• Journal of the Korean Geotechnical Society
• /
• v.34 no.12
• /
• pp.29-42
• /
• 2018

Shale and mudstone in Daegu-Gyungbuk area have low strength and resistance to weathering compared to other rocks. Therefore, it is necessary to evaluate their strength depending on the degree of saturation and crack development. In this study, shales and mudstones were collected from several construction sites in Daegu-Gyungbuk area. Their basic material properties such as porosity, SEM, chemical component, and durability were tested. A porosity (absorptivity) of mudstone was 31% (25%), which was 6 (8) times higher than that of shale. Some mudstone was easily disintegrated with water and it consisted of highly-active clay mineral such as smectite type. These rocks were prepared by small cube specimens for unconfined compression test. An unconfined compressive strength of dry rock was compared with saturated one. Microwave oven was operated step by step to stimulate void water within a saturated rock, which resulted into high temperature and micro crack initiation within rocks. A strength of microwaved rocks was compared with operation time and crack initiation. As a result, the average unconfined compressive strength of dry and saturated shale was 62 and 33 MPa, respectively. The strength of mudstone for each condition was 11 and 4 MPa. When a rock became saturated, its strength decreased by 47% and 64% for shale and mudstone at average. In addition to saturation, a rock was in the microwave for 15 secs, its strength decreased into 49% for shale and 52% for mudstone. When a microwave oven operated up to 20 sec, a rock was crushed into several pieces and its temperature was approximately 200 degrees.

• Korean Journal of Heritage: History & Science
• /
• v.37
• /
• pp.349-369
• /
• 2004

Today, in the cultural properties research, there are several methods for knowing the culture of the past through a lot of information that remains and relics contain. Especially, statistical method like presumption of producing center were introduced from computer development at the early 20th century. This study showed the characteristic about firing historic sites presumed as a tile-kiln in the remains of Cheonwang temple sites, Hanam, Gyeonggi province. Also, I used nature scientific methods for correlation between tiles excavated at historic sites and circumference building and obtained there results as follows. First, soft tile parts showed similar water suction ratio(over 10%) like another tiles, except hard tile parts. Second, identification about mineral crystallization in a sample showing low water suction ratio confirmed a result that Mullite, Tridymite, Cristobalite as high temperature crystal form were presented. I know that firing temperature was higher than the other tile parts from this result. Third, statistical analysis from micro-component resulted that tiles excavated at firing historic sites and Cheonwang temple sites were closely connected. As the results, I knew that the tiles got a supply after the establishment of tile-kiln, not at a long distance at the period of Cheonwang temple construction.

• Journal of Life Science
• /
• v.32 no.6
• /
• pp.455-462
• /
• 2022

This study examined changes in the body composition of Protaetia brevitarsis larvae fed sulfur and selenium. Among the general chemical components, an increase in protein was observed in the sulfur-fed group, whereas an increase in fatty acid was found in the groups fed selenium and sulfur/selenium. The structural amino acid showed some tendency to be increased compared to the control group, but this was especially true in the sulfur-fed group. The free amino acid were increased in the groups fed selenium and sulfur/selenium, with GABA, Glu, and Pro, in particular, being increased in the group fed sulfur/selenium. Among the essential amino acids, Met, Trp, and Val tended to be increased in selenium and sulfur/selenium groups. Saturated and polyunsaturated fatty acids showed a tendency to increase in the group fed sulfur/selenium, but monounsaturated fatty acid tended to be decreased in the group. In particular, no oleic acid was detected in the sulfur/selenium group, whereas palmitic acid, palmitoleic acid, and linoleic acid were increased. From observations of these body composition changes associated with the feeding of sulfur and selenium, it is estimated that the group fed sulfur/selenium would likely undergo a pronounced change in body composition. Therefore, we suggest that it is possible to manufacture a food that has enhanced functionality by appropriately adjusting the diet of Protaetia brevitarsis larvae.

