• Korean Chemical Engineering Research
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• v.46 no.5
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• pp.880-885
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• 2008

Spray pyrolysis was applied to prepare spherical silica particles with mesopores of a regular structure. The physical properties such as surface area, pore size, pore structure, particle size, and morphology were studied by BET, SEM, SAXS, and DLS analysis. At a fixed gas flow rate, the BET surface area changed from 200 to $1,290m^2/g$ as changing the CTAB/TEOS molar ratio from 0.05 to 0.3. At a fixed CTAB/TEOS ratio, the surface area of silica particles was varied from 1,062 to $1,305m^2/g$ with changing the gas flow rate from 10 to 40 l/min. The average pore size measured by BJH desorption was about $21{\sim}23{\AA}$ and not significantly influenced by the CTAB/TEOS ratio and the gas flow rate. Finally, the highest surface area which was $1,305m^2/g$ were obtained when the CTAB/TEOS ratio and the gas flow rate were 0.2 and 20 l/min, respectively. According to SAXS analysis, the prepared silica particles showed a strong peak at $2{\theta}=2.6^{\circ}$ and two minor peaks around $2{\theta}=4.4^{\circ}$ and $5.1^{\circ}$, which are due to regular mesopores of hexagonal structure. The morphology of silica particles prepared were spherical shape and the average particle size was $1.0{\mu}m$.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.559-563
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• 2015

Monitor of All-sky X-ray Image (MAXI) is a Japanese X-ray all-sky surveyer mounted on the International Space Station (ISS). It has been scanning the whole sky since 2009 during every 92-minute ISS rotation. X-ray transients are quickly found by the real-time nova-search program. As a result, MAXI has issued 133 Astronomer's Telegrams and 44 Gamma-ray burst Coordinated Networks so far. MAXI has discovered six new black holes (BH) in 4.5 years. Long-term behaviors of the MAXI BHs can be classified into two types by their outbursts; a fast-rise exponential-decay type and a fast-rise flat-top one. The slit camera is suitable for accumulating data over a long time. MAXI issued a 37-month catalog containing 500 sources above a ~0.6 mCrab detection limit at 4-10 keV in the region ${\mid}{b}{\mid}$ > $10^{\circ}$. The SSC instrument utilizing an X-ray CCD has detected diffuse soft X-rays extending over a large solid angle, such as the Cygnus super bubble. MAXI/SSC has also detcted a Ne emission line from the rapid soft X-ray nova MAXI J0158-744. The overall shapes of outbursts in Be X-ray binaries (BeXRB) are precisely observed with MAXI/GSC. BeXRB have two kinds of outbursts, a normal outburst and a giant one. The peak dates of the subsequent giant outbursts of A0535+26 repeated with a different period than the orbital one. The Be stellar disk is considered to either have a precession motion or a distorted shape. The long-term behaviors of low-mass X-ray binaries (LMXB) containing weakly magnetized neutron stars are investigated. Transient LMXBs (Aql X-1 and 4U 1608-52) repeated outbursts every 200-1000 days, which is understood by the limit-cycle of hydrogen ionization states in the outer accretion disk. A third state (very dim state) in Aql X-1 and 4U 1608-52 was interpreted as the propeller effect in the unified picture of LMXB. Cir X-1 is a peculiar source in the sense that its long-term behavior is not like typical LMXBs. The luminosity sometimes decreases suddenly at periastron. It might be explained by the stripping of the outer accretion disk by a clumpy stellar wind. MAXI observed 64 large flares from 22 active stars (RS CVns, dMe stars, Argol types, young stellar objects) over 4 years. The total energies are $10^{34}-10^{36}$ erg $s^{-1}$. Since MAXI can measure the spectrum (temperature and emission measure), we can estimate the size of the plasma and the magnetic fields. The size sometimes exceeds the size of the star. The magnetic field is in the range of 10-100 gauss, which is a typical value for solar flares.

• Polymer(Korea)
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• v.37 no.4
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• pp.486-493
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• 2013

The structure, morphology, and physical properties of syndiotatic poly(vinyl alcohol) (s-PVA) gel spun fibers were investigated to prepare polymeric embolization coils. S-PVA was prepared by saponification of the poly(vinyl acetate)/poly(vinyl pivalate)(PVAc/PVPi) copolymer. The viscosity of s-PVA solutions showed shear thinning behavior and the solution formed a homogeneous phase. Based on shear viscosity change with concentration, the optimum dope concentration was selected as 13 wt%, after which s-PVA fibers were spun and the solvent was removed. The fibers were then drawn with a maximum draw ratio of 15. A polymeric embolization coil was made of the s-PVA gel-spun fibers. The fibers were wound densely onto rigid rod and then annealed at different annealing temperatures. The polymeric embolization coil annealed at $200^{\circ}C$ was similar to metallic coils and its shape was maintained well after extension. Overall, gel-spun PVA fibers performed well for the preparation of primary and secondary coils to replace metallic coils.

