• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.26 no.2
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• pp.110-123
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• 2021

We investigated geochemical constituents of pore-water and sediment, rates of organic carbon (C_org) oxidation and sulfate reduction (SR), and benthic nutrient flux (BNF) to elucidate characteristic of C_org oxidation and its control in the coastal area near Lake Shihwa. The study sites were selected in the vicinity of Soraepogu (E0), Songdo tidalflat (E1) and Oido dock (E3) and in front of floodgate Shihwa tidal plant (E5). The C_org contents in the sediments and concentrations of ammonium and phosphate in pore water exhibited the highest value at EO, and gradually decreased toward the outer sea (E1, E3, E5). Rates of anaerobic C_org oxidation (260.6 mmol C m^-2 d^-1) and SR (91.4 mmol S m^-2 d^-1) at E0 were 4-9 and 6-54 times higher than at the site of outer sea (E1, E3, E5). Rates of SR at E3 and E5 accounted for 11-23% of anaerobic C_org oxidation, whereas it comprised 47-70% of anaerobic C_org oxidation at E0 and E1. Rates of C_org oxidation and SR showed a highly positive correlation with the concentration of dissolved organic carbon (r² = 0.795 and 0.777, respectively). The BNF at E0, E1, and E3 accounted for 120-510% and 26-178%, respectively, of the N and P required for primary production in the water column. Overall results suggest that the C_org oxidation in the sediment controlled by concentration of dissolved organic carbon in the pore water and the excessive C_org oxidation stimulates the benthic nutrient flux, which may cause a phytoplankton bloom in the water column.

• Geophysics and Geophysical Exploration
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• v.13 no.3
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• pp.249-255
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• 2010

Since the 1990's, a number of ULF geomagnetic disturbance associated with earthquake occurrences have actively been reported, and polarization analysis of geomagnetic fields becomes one of potential candidates to be capable of predicting short-term earthquake. This study develops the modified polarization analysis method based on the previous studies, and analyzes three-component geomagnetic fields obtained at Cheongyang geomagnetic observatory using the developed method. A daily polarization value (the ratio of spectral power of horizontal and vertical geomagnetic field) is calculated with a focus on the 0.01 Hz band, which is known to be the most sensitive to seismogenic ULF radiation. We analyze a total of 10 months of geomagnetic data obtained at Cheongyang observatory, and compare the polarization values with the Kp index and the earthquake occurred in the analysis period. The results show that there is little correlation between the temporal variations of polarization values and Kp index, but remarkable increases in polarization values are identified which are associated with two earthquakes. Comparison the polarization values obtained at Cheongyang and Kanoya observatory indicates that the increases of polarization values at Cheongyang might be due to not global geomagnetic induction but the locally occurred earthquakes. Furthermore, these features are clearly shown in normalized polarization values, which take account in the statistical characteristics of each geomagnetic field. On the basis of these results, polarization analysis can be used as promising tool for monitoring the earthquake-precursory phenomenon.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.6
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• pp.781-787
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• 2014

The dimensionless extinction constants of particulate matter for F-76 diesel and JP-8 aviation fuels were measured at both 633 nm and 853 nm in the transmission cell where the simultaneous gravimetric measurement of PM concentration is compared to the light extinction measurement. For the F-76 diesel PM, the average value of the dimensionless extinction constants at 633 nm was 8.8 whereas that of the dimensionless extinction constants for JP-8 was 9.8 at the same wavelength. As the wavelength is increased to 853 nm, the average value for the F-76 diesel was reduced to 8.2 whereas that for JP-8 was decreased to 8.9.