• Economic and Environmental Geology
• /
• v.55 no.3
• /
• pp.219-229
• /
• 2022

Bentonite is being considered as a candidate for buffer material in geological disposal systems for high-level radioactive wastes. In this study, the effect of cement-bentonite interactions on bentonite alteration was investigated by reviewing the literature on studies of cement-bentonite interactions. The major bentonite alteration by hyperalkaline fluids produced by the interaction of cementitious materials with groundwater includes cation exchange, montmorillonite dissolution, secondary mineral precipitation, and illitization. When the hyperalkaline leachate from the reaction of the cementitious material with the groundwater comes into contact with bentonite, montmorillonite, the main component of bentonite, is dissolved and a small amount of secondary minerals such as zeolite, calcium silicate hydrate, and calcite is produced. When montmorillonite is continuously dissolved, the physicochemical properties of bentonite may change, which may ultimately causes changes in bentonite performance as a buffer material such as adsorption capacity, swelling capacity, and hydraulic conductivity. In addition, the bentonite alteration is affected by various factors such as temperature, reaction period, pressure, composition of pore water, bentonite constituent minerals, chemical composition of montmorillonite, and types of interlayer cations. This study can be used as basic information for the long-term stability verification study of the buffer material in the geological disposal system for high-level radioactive wastes.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.32 no.4
• /
• pp.302-324
• /
• 2022

Objectives: The objective of this study is to investigate exposure to occupational carcinogens in the nationwide electronics industries and to establish a strategy for control of occupational carcinogens in South Korea. Methods: We evaluated occupational carcinogens as defined by International Agency for Research on Cancer (IARC) using a nationwide work environment measurement database on the electronics industry in South Korea measured between 2013 and 2017 in accordance with the Occupational Safety and Health Act. Results: The number of occupational carcinogens found in the electronics industry in South Korea were: 20 for IARC Group 1, 14 for Group 2A, and 30 for Group 2B. The occupational carcinogens (Group 1) most frequently exposed were strong-inorganic-acid mists containing sulfuric acid (sulfuric acid), welding fumes, mineral oils (untreated or mildly treated), nickel compounds, silica dust, crystalline substances in the form of quartz or cristobalite, formaldehyde, arsenic and inorganic arsenic compounds, chromium (VI) compounds, trichloroethylene, cadmium and cadmium compounds, vinyl chloride, ethylene oxide, wood dust, beryllium and beryllium compounds, 1,3 butadiene, benzene, and others. Among them, the carcinogens (Group 1) exceeding the acceptable standard were trichloroethylene, formaldehyde, and ethylene oxide. The working environment measurement system as regulated by Occupational Safety and Health Act is not properly assessed and managed for occupational carcinogens in South Korea. A component analysis for all materials used should be set up to practically reduce occupational carcinogens. A ban on the use of occupational carcinogens and the development of alternative materials are needed. The occupational carcinogens below the acceptable standards should be carefully examined and a new standard for exposure needs to be established. Conclusions: The Occupational Safety and Health Act should be improved to identify and monitor occupational carcinogens at work sites. A strategy for occupational safety and health systems should be provided to give direction to workers' needs and right to know.

• The Journal of Engineering Geology
• /
• v.33 no.1
• /
• pp.69-83
• /
• 2023

Forest fires increase the risk of subsequent soil erosion and mass movement in burned areas, even under rainfall conditions below landslide alert thresholds, by destroying plants and vegetation and causing changes to soil properties. These effects of forest fires can alter runoff in burned areas by altering soil composition, component minerals, soil water repellency, soil mass stability, and soil fabric. Heat from forest fires not only burns shallow organic matter and plants but also spreads below the surface, affecting soil constituents including minerals. This study analyzed X-ray diffraction and physical properties of topsoil and subsoil obtained from both burned and non-burned areas to identify the composition and distribution of clay minerals in the soil. Small amounts of mullite, analcite, and hematite were identified in burned soils. Vermiculite and mixed-layer illite/vermiculite (I/V) were found in topsoil samples from burned areas but not in those from non-burned areas. These findings show changes in soil mineral composition caused by forest fires. Expansive clay minerals increase the volume of soil during rainfall, degrading the structural stability of slopes. Clay minerals generated in soil in burned areas are therefore likely to affect the long-term stability of slopes in mountainous areas.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.1B
• /
• pp.149-152
• /
• 2008

The reaction between iron oxide and ferrous iron is known to be the adsorption of ferrous iron onto the oxide surfaces that produces Fe(II)-Fe(III) (hydr)oxides and ferrous oxide oxidized to ferric ion which is the reducing agent of the target compounds. In our investigations on DS/S using ferrous modified steel slag, the results did not follow the trends. FeO and Fe(II), the major component of steel slag, were used to investigate the degradation of TCE. Degradation did not take place for the first and suddenly degraded after awhile. Degradation of TCE in this system was unexpected because Fe(II)-Fe(III) (hydr)oxides could not be produced in absence of ferric oxide. In this study, the characteristics of FeO/Fe(II) system as a reducing agent were observed through the degradation of TCE, measuring byproducts of TCE and the concentration of Fe(II) and Fe(III). Adsorption of ferrous ion on FeO was observed and the generation of byproducts of TCE showed the degradation of TCE by reduction in the system is obvious. However it did not correspond with the typical reducing mechanisms. Future research on this system needs to be continued to find out whether new species are generated or any unknown mineral oxides are produced in the system that acted in the degradation of TCE.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.34 no.3
• /
• pp.86-91
• /
• 2024

