• Journal of Korean Society of Environmental Engineers
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• v.31 no.1
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• pp.21-28
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• 2009

Physico-chemical characteristics of the Ca-based and Na-based dry sorbents were compared using thermo-gravimetric analysis (TGA) and temperature programmed desorption (TPD) methods. The studied characteristics were thermal stability, sulfur dioxide ($SO_2$) absorption capacity and absorption rate at $250^{\circ}C$ which is a typical temperature before a fabric filter, and $SO_2$ absorption capacity at an ambient temperature. Calcium hydroxide ($Ca(OH)_2$) started to decompose into calcium oxide (CaO) at $390^{\circ}C$ and completed at 480~$500^{\circ}C$, showing 76% of an original $Ca(OH)_2$ weight. Sodium bicarbonate ($NaHCO_3$) also converted to sodium carbonate ($Na_2CO_3$) between $95^{\circ}C$ and $190^{\circ}C$, decreasing the weight to 63% of its initial weight. Among four sorbents tested at $250^{\circ}C$, sodium carbonate had the highest capacity, absorbing 0.35 g $SO_2$/g sorbent. Calcium oxide and calcium hydroxide followed that showing 0.156 g and 0.065 g $SO_2$ absorption per absorbent respectively. Ca-based absorbents showed slower rate than sodium carbonate because of initial stagnant step. However, calcium hydroxide caught more $SO_2$ than sodium carbonate at ambient temperature. From this work, it can be concluded that Ca-based absorbent is a proper sorbent for $SO_2$ treatment at low temperature and sodium carbonate, at high temperature.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.6
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• pp.422-429
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• 2013

It is generally known that the increase of the Earth surface temperature due to the global warming together with the land desertification by rapid urban development has caused severe climate and weather change. In desert or desertification land, it is observed that there are always severe flooding phenomena, even if desert sand has the high porosity, which could be believed as the favorable condition of rain water infiltration into ground water. The high runoff feature causes possibly another heavy rain by quick evaporation with the depletion of underground water due to the lack of infiltration. The basic physics of desert flooding is reasonably assumed due to the thermal buoyancy of the higher temperature of the soil temperature than that of the rain drop. Considering the importance of this topic associated with water resource management and climate disaster prevention, no systematic investigation has, however, been reported in literature. In this study, therefore, a laboratory scale experiment together with the effort of numerical calculation have been performed to evaluate quantitatively the basic hypothesis of run-off mechanism caused by the increase of soil temperature. To this end, first, of all, a series of experiment has been made repeatedly with the change of soil temperature with well-sorted coarse sand having porosity of 35% and particle diameter, 2.0 mm. In specific, in case 1, the ground surface temperature was kept at $15^{\circ}C$, while in case 2 that was high enough at $70^{\circ}C$. The temperature of $70^{\circ}C$ was tested as this try since the informal measured surface temperature of black sand in California's Coachella Valley up to at 191 deg. $^{\circ}F$ ($88^{\circ}C$). Based on the experimental study, it is observed that the amount of runoff at $70^{\circ}C$ was higher more than 5% compared to that at $15^{\circ}C$. Further, the relative amount of infiltration by the decrease of the surface temperature from 70 to $15^{\circ}C$ is about more than 30%. The result of numerical calculation performed was well agreed with the experimental data, that is, the increase of runoff in calculation as 4.6%. Doing this successfully, a basic but important research could be made in the near future for the more complex and advanced topic for this topic.

• Journal of Bio-Environment Control
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• v.32 no.1
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• pp.48-56
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• 2023

High-pressure sodium (HPS) lamps have been widely used as a useful supplemental light source to emit sufficient photosynthetically active radiation and provide a radiant heat, which contribute the heat requirement in greenhouses. The objective of this study to analyze the thermal characteristics of HPS lamp and thermal behavior in supplemented greenhouse, and evaluate the performance of a horizontal leaf temperature of sweet pepper plants using computational fluid dynamics (CFD) simulation. We simulated horizontal leaf temperature on upper canopy according to three growth stage scenarios, which represented 1.0, 1.6, and 2.2 plant height, respectively. We also measured vertical leaf and air temperature accompanied by heat generation of HPS lamps. There was large leaf to air temperature differential due to non-uniformity in temperature. In our numerical calculation, thermal energy of HPS lamps contributed of 50.1% the total heat requirement on Dec. 2022. The CFD model was validated by comparing measured and simulated data at the same operating condition. Mean absolute error and root mean square error were below 0.5, which means the CFD simulation values were highly accurate. Our result about vertical leaf and air temperature can be used in decision making for efficient thermal energy management and crop growth.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.6
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• pp.263-271
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• 2015

