• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.1
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• pp.39-55
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• 2022

This study carried out the laboratory tests for AE signal attenuation to determine the attenuation coefficient (α) of silo concrete in Gyeongju low and intermediate-level disposal environments. The concrete samples were prepared by satisfying the concrete mixing ratio used in the Gyeongju disposal silo, and these samples were additionally exposed depending on the temperature conditions and saturation and, dry condition. As a result of attenuation tests according to the transmission distance on three concrete specimens for each disposal condition, the AE amplitude and absolute energy measured on the saturated concrete were higher than that of the dry concrete in the initial range of the signal transmission distance, but the α of the saturated concrete was higher than that of the dry concrete. Regardless of the saturation and dry conditions, the α tended to decrease as the temperature increases. The α had a more major influence on the saturation and dry condition than the temperature condition, which means that the saturation and dry condition is the main consideration in measuring the signal attenuation of a concrete disposal structure. The α of concrete in the disposal environment expect to be used to predict the integrity of silos concrete in Gyeongju low and intermediate-level disposal environments by estimating the actual AE parameter values at the location of cracks and to determine the optimum location of sensors.

• 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.

• Journal of the Korean Wood Science and Technology
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• v.48 no.4
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• pp.472-487
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• 2020

With the emergence of abnormal climate due to the rapid industrialization, the importance of water quality management and management costs are increasing every year. In Korea, for the management of total phosphorus and total nitrogen, the major materials causing the water quality pollution, coagulants are injected in sewage treatment plants to process organic compounds. However, if the coagulant is injected in an excessive amount to PAC (Poly Aluminium Chloride), a secondary pollution problem might occur. As such, a study on the applicability of natural material-based coagulant is being conducted in Korea. Thus, this study aimed to evaluate the applicability of a mixed coagulant developed by analyzing water quality pollutants T-P, T-N as well as their turbidity, in order to derive the optimum mixing ratio between PAC and torrefied wood flour for the primary settling pond effluent. Under the condition where the content of PAC (10%) and torrefied wood flour is 1%, T-P showed the maximum removal efficiency of 92%, and T-N showed approximately 22%. This indicates that removal of T-N which includes numerous positively charged organic compounds that are equivalent to mixed coagulant is not well accomplished. Turbidity showed the removal efficiency of approximately 91%. As such, 1% of torrefied wood flour was determined to be the optimum addition. As a result of analyzing the removal efficiency for organic compounds by reducing PAC concentration to 7%, T-P showed a high maximum removal efficiency of 91%, T-N showed 32%, and turbidity showed the maximum of 90%. In addition, a coagulation process is performed by using the mixed coagulant based on 1% content of torrefied wood flour produced in this study by performing a coagulation performance comparative experiment with PAC (10%). As a result, PAC concentration was reduced to 30-50%, a similar performance with other coagulants in market was secured, PAC injection amount was reduced that an economic effect can be achieved, and it is considered to perform a stable water treatment that reduces the secondary pollution problem.

• The Korean Journal of Mycology
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• v.41 no.1
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• pp.21-27
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• 2013

This study was carried out to investigated optimum mixing ratio of Korean natural Acer tegmentosum for production of functional oyster mushroom. Total nitrogen and carbon sources of Acer tegmentosum were 0.2% and 44.4%, respectively and C/N ratio was 234. Total nitrogen source and pH of substrate mixed with Acer tegmentosum were 2.7~2.9 and 4.8~5.0, respectively. The contents of $P_2O_5$, $K_2O$ and MgO at Acer tegmentosum media were higher than that of the control. Mycerial growth was the fastest at Acer tegmentosum 10%, and slower by increase of Acer tegmentosum substrate. Yields of fruiting body was the highest to 159 g/850 mL at 10% of Acer tegmentosum and dimeter and thick of pileus were the highest, too. The L value of pileus and stipes were decreased by increase of Acer tegmentosum substrate, but there was no significant difference in the a-value and the b-value. The contents of $P_2O_5$ and $K_2O$ of fruiting body were increased at Acer tegmentosum substrate, but there was no significant difference in contents of CaO, MgO and $Na_2O$.

