• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.7
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• pp.19-26
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• 2018

This study tested 25 lightweight aggregate concrete (LWAC) mixtures using the expanded bottom ash and dredged soil granules to examine the compressive strength gain of such concrete with different ages. The test parameters investigated were water-to-cement ratios and the natural sand content for the replacement of lightweight fine aggregate. The compressive strength gain rate in the basic equation specified in fib model code was experimentally determined in each mixture and then empirically formulated as a function of the water-to-cement ratio and oven-dried density of concrete. When compared with 28-day compressive strength, the tested LWAC mixtures exhibited relatively low gain ratios (0.49~0.82) at an age of 3 days whereas the gain ratios (1.16~1.41) at 91 days were higher than that (1.05~1.15) of the conventional normal-weight concrete. Thus, the fib model equations tend to overestimate the early strength gain of LWAC but underestimate the long-term strength gain. The proposed equations are in good agreement with the measured compressive strength development of LWAC at different ages, indicating that the mean and standard deviation of the normalized root mean square errors determined in each mixture are 0.101 and 0.053, respectively.

• Nuclear Engineering and Technology
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• v.54 no.2
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• pp.442-448
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• 2022

Intermediate-level radioactive waste (ILW) is not subject to legal approval for cave disposal in Korea. To solve this problem, a spent resin treatment device that separates ¹⁴C-containing resin from zeolite/activated carbon and desorbs ¹⁴C through a microwave device has been developed. In this study, we evaluated the radiological safety of the operators performing repair work in the event of a failure in such a device treating 1 ton of spent resin mixture per day. Based on the safety evaluation results, it is possible to formulate a design plan that can ensure the safety of workers while developing a commercialized device. When each component of the resin treatment device can be repaired from the outside, the maximum and minimum allowable repair times are calculated as 263.2 h and 27.7 h for the ¹⁴C-detached resin storage tank and zeolite/activated carbon storage tank, respectively. For at least 6 h per quarter, the worker's annual dose limit remains within 50 mSv/year; further, over 5 years, it remained within 100 mSv. At least 6 h of repair time per quarter is considered, under conservative conditions, to verify the radiological safety of the worker during repair work within that time.

• Nuclear Engineering and Technology
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• v.26 no.4
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• pp.562-569
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• 1994

In this study improvement of transient analysis model, KOTRAC, for the passive reactor has been performed. In the KOTRAC, mixture drift flux model is adopted to simulate thermal hydraulic behavior, which can simulate ECCS injection in the passive plant. However, there is a difficulty to handle complete phase separation phenomena due to the near-zero density, which may occur in the pressurizer surge line or horizontal flow paths. In this study, a couple of model changes to over-come Courant limit feilure has been examined. One of key features is to substitute flow distribution parameters with Ishii's correlation. Corrected results are nil compared to those of RELAP/MOD3 analysis.

• Korean Journal of Plant Tissue Culture
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• v.25 no.2
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• pp.81-88
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• 1998

The Southeast Asian javanica rice variety Tinawen was investigated for efficient protoplast culture and plant regeneration from cell suspension-derived protoplasts using a feeder cell culture method. Feeder cells of both Lolium multiflorum and Oryza ridleyi, either alone, or in combination, were employed and plants were regenerated from protoplast-derived colonies on several plant regeneration media. Dehydration of protoplast-derived colonies was also investigated as a means of enhancing plant regeneration. In the presence of L. multiflorum or O. ridleyi feeder cells, the protoplast plating efficiency ranged from 0.09% to 1.48%, depending on the feeder cell type and the age of the cell suspension. L. multiflorum feeder cells induced approximately 6-fold higher plating efficiency compared with those of O. ridleyi. The plant regeneration frequencies were 19.3-31.7% with L. multiflorum, 13.0-18.0% with O. ridleyi and 18.0-22.0% with a mixture of both in various plant regeneration media when protoplast-derived colonies were dehydrated, while for the non-dehydrated colonies, the values were 2.0-7.0%, 3.0-5.0% and 0-4.0%, respectively. Flow cytometric analysis of 34 protoplast-derived plants showed that the majority of plants were diploids and only 2 plants were tetraploids. The plants which were transferred to glasshouse were fertile.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.3
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• pp.180-187
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• 2014

The purpose of this study is to evaluate on the mechanical properties of High Volume Mineral Admixture(HVMA) high strength concrete to reduce the amount use of Ordinary Potland Cement, to discover the optimized HVMA binder and to test HVMA concrete based on the change of W/B and curing temperature. The results were shown as follows: The HVMA binder using the mixture of combined heat power plant fly ash and anhydrous gypsum known as inorganic activators with the mixture of blast furnace slag and fly ash was optimized. The mixture of HVMA high strength concrete at 26% of W/B ratio had a good result on flow characteristic and mechanical properties. High strength HVMA concrete over 50MPa is possibly manufactured over curing temperature $20^{\circ}C$.

• International Journal of Highway Engineering
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• v.14 no.4
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• pp.9-18
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• 2012

PURPOSES : This study evaluated the field applicability and laboratory performance of warm-mix asphalt (WMA) as an alternative technology in asphalt pavement. METHODS : The pilot road using two different types of WMA mixture and one HMA mixture was constructed in Waegwan-Seokjeok road construction site and the mixtures were sampled at the asphalt plant for laboratory testings. The field applicability was assessed in environmental aspects, such as $CO_2$ emission, and in aspects of constructibility using the existing equipment and procedure, i.e., thickness and density measurement. The laboratory testings included the moisture susceptibility test by AASHTO T283, dynamic modulus test, triaxial repeated load permanent deformation test, and the fatigue test. RESULTS : The temperatures for production and compaction of WMA were $20{\sim}30^{\circ}C$ lower than those for HMA and therefore, the noxious gas emission were significantly reduced. The field density of WMA pavements was similar or better than that of HMA pavement. From the laboratory testings, it was found that WMA mixtures exhibit comparable performance to HMA mixture in moisture susceptibility, permanent deformation, and fatigue performance. CONCLUSIONS : With these results, it would be concluded that WMA could replace the existing HMA technology without any significant issue. To support this conclusion, it is necessary to track the long-term performance of WMA in pilot road.

