• Korean Journal of Ecology and Environment
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• v.36 no.1 s.102
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• pp.83-94
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• 2003

Concentrated releases of zinc into water usually results from discharges associated with industrial purpose. The released zinc into soil is corroded and released into water. In aquatic environment, exess zinc is toxic to the organisms and causes the growth inhibition and malformation of them as a heavy metal. In this study, excess zinc toxicity was tested by FETAX (frog embryo teratogenetic assay with Xenopus)as in vivo system. Xenopus embryos at st.9 were exposed to $100{\sim}900\;{\mu}M$ of zinc for 7 days and 81% of individuals were survived in 100 ${\mu}M$, and 25% were survived in 1000M of zinc solution. In external malformations, swelled belly and intestinal dysplasia were common, and all of tested individuals showed these malformations in 200 ${\mu}M$ or higher concentration of zinc. In 400 ${\mu}M$ or higher concentration, all of tested tadpoles showed faded heart. Also, hypo-pigmentation, lens hernia and loose digestive track were very frequently found in 100 ${\mu}M$ of zinc. The histological study with paraffin section of zinc treated tadpoles showed following abnormalities; regeneration of photoreceptor on retina, reduced vitreous chamber in eye, reduction of red blood cells in heart, abnormal liver, swelling of pronephric cell, muscle dysplasia and palatal papilloma. These abnormalities may be caused by the degeneration of mitochondria, inhibition of cell adhesion, and the formation of leghemoglobin by zinc due to the substitution of $Ca^{2+}$ by $Zn^{2+}$. The body length was reduced due to the excess zinc. From a statistical result, body lengths of 300 ${\mu}M$ or higher concentrative g개ups was significantly reduced comparing that of control group. Recently, many spontaneous malformations and reduction of amphibians are reported, From the results of present study, excess zinc mi호t be a factor of amphibian reduction, and the control of zinc discharges is very important.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.9
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• pp.636-642
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• 2013

In order to overcome drawbacks (i.e., filtration and recovery) of conventional powder type photocatalysts, nano-ZnO/Laponite/PVA (ZLP) photocatalyzed adsorption balls were developed by using in situ mixing of nanoscale ZnO as a photocatalyst, and Laponite as both adsorbent and supporting media in deionized water, followed by the poly vinyl alcohol polymerization with boric acid. The optimum mixing ratio of nano-ZnO:Laponite:PVA:deionized water was found to be 3:1:1:16 (by weight), and the mesh and film produced by PVA polymerization with boric acid might inhibit both swelling of Laponite and detachment of nanoscale ZnO from ZLP balls. Drying ZLP balls with microwave (600 watt) was found to produce ZLP balls with stable structure in water, and various sizes (55~500 ${\mu}m$) of pore were found to be distributed based on SEM and TEM results. In the initial period of reaction (i. e., 40 min), adsorption through ionic interaction between methylene blue and Laponite was the main removal mechanism. After the saturation of methylene blue to available adsorption sites for Laponite, the photocatalytic degradation of methylene blue occurred. The effective removal of methylene blue was attributed to adsorption and photocatalytic degradation. Based on the results from this study, synthesized ZLP photocatalyzed adsorption balls were expected to remove recalcitrant organic compounds effectively through both adsorption and photocatalytic degradation, and the risks of environmental receptors caused by detachment of nanoscale photocatalysts can be reduced.

• Korean Journal of Food Science and Technology
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• v.50 no.2
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• pp.191-197
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• 2018

This study investigated the influence of starch extraction (ST-EX) solutions on the extraction yield and characteristics of Chinese yam (CY) starches from domestic Dioscorea batatas. Ascorbic acid (VitC), $Na_2S_2O_3$, $NaHCO_3$, and $Na_2CO_3$ were used as ST-EX solutions (0.4%, w/v). The extracted CY starches were examined for ST-EX yield, chemical composition, size distribution, X-ray diffraction, solubility, swelling power, gelatinization, and pasting viscosity. The highest ST-EX yield was obtained from $NaHCO_3$, followed by VitC. Lower protein content, relative crystallinity, and gelatinization enthalpy were found in CY starches from alkaline ST-EX solutions ($NaHCO_3$ and $Na_2CO_3$). Size distribution and gelatinization temperature did not generally differ for CY starches from the different ST-EX solutions. Pasting viscosities increased in the order from $Na_2CO_3$ > $Na_2S_2O_3$ > $NaHCO_3$ > VitC ST-EX solutions. Thus, VitC may be most appropriate to extract CY starch from Dioscorea rhizomes, considering its ST-EX yield, total starch content, and variation in pasting viscosity.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.17 no.2
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• pp.183-202
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• 2019

