• Title/Summary/Keyword: exposed condition

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Study on the Reliability Analysis of Wood Floor System Exposed to Fire (화염에 노출된 목재 마루 시스템의 신뢰성 해석에 관한 연구)

  • Kim, Gwang-Chul;Lee, Jun-Jae
    • Journal of the Korean Wood Science and Technology
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    • v.32 no.5
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    • pp.66-74
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    • 2004
  • Fire performance is the important criterion for evaluating of safety of wood structures which exposed to the standard fire condition. Endurance time and time-to-failure are used as the criteria for fire performance in many countries. Reliability analysis about wood floor system which exposed to fire was carried out as preliminary research for reliability-based design on fire. Analyses were conducted by two methods, numerical analysis method and deterministic method.. They didn't show the difference between two methods. The reliability of floor exposed to fire showed strong dependence on the coefficient of variation of member and did not be influenced by the strength or load of member.

A Study on the Strength Properties of Mortar Under Various Types and Contents of Accelerators for Freezing Resistance (내한촉진제의 종류 및 혼입양 변화에 따른 모르터의 강도특성에 관한 연구)

  • Lee, Sang-Soo;Won, Cheol;Park, Sang-Joon;Kim, Dong-Seok
    • Journal of the Korea Institute of Building Construction
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    • v.2 no.2
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    • pp.151-156
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    • 2002
  • When fresh concrete is exposed to low temperature, the concrete may suffer frost damage due to freezing at early ages and strength development may be delayed. One of the solution methods for resolve these problems is to reduce freezing temperature of concrete by the use of chemical admixture called Accelerators for freezing resistance. In this study, we investigate the effect on strength development of cement mortar using accelerators for freezing resistance with the variance curing condition. As the result of this study, the mortar using accelerators for freezing resistance show that continuously strength development in curing condition of -5$^{\circ}C$. And compressive strength under the variance temperature condition was higher than constant temperature condition in same maturity.

The Effect on Strength Development of Cement Mortar using Accelerators for Freezing Resistance with the Curing Condition (양생조건이 내한촉진제를 사용한 시멘트 모르타르의 강도증진에 미치는 영향에 관한 연구)

  • Won, Cheol;Kim, Dong-Seok;Park, Sang-Joon;Lee, Sang-Soo;Kim, Young-Jin
    • Proceedings of the Korea Concrete Institute Conference
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    • 2001.11a
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    • pp.533-536
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    • 2001
  • When fresh concrete is exposed to low temperature, the concrete may suffer frost damage due to freezing at early ages and strength development may be delayed. One of the solution methods for resolving these problems is to reduce freezing temperature of concrete by the use of chemical admixture called Accelerators for freezing resistance. In this study, we investigate the effect on strength development of cement mortar using accelerators for freezing resistance with the variance curing condition. As the result of this study, the mortar using accelerators for freezing resistance show that continuously strength development in curing condition of -5$^{\circ}C$. And compressive strength under the variance temperature condition was higher than fixed temperature condition in same maturity.

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On-Site Conservation of the Underwater Objects Excavated (해저 발굴유물의 현장 보존처리)

  • Moon, Whan-Suk;Kim, Byung-Keun;Yang, Soon-Seok
    • 보존과학연구
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    • s.25
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    • pp.133-150
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    • 2004
  • Once the object has been excavated at underwater condition, it should be subjected to condition that may cause its deterioration. Therefore, it is important that the object immediately keeps stable environment. It means that the object was excavated at underwater and it exposed the deterioration condition, as soon as possible it was not dried on surface, especially metallic and organic material. Iron objects is particularly notorious for rapid disintegration that it kept wet or stored in a stable environment. Ceramics, glass and stone were handled carefully that it prevented physical damage by mishandling. Organic materials of wood, leather, rope, bone must not be allowed to dry out because the creaking, shrinking and warping are well known disintegration. Therefore objects is basis of keeping stable condition in on-site and then it will have to pass through a detailed conservation process in the laboratory.

