• Journal of The Geomorphological Association of Korea
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• v.19 no.4
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• pp.27-37
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• 2012

This study investigated granite landforms formed by Hantan-gang fluvial erosion and deposition, or by weathering in the area neighboring the Seungil-gyo bridge in Cheorwon-gun Gangwon-do Korea, in which the contact zone of Myeongseongsan granite and Cheorwon lava plateau creates a unique landform. Major granite landforms are deeply weathered hill, sheet erosional landform, paleo-landform surface and paleosoil, micro-fluvial landforms such as pothole and groove, granite rampart, sand bar and boulder bar, former riverbed. And river cliffs on a weakly weathered dome act as a barrier to lateral shifting of the river.

• Applied Microscopy
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• v.30 no.1
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• pp.11-20
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• 2000

The morphological changes in normal and weathering hair shafts of the human scalp were investigated by using the transmission and scanning electron microscopes. The hair shaft composed of cuticular layer, cortex and medula. The surface of normal hairs are smooth and covered by imbricated cuticular scales. The cuticular layer consists of five to seven cuticle cells. These cells, which are flat and thin, measuring about $100{\mu}m$ long and $0.4{\mu}m$ thick, appears intercellular membrane complex in diameter 25 nm. The cortex composed of melanin granules and cornified cells, which multicomponent concentric microfibrils in diameter about 8 nm give rise to macrofibrils in diameter $0.5{\mu}m$ to $0.8{\mu}m$ encased in limiting membrane. The melanin granules are spherical shaped about $0.5{\mu}m$ in size and scattered between macrofibrils. The medulla in the normal hairs are $16{\mu}m$ in diameter centrally region of cortex. Normal hair shafts undergo progressive degenerative changes due to a variety of environmental insults. In the initial weathering process of hair, the cuticular scales became irregularly raised and broken, and then cuticle cells formed cytoplasmic vacuolation, following dissociated intercellular membrane complex, ultimately entirely lost and nuded cortex. Occasionally, transverse fissures were seen at hair shafts indicating that the hairs were deteriorated. Complete removal of the cuticular layer in the heavily damaged cortex portions appeared splitting of the cortical cell into its macrofibrils and scattering of melanin granules.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.57.4-58
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• 2021

Asteroids have undergone various processes such as impacts, space weathering, and thermal evolution. Because they expose their surfaces to space without atmosphere, these evolutional processes have been recorded directly on their surfaces. The remote-sensing observations have been conducted to reveal these evolutional histories of the target asteroids. For example, crater and boulder distributions are unambiguous evidence for past nondestructive impacts with other celestial bodies. Multiband and spectroscopic observations have revealed space-weathering history (as well as compositions). Whereas most physical quantities have been examined intensively using spacecraft and telescopes, only a little has been studied on "the grain size". It is one of the fundamental physical quantities for diagnosing the collisional and thermal history of asteroids. Our group has conducted polarimetric research of asteroids (as well as Moon [1]) to determine the particle size and further investigate the evolutional histories of target asteroids [2],[3]. For example, the existence of regolith on an S-type asteroid, Toutatis, was suggested almost twenty years before space exploration [4]. Moreover, we reported that near-Sun asteroids indicate a signature of submillimeter grains, which could be created by a thermal sintering process by solar radiation [5]. However, it is important to note that in-situ polarimetry has not been reported on the asteroid surface, although the Korean Lunar Exploration Program aims to do polarimetry on the lunar surface [6]. Therefore, it is expected that the polarizer mounted on the Korean Apophis spacecraft can make the first estimate of the grain size and its regional variation over the Apophis surface. In this presentation, we outline research of S-type asteroid surfaces through remote-sensing observations and consider the role of polarimetry. Based on this review, we consider the purpose, potentiality, and strategy of the polarimetry using the onboard device for the Apophis spacecraft. We will report a possible polarization phase curve of Apophis estimated from ordinary chondrites and past observational data of S-type asteroids, taking account of the space weathering effect. Based on this estimation, we will consider the strategy of how to determine the particle size (and space weathering degree) of the Apophis surface. We will also mention the detectability of dust hovering on the surface.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.157-171
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• 2009

