• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.20 no.4
• /
• pp.199-205
• /
• 2015

Nitrogen and phosphorus are the limiting elements for growth of phytoplankton, which is a major primary producer of marine ecosystem. Incidentally the stoichiometry of N/P of ocean waters, measured by the (nitrate + nitrite)/phosphate ratio converges to a constant of 16. This characteristic ratio has been used widely for the understanding the ecosystem dynamics and biogeochemical cycles in the ocean. In the East Sea, several key papers were issued in recent years regarding the climate change and its impact on ecosystem dynamic and biogeochemical cycles using N/P ratio because the East Sea is a "miniature ocean" having her own meridional overturning circulation with the appropriate responding time and excellent accessibility. However, cited N/P values are different by authors that we tried to propose a single representative value by reanalyzing the historical nutrient data. We present N/P of the East Sea as $12.7{\pm}0.1$ for the year 2000. The ratio reveals a remarkable consistency for waters exceeding 300m depth (below the seasonal thermocline). We recommend to use this value in the future studies and hope to minimize confusion for understanding ecosystem response and biogeochemical cycles in relation to future climate change until new N/P value is established from future studies.

• Journal of the Korean Electrochemical Society
• /
• v.6 no.3
• /
• pp.169-173
• /
• 2003

Electrochemical capacitor made with metal oxide electrode uses rapid and reversible protonation/deprotonation of metal oxide material under the aqueous acidic solution, generally. Electrochemical stability window of aqueous electrolyte-type capacitor is narrow compared to that of organic electrolyte-type capacitor. Electrochemical characteristics of electrochemical capacitor made with metal oxide electrode and lithium or ammonium cation based organic electrolyte were evaluated. Electrochemical capacitor based on $RuO_2$ electrode material and 1M $LiPF_6$ in mixed solvents of EC, DEC, and EMC has anodic and cathodic specific capacitance of 145 and $142F/g-RuO_2{\cdot}nH_2O$, respectively, by using cyclic voltammetry with scan rate of 2mV/sec $g-RuO_2$ in potential range of $2.0\~4.2V(Li|Li^+))$.

• Journal of the Korean Ceramic Society
• /
• v.35 no.6
• /
• pp.594-602
• /
• 1998

Titanium hydroxide (TiO({{{{ {OH }_{2 } }})) fine particles were produced by the reverse micelle technique. For the formation of titanium hydroxide (TiO({{{{ {OH }_{2 } }})) particles with the technique reversed micellar solution was prepared by solubilizing water into organic solvent (isooctane) with a surfactant and titanium alkoxide (tetraisopropyl orthotitanate) diluted with isopropyl alcohol was added to the reversed micellar solution. The hdrolyzed species (TiO({{{{ {OH }_{2 } }})) was formed by the hydrolysis of titanium alkoxide and titanium dioxide is then formed by the condensation of the hydrolyzed species. There are several process variables such as surfactants concentration of surface cosurfactant hydrolysis temperature and pH. In this work the ef-fects of process variables on paticle shapes particle size distribution and paticle agglomeration were bi-nodal for an anionic surfactant(AOT) in the whole range of temperature pH and surfactant concentration of this experiment. The addition of ethanol as a cosurfactant resulted in narrow particle size distribution of the experiment. The additiono of ethanol as a cosurfactant resulted in narrow particle size distribution and 0.12${\mu}{\textrm}{m}$ of smaller average particle diameter. FT-IR spectrum of particles shows the absorption peak of Ti-OH bonding and Ti-O bonding. An exothermic peak around 41$0^{\circ}C$ in TGA-DTA curve shows that crys- tallized anatase phase appears and completely transits to anatase around 45$0^{\circ}C$.

• Nuclear Engineering and Technology
• /
• v.25 no.1
• /
• pp.51-62
• /
• 1993

A computational program ［TDET］ of the particle transport equation is developed on radiation shielding problem in two-dimensional cartesian geometry based on the discrete element method. Not like the ordinary discrete ordinates method, the quadrature set of angles is not fixed but steered by the spatially dependent angular fluxes. The angular dependence of the scattering source term in the particle transport equation is described by series expansion in spherical harmonics, and the energy dependence of the particles is considered as well. Three different benchmark tests are made for verification of TDET : For the ray effect analysis on a square absorber with a flat isotropic source, the results of TDET calculation are quite well conformed to those of MORSE-CG calculation while TDET ameliorates the ray effect more effectively than S$_{N}$ calculation. In the analysis of the streaming leakage through a narrow vacuum duct in a shield, TDET shows conspicuous and remarkable results of streaming leakage through the duct as well as MORSE-CG does, and quite better than S$_{N}$ calculation. In a realistic reactor shielding situation which treats in two cases of the isotropic scattering and of linearly anisotropic scattering with two groups of energy, TDET calculations show local ray effect between neighboring meshes compared with S$_{N}$ calculations in which the ray effect extends broadly over several meshes.eshes.

