• Journal of the Korean Wood Science and Technology
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• v.10 no.1
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• pp.5-37
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• 1982

Plywood used for construction as a decorative inner material is inflammable to bring large fire accidents and burn out human life and their properties. To diminish the fire disaster, fire retardant plywood has been required indeed. In the methods of manufacturing the fire retardant plywood the soaking method is occasionally used. However after soaking plywood into fire retardant chemical solutions, redrying of soaked plywood is the most important. In this study, 3.5mm thin and 5.0mm thick plywoods were selected for fire retardant treatment. Treating solutions were prepared for 20% dilute solutions of ammonium sulfate, monoammonium phosphate, diammonium phosphate, borax-boric acid and minalith, and water solution. 1-, 3-, 6-, and 9 hour-soaking treatments were applied and after treatments hot plate drying was applied to those treated plywoods at $90^{\circ}C$, $120^{\circ}C$ and $150^{\circ}C$, of press temperature. Drying rates, drying curves, water absorption rates of fire retardant chemicals, weight per volume and fire retardant degree of plywood were investigated. The results may be summarized as follows: 1. The plywoods treated with ammonium sulfate, monoammonium phosphate and diammonium phosphate and diammonium phosphate showed increase of chemical absorption rate with proportion to increase of treating time, but not in case of the plywood treated with borax-boric acid and minalith. 2. In the treatment of definite time, the absorption rate per unit of volume of plywood showed higher in thin plywood (thickness of 3.5mm) than in thick plywood (thickness of 5.0mm). In both thin and thick plywoods, the highest absorption rate was observed in 9 hour-treatment of ammonium sulfate. The value was 1.353kg/$(30cm)^3$ in thin plywood and 1.356kg/$(30cm)^3$ in thick plywood. 3. The volume per weight of plywood after chemical treatment increased remarkably and. after hot plate drying, the values were to a little extent higher than before chemical treatment. 4. The swelling rates of thickness in chemical-treated plywoods increased similarly with that of water-treated plywood in 1- and 3 hour-treatment of both thin and thick plywoods. But in 6- and 9 hour-treatment, the greater increased value showed in water-treated ply wood than any other chemical, especially in thick plywood. 5. The shrinkage rates after hot plate drying showed the same tendency as the swelling rate, and the rate showed the increasing tendency with proportion to increase of treating time in thick plywood of both chemical and water treatments. 6. Among drying curves, the curves of water-treated plywood placed more highly than chemical-treated plywood without-relation to thickness in 6- and 9 hour-treatment except in 1- and 3 hour-treatment. 7. The drying rate related to thickness of treated plywood, was twice above in thin plywood compared with thick plywood. 8. The drying rate remarkably increased with proportion to increase of the plate temperature and, the values were respectively 1.226%/min., 6.540%/min., 25.752%/min. in hot plate temperature of $90^{\circ}C$, $120^{\circ}C$, $150^{\circ}C$ in thin plywood and 0.550%/min., 2.490%/min, 8.187%/min, in hot plate temperature of $90^{\circ}C$, $120^{\circ}C$, $150^{\circ}C$ in thick plywood. 9. In the treatment at $120^{\circ}C$ of hot plate temperature, the drying rates of chemical-treated plywood showed the highest value in monoammonium phosphate of thin plywood and in diammonium phosphate of thick plywood. But the drying rate of water-treated plywood was highest in 6- and 9 hour-treatment. 10. The fire retardant degree of chemical-treated plywood was higher than that of the untreated plywood as shown in loss of weight, burning time, flame-exhausted time and carbonized area. 11. The fire-retardant effect among fire retardant chemicals were the greatest in diammonium phosphate, the next were in monoammonium phosphate and ammonium sulfate, and the weakest were in borax-boric and minalith.

• Journal of the Korean GEO-environmental Society
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• v.13 no.1
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• pp.31-36
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• 2012

Recently, industrial by-products are exponentially growing because energy consumption is increasing due to rapid industrial development and improved living standards. The purpose of this study is to determine the proper mixing ratio to meet the liner conditions(must be less than $1{\times}10^{-7}$cm/sec), using pond ash and bentonite as liner. As the result of the compaction test, depending on the increase mixing ratio of bentonite, the maximum dry unit weight was decreased but the optimum moisture content was tended to be increased at the compaction curve. As the result of the permeability test, depending on the increase mixing ratio of bentonite, the coefficient of permeability showed tendency to be decreased in the form of index and the tendency was caused by the hydration reactions filling the void of the pond ash. When the mixing ratio of bentonite was approximately over 15%, it was satisfied with the land fill liner conditions. In other words, it is necessary to consider other mixtures containing the cement or another material in the economical aspect for application of the pond ash.