In this study, the characteristics of mortar using carbondioxide conversion capture materials (CCMs), fabricated by reacting CO₂ with desulfurization gypsum (DG) by-produced from a oil refinery, as a cement mixture. Based on the chemical component and particle size analysis results, it estimated that desulfurized gypsum reacted with carbon dioxide to produce carbonate crystals such as CaCO₃. Using CCMs as a cement mixture, physical property and durability analysis were conducted by measuring such as workability, compressive strength, compressive strength ratio after freezing-thawing and accelerated carbonation depth. The experimental results showed that as the content of the admixture increased, workability and compressive strength characteristics decreased. Compressive strength after freezing-thawing and accelerated carbonation depth also showed similar characteristics to the physical property measurement results. In addition, compared to desulfurized gypsum, using CCMs showed better physical properties and durability. This was assumed to be due to differences in the crystal phases of the mixed materials such as free-CaO and CaCO₃.

• Journal of the Korea Institute of Building Construction
• /
• v.24 no.5
• /
• pp.565-575
• /
• 2024

This research was initiated to establish quality standards and testing methods for fine dust in aggregates, a component currently not regulated under the Korean Industrial Standards(KS) KS F 2527 for Concrete Aggregates. With limited existing research and no definitive quality or testing standards for fine dust, this study sought to provide a quantitative analysis of fine dust in aggregates and to set forth quality standards based on the dust content through a concrete performance evaluation. The experimental findings showed that the primary chemical constituents of the fine dust were aluminum oxide(Al₂O₃), iron oxide(Fe₂O₃), and silicon dioxide(SiO₂). It was observed that increasing levels of fine dust in the aggregates led to higher values of the fine dust index(Al₂O₃+Fe₂O₃). This escalation in the fine dust index corresponded with an increase in the unit water content of the concrete and a consequent decline in compressive strength. Based on these observations, a maximum allowable limit for the fine dust index in aggregates was proposed at 23%. This limit was derived from the correlation between fine dust content and a 15% reduction in compressive strength of standard concrete specimens. The proposed evaluation method for the fine dust index based on its content in aggregates is expected to enhance concrete performance and ensure structural stability. This contribution to the field addresses a significant gap in the standards and provides a foundation for further research and standardization in the construction materials industry.

• The Korean Journal of Food And Nutrition
• /
• v.23 no.1
• /
• pp.1-7
• /
• 2010

In this study, nutritional analysis was done on regular rice bran and fermented rice bran toward increasing their availability and use. Regular and fermented rice bran were extracted 10 times at $98^{\circ}C$ for 4 hours each with water, extracted with 60% ethanol at $60^{\circ}C$ for 4 hours, then concentrated and extracted twice by freeze-drying. When rice bran was fermented, moisture, protein, and ash contents increased, while fats and carbohydrates decreased. Out of fatty acids, the saturated fatty acid content of regular rice ran was found to be 17.7%, and 20.5% when fermented while the unsaturated fatty acid components of rice ran and fermented rice bran were found to be 82.3 and 79.5%, respectively. In both kinds of bran, palmitic acid, oleic acid and linoleic acid represented over 90% of the fatty acid content. In rice bran the fatty acid composition was 15.1% palmitic acid, 40.6% oleic acid and 39.5% linoleic acid, while that of fermented rice bran was 13.2% palmitic acid, 43.2% oleic acid and 31.3% linoleic acid. Out of free sugars fermented rice bran contained 0% fructose, 0.0099% glucose, 0.0039% maltose and 0.3233% sucrose. These results with which those of regular rice bran were silmilar were according to the normal sugar composition of rice in general. The vitamin C content of rice bran was 53 mg/100 g and that of fermented rice bran 7 mg/100 g. In neither kind of rice bran was vitamin A detected. Out of 18 minerals analyzed, Ca, K, Mg, and Mn were the most abundant minerals in both kinds of rice bran. Fermented rice bran had a higher K content with 3,163 mg/100 g, than normal rice bran, Mg content was 1,178 mg/100g. Fermented rice bran had a higher total mineral content.