Commercial AR(Alkali Resistant)-glass fiber has a good chemical resistant property, but also has a problem of difficulty in fiberizing process because of high viscosity in melted glass compare with E-glass fiber which is the most widely used for reinforced fiber of composite materials. In this study, we fabricated AR-glass fiber with low zirconia contents compare with commercial AR-glass fiber relatively, and measured properties against E-glass fiber. We obtained transparent clear glass with zirconia contents of 0.5~16 wt% by melting at $1600^{\circ}C$ for 2 hours. These AR-glass samples had high visible transmittance of 89~90 %, softening temperature of $703{\sim}887^{\circ}C$. And softening temperatures of them were increased according to the increasing zirconia contents. Compare with E-glass, AR-glass contains 4 wt% zirconia has different value of $-94^{\circ}C$ in softening temperature, $+68^{\circ}C$ at Log3 temperature and $-13^{\circ}C$ at Log5 temperature in viscosity. We could verify good alkali resistant property of the AR-glass fiber with SEM after dipping in alkali solution for 48~72 hours, and also high tensile strength, 1.7 times compare with E-glass fiber at 48 hours and 2.2 times at 72 hours. We conclude that this AR-glass fiber can be widely used as general alkali resistant glass fiber because of easy manufacturing condition and good properties even though it has low zirconia contents.

• Korean Journal of Agricultural and Forest Meteorology
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• v.7 no.4
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• pp.274-281
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• 2005

The climate of the Uisong Area is wet in the heat of summer and cold and dry in winter, The climate is highly consistent. The typical forest soil of the Uisong Area has an acidity of pH 4.5-5.6. The thickness of soil A layers is thin to an average of 10-20 cm and is a typical brown forest soil type. The growth characteristic of this climate and soil environment is as follows. In the case of Larix leptolepis, it takes 5-9 years to reach 6 cm diameter, The annual growth rate falls off greatly at an age of 17-19 years. The change of annual rings is more apparent on the north slopes compared with the east and northeast slopes. Pinus rigida takes 7-9 years to reach a 6 cm diameter. Annual growth rates of Pinus rigida fall greatly when age reaches 19 years. The change of annual ring growth of Pinus rigida was most apparent in the west and northeast slopes compared with the south and east slopes. In the case of Pinus koraiensis, the change of the annual ring width according to the characteristics of the slope is not important. Pinus koraiensis takes 6 yearsto reach the 6cm diameter, and annual growth rate fell off at age 19 years. In the case of Quercus acutissima, the growth of the valley trees is more stable than for trees grown at the mountain base. Annual growth rate of Quercus autissima fell off 19 years after planting. Ring growth of Robinia pseudo-acasia on northeast slopes appears much like that on northwest slopes. In conclusion, the main silviculture species reaches a 6 cm diameter in 5-9 years of growth, and the annual growth rate begins to fall between years 13 and 19 in the Uisong Area.

• Korean Chemical Engineering Research
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• v.51 no.6
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• pp.766-773
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• 2013

A transparent film was fabricated based on bacterial cellulose (BC), BC has excellent physical strength and stability at high temperature and it is an environmental friendly flexible material. In order to improve the conductivity, silver nanowire (AgNW) and/or graphene were introduced to the BC membrane. The aspect ratio of the AgNW synthesized in this study was 214, with a length of $15{\mu}m$ and width of 70 nm. The higher aspect ratio improved the conductivity by reducing the contact resistance. The thermal and electrical properties of 7 types of films prepared were investigated. Each film was fabricated with rectangular shape ($2mm{\times}2mm{\times}50{\mu}m$). The films were scored with a net shape by a knife, and filled with AgNW and graphene to bestow conductivity. The film filled with AgNW showed favorable electrical characteristics with a thickness of $350{\mu}m$, electron concentration of $1.53{\times}10^{19}$, electron mobility of $6.63{\times}10^5$, and resistivity of 0.28. The film filled with graphene had a thickness of $360{\mu}m$, electron concentration of $7.74{\times}10^{17}$, electron mobility of 0.17, and resistivity of 4.78. The transmittances at 550 nm were 98.1% and 80.9%, respectively. All the films were able to light LEDs bulbs although their brightness differed. A thermal stability test of the BC and PET films at $150{\pm}5^{\circ}C$ showed that the BC film was more stable, whereas the PET film was quickly banded. From these results, it was confirmed that there it is possible to fabricate new transparent conductivity films based on BC.

