• Title/Summary/Keyword: cyclic humidity

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Analysis of Chloride Ion Penetraion for Marine Concrete Structure with Cyclic Humidity Environment (건습이 반복되는 환경하의 해양콘크리트 구조물에 대한 염소이온 침투 해석)

  • Han, Sang-Hun
    • Ocean and Polar Research
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    • v.26 no.1
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    • pp.43-50
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    • 2004
  • The diffusion model, which considers diffusion and sorption, is proposed. The FEM program developed on the basis of the diffusion model provides the estimation of chloride concentration according to cyclic humidity and sorption. After the humidity diffusion analysis is carried out, the chloride ion diffusion and sorption analysis are conducted on the basis of the preestimated humidity data in each element. Each element has different analysis variables at different ages and locations. At early ages, the difference between inner and outer relative humidity causes the chloride ion penetration by sorption. As the humidity diffusion reduces the difference with age, the effect of sorption on the chloride ion penetration decreases. By the way, the cyclic humidity increases the effect of sorption on the chloride ion penetration at early ages, and the quantity of chloride ion around steel at later ages. Therefore, the in situ analysis of chloride ion penetration for marine concrete structures must be performed considering the cyclic humidity condition and the long term sorption.

Analysis of Chloride Ion Penetration for Harbor Concrete Structure with In-situation Environment (항만 콘크리트 구조물의 현장환경변화에 따른 염소이온 침투해석)

  • Han, Sang-Hun;Jang, In-Sung
    • Proceedings of the Korea Concrete Institute Conference
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    • 2004.11a
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    • pp.225-228
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    • 2004
  • In order to estimate the chloride ion penetration, the model, which considers diffusion and sorption, is proposed on the basis of Finite Element Method (FEM). The FEM program provides the estimation of chloride concentration according to cyclic humidity and sorption. After the humidity diffusion analysis is carried out, the chloride ion diffusion and sorption analysis are conducted on the basis of the preestimated humidity data in each element. Each element has different analysis variables at different ages and locations. At early ages and constant outer humidity, the difference between inner and outer relative humidity causes the chloride ion penetration by sorption. As the humidity diffusion reduces the difference with age, the effect of sorption on the chloride ion penetration decreases. By the way, the cyclic humidity increases the effect of sorption on the chloride ion penetration at early ages, and the quantity of chloride ion around steel at later ages. Therefore, the in-situ analysis of chloride ion penetration for marine concrete structures must be performed considering the cyclic humidity condition and the long term sorption.

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The preliminary study of developing strong corrugated box board against aggravated service condition(I) (환경변화에 강한 골판지 개발을 위한 기초연구(제1보))

  • 서영범;오영순
    • Journal of Korea Technical Association of The Pulp and Paper Industry
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    • v.30 no.1
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    • pp.29-43
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    • 1998
  • This study was to investigate the effect of .compressive load and cyclic humidity(2$0^{\circ}C$, 65% and 90% RH) on the physical and mechanical properties of corrugated board. Corrugated boards in the study were under compressive load and under cyclic humidity, and their properties were compared to those without load. Results were summarized as follows ; 1 Statistically significant correlation was shown between the ring crush of the boards and the compressive strength of cylinder specimen made from the boards. So we could study the compressive behavior of board with cylinder specimen. 2. The boards under the compressive load increased their moisture content and thickness much more than those without load both in constant and in cyclic RH. 3. The compressive and tensile strength of board samples were inversely and closely proportional to the sheet moisture content regardless of their load and humidity history. 4. The moisture content did not show any significant proportionality to the change of burst strength of boards within this experiment. 5. Board reconditioning in standard condition led to the recovery of the strength loss that had occurred under various load and humidity condition. 6. The handsheets prepared from the boards that had experienced compressive load and cyclic humidity, and those with no-load and 65% RH did not show any significant difference in strength properties. No physical damage or load-carrying properties of the wood fiber were observed by the compressive load and cyclic humidity history.

