerical application, the application of unstructured grid feature is essential, since the tidal creek has complicated shape and form. For this purpose, the FVCOM is applied to the study area and simulation is performed for 2 different cases. In case A, geographic characteristics of the tidal creek is ignored in the numerical grid and in case B, the tidal creek are constructed using unstructured grid. And these 2 cases are compared with the field measured cross-channel mass transport data. The cross-channel mass transport at the Yeomha waterway mouth and Incheon harbor was measured in June, 9~10 (Spring tide) and 17~18 (Neap tide), 2009. CTD casting and ADCP cross-channel transect was conducted 13 times in one tidal cycle. The observation data analysis results showed that mass transport has characteristic of the ebb dominance Line 1 (Yeomha waterway mouth), on the other hand, a flood dominant characteristic is shown in Line 2 (Incheon harbor front). By comparing the numerical model (case A & B) with observation data, we found that the case B results show much better agreement with measurement data than case A. It is showed that the geographic feature of tidal creek should be considered in grid design of numerical model in order to understand the mass transport characteristics over large tidal flat area.