• Structural Engineering and Mechanics
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• v.75 no.5
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• pp.621-631
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• 2020

A laboratory experiment is conducted is to investigate the behaviour of a low-mass-ratio and high aspect ratio flexible cylinder under vortex-induced vibration (VIV). A flexible cylinder with aspect ratio of 100 and mass ratio of 1.17 is towed horizontally to generate uniform flow profile. The range of Reynolds number is from 1380 to 13800. Vibration amplitude, in-line and cross-flow frequency response, amplitude trajectory, mean tension variation and hydrodynamic force coefficients are analyzed based on the measurement from strain gauges, load cell and CCD camera. Experimental results indicate that broad-banded lock-in region is found for the cylinder with a small Strouhal number. The frequency switches in the present study indicates the change of the VIV phenomenon. The hydrodynamic force responses provide more understanding on the VIV of a low mass ratio cylinder.

• Journal of Astronomy and Space Sciences
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• v.23 no.3
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• pp.189-198
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• 2006

We present newly observed BVRI CCD light curves for low mass ratio contact binaries, HN UMa and II UMa. The absolute dimensions of these objects were obtained by applying the Wilson-Devinney program to previously published spectroscopic analysis and to our observed photometric data. The evolutionary status of all 21 low mass ratio contact binary system including HN UMa and II UMa was then considered. The secondaries of all low mass ratio contact binaries are located below the zero age main sequence in HR diagram. This phenomenon could be explained by mass loss from the secondary component in the low mass contact binary system because even small mass loss affects luminosity decrease in the low mass stars.

• Journal of Astronomy and Space Sciences
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• v.26 no.1
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• pp.1-8
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• 2009

We present new B, V, and R CCD photometric light curves for the low mass ratio contact binary FP Boo. A new photometric solution and absolute physical dimensions of the system were derived by applying the Wilson-Devinney program to our observed light curves and to previously published Rucinski et al.'s radial velocity curves. From the H-R diagram of 24 low mass ratio contact binary system including FP Boo, the evolutionary stage of FP Boo was found to coincide with those of the general low mass ratio contact binary systems. The light curves obtained in this season show a small asymmetry in their shapes.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.8
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• pp.690-696
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• 2003

This paper presents the heat recovery performance of water fluidized-bed heat exchanger. Temperature and humidity ratio of waste gas are considered as important parameters in this study. Therefore, the heat recovery rate through water fluidized-bed heat exchanger for exhaust gases with various temperatures and humidity ratios can be estimated from the results of this study. Mass flow ratio (the ratio of mass flow rate of water to that of gas) and temperature of inlet water are also considered as important operating variables. Increase of heat recovery rate can be obtained through either high mass flow ratio or low temperature of inlet water with resultant low recovered temperature. The heat recovery performance with the mass flow ratio of about up to 10 has been investigated. The effect of number of stages of water fluidized-bed on the heat recovery performance has been also examined in this study.

• Journal of Astronomy and Space Sciences
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• v.22 no.3
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• pp.223-232
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• 2005

New BVR CCD light curves of the low mass ratio contact binaries, V410 Aur and V776 Cas, were observed with the 61 cm reflector and a 2K CCD camera at the Sobaeksan Astronomical Observatory. The absolute dimensions of the low mass ratio contact binaries, V410 Aur and V776 Cas, were obtained using WD program from the published spectroscopic and newly observed photometric data. The evolutionary status of this type of binary system including V410 Aur and V776 Cas has been considered. We reconfirmed that the primary stars of the low mass contact binary system were located on the TAMS and secondary stars were located under the ZAMS in H-R diagram.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.427-430
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• 2002

The present parer outlines the system identification and vibration control performance of air traffic control tower of Yangyang international airport with tuned mass damper(TMD). From the free vibration test, natural frequency, damping ratio and mode shape of tower are obtained and these values are compared with the values from numerical analysis. In the vibration control test to evaluate the vibration control performance, equivalent damping ratio increased by tuned mass damper are obtained in case the TMD is operated as passive mode. Damping ratio of tower evaluated from free vibration test is about $1.0{\%}$. It is very low value than damping ratio recommended in general code. Damping ratio of passive mode is about $5{\%}$. These equivalent damping ratio increased by TMD is enough to enhance the serviceability of tower structure under wind load.

