• Korean Journal of Weed Science
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• v.12 no.1
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• pp.46-51
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• 1992

The survey of weed population in paddy field was carried out to invegstigate the weed group on 340 fields in Kyonggi Area in 1991. The weed species observed include 4 species of grasses, 7 species of sedges, and 14 species of broadleaf weeds, and the ratio of annual weed vs perennial weed was 25 : 75. Major dominant weed species were Eleocharis kuroguwai, Sagitaria trifolia, Echinochloa crusgalli and Cyperus serotinus. The dominant weed species in South Plain Region were Echinochloa crusgalli, Eleocharis kuroguwai, Sagitariu trifolia, Cyperus strotinus, in West Coast Region were Eleocharis kuroguwai, Sagitaria trifolia, Echinochloa crusgalli, Cyperus serotinus, in East Interior Region were Eleocharis kuroguwai, Sagitaria trifolia, Echinochloa crusgalli, Cyperus difformis and were Sagitaria trifolia, Eleocharis kuroguwai, Echinochloa crusgalli and Monochoria vaginalis in North Region. The dominant weed species in Normal and Poorly drained soil were Eleocharis kuroguwdi, Sagitaria trifolia, Echinochloa crusgalli and Cyperus serotinus and were Scirpus maritinus, Cyperus serotinus, Echinochlod crusgalli and Myriophyllum verticillatum in Saline Soil. More and many weeds were growing in single cropped field than double cropped field.

• 한국전산유체공학회:학술대회논문집
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• 2005.04a
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• pp.104-108
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• 2005

The Korean high speed train runs at 300 km/h, ballast-flying phenomenon often happens by strong train-wind. It is important to consider the prevention of ballast-flying phenomenon, because the train under-body and fares or walker around a rail might be damaged. In this study, Numerical analysis of the flow field of under-body of train and study of heighter-effect were conducted to decrease the speed of under-body. The shape of under-body was simplified for convenience of meshing and analysis. According to results of Taguchi's design by orthogonal arrays, a height of tie is dominant in the flow field, so if the heighter is installed on tie, the speed of under-body might be decreased. The result of this study is useful to build a new high-speed-line.

• Korean journal of applied entomology
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• v.31 no.2
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• pp.113-121
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• 1992

The study was conducted to investigate the community structure of superfamily Coreoidea (Geocorisae: Hemiptera) in Mt. Kyeryongsan from August, 1989 to August, 1990. The collected coreoid insects were composed of 17 species, 13 genera, and 2 families. Percentages of coreoid insects found in each observed zone were 47.4% (13 species) in the paddy bank, 37.4 % (13 species) in the weedy field and 15.2% (11 species) in the shrubs. Dominant species and Simpson's dominance indices were Riptortus clavatusa and Stictopleurus crassicornis ($\lambda$=0.128) in the paddy field, Cletus schmidti and Homoeocerus dilatatus ($\lambda$=0.141) in the weedy field, Riptortus clavatus and Homoeocerus dilatatus ($\lambda$=0.199) in the shrubs. Seasonal dominant species were Cletus trigon us and Rhopalus maculatus ($\lambda$=0.149) in Spring, Cletus schmidti and Homoeocerus dilatatus ($\lambda$=0.132) in Summer, and Riptortus clavatus and Cletus schmidti ($\lambda$=0. 386) in Autumn. Species diversity indices(H') in the paddy bank, weedy field, and shrubs were 0.931, 0.916, and 0.810, respectively. Eveness indices(J') were 0.836, 0.800, and 0.778, respectively. Community structures were almost similar between the paddy bank and the weedy field.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.6
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• pp.701-713
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• 2003

The BEM is a highly efficient method in the sense of economical computation. However, boundary integration is not easy for the complex geometry and moving surface, e.g. a rotating blade. Thus, Kirchhoff surface is designed in an effort to overcome the difficulty resulting from complex boundary conditions. A Kirchhoff surface is a fictitious surface which envelopes acoustic sources of main concern. Acoustic sources may be distributed on each Kirchhoff surface element according to their acoustic characteristics. In this study, an axial fan is assumed to have unsteady loading noise as a dominant source. Dipole sources can be modeled to solve the FW-H equation. Acoustic field is then computed by determining Kirchhoff surface on which near-field is implemented, to analyze the effect of Kirchhoff surface on it. The optimal shape and the location of Kirchhoff surface are discussed by comparing with experimental data acquired in an anechoic chamber.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.3
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• pp.275-281
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• 2016

The aim of this study was to examine the selected soil chemical properties of paddy fields in different topographic areas to efficiently manage nutrient valances of the paddy fields in Jeonbuk Province. Three-hundred soil sampling sites in paddy fields were selected from the different topographic areas in Jeonbuk Province. The soil samples were collected every four years from 1999 to 2015. Soil pH and exchangeable K and Mg concentrations declined during the experimental periods. However, almost all the chemical properties were within the proper levels for paddy soil, except exchangeable Mg concentration. Distributed areas of the paddy fields with soil pH below 5.5 continuously increased, but the paddy fields with lower concentrations of soil organic matter and available $P_2O_5$ than the proper levels declined after 2007. In addition, the paddy fields with available $SiO_2$ below the proper concentration decreased from 83.3% of the total paddy fields studied in 1999 to 61.0% of the total fields investigated in 2015. The paddy fields with lower exchangeable K and Mg than the proper levels increased after 2003 whereas the fields with lower exchangeable Ca concentration decreased. Dominant landform of coastal and plain areas was fluvio-marine plains that was distributed in 53.7% and 40.9%, respectively. Local valley and fans was a dominant landform of mountainous and middle-mountainous areas, which was 51.8% and 67.6%, respectively. Dominant soil textures distributed in coastal and plain areas were silty loam and loam. Those in mountainous and middle-mountainous areas were sandy loam and loam, respectively. Soil pH was relatively higher in coastal area and the comparatively higher content of soil organic matter was found in costal area than other areas. The concentrations of available $P_2O_5$, exchangeable Ca, and exchangeable Mg were generally higher in mountainous, coastal, plain areas, respectively, but available $SiO_2$ and exchangeable K concentrations were not significantly different among the different topographic areas.