A 151 storey super high-rise building located in an area of reclaimed land constructed over soft marine clay in Songdo, Korea is currently under design. This paper describes the design process of the foundation system of the supertall tower, which is required to support the large building vertical and lateral loads and to restrain the horizontal displacement due to wind and seismic forces. The behaviour of the foundation system due to these loads and foundation stiffness influence the design of the building super structure, displacement of the tower, as well as the raft foundation design. Therefore, the design takes in account the interactions between soil, foundation and super structure, so as to achieve a safe and efficient building performance. The site lies entirely within an area of reclamation underlain by up to 20m of soft to firm marine silty clay, which overlies residual soil and a profile of weathered rock. The nature of the foundation rock materials are highly complex and are interpreted as possible roof pendant metamorphic rocks, which within about 50m from the surface have been affected by weathering which has reduced their strength. The presence of closely spaced joints, sheared and crushed zones within the rock has resulted in deeper areas of weathering of over 80m present within the building footprint. The foundation design process described includes the initial stages of geotechnical site characterization using the results of investigation boreholes and geotechnical parameter selection, and a series of detailed two- and three-dimensional numerical analysis for the Tower foundation comprising over 172 bored piles of varying length. The effect of the overall foundation stiffness and rotation under wind and seismic load is also discussed since the foundation rotation has a direct impact on the overall displacement of the tower.

• The Journal of Engineering Geology
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• v.17 no.3
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• pp.359-365
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• 2007

Freezing and thawing cycle is one of the major weathering-induced factors in the mechanical weathering of the rock mass. This natural process accelerates rock weathering process by breaking down the parent rock materials and makes soil or weathered rock formation in a rock slope surface zone. It can also cause reduction of the shear strength in slopes. It is important to calculate the deterioration depth caused by freezing-thawing for a slope stability analysis. In this study, deterioration depths of rock slope due to freezing-thawing were calculated using the 1-D heat conductivity equation. The temperature distribution analysis was also carried out using collected temperature distribution data for last five years of several major cities in Korea. The analysis was performed based on the distributed rock types in study areas. Thermal conductivities, specific heats and densities of the calculation rocks are tested in the laboratory. They are thermal properties of rocks as input parameters for calculating deterioration depths. Finally, the paper is showing the calculated deterioration depths of each rock type slopes in several major cities of Korea.

• Journal of the Mineralogical Society of Korea
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• v.28 no.3
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• pp.255-263
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• 2015

To investigate the effect of the weathering process of biotite on Cs sorption, sorption experiment of Cs with $10^{-3}M$ solution was carried out on the biotite reacted at different reaction times at pH 2 and 4, and 1 M solutions of Na, K, Ca, Mg, Rb, and Cs. Peak changes were observed for some samples by XRD, indicating that new mineral phase formed by biotite weathering. Among several factors, cations in solutions have the most significant influence on the mineralogical changes. The samples reacted with Na showed the most outstanding change with increasing peak width and appearance of $12{\AA}$ peak and $14{\AA}$ peak. This new peaks indicate the formation of hydrobiotite and vermiculite. The new peaks had stronger peak intensity for the sample reacted at pH 4 than that at pH 2, probably due to the fast dissolution of small particles and edges and resultant decrease in the formation of expandable layers. The biotite reacted at Mg solution showed small intensity at $14{\AA}$. Based on XRD results, the degree of biotite weathering was in the order of Na, Mg, and Ca. The samples reacted with K, Rb, Cs solutions did not show noticeable mineralogical changes caused by weathering. The amount of sorbed Cs on weathered biotite showed close relationship with the degree of weathering indicated by XRD. At both pH 2 and 4, the biotite reacted with Na solution showed the highest Cs sorption, and those with Mg and Ca solutions showed the next highest ones. The sorbed amounts of Cs on the bitote reacted with K, Rb, Cs solutions were relatively low. This indicates that at the Cs concentration ($10^{-3}M$) which we used for this experiment and which was much higher than the maximum Cs concentration sorbed on the frayed edge site, expandable layer plays more important role than frayed edge. In the cases of K, Rb, and Cs solutions, Cs sorption was decreased because K is the same cations as the one in the interlayer or the sorption of Rb and Cs on the frayed edge prevents the formation of expandable layers.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.48.3-49
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• 2021