• Journal of the Korean GEO-environmental Society
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• v.2 no.3
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• pp.47-56
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• 2001

In the present study, mainly to determine the embarkation time of equipment in dredged clay fills, an analytical approach is performed to predict a variation of the undrained shear strength in the outermost layer. In this approach, Gibson's non-dimensional linear constant defining the relationship between the void ratio and the effective stress is employed. Also in this approach, void ratios and settlements associated with the volume change due to the self-consolidation and the desiccation shrinkage are evaluated at various elapsed times based on the finite difference solution technique proposed by the authors(1999) and the developed computer program named as DSCON. Predicted results(water content ratio, unit weight and undrained shear strength) are compared with those of laboratory model tests conducted with soil samples obtained from the Koheung site. Based on the predicted undrained shear strengths, possible embarkation time of a equipment is also evaluated. In addition, further analyses are made to indirectly verify the efficiency of the analytical approach proposed in the present study using the PSDDF computer program which can consider the drainage efficiency.

• Journal of the Korean Society of Food Science and Nutrition
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• v.25 no.4
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• pp.551-559
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• 1996

To examine the effects of dietary fibers on gastrointestinal physiology, rats were fed with diets containing 10% sodium alginate,10% cellulose, or fiber-free diets for 5 weeks. The results obtained were as follows: The chronic consumption of sodium alginate induced a significant decrease in body weight gain and feeding efficiency, but a significant increase in length and weight of small intestine. Fecal bulk and weight were higher in fiber-fed group than fiber-free group. The chronic consumption of dietary fiber induced a significant increase in fecal output, resulting in tile decrease of apparent digestibility of protein and lipid. Pancreatic protease activity was lower in fiber-fed group than fiber-free group, whereas pancreatic amylase and lipase activities were not affected. Scanning electron microscopy(SEM) and light microscopy(LM) studies showed small intestine microvilli with numerous ridges and convolutions and goblet cells in fiber-fed groups. As a result of this study, it is concluded that the chronic consumption of dietary fiber decreases apparent digestibility of nutrients and induces morphological and biochemical adaptation of digestive organs.

• The Korean Journal of Zoology
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• v.29 no.3
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• pp.201-207
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• 1986

The authors attempted to investigate the oxygen consumption rate of sexuals in the water-striders, Gerris paludum insuralis, at four temperature groups of 25, 30, 35 and $40^\\circ C$ in a series of studies on respiration of a heminetabolous insects. THe results are summarised as follows: (1) At $30^\\circ C$, the change of oxygen consumption rate according to the lapse of time was small in comparison with the other three temperature groups which shows a cyclic decreasing pattern. The rate during initial and final 5 minutes was much alike. Thereupon, the optimum temperature was regarded as $30^\\circ C$. (2) The oxygen consumption rate of male was higher than that of female. (3) The oxygen consumption rates at 25, 30, 35 and $40^\\circ C$ were 0.42, 0.49, 0.79 and 1.11 $\\mu$l/mg/h respectively. That is, the rate was increased as the temperature was increased. (4) The $Q_10$ of male showed a high value in the lower temperature interval ($25^\\circ C \\sim 35^\\circ C$), but the female showed a high value in the higher temperature interval ($30^\\circ C \\sim 40^\\circ C$). The mean $Q_10$ was 2.12. (5) The respiratory rate was decreased as the body weight was increased in the above fresh weight of 10mg and dry weight 5 mg. (6) The upper temperature threshold for respiration was $48.31^\\circ C$ and the lower temperature threshold was $17.68^\\circ C$. (7) The ceasing time of breathing at the other three temperature groups except $30^\\circ C$ was infered to be about 110 minutes after the start of experiment.

• Journal of the Korea Organic Resources Recycling Association
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• v.23 no.4
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• pp.86-94
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• 2015

Torrefaction is a thermochemical process proceeded at the temperature around $250^{\circ}C$ in an inert gas condition. By torrefaction, the hemicellulose portions contained in biomass are broken down to change into the volatile gas which is removed from biomass eventually. The main purpose of biomass torrefaction is to improve the energy density of the biomass to minimize the transport energy consumption, though the flammability can be elevated for transportation. In this study two types of solid biomass fuel, waste wood and rice straw, were torrefied at various temperature range from $200^{\circ}C$ to $300^{\circ}C$ to evaluate the torrefied biomass characteristics. In addition torrefied biomass were tested to evaluate the combustion characteristics using TGA (Thermogravimetric Analysis). After the torrefaction of biomass, the C/H (carbon to hydrogen ratio) and C/O (carbon to oxygen ratio) were measured for aquisition of bio-stability as well as combustion pattern. Generally C/H ratio implies the soot formation during combustion, and the C/O ratio for bio-stability. By torrefaction temperature at $300^{\circ}C$, C/H ratio and C/O ratio were increased by two times for C/H and three times for C/O. The torrefied biomass showed similar TGA pattern to coal compared to pure biomass; that is, less mass decrease at lower temperature range for torrefied biomass than the pure biomass.

