• Korean Journal of Weed Science
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• v.14 no.1
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• pp.49-55
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• 1994

A study was conducted to determine the effect of depth of burial, soil temperature and/or moisture on tuber sprouting of E, kuroguwai. Tubers were evenly distributed in the upper 30cm of soil. Tuber weight increased as depth of tuber formed increased. No dormancy in newly formed tubers was found, whereas mature tubers were dormant. When new tubers were subjected both to continuous $5^{\circ}C$ and to gradual decreasing temperatures regimes ranged from 20 to $1^{\circ}C$ for 30 days, the tubers remained non-dormant. Viability of tubers was reduced when buried at 5cm depth in dry and moist soil conditions, but no reduction was obtained when buried at 25cm depth, regardless of soil moisture conditions employed. Percent sprouting of tubers buried at 25cm depth increased with increasing duration of burial in three soil moisture conditions studied, wherease in dry and moist conditions percent sprouting of tubers buried at 25cm depth increased by 60-day burial and thereafter decreased. In submerged condition, tuber sprouting was greater when buried at 5cm depth than when buried at 25cm depth, and increased as duration of burial increased at the both depths.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.6 no.1_2
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• pp.76-80
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• 1973

Cyclina sinensis is an edible bivalve inhabiting wide tidal flats which are exposed to the air at ebb tide along the western coast of Korea. Over the period of June to September 1971, some specimens from a tidal flat near Inchon were submerged in sea water with various concentrations of ammonium hydroxide added and careful observations were made on their fertilization, early development, and metamorphosis of the larvae. The highest rate of fertilization was demonstrated by individuals treated with 1/1000 normal solution of ammonium hydroxide and their fertilized eggs followed normal development, i.e., two cell stage 1.5 hours after fertilization, blastular stage after 4 hours, and trochophore stage after 6 hours. Within 24 hrs after fertilization C. sinensis larvae have acquired the form of early straight-hinge veliger with the mean prodissoconch I with the length of $110\mu$. It takes seven days to get the umbo stage with the mean shell length of $190\mu$ and twenty days to get the morphosing stage with the mean shell length of $260\mu$. The larvae were cultured to the metamorphosing stage with the shell length of $270\mu$ in the laboratory condition.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.6
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• pp.561-567
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• 1987

The purpose of this study was to find out the removal capacity of harmful ammonia by different filter media in the submerged biological filters in a given space of chamber. Four materials, pile cloth, corrugated skylight roofing plate, embossed plastic plate, and gravel, were used as the experimental filter media. Each filter medium was placed in two aquariums, each aquarium measuring $90cm\times60cm\times60cm\;(depth)$. Under the normal operating condition, the average of mean ammonia removal rates during the first and second functioning periods by each filter material which occupied tile space in the filter chamber (aquarium) was as follows: 1. Pile cloth: $8.381\;g{\cdot}m^{-3}.\;day^{-1}$ 2. Corrugated skylight roofing plate: $7.834\;g{\cdot}m^{-3}.\;day^{-1}$ 3. Embossed plastic plate: $7.797\;g{\cdot}m^{-3}.\;day^{-1}$ 4. Gravel: $7.051\;g{\cdot}m^{-3}.\;day^{-1}$ Thus, there were no significant differences between the media, but at the time of practical application of these materials, some other factors such as investment cost, easiness for the removal of excess detritus accumulated in tile interstices of filter media, etc. should be fallen into consideration. When large units are required, in particular, removal of excess detritus from tile gravel bed is extremely difficult, and in case of pile cloth filters the installation work is much complicated and a problem in supporting the structure when drained also exists. In these respects, corrugated skylight roofing plate and embossed plastic plate seem to be more optimal, but again in practice the local situation for the availability and the price of the materials should be rechecked and the fitness of tile materials in the particular filter chambers under use or under consideration for construction must be taken into account.

• 한국균학회소식:학술대회논문집
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• 2015.11a
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• pp.37-37
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• 2015

