• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.58-58
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• 2011

Nickel-ceramics nanocomposite coatings can be applied as the wear resistance coating, corrosion protection of underlying materials, and decorative coatings. Hence, Nickel based nanocomposite coatings, especially Ni-SiC, have been extensively studied in recent years. However, more often agglomeration problem of the nanoparticles in the nickel matrix can cause deterioration of the mechanical properties rather than improvement. The homogeneous distribution of the nanoparticles in the matrix coating is still being challenging. In this experiment, electrochemical deposition of Ni-SiC composite coating was done in presence of ultrasound. The effects of different ultrasonic powers and frequencies on the nanoparticle dispersion were studied. The electrodeposition was carried out in nickel sulfamate bath by applying pulse current technique. Compared to the conventional mechanical stirring technique to prevent nanoparticles agglomeration and sedimentation during composite electrodeposition, the aid of ultrasonic dispersion along with mechanical stirring has been found to be more effective not only for the nanoparticles dispersion, but also for the mechanical properties of the electrodeposited coatings. Nanoparticles were found to be distributed homogeneously with reduced agglomeration. The microstructure of the composite coating has also been changed, allowing some random orientations of the nickel crystallite grain growths, smooth surface, and finer grains. As a consequence, better mechanical properties of the composites were observed.

• Composites Research
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• v.25 no.6
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• pp.198-204
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• 2012

The objective of this study is to improve the mechanical properties in abaca fabric/epoxy composites produced using a VARTM process. The mechanical properties were improved by increasing the surface roughness of the fabric through plasma polymerization and improving the interfacial adhesion between the epoxy and the fabric through changing its hydrophilic properties to the hydrophobic properties. Plasma polymerization at atmospheric pressure and room temperature was used, and the optimal polymerization time to improve the mechanical properties was investigated. NaOH treatment on the fabric was also carried out for the comparison. The composite fabricated using the fabric polymerized for 10 seconds shows the highest tensile strength compared to that of none-polymerized or NaOH treated. Plasma polymerization for more than 20 seconds exhibits decrease in the tensile strength. As a result, the plasma polymerization for more than 20 seconds may have caused some damages on the surface of the fabrics. Also, the hydrophilic abaca represents a tendency of presenting the hydrophobic properties in absorption and sedimentation tests.

• Korean Journal of Soil Science and Fertilizer
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• v.33 no.3
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• pp.175-181
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• 2000

This study was carried out to investigate the change of soil physical properties in long-term fertilized paddy soils with a Fine silty family of Typic Halpaqueps (Pyeongtaeg series). Treatments fertilized consisted of no fertilizer, compost, NPK, NPK+compost for thirty one years and of NPK+silicate for seventeen years. Water stable aggregate and degree of aggregate stability, which were higher in surface-soil than sub-soil, were high in order of NPK + compost > NPK + silicate > compost > NPK > no fertilizer plot. The ratio of aggregate larger than 0.5mm was high at compost and silicate plots but that smaller than 0.5mm was high at no fertilizer and NPK plots. And this aggregate stability showed negative correlation with soil hardness and bulk density ; positive correlation with sedimentation volume of soils in water. Sedimentation volume of soils in water was a little higher in surface-soil than sub-soil and in wet soil than dry soil, respectively. Pore space ratio and water retention capacity of soils were the most increased by the application of compost and not affected by silicate as in cases of liquid limit and plastic limit. Ignition loss of soils was high in order of NPK + compost > compost > NPK + silicate > NPK > no fertilizer plot. And field shattering ratio of soil mass smaller than 25.4mm was relatively high in NPK + compost, compost, and silicate plots.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.4
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• pp.427-436
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• 2004

Sedimentation is one of the most common and important units in conventional water treatment plants. Structure such as various baffle walls and inclined plate settler may be obstacles to the horizontal flow when it is poorly designed. Therefore, the effects of these structures on characteristics of hydraulic flow must be evaluated to improve the settling efficiency of the floc. The hydraulic characteristic of the four sedimentations at the three real WTPs (water treatment plants), which have different structural properties respectively inside the settling basin, were investigated by tracer (fluoride) test. The inclined plate settler installed inside settling basin caused a undesirable impact on horizontal flow and produced dead zone. Intermediate baffle and solid baffle wall under the inclined plate settler at GE plant help to minimize the formation of density currents and flow short circuiting. However, installing perforated baffle under the inclined plate settler at other plants could not induce even distribution of flow. NaF used as a tracer was recovered more than 90% at investigated all basin. Morill index ($t_{90}/t_{10}$), Modal index ($t_p/T-HRT$) and short-circuiting index ($[M-HRT-t_p/M-HRT$) were determined from tracer test results performed at three WTPs. Those indices ranged 2.99~3.45, 0.44~0.72 and 0.23~0.47, respectively.

