• Tunnel and Underground Space
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• v.15 no.1 s.54
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• pp.55-60
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• 2005

In this study, the 1/20 reduced-scale experiments using Froude scaling were conducted to investigate the effect of longitudinal ventilation on the variation of burning rate in tunnel fires. The methanol square pool fires with heat release rate ranging from 3.57 kW to 10.95 kW were used. The burning rate of fuel was obtained by measured mass using load cell and temperature distribution were measured by K-type theomocouples in order to investigate smoke movement. The wind tunnel was connected with one side of the tested tunnel, and logitudinal ventilation velocity in the tested tunnel was controlled by power of the wind tunnel. In methanol fire case, the increase in ventilation velocity decreased the turning rate due to the direct cooling of fire plume. For the same dimensionless velocity(V), homing rate decreased as the size of pool fire increased.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.39.2-39.2
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• 2018

RR Tel is an interacting binary system in which a hot white dwarf (WD) accretes matter from a Mira variable via gravitational capture of the stellar wind. We present a high-resolution optical spectrum of RR Tel obtained with MIKE at Magellan-Clay telescope, Chile. We find broad emission features at 6825, 7082, 7023, and $7053{\AA}$, which are formed through Raman scattering of far-UV O VI ${\lambda}{\lambda}$ 1032 and $1038{\AA}$, C II ${\lambda}{\lambda}$ 1036 and $1037{\AA}$ with atomic hydrogen. Raman O VI 6825 and 7082 features are characterized by double-peaked profiles indicative of an accretion flow with a characteristic speed ~ 30km/s, whereas the Raman C II features exhibit a single Gaussian profile with FWHM ${\sim}10{\AA}$. Monte Carlo simulations for Raman O VI and C II are performed by assuming that the emission nebula around the WD consists of the inner O VI disk with a representative scale of 1 AU and the outer part with C II sphere. The best fit for Raman profiles is obtained with an asymmetric matter distribution of the O VI disk, the mass loss rate of the cool companion ${\dot{M}}{\sim}2{\times}10^{-6}M_{{\odot}/yr}$ and the wind terminal velocity v~10 km/s. We also find O VI doublet at 3811 and $3834{\AA}$, which are blended with other emission lines. Our profile decomposition shows that the O VI ${\lambda}{\lambda}$ 3811, 3834 doublet have a single Gaussian profile with a width ~ 25 km/s. A comparison of the restored fluxes of C II ${\lambda}{\lambda}$ 1036 and 1037 from Raman C II features with the observed C II ${\lambda}1335$ leads to an estimate of a lower bound of N(CII) > $9.87{\times}10^{13}cm^{-2}$ toward RR Tel, which appears consistent with the presumed distance D ~ 2.6 kpc.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.1
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• pp.1-8
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• 2015

Wind power systems have gained much attention due to the relatively high reliability, good infrastructures and cost competitiveness to the fossil fuels. Advances have been made to increase the power efficiency of wind turbines while less attention has been focused on structural integrity assessment of structural sub-systems such as towers and foundations. Among many parameters for integrity assessment, the most perceptive parameter may be the induced horizontal displacement at the hub height although it is very difficult to measure particularly in large-scale and high-rise wind turbine structures. This study proposes an indirect displacement estimation scheme based on the combined use of inclinometers and accelerometers for more convenient and cost-effective measurements. To this end, (1) the formulation for data fusion of inclination and acceleration responses was presented and (2) the proposed method was numerically validated on an NREL 5 MW wind turbine model. The numerical analysis was carried out to investigate the performance of the propose method according to the number of sensors, the resolution and the available sampling rate of the inclinometers to be used.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.3
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• pp.307-317
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• 2011

