• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.4
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• pp.51-60
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• 1987

A two dimensional negatively buoyant flow from a shallow channel into rectangular ponds is analysed numerically by a finite difference scheme in a stretched coordinate system. In rectangular ponds, the confuguration of plunge flow largely depends on the densimetric Froude number, $Fr_e$, of the inflow. The velocity of front of the plunging flow increases with increasing negative buoyanty(decrease of $Fr_e$). The location of stable plunge point and maximun travel distance of plunge point are found to be a function of dimensionless time and densimetric Froude number. Large vortices develop on the both sides of negative buoyant flow or plunge flow.

• Environmental Engineering Research
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• v.19 no.3
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• pp.185-195
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• 2014

Despite the enormous technical and economic efforts to improve environmental conditions, currently about 40% of the global population (or 2 billion people) are still lack access to safe water supply and adequate sanitation facilities. Pollution problems and transmission of water- related diseases will continue to proliferate. The rapid population growth and industrialization will lead to a reduction of arable land, thus exacerbating the food shortage problems and threatening environmental sustainability. Natural systems in this context are a transdisciplinary approach which employs the activities of microbes, soil and/or plants in waste stabilisation and resource recovery without the aid of mechanical or energy-intensive equipments. Examples of these natural systems are: waste stabilisation ponds, aquatic weed ponds, constructed wetlands and land treatment processes. Although they require relatively large land areas, the natural systems could achieve a high degree of waste stabilisation and at the same time, yield potentials for waste recycling through the production of algal protein, fish, crops, and plant biomass. Because of the complex interactions occurring in the natural systems, the existing design procedures are based mainly on empirical or field experience approaches. An integrated kinetic model encompassing the activities of both suspended and biofilm bacteria and some important engineering parameters has been developed which could predict the organic matter degradation in the natural systems satisfactorily.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.3
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• pp.323-329
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• 2005

In this paper, performance of a hybrid sequential aerobic-anaerobic natural system was investigated. Continuous aerobic and anoxic conditions were created by alternatively placing waste stabilization pond (WSP) and wale. hyacinth pond (WHP). Two pilot-scale treatment lines were built and operated; The first consists of WSP integrated with WHP and the second of WSP connected with Dark Pond(DP), namely control system ponds which were used to examine the effects of water hyacinth on nitrification and de-nitrification. The overall performance in nitrogen was 86% reduction in WSP-WHP and 36% in WSP-control pond system. Nitrogen was mostly removed by nitrification and de-nitrification which simultaneously occurred in the same water hyacinth ponds. For the de-nitrification, benthic layer was found out to be adequate support as a carbon source. In addition, WSP-WHP system was very effective in reducing phosphorus. Overall P removal efficiency in WSP-WHP is 81%, while it is only 16% in WSP-control. difference in phosphorus reduction between those two systems is thought to be caused by the plants and probably their roots producing extra-cellular materials, but these aspects need to be further studied.

• Korean Journal of Ecology and Environment
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• v.41 no.1
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• pp.54-65
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• 2008

The seasonal dynamics of phytoplankton and water quality were evaluated bimonthly at 7 park ponds in the capital region from October 2004 to August 2005. With out the change of water temperature $(0.4\sim26.0^{\circ}C)$, cyanobacteria dominated in park ponds such as Gyungbokgung Gyunghyaeru and Seokchon reservoir. The standing crops of phytoplankton was significant related with cell densities of cyanobacteria (r=0.993), while they did not significant correlation with environmental factors. Almost of all park ponds in the capital region were classified as eutrophic state with high TP concentrations and TN/TP ratios less than 10. Major dominant cyanobacteria were as followed; Anabaena sp., Aphanocapsa elachista, Lyngbya contorta, Merismopedia elegans, Microcystis aeruginosa, M. wesenbergii, Microcystis sp., Oscillatoria sp., Phormidium tenue, and Plectonema sp. To date, although the concentration of chlorophyll-${\alpha}$ and cyanobacterial densities in the capital region was below the 'danger' level of WHO guidelines value, the monitoring of cyanobacterial densities and its toxin (microcystin) in recreational/bath water should be continued.

• Journal of Aquaculture
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• v.20 no.4
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• pp.278-288
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• 2007

