• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.342-343
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• 2009

Paper factories use a large amount of water and same amount of wastewater is generated. It is important to purity and recycle the wastewater because of water shortages and water pollution. The existing water treatment facilities like precipitation process need large-scale equipment and wide space to purity the wastewater of paper factory. High gradient magnetic separation (HGMS) system has the merits to purity rapidly because of large voids at filter and to occupy small space. In this paper, two types of superconducting magnets were used for HGMS systems. Cryo-cooled Bi-2223 superconducting magnet system with 70 mm room temperature bore and 200 mm of height was prepared. Cryo-cooled Nb-Ti superconducting magnet with 100 mm room temperature bore and 600 mm of height was used for magnetic separator. Magnetic filters were designed by the analysis of magnetic field distribution at superconducting magnets. The various magnetic seeding reactions were investigated to increase the reactivity of coagulation. The effects of magnetic separation of wastewater were investigated as variation of magnetic field strength and flow rate of wastewater.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.45 no.2
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• pp.112-117
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• 2000

This study was conducted to evaluate the drought tolerance of Japonica and Indica rice cultivars during germinating and seedling stages by using the polyethylene glycol (PEG) solution. Each 5 cultivars of Japonica and Indica were cultured from 14 days after seeding(DAS) to 21 DAS using the PEG solution in a moderate water potential (-0.63 MPa). The lengths of radicle and plumule during the germinating stage were inhibitied by the PEG treatment to about 50% and 85%, respectively. The application of PEG to the seedling of two rice types caused to inhibit the plant height and leaf age about 23 % and 10%, respectively. Shoot and root dry weights by PEG treatment were inhibited more severely in Japonica than those in Indica. The difference on delaying of leaf area expansion between both rice types was not found with treatment of PEG, while the leaf color was increased in both Japonica and Indica by 19.9% and 9.2%, respectively. The average photosynthetic ability was inhibited more in Japonica to 36.0% than did Indica to 27.9%. The stomatal conductance was severely affected by PEG treatment, and the degree was varied in both rice types, ranged with 80-85% in Japonica and 29.3-81.6% in Indica. These results indicate there is little relationship between seed germination and seedling growth under the stress of low water potential.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.49 no.4
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• pp.284-288
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• 2004

The response of dissolved oxygen (DO) concentrations caused significant change in root number, root length, coleoptile length, shoot length and leaf age of seedlings. The genotypic difference in the effect of DO also highly significant (P<0.01) for all of the seedling traits. The number and length of root were extremely inhibited at the condition of $0.39\pm0.09$ DO concentration. While the coleoptile elongated markedly in the lowest DO concentrations, the shoot did not develop. The root growth was improved slightly at the $1.39\pm0.27mg L^{-1}$, however, there were no difference among genotypes at these two low DO concentrations. As the DO concentration become higher, the growth of root and shoot was improved remarkably. Root number, root length and shoot length was significantly different between $20\;and\;30^{\circ}C$ in DO rich and normal conditions, the development of those traits were apparently accelerated in high water temperature, however those traits of seedlings in DO deficiency were not different between the two temperatures except for shoot length. On the other hand the coleoptile length was not affected by the stagnant water temperature; it was stimulated by the low DO concentration. The competition of DO was greater as the seedling density was increased in the stagnant water, therefore the seedlings grown under high density have long and white coleoptiles, and the growth of roots and shoots was retarded severely.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.05a
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• pp.4-4
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• 2009

Paper factories use a large amount of water and same amount of wastewater is generated. It is important to recycle the wastewater because of water shortages and water pollution. The existing water treatment facilities like precipitation process need large-scale equipment and wide space to purify the wastewater of paper factory. High gradient magnetic separation (HGMS) system has the merits to purify rapidly because of large voids at filter and to occupy small space. In this paper, two types of superconducting magnets were used for HGMS systems. Cryo-cooled Bi-2223 superconducting magnet system with 70 mm room temperature bore and 200 mm of height was prepared. Cryo-cooled Nb-Ti superconducting magnet with 100 mm room temperature bore and 600 mm of height was used for magnetic separator. Magnetic filters were designed by the analysis of magnetic field distribution at superconducting magnets. The various magnetic seeding reactions were investigated to increase the reactivity of coagulation. The effects of magnetic separation of wastewater were investigated as variation of magnetic field strength and flow rate of wastewater.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.47 no.2
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• pp.80-84
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• 2002