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A Study on the Operational Environment of Signalling System (신호시스템 운용환경에 관한 연구)

  • 정의진;이종우;황종규
    • Proceedings of the KSR Conference
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    • 2000.05a
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    • pp.164-171
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    • 2000
  • To determine operational requirement, the environmental condition for an equipment must be investigated, and to certify equipment's normalized operation, appropriate test must be carried out under the considered environmental condition. The actual environmental conditions to which equipment is likely to be exposed are normally complex and will comprise a number of environmental factors and corresponding parameters, When defining the environmental conditions for a certain application it is, therefore, necessary to list the factors involved and select the appropriate severity. For the preparation to determine operational requirement, environmental condition of equipment is investigated. The environmental condition is structured in two separate such as requirements, guidance and test specifications. For the first step, environmental requirements are considered

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Effects of solar UV radiation on photosynthetic performance of the diatom Skeletonema costatum grown under nitrate limited condition

  • Li, Gang;Gao, Kunshan
    • ALGAE
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    • v.29 no.1
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    • pp.27-34
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    • 2014
  • Availability of nutrients is known to influence marine primary production; and it is of general interest to see how nutrient limitation mediates phytoplankton responses to solar ultraviolet radiation (UVR, 280-400 nm). The red tide diatom Skeletonema costatum was cultured under nitrate (N)-limited and N-replete conditions and exposed to different solar irradiation treatments with or without UV-A (315-400 nm) and UV-B (280-315 nm) radiation. Its photochemical quantum yield decreased by 13.6% in N-limited cells as compared to that in N-replete ones under photosynthetically active radiation (PAR)-alone treatment, and the presence of UV-A or UV-B decreased the yield further by 2.8 and 3.1%, respectively. The non-photochemical quenching (NPQ), when the cells were exposed to stressful light condition, was higher in N-limited than in N-replete grown cells by 180% under PAR alone, by 204% under PAR + UV-A and by 76% under PAR + UV-A + UV-B treatments. Our results indicate that the N limitation exacerbates the UVR effects on the S. costatum photosynthetic performance and stimulate its NPQ.

Stemness and Proliferation of Murine Skin-Derived Precursor Cells under Hypoxic Environment

  • Kim, Hyewon;Park, Sangkyu;Roh, Sangho
    • International Journal of Oral Biology
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    • v.41 no.2
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    • pp.69-74
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    • 2016
  • Skin-derived precursors (SKPs) have potential to differentiate to various cell types including osteoblasts, adipocytes and neurons. SKPs are a candidate for cell-based therapy since they are easily accessible and have multipotency. Most mammalian cells are exposed to a low oxygen environment with 1 to 5% $O_2$ concentration in vivo, while 21% $O_2$ concentration is common in in vitro culture. The difference between in vitro and in vivo $O_2$ concentration may affect to the behavior of cultured cells. In this report, we investigated the effect of hypoxic condition on stemness and proliferation of SKPs. The results indicated that SKPs exposed to hypoxic condition for 5 days showed no change in proliferation. In terms of mRNA expression, hypoxia maintained expression of stemness markers; whereas, oncogenes, such as Klf4 and c-Myc, were downregulated, and the expression of Nestin, related to cancer migration, was also downregulated. Thus, SKPs cultured in hypoxia may reduce the risk of cancer in SKP cell-based therapy.

Effect of Moisture Migration in Concrete with Hating Rate on Concrete Spalling (가열속도에 따른 콘크리트 내부의 수분이동이 폭렬발생에 미치는 영향)

  • Choe, Gyeong-Cheol;Kim, Gyu-Yong;Nam, Jeong-Soo;Kim, Hong-Seop;Yoon, Min-Ho;Hwang, Ui-Chul
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2017.05a
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    • pp.246-247
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    • 2017
  • In this study, it reviewed the effect of moisture migration in concrete with heating rate on concrete spalling. Concrete specimens with compressive strength 30MPa and 110MPa are used and its size is □100×100×h200mm. And, two kinds of heating rate are set such as IS0 834 and 1℃/min. As a result, in the concrete specimen exposed to ISO 834 standard heating condition, moisture could migrate through pore network and surface concrete pieces fall out by generating moisture clog near the surface in 110MPa concrete specimen. Meanwhile, In the case of concrete specimens exposed to 1℃/min. heating condition, it is appeared that moisture could not migrate because temperature is distributed uniformly. Therefore, surface spalling is not occurred with low heating rate. However, in the case of 110MPa concrete specimen is exploded even though it heated by low heating rate.

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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.