Shrimp culture in Korea had been rapidly developed during 1990's and the production of farmed shrimp reached 3,268 mt from 2,605 ha in 2001. However the shrimp production decreased to 2,368 mt in 2004 because of the mass mortality due to outbreak of white spot syndrome virus (WSSV). WSSV which is one of the most serious threats associated with cultured shrimp around the world has given the economic damages to shrimp culture industry every year since it was found from the shrimp ponds in the west coast of the South Korea in 1993. Various polyculture technologies of shrimp with shellfish, finfish or seaweeds have been implemented to reduce economic damages by mass mortalities of shrimp. Among them, the polyculture of shrimp with carnivorous fish can suppress or delay the viral outbreak of shrimp ponds because the fish may selectively eat the moribund shrimps infected by virus. To determine the selective predatory effect of river puffer Takifugu obscures on WSSV infected shrimp, postlarvae of Litopenaeus vannamei and Fenneropenaeus chinensis. One-year old river puffers were stocked to four earthen ponds of $1,616-1,848\;m^2$ in surface area as followings: polyculture LvP, L. vannamei ($43.4/m^2$)+puffer ($0.22/m^2$); control Lv, L. vannamei ($46.9/m^2$); polyculture FcP, F. chinensis ($30.3/m^2$)+puffer ($0.25/m^2$); control Fc, F. chinensis ($24.6/m^2$). Ponds of control Fc and polyculture FcP had mass mortalities by WSSV outbreak on the $51^{st}$ and $57^{th}$ days of culture respectively. The shrimps of polyculture LvP and control Lv were harvested on the $95^{th}\;day$. Shrimp survival rates of polyculture LvP and control Lv were 32.4% and 18.2% respectively and shrimp productivity of polyculture LvP was 69.2% higher than that of control Lv. Concentration of nutrients (TAN, $NO_2-N$, $NO_3-N$) was maintained within optimal ranges for shrimp growth although that of polyculture ponds showed at least two times higher than that of control ponds. The results suggest that polyculture of L. vannamei with river puffer is higher than monoculture in survival rate and productivity. In addition, F. chinensis should be carefully cultured because this species shows much higher susceptibility to WSSV than L. vannamei.

• Proceedings of the Korean Society of Applied Entomolohy Conference
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• 2001.11a
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• pp.61-61
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• 2001

• Journal of the Korean Institute of Rural Architecture
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• v.11 no.2
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• pp.45-52
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• 2009

In our traditional living lives, our ancestors have been succeeded in and developed the shortage-replenishing materials to balance with the nature and supplement the condition of geography by the measures, called the BiBo, in order to be harmonized with the nature. This study is purposed to find the meaning and quality of the BiBo materials distributed throughout the agriculture village in Yeoungdong area, Gangwon province in terms of scenery perspectives. It is found that there are 56 village forests, 18 BiBo symbolic properties and 2 BiBo ponds in Yeoungdong area, Gangwon province. Among these, village forests are largely consisting of pine trees and most of them are functioned for water-entrance defender. Including these village forests, the BiBo symbolic properties are important historic and cultural resources in this area and expected to be used as the income-source of the farm village.

• The Journal of Fisheries Business Administration
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• v.13 no.1
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• pp.85-97
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• 1982

This study involves a blending of intensive and extensive shrimp culture techniques for a hypothetical shrimp farm which uses a combination of heated raceway nurseries and extensive grow-out ponds per year. The present value method of economic analysis is used to determine economic feasibility. The biological data in this reports were obtained from published or personal communications from leaders in the field of shrimp aquaculture. The proposed system showed economic feasibility using the present value method with discount rates of 10% and 12%. The most profitable scenario, the culture of three crops of Penaeus vannamei showed a 1.26 year payback period and 120% annual average rate of return. The breakeven price was ＄1.25/1b., which is ＄1.52 less than the market price of ＄2.77. Breakeven production was 724 1bs/acre, which is 8761bs. less than the assumed 1,600 1bs/acre. All other scenarios 1.2 and 3 crops for P. stylirostris and P. setiferus showed economic feasibility also.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.1238-1241
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• 2004

Yongsan river 4th agricultural comprehensive development project is being developed in order to strengthen the competitiveness in the southwest sea-side district, to construct the area for the special product and so on. Different from other development project, this project is to use water from its watershed by means of using regulating reservoirs, small reservoirs and farm ponds. but the number or regulating reservoirs, small reservoirs and farm ponds involved in this project are 7, 147 and 13 respectively. So it is necessary to develope the irrigation water management system for the purpose of efficient water use in Yougsan river fourth district. In this study, the irrigation water management system was developed and by using this system. efficient water using plans could be established.

• Journal of Species Research
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• v.9 no.1
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• pp.68-76
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• 2020

We identified 22 ciliate species, including five unrecorded ciliate species, from temporary ponds on a grass lawn. The five unrecorded species are as follows: class Nassophorea - Pseudomicrothorax agilis Mermod, 1914, Nassula exigua Kahl, 1931, class Colpodea - Cyrtolophosis mucicola Stokes, 1885, Maryna ovata (Gelei, 1950) Foissner, 1993, and class Spirotrichea - Meseres corlissi Petz & Foissner, 1992. Most of these 22 ciliate species disappeared from a raw culture within a few days (probably encystment), and a few cells were available from some species that resulted in incomplete identifications (e.g., genus-level). About the unrecorded five ciliate species, they are small in size (<60 ㎛ in vivo), and two of them live in a hyaline dwelling-tube, which is easily deserted by a cell with a stress. Their taxonomic classification is summarized as three classes, five orders, five families, and five genera. Here, we provide brief descriptions, micrographs of their morphology, and some remarks.