• Nuclear Engineering and Technology
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• v.55 no.6
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• pp.2335-2347
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• 2023

As medical facilities are usually built at urban areas, special concrete aggregates and evaluation methods are needed to optimize the design of concrete walls by balancing density, thickness, material composition, cost, and other factors. Carbon treatment rooms require a high radiation shielding requirement, as the neutron yield from carbon therapy is much higher than the neutron yield of protons. In this case study, the maximum carbon energy is 430 MeV/u and the maximum current is 0.27 nA from a hybrid particle therapy system. Hospital or facility construction should consider this requirement to design a special heavy concrete. In this work, magnetite is adopted as the major aggregate. Density is determined mainly by the major aggregate content of magnetite, and a heavy concrete test block was constructed for structural tests. The compressive strength is 35.7 MPa. The density ranges from 3.65 g/cm³ to 4.14 g/cm³, and the iron mass content ranges from 53.78% to 60.38% from the 12 cored sample measurements. It was found that there is a linear relationship between density and iron content, and mixing impurities should be the major reason leading to the nonuniform element and density distribution. The effect of this nonuniformity on radiation shielding properties for a carbon treatment room is investigated by three groups of Monte Carlo simulations. Higher density dominates to reduce shielding thickness. However, a higher content of high-Z elements will weaken the shielding strength, especially at a lower dose rate threshold and vice versa. The weakened side effect of a high iron content on the shielding property is obvious at 2.5 µSv=h. Therefore, we should not blindly pursue high Z content in engineering. If the thickness is constrained to 2 m, then the density can be reduced to 3.3 g/cm³, which will save cost by reducing the magnetite composition with 50.44% iron content. If a higher density of 3.9 g/cm³ with 57.65% iron content is selected for construction, then the thickness of the wall can be reduced to 174.2 cm, which will save space for equipment installation.

• Journal of the Korea Institute of Building Construction
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• v.9 no.5
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• pp.79-86
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• 2009

In a steel structure, spray-applied fire resistive materials are crucial in preventing structural strength from being weakened in the event of a fire. The quality control of such materials, however, is difficult for manual workers, who can frequently be in short supply. These skilled workers are also very likely to be exposed to environmental hazards. Problems with construction work such as this, which are specifically the difficulty of achieving quality control and the dangerous nature of the work itself, can be solved to some degree by the introduction of automated equipment. It is, however, very difficult to automate the work process, from operation to the selection of a location for the equipment, as the environment of a construction site has not yet been structured to accommodate automation. This is a fundamental study on the possibility of the automation of spray-applied fire resistive coating work. In this study, the linkability of the cutting-edge RTLS to an automation system is reviewed, and a scenario for the automation of spray-applied fire resistive coating work and system composition is presented. The system suggested in this study is still in a conceptual stage, and as such, there are many restrictions still to be resolved. Despite this fact, automation is expected to have good effectiveness in terms of preventing fire from spreading by maintaining a certain level of strength at a high temperature when a fire occurs, as it maintains the thickness of the fire-resistive coating at a specified level, and secures the integrity of the coating with the steel structure, thereby enhancing the fire-resistive performance. It also expected that if future research is conducted in this area in relation to a cutting-edge monitoring TRS, such as the ubiquitous sensor network (USN) and/or building information model (BIM), it will contribute to raising the level of construction automation in Korea, reducing costs through the systematic and efficient management of construction resources, shortening construction periods, and implementing more precise construction

• Economic and Environmental Geology
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• v.12 no.2
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• pp.51-73
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• 1979