We study the process of panspermia in Milky Way-like galaxies by modeling the probability of successful travel of organic compounds between stars harboring potentially habitable planets. To this end, we apply the modified habitability recipe of Gobat & Hong (2016) to a model galaxy from the MUGS suite of zoom-in cosmological simulations. We find that, unlike habitability, which only occupies narrow dynamic range over the entire galaxy, the panspermia probability can vary be orders of magnitude between the inner (R, b = 1~4 kpc) and outer disk. However, only a small fraction of star particles have very large values of panspermia probability and, consequently, the fraction of star particles where the panspermia process is more effective than prebiotic evolution is much lower than from naïve expectations based on the ratio between panspermia probability and natural habitability. The lunar surface progressively darkens and reddens as a result of sputtering from solar wind particles and bombardment of micrometeoroids. The extent of exposure to these space weathering agents is frequently calculated as the location in a diagram of reflectance at 750 nm

• Korean Journal of Fisheries and Aquatic Sciences
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• v.21 no.4
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• pp.259-268
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• 1988

Clay deposits in the vicinity of the Gwangpo Bay, southern coast of Korea, occur restrictively in anorthositic masses. Laumontite and meta-halloysite are the predominant clay minerals with iron oxides at the uppermost surface. Chlorite and halloysite occur in deeper zone. Beneath the main clay horizon, but not above, some anorthositic rocks are pervasively altered to quartz, sericite, chlorite, pyrite and montmorillonite along the hydrothermal channels. The hypotheses of hydrothermal and weathering origins of the clay minerals are tested by multi-component equilibrium calculations of the reactions of modified hydrothermal water and rain water with anorthositic rocks at $100^{\circ}C\;and\;25^{\circ}C$, respectively. The calculated mineralogy from the reaction with rain water resembles natural mineral assemblage except for abundance in laumontite. The result implies that the weathering process is the main machanism of the formation of clay deposits in the area.

• Polymer(Korea)
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• v.32 no.3
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• pp.213-218
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• 2008

About 17% of historical properties in Korea were made of stones and most of them are exposed to weathering, as such that discoloring, cracking, and shattering occur from physical, chemical, mechanical, and biological effects due to outdoor placement. Proper treatments for conservation are necessary to prevent the weathering damage and to retain the original shape of stones. MMA, an acrylic monomer having low viscosity can be impregnated deep inside stones by consecutive compression and decompression process in a pressurized vessel. After the polymerization of MMA impregnate, the space inside of the stone was filled with PMMA. It is expected that water repellent and weather resistant properties will be improved because of the improved bonding of constituent materials in stones. In this study, moisture absorption, chemical resistance, and mechanical property of two domestic granites were examined after treating them with MMA for the purpose of determining the conservation value of this method that was possibly useful to the conservation of stone cultural assets.

• Applied Chemistry for Engineering
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• v.23 no.6
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• pp.567-571
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• 2012

The discoloration of traditional paintings could be induced by various chemical reactions of inorganic pigments due to temperature, humidity, light and air pollution. In this study, we made artificial samples including azurite and malachite as inorganic pigments using the traditional method on hanji called 'Korean paper'and investigated the artificial aging process occurred by the interaction between pigments and environmental factors. It was found that the azurite was influenced by the humidity of weathering tests and the salt fog of salt spray tests according to XRD and TGA results. However, it was shown that the malachite was chemically changed by the ultraviolet radiation of weathering tests and UV radiation tests according to color difference and TGA results.