• Economic and Environmental Geology
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• v.54 no.2
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• pp.233-245
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• 2021

Many studies on the microstructures in rocks have been conducted using experimental methods with various equipment as well as natural rock studies to see the development of microstructures and understand their mechanisms. Grain boundary migration of mineral aggregates in rocks could cause grain growth or grain size changes during metamorphism or deformation as one of the main recrystallization mechanisms. This study suggests improved ways regarding the analog material experiments with reformed equipment to see sequential observations of these grain boundary migration. It can be more efficient than the existing techniques and carry out an appropriate microstructure analysis. This reformed equipment was implemented to enable optical manipulation by mounting polarizing plates capable of rotating operation on a stereoscopic microscope and a deformation rig capable of experimenting with analog materials. The equipment can automatically control the temperature and strain rate of the deformation rig by microcontrollers and programming and can take digital photomicrographs with constant time intervals during the experiment to observe any microstructure changes. The composite images synthesized using images by rotated polarizing plates enable us to see more accurate grain boundaries. As a rock analog material, norcamphor(C7H10O) was used, which has similar birefringence to quartz. Static grain growth and simple shear deformation experiments were performed using the norcamphor to verify the effectiveness of the equipment. The static grain growth experiments showed the characteristics of typical grain growth behavior. The number of grains decreases and the average grain size increases over time. These case experiments also showed a clear difference between the growth curves with three temperature conditions. The result of the simple shear deformation experiment under the medium temperature-low strain rate showed no significant change in the average grain size but presented the increased elongation of grain shapes in the direction of about 53° regarding the direction perpendicular to the shearing direction as the shear strain increases over time. These microstructures are interpreted as both the plastic deformation and the internal recovery process in grains are balanced by the deformation under the given experimental conditions. These experiments using the reformed equipment represent the ability to sequentially observe changing the microstructure during experiments as desired in the tests with the analog material during the entire process.

• Economic and Environmental Geology
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• v.56 no.6
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• pp.847-870
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• 2023

The safe disposal of high-level radioactive waste requires accurate predictions of the long-term geochemical behavior of radionuclides. To achieve this, the present study was conducted to model geochemical behaviors of uranium (U), plutonium (Pu), and palladium (Pd) under different hydrogeochemical conditions that represent deep groundwater in Korea. Geochemical modeling was performed for five types of South Korean deep groundwater environment: high-TDS saline groundwater (G1), low-pH CO₂-rich groundwater (G2), high-pH alkaline groundwater (G3), sulfate-rich groundwater (G4), and dilute (fresh) groundwater (G5). Under the pH and Eh (redox potential) ranges of 3 to 12 and ±0.2 V, respectively, the solubility and speciation of U, Pu, and Pd in deep groundwater were predicted. The result reveals that U(IV) exhibits high solubility within the neutral to alkaline pH range, even in reducing environment with Eh down to -0.2 V. Such high solubility of U is primarily attributed to the formation of Ca-U-CO₃ complexes, which is important in both G2 located along fault zones and G3 occurring in granitic bedrocks. On the other hand, the solubility of Pu is found to be highly dependent on pH, with the lowest solubility in neutral to alkaline conditions. The predominant species are Pu(IV) and Pu(III) and their removal is predicted to occur by sorption. Considering the migration by colloids, however, the role of colloid formation and migration are expected to promote the Pu mobility, especially in deep groundwater of G3 and G5 which have low ionic strengths. Palladium (Pd) exhibits the low solubility due to the precipitation as sulfides in reducing conditions. In oxidizing condition, anionic complexes such as Pd(OH)₃^-, PdCl₃(OH)₂^-, PdCl₄^2-, and Pd(CO₃)₂^2- would be removed by sorption onto metal (hydro)oxides. This study will improve the understanding of the fate and transport of radionuclides in deep groundwater conditions of South Korea and therefore contributes to develop strategies for safe high-level radioactive waste disposal.