• Journal of Plant Biology
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• v.27 no.1
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• pp.25-32
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• 1984

A study on the dominance-diversity of forest vegetation in Mt. Seolag was conducted from May 1981 to Aug. 1983. Based on the field data, the dominance-diversity curves were for 16 sites including slopes and vallies. The curves are grouped in two types, lognormal distribution at the sites of mature vegetation and geometric series at the disturbed or rocky sites. It seems that the curves express the nature of their ecocline, by the hypotheses of some investigators, i.e. Random Niche hypothesis, Niche Pre-emption hypothesis, Lognormal distribution and Logarithmic series. The dominance concentration among the southern, northern and western slope, H'=1.282 at southern slope and H'=1.385 at western slope. Dominance-diversity curves of 16 sites showed Preston's lognormal distribution with small variations among them. It seems that the dominance diversity reflects the differences in the coenocline of their sites. The top 10 dominant species in species sequence of 113 tree species in whole the mountain, were noticed: Quercus mongolica, Pinus densiflora, Acer pseudo-siebold anum, Quercus serrata, Carpinus laxiflora, Styrax obassia, Fraxinus rhynchophylla, Tilia amurensis, Lindera obtusiloba and Abies holophylla in order.

• Korean Journal of Soil Science and Fertilizer
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• v.29 no.2
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• pp.199-206
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• 1996

Vegetation succession and changes in soil chemical properties were investigated in 10 abandoned rice fields in Kyunggi Province in 1995. Annual weeds were dominant at the first year of abandonment, later on Perennial weeds became dominant as the period of abandonment progressed. The number of Salicaceae(willow family) increased rapidly as the abandonment period further progressed. In cultivated fields, soil pH and cation contents are slightly higher in subsurface layer than surface layer. In abandoned fields, however, pH of surface layer was getting higher than subsurface soil layer with the lapse of time. Similar trends were observed in case of exchangeable Ca and Mg contents.

• Journal of Ecology and Environment
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• v.33 no.3
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• pp.229-236
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• 2010

We conducted field surveys of amphibians and reptiles over a two-year period in 16 lagoons along the eastern coastline of South Korea, and determined the habitat characteristics correlated with the number of amphibian and reptilian species and individuals. We documented 11 amphibian species and 8 reptilian species. The dominant amphibian species was the black-spotted pond frog (Rana nigromaculata), and the dominant reptilian species was the red-eared turtle (Trachemys scripta elegans), an invasive species. Among the 14 habitat characteristics, connectivity to mountainous area significantly affected the number of amphibian and reptilian individuals. Other factors, including emerged plant cover, salinity, pH, the number of birds for amphibians and connectivity to agricultural land, lagoon perimeter length for reptiles also influenced the number of species or individuals of them. Our results demonstrate that these lagoons are home to more amphibians and reptiles than has been previously known. To effectively conserve herpetofauna in the lagoon ecosystem, lagoons as well as surrounding wetlands, grasslands, and mountainous areas should be protected.

• Korean journal of applied entomology
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• v.20 no.3 s.48
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• pp.168-172
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• 1981

This work was carried out to study field biology of Agrotis tekienis B. in Korea for two years (1979 and 1980), The species was found to be the dominant species among cutworms giving damage to young Plants in Spring with making up approximately $80\%$ or more of cutworms collected at Suweon and Jeonju from March to early June. During April and May which is the most critical period as far as plant damage by cutworms is concerned, those of A. tokionis larvae collected were at 5th and 6th instar. A. tokionis larvae enter a summer diapause from late May to early July and Agrotis ipsilon became the dominant species. It is also suggested that A. tokionis larvae be called as the 'dark grey cutworm', based upon its larval body color.

• Korean Journal of Weed Science
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• v.15 no.4
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• pp.305-312
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• 1995

Weed communities in the dry-direct seeded rice(Oryza sativa L.), soybean(Glycine max(L.) Merr.), and dry-direct seeded rice-soybean rotation system from the transplanted rice field were investigated in order to identify a change in weed species by paddy-upland rotation. Echinochloa species was the most dominant species in the dry-direct seeded rice and their great increase was observed in the continued practices of dry-direct seeded rice. Echinochloa spp., Chenopodium ficifolium, and Digitaria spp. were identified as the major weeds in soybean cultivation in paddy field. Practice of soybean rotation in the dry-seeded rice reduced weed occurrence, particularly at the soybean after 2-yr continued dry-direct seeded rice and at dry-direct seeded rice culture after 2-yr continued dry-direct seeded rice and at dry-direct seeded rice culture after 2-yr soybean compared to the continued cultures of rice or soybean. In addition, cultivation of dry-direct seeded rice or soybean culture in the paddy rice field seemed to be helpful for suppression of perennial weeds(Eleocharis kuroguwai, Cyperus serotinus, Scirpus juncoides) and aquatic weeds(Monochoria vaginalis, Sagittaria spp. Potamogeton distinctus).