• Geomechanics and Engineering
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• v.15 no.1
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• pp.677-686
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• 2018

Aimed at serious casing damage problem during the process of oilfield development by injecting water, based on seepage mechanics, fluid mechanics and the theory of rock mechanics, the multi-physics coupling theory was also taken into account, the mathematical model for production of petroleum with water flooding was established, and the method to solve the coupling model was presented by combination of Abaqus and Eclipse software. The Q9G3 block in Jibei oilfield was taken for instance, the well log data and geological survey data were employed to build the numerical model of Q9G3 block, the method established above was applied to simulate the evolution of seepage and stress. The production data was imported into the model to conduct the history match work of the model, and the fitting accuracy of the model was quite good. The main mechanism of casing damage of the block was analyzed, and some wells with probable casing damage problem were pointed out, the displacement of the well wall matched very well with testing data of the filed. Finally, according to the simulation results, some useful measures for preventing casing damage in Jibei oilfield was proposed.

• Korean Journal of Remote Sensing
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• v.35 no.4
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• pp.535-544
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• 2019

This study demonstrated the ability of a Landsat-8 OLI multispectral data to identify and delineate hydrothermal alteration zones around auriferous prospects within the crystalline basement, North-western Nigeria. Remote sensing techniques have been widely used in lithological, structural discrimination and alteration rock delineation, and in general geological studies. Several artisanal mining activities for gold deposit occur in the surrounding areas within the basement complex and the search for new possible mineralized zones have heightened in recent times. Systematic Landsat-8 OLI data processing methods such as colour composite, band ratio and minimum noise fraction were used in this study. Colour composite of band 4, 3 and 2 was displayed in Red-Green-Blue colour image to distinguish lithologies. Band ratio ${\frac{4}{2}}$ image displayed in red was used to highlight ferric-ion bearing minerals(hematite, goethite, jarosite) associated with hydrothermal alteration, band ratio ${\frac{5}{6}}$ image displayed in green was used to highlight ferrous-ion bearing minerals such as olivine, amphibole and pyroxenes, while ratio ${\frac{6}{7}}$ image displayed in blue was used to highlight clay minerals, micas, talc-carbonates, etc. Band rationing helped to reduce the topographic illumination effect within images. The result of this study showed the distribution of the lithological units and the hydrothermal alteration zone which can be further prospected for mineral reserves.

• Progress in Medical Physics
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• v.16 no.2
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• pp.53-61
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• 2005

The quality factors for cylindrical ionization chambers for kV X-rays were determined by Monte Carlo calculation and measurement. In this study, the X-rays of 60-300 kV beam (lSO-4037) installed in KFDA and specified in energy spectra and beam qualities, and the chambers of PTW N23333 and N30001 were investigated. In calculations, the $R_{\mu}\;and\;R_{Q,Q_{0}}$ in IAEA dosimetry protocols were determined from the air kerma and the cavity dose obtained by theoretical and Monte Carlo calculations. It is shown that the N30001 chamber has a flat response of $\pm1.7\%$ in $110\~300kV$ region, while the response range of two chambers were shown to $\pm3\~4\%$ in $80\~250kV$ region. From this work we have discussed dosimetry protocol for the kV X-rays and we have found that the estimation of energy dependency is more important to apply dosimetry protocol for kV X-rays.

• Journal of the Korean Magnetics Society
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• v.21 no.4
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• pp.127-131
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• 2011

In this paper, we study the electronic and magnetic properties of Cr substituted SiTe in the rock-salt structure compound using the full potential linearized augmented plane wave method within the generalized gradient approximation to the exchange correlation potential. Two stoichiometries are studied: $CrSi_3Te_4$ with 25 %, and $CrSiTe_2$ with 50 % Cr substitution. We found, from the total energy calculations, that the equilibrium lattice constant for cubic $CrSi_3Te_4$ is 11.64 a.u. and a = 7.89 a.u. and c = 11.13 a.u. for tetragonal $CrSiTe_2$. The integer value of the calculated magnetic moment per unit cell, $4{\mu}_B$ for $CrSiTe_2$ suggests that this compound is halfmetallic. The magnetic moment per unit cell for $CrSi_3Te_4$ is slightly larger than $4{\mu}_B$. The magnetic moment on Cr atoms are 3.61 and $3.62{\mu}_B$ in the $CrSi_3Te_4$ and $CrSiTe_2$, respectively. The presence of Cr atoms causes that the other atoms become slightly magnetized in both compounds. The electronic properties and the magnetism are discussed with the calculated spin-polarized density of states.