In spite of simple and cheap cultivation method, water broadcast-seeded rice demonstrates uneven and unstable seedling establishment per unit land area and requires more herbicide and labor-input for weed control. Three experiments were conducted in a phytotron at 18$^{\circ}C$ to evaluate the adaptability of seed-mat mulching cultivation technologies in water seeded rice for the uniform seedling establishment and the inhibition of weed occurrence without herbicide application. Five different kinds of mat with different mesh sizes and fabric properties were tested. The emergence of rice was the highest in Lawn-mat treatment, being comparable with the control, in which seeds were sown without mat. The Lawn-mat also exhibited the lowest mat tension. Mat tension may influence the emergence of rice. And once it was soaked in water, it didn't maintain its original shape any more. The emergence rate of rice was the lowest in Safer-mat treatment. In Lawn-mat treatment, which was the most effective for rice emergence in the first study, the differences of emergence and seedling establishment of rice depending on the seeding position (upper, beneath, and between mats) treatments were negligible, while they were higher in dry seeds than in pre-germinated seeds treatment. The emergence as affected by the kinds of mat also showed the same trend when tested using barnyard grass. Depending on the kinds of mat, the inhibition effect of weeds was the greatest in Safer-mat and the poorest in Lawn-mat. These results strongly suggest the possibility that the uniform seedling establishment and weed management without chemical could be achieved simultaneously by seed-mat mulching through the combination of effective mat for the emergence of rice and another efficient mat for the inhibition of weed occurrence. This possibility was also tested in the field.

• Korean Journal of Weed Science
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• v.17 no.1
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• pp.31-43
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• 1997

This study was carried out to investigate classfication of weedy rice (Oryza sativa) based on isozymes esterase and peroxidase, growth and developmental difference of weedy rices and rices grown under dry and water condition, and weedy rice control and tolerant difference of weedy rices in various herbicides using weedy rices collected from thirteen strains of Chonnam, one Chonbuk, two Kyeongki and two rice cultivars. 1. The collected weedy rices were classified into three groups based on isozyme esterase and peroxidase using polyacrylamide gel electrophoresis(PAGE) method. The classified groups were not same each other. 2. Plant height was taller in collected weedy rices than rice cultivars at 18 days after seeding under dry and water conditions, but number of leaves, shoot fresh weight, root fresh weight and root length were not significantly different between collected weedy rices and rice cultivars. In addition, growths of collected weedy rices were greater in dry- than water-condition. 3. After thiobencarb(S-4-chlorobenzyl diethythiocarbamate), molinate(S-ethyl hexahydro-1H-azepine-1-carbothioate) and oxadiazon(5-tert-butyl-3(2,4-dichloro-5-isopropoxyphenyl)-1,3,4-oxadiazol-2-one) were applied at 6 days before seeding, the weedy rices controlled 100% by thiobencarb at 2.1kg ai/ha and 024kg ai/ha oxadiazon treatment but controlled 26% to 67% by molinate at 6.5kg ai/ha. Rice due to the herbicides was injured severely(25% to 100%) in flood condition at time of rice seeding after oxadiazon at 0.48kg ai/ha and 2.1kg ai/ha thiobencarb application, except for molinate which injured rice slightly(4% to 13%) in drain condition. The collected weedy rices to all experimented herbicides showed slight intraspecific variations. The intraspecific variations of weedy rices decreased in the order of thiobencarb>molinate>oxadiazon.