• Journal of the Korean Ceramic Society
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• v.36 no.10
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• pp.1094-1101
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• 1999

Liquid phase sintered silicon carbides were obtained by sintering of $\alpha$-SiC and $\beta$-SiC powders as starting materials at 2173K and 2273K respectively. The SiCplatelet seeds of different sizes were obtained by a repeated ball milling and sedimentation. Their mean size (d50) were 2.217 ${\mu}{\textrm}{m}$ 13.67 ${\mu}{\textrm}{m}$, 22.17${\mu}{\textrm}{m}$ respectively 6wt%Al2O3-4 wt% Y2O3 was used as the sintering additives for the liquid phase sintering. The two silicon carbides had a bimodal microstructure consisting of small matrix grains and large platelike grains when the SiCplatelet seeds were added. In the case of the $\beta$-SiC the appreciable phase transformation occurred as sintering temperature increased from 2173K to 2273K and resulted in matrix shape change from equiaxed into platelike grains. In contrast there was no shape change for the $\alpha$-SiC. The size of large grains in the $\alpha$-SiC of large grains in the $\alpha$-SiC was larger than that of the large grains in the $\beta$-SiC These results suggested that the growth of the $\alpha$-SiCplatelet in the $\alpha$-SiC matrix was more favored than that of the $\alpha$-SiCplatelet in the $\beta$-SiC matix. The three point flexural strength decreased as the added seed size increased. Fracture toughness values of samples sintered at 2273K were higher than those of samples sintered at 2173K.

• Culinary science and hospitality research
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• v.15 no.1
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• pp.202-208
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• 2009

This study was conducted to investigate the differences on physicochemical properties and cookie potentialities of Korean wheat cultivars. The protein contents of the wheat cultivars ranged from 8.80$\pm$0.76% to 11.19$\pm$0.25%. Korean wheat cultivars had sedimentation values of 19.82 mL to 35.54 mL. Their peak viscosity range measured by Amylograph was from 60 BU to 640 BU. Diameter of cookies for soft wheat was 8.28 cm and Korean wheat cultivars ranged from 7.63 cm to 8.55 cm. Olgeunmil resulted in a higher cookie diameter and top grain score than the soft wheat. Protein content had significantly negative correlations with the coefficient of cookie diameter(r=-0.838$^*$) and with the top grain score(r=-0.751$^*$). There was a significant correlation between protein content and sedimentation value(r=0.762$^*$).

• Food Engineering Progress
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• v.13 no.1
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• pp.50-55
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• 2009

The effect of active gluten supplementation on the quality properties of rice bagel was investigated. Water hydration capacity of rice flour increased as the amount of gluten increased, whereas alkaline water retention capacity decreased. Pelshenke value and sedimentation value were incerased as the amount of gluten increased, but these values are lower than those of strong wheat flour. Peak viscosity, setback, peak height, and peak width decreased as the amount of gluten increased. When the active gluten of 23% was added to the rice flour, the specific loaf volume of bagel increased more that two times compared with the active gluten of 11%. Hardness, gumminess, and chewiness were decreased as the amount of gluten increased. Specific loaf volume of bagel showed highly positive correlation in water hydration capacity, Pelshenke value, and sedimentation value of which values were r=0.962, r =0.964, and r =0.966, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.2
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• pp.159-169
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• 2004