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Comparison of Dynamic Sorption and Hygroexpansion of Wood by Different Cyclic Hygrothermal Changing Effects

  • Yang, Tiantian;Ma, Erni
    • Journal of the Korean Wood Science and Technology
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    • v.44 no.2
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    • pp.191-203
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    • 2016
  • To investigate the dynamic sorptive and hygroexpansive behaviors of wood by different cyclic hygrothermal changing effects, poplar (populus euramericana Cv.) specimens, were exposed to dynamic sorption processes where relative humidity (RH) and temperature changed simultaneously in sinusoidal waves at 75-45% and $5-35^{\circ}C$ (condition A) and where RH changed sinusoidally at 75-45% but temperature was controlled at $20^{\circ}C$ (condition B), both for three cyclic periods of 1, 6, and 24 h. Moisture and dimensional changes measured during the cycling gave the following results: Moisture and transverse dimensional changes were generally sinusoidal. Moisture and dimensional amplitude increased with increasing cyclic period but all were lower for thicker specimens. The amplitude ratio of condition A to condition B ranged from 1.0 to 1.6 with the maximum value of 1.57 occurring at the shortest cyclic period, not as much as expected. T/R increased as cyclic period increased or specimen thickness decreased. T/R from condition B was weaker than that from condition A. Sorption and swelling hysteresis existed in both conditions. Sorption hysteresis was negatively related to cyclic period but in positive correlation with specimen thickness. Sorption hysteresis was found more obvious in condition B, while moisture sorption coefficient and humidity expansion coefficient showed the opposite results.

Physical Properties of Linerboard and Corrugated Fiberboard at the Cyclic Condition of Low Humidity (저습도 사이클 조건에서의 라이너지와 골판지의 물성)

  • Youn, Hye-Jung;Lee, Hak-Lae;Chin, Seong-Min;Choi, Ik-Sun
    • Journal of Korea Technical Association of The Pulp and Paper Industry
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    • v.39 no.2 s.120
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    • pp.38-44
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    • 2007
  • The hygroscopic property of paper is important for convertability and end use performance. When the board and corrugated fiberboard are exposed to low relative humidity, a trouble of score (or crease) cracking could occur. In this study, we evaluated the moisture content and mechanical properties of linerboard and corrugated board at the cyclic condition of low humidity to prevent a score crack trouble. As the relative humidity decreased from 50% to 38% and 25%, the moisture content of linerboard decreased about 7% to 6% and 4%. At low humidity, most of mechanical properties were improved except for strain. The linerboard exposed at 25% RH showed a remarkable reduction of strain by 11%. At the same relative humidity, linerboard and corrugated fiberboard showed the different property values depending on moisture hysteresis.

Analysis of Chloride ion Penetration for In-Situation Harbor Concrete Structures (현장 항만 콘크리트 구조물에 대한 염소이온 침투 해석)

  • Han Sang-Hun
    • Journal of the Korea Concrete Institute
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    • v.17 no.5 s.89
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    • pp.751-760
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    • 2005
  • The chloride penetration model, which considers diffusion and sorption, is proposed. The FEM program developed on the basis of the diffusion and sorption model provides the estimation of chloride concentration variation according to cyclic humidity and temperature. The humidity diffusion analysis is carried out, and the chloride ion diffusion and sorption analysis are conducted on the basis of the pre-estimated humidity data in each element. Each element has different variables at different ages and locations in analysis. At early ages, the difference of relative humidity between inner and outer concretes causes the chloride ion penetration by sorption. As the humidity diffusion reduces the difference of relative humidity between inner md outer concretes with age, the effect of sorption on the chloride ion penetration decreases with age. The cyclic humidity increases the effect of sorption on the chloride ion penetration at early ages, and increases the quantity of chloride ion around steel at later ages. Therefore, the in-situ analysis of chloride ion Penetration for harbor concrete structures must be Performed considering the cyclic humidity conditionandthelongtermsorption.

The humidity sensitive characteristics of $CaZrO_3$ ceramics ($CaZrO_3$ 세라믹스의 감습 특성)

  • Yuk, Jae-Ho;Kim, Yong-Woon
    • 전자공학회논문지 IE
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    • v.43 no.3
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    • pp.1-5
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    • 2006
  • [ $CaZrO_3$ ] humidity sensors were prepared using the solid-state synthetic method and their humidity sensitive characteristics have been investigated. It was found that the impedance of the humidity sensors decreased with increasing relative humidity and the humidity sensitivity depended on the applied frequencies. The sensitivity of sensor is stable with heat treatment and a negligible hysteresis under cyclic humidity changes is shown, and the activation energy for electrical conduction is reduced with water adsorption.