• Weed & Turfgrass Science
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• v.3 no.4
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• pp.323-328
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• 2014

This study was conducted to find out the effects of aerial application by unmanned helicopter (AAUH) on controlling weeds under water-seeded rice cultivation. Foliar herbicide (bentazone sodium + fenoxaprop-P-ethyl) was applied with diluted 8-times (standard concentration pest control) as AAUH. Foliar herbicide treatment with standard and two times amount were little damage, but with more than three times amount showed great damage in rice growth. Six annual and two perennial weeds were major weeds occurred in the experimental paddy field. On foliar herbicide treatment 25 days after direct seeding, AAUH showed high control values against weeds (96.3% for annual weeds and 99.8% for perennial weeds). There was no significant difference in weed control values between AAUH and conventional application. There was no spray injury against rice plants with aerial application. In the experiment for good spray timing (15, 20 and 25 days after direct seeding) 15 days showed highest weed control values with 98.5% to annual weeds and 99.8% to perennial weeds and no spray injury.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.2
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• pp.207-212
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• 2008

This study focused on shorten the period of the struvite crystal birth and development by adding seed materials. For this purpose, three different seed materials were selected: sand, anthracite and struvite. The experiments has been conducted to evaluate the effect of the particle size of the selected seed material on the struvite crystallization, and to study the mixing effect which can be expressed by the value of $G{\cdot}t_d$(the multiple of mean velocity gradient(G) and mixing time($t_d$)). It was observed in this study that the removal efficiency of ammonia nitrogen increased by 9%, 11%, and 20% for sand, anthracite, and struvite added as the seed material, respectivley. This indicated that the struvite crystallization efficiency had a close correlation with the specific surface area of the seed particle. It was found that when struvite was selected as the seed material, the struvite crystallization proceeded at lower $G{\cdot}t_d$ value as compared with other seed materials. This observation implied that the secondary crystal birth would be dominated in this reaction. It was concluded in this study that the particle size was not significant factor on the struvite crystallization, while the $G{\cdot}t_d$ value was a considerably important factor in terms of the theory of the struvite crystal birth.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.42 no.4
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• pp.373-377
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• 1997

The bird repellent, methiocarb 50% WP, has been used to reduce the bird damage in the crop field in the European countries. The bird damage occaisonally would occur in the wet direct seeded rice and in soybean field, and resulted in decreasing the crop productivity by the reduction of seedling emergence rate. In this experiment, rice seeds, Hwasungbyeo(Oryza sativa), were coated with the different application rate of methiocarb, 5, 10 and 15 per kg seed, and soybean, Taegwangkong(Glycine max), 2.5, 5.0 and 7.5g. In rice, the seeds coated with 10 and 15g of methiocarb were not lost by bird, while those with 5g and control were lost to 37 and 50% of total seeds, respectively. No damage by birds was observed in rice seedling when the coleoptile and radicle of rice were emerged at 7 days after the water seeding. The crop injury of methiocarb reducing the emergence rate of seedlings, shortening the shoot length, and decreasing the leaf number was occurred at the treated of methiocarb 15g per kg seed. In soybean, the loss of the sprouting by birds was lower in the treatment of methiocarb 7.5g per kg seed than that in both the control and the treatments of methiocarb, 2.5 and 5.0g per kg seed. No crop injury by the treatment of methiocarb was observed in all application rate.

• Korean Journal of Environmental Agriculture
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• v.17 no.3
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• pp.227-233
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• 1998

To mitigate the methane emission from rice paddy fields, effects of nitrogen fertilizers source and cultural patterns were evaluated on silty loam soils. And a pot experiment was carried out to find out the effects of nitrogen fertilizers on soil pH, Eh, sulfate concentration of soil water in flooded soil. In transplanting cultivation, the total methane emission depending on fertilizers was $32.9gm^{-2}$ for urea ; $30.3gm^{-2}$ for ammonium sulfate ; $26.4gm^{-2}$ for coated urea. Methane emitted in direct seeding on dry soil was $24.7gm^{-2}$ for urea ; $16.7gm^{-2}$ for ammonium sulfate : and $22.8gm^{-2}$ for coated urea. Thus, the methane emission rate of direct seeding on dry soil was 29.7% lower than transplanting. According to the nitrogen fertilizers, the methane emission rate by ammonium sulfate and coated urea were reduced 18.4 and 15.9% in comparison with urea, respectively. In pot experiments, pH in flooded soils depending on nitrogen fertilizers dereased in order of urea > coated $urea{\fallingdotseq}no$ fertilizer > ammonium sulfate and the order was coincided with that of total $CH_4$ emission from flooded soil. Soil Eh was highest in ammonium sulfate application followed by coated urea, no fertilizer, urea. And sulfate concentrations of soil water were in order of ammonium sulfate > coated urea > urea > no fertilizer.