• 한국도로학회:학술대회논문집
• /
• 2008.10a
• /
• pp.419-422
• /
• 2008

• Magazine of the Korea Concrete Institute
• /
• v.6 no.4
• /
• pp.102-112
• /
• 1994

The drying shrinkage of concrete has a close relation to the water movement. Since the diffusion process of water in concrete is strongly dependent on the temperature and the pore humidity, the process is highly nonlinear phenomena. This study consists of two parts. The first is the development of a finite element program which is capable of simulating the rnoisture distri- ,bution in concrete, and the other is the estimation of the differential drying shrinkage and stress considering creep by using the modified elastic modulus due to inner temperature change and maturity. It is shown that the analytical results of this study are in good agreement with experlimental data in the literatures, and results calculated by BP-KX model. The internal stress caused by moisture distribution which was resulted from the diffusion process, was calculated :quantitatively. The tensile stress which occured in the drying outer zone mostly exceeded the tensile strength of concrete, and necessarily would result in crack formation.

• Journal of the Korean Wood Science and Technology
• /
• v.23 no.4
• /
• pp.67-73
• /
• 1995

This study was undertaken to investigate the effect of heat treatment on the dynamic viscoelasticity of three species of Phyllostachys bambusoides, Phyllostachys nigra var. henonis and Phyllostachys pubescens, grown in southern Korea. The bamboo was treated for 3~24 hours at $60{\sim}180^{\circ}C$, and then was treated in a climatic chamber for 3~48 hours at $40^{\circ}C$ and 95% relative humidity. The results obtained are summarized as follows : 1. Dynamic Young's modulus decreased with increasing temperature and duration of the heat treatment. 2. Internal friction decreased with increasing treatment duration. 3. Moisture absorption decreased with increasing temperature and duration of the heat treatment. 4. Dynamic viscoelasticity decreased, whereas internal friction slowly increased, with increasing moisture content.

• Journal of the Korean Society of Tobacco Science
• /
• v.14 no.1
• /
• pp.57-65
• /
• 1992

The quality of cut tobacco will be deteriorated due to weather conditions such as temperature and relative humidity, when shipping and long term storaging. The change of equilibrium moisture contents in cut tobacco were under influence of relative humidity and temperature but not humectants. Therefore internal packing materials are necessary for cut tobacco to maintain initial quality, including taste, flavour and musty smell during shipping or storaging. When packing cut tobacco for shipping or long term storaging, desiralbe packing density was 200/$m^2$, For the long term storage under R.H 90% and 3$0^{\circ}C$, polyethylene film thickness suitable for packing material are above 100$\mu$, which resulted in 42days of shelf life.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2020.06a
• /
• pp.31-32
• /
• 2020

Concrete changes its internal moisture distribution depending on the external environment, and changes in the condition of the material's interior over time affect the performance of the concrete. These effects are closely related to the long-term behavior and durability of concrete, and the degree of deterioration varies from climate to climate in each region. In this study, we use actual climate data from each region with distinct climates. A multi-physical analysis based on the method was conducted to predict the difference and degree of deterioration rate by climate.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.36 no.3
• /
• pp.142-149
• /
• 2013

Among ammunitions which are stored in a war field, the lifespan of propelling gunpowder is affected by storage environment such as storage temperature, humidity, and exposure to sunlight. These are because Nitrocellulose (NC) which is the main component of propelling gunpowder can be naturally disassembled to unstable substances similar with other nitric acid ester. We can't prevent it fundamentally from being disassembled, but to restrain induction of automatic disassembly by decomposition product, a decomposition product ($NO_2$, $NO_3$, and $HNO_3$) and tranquillizer DPA (Diphenylamine), having high reactivity, are added into a propellant. For this, it will decrease the velocity of tranquillizer which can also affect the velocity of producing the decomposition product of NC, storage temperature or humidity of propelling gunpowder is higher, drop of tranquillizer content is much faster. Therefore, to extend storage lifespan of propelling gunpowder, it is really important to control storage temperature or humidity inside the magazine. Hereupon, according to the manufacture of small scale model magazine and the result of performing experiments and measuring variation of inside temperature (storage temperature), using roof types that have a steel slate structure of magazine among ground magazines, this research shows the differences in details.