• Journal of Astronomy and Space Sciences
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• v.21 no.2
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• pp.83-92
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• 2004

The absolute dimensions of low mass contact binary, GR Vir and HV Aqr were obtained using WD program from the published spectroscopic and photometric observational data. The evolutionary status of this type of system including GR Vir and HV Aqr has been considered. The primary stars of low mass contact binary system were located on the Terminal Age Main-sequence and secondary stars were located under the Zero Age Main-sequence in H-R diagram.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.4
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• pp.283-289
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• 2008

An experimental investigation was conducted to investigate the heat/mass transfer for impingement/effusion cooling system with inclined jet. Jets with inclined angle of 60 are applied to impingement/effusion cooling. At the jet Reynolds number of 10,000, the experiments were carried out for blowing ratios ranging from 0.0 to 1.5. The local heat/mass transfer coefficients on the effusion plate are measured using a naphthalene sublimation method. The result indicates that the inclined jet causes the non-uniform and low heat/mass transfer compared to the vertical jet. At stagnation region, the peak position is shifted from the geometrical center of injection hole due to Coanda effect and its level is higher than that of vertical jet due to increase in turbulence intensity by steep velocity gradient near the stagnation region. Further, the secondary peak region disappears because the interaction between adjacent wall jets weakens. When the initial crossflow occurs, the distorted heat/mass transfer pattern appears. As the blowing ratio (crossflow rate) increases, the heat/mass transfer distributions become similar to those of the vertical jet. This is because the effect of crossflow is dominant compared to that of inclined jet under high blowing ratio $(M{\geq}1.0)$. At low blowing ratio $(M{\leq}0.5)$, averaged Sh value is 10% lower than that of vertical jet, whereas its value at high blowing ratio $(M{\geq}1.0)$ is similar to that of vertical jet.

• Geomechanics and Engineering
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• v.33 no.6
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• pp.553-565
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• 2023

As the structure of broken rock mass is complex, with obvious discontinuity and anisotropy, it is generally necessary to reinforce broken rock mass using grouting in underground construction. The purpose of this study is to experimentally investigate the mechanical properties of broken rock mass after grouting reinforcement with consideration of the characteristics of broken rock mass (i.e., degree of fragmentation and shape) and a range of reinforcement methods such as relative strength ratio between the broken rock mass and cement-based grout stone body (λ), and volumetric block proportion (VBP) representing the volumetric ratio of broken rock mass and the overall cement grout-broken rock mass mixture after the reinforcement. The experimental results show that the strength and deformation of the reinforced broken rock mass is largely determined by relative strength ratio (λ) and VBP. In addition, the enhancement in compressive strength by grouting is more obvious for broken rock mass with spherical shape under a relatively high strength ratio (e.g., λ=2.0), whereas the shape of rock mass has little influence when the strength ratio is low (e.g., λ=0.1). Importantly, the results indicate that columnar splitting failure and inclined shear failure are two typical failure modes of broken rock mass with grouting reinforcement.

• Korean Journal of Community Nutrition
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• v.14 no.6
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• pp.789-797
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• 2009

In order to investigate the effects of frequent eating-out and breakfast skipping of working men on body mass index and nutrients intake status, working male adults aged 20 or over were selected (n = 1883) from the data of 2001 Korea national health and nutrition survey. The subjects were divided into 4 groups according to the eating-out frequency(high: once or more daily, low: less than once daily) and breakfast eating or not. Four groups were high eating-out with breakfast eating (n = 609), high eating-out with breakfast skipping (n = 192), low eating-out with breakfast eating (n = 877), and low eating-out with breakfast skipping (n = 205). High eating-out group showed higher body mass index (BMI) than low eating-out group, but the difference of BMI was disappeared when adjusted with age, residence region and family income. However high eating-out group in case of breakfast eating, compared with the low eating-out, showed higher intakes or densities of energy, fat, fat-energy% and higher ratio of energy-fat overintake, and also showed higher mean nutritional adequacy ratio and lower ratio of nutrients intake deficiency. Calcium, iron, vitamin A and C intakes were not affected by eating-out frequency, but were lowered by breakfast skipping. Breakfast skipping also decreased intake frequency of unprocessed cereals and increased those of ramyon and carbonated and alcoholic beverages. From the results frequent eating-out with breakfast eating caused increased intakes of energy and fat, but did not cause BMI increase. Breakfast skipping, but not eating-out, had negative influences on mineral and vitamin intakes. Accordingly good eating-out as well as breakfast eating should be exceedingly emphasized at nutrition education for the working males.