• Ocean and Polar Research
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• v.31 no.3
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• pp.247-255
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• 2009

We measured phosphate benthic fluxes and conducted phosphate adsorption experiments in order to find out the effects of adsorption on phosphate benthic fluxes in the intertidal sediments of Keunso Bay during summer and winter. Organic carbon contents showed little variation with season at St. S1, but noticeable changes were observed at St. S2, which were three times higher in winter than in summer. The higher organic carbon contents in winter resulted from the bloom of benthic algae in surface sediments. Pore water phosphate concentrations were much higher in summer than in winter. The higher phosphate concentration in summer was probably due to the faster remineralization rate of organic matter in summer. At St. S1, benthic fluxes of phosphate showed a negative value in summer and a positive value in winter. However, St. S2 had a negative benthic flux both in summer and winter. The negative benthic flux was ascribed to the phosphate adsorption on iron oxides in surface sediments. The equilibrium concentrations of phosphate obtained from the adsorption experiment were three times higher at St. S1 than at St. S2. The relatively high adsorption coefficient and low equilibrium concentration indicated that phosphate was strongly adsorbed on the surface sediments of Keunso Bay. The strong adsorption affinity significantly reduced benthic fluxes of phosphate in the intertidal sediments.

• Ocean and Polar Research
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• v.38 no.4
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• pp.271-286
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• 2016

We evaluate the temperature and salinity fields in the East Sea reproduced by the global ocean reanalysis data using HYbrid Coordinate Ocean Model (HYCOM for short). Temporal correlation of Sea Surface Temperature (SST) change between HYCOM and the Group for High Resolution Sea Surface Temperature (GHRSST) are higher in summer than winter. Though distributions of temperature and salinity in the HYCOM are similar to those from historical data (World Ocean Atlas 2013 V2), salinity in the HYCOM is lower (highter) in the region where the salinity is high (low). Temperature fields in the Ulleung basin of HYCOM are quite similar to those derived from Pressure-recording Inverted Echo Sounder (PIES), such as the correlation coefficient is higher than 0.7. This indicates that the HYCOM represents well the circulation and meso-scale phenomena in the Ulleung basin.

• Ocean and Polar Research
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• v.39 no.2
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• pp.73-84
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• 2017

The probability distribution of ichthyoplankton is important for enhancing the precision of sampling while reducing unnecessary surveys. To estimate the ichthyoplankton detection proportion (IDP) and its margin of error (ME), the monitoring information of the chub mackerel's (Scomber japonicus) ichthyoplankton presence-absence sampling data has been were collected over approximately 30 years (from 1982 to 2011) in the Korean coastal seas. Based on the computed spatial distributions of the mackerel's IDP and ME, the confidence interval (CI) range, defined as 2 ME, decreases from approximately 80% to 40% as the sample size n increases from 4 to 24 and the ME is approximately 40% in the typical (seasonal survey) case n = 4 per year. The IDP and ME off Jeju Island are relatively high at the 0.5-degree smoothing level. After increasing the spatial smoothing level to 1.0-degree, the ME decreased, and the spatial distribution pattern also changed due to the over-smoothing effects. In this study, the 0.5-degree smoothing is more suitable for the distribution pattern than the 1.0-degree smoothing level. The area of the high IDP and the low ME on the mackerel's ichthyoplankton was similar to the estimated spawning ground in the Korean peninsula. This information could contribute to enhancing for the spawning ecology surveys.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.3
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• pp.445-450
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• 2015

Generally, Low Earth Orbit (LEO) satellites are used to collect image or video from earth's surface. The collected data are stored on-board and/or transmitted to the main ground station directly or via polar ground station using terrestrial line. Today, an intersatellite link between a LEO and a GEO satellite allows transmission of the collected data to the main ground station through the GEO satellite. In this study, an approach for a continuous communication starting from LEO through GEO to ground station is proposed by determining the optimum ground station locations. In doing so, diverse ground stations help to determine the GEO orbit as well. Cross-correlation of the long term daily rainfall averages are multiplied with the logarithmic correlation of the sites to calculate the joint correlation of the diverse ground station locations. The minimum values of this joint correlation yield the optimum locations of the ground stations for Q/V-band communication and satellite control operations. Results for several case studies are listed.

• Textile Coloration and Finishing
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• v.23 no.2
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• pp.76-82
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• 2011

Ultra High molecular weight polyethylene(UHMWPE) films were photooxidized by UV/ozone irradiation. Reflectance of the irradiated films decreased in the low wavelength regions of visible light, indicating destructive interference of visible light due to roughened surface. The UV treatment developed the nano-scale roughness on the UHMWPE films surface, which increased by two-fold from 82.6 to 156.6nm in terms of peak-valley roughness. The UV irradiation caused the oxygen content of the UHMWPE film surface to increase. Water contact angle decreased from $83.2^{\circ}$ to $72.9^{\circ}$ and surface energy increased from 37.8 to 42.6mJ/$m^2$ with increasing UV energy. The surface energy change was attributed to significant contribution of polar component rather than nonpolar component indicating surface photooxidation of UHMWPE films. The increased dyeability to cationic dyes may be due to the photochemically introduced anionic and dipolar dyeing sites on the film surfaces.

