• International Journal of High-Rise Buildings
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• v.8 no.2
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• pp.107-116
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• 2019

The use of computational fluid dynamics (CFD) is becoming an increasingly popular means to model wind flows in and around buildings. The first published application of CFD to both indoor and outdoor building airflows was in the 1970's. Since then, CFD usage has expanded to include different aspects of building design. Wind tunnel testing (WTT) on buildings for wind loads goes back as far as 1908. Gustave Eiffel built a pair of wind tunnels in 1908 and 1912. Using these he published wind loads on an aircraft hangar in 1919 as cited in Hoerner (1965 - page 74). The second of these wind tunnels is still in use today for tests including building design ($Damljanovi{\acute{c}}$, 2012). The Empire State Building was tested in 1933 in smooth flow - see Baskaran (1993). The World Trade Center Twin Towers in New York City were wind tunnel tested in the mid-sixties for both wind loads, at Colorado State University (CSU) and the [US] National Physical Laboratory (NPL), as well as pedestrian level winds (PLW) at the University of Western Ontario (UWO) - Baskaran (1993). Since then, the understanding of the planetary boundary layer, recognition of the structures of turbulent wakes, instrumentation, methodologies and analysis have been continuously refined. There is a drive to replace WTT with computational methods, with the rationale that CFD is quicker, less expensive and gives more information and control to the architects. However, there is little information available to building owners and architects on the limitations of CFD for flows around buildings and communities. Hence building owners, developers, engineers and architects are not aware of the risks they incur by using CFD for different studies, traditionally conducted using wind tunnels. This paper will explain what needs to happen for CFD to replace wind tunnels. Ultimately, we anticipate the reader will come to the same conclusion that we have drawn: both WTT and CFD will continue to play important roles in building and infrastructure design. The most pressing challenge for the design and engineering community is to understand the strengths and limitations of each tool so that they can leverage and exploit the benefits that each offers while adhering to our moral and professional obligation to hold paramount the safety, health, and welfare of the public.

• Journal of Powder Materials
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• v.28 no.5
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• pp.423-428
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• 2021

Here, we report the development of a new and low-cost core-shell structure for lithium-ion battery anodes using silicon waste sludge and the Ti-ion complex. X-ray diffraction (XRD) confirmed the raw waste silicon sludge powder to be pure silicon without other metal impurities and the particle size distribution is measured to be from 200 nm to 3 ㎛ by dynamic light scattering (DLS). As a result of pulverization by a planetary mill, the size of the single crystal according to the Scherrer formula is calculated to be 12.1 nm, but the average particle size of the agglomerate is measured to be 123.6 nm. A Si/TiO₂ core-shell structure is formed using simple Ti complex ions, and the ratio of TiO₂ peaks increased with an increase in the amount of Ti ions. Transmission electron microscopy (TEM) observations revealed that TiO₂ coating on Si nanoparticles results in a Si-TiO₂ core-shell structure. This result is expected to improve the stability and cycle of lithium-ion batteries as anodes.

• Journal of Powder Materials
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• v.28 no.5
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• pp.389-395
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• 2021

Oxide dispersion-strengthened (ODS) steel has excellent high-temperature properties, corrosion resistance, and oxidation resistance, and is expected to be applicable in various fields. Recently, various studies on mechanical alloying (MA) have been conducted for the dispersion of oxide particles in ODS steel with a high number density. In this study, ODS steel is manufactured by introducing a complex milling process in which planetary ball milling, cryogenic ball milling, and drum ball milling are sequentially performed, and the microstructure and high-temperature mechanical properties of the ODS steel are investigated. The microstructure observation revealed that the structure is stretched in the extrusion direction, even after the heat treatment. In addition, transmission electron microscopy (TEM) analysis confirmed the presence of oxide particles in the range of 5 to 10 nm. As a result of the room-temperature and high-temperature compression tests, the yield strengths were measured as 1430, 1388, 418, and 163 MPa at 25, 500, 700, and 900℃, respectively. Based on these results, the correlation between the microstructure and mechanical properties of ODS steel manufactured using the composite milling process is also discussed.