• Ecology and Resilient Infrastructure
• /
• v.9 no.4
• /
• pp.237-246
• /
• 2022

Owing to their high bioproductivity and unique physical environment, estuarine wetlands are gaining importance in national biodiversity management and habitat conservation. With regard to conservation and management of estuarine wetlands, this study analyzed the ecological characteristics of Gahwacheon Estuarine Wetland, an open estuary with various habitat types. Data from vegetation and biotic surveys have shown that 12 plant communities of five physiognomic vegetation types, including lentic herbaceous vegetation, halophytic herbaceous vegetation, and chasmophytic herbaceous vegetation. Due to the discharge of Namgang Dam and the effect of the tide, vegetation are distributed along the narrow waterside area. In terms of biodiversity, a total of 715 species, including 12 endangered wildlife species, were identified. Species diversity was relatively high in sections I and III where various riverbed structures and microhabitats were distributed. Due to the effect of the brackish water area following the inflow of seawater, endangered wildlife of various functional groups were also found to be distributed, indicating the high conservation value of that area. The collection of ecological information of the Gahwacheon Estuarine Wetland can be used as a framework for establishing the basis for conservation and management of the estuarine ecosystem and support policy establishment.

• The Journal of the Petrological Society of Korea
• /
• v.7 no.2
• /
• pp.111-131
• /
• 1998

The migmatitic gneiss in the Odesan Gneiss Complex has small amount of quartzite, amphibolite and marble and the Kuryong Group which contact with migmatitic gneiss unconformitly, also contains some amphibolite. Preview studies of this area had regarded that the amphibolites contact with marble had been produced by metasomatism from the pelitic and calcareous sediments mixtures, but the amphibolite is reinterpreted as igneous origin. $SiO_2$ content of the amphibolite is 45.9~52.7 wt%, which corresponds to basaltic composition. MgO content has narrow range (4.6~6.87 wt%) and major and trace element are plotted against MgO,$TiO_2, P_2O_5$, Hf, Zr are reduced and Cr and Ni are increased their content with increasing MgO. This phenomenon indicates that the basaltic magma as the protolith of the amphibolite had frationated with the crystallization of the pyroxene and/or olivine. REE pattern has smoothly decrease from LREE to HREE. Eu/Eu(0.83~1.19) show the flat Eu anomaly, which indicate small fractional crystallization of plagioclase. HREE is enriched in the garnet-bearing amphibolites. Several discrimination diagram for the basaltic magma show that the amphibolite of the study area is originated tholeiitic basaltic magma indicating continental rift environment. Due to determine the metamorphic condition garnet-hornblende geothermometry and hornblende-plagioclase geobarometry are used. Peak metamorphic temperature range of the amphibolite $788~870^{\circ}C$ and is deduced toward the northeastern part. The calculated temperature from the amphibolite has slightly higher than the temperature of the metapelites but the trend of metamorphic grade which decrease from western to eastern part progradly is similar to each other. The metamorphic pressure calculated by garnet- hornblede-plagioclase geobarometry is 4~5kb. But ilmenite-plagioclase pair enclosed in garnet show 8 kb at $700^{\circ}C$ by garnet-ilmenite-rutile-plagioclase geobarometery. The zonal profile of garnet in sample 84 shows the bell-shape profile, which grossular content decreases whereas pyrope content increases progressively. This means that the amphibolite has undergone the clockwise P-T-t path which is shown in the migmatitic gneiss of the Odesan Gneiss Complex.

• Korean Journal of Heritage: History & Science
• /
• v.52 no.1
• /
• pp.272-287
• /
• 2019

The Korean Demilitarized Zone (DMZ) was established in 1953 by the Korean War Armistice Agreement. It extends from the estuary of the Imjin River, in the west, to the coast of the East Sea. It is 4 km in width and 148 km in length. However, the ecosystems of the civilian control zone (CCZ) located between the southern border of the DMZ and the civilian control line (CCL) and the CCZ in the estuary of the Han River and the Yellow Sea are similar to those in the DMZ, and, therefore, the ecosystems of the DMZ and the CCZ are collectively known as the "ecosystems of the DMZ and its vicinities." The flora in the DMZ and its vicinities is composed of 1,864 species, which accounts for about 42% of all the vascular plant species on the Korean Peninsula and its affiliated islands. Conducting a detailed survey on the vegetation, flora, and fauna in the DMZ is almost impossible due to the presence of landmines and limitations on the time allowed to be spent in the DMZ. However, to assess the environmental impact of the Munsan-Gaesong railroad reconstruction project, it was possible to undertake a limited vegetation survey within the DMZ in 2001. The vegetation in Jangdan-myeon, in Paju City within the DMZ, was very simple. It was mostly secondary forests dominated by oaks such as Quercus mongolica, Q. acutissima, and Q. variabilis. The other half of the DMZ in Jangdan-myeon was occupied by grassland composed of tall grasses such as Miscanthus sinensis, M. sacchariflorus, and Phragmites japonica. Contrary to the expectation that the DMZ may be covered with pristine mature forests due to more than 60 years of no human interference, the vegetation in the DMZ was composed of simple secondary forests and grasslands formed on former rice paddies and agricultural fields. At present, the only legal protection system planned for the DMZ is the Natural Environment Conservation Act, which ensures that the DMZ would be managed as a nature reserve for only two years following Korean reunification. Therefore, firstly, the DMZ should be designated as a site of domestic legally protected areas such as nature reserve (natural monument), scenic site, national park, etc. In addition, we need to try to designate the DMZ as a UNESCO Biosphere Reserve or as a World Heritage site, or as a Ramsar international wetland for international cooperation. For nomination as a world heritage site, we can emphasize the ecological and landscape value of the wetlands converted from the former rice paddies and the secondary forests maintained by frequent fires initiated by military activities. If the two Koreas unexpectedly reunite without any measures in place for the protection of nature in the DMZ, the conditions prior to the Korean War, such as rice paddies and villages, will return. In order to maintain the current condition of the ecosystems in the DMZ, we have to discuss and prepare for measures including the retention of mines and barbed-wire fences, the construction of roads and railroads in the form of tunnels or bridges, and the maintenance of the current fire regime in the DMZ.