• Geotechnical Engineering
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• v.14 no.5
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• pp.39-52
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• 1998

The pupose of the present paper is to estimate the effects of constraint condition of pile head, ground condition(dry unit weight. $\gamma_4$) and embedded pile lengths on the behavior of single pile which is embedded in normally consolidated clay. BBperiment functions can be quantified to these effects obtained from the results of model teats. The ground of model tests is normally consolidated( NC ) clay under three kinds of effective vertical stress. The results of the model tests using the steel pile of two different embedded pile length and of free-head and fired-head show that the lateral load-deflection relationship is to be elasto plastic behavior below $\gamma_d/\gamma_{dmax}$: 0.84 and that the reduction of lateral load of beyond maximum lateral load($Q_{max}$) at each model test is significantly time-dependent. In this study, it is shown that the displacement relationship can be fitted to exponential function of time by model best results. The effect of ground conditions on the ultimate and yield lateral load is fitted to exponential function including the ratio of dry unit weight to maximum dry unit weight. When tests by results are compared with those from Broms and Budhu et at., the predicted results are over-estimated about 27-87 ayo. In effectivity of constraint condition of pile head on the lateral load-deflection response, the $Q_{fixed}/Q_{gree}-y/D$ relationship is highly non-linear and fitted to parabolic function.

• Tunnel and Underground Space
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• v.19 no.5
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• pp.373-387
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• 2009

Considering the current construction technology and research status of deep repository tunnels for radioactive waste disposal, it is inevitable to use cementitious materials in spite of serious concern about their long-term environmental stability. Thus, it is an emerging task to develop low pH cementitious materials. This study reviews the state of the technology on low pH cements developed in Sweden, Switzerland, France, and Japan as well as in Finland which is constructing a real deep repository site for high-level radioactive waste disposal. Considering the physical and chemical stability of bentonite which acts as a buffer material, a low pH cement limits to $pH{\leq}11$ and pozzolan-type admixtures are used to lower the pH of cement. To attain this pH requirement, silica fume, which is one of the most promising admixtures, should occupy at least 40 wt% of total dry materials in cement and the Ca/Si ratio should be maintained below 0.8 in cement. Additionally, selective super-plasticizer needs to be used because a high amount of water is demanded from the use of a large amount of silica fume.

• Korean Journal of Agricultural and Forest Meteorology
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• v.20 no.2
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• pp.228-232
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• 2018

Process-based crop models have been used to assess the impact of climate change on crop production. These models are implemented in procedural or object oriented computer programming languages including FORTRAN, C++, Delphi, Java, which have a stiff learning curve. The requirement for a high level of computer programming is one of barriers for efforts to develop and improve crop models based on biophysical process. In this study, we attempted to develop a Chinese cabbage model using Microsoft Excel with Visual Basic for Application (VBA), which would be easy enough for most agricultural scientists to develop a simple model for crop growth simulation. Results from Soil-Plant-Atmosphere-Research (SPAR) experiments under six temperature conditions were used to determine parameters of the Chinese cabbage model. During a plant growing season in SPAR chambers, numbers of leaves, leaf areas, growth rate of plants were measured six times. Leaf photosynthesis was also measured using LI-6400 Potable Photosynthesis System. Farquhar, von Caemmerer, and Berry (FvCB) model was used to simulate a leaf-level photosynthesis process. A sun/shade model was used to scale up to canopy-level photosynthesis. An Excel add-in, which is a small VBA program to assist crop modeling, was used to implement a Chinese cabbage model under the environment of Excel organizing all of equations into a single set of crop model. The model was able to simulate hourly changes in photosynthesis, growth rate, and other physiological variables using meteorological input data. Estimates and measurements of dry weight obtained from six SPAR chambers were linearly related ($R^2=0.985$). This result indicated that the Excel/VBA can be widely used for many crop scientists to develop crop models.

• The Journal of Engineering Geology
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• v.17 no.3
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• pp.425-434
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• 2007

In this paper, the stability standards of slopes reclaimed by soils mixed with stone dust were proposed to manage the stone dust as recovery soils. First of all, the mixed ratio between stone dust and natural soil is classified into 5 groups, and a series of soil test was performed in each group. As the results of tests, the shear strength and the maximum dry unit weight were increased in decrease of the mixed ratio of stone dust. On the basis of the investigation to the safety factor standards of embankment slopes in and outside the country, a slope stability rank of slopes reclaimed by mixed soils were divided into 3 stages such as unstable stage, attention stage and stable stage. The slope angle, the slope height and the mixed ratio with stone dust were proposed by the result of stability analysis of slopes reclaimed by mixed soils. As the result of slope stability analysis, the slope angle of 1 : 1.8 at the reclaimed slope should be constructed in case of the slope height of 10 m. Also, the slope angle of 1 : 1.8 and the mixed ratio of stone dust less than 50% should be constructed in case of the slope height of 15 m. The analysis result of reclaimed slope constructed inside the quarry is similar to that of reclaimed slope constructed on the open ground in same conditions of the slope angle, the slope height and the mixed ratio with stone dust. The proposed stability standards of slopes reclaimed by soils mixed with stone dust can be used practically at the quarrying site.