• Economic and Environmental Geology
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• v.32 no.1
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• pp.43-51
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• 1999

In order to remediate hazardous waste site, a process of electrokinetically purging chemicals from saturated soil is examined by laboratory experiments. Electrokinetic soil remediation is one of the most promising soil decontamination processes that habe igh removal efficiency and time-effectiveness in low-permeability soils such as clay. Being combined with several mechanisms-electromigration, elec troosmosis, diffusion and electrolysis of water, electrokinetic soil processing can remove non-polar organics as well as ionic contaminants. The objectives of this study are; 1) the exploration of the feasibility of electrokinetic soil processing on the removal of heavy metals, 2) the investigation of applicability to the tailing-soils in aban doned mining area, 3) the examination of effects of soil pH and conductivity on the transport phenomena of elements in soils, and 4) the investigation of the applicability of the ionexchange membrance to the efficient collection of heavy metals removed from contaminated soils. With the result of this study, it is suggested that the removal efficiency is significantly influenced by applied voltage & current, type of purging solutions, soil pH, permeability and zeta potentials of soil. Although further study should be needed, it is possible to collect removed heavy metals with ion-exchange membrance in cathode compartment.

• Journal of Power System Engineering
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• v.17 no.5
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• pp.30-37
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• 2013

For vessels operating in the cold climate regions, the ballast water inside or hopper tanks above the waterline may be frozen, starting at the top of the tank and at the side walls. Therefore, countermeasures against freeze-up of the ballast tank such as air-bubbling system, hot steam injecting system, heating coil system and water circulating system are taken to prevent freeze-up phenomenon; however, there are no rigorous investigations of anti-freezing to examine the effectiveness and validity of systems against freeze-up of the ballast tank, in which the temperatures are about -$25^{\circ}C$ (ambient air temperature) and $0^{\circ}C$ (sea water), respectively. In this paper, to ensure reasonable specifications for cold regions if the measures from the above-mentioned systems against freeze-up are effective, the phenomenon of ballast tank freeze-up is simulated and discussed in low temperature conditions. With the results using the commercial CFD code, CFX 14, the most cost-effective solution is conducted to prevent being frozen along the outer surface.

• Macromolecular Research
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• v.13 no.5
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• pp.409-417
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• 2005

The surface of rutile titania nanoparticles was chemically modified by reacting with alkoxy silane. The surface and rheological properties in silicone oil having a wide range of viscosity were investigated. Total surface free energy($\gamma_S$) of the titania particles decreased from 53.12 to 26.94 mJ/$m^2$ as the silane used for surface treatment was increased from 0 to 5.0 wt$\%$. The surface free energy of neat silane was 25.5 mJ/$m^2$, which is quite close to that oftitania particles treated with 5.0 wt$\%$ silane. Due to the hydrophobic nature oftreated-titania, the contact angle was accordingly higher for polar solvent in the order of water>ethylene glycol> formamide>$\alpha$-bromonaphthalene. In sum of rheological behavior, as the applied shear stress or viscosity of the silicone oil increased, the titania particles tend to form layers and agglomerated clusters, showing shear-thinning and shear-thickening behaviors, sequentially. A good dispersion of discrete titania particles obeying a Newtonian flow behavior was achieved at a surface energy or low concentration of silane-treated titania particles in hydrophobic silicone oil.

• Ocean and Polar Research
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• v.21 no.2
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• pp.117-126
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• 1999

To meet increasing needs for environmentally sustainable management of coastal area, there has been compelling pressure to establish a cost-effective and long-term coastal water quality (CWQ) monitoring system. A remote CWQ monitoring system, STAMP, has been developed and is in operation along the route between Kyema harbor and Anma Island in the southwestern coastal area of Korea. STAMP uses a PCS phone as a telemetry unit to transmit acquired data for monitoring general water quality parameters, and a routinely operating coastal passenger ship or car ferry. STAMP has various merits of low-cost operations; long-term monitoring with secure instrumentation; and stable real-time telemetry of acquired data with-out the loss and noise. It is expected that the system will serve as a very useful tool in the CWQ managing programs of Korea taking the advantage of many coastal passenger ships in various routes including the ships departing from the coastal industrial cities. The acquired data compiled on suspended surface sediment concentrations (SSSC) will be also valuably helpful in understanding the sediment budget across the routes of the vessel.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.43.2-43.2
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• 2009

Electron microbursts are the intense electron precipitation which durations are less than one second. We measured the energy spectra of the microbursts from 170 keV to 340 keV with solid state detectors aboard the low-altitude (680km), polar-orbiting Korean STSAT-1 (Science and Technology SATellite). The data showed that the loss cone at these energies is empty except when microbursts abruptly appear and fill the loss cone in less than 50 msec. This fast loss cone filling requires pitch angle diffusion coefficients larger than ~ 10-2rad2/sec, while ~10-5 rad2/sec was proposed by a wave particle interaction theory. We recalculated the diffusion coefficient, and reviewed of electron microburst generation mechanism with test particle simulations. This simulation successfully explained how chorus waves make pitch angle diffusion within such short period. From considering the resonance condition between wave and electrons, we also showed ~ 100 keV electrons could be easily aligned to the magnetic field, while ~ 1MeV electrons filled loss cone partially. This consideration explained why precipitating microbursts have lower e-folding energy than that of quasi-trapped electrons, and supports the theory that relativistic electron microbursts that have been observed by satellite in-situ measurement have same origin with ~100 keV electron microbursts that have been usually observed by balloon experiments.