• Journal of Power System Engineering
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• v.15 no.4
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• pp.75-78
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• 2011

There are various types of materials used in electronic industry, such as electrode material, conductor, insulator, anode, cathode and semiconductor. Electrode material type is Cu, Ti, ZnO and so on. Especially if we use mixed ZnO in soil cement or silica gel, we can have advantages in ice road to prevent freezing. We have great impact if we use supported in inorganic substances like silica gel. In this paper we have studied that ZnO supported silica gel and its properties. Zinc acetate dissolved in distilled water were loaded on the silica gel by the reaction with ammonia at $80^{\circ}C$. And we investigated particle structures of ZnO by scanning electron microscopy(SEM) and X-ray diffraction(XRD).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.635-636
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• 2006

• Journal of The Geomorphological Association of Korea
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• v.24 no.3
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• pp.27-45
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• 2017

At the upper part of terrace deposits at Jeongdongjin area, there is a structure in which reddish brown and grayish white layers laying horizontally. Previous studies have reported the existence of these structures within the deposits and suggested the theoretical background related to the formation process. However, the analysis of physical properties and chemical composition such as particle size, classification, etc. of the materials constituting the reddish brown and grayish white layers is scarcely done. In this study, the physico - chemical properties of gray - white and reddish brown beds are investigated. The mean grain size of the particles was less than $4{\varphi}$ in both layers and the reddish brown layer was more coarse. The results shows that the sorting of the grayish white layer is better. The chemical composition of both layers shows that the average concentration of $SiO_2$, $Al_2O_3$ and $K_2O$ of the grayish white layer was higher than those of the reddish brown layer. The concentration of $Fe_2O_3$ of reddish brown lyaer was 3 times higher than those of the grayish white layer. The degree of chemical weathering (CIA) is 90 or so in both the reddish brown and grayish white layers, indicating a significant level of chemical weathering. In conclusion, reddish brown layers had been formed by the processes related to the migration of iron and the migration of water that induced aggregation after the formation of sediments (psudo-gleization). In this study area, a vertical layer of grayish white which cuts off horizontal reddish brown and grayish white color was found. The vertical layer or wedge similar to a ice-wedge or columnar structure that in a cold environment, and there is a difference in shape and size. The vertical layer appears to have occurred three or more cycles. The vertical layers begin to form at a certain height within the outcrop and descend downwards, which of course is difficult to see as directing certain times.

• Journal of the Korean Geotechnical Society
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• v.25 no.10
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• pp.111-122
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• 2009

Dissolution of some of geo-materials may yield the loss of the soil strength and the settlement of earth structures. The goal of this study is to monitor the several physical behaviors of soluble mixtures during dissolution. Sand-salt mixtures are used to monitor the meso to macro response including the settlements and shear waves. The mixtures of photoelastic and ice disks are used to monitor micro to meso behavior of soluble mixture including the void ratio, force chain, coordination number and horizontal force changes. In the sand-salt mixtures, shear waves are measured by using bender elements in conventional oedometer cells. In the photoelastic disk - ice disk mixtures, micro to meso response are measured by digital images and load cells. The shear wave velocity decreases at the initial stage of the dissolution, and then increases and approaches to asymptotic value. The larger dissoluble particle and the more random packing produces the severe horizontal fore change. After dissolution, the void increases and the coordination number decreases. This study demonstrates that the particle level behavior such as the changes of the force chain, void ratio, and coordination number affects the global behavior such as the change of the shear wave velocity and horizontal force of the system.

• Journal of the Korean GEO-environmental Society
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• v.18 no.1
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• pp.31-35
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• 2017

The mechanical characteristics of frozen sand greatly depend on the frozen temperature and the fine contents according to the previous study by Chae et al. (2015). There are two hypotheses to explain this experimental results; one is the unfrozen water contents greatly affected by the fine contents and frozen temperature and the other is the sand particle spacing greatly affected by the pore-ice. To evaluate the latter hypothesis, the micro X-ray CT scan was performed. The micro X-ray CT scanning, one of the actively performed interdisciplinary research area, has a high resolution with micrometer unit allows to investigate internal structure of soils. In this study, X-ray CT technique was applied to investigate the effect of the frozen temperature and fine contents on the sand particle minimum and average spacing with the developed image processing techniques. Based on the spacing analysis, the frozen temperature and fine contents have little influence on the sand particle spacing in the frozen sand specimens.

• Asia-Pacific Journal of Atmospheric Sciences
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• v.54 no.4
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• pp.527-544
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• 2018

This paper presents a nighttime sea fog detection algorithm incorporating unsupervised learning technique. The algorithm is based on data sets that combine brightness temperatures from the $3.7{\mu}m$ and $10.8{\mu}m$ channels of the meteorological imager (MI) onboard the Communication, Ocean and Meteorological Satellite (COMS), with sea surface temperature from the Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA). Previous algorithms generally employed threshold values including the brightness temperature difference between the near infrared and infrared. The threshold values were previously determined from climatological analysis or model simulation. Although this method using predetermined thresholds is very simple and effective in detecting low cloud, it has difficulty in distinguishing fog from stratus because they share similar characteristics of particle size and altitude. In order to improve this, the unsupervised learning approach, which allows a more effective interpretation from the insufficient information, has been utilized. The unsupervised learning method employed in this paper is the expectation-maximization (EM) algorithm that is widely used in incomplete data problems. It identifies distinguishing features of the data by organizing and optimizing the data. This allows for the application of optimal threshold values for fog detection by considering the characteristics of a specific domain. The algorithm has been evaluated using the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) vertical profile products, which showed promising results within a local domain with probability of detection (POD) of 0.753 and critical success index (CSI) of 0.477, respectively.