The zinc-lead deposits at the Yeonhwa I mine were investigated in terms of ore-forming geologic setting, structural style of ore control, geometry of individual orebodies, zoning, paragenesis and chemical composition of skarn minerals, as well as metal grades and ratios of selected orebodies. The Yeonhwa I mine is characterized by a large swarm of chimney type massive orebodies with thin skarn envelopes, boldly developed through a thick sequence of Pungchon Limestone, the overlying Hwajeol Formation, and the underlying Myobong Slate of Cambrian age. Nearly 20 orebodies of similar shape, but of varying size are arranged in a V-shaped pattern with northwest and northeast trends, clearly indicating an outstanding ore control by a conjugate system of fractures with these trends. Important orebodies are the Wolam 1, 2, 3, and 5 orebodies in the west, and the Namsan 1, 2, 3. and 5 orebodies in the east, among others. The Wolam 1 orebody, which was observed from the -360 level through the -240, -120, and 0 levels to the surface outcrops (totaling a vertical height of about 500m), shows a vertical variation in skarn mineralogy, ranging from pyroxene-garnet zone on the lower levels. through pyroxene (without garnet) zone on the intermediate levels, and finally to rhodochrosite vein on the upper levels and surface. Microprobe analyses of pyroxene and garnet on a total of 14 mineral grains revealed that pyroxenes are manganoan salitic in most samples, with downward increase of Fe and Mn, whereas garnets are highly andraditic, containing fractions of subordinate grossular with downward decrease of Fe. This indicates a reverse relationship of Fe-contents between pyroxene and garnet with depth. Ore minerals are major sphalerite, subordinate galena, and minor chalcopyrite. Sulfide gangue minerals include major pyrrhotite, and minor pyrite and marcasite of later age. Two types of variational trends in metal grades and ratios with depth are present on the plots of assay data from the Wolam orebodies: one is a steady upward increase in Pb, Zn, and Pb:Zn ratios, with a terminal decline at the top of orebody: the other is an irregular or sinusoidal change. The former is characteristic of chimney-type orebodies, whereas the latter is of vein· shaped orebodies. The Pb grades show large variations among orebodies and from level to level, whereas the Zn grades are relatively constand or less variable.

• Korean Journal of Mineralogy and Petrology
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• v.34 no.3
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• pp.157-167
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• 2021

Lead (Pb) is one of the key trace elements, exhibiting a peculiar partitioning behavior into silicate melts in contact with minerals. Partitioning behaviors of Pb between silicate mineral and melt have been known to depend on melt composition and thus, the atomic structures of corresponding silicate liquids. Despite the importance, detailed structural studies of Pb-bearing silicate melts are still lacking due to experimental difficulties. Here, we explored the effect of lead content on the atomic structures, particularly the evolution of silicate networks in Pb-bearing sodium metasilicate ([(PbO)_x(Na₂O)_1-x]·SiO₂) glasses as a model system for trace metal bearing natural silicate melts, using ²⁹Si solid-state nuclear magnetic resonance (NMR) spectroscopy. As the PbO content increases, the ²⁹Si peak widths increase, and the maximum peak positions shift from -76.2, -77.8, -80.3, -81.5, -84.6, to -87.7 ppm with increasing PbO contents of 0, 0.25, 0.5, 0.67, 0.86, and 1, respectively. The ²⁹Si MAS NMR spectra for the glasses were simulated with Gaussian functions for Qⁿ species (SiO₄ tetrahedra with n BOs) for providing quantitative resolution. The simulation results reveal the evolution of each Qⁿ species with varying PbO content. Na-endmember Na₂SiO₃ glass consists of predominant Q² species together with equal proportions of Q¹ and Q³. As Pb replaces Na, the fraction of Q² species tends to decrease, while those for Q¹ and Q³ species increase indicating an increase in disproportionation among Qⁿ species. Simulation results on the ²⁹Si NMR spectrum showed increases in structural disorder and chemical disorder as evidenced by an increase in disproportionation factor with an increase in average cation field strengths of the network modifying cations. Changes in the topological and configurational disorder of the model silicate melt by Pb imply an intrinsic origin of macroscopic properties such as element partitioning behavior.

