• Journal of the Korea Concrete Institute
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• v.24 no.4
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• pp.481-490
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• 2012

Evaluation of chloride penetration is very important, because induced chloride ion causes corrosion in embedded steel. Diffusion coefficient obtained from rapid chloride penetration test is currently used, however this method cannot provide a correct prediction of chloride content since it shows only ion migration velocity in electrical field. Apparent diffusion coefficient of chloride ion based on simple Fick's Law can provide a total chloride penetration magnitude to engineers. This study proposes an analysis technique to predict chloride penetration using apparent diffusion coefficient of chloride ion from neural network (NN) algorithm and time-dependent diffusion phenomena. For this work, thirty mix proportions with the related diffusion coefficients are studied. The components of mix proportions such as w/b ratio, unit content of cement, slag, fly ash, silica fume, and fine/coarse aggregate are selected as neurons, then learning for apparent diffusion coefficient is trained. Considering time-dependent diffusion coefficient based on Fick's Law, the technique for chloride penetration analysis is proposed. The applicability of the technique is verified through test results from short, long term submerged test, and field investigations. The proposed technique can be improved through NN learning-training based on the acquisition of various mix proportions and the related diffusion coefficients of chloride ion.

• The Korean Journal of Mycology
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• v.41 no.4
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• pp.236-242
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• 2013

It is known not only that antifungal compounds such as sparassol, methyl orsellinate (ScI) and methyl-dihydroxy-methoxy-methylbenzoate (ScII) were produced during submerged culture from Sparassis crispa, but also that ScI and ScII were appeared higher antifungal activity than sparassol. The aim of this study, antifungal compounds of Sparassis latifolia were purified from mycelial culture media and identified by using NMR and ESI-MS. Based on HPLC analysis, methyl orsellinate and sparassol were detected at 15 min and 31 min of retention time, respectively. The compounds derived from S. latifolia were classified into four production patterns according to their strains. The strains originated from host plant Larix kaempferi and Pinus koraiensis showed different patterns of compound production, whereas the strains originated from host plant P. densiflora and Abies holophylla showed almost same patterns. There was no correlation between mycelial biomass and compound production. KFRI 645 strain from L. kaempferi exhibited higher methyl orsellinate production (0.170 mg/ml). Sparassol was produced by KFRI 747 from P. densiflora (0.004 mg/ml). Thus, our result revealed the new fact that methyl orsellinate and sparassol have different patterns according to the strains originated from different host plants.

• Korean Journal of Soil Science and Fertilizer
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• v.17 no.4
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• pp.399-405
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• 1984

The results of these experiments which were carried out to investigate the effects of rice straw for nitrogen metabolism and acetylene reducing activity, during rice plants were cultured under the percolated condition, are as follows. Azotobacter had tendency to increase with the passage of time, but decreased when rice straw was added. Population change of Clostridia was little as rice grew. Blue green algae increased until heading stage but decreased after the stage. And the application of rice straw increased the number of microorganisms. Thiorhodaceae were never detected, but yeast tended to increase slightly with passing time. Acetylene reducing activity was increased with increasing the number of nitrogen fixing microorganisms, and nitrogen fixing activity was between 0.2kg N/10 a and 0.4kg N/10 a during the growing season of rice plants. Though acetylene reducing activity was promoted by the use of rice plants on non-plant area, but the activity was not clearly affected by percolation.

• Proceedings of the KSRS Conference
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• v.1
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• pp.34-37
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• 2006