• Radiation Oncology Journal
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• v.13 no.3
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• pp.285-289
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• 1995

Purpose : We compared the calcualted percent depth dose curves of 6 MeV electron beam to that of measured to evaluate the usefulness of Monte-carlo simulation method in radiation physics. Materials and Methods : The radiation dose values of 6 MeV electron beam using EGS4 code with one million histories in water were compared values that were measured from the depth dose curve of electron beam irradiated by medical accelerator ML6M. The central axis dose values were calculated according to the changing field size. such as $5{\times}5,\;10{\times}10,\;15{\times}15,\;20{\times}20cm^2$. Results : The value calculated showed a very similar shape to depth dose curve. The calculated and measured value of $D_max$ at $10{\times}10cm^2$ cone is 15mm and 14mm respectively. The calculated value of the surface radiation dose rate is $65.52\%$ and measured one is $76.94\%$. The surface radiation dose rate has varied from $64.43\%$ to $66.99\%$. The calculated values of $D_max$ are in the range between 15mm and 18mm. The calculated value was fitted well with measured value around the $D_max$ area, excluding build up range and below the $90\%$ depth dose area. Conclusion : This result suggested that the calculation of dose value can be replace the direct measurement of the dose for radiation therapy. Also, EGS4 may be a very convenient program to assess the effect of radiation dose using by personal computers.

• Journal of the Korean earth science society
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• v.33 no.4
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• pp.329-336
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• 2012

In September 2009, a perfectly preserved fossil of a dinosaur egg nest was discovered in the Cretaceous formations of the Aphaedo area in Shinan, Jeollanam-do, South Korea. In order to estimate the age of dinosaur eggshells and the depositional age of the Cretaceous sediments in Aphaedo area, a whole-rock K-Ar dating was carried out on volcanic pebbles showing a sedimentary structure contemporaneous with the Aphaedo strata, acidic tuffs overlaying the strata conformably, and acidic dike rocks intrude to both of them. Volcanic rocks observed in the strata are 3-20 cm in diameter as pebbles found in lenticular conglomerate and pebble bearing mudstone strata. K-Ar whole-rock dating was performed on six different volcanic pebbles which show a sedimentary structure contemporaneous with the dinosaur egg nest contained in the strata, and all samples show Late Cretaceous ages: Cenomanian ($97.6{\pm}1.9$Ma), Coniacian ($87.6{\pm}1.7$ Ma), Santonian ($84.5{\pm}1.7$Ma) or Campanian ($82.5{\pm}1.6$, $77.3{\pm}1.5$, $75.7{\pm}1.5$ Ma). The K-Ar whole-rock age of acidic tuffs overlaying the Cretaceous formation conformably was estimated to be Campanian ($79.2{\pm}1.6$ or $77.3{\pm}1.5$Ma), when the dating was carried out under the same conditions. The acidic dike intruding both Cretaceous formation and acidic tuff showed a K-Ar whole-rock age of $70.9{\pm}1.4$Ma (Campanian). Therefore, the depositional age of the Cretaceous formation in the Aphaedo area and the time when dinosaurs lived in the study area are considered to be 77-83 Ma. Such results indicate that the ages of dinosaur eggshells from Aphaedo area can be correlated with the ages of the Seonso Formation (81Ma) with dinosaur egg nest fossils and the Uhangri Formation (79-81Ma) with dinosaur, pterosaur and web-footed bird tracks.

• 한국지구물리탐사학회:학술대회논문집
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• 2006.06a
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• pp.201-206
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• 2006

Earth sciences is undergoing a gradual but massive shift from description of the earth and earth systems, toward process modeling, simulation, and process visualization. This shift is very challenging because the underlying physical and chemical processes are often nonlinear and coupled. In addition, we are especially challenged when the processes take place in strongly heterogeneous systems. An example is two-phase fluid flow in rocks, which is a nonlinear, coupled and time-dependent problem and occurs in complex porous media. To understand and simulate these complex processes, the knowledge of underlying pore-scale processes is essential. This paper presents a new attempt to use pore-scale simulations for understanding physical properties of rocks. A rigorous pore-scale simulator requires three important traits: reliability, efficiency, and ability to handle complex microstructures. We use the Lattice-Boltzmann (LB) method for singleand two-phase flow properties, finite-element methods (FEM) for elastic and electrical properties of rocks. These rigorous pore-scale simulators can significantly complement the physical laboratory, with several distinct advantages: (1) rigorous prediction of the physical properties, (2) interrelations among the different rock properties in a given pore geometry, and (3) simulation of dynamic problems, which describe coupled, nonlinear, transient and complex behavior of Earth systems.

