• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.854-859
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• 2006

The density of coarse grained materials which is used in rock-fill dam or the piling the ground are used as $1.85\sim2.10g/cm^3$. Hereupon, the effect of variation of density on shear strength of ones was analyzed from the results of large scale shear test. The sample for the test was obtained from the local quarry sites. The test conditions are that density(1.85 versus $2.10g/cm^3$), material size range$(76.3\sim2.0\;mm)$, water content(air dry condition) and uniformity coefficient(5.0) Test result shows that the shear strength of $2.10g/cm^3$ is relatively larger than that of $1.85g/cm^3$.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.73.1-73.1
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• 2018

We investigated shock history of three achondrite meteorites: NWA 3117, a howardite from asteroid Vesta, NWA 2727, a breccia from the Moon, and NWA 856, a shergottite from Mars. Shock histories were evaluated from deformation of plagioclase feldspars. Feldspar grains were classified based on observations in cross-polarized light as undulatory, mosaic, mosaic-recrystallized or maskelynite. This sequence represents increasing deformation of original feldspar crystals. Undulatory crystals have wavy extinction, mosaic crystals have patchy extinction, and mosaic-recrystallized grains appear as if they were originally coarse-grained and have recrystallized to mosaics of small equant crystals. Maskelynite grains are isotropic, indicating transformation to glass. Based on feldspar deformation, the degrees of impact processing are NWA 856 > NWA 3117 > NWA 2727. The high deformation of NWA 856 is expected because this sample is from Mars, which is a large parent body and requires a powerful impact to accelerate a rock to escape velocity. In contrast, the parent body of NWA 3117 (Vesta) is smaller than that of NWA 2727 (the Moon), yet NWA 3117 appears more highly deformed than NWA 2727. One possible explanation is that NWA 2727 is from a relatively young part of the Moon, which has not been exposed to impacts as long as the surface of Vesta.

• Geomechanics and Engineering
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• v.14 no.1
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• pp.29-42
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• 2018

This paper presents the results of an empirical study in which square rock-like blocks containing two parallel pre-existing rough non-persistent joints were subjected to uniaxial compression load. The main purpose of this study was to investigate uniaxial compressive strength and deformation modulus of jointed specimens. Response Surface Method (RSM) was utilized to design experiments and investigate the effect of four joint parameters, namely joint roughness coefficient (JRC), bridge length (L), bridge angle (${\gamma}$), and joint inclination (${\theta}$). The interaction of these parameters on the uniaxial compressive strength (UCS) and deformation modulus of the blocks was investigated as well. The results indicated that an increase in joint roughness coefficient, bridge length and bridge angle increased compressive strength and deformation modulus. Moreover, increasing joint inclination decreased the two mechanical properties. The concept of 'interlocking cracks' which are mixed mode (shear-tensile cracks) was introduced. This type of cracks can happen in higher level of JRC. Initiation and propagation of this type of cracks reduces mechanical properties of sample before reaching its peak strength. The results of the Response Surface Methodology showed that the mutual interaction of the joint parameters had a significant influence on the compressive strength and deformation modulus.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.9
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• pp.1220-1228
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• 2003

The mirage technique is proved to be powerful in measuring the thermal diffusivity of materials. In particular, its contactless nature makes it suitable for delicate samples and microscale structures. In this study, thermal-wave-coupling method is developed in a general form for both thermally thin and thick samples. In the suggested measuring scheme, the probe beam can be positioned close to the pump beam and the absolute position need not be measured. Therefore the new scheme provides a relatively simple yet effective way to determine the thermal diffusivity of thermally thick samples. Thermal diffusivities of bulk samples like Ni and Al were measured and the characteristics of mirage signal for a thin film were observed by using the mirage experimental setup. The apparent thermal diffusivity was measured by varying such parameters as probe beam height, size of pump beam, power of pump beam, and surface condition of sample. From the practical standpoint, it is shown that the size of the pump beam is the most important factor for accurate thermaldiffusivity measurement. Experiments using thin-film samples show that the thermal diffusivity of a substrate covered with thin film can be measured by photothermal mirage signals.

• Journal of Soil and Groundwater Environment
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• v.16 no.6
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• pp.95-105
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• 2011

Total extraction method and environmental standards for heavy metals in soils were revised in regulation recently. In case of Area 3, as the law amended, the soil pollution level has gone up to 4 to 13 times higher depending on the type of heavy metal. In this study, it compares the properties of heavy metals of soil by sequential extraction and total extraction methods depending on the analysis method, using the soil around mine. In case of arsenic, the soil pollution level has gone up to 4 times higher, but 6 to 10 times in the sample soil. Also, according to the results of portability evaluation depending on the type of existence form of heavy metal it exists as residual form in mine waste rock, which is less likely to move, while it exists as migrated form in tailing. Therefore, it should be considered to evaluate the soil pollution and decide the contaminated bounds depending on the existence form of heavy metals on soil to restore the polluted soil.

