• Proceedings of the Korea Air Pollution Research Association Conference
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• 2006.04a
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• pp.235-236
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• 2006

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2007.10a
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• pp.440-441
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• 2007

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2004.11a
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• pp.326-327
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• 2004

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2004.11a
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• pp.191-192
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• 2004

• International Union of Geodesy and Geophysics Korean Journal of Geophysical Research
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• v.22 no.1
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• pp.6-23
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• 1994

A disconnection event (DE) of the cometary plasma tail is one of most spectacular phenomena observed in comets. Yet, for years it has remained one of the great unsolved problems I astronomy and space physics. The solar wind is thought to play a major role in the creation of comet plasma tail (type Ⅰ) disconnection events. The goal of this paper is to present a mechanism that explains the disconnection event in terms of the local conditions at the comet. Comparison of the solar wind conditions and 16 DEs in Halley's comet shows that DEs are associated primarily with crossings of the heliospheric sector boundary and apparently not with any other properties of the solar wind, such as a high speed stream[Yi et al., 1994]. A 3-dimensional resistive magnetohydrodynamic simulation in this paper supports this association by showing that only front-side magnetic reconnection between the reversed interplanetary magnetic fields that exist when a comet crosses the heliospheric sector boundary [Niedner and Brandt, 1978] could reproduce the morphology of a DE, including ray formation [Brandt, 1982].

• Journal of the Korean Ceramic Society
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• v.23 no.1
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• pp.1-6
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• 1986

The shrinkage rate of solid state sintering has been theoretically derived by combining the rate equation of material transport and the net free energy change resulting from the decrease of solid-vapor interface and the increase of grain boundary during sintering. For a sinteing model an idealized situation of the spherical particles with BCC packing was taken as the initial condition and the shrinkage was assumed to occur by forming the flat circualr grain boundaries on each particle. The plotted shrinkage rates as a function of grain boundary to surface energy ratio $(gamma_g/gamma_s)$ have shown that the relative density increases linearly at the initial stage of sintering but the shrinkage rate is decreased upon further sintering due to a decrease in driving force for densificaton. It has been also shown that the densification is critically affected by the $gamma_g/gamma_s$ ratio. In order to get the complete densificatin the ratio should be less than $sqrt{3}$. Any additive or atmospheric condition causing the decrease of$_g/gamma_s$ ratio will enhance sintering.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2002.11a
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• pp.223-224
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• 2002

This study is motivated by the discrepancies found in previous studies that compared the observed photochemically reactive species in the marine boundary layer (MBL) with the model simulations. In particular, HCHO was underpredicted in PEM-Tropics (B) and overpredicted in TRACE-A, $H_2O$$_2$ overpredicted, $CH_3$OOH overpredicted, and $CH_3$OH significantly overpredicted (Thompson et al., 1993; Heikes et at., 1996; Davis et al., 1996; Jacob et al., 1996; Schultz et al., 1997; Suhre et al., 1998). (omitted)

• Journal of Wind Energy
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• v.9 no.4
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• pp.40-46
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• 2018

In this study, a three-dimensional Navier-Stokes simulation around Wido Island was performed to analyze the wake effect behind an island. A 10 m/s wind speed and pressure boundary conditions were assigned for the inflow and outflow boundary conditions, respectively. Wido Island was modeled using GIS data. A prevailing wind from the north-northwest direction was determined based on QuikSCAT satellite data. A computational domain of $40km{\times}20km{\times}5km$ covering Wido Island was applied for numerical analysis. Sixty points were specified to extract the wind speed data. A wind speed profile inside the atmospheric boundary layer was compared with a wind profile using a simple power law. It turns out that the wake effect decreases the mean wind speed by 5% more or less, which corresponds to a 14% decrease in wind energy. Thus, the installation of a meteorological mast or development of a wind farm behind Wido Island is not highly recommended.

• Wind and Structures
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• v.37 no.2
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• pp.163-178
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• 2023

The paper reviews and discusses the substantive changes to the ASCE 49-21 Standard, Wind Tunnel Testing for Buildings and Other Structures. The most significant changes are the requirements for wind field simulations that utilize (i) partial turbulence simulations, (ii) partial model simulations for the flow around building Appurtenances, along with requirements for determining wind loads on products that are used at multiple sites in various configurations. These modifications tend to have the effect of easing the precise scaling requirements for flow simulations because it is not generally possible to construct accurate models for small elements placed, for example, on large buildings at the scales typically available in boundary layer wind tunnels. Additional discussion is provided on changes to the Standard with respect to measurement accuracy and data acquisition parameters, such as duration of tests, which are also related to scaling requirements. Finally, research needs with respect to aerodynamic mechanisms are proposed, with the goal of improving the understanding of the role of turbulence on separated-reattaching flows on building surfaces in order to continue to improve the wind tunnel method for determining design wind loads.

• Asian Journal of Atmospheric Environment
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• v.9 no.1
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• pp.1-11
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• 2015

Increasing ozone concentrations are observed over Japan from year to year. One cause of high ozone concentration in the Kanto region, which includes areas inland from large coastal cities such as metropolitan Tokyo, is the transportation of precursors by sea breezes. However, high ozone concentrations are also observed in the morning, before sea breezes approach inland areas. In this point, there would be a possibility of residual ozone existing above the nocturnal boundary layer affects the ozone concentration in the following morning. In this study, we utilized the Weather Research and Forecasting model and the Community Multiscale Air Quality model to evaluate the effect of regional precursors and residual ozone on ozone concentrations over the inland Kanto region. The results show that precursors emitted from non-metropolitan areas affected inland ozone concentrations more than did precursors from metropolitan areas. Moreover, calculated results indicate downward transportation of residual ozone, resulting in increased concentration. The residual ozone was also affected by precursors emitted from non-metropolitan areas.