• The Journal of Engineering Geology
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• v.23 no.3
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• pp.235-246
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• 2013

P-wave velocity was measured by the low frequency flaw detector in order to analyze the weathered state of a halo stone Buddha, Unju temple, Hwasun, Korea. By the results of laboratory tests on a fresh acidic tuff with the same rock of a halo stone Buddha, average absorption, average P-wave velocity, and average uniaxial compressive strength were 5.38%, 4,008 m/s, and 70.1 MPa, respectively. The results correspond to moderately strong rock. Average P-wave velocity of a halo stone Buddha measured by the low frequency flaw detector was 2,257 m/s in the left zone, 3,437 m/s in the right zone, and 2,802 m/s overall. Weathering index of a halo stone Buddha was 0.45 in the left zone, 0.21 in the right zone, and 0.33 overall. Comparing the results of a halo stone Buddha with them of laboratory tests, weathered state of a halo stone Buddha was analyzed highly weathered state in the left zone and moderately weathered state in the right zone. Furthermore, it suggests that the left zone of a halo stone Buddha was affected weathering more than the right one. Overall a halo stone Buddha corresponds to moderately weathered state of weathering degrees. In conclusion, it is considered that low frequency flaw detector may be applicable as a valuable method on analyzing the P-wave velocity of the stone cultural heritage with an irregular surface.

• Journal of the Korean earth science society
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• v.38 no.2
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• pp.141-149
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• 2017

The geology of Saok island area in Jeollanam-do can be divided into 4 lithologic types: Jurassic granite, Cretaceous sedimentary rocks, acidic tuff and acidic dikes. In the Saok island area, dinosaur and web-footed bird footprints, arthropod trackway and silicified wood were found recently in the Cretaceous sedimentary rocks which composed of alternating light grey sandstone, shale and mudrock. The fossil-bearing sedimentary rock is overlain by an acidic tuff, and the sedimentary rock and acidic tuff are cut by acidic dykes. In order to constrain the depositional age of the Cretaceous sedimentary rocks in Saok island area, SHRIMP U-Pb zircon ages were determined in the tuffaceous sandstone and overlying acidic tuff. Zircon U-Pb ages of the sandstone and tuff are $83.58{\pm}0.86$ and $79.80{\pm}0.75Ma$, respectively, which belong to the Campanian of the Late Cretaceous. The U-Pb age of the acidic tuff indicates the eruption time of acidic tuff and thus the minimum age of the fossil-bearing sedimentary rocks in this area. Therefore, the formation age of the dinosaur and web-footed bird footprints can be constrained between 83.6 and 79.8 Ma.

• Journal of Radiation Protection and Research
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• v.37 no.3
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• pp.149-158
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• 2012

In this paper, we measured the variations of radon concentrations in groundwater using low-level Liquid Scintillation Counter (LSC), an instrument for analyzing the alpha and beta radionuclides at its 10 sites around the Kumjung-Gu, north-western of Busan. Optimization of Pulse Shape Analyzer (PSA) to determinate the highest value of figure of merit (FM) was decided using Quantulus 1200 LSC with radium-226 source, the optimal PSA level was shown in the range of 100 to 110. The results show that the Minimum Detectable Activity (MDA) of radon concentrations is 0.61 $Bq{\cdot}L^{-1}$ for 20 minutes in PSA level. We find that the average radon concentration in groundwater is high in granitic rock area and low in volcanic rock area. (Biotite granite : 191.39 $Bq{\cdot}L^{-1}$, Micro graphic granite : 141.88 $Bq{\cdot}L^{-1}$, Adamellite : 92.94 $Bq{\cdot}L^{-1}$, Andesite (volcanic) : 35.35 $Bq{\cdot}L^{-1}$). No significant seasonal variation pattern is observed from the long-term variation analysis from 10 selected sites. We have not seen the significant correlation of radon concentration to groundwater temperature, atmospheric temperature, atmospheric pressure and rainfall. The concentration variation is probably caused by more complex factors and processes.