• Ocean and Polar Research
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• v.24 no.2
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• pp.123-134
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• 2002

Seasonal variations of settling particles and metal fluxes were monitored at a nearshore site of Marian Cove, King Geroge Island, Antarctica from 28th February 1998 to 22nd January 2000. Near-bottom sediment traps were deployed at 30m water depth of the cove, and sampling bottles were recovered every month by SCUBA divers. Total particulate flux and metal concentrations were determined from the samples. Total particulate flux showed a distinct seasonality, high in austral summer and low in austral winter: the highest flux $(21.97g\;m^{-2}d^{-1})$ was found in February of 1999, and the lowest $(2.47g\;m^{-2}d^{-1})$ in September of 1998, when sea surface was frozen completely. Lithogenic particle flux accounted for 90% of the total flux, and showed a significantly negative correlation with the thickness of snow accumulation around the study site. It was suggested that the most of the lithogenic particles trapped in the bottles was transported by melt water stream from the surrounding land. Fluxes of Al, Fe, Ti, Mn, Zn, Cii, Co, Ni, Cr, Cd, and Pb showed similar seasonal variations with the total flux, and their averaged fluxes were 34000, 9000,960, 180, 13.8, 17.6, 3.0,2.1, 5.4, 0.02, and $1.5nmol\;m^{-2}d^{-1}$ respectively. Among the metals, Cu and Cd showed the most noticeable seasonal patterns. The Cd flux correlated positively with the fluxes of biogenic components while the Cu flux correlated with both the lithogenic and biogenic particle fluxes. The Cu flux peak in the late summer is likely related to a substantial amount of inflow of ice melt water laden with Cu-enriched lithogenic particles. On the other hands, the Cd flux peak in the early spring may be associated with the unusually early occurred phytoplankton bloom.

• Polymer(Korea)
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• v.32 no.6
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• pp.529-536
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• 2008

We manufactured poly (L-lactide-co-glycolide) (PLGA) scaffolds impregnated demineralized bone particle (DBP) and hyaluronic acid (HA) by ice-particle leaching method and tested their ability of sustained release of brain derived neurotrophic factor (BDNF). BDNF (50 and 200 ng) mixed with PLGA, DBP/PLGA, HA/PLGA and DBP/HA/PLGA scaffold. The release profiles of BDNF from BDNF loaded scaffolds were assayed using ELISA. Morphological changes of scaffolds by BDNF release were also observed by SEM. BDNF stably and sustainedly released from DBP/HNPLGA than from PLGA and DBP/PLGA scaffolds. DBP/HA/PLGA scaffolds showed the great structural changes, which demonstrated BDNF release amount from DBP/HA/PLGA scaffolds were highest in all groups. We suggest that BDNF loaded DBP/HNPLGA scaffold would be very useful for nerve regeneration.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.11a
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• pp.227-233
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• 2008

Porous concrete has large continuous voids of 20-30 % by volume, and this concrete is attractive as environmental material in Japan i.e. permeable road pavement, river bank protection with vegetation and green roof system which influence thermal environment. It is necessary to confirm the frost resistance when constructing porous concrete structure in cold region. However applicable test method and evaluation criterion of porous concrete has not defined yet. Therefore, the object of this study is to investigate the frost resistance of porous concrete and this investigation attempts to address this concern by comparing 4 kinds of specified freezing and thawing tests methods (JIS A1148 procedure A/B and RILEM CIF/CDF test) in consideration of actual environment. RILEM freeze-thaw tests are different from JIS A1148 freeze-thaw tests, which are widely adopted for evaluating the frost resistance of conventional concrete in Japan, in water absorption, cooling rate, length of freezing and thawing period, and number of freezing and thawing cycles. RILEM CIF test measures internal damage and is primarily applicable for pure frost attack. CDF test is appropriate for freeze-thaw and de-icing salt attack. JIS A1148 procedure A/B showed extremely low frost resistance of porous concrete if the large continuous voids were filled with water and the ice expansion in the large continuous voids set in during cooling. Frost resistance of porous concrete was improved by mixing coarse aggregate (G7) which particle size is smaller and fine aggregate in JIS freezing and thawing tests. RILEM CIF/CDF test showed that freeze-thaw and de-icing resistance of porous concrete was seems to be superior in that of conventional concrete.

• The Journal of the Acoustical Society of Korea
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• v.31 no.6
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• pp.391-398
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• 2012

In this paper, prediction of centrifugal fan was conducted through combination the hybrid CAA method which was used to predict the fan noise with the FRPM technique which was used to generate the broadband noise source. Firstly, flow field surround the centrifugal fan was computed using the RANS equations and noise source region was deducted from the computed flow field. Then the FRPM technique was applied to the source region for generation of turbulence which satisfies the stochastic features. The noise source of the centrifugal fan was modeled by applying the acoustic analogy to the synthesized flow field from the computed and generated flow fields. Finally, the broadband noise of the centrifugal fan was predicted through combination the modeled noise source with the linear propagation which was realized using the boundary element method. It was confirmed that the proposed technique is efficient to predict the tonal and broadband noises of centrifugal fan through comparison with the measured data.