• ALGAE
• /
• v.20 no.2
• /
• pp.133-140
• /
• 2005

Daily variation of phytoplankton community and environmental parameters were investigated at the lower Nakdong River (Mulgum) from January 2002 to December 2003 to investigate the dynamics of a phytoplankton community in detail. The daily results of water quality in this investigation showed pH (8.1 $\pm$ 0.7), DO (10.3 $\pm$ 2.7 $mg{\cdot}l^{-1}$), water temp. (18.8 $\pm$ 7.4°C), BOD (2.4 $\pm$ 1.0 $mg{\cdot}l^{-1}$), COD (5.3 $\pm$ 1.2 $mg{\cdot}l^{-1}$) and chl. a (43.5 $\pm$ 35.1 mg ${\cdot}m^{-3}$). The results of nutrient factors were the following: TN (3.1 $\pm$ 0.8 $mg{\cdot}l^{-1}$), NO3-N (2.5 $\pm$ 0.5 $mg{\cdot}l^{-1}$), TP (90 $\pm$ 48 ${\mu}g\;{\cdot}\;l^{-1}$), PO4-P (43 $\pm$ 30 ${\mu}g\;{\cdot}\;l^{-1}$). Dominant phytoplankton species during the study period were diatom (Stephanodiscus hantzschii, Aulacoseira granulata var. angustissima and A. italica) and cyanobacteria (Microcystis aeruginosa, Aphanizomenon flos-aquae). The small centric diatom, Stephanodiscus hantzschii, was repeatedly dominant from late fall to the following spring (mean and maximum cell density, 2.3 × 103 $\pm$ 3.8 × 103, 4.5 × 105 cells $ml^{-1}$, respectively). Pinnate diatom, Aulacoseira granulata var. angustissima and A. italica, were frequently observed all season except January to March. Cyanobacteria, Microcystis aeruginosa and Aphanizomenon flos-aquae, proliferated in summer of 2002 except in 2003 due to heavy precipitation. The dominant zooplankton species (March-early May) was rotifer (Brachionus, Keratella, Polyarthra) and cladocerans (Diaphanosoma). The daily observed dynamics of the phytoplankton community in the lower Nakdong River in this study may play an important role in increasing the detailed resolution of limnological information and serving as ecological data for future studies.

• Proceedings of the Korean Magnetic Resonance Society Conference
• /
• 1999.02a
• /
• pp.12-12
• /
• 1999

• Proceedings of the Korean Radioactive Waste Society Conference
• /
• 2018.05a
• /
• pp.407-408
• /
• 2018

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
• /
• 2008.04a
• /
• pp.200-203
• /
• 2008

Water mist fire suppression system utilizes the fire suppression features such as cooling of fire source, dilution of ambient oxygen, and shielding of radiation heat with the evaporation of microscopic water droplets. The momentum of water mist is relatively low and the infiltration of water mist to the fire source is not effective. In addition to lower penetration force, the evaporated water vapor is liable to decline to limited portion of fire source due to its light weight and sparse density. On the other hand, the cycling water mist system is expected to improve the penetration force of water mist as well as the dilution coverage capability with the stratified spray characteristics. At this paper we present the analyzed fire suppression capability of intermittent water spray pattern by use of FDS which is computational fire dynamics fire model. We expect this analysis shall be supportive to the development of the prototype of water mist nozzle.

• Korean Journal of Soil Science and Fertilizer
• /
• v.45 no.3
• /
• pp.353-359
• /
• 2012

The identification of effective root zone would clarify dynamics of plant available water and soil water balance. Using the relationship between soil properties and electrical resistivity (ER) the purpose of this research is to identify soil zone affected by a plant root activity using electrical resistivity tomography (ERT) technique. Four plastic containers were prepared for two different soil textures (clay and sandy loam) and one container for each texture was selected for planting four corn seedlings (Zea mays L.) and the others were prepared for the blank. For ERT monitoring, we prepared 0.8 m plastic sticks with 17 electrodes installed with 5 cm space. The Ministing (AGI Inc., Texas) instrument for electrical resistivity measurement and semi-auto converter of electrode arrangement were set up for dipole-dipole array. During 2 months of the corns growing, ERT monitoring was made 3 to 4 days after the irrigation practice. Despite of the same amount water supplied into soils, two textures showed very different apparent resistivity values due to different clay content. The apparent electrical resistivity is consistently lower in clay loam comparing to sandy loam soil implying that plant root does not significantly alter the overall trend of resistivity. When plant root system, however, is active both soils with plants showed 2-7 times higher electrical resistivity and higher coefficient variation than soils without plant, implying the effect of root system on the resistivity, in which may caused by. This result suggests plant root activities regulating the soil water dynamics mainly control the variation of electrical resistivity over soil textural difference. Therefore the identification of water uptake zone would highly be correlated to plant root activities, thus ERT will be feasible approach to identify spatial characteristics of a plant root activity.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.24 no.4
• /
• pp.548-561
• /
• 2019

