• Journal of Soil and Groundwater Environment
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• v.13 no.5
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• pp.33-46
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• 2008

A series of three-dimensional numerical simulations using a generalized multidimensional hydrodynamic dispersion numerical model is performed to simulate effectively and to evaluate quantitatively impacts of fault existence on densitydependent groundwater flow and salt transport in coastal aquifer systems. A series of steady-state numerical simulations with calibration is performed first for an actual coastal aquifer system which contains a major fault. A series of steadystate numerical simulations is then performed for a corresponding coastal aquifer system which does not have such a major fault. Finally, the results of both numerical simulations are compared with each other and analyzed. The results of the numerical simulations show that the major fault produces hydrogeologically significant heterogeneity and true anisotropy in the actual coastal aquifer system, and density-dependent groundwater flow, salt transport, and seawater intrusion patterns in the coastal aquifer systems are intensively and extensively dependent upon the existence or absence of such a major fault. Especially, the major fault may act as a pathway for groundwater flow and salt transport along the direction parallel to its plane, while it may also behave as a barrier against groundwater flow and salt transport along the direction perpendicular to its plane.

• Journal of Environmental Science International
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• v.30 no.5
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• pp.413-424
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• 2021

In this study, we quantitatively analyze the effect of ocean emission sources on the simulated O₃ concentrations in South Korea using the community multi-scale air quality (CMAQ) model. To analyze changes in O₃ concentrations by ocean emissions, two different CMAQ simulations considering ocean emissions (OE case) and without considering ocean emissions (NE case) were conducted during the Korea-United States air quality (KORUS-AQ) campaign period (May-June 2016). The changes in the simulated O₃ concentrations due to the effect of ocean emissions (OE case-NE case) appeared mostly in the ocean areas (+1.201 ppbv). The effect of ocean emissions was positive during the daytime (+1.813 ppbv), but negative during the nighttime (-0.612 ppbv). Analysis using the integrated process rate (IPR) confirmed that the increase or decrease in O₃ concentration by ocean emissions was mainly due to chemical processes. Further analysis using the integrated reaction rate (IRR) showed that the daytime increase in O₃ concentration was mainly attributable to the increased O₃ production via O + O₂ + M → O₃ + M reaction as photolysis of NO₂ increased due to the added ocean emissions. The nighttime decrease in O₃ concentration was mainly due to the increased O₃ titration by NO (NO + O₃ → O₂ + NO₂) due to the increased NO emission. These results indicate that the changes in the concentration O₃ in the sea area by the effect of ocean emissions are mainly due to increased NO_x emissions. However, there could be a number of uncertainties in ocean emissions data used in this study, thus continuous comparative research using the most updated data will need to be carried out in the future.

• Economic and Environmental Geology
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• v.53 no.6
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• pp.645-654
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• 2020

We present the K-Ar age dating results of <0.1㎛ fraction of the selected fault rocks from the Yangsan fault in the Yeonghae area. Based on the mineralogical characterization, the <0.1㎛ fractions were mostly composed of 1Md illite polytype, or I-S interstratified mineral, which should be formed by fault activation. Therefore, we determined the timings of fault activation events by analyzing K-Ar age-dating for the <0.1㎛ fractions. Accordingly, the activation timings of Yangsan Fault in the Yeonghae area were determined as 45.5±1.1 Ma, 50.9±1.2 Ma, 58.2±1.3 Ma, 60.8±1.4 Ma, 65.3±1.6 Ma, 66.8±1.5 Ma, 67.1±1.5 Ma, and 75.1±1.7 Ma. These results indicate that at least 5-times of major fault events occurred in the Yangsan fault from late Mesozoic to Cenozoic Era. In the outcrop, age dating results tend to be younger age from the location of the oldest sample(75.1±1.7 Ma) toward to the both sides. From the results, it suggests that the fault activation extends from the location of oldest age saple to both sides. This geochronological research of the multiple fault activation ages for the Yangsan Fault will provide crucial information for establishing the tectonic evolution model in the southeastern part of the Korean Peninsula.

• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.27.3-28
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• 2008

In this study, we report a new Monte Carlo ray tracing technique for estimating GOCI (Geostationary Ocean Color Instrument) radiative transfer characteristics and imaging performance simultaneously. First, a full scale GOCI optical model was constructed with measured characteristics at the component level and placed in the geostationary orbit. An optical model of approximated GOCI target area centered at the Korean penninsular was then built using the USGS coastal line data and representative land and sea surface reflectivity data. The light rays launched from a simulated sun model travel to the Earth surface, where they are reflected and scattered. Some of the light rays that are headed to the GOCI model in the orbit were selected and traced, as they have entered into the GOCI aperture. As they pass through each GOCI optical part, the ray path and intensity are adjusted according to the measured characteristics for reflection, transmission, refractive index and surface scattering. The ray-traced imaging and radiative transfer performance indicators confirm that the computer generated GOCI optical system with measured characteristics can be used for in-orbit operation simulation following the designed measurement sequence. The computational technique and its implications as a operation support tool are discussed.

• Journal of the Earthquake Engineering Society of Korea
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• v.25 no.2
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• pp.71-81
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• 2021

This paper presents a real-time, false-pick filter based on deep learning to reduce false alarms of an onsite Earthquake Early Warning (EEW) system. Most onsite EEW systems use P-wave to predict S-wave. Therefore, it is essential to properly distinguish P-waves from noises or other seismic phases to avoid false alarms. To reduce false-picks causing false alarms, this study made the EEWNet Part 1 'False-Pick Filter' model based on Convolutional Neural Network (CNN). Specifically, it modified the Pick_FP (Lomax et al.) to generate input data such as the amplitude, velocity, and displacement of three components from 2 seconds ahead and 2 seconds after the P-wave arrival following one-second time steps. This model extracts log-mel power spectrum features from this input data, then classifies P-waves and others using these features. The dataset consisted of 3,189,583 samples: 81,394 samples from event data (727 events in the Korean Peninsula, 103 teleseismic events, and 1,734 events in Taiwan) and 3,108,189 samples from continuous data (recorded by seismic stations in South Korea for 27 months from 2018 to 2020). This model was trained with 1,826,357 samples through balancing, then tested on continuous data samples of the year 2019, filtering more than 99% of strong false-picks that could trigger false alarms. This model was developed as a module for USGS Earthworm and is written in C language to operate with minimal computing resources.

• Journal of the Korean earth science society
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• v.36 no.6
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• pp.567-579
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• 2015

The accurate simulation of micro-scale weather phenomena such as fog using the mesoscale meteorological models is a very complex task. Especially, the uncertainty arisen from initial input data of the numerical models has a decisive effect on the accuracy of numerical models. The data assimilation is required to reduce the uncertainty of initial input data. In this study, the limitation of the mesoscale meteorological model was verified by WRF (Weather Research and Forecasting) model for a summer fog event around the Nakdong river in Korea. The sensitivity analyses of simulation accuracy from the numerical model were conducted using two different initial and boundary conditions: KLAPS (Korea Local Analysis and Prediction System) and LDAPS (Local Data Assimilation and Prediction System) data. In addition, the improvement of numerical model performance by FDDA (Four-Dimensional Data Assimilation) using the observational data from AWS (Automatic Weather System) was investigated. The result of sensitivity analysis showed that the accuracy of simulated air temperature, dew point temperature, and relative humidity with LDAPS data was higher than those of KLAPS, but the accuracy of the wind speed of LDAPS was lower than that of KLAPS. Significant difference was found in case of relative humidity where RMSE (Root Mean Square Error) for LDAPS and KLAPS was 15.7 and 35.6%, respectively. The RMSE for air temperature, wind speed, and relative humidity was improved by approximately $0.3^{\circ}C$, $0.2m\;s^{-1}$, and 2.2%, respectively after incorporating the FDDA.

• Bulletin of the Korean Space Science Society
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• 2003.10a
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• pp.63-63
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• 2003