• Journal of Preventive Medicine and Public Health
• /
• v.39 no.2
• /
• pp.171-176
• /
• 2006

Objectives : The objective of this study is to assess the factors influencing biological monitoring of textile coating factory workers exposed to N,N-dimethylformamide(DMF). Methods : We studied 35 workers who were occupationally exposed to DMF from 9 textile coating factories. The study was carried out in two phases; summer and winter. While air concentration of DMF, temperature and humidity were assessed in order to monitor the atmospheric conditions, biological monitoring was done to determine the internal dose by analyzing the N-methylformamide(NMF) collected from urine at the beginning and end of the shift. Questionnaires and medical surveillance were also obtained during the two phases. Results : Median air concentrations of DMF in winter and summer were 1.85 ppm and 2.78 ppm respectively. Also the difference between the urinary NMF concentration at the beginning and end of the shift $({\Delta}NMF)$ was always significant in each season (P < 0.001). The correlations between log DMF in air, log end-of-shift urinary NMF (r=0.555, P < 0.001) and log ${\Delta}NMF$ (r = 0.444, P < 0.001) was statistically significant in summer. The temperature, humidity, a shift system and different styles of clothing worn were significantly different during the two phases. In a multivariate analysis, temperature and the concentration of DMF in the air were the main factors influencing biological monitoring of textile coating factory workers. Conclusions : Concerning more comprehensive prevention measures to reduce exposure for those workers occupationally exposed to DMF, dermal exposure conditions such as temperature and humidity together with the air concentration of DMF should be assessed and biological monitoring is necessary to reduce adverse health effects, especially during the summer.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.9 no.2
• /
• pp.1-9
• /
• 2009

Water binder ratio combine high-performance concrete shrinkage of less than 0.4 to determine the transformation to a total shrinkage of water to move outside and internal consumption of moisture due to drying shrinkage and autogenous shrinkage, and then, the relative humidity changes and strain to be approached by surface physics describe the relationship between self-desiccation and autogenous shrinkage was set. To verify the self-desiccation in the humidity shrinkage and humidity measurements performed, and the research model, Tazawa, CEB-FIP model than to let the measure and the most similar results in this study based on self-desiccation model, autogenous shrinkage didn't represent the linear shrinkage by the drying shrinkage of the external moving but exponential relationships, unlike with the nature and rapid in the early age properly describes the attributes in shrinkage could see. After this research to move moisture and to reflect the shrinkage model, temperature, moisture transfer, strain analysis by multi-physics model is very similar to the results of mock-up specimen measurements performed for this research, the value measured by the internal consumption of moisture, therefore self-desiccation and a multi-physics model considering autogenous shrinkage might be relevant.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.11a
• /
• pp.264-265
• /
• 2008

While the reliability of bulk insulation has become important particularly in multilayer boards and embedded boards, electronics are to be used under various environments such as at high temperature and in high humidity. We observed internal space charge behavior for two types of epoxy composites under dc electric fields to investigate the influence of water at high temperature. In the case of glass/epoxy specimen, homocharge is observed at water-treated specimen, and spatial oscillations become clearer in the water-treated specimens. Electric field in the vicinity of the electrodes shows the injection of homocharge. In aramid/epoxy specimens, heterocharge is observed at water-treated specimens, i.e. negative charge accumulates near the anode, while positive charge accumulates near the cathode. Electric field is enhanced just before each electrode. In order to further examine the mechanism of space charge formation, we have developed a new system that allows in situ space charge observation during ion migration tests at high temperature and high humidity. Using this in situ system.

• Journal of the Korean Electrochemical Society
• /
• v.6 no.3
• /
• pp.212-216
• /
• 2003

The humidification measurement system designed in laboratory was used to measure relative humidity and temperature of reaction gases passing through internal or external humidifier which was used in proton exchange membrane fuel cell test station. The relative humidity of gases was stabilized after $10\~20$ minutes and thus credibility of data could be assured. The effect of relative humidity on fuel cell performance could be analyzed by humidity measurement system. Extreme caution was needed to avoid humidity sensor mal-function or failure which is probable in experiment of high humidity condition near $100\%$. The amount of water carried by gas through humidifier was increased along the flow rate of gas. However, the extent of increase was lowered at high gas flow rate. These phenomena could be analyzed as residence time effect of gas in humidifier.