• Ocean and Polar Research
• /
• v.25 no.2
• /
• pp.183-200
• /
• 2003

In order to assess the ecological changes induced by organic pollutants of the Shihwa Lake, BPI (Benthic Pollution Index) based on the benthic faunal community was employed. It was modified from Infaunal Trophic Index (ITI), and recommended as a pollution detecting method for the environmental assessment. The BPI values were calculated from the benthos data, which were collected for three terms: in 1980, before the Shihwa Lake was built up; in 1994-1997, which the Shihwa Lake was completely isolated from the outer seawater; in 1997-1999, after inflow of the outer seawater. Since the Shihwa Dike was constructed in February 1994, the pollution intensity of the lake had been increased from the narrow and inner part of the former Gyeonggi Bay and spread fast along the coast line of the Shihwa Lake. Then, in 1996 it showed the very high BPI levels all around the Lake. This serious polluted condition had been lasted till 1997, when the inflow of the seawater was begun. In 1998, from the nearest part of the Shihwa Gate, the BPI levels gradually became low in most area of the Lake, except its inner and narrow part. These greatly lowered BPI levels mean that the seawater inflow could be assumed to affect positively in the lake. Furthermore, BPI gave the same results from the other environmental assessment based on the abundance and the species richness of macrobenthic community. It shows that BPI could be useful as an effective method to assess the marine environment and evaluate the status of environmental conditions.

• Journal of the Korean Chemical Society
• /
• v.19 no.5
• /
• pp.386-393
• /
• 1975

Polystyrene and polystyrene blended with SBR were subjected to the mechanical degradation by roll mastication. The results obtained are as follows. 1. For the polystyrene which is blended with SBR, the overall shape of the molecular weight distribution curve moves from the higher molecular weight portion to the lower molecular weight portion, becomes narrower in breadth, and its peak becomes higher as the degradation proceeds. The final molecular weight distribution exhibits a relative uniformity. This is due to the fact that only the polymer molecules with the high molecular weight consisted in original polystyrene are degraded mechanically and produced the polymer molecules with the low molecular weight. 2. The scission number of polystyrene chains increases with mastication time, and the number of degraded polymer chains produced when the polymer is masticated for 100 minutes at 140, 150 and $160^{\circ}C$ are $2.36{\times}10^{20},\;1.76{\times}10^{20}\;and\;1.52{\times}10^{20}$, respectively. 3. The rate of the degradation of polystyrene decreases with the mastication temperature. The activation energy is found to have the negative value, -8.7 kcal/mole. Therefore it is indicated that the mechanical degradation is a chemical process of which the activation energy is supplied mechanically.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.18 no.1
• /
• pp.32-39
• /
• 2013

Although space-borne satellites are useful in obtaining information all around the world, they cannot observe at a suitable time and place. In order to overcome these limitations, an airborne remote sensing system was developed in this study. It is composed of a SAR sensor and a thermal infrared sensor. Additionally GPS, IMU, and thermometer/hygrometer were attached to the plane for radiometric and geometric calibration. The brightness of SAR image varies depending on surface roughness, and capillary waves on the sea surface, which are easily generated by sea winds, induce the surface roughness. Thus, sea surface wind can be estimated using the relationship between quantified SAR backscattering coefficient and the sea surface wind. On the other hand, thermal infrared sensor is sensitive to measure object's temperature. Sea surface temperature is obtained from the thermal infrared sensor after correcting the atmospheric effects which are located between sea surface and the sensor. Using these two remote sensing sensors mounted on airplane, four test flights were carried out along the west coast of Korea. The obtained SAR and thermal infrared images have shown that these images were useful enough to monitor coastal environment and estimate marine meteorology data.