dsRNA was found in malformed cultures of Lentinula edodes strain FMRI0339, one of the three most popular sawdust cultivated commercial strains of shiitake, and was also found in healthy-looking fruiting bodies and actively growing mycelia. Cloning of the partial genome of the dsRNA revealed the presence of the RdRp sequence of a novel L. edodes mycovirus (LeV), and sequence comparison of the cloned amplicon showed an identical sequence to known RdRp genes of LeV found in strain HKA. The meiotic stability of dsRNA was examined by measuring the ratio of the presence of dsRNA among sexual monokaryotic progeny. More than 40% of the monokaryotic progeny still contained the dsRNA, indicating the persistence of dsRNA during sexual reproduction. Comparing the mycelia growth of monokaryotic progeny suggested that, although variations in the growth rate existed among progeny and virus infection was observed in highly actively growing progeny, there appeared to be a tendency toward a lower frequency of virus incidence in actively growing progeny. This study attempted to cure the edible mushroom L. edodes strain FMRI0339 of the L. edodes mycovirus (LeV) in order to obtain an isogenic virus-free fungal strain as well as a virus-infected strain for comparison. Mycelial fragmentation, followed by being spread on a plate with serial dilutions resulted in a virus-free colony. Viral absence was confirmed with gel electrophoresis after dsRNA-specific virus purification, Northern blot analysis, and PCR using reverse transcriptase (RT-PCR). Once cured, all of fungal cultures remained virus-free over the next two years. Interestingly, the viral titer of LeV varied depending on the culture condition. The titer from the plate culture showed at least a 20-fold higher concentration than that grown in the liquid culture. However, the reduced virus titer in the liquid culture was recovered by transferring the mycelia to a plate containing the same medium. In addition, oxygen-depleted culture conditions resulted in a significant decrease of viral concentration, but not to the extent seen in the submerged liquid culture. Although no $discernable phenotypic changes in colony morphology were observed, virus-cured strains showed significantly higher growth rates and mycelial mass than virus-infected strains. We were also explored effects of LeV on fruiting body formation and mushroom yield. The fruiting body formation yield of virus-free L. edodes was larger than virus-infected L. edodes. These results indicate that LeV infection has a deleterious effect on mycelial growth and fruiting body formation. In addition, we have been investigated host-parasite interaction between L. edodes and its mycovirus interaction to study viral mechanism by establishment of proteomics.

• Korean Journal of Weed Science
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• v.18 no.1
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• pp.12-19
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• 1998

The pattern of rice cultivation in Korea is changing from hand transplanting and machine transplanting into direct-seeding for low input and cost-down practices. However, there are still some obstacles to establish the direct-seeding cultural practices because of poor seedling stand, lodging, and weed infestation. In particular, there were much more and wide weed occurrence in direct-seeding rice as compared with the transplanted rice. Weed occurrence in terms of dry weight of weeds was highest in dry direct-seeded rice followed by sowing an puddled soil, sowing on submerged soil in order as compared with transplanting with infant rice seedling. Echinochloa crux-galli was a common dominant weed with 35~44% distribution in any direct-seeding methods. The dominant weed species were E. crux-galli, Cyperus difformis, C. serotinus, and Ludwigia prostrata in dry-seeded rice. The dominant weed species in water-seeded rice were E. crus-galli, Eleocharis kuroguwai, Scirpus juncoides, and Monochoria vaginalis. Yield loss of rice due to weeds at weedy condition was 96% in dry direct-seeded rice. In water-seeded rice, yield loss was 61%, whereas yield loss was 40% in machine transplanting with infant rice seedling.

• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.2
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• pp.45-52
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• 2002

An experimental investigation on the structure and dynamic behavior of two dimensional over-expanded air jets exiting into water was carried out. The hish speed digital video imaging and static pressure distribution measurement were made to characterize the structure and time-dependant behavior of the jets. Mach number at the jet exit was 2.0 and was slightly less than the value predicted by the ideal nozzle calculation. Variance of jet spreading angle at different stagnation condition was measured as a function of mass flow rate. Periodic nature of the air jet distortion in water was observed and the frequency of the repetition was approximately 5-6 Hz for all cases tested. Three characteristic length scales were defined to characterize jet structure. $L_1$, maximum width of the plume when the periodic instability occurs, $L_2$, width of the jet where secondary reverse flow entrained jet flow and $L_3$, distance from the jet exit to the location where entrainment of the secondary reverse flow occurs. The ratio of $L_1$ and $L_2$ decreased with increasing stagnation pressure, i.e. mass flow rate. $L_3$ increased with increasing stagnation pressure. The temporal behavior of static pressure measurements also showed peak around frequency of 5, which corresponds the frequency obtained by visual measurements

• Transactions of the KSME C: Technology and Education
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• v.5 no.2
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• pp.135-143
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• 2017

The domestic unique research reactor, HANARO (Hi-flux Advanced Neutron Application ReactOr), has been constructed with the open-pool, the core is submerged in, for the multi-purpose neutron application. The reactor has a primary cooling system to remove the fission heat from the core and its connected fluidic systems. Since the works are required at the reactor pool top as a characteristic of the research reactor, the radiation shall be minimized with the operation of the hot water layer system to avoid unnecessary radiation exposure on the workers during work at the pool top. Moreover, the pool water management system is connected to the reactor pool to maintain the pool temperature below $50^{\circ}C$ to minimize the uprising radioactive gas or impurity from the colder pool bottom. For the efficient flow rate of the PWMS, the thermal capacity of heat exchanger is selected with 260 kW in the normal operation condition. In this paper, the modeling is formulated to figure out whether or not each pool temperature maintains below the temperature limit and the calculation results show that the designed PWMS heat exchanger has enough capacity with the design margin regardless of the reactor operation mode.