• The Korea Journal of Herbology
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• v.21 no.2
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• pp.9-13
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• 2006

Objectives : To determine the DNA sequence of the 18S rRNA gene of the Rehmannia glutinosa and analyze it phylogenetically Methods : Dried root of the Rehmannia glutinosa was ground with a mortar and pestle. Glass beads(0.5 mm in diameter), TE buffer and SDS solution were added to that. The mixture was vortexed vigorously and extracted with the mixture of phenol, chloroform and isoamyl alcohol and with the mixture of the chloroform and isoamyl alcohol. The nucleic acids were precipitated with ethanol and resuspended in TE buffer. Contaminating RNA was digested with RNAse A and the DNA was purified further with the Geneclean Turbo Kit. This DNA was used as a template for amplification of the 18S rRNA gene by PCR. The PCR product was cloned in the pBluescript SK II plasmid by blunt-end ligation and the DNA sequence of the insert was determined. This DNA sequence was analyzed phylogenetically by the BLAST program. Results and Conclusion : Vortexing the ground powder of the dried plant root with glass beads during cell lysis improved recovery of DNA. The DNA sequence of the Rehmannia glutinosa 18S rRNA gene was determined and deposited at the GenBank as the accession number DQ469606. Phylogenetic analysis of that sequence showed the relationship between the members of the family of Scrophulariaceae and also the close relationship of the Buddleja davidii to the members of the Scrophulariaceae family.

• Korean Journal of Agricultural Science
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• v.3 no.1
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• pp.53-60
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• 1976

The purpose of this study was to evaluate the value of briquet ash as a component of rooting media in Chrysanthemum morifolium. Various rooting media were made in mixture at different ratio and alone using sand, vermiculite and briquet ash as components of soil mixture. In order to investigate the effect of the particle size of briquet ash on rooting of stemouttings, various particle sizes were used as rooting media. Rooting ratio, number of root and root length were examined to evaluate the effect of the various rooting media and the particle sizes of briquet ash. The important conclusions of this study are summerized as follows; 1. Briquet ash was better rooting medium than sand, but it showed more effective result when it was used in mixture with other rooting media. 2. The particle size of briquet ash as a rooting medium to produce a healthy vegetatively propagated plant showed the best result at 2-3mm.

• Korean Journal of Soil Science and Fertilizer
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• v.50 no.5
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• pp.401-408
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• 2017

Organic amendments such as animal waste compost, lime-bordeaux mixture, and lime sulphur mixture contain heavy metal(loid)s which are toxic to human being, animal, and plant. The objective of this study was to compare heavy metal(loid)s contamination of soil between conventional and organic farm. Soil samples were collected from 10 conventional and 38 organic fruit farms. At each sampling point, top (0~15 cm) and sub soil (15~30 cm) were taken using hand auger. Total concentration for arsenic (As), cadmium (Cd), copper (Cu), nikel (Ni), lead (Pb), and zinc (Zn) in the collected soil were measured. The pollution index (PI) for heavy metal in organic farms indicated it was unpolluted area. However, mean value of PI for organic farms (0.143) was higher than that for conventional farms (0.122). High Geoaccumulation index (Igeo) for Cu, Pb, and Zn implied that grape farms were more polluted than others fruit farms because a lot of lime-bordeaux mixture and lime sulphur were applied in organic grape farms. Especially, top soils showed higher level of contamination than sub soil. Based on the above results, organic amendments might cause accumulation of heavy metals in soil. Therefore, particular attention should be paid for concentration of Cu, Pb, and Zn, when organic amendments are used in the organic fruit farms.

• Korean Journal of Soil Science and Fertilizer
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• v.48 no.1
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• pp.44-49
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• 2015

Urea has been the most useful N-source, due to lower cost per unit of N. But nitrogen use efficiency of urea may be reduced because of losses from agricultural system by volatilization of ammonia to atmosphere. This study was conducted to evaluate the nitrogen efficiency and growth of hot pepper (Capsicum annuum L.) by mixed treatment with nitrogen and zeolite. They were treated with N $161kg\;ha^{-1}$, N $230kg\;ha^{-1}$, nitrogenzeolite mixture (NZM) $161kg\;ha^{-1}$, NZM $230kg\;ha^{-1}$ and N $0kg\;ha^{-1}$, respectively. In the soil chemical properties after experiment, soil pH decreased but available $P_2O_5$, EC and total nitrogen increased in nitrogen-zeolite mixture treatment. $NO_3-N$ content in the soil showed the highest level in NZM $230kg\;ha^{-1}$. NZM $161kg\;ha^{-1}$ treatment increased growth and yield of hot pepper compared to urea alone. Nitrogen utilization efficiency of hot pepper plant was 47.15% at the treatment of NZM $161kg\;ha^{-1}$, while 36.74% at N $230kg\;ha^{-1}$. These results showed that application of mixture of nitrogen and zeolite had positive influence to improve the efficiency of nitrogen utilization and increase of red pepper yield.