• Food Science and Industry
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• v.49 no.4
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• pp.40-63
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• 2016

John Glenn, America's first man to eat anything in the near-weightless environment of Earth orbit, found the task of eating fairly easy. With improved packaging came improved food quality and menus. By the time of the Apollo Program, the quality and variety of food increased even further. Apollo astronauts were the first to have hot water, which made rehydrating foods easier and improved the food's taste. Thermostabilized pouches were also introduced on Apollo. The task of eating in space got a big boost in Skylab. It also had a food freezer and refrigerator a convenience offered by no other vehicle before or since. Two different food systems will be used for future long-duration missions to other planets, one for traveling to and from the distant body and one for use on the surface of the moon or Mars. The transit food system will be similar to the space station food system with the exception that products with three-to five-year shelf lives will be needed. Thus, this part of the trip will be similar to what occurs aboard space missions now. The surface food system, be it lunar or planetary, will be quite different. It will be similar to a vegetarian diet that someone could cook on Earth. Once crew members arrive on the surface and establish living quarters, they can start growing crops. Once the crops are processed into edible ingredients, cooking will be done in the spacecraft's galley to make the food items. Disposal of used food packaging will be an issue since there will be no Progress vehicles to send off and incinerate into the Earth's atmosphere. Packaging materials will be used that have less mass but sufficient barrier properties for oxygen and water to maintain shelf life as those now in use.

• Journal of the Korean earth science society
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• v.42 no.1
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• pp.118-131
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• 2021

The purpose of this study was to investigate the characteristics of evidence-based reasoning practiced by middle school gifted students. Data were collected through an online task in which middle school students in gifted education institutes of a university located in the metropolitan area, Korea, performed inquiry about the shape of a planet's orbit. The students were given data of Mercury's greatest elongations and asked to draw the planet's orbit with the data. Each of the students was also asked to provide his or her hypothesis of Mercury's orbit before the drawing and to reason about the orbit again using his or her own drawing as evidence. The content analysis of the students' reports revealed 5 different types of judgement about the shape of Mercury's orbit, 4 types of reasoning about the hypothesis and evidence, and the characteristics of evidence-based reasoning within the judgement types. Based upon the analysis results, the importance of proper interpretations of evidence in evidence-based reasoning, the core role of the theory-evidence coordination, and the usefulness of working with multiple hypotheses were discussed. In addition, implications for earth science education were suggested.

• Journal of the Korean Geotechnical Society
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• v.38 no.9
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• pp.19-33
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• 2022

Planarity geotechnical exploration missions were actively performed during the 1970s and there was a period of decline from the 1 990s to the 2000s because of budget. However, exploring space resources is essential to prepare for the depletion of Earth's resources in the future and explore resources abundant in space but scarce on Earth, such as rare earth and helium-3. Additionally, the development of space technology has become the driving force of future industry development. The competition among developed countries for exoplanet exploration has recently accelerated for the exploration and utilization of space resources. For these missions and resource exploration/mining, geotechnical exploration is required. There have been several missions to explore exoplanet ground, including the Moon, Mars, and asteroids. There are Apollo, LUNA, and Chang'E missions for exploration of the Moon. The Mars missions included Viking, Spirit/Opportunity, Phoenix, and Perseverance missions, and the asteroid missions included the Hayabusa missions. In this study, space planetary mineral resource exploration technologies are explained, and the future technological tasks of Korea are described.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.2
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• pp.57-65
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• 2022

In this study, the effect of the initial particle size distribution (PSD) of (K_0.5Na_0.5)NbO₃ powders on the microstructure of sintered ceramics was investigated. (K_0.5Na_0.5)NbO₃ powders with uni-, bi-, tri-, and quad-modal PSDs were obtained through a planetary ball-mill. For the specimens sintered at 1080℃, the growth of abnormal grains was promoted from the powders exhibiting quad- and tri-modal PSDs with a high content of large particles, resulting in a microstructure in which huge abnormal grains were predominant. However, as the number of peaks in PSD and the overall particle size decreased, the abnormal grain growth was suppressed and the grain growth of small particles started, resulting in a microstructure with a uniform grain size. For the specimens sintered at 1100℃, huge abnormal grains were not observed due to the decrease in the critical driving force for 2D nucleation even when powders with quad- and tri-modal PSDs were used. It was confirmed that when powder with unimodal PSD was used, a uniform microstructure that was not significantly affected by the sintering temperature could be obtained. The results of this study demonstrate that the microstructure of (K_0.5Na_0.5)NbO₃-based ceramics can be controlled by controlling the particle size of the initial powder.

