• Korean Journal of Food Science and Technology
• /
• v.31 no.1
• /
• pp.128-137
• /
• 1999

In this study, shiitake mushrooms were dried by hot air, vacuum and freeze drying methods and theire physical properties were compared. Since the pore size affects the amount of absorption, the characteristics of water sorption were investigated at various humidities and temperatures. Results showed that the freeze dried product had the greatest pore area and the highest absorption capacity. However, all the dried samples showed similar quality. The browning degrees were severely changed with increased relative humidities and temperatures. Among these drying methods, the freeze drying gave the greatest change in browning degree. The GAB monolayer moisture contents of the dried shiitake mushroom were $5.3{\sim}7.7%$. The prediction model was also provided using parameters such as relative humidity, temperature and pore area.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.1
• /
• pp.229-236
• /
• 2003

Ultrasonic propagation velocities of both the dilatational and shear waves through the weathered tuff soil sampled from the area tying between Ulanbator and Beijing were measured under temperature condition of near subzero by means of sing-around method. After comparing the results with obtained data on unfrozen water content, a linear relation between velocities and unfrozen water content was performed with high coefficient value. Experimental results of two kinds of rather uniform materials, namely, glass-beads and silica micro-beads, testified the similar linear relations. In addition, the change rate of dilatational wave velocities with the change of volumetric unfrozen water content was not dependent on soil type. Although a rational theory of the ultrasonic velocities dependence on the unfrozen water content is not yet proposed, the presented empirical relationships may suggest the appropriate evaluation to the effect of unfrozen water on dynamic characteristics of frozen soil.

• Solar Energy
• /
• v.19 no.2
• /
• pp.57-65
• /
• 1999

In this study $H_2O$-NaCl mixture was selected as a cold thermal storage material and its phase change temperature($liquid{\Leftrightarrow}solid$) was controlled with the molar concentration of NaCl. Ion dipole interaction mechanism and the fusion and crystallization structure of $H_2O$-NaCl were visualized with the low and high concentration of NaCl in the heating and cooling processes. In this study, the original cause of the appearance of two steps phase change period in heating and cooing processes were found by the visualization of the ion dipole interaction mechanism of $H_2O$-NaCl, and the theoretical equation of the phase change temperature variation in the NaCl high molar concentration was rearranged.

• The Journal of Engineering Geology
• /
• v.11 no.1
• /
• pp.13-23
• /
• 2001

Rock slope near the road or railroad is affected by the outside temperature and iterative freezing-thawing process during winter and early spring. The purpose of this study is to analyze the stability of rock slope which is iniluenced by deterioration due to the freezing-thawing. Method of analysis is homogenization method which find the strength property of discontinuous rock mass and as a strength failure criterion, Drucker-Prager failure criterion is used, The deterioration property of real rock is obtained by a freezing-thawing labordtory test of tuff and this quantitative property is used as a basic data of stability analysis of rock mass. To evaluate the deterioration depth due to the freezing-thawing in the field rock slope, one dimensional heat conductivity equation is used and as a a result we can find the depth of which is affected by a temperature. After determined the freezing-thawing depth of model slope, the pattern of rock mass strength value of model rock slope which excess the limit of self-load is analyzed.

• Journal of the Korean Geosynthetics Society
• /
• v.12 no.3
• /
• pp.75-79
• /
• 2013

The frost depth is one of important factors in the design of structures such as roadways, buried pipeline, and foundations. A frost indicator with methylene blue solution has several advantages with respect to installation cost, maintenance, and simple measurement. However, as a geotechnical engineering aspect, the accuracy of the frost indicator has not been proved yet. This paper presents experimental and field investigations of the accuracy of the frost indicator and contour maps of maximum frost depth. The contour maps of maximum frost depth can be applied to design geo-infrastructure in South Korea.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.13 no.6 s.58
• /
• pp.126-134
• /
• 2009

Generally, reinforced concrete structures exposed to the outside temperature are affected by freezing and thawing process during winter and early spring. These freeze-thawing process can lead to the reduction in durability of concrete as cracking or surface spalling. This paper is to study the flexural behavior of RC beams exposed to freeze-thawing environments. To compare the difference in flexural behavior of RC Beams, limited tests were conducted under different types of Longitudinal steel ratio and freeze-thawing cycles. For this purpose, fourteen small-scale RC beams ($100mm{\times} 100mm {\times}600mm$) were strengthened in monotonic and cyclic loadings, subjected to up to 150, 300 cycles freeze-thawing from $-18{\sim}4^{\circ}C$. It is thought that experimental results will be used as basic data to evaluate flexural behavior of RC beams exposed to freeze-thawing.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1996.04a
• /
• pp.48-51
• /
• 1996

Recently, frost damage of storage tank for admixture agent caused by low temperature in winter and quality deterioration of admixture agent ofen happened. But, many problems are caused because of no applicable regulations of admixture agent facility and so on. Therefore, this study presents the reference data about using and quality control of admixture agent in practice and the judgement data about working out a counter plan of suitable heat insulation of injecion equipment of admixture agent exposed at outside in winter by measuring the freezing point of admixture agent for concrete.

• Journal of the Korean Geotechnical Society
• /
• v.30 no.9
• /
• pp.57-66
• /
• 2014

The ground in cold region consists of active and permafrost layers. The active layer at the unstable state may cause ground corrosion and uplift, when the temperature of frozen ground increases due to seasonal changes. The thermosyphon is one of the stabilization methods to maintain the ground stability in the frozen ground. The thermosyphon is a closed two-phase convection device that extracts heat from the ground and discharges it into the atmosphere. In this study, ground freezing experiment using a thermosyphon and simulated ground with the isolation material was conducted to evaluate the thermal performance of the thermosyphon. In order to consider the thermal performance of the thermosyphon, commercial numerical program (TEMP/W) was adopted. Likewise, the thermal performance of thermosyphon and thermal properties of ground were applied in the numerical model. In a series of comparisons with experiment results and numerical study, thermal performance of thermosyphon can be evaluated.

• Journal of the Korea Institute of Building Construction
• /
• v.2 no.2
• /
• pp.151-156
• /
• 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.

• Journal of the Korean GEO-environmental Society
• /
• v.20 no.4
• /
• pp.17-21
• /
• 2019

In the cold region, the frozen damages in highway tunnels and regular road tunnels have widely been investigated and reported, but the measurement has not been sufficient made. The average temperature in cold region is below the zero, resulting in that the damage due to freezing at the entrance/exit of tunnel is more severe than in the middle of tunnel. In this study, a heating element was developed to prevent the tunnel lining from being frozen by enforcing to increase the temperature of tunnel lining. Then field tests using the developed heating element were performed and it was ensured that the temperature of tunnel lining increased after a certain time.