• The Korean Journal of Pesticide Science
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• v.4 no.3
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• pp.47-51
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• 2000

A some of synthesized 2,3-dihydro-2,2,4,6,7-pentamethylbenzofuran-5-yl substituents in 5-benzofuryl-2-[1-(alkoxyimino)alkyl]-3-hydroxycyclohex-2-en-1-one derivatives as substrates were found to show herbicidal activity against rice plant (Oryza sativa L.) and barnyard grass (Echinochloa crus-galli) with post emergence under submerged conditions. The substrate with $R_{1}$=methyl substituents, $1{\sim}5$ showed the higher herbicidal activity to the seed, 3 leaf stage of rice plant and barnyard grass. The structure activity relationships (SARs) on the herbicidal activity of $R_{1}$ and $R_{2}$ on the azomethine bond in substrate were analysized. In the condition of $R_{1}$ groups are same, the herbicidal activity against 3 leaf stage of rice plant were governed by the optimal hydrophobicity $(logP)_{opt.}=4.57$. Whereas, in the case of barnyard grass, the herbicidal activities were largely dependent upon the steric effect, $B_{2}$ constant than hydrophobicity. In order to take the selective herbicidal activity between rice plant and barnyard grass, it is assumed that the (S) should be a round shape with higher hydrophobicity (logP>4.57) than optimal value. Also, the $R_{1}$ groups must be small and the $R_{2}$ groups are advisable to be unsaturate.

• Korean Journal of Soil Science and Fertilizer
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• v.17 no.2
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• pp.101-107
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• 1984

The suitable paddy soil for application of rice straw under well to moderately well drained soil, the yield and yield components were pronounced more than poorly drained soil. Based on laboratory experiment, application of rice straw promoted the decrease of oxidation-reduction potential in well to moderately well drained soil. This results seems to be enhanced the release of some mineral nutrients such as calcium, potassium, silicon, and increases of availability of soil phosphorus. This explains reason why soil condition became more favorable for the increases of mineral nutrient in rice plant. On the contrary, poorly drained soils, became readily reduced even without application or rice straw, when soil wat submerged. Application of rice straw did not promoted the decrease of oxidation-reduction potential as much as in well drained soil. It was suggested that in this type of soil series, the release of mineral nutrients and the additional increase of available soil phosphorus did not proceed well. It was also suggested that the retardation of root development owing to accumulation of toxic substances such as organic acid, hydrogen sulfide or some other reducing substances formed by the application of rice straw in poorly drained soil series might be considered. In fact, the effect of rice straw on the yield of brown rice became lower.

• Journal of Korean Society on Water Environment
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• v.34 no.4
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• pp.363-374
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• 2018

The Han River serves as an important water resource for the city of Seoul, Korea and in the neighboring metropolitan areas. From the Paldang dam to the Jamsil submerged weir, the 4 water intake stations that are located for the Seoul metropolitan population were under review in this study. Therefore the water quality management in this section is very important to monitor, analyze and review to rule out any safety concerns. In this study, a 3-D hydrodynamic model, EFDC (Environmental Fluid Dynamics Code), was applied to the downstream of the Paldang Dam in the Han River, which is about 23 km in length, to determine issues related to water resource management. The 3-D grid was composed of 2,168 horizontal grids and three vertical layers. In this case, the hydrodynamic model was calibrated and verified with an observed average daily water surface elevation, water temperature and flow rate data for 3 years (2013~2015). The developed EFDC model proved to reproduce the hydrodynamics of the Han River well. The composition ratios of the noted incoming flows at the monitored intake stations for 3 years and their flow patterns in the river were analyzed using the validated model. It was found that the flow of the Wangsuk Stream depended on the Paldnag dam discharge, and it was noted that the composition ratios of the stream at the intake stations changed accordingly. In a word, the Wangsuk Stream moved mainly along the right bank of the Han River under the condition of a normal dam flow. As can be seen, when the dam discharge rate was low, the incidence of lateral mixing was often seen. The scenario analyses were also conducted to predict the transport of conservative pollutants as in the case of a chemical spill accident. Generally speaking, when scenarios were applied, the arrival time and concentration of pollutants at each intake station was thus predicted.