When tsunami waves propagate across open ocean they are steered by Coriolis force and refraction due to gentle gradients in the bathymetry on scales longer than the wavelength. When the wave encounters steep gradients at the edges of continental shelves and at the coast, the wave becomes non-linear and conservation of momentum produces squirts of surface current at the head of submerged canyons and in coastal bays. HF coastal ocean radar is well-conditioned to observe the current bursts at the edge of the continental shelf and give a warning of 40 minutes to 2 hours when the shelf is 50-200km wide. The period of tsunami waves is invariant over changes in bathymetry and is in the range 2-30 minutes. Wavelengths for tsunamis (in 500-3000 m depth) are in the range 8.5 to over 200 km and on a shelf where the depth is about 50 m (as in the Great Barrier Reef) the wavelengths are in the range 2.5 - 30 km. It is shown that the phased array HF ocean surface radar being deployed in the Great Barrier Reef (GBR) and operating in a routine way for mapping surface currents, can resolve surface current squirts from tsunamis in the wave period range 20-30 minutes and in the wavelength range greater than about 6 km. There is a trade-off between resolution of surface current speed and time resolution. If the radar is actively managed with automatic intervention during a tsunami alert period (triggered from the global seismic network) then it is estimated that the time resolution of the GBR radar may be reduced to about 2 minutes, which corresponds to a capability to detect tsunamis at the shelf edge in the period range 5-30 minutes. It is estimated that the lower limit of squirt velocity detection at the shelf edge would correspond to a tsunami with water elevation of less than 5 cm in the open ocean. This means that the GBR HF radar is well-conditioned for use as a monitor of small and medium scale tsunamis, and has the potential to contribute to the understanding of tsunami genesis research.

• Journal of Korea Water Resources Association
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• v.43 no.7
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• pp.657-666
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• 2010

The adjustment processes of mining pits in the disturbed channels by sand or gravel mining were investigated by laboratory experiments in this study. The pit migrated with speed when the river bed was steep. The pit migrated slow and steady when the pit was filling with sand, but the pit migrated with speed after the filling processes was finished. The submerged angle of repose in the pit was nearly constant during the pit was filling. The pit was filled with sand with speed as the channel slope was increased. It took time for the pit to be filled with sand as the pit dimension was increased. This meant that the disturbed channels by sand or gravel mining to adjust the new environment was dependent on the slope of the channels and the dimension of the pits. The dimensionless pit length was short and the dimensionless pit depth was shallow as the time was increased. The dimensionless pit depth was shallow, but the dimensionless pit migration speed was increased as the dimensionless shear velocity and the migration speed of the pit were increased. The dimensionless pit depth was increased with the dimensionless bar migration speed. The shape of the pit was deformed and migrated downstream in accordance with the location and shape of the biased bar front which was developed upstream.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.38 no.5
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• pp.398-404
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• 1993

This study was conducted in order to obtain the information for yield improvement in saline paddy. Saline concentration, growth and yield of rice, being subjected to different flooding times and days to transplanting were investigated in saline paddy with 0.35 % and 0.5 % salt concentration. Saline concentration of soil was increased to 0.41 % just after rotary in the paddy with 0.35 % salinity, but decreased to 0.20 % after 3 to 4 times of flooding treatment. And also that of surface water was decreased from 0.2 % to 0.11 %. Saline concentration of soil in 5cm depth was decreased to 0.31 % by one time flooding and to 0.22% by 3～4 times flooding but salinity below 7cm depth showed slight decrease. Seedling death was exceeded 37 % when transplanted one day after rotary in the paddy with 0.35% salinity. Death ratio was decreased to 20% by three times flooding and transplanting six days after rotary. In paddy with 0.5 % salinity, death ratio was high but the tendency was very similar to 0.35 % field. In 0.35 % saline paddy field, yields were increased by 14 % by three times flooding and transplanting six days after rotary as compared to one time flooding and transplanting are day after rotary. Therefore, 3 to 4 times flooding and transplanting 5 to 6 days after rotary are desirable in high saline paddy.