• Journal of the Korea Convergence Society
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• v.9 no.3
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• pp.257-263
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• 2018

Hyperthermia supplies RF high-frequency energy above 1MHz to the tumor tissue through the electrodes. And the temperature of the tumor tissue is increased to $42^{\circ}C$ or more to cause thermal necrosis. A mathematical model can be derived a human body model for absorption and transmission of electromagnetic energy in the human model and It is possible to evaluate the distribution of temperature fields in biological tissues. In this paper, we build the human model based on the adult standard model of the geometric shape of the 3D model and use the FVM code. It is assumed that Joule heat is supplied to the anatomical model to simulate the magnetic field induced by the external electrode and the temperature distribution was analyzed for 0-1,200 seconds. As a result of the simulation, it was confirmed that the transferred energy progressively penetrates from the edge of the electrode to the pulmonary tumors and from the skin surface to the subcutaneous layer.

• Journal of the Korean GEO-environmental Society
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• v.21 no.7
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• pp.17-26
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• 2020

The soft ground in the southwest coastal area composed of marine clay is greatly influenced by sediment composition, particle size distribution, particle shape, adsorption ions and pore water characteristics, tide and temperature. In addition, the geotechnical properties are very complex due to stress history, change in pore water, dissolution process and gas formation. In this study, the physical and mechanical properties of the soft ground were evaluated through field tests and laboratory tests to investigate the strength increase characteristics according to consolidation on the soft ground in the southwest coast. In addition, in order to understand the consolidation behavior of soft ground such as subsidence, pore water pressure, horizontal displacement of soil by embankment load, measuring instruments such as pore water pressuremeter, settlement gauge, inclinometer and differential settlement gauge was installed, and a piezocon penetration test was carried out step by step to confirm the increase in shear strength of the ground. Through this, it was confirmed that the shear strength of the ground is increased according to the stages of filling. In addition, by evaluating the properties of consolidation behavior, strength increase and consolidation prediction by empirical methods and theories were compared to analyze the characteristics of strength increase rate and consolidation behavior in consideration of regional characteristics.

• Resources Recycling
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• v.19 no.1
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• pp.33-39
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• 2010

The spheric sintered body with $6{\pm}2mm$ diameter was manufactured in a rotary kiln at $1125^{\circ}C$/15 min using green body formed by pelletizing the batch powder composing of coal bottom ash produced from power plant and dredged soil by 70:30, wt%. And the physical properties of sintered body (BD) were analyzed to confirm the possibility for applying to an absorbent to restore a contaminated soil. The sintered body had a giant pore above 100 ${\mu}m$ and a fine pore below 10 ${\mu}m$, and bulk density was 1.4. Also its specific surface area, porosity and void proportion were $12.0m^2/g$, 30.1% and 38.2% respectively. The crushed body (BD-C), produced by crushing a BD specimen into an irregular shape with a aspect ratio of about 2, was similar to BD specimen at bulk density and pore size distribution. But it had superior values of specific surface area, porosity and void proportion compared with BD specimen owing to a decreased apparent volume due to conversion of closed pore existed at interior of BD to open pore during a crushing process. The IEP of sintered body occurred at about pH=5, so the optimum pH condition of reacting aqueous solution could be known before bonding a microbe to the sintered body. Hence, the optimum void proportion and porosity of an absorbent can be obtained by appropriate mixing a BD with BD-C from the base data calculated in this study.

• The Journal of Engineering Geology
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• v.25 no.4
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• pp.473-484
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• 2015

Geophysical exploration using electric resistivity, ground penetrating radar (GPR), and impedance high-frequency (ZHF) surveys was conducted in Gujwa-eup, Jeju City, Jeju Island, an island in the Korea Strait, to confirm the existence of new caves near known caves. The exploration revealed a number of anomaly zones, presumed to be caves; 27 sites at suitable locations and depth ranges were selected for drilling and further surveys. However, contrary to predictions, most of the anomaly zones were clinker layers or paleosols intercalated with lavas. Only five boreholes intersected caves. The clinker layers and paleosols were possibly detected as anomalies owing to their different physical properties from the other rocks. Two of the five cave-finding boreholes penetrated Yongcheon Cave; a new cave was found at the other. The two boreholes that penetrated Yongcheon Cave were drilled in areas where the cave has not been previously reported, and thus helped correct an error in the cave distribution map. The cave newly discovered in this boring exploration is 180 m long, and it is connected to the upstream part of Dangcheomul Cave (110 m). The cave contains well-developed lava helictites, lava levees, and ropy structures; carbonate speleothems such as soda straws, stalagmites, columns, and curtain shawls are also well preserved. Notably, the unique shape of the carbonate speleothems is attributed to their growth in relation to the cavern water that flowed into the cave along plant roots.

