• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.12
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• pp.1073-1080
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• 2000

Thermal diode is a device which allows heat to be transferred in one direction by convection due to density difference of fluid ,and blocks heat flow in the opposite direction. It is simple in construction and low in cost. And so, it is used as heat collection system of solar energy. In order to acquire a basic design data, thermal diode heat collection system has been studied experimentally for flux Rayleigh numbers from $2\times10^8\;to\;8\times10^8$. The heat transfer rate of this system is shown 10~47% higher than that of other earlier research results. He correlation obtained in this study is Nu=0.0037(Ra^*)^{0.429}(d^*)^{0.05}\frac{(Lr)}{H}^{0.415}$.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.37.1-37.1
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• 2011

We report untwisting chromospheric surges of AR 10930. Hinode Solar Optical Telescope (SOT) observed AR 10930 on the west limb continuously from 11:21 UT December 18 to 09:58 UT December 19, using the Ca II H broadband filter. During the observation, rise and fall motion accompanying rotation appeared recursively. There occurred a total of 14 surges at AR 10930 over 17 hours. The average duration was 45 minutes, and the average width, and length were 8 Mm, and 39 Mm, respectively. The dynamic properties including number of turns from the rise to the fall, the axial speed and acceleration are also analyzed. We speculate that the surges occurred by recursive reconnections between the twisted prominence and large untwisted flux tube.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.34.2-34.2
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• 2011

In this talk we explain U-loop emergence, in which U-shaped field lines emerge into the solar surface against gravitational force. In principle, they hardly emerge because mass tends to accumulate at the bottom of U-loops, thereby decreasing buoyancy. A key is found to be the shape of U-loops, that is, if U-loops have a shallow dip whose depth is of the order of the photospheric gravitational scale height, then a diverging flow is generated via a siphon-like mechanism by which the mass accumulated at the dip of the loops is drained out to enhance buoyancy. This successfully makes U-part of the loops emerge against gravity. We also discuss the relation between U-loop emergence and the so-called flux cancellation observed on the Sun in which opposite polarity regions apparently approach together and disappear.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.1
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• pp.82-89
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• 2016

This paper presents computational fluid dynamics (CFD) analysis on passenger thermal comfort in a train. Human thermal comfort in vehicles depends mainly on air temperature, mean radiant temperature, air velocity, humidity, and direct solar flux, as well as the level of activity and thermal properties of clothing and seat. The velocity and temperature distribution in a train with and without passengers are reported. The thermal comfort in a passenger train are also presented based on PMV and PPD indices with 16 segments of the human body.

• International Journal of Air-Conditioning and Refrigeration
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• v.9 no.4
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• pp.10-16
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• 2001

An experimental study for free convective heat transfer in a thermal diode type enclosure is presented. The thermal diode is a device which allows heat to be transferred in one direction by convection due to density difference of the fluid, and consists of a rectangular-paralle-logrammic enclosure with a guide vane. It is used as heat collection system of solar energy due to its simple construction and low cost. Experimental parameters were guide vane thickness, the inclination angles of the parallelogrammic enclosure, and the lengths of the rectangular enclosure part. The parameter range of the flux Rayleigh numbers was $2.4\times{10}^8$~$9.8\times{10}^8$. The heat transfer rate of this system was shown 10~47% higher than that of other earlier research results without the guide vane. The correlation for fixed $\phi=60^\circ$ was obtained, Nu=0.0037(Ra^*)^{0.429}(d^*)^ {0.050}(Lr/H)^{0.0415}$.

• Journal of the Semiconductor & Display Technology
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• v.16 no.3
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• pp.20-24
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• 2017

For process improvement and cutting down on expenses in solar cell industry, it is necessary to improve recycling process of wafer manufacturing. In this research, a study is introduced to develop classifier which is for recycling of abrasive. First of all, recycling process of wafer manufacturing is analyzed. And then, 3 steps of experiments such as oil removal, impurities removal and classification were executed. For the classification of slurry, a classifier is designed and manufactured. From experiments, it is verified that ultra sound vibration and flux are very important factors for classification. By experiencing the recycling processes and making devices, the technique can be initiated industry if needed such as decreasing waste and cutting down on expenses.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.70.2-70.2
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• 2019

Recent observational works have reported spiral wave patterns (SWPs) in sunspots, but there is a lack of samples to derive the physical properties. In this presentation, we suggest the automatic method to detect the SWPs in observational data and present their statistical properties. From our method, we find more than 1000 SWPs observed by the Atmospheric Imaging Assembly onboard in the Solar Dynamic Observatory from 2013 to 2018. From our samples, more than half of the SWPs has the one spiral arm. The predominant oscillation period is 2 to 3 minutes. The rotating direction of the spiral arms does not depend on the latitude and the polarity of the sunspots. Our statistical results support the physical model suggested by Kang et al. (2019) that explain the generation of SWPs as the depth of the wave driving source and azimuthal modes in the straight vertical magnetic flux tube.