There are many actuators and sensors used for attitude control system for KOMPSAT such as Reaction Wheel Assembly, Magnetic Torque Assembly, Dual Thruster Module, Solar array Drive, Three Axis Magnetometer, Conical Earth Sensor, Fine Sun Sensor Assembly, Coarse Sun Sensor Assembly, Gyro Reference Assembly and so on. For KOMPSA T satellite it has been considered using the Magnetic Torquer (MTQ) generating the magnetic dipole moment. In general, the magnetic dipole moment for satellite attitude control system is used for dumping out the excessive reaction wheel momentum so that the reaction wheel speed is not saturated. The objective of this study is to analyze the magnetic field characteristics generated by the Magnetic Torquer using the Maxwell 2D Field Simulator software. Currently, the developing model (DM) of the MTQ is being developed and manufactured at a company under the supervision of KARL MTQ is an electromagnet consisting of a ferromagnetic cylindrical core on which an excitation coil is wound. A current is passed through the coil to produce a dipole momentum in the ferromagnetic core. The configuration of the MTQ will be introduced in the presentation. The 2 dimensional model of the MTQ is drawn as axisymmetric models in RZ plane, and each corresponding material is assigned to the each MTQ object, the core, coil, and background. After the boundary conditions, current sources, and solution parameters are set up, the magnetic field intensities, directions, and other values specified by users can be calculated by using the finite element analysis. The theoretical magnetic field quantities obtained by the Maxwell 2D Simulator can be used for the basis of the development of the MTQ.

• Journal of Biomedical Engineering Research
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• v.23 no.2
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• pp.131-137
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• 2002

The remote monitoring system including hemodynamic information and pump status of the implanted animal could be helpful during the in vivo experiment or clinical trial for an artificial heart Implantation. In order to monitor the course of the in vivo experiment continuously and anywhere, web-based remote monitoring system was developed, which can monitor pressures(AoP, LAP, RAP, PAP) and flow information as well as the pump operating conditions. The system consists of data sending, storing viewer part. The data sending part was constructed using component object model and the viewer part was constructed using the Java applet. In addition, the dialog box was introduced to communicate earth other instantly and the alarming function was also introduced when the hemodynamic values were out of the desired ranges. The developed remote monitoring system was applied during the in vivo experiment of the BVAD (Bi-ventricular Assist Device) implantation for 1 month and showed designed work without failure.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.2
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• pp.193-201
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• 2014

This paper presents the development of simulation system on EPB shield TBM Hood operation. In recent, EPB shield TBM is widely used in the tunnel construction. Since the hood system of the EPB shield TBM is most important to excavate the tunnel, it is necessary to perform the simulation of hood system to investigate the design and operation parameters prior to tunnel construction. In order to carry out this study, the scaled simulation system was designed and developed. The model tests were performed to verify the developed system. During the simulation, the earth pressures developed in the chamber during tunnelling were measured to evaluate the operation technique. The test results obtained by the developed simulation system show clearly the similar behaviour of TBM hood compared with the field data. It was also found that the ground loss during tunnelling is dependent on the change of earth pressure in chamber. Therefore, the simulation system developed in this study will be very useful to evaluate the operation technique of the TBM hood prior to tunnel construction. In addition, this system will be applied in a various condition of ground to get the operating information.

• Atmosphere
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• v.23 no.3
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• pp.293-305
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• 2013

Nonhydrostatic effects on convectively forced mesoscale flows in two dimensions are numerically investigated using a nondimensional model. An elevated heating that represents convective heating due to deep cumulus convection is specified in a uniform basic flow with constant stability, and numerical experiments are performed with different values of the nonlinearity factor and nonhydrostaticity factor. The simulation result in a linear system is first compared to the analytic solution. The simulated vertical velocity field is very similar to the analytic one, confirming the high accuracy of nondimensional model's solutions. When the nonhydrostaticity factor is small, alternating regions of upward and downward motion above the heating top appear. On the other hand, when the nonhydrostaticity factor is relatively large, alternating updraft and downdraft cells appear downwind of the main updraft region. These features according to the nonhydrostaticity factor appear in both linear and nonlinear flow systems. The location of the maximum vertical velocity in the main updraft region differs depending on the degrees of nonlinearity and nonhydrostaticity. Using the Taylor-Goldstein equation in a linear, steady-state, invscid system, it is analyzed that evanescent waves exist for a given nonhydrostaticity factor. The critical wavelength of an evanescent wave is given by ${\lambda}_c=2{\pi}{\beta}$, where ${\beta}$ is the nonhydrostaticity factor. Waves whose wavelengths are smaller than the critical wavelength become evanescent. The alternating updraft and downdraft cells are formed by the superposition of evanescent waves and horizontally propagating parts of propagating waves. Simulation results show that the horizontal length of the updraft and downdraft cells is the half of the critical wavelength (${\pi}{\beta}$) in a linear flow system and larger than ${\pi}{\beta}$ in a weakly nonlinear flow system.