For design and performance assessment of a high-level radioactive waste (HLW) disposal system, it is necessary to understand the characteristics of coupled thermo-hydro-mechanical (THM) behavior. However, in previous studies for the Korean Reference HLW Disposal System (KRS), thermal analysis was performed to determine the spacing of disposal tunnels and interval of disposition holes without consideration of the coupled THM behavior. Therefore, in this study, TOUGH2-MP/FLAC3D is used to conduct THM modeling for performance assessment of the Korean Reference HLW Disposal System (KRS). The peak temperature remains below the temperature limit of $100^{\circ}C$ for the whole period. A rapid rise of temperature caused by decay heat occurs in the early years, and then temperature begins to decrease as decay heat from the waste decreases. The peak temperature at the bentonite buffer is around $96.2^{\circ}C$ after about 3 years, and peak temperature at the rockmass is $68.2^{\circ}C$ after about 17 years. Saturation of the bentonite block near the canister decreases in the early stage, because water evaporation occurs owing to temperature increase. Then, saturation of the bentonite buffer and backfill increases because of water intake from the rockmass, and bentonite buffer and backfill are fully saturated after about 266 years. The stress is calculated to investigate the effect of thermal stress and swelling pressure on the mechanical behavior of the rockmass. The calculated stress is compared to a spalling criterion and the Mohr-Coulumb criterion for investigation of potential failure. The stress at the rockmass remains below the spalling strength and Mohr-Coulumb criterion for the whole period. The methodology of using the TOUGH2-MP/FLAC3D simulator can be applied to predict the long-term behavior of the KRS under various conditions; these methods will be useful for the design and performance assessment of alternative concepts such as multi-layer and multi-canister concepts for geological spent fuel repositories.

• Korean Journal of Food Science and Technology
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• v.53 no.4
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• pp.486-494
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• 2021

A rice (Oryza sativa L.) cultivar of the SPP (stakeholder participatory program) and ordinary rice were characterized based on water-absorption properties and cooked rice texture. During rice soaking, the rice grain transformed from transparent to opaque (white), indicating that water molecules diffused into the rice grain during soaking. In addition, cracks in the internal structure of soaked rice gradually increased with an increase in soaking time. Water absorption increased rapidly up to 20 min, but no increment was observed after 30 min of soaking. At this point, the entire areas of the soaked rice grain turned white, indicating that water absorption had reached saturation. SPP rice showed lower hardness and higher stickiness in its cooked form than ordinary rice, suggesting that SPP rice could be a more preferable choice than ordinary rice. Furthermore, cooked SPP rice was more edible in terms of hardness and stickiness after being kept warm for 12 h than ordinary rice. These results indicated that cooked SPP rice exhibited slow retrogradation and improved taste.

• Tunnel and Underground Space
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• v.32 no.6
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• pp.491-501
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• 2022

Bentonite has been proposed as a buffer and backfill material for high-level radioactive waste repository. Under such repository environment conditions, bentonite is subjected to combined thermal, hydrological, mechanical, and chemical processes. This study evaluates the feasibility of applying X-ray CT technology on the characterization of bentonite under hydration conditions using a newly developed testing cell. The cylindrical cell is made of platic material, with a removable cap to place the sample, enabling to apply vertical pressure on the sample and to measure swelling pressure. The hydration test was carried out with a sample made of Gyeonju bentonite, with a dry density of 1.4 g/cm³, and a water content of 20%. The sample had a diameter of 27.5 mm and a height of 34 mm. During the test, water was injected at a constant pressure of 0.207 MPa, and lasted for 7 days. After one day of hydration, bentonite swelled and filled out the space inside the cell. Moreover, CT histograms showed how the hydration process induced an initial increase and later progressive decrease on the density of the sample. Detailed profiles of the mean CT value, CT standard deviation, and CT gradient provided more details on the hydration process of the sample and showed how the bottom and top regions exhibited a decrease on density while the middle region showed an increase, especially during the first two days of hydration. Later, the differences in CT values with respect to the initial state decreased, and were small at the end of testing. The formation and later reduction of cracks was also characterized through CT scanning.