• Journal of Electrochemical Science and Technology
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• v.14 no.2
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• pp.184-193
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• 2023

This study investigates the effects of a carbon fiber layer formed on the surface of an etched aluminum current collector on the electrochemical properties of the activated carbon electrodes for an electric double layer capacitor. A particle size analyzer, field-emission SEM, and nitrogen adsorption/desorption isotherm analyzer are employed to analyze the structure of the carbon fiber layer. The electric and electrochemical properties of the activated carbon electrodes using a carbon fiber layer are evaluated using an electrode resistance meter and a charge-discharge tester, respectively. To uniformly coat the surface with carbon fiber, we applied a planetary mill process, adjusted the particle size, and prepared the carbon paste by dispersing in a binder. Subsequently, the carbon paste was coated on the surface of the etched aluminum current collector to form the carbon under layer, after which an activated carbon slurry was coated to form the electrodes. Based on the results, the interface resistance of the EDLC cell made of the current collector with the carbon fiber layer was reduced compared to the cell using the pristine current collector. The interfacial resistance decreased from 0.0143 Ω·cm² to a maximum of 0.0077 Ω·cm². And degradation reactions of the activated carbon electrodes are suppressed in the 3.3 V floating test. We infer that it is because the improved electric network of the carbon fiber layer coated on the current collector surface enhanced the electron collection and interfacial diffusion while protecting the surface of the cathode etched aluminum; thereby suppressing the formation of Al-F compounds.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.37.2-37.2
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• 2021

Turbulence produces the density and velocity fluctuations in molecular clouds, and dense regions within the density fluctuation are the birthplace of stars. Also, turbulence can produce non-thermal pressure against gravity. Thus, turbulence plays a crucial roles in controlling star formation. However, despite many years of study, the detailed relation between turbulence and star formation remain poorly understood. As part of the Taeduk Radio Astronomy Observatory (TRAO) Key Science Program (KSP), "mapping Turbulent properties In star-forming MolEcular clouds down to the Sonic scale (TIMES; PI: Jeong-Eun Lee)", we mapped two star-forming molecular clouds, the Orion A and the ρ Ophiuchus molecular clouds, in six molecular lines (¹³CO 1-0/C¹⁸O 1-0, HCN 1-0/HCO⁺ 1-0, and CS 2-1/N₂H⁺ 1-0) using the TRAO 14-m telescope. We applied the Principal Component Analysis (PCA) to the observed data in two different ways. The first method is analyzing the variation of line intensities in velocity space to evaluate the velocity power spectrum of underlying turbulence. We investigated the relation between the star formation activities and properties of turbulence. The other method is analyzing the variation of the integrated intensities between the molecular lines to find the characteristic correlation between them. We found that the HCN, HCO⁺, and CS lines well correlate with each other in the integral shaped filament in the Orion A cloud, while the HCO⁺ line is anti-correlate with the HCN and CS lines in L1688 of the Ophiuchus cloud.

• Nuclear Engineering and Technology
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• v.55 no.7
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• pp.2380-2387
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• 2023

Hyperspectral data and its ability to explore the minerals and their associated rocks have a remarkable application in mineral exploration and lithological characterization. The present study aims to explore the radiation shielding aspects of the iron ore in Kerala with the aid of the Hyperion hyperspectral dataset. The reflectance-spectra obtained from the laboratory conditions as well as from the image show various absorptions. The results from the spectra are validated with geochemical data and GPS points. The Monte Carlo simulation employed to evaluate the radiation shielding ability. Raising the oxygen ions caused a noteworthy decrease in the µ values of the studied rocks which is accompanied by an increase in Δ_0.5 and Δ_eq values. The Δ_0.5 and Δ_eq values increased by factors of approximately 77 % with raising the oxygen ions between 44.32 and 47.57 wt.%. The µ values varies with the oxygen concentrations, where the µ values decreased from 2.531 to 0.925 cm^-1 (at 0.059 MeV), from 0.381to 0.215 cm^-1 (at 0.662 MeV), and from 0.279 to 0.158 cm^-1 (at 1.25 MeV) with raising the oxygen ions from 44.32 to 47.43 wt.%.