• Journal of Mushroom
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• v.11 no.4
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• pp.219-225
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• 2013

This study was carried out to investigated optimum mixing ratio of Korean natural Juglans mandshurica using as functional plants. Total nitrogen and carbon source of J. mandshurica was 0.21% and 46.0%, respectively and C/N ratio was 219. Total nitrogen source and pH of substrate mixed with J. mandshurica was 2.3~2.9 and 5.0, respectively. The contents of CaO, MgO and $Na_2O$ at J. mandshurica media were higher at harvest media than inoculation media. Mycelial growth was the fastest at J. mandshurica 20%, and slower by increase of J. mandshurica substrate. Yields of fruiting body show the highest to 163 g/850 mL of medium which are addition 10% of J. mandshurica sawdust, and diameter and thick of pileus were the highest, too. The L value of pileus and stipes were increased by increase of J. mandshurica substrate, but there was no significant difference in the a-value and the b-value. The contents of $P_2O_5$ and $K_2O$ of fruiting body were increased at J. mandshurica substrate, but there was no significant difference in contents of CaO, MgO and $Na_2O$. The contents of Cu of fruiting body was decreased by increase of J. mandshurica substrate, but Fe, Mn and Zn were increased.

• Journal of Radiation Protection and Research
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• v.22 no.1
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• pp.35-46
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• 1997

A simple and precise method of $^{14}C$ was developed to analyze $^{14}C$ in the environment samples using a commercially available $^{14}CO_2$ absorbent and a liquid scintillation counter. An air sampler and a combustion system were developed to collect HTO and $^{14}CO_2$ in the air and the biological samples simultaneously. The collection yield of $^{14}CO_2$ by the air sampler was in the range of 73-89% . The yield of the combustion system was 97%. In preparing samples for counting, the optimum ratio of $CO_2$ absorbent to the scintillator for mixing was 1:1. No variation of the specific activity of $^{14}C$ in the counting sample was observed up to 70 days after preparation of the samples. The detection limit for$^{14}C$ was 0.025 Bq/gC, which is the level applicable to the natural level of $^{14}C$. The analytical result of $^{14}C$ obtained by the present method were within ${\pm}6%$ of the relative error from the one by the benzene synthesis. The specific activity of $^{14}C$ in the air collected at Taejon during the period of October 1996 ranged from 0.26 to 0.27 Bq/gC. The specific activity of $^{14}C$ in the air collected at 1km from the Wolsong nuclear power plant a 679 MWe PHWR, was $0.54{\pm}0.03$ Bq/gC. The ranges of specific activities of $^{14}C$ in the pine needles and the vegetations from the areas around the Wolsong nuclear power plant were 0.56-0.67 Bq/gC and 0.23-1.41 Bq/gC, respectively.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.4
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• pp.286-294
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• 2014

The purpose of this study is to investigate the effects of applying density current generator (hereafter referred to as DCG to large lakes on the operating conditions of DCG, de-stratification, water quality improvement and inhibition of algae occurrence. As a result of a survey conducted to derive the optimum operating parameters of DCG in a condition to minimize eco-toxicity, the following conclusions were obtained. During the survey period, a marked stratification appeared in September to October 2011 and May 2012. At this time, the average depth of water to form thermocline was found to be $5{\pm}2$ m, so the location of discharge port for the operation of DCG was determined to be about 5 m below from the surface. To minimize the adverse effects of benthos and obtain the effect of water mixture at the time of water circulation, the mixing ratio of surface water and deep water was designed to be 3:1 by means of ecotoxicological assessment on the DCG operating characteristics. To select the appropriate operating hours for DCG, DCG was operated by 12 hr, 24 hr, 36 hr and 48 hr. As its result, the formation of thermocline did not occur during the operation of 36 hr. Also, It was effected that start reoperating from 3rd day after stop 2days under the condition of operated during 36 hr with calculated power consumption. Under the above conditions, the results of DO and water temperature analysis during the operation of DCG showed that the stratification, which was distinct previously, appeared to be weak, and relatively lower levels than those before operation were found as a result of water quality analysis on COD and chlorophyll-a, which leads to the conclusion that the water body is maintained at a stable condition due to the circulation of water by the occurrence of density current resulting from the operation of DCG.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.6
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• pp.718-724
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• 1999