• Journal of the Korean Geotechnical Society
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• v.26 no.12
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• pp.19-30
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• 2010

Bentonite-based grout has been widely used to seal a borehole constructed for a closed-loop vertical ground heat exchanger in a geothermal heat pump system (GHP) because of its high swelling potential and low hydraulic conductivity. Three types of bentonites were compared one another in terms of viscosity and thermal conductivity in this paper. The viscosity and thermal conductivity of the grouts with bentonite contents of 5%, 10%, 15%, 20% and 25% by weight were examined to take into account a variable water content of bentonite grout depending on field conditions. To evaluate the effect of salinity (i.e., concentration of NaCl : 0.1M, 0.25M, and 0.5M) on swelling potential of the bentonite-based grouts, a series of volume reduction tests were performed. In addition, if the viscosity of bentonite-water mixture is relatively low, particle segregation can occur. To examine the segregation phenomenon, the degree of segregation has been evaluated for the bentonite grouts especially in case of relatively low viscosity. From the experimental results, it is found that (1) the viscosity of the bentonite mixture increased with time and/or with increasing the mixing ratio. However, the thermal conductivity of the bentonite mixture did not increase with time but increased with increasing the mixing ratio; (2) If bentonite grout has a relatively high swelling index, the volume reduction ratio in the saline condition will be low; (3) The additive, such as a silica sand, can settle down on the bottom of the borehole if the bentonite has a very low viscosity. Consequently, the thermal conductivity of the upper portion of the ground heat exchanger will be much smaller than that of the lower portion.

• Food Engineering Progress
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• v.23 no.1
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• pp.7-15
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• 2019

The impregnation of solid foods into the surrounding hypotonic or hypertonic solution was explored as a method to infuse NaCl in pork loin cube without altering its matrix. Mass transfer kinetics using a diffusive model as the mathematical model for moisture gain/loss and salt gain and the resulting textural properties were studied for the surrounding solutions of NaCl 2.5, 5.0, 10.0 and 15% (w/w). It was possible to access the effects of brine concentration on the direction of the resulting water flow, quantify water and salt transfer, and confirm tenderization effect by salt infusion. For brine concentrations up to 10% it was verified that meat samples gained water, while for processes with 15% concentration, pork loin cubes lost water. The effective diffusion coefficients of salt ranged from 2.43×10^-9 to 3.53×10^-9 m²/s, while for the values of water ranged from 1.22×10^-9 to 1.88×10^-9 m²/s. The diffusive model was able to represent well salt gain rates using a single parameter, i.e. an effective diffusion coefficient of salt through the meat. However, it was not possible to find a characteristic effective diffusion coefficient for water transfer. Within the range of experimental conditions studied, salt-impregnated samples by 5% (w/w) brine were shown with minimum hardness, chewiness and shear force.

• Korean journal of food and cookery science
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• v.26 no.5
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• pp.636-648
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• 2010

Two types of wild grape extracts(WGE) prepared by different methods were added into butter-top bread at different concentrations(0, 5, 10, 15, 20% of water). Then, the resulting breads were analyzed for their physicochemical and sensory properties in order to identify whether or not the WGE-enriched breads were comparable to control bread in terms of qualities and preferences. Wild grape sugar mixture(WGS), which was prepared by osmotic dehydration of wild grape fruits with the same amounts of sugar, presented significantly lower moisture content and titratable acidity as well as higher pH and sugar content compared to wild grape juice(WGJ), which was produced by boiling the fruits in a vacuum jar and squeezing. The pH of the doughs and breads containing WGE tended to decrease with increasing amounts of WGE, and this phenomenon was more appreciable in those containing WGJ than WGS. This was presumably due to the higher contents of tartaric acid in WGJ. For both types of extracts, hardness, gumminess, and chewiness of the doughs decreased with the addition of WGE, nevertheless, which properties were not remained in the resulting breads. This could be partially attributed to the relatively high degree of baking loss and lower pH of the WGE-enriched breads than those of control bread. Contrary to the mechanical analyses, the sensory properties of the breads were dependent on the WGE type. That is, WGJ-enriched bread showed lower consistency and moistness than control bread, which consequently led to relatively lower overall acceptability. However, WGS addition did not adversely affect the sensory properties of the bread. In particular, addition of 5% WGS somewhat improved the physical and sensory qualities of the bread. Thus, WGE-enriched bread could be produced without loss of bread quality when prepared with 5% WGS.