• Economic and Environmental Geology
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• v.53 no.4
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• pp.383-395
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• 2020

The stratigraphical position of the Haengmae Formation can provide clues towards solving the hot issue on the Silurian formation, also known as Hoedongri Formation. Since the 2010s, there have been several reports denying the Haengmae Formation as a lithostratigraphic unit. This study aimed to clarify the lithostratigraphic and chronostratigraphic significance of the Haengmae Formation. The distribution and structural geometry of the Haengmae Formation were studied through geologic mapping, and the correlation of relative geologic age and the absolute age was performed through conodont biostratigraphy and zircon U-Pb dating respectively. The representative rock of the Haengmae Formation is massive and yellow-yellowish brown pebble-bearing carbonate rocks with a granular texture similar to sandstone. Its surface is rough with a considerable amount of pores. By studying the mineral composition, contents, and microstructure of the rocks, they have been classified as pebble-bearing clastic rocks composed of dolomite pebbles and matrix. They chiefly comprise of euhedral or subhedral dolomite, and rounded, well-sorted fine-grained quartz, which are continuously distributed in the study area from Biryong-dong to Pyeongan-ri. Bedding attitude and the thickness of the Haengmae Formation are similar to that of the Hoedongri Formation in the north-eastern area (Biryong-dong to Haengmae-dong). The dip-direction attitudes were maintained 340°/15° from Biryong-dong to Haengmae-dong with a thickness of ca. 200 m. However, around the southwest of the studied area, the attitude is suddenly changed and the stratigraphic sequence is in disorder because of fold and thrust. Consequently, the formation is exposed to a wide low-relief area of 1.5 km × 2.5 km. Zircon U-Pb age dating results ranged from 470 to 449 Ma, which indicates that the Haengmae Formation formed during the Upper Ordovician or later. The pebble-bearing carbonate rock consisted of clastic sediments, suggesting that the Middle Ordovician conodonts from the Haengmae Formation must be reworked. Therefore, the above-stated evidence supports that the geologic age of the Haengmae Formation should be Upper Ordovician or later. This study revealed that the Haengmae Formation is neither shear zone, nor an upper part of the Jeongseon Limestone, and is also not the same age as the Jeongseon Limestone. Furthermore, it was confirmed that the Haengmae Formation should be considered a unit of lithostratigraphy in accordance with the stratigraphic guide of the International Commission on Stratigraphy (ICS).

• Journal of the Korean Ceramic Society
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• v.41 no.5
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• pp.395-400
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• 2004

The effects of compositions of binders on the rheological properties of mixtures and the preparation conditions on the formation of defects and the debinding characteristics of compacts for the injection molding of ceramic powders (65 wt% aluminaㆍ35 wt% feldspar) were studied. Ceramic powders were coated with 2 wt% of stearic acid and then mixed with 15, 20, and 25 wt% of Paraffin Wax (PW) and High Density Polyethylene (HDPE) as binders at $160^{\circ}C$ for 2 h. Rheological properties were investigated by using capillary rheometer. Apparent viscosities of mixtures were 80∼300 Paㆍs at 1,000$s^{-1}$ of a shear rate, it was good for the injection molding and depending on the compositions of binders. Short shot was formed at 15H5P5 (the ratio of HDPE : PW=5 : 5 in 15 wt% of binders) compacts without injection pressures and any noticeable defects were not formed at 45 kgf/$cm^{2}$ in 20H5P5 compacts. PW and HDPE were removed by the solvent extraction and thermal debinding method. Thermal debinding of HDPE at $450^{\circ}C$ for 5 h, which followed the extraction of PW was using n-heptane solvent at $70^{\circ}C$ for 5 h. Continuous pores in compacts, which facilitate the removal of HDPE by the thermal debinding, were found to form in the compacts when PW was removed by the solvent extraction. The optimum composition of binder at which binder was removed by thermal debinding without defects while maintaining the compact strength was 20H5P5. Bulk density, porosity and 3-point bending strength of 20H5P5 compact sintered at 1,30$0^{\circ}C$ for 5 h were 2.8, < 3%, and 2,400 kgf/$cm^{2}$, respectively, and can be used as a structural materials.