This study was investigated the changes of the properties of matter such as the gel formation of the combined fish based on the mixed rate between the ocean jumbo squid and Alaska pollock surimi, and compared the relationships between the gel formation and water holding capacity. The changes of the gel formation based on 20 min fish grinding time and $2.5\%$ salt concentration according to the mixed rate was thought as the optimal addition limit. There was no significant function of gel product more than $20\%$ Jumbo squid meat. The more squid meat in the mixed meat could make the lower breaking stress but 7:3 rate of pollock : squid could retain breaking strain. The effect of the moisture content on mixed fish meat was studied and the drastic decrease of the gel formation and water holding capacity was indicated in $78\%$.

• The Korean Journal of Mycology
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• v.4 no.1
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• pp.31-44
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• 1976

The studies were carried out to examine the effects of supplementation of nutritional substances and physical conditions in substrate on the mycelial growth and yield of fresh sporophores of winter mushroom, Flammulina velutipes(Curt. ex Fr.) Sing. and to obtain further informations on the nutritional requirements of the fungus with reference to improvement of substrate through [analysis of chemical composition of the substrates during the cultivation period. The results obtained are summarized as follows: 1. The best yield of fresh sporophores, 84.4 g per 280 g substrate in a bottle, was obtained from the mixture of poplar sawdust 10 and rice bran 3 by volume when Flammulina velutipes was cultivated on the poplar sawdust supplemented by rice bran, wheat bran, cattle manure and various combinations of these materials as nutrient sources. The substrates of poplar sawdust 10 plus rice bran 3 and 2 or wheat bran 3 with a higher yield of fresh sporophores showed a comparatively higher content of total nitrogen. total sugar, and potassium. 2. The mycelial growth of the fungus was compared on the substrates of poplar sawdust supplemented by the several nutrient sources and poplar sawdust alone. The fastest linear growth occurred on substrates of poplar sawdust alone and poplar sawdust plus cattle manure deficient in sugar and nitrogen sources, but mycelial density was more sparse on the substrates. Also, growth in a solution extracted from these substrates was very meager. 3. In the substrates which varied with bulk density and moisture content optimum bulk density and moisture content for mycelial growth was 0.2g/cc and 72% on a dry weight basis, respectively, but the highest yield of fresh sporophores was obtained at the bulk density of 0.3g/cc and moisture content of 67%. 4. By increasing the ratio of rice bran in poplar sawdust the loss of total weight and ash, content at each stage was increased, and during the cultivation period of 75 days, loss of total weight of the substrates at inoculation was 17.8 to 28.8% and ash content increased about 12%. 5. 11 to 14% of the cellulose and 3 to 4% of the lignin content per original substrate were decreased without a great difference depending of the mixing ratio of rice bran. The soluble glucose concentration in the substrates was increased during the same period. 6. In the process of vegetative and reproductive growth of the fungus upon the substrates, the total nitrogen was increased in quantity per dry weight of sample but was reduced in absolute quantity to a minute extent. There is no great changes in content of organic nitrogen including amino acid nitrogen, and hydrolysable ammonium nitrogen during the vegetative growth period, but occurrence of sporophores resulted in a decrease in the nitrogen content of these forms. On the one hand, by an increase of additive amounts of rice bran, nitrogen contents of these forms were higher and the reduction range during the reproductive growth period became wider. 7. Mycelial growth of the fungus was accelerated in various liquid media supplemented with organic nitrogen sources such as peptone and yeast extract in comparison with addition of inorganic nitrogen sources. Furthermore, mycelial growth was mere vigorous in the media with higher content of organic nitrogen sources.