This paper is to investigate the possibility of the elastic seismic design for highrise buildings through seismic performance evaluation for potential earthquakes that wind-designed highrise buildings located in strong wind zone and low seismicity can be experienced. Highrise steel diagrid frames which is the most loved structural system in recent years were wind-designed and the substantial system overstrength due to wind design procedure is verified, For the highrise steel diagrid frames, the response spectrum analysis and the seismic performance evaluation by various soil sites were conducted. It was showed that highrise steel diagrid frames with slenderness of greater than 5.2 under strong wind and low seismic zones such as Korea peninsula can resist elastically for the 500 year return period earthquake and have the possibility of seismic design for the 2400 year return period earthquake. In the member level, highrise steel diagrid frames with slenderness of greater than 5.2 all presented the immediate occupancy level regardless of soil sites for the 500 year return earthquake and excluding the $S_E$ soil site for the even 2400 year return period earthquake. In the system level, highrise steel diagrid frames with slenderness of greater than 5.2 showed the immediate occupancy level for $S_A$ and $S_B$ soil sites and the life safety for $S_C$ to $S_E$ soil site in the 500 year return period. The seismic performance level of highrise steel diagrid frames for the 2400 year return period earthquake displayed one step lower than the 500 year return period earthquake.

• Journal of the Korean Solar Energy Society
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• v.32 no.6
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• pp.76-84
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• 2012

This study conducted experiments to measure air currents in an experimental building according to external conditions, types of induction ducts, and types of internal sockets by applying an external induction duct comprised of inducing openings and lines and induction units to the kitchen and bathroom vents at the rooftop of a super high-rise apartment building in order to help to improve the venting performance. The study also proposed the optimization of the external induction-style kitchen and bathroom vents capable of wind power generation. (1) As for air current distribution according to vent velocity changes, it increased the venting performance of the kitchen and bathroom by 1.0m/s at vent velocity of 2.0m/s or higher and allowed for wind power generation. (2)As for air current distribution according to external velocity changes, it increased the venting performance of the kitchen and bathroom by 1.2m/s at external velocity of 2.0m/s or higher and allowed for wind power generation. (3)As for air current distribution according to wind direction changes($0{\sim}180^{\circ}$), it was favorable for higher vent velocity when the angle between the external induction duct direction and prevailing wind direction was within ${\pm}30^{\circ}$. (4)As for air current distribution according to induction duct type, the[M1] type combining the inducing openings and lines with the induction units recorded the highest improvement effects in the kitchen and bathroom venting performance by increasing vent velocity by 46%. (5)As for air current distribution according to the changing types of internal sockets where the main ducts of the kitchen and bathroom are connected to the external induction ducts, the venturi tube type[Sv] increased vent velocity by 66% based on the smoothest external inflow.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.1
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• pp.56-66
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• 2008

Subtidal surface currents are derived from HF radar measurements in the Saemangeum coastal ocean of the Yellow sea in July 2002 and from September to November 2004. The surface current field is analyzed to examine the effect of wind, river plume and coastline change on the spatial distribution and temporal variation of the surface currents. In July 2002, average wind speed was 0.5 m/s and freshwater discharge from the Keum River was $0.88{\times}10^7\;ton/day$. Temporal mean currents ($\overline{U}$) flow to the northwest with speed of $7{\sim}10\;cm/s$ near the Keum River estuary, to the west as fast as 13 cm/s near the opening gap of the Saemangeum $4^{th}$ dyke, and to the northwest off the Gogunsan-archipelago. This flow pattern is a result of the Keum River plume dispersal and tide-residual currents from the opening gap of the Saemangeum $4^{th}$ dyke. Time series of spatially-averaged current (<$U-\overline{U}$>) direction is highly (r=0.98) correlated with wind direction. From September to November 2004, the opening gap of the Saemangeum $4^{th}$ dyke was closed, northwesterly wind blew with speed of 2.5 m/s on average and the Keum River discharge was $1.19{\times}10^7\;ton/day$. Temporal mean current field ($\overline{U}$) has weak surface flow in most of the coastal ocean and relatively strong currents flow to the southwest with speed of 10 cm/s along the shape coastline of the Gogunsan-archipelago and the Saemangeum $4^{th}$ dyke. The strong flow is generated by the prevailing northwesterly wind which pushes the Keum River plume toward the Saemangeum $4^{th}$ dyke. The residual currents from the opening gap of the Saemangeum $4^{th}$ dyke disappeared and correlation coefficient between time series of spatially-averaged current () direction and the wind direction is 0.69.