• Korean Journal of Remote Sensing
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• v.40 no.4
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• pp.387-396
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• 2024

Most very high-resolution (VHR) satellite images provide rational polynomial coefficients (RPC) data to facilitate the transformation between ground coordinates and image coordinates. However, initial RPC often contains geometric errors, necessitating correction through matching with ground control points (GCPs). A GCP chip is a small image patch extracted from an orthorectified image together with height information of the center point, which can be directly used for geometric correction. Many studies have focused on area-based matching methods to accurately align GCP chips with VHR satellite images. In cases with seasonal differences or changed areas, edge-based algorithms are often used for matching due to the difficulty of relying solely on pixel values. However, traditional edge extraction algorithms,such as canny edge detectors, require appropriate threshold settings tailored to the spectral characteristics of satellite images. Therefore, this study utilizes deep learning-based edge information that is insensitive to the regional characteristics of satellite images for matching. Specifically,we use a pretrained pixel difference network (PiDiNet) to generate the edge maps for both satellite images and GCP chips. These edge maps are then used as input for normalized cross-correlation (NCC) and relative edge cross-correlation (RECC) to identify the peak points with the highest correlation between the two edge maps. To remove mismatched pairs and thus obtain the bias-compensated RPC, we iteratively apply the data snooping. Finally, we compare the results qualitatively and quantitatively with those obtained from traditional NCC and RECC methods. The PiDiNet network approach achieved high matching accuracy with root mean square error (RMSE) values ranging from 0.3 to 0.9 pixels. However, the PiDiNet-generated edges were thicker compared to those from the canny method, leading to slightly lower registration accuracy in some images. Nevertheless, PiDiNet consistently produced characteristic edge information, allowing for successful matching even in challenging regions. This study demonstrates that improving the robustness of edge-based registration methods can facilitate effective registration across diverse regions.

• Journal of Astronomy and Space Sciences
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• v.22 no.2
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• pp.147-174
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• 2005

To understand the physical processes that control the high-latitude lower thermospheric dynamics, we quantify the forces that are mainly responsible for maintaining the high-latitude lower thermospheric wind system with the aid of the National Center for Atmospheric Research Thermosphere-Ionosphere Electrodynamics General Circulation Model (NCAR-TIEGCM). Momentum forcing is statistically analyzed in magnetic coordinates, and its behavior with respect to the magnitude and orientation of the interplanetary magnetic field (IMF) is further examined. By subtracting the values with zero IMF from those with non-zero IMF, we obtained the difference winds and forces in the high-latitude 1ower thermosphere(<180 km). They show a simple structure over the polar cap and auroral regions for positive($B_y$ > 0.8|$\overline{B}_z$ |) or negative($B_y$ < -0.8|$\overline{B}_z$|) IMF-$\overline{B}_y$ conditions, with maximum values appearing around -80$^{\circ}$ magnetic latitude. Difference winds and difference forces for negative and positive $\overline{B}_y$ have an opposite sign and similar strength each other. For positive($B_z$ > 0.3125|$\overline{B}_y$|) or negative($B_z$ < -0.3125|$\overline{B}_y$|) IMF-$\overline{B}_z$ conditions the difference winds and difference forces are noted to subauroral latitudes. Difference winds and difference forces for negative $\overline{B}_z$ have an opposite sign to positive $\overline{B}_z$ condition. Those for negative $\overline{B}_z$ are stronger than those for positive indicating that negative $\overline{B}_z$ has a stronger effect on the winds and momentum forces than does positive $\overline{B}_z$ At higher altitudes(>125 km) the primary forces that determine the variations of tile neutral winds are the pressure gradient, Coriolis and rotational Pedersen ion drag forces; however, at various locations and times significant contributions can be made by the horizontal advection force. On the other hand, at lower altitudes(108-125 km) the pressure gradient, Coriolis and non-rotational Hall ion drag forces determine the variations of the neutral winds. At lower altitudes(<108 km) it tends to generate a geostrophic motion with the balance between the pressure gradient and Coriolis forces. The northward component of IMF By-dependent average momentum forces act more significantly on the neutral motion except for the ion drag. At lower altitudes(108-425 km) for negative IMF-$\overline{B}_y$ condition the ion drag force tends to generate a warm clockwise circulation with downward vertical motion associated with the adiabatic compress heating in the polar cap region. For positive IMF-$\overline{B}_y$ condition it tends to generate a cold anticlockwise circulation with upward vertical motion associated with the adiabatic expansion cooling in the polar cap region. For negative IMF-$\overline{B}_z$ the ion drag force tends to generate a cold anticlockwise circulation with upward vertical motion in the dawn sector. For positive IMF-$\overline{B}_z$ it tends to generate a warm clockwise circulation with downward vertical motion in the dawn sector.