• Journal of the Korean Society of Clothing and Textiles
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• v.33 no.5
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• pp.711-720
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• 2009

Leaf fibers have many good properties; they are strong, long, cheap, abundant and bio-degradable. Since they, however, contain a great quantity of non-cellulose components, they have been used for the materials of mats, ropes, bags and nets rather than those of clothing. In this study, we investigated the characteristics of leaf fibers in order to promote the use of leaf fibers for the materials of clothing as well as develop the high value-added textile fibers. Leaf fiber plants including New Zealand Flax, Henequen and Banana plant, which have various nature and shape, were used. New Zealand Flax and Henequen leaves were cut from lower part of plants. Banana leaves and pseudo-stems were peeled and cut from the stem of Banana plants. First, the thin outer skins like film of leaves, veins and stems were removed before retting. The chemical retting had been processed for 1hour, at 100 in 0.4% $H_2SO_4$ aqueous solution(liquid ratio 50:1). Then, the retted leaf fibers had been soaked for 1hour, at room temperature in 0.5% NaClO solution(v/v) to remove the miscellaneous materials. We investigated the physical characteristics of three leaf fibers including the transversal and longitudinal morphology, the contents(%) of pectin, lignin and hemicellulose, the length and diameter of fibers, the tensile strength of the fiber bundles, and the fiber crystallinity and the moisture regain(%). The lengths of fiber from three leaf fibers were similar to their leaf lengths. The fiber bundles were composed of the cellulose paralleled to the fiber axis and the non-cellulose intersecting at right angle with the fiber axis. The diameters of New Zealand Flax, Henequen and Banana fibers were $25.13{\mu}m$, $18.16{\mu}m$ and $14.01{\mu}m$, respectively and their tensile strengths were 19.40 Mpa, 32.16 Mpa and 8.45 Mpa, respective. The non-cellulose contents of three leaf fibers were relatively as high as 40%. If the non-cellulose contents of leaf fibers might be controlled, leaf fibers could be used for the materials of textile fiber, non-wovens and Korean traditional paper, Hanjee.

• Journal of Soil and Groundwater Environment
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• v.11 no.3
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• pp.52-58
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• 2006

Kim and Lee (2005) suggested Minimum Entropy Deconvolution (MED) to estimate the temporal sequence of the relative recharge. However this study by Kim and Lee (2005) was just related to the verification of the conceptual approach with MED. In this study, we try to characterize the applicability of MED in the case of spatially heterogeneous recharge (distance from recharge area). Simulated results were recorded with some specific sampling points. Estimated results from this study show higher than 0.8 in cross-correlation with the original recharge sequence. In addition, the physical and mathematical meanings of the applied filter length was also investigated. It was revealed that the length of filter is highly related to the spatial distance between recharge area and the monitoring site, and the apparent shape of hydraulic head change.

• Korean Journal of Organic Agriculture
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• v.22 no.3
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• pp.423-434
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• 2014

This study was conducted to investigate the hypoglycemic effects and the production conditions of the Korean organic native rice cultured by Ganoderma lucidum. The broth culture of Ganoderma lucidum, the innoculation and culture of Ganoderma lucidum to the Korean organic native rice, and the oral administration of the Korean organic native rice cultured by Ganoderma lucidum to the streptozotocin-induced diabetic rats, were carried out. Then, the blood glucose level, the serum total cholesterol and triglyceride, and the activities of alanine aminotransferase and aspartate aminotransferase, were analyzed. The pH 4.5 at $30^{\circ}C$ was the optimal condition of the broth culture of Ganoderma lucidum. When the physical shape and the smell of the produced rice were considered, the optimal conditions to produce the Korean organic native rice cultured by Ganoderma lucidum, were the seeding of Ganoderma lucidum to Korean organic native rice in the rate of 7.5% weight, and the culture period of 9days at $28^{\circ}C$. In streptozotocin-induced diabetic rats, the blood glucose level of the dieted group by the Korean organic native rice cultured by Ganoderma lucidum for 2 weeks, were significantly decreased when compared with the control. And, the levels of the total cholesterol and triglyceride in serum were ranked less than those of the control. Also, in streptozotocin-induced diabetic rats, the activities of alanine aminotransferase and aspartate aminotransferase in the serum of the dieted group by the Korean organic native rice cultured by Ganoderma lucidum for 2 weeks, were lower than those of the control.