Dimensional Responses of Wood Under Cyclical Changing Temperature at Constant Relative Humidity

  • Yang, Tiantian;Ma, Erni;Shi, Yi
    • Journal of the Korean Wood Science and Technology
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    • v.43 no.5
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    • pp.539-547
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    • 2015
  • To investigate dimensional responses of wood under dynamic temperature condition, poplar (populous euramericana Cv.) specimens, 20 mm in radial (R) and tangential (T) directions with two thicknesses of 4 and 10 mm along the grain, were exposed to cyclic temperature changes in square wave between $25^{\circ}C$ and $40^{\circ}C$ at 60% relative humidity (RH) for three different cycling periods of 6 h, 12 h and 24 h. R and T dimensional changes measured during the cycling gave the following results: 1) Transverse dimensional changes of the specimens were generally square but at an opposite phase and lagged behind the imposed temperature changes. The phase lag was inversely correlated with cycling period, but positively related to specimen thickness, while the response amplitude was directly proportional to cycling period, but in a negative correlation with specimen thickness. 2) The specimens showed swelling hysteresis behavior. The heat shrinkage coefficient (HSC) became greater as cycling period increased or specimen thickness decreased. 3) Dimensional changes of the specimens produced deformation accumulation during repeated adsorption and desorption. The deformation accumulating ratio decreased with an increase in cycling period and specimen thickness. 4) Wood suffered 1.5 times as many dimensional changes per unit temperature variation as per unit humidity variation, and this deformation behaved even more seriously under static condition.

Experiment of frost growth on the parallel plates in the condition of laminar and low humidity (층류유동 저습도 조건에서의 평행평판형 냉각판 서리성장 실험)

  • 한흥도;노승탁
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.11 no.4
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    • pp.440-447
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    • 1999
  • The frosting characteristics on the vertical parallel plates with three cooling plates were experimentally investigated. The experimental parameters were the cooling plate temperature, the air humidity, the air temperature, the air Reynolds number, and the location. The frosting conditions were limited to air temperatures from 10 to $15^{\circ}C$ , air Reynolds numbers from 1600 to 2270, air humidity ratios from 0.00275 to 0.0037kgw/kga and cooling plate temperatures from -10 to $-20^{\circ}C$. Frost growth and density toward the front of the plate were more thick and dense than toward the rear. Frost growth increased with decreasing plate temperature and increasing humidity. In the conditions of the laminar flow, dew point below $0^{\circ}C$and non-cyclic frosting period, frost thickness increased with increasing air temperature. The reason of increasing frost thickness with increasing air temperature was sublimation-ablimation process. The average growth thickness along the locations showed little dependence on the Reynolds numbers.

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Cut Edge Corrosion of Painted Zn and 55%Al-Zn Coated Steels under Alternate Wetting and Drying

  • Nishikata, A.;Tsuda, T.;Tsuru, T.
    • Corrosion Science and Technology
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    • v.9 no.1
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    • pp.34-38
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    • 2010
  • Electrochemical study on cut edge corrosion of prepainted Zn coated (GI) and 55%Al-Zn coated (GL) steels has been performed in wet-dry cyclic conditions. Maximum width of delaminated polymer coating from the cut edge for GI and GL specimens was evaluated under wet-dry cyclic conditions. The cyclic tests were carried out for 1000 h by changing of relative humidity, where the salt of NaCl was deposited on the specimen every 48 h. The cut edge corrosion test under NaCl deposit indicated that the delamination of the GL specimen progresses at a higher rate than the GI. The electrochemical corrosion monitoring was also performed under condition of alternate exposure to immersion in NaCl solution and drying at 60%RH and $25^{\circ}C$. On the basis of the results of the delamination tests and electrochemical measurements, the mechanism of cut edge corrosion for GI and GL were discussed.