• Journal of the Korea Concrete Institute
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• v.24 no.4
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• pp.481-490
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• 2012

Evaluation of chloride penetration is very important, because induced chloride ion causes corrosion in embedded steel. Diffusion coefficient obtained from rapid chloride penetration test is currently used, however this method cannot provide a correct prediction of chloride content since it shows only ion migration velocity in electrical field. Apparent diffusion coefficient of chloride ion based on simple Fick's Law can provide a total chloride penetration magnitude to engineers. This study proposes an analysis technique to predict chloride penetration using apparent diffusion coefficient of chloride ion from neural network (NN) algorithm and time-dependent diffusion phenomena. For this work, thirty mix proportions with the related diffusion coefficients are studied. The components of mix proportions such as w/b ratio, unit content of cement, slag, fly ash, silica fume, and fine/coarse aggregate are selected as neurons, then learning for apparent diffusion coefficient is trained. Considering time-dependent diffusion coefficient based on Fick's Law, the technique for chloride penetration analysis is proposed. The applicability of the technique is verified through test results from short, long term submerged test, and field investigations. The proposed technique can be improved through NN learning-training based on the acquisition of various mix proportions and the related diffusion coefficients of chloride ion.

• Journal of the Korean Electrochemical Society
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• v.14 no.4
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• pp.231-238
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• 2011

In this work, the numerical analysis for the zincate behavior at a zinc electrode with an electrolyte flow was carried out for a ZAFC. The Nernst-Planck equation with a boundary condition of Butler-Volmer type was adopted to describe electrochemical effects of mass transfer, migration, kinetics of electrode. The Navier-Stokes equation, coupling to the Nernst-Planck equation, is also applied to describe the internal electrolyte flow fields. The validity of the numerical model is proved through the comparative analysis between numerical and experimental results. The concentration of zincate and the current density were also investigated at a zinc anode according to various electrolyte velocities. We have found the concentration of zincate decreased and the current density increased with an increase in the electrolyte velocity.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.1
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• pp.25-29
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• 2020

This study demonstrates direct-patternable amorphous TiO_x resistive switching (RS) device and the fabrication method using photochemical metal-organic deposition (PMOD). For making photosensitive stock solutions, Ti(IV) 2-ethylhexanoate was used as starting precursor. Photochemical reaction by UV exposure was observed and analyzed by Fourier transform infrared spectroscopy and the reaction was completed within 10 minutes. Uniformly formed 20 nm thick amorphous TiO_x film was confirmed by atomic force microscopy. Amorphous TiO_x RS device, formed as 6 × 6 ㎛ square on 4 ㎛ width electrode, showed forming-less RS behavior in ±4 V and on/off ratio ≈ 20 at 0.1 V. This result shows PMOD process could be applied for low temperature processed ReRAM device and/or low cost, flexible memory device.

• Journal of the Korean Society of Groundwater Environment
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• v.1 no.2
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• pp.105-112
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• 1994

To investigate the migration behavior of contaminants in rocks. adsorption and diffusion experiments for Sr as a sorbing contaminant and for Cr-EDTA as a non-sorbing contaminant were carried out on granitic rocks. The Sr adsorption on separated minerals and crushed rocks tends to slightly increase with increasing pH. It also greatly decreases with the increase of ionic strength in NaCl solution. Among separated minerals, biotite and sericite have adsorbed much more amount of Sr than other rock-forming minerals, such as quartz, plagioclase, and potassic feldspar, because the specific surfaces and cation exchange capacities of phyllosilicates are generally much greater than those of the other rock-forming minerals. The intrinsic diffusion coefficients of Cr-EBTA for granitic rocks differ little from those of Sr. This indicates that they are independent of water-rock interactions. Experimental data show that the intrinsic diffusion coefficients are positively correlated with the porosities of the rocks. They are close to the theoretically predicted values, especially in pre-steady state diffusion region, with the increase of rock sample thickness.

• Journal of Korean Neurosurgical Society
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• v.59 no.6
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• pp.551-558
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• 2016

Malignant glioma cells invading surrounding normal brain are inoperable and resistant to radio- and chemotherapy, and eventually lead to tumor regrowth. Identification of genes related to motility is important for understanding the molecular biological behavior of invasive gliomas. According to our previous studies, Metallothionein 1E (MT1E) was identified to enhance migration of human malignant glioma cells. The purpose of this study was to confirm that MT1E could modulate glioma invasion in vivo. Firstly we established 2 cell lines; MTS23, overexpressed by MT1E complementary DNA construct and pV12 as control. The expression of matrix metalloproteinases (MMP)-2, -9 and a disintegrin and metalloproteinase 17 were increased in MTS23 compared with pV12. Furthermore it was confirmed that MT1E could modulate MMPs secretion and translocation of NFkB p50 and B-cell lymphoma-3 through small interfering ribonucleic acid knocked U87MG cells. Then MTS23 and pV12 were injected into intracranial region of 5 week old male nude mouse. After 4 weeks, for brain tissues of these two groups, histological analysis, and immunohistochemical stain of MMP-2, 9 and Nestin were performed. As results, the group injected with MTS23 showed irregular margin and tumor cells infiltrating the surrounding normal brain, while that of pV12 (control) had round and clear margin. And regrowth of tumor cells in MTS23 group was observed in another site apart from tumor cell inoculation. MT1E could enhance tumor proliferation and invasion of malignant glioma through regulation of activation and expression of MMPs.