• 한국해양학회지
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• v.29 no.4
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• pp.325-337
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• 1994

The distributions of heat and momentum fluxes on the surface over the oceans around the Korean Peninsula are obtained based on the surface-layer flux model of Kim and Kang (1994), and their seasonal variations are examined in the present study. the input data of the model is the oceanatmosphere data with a grid interval of 2$^{\circ}$ in longitude and latitude. The atmosphere data, which are the pressure, temperature, and specific humidity on the 1000 mb level for 3 year period of 1985∼1987, are obtained from the European center for Medium Range Forecast. The sea surface temperature (SST) is obtained from National Meteorological Center (NMC). The solar insolation and longwave radiation on the ocean surface are obtained, respectively, from the NASA satellite data and based on an emprical formula. It is shown from the net heat flux that the oceans near Korea lose heat to the atmosphere in January and October with the rates of 200∼ 400 Wm/SUP -2/ and 100 Wm/SUP -2/, respectively. But the oceans are heated by the atmosphere in April and July with about the same rate of 100 Wm/SUP -2/. The annualmean net heat flux is negative over the entire domain except the northern part of the Yellow Sea. The largest annual-mean cooling rate of about 120 Wm/SUP -2/ is appeared off the southwest of Japan. In the East Sea, the annual-mean cooling rate is 60∼90 Wm/SUP -2/ in the southern and northern parts and about 30 Wm/SUP -2/ in the middle part. The magnitude of wind stress in january is 3∼ 5 times bigger than those of the other months. As a result, the spatial pattern of annual-mean wind stress is similar to that of January. It is also shown that the annual-mean wind stress curl is negative. in the East China Sea and the South Sea,but it is positive in the northern part of the Yellow Sea.In the East sea,the stress curl is positive in the southeast and northern parts and negative in the northwestern part.

• Korean Journal of Remote Sensing
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• v.33 no.3
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• pp.301-311
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• 2017

Aerosol optical properties as well as vertical location of layer can alter the radiative balance of the Earth by reflecting and absorbing solar radiation. In this study, radiative transfer model (RTM) and satellite-based analysis have been used to quantify the top-of-atmosphere (TOA) radiative effect of aerosol layers in the cloudy atmosphere of the northeast Asia. RTM simulation results show that the atmospheric warming effect of aerosols increases with their height in the presence of underlying cloud layer. This relationship is higher for stronger absorbing aerosols and higher surface albedo condition. Over study region ($20-50^{\circ}N$, $110-140^{\circ}E$) and aerosol event cases, it is possible to qualitatively identify absorbing aerosol effects in the presence of clouds by combining the UV Absorbing Aerosol Index (AAI) derived from Total Ozone Mapping Spectrometer (TOMS), cloud parameters derived from the Moderate Resolution Imaging Spectro-radiometer (MODIS), with TOA Upward Shortwave Flux (USF) from the Clouds and the Earth's Radiant Energy System (CERES). As the regional-mean radiative effect of aerosols, 6 - 26 % lower the USF between aerosols and cloud cover is taken into account. These results demonstrate the importance of estimation for the accurate quantification of aerosol's direct and indirect effect.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.52 no.1
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• pp.1-11
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• 2007

Light is an environmental component inevitably regulating photosynthesis and photo-morphogenesis, which are involved in the plant growth and development. Studies were conducted at the International Rice Research Institute, Philippines in 2004 and 2005, with aims to investigate 1) morphological responses of rice plants to low radiation, 2) morphological alteration of shade-grown plants when exposed to high light intensity, and 3) photosynthetic responses of shade-grown rice plants. Reduction in solar radiation by 40% induced increases in the area on a single leaf basis, biomass partitioning to leaves, and chlorophyll meter readings but brought about retardation of tiller development and decrease in above-ground biomass production of rice varieties. When the shade-grown plants from two weeks of transplanting to panicle initiation were exposed to full solar radiation after panicle initiation, they demonstrated less increase in chlorophyll meter readings and more decrease in leaf nitrogen concentrations from panicle initiation to flowering than control plants that were grown under the ambient solar radiation for whole growth period after transplanting. Shade-grown rice plants exhibited lower carbon assimilation rates but higher internal $CO_2$ concentrations on a single leaf basis than control plants, when measurements for shade-grown rice plants were made under the shading treatments. But when the measurements for shade-grown plants were made under the full solar radiation, light-saturated carbon assimilation rates were similar to control plants. Response of photosynthetic rates to varying light intensities was not considerably different between shading treatments and control. Yield reduction was observed in the shading treatments from panicle initiation to flowering and from flowering to physiological maturity, mainly by less spikelets per panicle and poor grain filling, respectively.