• Journal of the Korean Institute of Gas
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• v.8 no.3 s.24
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• pp.31-36
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• 2004

Electrofusion(EF) joints have been widely used as they are easy to fuse and suitable for high-quality joints for polyethylene(PE) pipes. This paper studies the cause of defects and classifies 5 types of defects. The defect detection technique for electrofusion joints of polyethylene piping is utilized by the ultrasonic phased array technique to obtain ultrasonic images of electrofusion joints. Test sample joints have been designed and fabricated using artificial defects which were made using paper. Finally, we studied the condition of electrofusion in the field and analyzed the main causes of defects. And we classified the defect types as local lack of fusion, sand inclusion, voids or air inclusion, short stab, excess penetration or excess bead.

• Proceedings of the KIEE Conference
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• 1998.07a
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• pp.235-237
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• 1998

Gradient coil offers the spatial informations of sample or patient in Nuclear Magnetic Resonance Imaging(NMRI) and its gradient field linearity over the field of view(FOV) has many influence on the MR imaging. Accurate and good quality MR imaging can be acquired by the high gradient field linearity over the FOV. So it is an important part to design of gradient coil with good linearity in the wide imaging range. Usually, Z-directional gradient field is generated by using the Helmholtz type coil which is consisted of one-pair loop with anti-current path. It gets less about 40% linearity of the diameter spherical volume(DSV). In this study, we calculated optimized geometrical parameters of two-pair loop system to cancel odd terms up to $B_7$ included effectively. we also analyzed and compared the gradient field distribution and linearity of the common Helmholtz coil with them of the two-pair loop system.

• Journal of the Korean earth science society
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• v.29 no.3
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• pp.246-254
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• 2008

This study has been performed to evaluate the possibility of utilizing feldspar porphyry as an adsorbent for heavy metals in natural water. The research sample rock 'Maekbansuk' was altered feldspar porphyry which included chlorite, epidote and calcite formed by a prophylitic alteration process. In extraction tests, the majority of extracted elements were Ca and Na, which were extracted in much greater abundance from the groundmass than from the feldspar phenocryst. In adsorption tests, the adsorption capacities of Pb, Fe and Cu within an hour of reaction time were 99, 98 and 97%, respectively, but that of As remained 25% for a full 24 hours. The high adsorption capacities of altered feldspar porphyry for Pb, Fe and Cu suggest its potential utilization as a heavy metal adsorbent fur water purification.

• Nuclear Engineering and Technology
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• v.30 no.6
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• pp.518-530
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• 1998

A natural analogue study has been performed for the Koongarra uranium ore deposit in Australia as an international agreement of the Analogue Studies in the Alligator Rivers Region (ASARR). Rocks obtained from the Koongarra deposit, Northern Territory of Australia, were examined in order to understand uranium migration processes of primary and secondary ore-body in both weathered and unweathered zones. Total alpha activities of rock samples were measured to compare the relative amount of uranium in the sample. Uranium distributions have been investigated by means of both the alpha-autoradiography and the fission track registration technique after irradiation in a flux of thermal neutrons (~10$\times$$10^{13}$nㆍ$cm^{-2}$ㆍs$^{-1}$) for 2 minutes. The mineral phases corresponding to the registered alpha-tracks and fission tracks were identified by petrological observation with optical microscope as well as X-ray diffraction and electron microprobe analysis (EPMA). Uranium was found mostly inside of the fracture of the quartzite and its mineral phase was identified as sklodowskite. The mineral phase associated with high uranium concentration was found as illeminite by petrological observation with optical microscope as well as EPMA.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.19 no.4
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• pp.517-532
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• 2021

Safe geological disposal of spent nuclear fuel (SNF) requires knowledge of the deep hydrochemical characteristics of the repository site. Here, we conducted a set of deep hydrochemical investigations using a 750-m borehole drilled in a model granite system in Wonju, South Korea. A closed investigation system consisting of a double-packer, Waterra pump, flow cell, and water-quality measurement unit was used for in situ water quality measurements and subsequent groundwater sampling. We managed the drilling water labeled with a fluorescein dye using a recycling system that reuses the water discharged from the borehole. We selected the test depths based on the dye concentrations, outflow water quality parameters, borehole logging, and visual inspection of the rock cores. The groundwater pumped up to the surface flowed into the flow cell, where the in situ water quality parameters were measured, and it was then collected for further laboratory measurements. Atmospheric contact was minimized during the entire process. Before hydrochemical measurements and sample collection, pumping was performed to purge the remnant drilling water. This study on a model borehole can serve as a reference for the future development of deep hydrochemical investigation procedures and techniques for siting processes of SNF repositories.