• Economic and Environmental Geology
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• v.51 no.2
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• pp.77-85
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• 2018

There would be a possibility of uranium contamination around the nuclear power plants and the underground waste disposal sites, where the uranium could further migrate and diffuse to some distant places by groundwater. It is necessary to understand the biogeochemical behaviors of uranium in underground environments to effectively control the migration and diffusion of uranium. In general, various kinds of microbes are living in soils and geological media where the activity of microbes may be closely connected with the redox reaction of nuclides resulting in the changes of their solubility. We investigated the adsorption and precipitation behaviors of dissolved uranium on some solid materials using hydrogen gas as an electron donor instead of organic matters. Although the effect of hydrogen gas did not appear in a batch experiment that used granite as a solid material, there occurred a reduction of uranium concentration by 5~8% due to hydrogen in an experiment using bentonite. This result indicates that some indigenous bacteria in the bentonite that have utilized hydrogen as the electron donor affected the behavior (reduction) of uranium. In addition, the bentonite bacteria have showed their strong tolerance against a given high temperature and radioactivity of a specific waste environment, suggesting that the nuclear-biogeochemical reaction may be one of main mechanisms if the natural bentonite is used as a buffer material for the disposal site in the future.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.3
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• pp.189-195
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• 2001

The characteristics of echolocation signals of the Common Dolphin, Delphinus Delphis was observed by the hydrophone in order to detect exactly distribution and migration on whales and dolphins in Korean Coastal waters. It's observation was carried out at the position of 13 mm off Gam-Po of Korean east-southern sea at 3rd-5th. April and 13th-15th. October, 1999. The results obtained are summarized as follows: (1) The frequency range of ship's noise and ambient noise in the observed station was 0.5-0.3 kHz, that ones could be influenced to the behavior of common dolphins which carry out echolocation using low-frequency. (2) The common dolphin was radiated single click of 8.6 ms and double click of 4.8 ms pulse width during these observation (3) The high click frequencies of common dolphin were 5.10 kHz, 7.22 kHz, 10.60 kHz with the click pulse width of 4.0 ms, 2.6 ms, 1.0 ms, respectively. In case of low-frequency 1-2 kHz, that is, 1.12 kHz, 1.38 kHz, 1.82 kHz, pulse width were 22.4 ms, 2.05 ms, 11.9 ms, respectively and they showed a tendency using triple click signal. (4) The pulse width, pulse recurrence interval and frequency range of the observed echolocation signals were 2.4-8.4 ms, 9.0-40.0 ms, 0.60-10.63 kHz respectively, and frequency spectrum level was 100-125 dB for single, double, triple click signals.

• Journal of Korea Water Resources Association
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• v.41 no.4
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• pp.423-432
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• 2008

The local migration or movement behavior of fishes in streams are related to feeding, spawning, growing, dispersing, and refuging. The pale chub (Zacco platypus) is a dominant species that migrates locally and inhabits in river and stream in Korea. However, dams, weirs, culverts and other regulatory structures are physical barriers that limit fish movement and fragment habits and populations. If main stream and off-channel habitats are connected with culverts, they would restrict the small fish as pale chub movement due to the high flow velocities and low depths. But in Korea, there is no experimental study to evaluate the swimming performance of species in Korea. Therefore, it is difficult to proposed that design guidelines for pass fishes through culverts. The purpose of this experimental study is to evaluate the swimming performance of pale chubs. A series of swimming performance test has been used in both of the fixed velocity and the incremental velocity methods in an experimental flume. As a result, the critical swimming speed for pale chub(body length 8.9 cm) was found to be about 0.7 m/s. Therefore, the flow velocity for culvert design in the low flow condition should not be exceed the its swimming ability, especially 0.7 m/s for pale chubs(body length 8.9 cm). And the minimum depth for culvert design in the low flow condition should not be lower than the fish body height add a dorsal fin height.