• Applied Chemistry for Engineering
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• v.17 no.5
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• pp.521-526
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• 2006

A membrane bioreactor (MBR) is an effective tool for wastewater treatment with recycling. MBR process has several advantages over conventional activated sludge process (ASP); reliability, compactness, and quality of treated water. The resulting high-quality and disinfected effluents suggest that MBR process can be suitable for the reused and recycling of wastewater. An anoxic/oxic (A/O) type MBR was applied to simultaneous removal of organics and nutrients in sewage. At first, the efficiency of submerged MBR process was investigated using a hollow fiber microfiltration membrane with a constant flux of $10.2L/m^2{\cdot}h$ at each solids retention time (SRT). Results showed that protein/carbohydrate (P/C) ratio increased and total extracellular polymeric substances (EPS) remained constant with SRT increased. Secondly, A/O type MBR with a reverse osmosis (RO) membrane was employed to treat the municipal wastewater. The performance of A/O type MBR-RO process is better for the treatment of organics and nutrients than ASP-MF-RO process in terms of consistent effluents quality.

• International Journal of Highway Engineering
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• v.4 no.4 s.14
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• pp.13-21
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• 2002

This study examines the importance of conditioning temperature and period before measuring fundamental properties of asphalt mixture. Marshall specimens were made and cured in the air for one day and conditioned by submerging at $60^{\circ}C$ water for 30 min before loading. It was observed that if the specimen was cured in a lower (or higher) than normal lab temperature ($25^{\circ}C$) before submerging, the measured values were not consistent. Indirect tensile strength (ITS) was also measured on the specimens cured at different temperatures. Although there is no regulation specifying how long the specimen should be conditioned before testing, it is recommended that the conditioning time be for the specimen to be at $25^{\circ}C$. Test must be conducted for the specimen cured well before conditioning for desired test. If curing temperature was lower or higher than normal, and mixture was not properly cured, then test results would not be reliable. This study showed how long the specimen should be submerged at $60^{\circ}C$ for Marshall test and conditioned at $25^{\circ}C$ for ITS test for the specimens cured in different temperature.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.22 no.3
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• pp.69-76
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• 2017

Eelgrass, Zostera marina is a marine flowering plant that grows in submerged habitats for most of its lifetime, and experiences desiccation stress when exposed to air. Although the desiccation stress observed in adult eelgrass has been frequently studied, there has been little research on desiccation stress in eelgrass seeds. To survey desiccation stress in eelgrass seeds, we studied the germination rate and moisture content upon desiccation caused by exposure to air. The germination rate of the eelgrass seeds exposed to air for 1 hour at $20^{\circ}C$ and 50% relative humidity decreased markedly, and it decreased consistently as the exposure time increased. Eelgrass seeds exposed to air for longer than 11 hours did not germinate. As the exposure time of eelgrass seeds to air increased, the germination rate and moisture content decreased, showing a negative correlation. In addition, eelgrass seeds exposed to air at $30^{\circ}C$ showed significantly lower germination rates than those exposed to air at $10^{\circ}C$ or $20^{\circ}C$. Our results revealed that desiccation causes a decrease in the germination of eelgrass seeds, which will provide useful information for eelgrass habitat restoration using seeds.

• Journal of the Korea Organic Resources Recycling Association
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• v.19 no.1
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• pp.64-78
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• 2011

Surface of hydrophobic polyethylene membrane was modified to become hydrophilic by ion beam irradiation. Submerged membrane filtration reactors contained pristine membrane or surface-modified membrane and the influent to reactors was pickled radish wastewater. The objectives of this study was to investigate the variation of flux and pressure and the characteristics of pollutant removal such as organics, suspended solids and nutrients with time. The result of experiments using intermittent pristine membrane showed the occurrence of severe fouling by increasing permeate pressure rapidly in case of pickled radish wastewater but in synthetic wastewater, this phenomenon was not occurred. In experiments of variation flux after chemical cleaning and water cleaning in pristine membrane, chemical cleaning must be necessary for renewals of pollutant membrane. Performance of intermittent operation is higher than that of continuous operation. Reaching fouling time in the case of surface-modified membrane is 6 times as long as pristine membrane. According this reason, replacement expense of surface-modified membrane could be 1/6 of that of pristine membrane. Effluent from this process was relatively good water quality and performance in the removal efficiency of SS, nitrogen and phosphorus was particularly higher.