• Journal of the Mineralogical Society of Korea
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• v.23 no.2
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• pp.117-124
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• 2010

The sorption of $AsO_4,\;SeO_3,\;CrO_4$ on schwertmannite and thermal analysis of sorbed samples were carried out. The results of sorption experiments showed that sorption characteristics of those three oxyanions on schwertmannite can be divided into two groups. The extent of sorption of $AsO_4$ and $SeO_3$ were 100% at up to 1 mM solution concentration, and they increased no more significantly. This can be interpreted as $AsO_4$ and $SeO_3$ substituting $SO_4$ in schwertmannite strucure by the ratio of 1 : 1. The extent of the sorption of $CrO_4$ was much lower than those of other two oxyanions. Thermal analysis was performed using two kinds of sorbed samples at 0.1 and 1.25 mM concentrations. The results of the thermal analysis showed that the samples sorbed by three different oxyanions have different thermal characteristics. The samples sorbed by $AsO_4$ showed smaller weight loss around $600^{\circ}C$ than the original loss of pure schwertmannite, and it is attributed to the substitution of $AsO_4$ for $SO_4$, which was caused by the loss of $SO_4$, than pure schwertmannite due to the substitution of $SO_4$ by $AsO_4$. It also showed additional weight loss around $600^{\circ}C$ due to the decomposition of $AsO_4$ at that temperature. The weight loss of samples sorbed by $SeO_3$ started at slightly lower temperature than that sorbed by $SO_4$ and kept that loss at wider temperature range, probably indicating that the decomposition of $SeO_3$ occurs at slightly lower temperature. However, for the samples sorbed by $CrO_4$, the weight loss caused by the decomposition of $SO_4$ was also smaller and there was no additional weight loss at higher temperature due to the thermal stability of $CrO_4$, indicating that $SO_4$ was also substituted by $CrO_4$ in schwertmannite. Sorption experiment and thermal analysis indicate that $CrO_4$ sorbs on schwertmannite by substiuting $SO_4$, but the affinity to $SO_4$ or instability of $CrO_4$ in scwertmannite structure probably prohibit perfect 1 : 1 substitution.

• Economic and Environmental Geology
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• v.34 no.5
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• pp.423-435
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• 2001

The gold-silver vein deposits in the Mugeug mineralized area are emplaced in late Cretaceous biotite granite associated with the pull-apart type Cretaceous Eumseong basin. Mugeug mine in northern part is composed of multiple veins showing relatively high gold fineness and is characterized by sericitization, chloritization and epidotization. The ore-forming fluids were evolved by dilution and cooling mechanisms at relatively high temperature and salinity (=30$0^{\circ}C$,1~9 equiv. wt. % NaCl) and highly-evolved meteoric water ($\delta$$^{18}$ O;-1.2~3.7$\textperthousand$) and gold mineralization associated with sulfides tormed at temperatures between 260 and 22$0^{\circ}C$ and within sulfur fugacity range of 10$^{-11.5}$ ~ 10$^{-13.5}$ atm. In contrast, Geumwang, Geumbong and Taegueg mines show the low fineness values, in southern part are characterized by increasing tendency of simple and/or stockwork veins and by kaolinitization, silicificatitan, carbonatization and smectitization. These droposits formed at relatively low temperature and salinity (<23$0^{\circ}C$, <3 equiv. wt. % NaCl) from ore-forming fluids containing greater amounts of less-evolved meteoric waters ($\delta$$^{18}$ O;-5.5~4.0$\textperthousand$), and silver mineralization representing various gold-and/or silver-bearing minerals formed at temperatures between 200 and 15$0^{\circ}C$ and from sulfur fugacity range of 10$^{-15}$ ~10$^{-18}$ atm These results imply that mineralization in the Mugueg area formed at shallow-crustal level and categorize these deposits as low-sulfidation epithermal type. The genetic differences between the northern and southern parts reflect the evolution of the hydrothermal system due to a different physicochemical environment from heat source area (Mugeug mine) to marginal area (Taegeum mine) in a geothermal field.

• Journal of the Korean Electrochemical Society
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• v.24 no.3
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• pp.52-64
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• 2021

The effect of Fe and BO₃ doping on structure, thermal, and electrical properties of Li_1+xFe_xTi_2-x(PO₄)_3-y(BO₃)_y (x = 0.2, 0.5)-based glass and glass ceramics was investigated. In addition, their crystallization behavior during sintering and ionic conductivity were also investigated in terms of sintering temperature. FT-IR and XPS results indicated that Fe²⁺ and Fe³⁺ ions in Li_1+xFe_xTi_2-x(PO₄)_3-y(BO₃)_y glass worked as a network modifier (FeO₆ octahedra) and also as a network former (FeO₄ tetrahedra). In the case of the glass with low substitution of BO₃, boron formed (PB)O₄ network structure, while boron preferred BO₃ triangles or B₃O₃ boroxol rings with increasing the BO₃ content owing to boic oxide anomaly, which can result in an increased non-bridging oxygen. The glass transition temperature (GTT) and crystallization temperature (CT) was lowered as the BO₃ substitution was increased, while Fe²⁺ lowered the GTT and raised the CT. The ionic conductivity of Li_1+xFe_xTi_2-x(PO₄)_3-y(BO₃)_y glass ceramics were 8.85×10^-4 and 1.38×10^-4S/cm for x = 0.2 and 0.5, respectively. The oxidation state of doped Fe and boric oxide anomaly were due to the enhanced lithium ion conductivity of glass ceramics.