The surfgrass Phyllospadix japonicus is a dominant seagrass species playing critical ecological roles on the eastern coast of Korea. However, few studies have been conducted on the ecological characteristics of this species, generally due to the turbulent water conditions in its habitat. In this study, to examine the growth dynamics of P. japonicus, we investigated monthly changes in morphological characteristics, density, biomass, and leaf productivity as well as changes in the underwater irradiance, water temperature, and water column nutrient concentrations of its habitat from August 2017 to July 2018. Underwater irradiance and water temperature showed clear seasonal changes increasing in spring and summer and decreasing in fall and winter. Nutrient availability fluctuated substantially, but did not display any distinct seasonal trend. Morphological characteristics, shoot density, biomass, and leaf productivities of P. japonicus exhibited significant seasonal variations, increasing in spring and decreasing in fall months. Spadix of P. japonicus occurred from March to August, with the maximum spadix percentage(15.8%) occurred in May 2018. The average leaf productivity of P. japonicus per shoot and area were 2.1 mg sht^-1 d^-1 and 7.5 g m^-2 d^-1, respectively. The optimum water temperature for the growth of P. japonicus in this study was between 13-14℃. The productivity of P. japonicus was not correlated with underwater irradiance, water temperature and nutrient concentrations. These results suggest that the study site provide sufficient amount of underwater irradiance, suitable water temperature range and nutrients for the growth of P. japonicus.

• Journal of applied mathematics & informatics
• /
• v.20 no.1_2
• /
• pp.197-208
• /
• 2006

This paper deals with the exact solution of surface gravity waves in an ocean with irregular bed topography. In order to obtain water surface elevation and run-up of infra-gravity waves when the bed is either wavy or exponential, closed form solutions are obtained. Numerical computations indicate that when solitary wave or sinusoidal wave conditions are applied at the boundary, water surface elevation attains near Gaussian profile.

• International Journal of Air-Conditioning and Refrigeration
• /
• v.10 no.1
• /
• pp.19-30
• /
• 2002

This paper addresses characteristics of compressible flow dynamics inside a pipe with an accumulator and an inlet orifice. It also presents a simple but stable numerical method associated with the accumulator-orifice calculation. In particular, a focus is given to developing a method of finding an optimum design of the accumulator-orifice system (i.e., the accumulator size and the throttle resistance) that gives the most effective dissipation of the water-hammering problem. It is found that there exists indeed an optimum set of parameter values for the most effective dissipation of the wave energy.

• Korean System Dynamics Review
• /
• v.9 no.2
• /
• pp.105-128
• /
• 2008

City of Gyeongju's referendum finally offered the long-waited low-level radioactive waste disposal site in November 2005. Gyeongju's positive decision was due to the various economic rewards and incentives the national government promised to the city. 300 billion won for an accepting bonus, the location of the headquarter building of the Korean Hydro and Nuclear Power Co., and the accelerator research center and 3.25 trillion won for supporting regional development program implementation. All of the above will affect the city's infrastructure and the citizens' economic and social lives. Population, land use, economic structure, SOC and quality of life will be affected. Some will be very positive, and some will be negative. This research project will see the future of the city and forecast the demographic, economic, physical and environmental changes of the city via computer simulation's system dynamics technique. This kind of simulation will help City of Gyeongju's what to prepare for the future. The population forecasting of the year 2046 will be 662,424 with the waste disposal site, and 327,274 without the waste disposal site in Gyeongju. The waste disposal site and regional supporting program will increase 184,246 Jobs more with 1,605 agriculture and fishery, 5,369 manufacturing shops and 27,577 shops. The population increase will bring 96,726 more houses constructed in the city. Land use will also be affected. More land will be developed. And road, water plant and waste water plant will be expanded as much. The city's financial structure will be expanded, due to the increased revenues from the waste disposal site, and property tax revenues from the middle-class employees of the company, and the high-powered scientists and technologists from the accelerator research center. All in all, the future of the city will be brighter after operating the nuclear waste disposal site inside the city.

• Nutritional Sciences
• /
• v.8 no.2
• /
• pp.83-88
• /
• 2005

This study was to investigate the effect of psyllium seed husk (PSYL) on postprandial glucose control and insulin secretion dynamics in Sprague-Dawley rats. In experiment 1, the rise in postprandial serum glucose was monitored during a 240-min period using a maltose loading test In normal rats given 16.6 mg/l00 g B.W./ml of PSYL orally, all the blood glucose levels during the 240-min period did not show statistically significant differences from the corresponding levels in normal rats given water. However, in streptozotocin-induced diabetic rats given the same amount of PSYL, the blood glucose level at 30 min was significantly lower than that in diabetic rats given water, and the peak time of the rise in the postprandial glucose was delayed In experiment 2, the normal (N) and diabetic (Db) rats were given PSYL (25 mg/l00 g B.W./ml/day) orally for 5 days. Blood samples were collected in order to measure the s-glucose and s-insulin levels. The final s-glucose level at day 5 in Db-PSYL was significantly lower than that in the corresponding control rats (Db-CONT) and the final s-insulin level in Db-PSYL was significantly greater than that in Db-CONT. In vitro 40-min pancreas perfusion was performed at day 5 in order to examine the insulin secretion dynamics. Results showed that the amounts of insulin secreted during the first phase (11-20 min) and the second phase (21-40 min) in the Db-PSYL were significantly greater than those in Db-CONT. Therefore, it is concluded that psyllium seed husk could be beneficial for controlling postprandial glucose levels in the stretozotocin-induced diabetic rats, and it may be partially mediated by insulin secretion dynamics.