Sedimentation and depositional pattern of the fine-grained sediments in the southeastern inner shelf of Korea were studied using a very high-resolution seismic profiles and sediment data. The recent mud deposits up to 45 m thick are distributed in the inner shelf forming a nearshore belt from the eastern part of Geoje Island to off the Pohang along the coast. The sediment in this area consists of homogeneous mud with mean grain size between $8.6\;to\;5.3\phi$ and does not show any distinct variability It gradually becomes finer and well sorted northeastward along the coast. Sediments normally appear as structureless massive mud but X-radiographs show that some bioturbation and faint lamination are present. The sediments accumulate at a rate of 0.18-0.44 cm/yr and the rate coincides well with the long-term (a 1000-year scale) accumulation based on very high-resolution seismic data. Distribution of wet bulk density and velocity shows a gradual increase from the southeastern part of Ulsan to off Pohang, whereas porosity shows a reverse pattern. Correlations between velocity and porosity/mean grain size are different from other regions compared, due to the difference of sediment texture and sedimentary environment. The recent shelf deposits are seismically characterized by three distinct facies: 1) well-stratified (near the river mouth), 2) semi-transparent (eastern part of Geoje Island), and 3) transparent (off Ulsan). The results suggest that fine-grained sediment derived from rivers, forming a nearshore mud belt, have been transported northeastward by the northeastward-flowing coastal current.

• 한국해양학회지
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• v.30 no.4
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• pp.302-319
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• 1995

The geochemical properties, sedimentation rates, foraminiferal distributions, and oxygen and carbon isotope records of sediment from Cores S-2 and S-19 were studied to investigate late Holocene paleoceanographic and paleoclimatic changes of the admiralty and Maxwell Bay, King George Island, Antarctica. Total organic carbon contents increased from the lower part to the upper part of Cores S-2 and S-19, whereas calcium carbonate contents decreased from the lower part to the upper part of Cores S-2 and s-19,whereas calcium carbonate contents decreased from the lower part to the upper part of Cores S-2 and S-19. Twenty-seven foraminiferal species were identified, and Globocassidurina biora was mostly a bundant in sediment samples. The sedimentation rates ranged from 24 cm/kyr to 237 cm/kyr based on /SUP 14/C-age dating of G. biora. The sedimentation rates increased rapidly in the upper part of the Cores. б/SUP 18/O values ranged from 0.3% to 6.2% and б/SUP 13/C values ranged from -3.0% to 0.0% with several fluctuations of the values. The lowest part of Core S-2, at 128 cmbsf in depth, had a /SUP 14/C-age of 3,100${\pm}$60 yr B.P. and the lowest part of Core S-19, at 230 cmbsf in depth, of 7,400${\pm}$ yr B.P. The results of geochemical and sedimentological analyses of the core sediments suggested five stages of paleoceanographic and paleoclimatic changes as follows: war,-cold stage of 7,500∼6,500 yr B.P., cold stage of 6,500∼3,600 yr B.P., cold-warm stage of 3,600∼2,770 yr B.P., warm stage of 2,770∼2,380 yr B.P. and cold-warm stage of 2,380∼2,100 yr B.P.

• Analytical Science and Technology
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• v.28 no.1
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• pp.33-39
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• 2015

CdS-QD particles are a nano-sized semiconducting crystal that emits light. Their optical properties show great potential in many areas of applications such as disease-diagnostic reagents, optical technologies, media industries and solar cells. The wavelength of emitting light depends on the particle size and thus the quality control of CdS-QD particle requires accurate determination of the size distribution. In this study, CdS-QD particles were synthesized by a simple ${\gamma}$-ray irradiation method. As a particle stabilizer polyvinyl pyrrolidone (PVP) were added. In order to determine the size and size distribution of the CdS-QD particles, sedimentation field-flow fractionation (SdFFF) was employed. Effects of carious parameters including the the flow rate, external field strength, and field programming conditions were investigated to optimize SdFFF for analysis of CdS-QD particles. The Transmission electron microscopy (TEM) analysis show the primary single particle size was ~4 nm, TEM images indicate that the primarty particles were aggregated to form secondary particles having the mean size of about 159 nm. As the concentration of the stabilizer increases, the particle size tends to decrease. Mean size determined by SdFFF, TEM, and dynamic light scattering (DLS) were 126, 159, and 152 nm, respectively. Results showed SdFFF may become a useful tool for determination of the size and its distribution of various types of inorganic particles.